Structural, optical and electrical characterizations of spray deposited CdMoO₄ and CdWO₄ thin films

Abstract

Preparation of cadmium molybdate (CdMoO₄) and cadmium tungstate (CdWO₄) thin films for the first time by 'spray pyrolysis' using their ammonical solution as precursor, is reported here. Growth of the films takes place by pyrolytic decomposition of the spraying precursor so lution onto the preheated glass substrates X-ray diffraction studies confirm the polycrystalline, single-phase nature of the sintered films. Scanning electron microscopic images of the thin films clearly show aggregates of microcrystallites. Optical absorption spectrum in the range 350-850 nm shows direct as well as indirect optical transitions in both the materials. The plot of log (ϭ)<i> </i>versus 1/<i>T, </i>within the temperature range 310-600 K for both the films indicates their semiconducting nature and shows a break in the curves. The thermal activation energies below and above the break temperature have been estimated to be 0.73 eV and 0.10eV for CdMoO₄ ; and 0.98 eV and 0.14 eV for CdWO₄ , respectively. The data have been analyzed using valence and conduction band model.