Chemical Vapor Deposition of Silicon Carbide Epitaxial Films and Their Defect Characterization

A chemical vapor deposition (CVD) system was designed and fabricated in our laboratory and SiC homo-epitaxial layers were grown in the CVD process using silicon tetrachloride and propane precursors with hydrogen as a carrier gas. The temperature field was generated using numerical modeling. Gas flow rates, temperature field, and the gradients are found to influence the growth rates of the epitaxial layers. Growth rates were found to increase as the temperature increased at high carrier gas flow rate, while at lower carrier gas flow rate, growth rates were observed to decrease as the temperature increased. Based on the equilibrium model, “thermodynamically controlled growth” accounts for the growth rate reduction. The grown epitaxial layers were characterized using various techniques. Reduction in the threading screw dislocation (SD) density in the epilayers was observed. Suitable models were developed for explaining the reduction in the SD density as well as the conversion of basal plane dislocations (BPDs) into threading edge dislocations (TEDs).     

p-Si TFT栅绝缘层用SiN薄膜的研究

以NH3和SiH4为反应源气体,采用射频等离子体增强化学气相沉积(RF-PECVD)法在多晶硅(p-Si)衬底上沉积了一系列SiN薄膜,并利用椭圆偏振测厚仪、超高电阻-微电流计、C-V测试仪对所沉积的薄膜作了相关性能测试.系统分析了沉积温度和射频功率对SiN薄膜的相对介电常数、电学性能及界面特性的影响.分析表明,沉积温度和射频功率主要是通过影响SiN薄膜中的Si/N比影响薄膜的性能,在制备高质量的p-Si TFT栅绝缘层用SiN薄膜方面具有重要的参考价值.     

户外柜式通讯电源系统设计的自然环境因素分析

列举了影响户外柜式通讯电源系统的自然环境因素，并论述了各个因素对产品可靠性的影响机理，提出了产品设计时需要考虑的要点。为该类产品的环境适应性设计和可靠性设计提供了必要的参考，对其它户外电子设备也有借鉴意义。     

中国医学物理学的过去、现在与未来

医学物理（medical physics，MP）是把物理学的原理和方法应用于人类疾病的预防、诊断、治疗和保健的一门交叉学科，是物理学与医学实践相结合的一门独立的分支学科．它是研究人类疾病诊、治过程中的物理现象，并用物理方法表达这种现象．医学物理包括放射肿瘤物理（rsdiation oncdogy physics，ROP）、医学影像物理（medical imaong physics，MIP）、核医学物理（nuclear medicine physics，NMP），其他非电离辐射如核磁、超声、微波、射频、激光等物理因子在医学中的应用，和保健物理（heath physics，HP）等分支内容．医学物理学和生物医学工程学（biomedical engineefing，BME）是一对栾生的兄弟学科，分别从物理学的角度（前者）和工程学的角度（后者）研究人类疾病诊断、治疗及健康保健过程中的生命现象和采取相应的物理措施和工程手段。医学物理学与物理医学（physical medicine，PM）是完全两个不同的概念，前者是物理学的分支，后者是医学的分支．自上世纪60年代以来，中国医学物理学有了很大的进展，推动了中国现代放射肿瘤学、核医学和医学影像学的发展；成立了自己的学术组织，并成为国际医学物理组织（IOMP）的成员国组织．随着中国逐步奔入小康社会，为适应人民大众对健康的需求和现代化医院发展的需要，中国医学物理应该加快发展．     

高考物理实验试题设计趋势分析

对近年各地区高考物理实验试题命题改革趋势进行了分析,以具体类型题为例,对2007年高考物理实验试题设计趋势作以预测.     

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采用TORAY代码对HL-2A装置ECRH系统在单零点偏滤器位形下的波与等离子体相互作用的情况进行了模拟计算,研究了等离子体和波参数对ECRH波迹和功率沉积以及电流驱动的影响。根据数值计算结果,HL-2A装置ECRH系统在等离子体线平均密度为3.0×1013cm-3、中心电子温度为1.19keV的情况下,以O模作为入射波垂直入射时的单次吸收系数为99.3%,最大电流驱动效率为0.005×1020A.W-1.m-2。     

Adaptive modeling, adaptive data assimilation and adaptive sampling

For efficient progress, model properties and measurement needs can adapt to oceanic events and interactions as they occur. The combination of models and data via data assimilation can also be adaptive. These adaptive concepts are discussed and exemplified within the context of comprehensive real-time ocean observing and prediction systems. Novel adaptive modeling approaches based on simplified maximum likelihood principles are developed and applied to physical and physical–biogeochemical dynamics. In the regional examples shown, they allow the joint calibration of parameter values and model structures. Adaptable components of the Error Subspace Statistical Estimation (ESSE) system are reviewed and illustrated. Results indicate that error estimates, ensemble sizes, error subspace ranks, covariance tapering parameters and stochastic error models can be calibrated by such quantitative adaptation. New adaptive sampling approaches and schemes are outlined. Illustrations suggest that these adaptive schemes can be used in real time with the potential for most efficient sampling.     

Implications of the nuclear EMC effect

The discovery more than twenty years ago, by the EMC Collaboration, that the deep-inelastic-scattering DIS structure functions are influenced by the nuclear environment stunned the nuclear physics community and brought quarks and gluons into the field with great impact. A great length of time has passed, but despite a semi-infinite number of papers on the subject, there is no explanation that is universally accepted. Many models (related in one way or another to QCD) have been successful in reproducing data for deep inelastic scattering on nuclear targets, but fewer have described both the DIS and nuclear Drell-Yan experiments. Although there are some positive indications, no model has been used to predict correctly and unambiguously new independent phenomena. We review the history and discuss the best experimental prospects for future discovery.     

Statistical equilibrium in simple exchange games I

This erratum corrects a mistake in reference [E. Scalas, U. Garibaldi, S. Donadio, Eur. Phys. J. B 53, 267 (2006)]. In that paper, we needed an aperiodic version of the BDY game, but, in formula (1), we incorrectly presented a periodic transition matrix of period 2 in the special case of g = 2 agents. Here, we present the right aperiodic version.     

Absorption spectrum of a resonantly driven degenerate V-type atom with a dc-field coupling between excited states

We study the absorption spectra of a degenerate V-type atom, where a resonant driving field and a probe field drive different branches of transitions and a dc field is applied to drive the transition between two excited states. The effects of vacuum induced coherence (VIC) on the absorption spectra are investigated. It is demonstrated that in some special cases the VIC can lead to the depression of absorption and narrow resonance. The origin of these features are discussed. When the pump field and the dc field have the same intensity, it is interesting to find that the whole absorption spectrum comes mainly from the absorptions induced by the interferences among different transitions between dressed states.