Structural and optical characteristics of α-Bi2O3/ Bi2O(3-x):Ho3+ thin films deposited by pulsed laser deposition for improved green and near-infrared emissions and photocatalytic activity

Abstract

Pulsed laser deposited films on glass substrate deposited at different substrate temperatures (Ts) and partial pressures of oxygen, Ho3+-doped Bi2O3 films were produced. The degradation capability of the Rhodamine B dye using the Bi2O3:Ho3+ films was explored. The impact of the Bi2O3:Ho3+ content on the dye degradation performance was analyzed. The X-ray powder diffraction patterns showed that the films deposited at 400 °C had an α-Bi2O3 phase. The impacts of various Ts and O2 partial pressures were correlated with the surface morphology and the thickness of the films using results of field emission scanning electron microscope. The thin films deposited at a low O2 partial pressure of 5–20 mTorr at Ts = 400 °C exhibited nano-needles with an average size of 80 nm and a length of ∼750 nm. The estimated band gap of the prepared films was found to vary between 2.6 and 3.0 eV. The photoluminescence (PL) of the Bi2O3:Ho3+ thin films excited at 450 nm showed an intense green band emission observed at 548 nm, and the feeble emissions at 654 and 753 nm were ascribed to the transitions of Ho3+. The nano-needle particles of the α-Bi2O3:Ho3+ exhibited a maximum PL intensity for the 20 mTorr O2 partial pressure thin film. The films prepared in vacuum and with an O2 partial pressure of 5 mTorr exhibited a 41 % dye degradation efficiency during a duration of 270 min of the photocatalysis experiment.