Germanium oxidation occurs by diffusion of oxygen network interstitials

Density functional modeling is used to show that germanium oxidation occurs by the diffusion of network oxygens across the film as peroxyl bridges, not by molecular O-2 interstitials (O-2*). The smaller O bond angle of GeO2 leads to lower order rings in the amorphous GeO2 network than in SiO2. This leads to narrower interstitial diffusion channels, and less dilation of the interstitial volume around the transition state. This raises the migration barrier of O-2* in GeO2, so that the overall diffusion energy of O-2* in GeO2 is now higher than that of a network O interstitial. The low formation energy of the O vacancy in GeO2 leads to GeO2 being O-poor very near the Ge/GeO2 interface, but the lower overall diffusion energy of the O network interstitial than the vacancy leads to the network interstitial dominating diffusion. Published by AIP Publishing.