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.