Structural studies of sulfur-passivated GaAs (100) surfaces with LEED and AFM

Abstract

We present the results of Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and atomic force microscopy (AFM) analysis of sulfur-passivating layers on the GaAs (100) surface. The GaAs surfaces were passivated with both inorganic [(NH 4) 2S x ] and organic [octadecylthiol (ODT)] S-based compounds. We prepared the inorganic sulfur-passivated GaAs(100) surfaces with a wet chemical treatment using (NH 4) 2S solution. This was followed by thermal annealing of the treated sample in an ultra-high vacuum (UHV). After ex-situ and in-situ treatments, the surface resulted in a (2×1) LEED pattern. The LEED data ( I– E curves) were recorded and compared with dynamical LEED calculations for different structural models for the sulfur-passivated GaAs (100) surface. The results showed that the sulfur-passivated (2×1) surface structure is an arsenic–sulfur dimer on a Ga-terminated substrate. The ex-situ AFM results also revealed a (2×1) structure for the inorganic passivation and a very smooth surface for the organic ODT in the ethanol-treated sample.