Effect of in situ thermal treatment during growth on crystal quality of GaN epilayer grown on sapphire substrate by MOVPE

GaN epilayers on sapphire substrate grown by metalorganic vapor-phase epitaxy (MOVPE) in a horizontal-type low-pressure two-channel reactor were investigated. Samples were characterized by X-ray diffraction (XRD), Raman scattering, atomic force microscopy (AFM) and photoluminescence (PL) measurements. The influence of the temperature changes between low temperature (LT) deposited GaN buffer and high temperature (WT) grown GaN epilayer on crystal quality of epilayer was extensively studied. The effect of in situ thermal annealing during the growth on improving the GaN layer crystal quality was demonstrated and the possible mechanism involved in such a growth process was discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

InAs self-assembled nanostructures grown on InP(001)

The 6-period stacked layers of self-assembled InAs quasi-quantum wires(qQWRs) and quantum dots(QDs) embedded into InAlAs on InP(001) substrates have been prepared by solid molecular beam epitaxy. The structures are characterized by atomic force microscopy(AFM) and transmission electron microscopy(TEM). From AFM we have observed for the first time that InAs qQWRs and QDs coexist, and we explained this phenomenon from the view of the energy related to the islands. Cross-sectional TEM shows that InAs qQWRs are vertically aligned every other layer along the growth direction [001], which disagrees with conventional vertical self-alignment of InAs QDs on GaAs substrate.

A study of the interface of CeO2/Si heterostructure grown by ion beam deposition

Epitaxial cerium dioxide films on single-crystal silicon substrates (CeO2/Si) have been grown by a dual mass-analyzed low-energy ion beam deposition (IBD) system. By double-crystal X-ray diffraction (XRD), Full Width at Half Maximum (FWHM) are 23' and 33' in the rocking curves for (222) and (111) faces of the CeO2 film, respectively, and the lattice-mismatch Delta a/a with the substrate is about - 0.123%. The results show that the CeO2/Si grown by IBD is of high crystalline quality. In this work, the CeO2/Si heterostructure were investigated by X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) measurements. Especially, XPS and AES depth profiling was used to analyze the compositions and structures in the interface regions of the as-grown and post-annealed CeO2/Si. It was found that there was no silicon oxide in the interface region of the as-grown sample but silicon oxide in the post-annealed sample. The reason for obtaining such high quality heterostructure mainly depends on the absence of silicon oxide in the surface at the beginning of the deposition. (C) 1998 Elsevier Science Ltd. All rights reserved.

Theoretical and Experimental Studies of an Ultra-compact Photonic Crystal Corner Mirror Based on Silicon-On-Insulator

An ultra-compact silicon-on-insulator based photonic crystal corner mirror is designed and optimized. A sample is then successfully fabricated with extra losses 1.1 +/- 0.4dB for transverse-electronic (M) polarization for wavelength range of 1510-1630nm.

社区宽带综合业务网服务质量保证的研究

社区宽带综合业务网络系统使用交换式以太网技术，在一个物理网络上为社区用户提供Internet接入、数字电视、IP电话等服务，对三网融合进行了实践性探讨。提出并实现了一套保证系统服务质量的方法，并在测试中取得了满意的效果。

我国的风电技术和风电发展

发展风力发电是我国能源战略的一项重要内容。文章首先介绍了我国风电利用的总体状况；然后从风机叶片制造、控制系统及整机制造等方面，详述了现阶段我国风电设备的基本状况；最后对我国风电发展障碍进行了分析。并提出了相关建议。

以流化床换热回收柴油机废气余热的试验研究

传统的对流换热式柴油机余热锅炉存在受热面容易污染和传热系数低的缺点。利用流化床换热可以解决这个问题。本文介绍了在30kW柴油机上所作的试验研究。取得的结果令人满意，为工业应用提供了有用的设计参数