Evolution of Atomistic Topology at H₂O/GaSb(100) Interface under Ambient Conditions and GaSb Surface Passivation

Gallium antimonide (GaSb) has emerged as a promising light absorber in solar cells and optoelectronics because of its high hot-carrier mobility. Here, the interfacial physiochemical process of H₂O/GaSb(100) under a series of isothermal and isobaric conditions was investigated using ambient pressure X-ray photoelectron spectroscopy. At room temperature and elevated H₂O vapor pressures, we observed the dissociative adsorption of H₂O onto the GaSb(100) surface and the preferential formation of (HO)Ga-Sb(H) (atop) and Ga-O(H)-Ga-Sb(H) (bridge) over (H)Ga-O(H)-Sb(H) (bridge), that is, the GaSb(100) surface was covered by hydroxyls instead of oxides. The oxyhydroxylation of the GaSb(100) surface was significantly enhanced at elevated temperatures, coupled with gradual desorption of surface Sb from 373 to 573 K in the form of SbH₃. Meanwhile, large-scale oxyhydroxylation of GaSb(100) surface at 573 K was captured by on-line mass spectrometry, where the increment in H₂O consumption and the generation of H₂ were observed. When the temperature reaches 673 K and above, the surface oxyhydroxides formed under lower temperatures desorbs quickly, leaving behind a Sb-terminated GaSb surface and preventing any further H₂O dissociative adsorption. The combinative isothermal and isobaric study offers a full picture of the H₂O/GaSb(100) interface in terms of the atomistic topological and structural evolutions under various H₂O pressures and temperatures. The present study provides a possible venue for low-cost surface passivation of GaSb and III-V semiconductor-based electronic devices.