Controlled nucleation of metal-sulfide layers via surface functionalization with sulfur species: Enhanced initial growth of GaSx thin films

The initial stages of the atomic layer deposition of metal-sulfide thin films are hindered by delayed nucleation and poor film continuity. The present work explores the nucleation of gallium sulfide (GaSx) films using hexakis(dimethylamino)digallium and H2S as precursors. Smooth amorphous GaSx layers were deposited, with their composition confirmed by XPS and their structure examined by TEM. Postdeposition annealing in H2S was attempted to induce crystallinity. To address the nucleation barrier, a novel surface functionalization strategy was developed: replacing surface hydroxyl groups with sulfur-containing species prior to deposition. Different functionalization treatments were tested, which significantly enhanced nucleation, as demonstrated by accelerated initial growth and improved film uniformity even at low cycle numbers. These results establish chemically specific surface functionalization as an effective strategy to promote controlled nucleation of sulfide thin films.