Oxygen and vacancy defects in silicon. A quantum mechanical characterization through the IR and Raman spectra

Abstract

The Infrared (IR) and Raman spectra of various defects in silicon, containing both oxygen atoms (in the interstitial position, Oi) and a vacancy, are computed at the quantum mechanical level by using a periodic supercell approach based on a hybrid functional (B3LYP), an all-electron Gaussian-type basis set, and the Crystal code. The first of these defects is VO: the oxygen atom, twofold coordinated, saturates the unpaired electrons of two of the four carbon atoms on first neighbors of the vacancy. The two remaining unpaired electrons on the first neighbors of the vacancy can combine to give a triplet (Sz = 1) or a singlet (Sz = 0) state; both states are investigated for the neutral form of the defect, together with the doublet solution, the ground state of the negatively charged defect. Defects containing two, three, and four oxygen atoms, in conjunction with the vacancy V, are also investigated as reported in many experimental papers: VO2 and VOOi (two oxygen atoms inside the vacancy, or one in the vacancy and one in interstitial position between two Si atoms) and VO2Oi and VO22Oi (containing three and four oxygen atoms). This study integrates and complements a recent investigation referring to Oi defects [Gentile et al., J. Chem. Phys. 152, 054502 (2020)]. A general good agreement is observed between the simulated IR spectra and experimental observations referring to VOx (x = 1–4) defects.

Investigation of the stability and charge states of vacancy in clusters Si29 and Si38

“…For example, the stable states of the vacancy and its complexes with impurities, their formation energies were theoretically investigated in previous researches [1][2][3][4][5]. The experimental studies [6][7][8][9][10] indicated the possibility of forming the complexes of a vacancy with an impurity oxygen and hydrogen atoms in stable states, and the kinetic energies of the formation are given. This type of defects are very mobile and could be identified directly only in the silicon of 𝑝-type.…”