Simultaneous H ₂ O:O ₂ Co‐Reactant Pulsing for Functional Property Control of Atomic Layer Deposited ZnO, TiO ₂ , and Al ₂ O ₃ Thin Films

ABSTRACT Fabrication of metal‑oxide thin films with precisely controlled crystallographic texture and defect chemistry is an increasingly important target in atomic layer deposition (ALD), in efforts to optimize the application performance of these thin films. Here, we implement a novel ALD approach in which two co‐reactants, H ₂ O and O ₂ , are simultaneously pulsed for the property control of ZnO, TiO ₂ , and Al ₂ O ₃ thin films. Compared to the conventional ALD processes involving only H ₂ O as the co‐reactant, this co‑pulsing scheme is found to modulate the surface termination and deposition chemistry. For the ZnO films deposited from diethyl zinc (DEZ), the major advantage is the significantly enhanced c ‐axis textured film growth, whereas the Al ₂ O ₃ films deposited from trimethyl aluminum (TMA) become more transparent and hydrophilic. For the TiO ₂ films deposited from TiCl ₄ , the deposition chemistry is less affected, but yet major effects are seen in the degree of crystallinity. In general, our H ₂ O:O ₂ co‑pulsing ALD approach emerges as a versatile and ligand‑dependent tool to tailor the surface hydroxylation/hydration as well as structural and optical properties.