Structural and electrochemical properties of vanadium oxide thin films grown by d.c. and r.f. reactive sputtering at room temperature

Vanadium oxide thin films were grown at room temperature by direct current and radio-frequency reactive sputtering systems to compare the structural and electrochemical properties. Rutherford backscattering spectrometry and Fourier transform infrared measurements reveal that the composition of the as-deposited films consists of the V₂O₅ phase regardless of the deposition methods. Wide-angle X-ray diffraction measurements show that the crystallinity of the as-deposited V₂O₅ films is different depending on the deposition method. Films deposited by direct current reactive sputtering were amorphous, whereas films deposited by radio-frequency reactive sputtering were crystalline. Scanning electron microscopy measurements show that the V₂O₅ films grown by radio-frequency reactive sputtering had a large grain size but the films grown by direct current reactive sputtering were amorphous. Charge–discharge measurements taken at room temperature with a constant current clearly indicate that the films grown by direct current sputtering demonstrated typical amorphous behavior, whereas the V₂O₅ films grown by radio-frequency sputtering demonstrated the discharge behavior of crystalline V₂O₅. The origin of the structural and electrochemical properties of film grown by radio-frequency reactive sputtering is a self-bias effect. The self-bias effect induces ion bombardment during the growth of vanadium oxide thin film. These results suggest that direct current reactive sputtering is more desirable for growing amorphous V₂O₅ thin film than radio-frequency reactive sputtering.     

Atmospheric effects of friction,friction noise and wear with silicon and diamond. Part II. SEM tribometry of silicon in vacuum and hydrogen

Scanning electron microscope (SEM) tribometric data on polycrystalline silicon (poly-Si) vs. poly-Si, Si(100) vs. Si(100) and Si(111) vs. Si(111) interfaces, obtained in Torr and in 0.2 Torr partial pressure of hydrogen gas ( ) from room temperature to 850^°C, were performed under standard and much slower thermal ramping rates. The friction data were analyzed per the methodology described in part I of this paper series. The results indicate a highly beneficial friction- and wear-reducing regime within a relatively narrow thermal region. This desirable region coincides with some chemisorption of excited species of molecular hydrogen just before the mass thermal desorption of surface hydrides. These data represent the tribochemical equivalent of a method routinely used in electronics, whereby deep electron traps (dangling Si bonds) are passivated by baking in molecular hydrogen. The also exerts a moderating influence on the size of the friction noise at all test temperatures. However, the general level of friction beyond the beneficial thermal region is high. In parallel, the general wear rate of Si representative of the entire range of standard thermal ramping in both atmospheric environments is in the extremely high 10^-12m³/(N m) range. Operating strictly in the beneficial, low-friction thermal regime resulted in a several orders-of-magnitude reduction in the wear rate over those measured under standard thermal ramping conditions. Although the results confirm previous findings that Si is not a good material of construction for miniaturized moving mechanical assemblies (e.g., microbearings and gears), there seems to be some limited possibility of gas-phase lubrication of Si micromechanisms with rarefied hydrogen at surface temperatures between 100 and 300^°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

唐钢薄板坯内部横裂纹的分析研究

通过研究钢的高温性能,分析薄板坯连铸工艺及板坯内部横裂纹形成的机理,提出了改善薄板坯内部质量的途径。     

TiB_2/ZrB_2/SiC复合功能材料的微观结构与力学性能

采用放电等离子烧结工艺,制备TiB2/ZrB2/SiC复合功能材料。用X射线衍射仪和场发射扫描电镜分析观察复合材料的物相组成及微观形貌。并测试复合材料的抗弯强度、断裂韧性及硬度。结果表明:两次球磨后的TiB2/ZrB2/SiC粉体粒度较小(2~4μm),且分布较均匀,几乎没有团聚现象。烧结后的复合功能材料中有(TixZry)B2固溶体相生成。当加入ZrB2的体积分数为30%时,生成的(TixZry)B2固溶体在复合材料中起到了很好的晶粒细化与界面融合作用,所以TZS30复合陶瓷材料比TZS0复合陶瓷材料的抗弯强度和断裂韧性分别提高了119.8%和98.9%。利用TiB2/ZrB2/SiC复合陶瓷材料在高温摩擦作用下与氧的化学反应,可以实现自润滑。     

有机硅氧烷对硅橡胶网络的补强作用

本文通过硅氧烷水解的途径对乙烯基封端的聚二甲基硅氧烷(PDMS)在交联前后导入不变形或可变形的补强填充剂的新方法进行了研究,并此较了它们的补强性能。实验结果表明:交联后的 PDMS 网络,用四乙氧基硅烷(TEOS)水解得到的二氧化硅粒子具有最佳的补强性能,这种方法要比其他硅氧烷水解获得的补强效应大得多。实验也指出:液体硅橡胶在交联前引入的二氧化硅补强剂是完全可能的。它能形成一种稳定的橡胶一填料分散体系,并有相当的补强作用。但它的补强效应不如交联后引入补强剂的方法好。     

透视/遮阳/控温/红外隐身多功能集成序构薄膜研究

为了解决光学材料多功能耦合与集成的光谱诉求及其材料设计冲突难题,本文提出一种基于［TiAlN/Ag］²/TiAlN序构复合薄膜开展可见光透射诱导与红外辐射抑制的协同设计方法,诠释序构薄膜材料多功能耦合的新原理与新机制,并对其光学兼容性能测试表征。研究表明,构筑的［TiAlN（厚度30 nm）/Ag（厚度15 nm）］²/TiAlN（厚度30 nm）序构复合薄膜具备带通状选择性透射与中远红外低辐射的光学特性,可较好实现透视、遮阳、低辐射控温与红外隐身多功能兼容效果,在军用车辆、绿色建筑等特种玻璃的辐射控温与红外隐身领域有应用潜力。     

ZnO薄膜发光特性的研究进展

ZnO薄膜具有压电、光电、压敏、气敏、发光等多种特性,应用极为广泛。针对ZnO薄膜的发光特性,对ZnO薄膜的制备、影响其发光特性的因素及其发光机理的研究进展进行了综述。     

一种新型的激光—等离子体辅助化学气相沉积装置的研究

为探索用激光离子体共同辅助化学气相沉积过程以实现室温沉积的可能性，设计并制造了一种新型的ＣＶＤ装置，实际了ＳｉＨ４－ＮＨ３－Ｎ２体系制取Ｓｉ３Ｎ４膜的试验。结果表明，激光和等离子体是可以相互促进，共同辅助ＣＶＤ过程的，且两者均处于较代的能量水平。     

Hydrogen plasma treatment of very thin p-type nanocrystalline Si films grown by RF-PECVD in the presence of B(CH3)3

Abstract

We have characterized the structure and electrical properties of p-type nanocrystalline silicon films prepared by radio-frequency plasma-enhanced chemical vapor deposition and explored optimization methods of such layers for potential applications in thin-film solar cells. Particular attention was paid to the characterization of very thin (～20 nm) films. The cross-sectional morphology of the layers was studied by fitting the ellipsometry spectra using a multilayer model. The results suggest that the crystallization process in a high-pressure growth regime is mostly realized through a subsurface mechanism in the absence of the incubation layer at the substrate-film interface. Hydrogen plasma treatment of a 22-nm-thick film improved its electrical properties (conductivity increased more than ten times) owing to hydrogen insertion and Si structure rearrangements throughout the entire thickness of the film.