Silicon Cluster Terminated by Hydrogen, Fluorine and Oxygen Atoms: A Correlation with Visible Luminescence of Porous Silicon

Abstract

The effect of hydrogen, fluorine and oxygen surface termination atoms together with size dependence of the Si-cluster on the electronic structure are considered, using semiempirical molecular orbital calculations. The results show that the electronic structure of the Si-cluster is strongly affected by the presence of oxygen terminators which enhance the carrier localization. The transition probability between the electronic states support the high efficiency of visible luminescence. The hydrogen termination leads to a stable Si-cluster structure. Our calculations suggest that surface conditions of the Si-cluster and its size, are responsible for the visible luminescence properties of porous Si. The oxygen surface termination of the Si-ciuster is one of the requisite conditions to obtain luminescence in the red-orange region.