Photoemission study of the interaction of Al with a GaAs (110) surface

A room-temperature reaction between Al adsorbate atoms and a GaAs (110) surface is observed by means of soft X-ray photoemission techniques. Evidence of two states of Al which are distinct from the bulk Al metal is seen at submonolayer coverages. The sequential appearance of these states suggest that both Al chemisorbed on the surface and Al replacing Ga in the surface lattice are present. The possible influence of surface lattice reconstruction and Al proximity effects on the replacement reaction is discussed. The replacement reaction is important in the context of metal contacts to GaAs (both ohmic and Schottky barriers) as well as for GaAs—AlGaAs heterojunctions.     

Photochemical transformations of quaternary ammonium tetrachlorocuprates on an aerosil surface

EPR measurements show that the products of photolysis of quaternary ammonium tetrachlorocuprates with 405-nm light in a solvent frozen at 77 K and on an aerosil surface are identical. As compared to matrix isolation at low temperature, immobilization on an aerosil surface makes it possible to extend the temperature range of existence of copper(II) organic products of photolysis by at least 50 K.     

分子和金表面相互作用的第一性原理研究

硫氢官能团可以很强地吸附于金表面上,从而可作为连接体用于纳米电子学中的分子器件.从第一性原理出发利用密度泛函理论研究了4,4′二巯基联苯分子和金表面的相互作用,并利用了前线轨道理论和微扰理论定量地确定了该相互作用能常数.计算结果表明,当含有硫氢官能团的有机分子化学吸附于金表面时,硫原子将与金原子形成以共价键为主的混和键,此时一些分子轨道扩展于金原子和有机分子中,这些轨道为分子结中电子的输运提供了通道,从而可使分子线的电导呈现出欧姆特性.而其他分子轨道具有局域性,此时电子的输运只能通过隧道效应来实现. 关键词： 化学吸附 分子线 分子电子学     

Resonant photoemission study of Ti interaction with GaN surface

Ti/GaN interface formation on GaN(0 0 0 1)-(1 × 1) surface has been investigated by means of resonant photoelectron spectroscopy (for photon energies near to Ti 3p → 3d excitation). The sets of photoelectron energy distribution curves were recorded for in situ prepared clean GaN surface and as a function of Ti coverage followed by post-deposition annealing. Manifestations of chemical reactions at the Ti/GaN interface were revealed in the valence band spectra as well as in the Ga 3d core level peak—the discerned contribution of Ti 3d states to the valence band turned out to be similar to that reported in the literature for titanium nitride. The interaction between Ti and N was further enhanced by post-deposition annealing. The study was complemented with SIMS and AFM measurements.     

Chemisorption of vapors of bifunctional α-amino acids on the chlorinated surface of aerosil

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 52, No. 1, pp. 134–137, January, 1990.     

Infrared study of the interaction of acrylic bone cement with bone structurein vitro

Infrared Spectroscopy was used for the characterization of some commercial bone cements and investigation of their inter-action with compact bone in vitro. The IR spectra of the cements and their mixtures with bone powder were recorded at various periods ranging from day one to 8 weeks. The quantitative analysis of the IR spectra of the mixtures provided a strong evidence that a certain reaction takes place between the acrylic resin and bone powder. It was found that the rate of reaction depends on the concentration of the bone powder and time. In any event, the rate of reaction showed a maximum value at 45-days for all concentrations. It was concluded that, a bond is formed between the cement and the bone powder, and this bond is not perfect.     

Cherenkov interaction of vortices with a free surface

The interaction of vortex filaments in an ideal incompressible fluid with the free surface of the latter is investigated in the canonical formalism. A Hamiltonian formulation of the equations of motion is given in terms of both canonical and noncanonical Poisson brackets. The relationship between these two approaches is analyzed. The Lagrangian of the system and the Poisson brackets are obtained in terms of vortex lines, making it possible to study the dynamics of thin vortex filaments with allowance for finite thickness of the filaments. For two-dimensional flows exact equations of motion describing the interaction of point vortices and surface waves are derived by transformation to conformal variables. Asymptotic steady-state solutions are found for a vortex moving at a velocity lower than the minimum phase velocity of surface waves. It is found that discrete coupled states of surface waves above a vortex are possible by virtue of the inhomogeneous Doppler effect. At velocities higher than the minimum phase velocity the buoyant rise of a vortex as a result of Cherenkov radiation is described in the semiclassical limit. The instability of a vortex filament against three-dimensional kink perturbations due to interaction with the “image” vortex is demonstrated. Zh. éksp. Teor. Fiz. 115, 894–919 (March 1999)     

The interaction of dimethylsulfoxide with a gold surface

The interaction of dimethylsulfoxide (DMSO) with a Au(100) surface was studied by means of TDS, XPS and ΔΦ measurements. At monolayer coverages, DMSO desorbs from two states situated at the relatively high temperatures of 240 and 275 K. The adsorbed molecule, however, shows no chemical shifts in its core levels. This is rationalized by a bidentate bonding of DMSO to the surface through the electron lone-pairs on the O and S atoms. The adsorption geometry agrees also with the behavior of the work function (ΔΦ_DMSO = − 770 meV).     

A molecular beam study on the interaction of NO with a Pt(111) surface

NO adsorbs on Pt(111) with a (temperature independent) initial sticking coefficient S₀=0.88. The fraction of molecules not being chemisorbed is directly inelastically scattered back due to failure of translational energy accommodation. The nonlinear variation of s with coverage can well be described by a precursor-state model, the precursor state being formed by NO molecules translationally and rotationally accommodated in a physisorbed second layer. Dissociation is essentially restricted to defect sites and is negligible on perfect (111) planes. These defect sites (present in small concentration) are first populated and are also sampled by the modulated beam technique yielding an activation energy for desorption E_d = 33.1 kcal/mole and preexponential factor v_d = 10^15.5s^?1. Isothermal desorption measurements yielded E_d and v_d as a function of coverage: E_d rapidly drops from its initial value (at defect sites) to about 27 kcal/mole — which value is considered as representing the adsorption energy on a perfect (111) plane — and then decreases continuously due to effective repulsive interactions. Simultaneously v_d is decreasing to about 10¹² s^?1 at θ = 0.25 which marks the equilibrium coverage to be reached at 300 K. If the surface is precovered with oxygen atoms the NO sticking coefficient is reduced to 0.6, and the desorption parameters are lowered to E_d = 17.1 kcal/mole and v_d= 10^12.6s^?1 (at zero NO coverage).     

On the interaction of a hydrogen atom with a lithium metal surface

In this paper we adopt a molecular cluster approach to study the interaction of a hydrogen atom with a (100) surface of solid lithium metal. In this study, the spin-unrestricted Hartree-Fock equation is solved for the molecular cluster. We also solve for the potential energy surface of the LiH molecule and the Li₂ molecule. We find that the essential features of the hydrogen surface interaction can be understood in terms of the molecule two body interactions. We also find that the hydrogen atom sits below the surface of the Li metal rather than above the surface.     

A LEED/UPS study on the interaction of oxygen with a Ni(111) surface

Exposure of a Ni(111) surface to oxygen leads at first to the formation of a chemisorbed overlayer which is characterized by a 2 × 2-superstructure and a maximum in the photoemission spectrum (hv = 40.8 eV) centered at 5.6 eV below the Fermi level E_F. The emission from the Ni d-states is nearly unaffected at this stage of interaction. After high oxygen exposures the epitaxial growth of NiO can be identified from the LEED pattern. The corresponding photoelectron spectrum is strongly altered and exhibits close agreement with the transition energies as calculated by Messmer et al. for a NiO₆^10- -cluster.     

Studying the interaction of 10-keV electrons with a dielectric surface

The grazing incidence interaction of a 10-keV electron beam with a planar surface of plexiglass is studied experimentally. Moreover, the electron passage through flat channels formed by such surfaces is investigated. The experiments reveal the presence of a guiding effect of the electron passage as in the case of a glass surface. However, there are some features, such as the existence of an initial elevation angle for the case of negative inclination angles of the plate. The formation of self-consistent charge on the surface of the plexiglass and its drain when the current is turned off occur more slowly than on the glass surface. This fact points to the difference in the surface conductivity of insulators.     

Width of the quasiparticle spectral function in a two-dimensional electron gas with spin-orbit interaction

The results of an investigation of the width of the electron and hole spectral functions in an isotropic electron gas with the Rashba spin-orbit interaction as a function of the wave vector within the G ⁰ W ⁰ approximation are reported. This kind of electron gas is used to simulate two-dimensional systems formed by electrons in In _x Ga_{1 − x} As layers of various heterostructures and by surface electron states on Au(111). It is demonstrated how the width of the spectral function changes as a result of the spin-orbit interaction and how it depends on the branch index of the energy spectrum split by this interaction.