半导体的CO2激光退火和合金化

本文主要研究连续CO₂激光对半导体的照射效应。实验结果与理论分析说明,用连续CO₂激光照射可将半导体样片加热到所需的温度。与其它短波长的激光不同,波长为10.6μm的连续CO₂激光照射半导体有如下特点:CO₂激光是借助于自由载流子吸收与半导体耦合;样片在深度方向被均匀加热;激光背面照射可以增强退火效果。连续CO₂激光照射可以固相外延再生长的方式使As离子注入Si的损伤层退火恢复。在再生长的过程中注入的As离子进入替位,电激活率很高,而且不发生杂质再分布。将连续CO₂激光背面照射成功地应用于GaAsFET制备欧姆接触,既可避免激光正面照射对器件结构的破坏,又能得到比热退火为好的电学性能。 关键词：     

凸表面单排孔30°喷射气膜冷却流场近场特性的实验研究

本文对弯曲通道凸壁面单排孔30°喷射时气膜冷却流场的近场特性作了比较精细的测量,测量的数据包括壁面静压分布、速度矢分布及气膜冷却有效温比分布。测量表明,弯曲通道凸壁面上30°喷射时对流场的干扰,在孔近场区是显著的,在孔下游约一倍孔径的范围内,流向及侧向的压力变化均甚大;而在进一步下游,主流绕流射流所产生的结构复杂的“绕流区”也是明显的.由于壁面曲率的影响,射流贴附壁面的程度,在M<1.0时,要优于平壁;而当M>1.0时,由于射流的“穿透”作用,其附壁程度又劣于平壁.在X/D>10之后,射流产生的扰动已趋衰减,射流的侧向扩散使流场的三维特征逐渐消失,而接近于二维连续缝槽气膜冷却流场的规律.在本试验条件下,M=0.5左右,可以获得最佳的气膜冷却效果。     

一类线性微分方程解的零点分布

一、引言关于 k 阶线性常微分方程解的零点分布,S.Bank,G.Frank 和 I.Laine 最近证明了如下的结果.     

叶型偏差对整机环境中涡轮性能的影响

叶型加工和装配的误差可能会对涡轮部件乃至发动机整机的性能产生显著的影响。本文针对某整机环境中的涡轮部件,采用数值模拟结合实验的方法,研究了涡轮叶型偏差对其气动性能的影响。结果表明:在整机环境中,叶型偏差首先导致涡轮部件气动性能的微小变化,而整台发动机的工作点随之改变,导致涡轮部件的来流条件、各级涡轮的转速和速度三角形以及其内部的流动细节均会发生明显的变化,最终叶型偏差对涡轮部件气动性能的影响被显著放大。     

有效教学要真正做到“以学定教”——听优质课展评有感

要提高教学的有效性,"以学定教"是比较有效的方法和手段,已得到广大教师的认同.但是教师未必都能做到真正了解学生,进而采取恰当策略以有效达到教学目标.笔者有幸作为评委参加了区物理优质课评选活动,听取了数位教师讲同一节课"杠杆及其平衡条件",从不同的教学设计及教学效果对比来看,只有真正做到"以学定教",即教师能根据学生的成长需求、学习准备、个性特点、发展潜能等设计     

探究电磁感应定律计算公式两种方法的比较

采用数字示波器可以记录磁铁穿过感应线圈中产生的感应电动势的峰值,进而进行定量研究法拉第电磁感应定律;电脑音频编辑软件Cool Edit Pro也可以像数字示波器一样记录感应电动势的峰值,同样可以探究感应电动势的大小.     

纳米羟基磷灰石的合成方法研究进展

羟基磷灰石(Hydroxyapatite,HAP)是一种重要的生物、医药、重金属污染土壤/水体修复材料,本文总结了HAP的结构、组成、发展历程及应用,并从干法、湿法两个大方面系统总结了羟基磷灰石的合成方法及各种方法的优劣,对HAP合成方法的改进方向及应用前景进行了展望.     

Simultaneous measurement of SO2 and NO2 concentration using an optical fiber-based LP-DOAS system

SO2 and NO2 are the most important pollution in atmosphere.An optimized long path(LP)differential optical absorption spectroscopy(DOAS)system of high light intensity at an ultraviolet(UV)wavelength is proposed and used to measure the concentration of SO2 and NO2 simultaneously.In contrast to the traditional DOAS,the system adopted a Y-type optical fiber structure instead of a combination of mirrors in the telescope.The UV light intensity test shows that the light intensity of UV can arrive to above 80% of the max measuring range when the light path reaches 135 m,and the integral time of the spectrograph is only 15 ms.The system is proved to be efficacious through laboratory calibration.The maximum error of SO2 calibration is 4.19%,and is 5.22% for NO2.The error of the SO2 and NO2 mixture calibration is within 10%.Field measurement is implemented in a wastewater treatment plant in winter.The measurement light path is 738 m.The concentration of SO2 varies from 6μg/m^3(2.26 ppb)to 20μg/m^3(7.52 ppb),and the concentration of NO2varies from 100μg/m^3(53.2 ppb)to 200μg/m^3(106.4 ppb)approximately.The results are in accordance with the data from a monitoring station nearby in magnitude order and variation tendency mostly.     

Coupling characteristics of laterally coupled gratings with slots

Laterally-coupled ridge-waveguide distributed feedback lasers fabricated without epitaxial regrowth steps have the advantages of process simplification and low cost. We present a laterally coupled grating with slots. The slots etched between the ridge and grating area are designed to suppress the lateral diffusion of carriers and to reduce the influence of the aspect-ratio-dependent-etching effect on the grating morphology in the etching process. Moreover, the grating height in this structure can be decreased to lower the aspect ratio significantly, which is advantageous over the conventional laterally coupled ridge waveguide gratings. The effects of five main structural parameters on the coupling characteristics of gratings are studied by MODE Solutions. It is found that varying the lateral width of the grating can be used as an effective way to tune the coupling strength; narrow slots (100 nm and 300 nm) and wide ridge (2 μm-4 μm) promote the stability of grating coupling coefficient and device performance. It is important to note that the grating bottom should be fabricated precisely. The comparative study of carrier distribution and mode field distribution shows that the introduction of narrow slots can strengthen the competitive advantage and stability of the fundamental mode.