PREPARATION AND TRANSPORT PROPERTIES OF SUPERCONDUCTING BPSCCO THIN FILMS

The perparation of BPSCCO thin films by DC magnetron sputtering is reported. We prepared high mass density target of Bi2Pb0.6Sr2Ca2Cu3O10. By varying the substrate temperature, ratio of Ar and O2 pressure as well as the distance between target and substrate, we were able to optimize the process for c -axis oriented thin films of Bi-Compounds. As deposited films show Tcon at about 95K. These films were examined using the electron-probe microanalysic (EMPA) and X-ray diffraction (XRD). The results of electrical resistivity and Hall effect have been discussed. Hall voltage in the mixed state is strongly nonlinear, showing certain features that suggests that vortex depinning mechanism plays an important role in the Hall effect behaviour.     

DIAGNOSTICS OF ARC PLASMA BY MOIRE DEFLECTOMETRY

This paper presents a new method to diagnose the welding arc temperaturefield on the basis of plasma physics,Talbot effect and Moire techniques.This method hasadvantages of immunity to mechanical shock and vibration,tunable sensitivity and conside-rable simple optical system.     

Fabrication of high growth rate solar-cell-quality μc-Si:H thin films by VHF-PECVD

Several series of Si:H films were fabricated by the very high frequency plasma enhanced chemical vapour deposition (VHF-PECVD) at different substrate temperatures (T_s) and silane concentration (SC=[SiH_4]/[SiH_4+H_2]%). The results of Raman spectroscopy showed structural evolution of the Si:H films with the variation of T_s and SC. The results of x-ray diffraction (XRD) measurements indicated that T_s also influences the crystal orientation of the Si:H films. The modulation effect of T_s on crystalline volume fraction (X_c) is more evident for the high SC, which shows different trend compared to low SC. In addition, the growth rate of the films also showed a regular change with the variation of SC and T_s. Different samples in the series showed a similar increase in dark conductivity and a decrease in photosensitivity with increasing T_s and decreasing SC. Device-quality microcrystalline silicon materials were deposited at a high growth rate, characterized by relatively low dark conductivity and relatively high photosensitivity in a certain crystalline range. The microcrystalline silicon solar cell with a conversion efficiency of 4.55% has been prepared by VHF-PECVD.     

Influence of p-layer on the performance of n-i-p μc-Si:H thin film solar cells

The high pressure radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) process was adopted to prepare the n-i-p microcrystalline silicon solar cells,the influence of p-type layers on the performance of the solar cells was investigated,and the optimum p layer suited to the n-i-p microcrystalline silicon solar cells was obtained.The experimental results demonstrate that the performance of the solar cells can be highly affected by the structural and optical properties of the p-layers,and the performance of solar cells can be greatly improved by optimizing p layers.We have achieved an initial active-area efficiency of 8.17% (V oc =0.49 V,J sc =24.9 mA/cm 2 ,FF=67%) for the μc-Si:H single-junction n-i-p solar cells and an initial active-area efficiency of 10.93% (V oc =1.31 V,J sc =13.09 mA/cm 2 ,FF=64%) for the a-Si:H/μc-Si:H tandem n-i-p solar cells.     

EFFECT OF THE INERTIAL TERM ON THE CDW TRANSPORT PROPERTIES Ⅱ. NUMERICAL SOLUTIONS

Using the classical particle model with an inertial term, we have numerically analyzed the effect on the nonlinear transport properties of the CDW system,e.g., the hysteresis effect, the interference phenomena between the dc and ac applied fields. Our calculations demonstrate the importance of the inertial effect on the sliding CDW states. Some results are probably new, and important to experimental observations; for example, the zero step width region exists for the 1/2 subharmonic step in its variation with amplitude of the ac driving field.     

1.5μm LUMINESCENCE CHARACTERISTIC OF ERBIUM IN B, P DOPED a-SiO:H FILMS

Hydrogenated amorphous silicon films co-doped with oxygen (O), boron (B) and phosphorus (P) were fabricated using PECVD technique. The erbium (Er) implanted samples were annealed in a N₂ ambient by rapid thermal annealing. Strong photoluminescence (PL) spectra of these samples were observed at room temperature. The incorporation of O, B and P could not only enhance the PL intensity but also the thermal annealing temperature of the strongest PL intensity. It seems that the incorporation of B or P can decrease the grain boundary potential barriers thus leading to an easier movement of carriers and a stronger PL intensity. Temperature dependence of PL indicated the thermal quenching of Er-doped hydrogenated amorphous silicon is very weak.     

POTENTIAL SAFE TERMINATION BY LASER ABLATION OF HIGH Z IMPURITY IN THE HL-1M TOKAMAK

A preliminary experiment for triggering a plasma current quench by high Z impurities has been performed on the HL-1 M tokamak. Using injection of impurity with the higher charge of the nuclei allows us to increase the radiation cooling. It can be a simple and potential approach for decreasing significantly the plasma thermal energy before a disruption and for safe termination of the plasma.     

DETECTION OF A TIMING SIGNAL IN NOISE PRODUCED BY A HIGH SPEED MOVING BODY ENTERING INTO WATER

A detailed analysis of the characteristics of entry-water noise and hydrodynamic noise producedby a high speed body moving into water is given. The properties of the received timing signal which is emitted form a sound source carried by themoving body are discussed.General principles of choosing the parameters,particularly the power ofthe sound signal source and the threshold level of the receiver for detecting the received timing signalin the noise background mainly caused by these two kinds of noise mentioned above are discussed indetail.Finally,under assumed conditions numerical values of the two parameters are estimated.Theresults are supported by experiments.     

ELECTRONIC AND OPTICAL PROPERTIES OF WURTZITE GaN:——A THEORETICAL APPROACH

The band structures of wurtzite GaN(α-GaN) are studied using the nearest and second-nearest neighbour semi-empirical tight-hinding method in sp³ s^* model. The calculated direct fundamental gap of α-GaN is 3.45 eV, which is in good agreement with the experimental data. The density of states and the imaginary pert of dielectric function (ε₂ (ω)) are evaluated to he in the regions - 10.0 - 12 eV and (1.0 - 10.0 eV, respectively. There are mainly three peaks at 6,4, 7,5, 8.4 eV, dominating the ε₂(ω) spectrum. The two components of the ε₂(ω) (i. e. ε_2xy(ω) and ε_2z(ω) ) are also calculated; and the real prat of dielectric function, reflectivity, absorption coefficient, and refractive index are all studied.     

电子回旋共振等离子体增强沉积氟化非晶碳薄膜的光学性质

用紫外可见光透射光谱(UV-VIS)并结合键结构的X射线光电子能谱(XPS)和红外谱(FTIR)分析,研究了电子回旋共振等离子体增强化学气相沉积法制备的氟化非晶碳薄膜的光吸收和光学带隙性质.在微波功率为140—700W、源气体CHF₃∶C₆H₆比例为1∶1—10∶1条件下沉积的薄膜,光学带隙在1.76—2.85eV之间.薄膜中氟的引入对吸收边和光学带隙产生较大的影响,吸收边随氟含量的提高而增大,光学带隙则主要取决于CF键的含量,是由于强电负 关键词： 氟化非晶碳薄膜 光吸收与光学带隙 电子回旋共振等离子体     

MICROSTRUCTURE OF SiOx:H FILMS PREPARED BY PLASMA ENHANCED CHEMICAL VAPOR DEPOSITION

The micro-Raman spectroscopy and infrared (IR) spectroscopy have been performed for the study of the microstructure of amorphous hydrogenated oxidized silicon (a-SiO_x:H) films prepared by Plasma Enhanced Chemical Vapor Deposition technique. It is found that a-SiO_x:H consists of two phases: an amorphous silicon-rich phase and an oxygen-rich phase mainly comprised of HSi-SiO₂ and HSi-O₃. The Raman scattering results exhibit that the frequency of TO-like mode of amorphous silicon red-shifts with decreasing size of silicon-rich region. This is related to the quantum confinement effects, similar to the nanocrystalline silicon.     

用脉冲多弧离子放电技术镀制类金刚石薄膜及其化学结构和物理特性

利用脉冲多弧离子镀膜技术，以石墨为阴极镀制的无定形碳膜，其化学结构可用Raman光谱仪进行。薄膜的硬度和电阻率物理特性，可用常规方法测量。     

高电导a-Si:H:Y合金的电输运特性

本文报道由rf溅射技术将稀土元素Y掺入非晶硅,当掺Y浓度为20％左右时,获得了室温直流电导率为2×10¹Ω^-1·cm^-1的a-Si:H:Y合金膜。测量表明该合金膜是n型。变温电导测量指出,在测量温度范围内lnσ与l/T的关系可拟合于两条直线。对于衬底温度为260℃,290℃和330℃溅射的合金膜,其转折点分别出现在～70℃,～75℃和～90℃。这表明a-Si:H:Y合金膜存在两种电传导机制:在室温附近电子在Y施主杂质带内跳跃传导,在高温情况下电子在导带延展态内传导。并且得到Y施主杂质带中心处于导带E_c以下0.06—0.07eV。 关键词：     

透光导电ITO膜的制备及其光电特性的研究

采用溶胶-凝胶方法制备ITO膜,并从制备工艺上研究了各种因素对ITO膜光电特性的影响.最后制出的ITO膜厚度约为50nm,在可见光区平均透射比达97%,最高达99.55%,电阻率在2.0Ω·cm左右,最低达到0.31Ω·cm.     

电子回旋共振等离子体增强化学气相沉积a-CFx薄膜的化学键结构

使用CHF₃和C₆H₆混合气体做气源,在一个电子回旋共振等离子体增强化学气相沉积装置中制备了氟化非晶碳(a-CF_x)薄膜.利用发射光谱研究了等离子体中形成的各种碳氟、碳氢基团随放电宏观参量的变化规律,对薄膜做了傅里叶变换红外光谱和X射线光电子能谱分析,证实等离子体中的CF₂,CF和CH基团是控制薄膜生长、碳/氟成分比和化学键结构的主要前驱物 关键词： 氟化非晶碳薄膜 电子回旋共振等离子体     

电子回旋共振等离子体增强化学气相沉积a-CF_x薄膜的化学键结构

使用CHF3 和C6H6混合气体做气源 ,在一个电子回旋共振等离子体增强化学气相沉积装置中制备了氟化非晶碳 (a CFx)薄膜 .利用发射光谱研究了等离子体中形成的各种碳 氟、碳 氢基团随放电宏观参量的变化规律 ,对薄膜做了傅里叶变换红外光谱和X射线光电子能谱分析 ,证实等离子体中的CF2 ,CF和CH基团是控制薄膜生长、碳 /氟成分比和化学键结构的主要前驱物     

尿素夹层二硫化钛化合物的合成及其热、电输运性质研究(英文)

我们成功的制备出了含不同成分尿素的夹层化合物(NH2CONH2)xTiS2,并研究了它们在低温(5～310K)下的热、电输运性质.夹层后晶格常数、热、电输运行为的变化也证实了尿素分子成功的夹层到TiS2的范德华尔斯层间.研究结果表明:尿素分子的夹层成功的降低了材料的热导率,特别是在浓度为12.5mmol/L尿素的苯溶液中合成的样品的热导率大约1.5Wm-1 K-1(仅为纯TiS2的50%),而且尿素分子的夹层使得材料在低温下的导电行为从金属性转变为半导体性.     

湿化学法合成Co掺杂ZnO薄膜的微结构及发光特性

采用湿化学法在ITO玻璃衬底上制备了纳米棒结构的Co掺杂ZnO薄膜.XRD结果表明Co掺杂的ZnO没有出现杂相.SEM结果表明掺杂样品是由ZnO纳米棒团簇结构组成,且团簇的密度随着Co掺杂浓度的增大而增大.光致发光光谱表明Co掺杂导致薄膜的带隙发生红移.     

液体混合物导热率的测量及导热率数据的理论预测

液体混合物导热率的测量及导热率数据的理论预测童景山，唐建，高光华，梁燕波（清华大学化学工程系北京１０００８４）关键词导热率，液体混合物，测量仪，预计法１测量原理与测量装置本文报道的这种仪器，它不仅可用来测量有机化合物的液相导热率，而且也可测量高导热率...