A theoretical study of the dependence of the AS_xSi_6−x cluster structures and properties on composition

Abstract

The effect of the composition ratio between arsenic and silicon atoms on the structures and properties of As x Si 6Àx (x ¼ 0-6) have been systematically investigated using the density functional theory at the B3LYP/6-311þG* level. The As x Si 6Àx clusters prefer substitutional rather than attaching structures; the Si-rich clusters favor Si 6 -like structures, whereas the As-rich clusters prefer As 6 -like structures. The As atoms locating at the framework may explain the difficulty of removal of arsenic impurities from polycrystalline silicon. In general, the average binding energies gradually decrease, implying the As x Si 6Àx clusters become increasingly unstable as x increases. Both the HOMO-LUMO gaps and the As-dissociation energies present a strong even-odd alternation, implying alternating chemical stability, with the even x members being more stable than the odd ones. The dissociation energies of an As atom from As x Si 6Àx are: 3.07, 2.84, 1.84, 2.52, 1.86, and 2.85 eV, for x ¼ 1-6, respectively, and 3.80, 3.08, 2.64, 3.01, 2.93, 3.16 eV for Si (x ¼ 0-5). These dissociation energy results Correspondence