Optical, electrical and structural characterization of ZnO:Al thin films prepared by a low cost sol–gel method

ZnO:Al thin films were prepared on glass and silicon substrates by the sol–gel spin coating method. The x-ray diffraction (XRD) results showed that a polycrystalline phase with a hexagonal structure appeared after annealing at 400 °C for 1 h. The transmittance increased from 91 to about 93% from pure ZnO films to ZnO film doped with 1 wt% Al and then decreased for 2 wt% Al. The optical band gap energy increased as the doping concentration was increased from 0.5 wt% to 1 wt% Al. The metal oxide semiconductor (MOS) capacitors were fabricated using ZnO films deposited on silicon (100) substrates and electrical properties such as current versus voltage (I–V)(I–V) and capacitance versus voltage (C–V)(C–V) characteristics were studied. The electrical resistivity decreased and the leakage current increased with an increase of annealing temperature. The dielectric constant was found to be 3.12 measured at 1 MHz. The dissipation value for the film annealed at 300 °C was found to be 3.1 at 5 V.

► ZnO:Al thin films were prepared on glass and silicon substrates by sol–gel spin coating.
► XRD results confirm that a hexagonal structure appeared after annealing at 400 °C for 1 h.
► Optical transmittance and optical band gap energy with Al doping was investigated.
► MOS capacitors were fabricated using ZnO films deposited on silicon (100) substrates.
► Electrical properties were evaluated with annealing temperature.