Finite element analysis of the indentation stress characteristics of the thin film/substrate systems by flat cylindrical indenters

The indentation stress characteristics of thin film/substrate systems by the flat cylindrical indenters have been simulated by means of the finite element method (FEM). The emphasis was put on the stress distribution ahead of the indenters. The influences of the friction coefficient between the indenter and the thin film, the thickness and hardening modulus of the thin film have been considered. It is found that the stress distribution was not affected by the friction coefficient. But the influence of the thickness and hardening modulus of the thin film on the stress distribution was obvious. At small indentation depth, the plastic deformation occurs at the edge of the indenter only, and the zone will propagation both vertically and laterally with the indentation depth increasing. When the indentation depth reaches a certain value, the thin film at the interface will occur the deformation plastic zone for the case studied in this paper. At lager depths, the two plastic zones will connect, and then the plastic zone propagates along the lateral direction. Beside, it is also found that the maximum of the Mises stress and the shearing stress on the interface occur at 0.8r and r(r is the radius of the indenter), respectively.     

Determination of transient creep parameters for HPSN by dynamic bending tests

A procedure is proposed which allows to determine creep parameters, mainly in the transient creep range, by dynamic bending tests. From measurements on HPSN at 1200° C creep exponents in the range 5<n<12 were found. The influence of creep on bending strength is investigated.     

The calculation of the relaxed creep strain in four-point bending tests

Abstracts are not published in this journal     

The calculation of the relaxed creep strain in four-point bending tests

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Heat transfer in YBaCuO thin film/sapphire substrate system

The thermal boundary resistance at the YBaCuO thin film/Al₂O₃ substrate interface was investigated. The transparency for thermal phonons incident on the interface as well as for phonons moving from the substrate was determined. We have measured a transient voltage response of current-biased films to continuously modulated radiation. The observed knee in the modulation frequency dependence of the response reflects the crossover from the diffusion regime to the contact resistance regime of the heat transfer across the interface. The values of transparency were independently deduced both from the phonon escape time and from the time of phonon return to the film which were identified with peculiarities in the frequency dependence. The results are much more consistent with the acoustic mismatch theory than the diffuse mismatch model.We are grateful to A. Elantev for helpful discussion. We acknowledge the financial support of the Russian Scientific Council on the HTS problem (Project No. 90462).     

低能电子束制备硅基纳米薄膜微结构研究

本文提出了一种新颖的结合自组装技术和电子束直写曝光以及选择性化学沉积制备图案化薄膜方法。利用X-射线光电子能谱（XPS），扫描电子显微镜（SEM），透射电子显微镜（TEM）紫外可见光谱仪（Analytic Jena AG）进行了表征。结果表明该方法取得了选择性较好的图案化金薄膜微结构图形。文中对胶体金纳米颗粒尺寸的选择以及金薄膜图案的粘附性能也进行了探讨。该方法有望应用于微／纳电子工业中。     

Hydrogen effect on fracture toughness of thin film/substrate interfaces

The effect of hydrogen on the interface fracture toughness of two nano-film/substrate structures, Ni/Si and Cu/Si, were evaluated using four-point bend specimens with and without hydrogen charging. Hydrogen typically decreases the fracture toughness of materials. However, we found in this study that the interfacial toughness between the Ni film and the Si substrate increased due to the presence of hydrogen, while that of Cu/Si decreased. Nanoindentation experiments for the Ni and Cu films revealed that local plasticity in the Ni and Cu films is promoted by the charged hydrogen. The critical stress intensity at the Ni/Si interface crack considering the plasticity of Ni, namely the true fracture toughness, is scarcely influenced by the existence of hydrogen. The apparent increase in fracture toughness of the Ni/Si interface is due to the large stress relaxation near the crack tip caused by softening due to the presence of hydrogen. Although the promotion of plastic deformation of Cu relaxes the stress intensity at the Cu/Si interface crack, the apparent interfacial toughness still decreases because of the significant decrease in the true toughness due to the presence of hydrogen.     

Sputter deposited ZnO nanowires/thin film structures on glass substrate

Integrated ZnO nanowires/thin film structures were grown using radio-frequency magnetron sputter deposition on amorphous glass substrates having an electroless plated copper surface layer. The growth took place under different deposition times and O₂/Ar ratios. The substrate was not heated or biased during the deposition. Regardless of the O₂/Ar ratio, both nanowires and the film grew simultaneously. However, the growth of the nanowires and the film was diffusion-controlled and reaction-controlled, respectively. On the other hand, the O₂/Ar ratio substantially affected the crystal structure and morphology of the resulting ZnO deposits.     

Analysis of thermally induced delamination of thermoelectric thin film/substrate system

Thermoelectric thin film/substrate structures have many practical applications such as in heat recovery systems. The general problem of thermally induced delamination between a thermoelectric thin film and a substrate is investigated. The temperature varies along the length direction but is constant along the thickness direction of the film. Analytical solutions of the temperature field in the film and the stress intensity factors (SIFs) at the delamination crack tips are obtained. The combined heat convection and heat radiation between the film surfaces and the surrounding medium (i.e., the air) are taken into account. Numerical results show that the SIFs sharply increase as the tips of the delamination crack approach the ends of the film. The combined heat convection and heat radiation can increase or decrease the SIFs. The mechanism for the delamination propagation in the thermoelectric film/substrate system is examined. The critical (permissible) temperature difference across the film governing the delamination propagation is identified.     

Instability-induced wrinkling in thermoelectric thin film/substrate structures for thermal protection systems in supersonic space shuttle applications

ABSTRACT

This paper examines the behavior of wrinkling instability of a thermoelectric thin film bonded to substrate. The critical temperature differences for wrinkling occurrence and buckling initiation are obtained. Damage growth following wrinkling is also determined. These critical temperatures can provide guidelines for the design of thermoelectric thin film devices. Numerical results show that the stability of thermoelectric thin film is affected by the electric current. The critical temperature differences become smaller when the electric current density in thermoelectric thin film is higher. Effect of the wavelength of wrinkling on the critical temperature differences of wrinkling occurrence is also identified.     

Effects of elastic anisotropy on the surface stability of thin film/substrate system

The surface stability of thin film/substrate system is an important problem both in the film synthesis and reliability of micro electrical and mechanical system (MEMS). In this work, the elastic anisotropy effect on surface stability of thin film/substrate system was considered. The theoretical analysis indicates that elastic anisotropic influence could play an important role in the surface stability of thin film/substrate system. And the anisotropy effect should be considered both in the thin film synthesis process and its service reliability. In addition, there exists an nondimensional parameter k for cubic crystalline thin film materials in evaluating the anisotropic effect. When k is larger than one unit, the surface stability will be weakened by anisotropic effect; vice versa. The method used in present work could be easy extended to multi-layered thin film/substrate system and help us to consider the elastic anisotropy effect.     

The bending of silicon wafers by thin polycrystalline silicon film deposition and by film doping using boron diffusion

The existence of stress at the interface between a monocrystalline silicon substrate and a thin (under 1 μm) polycrystalline silicon film was demonstrated using X-ray topography. The wafer-bending direction was studied for a polycrystalline film doped by boron prediffusion and by prediffusion followed by drive-in diffusion. Wafer bending in the presence of SiO₂ thermal growth between the monocrystalline substrate and the polycrystalline film was also investigated. The causes of the wafer bending and its change during polycrystalline film doping are discussed.     

Deposition of ZnO thin film on polytetrafluoroethylene substrate by the magnetron sputtering method

Due to the excellent optical and electrical properties, ZnO thin films deposited on flexible substrates can be used as technologically promising electron devices. Polytetrafluoroethylene (Teflon) had many advanced properties, such as high dielectric strength over various frequencies, low dissipation factor, and high surface electrical resistivity, which had made Teflon a competitive polymer choice in a variety of microelectronic applications. In our work, ZnO film was firstly deposited on Teflon substrate by the magnetron sputtering method. X-ray diffraction data revealed that the ZnO grains were highly c-axis-oriented and nanostructured with the size of 10–30 nm, which was in accordance with the experimental result of Scanning Electron Microscopy.     

SrTiO3衬底上溅射法外延生长PLZT薄膜

用射频磁控溅射法在SrTiO3衬底上外延生长PLZT薄膜,研究了不同的溅射工艺对薄膜生长速率的影响,探讨了不同的后期热处理条件与薄膜取向度的关系.在SrTiO3衬底上成功制备出外延生长的、厚度达1.5μm的PLZT薄膜.     

SEM in-situ investigation on failure of nanometallic film/substrate structures under three-point bending loading

Three-point bending tests on nanocrystalline Cu or Cu/Ni-film/Cu-substrate samples were conducted in-situ with scanning electron microscopy (SEM) observations. The SEM in-situ observations show undulation deformation of the surface of thin film, as the thin film fractures easily at the concave–convex points of deformation and multi-cracks appear on the surface of the thin film in a periodic fashion. The critical wavelength of undulation is calculated based on experimental observations, which are comparable with the theoretical predictions. For the Cu/Ni multi-layered films/substrate structures, the micro-cracking pattern depends on the interfacial strength between the film and the substrate, rather than the interfacial strength between the layers of films.     

Multiple film cracking in film/substrate systems with residual stresses and unidirectional loading

Multiple film cracking in film/substrate systems is analyzed in the present study. Specifically, the experimental measurements of multiple cracking of SiO _x films of various thicknesses on polyethylene terephthalate substrates are analyzed. The system is subjected to both residual stresses and unidirectional tensile loading. Considering a three- dimensional geometry, an analytical model is developed to derive the stress distribution in the system, and the film-cracking problem is analyzed using both the strength and the energy criteria. Compared to the strength criterion, the energy criterion shows better agreement with the measurements of the crack density versus applied strain relation.     

基片上薄膜生长过程的计算机模拟

根据薄膜的成核统计理论,考虑吸附粒子的碰撞、迁移、蒸发等因素,针对薄膜单层和多层核生长类型的生长,用计算机进行仿真模拟.同时研究了几种因素对粒子沉积成膜的影响.根据计算机模拟情况,得出了粒子百分变化与成团粒子百分变化关系、生长过程对粒子沉积成膜的影响.论证了按成核理论下的随机统计规律生成的多层粒子膜,其厚度方面的不均匀性与实际是一致的.并给出了计算机模拟研究薄膜微观生长过程的立体图象.     

Irradiation tests of thin substrate materials for nuclear targets

The resistance against alpha radiation of several thin plastic foils (formvar, parylene, polyimide, polypropylene, polysulfone, vyns), to be used as substrates for nuclear targets, was examined using alpha particles from an ²⁴¹Am source (in air and in vacuum) and from a cyclotron. The results depended on the experimental conditions, but the best results were always obtained using polyimide foils.     

玻璃衬底上钯多晶膜的制备

在乙二醇和乙酰丙酮混合溶剂中将钯多晶膜沉积在玻璃片上.钯膜表面平整,由球形钯晶小颗粒密堆积而成,颗粒均匀,形状规则,直径约为130nm.对混合溶液进行了研究,给出了制备均匀的钯膜的最佳反应条件.颗粒大小和膜层厚度可以通过改变反应条件加以控制.探讨了溶剂所起的作用,提出了混合溶剂中钯膜沉积的可能机理.