Properties of Sm‐doped CaNb2O6 thin films deposited by radio‐frequency magnetron sputtering

Abstract

Sm‐doped CaNb2O6 (CaNb2O6:Sm) phosphor thin films were prepared by radio‐frequency magnetron sputtering on sapphire substrates. The thin films were grown at several growth temperatures and subsequently annealed at 800 °C in air. The crystallinity, surface morphology, optical transmittance, and photoluminescence of the thin films were investigated by X‐ray diffraction, scanning electron microscopy, ultraviolet‐visible spectrophotometry, and fluorescence spectrophotometry, respectively. All of the thin films showed a main red emission radiated by the transition from the 4G5/2 excited state to the 6H9/2 ground state of the Sm3+ ions and several weak bands under ultraviolet excitation with a 279 nm wavelength. The optimum growth temperature for depositing the high‐quality CaNb2O6:Sm thin films, which was determined from the luminescence intensity, was found to be 400 °C, where the thin film exhibited an orthorhombic structure with a thickness of 370 nm, an average grain size of 220 nm, a band gap energy of 3.99 eV, and an average optical transmittance of 85.9%. These results indicate that the growth temperature plays an important role in controlling the emission intensity and optical band gap energy of CaNb2O6:Sm thin films.