Sudip. K. Sinha
Abstract
We report the thermal annealing effect of ZnO-SnO2 composite thin films deposited by pulsed laser deposition on its structural, electrical, and optical properties. The results present a consistent portrayal of the evolution of ZnO-SnO2 composite oxide films phase formation in post-annealed condition ...
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We report the thermal annealing effect of ZnO-SnO2 composite thin films deposited by pulsed laser deposition on its structural, electrical, and optical properties. The results present a consistent portrayal of the evolution of ZnO-SnO2 composite oxide films phase formation in post-annealed condition and its subsequent effect on various physical properties. X-ray diffraction confirms that the films transform from nearly amorphous to fully crystalline state on thermal annealing at 600 °C. X-ray photoelectron spectroscopy reveals a small shift in Sn-3d peak towards lower energy and O-1s and Zn-2p < /em> peaks towards higher binding energy with increasing ZnO concentration and confirms the formation of combined oxides of ZnO and SnO2. The average optical transmission is greater than 80 % in the visible region of the annealed ZnO-SnO2 composite films. The lowest electrical resistivity of 9.8 × 10 -4 Ωcm has been obtained in the film containing 25 wt % ZnO. Our results suggest that annealed ZnO-SnO2 composite films with improved electrical and optical properties could find potential use in thin film solar cells or touch pad control panels.
Sudip K. Sinha
Abstract
Pure and Al-doped single-crystalline 1-D SnO2 based nanostructures were synthesized via a catalyst free simple chemical vapour transport and condensation process in Ar/O2 atmosphere. The crystalline structure, morphology and defect states of pure and Al-doped SnO2 nanostructures have been investigated ...
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Pure and Al-doped single-crystalline 1-D SnO2 based nanostructures were synthesized via a catalyst free simple chemical vapour transport and condensation process in Ar/O2 atmosphere. The crystalline structure, morphology and defect states of pure and Al-doped SnO2 nanostructures have been investigated in detail. Incorporation of Al in the interstitial voids of tetragonal SnO2 lattice is proved by investigating through various analytical techniques. Al doping in SnO2 significantly increases its defect concentration as demonstrated by photoluminescence spectra. The PL spectra for pure and Al-loaded SnO2 samples shows a less intense excitonic peak at ~384 nm in the UV region apart from the broad and intense yellow emission peak centred at around ~596 nm and a shallow peak at ~672 nm, respectively. For the development of stable and economically viable sensor modules for ammonia vapour detection, sensitivity at three different concentration of NH3 vapours (25ppm, 50 ppm and 100 ppm) were investigated by varying the operating temperature (250–400 °C). The minimum sensitivity for Al-doped SnO2 nanobelts was found to be 0.47 (at 25 ppm and 250 °C) and the maximum as 1.85 (at 100 ppm and 350 °C), which is 2-3 times higher than that for pure SnO2 nanowire assembles. Our results are found to be reproducible after cross examination by repeated observations. The response time (35–110 s), and recovery time (50–120 s) of our Al-doped SnO2 nanostructured sensors, for different concentrations of NH3 vapours, are equivalent or less if compared to those of available metal-oxide sensors in market.
