PZT铁电薄膜Sol-Gel技术制备和电性能研究

以乙酸铅(Pb(CH₃COO)₂·3H₂O)、钛酸四丁酯(Ti(OC₄H₉)₄)、硝酸锆(Zr(NO₃)₄·5H₂O)替代锆醇盐为原料,通过在Pt/Ti/SiO₂/si基片与PZT薄膜之间引入PT种子层,采用改进的sol-gel工艺制备出无裂纹,致密性好,晶粒尺寸小且分布均匀的单一钙钛矿结构的Pb(Zr_0.53Ti_0.47)O₃铁电薄膜.实验结果表明,具有PT种子层的PZT铁电薄膜电性能较好.经600℃热处理的具有PT种子层的PZT薄膜,在1kHz测试频率下,其剩余极化强度和矫顽场分别为20μC/cm²和59kV/cm,介电常数和介电损耗分别为385和0.030.     

微波法快速制备高稳定性纳米羟基磷灰石

以Ca(NO₃)₂·4H₂O和(NH₄)₂HPO₄为前驱物,采用微波法快速制备出由30nm左右的小颗粒自组装成短捧状的纳米羟基磷灰石粉末,并分析了其自组装的原因。采用XRD,IR,TG-DTA,TEM对其进行了测试,并探讨了不同的微波辐射时间、微波功率、低温煅烧对羟基磷灰石粉体的热稳定性的影响。研究结果证实:随微波辐射反应溶液时间的延长,HAP的热稳定性提高,微波辐射反应溶液的最佳时间是1h;随微波功率的升高,HAP的热稳定性提高;微波辐射反应溶液时间为1h、微波功率为700W、500℃保温HAP3h,HAP在1200℃稳定存在。     

化学气相沉积碳化硅的热力学分析

根据吉布斯自由能最小原理, 采用FACTSAGE计算软件, 重点对MTS/H₂体系化学气相沉积碳化硅进行了均相平衡计算,评价了体系中主要化合物对沉积碳化硅的作用. 结果表明,低温和高压下, SiCl₄和CH₄的含量最多, 不饱和物质和自由基的含量非常少, 温度的升高和压力的下降可显著提高不饱和物质和自由基的浓度; 高温和低压下, SiCl₂和C₂H₂可能是形成碳和硅的主要先驱体, 其它稳定物质如碳氢化合物、有机硅化合物和硅烷等由于浓度太小和表面反应粘结系数低, 对碳化硅的沉积可以不予考虑; 体系中几乎没有含Si--C和Si--Si键的物质, 说明碳化硅是经过碳和硅独立形成, 二者的相对速率决定了碳硅比.     

MnOOH纳米棒的低温水热合成

以KMnO₄ 和N₄ (CH₂)₆为主要原料, 在130℃反应16h, 水热法制备了MnOOH纳米棒, 并利用X射线粉末衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段对产物进行了表征. 探索了KMnO₄ 和N₄ (CH₂)₆间的摩尔比以及反应温度对合成产物的影响. 实验结果表明:产物为具有单斜结构的MnOOH纯相, 形貌为棒状, 呈现单晶特性.     

WC-Co硬质合金基体上高附着力金刚石薄膜的制备

采用微波等离子体化学气相沉积(CVD)法在WC-Co硬质合金基体上制备金刚石膜, 研究了TiN_x中间层的引入对金刚石薄膜质量及其附着性能的影响. 结果表明, 在酸浸蚀脱钴处理的基础上, 通过预沉积氮含量呈梯度变化的TiN_x中间过渡层, 可在硬质合金基体上制备出高质量的金刚石薄膜; 压痕法测试其临界载荷达1000N.     

ZrO2对NiO/CeO2/γ-Al2O3复合催化剂结构的影响

以Ni(NO₃)_2·6H₂O、Al(NO₃)₃·9H₂O、ZrOCl_2·8H₂O和Ce(NO₃)_3·6H₂O为原料,采用共沉淀法分别制备了NiO/CeO₂/γ-Al₂O₃和NiO/CeO₂-ZrO₂/Al₂O₃催化剂.通过X射线衍射（XRD）、透射电子显微镜（TEM）和近边X射线吸收精细结构（XANES）等方法对催化剂的组成结构进行表征.结果表明,煅烧温度高于600℃时,NiO/CeO₂/γ-Al₂O₃催化剂中的NiO与γ-Al₂O₃载体发生作用,形成NiAl₂O₄尖晶石;而NiO/CeO₂-ZrO₂/Al₂O₃催化剂中,NiO能够稳定存在,没有NiAl₂O₄尖晶石生成,且Al₂O₃与CeO₂和ZrO₂作用形成一种新的Zr_0.30Ce_0.45Al_0.25O_1.87固溶体.     

高透光率Nd:YAG透明陶瓷的制备与性能研究

以Y(NO₃)₃·6H₂O、Al (NO₃)₃·9H₂O、(NH₄)₂SO₄和Nd(NO₃)₃为原料, NH₄HCO₃为沉淀剂, 以TEOS作为添加剂, 采用共沉淀法制备出Nd:YAG前驱体粉体; 前驱体经过1200℃煅烧5h后, 得到分散性好, 颗粒近似球型、纯YAG立方相的Nd:YAG纳米粉体, 其平均粒径约为100nm. 煅烧后的粉体压制成素坯, 在1700～1800℃煅烧10h, 可获得透光性良好的Nd:YAG激光透明陶瓷, YAG晶粒的平均尺寸为15μm, 晶界处和晶粒内没有杂质、气孔存在, 无散射中心. 1.5mm厚的样品在近红外波长为1064nm处透过率为83.5%, 基本接近于透明Nd:YAG晶体的理论值.     

热丝CVD生长SiCN薄膜的研究

在HFCVD系统中采用SiH₄/CH₄/H₂/N₂混合气体成功的制备了SiCN薄膜.SEM照片显示制备的SiCN薄膜由棒状结构构成,而在HRTEM下发现这些棒状结构是由生长在无定型SiCN基体当中的纳米晶粒组成的.进一步的SAED和XRD分析说明SiCN纳米晶粒具有类似于α-Si₃N₄的结构.XPS和FTIR分析表明薄膜中含有Si、C、N和O几种元素以及C=N、Si-N和C-N等共价键,但是并没有观察到C-Si的存在.由实验得出结论,SiCN晶体的生长包括两个步骤:α-Si₃N₄团簇的生长和C取代其中Si的过程.     

四方相BaTiO3薄膜的自组装制备与表征

以(NH₄)₂TiF₆、 Ba(NO₃)₂ 和H₃BO₃为主要原料, 采用自组装单层膜(SAMs)技术, 以三氯十八烷基硅烷(octadecyl-trichloro-silane, OTS)为模版, 在玻璃基片上制备了四方相钛酸钡晶态薄膜. 改性基板的亲水性测定与原子力显微镜（AFM）测试表明, 紫外光照射使基板由疏水转变为亲水, 能够对OTS-SAM起到修饰作用. 金相显微镜观察结果显示,OTS单分子膜指导沉积的薄膜样品表面均匀, 表明OTS SAM对钛酸钡薄膜的沉积具有诱导作用; X射线衍射（XRD）与扫描电镜（SEM）表征显示, 空气中600℃下保温2h实现了薄膜由非晶态向四方相BaTiO₃晶态薄膜的转化过程, 制备的钛酸钡薄膜在基板表面呈纳米线状生长, 线长约在500～1000nm之间, 相互连接的晶粒大小约为100nm. 文章同时对自组装单层膜和钛酸钡薄膜的形成机理进行了探讨.     

Si过渡层对梯度影响类金刚石薄膜结合力的影响研究

实验利用双放电腔微波-ECR等离子体源设备,采用复合PVD（physical vapor deposition）和PECVD（plasma enhanced chemical vapor deposition）的方法, 先后在NiTi基体上沉积Si和Si/α-C∶H过渡层,然后制备类金刚石薄膜.Raman光谱和透射电镜表明制备的梯度薄膜是典型的类金刚石薄膜,划痕的测试结果表明, Si过渡层沉积时间影响着梯度类金刚石薄膜与NiTi合金基体之间的结合强度,当沉积时间在60min左右时可获得具有最好结合强度的梯度薄膜,而超过或低于这个时间值会导致膜基结合强度降低.     

Homogeneous nanocrystalline cubic silicon carbide films prepared by inductively coupled plasma chemical vapor deposition

Silicon carbide films with different carbon concentrations x(C) have been synthesized by inductively coupled plasma chemical vapor deposition from a SiH(4)/CH(4)/H(2) gas mixture at a low substrate temperature of 500?°C. The characteristics of the films were studied by x-ray photoelectron spectroscopy, x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared absorption spectroscopy, and Raman spectroscopy. Our experimental results show that, at x(C) = 49?at.%, the film is made up of homogeneous nanocrystalline cubic silicon carbide without any phase of silicon, graphite, or diamond crystallites/clusters. The average size of SiC crystallites is approximately 6?nm. At a lower value of x(C), polycrystalline silicon and amorphous silicon carbide coexist in the films. At a higher value of x(C), amorphous carbon and silicon carbide coexist in the films.     

Stress and phase purity analyses of diamond films deposited through laser-assisted combustion synthesis

Diamond films were deposited on silicon and tungsten carbide substrates in open air through laser-assisted combustion synthesis. Laser-induced resonant excitation of ethylene molecules was achieved in the combustion process to promote diamond growth rate. In addition to microstructure study by scanning electron microscopy, Raman spectroscopy was used to analyze the phase purity and residual stress of the diamond films. High-purity diamond films were obtained through laser-assisted combustion synthesis. The levels of residual stress were in agreement with corresponding thermal expansion coefficients of diamond, silicon, and tungsten carbide. Diamond-film purity increases while residual stress decreases with an increasing film thickness. Diamond films deposited on silicon substrates exhibit higher purity and lower residual stress than those deposited on tungsten carbide substrates.     

Adhesion Enhancement of Diamond Films on Various Substrates by Carbide Interlayer

Diamond films were prepared on various substrates by a combustion flame technique using an oxyacetylene torch. During the deposition, a carbide interlayer was formed between the surface of the substrate and deposited diamond. The hard interlayers were seen on the molybdenum, tungsten as well as silicon substrates. The adhesion of diamond on the molybdenum substrate was improved with increase in the hardness of the carbide layer. This result strongly supports the premise that the carbide interlayer and/or carbon diffused layer enhances the adhesion of diamond to substrates.     

无支撑优质金刚石膜研制中的相关问题探讨

无支撑优质金刚石膜在微波真空器件和光学器件中的广泛应用,有赖于制备成本的下降和工艺的完善。结合微波等离子体化学气相沉积(MPCVD)金刚石膜的工艺研究结果,本文就沉积速率、晶面取向以及内应力的相关问题进行了初步探讨。对于给定的设备,沉积速率与多种因素有关,包括膜的质量、膜厚均匀性和有效沉积面积、以及形核的密度。在通常情况下,金刚石膜呈(111)择优取向,而样品位置下移5mm后,观察到(100)取向。对内应力的初步研究表明,CH4/H2比例较低(1.5)时,金刚石膜的内应力趋向于压应力,而(100)取向的出现则有助于使内应力降到最低。     

In Situ Thermocouples in Macro-Components Fabricated Using SALD and SALDVI Techniques. I. Thermochemical Modeling

To fabricate macro-structural SiC components containing an In Situ SiC/C thermocouple using an integrated SALD and SALDVI technique, thermodynamic analyses on the involved reactant gases have been performed with the CET89 code based on the minimization of the system free energy. The gaseous precursors considered include tetramethylsilane (TMS) and methyltrichlorosilane (MTS) for the deposition of silicon carbide, and methane, ethylene and acetylene for the deposition of carbon. Reactions between disilane and acetylene and between TMS and ammonia have also been thermodynamically calculated for the deposition of silicon carbide and silicon nitride (for use as an insulation layer between the thermocouple and the matrix), respectively. Based on these analyses, four characteristic temperature zones have been defined for the decomposition of silicon carbide from TMS. A silicon nitride deposition map has been built for the TMS and ammonia system. The deposition temperature range of silicon nitride is found to increase with the total pressure of TMS plus ammonia and the addition of hydrogen, and be affected by the ratio of TMS to ammonia. The addition of hydrogen also introduces a stable silicon carbide and silicon nitride mixture zone that otherwise does not exist. The co-deposition of graphite with silicon carbide and silicon nitride is found in the TMS-containing systems at certain conditions. However, the threshold temperature at which graphite co-deposition occurs can be increased by the addition of hydrogen, thereby eliminating or reducing the graphite co-deposition. Based on these thermodynamic analyses, the gaseous precursors for the deposition of silicon carbide, silicon nitride and carbon have been selected for further experimental evaluation, the result of which is reported in part II of this series.     

Adhesion improvement of diamond films on cemented carbides with copper implant layer

The deposition of diamond films on cemented carbides is strongly influenced by the catalytic effect of cobalt under typical deposition conditions. Decreasing the content of Co on the surface of the cemented carbide is often used for the diamond film deposition. But the leaching of Co from the WC-Co substrate leads to a mechanical weak surface, often causing poor adhesion. In this paper we adopt a copper implant layer to improve the mechanical properties of the Co leached substrate. The copper implant layer is prepared with vaporization. The diamond films are grown by microwave plasma chemical vapor deposition from the CH₄/H₂ gas mixture. The morphology and the quality of the diamond films have been characterized by scanning electron microscopy and Raman spectroscopy. A Rockwell apparatus has evaluated the adhesion of the diamond on the substrate. The results indicate that the diamond films have good adhesion to the cemented carbide substrate due to the recovery of the mechanical properties of the Co depleted substrate after the copper implantation and less graphite formation between the substrate and the diamond film.     

Surface nano-structured silicon carbide thin film produced using hot filament decomposition of ethylene at low temperature on silicon wafer

The structure and spectroscopic properties of nano-structured silicon carbide (SiC) thin films were studied for films obtained through deposition of decomposed ethylene (C₂H₄) on silicon wafers via hot filament chemical vapor deposition method at low temperature followed by annealing at various temperatures in the range 300-700 °C. The prepared films were analyzed with focus on the early deposition stage and the initial growth layers. The analysis of the film's physics and structural characteristics was performed with Fourier transform infrared spectroscopy and Raman spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, and X-ray diffraction. The conditions for forming thin layer of cubic SiC phase (3C-SiC) are found. X-ray diffraction and Raman spectroscopy confirmed the presence of 3C-SiC phase in the sample. The formation conditions and structure of intermediate SiC layer, which reduces the crystal lattice mismatch between Si and diamond, are essential for the alignment of diamond growth. This finding provides an easy way of forming SiC intermediate layer using the Si from the substrate.     

Structure of diamond polycrystalline films deposited on silicon substrates

The article presents results of structural studies of polycrystalline diamond thin films deposited by hot filament CVD on silicon substrates. The films were characterized using Scanning Electron Microscopy (SEM), Raman Spectroscopy (RS), Electron Backscattered Diffraction (EBSD), Energy Dispersive Spectroscopy (EDS) and Secondary Ion Mass Spectroscopy (SIMS). Both the EBSD patterns and Raman spectra confirm that the grains visible in the electron micrographs are diamond micro-crystallites. The residual stress in the films is found to be in the range between −4.29 GPa and −0.56 GPa depending on the sample thickness. No evidence of lonsdalite and graphite has been registered in the polycrystalline material of the investigated samples. Evidence of the existence of silicon carbide at the diamond/silicon interface is presented. It is also suggested that an amorphous carbonaceous film covers the silicon surface in the regions of holes in the thin diamond layers.     

fabrication of diamond membranes for MEMS using reactive ion etching of silicon

Polycrystalline diamond thin film has been grown on a silicon substrate using high pressure microwave plasma-assisted chemical vapor deposition from a gas mixture of methane and hydrogen at a substrate temperature of 950°C. A simple process flow has been developed to fabricate optically transparent polycrystalline synthetic diamond membranes/windows employing reactive ion etching (RIE) of a single crystal silicon substrate using an electron beam evaporated aluminum thin film mask pattern formed by photolithography. Scanning electron microscopy has been used to study the morphology of as-grown diamond thin films.     

Deposition of Diamond Films in a Closed Hot Filament CVD System

A closed system hot filament chemical vapor deposition (CVD) reactor has been used to deposit diamond films on silicon substrates. A fixed charge of hydrogen gas is fed into the deposition system until the desired deposition pressure level is reached. A solid graphite cylindrical rod held above the tungsten filament was the carbon source. System parameters for diamond film growth have been determined. The diamond structure of the films has been verified by x-ray diffraction (XRD). Morphology typical of CVD diamond films has been observed in scanning electron microscopy (SEM). The quality of the diamond films has been evaluated by micro-Raman spectroscopy.