Atomic layer Deposition (ALD) is an important process for highly controlled growth on the atomic scale. ALD is normally used to grow monolayers of metal oxides for applications in microfabrication of electronics. There has been recent focus advancing ALD beyond monolayers and into more selective growth which would allow for novel nanostructures to be constructed and tested for emergent phenomena and properties. Most of this research has focused on area selective ALD but going one step further for site selectivity would open access to the highest level of control and bring new capabilities to ALD technology. Here, we use a combination of first principles computational chemistry and experimental collaboration to investigate site selective hydration for site selective ALD. The feasibility of site-selective hydration is investigated amongst four rutile TiO2 facets (110, 100, 101 and 001) and their most prevalent step edges. First principles simulations of asymmetric slab models were utilized to create accurate representations of pristine terrace and step edge sites. The adsorption free energies for molecular and dissociative adsorption of H2O were calculated to evaluate this strategy as a viable route to step edge selectivity. We predict that selective hydroxylation is possible on the 110 and 001 step edges and further computationally evaluate three metalorganic ALD precursors for their compatibility with the selective hydration strategy. Experimental evidence for delayed nucleation of ALD on rutile 001, 110, and 100 TiO2 single crystals corroborates predictions of dehydration of the surface and suggests the possibility of site-selective ALD.

Selective hydration of Rutile TiO2 for applications in Atomic Layer Deposition

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