Simulation of Electron and Hole States in Si Nanocrystals in a SiO2 Matrix: Choice of Parameters of the Empirical Tight-Binding Method

Resumo

The problem of the optimal choice of parameters of the empirical tight-binding method to simulate the quantum-confined levels of Si nanocrystals embedded into an amorphous SiO₂ matrix is studied. To account for tunneling from nanocrystals to SiO₂, the amorphous matrix is considered as a virtual crystal with a band structure similar to that of SiO₂ β-cristobalite and with a lattice constant matched to the lattice constant of bulk Si. The electron density distributions in k space for electrons and holes quantum-confined in a Si nanocrystal in SiO₂ are calculated in a wide energy region, which provides a means to see clearly the possibility of the existence of efficient direct optical transitions for hot electrons at the upper quantum-confined levels.