Structural, electrical and optical properties of undoped ZnO thin films using ion beam sputtering and spray pyrolysis techniques

摘要

In this work, the structural, electrical and optical properties of undoped ZnO amorphous thin films prepared using Ion Beam Sputtering (IBS) and spray pyrolysis deposition techniques are presented. From the structural measurements, a transition from amorphous to polycrystalline phase has been observed at around 130 degrees C. From the optical measurements, the energy gap has been determined and showed an increase with the thickness of the films. The electric conductivity shows three different regimes. At low temperatures (T < 300 K), the electric conductivity increases linearly with temperature (semiconducting behaviour). At around 300 K, the conductivity is almost independent of temperature. For T > 300 K, the conductivity decreases almost linearly with temperature (metallic behaviour). This metallic behaviour might be related to the oxygen adsorption above room temperature. In addition, three regimes have been identified for the conduction mechanisms from the variation of both the electric conductivity and the seebeck coefficient as a function of temperature. Comparison between the results obtained by the two techniques is presented.