稀释AgNO3交换玻璃光波导的特性

本文对稀释ＡｇＮＯ３交换玻璃光波导进行了实验研究，实验结果表明：波导的折射率ｎ０随溶化物稀度的增加而降低，因此，Ａｇ＾＋离子交换玻璃光波导的折射率可通过选用不同的溶化物稀度而精确的控制。     

Gd3Ga5O12:Ag薄膜电致发光浓度和退火温度特性的研究

本文研究了Ａｇ＾＋的浓度对Ｇｄ３Ｇａ５Ｏ１２薄膜光致发光和电致发光的影响。当Ａｇ＾＋沈度达到０．２ａｔ＾,薄膜的光发生很强的淬灭,但是电致发光的淬灭肖度却达１ａｔＴ％,通过对不同浓度的薄膜样品的吸收光谱的测量,发现随着Ａｇ＾＋的浓度的升高,吸收边生红移。由于Ｇｄ３Ｇａ５Ｏ１２：Ａｇ薄膜电致发光有一部分是属于逞间激发,所以电致发光的淬灭浓度要比光致发光高。Ｇｄ３Ｇａ５Ｏ１２：Ａｇ薄膜的退火有助于提高     

ZnS：Mn^2＋纳米晶与钠硼硅玻璃复合体中的g因子漂移

对ＺｎＳ：Ｍｎ＾２＋纳米晶钠硼硅玻璃复合体进行了ＥＰＲ实验研究,确定Ｍｎ＾２＋在ＺｎＳ基质晶格中有３种形态：替位态（Ｍｎ＾２＋）ｓｕｂ,间隙态（Ｍｎ＾２＋）ｉｎｔ和Ｍｎ团簇。观测到ｇ因子随纳米晶粒径的减小而增大。对ｇ值进行了理论拟合,结果与实验符合很好。分析和讨论了这种量子限域下ＺｎＳ的ｓｐ＾２和Ｍｎ的３ｄ＾５电子态杂化所引起的ｇ－漂移。     

溶胶—凝胶沉积PbTiO3薄膜成分和结构的XPS分析

对通过Ｓｏｌ－ｇｅｌ工艺制备的ＰｂＴｉＯ３薄膜在Ａｒ＾＋溅射前后作了ＸＰＳ全扫描和窄扫描测量，结果表明，除了薄膜原始表面有化学吸附氧和污染碳外，薄膜中没有残余的单质碳或其他杂质元素存在，薄膜的元素组成与化学计量比一致，薄膜表面无富集Ｐｂ。各元素的化学状态证实薄膜系ＰｂＴｉＯ３钙钛矿型结构，Ａｒ＾＋溅射引起Ｐｂ择优溅射和化合物分解，以致Ａｒ＾＋溅射后薄膜表面元素组成与化学状态严重偏离薄膜体内层的真实     

多媒体视频处理子系统的设计与实现（下）

用矿化度０．９２ｇ／ｌ的ＨＣＯ＾－３－Ｎａ＾＋．Ｍｇ＾２＋型地下水对黄土地区无作物农田进行定额灌溉，观测分析灌溉水入渗作用对黄土相关易溶阳离子的影响。结果表明，土壤表层的Ｃａ＾２＋，Ｍｇ＾２＋，Ｎａ＾＋均产生明显的淋溶解析作用 ，点淋溶率最大值分别为４９．３％、７３％、１８．８％和５４．９％；Ｋ＾＋和在０．２ｍ以下趋于稳定；     

小鼠精子附睾成熟过程中Ca^2＋及Ca^2＋—ATPase的研究

利用焦锑酸钾方法和电镜酶组织化学定位方法，研究了小鼠精子在附睾成熟过程中的Ｃａ＾２＋及Ｃａ＾２＋－ＡＴＰａｓｅ变化。结果发现：附睾头中的精子内元Ｃａ＾２＋或极低，而Ｃａ＾２＋－ＡＴＰａｓｅ活性极强，可能是由于Ｃａ＾２＋－ＡＴＰａｓｅ的作用将Ｃａ＾２＋从精子内排出了精子外；在附睾体中，精子Ｃａ＾２＋－ＡＴＰａｓｅ活性降低，而Ｃａ＾２＋浓度迅速上升，并且发现Ｃａ＾２＋来自于附睾管细胞；到了附睾尾部，精     

（Nd,Er）：YAG晶体中Nd^3＋和Er^3＋离子间相互作用

用激光加热基座法生长了Ｅｒ：ＹＡＧ、（Ｎｄ、Ｅｒ）：ＹＡＧ和Ｎｄ：ＹＡＧ单晶光纤，测试了单晶光纤的透过率谱和Ｅｒ＾３＋离子＾４Ｉ１１／２、＾４Ｉ１３／２态，Ｎｄ＾２＋离子＾４Ｆ３／２态的固有寿命τ０，双掺晶体中这些态的平均寿命τ０。讨论了Ｎｄ＾３＋离子对Ｅｒ＾３＋离子的敏化作用。     

Ge和GaAs线膨胀系数和能隙的温度关系

用３个特征频率的爱因斯坦模型，以Ｇｒｕｎｅｉｓｅｎ参数γｉ和约化的电子－声子耦合强度（ｇ＾２Ｆ）Ｗｉ为参数，较好地拟事子Ｇｅ和ＧａＡｓ的线膨胀系数与能隙的温度关系的实验曲线，结果表明ＴＡ的声子的负的Ｇｒｕｎｅｉｓｅｎ参数是引起低温区Ｇｅ和ＧａＡｓ的线膨胀系数反常的原因，同时，Ｇｅ和ＧａＡｓ的价带项状态的（ｇ＾２Ｆ）ｗｉ为正值，而导带底状态的相应量为负值。     

宽带ISDN的概貌与宽带业务（二）

在自然干旱条件下，进行田间小区试验，用１％ＣａＣｌ２，５０μｇ／ｍｌＧＡ及其１：１的Ｃａ＋ＧＡ混合剂处理小麦种子，观察对后期生长某些生理变化与籽粒产量的关系。结果表明，药剂处理对灌浆期叶片含水量、叶绿素含量、光合作用参数、籽粒干物质积螺都有不同程度的效应。其中以Ｃａ＾２＋处理的效果最佳。     

小鼠精子获能及顶体反应过程中Ca^2＋及Ca^2＋—ATPase的研究

利用焦锑酸钾电镜定位Ｃａ＾２＋的技术，及铅捕获法定位细胞Ｃａ＾２＋－ＡＴＰａｓｅ的技术，研究小鼠了获能及顶体反应过程中Ｃａ＾２＋及Ｃａ＾２＋－ＡＴＰａｓｅ的变化，结果表明，获能前精子顶体囊外缘有Ｃａ＾２＋分布，顶体膨胀时，Ｃａ＾２＋消失，开始顶体反应时，顶体外膜，顶体囊泡及顶体后区有Ｃａ＾２＋分布，顶体反应后，仅顶体后区有Ｃａ＾２＋分布精子尾部线粒体及轴丝始终有Ｃａ＾２＋分布。     

Concerning the energy levels of silver in Ge-Si alloys

The emission from impurity states of silver (an element of the IB subgroup) in a Ge-Si alloy, containing 18 at % Si, has been studied. The donor level of silver has been found in crystals doubly doped with gallium and silver, while its first acceptor level has been revealed in crystals doped with only silver. Single crystals were grown by pulling from a melt using a feeding rod. Doping with gallium was performed by introducing this element into the feeding rod, and silver was introduced into the crystals via diffusion. The positions of the donor and first acceptor Ag levels with respect to the top of the valence band were found by analyzing the temperature dependence of the Hall coefficient and the electroneutrality equation for the crystal: 0.06 and 0.29 eV, respectively.     

Strain-induced modifications of the band structure ofInxGa1-xP-In0.5Al0.5Pmultiple quantum wells

The effect of strain on the band structure of In_xGa_1-xP-In_0.5Al_0.5P multiple quantum wells (MQW's) has been investigated from high-pressure and low-temperature photoluminescence measurements. The biaxial strain in the wells was varied between +0.6% compressive to -0.85% tensile strain by changing the well composition x from 0.57 to 0.37. Strain increases the valence band offsets in either tensile or compressively strained structures. Whereas relatively insensitive to tensile strain, the valence band offsets showed a strong dependence on the magnitude of the compressive strain. Good agreement is found between the measured valence band offsets and those predicted by the model solid theory, except for the largest compressively strained MQW's, for which the model calculations underestimate the measured valence band offset. Strain and the associated variations in composition also modified the separation among the well states associated with Γ_1c, L_1c , and X_1c. From these results, the bandgaps of each conduction band extrema were calculated in In_xGa_1-xP for 0.37相似文献   

电镜能谱仪中过渡金属元素的化学价态分析

本文利用电子探针－能谱仪（ EPMA-EDS）对试样微米区域内过渡金属元素的化学价态进行了分析。研究结果表明,过渡金属元素的化学价态可以通过特征X射线Lα／Kβ强度比值结果进行区分,但试样形状、组成成分和化学结构等都可能影响化学价态的判断。此外,本文结合电子－离子碰撞的相关理论对实验结果进行了合理的解释,并将此方法应用到未知样品元素价态的判断中。研究结果对样品内部过渡金属元素化学价态的判断具有重要参考价值。     

Valency configuration of transition metal impurities in ZnO

We use the self-interaction corrected local spin-density approximation to investigate the ground state valency configuration of transition metal (TM=Mn, Co) impurities in n- and p-type ZnO. We find that in pure Zn_1−xTM_xO, the localized TM²⁺ configuration is energetically favored over the itinerant d-electron configuration of the local spin density (LSD) picture. Our calculations indicate furthermore that the (+/0) donor level is situated in the ZnO gap. Consequently, for n-type conditions, with the Fermi energy ε_F close to the conduction band minimum, TM remains in the 2+ charge state, while for p-type conditions, with ε_F close to the valence band maximum, the 3+ charge state is energetically preferred. In the latter scenario, modeled here by co-doping with N, the additional delocalized d-electron charge transfers into the entire states at the top of the valence band, and hole carriers will only exist, if the N concentration exceeds the TM impurity concentration.     

Electron spectrum and scattering of charge carriers in PbTe:(Na + Te)

Within the framework of the two-band model with the interband scattering taken into account, the concentration dependences of kinetic coefficients in PbTe:(Na + Te) were calculated in the range of 100–300 K. The results of the comparison between calculated and experimental data for temperatures of ∼100 K have a contradictory character. The assumption about the existence of quasi-local states related to the introduction of Na + Te in the hole’s energy spectrum makes it possible to overcome these difficulties. The resonance scattering of charge carriers in these states introduces both quantitative (electric conductivity) and qualitative (thermopower, Lorentz number) modifications in the temperature and concentration behavior of transport properties. On the basis of the analysis of results, the conclusion is made that the role of the resonance scattering is basic at low temperatures. The mechanism of formation of quasi-local states in the valence band of materials of this group is proposed.     

Pure strain effect on differential gain of strained InGaAsP/InPquantum-well lasers

The effect of pure strain on the differential gain of strained InGaAsP/InP quantum-well lasers (QWLs) is analyzed on the basis of the valence band structures calculated by k×p theory. By using an InGaAsP quaternary compound as an active layer, it becomes possible to study the relationship between the differential gain and strain (both tensile and compressive) when both the quantum-well thickness and the emission wavelength are kept constant. It is shown that the tensile strain not only reduces the density of states in the valence band but also increases the energy spacings between the first two valence subbands. It is concluded that tensile strain has a more pronounced impact on the improvement of differential gain in InP-based, strained QWLs as compared with compressive strain     

Thermoelectric Properties of TlCu3Te2 and TlCu2Te2

We performed thermoelectric characterizations on TlCu₃Te₂: (Tl¹⁺)(Cu¹⁺)₃ (Te²⁻)₂ and TlCu₂Te₂: (Tl¹⁺)(Tl³⁺)(Cu¹⁺)₄(Te²⁻)₄, in order to understand the relationship between the thermoelectric properties (especially the lattice thermal conductivity κ _lat) and the valence states of Tl. The thermal conductivity of TlCu₂Te₂ is high (about 8 W m⁻¹ K⁻¹), while that of TlCu₃Te₂ is extremely low (around 0.5 W m⁻¹ K⁻¹) like other thallium tellurides. This high κ of TlCu₂Te₂ was caused not only by its large electronic contribution but also by its intrinsically high κ _lat. The present study implies that the valence states of Tl would play some important roles in determining the magnitude of κ _lat.     

X-ray absorption and emission spectroscopy of ZnO nanoparticle and highly oriented ZnO microrod arrays

The electronic structures of ZnO nanoparticles and microrod arrays are studied by O 1s X-ray absorption spectroscopy (XAS) and O Kα X-ray emission spectroscopy (XES). We show that the present LDA+U^SIC calculation approach is suitable to correct the LDA self-interaction error of the cation d-states. The atomic eigenstates of 3d in zinc and 2p in oxygen are energetically close, which induces strong Zn-3d-O-2p hybridization. This anomalous valence band cation-d-anion-p hybridization is affected when the localization of the Zn 3d-states is taken into account. Experimentally, the XES spectra show energy dependence in the spectral shape revealing selected excitations to the Zn 3d, 4s and 4p states, hybridized with O 2p states. Strong anisotropic effects are observed for the highly oriented ZnO rods, but not for the isotropic spherical nanoparticles. The nanostructured ZnO has primarily bulk XAS and XES properties.     

零维量子阱的电子结构

<正> 最近半导体超晶格已经由二维发展到一维,甚至零维。因为在零维超晶格中电子运动在三个方向上受到约束,预料将会出现更加明显的量子尺寸效应,例如:将出现一系列分立的量子能级,这些能级与超晶格的大小有很强的依赖关系。目前,已经有一些零维超晶格光学和电学性质的测量。在微电子领域,已经有人将硅的超细微粒排成有规则的列阵,试图构造记忆元件。在化学领域,半导体的微细晶粒可用作催化剂或光敏器等。     

氮掺杂对4H—SiC电子结构的影响

采用广义梯度近似的密度泛函理论方法计算了4H—SiC的本征态的电子结构以及4H—SiC材料N掺杂后的电子结构,计算结果表明：与本征态相比,N掺杂后的4H—SiC的导带与价带均向低能端移动,导带移动幅度大于价带,使得掺杂后的禁带宽度小于本征态的禁带宽度：导带底进入N的2s态和2p态,但它们所占比重小,掺杂浓度变化对导带底...