Grain effect in electronic properties of silicon epitaxial nanostructures

Abstract

The electronic properties of grained nanocrystalline silicon (1 1 1) films were theoretically studied within the self-consistent semiempirical LCAO method. Grains in the films were found to provide a direct band gap and their interaction results in the gap reduction with respect to the one in the isolated grain. The gap value varied from 1.55 to 3.04 eV depending on the film thickness as well as on the lateral size of the grains. Grained layer stacking inside the film induces a considerable increase of the gap as compared to the unstacked film of the same effective thickness. New simple approach based on the effective mass theory (EMT) has been developed and successfully applied to simulate the electronic properties of nanocrystalline films accounting for confinement effects and interaction between the grains. It consistently reproduces main features of the properties of the grained films derived from LCAO calculations.