Bi-doped silica glass: A combined XPS - DFT study of electronic structure and pleomorphic imperfections

The results of X-ray photoelectron spectroscopy analysis (core-levels, valence band) and first-principles modelling of bismuth implanted silicon dioxide electronic structure at various Bi-concentrations are reported. Most attention is paid to the study of Bi-O-Si chemical linkages and theoretically derived scenarios of Bi-embedding into SiO2 host-matrix. XPS analytics performed demonstrates the presence of spectral features related both with bismuth-bismuth and pleomorphicaly stretched bismuth-oxygen (Bi/O-Si-O) bonds fabrication at lowest employed pulsed-periodical Bi-ion fluence 5 x 10(16) cm(-2). The latter provides pleomorphic spectral separation of oxygen 2s band into O(1) 2s and O(11) 2s sub-bands. It was found that bismuth pairs of stoichiometric and nonstoichiometric (interstitial) impurities are responsible for that. Further increase in ion fluence up to 3 x 10(17) cm(-2) yields, in the main, the growth of alpha-Bi2O3-like frameworks within the volume of initial amorphous SiO2-host what have been interpreted as an appearance of stoichiometric Bi-impurity pairs. The results obtained well agree with our previous investigations of electronic structure of Bi-doped oxide host-matrices and theoretical MD-Tersoff third-party data. New approach toward modelling realistic process of ion-implantation was proposed and discussed. (C) 2020 Elsevier B.V. All rights reserved.