Impact of bridge- and double-bonded oxygen on OH-terminated Si quantum dots: A density-functional-Hartree-Fock study

We investigated Si core approximants completely terminated with hydroxyl (CH) groups for emulating a SiO2 environment by Density Functional-Hartree-Fock (DF-HF) Calculations. As approximants we chose Si-10(OH)(16), Si-35(OH)(36) and Si-84(OH)(64), having quantum dot (QD) diameters of d(QD) 7.3, 11 and 14.8 angstrom, respectively. The impact on the electronic structure was considered by exchanging two OH groups for one double-bonded oxygen (=O)or one Si atom for one bridge-bonded oxygen (>O). We find that the influence of >O and =O on the electronic structure of otherwise completely OH-terminated Si core approximants only alters the ground state HOMO-LUMO gap for the smallest Si cores. The impact of >O and =O on the electronic structure and the optical absorption edge of Si QDs embedded in SiO2 is small and should not alter the ground state electronic behaviour of Si QDs embedded in a SiO2 matrix. (C) 2008 Elsevier B.V. All rights reserved.