铅测定中的二条谱线对比

本文介绍了对铅的二条灵敏谱线进行的实验对比,结果证明２１７．０ｎｍ谱线的灵敏度增加一倍以上,其他指标也接近２８３．３ｎｍ谱线,可以用于卫生检测。     

GaN Films Grown on Si （111） Substrates Using a Composite Buffer with Low Temperature A1N Interlayer

A GaN interlayer between low temperature （LT） A1N and high temperature （PIT） A1N is introduced to combine HT AIN, LT A1N and composition-graded A1GaN as a novel buffer layer for GaN films grown on Si （111） substrates. The crystal quality, surface morphology and strain state of the GaN film with this new buffer are compared with those of GaN grown on a conventional buffer structure. By changing the thickness of LT A1N, the crystal quality is optimized and the crack-free GaN film is obtained. The in-plane strain in the GaN film can be changed from tensile to compressive strain with the increase in LT A1N thickness.     

Fabrication of VO_2 thin film by rapid thermal annealing in oxygen atmosphere and its metal–insulator phase transition properties

Vanadium dioxide thin films have been fabricated through sputtering vanadium thin films and rapid thermal annealing in oxygen. The microstructure and the metal–insulator transition properties of the vanadium dioxide thin films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and a spectrometer. It is found that the preferred orientation of the vanadium dioxide changes from(1ˉ11) to(011) with increasing thickness of the vanadium thin film after rapid thermal annealing. The vanadium dioxide thin films exhibit an obvious metal–insulator transition with increasing temperature, and the phase transition temperature decreases as the film thickness increases. The transition shows hysteretic behaviors, and the hysteresis width decreases as the film thickness increases due to the higher concentration carriers resulted from the uncompleted lattice. The fabrication of vanadium dioxide thin films with higher concentration carriers will facilitate the nature study of the metal–insulator transition.     

Fabrication of 4-Inch Nano Patterned Wafer with High Uniformity by Laser Interference Lithography

We report the fabrication of 4-inch nano patterned wafer by two-beam laser interference lithography and analyze the uniformity in detail. The profile of the dots array with a period of 800 nm divided into five regions is characterized by a scanning electron microscope. The average size in each region ranges from 270 nm to 320 nm,and the deviation is almost 4%, which is approaching the applicable value of 3% in the industrial process. We simulate the two-beam laser interference lithography system with MATLAB software and then calculate the distribution of light intensity around the 4 inch area. The experimental data fit very well with the calculated results. Analysis of the experimental data and calculated data indicates that laser beam quality and space filter play important roles in achieving a periodical nanoscale pattern with high uniformity and large area. There is the potential to obtain more practical applications.     

Characteristic improvements of thin film AlGaInP red light emitting diodes on a metallic substrate

We report a type of thin film Al Ga In P red light emitting diode(RLED) on a metallic substrate by electroplating copper(Cu) to eliminate the absorption of Ga As grown substrate.The fabrication of the thin film RLED is presented in detail.Almost no degradations of epilayers properties are observed after this substrate transferred process.Photoluminescence and electroluminescence are measured to investigate the luminous characteristics.The thin film RLED shows a significant enhancement of light output power(LOP) by improving the injection efficiency and light extraction efficiency compared with the reference RLED on the Ga As parent substrate.The LOPs are specifically enhanced by 73.5% and 142% at typical injections of 2 A/cm~2 and 35 A/cm~2 respectively from electroluminescence.Moreover,reduced forward voltages,stable peak wavelengths and full widths at half maximum are obtained with the injected current increasing.These characteristic improvements are due to the Cu substrate with great current spreading and the back reflection by bottom electrodes.The substrate transferred technology based on electroplating provides an optional way to prepare high-performance optoelectronic devices,especially for thin film types.     

Effect of Dopant Concentration in a Base Layer on Photocurrent——Voltage Characteristics of Photovoltaic Power Converters

It is known that the p–n junction of an absorption region is a crucial part for power conversion efficiency of photovoltaic power converters. We fabricate four samples with different dopant concentrations in base layers.The dependences of power conversion efficiency and fill factor on input power are displayed by photocurrent–voltage measurement. Photoluminescence characteristics under open circuit and connected circuit conditions are also studied. It is found that the status of p–n junction mat...     

气源MBE外延自组装GeSi量子点的光致荧光

利用气源分子束外延技术(MBE)制作了GeSi自组装量子点样品。利用原子力显微镜(AFM)和光致荧光(PL)光谱研究了该量子点的形貌和光学性质。气源MBE在较低温度下生长的量子点材料具有较高的量子点覆盖度。200K以下载流子以局域激子形式束缚在量子点中,激子束缚能约为17meV。升温至200K,载流子的输运过程发生变化。对量子点PL积分强度与温度关系曲线进行拟合得到量子点中空穴跃迁至浸润层的热激活能为129meV。     

界面生长中断对GaAs (111)衬底上 AlGaAs/GaAs量子阱电子自旋寿命的影响

用固源分子束外延技术(SSMBE)在GaAs(111)衬底上,采用不同的界面中断时间生长了多组AlGaAs/GaAs多量子阱样品(MQWs),通过室温发光光谱和时间分辨克尔旋转谱(TRKR)研究了界面生长中断对发光光谱半峰全宽(FWHM)和量子阱中电子自旋弛豫时间(自旋寿命)的影响,发现了自旋寿命随着界面生长中断时间的增加呈现先减小后增加的趋势,此变化趋势与荧光光谱半峰全宽表征的材料质量随中断时间的变化一致,适当的界面生长中断时间能有效的增加GaAs(111)衬底上AlGaAs/GaAs多量子阱中电子自旋寿命。     

Er∶Yb∶YCOB晶体制备及其激光二极管抽运激光特性

研究了Er∶Yb∶YCa4O(BO3)3(简称Er∶Yb∶YCOB)的多晶制备和单晶生长,用提拉法生长出光学质量优良的Er∶Yb∶YCOB单晶,测量了其吸收光谱和荧光光谱,分析了其能级和泵浦原理,并进行了以激光二极管为抽运源的激光试验,实现了Er∶Yb∶YCOB晶体的在1.55μm附近110mW的激光输出,且斜效率达18.9;.