REFLECTANCE ANISOTROPY OF THE SI(100)1X2-AS SURFACE - DISCRETE DIPOLECALCULATION

The reflectance anisotropy (RA) spectrum of the Si(100)1X2-As surface is calculated using the discrete dipole model. The semiconductor is tr eated as a slab of pointlike dipole-polarisable bonds coupled by dipol ar electrostatic fields. The response of the polarisable bonds to ligh t in normal incidence is expressed in terms of the normal modes of the polarisable bonds which are called dipole waves. These may be classif ied as surface-localised, surface resonance and bulk dipole waves. We give an analysis of the optical response of this surface in terms of d ipole moments localised on bonds that would be too cumbersome to imple ment using a band structure. The discrete dipole RA spectrum is compar ed to the experimental spectrum for this surface and a density functio nal calculation of the spectrum. The discrete dipole spectrum contains the same features as experiment. The origin of the peaks in the RA sp ectrum is discussed in terms of excitation of dipole waves polarised p arallel and perpendicular to the arsenic dimer axes and also in terms of excitation of dipole moments in particular bonds. Parameters for th e calculation were obtained from ab initio calculations on clusters. ( C) 1997 American Vacuum Society. [S0734-2101(97)01606-0].