杂质对光学薄膜激光损伤阈值的影响

通过对一系列１０６μｍＨｆＯ２／ＳｉＯ２全反膜样品进行的激光损伤阈值测试,以及二次离子质谱杂质含量测定的结果进行的比较分析,提出了减小膜系制备过程中杂质污染是提高光学薄膜激光损伤阈值行之有效的途径。将理论分析运用于具体生产实践中,获得了令人满意的结果。     

光学薄膜激光损伤的光斑效应研究

采用两种不同的激光损伤阈值定义,对光学薄膜激光损伤的光斑效应进行了详细的实验研究。     

熔石英亚表面杂质对激光损伤概率的影响

基于Mie理论和热传导方程,结合ICP-OES对熔石英亚表面杂质粒子的主要成分测量,建立了计算吸收性杂质粒子诱导熔石英光学元件表面损伤概率的模型。通过该模型理论研究了不同种类的杂质粒子诱导损伤所需的临界能量密度随粒子尺寸的变化,以及不同尺寸分布的杂质粒子诱导熔石英表面的损伤概率。通过损伤实验测试获得了不同光斑尺寸的355 nm激光辐照作用下熔石英表面的损伤概率,与理论计算结果进行对比,在相同粒子分布参数下,分析了三种杂质粒子对损伤概率的贡献（Cu Al CeO2）。通过该模型能够分析光学基底或薄膜亚表面中不同潜在的杂质吸收性粒子对光学元件损伤概率的影响。     

飞秒激光作用下薄膜的阈值损伤到膜层剥落

在飞秒单脉冲激光损伤HfO_2/SiO_2薄膜样品实验中,随着激光能量密度升高,膜层从缺陷导致的点损伤发展到整层剥落,损伤区域轮廓由模糊变清晰.研究表明,尺度在纳米量级的颗粒缺陷会产生局部的场增强效应,该效应与薄膜干涉场叠加,造成了阈值损伤阶段损伤区域出现大量损伤点,且由于飞秒激光对包括缺陷在内的薄膜材料的本征损伤特性,使其损伤行为较为确定,随着激光能量的提升,薄膜出现更大面积的规则烧蚀区,此时干涉场的作用上升到主导地位,膜层的整层剥落行为掩盖了缺陷的诱导作用.     

激光聚焦熔石英表面产生击穿的热力学效应分析

利用纳秒激光脉冲辐照熔石英玻璃产生击穿的方法,仔细观测了熔石英表面损伤的微观形貌,并基于激光击穿过程的热力学效应对损伤机理进行了研究。研究表明:激光脉冲能量的沉积主要是基于激光等离子体的逆韧致吸收效应,高温高压等离子体是导致熔石英玻璃损伤的主要因素;熔石英玻璃在击穿过程中伴随着温度升高、材料熔化、气化以及电离等过程,这些效应使得玻璃发生相变以及断裂,而冲击波效应会使得相变材料发生去除辐照区周围玻璃发生剥离而形成大范围的坑状破坏点。     

光学薄膜激光损伤的波长效应

本文报道了采用三种波长的单横模脉冲激光对ZrO_2、TiO_2和Ti_3O_5的单层膜和多层膜的激光损伤阈值和损伤形貌。研究了损伤阈值与波长的关系。     

近阈值能量密度下薄膜的激光损伤特点

采用毫米量级大光斑的近单模的激光器 ,控制入射薄膜表面的激光能量 ,获得了几种常见单层膜和增透膜的损伤形貌 ,实验结果表明 ,薄膜的损伤可区分为熔化型和应力型两种 ,薄膜表面等离子体对损伤斑点的扩大有重要作用。     

近阈值能量密度下薄膜的激光损伤特点

采用毫米量级大光斑的近单模的激光器,控制入射薄膜表面的激光能量,获得了几种常见单层膜和增透膜的损伤形貌,实验结果表明,薄膜的损伤可区分为熔化型和应力型两种,薄膜表面等离子体对损伤斑点的扩大有重要作用。     

强激光对光学薄膜的损伤机理

以光学薄膜在强激光照射下损伤机理的研究为目的，从实验和理论结构探讨了影响损伤阈值的因素及薄膜的损伤机理，从而提出了如何选择高阈值的薄膜的建议。     

表面杂质和节瘤缺陷诱导薄膜元件热熔融损伤

在高功率激光系统中,光学薄膜元件表面杂质和体内节瘤缺陷是导致薄膜元件损伤的关键因素。通过建立强激光连续辐照下光学薄膜元件的热分析模型,分析在不同激光辐照时间和功率密度下,表面杂质和节瘤缺陷对光学薄膜元件损伤的影响及其规律。结果表明,在强激光连续辐照下,当表面杂质粒子尺寸处于一定范围内时,随着杂质粒子尺寸的增大,薄膜元件上的最高温度随之升高,且大而浅的节瘤缺陷种子对膜层的温升影响较大。随着激光功率密度的提高和激光辐照时间的增长,表面杂质造成薄膜元件热熔融损伤的粒子尺寸范围越大,节瘤缺陷造成薄膜元件热熔融损伤的种子深度和尺寸范围也越大。     

空气中多杂质颗粒对光传输的影响特性研究

为了研究空气中杂质颗粒对光传输的影响,采用有限元法分析了有多个杂质微粒同时存在的情况下,颗粒物连接处的光强分布情况,取得了不同颗粒物之间的强度差异数据,并给出了一种解决复杂多杂质微粒存在情况下的通用解决方案。结果表明,对于球体颗粒物杂质,当同时有两个杂质微粒存在时,穿过杂质的微粒呈现出从低到高的趋势,在杂质微粒互相接触的区域光强达到最大值;对于立方体杂质微粒,光强分布呈现出较强的波动特性,且光强强度比球体杂质微粒的光强强度在数量级上多了100倍。该研究模型可移植性强,能推广应用到多个领域,这一结果对后续开展光在气体中传播的理论是有帮助的。     

微粒场全息术中记录介质的选择和处理研究

针对微粒场全息记录的特点,讨论了记录介质的分辨率和记录介质大小的选择;分析了全息记录介质的感光成像原理,对激光能量的高斯分布和曝光量对微粒场记录的影响进行了研究,给出了光束位置和曝光量对实验的影响结果,并对选用的3种记录介质在给定的处理工艺下的特性曲线进行了对比测试;选定的SY-2型记录介质,记录微粒场时适宜的曝光量为180μJ/cm2.     

The effects of heavy impurity doping on AlGaAs/GaAs bipolartransistors

The effects of heavy impurity doping on the electrical performance of AlGaAs/GaAs heterojunction bipolar transistors are examined. Electrical measurements of GaAs diodes and transistors demonstrate that the electron current injected into p⁺-GaAs is unexpectedly large. These results provide evidence for a large effective bandgap shrinkage in p⁺-GaAs. The results are presented in a form suitable for device modeling. For the heavy p-type doping commonly used in the base of an n-p-n AlGaAs/GaAs heterojunction bipolar transistor, the effective bandgap shrinkage is comparable in magnitude to the bandgap variation designed into the device by its compositional variation. Two examples demonstrate that such effects must be considered when analyzing or designing such devices     

Susceptor effects on the morphological and impurity properties of 4H-SiC epilayers

The morphological and impurity properties of 4H-SiC epilayers grown using graphite susceptors coated with vitreous carbon, SiC, TaC, and NbC were compared. Metal carbide coated susceptors produced epilayers with smooth morphologies and no thick backside polycrystalline SiC deposition. Epilayers grown using metal carbide coated susceptors possessed more than 10 times higher intentional N₂ doping efficiencies and more than 10 times lower unintentional Al concentrations compared to epilayers grown using vitreous carbon coated susceptors. Metal carbide coated susceptors permitted doping control and abrupt p.n. junctions, and possessed more than 10 times longer lifetimes compared with vitreous carbon or SiC coated susceptors.     

A study on hot carrier effects on N-MOSFETs under high substrate impurity concentration

A systematic investigation of the influences of high substrate doping on the hot carrier characteristics of small geometry n-MOSFETs down to 0.1 /spl mu/m has been carried out. Results indicate that the dependence of substrate current and impact ionization rate on substrate impurity concentration is reversed in long channel and short channel devices. In the long channel case, both increase with rising substrate impurity concentration, while they decrease in the case of short channel devices. An explanation for this phenomenon based on the lucky electron model has been developed. The dependence of other characteristics on impurity concentration has also been studied. The dependence of off-leakage current has been found to fall as the gate oxide is reduced in thickness. Regarding the dependence of hot carrier degradations, the degradation of drain currents becomes smaller as the substrate impurity concentration increases in the case of short channel devices. Further, in the extremely high impurity doping region, a new hot carrier degradation mode was found, in which the maximum transconductance values of n-MOSFETs increase after hot carrier stress. This new degradation mode can be explained in terms of effective channel length shortening caused by electron trapping.<>     

高重复频率脉冲激光对光学薄膜的损伤

本文介绍了光学薄膜在高重复频率脉冲激光作用下的损伤阈值，与单次脉冲激光相比下降了二个数量级。论文并探讨了在高重复频率激光作用下光学薄膜损伤的主要原因及提高损伤阈值的方法。     

Electron-beam doping-electron radiation effects in impurity overlayers and semiconductor substrates

3-9 MeV electrons were used to introduce impurity Ge atoms into Si wafers from Ge sheets, which are in contact with a Si surface at 20-60‡C in water bath. Concentration-dependent diffusivities of ∼10-18-10^-14 cm²sec^-1 for Ge in Si were measured. Activation energies of sputtering yield for Ge and of the diffusivity of Ge in Si are estimated to be ∼0.3 eV and ∼0.58 eV, respectively. In a case of hot (∼250‡C) irradiation in ∼1x10^-3 Torr vacuum, also the similar concentration profiles of impurity atoms in the substrates were observed.     

Damage effects on low noise amplifiers with microwave pulses

The damage effect experiment is carried out to the low noise amplifiers (LNAs) based on Bipolar Junction Transistor (BJT) and Pseudomorphic High Electronic Mobility Transistor (PHEMT) by microwave pulse injection experiment platform. The essence of the LNA damage with microwave pulses is the damage to the core semiconductor device. The influence rule upon the damage power of the LNA by different microwave pulse widths and pulse numbers is obtained. The injection, reflection and output waveforms are measured by high frequency oscilloscope and the typical damage waveforms of the LNA are analyzed. Inspection is made on the damaged semiconductor device by a scanning electron microscope (SEM) and the microscopic damage images of the semiconductor devices with different pulse widths and pulse numbers are analyzed in comparison.     

Investigation of the influence of external effects on the behavior of gold impurity in silicon

Properties of gold atoms in silicon and the change of their energy levels under uniform pressure are investigated. The investigations demonstrated that the band gap of silicon varies under the influence of pressure (P) and temperature (T) with a rate ?E/?P=?1.5×10^?11 eV/Pa and ?E/?T=?3.2×10^?6 eV/K.