Depth profile study on Raman spectra of high-energy-electron-irradiated hydrogenated amorphous silicon films

According to the different penetration depths for the incident lights of 472 nm and 532 nm in hydrogenated amorphous silicon (a-Si:H) thin films, the depth profile study on Raman spectra of a-Si:H films was carried out. The network ordering evolution in the near surface and interior region of the unirradiated and irradiated a-Si:H films was investigated. The results show that there is a structural improvement in the short- and intermediate-range order towards the surface of the unirradiated a-Si:H films. The amorphous silicon network in the near and interior region becomes more disordered on the short- and intermediate-range scales after being irradiated with high energy electrons. However, the surface of the irradiated films becomes more disordered in comparison with their interior region, indicating that the created defects caused by electron irradiation are concentrated in the near surface of the irradiated films. Annealing eliminates the irradiation effects on a-Si:H thin films and the structural order of the irradiated films is similar to that of the unirradiated ones after being annealed. There exists a structural improvement in the short- and intermediate-range order towards the surface of the irradiated a-Si:H films after being annealed. Supported by the National Outstanding Young Scientists Foundation of China (Grant No. 60425101) and the Science Foundation of General Armament Department of China (Grant No. 06DZ02)     

隔热结构中非晶硅的释H_2机理与工艺研究

对采用等离子增强化学气相淀积法(PECVD)制备的氢化非晶硅(a-Si:H)薄膜进行了退火释H2实验,并对三文治结构膜层生长工艺作了改进。红外透射光谱表明:提高退火温度及增加退火时间会造成Si-H键断裂释放H2影响器件结构完整;不断改进设计,最终采用精简有效热敏面积及将退火工艺提前以扩张释H2渠道的方案,获得600℃退火后仍保持完整三文治结构的优化设计流程。     

C60膜的波导拉曼散射效应

本文首次报导粗糙玻璃表面上Ｃ６０薄膜的波导拉曼散射，相对于未粗化玻璃表现情形，在同样实验条件下，观察到大的增强，文中基于薄膜中波导模的同步激发解释了这一效应。     

Optical and electrical properties of hydrogenated silicon oxide thin films deposited by PECVD

In this work, n-type amorphous silicon oxide thin films were deposited by RF-PECVD method using a gas mixture of SiH4, CO2, H2, and PHy The deposition rate, refractive index, band gap, crystalline volume fraction, and conductivity of the silicon oxide thin films were determined and analyzed. The film with refractive index of 1.99, band gap of 2.6eV and conductivity of 10-7 S/cm was obtained, which was suitable for the intermediate reflector layer.     

High rate deposition of microcrystalline silicon films by high-pressure radio frequency plasma enhanced chemical vapor deposition (PECVD)

Hydrogenated microcrystalline silicon (μc-Si:H) thin films were prepared by high-pressure radio-frequency (13.56 MHz) plasma enhanced chemical vapor deposition (rf-PECVD) with a screened plasma. The deposition rate and crystallinity varying with the deposition pressure, rf power, hydrogen dilution ratio and electrodes distance were systematically studied. By optimizing the deposition parameters the device quality μc-Si:H films have been achieved with a high deposition rate of 7.8 ?/s at a high pressure. The V _oc of 560 mV and the FF of 0.70 have been achieved for a single-junction μc-Si:H p-i-n solar cell at a deposition rate of 7.8 ?/s. Supported by the National Natural Science Foundation of China (Grant No. 50662003) and the State Development Program for Basic Research of China (Grant No. G2000028208)     

Structural evolution and electronic properties of phosphorus-doped hydrogenated amorphous silicon thin films deposited by PECVD

The relationship between structure and electronic properties of phosphorus-doped hydrogenated amorphous silicon(a-Si:H) thin films was investigated.Samples with different features were prepared by plasma enhanced chemical vapor deposition(PECVD) at various substrate temperatures.Raman spectroscopy and Fourier transform infrared(FTIR) spectroscopy were used to evaluate the structural evolution,meanwhile,electronic-spin resonance(ESR) and optical measurement were applied to explore the electronic properties of P-doped a-Si:H thin films.The results revealed that the changes in materials structure affect directly the electronic properties and the doping efficiency of dopant.     

退火对nc-Si镶嵌复合薄膜结构及发光特性的影响

采用减压化学气相沉积方法，依靠纯N2稀释的SiH4气体的热分解反应，在玻璃表面生长了纳米硅
镶嵌的复合薄膜.实验研究了退火前后薄膜样品的结晶状态和光致发光特性.结果表明，未退火样品的光致
发光特性随沉积温度升高反而减弱.当退火温度＞600℃时，晶化趋势明显；当退火温度＜600℃时，对晶
化的影响不显著，但提高退火温度或延长退火时间可以增加光致发光谱(PL)强度.通过HRTEM分析证实了薄
膜为纳米硅镶嵌复合的特殊结构.并通过Raman、PL、HRTEM的比较分析，认为在退火前后分别有两种不同
的发光机制起主导作用.     

非晶硅薄膜晶体管关态电流的物理模型

基于器件有源层内纵向电场变化模型,提出了背沟界面能带弯曲量与栅源电压的近似方程,并针对背沟电子传导机制建立器件反向亚阈电流模型;基于空穴的一维连续性方程,提出有源层内空穴逃逸率的物理模型,并针对前沟空穴传导机制建立器件泄漏电流模型．实验结果验证了所提关态电流物理模型的准确性,曲线拟合良好．     

低温高速率沉积非晶硅薄膜及太阳电池

采用射频等离子体增强化学气相沉积(RF-PECVD)技术,保持沉积温度在125℃制备非晶硅薄膜材料及太阳电池。在85 Pa的低压下以及400～667 Pa的高压下,改变Si H4浓度和辉光功率等沉积参数,对本征a-Si材料的性能进行优化。结果表明,在高压下,合适的Si H4浓度和压力功率比可以使a-Si材料的光电特性得到优化,并且薄膜的沉积速率得到一定程度的提高。采用低压低速和高压高速的沉积条件,在125℃的低温条件下制备出效率为6.7%的单结a-Si电池,高压下本征层a-Si材料的沉积速率由0.06～0.08 nm/s提高到0.17～0.19 nm/s。     

Synthesis of vertically aligned carbon nanotube arrays on silicon substrates

In 1991, Ijima first observed carbon nanotubes (CNTs) using a high-resolution transmission electron microscope[1]. CNTs represent a new material with unique struc-tural, electrical, mechanical, physical and chemical properties, and have received much attention from researchers worldwide. A significant amount of work has been done in the past decade to reveal the properties and synthesis of CNTs and great progress has been made. The focus of researches has transferred recently to the large-…     

Simple method to rapidly fabricate chain-like carbon nanotube films and its field emission properties

A simple process to fabricate chain-like carbon nanotube (COT) films by microwave plasma-enhanced chemical vapor deposition (MPCVD) was developed successfully. Prior to deposition, the Ti/Al2O3 substrates were ground with Fe-doped SiO2 powder. The nano-structure of the deposited films was analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The field electron emission characteristics of the chain-like carbon nanotube films were measured under the vacuum of 10-5 Pa. The low turn-on field of 0.80 V/μm and the emission current density of 8.5 mA/cm2 at the electric field of 3.0 Vμ/m are obtained. Based on the above results, chain-like carbon nanotube films probably have important applications in cold cathode materials and electrode materials.     

Effect of additives on the sintering of amorphous nano-sized silicon nitride powders

Amorphous nano-sized silicon nitride powders were sintered by liquid phase sintering. The influences of the additives of Y₂O₃ and Al₂O₃ prepared by two different ways, the polyacrylamide gel method and the precipitation method, were investigated. The grain sizes of the additives prepared by the first method were finer than those of prepared by the latter method. When sintered at the same temperature, 1700°C, the average grain size of the silicon nitride is 0.3 μm for the sample with the former additives, which is much finer than the one with the latter additives. The density of additives prepared by precipitation method is clearly lower than those of prepared by polyacrylamide gel method. Funded by the National Postdoctoral Foundation of China(No.20060400787)     

非、单晶硅太阳能电池组件比功率发电量比较

为测试非晶硅和单晶硅太阳能电池组件的实际发电能力,设计了由电子模拟负载和直流安时计组成的发电量测量装置,对两种太阳能电池组件的发电量进行实验测试比较.提出比功率发电量这一物理量,直观表达太阳能电池组件的发电性能.实验表明,在晴天直射强光和阴雨天弱散射光环境下,非晶硅太阳能电池板的比功率发电量均大于单晶硅.     

金刚石薄膜的研究概况

介绍了金刚石薄膜的制备方法及应用前景,简要分析了金刚石薄膜未来的研究重点.     

线形同轴耦合微波等离子体诊断及硅薄膜制备

开发了一种新型线形同轴耦合大面积微波等离子体源,针对该新型等离子体源放电空间等离子密度及分布的不明确性,利用朗缪尔单探针法研究了不同放电参数下该等离子体源等离子体密度及空间分布情况。以微波功率,氢氩总流量(氢氩流量比为3∶1)和距石英管的距离Z为3个因素设计正交实验探究了宏观放电参量对等离子体参数的影响。测试结果表明该型等离子体源的电子密度均在1010cm-3以上。其次,诊断了在距石英管Z为14 cm处,等离子体参数沿空间水平的分布情况,探究薄膜的最佳沉积区域。最后,根据等离子诊断情况进行硅薄膜的沉积,由XRD结果表明薄膜为多晶结构,拉曼光谱显示沉积硅薄膜晶化率均在92%以上,沉积速率在8 nm/min。     

Fabrication and its characteristics of low-temperature polycrystalline silicon thin films

In order to reduce the cost of solar cells or flat-panel display, it is very important to synthesis poly-crystalline silicon films on low cost substrate such as glass at low temperature. In this work, electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition (PECVD) system was successfully applied to synthesize poly-Si thin-film on common glass substrate using H2 as the plasma source and SiH4 (Ar:SiH4=19:1) as the precursor gas at low temperature. Since the multicusp cav- ity-coupling ECR plasma source was adopted to provide active precursors, the growth temperature decreased to lower than 200℃. In the plasma, the electron temperatures kTe are ~2―3 eV and the ion temperatures kTi≤1 eV. This leads to non-remarkable ion impacts during the film deposition. The characteristic of poly-Si films was investigated. It was shown that the crystalline fraction Xc of the films can be up to 90% even deposit at room temperature, and the film was (220) preferably oriented. The growth behaviors of the film between the interface of glass and Si films were also discussed in detail.     

Adhesive strength of CVD diamond thin films quantitatively measured by means of the bulge and blister test

Large advancement has been made in understanding the nucleation and growth of chemical vapor deposition (CVD) diamond, but the adhesion of CVD diamond to substrates is poor and there is no good method for quantitative evaluation of the adhesive strength. The blister test is a potentially powerful tool for characterizing the mechanical properties of diamond films. In this test, pressure was applied on a thin membrane and the out-of-plane deflection of the membrane center was measured. The Young’s modulus, residual stress, and adhesive strength were simultaneously determined using the load-deflection behavior of a membrane. The free-standing window sample of diamond thin films was fabricated by means of photolithography and anisotropic wet etching. The research indicates that the adhesive strength of diamond thin films is 4.28±0.37 J/m2. This method uses a simple apparatus, and the fabrication of samples is very easy.     

基片预处理对CVD金刚石薄膜形核的影响

微波辅助等离子体化学气相沉积法是目前低压气相合成金刚石薄膜方法中应用最普遍、工艺最成熟的方法,形核是CVD金刚石沉积的第一步．利用微波辅助等离子体化学气相沉积装置,研究了硅基片预处理方式对金刚石薄膜形核密度的影响．在工作气压为5-8kPa,微波功率为2500—5000W,甲烷流量为4-8cm^3／min,氢气流量为200em3／min,沉积温度为500℃-850℃的条件下,在单晶Si基片上沉积金刚石薄膜．通过扫描电子显微镜形貌观察表明,基片预处理能够显著提高金刚石形核密度,同时用拉曼光谱表征了金刚石薄膜的质量,     

辅助气体对分阶段制备金刚石膜的影响

采用形核 甲烷/氢气生长-辅助气体/甲烷/氢气生长的新工艺,在镜面抛光的单晶硅片上制备了金刚石膜,并用扫描电子显微镜和激光拉曼光谱等测试方法对薄膜的表面形貌和质量性能进行了表征;研究了添加辅助气体对已有金刚石晶型生长的影响.结果表明:以甲烷/氢气为气源时,金刚石膜生长率一般为1.8 μm/h,当分别加入氧气、二氧化碳、氮气时,其生长率都有所提高,其中加入二氧化碳时,其生长率是甲烷/氢气为气源的3倍多,但是加入氩气时,其生长率下降;通过新工艺,在加入氮气或氩气时,第一生长阶段为微米,而第二生长阶段为纳米尺寸,最后制备出具有微/纳米双层复合金刚石膜.     

The growth of carbon nanotube with chemical vapor deposition under different process parameters

Whether the active catalytic species are in a liquid,solid phase,surface premelting or surface processes during CNT or other nanowire growth are controversial.In order to explore the mechanism for catalytically grown carbon nanotube (CNT),the mechanism for CNT grown under different temperatures was proposed tentatively.With ethanol chemical vapor deposition (CVD),carbon n.anotubes (CNTs) were synthesized controllably on Si substrates using cobalt (Co) as a catalyst.The effects of the Co particle size,growth...