Formation of the ‘ionic part’ in the Si-Si bond of chemisorbed Si overlayers on metallic terminated GaAs(100) and InAs(100) surfaces

Abstract

We present the results of an experimental and theoretical study of charge transfer in the MBE silicon overlayers grown on metallic-terminated GaAs(100) and InAs(100) surfaces. The existence of charge transfer on silicon atoms has been determined from the shifts of Si 2s and Si 2p core levels. The position of Si core levels was fixed by XPS. The electron density distribution and hence the net charge have been calculated using Green's function method in a tight-binding approach including the intra-atomic Coulomb interaction. Theoretical calculations and experimental measurements have shown the existence of a considerable charge transfer in the Si Si bond between atoms of the first and the second Si overlayers. This charge transfer is about 0.4 e while the charge transfer between Si atoms and substrate is smaller and is approximately equal to 0.1 e. This caused the electric dipole moment formation and hence the chemical shift of core levels by about 1 eV for both Si GaAs and Si InAs interfaces.