Abstract Submitted to Thin Films 2010

Abstract

[This data base has been modified on 15 April 2014 There are 67 submissions ].

MPF 2041, Poster, Characteristic Studies on the Ni-Based Amorphous Thin Film Fabricated by Magnetron Sputtering Process

C.W Chu1;C.H Hwang2; C.C Wang3; W.S Hwang4
1Mirdc; Taiwan
2NCKU;Taiwan
3NCKU;Taiwan

The Ni65Crl7.5Al10V17.5 amorphous alloy (NiCrAlV) was selected as the target material for preparing a series of thin film coatings on on the Hard Magnetic NdFeB substrate by magnetron sputtering process. The microstructure of these as-prepared NiCrAlV and (NiCrAlV)N thin films were examined by X-ray diffraction and TEM observation. In parallel, the properties characterization of these NiCrAlV and NiCrAlVN alloy thin films including hardness measurement by nano indentation, wetting ability by contact angle measurement, adhesion capability by scratch test, surface roughness analyzed by atomic force microscopy (AFM) and the wear resistance evaluated by pin-on disc method were investigated and compared to the commercial hard coatings. The results revealed that all of these NiCrAlV and (NiCrAlV)N thin films present a typical amorphous microstructure and smooth surface with roughness about 1 nm. This feature makes these amorphous NiCrAlV and (NiCrAlV)N thin films posses a lower wettability as well as a higher wear resistance.

MPF 2042, Oral, Characteristic Studies Thermal Stability on the Ti-Based Thin Film for Fabricated by Magnetron Sputtering Process

C.H Hwang1;C.W Chu2; W.S Hwang3; Y.C Lin4
1MIRDC; Taiwan
2NCKU;Tajikistan

The TiAN amorphous alloy (A:Ta.Al.W.etc) was selected as the target material for preparing a series of thin film coatings on the DC53 substrate by magnetron sputtering process. The microstructure of these as-prepared TiAN thin films were examined by X-ray diffraction and TEM observation. In parallel, the properties characterization of these TiAN and TiAN alloy thin films including hardness measurement by nano indentation, wetting ability by contact angle measurement, adhesion capability by scratch test, surface roughness analyzed by atomic force microscopy (AFM) and the wear resistance evaluated by pin-on disc method were investigated and compared to the commercial hard coatings. The results revealed that all of these TiAN thin films present a typical amorphous microstructure and smooth surface with roughness about 1 nm. It was found TiAN multiplayer coatings could effectively improved the high thermal stability of DC53 substrate , and the coating did not spell off after 100 times thermal cycles at 800℃.

MPF 2058, Oral, Nanocomposite Mo-Ag-N self-lubricating hard coatings fabricated by magnetron sputtering

Yang Junfeng1;Prakash Braham2; Jiang Yan1; Wang Xianping1; Fang Qianfeng1
1Institute of Solid State Physics, Chinese Academy of Sciences; China
2Department of Applied Physics and Mechanical Engineering, Lulea University of;Sweden

Mo-Ag-N nanocomposite coatings were prepared by d.c. magnetron sputtering technique from a Mo target with embedded Ag pellets onto Si (100) substrates, followed by vacuum annealing at temperature ranging from 500 to 800 oC for 1hour. SEM, EDS, XRD, nanoindenter, and micro-macro tribometer were used to investigate the influence of Ag content and annealing temperature on microstructure, surface morphology and mechanical properties. As-deposited Mo-Ag-N coatings consisted of fcc γ-Mo2N phase and fcc Ag phase where Ag uniformly distributed into Mo-N coatings. The hardness of Mo-Ag-N coatings initially increased to maximum value of 32 GPa for coatings containing 6 at.% Ag and then decreased with the further increase of Ag, whereas friction coefficient decreased monotonously with the increase of Ag content. With the increase of annealing temperature hardness, friction coefficient, and wear resistance decreased due to accumulation of a large amount of Ag particles or agglomerations onto surface resulted from high temperature intriguing phase segregation or diffusion.

MPF 2070, Poster, Structural, mechanical and corrosion resistance properties of gradient/monolithic coatings deposited by PVD and PACVD methods onto the magnesium alloys

Tanski Tomasz;
Division of Materials Processing Technology and Computer Techniques in Materials Science, Institute of Engineering Materials and Biomaterials, Silesian University of Technology; Poland

In this work gradient/monolithic films consisting of three layers (Ti/TiCN/TiAlN, Ti/TiSiN/TiSiN, Ti/DLC/DLC) as hard protective films were deposited on AZ61 cast magnesium alloy by cathodic arc evaporation method. A thin metallic layer (Ti) was deposited prior to deposition of the gradient coatings to improve adhesion. The microstructure, chemical composition and mechanical properties of the obtained films were analysed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy. The tribological behavior of coated AZ61 magnesium alloy was investigated using a ball-on-disk tribotester. The microhardness tests of coatings were made with the SHIMADZU DUH 202 ultra-microhardness tester. Investigation of the electrochemical corrosion behaviour of the samples was done with the method of potentiodynamic polarization curves in 1-M NaCl solution. It was found that the structure of the PVD coatings consisted of fine crystallites, while their average size fitted within the range 15–30 nm, depending on the coating type. SEM micrographs showed that, deposited coatings are characterized by compact structure without delamination or defects and they closely adhere to one. The wear resistance and surface hardness of AZ61 magnesium alloy can be significantly improved by a used coatings, in particular of Ti/DLC/DLC protective film due to its high hardness and low friction coefficient. Thin, hard coatings on a soft substrate, e.g. Mg-Al alloys, turn out to be an advantageous material combination from the mechanical point of view.

MPF 2078, Poster, Study on torsional fretting wear behaviors of bonded MoS2 solid lubricant coating prepared on medium carbon steel

luo jun2;Cai Zhenbing1; Mo Jiliang1; Zhu Minhao1
1Tribology Research Institute, Traction Power State Key Laboratory, Southwest Jiaotong University, Chengdu 610031, China; China
2The Department of Chemistry and Materials, Guiyang University, Guiyang, 550005, China;China

Fretting is a significant failure mechanism for various assembled contact elements. Torsional fretting phenomena as one of four basic fretting modes exist in many natural and engineering applications. An experimental analysis of the fretting behavior in the presence of a MoS2 bonded solid lubrication coating was presented. Dynamic analysis in combination with microscopic examinations has been performed by using SEM, EDX, optical microscope (OM), and surface profilometer. Experimental results showed that the coating effectively reduced the friction torque and improved the wear resistance, and strongly modified fretting regime behaviour compared to that of non-coating condition. In summary, the coating presented a better capability for alleviating torsional fretting wear.

MPF 2087, Poster, A study on wear and corrosion resistance of thermal sprayed Ni-MoS2 composite coating

Chang Chia-Hua;
Department of Mechanical Engineering, National Central University, Taoyuan; Taiwan

Composite coating techniques are becoming more and more popular for their peculiar performances. In this study, corrosion and wear resistance of thermal sprayed Ni-MoS2 composite coatings on the AISI 1020 steel substrate were investigated. The Ni- MoS2 composite powder containing 25 wt.% of dispersed MoS2 were prepared by electroplating, the powder size are in the range of 60μm~90μm. The Ni-MoS2 composite coatings were fabricated subsequently by HVOF thermal spraying process. The Ni-MoS2 composite coatings are characterized for structural, surface morphological and compositional analyses by means of micro-hardness, SEM/EDS, XRD and ICP-AES. Electrochemical AC impedance, ASTM 117 salt-fog spray and potentiodynamic polarization test were carried out to examine the anti-corrosion performance of composite coating. Ball-on-disc dry wear tests based on ASTM G99 standard were performed in room temperature to evaluate its anti-wear properties. The surface analysis results indicated that the HVOF Ni-MoS2 coatings is composed of Ni matrix and dispersed MoS2 particles. The Electrochemical test results show that there is no significant effect on improvement of corrosion resistance by the addition of MoS2 powders. The weight loss of Ni-MoS2 composite coatings are 30 times smaller than arc spraying Ni coating. It revealed that the anti-wear properties of Ni coating is obviously improved by the addition of MoS2 powders.

MPF 2093, Oral, Tribological properties of DLC coatings with varying Cr concentration in water lubrication

Wang Qianzhi1;Zhou Fei1; Zhou Zhifeng3; Ding Xiangdong2; Wang Chundong4; Zhang Wenjun4; Li Lawrence Kwok-Yan3
1State Key Laboratory of Mechanics and Control of Mechanical Structures,Nanjing University of Aeronautics and Astronautics, Nanjing, 210016,; China
2State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University;China
3Department of Mechanical and Biomedical Engineering,City University of Hong Kong;China
4Department of Physics & Materials Science ,City University of Hong Kong;China

A series of DLC coatings with varying Cr concentration were successfully synthesized on 316L stainless steel wafers using unbalance magnetron sputtering by adjusting current of Cr target (0~2A) in a mixture atmosphere of Ar and N2 gases. The composition and microstructure of as-deposited Cr-DLC coatings were characterized by Raman spectrum, X-ray diffraction spectrum, X-ray photoelectron spectroscopy and scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). The hardness, elastic modulus and tribological properties of Cr-DLC coatings in water were investigated by Nanoindentation and ball-on-disc tribometer. The concentration of Cr increased from 3at.% to 14.09at.% with increment in current of Cr target, and the C-C, C=C, Cr-Cr and Cr-O bonds exhibited in low Cr-containing DLC coatings(<4.9at%) whilst the novel Cr-C bonds with above-mentioned bonds all exhibited in high Cr-containing DLC coatings(>4.9at%). The Cr7C3(421) or Cr(110) preferred orientation exhibited in XRD spectra of Cr-DLC containing fabricated at 0.5A, 1.5A and 2A while the XRD spectrum of Cr-DLC containing fabricated at 1A was extremely similar with that of pure DLC coatings, and Cr-DLC coatings deposited at 1A possessed highest hardness and H3/E2 ratio of 13.7GPa and 0.073, respectively. The lower friction coefficient(0.08~0.1) of low Cr-containing DLC coatings(<4.9at.%) sliding against SUS440C in water lubrication was obtained while that of high Cr-containing DLC coatings(>4.9at.%) increased sharply to 0.21~0.28 due to abrasive wear. Furthermore, the specific wear rate of high Cr-containing DLC coatings was higher than that of low Cr-containing DLC coatings by two orders of magnitude due to severe wear and even delamination.

MPF 2098, Invited Lecture, Mechanical Properties of Graphene

ZHANG Yong-Wei;
Department of Engineering Mechanics, Institute of High Performance Computing; Singapore

Understanding the structural and mechanical properties of graphene is important for the development of graphene-based electronic and sensing devices. We report our recent research work on the mechanical properties of graphene using molecular dynamics/mechanics simulations. We have characterized edge mechanical properties of graphene nanoribbons, and shown that edge stresses introduce intrinsic ripples in free-standing graphene sheets even in the absence of any thermal effects. Based on elastic plate theory, we identify scaling laws for the amplitude and penetration depth of edge ripples as a function of wavelength. We demonstrate that edge stresses can lead to twisting and scrolling of nanoribbons as seen in experiments. We also study how thermal fluctuation affects the elastic bending rigidity. It is found that the bending rigidity of single-layer graphene decreases exponentially. This is in stark contrast with recent atomistic Monte Carlo simulation result that the bending rigidity of a single-layer graphene increases with increasing temperature. We have investigated the mechanical properties of hydrogen functionalized graphene for H-coverages spanning the entire range from graphene (H-0%) to graphane (H-100%). It is found that the Young’s modulus, tensile strength, and ductility of the functionalized graphene deteriorate drastically with increasing H coverage up to about 30%. Beyond this limit the mechanical properties remain insensitive to H-coverage. The underlying reasons are discussed. We have also studied the epitaxial relation between graphene nanoflakes and Si-terminated SiC surface. It is found the rotation angle of the nanoflakes plays an important role in determining epitaxial relation.

MPF 2106, Poster, Development of a Novel Nanodiamond Impregnated Polishing Pad for CMP of Oxide Film

Tsai Ming-Yi;
Department of Mechanical Engineering, National Chin-Yi University of Technology; Taiwan

Chemical-mechanical polishing (CMP) is a method commonly employed in the fabrication of silicon wafers with a planar surface. Industrial CMP pads generally are made of porous polyurethane. The pad has a porous structure in order to reduce the contact area between the wafer and the pad during the polishing process. In addition, the pores serve as a reservoir for storing the slurry. However, the pad does not possess a sufficiently uniform pore distribution to affect surface asperities. In addition, the pore diameters vary considerably, resulting in the accumulation of reaction product onto the pores. This study aimed to fabricate a CMP polishing pad by impregnating a polyurethane matrix with nanodiamond particles (5-10 nm) and graphite particles. Two kinds of pads—one employing 0.1 wt% hydrogenated nanodiamond and another employing 1wt% nanodiamond—were fabricated and their performance was compared with that of a conventional polyurethane polishing pad. Hydrogenated diamond was obtained by heat-treating graphite particles under a layer of hydrogen ions at a temperature of about 600°C for 30 min so as to disperse them uniformly in the polyurethane matrix. The surface characteristics and contact angle of the diamond-impregnated pads as well as the removal rate and non-uniformity of a dielectric oxide film polished with these pads were investigated and compared with the corresponding values for a conventional polyurethane pad. The results of this study confirmed that the novel polishing pad provided the smallest contact angle for slurry. Therefore, the fabricated pad has a higher ability to retain slurry than the conventional polishing pad. The site to be polished can be lubricated by wetting, thus enabling faster polishing of the wafer without damaging the local circuitry. Oxide CMP tests revealed that the novel polishing pad provided the highest wafer removal rate and exhibited maximum uniformity.

MPF 2114, Invited Lecture, Super-hard or super-tough? Nanomechanics for improving the toughness and durability of hard nanocomposite films

Beake Ben;
Micro Materials Ltd; United Kingdom

The link between the deposition conditions, microstructure, mechanical properties and tribological performance of hard nanocomposite films is currently an area of intense research. Understanding the link between mechanical properties and tribological performance will be key to their successful applications. Rather than be super-hard, it may be desirable that they are super-tough. TiFeN, TiN and TiFeMoN nanocomposite films with a wide range of mechanical properties have been deposited on Si using a dual ion beam system to investigate the correlation between mechanical properties and performance. Mechanical properties were determined by nanoindentation, tribological behaviour assessed by nano-scratch testing and their dynamic toughness by nano-impact testing. Failure behaviour of the films was strongly correlated with the ratio of hardness to modulus (H/E) in the film. In the nano-scratch test nanocomposite thin films of TiFeN with very high H/E ratios failed dramatically at low critical load, with failure leading to large-area delamination. Films with slightly lower H/E were found to possess a more optimum combination of hardness and toughness for applications where they could be exposed to high shearing forces and do not show the same failure behaviour. In the nano-impact test films with high resistance to plastic deformation (H^3/E^2) showed improved performance at low impact forces but not at higher forces. Their suitability for high temperature applications has been investigated using a recently developed high temperature friction module for a commercial nanomechanical test instrument (NanoTest) enabling nano-scale friction measurement at 750C.

MPF 2116, Oral, Nanoindentation study on the creep resistance of eutectic SnBi solder alloy with metallic nano-fillers

Shen Lu;Tan Zheng Yu2; Chen Zhong2
Institute of Materials Research and Engineering; Singapore
2School of Materials Science and Enginering, Nanyang Technological University;Singapore

Eutectic SnBi alloy (melting temperature 139 C) is an attractive soldering material for temperature-sensitive electronic devices. With its excellent yield strength and fracture resistance, SnBi alloy has become one of the promising candidates to replace the Pb-based solders. However, due to its high homologous temperature, the prominent time-dependent deformation at service temperatures hinders its wide applications. In the present study, low concentration (less than 4 wt%) of reactive nano metallic fillers, i.e., Cu and Ni, have been added into the SnBi eutectic alloy aiming to enhance its creep resistance. The elastic, plastic and creep properties are characterized by nanoindentation constant strain rate (CSR) measurement. The addition of the fillers has refined the microstructure of the solder matrix and thus causing it to harden moderately. The newly formed intermetallic phase, mainly located at the Sn-Bi phase boundaries, has least contribution to the elastic property as the elastic modulus does not show significant change with filler addition. The creep resistance of the filler modified SnBi eutectic alloys has significantly improved over the one without fillers. Two regions of stress-dependent creep rates were found in the alloys with and without metallic fillers. An optimum filler concentration for creep resistance was found and the reason was discussed in this study.

MPF 2127, Oral, Mechanical, Tribological and Corrosion Properties of CrBN Films Deposited by Magnetron Sputtering

Jahodova Vera;Ding Xing-zhao1; Seng Debbie H.L.2; Gulbinski Witold3; Louda Petr4
1Singapore Institute of Manufacturing Technology; Singapore
2Institute of Materials Research and Engineering;Singapore
3Koszalin University of Technology;Poland

Cr-B-N coatings were deposited on high speed steel and stainless steel substrates by a combined DC/RF magnetron sputtering process. The boron content in the as-deposited coatings was analyzed by time-of-flight secondary ion mass spectroscopy (TOF-SIMS). Coatings’ microstructure, mechanical and tribological properties were characterized by X-ray diffraction (XRD), nanoindentation and pin-on-disc tribometer experiments. The corrosion behavior of the Cr-B-N coatings was evaluated by electrochemical potentiodynamic polarisation method in a 3 wt% NaCl solution. It was found that with incorporation of boron atoms into the CrN coatings, hardness, wear- and corrosion-resistance were all improved evidently.

MPF 2130, Oral, Elasticity modulus, hardness and creep performance of SnBi alloys using nanoindentation

Lu Shen1;Pradita Septiwerdani2; Zhong Chen2
1Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research); Singapore
2School of Materials Science and Engineering, Nanyang Technological University;Singapore

Abstract A series of SnBi alloys with Bi concentration ranging from 3% to 70% have been studied by nanoindentation technique at room temperature. Constant strain rate (CSR) method was used to evaluate the modulus, hardness and the creep stress exponents of the alloys. The single phase of Sn containing 3%Bi (Sn-3Bi) effectively enhances the modulus of the Sn matrix. However, the modulus of the SnBi alloy monotonically decreases when Bi concentration is higher than 3% (which is the Bi saturation concentration in Sn at room temperature). Sn-10%Bi possesses the highest hardness and creep resistance among all the SnBi alloys. The strong resistance to the plastic deformation of the Sn-10%Bi is believed to be attributed to the hardening by the precipitated Bi phase distributed at the Sn-rich phase grain boundaries. The single phase Sn-3%Bi alloy shows a high stress exponent of creep deformation, n = 12.25, for the whole stress range from 183 to 272 MPa. Two stress sensitive ranges are found in the samples in two-phase SnBi alloys. The eutectic concentration (Sn-58% Bi) shows the lowest stress exponents of 5.20 at higher stress range and 2.35 at lower stress range. In addition to eutectic phase, the primary phases formed in Sn-50%Bi and Sn-70%Bi samples significantly enhances the stress exponents of the alloy in the two stress ranges. The deformation morphology is investigated by scanning electron microscopy (SEM) and the possible creep mechanisms are proposed. Key words: nanoindentation, creep, low melting point solder, eutectic, stress exponents

MPF 2132, Oral, Microstructural evolution and mechanical reliability of a submicron Ni(P) thin film in lead-free soldering

Ho C. E.1;Wu W. H.1; Wang C. C.1; Wang H. K.12
1Department of Chemical Engineering & Materials Science, Yuan Ze University; Taiwan

The Ni–based plating, such as electrolytic–type Au/Ni or electroless–type Au/Pd(P)/Ni(P), is widely deposited over the Cu pads/traces for packaging applications today. The function of the Au film is for oxidation protection and is usually deposited with a thickness ranging from 0.05 μm to 1 μm. The underlying Ni (or Ni–P alloy) acts as a diffusion barrier, preventing the rapid reaction between solder and Cu. The insertion of Pd(P) film (customarily 0.1 μm – 0.3 μm in thickness) between Au and Ni(P) prevents the galvanic corrosion in the Ni(P) surface caused by the Au electrolyte. The Ni thickness usually exceeds 5 μm and is not exhausted completely within the lifespan of the electronic products. However, Ni is a magnetic material and may seriously disturb the transport of wireless communication signals in the RF (radio frequency) device operation. It is therefore necessary to reduce the Ni thickness to a submicron level, avoiding the magnetic disturbance in the related applications. The aim of this study is to evaluate the solderability between liquid 96.5Sn–3Ag–0.5Cu alloy (wt.%) and solid Au/Pd(P)/Ni(P)/Cu pad, where the Ni(P) film is only 0.8 μm thick and can be consumed entirely during soldering. The liquid–solid reaction was carried out in an IR–enhanced convention reflow oven for a time period of 80 s–240 s at 260 °C. After the reaction, the couples were cross sectioned and then metallurgically polished to reveal the interior microstructures. FIB and FE–TEM were employed to characterize the microstructures of the reaction zone. To evaluate mechanical response of various interfacial microstructures, a batch of reaction couples was subsequently examined using a high–speed ball shear (HSBS) test. A detailed discussion on the role of submicron Ni(P) in the reaction system will be made in this study.

MPF 2141, Poster, Structures and mechanical properties evaluation of Cr-Ti-B-N coatings

Ho Li-Wei1;Lee Jyh-Wei2; Chen Hsien-Wei3; Chan Yu-Chen3; Duh Jenq-Gong3
1Department of Materials Engineering, Ming Chi University of Technology, Taipei; Taiwan
2Center for Thin Film Technology and Applications, Ming Chi University of Technology, Taipei;Taiwan
3Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu;Taiwan

In this study, five Cr-Ti-B-N thin films with different Cr and B contents ranging from 37.3 to 17.9 at% and 4 to 17 at%, respectively, were fabricated on silicon substrates and AISI420 stainless steel discs by pulsed DC a magnetron sputtering using the Cr and TiB2 targets. The X-ray diffractometer (XRD) and fourier transform infrared spectroscopy (FTIR) were used to characterize the phases. The atomic force microscopy (AFM) was used to examine the surface roughness. The scanning electron microscope (SEM) and transmission electron microscopy (TEM) were used to investigate the microstructures. The electron probe microanalyzer (EPMA) was used to explore the chemical compositions. The nanoindenter, scratch tester and pin-on-disc wear tester were utilized to evaluate the mechanical properties of Cr-Ti-B-N thin films. It was found that the Cr and B contents showed strong influences on the structures and mechanical properties of Cr-Ti-B-N coatings. Optimal mechanical properties with stable chemical compositions were also suggested in this work.

MPF 2143, Poster, The effects of Si contents on the mechanical and tribological properties of CrZrSiN thin films

Tseng Tzu-Chin1;Lee Jyh-Wei2
1Department of Materials engineering, Ming Chi University of Technology Taipei Taiwan.; Taiwan
2Center for Thin Film Technology and Applications, Ming Chi University of Technology, Taipei, Taiwan;Taiwan

CrZrSiN coatings with various silicon contents were fabricated on the Si wafer and AISI420 steels by a reactive magnetron sputtering system. The crystalline structure of coatings were determined by a glancing angle X-ray diffractometer. Microstructures of thin films were examined by a scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The mechanical properties were measured by nanoindentation, scratch test and pin-on-disk wear test. It was found that the hardness and tribological properties were influenced by Si contents of CrZrSiN coatings. Optimal silicon concentration for the CrZrSiN coating was proposed in this study.

MPF 2162, Poster, The effects of boron and nitrogen contents on the microstructure and mechanical properties of Cr-B-N thin films.

Tsai Wang-Ting1;Ho Li-Wei1; Lee Jyh-Wei2
1Department of Materials Engineering, Mingchi University of Technology, Taipei, Taiwan; Taiwan
2Center for Thin Film Technology and Applications, Ming Chi University of Technology Taipei Taiwan.;Taiwan

In this study, the low nitrogen contained Cr–B–N coatings was deposited using CrB2 and Cr targets by a pulsed DC reactive magnetron sputtering system at 250 °C and −150 V substrate bias. The X-ray diffractometer (XRD) was adopted to evaluate the crystalline structure. An atomic force microscopy (AFM) was performed to measure the surface roughness. The transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) were utilized to observe the cross-sectional microstructure. The mechanical properties were measured by a nanoindenter, scratch and pin-on-disk wear tester. It was found that the thin film was mainly the CrB2 and BN phases. The boron and nitrogen contents had significant effects on the microstructure and mechanical properties of Cr-B-N thin films.

MPF 2167, Oral, Integrated atomics simulation of indentation and tension process of double crystal nano-thin film

Chen Jiaxuan1;Liang Yingchun2; Wang Quanlong3; Wang Liquan4
1Center for Precision Engineering, Harbin Institute of Technology; China
2School of Mechanical and Electrical Engineering, Harbin Engineering University;China

In the recent years, the deformation of single-crystal nanowire, nanorod and nano-thin film was frequently investigated to examine the processes governing deformation on the nanometer length scale. However, the deformation process and mechanical properties of nanowire, nanorod and nano-thin film are sensitive significantly to the surface defects and stress states of them. Integrated Molecular dynamics simulation model of nano indentation and tension process with one specimen are established and performed to analyze the nanoindentation mechanism and mechanical properties of double crystal copper thin film. Firstly, a triangle pyramid shaped indenter is utilized to enter the double crystal copper thin film at different indentation depths by molecular dynamics simulation. After that, the triangle pyramid tip begin to move along the opposite direction,and withdraw from the double crystal copper thin film to finish the indentation process. In the end, the tensile loads are applied to the two sides of the nano-thin film after the indentation process to achieve tensile simulation. Through the visualization technique of atoms slip vector and bond pair analysis, the structure of molecular-cluster and defects in copper nano-thin film such as dislocations and stacking atoms are identified in the indentation process and in tensile process. The effects of grain boundaries between the two layers of thin film on evolution of dislocation are investigated in the indentation process. It is found that Dislocations nucleate firstly near the indenter when indenter enters the copper nano-thin film. The interfacial misfit dislocation between the two layers of thin film impeding dislocations downward when those dislocations approach to the grain boundary, which lead to changes the direction of dislocation line motion. When the indenter is close to the interface of the two layers of nano-thin film, dislocation nucleate from the interface of the layers of thin film again. After the indentation process, the states of the residual stress and the number of defects remaining in the double crystal copper nano-thin film are different with different indention depths. It is also found that the yield stress of the double crystal copper nano-thin film is sensitive to the states of the residual stress and the number of defects remaining in it.

MPF 2170, Poster, Optimizing Hydrophobic and wear-resistant properties of CrAlN coatings

Yang Yu-Sen1;Cho Ting-Pin2; Lin Jia-Hau3
1Department of Mechanical and Automation, National Kaohsiung First University of Science and Technology; Taiwan
2Institute of Engineering Science and Technology, National Kaohsiung First University of Science and Technology;Taiwan
3Department of Mechanical and Automation, National Kaohsiung First University of Science and Technology;Taiwan

The objective of this study is to develop a hydrophobic and wear-resistant CrAlN coating. CrAlN coatings were deposited in Ar/N2 plasma by using reactive magnetron sputtering process. Two DC powered Cr targets and two medium frequency (MF) powered Al targets were used. The hydrophobic and wear-resistant properties of the coatings were evaluated by using water contact angle (WCA) measurement and ball-on-disc tests, respectively. Microstructure and surface morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In the experimental design, L18 (21×37) orthogonal array experiments were used for the statistical purpose to optimize deposition parameters. Eight process control factors were selected such as Cr and Al targets current, substrate bias and target to substrate distance in order to study their contributions to the hydrophobic and wear-resistant properties of CrAlN coatings. For optimizing and balancing the performance of these two properties, a grey relational analysis is applied to combine the two signal-to-noise ratios of self-property in a performance index. With the grey Taguchi multi-objective optimization (GTMO) approach, the optimal experimental parameters can be determined. For film properties, The WCA increased from 65.4 to 103.2°, and wear rate decreased from 3.6E-5 to 1.2E-5 (mm3N-1m-1). The effects of microstructure and morphology on hydrophobic and wear-resistant properties were also discussed.

MPF 2178, Poster, Effect of incident angle on thin film growth: a molecular dynamics simulation study

Cao Yongzhi;Wu Chao; Zhang Junjie; Yu Fuli
Center for Precision Engineering, Harbin Institute of Technology; China

In current study molecular dynamics simulations are performed to evaluate effect of incident angle on Al thin film growth on Cu substrate. Simulation results reveal that the epitaxy mode dominates the Al thin film growth under the incident energy of 0.1 ev. However, there exists a critical incident angle at which the film-mixing mode also plays important role in Al thin film growth. Subsequently, the influence of the difference in thin film growth mode resulted from incident angle on the structure and morphology of Al thin film is studied.

MPF 2191, Oral, Sol-Enhanced Au-TiO2 Nanocomposite Coatings

JU Ying;Sharifi Marzieh; WANG Yuxin; DICKINSON Michelle; GAO Wei
Department of Chemical and Materials Engineering,The University of Auckland; New Zealand

Abstract: We have developed a novel technique to produce nanostructured composite gold (Au) coatings with superior hardness and wear resistance. A small amount of transparent TiO2 sol has been added into the traditional Au electroplating solution to synthesize highly dispersive nano-particles reinforced composite coatings in situ. TiO2 nanoparticles and Au ions deposited together onto brass or Cu substrates. The phase structure was analyzed by X-ray diffraction (XRD). Mechanical property was investigated by nano indentation and wear tests. The results indicate that the hardness and Young’s modulus was increased to 3.7 GPa and 114.3 GPa, respectively, compared to 2.5 GPa and 93.6 GPa of the traditional Au coatings. The scratch displacement, width of wear track and loss volume of wear was improved from 54.6 nm, 95 µm and 0.24*10-3 mm3 to 24.4 nm, 65 µm and 0.076*10-3 mm3. The hardening mechanisms and thermal stability of the nano composite coatings have been studied by electron microscopy and microanalysis. Keywords: Gold coating, nano-structured composite, nano-mechanical properties, wear resistance

MPF 2198, Oral, Investigation of interconnect design on interfacial cracking energy of Al/TiN barriers under a flexural load

Chang-Chun Lee1;Yen-Fu Su2; Chih-Sheng Wu1; Kuo-Ning Chiang2
1Department of Mechanical Engineering, Chung Yuan Christian University; Taiwan
2Department of Power Mechanical Engineering, National Tsing Hua University;Taiwan

Thin film technology integrated into the fabrications of semiconductor transistors is giving rise to significant challenges in multi-level backend of line (BEOL) interconnects. The interfacial adhesion of thin films between Al metal and TiN barrier is one of the major concerns dominating the interconnect reliability. The interfacial delamination is usually introduced by the thermal stress resulted from coefficient of thermal extension (CTE) mismatch among material components. The foregoing phenomenon could be regarded as an effect of bending moment induced on the concerned interface of dissimilar materials. It is interesting to analyze interconnect design on interfacial cracking energy of Al/TiN barriers under a flexural load. Accordingly, the present research proposes a robust estimation of interfacial cracks using simulation-based methodologies to satisfy the requirement for mechanical designs in multi-level interconnected systems. A constant bending moment could be generated by the framework of the four-point bending test (4-PBT). By constructing 4-PBT simulated model, the interfacial fracture energy of Al/TiN films is predicted via finite element analysis (FEA), combined with the J-integral method and modified virtual crack closure technique (VCCT). In the meanwhile, the foregoing simulated approaches are verified by related experimental data. The primary results highlight a significant increase in the energy release rate (G) induced by the passing of a crack along the interface of Al/TiN films through the region below a metal line with a high degree of hardness. Moreover, the arrest of crack growth along the interface of Al/TiN stacked films is possible when the interfacial crack is above the region of low-k dielectric with an extremely low modulus. In other words, dielectrics with a lower modulus would have the capacity to restrain progressive crack growth.

MPF 2201, Poster, Effect of water vapor on the oxidation behavior of NiAl alloys modified by reactive elements

Yan Kai;Guo Hongbo; Gong Shengkai
Materials Science and Engineering School, Beihang University,; China

Turbines fired with syngas or hydrogen derived from coal gasification will significantly increase water vapor content of the combustion gas at the turbine inlet. The effect of increased water vapor on β-NiAl alloys modified by reactive elements such as Dy, Hf, and Zr was investigated at 1100 °C. The microstructures of the modified alloys were investigated by scanning electron microscope (SEM) equipped with energy dispersive spectroscope (EDS) and back scatter detector. With increasing the water vapor content, the spallation of alumina scale grown on the doped alloys was accelerated, but the growth rate of the scale did not change significantly. Compared to the undoped NiAl alloy, the reactive element additions appeared to improve the oxidation resistance of the NiAl alloys and significantly change the microstructure of the alumina scale in water vapor atmosphere at high temperature.

MPF 2204, Oral, Estimation of Tip-Grit Scratch Energy on Copper Thin Film in Liquid Environment with AFM

Chao Chun-Chieh;Chao-Chang A. Chen; Huang Kuo-Wei
Mechanical Department National Taiwan University of Science and Technology; Taiwan

Atomic force microscopy (AFM) has been popularly applied on nano-surface roughness measurement instrument and also the nano-scratching device due to tip function variety. This paper is to attach a 400 nm oxide silica grit on AFM tip for investigating the tip-grit scratching phenomena on copper film on silicon wafer under dry, deionized water (DI-water) and chemical slurry environment, respectively. The specific tip-grit scratch energy (TGSE) of the removed material per unit volume has been estimated based on the developed tip stiffness models and also experimental observation by the Scanning Electron Microscopy (SEM) and the analysis on the Energy Dispersive Spectrometer (EDS). Experimental results have shown that the specific TGSE increases as increasing the tangent force. For different test environments with constant applied forces, different scratch depths have been observed and the larger depths happen when tests in chemical slurry than that in DI-water due to the chemical passiviation of copper film. Some debris have also been observed and some elements including silica, oxygen, carbon and copper have been found on the tip by the analysis of SEM and EDS. As compared with the Chemical Mechanical Polishing (CMP) process, the tip-grit scratch behavior can in some way to assist in finding the mechanism of Cu-CMP process. Further study can focus on applying such results on the Cu-CMP process with low residual stress of the metal film.

MPF 2208, Poster, Oxidation resistance and structural evolution of coatings

Du-heng Tsa;
Departent o Materils Science nd Engineering, ational University; Åland Islands

The (TiVCrZrHf)N coatings were deposited on Si substrates by reactive magnetron sputtering technique from a TiVCrZrHf alloy target in Ar+N2 mixture atmosphere, and their oxidation behaviors as well as the oxidized structure were studied after static oxidation tests in air at different temperatures. The evolution of chemical composition, microstructure, hardness, and As-deposited coating had a continue variation in structure, from amorphous to columns with FCC phase and it had no was stable at a high value of increased at 500 oC. Therefore, the hardness of (TiVCrZrHf)N coating decreased to 11.85 GPa drastically. With annealing temperature increased above 600 oC, the coating was almost fully oxidized and become quite porous and loose. Accordingly, a very low hardness of only 2.3 GPa was obtained. The electrical

MPF 2218, Oral, Application of Cathodic Arc Physical Vapour Deposition (CAPVD) for varying Ti(C,N) properties in cutting tool application

Siow Ping Chuan1;A. Ghani Jaharah1; Ria Jaafar Talib2; Ghazali Mariyam Jameelah1; Che Haron Che Hassan1
1Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia.; Malaysia
2Advanced Materials Research Centre SIRIM Berhad, Lot 34, Jalan Hi-Tech 2/3, Kulim Hi-Tech Park, 09000 Kulim, Kedah.;Malaysia

Physical vapour deposition (PVD) of hard coatings such as titanium nitride (TiN) have been in industry since 1980s, and cathodic arc deposition was one of the techniques that responsible for the early commercial success of hard coatings on high speed steel tooling. The rapid progress in coating technology and materials is due to the acceptance of coating properties that could improve the wear resistance and thus prolongs the cutting tool life, i.e. a way to increase productivity and saving manufacturer billions of dollars worldwide. Nevertheless, coating performance is highly dependent on the mechanical and chemical properties of the coating been deposited. The application of hard coating has been increased in the past few decades, due to its attractive high hardness, low coefficient of friction, and high chemical stability. Ti-based hard coatings are popularly utilised in cutting tool applications. TiCN coating can has a wide range of compositions, from carbon rich to nitrogen rich, which lends itself eminently to the tailoring of composition and properties during deposition. Current TiCN coating that available in market could reach microhardness of 0.05 HV 3000 and 0.4 coefficient of friction, mechanical properties top listed among Ti-based coating. Properties of TiCN lies on its composition, and can be controlled by controlling the C-N ratio. Hence, an experimental study is carried out to varying the properties of TiCN through cathodic arc physical vapour deposition (CAPVD). The substrate materials are in-house developed carbide-based cutting tools. Ball on disc test and microhardness inspection show that hardness and coefficient of friction of Ti(C,N) were successfully optimized through CAPVD technique. Keywords: TiCN; cathodic arc physical vapour deposition (CAPVD); Tool coating

MPF 2219, Invited Lecture, Effects of Electrical cycling on morphology, nanomechanical and interfacial reliability of electrode materials in thin film lithium ion microbatteries

Zhu Jing;Zeng Kaiyang; Li Lu
Mechanical Engineering Dept, National Univ, of Singapore; Singapore

Recently much attention has been paid to the thin film lithium ion microbatteries, which have great potential for applications in portable electronic devices, electrical vehicles, MEMS and many others. Due to various interrelated processes occurring during electrical charge/discharge cycling, aging of thin film battery occurs and it has complex mechanisms. Apart from the changes of the bulk properties, such as changes in impedance and nanostructure, aging can also attribute to the mechanical failure due to the large volume change induced by new phase and residual stress. Therefore, the interfacial properties of electrode films is critical issues due to their significant roles in the structural integrity and reliability, especially for all-solid-state thin film batteries, this motivates us to study the effects of electrical cycling on the mechanical properties issues of thin films microbatteries. In this study, the morphology, volume, strain, phases, nanomechanical and interfacial reliability of the anode and cathode materials in thin film lithium ion microbattery are studied using various in-situ and ex-situ characterization techniques, including nanoindentation, focused-ion beam (FIB) imaging, biased scanning probe microscopy, and electrochemical strain microscopy (ESM). It is found that all of the properties are significantly affected by the electrical cycling, new phases are formed and disappeared with the lithiation and de-lithiation processes. These studies provide new perspectives for understanding the aging and electrochemical processes in thin film lithium ion batteries. In additional to the electrical performance of the battery, mechanical stability is also an important factor which contributes to the life and performance of the lithium ion batteries.

MPF 2224, Oral, Surface Mechanical Property Assessment of Ultra-Thin HfO2 Films

Fu Wei-En;
Center for Measurement Standards, Industrial Technology Research Institute; Taiwan

The mechanical performance of ultra-thin films deposited on a solid surface is critical to the integration compatibility of processes and the long-term reliability for the applications in electronic circuits. The criteria of reliability include wear resistance, thermal fatigue, and stress-driven failure that also depend on film adhesion significantly. The adhesion and variations in mechanical properties induced by thermal annealing of ultra-thin HfO2 films deposited on silicon wafers (HfO2/SiO2/Si) are not fully understood. In this work, the mechanical properties of an atomic layer deposited HfO2 (thickness ≈10 nm) on a silicon wafer were characterized by the diamond-coated tip of an atomic force microscope and compared with those of annealed samples. The results indicate that the annealing process leads to the formation of crystallized HfO2 phases for the atomic layer deposited HfO2. The HfSixOy complex formed at the interface between HfO2 and SiO2/Si, where the thermal diffusion of Hf, Si, and O atoms occurred. The annealing process increases the surface hardness of crystallized HfO2 film and therefore the resistance to nano-scratches. In addition, the annealing process significantly decreases the harmonic contact stiffness (or thereafter eliminate the stress at the interface) and increases the nano-hardness, as measured by vertically sensitive nano-indentation. Quality assessments on as-deposited and annealed HfO2 films can be thereafter used to estimate the mechanical properties and adhesion of ultra-thin HfO2 films on SiO2/Si substrates.

MPF 2227, Poster, Oxidation resistance and structural evolution of (TiVCrZrHf)N coatings

Du-Cheng Tsai;Tien-Jen Lin; Li-Yu Kuo; Hui-Hsun Yin; Rong-Hsin Huang; Fuh-Sheng Shieu1
Department of Materials Science and Engineering, National Chung Hsing University; Taiwan

The (TiVCrZrHf)N coatings were deposited on Si substrates by reactive magnetron sputtering technique from a TiVCrZrHf alloy target in Ar+N2 mixture atmosphere, and their oxidation behaviors as well as the oxidized structure were studied after static oxidation tests in air at different temperatures. The evolution of chemical composition, microstructure, hardness, and electrical resistivity of these coatings after annealing at different temperatures in air were systematically analyzed. As-deposited coating had a continue variation in structure, from amorphous to columns with FCC phase and it had no significant change in structure with increasing annealing temperature to 300 oC. Similarly, the hardness of (TiVCrZrHf)N coating was stable at a high value of 31.24 GPa up to an annealing temperature of 300 °C. However, a thin oxide overlayer was present at 400 °C and the oxide thickness increased at 500 oC. Therefore, the hardness of (TiVCrZrHf)N coating decreased to 11.85 GPa drastically. With annealing temperature increased above 600 oC, the coating was almost fully oxidized and become quite porous and loose. Accordingly, a very low hardness of only 2.3 GPa was obtained. The electrical resistivity of the coatings basically followed the same trend as the hardness. The electrical resistivity of as-deposited (TiVCrZrHf)N coating was about 144 μΩ-cm, followed by a apparent increase to 100 Ω-cm due to formation of oxide phases.

MPF 2244, Poster, Microstructure control in TiAlN/SiNx multilayers for improvement of mechanical and tribological properties

Chan Yu-Chen;
Department of Material Science and Engineering, National Tsing-Hua University; Taiwan

TiAlN/SiNx multilayers with various modulation periods are deposited on silicon wafers and tool steels by r.f. reactive magnetron sputtering. Microstructural characterizations by scanning electron microscope (SEM) and transmission electron microscope (TEM) reveal the dependence for the thickness of SiNx (lSiNx) on the crystallization, microstructure evolution and growth mechanisms in multilayers. A transition from epitaxial stabilization of crystallized SiNx to amorphized structure occurs when lSiNx increases beyond a critical value. Meanwhile, microstructures of films changes from fine columnar to defect-free feature. The hardness is significantly ameliorated in coherent multilayers with crystallized SiNx. With increasing lSiNx, the amorphous SiNx alters the super-lattice structure, leading to the appreciable decrease in hardness. Nevertheless, the fine-grained coatings exhibit enhanced H3/Er2 ratios and anti-scratched characteristics, implying its superior resistance to plastic deformation. In the ball-on-disc wear tests, the friction coefficients are effectively reduced in multilayers. Through the detailed analysis on the worn tracks by Fourier transform infrared spectroscopy (FTIR), the improved friction behaviors in multilayers can be attributed to the formation of self-lubricating layers, especially in multilayers with amorphous SiNx. Two anti-wear mechanisms on the basis of hardness enhancement and microstructure densification are proposed to elucidate the favorable durability of TiAlN/SiNx multilayers.

MPF 2247, Oral, Effect of N2/Ar Amount on Structural and Hardness Properties of TaAgN Thin Films Deposited by Cylindrical DC Magnetron Sputtering

Hantehzadeh Mohammad Reza;Foadi Farnaz; Darabi Elham; Ghoranneviss Mahmood
Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran; Iran

TaAgN thin films have been deposited on 304 stainless steel substrate by cylindrical DC magnetron sputtering under different N2/Ar reactive gas ratios. N2 amounts were chosen as 1.5%, 3%, 4.5%, 7.5%, 10.5%, 15%. The influence of N2/Ar ratio on the thin films morphology, structure and hardness was investigated by AFM, XRD and nanoindentation method, respectively. It has been observed that while N2 amount increases up to 7.5%, Ag islands grow more and more. Therefore, RMS surface roughness increases up to 7.5% and then decreases. XRD results show TaN, Ta2N and Ag crystalline structures. Hardness measurement revealed that all films hardness were much higher than those for bulk silver or tantalum and the highest hardness value was obtained for 1.5% N2 amount.

MPF 2258, Oral, Self-lubricating CrAlN/VN multilayer coatings: Mechanical and tribological properties

Qiu Yuexiu;
Central Iron and Steel Research Institute; China

Vanadium nitride (VN) is easily oxidized to form vanadium oxides and becomes lubricious under stress. As CrAlN is hard thus CrAlN/VN multilayer coatings render both hardness and lubricious properties which are attractive in high speed dry machining. This study investigated the effect of multi-layering on the coating’s mechanical and tribological properties. The CrAlN/VN multilayer coatings were deposited on AISI M2 high speed steel discs and Si wafer (100) substrates in an In-line magnetron sputtering system. A period contains one layer of CrAlN plus its adjacent one layer of VN. The period thickness (Λ) varies from 3 nm to 30 nm; the total number of the period varies from 30 to 300. X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electron probe micro-analyzer were employed to characterize the microstructures and chemistry. Nanoindentation was performed in mechanical evaluation. Ball-on-disc wear test at room temperature and 700 °C were used to study tribological behaviors. The period effects on the multilayer coatings were explored and the self-lubricating mechanism was revealed simultaneously.

MPF 2259, Poster, Effects of Target Power and Impulse Duration on the Characterization of Ti-MoS2 Coatings by High Power Impulse Magnetron Sputtering

Chang Chi-Lung;
Department of Materials Science and Engineering, MingDao University; Taiwan

In this work, titanium-containing molybdenum disulfide (MoST) thin films have been deposited using high power impulse magnetron sputtering (HiPIMS) in an argon atmosphere with titanium and molybdenum disulfide targets. The substrate rotated between two facing magnetron cathodes while different powers and impulse durations was applied to the molybdenum disulfide and titanium target. This paper presents a study of HiPIMS method by optical emission spectroscopy (OES), confronting between the plasma density. Hardness and friction coefficient were measured by a CSMTM nanohardness tester and ball-on-disk tribometer. The results show that a lower value of titanium target power corresponds to a lower hardness and friction coefficient value. On the other hand, no obviously difference by change impulse duration in the value of friction coefficient. However, a lower value of hardness is occurred in impulse duration of 50 μs at fixed target power.

MPF 2264, Poster, CrTaN hard coatings prepared by biased DC sputter deposition

CHEN Yung-I1;LIN Kun-Yi1; CHOU Chau-Chang2
1Institute of Materials Engineering, National Taiwan Ocean University; Taiwan
2Department of Mechanical and Mechatronic Engineering, National Taiwan Ocean University;Taiwan

CrTaN coating was proposed as an appropriate protective coating for glass molding dies, which was attributed to its high hardness of 16–27 GPa, and low surface roughness of 2–3 nm Ra both in the as-deposited and annealed states. The in-diffusion of oxygen during annealing in a glass molding environment was restricted by the formation of a Cr2O3 surface scale. In this study, we fabricated CrTaN coatings by reactive direct current magnetron co-sputtering onto silicon substrates with various biased voltages. The CrTaN coatings were annealed at 600 oC for 4 hours in a 50 ppm O2-N2 atmosphere, to assess the fabricated layers effectiveness as a protective coating for glass molding dies. The effects of biased voltage on the structure variation, mechanical properties, surface roughness, and oxygen diffusion depths were investigated.

MPF 2328, Poster, Existence patterns of Dy in β-NiAl from first-principles calculations

Zhang Tian;Guo Hongbo
Material Sicence and Engineering Dept., Beihang University; China

β-NiAl is a promising material for high temperature applications, especially as bond coat in thermal barrier coatings (TBCs), however the poor cyclic oxidation property limits the application of NiAl. Dy addition in NiAl can significantly improve the cyclic oxidation property of NiAl. However the mechanism of Dy is still unclear, even the existence pattern of Dy in NiAl is unspecified which obstructs the further investigation. Therefore in this paper, we focus on the existence pattern of Dy in NiAl. The impurity formation energy of Dy in stoichiometric NiAl, Ni-rich and Al-rich NiAl in substitution cases are studied from first-principles theory, the results show Dy can hardly substitute either Ni or Al atom in NiAl, which is consistent with experimental results. However, the calculated solid solution energies of Dy in Ni-rich, Al-rich and stoichiometric NiAl indicate Dy can be easily dissolved in Al vacancies in all three types of NiAl, thus a new existence pattern of Dy in NiAl are proposed, which provides foundation to further investigation about how Dy enhances the lifetime of the thermal barrial coatings.

MPF 2338, Oral, High dose ion irradiation effects on immiscible AlN/TiN nano-scaled multilayers

Milosavljevic Momir1;Obradovic Marko1; Grce Ana1; Perusko Davor1; Pjevic Dejan1; Kovac Janez2; Drazic Goran2
1VINCA Institute of Nuclear Sciences, Belgrade University, P.O.Box 522, 11001 Belgrade; Serbia and Montenegro
2Jozef Stefan Institute, Jamova 39, 1000 Ljubljana;Slovenia

Development of new radiation tolerant materials is of fundamental interest in various nuclear and non-nuclear applications. In a radiation environment energetic particles can induce various defects, damage and eventual degradation of the protective materials. High strength multilayers composed of immiscible constituents have emerged as interesting materials for these purposes, offering the advantages of: multiple interfaces that act as a sink for radiation induced defects; and mutual immiscibility which prevents interface mixing and diffusion that can cause degradation. It has been shown that nano-scaled multilayers of immiscible metals exhibit a remarkable radiation tolerance, as compared to single component systems. In this work we have studied ion radiation tolerance of immiscible AlN/TiN multilayered system. The AlN/TiN multilayers with an individual layer thickness of ~ 4-30 nm were deposited by reactive sputtering on (100) Si wafers. The structures consisted of 10-50 alternate AlN and TiN layers with a total thickness of around 250 nm. Argon and xenon ion energies were chosen to give a projected ion range around mid-depth of the deposited structures. Irradiation doses were from 1-8x1016 ions/cm2. Compositional and structural characterizations of the samples were performed by Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). It was found that the structures exhibit a good ion irradiation stability up to the medium doses applied. The highest dose induced a substantial grain growth in individual layers, which pronouncedly exceeded the original sub-layer thickness. This caused disordering of the multilayered structure, although the AlN and TiN grains remained chemically separated. The results are compared to other systems and discussed in the light of the existing ion beam mixing models. They can be interesting towards developing new radiation tolerant materials.

MPF 2341, Oral, Improved Al2O3 adhesion of electron beam physical vapor deposited Dy/Hf-doped β-NiAl coatings

Li Dongqing;Guo Hongbo; Gong Shengkai; Xu Huibin
School of Materials Science and Engineering, Beihang University; China

Dy/Hf-doped β-NiAl coatings and undoped β-NiAl coating were deposited onto NiAl substrates by electron beam physical vapor deposition (EB-PVD). The microstructures and spallation failure of the alumina scales grown on the doped and undoped coatings were comparatively investigated. Grain refinement was achieved by Dy/Hf doping in the NiAl coating, which is beneficial to selective oxidation. For the alumina scales formed on the Dy/Hf-doped coatings, a double-layer structure consisting of columnar grains and underlying equiaxed grains was observed. Oxide scale fracture induced by scratching on the coating surface took place within the scale (cohesive failure) for the Hf-doped and co-doped coatings instead of at the scale/coating interface (adhesive failure) for the undoped and Dy-doped coatings. It is possible that the scale/coating interfacial bonding was more effectively strengthened by Hf ion segregation than Dy, therefore only the equiaxed grain layer spalled during scratching.

MPF 2347, Oral, Microstructure, mechanical and tribological properties of non-reactive unbalanced dc magnetron sputtered NbB2 coatings

GRASSER Stephan1;POLCIK Peter2; MITTERER Christian1
1Department of Physical Metallurgy and Materials Testing, Montanuniversität, Franz-Josef-Strasse 18, 8700 Leoben; Austria
2PLANSEE Composite Materials GmbH, Siebenbürgerstrasse 23, 86963 Lechbruck am See;Germany

Niobium diboride (NbB2) is a ceramic compound crystallizing in the AlB2 structure, characterized by its strong covalent B-B bonding. Coatings based on AlB2 structures (e.g. TiB2) are well known for their high hardness, high melting point, good electric conductivity and excellent wear and corrosion resistance, especially against non-ferrous metals. The aim of this work is to establish a fundamental understanding of the microstructure as well as mechanical and tribological properties of NbB2-based hard coatings. NbB2 coatings were synthesized by non-reactive unbalanced dc magnetron sputtering from powder-metallurgically produced NbB2-targets with varying deposition temperatures (room temperature to 400°C) and bias voltages (floating to -70 V) on (100) silicon and high-speed steel substrates. Scanning electron microscopy showed a dense and very fine-grained coating morphology. Elastic recoil detection analysis revealed an under-stoichiometric composition, where B is lost due to scattering processes during the transport from target to substrate. Nevertheless, X-ray diffraction analysis confirmed formation of the hexagonal NbB2-phase with a preferred (101)-texture. The residual stress level as measured by cantilever beam method and hardness as studied by nanoindentation increased with increasing bias voltage up to -2.0 GPa and 44 GPa, respectively. The NbB2 coatings showed good adhesion and excellent tribological properties at elevated temperatures.

MPF 2350, Poster, TRIBOLOGICAL PROPERTIES OF TETRAHEDRAL AMORPHOUS CARBON LAYERS (ta-C) ON HSS- STEEL DRILLERS

Guenther Katja;Scholze Stefan; Nieher Maren; Weissmantel Steffen; Marquardt Franka
University of Applied Sciences Mittweida; Germany

Several micrometer thick super-hard tetrahedral amorphous carbon (ta-C) films have been prepared by pulsed laser deposition on polished High-Speed-Steel (HSS)- substrates and HSS- driller. The first aim was to investigate if and how various process parameters influence the tribological properties and the wear parameters of these ta-C layers on polished steel substrates. Furthermore the influences of an intermediate layer and of internal stress in these ta-C layers on the drill process were analyzed. It will be shown, that an intermediate layer of tungsten carbide optimizes the adhesion of the ta-C layers at the HSS- drillers. Built up edge and wear of the drillers is reduced by improving the mechanical properties of the ta-C layers by adjusting the ablation process and stress reduction process. Drill- tests with these ta-C coated HSS- drillers in an aluminium cast alloy (G-AlSi12(Cu)) with minimal quantity lubrication shows a high reduction of the demand for energy as well as a strong increase of the durability of these drillers up to 400 times and more. Hence it is possible to elevate the cost effectiveness in case of ta-C coated drillers.

MPF 2363, Oral, Plastic curving of thin films as incommensurate epitaxial layers on a flexible substrate

Dobovsek Igor1;
1Faculty of Mathematics and Physics, University of Ljubljana; Slovenia

In fabrication of high-precision devices, the growth of thin layers on a bulk substrate is one of the most important and demanding parts of the process. It has been observed experimentally that particular growth mode depends on a balance between the interfacial energies of the substrate and the epitaxial layer and the lattice mismatch between the layers. The stress associated with misfit strain between the thin film and a substrate is the main source and the driving force for formation of structural defects. Because thin films contain a large number of lattice defects, the natural response of the system under such circumstances is formation of strain relaxing mechanisms. In the unstrained or relaxed epitaxial film, the substrate and the film retain their bulk lattice constants and the film is not commensurate with the substrate. In this case, the misfit dislocations accommodate the mismatch locally where the average spacing between misfit dislocations depends on the misfit constant. From a perspective of modeling, we consider the problem of relaxation of coherency stresses by lattice dislocations, which can be represented as edge dislocations uniformly distributed along the interface, and can be associated with the concept of dislocation density according to the mathematical theory of continuously distributed dislocations. The orientations of dislocation lines are constrained within the plane of epitaxial layer, while the sum of Burgers vectors of corresponding misfit dislocations is decomposed into a set of arrays of discrete Burgers vectors of surface dislocations confined to the interface. In the process of mathematical development, we use the modified version of Frank-Bilby equation to accommodate the requirements of the modeling. Such system is then enforced to satisfy the boundary conditions according to the geometry of the epitaxial thin film and the substrate together with the corresponding compatibility conditions. The main task in mathematical formulation of the problem is calculation of the local distribution of misfit dislocation density at an interface of epitaxial layer. The dislocation density tensor is then connected with the deformation and rotation tensors and subsequently with the curvature of the system. It is shown that the curvature of the system stems from the plastic part of the distortion tensor, which under certain circumstances can be perceived as a misfit eigenstrain of the layer. The derived results are analyzed in detail for a particular choice of geometrical and material data of the thin film and the substrate.

MPF 2366, Poster, Mechanical properties of as-deposited c-BN-films and effects of post treatment by fluorine laser irradiation

Bertram René1;Weissmantel Steffen1; Reisse Guenter2
1University of Applied Sciences Mittweida; Germany
2Laserinstitut Mittelsachsen e.V.;Germany

We present the effects of pulsed laser irradiation of as-deposited c-BN-films using photons of 157 nm wavelength and 7.9 eV energy, respectively. The films were deposited by pulsed laser deposition (PLD) using a KrF excimer laser of 248 nm wavelength and up to 30 J/cm² laser fluence on the pyrolytic hexagonal boron nitride target with additional ion beam bombardment of the growing film using a mixture of nitrogen and argon ions produced in a r.f. ion source with 700 eV ion energy. These layers were analyzed in their mechanical properties depending either on the deposition parameters as well as on the layer structure. The irradiation of such coatings with a fluorine laser was found to influence the number and size of sp2-bonded hBN particulates and thus the further c-BN growth as well as the sp3/ sp2 ratio. So, alternating deposition of sub-layers and irradiation should directly affect the quality of the entire c-BN-films. Furthermore experiments were done to obtain the optimal value of thickness of the c-BN sublayer for reducing the intrinsic shear stress by fluorine laser irradiation. The influence of the irradiation with photons of 157 nm wavelength of h-BN/ c-BN layer systems on the shear stress, which limited the film thickness so far, was investigated and will be presented.

MPF 2373, Oral, Magnetron sputtered Ti/SiC multilayer thin films for tribological applications

Sharma Harish;Choudhary Nitin; Kaur Navjot; Kaur Gurpreet; Kaur Davinder
Functional Nanomaterials Research Lab, Department of Physics and Center of Nanotechnology, Indian Institute of Technology, Roorkee, India-247667; India

Ti/SiC multilayers with various constituent layer thicknesses were successfully deposited on silicon (100) substrate by magnetron sputtering using Ti and SiC targets. The structural properties were studied by X-ray diffractometer, field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). XRD results show that the SiC films were amorphous in nature while Ti films grow along (100) plane. Nanoindentation studies show significant improvement in the hardness (45 GPa) and elastic modulus (490 GPa) in the SiC/Ti multilayers when compared with Ti and SiC monolayers. The multilayer structure with excellent structural and mechanical properties could be a potential material for tribological industry applications.

MPF 2379, Poster, A study on microstructure and tribological behavior of arc-deposited Ti-N-O films on 304 stainless steel

Hsu Cheng-Hsun;Lee Chun-Ying; Lin Ya-Huei
Department of Materials Engineering, Tatung University; Taiwan

In this study, the cathodic arc evaporation technique, by using the titanium target and controlling the flow rate of N2/O2 reactive gases, was utilized to deposit different Ti-N-O films on AISI 304 stainless steel. The coating morphology and structure were analyzed using SEM, XRD and TEM, respectively. Moreover, the coating properties including adhesion, hardness, elastic modulus, and tribological behavior were all explored to evaluate the impact of N2/O2 ratio on the coating microstructure and properties. The results showed that the Ti-N-O films were a composite crystallize consisting of TiN and Anatase-TiO2. When the N2/O2 value was suitably controlled at 4, the composite film had a better adhesion strength (HF1), high hardness (22.8GPa), and high elastic modulus (217.5 GPa) in comparison to the films deposited by other N2/O2 values. As a result, AISI 304 stainless steel with the Ti-N-O coatings remarkably reduced the friction coefficient from 0.8 to 0.4. Keywords: AISI 304, Cathodic arc evaporation, Ti-N-O film, N2/O2 ratio, Friction coefficient

MPF 2391, Poster, Microstructure and properties of SiC-based cermet thin films

Meng Fanping;Ge Fangfang; Huang Feng
Ningbo Institute of Material Technology&Engineering, Chinese Academy of Sciences; China

The SiC/Ni and SiC/Al composite thin films were fabricated by magnetron co-sputtering, and were analyzed by the Four-point probe, Ultraviolet-infrared spectrophotometer, XRD, SEM, Raman spectrum, and nanoindentation. It was found that the adding of Ni and Al presented the obviously different effect on the properties of SiC film. The resistivity of SiC film reduced by four orders of magnitude with the 20 at.% Ni addition, while that of SiC film increased 15 times with the same amount of Al addition. Aluminum caused almost no influence on the transmissivity of the films. Nickel, however, dramatically changed the transmissivity in the visible range. The plasticity index and wear scar indicated that SiC films with Ni addition exhibited a better toughness. As nickel and aluminum may exist in different forms, the films were deposited with different intrinsic microstructures, which lead to different properties.

MPF 2410, Poster, Thermostability and Oxidation Characteristics of Ni-P-Based Coatings

CHANG CHI-KUN;LIU KUN-YUAN; HSIAO YOU-CHEN; WU FAN-BEAN
National United University; Taiwan

The ternary Ni-P-based alloy coatings, including Ni-Al-P, Ni-W-P, and Ni-Ru-P, were manufactured through magnetron sputtering using pure metal and Ni-P alloy dual-target arrangement. The addition of Al, W, and Ru, metal elements was controlled at 10-12 at.% for comparison. All the ternary coatings showed a Ni(111) nanocrystalline microstructure with P and functional elements incorporated at a fabrication process temperature of 200ºC. Under a heat treatment at 500ºC in vacuum, the Ni-W-P remained a nanocrystalline feature. On the other hand, significant Ni recrystallization and NixPy intermetallic compounds precipitation were observed in Ni-Al-P and Ni-Ru-P coatings after annealing at 500ºC. The Ni-W-P exhibited a superior thermostability amongst Ni-P-based coatings in vacuum annealing condition. The elemental depth profiles of the Ni-P-based coatings under air annealing at 475ºC for 30 min were analyzed by Auger Electron Spectrometry, AES. The Ni-W-P and Ni-Ru-P coatings exhibited an oxidation depth around 150 nm, while a limited oxidation penetration of less than 75 nm was revealed for the Ni-Al-P film. The nickel oxide formed and dominated the top layer both of Ni-W-P and Ni-Ru-P coatings. For the Ni-Al-P film, the out-diffusion of Al formed a solid Al2O3 layer, which in turn suppressed the further oxidation of Ni and Al. A better oxidation resistance and thermostability for the Ni-Al-P film in air annealing was revealed.

MPF 2418, Poster, Impact of Mechanical Stress on Hole Mobility in PMOSFET with a SiGe Thin Film

Cheng S.-Y.;Chang S. T.
Dept. of E. E., National Chung Hsing University; Taiwan

Hole mobility in high Ge-content SiGe inversion layer is investigated by a split C-V measurement and theoretical k.p calculation. The two dimensional hole gas subband structure is calculated by solving the k.p Schrodinger equation self-consistently with the electrostatic potential. Four important scattering mechanisms are included, namely optical phonon scattering, acoustic phonon scattering, alloy scattering, and surface roughness scattering. The model parameters are calibrated by matching the measured low-field mobility of SiGe thin film on Si substrate. The calibrated model reproduces experimental data of mobility in PMOSFET with a SiGe thin film on different orientation substrates. The impact of mechanical stress was also explore on the SiGe PMOSFET. With mechanical stress applied to the channel in SiGe PMOSFET, the corresponding piezoresistance coefficients of SiGe were obtained.

MPF 2421, Poster, Impact of Strain and Carbon Content on Subband Structure and Effective Mass of Silicon-Carbon Alloy Inversion Layer in PMOSFET

Fan J.-W.2;Chang S. T.1; Lin C.-Y.2
1Dept. of E. E., National Chung Hsing University; Taiwan
2Dept. of Phys., National Chung Hsing University;Taiwan

Subband structure and effective mass of silicon-carbon alloy inversion layer in PMOSFET are studied theoretically in this work. The strain condition considered in calculations are intrinsic strain resulting from growing the silicon-carbon alloys on the (001) Si substrate and mechanical uniaxial stress. The quantum confinement effect resulting from the vertical effective electric field is incorporated into the k.p calculation. Various effective masses such as quantization effective mass, density of states effective mass, conductivity effective mass, as well as subband structure of silicon-carbon alloy inversion layer for PMOSFET under substrate strain and various effective electric field strengths are all investigated.

MPF 2424, Poster, Mechanical and Tribological Properties of Tungsten-doped Hydrogenated Diamond-like Carbon Films

Yang Lamaocao1;Huo Lixia2; Zhou Hui3; Zhen Jun4
1Science and Technology on Surface Engineering Lab, Lanzhou Institute of Physics; China
2Science and Technology on Surface Engineering Lab, Lanzhou Institute of Physics;China
3Science and Technology on Surface Engineering Lab, Lanzhou Institute of Physics;China
4Science and Technology on Surface Engineering Lab, Lanzhou Institute of Physics;China

Tungsten-doped hydrogenated diamond-like carbon films were deposited on Si and 440C stainless steel substrates by PECVD assisted unbalanced magnetron sputtering technology. Microstructure of these films were analyzed by SEM、Raman spectroscopy and IR spectroscopy. Hardness and Young’s modulus were tested on CSM Nano-hardness tester. Tribological properties of the films with and without lubricants were studied on ball-on-disk tester in different atmosphere (ambient and vacuum). The results show that the films have typical diamond-like structure and hydrogen contents are relatively high. The films also show excellent mechanical properties. The friction of the films with lubricants in vacuum is lower than the dry condition. The tribological behavior at ambient atmosphere shows almost the same properties with and without lubricants. All of the results indicated the films have excellent tribological properties, in vacuum or ambient, with or without lubricants.

MPF 2427, Poster, Hygrothermal Effects on Polyimide Bonded Molybdenum Disulfide Dry Film Lubricant

Huo Lixia1;Yang Lamaocao2; Zhou Hui3
1Science and Technology on Surface Engineering Laboratory, Lanzhou Institute of Physics; China
2Science and Technology on Surface Engineering Laboratory, Lanzhou Institute of Physics;China
3Science and Technology on Surface Engineering Laboratory, Lanzhou Institute of Physics;China

In this study, polyimide bonded molybdenum disulfide dry film lubricant was deposited on titanium alloy. This film was exposed to a highly aggressive humidity durability test, test conditions were 70℃ ,99% relative humidity for 650 hours. The effects of hygrothermal on the chemical structure of the binder were studied by FTIR. And the changes of surface chemical components were investigated by XPS. The friction and wear behaviors of the dry film lubricants after hygrothermal test were studied by ball-on-disc tribometer. Pull off adhesive tester was used to evaluate the adhesion strength of the dry film lubricant. Results indicated that hygrothermal may cause polyimide resin of the film surface hydrolysing and molybdenum disulfide oxidating. The wear life of the film after hygrothermal test decreased and the friction coefficient curve showed variation significantly. Adhesion of the film also decreased to some extent.

MPF 2442, Poster, The influence of temperature on the transformation of crystal structure of corrosion production films formed on L360NCS

ZHENG Shuqi;LIU Liwei; ZHOU Chengshuang; CHEN Changfeng; CHEN Liqiang
Department of Materials Science and Engineering, China University of Petroleum Beijing; China

The crystal structures of corrosion production films of L360NCS formed in the environment with 1MPa H2S partial pressure were investigated in this paper. From the hydrogen permeation curves, it was found that the times to form the steady corrosion production films on metal surface were different with the increasing of temperatures. It needed 270 hours to form the steady films on the surface of L360NC at 25oC however it needed only 10 hours at 80oC. The crystal structure of corrosion production films is cubic FeS along with the nucleation of some needle-like crystals on cubic FeS. At 35oC, more needle-like crystals are nucleate and grow. When it is 50oC, the surface of metal is covered by needle-like FeS crystal. However, when the temperature increases 80oC, the structure are different from the former crystal structures formed at low temperatures. The bottom and outer layers of the corrosion production films are all composed of compact crystal structures, which are beneficial to the corrosion resistance of L360NCS in acid environment.

MPF 2443, Poster, Transport Properities of P-Channel Poly-Si TFTs under Mechanical Bending

Lin W.-K.;Chang S. T.
Dept. of E. E., National Chung Hsing University; Taiwan

The technologies of stress-enhanced mobility have been used extensively in the silicon industry. The mechanical stress effects on complementary metal-oxide semiconductor (CMOS) and optical devices have been reported. However, only few studies about the stress effects on poly-Si TFTs were reported in the past, especially in p-channel poly-Si TFTs. In this work, the electrical performance of p-channel poly-Si TFTs is investigated under different stress conditions. The current change of p-channel polycrystalline silicon thin-film transistors is analyzed experimentally and theoretically under different stress conditions. Under the uniaxial stress parallel to the channel, the saturation drain current degradation is observed. An enhanced current gain can be found when the uniaxial stress is applied perpendicular to the channel. Theoretical mobility calculations are qualitatively in agreement with experimental results.

MPF 2457, Oral, Nanoharndness of LY12 Subsurface Thin Film Structure Induced by Burnishing Processing

Luo Hongyun;Han Zhiyuan; Zou Jian; Zhong Qunpeng
School of Materials Science and Engineering, Beihang University; China

The burnishing is particularly attractive due to its ability to generate a work hardened near surface layer (“thin and hardness film”) with deep compressive residual stresses, and meanwhile retain a relatively smooth surface finish. Nanosubsurface was obtained by the burnishing processing at room temperature. The basic relationship between nanohardness and microstructure was investigated in the present work. The crystalline structure was investigated by using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nanocrystalline grain (NG) was found in the “thin and hardness film”(with a thickness of about 20μm from the top of the burnished surface). The XRD results also showed that the dislocation density and average grain size (37~60nm) various with the nominal burnishing depth. The nanohardness were investigated by using the nanoindentation technique. The nanohardness of the burnished NG subsurface film achieved the highest value about H=2.9 Gpa, when the nominal burnishing depth ap=15μm.The nanohardness increases with the increase of the amount of grain boundary and dislocation density which are two main factors which affect the nanohardness of burnished NG film.

MPF 2492, Poster, Mechanical properties measurement of ITO-coated PET substrate

Hsu Jiong-Shiun1;Chao Lu-Ping2; Chung Lun-Wei2
1Department of Power Mechanical Engineering, National Formosa University; Taiwan
2Department of Mechanical and Computer-Aided Engineering, Feng Chia University;Taiwan

Since the polyethylene terephthalate (PET) sheet has advantages including flexible, high resistance to impact, and excellent optical properties, they have been more and more used in flexible electronics, solar cell, etc. In addition, PET is not conductive and a rather thin layer of indium tin oxide (ITO) is usually deposited on it as the electrode. Because the PET is soft but the ITO film is stiff, the significant residual stress may be induced to endanger the reliability of the products. Therefore, characterization of mechanical properties of ITO-coated PET substrate is growingly important. In this paper, the bulge test combined with phase-shifting shadow moiré was established to measure the residual stress and bi-axial modulus of ITO-coated PET substrate. The measurement result was substituted into the finite element model to verify the precision of the measurement result. Besides, it was found that the residual stress and bi-axial modulus decreases and increases, respectively, as the thickness of PET substrate become thin.

MPF 2503, Poster, Effects of hydrogen on the structure and mechanical behavior of diamond-like carbon films synthesized by RF plasma enhanced chemical vapor deposition

Hsu Jiong-Shiun1;Tzeng Shinn-Shyong2; Chih Ya-Ko3; Chang Ching-Yuan1
1Department of Power Mechanical Engineering, National Formosa University; Taiwan
2Department of Materials Engineering, Tatung University;Taiwan
3Center for Measurement Standards, Industrial Technology Research Institute (ITRI);Taiwan

Diamond-like carbon (DLC) films were synthesized by RF plasma enhanced chemical vapor deposition using acetylene as the carbon source and the effects of hydrogen in the reaction atmosphere and hydrogen plasma post-treatment on the structure and mechanical behavior of DLC films were investigated. The surface roughness was characterized by AFM and film thickness was measured by α-step analysis. Both roughness and thickness decrease with increasing concentration of hydrogen. The hardness of DLC films measured by nanoindentation increased with the increase of hydrogen/acetylene ratio. The curvature of DLC films were measured by Fizeau interferometer and the residual stress was calculated using the Stoney’s equation. The residual stress was found to increase with increasing of hydrogen/acetylene ratio. The wear behavior of DLC films with different hydrogen/acetylene ratios was studied and a lower wear depth was found for the DLC film with a hydrogen concentration of 0.5. For the hydrogen plasma post treatment, surface roughness decreased with increasing post-treatment time and a lower wear depth was also measured.

MPF 2509, Oral, Comparative Study between Palladium-Phosphorus and Pure Palladium Thin Film in the Metallurgical Reaction between Tin-Silver-Copper Alloy and Gold/Palladium/Nickel Multi-Layer

Ho C. E.;Lin Y. C.; Wang C. C.; Wu W. H.
Department of Chemical Engineering & Materials Science, Yuan Ze University; Taiwan

Deposition of Pd (or Pd-P) over the Ni(P) metallization pads, such as Pd/Ni(P) or Au/Pd/Ni(P), has received a great deal of attention in microelectronic industry due to its acceptable bondability with Au wires and low material cost in comparison with the traditional Au/Ni(P) configuration. The Pd film deposited via a formic-acid-based solution is high purity and possesses a polycrystalline structure. On the other hand, an amorphous structure dissolved with a specific amount of phosphorus (P), i.e., Pd(2-5% P), is obtained as an alkaline hypophosphite-based solution is employed. This study aimed at evaluating the solderability of a Au/Pd/Ni(P) tri-layer with/without incorporation of P into the Pd film. Experimentally, the interfacial microstructures between 96.5 wt.% Sn-3 wt.% Ag-0.5 wt.% Cu alloy and Au/Pd/Ni(P) films after soldering and subsequently reacting at 180 °C were systematically investigated through a scanning electron microscope (SEM), electron probe microanalyzer (EPMA), and field–emission transmission electron microscope (FE–TEM). Additionally, mechanical response of the bonding interfaces of the two various film structures (i.e., pure Pd and Pd-P) was also carefully investigated through a high-speed-ball shear (HSBS) test.

MPF 2563, Oral, Investigation of texture characteristics of deformed layers in burnished 2024 aluminum alloy subsurface by EBSD

Zou Jian;Luo Hongyun; Han Zhiyuan; Lv Jin-long
Department of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Xueyuan Road 37; China

Abstract The texture of different burnished subsurface layers of 2024 aluminum alloy was characterized by EBSD and the texture gradient of them was discussed in this study. The burnished subsurface was divided into four layers, surface layer, near surface layer, near bulk layer and bulk layer. It was found that the texture of the bulk layer was the typical FCC rolling β-fiber texture(running through the orientation space from the copper orientation {112}<111> over the S orientation {123}<634> to the brass orientation {011}<112>) which was the original texture; in the near bulk layer, the β-fiber texture (specially brass component) was weaker compared with the original β-fiber texture in the bulk layer; then the α-fiber texture (<110>//radial direction) began to develop, and both α-fiber and β-fiber texture were present in the near bulk layer; while in the near surface layer the β-fiber texture (specially brass component and S component) was strengthen; the shear strain was so intensity in the surface layer that almost all the β-fibe texture rotated around the X axis of the cyclinder specimen to shear texture including the {023}<233> orientation and r-cube {014}<100> orientation. It was found that the texture evolved with the gradient of burnishing force at the subsurface. The EBSD studies also indicated the nano/ultrafine grain inside the near surface layer.

MPF 2575, Poster, Mechanical and Tribological Properties of CrN/WN Multilayer Coatings Deposited by High Power Impulse Magnetron Sputtering

Wu Chia-Hao1;Wu Bo-Yi1; Chen Wei-Chih2; Wu Wan-Yu1; Chang Chi-Lung12; Wang Da-Yung12
1Department of Materials Science and Engineering, MingDao University; Taiwan
2Surface Engineering Research Center, MingDao University;Taiwan

Chromium nitride/tungsten nitride (CrN/WN) multilayer coatings were deposited on tungsten carbide substrates by high power impulse magnetron sputtering technique. The CrN/WN multilayer coating was deposited using Cr and W target materials by two facing magnetron cathodes while different powers and impulse durations were applied. The morphology and microstructure of the films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and electron probe micro-analyses (EPMA). The mechanical and tribological properties were evaluated using a nanoindentor and a conventional ball-on-disk tribometer, respectively. The multilayer CrN/WN coatings exhibited a low surface roughness between 3 and 16 of Ra value, and a highest hardness of approximately 22 GPa. Wear test results show that the multilayer CrN/WN film has a variable coefficient of friction with values between 0.4 and 09, which strongly depends on the deposition conditions of HIPIMS.

MPF 2580, Oral, Mechanical stability of titanium and plasma polymer nanoclusters in nanocomposite coatings

PALESCH Erik1;MAREK Ales2; SOLAR Pavel3; KYLIAN Ondrej3; VYSKOCIL Jiri2; BIEDERMAN Hynek3; CECH Vladimir1
1Institute of Materials Chemistry, Brno University of Technology, Brno; Czech Republic
2HVM Plasma, spol. s r.o., Prague;Czech Republic
3Faculty of Mathematics and Physics, Charles University, Prague;Czech Republic

Fabrication of surfaces with controllable topography in nanoscale is demanded by catalytic, photovoltaic, and biocompatible applications. One way how to control the surface topography very effectively is a deposition of nanoparticles of tunable size that is followed by deposition of overcoating film (matrix) forming nanocomposite coating. This two-step process enables to control the surface topography and surface chemistry of nanocomposite coating independently. In this study, titanium and plasma polymer nanoclusters were deposited by a gas aggregation cluster source. The source consists of a planar magnetron mounted within a water cooled aggregation chamber. The outlet of the chamber was equipped with a nozzle of variable diameter. Another planar magnetron was used to overcoat the layer of nanoclusters by thin film. Titanium nanoclusters were deposited using Ti target at a power of 250 W and argon gas operated at a pressure of 200 Pa, while plasma polymer clusters were deposited using carbon target and a gas mixture of argon (10.7 sccm) and hexane (0.8 sccm) operated at 160 Pa and 120 W. The nanoclusters were deposited on planar glass coated by Ti film of 80 nm thickness and polished TiAlV substrates positioned 45 mm away from the nozzle of cluster source. Typical size of clusters was 20-70 nm for titanium and 80-170 nm for plasma polymer. Mechanical stability of deposited nanoclusters and those overcoated by titanium film of thickness up to 0.2 micron was analyzed by a 2D TriboScope (Hysitron Inc.) attached to an NTegra Prima Scanning Probe Microscope (NT-MDT). A Berkovich diamond indenter with a radius of curvature of 110 nm was used to make scratches on nanocluster layers or nanocomposite coatings under loading ranging from 1 microN to 10 mN. AFM images of scratches enabled us to evaluate the minimum loading needed to move the nanoclusters. The overcoated clusters were deformed at invariable position or removed from scanning area if 2D raster scanning at selected loading was employed. The nanoindentation measurements were carried out to optimize the thickness of overcoating film that is sufficient to stabilize position of nanoclusters in nanocomposite coating.

MPF 2608, Poster, Investigations on thermal stability of (Ti, Ta)N coatings

Lin Huey-Jiuan;
Department of Materials Science and Engineering, National United University; Taiwan

Glass molding, with lower cost and higher process rate as compared to the traditional glass forming process, is widely applied for mass glass product. During process, the molding dies need to endure a thermal cycle of the temperature ranging from room temperature to around 500oC under high pressing loads. Moreover, Glass behaves a high activity in the high temperature environment, and is easily to react with the mold materials and produces the sticking phenomenon. The accuracy and mechanical properties of mold are also depredated with thermal shock during cycling of molding process. Therefore, one of key techniques of glass molding process is to improve the lift time of mold, to reduce production costs, and to provide high reliability glass components. In this study, (Ti, Ta)N coatings were deposited on tool steel by RF magnetron sputtering method. The experimental parameters were designed by Taguchi method, including power, bias, thickness and substrate temperature. The surface morphology and roughness of films were characterized by scanning electronic microscopy and atomic force microscopy, respectively. The grazing incident angle X-ray diffractometer and X-ray photoelectron spectroscopy were used to identify crystal structure and surface chemical bonding of coatings. The effects of experimental parameters on thermal stability of coatings were investigated by thermal cycling and molding tests. It was found that (Ti, Ta)N/TiN/Ti multilayer coatings could effectively improve the high thermal stability of tool steel. The coatings did not spall off after 1000 times thermal cycling at 500oC. and not sticking on the substrate after the molding test.

MPF 2612, Oral, Determination of Young’s modulus and Poisson ratio of thin films by X-Ray Methods

Fu Wei-En;Chang Yong-Qing; He Bo-Ching
Center for Measurement Standards, Industrial Technology Research Institute; Taiwan

Accurate determination of Poisson's ratio and the Young's modulus is critical when characterize the mechanical properties of ultra-thin films. In this work, a method to simultaneously measure the Yong’s modulus and Poisson ratio of ultra-thin films by X-Ray techniques combined with four-point bending instrument is presented. The four-point bending was carried out to purposely induce stresses on the films and a curvature to the film/wafer system. The induced stresses were measured by the grazing incidence X-ray diffraction. Poisson's ratio was, then, evaluated from analysis of the X-ray diffraction data to obtain a strain- cos2α•sin2ψ plot. Meantime, the curvature of the film/wafer system was measured by the X-ray rocking curve. According to the Stoney’s equation, the induced stresses in films can also be obtained through the analysis of the curvatures. As a result, the Young's modulus of the films was evaluated from that plot as well as from the induced stress, which was determined by induced film/wafer curvature. The method was applied to determine ultra-thin HfO2 films (~10 nm). The estimated Poisson's ratio and the Young's modulus of the films were 0.16 ± 0.02 and 165 ± 20 GPa, respectively, which are comparable to those reported in the literature.

MPF 2641, Oral, Effects of Bond Coat Modification on the Thermal Cyclic Oxidation Behavior of Plasma Sprayed MCrAlY/YSZ Thermal Barrier Coatings

Tsai Pi-Chuen1;Tsai Pi-Chuen2; Yang Chung-Wei; Huang Her-Yueh
1Department of Materials Science and Engineering, National Formosa University; Taiwan
2Graduate Institute of Materials Science and Green Energy Engineering, National Formosa University;Taiwan

In this study, the Hastelloy-X superalloy coupons were firstly overlaid by a NiCrAlY bond coating utilizing air plasma spray (APS) process. Then some selected sprayed specimens were modified by pre-oxidation at electrical furnace for 4 hours. In addition, a platinum thin film approx. 7 μm thick was then introduced to selected samples of NiCrAlY coatings by a magnetron sputtering deposition process. Then some of the APS sprayed superalloy coupons and the samples with Pt coating were pack aluminized for 4 hours at 850oC to produce NiAl and PtAl2 aluminide phases on their surfaces, respectively. After that an yttria stabilized zirconia (YSZ) top coat were sprayed on the top of all samples by air plasma spraying (APS) process. All specimens were then subjected to a thermal cycling test at 1100 ℃. Thermal cycling tests were 1 hour at 1100 ℃ followed by 10 min of forced-air cooling to ambient temperature outside the furnace. The weights of all the specimens were measured every cycle or every other cycle. Then effects of pre-oxidation, aluminizing and Pt-aluminizing relative to cyclical oxidation performance and microstructure evolutions of the coatings were evaluated. Scanning electron microscopy (SEM), X-ray diffractometry (XRD) and electron probe microanalyzer (EPMA) were used to identify crystalline phases and microstructures of each coating. Cyclic test results showed that the life times of the plasma-sprayed MCrAlY/YSZ thermal barrier coatings were enhanced about 60% by Pt-aluminizing process while pre-oxidation and aluminizing have detrimentory effects. The oxidation behavior and microstructure evolution of the bond coat and the failure of the top coat were evaluated and discussed in this study. (Key word: Thermal barrier coatings; Pt aluminizing; Oxidation resistance; Plasma spraying; Bond coat modification.)

MPF 2666, Oral, Zr-based TFMG for Fatigue-property Improvements of 7075-T6 Aluminum Alloy

Chang Yue Zon1;Tsai Pei Hua2; Li Jia Bin1; Jang Jason Shian Ching3; Jian Sheng Rui2; Liu Kun Min1; Wong Pei Chun1
1Department of Mechanical Engineering, National Central University; Taiwan
2Department of Materials Science and Engineering, I-Shou University;Taiwan
3Institute of Materials Science and Engineering, National Central University;Taiwan

The superior mechanical properties of thin film metallic glass (TFMG), such as high strength and good bending ductility, coupled with good adhesion between the film and the substrate as well as the reduced surface roughness, and high compressive residual stress of the metallic film yield the fatigue property improvement of aluminum alloy. We proposed with the Zr-based and Zr-Cu based TFMG as promising coating for aluminum alloy fatigue property enhancement. According to the four-point-bending fatigue results, 7075-T6 aluminum alloy with a Zr-based TFMG improved its fatigue life cycle 22 times at a stress level of 250 MPa than the bare one. And the other fatigue life cycle of Zr-Cu based TFMG is further improved 44 times which ups to 107 cycles. The improvements of TFMG coating samples in fatigue limit were 235 MPa (56.7 % increase) and 250 MPa (66.7 % increase) for Zr-based and Zr-Cu based TFMG, respectively, and 150 MPa for uncoated sample. Thus demonstrating MGTF as promising coating materials for improving the fatigue properties of material and further applied to aerospace, automobile industry and bicycle manufacturing etc. Key words: MGTF, Vacuum Sputtering, Adhesion, Four-Point-Bending, Fatigue Property

MPF 2670, Poster, Deformation behaviors of AlN thin films under depth-sensing indentation

Sheng-Rui Jian;
Department of Materials Science and Engineering, I-Shou University; Taiwan

The nanomechanical responses to the contact-induced deformation in AlN thin films deposited on Si(111) substrates by a helicon sputtering system were studied by combining the nanoindentation and cross-sectional transmission electron microscopy (XTEM) techniques. In addition, the crystalline structure and surface roughness of AlN thin films are characterized by using X-ray diffraction (XRD) and atomic force microscopy (AFM). Samples for XTEM examinations were prepared by using focused ion beam (FIB) milling to reveal the cross-section of the indented area. From XTEM observations, there are evidences of radial crack along the columnar grain boundary underneath the center of Berkovich indentation and, shear steps in the interface. XTEM results also indicate clear median crack and slip bands on {111} planes and, an indentation-induced phase transformation zone within the silicon substrate, wherein metastable phases of Si-III and Si-XII, as well as the amorphous phases are observed. Furthermore, no delamination was observed in the AlN thin film/substrate interface.

MPF 2695, Oral, PVD gradient coatings on sialon tool ceramics

Dobrzanski Leszek;Staszuk Marcin
Institute of Engineering Materials and Biomaterials, Silesian University of Technology; Poland

The paper presents the research involving the PVD coatings obtained on an unconventional substrate such as sialon ceramics. The main objective of the work is to investigate the structure and properties of multilayer gradient coatings produced in PVD processes on sialon ceramics, and to define the influence of the properties of the coatings such as microhardness, adhesion, thickness and size of grains on the applicable properties of cutting edges covered by such coatings. The investigation studies pertaining to the following have been carried out: the structures of the substrates and coatings with the application of transmission electron microscopy; the structure and topography of coating surfaces with the use of electron scanning microscopy; chemical composition of the coatings using the GDOES and EDS methods; phase composition of the coatings using X-ray diffraction and grazing incident X-ray diffraction technique (GIXRD); grain size of the investigated coatings using Scherrer’s method; properties of the coatings including thickness, microhardness, adhesion and roughness; properties of the operating coatings in cutting trials. Good adhesion of the coatings to the substrate from sialon ceramics (Lc=53 - 112N) has been demonstrated by the coatings containing the AlN phase of the hexagonal lattice having the same type of atomic (covalence) bond in the coating as in the ceramic substrate. The damage mechanism of the investigated coatings depends to a high degree on their adhesion to the substrate.

MPF 2711, Poster, Integrated atomics simulation of indentation and tension process of double crystal nano-thin film

Chen jiaxuan;
Integrated atomics simulation of indentation and tension process of double crystal nano-thin film; China

In the recent years, the deformation of single-crystal nanowire, nanorod and nano-thin film was frequently investigated to examine the processes governing deformation on the nanometer length scale. However, the deformation process and mechanical properties of nanowire, nanorod and nano-thin film are sensitive significantly to the surface defects and stress states of them. Integrated Molecular dynamics simulation model of nano indentation and tension process with one specimen are established and performed to analyze the nanoindentation mechanism and mechanical properties of double crystal copper thin film. Firstly, a triangle pyramid shaped indenter is utilized to enter the double crystal copper thin film at different indentation depths by molecular dynamics simulation. After that, the triangle pyramid tip begin to move along the opposite direction,and withdraw from the double crystal copper thin film to finish the indentation process. In the end, the tensile loads are applied to the two sides of the nano-thin film after the indentation process to achieve tensile simulation. Through the visualization technique of atoms slip vector and bond pair analysis, the structure of molecular-cluster and defects in copper nano-thin film such as dislocations and stacking atoms are identified in the indentation process and in tensile process. The effects of grain boundaries between the two layers of thin film on evolution of dislocation are investigated in the indentation process. It is found that Dislocations nucleate firstly near the indenter when indenter enters the copper nano-thin film. The interfacial misfit dislocation between the two layers of thin film impeding dislocations downward when those dislocations approach to the grain boundary, which lead to changes the direction of dislocation line motion. When the indenter is close to the interface of the two layers of nano-thin film, dislocation nucleate from the interface of the layers of thin film again. After the indentation process, the states of the residual stress and the number of defects remaining in the double crystal copper nano-thin film are different with different indention depths. It is also found that the yield stress of the double crystal copper nano-thin film is sensitive to the states of the residual stress and the number of defects remaining in it.

MPF 2714, Oral, Microstructural Analysis of PVD-coated Zn-Mg thin films

La Jounghyun1;Kim Bom-Sok1; Lee Sang-Yul1; Kim Tae-Yeob2; Hong Seok-Jun2; Lee Sang-Yong3
1Center for Surface Technology and Applications, Department of Materials Engineering, Korea Aerospace University; Korea (south)
2Dry Coating Research Project Team, POSCO Technical Research Laboratories;Korea (south)
3Faculty of Advanced Materials Engineering, AnDong National University;Korea (south)

ABSTRACT In this work, much effort was made to develop the proper processing conditions to synthesize dense Zn-Mg alloy thin films using unbalanced magnetron sputtering process. The Zn-Mg alloy thin films synthesized under these conditions with various Mg contents were investigated by Field emission-scanning electron microscope (FESEM), glow discharge optical emission spectroscopy (GDOES), and X-Ray diffraction (XRD). Characteristics such as adhesion strength, and corrosion resistance of the Zn-Mg alloy thin films were investigated as well. As the Mg content in the thin films increased, the density of synthesized Zn-Mg alloy thin films and the amount of inter-metallic compound of Zn11Mg2 increased. In case of Zn-Mg thin films synthesized with high Mg containing target, very dense and amorphous thin film could be obtained. The preliminary results indicated that using unbalanced magnetron sputtering process, dense Zn-Mg alloy thin films could be synthesized under very limited and controlled processing conditions. As the Mg content in the thin films and the power density of target increased, the density of Zn-Mg alloy thin films and the amount of inter-metallic compound of Zn11Mg2 increased. Also observed was the increase in hardness of Zn-Mg alloy thin films proportional to Mg content in the thin films. Detailed investigation on the microstructural characteristics of the Zn-Mg thin films depending upon various processing variables is being made and corresponding properties of the thin films will be illuminated. KEYWORDS Unbalanced magnetron sputtering, Zn-Mg thin films, Microstructure, Adhesion, Corrosion resistant Acknowledgement This study is financially supported by the Smart Coating Steel Development Center, WPM (World Premier Materials) Program of the Korea Ministry of Knowledge Economy.

MPF 2720, Oral, A loose column-structured Al layer as lift-off material for microtensile testing of fracture toughness of thin films

Zhang Xiaomin1;Zhang Sam2
1School of Materials and Mineral Resources, Xi’an University of Architecture and Technology; China
2School of Mechanical and Aerospace Engineering, Nanyang Technological University;Singapore

The geometry size of the thickness of a thin film brings extremely difficulties in applying standard testing methods of fracture toughness for bulk materials to the thin film. It has been proven that clamping a freestanding thin film and then applying a force of micro-Newton or even nano-Newton to the film for testing is an awful task. Lately, a new microtensile testing method for the fracture toughness of thin films has been proposed by the authors, in which the above difficulties were avoided through microtension of a substrate. In the method, the usual photolithography technique is used to form freestanding film strips on silicon substrate for the micortensile testing. As etching method is only available for few certain kind of materials, lift-off process is the preferred way to form film strips: making a desired pattern with a layer of photoresist on substrate surface at first, and then resolving the photoresist after a film has been deposited on open substrate surface. Unfortunately, many films concerned are deposited under raised temperature higher than that the polymeric photoresist can endure. In this paper, a novel material is firstly proposed to serve as the lift-off layer. That is the loose column-structured aluminum as shown in Fig.1. The new kind of aluminum structure has about 20% void space between column crystal particles, which enable the AZ9260 developer goes from the top to the bottom of the Al layer instantly, resulting a much greater etching rate of Al layer. Experimental result shows that only less than one minute is required to etching away 5 microns layer of Al. As aluminum can survive 400 to 500℃,it extends the usage of the proposed fracture toughness testing method of thin films to a large variety of vacuum deposited films. A testing of 535nm SiO film is shown as a case study, giving the fracture toughness of 2.15 MPam1/2 .