Red photoluminescence of pulsed laser deposited Eu:NaY(MoO4)2 thin film phosphors on sapphire substrates

Abstract

We have successfully fabricated Eu3+ ion doped NaY(MoO4)2 thin film phosphors using a pulsed laser deposition (PLD) method and studied their photoluminescence properties. The NaY(MoO4)2 thin films were deposited on single crystal sapphire substrates (0001) using deposition temperatures of 300 and 600 °C and O2 partial pressures of 100 and 300 mTorr. The properties of the NaY(MoO4)2:Eu3+ thin films were characterized by means of X-ray photoelectron spectroscopy (XPS), analyzing photoluminescence (PL) spectra, X-ray diffraction (XRD), atomic force microscopy (AFM) and field-emission scanning electron microscopy (FE-SEM). The degree of crystallinity increased with an increase in oxygen pressure and the thickness was around 220 nm for the films coated on the Al2O3 substrate. The photoluminescent property of the thin films was enhanced by increasing substrate temperature and the film deposited at 300 mTorr exhibited the highest luminance. Intense and efficient PL emission was observed from the thin films. The broad absorption bands covering the UV region from 215 to 350 nm are attributable to the O → Mo and O → Eu charge transfer transitions. The thin film phosphors show a strong red emission at 617 nm due to the electric dipole transitions of 5D0 → 7F2 of Eu3+ ions, which clearly indicates that the Eu3+ occupies a non centro-symmetic site.