Effect of zinc oxide doping on the structural and optical characterization of nanostructured molybdenum oxide films.

Undoped and zinc oxide (ZnO) doped molybdenum oxide (MoO3) films were prepared by RF magnetron sputtering technique. The influence of doping and post annealing temperature on the structural and optical properties of these films were investigated systematically using X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-VIS spectroscopy and photoluminescence spectroscopy (PL). The XRD patterns indicate the presence of stoichiometric orthorhombic alpha-MoO3 phase in the annealed (573 and 673 K) undoped molybdenum oxide films and in ZnO doped molybdenum oxide film (annealed at 673 K). The crystalline grain size in the films was investigated using Debye Scherrer formula and corrected using Hall-Williamson equation. The SEM and AFM images revealed the distribution of nano leafs, nanorods and nanograins. Nanorods of length 1.4 microm and diameter 149 nm can be observed in ZnO doped films. The optical band gap energy was found to increase with increase in annealing temperature and particle size. These nanostructures show a room temperature PL emission in the UV and visible region.

Micro-structural, electrical and spectroscopic investigations of pulsed laser ablated palladium incorporated nanostructured tungsten oxide films.

Pure and Pd incorporated (0.5, 1 and 5 wt%) WO3 films are prepared on quartz substrates using pulsed laser ablation (PLD) technique in an oxygen ambient of 0.12 mbar, at a substrate temperature (Ts) of 873 K. Palladium incorporation effects on the microstructure, optical and electrical properties of tungsten oxide films are systematically investigated using techniques like X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), micro-Raman spectroscopy, UV-Vis absorption spectroscopy and temperature dependent electrical resistivity measurements. The micro-structural analysis by XRD and micro-Raman indicates that Pd addition can perturb the tungsten oxide lattice and suppress the grain growth. Optical band gap values of the films increases from 3.17 eV for pure WO3 to 3.29 eV for 5 wt% Pd incorporated WO3 films. All the films present high transparency in the visible spectral range. The electrical resistivity studies of the pure and Pd incorporated films done at room temperature and for the range of temperature; 170-450 K reveal that Pd addition can lower the resistivity of the WO3 thin films. Room temperature resistivity as well as activation energy of the film decreases exponentially with Pd incorporation concentration. Highly transparent, nanocrystalline and semiconducting WO3 films with low resistivity obtained by Pd incorporation can make WO3 suitable for microelectronics industry and for gas sensing applications.