Empirical pseudopotential method with nonspherical passivants for the atomistic study of silicon nanostructures

Abstract

Atomistic calculations of passivated nanostructures remain difficult due to the computational demands related to the high number of atoms to be typically considered. The empirical pseudopotential method (EPM) offers a good alternative in this sense, but finding trustable pseudopotentials for passivants in this method is still elusive. Following the idea of extracting nonspherically symmetric potentials from density functional theory (DFT) calculations, hydrogen pseudopotentials for silicon passivation are derived here and used to calculate the electronic states of low-dimensional structures within the EPM scheme. The single-particle Schr\odinger equation is solved with the ensuing pseudopotentials for slabs with surfaces on the (111), (110), and (100) planes, as well as for passivated quantum dots and wires of different size. In all cases, the band gap is traced as a function of the sample size, showing good convergence towards the bulk value. For the slabs, the surface local density of states is also calculated and compared successfully to experiments. The derivation of the nonspherical pseudopotentials is based on an analytic formulation of the crystal potential and its connection to a series of DFT calculations, resulting in reliable, highly transferable and first-principles based passivant pseudopotentials to be used with the EPM.