Energy gap of nanoscale Si rods

The electronic structure of silicon rods has been studied by means of the tight-binding recursion method to investigate the dependence of the energy gap (Eg) on a rod length and the direction of the rod axis. An empirical expression for Eg is derived from numerical results for the rods in 〈100〉, 〈110〉, and 〈111〉 directions. This expression is applicable to the energy gaps of wires and crystallites, which can be regarded as limiting cases of rods.