Chemical, structural, and electronic properties of sulfur-passivated InP(001) (2×1) surfaces treated with (NH4)2S<i>x</i>

Abstract

Some chemical, structural, and electronic properties of (NH4)2Sx-treated InP(001) surfaces have been studied using x-ray photelectron spectroscopy, x-ray photoelectron diffraction and reflection high-energy electron diffraction. A (2×1) surface reconstruction is observed for substrates heated in vacuum at a transition temperature of about 200–350 °C. Sulfur atoms are only bonded to indium atoms and the exchange between phosphorus and sulfur occurs in the first five atomic planes leading to the formation of an InP1−xSx pseudomorphic overlayer. The sulfur surface concentration varies from about 0.85±0.15 after annealing at 350 °C to 0.5±0.15 monolayer at 550 °C. The sulfidation treatment results in (2×1) reconstructed surfaces of high thermal stability up to 560 °C and of high chemical stability. Unpinned ultraclean surfaces, free of carbon and oxygen, are obtained after vacuum annealing at 550 °C.