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Several models of oxygenated and hydrogenated surfaces of Si quantum wellsand Si nanocrystals of variable shapes have been constructed in order to assesscurvature effects on energy gaps due to the three Si-suboxides. Si-suboxides inpartially oxydized models of nanocrystals of spherical shapes (or quantum dots)are shown to reduce energy gaps compared to the hydrogenated nanocrystals,consistent with previous results in the literature. This trend is shown to bereversed when planar interfaces are formed in Si-NC inside SiO2 thin films, asin Si quantum wells. At planar interfaces (or surfaces) the electronic chargedensity is shown to become extended and to distribute among the Si-suboxides,thus generating along these planar interfaces extended, or delocalized, states.This delocalization of the electronic states then increase the energy gapcompared to equivalent hydrogenated interfaces (or surfaces). Determination ofgeometric effects of curvature on the band gaps are based on density functionaltheory (DFT) using the real-space numerical approach implemented in the``Pseudopotential Algorithm for Real-Space Electronic Structure'' (PARSEC)program. A method for measuring interface effects due to Si-suboxides in Si-NCin SiO2 is also suggested: by comparing photoluminescence (PL) between as-grownand annealed Si-NC samples. The DFT calculations suggest that blueshift of morethan 0.2 eV of the PL should be observed in as-grown samples havingSi-suboxides at their planar interfaces, in comparison to annealed samplesabove 950 degree Celcius that have fewer or no Si-suboxides once annealed,providing that the bulk of Si-NC remains unaltered.

Curvature Effects on Optical Response of Si nanocrystals in SiO2 having Interface Silicon Suboxides