The electronic and optical properties of amorphous silica with hydrogen defects by ab initio calculations

Abstract

Hydrogen can be trapped in the bulk materials in four forms: interstitial molecular H 2 , interstitial atom H, O − H + (2Si=O-H) + , Si−H − ( ) − to affect the electronic and optical properties of amorphous silica. Therefore, the electronic and optical properties of defect-free and hydrogen defects in amorphous silica were performed within the scheme of density functional theory. Initially, the negative charged states hydrogen defects introduced new defect level between the valence band top and conduction band bottom. However, the neutral and positive charged state hydrogen defects made both the valence band and conduction band transfer to the lower energy. Subsequently, the optical properties such as absorption spectra, conductivity and loss functions were analyzed. It is indicated that the negative hydrogen defects caused the absorption peak ranging from 0 to 2.0 eV while the positive states produced absorption peaks at lower energy and two strong absorption peaks arose at 6.9 and 9.0 eV. However, the neutral hydrogen defects just improved the intensity of absorption spectrum. This may give insights into understanding the mechanism of laser-induced damage for optical materials.

UV-shielding and wavelength conversion by centric diatom nanopatterned frustules

“…It is thus interesting to notice that, for blue and red radiation, the intensity in the central spot is amplified over three times the incident radiation. Due to the optical properties of hydrated amorphous silica 49 , in this case no significant absorption is detected if compared to UV irradiation, but still some light, away from the hotspot, is lost due to scattering and/or reflection.…”