Conductive-Atomic Force Microscopy Investigation of the Electrical Properties of Low Temperature Deposed ZnO Transparent Thin Films

The paper presents the investigation by conductive-atomic force microscopy (C-AFM) of the variation of the local conductivity and topography of the transparent ZnO thin films deposed onto soda lima glass substrates by spin-coating of pre-prepared ZnO nanoparticles. With conductivity measurements at the nanometer level, the chemical and crystalline structure of the thin films obtained at temperature below 200 °C was investigated by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction, respectively, as a function of the number of the deposed layers and conditions of their deposition, such as deposition rate and the temperature of post-deposition annealing. The increase of the thermal treatment temperature, from 120 to 180 °C, leads to increased values of all thin films, most notably for the thickest sample with three layers deposed at 500 rpm that shows the highest decrease of thickness, indicating the highest compaction. The samples with three layers post-treated at 180 oC show grain growth associated with increased roughness.