GaSb(001) was treated with (NH4)(2)S-x and the evolution of the interfacial chemistry was investigated, in situ, with monochromatic X-ray photoelectron spectroscopy (XPS), following heat treatment and exposure to trimethylaluminum (TMA) and deionized water (DIW) in an atomic layer deposition reactor. Elemental Sb (Sb-Sb bonding) as well as Sb3+ and Sb5+ chemical states were initially observed at the native oxide/GaSb interface, yet these diminished below the XPS detection limit after heating to 300 degrees C. No evidence of Ga-Ga bonding was observed whereas the Ga1+/Ga-S chemical state was robust and persisted after heat treatment and exposure to TMA/DIW at 300 degrees C. (C) 2011 Elsevier B.V. All rights reserved.