Process induced pre-existing defects in non-crystalline SiO2 and GeO2 at vacated O-atom bonding sites and comparisons with Ge-S(Se) alloy bonding sites

Three related topics are addressed in this article: (i) X-ray spectroscopy (XAS) studies of remote plasma deposited (RPD) nc-SiO2 and nc-GeO2 emphasizing (a) band-edge states and (b) pre-existing bonding defects; (ii) interpretation of X-ray absorption and photoemission spectra based on many electron theory, and in particluar charge transfer multiplets (CTs); and (iii) band-edge electronic structure and intrinsic defects in nc-SiO2 and nc-GeO2 thin films and their interfaces with Si and Ge substrates. The most significant result is the identification of local atomic structure in medium range order (MRO) clusters in which the pre-existing defects are embedded. These defects are vacated O-atom sites in which O-atoms have never been resident. They are confined to 1 nm scale chemically-ordered clusters distributed non-periodically with quartz-structured 4-fold coordinated Si(Ge) and 2-fold coordinated O bonding in 12-atom regular rings. Vacated O-atom sites defects are formed during processing and annealing, and reducing macroscopic as well as local bond-strain strain. They are qualitatively different, and readily distinguished from defects introduced by electrical, and by X-ray, γ-ray or high energy electron stressing of nc-SiO2 and nc-GeO2.