The effect of ruthenium oxidation on the decomposition of SiH4.

In chemical vapor deposition, the interaction of the precursor molecule with the substrate can crucially influence the deposition process and provide pathways to tailor the growth. Here, we report mechanistic differences of Si growth from silane (SiH4) at pristine and oxidized surfaces of Ru(0001) in a combined in situ X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) study. Silane decomposition is essentially barrierless and thus very efficient on Ru(0001), where it saturates at approximately a monolayer of silicon. Similarly, silane readily decomposes on a thin intermediate phase of Ru oxide, which is structurally different from thicker RuO2 layers, and induces a transformation to a compound with oxidized Si and reduced Ru. In contrast, the bulk-like RuO2 phase is observed to be fully inert towards the decomposition of SiH4 at room temperature. This difference between the two oxides is suggested to originate from disorder and the availability of active sites in the thin Ru oxide layer. The surface-assisted deposition of silicon on Ru can thus be modified and inhibited using oxidation, depending on the nature of the oxide layer.