Europium incorporated barium titanate thin films for optical applications

Abstract

BaTiO3:Eu (BT:Eu) thin films were deposited onto quartz substrates by RF magnetron sputtering. The effect on structural, morphological, optical and photoluminescence (PL) properties in the films with different Eu concentrations (0–5 wt%) were investigated. The X-ray diffraction (XRD) pattern of the undoped BT thin film revealed a tetragonal (T) phase with orientations along (101) plane. From XRD pattern, the crystallinity of the films increased with increase in Eu concentration. The SEM images revealed that the films exhibited tetragonal shape, crack free and good adherence to the substrate. Atomic force microscopy studies showed an increase of grain growth with doping concentration. The rms roughness value increased with increase in Eu concentration and the film surface revealed positive skewness and high value of kurtosis which make them suitable for tribological applications. X-ray photoelectron spectroscopy revealed the presence of barium, titanium, europium and oxygen in BT:Eu film. An average transmittance of >80 % (in visible region) was observed for all the films. Optical band gap of Eu doped BT films decreased from 3.86 to 3.53 eV. Such films with optical properties such as high transparency, decrease in band gap and high refractive index are suitable for optoelectronic applications. PL properties showed a sharp line at 625 nm and a broad line at 552 nm due to europium (Eu3+) transitions. PL phenomena were observed, owing to the electronic structure of Eu3+ ions as well as BT nanocrystallites in the films. The sharp and intense red luminescence is useful for photoelectric devices and optical communications.