溅射功率对二氧化锆薄膜结构及力学性能的影响研究

为了研究溅射功率对二氧化锆薄膜结构及力学性能的影响,使用射频反应磁控溅射技术在常温下以玻璃为基底使用不同功率镀制了800 nm左右的ZrO2薄膜.利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对样品结晶情况,表面和断面形貌进行表征,结果显示镀制的ZrO2薄膜均为单斜晶体,晶粒尺寸变化不大;随着功率的升高,薄膜从纳米晶结构转变为柱状晶结构.使用纳米压痕仪对薄膜表面进行硬度和弹性模量测试,发现随着功率升高,硬度和弹性模量均出现上升趋势,进一步增加功率出现下降,再上升的变化;在沉积功率为65 W时,可得到厚度为800 nm,弹性恢复量,硬度,弹性模量和塑性指数均最高,分别为88.55％,25.42 GPa,228.6 GPa和0.314的ZrO2薄膜.不同的溅射功率会镀制出不同结构的二氧化锆薄膜,在常温低功率溅射条件下二氧化锆薄膜结构是影响其力学性能的重要因素.     

烧结温度对ZrO2薄膜表面形貌及力学性能的影响

采用溶胶-凝胶法在玻璃基体表面制备了经300℃,400℃和500℃烧结热处理的ZrO2薄膜.利用X射线衍射仪、原子力显微镜和纳米压痕仪研究了烧结温度对ZrO2薄膜表面形貌和力学性能的影响.实验结果表明,随着烧结温度的增加,ZrO2的晶体结构由少量的单斜晶相逐渐转变为单斜晶相和四方晶相的混合相.薄膜表面形貌逐渐改善,薄膜的表面粗糙度和颗粒度依次减小,薄膜的表面粗糙度分别为10.5 nm、7.2 nm和5.6 nm,ZrO2的粒径分别为188 nm、153 nm和130 nm.ZrO2薄膜的弹性模量和硬度都显著提高,薄膜的弹性模量分别为89.6 GPa、114.2 GPa和128.9 GPa,薄膜的硬度分别为7.6 GPa、10.3 GPa和15.1 GPa.     

磁控溅射Ta-C-N薄膜摩擦学性能研究

采用磁控溅射法在Si基片上沉积非晶态Ta-C-N薄膜。利用纳米压痕仪表征其纳米硬度和弹性模量;摩擦磨损实验检测其摩擦学性能;光学轮廓仪和扫描电镜观察磨痕形貌。结果表明:Ta-C-N薄膜具有较高的纳米硬度9.45 GPa和弹性模量225.71 GPa,同时具有较低的摩擦系数0.238,磨损率5.94×10-6 mm3.N-1.m-1,磨面较为平整光滑,体现了优越的摩擦磨损性能。     

纳米压痕法研究金刚石薄膜的力学性能

用热丝化学气相沉积法在硅基体上制备了大面积硼掺杂金刚石薄膜,硼的浓度大约为2×10~(20)/cm3。利用纳米压痕仪及其附件研究了薄膜和纳米划擦有关的力学性能。结果表明:薄膜具有较高的硬度,平均硬度约为30GPa,弹性模量约为419GPa;薄膜与基体的结合强度较高,薄膜发生剥落的第一次破坏力大约是4N。比较而言,薄膜中心区域的硬度高于边缘,结合强度则相反。     

连续刚度法对单晶硅片的力学性能的表征

利用纳米压痕仪通过连续刚度测量法对单晶硅片在压入过程中的接触刚度、硬度、弹性模量进行了连续测量.结果表明:当接触深度在20～32 nm左右时,单晶硅片的接触刚度与接触深度成直线关系,硬度和弹性模量基本保持不变,此时所测得的是单晶硅片表面氧化层的硬度和弹性模量,分别约为10.2 GPa和140.3 GPa.当接触深度在32～60 nm左右时,单晶硅片的接触刚度与接触深度成非直线关系,硬度和弹性模量随接触深度急剧增加,表明单晶硅片表面氧化层的硬度和弹性模量受到了基体材料的影响.当接触深度在60 nm以上时,单晶硅片的接触刚度与接触深度成直线关系,硬度和弹性模量基本保持不变,测得值为单晶硅的硬度和弹性模量,分别约为12.5 GPa和165.6 GPa.     

氧离子注人对金刚石薄膜微结构和力学性能的影响

采用扫描电镜（SEM）、Raman光谱和纳米压痕法研究了氧离子注入对低硼掺杂金刚石薄膜微结构和力学性能的影响。结果表明,薄膜中注入较高剂量的氧离子并退火后,晶粒尺寸减小。氧离子注入导致薄膜中金刚石含量减小;1000℃退火后,薄膜中金刚石含量增加为99．8％。氧离子注入后,薄膜中的内应力由拉应力转变为压应力;退火后,薄膜内应力再转变为柱应力。氧离子注入后的金刚石薄膜的硬度较注入前的薄膜硬度有所降低,但其硬度仍然大于40GPa并具有良好的弹性恢复率。薄膜的力学性能与薄膜中的金刚石含量、晶粒尺寸和应力值有直接关系。     

泥沙颗粒表面力学及摩擦性能测试分析

本文对材料纳米力学性能测试方法进行了研究,重点分析了颗粒材料纳米压痕测试的原理和方法.针对纳米压痕测试需求,设计了一种简易制样方法,实测了泥沙粒子表面硬度和弹性模量.并利用应变式直剪仪测试了泥沙颗粒表面摩擦性能.结果表明,泥沙颗粒表面纳米硬度及弹性模量分别为1.94 GPa和30.57 GPa,颗粒表面摩擦系数约为0.65.纳米压痕及直剪试验提供了丰富的颗粒材料近表面弹塑形变形和摩擦信息,是评价泥沙颗粒力学及摩擦性能的有效方法.     

溅射靶功率对类金刚石碳薄膜的结构和性能影响

为改善304不锈钢的性能,扩展其应用范围,采用磁控溅射技术在不同溅射靶功率下激发高纯石墨靶在p(100)单晶硅和304不锈钢表面沉积类金刚石碳薄膜。文章对所制备的系列类金刚石碳薄膜作了Raman光谱、X射线衍射(XRD)、原子力显微镜(AFM)、断口形貌的场发射电镜(FESEM)表征,并评价了其纳米硬度与摩擦磨损行为。结果表明:所制备的类金刚石碳薄膜为典型的非晶态微结构;随着靶功率的增大,类金刚石碳薄膜的sp3键含量先增多后减少,表面粗糙度先降低后升高,硬度与弹性模量先升高后降低;靶功率200 W时类金刚石碳薄膜取得最优性能,纳米硬度为11.4GPa,弹性模量为129.3GPa,摩擦系数为0.17,磨损率为5.2×10-7 mm3(N·m)-1。     

超声冲击处理S30408表面硬度研究

采用显微硬度测试以及纳米压痕技术测量超声冲击处理奥氏体不锈钢S30408硬度沿厚度方向的变化,分析超声冲击处理后材料表面力学性能的变化.结果表明:表面硬度和硬化层厚度的增加在冲击时间达到180 s后趋于平缓;处理后,S30408表层的弹性模量约为230 GPa,与未受处理影响区域相比,提高了28％;S30408沿厚度方...     

位移敏感压痕技术评价SiC硬质膜的力学性能

为了解决SiC硬质膜力学性能难测试的问题,提出以Oliver-Pharr模型为基础的位移敏感压痕技术来评价SiC硬质膜的硬度及弹性模量.为了解其可靠性,将此方法用于普通玻璃和不锈钢作为参考.选用厚度为315±15 μm的化学气相沉积(CVD)SiC硬质膜作为样品,实验以0.5 N/s的载荷速度进行加卸载,载荷峰值取10～30 N,结果表明:位移敏感压痕法计算出的普通玻璃和不锈钢的硬度分别为6.5 GPa和1.7 GPa,传统显微硬度计测试出的结果分别为5.3 GPa和1.8 GPa,其值比较接近;此方法计算出普通玻璃和不锈钢的弹性模量分别为65.1 GPa和178.4 GPa,与实际值70 GPa和190 GPa误差很小,因此表明该方法可靠性良好.利用位移敏感压痕技术得知CVD SiC硬质膜的硬度和弹性模量为37.7 GPa和456.4 GPa.另外根据维氏压痕形貌,应用JISR1607-1990标准,Anstis,Evans&Charles三断裂韧性公式,计算出普通玻璃和CVD SiC硬质膜KIC均值分别为0.78 MPa·m1/2和2.70 MPa·m1/2.此方法可广泛用于评价硬质膜的硬度和弹性模量等力学性能.     

Biaxial elastic modulus of very thin diamond-like carbon (DLC) films

The biaxial elastic modulus of very thin diamond-like carbon (DLC) films was measured by the recently suggested free overhang method. The DLC films of thickness ranging from 33 to 1100 nm were deposited on Si wafers by radio frequency plasma-assisted chemical vapor deposition (r.f.-PACVD) or by the filtered vacuum arc (FVA) process. Because the substrate was partially removed to obtain sinusoidal free overhang of the DLC film, this method has an advantage over other methods in that the measured value is not affected by the mechanical properties of the substrate. This advantage is more significant for a very thin film deposited on a substrate with a large difference in mechanical properties. The measured biaxial elastic moduli were reasonable values as can be judged from the plane strain modulus of thick films measured by nanoindentation. The biaxial elastic modulus of the film deposited by r.f.-PACVD was 90±3 GPa and that of the film deposited by FVA process was 600±50 GPa. While the biaxial elastic modulus of the film deposited by FVA is independent of the film thickness, the film deposited by r.f.-PACVD exhibited decreased elastic modulus with decreasing film thickness when the film is thinner than 500 nm. Although the reason for the different behavior could not be clarified at the present state, differences in structural evolution during the initial stage of film growth seem to be the reason.     

Microstructure and mechanical properties of CeO2 doped diamond-like carbon films

A kind of rare earth oxide, CeO₂, was doped into the diamond-like carbon (DLC) films with thickness of 180–200 nm, using unbalanced magnetron sputtering. All the adhesion strength of CeO₂ doped DLC films is increased, while the residual compressive stress is obviously decreased compared to pure DLC film. Specially, the residual compressive stress of the deposited films are reduced by 90%, when the CeO₂ content is in the range of 5–7%, from a value of about 4.1 GPa to 0.5 GPa. When the CeO₂ content is increased to 10%, the deposited films possess the highest adhesion strength of 85 mN, 37% higher than that of pure DLC film. The nanohardness and elastic modulus exist a transition point at 8% of CeO₂ content within the DLC film. Before this value, nanohardness and elastic modulus of CeO₂ doped DLC films are lower than those of pure DLC film, and after this value, they are higher or adjacent to those of pure DLC film. Auger electron spectroscopy shows a more widened interface of 6% CeO₂ doped DLC film compared to pure DLC film. The enhancement of adhesion strength is mainly attributed to the widening of the film-substrate interface, as well as the decrease of residual compressive stress.     

A method of determining the elastic properties of diamond-like carbon films

The elastic properties of diamond-like carbon (DLC) films were measured by a simple method using DLC bridges which are free from the mechanical constraints of the substrate. The DLC films were deposited on a Si wafer by radio frequency (RF) glow discharge at a deposition pressure of 1.33 Pa. Because of the high residual compressive stress of the film, the bridge exhibited a sinusoidal displacement on removing the substrate constraint. By measuring the amplitude with a known bridge length, we could determine the strain of the film which occurred by stress relaxation. Combined with independent stress measurement using the laser reflection method, this method allows the calculation of the biaxial elastic modulus, E/(1−ν), where E is the elastic modulus and ν is Poisson's ratio of the DLC film. The biaxial elastic modulus increased from 10 to 150 GPa with increasing negative bias voltage from 100 to 550 V. By comparing the biaxial elastic modulus with the plane–strain modulus, E/(1−ν²), measured by nano-indentation, we could further determine the elastic modulus and Poisson's ratio, independently. The elastic modulus, E, ranged from 16 to 133 GPa in this range of the negative bias voltage. However, large errors were incorporated in the calculation of Poisson's ratio due to the pile up of errors in the measurements of the elastic properties and the residual compressive stress.     

Experimental Observations of Substrate Fracture Caused by Residually Stressed Films

Model systems for studying thin-film cracking consisting of thin plates of alumina and soda-lime glass were diffusion bonded to silica substrates at high temperature. Upon slow cooling, substrate fracture was induced by residual stresses from the thermal and elastic mismatch of the film and substrate. In particular, multiple substrate cracks formed parallel to the interface. The observed crack paths closely followed predictions based on a zero mode II stress intensity. Crack depths were found to be strongly dependent on the relative substrate thickness and the Young's modulus ratio.     

Determination of the Elastic Modulus and Residual Stresses in Ceramic Coatings Using a Strain Gage

Formulas based on the beam theory are derived for calculating the in-plane elastic modulus and residual stresses in ceramic coatings. In addition to theoretical derivation, experimental data for SiC coating/graphite substrate composites are proposed. The results indicate that the modulus of SiC coatings is 359 GPa. The residual stresses are in compression and are functions of the ratio of substrate thickness to coating thickness.     

Mechanical Properties of Sputter-Deposited Titanium-Silicon-Carbon Films

The effect of SiC additions on the mechanical properties of TiC films was investigated. Ti-Si-C films with varying SiC content were deposited using dual-cathode radio-frequency magnetron sputtering. The nanoindentation hardness of these films increased with SiC content to a maximum of 20–22 GPa for films in the range of 15–30 at.% SiC. The elastic modulus was also measured, and the hardness to modulus ratio ( H / E ) increased with SiC content, indicating that hardness increases were due to microstructural effects. The residual stress was measured in several films, but was low in magnitude, indicating that hardness measurements were not influenced by residual stress. TEM examination of several films revealed that the SiC additions altered the film microstructure in a manner that could account for the observed hardness increases.     

Properties of Boron Nitride (BxNy) Films Produced by the Spin-Coating Process of Polyborazine

Boron-rich boron nitride (BN) films have been prepared on Si and SiO₂/Si substrates by the vacuum pyrolysis of spin-coated polyborazine films. Physical properties of the prepared films such as film strength, thermal conductivity, and dielectrics were determined. The BN films vacuum-pyrolyzed at 900°C showed residual N–H bonds with a 0.75 N/B ratio, interdiffusion phenomena, and preferred orientation at the interfacial zone. Hardness and the elastic modulus of the film increased to 1.6 GPa and 50 GPa by nanoindentation loading. It had a thermal conductivity of 134 W/(m·K) at 296.5 K, and a dielectric constant in the range of 5–7, with tan ∂ between 0.01 and 0.47, depending on the film thickness.     

Characterization of AFM cantilevers coated with diamond-like carbon

The resonance frequency of AFM cantilevers depends on the elastic modulus and on the dimensions of the cantilever. As for coated cantilevers, the resonance frequency will be determined not only by the properties of the cantilever, but also by the properties of the coating (elastic modulus and thickness). We have carried out a systematic investigation of cantilevers coated with several thicknesses of the DLC films. Measurements of the resonance frequency of the cantilevers, before and after the DLC coating, were used with a model to determine the elastic modulus of the DLC. The elastic modulus obtained for the DLC, with this model, was E₂=616 GPa. The AFM tip radii were also measured after coating and were found to increase with the DLC film thickness.     

Residual Stress in Siliceous Glass Between Mullite Crystals

A birefringence of siliceous glass, which is coexisting with mullite crystals, was studied by an optical polarizing microscope. The cause of the birefringence was assumed to be the residual stress induced by a large contraction difference between the mullite and glass on cooling. The stress has been evaluated to be as high as—0.3 GPa, and to correspond to the elastic one which began to develop at the glass transition point.