使用椭偏光谱研究氮化铝薄膜在不同温度下的光学性质

通过椭偏仪对生长在蓝宝石上的不同厚度氮化铝薄膜的变温光学性质进行了研究, 并采用托克-洛伦兹模型对椭偏实验数据进行了拟合分析, 精确得到了氮化铝薄膜的厚度和光学常数(折射率n, 消光系数k)等.研究的结果表明: 相比薄的氮化铝薄膜, 厚的氮化铝薄膜的折射率较大.随着温度的升高, 氮化铝的折射率、消光系数和带隙会向低能端单调地移动(红移);厚度对带隙随温度改变的影响较小, 对折射率则有一定的影响.     

激光清除输电线路异物时异物烧蚀特性分析

利用高能激光清除输电线路缠绕异物的方法取得了 较好的使用效果。以5种典型输电线路异物 材料为研究对象,建立有限元仿真模型,分析激光烧蚀异物的温度分布及其微观变化规律, 并进行了激光 烧蚀实验。结果表明,激光照射异物时,异物中心到边缘温度逐渐降低,高温的中心部分先 熔化,低温部 分热量积累使温升至熔点熔化,形成“V”形凹坑。在激光加热异物的过程是周向和纵深方 向同时发展的, 且纵深方向发展快于周向的发展速度。激光功率达到200 W时,可以 清除绝大部分有色异物,亮白色异物 也可被清除,激光清除异物的效率在1mm/s至2mm/s之间,激光清除异物的效率较高,此研 究成果为激光 应用于清除输电线路缠绕异物工作提供了重要依据。     

Yb3+/Er3+共掺ZnF2粉末上转换发光特性研究

为了研究ZnF₂作为基质材料、稀土离子Yb3+和Er3+共掺摩尔分数不同时的发光性能,采用高温固相法,在820℃时制备稀土掺杂ZnF₂样品,并对各个样品进行上转换发射光谱测试。将激发功率与上转换发射功率进行曲线拟合,确定Yb3+和Er3+光子吸收过程。结果表明,在980nm半导体激光器激发下,样品在可见光区域内存在533nm,555nm和655nm 3个上转换发射峰,发射的红光强度大于绿光强度,吸收光子数目依次为1.73,1.75,1.88,确定3个发射峰均对应于双光子吸收。此研究说明稀土离子掺杂ZnF₂材料将在上转换红色荧光粉领域有重要的应用前景。     

高稳定度大能量三波长脉冲激光系统研究

设计了一套高稳定度大能量输出的三波长Nd:YAG激光系统,用作激光清洗光源.该系统包括振荡级、放大级及后续波长切换系统.为解决激光棒热致双折射效应造成的输出能量下降和输出不稳定,在输出镜和激光工作物质之间插入λ1/4波片,并对波片的补偿效果进行了研究.结果表明:插入波片后振荡级输出能量提高了10％,稳定度明显提高.重复频率为10 Hz时,1064 nm激光经放大后单脉冲能量可达700 mJ,其单次通过倍频晶体BBO,得到532 nm激光的单脉冲能量为325.6 mJ,四倍频后得到266 nm激光的单脉冲能量为84 mJ.1h内测得的三波长激光输出能量不稳定度均小于0.6％.     

反应温度对亲核试剂引发点击化学制备聚合物分散液晶电光性能的影响

光聚合诱导相分离法是应用最广泛的制备聚合物分散液晶(PDLC)膜的方法。为了提高PDLC的对比度(CR),通常在PDLC膜中引入二色性染料。然而,目前商业化的染料掺杂PDLC膜还很少,因为光聚合诱导相分离法使用的紫外光会使染料分解;另外,染料会吸收紫外光导致预聚物的聚合速率变慢。亲核试剂引发点击化学反应是最近合成化学的研究热点,可在无紫外光的条件下发生。因此,用亲核试剂引发点击化学反应制备PDLC膜,有望克服传统光聚合诱导相分离法的缺点。本论文,采用亲核试剂引发巯基-烯烃点击化学反应制备PDLC膜,并研究了反应温度对PDLC电光性能的影响。结果表明,温度的改变导致液晶微滴的尺寸发生变化,进而对PDLC的电光性能产生影响。温度升高使得开态透过率(Ton)变小,阈值电压(V_(th))和饱和电压(V_(sat))升高。     

塑封半导体器件的可靠性保证措施

为了降低塑封半导体器应用于高可靠性产品领域中的质量风险,采用质量细化分析方法,针对塑封半导体器件本身在材料、结构等方面的特点,做了塑封半导体器件失效模式与机理的原理探讨。得出器件应用于产品前,应该进行温度适应性评估、二次筛选以及破坏性物理分析等先期工作。     

Ultra-high temperature (>300 °C) suspended thermodiode in SOI CMOS technology

This paper reports for the first time on the performance and long-term stability of a silicon on insulator (SOI) thermodiode with tungsten metallization, suspended on a dielectric membrane, at temperatures beyond 300 °C. The thermodiode has been designed and fabricated with minute saturation currents (due to both small size and the use of SOI technology) to allow an ultra-high temperature range and minimal non-linearity. It was found that the thermodiode forward voltage drop versus temperature plot remains linear up to 500 °C, with a non-linearity error of less than 7%. Extensive experimental results on performance of the thermodiode that was fabricated using a Complementary Metal Oxide Semiconductor (CMOS) SOI process are presented. These results are backed up by infrared measurements and a range of 2-D (dimension) and 3-D simulations using ISE and ANSYS software. The on-chip drive electronics for the thermodiode and the micro-heater, as well as the sensor transducing circuit were placed adjacent to the membrane. We demonstrate that the thermodiode is considerably more reliable in long-term direct current operation at high temperatures when compared to the more classical resistive temperature detectors (RTDs) using CMOS metallization layers (tungsten or aluminum). We also compare a membrane thermodiode with a reference thermodiode placed on the silicon substrate and assess their relative performance at elevated temperatures. The experimental results from this comparison confirm that the thermodiode suffers minimal piezo-junction/piezo-resistive effects.     

液体温度对空泡生长和溃灭过程的影响

采用光偏转测试系统研究了不同温度纯净水中激光空泡脉动过程,通过实验获得了激光空泡在靶表面膨胀和收缩全过程,确定了空泡的最大、最小泡半径、脉动周期和泡壁运动速度。实验采用0℃到70℃的纯净水,测量了空泡的泡半径和脉动周期等特征参量变化情况。实验结果表明,液体温度是影响空泡脉动的一个非常重要的因素,随着液体温度的增加空泡的最大泡半径和溃灭周期均呈增加趋势。给出了相应的理论解释。     

神经网络曲线拟合在温补晶振上的应用

石英晶振作为重要的频率源器件,其频率稳定度至关重要。但温度对石英晶振的影响很大。传统的微处理器温度补偿晶振中在拟合曲线时算法简单,导致软件引起的误差较大。利用了神经网络算法在曲线拟合上的应用,拟合出补偿电压与温度之间的函数关系,微处理器根据温度传感器采集的温度控制AD芯片产生补偿电压,从而使压控振荡电路输出稳定的频率的目的。实验结果表明:温度在-10⁸0℃时,频率稳定度达到±0.35 ppm,比未补偿时提高了近20倍,比其他曲线拟合方法得出的效果要好。     

Insights into corrosion in dye solar cells

The main issue in using low cost metals in dye solar cells is the corrosion caused by the liquid electrolyte. Contrary to typical applications of metals, the adverse effects of corrosion in dye solar cells are related to irreversible depletion of charge carriers from the electrolyte rather than consumption of the metal itself. It is calculated that the penetration rate due to corrosion should not exceed 10⁻⁴ mpy (a couple of nanometers per year) to ensure device lifetime longer than 1 year. This is 10 000 times slower rate than what is considered to be a general benchmark value for very low corrosion rate in the field of corrosion science and has a major effect on how corrosion should be investigated in the case of dye solar cells. Different methods, their applicability, and limitations to investigate corrosion in dye solar cells are evaluated here. The issue with most techniques is that they can detect metals that are clearly corroding, but they have significant limitations in proving a metal stable. Our investigation shows that the most reliable information on corrosion is obtained from complete dye solar cells that are exposed to working conditions. A combination of color analysis of the electrolyte to such measurement is proposed as a means to extrapolate future performance of the cells and estimate potential lifetimes of the dye solar cells in regards to corrosion. Copyright © 2014 John Wiley & Sons, Ltd.