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 (OH) groups for emulating a SiO2 environment by Density Functional–Hartree–Fock (DF–HF) calculations. As approximants we chose Si10(OH)16, Si35(OH)36 and Si84(OH)64, having quantum dot (QD) diameters of dQD7.3, 11 and 14.8 Å, 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.