Abstract
Epitaxial MgO (100) films have been grown on GaAs (100) by evaporation of Mg in the presence of 5 x 10(-6) Torr of oxygen. Prior to the growth of MgO, the GaAs (100) substrate was cleaned by Ar ion sputtering and annealing. MgO (100) on GaAs (100) was in situ characterized with Auger electron spectroscopy (AES), and ex situ by scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDX). X-ray diffraction patterns indicated that the MgO film has grown predominantly in the cubic phase with the (100) plane parallel to the GaAs (100) substrate. HRTEM results have confirmed the epitaxial growth of MgO with MgO (100)[001] parallel to GaAs (100)[001]. Despite the high lattice misfit, the epitaxial MgO (100) is grown on GaAs (100) due to the 4: 3 relationship (4 aMgO: 3 aGaAs) between MgO (100) and GaAs (100). The formation of a 4:3 superstructure reduces the lateral misfit between MgO (100) and GaAs (100) to approximate to 0.65%. To test the potential of MgO as a protection layer for III-V semiconductor based photo-electro catalytic devices for water splitting in alkaline media the reaction of MgO films with H2O and NaOH was investigated. Flake-like Mg(OH)(2) structures appear to have formed on top of the MgO films treated with NaOH.