Chlorinated precursor study in low temperature chemical vapor deposition of 4H-SiC

Low temperature (1300 °C) chemical vapor deposition (CVD) of SiC has gained interest in the last years for being less demanding in terms of reaction chamber lifetime, but also for allowing higher p-type dopant incorporation. Chloride-based CVD at low temperatures has been studied using chloromethane with tetrachlorosilane or silane, respectively and with or without controlled HCl addition. In this study we explore the use of methyltrichlorosilane (MTS) at growth temperatures (1300 °C) significantly lower than what is commonly used for homoepitaxial growth of SiC (1600 °C). MTS is a molecule containing all the needed precursor atoms; its effects are compared to the standard CVD chemistry, consisting of silane, ethylene, and HCl.Very different chemistries between the two precursor systems are proposed; in the case of MTS, C/Si ratios higher than 1 were required, however using the standard chemistry ratios lower than 1 were needed to obtain a defect-free epitaxial layer. We also demonstrate the need of using Cl/Si ratios as high as 15 to achieve a growth rate of 13 μm/h for 8° off-axis 4H-SiC epitaxial layers at 1300 °C. Limitations due to the low growth temperature are discussed in light of the experimental evidence on the growth mechanism as determined by the morphology degradation and the limited growth rate. Finally a comparison between the epilayers morphology obtained on 4H-SiC substrates with different off-cuts are presented, confirming the importance of lower C/Si ratios for 4° off-axis material and the inevitable growth of the cubic SiC polytype on on-axis substrates.     

Carbonylative Sonogashira Coupling in the Synthesis of Ynones: A Study of “Boomerang” Phenomena

The behaviour of several organophosphino‐palladium complexes immobilized on mesoporous silica during the palladium‐catalyzed synthesis of propynone by carbonylative Sonogashira coupling was studied, particularly concerning leaching/redeposition phenomena. The results demonstrated that this cross‐coupling reaction is catalyzed by soluble species. Furthermore, it is shown that the palladium leaching is not initiated by the oxidative addition step but rather by palladium‐decoordination from grafted ligand. Despite this decoordination, catalyst performance after recycling is adequate. Additionally, several parameters linked either to catalyst preparation or reaction procedures were shown to reduce leaching allowing one to achieve metal contamination levels close to the recommendation of the European Agency for the Evaluation of Medicinal Products. Interestingly, this heterogeneous palladium‐catalyzed procedure is fully selective toward the formation of ynones, allowing the preparation of various target compounds.

     

2009IEC／TC SC 77C年会

介绍了在法国召开的2009IEC／TCSC77C分技术委员会工作组会议讨论的IEC 61000—4—35、IEC 6100—5—9、IEC 6100—5—8三个标准项目实施情况、标准维护需求及新的技术工作。     

移动通信数据业务的功率控制

运用统计线性化的数值分析的方法（把非线性的功率控制方程线性化）,研究了在第三代移动通信中,短时数据业务在功率控制下的性能,提出了在移动台根据定位信息动态预定发射功率的方法,来补偿信道衰落,从而更好地消除远近效应,数值分析说明了这种方法的有效性。     

Observations of high temperature impinging-jet boiling phenomena

A high-speed video camera and microphone were used to capture the flow behavior and boiling sound of a free-surface water jet impinging on a high temperature surface during quench cooling. It was found that depending on the superheat of the surface considerably different flow patterns appeared. For cases where the initial surface temperature was above about 300 °C an almost explosive pattern appeared. This was in contrast to slightly lower temperatures where a liquid sheet flow structure was apparent. The change in phenomena was accompanied by a sudden change in the boiling sound and an increase in the heat transfer rate.     

异常网络流量中的相变理论研究

基于网络相变理论对网络异常流量的本质进行了研究,提出了基于Hurst参数反馈的动态拥塞缓解机制,理论分析和仿真结果验证了该方法的可行性和相对于传统方法的优越性,为异常流量的检测、控制研究做出了有益的探索。     

Considerations for the development of radiation resistant devices and VLSI circuits

The impact of radiation on Very Large Scale Integration (VLSI) silicon technology is discussed with a focus on Complimentary Metal-Oxide Semiconductor (CMOS). Effects of total dose, transient radiation, single event phenomena, and neutron fluence on devices and circuits are presented. General approaches to mitigating radiation effects are put forth. With proper considerations, VLSI CMOS can be enhanced to achieve several orders-of-magnitude increase in radiation tolerance.     

The annealing effect for structural, optical and electrical properties of dysprosium–manganese oxide films grown on Si substrate

Samples of (Dy–Mn) oxide thin films were prepared on quartz and Si(p) substrates for optical and electrical investigations. These samples were annealed at different temperatures and characterised by UV–VIS absorption spectroscopy, X-ray fluorescence (XRF) and X-ray diffraction (XRD). The XRF spectrum was used to determine the weight fraction ratio of Mn to Dy in the prepared samples. The XRD shows that Dy oxide and Mn oxide prevent each other to crystallise alone or making a solid solution even at 600 °C. However, compound of DyMnO₃ was formed through the solid-state reaction for T > 800 °C. The ac-conductance and capacitance were studied, as a function of frequency and gate voltage and the fixed and interface charge densities were determined. It was found that the “correlated barrier hopping” CBH model controls the frequency dependence of the conductivity, while the Kramers–Kronig (KK) relations explain the frequency dependence of the capacitance. The parameters of CBH model were determined and show that the ac-conduction in crystalline (Dy–Mn) oxide is realised by bipolaron mechanism, where the barrier height of hopping is equal to the bandgap determined the UV–VIS absorption spectroscopy.     

Turkish validation of the Game Transfer Phenomena Scale (GTPS): Measuring altered perceptions,automatic mental processes and actions and behaviours associated with playing video games

Studies on Game Transfer Phenomena (GTP) have demonstrated that experiencing altered sensorial perceptions, automatic thoughts and behaviours after playing video games are relatively common phenomena. The aim of this paper is twofold: (i) to validate the Turkish version of the GTP scale (GTPS), and (ii) to examine the prevalence and the relation between the various dimensions of GTP (e.g., visual perceptions, thoughts, behaviours) and video game players’ individual characteristics (e.g., demographics, gaming habits). A total of 954 frequent players were recruited online. Independently of the different samples used in the original validation of the GTPS and the current study, the findings obtained via confirmatory factor analysis showed that the GTPS-Turkish is reliable and valid and proved to be adequate for measuring GTP. A total of 99% of the players in the sample had experienced some type of GTP. Moreover, the correlational, univariate and multivariate analyses showed associations between various video game player characteristics and GTP. The most remarkable finding was that the prevalence of GTP was higher among minors than adults.     

扭臂式静电微驱动器的pulli-n现象分析

从扭臂式微驱动器模型出发,分析了器件在静电驱动条件下pulli-n现象的产生条件,并给出公式化结果。讨论了器件的几何结构参数对于pulli-n现象的影响,并对具体结构的器件给出了pulli-n角度和pulli-n电压等方面的分析结果。对于特定的扭臂结构,pulli-n角度为悬臂梁最大扭转角度的44.04%,且与扭臂的结构参数无关。