Tb3+-doped WO3 thin films: A potential candidate in white light emitting devices

Abstract

Good crystalline, highly ordered, highly transparent and efficient luminescent Tb3+-doped tungsten oxide (WO3) thin films are fabricated using Radio Frequency (RF) magnetron sputtering technique. XRD analysis shows that the prepared films are in monoclinic phase showing crystal growth along a-axis. Micro-Raman spectra also support the formation of monoclinic crystalline WO3 phase in the prepared thin films. Morphological studies reveal a porous nature for heavily Tb3+-doped WO3 films. Prepared films are very close to the chemical stoichiometry of WO3 and the added impurity Tb exists mainly in +3 oxidation state. The fabricated thin films show better transparency particularly in the visible region. The calculated band gap energy values are in the range of 3.08–3.24 eV. Thickness and optical constants of the prepared films are calculated using spectroscopic ellipsometric measurements. Low values of extinction coefficient also support better transparency of the deposited films in the visible region. Tb3+-doped WO3films exhibit strong blue, green and red emissions under UV excitation which suggest the possibility of using these luminescent films in white light emitting devices. The experimental value of decay time constants corresponds to intense green emission (546 nm) shows a slight increase with increase in Tb3+ concentration.