衬底温度对合成金刚石薄膜的影响

本文利用热丝化学气相沉积方法对不同温度下生长的金刚石薄膜样品进行了表征分析。通过扫描电镜照片分析,从成核理论方面得出了金刚石薄膜生长的最优化温度。     

衬底温度对合成金刚石薄膜的影响

本文利用热丝化学气相沉积方法对不同温度下生长的金刚石薄膜样品进行了表征分析。通过扫描电镜照片分析,从成核理论方面得出了金刚石薄膜生长的最优化温度。     

不同重力取向对金刚石薄膜生长的影响

本文采用热丝ＣＶＤ方法在不同方向的Ｓｉ衬底上生长金刚石薄膜。研究了金刚石薄膜的生长特性以及不同重力取向对金刚石薄膜成核密度、生长速度和晶体品质的影响。通过激光喇曼光谱、原子力显微镜（ＡＦＭ）、扫描电镜（ＳＥＭ）等测试得出：不同重力取向生长的金刚石薄膜成核密度和生长速度表现出明显的差别。     

汽相生长金刚石微粒及金刚石薄膜分析

用化学汽相沉积法已长出金刚石微粒及金刚石薄膜,并对它进行了扫描电镜观查,X-射线衍射分析,喇曼光谱分析,硬度测试,证明它确是金刚石并具有金刚石的性能.     

溶胶-凝胶法在金刚石表面涂覆纳米TiO2薄膜

通过溶胶-凝胶法制备二氧化钛溶胶，采用浸渍的方法在工业金刚石表面涂覆TiO2薄膜，扫描电镜和能谱分析结果表明，该方法可以在金刚石表面涂覆TiO2薄膜，薄膜将金刚石磨料包裹完全，红外光谱分析显示TiO2与基体金刚石表面形成稳定的Ti-O-C化学键．综合热分析对金刚石抗氧化性能检测结果为：涂膜金刚石较未涂膜金刚石抗氧化温度提高100℃。     

基于放电沉积的金刚石磨粒层制备实验研究

提出将电火花沉积技术用于金属材料/非金属材料之间的沉积，通过制备一种含有超硬磨粒金刚石的压缩粉体电极，采用放电沉积工艺实验将超硬磨粒金刚石与电极中的其他金属材料一起沉积到基体母材表面上，然后通过扫描电镜观察与分析，沉积层中的金刚石磨粒形状较好，分布较均匀，具有磨粒层的基本要素.实验结果表明，采用电火花放电沉积能制备金刚石磨粒层.     

陶瓷表面金属化Cu薄膜应力调控

利用直流磁控溅射方法在AlN陶瓷表面沉积了单层Cu薄膜，采用X射线衍射方法研究了沉积温度对薄膜应力的影响，并用有限元方法模拟不同温度下沉积的Cu薄膜中的热应力及变形分布情况.沉积的薄膜应力表现为张应力，并随沉积温度的升高先增大后减小，沉积温度为200 ℃左右时，薄膜应力达到最大值；在AlN表面引入过渡界面可明显地减小薄膜应力，并根据微观结构和物理性质的变化等对薄膜应力的变化进行了解释.     

栅极偏压对纳米金刚石薄膜沉积过程的影响

在HFCVD系统中施加栅极偏压和衬底偏压,采用双偏压成核和栅极偏压生长的方法成功制备了高质量的纳米金刚石薄膜.采用显微Raman高分辨率SEM和AFM等现代理化分析手段分析纳米金刚石膜的微结构,结果表明双偏压显著促进了金刚石的成核密度,平均晶粒尺寸在20 nm以内.试验观察和理论分析表明栅极偏压促进了热丝附近的等离子体浓度,提高了衬底附近的碳氢基团和氢原子浓度,提高了金刚石的成核密度、在保持晶粒的纳米尺寸的同时保持了较高的成膜质量和较低的生长缺陷.     

DLC,TiN薄膜的环境摩擦学特性研究

采用非平衡磁控溅射及电弧离子镀技术在304奥氏体不锈钢表面沉积了类金刚石(DLC)及TiN 薄膜.用纳 米压痕仪、表面粗糙度仪、扫描电镜等检测了薄膜的显微硬度、表面粗糙度及表面形貌.并用球—盘式摩擦磨损试 验仪评价了不同介质(干摩擦、水润滑、油润滑)条件下薄膜的摩擦磨损性能.结果表明:在干摩擦及水润滑条件 下,TiN,DLC两种薄膜均明显改善了基体的耐磨性和润滑性,DLC薄膜性能更佳.但相对于干摩擦,在水润滑条 件下,DLC薄膜的摩擦系数反而有所升高,这主要源于H2O 与O2 在摩擦过程中参与反应,降低了薄膜的力学性 能和化学惰性从而增加了粘着效应.在油润滑条件下,DLC,TiN 薄膜与基体摩擦系数相近甚至略高,薄膜的沉积 虽然有利于基体耐磨性能的提高,但并不能改善基体的润滑特性.     

TiO2 薄膜折射率的调控方法

采用电子束蒸发技术及其辅助工艺制备了TiO 2 薄膜,利用X射线衍射（XRD）、X射线光电子能谱（XPS）和原子力显微镜（AFM）对薄膜的组织结构进行了表征,采用紫外可见分光光度计研究了TiO 2 薄膜的折射率变化.结果表明：传统电子束蒸发镀制的TiO 2 薄膜的折射率低于块体值,通过调节氧气压、沉积速率和衬底温度可在1.97～2.22范围内调控其折射率;采用离子束辅助轰击可使薄膜致密化,获得折射率在2.06～2.42范围内变化的TiO 2 薄膜;利用斜角入射沉积可控制薄膜生长角度与孔隙率,实现折射率在 1.71 ～2.18范围内的调控.     

Diamond coating of titanium alloys

A titanium alloy was coated with a thin layer of synthetic diamond by chemical vapor deposition methods, achieving exceptional adhesion. Scientific and technological opportunities exist for the development of diamond-coated metal alloys and for a better understanding of adhesion mechanisms of hard, brittle coatings. An indentation method of wide applicability for measuring the adhesion of such coatings is discussed.     

High carrier mobility in single-crystal plasma-deposited diamond

Room-temperature drift mobilities of 4500 square centimeters per volt second for electrons and 3800 square centimeters per volt second for holes have been measured in high-purity single-crystal diamond grown using a chemical vapor deposition process. The low-field drift mobility values were determined by using the time-of-flight technique on thick, intrinsic, freestanding diamond plates and were verified by current-voltage measurements on p-i junction diodes. The improvement of the electronic properties of single-crystal diamond and the reproducibility of those properties are encouraging for research on, and development of, high-performance diamond electronics.     

Polycrystalline CVD Diamond Films with High Electrical Mobility

Advances in the deposition process have led to dramatic improvements in the electronic properties of polycrystalline diamond films produced by chemical vapor deposition (CVD). It is now possible to produce CVD diamond with properties approaching those of IIa natural diamonds. The combined electron-hole mobility, as measured by transient photoconductivity at low carrier density, is 4000 square centimeters per volt per second at an electric field of 200 volts per centimeter and is comparable to that of the best single-crystal IIa natural diamonds. Carrier lifetimes measured under the same conditions are 150 picoseconds for the CVD diamond and 300 picoseconds for single-crystal diamond. The collection distance at a field of 10 kilovolts per centimeter is 15 micrometers for the CVD diamond as compared to 30 micrometers for natural diamonds. The electrical qualities appear to correlate with the width of the diamond Raman peak. Also, although the collection distance at the highest fields in the films nearly equals the average grain size, there is no evidence of deleterious grain boundary effects.     

A nucleation site and mechanism leading to epitaxial growth of diamond films

A diamond nucleation site responsible for epitaxial growth of diamond on silicon by chemical vapor deposition (CVD) is identified in high-resolution transmission electron microscopic images. Other sites in the same sample leading to polycrystalline growth, but deleterious to epitaxial CVD growth, are also described. A mechanism for the heteroepitaxial growth of diamond is suggested, in which etching of the nondiamond carbon binder exposes and removes nonadherent nanodiamond nuclei, leaving intact only those directly nucleated on the silicon substrate. This work enhances our understanding of diamond nucleation and heteroepitaxial growth and its potential applications.     

Epitaxial growth and the art of computer simulations

The results of kinetic simulations of the aggregates formed during the deposition of atoms on a semiconductor surface are reviewed. Because the kinetic parameters are poorly known and the accuracy of the existing interatomic potentials has not been sufficiently tested, the goal has been to reach a qualitative understanding of the formation of unusual patterns during growth, such as the segregation of aluminum during the growth of aluminum-gallium-arsenide (AlGaAs) coherent tilted superlattices and the formation of thin, long, and parallel islands during the deposition of Si on an Si(100) surface. Kinetic mechanisms for these phenomena are proposed.     

磨料有序排布钎焊金刚石砂轮磨削硬质合金的性能研究

通过优化排布金刚石磨料研制出钎焊单层金刚石端面砂轮.以硬质合金为加工对象,研究了该砂轮的磨削性能.结果显示连续干磨时,金刚石磨粒的失效形式主要是磨耗磨损和断裂两类,没有出现传统的电镀和烧结工具磨粒大量脱落的现象.这表明钎料合金对磨粒的高强度把持和砂轮的高耐用度.此外,工件的磨削表面获得了良好的粗糙度,理论预测的粗糙度数值和试验数值基本一致.     

Three Mars years: viking lander 1 imaging observations

The Mutch Memorial Station (Viking Lander 1) on Mars acquired imaging and meteorological data over a period of 2245 martian days (3:3 martian years). This article discusses the deposition and erosion of thin deposits (ten to hundreds of micrometers) of bright red dust associated with global dust storms, and the removal of centimeter amounts of material in selected areas during a dust storm late in the third winter. Atmospheric pressure data acquired during the period of intense erosion imply that baroclinic disturbances and strong diurnal solar tidal heating combined to produce strong winds. Erosion occurred principally in areas where soil cohesion was reduced by earlier surface sampler activities. Except for redistribution of thin layers of materials, the surface appears to be remarkably stable, perhaps because of cohesion of the undisturbed surface material.     

Ultraviolet emission from a diamond pn junction

We report the realization of an ultraviolet light-emitting diode with the use of a diamond pn junction. The pn junction was formed from a boron-doped p-type diamond layer and phosphorus-doped n-type diamond layer grown epitaxially on the 111 surface of single crystalline diamond. The pn junction exhibited good diode characteristics, and at forward bias of about 20 volts strong ultraviolet light emission at 235 nanometers was observed and was attributed to free exciton recombination.     

Melting of diamond

Radiation from a Q-switched YAG laser, focused on the (100) face of a single crystal diamond anvil in a high-pressure diamond cell, caused a portion of the diamond anvil face to melt. Potassium bromide mixed with graphite was under pressure between the anvils when melting occurred. The diamond surface melted at pressures greater than approximately 120 kilobars and graphitized at lower pressures. Evidence for the melting and graphitization of the diamond was obtained by optical and scanning electron microscopy.     

MgB2 superconducting thin films with a transition temperature of 39 kelvin

We fabricated high-quality c axis-oriented epitaxial MgB2 thin films using a pulsed laser deposition technique. The thin films grown on (1 i 0 2) Al2O3 substrates have a transition temperature of 39 kelvin. The critical current density in zero field is approximately 6 x 10(6) amperes per cubic centimeter at 5 kelvin and approximately 3 x 10(5) amperes per cubic centimeter at 35 kelvin, which suggests that this compound has potential for electronic device applications, such as microwave devices and superconducting quantum interference devices. For the films deposited on Al2O3, x-ray diffraction patterns indicate a highly c axis-oriented crystal structure perpendicular to the substrate surface.