Luminescent Tb3+ doped barium tungstate thin films as a potential candidate for photonic applications

Abstract

Pulsed laser deposited barium tungstate films with different Tb3+ doping concentrations are prepared on quartz substrates. Their structural, morphological and optical properties are studied. All the films exhibit monoclinic crystalline structure with preferred direction of crystal growth along <2 0 2>. Raman spectra of the films exhibit characteristic modes of WO42− ions. UV–visible spectra show that with increase in Tb3+ doping concentration, average transmittance increases and bandgap energy decreases. Surface morphology of the films with low doping concentration show distribution of fairly well defined larger grains and agglomerated grain growth is observed for films with higher doping concentration. Photoluminescence spectrum of pure BaWO4 film shows emission around 414 nm. The Tb3+doped films under an excitation wavelength of 270 nm exhibit intense peak around 488 nm originating from the 5D4→7F6 intra-shell transitions in Tb3+ ions. Excitation wavelength 335 nm reveals another peak around 545 nm arising from the 5D4→7F5 transition in Tb3+ ions. Ellipsometric analysis shows that the refractive index of films is in the range1.25–1.92 at 550 nm. The thickness of the films obtained from lateral FESEM images and ellipsometry are very close to each other.