Author: Norberto Arzate
Norberto Arzate (2000)
"First, we obtain linear and non-linear optical spectra of clean Si(100) 2x1 reconstructed surfaces based on the model of polarizable bonds. The crystal is is modeled as an array of point-like polarizable dipoles where each dipole is considered to be at the middle of every Si-Si bond. The model incorporates the reconstruction of the surface through the local field effect. We calculate the optical spectra as a function of dimer buckling and it is shown that the structure which nicely reproduce the experimental reflectance anisotropy and second harmonic generation (SHG) spectra for the c(4 X 2) Si(100) surface. On the other hand, we apply a microscopic formalism to calculate the different contribution to the nonlinear second-order susceptibility required in the calculation of SHG."
This paper present theoretical calculations of reflectance anisotropy spectra (RAS) for overlayers of alkali atoms adsorbed on a crystalline metallic surface. We assume that the overlayer is formed by an ordered twodimensional (2D) array of adatoms that respond to the local electric field like point‐like harmonic oscillators. We consider overlayers with several rational coverages, assuming that the adsorbates occupy high symmetry sites which form a Bravais lattice that is commensurate with the substrate [1,2]. RAS spectra are obtained for the five 2D Bravais lattices. We found that RAS can be used to observe ordered phases when the ordered phase has a rectangular, centered‐rectangular or oblique symmetry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A theoretical study of the optical response of the adsorption of Sb atoms on the clean GaAs(110) surface is presented. The reflectance anisotropy spectroscopy (RAS) spectrum is calculated and analysed as a function of Sbcoverage. To capture some of the possible dynamical processes of Sb sub‐monolayer growth, a 1 × 3 unit cell is considered whose equilibrium geometry has been obtained by performing an ab‐initio pseudopotential calculation with the use of density functional theory within the local density approximation. The RAS is calculated via the ab‐initio scheme and also by using a semiempirical tight binding formalism. Some trends in the RAS spectra are identified as the clean surface is partially covered by Sb until the one monolayer coverage is achieved. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
We performed a study of the molecular adsorption of hydrogen on BN nanotubes. We present ab initio calculations for the linear optical response of single wall zigzag BN(6,0) nanotubes as a function of the hydrogen adsorption on the exterior surface of the nanotube. The calculation of the linear optical response is performed by using density functional theorywith the use of plane waves and pseudopotentials. We consider four different nanotube‐structures adsorbed with different coverage of molecular hydrogen.We find optimized atomic coordinates for such structures and calculate binding energies for the molecule of hydrogen on the nanotube.After having the linear response of the considered structures, we have calculated their energy loss function spectra. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
We present a theoretical study of the optical generation of one-photon spin and current injection onto In-adsorbed Si(111) surfaces with 4×2 and 8×2 reconstructions. The spin injection, under incidence of circularly polarized light into nonmagnetic semiconductors, creates spin-polarized electrons in the conduction bands. The current injection is a nonlinear second-order effect that is allowed in materials without inversion symmetry. In bulk centrosymmetric crystals, the optical injection of current can only be observed at the surface wherein the inversion of symmetry might be broken. We report calculations for the degree of spin polarization and current-injection spectra which are calculated in a full electronic band structure scheme at the level of GW scissor-energy correction. Our results show an anisotropic behavior of the spin- and current-injection optical response. We obtain maximum percentages of the degree of spin polarization of 30% and 35% for the 4×2 and 8×2 surface reconstructions, respectively. It is also possible to optically generate injection current coming mainly from the first two top layers on both In-adsorbed surface reconstructions
We present ab initio calculations of second harmonic generation (SHG) response of single wall zigzag pristine boron nitride nanotubes (BNNTs) and BNNTs modified by the molecular hydrogen adsorption.