Ge：SiO2的光敏缺陷的研究

研究了Ｇｅ；ＳｉＯ２光敏缺陷的特性，分别在４８８ｎｍＡｒ离子激光与１９３ｎｍＡｒ准分子激光作用下，由紫外吸收带，激光荧光的测量实验及电子自旋共振实验，发现光纤中５．１ｅＶ锗缺陷吸收带实验上是由５．０６ｅＶ可光致漂白带与５．１７ｅＶ不可漂白带组成；２９５ｎｍ的激发荧光与５．０６ｅＶ的缺氧锗缺陷对应，随５．０６ｅＶ缺陷吸收带的漂白而衰减；     

非掺杂半绝缘LECGaAs的光电流谱

研究了非掺杂半绝缘ＬＥＣＧａＡｓ的非本征室温（３００Ｋ）光电流谱,在０．４－０．７０９ｅＶ范围发现了一个光响应响应宽带Ｍ１。Ｍ１带在０．４６、０．４９、０．５６、０．６５和０．６９ｅＶ处出现五个峰,其中０．４６、０．４９、０．５６和０．６９ｅＶ峰的起始阈值分别为０．４４、０．４７、０．５１和０．６７ｅＶ。本文讨论了Ｍ１带的起源,提出了０．４４、０．４７和０．５１ｅＶ光电阈值与铜受主,ＥＬ３和氧施主     

ZnSe：A1深能级的研究

为研究ＺｎＳｅ中的本征缺陷和Ａ１在ＺｎＳｅ中的深能级行为，首先测量了Ｚｎｓｅ单晶体中的深能级，发现只存在Ｅｅ－０．３３ｅＶ一个电子陷阱．然后，通过热扩散的方法，在３００℃～７００℃温度范围内把Ａ１掺杂到ＺｎＳｅ单晶体中，结果发现存在Ｅｅ－０．３３ｅＶ和Ｅｅ－０．７０ｅＶ两个电子陷阱．本文从缺陷化学角度对ＺｎＳｅ中的本征缺陷和Ｅｅ－０．７０ｅＶ深能级的结构及起源进行了讨论．     

激光照射下石英玻璃的损伤机理研究

 提出了缺陷态电子的光吸收和价电子的双光子吸收是石英玻璃在紫外光激光照射下产生导带电子的两种重要机制的观点。在此基础上计算了石英玻璃的加热损伤阈值,并与实验结果进行了比较。给出了提高石英玻璃损伤阈值的方法。     

（Ba_（1－x）K_x）BiO_3芯态能级随组份的变化

本文用第一原理的ＬＤＦ－ＬＭＴＯ－ＡＳＡ方法，以超元胞Ｂａ４Ｂｉ４Ｏ（１２），（Ｂａ３Ｋ）Ｂｉ４Ｏ（１２），（ＢａＫ）Ｂｉ２Ｏ６，（ＢａＫ３）Ｂｉ４Ｏ（１２），Ｋ２Ｂｉ２Ｏ６五种“样本”计算由于Ｂｉ（＋３）和Ｂｉ（＋５）二种价态以及Ｋ掺杂引起各芯态能级化学位移的变化．“样本”的电子结构与实验相符，即Ｂａ４Ｂｉ４Ｏ（１２）是Ｅｇ＝２．０ｅＶ的半导体，（Ｂａ３Ｋ）Ｂｉ４Ｏ１２是Ｅｇ＝１．６ｅＶ其价带顶有少量空穴的半导体．其余“样本”是金属．芯态的ＬＤＦ本征值经原子模型△ＳＣＦ修正更接近实验值．用正态分布表达各芯态能级除化学位移外各种“环境因子”的影响，结合任意组份五种“样本”的伯努利分布，计算芯态电子能谱随ｘ的变化．结果表明，所有芯态的自旋一轨道分裂与实验完全相符，Ｂｉ（＋３）和Ｂｉ（＋５）二种价态引起各芯态化学位移的变化均小于０．２ｅＶ，Ｋ掺杂使各芯态结合能略有增加，其中Ｂｉ（４ｆ），Ｂａ（５ｄ）约１．３～１．５ｅＶ，其他芯态约０．４ｅＶ，以上计算结果与实验基本一致．     

碳对α的非卢瑟福背散射截面研究

报道了散射角为１７０°±１．５°，α粒子能量在５－９．０ＭｅＶ之间，ｃ的背散射截面的实验测量值；用Ｒ矩阵理论，通过与实验数据拟合，分析、给出了一套能级参数，并计算了能量范围在２－９．０ＭｅＶ，ｃ的背散射截面；讨论了对背散射分析感兴趣的窄而孤立的强共振峰４２５０±１０ＫｅＶ随靶厚、角度的变化关系以及截面变化缓慢的平坦区３．６－４．２０ＭｅＶ，６．４２５－６．７００ＭｅＶ能区的截面值与背散射角度的关系。 关键词：     

Si衬底上生长的GaAs薄膜中深中心发光的温度效应

测量了Ｓｉ衬底上生长的ＧａＡｓ薄膜中与深中心有关的发光带的变温光谱，研究了０．７８ｅＶ、０．８４ｅＶ和０．９３ｅＶ发光带的峰值位置和发光强度随着温度的变化关系，发现它们的发光强度随温度的变化服从描述非晶半导体中局域态发光的公式。最后讨论了这些发光带的来源。     

Si／Ge应变层异质结带的价带偏移理论计算

在应变异质结价带偏移从头算赝势法的理论计算中，建议一种以平均键能为参考能级的△Ｅｖ值理论计算方法，该方法在Ｓｉ为衬底，以Ｇｅ为衬底和自由共度生长等３种不同应变情况的Ｓｉ／Ｇｅ异质结价带偏移△Ｅｖ值计算中，分别得到０．７３１ｅＶ，０．２４３ｅＶ和０．５２１ｅＶ的计算结果。     

^11B快中子非弹性散射的理论计算

本文采用直接作用模型和扭曲波玻恩近似理论，计算了＾１１Ｂ的２．１４ＭｅＶ激发态在入射中子能量为７．５４－２０．０ＭｅＶ的非弹性散射的积分截面和角分布，计算结果与评价的实验值进行了比较，符合较好。对实验上所缺乏的数据作出了理论预期值。     

Si／Ge应变层超晶格的椭偏光谱

测量了几种不同组分的（Ｓｉ）Ｍ／（Ｇｅ）Ｎ应变超晶格材料的椭偏光谱（２．０～５．０ｅＶ），并得到了其介电函数谱；应用介电函数的临界点理论，研究了（Ｓｉ）Ｍ／（Ｇｅ）Ｎ应变超晶格材料的光学性质。发现短周期Ｓｉ／Ｇｅ应变超晶格除了具有明显的Ｅ１和Ｅ２带间跃迁外，还存在与应力和超晶格能带的折迭效应有关的跃迁峰，其能量分别位于２．３～３．０ｅＶ和３．３～４．０ｅＶ范围内     

Electronic structure of oxygen dangling bond in glassy SiO2: the role of hyperconjugation

The electronic structure and the nature of optical transitions in oxygen dangling bond in silica glass, the nonbridging oxygen hole center (NBOHC), were calculated. The calculation reproduced well the peak positions and oscillator strengths of the well-known optical absorption bands at 2.0 and 4.8 eV, and of the recently discovered absorption band at 6.8 eV. The 2.0 eV band was attributed to transition from the sigma bond between Si and dangling oxygen to nonbonding pi orbital on the dangling oxygen. The uniquely small electron-phonon coupling associated with the 2.0 eV transition is explained by stabilization of Si-O bond in the excited state by hyperconjugation effects.     

熔石英中过氧缺陷及中性氧空位缺陷的几何结构、电子结构和吸收光谱的准粒子计算

本文使用密度泛函理论研究了熔石英中peroxy linkage(POL)缺陷和中性氧空位(NOV)缺陷的几何结构,电子结构以及光学性质.采用自洽的准粒子GW计算结合求解Bathe-Salpeter方程的多体理论,研究了缺陷引起的电子结构和光学吸收谱的变化.首先研究了无缺陷非晶结构的电子结构与吸收谱,得到的结果与实验值非常接近.对POL的计算表明,其在基态下的局部结构与过氧化氢分子类似.采用多体理论计算得到的吸收谱表明其最低吸收峰位于6.3 eV处.这一结果不支持实验认为的位于3.8 eV处的吸收峰是由POL缺陷导致的说法.对于NOV缺陷,计算表明其基态的Si—Si键长为2.51?而三重态下的值则为3.56?.相应的GW+BSE计算表明中性氧空位缺陷导致了位于7.4 eV处的吸收峰,与实验测量结果一致.     

石英玻璃中导带电子的光吸收

分别用二阶和三阶微扰理论计算了 １９３ｎｍ 、３５５ｎｍ 激光照射下石英玻璃中导带电子的单光子吸收速率和双光子吸收速率。结果表明,电子空穴散射参与的单光子吸收和声学声子参与的双光子吸收都是材料中导带电子吸收激光能量的重要过程。     

Onset of sliding friction in incommensurate systems

Interstitial O3 molecules in 7.9 eV photon-irradiated silica are identified. Their optical absorption band at 4.8 eV nearly coincides with the 4.8 eV band of nonbridging oxygen hole centers. The O3-related band is distinguished by a smaller halfwidth (0.84 vs 1. 05 eV), by susceptibility to ultraviolet bleaching, by lack of correlation to the 1.9 eV luminescence band, and by rise of a singlet O2 luminescence band at 0.974 eV during photobleaching. This identification solves a long controversy on the nature of optical bands in silica and gives a tool for studying the mobility of atomic oxygen in SiO2.     

UV and vacuum-UV properties of ge related centers in gamma irradiated silica

Photochemical inhomogeneity in the reduction process of the optical activity related to Ge oxygen deficient point defects in silica, characterized by an absorption band centered at 5.15 v eV and two emission bands centered at 3.2 v eV and 4.3 v eV, have been investigated. We have made a comparative study of the stationary and time dependent photoluminescence under excitation in the UV (5 v eV) and in the vacuum-UV (7.4 v eV) ranges in natural silica samples with native and with n -irradiation bleached optical activity. Our measurements evidence that the same spectral features are observed in the native and in the irradiated samples, but for an intensity reduction in the irradiated ones. Moreover, the time decay of the photoluminescence at 4.3 v eV is the same independently from the irradiation of the sample. On the basis of these results it is suggested that the inhomogeneous distribution of defects is not changed by the irradiation.     

Stable structure and optical properties of fused silica with NBOHC-E' defect

First-principles method is used to simulate the stable structure and optical properties of a 96-atom fused silica.The preferable structure of NBOHC-E'(non-bridging oxygen hole center(NBOHC) and E' center) pair defect is predicted to be located at 2.4 A for the Si-O bond length.The quasi-particle GOWO calculations are performed and an accurate band gap is obtained in order to calculate the optical absorption properties.With the stretching of the Sil-O1 bond,an obvious redshift can be observed in the absorption spectrum.In the case of NBOHC-E' pair,the p-orbital DOS of Si1 atom will shift to the conduction band.Two obvious absorption peaks can be observed in the absorption spectrum.The calculation reproduced the peak positions of the well-known optical absorption bands.     

Absorption and luminescence spectroscopy of fused silica by multiple pulses irradiation at 355 nm

In this work, the effects of laser irradiation on fused silica at 355 nm are investigated by using transient absorption spectroscopy and luminescence spectroscopy. Our result shows that no transient absorption or luminescence in the spectra range from 400 nm to 600 nm is observed when laser energy density is below the damage threshold. When the laser energy density reaches the threshold, an initial damage site will be created. After subsequent laser pulses irradiation, the damage size grows. At the same time, the intensity of the transient absorption and luminescence spectra at the damage site also raises remarkably with the laser pulse number increasing. The absorption band from 420 nm to 520 nm is probably related to the absorption of impurity such as metal ion of iron, cerium and copper. Laser modified fused silica exhibits intense broad luminescence bands due to oxygen-deficiency centers at 444 nm and 580 nm.     

Electron-irradiation-induced radiolytic oxygen generation and microsegregation in silicon dioxide polymorphs

The first direct in situ observations of the production and microsegregation of radiolytic interstitial oxygen resulting from electron beam irradiation of crystal and amorphous oxygen deficient SiO2 polymorphs has been made using cathodoluminescence (CL) microanalysis (spectroscopy and microscopy). Previously unreported near-infrared CL emission is observed at 0.968+/-0.003 eV from crystal alpha-SiO2 (quartz) and at 0.971+/-0.003 eV from amorphous a-SiO2 (fused quartz and silica glasses) at 290 K. The energy and width of the near-infrared CL emission from electron-irradiated alpha-SiO2 polymorphs is consistent with the O2 (1)Delta(g)-->(3)Sigma(-)(g) transition associated with molecular oxygen.     

Luminescence center transformation in wet and dry SiO2

The main luminescent centers in SiO₂ films are the red luminescence R (1.85 eV) of the nonbridging oxygen hole center (NBOHC) and the oxygen deficient center (ODC) with a blue B (2.7 eV) and a UV band (4.4 eV). By means of a new “track-stop” technique we have investigated especially the initial luminescence behavior at the beginning of irradiation. Thus the blue-emitting center is produced under irradiation, but from existing precursors. Contrary to that, the dose behavior of the red (R) luminescence in wet and dry oxide is quite different, decreasing in wet oxide from a high initial level and increasing in dry oxide from almost zero. We propose a model of luminescence center transformation based on radiolytic dissociation and the reactions of mobile oxygen and hydrogen.