Reply to comment on the use of “Kramers-kronig analysis for the determination of the optical constants of thin surface films”

A LEED data reduction method is described and applied to Al (001) surface. The method consists of averaging rotation diagrams (azimuthal intensity profiles) obtained at constant electron energy between 500 and 1000 eV in the whole range of the colatitude angle of incidence. The method avoids certain difficulties, stemming e.g. from the energy dependence of the mean optical potential, that are present in other methods in which data obtained at different energies are averaged. The averaged data are analyzed using the two-beam Darwin theory. Values for the surface normal relaxation and mean optical potential are obtained from the study of the position, width and profiles of the averaged peaks. The (100) surface of aluminum is found not relaxed while the (110) surface is contracted. The values found for the mean optical potential are similar to those obtained from other sources. The precision of the averaging method for surface structure is not better than that of direct calculation. Experimental factors limiting the precision of the method (surface roughness, background interference due to Kikuchi lines) are specified.     

Two-dimensional models of threshold voltage and subthreshold current for symmetrical double-material double-gate strained Si MOSFETs

The two-dimensional models for symmetrical double-material double-gate(DM-DG) strained Si(s-Si) metal–oxide semiconductor field effect transistors(MOSFETs) are presented. The surface potential and the surface electric field expressions have been obtained by solving Poisson's equation. The models of threshold voltage and subthreshold current are obtained based on the surface potential expression. The surface potential and the surface electric field are compared with those of single-material double-gate(SM-DG) MOSFETs. The effects of different device parameters on the threshold voltage and the subthreshold current are demonstrated. The analytical models give deep insight into the device parameters design. The analytical results obtained from the proposed models show good matching with the simulation results using DESSIS.     

Vibrational properties of the Pt(111)-<Emphasis Type="Italic">p</Emphasis>(2 × 2)-K surface superstructure

The vibrational spectra of the Pt(111)-p(2 × 2)-K ordered surface superstructure formed on the platinum surface upon adsorption of 0.25 potassium monolayer are calculated using the interatomic interaction potentials obtained within the tight-binding approximation. The surface relaxation, the dispersion of surface phonons, the local density of surface vibrational states, and the polarization of vibrational modes of adatoms and substrate atoms are discussed. The theoretical results are in good agreement with the recently obtained experimental data.     

Cu表面弛豫和自扩散机制的修正嵌入原子法模拟

利用角度修正的嵌入原子方法研究了Cu（100），（110），（111）和（311）等8个面的弛豫，得到了与实验符合较好的结果．然后研究了Cu（100）面上的自扩散机制，得到了与实验和局域密度近似计算相符合的结论．还计算了（110）和（111）面的扩散势垒     

Numerical simulation of the EM scattering and Doppler spectrum of a low flying target above dynamic oceanic surface by using the FEM-DDM method

The Doppler (DP) spectrum of a moving target such as a ship, an iceberg or an air-plane above dynamic oceanic surfaces[1—3] is one of the most important subjects for ra-dar oceanic surveillance, target tracking and oceanic remote sensing[4—7]. With the ad-vancement of oceanic remote sensing and radar surveillance, the experimental observa-tion and theoretical modeling of oceanic clutter have been extensively studied, e.g. by using oceanic field measurement, wave tank experiment and some stud…     

萘酞菁LB膜取向液晶研究

利用二(3-叔丁基硅氧基)萘酞菁硅 (SiNc) Langmuir-Blodgett (LB) 膜对丝状液晶的定向进行了研究,发现在不同膜压下沉积的SiNc LB膜具有不同的定向效果.在15mN/m低膜压下沉积的LB膜上丝状液晶主要呈沿膜面水平排列,而30mN/m高膜压下沉积的LB膜则取垂直膜面取向.原子力显微镜(AFM)对相应的LB单层膜和多层膜进行的分子尺度上的形貌研究发现,高膜压条件下SiNc分子以分离的单体或聚集体形式非连续地在基片上呈线性堆积排列,形成一定的分子“纳米线”,并且大环平面垂直于基片 关键词：     

Surface dependence of the magnetic configurations of the ordered B2 FeCr alloy

Tight-binding linear muffin tin orbitals calculations with generalized gradient approximation were carried out for the magnetic configurations at the surface of the ferromagnetic ordered B2 FeCr alloys. For both (001) and (111) crystallographic phases, non ferromagnetic configurations are shown to be more stable than the ferromagnetic configuration of the bulk alloy. For (001) surface we display a c ground state for either Cr or Fe at the surface. For Cr top layer the magnetic moments are larger than in the bulk B2 FeCr while they are slightly enhanced for Fe top layer. For (111) surface an antiferromagnetic coupling between surface and subsurface is always obtained i.e. for either Fe or Cr at the surface. This change of coupling between Fe and Cr (from ferromagnetic to antiferromagnetic) is expected to be fundamental to any explanation of the experimental results obtained for the interface alloying at the Fe/Cr interfaces. Received 23 March 1998     

V(100)表面上S和O偏析的LEED—AES研究

用AES,LEED等表面分析手段,对V(100)表面上杂质S,O偏析作了详细研究。明确了S,O偏析关系;发现(8×1)-O,(4×1)-O两个新的表面结构;系统观察和分析了V(100)表面在不同S,O偏析量情况下的各种表面超结构,并获得这些表面超结构的相互关系。 关键词：     

Spin excitations in exchange-dominated regime on (1 0 0) and (1 1 0) antiferromagnetic surfaces

Theoretical investigations in the context of Heisenberg model have been made for (1 0 0) and (1 1 0) magnetic surface dynamics for a semi-infinite antiferromagnet geometry. The calculations apply to the exchange dominated regime and are based on a spin-wave operator and matching technique within the framework of non-interacting spin-wave theory. The theoretical formalism developed here does not include either relaxation or reconstruction at the surface and no electronic effects have been considered. Dispersion curves of surface spin-waves are obtained within a single framework by matching the evanescent and travelling solutions, respectively, obtained from the secular equation and satisfying the boundary conditions brought about by the surface. The excitation spectrum of the surface spin-waves has been obtained and compared with that for bulk spin-waves. The quantized bulk modes of the same energy travelling to and away from the surface are related to one another by reflection coefficients, for which sum rules are derived. The numerical results for the evolution of acoustic and optical modes are presented for two different surface planes, namely (1 0 0) and (1 1 0). The findings reported here show that: (i) the reduced coordination number for atoms near the surface as well as the surface orientation play an obvious and crucial part in the surface spin-wave spectra; (ii) the evolutions of bulk as well as surface modes undergo significant changes as a function of the bulk-surface exchange integrals for a given direction of propagation of the spin-wave modes along the surface.     

Hydrogen-induced instability of the Ge(105) surface

The structure and stability of the hydrogen-terminated (105) surface of Ge deposited on Si(105) substrates are investigated by scanning tunneling microscopy (STM). Investigations combining STM, electron energy loss spectroscopy, and theory reveal that Si incorporation into the surface Ge layer of hydrogen-terminated Ge/Si(105) drastically destabilizes the surface. The STM images obtained on this surface are well explained by the recently established rebonded-step structure model.     

Surface and interface states of (111) faces of semiconductors

The surface and interface states of the (111) and (1?1?1?) faces of Ge and GaAs have been studied self-consistently within the tight binding approach. The surface and interface states occupation and energy levels are determined. The results obtained for the surface are compared with available experimental evidence. Those obtained for the interfaces suggest that some relaxation must occur at the interfaces between Ge and GaAs.     

Surface states calculation for the (100), (110) and (111) faces of Si

Using essentially the Heine and Jones model of the band structure for diamond-type semiconductors and a 3-dimensional surface state secular equation, we have calculated the bands of surface states for the (100), (110) and (111) orientations of the surface plane of ideal Si. Our bands for the (110) surface are very similar to those obtained by Jones. Based on these bands of surface states, we can explain reasonably both optical and electrical measurements on the (111) surface.     

ZnS(110)表面原子几何与电子特性的计算

用总能量最小方法，确定了ZnS(110)表面的原子几何结构，得到与弹性低能电子衍射实验相符的结果．利用格林函数的散射理论方法，计算了题ZnS(110)表面的电子结构，与第一性原理的计算结果进行了比较．讨论了晶格弛豫对表面电子特性的影响． 关键词：     

The dynamical motion of atoms at the Ni(111) surface

One atom phonon spectral densities are presented for the vibrations of atoms at the Ni(111) surface both parallel and perpendicular to the surface. They are also presented for perpendicular motion of an adsorbed oxygen atom and the nickel atom immediately below it. The results are obtained using a continued fraction technique. They are compared with recent EELS data obtained by Ibach and Bruchmann.     

Surface treatment with linearly polarized laser beam at oblique incidence

An effective method for surface heat treatment with 10.6 μm linear polarized laser beam at oblique incidence is reported. A circular focused laser spot on the workpiece surface, simultaneously with 2.2–4 times increasing of the absorption are obtained in the 70–80° range of the incidence angle. The main element of the experimental setup is the astigmatic focusing head which focalize the laser beam into an elliptical spot of ellipticity >3 at normal incidence. At a proper incidence angle (obtained by the focusing head tilting) the focused laser spot on the work piece surface gets a circular form and p-state of polarization is achieved.We performed laser heat treatment (transformation hardening, surface remelting) of the uncoated surface, as well as the alloying and cladding processes by powder injection. An enhancement of the processing efficiency was obtained; in this way the investment and operation costs for surface treatment with CO₂ laser can be significantly reduced. Several technical advantages concerning the pollution of the focusing optical components, powder jet flowing and reflected radiation by the work piece surface are obtained.     

Spectral density of surface states for TiO and VO: (001) surface

We present a calculation of the spectral density of states for crystals of TiO and VO with (001) cleaved surfaces. The transfer matrix formalism is employed, with a hamiltonian including the O 2p and the metal 3d orbitals. Slater-Koster parameters obtained by Mattheiss (1972) from a bulk calculation are used. The results are obtained at three special points in the 2D Brillouin zone for three different (001) planes: surface plane, plane immediately below it and bulk plane. In the neighborhood of the point M there is an intrinsic surface state and a surface resonance due to the hybridization between ligand and metal orbitals. The surface state has mixed e_g and p_z symmetry along the Σ symmetry line and lies above the Fermi level. No surface relaxation or reconstruction is considered.     

ZnS(111)表面电子结构研究

利用Ｍｕｆｉｎ-Ｔｉｎ轨道线性组合（ＬＭＴＯ）法，采用ｓｌａｂ模型计算了半导体ＺｎＳ（１１１）表面的电子结构，给出了总体、局域及分波态密度，分析了两种ｓｌａｂ模型的表面稳定性和表面态．理论态密度曲线与ＺｎＳ（１１１）表面同步辐射光电子能谱相符合     

STM images from diamond surfaces: steps towards comparisons of experiment and theory

Stable clean and hydrogenated diamond (100) and (111) surface reconstructions found by density functional molecular dynamics (DFMD) are characterized in their surface electronic properties. For sufficiently large surface slab supercells we have calculated the spatially resolved charge densities of the highest occupied surface states at constant height, which are compared with recently obtained images from scanning tunneling microscopy. The calculated charge-density distributions represent signatures of the considered surfaces which might be used to understand and to classify as-grown diamond surfaces.     

Dielectric barrier discharge in needle-to-plane configuration: Model of surface charge relaxation

Relaxation process of surface charge owing to dielectric barrier discharge (DBD) in “needle – air gap – polyethylene terephthalate film – plane” configuration is considered. Experimental data of the surface charge relaxation (SCR) are obtained by means of the rotating capacitive probe. Taking into account Gaussian radial distribution of accumulated charge density, effective surface and volume electrical conductivities of a barrier dielectric, phenomenological model of SCR for any dielectric thickness is proposed and exact solutions are obtained. The adequacy of the model is confirmed by the numerical computation. There is a good agreement between the experimental results and the model calculations.     

Mo(001)表面声子、声子软化及再构

本文考虑最近邻及次近邻相互作用,连续地改变表面相互作用参数α_s和β_s,研究了Mo(001)表面声子及其软化,得到了声子稳定图,并分析了表面波的振动模式,讨论了表面波的软化与表面再构的关系。 关键词：