The Effect of Surface Terminations on the Initial Stages of TiO2 Deposition on Functionalized Silicon.

As atomic layer deposition (ALD) emerges as a method to fabricate architectures with atomic precision, emphasis is placed on understanding surface reactions and nucleation mechanisms. ALD of titanium dioxide with TiCl4 and water has been used to investigate deposition processes in general, but the effect of surface termination on the initial TiO2 nucleation lacks needed mechanistic insights. This work examines the adsorption of TiCl4 on Cl-, H-, and HO- terminated Si(100) and Si(111) surfaces to elucidate the general role of different surface structures and defect types in manipulating surface reactivity of growth and non-growth substrates. The surface sites and their role in the initial stages of deposition are examined by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Density functional theory (DFT) computations of the local functionalized silicon surfaces suggest oxygen-containing defects are primary drivers of selectivity loss on these surfaces.