Mechanistic study on In 2 O 3 atomic layer deposition using InCp and H 2 O/O 2

Abstract We investigate the atomic-layer-deposition (ALD) mechanism of In 2 O 3 using the InCp precursor with H 2 O and O 2 coreactants through density functional theory (DFT) calculations under experimentally relevant conditions. InCp adsorption on hydroxylated SiO 2 is strongly favorable, forming In–O bonds and releasing C 5 H 6 (g) with free-energy gains of −0.48 eV, enabling nearly complete saturation of surface –OH sites. During ALD cycling, the surface-bound In species appear as either Cp-containing or Cp-free motifs, and these two states exhibit distinct oxidation pathways. O 2 oxidizes Cp-free In sites to form In–O networks, with a decrease in the free energy by −0.96 eV. However, it cannot remove the remaining Cp ligand. Conversely, H 2 O readily converts the Cp ligand into –OH groups, reducing the free energy by −0.56 eV, while it cannot oxidize Cp-free In, which is strongly unfavorable. When supplied together, O 2 and H 2 O provide complementary reactivity that enables complete oxidation of both surface motifs, consistent with the experimentally observed high growth-per-cycle (GPC) in simultaneous exposure. These mechanistic insights clarify the origins of oxidant-dependent GPC trends and offer guidance for optimizing In 2 O 3 ALD processes for energy and electronic applications.