Optical properties and simulated x-ray near edge spectra for Y2O2S and Er doped Y2O2S

Abstract

The electronic and optical properties of Y2O2S and its Er+3 doped counterparts at various concentrations are analyzed using density functional theory (DFT) and simulated x-ray near edge (XANES) spectra. Our simulations are complemented by absorption experiments, which show Y2O2S:Er+3 light emissions in the visible and near infrared. These emissions correspond to Er f–f intraband transitions. We use DFT and DFT+U to calculate the band structure of the Y2O2S and its Er+3 doped counterparts, whereas optical properties are calculated using the independent particle approximation (IPA). The host Y2O2S optical properties are also calculated using the random phase approximation (RPA) and the many-body GW0 approximation. Our IPA calculations on the Y2O2S:Er+3 reveal transitions in the energy region of the bandgap, which are absent in the host spectrum. These are assigned to Er f–f intraband transitions in the visible and near infrared, by applying a rigid energy shift. Moreover, XANES calculations at the Er M5-edge reveal a pre-edge broad shoulder in the proximity of the Er 4f band, which is also supportive of the f–f intraband transitions.