Probing the Effects of Dimethyl Aluminum Isopropoxide Surface Reaction Byproducts on Atomic Layer Deposition Nucleation

Atomic layer deposition (ALD) processes that leverage a myriad of metal-organic and complementary reactant combinations have been identified to realize precise and conformal thin film growth. However, the effects of the ALD reaction byproducts on nucleation and growth mechanisms are rarely considered. Site-selective ALD processes provide an opportunity for the detailed investigation of uniform surface sites with atomistic accuracy. Intentional pretreatment with a known ALD reaction byproduct - isopropanol - enables a significant improvement in the nucleation rate reproducibility of dimethylaluminum isopropoxide and water ALD on rutile TiO2(110). In situ spectroscopic ellipsometry reveals a partially reversible byproduct binding that is site-selective for TiO2(110) surface oxygen vacancies. First-principles calculations reveal surface site-specific thermodynamics for adsorption of isopropanol and water that may influence ALD nucleation. The sensitivity of site-selective ALD motivates consideration of secondary surface reactions when designing precision deposition processes, including area- or site-selective ALD reactions.