Photoluminescence properties of BaMoO4 amorphous thin films

BaMoO4 amorphous and crystalline thin films were prepared from polymeric precursors. The BaMoO4 was deposited onto Si wafers by means of the spinning technique. The structure and optical properties of the resulting films were characterized by FTIR reflectance spectra, X-ray diffraction (XRD), atomic force microscopy (AFM) and optical reflectance. The bond Mo–O present in BaMoO4 was confirmed by FTIR reflectance spectra. XRD characterization showed that thin films heat-treated at 600 and 200 °C presented the scheelite-type crystalline phase and amorphous, respectively. AFM analyses showed a considerable variation in surface morphology by comparing samples heat-treated at 200 and 600 °C. The reflectivity spectra showed two bands, positioned at 3.38 and 4.37 eV that were attributed to the excitonic state of Ba2+ and electronic transitions within MoO2−4, respectively. The optical band gaps of BaMoO4 were 3.38 and 2.19 eV, for crystalline (600 °C/2 h) and amorphous (200 °C/8 h) films, respectively. The room-temperature luminescence spectra revealed an intense single-emission band in the visible region. The PL intensity of these materials was increased upon heat-treatment. The excellent optical properties observed for BaMoO4 amorphous thin films suggested that this material is a highly promising candidate for photoluminescent applications.

Room-temperature PL spectra of BaMoO4 thin films excited with the 488 nm line of an argon ion laser heat-treated at 200 °C for 2 h (a), 4 h (b), 8 h (c), 16 h (d), heat-treated at 600 °C in a microwave for 10 min (e) and in a resistive furnace for 2 h (f).Figure optionsDownload as PowerPoint slide