CdTe(110)弛豫表面电子态的计算

利用形式散射理论，采用次近邻的紧束缚模型计算了CdTe（110）弛豫表面的电子结构，给出了总体、局域及分波态密度，并给出了表面能带．所得到的结果与实验和第一原理计算结果符合得很好．通过分析表面态的变化，指出表面发生弛豫的原因主要是阴阳离子的p态电子的相互作用加强所致． 关键词：     

有限系统的电子结构研究

选取二维和三维亚方晶格作为有限系统的集团模型，在紧束缚近似下，分别计算了不同尺寸集团的态密度。探讨了态密度与集团大小的关系以及受表面效应的影响。     

超导体表面态

用紧束缚近似研究了半无限大超导体的表面电子态,得到两支表面态,其中一支是超导体所特有的.也计算了几个原子平面的态密度,在正文中用曲线表示出来.     

YBa_2Cu_3O_7基面电子态特性计算

用散射理论描述了 YBa2 Cu3O7( 0 0 1)面的电子能带结构。用近似到第三近邻的紧束缚模型得到了 YBCO的体电子态密度 ,Cu O及 Cu O2 的表面态密度和表面投影能带 ,进而分析了 Cu O和 Cu O2 的表面态密度的特点及与体态密度的差别。     

ZnSe/GaAs(100)界面电子结构的计算

利用形式散射理论的格林函数方法，采用紧束缚最近邻近似下的sp³s模型，计算了ZnSe/GaAs(100)两类界面(Se/Ga和As/Zn界面)的电子结构.分别给出了两类界面的界面带结构和波矢分辨的层态密度及其分波态密度.计算结构表明，在ZnSe/GaAs(100)两类界面的禁带隙中均无界面态，而在其价带区均存在三条束缚的界面带和四条半共振带；通过比较，分析了两类界面的界面态特征及其来源. 关键词：     

VC(001)弛豫表面构型与电子结构第一性原理研究

用第一性原理方法对VC(001)清洁表面的构型和电子结构进行了详细研究，与TiC(001)面类似，VC(001)面弛豫后形成表面皱褶，其表层V原子和C原子分别朝体相和真空方向移动. 能带计算结果表明，过渡金属碳化物(001)面的能带结构符合刚性带理论模型. 对于VC(001)面，表面态主要处在-30eV附近，其主要成分为表层C原子的2pz轨道. 此外，以表层V原子的3d轨道成分为主的表面态出现在费米能级附近，由于这些表面态以表面法线方向的轨道(3d２z和3dxz/dyz)为主要成分，因此在表面反应中将起到重要作用，从而体现出与TiC(001)面不同的反应性质. 关键词： 过渡金属碳化物 表面态 能带结构     

GaN(0001)表面电子结构和光学性质的第一性原理研究

采用基于第一性原理的密度泛函理论平面波超软赝势方法计算了(2×2)GaN(0001)清洁表面的能带结构、态密度、表面能、功函数和光学性质.发现弛豫后GaN(0001)表面的能带结构发生较大变化,表面呈现金属导电特性,导带底附近存在明显的表面态,在偶极矩的作用下表面电荷发生转移,Ga端面为正极性表面;计算获得了GaN(0001)表面的表面能和功函数分别为2.1J.m^-2和4.2eV;比较分析了GaN(0001)表面和体相GaN的光学性质,发现两者存在较大差异.     

Sb吸附在InP(110)表面电子性质的理论研究

利用形式散射的格林函数方法,研究了Sb在InP(110)表面单层吸附时的电子性质．分别计算了清洁的InP(110)弛豫表面和InP(110)-Sb(1ML)体系的表面态的性质,指出了表面态和表面共振态产生的原因．所得结果与实验相符. 关键词：     

用二维复式晶格有限集团模型计算聚乙炔的电子结构

以二维复式晶格作为有限系统的集团模型,在紧束缚近似下,计算了π电子在最近邻及次近邻跳跃集团的态密度.讨论了不同结构参数对态密度及带宽的影响.     

PbTe(001)表面原子几何结构和电子结构的第一性原理计算

用第一性原理的密度泛函理论计算了PbTe（001）表面的几何结构和电子结构.计算结果表明：PbTe（001）表面不发生重构，但表面几层原子表现出明显的振荡弛豫现象，其中第一、第二层间距减小4.5%，第二、第三层间距增加2.0%，并且表面层原子出现褶皱.表面带隙在X 点，带隙变宽，在基本带隙中不引入新的表面态，而导带底和价带顶附近等多处出现新的表 面共振态；弛豫后费米面处态密度很低，所以表面结构很稳定. 关键词： 密度泛函理论 表面几何结构 表面电子结构 PbTe     

Surface electronic structure of SnO2(110)

We report theoretical investigations on the surface electronic structure of the (110)-face of SnO₂, a semiconductor of rutile bulk structure. Starting with a tight binding Hamiltonian for the bulk, we determine the surface electronic structure using the scattering theoretic method. As results we obtain the surface bound states, the surface resonances and the wave-vector resolved surface layer densities of states. The dominant features are two backbond states in the stomach gap of the main valence band and two Sn-s derived states in the lower conduction band region. In the upper valence band region, only weak resonances occur, like in other materials with relatively strong ionicity.     

ZnTe(110)表面电子态及其弛豫对表面电子态的影响

给出了Ⅱ-Ⅵ族半导体化合物ZnTe(110)表面电子特性的理论研究.考虑最近邻的sp³s模型描述体态电子结构，使用散射理论方法，给出了理想和弛豫ZnTe(110)表面的波矢分辨的电子态密度和表面投影带结构.结果表明：弛豫的ZnTe(110)表面在带隙中没有表面态存在.在价带中的表面态及表面共振态和其他弛豫的Ⅲ-Ⅴ族及Ⅱ-Ⅵ族半导体的(110)表面具有相似的特征.与实验结果及第一性原理的自洽赝势计算结果相比，计算的结果符合得很好. 关键词：     

Electronic structure of ideal and relaxed InSb(110) surfaces

We report electronic structure calculations for the ideal and relaxed InSb (110) surfaces which were carried out using the tight binding scattering theoretic method. The bulk material is described by a realistic ETBM Hamiltonian and spin-orbit coupling has been taken into account explicitly. Our results show, that the spin-orbit interaction has only small influence on the surface electronic structure of InSb(110). Our results are discussed in terms of surface band structures, wavevector-resolved layer densities of states and angular-resolved weighted layer densities of states.     

Constant final state measurements of surface core-level binding energy shifts: InP(110) and GaAs(110)

The surface core-level binding energy shifts have been obtained for the In 4d and the P2p core-levels on the InP(110) surface. In agreement with previous studies of core-level shifts on the cleavage face of III–V semiconductors, the anion and cation shifts are of almost equal magnitude and are of opposite polarity (−0.31 and +0.30 eV respectively). The results are compared with a similar investigation of the GaAs(110) surface and discussed in terms of a recent calculation of surface core-level shifts for the (110) cleavage face of III–V semiconductors.     

Analysis of semiconductor surface phonons by Raman spectroscopy

Only recently Raman spectroscopy (RS) has advanced into the study of surface phonons from clean and adsorbate-covered semiconductor surfaces. RS allows the determination of eigenfrequencies as well as symmetry selection rules of surface phonons, by k-conservation limited to the Brillouin zone-center, and offers a significantly higher spectral resolution than standard surface science techniques such as high-resolution electron energy loss spectroscopy. Moreover, surface electronic states become accessible via electron–phonon coupling. In this article the fundamentals of Raman scattering from surface phonons are discussed and its potential illustrated by considering two examples, namely Sb-monolayer-terminated and clean InP(110) surfaces. Both are very well understood with respect to their atomic and electronic structure and thus may be regarded as model systems for heteroterminated and clean semiconductor surfaces. In both cases, localized surface phonons as well as surface resonances are detected by Raman spectroscopy. The experimental results are compared with surface modes predicted by theoretical calculations. On InP(110), due to the high spectral resolution of Raman spectroscopy, several surface modes predicted by theory can be experimentally verified. Surface electronic transitions are detected by changing the energy of the exciting laser light indicating resonances in the RS cross section. Received: 7 April 1999 / Accepted: 25 June 1999 / Published online: 16 September 1999     

Unoccupied electronic states in adsorbate systems

Experimental work on unoccupied electronic states in adsorbate systems on metallic substrates is reviewed with emphasis on recent developments. The first part is devoted to molecular adsorbates. Weakly chemisorbed hydrocarbons are briefly discussed. An exhaustive inverse photoemission (IPE) study of the CO bond to the transition metals Ni, Pb, and Pt is presented. Adsorbed NO is taken as an example to demonstrate the persisting discrepancies in the interpretation of IPE spectra. Atomic adsorbates are discussed in the second part. The quantum well state model is applied to interpret the surface states in reconstructing and non-reconstructing adsorption systems of alkali metals and hydrogen. A recent controversy on the unoccupied electronic states of the Cu(110)/O p(2×1) surface is critically reviewed. The quantum well state model is then compared to tight binding and local-density-functional calculations of the unoccupied bands and the deficiencies of the various approaches are pointed out. Finally, the relation between the surface state model and more chemically oriented models of surface bonding is briefly discussed.     

Effective surface potential method for calculating surface states

A novel formalism (the effective surface potential method) is developed for calculating surface states. Like the Green function method of Kalkstein and Soven and the transfer matrix method of Falicov and Yndurain, the technique is exact for simple tight binding Hamiltonians. As well as offering an alternative viewpoint, the present method provides a simple analytic expression describing the surface states. At each point k_s in the surface Brillouin zone the semi-infinite solid is viewed as an effective linear chain where each element of the chain is a planar layer. The solution to the linear chain problem can be expressed in terms of an effective potential h(k_s,E) at each energy E. A number of examples are presented in detail; “sp^d” Hamiltonians for a linear chain (d = 1), the honeycomb lattice (d = 2), the 111 surface of silicon (d = 3), and a dissected Bethe lattice. Various exact results are given, e.g. the extremities of surface state bands and the surface density of states of p-like (delta function) bands. The results of Kalkstein and Soven for the 100 surface of a simple cubic solid with a perturbation on the surface layer are rederived.