Structural and electrical characterisation of high-k ZrO2 thin films deposited by chemical spray pyrolysis method

As the applicability of high-k oxides in field-effect transistor became enormous, the physical and chemical understanding of their dielectric properties as well as preparation technique should be diligently studied. Herein, we have studied the deposition of zirconium oxide (ZrO2) thin film by chemical spray pyrolysis and we have investigated the influences of deposition temperature (200, 300, 400, 500 °C) and annealing temperature (500, 800 °C) on the morphological, structural, optical, and electrical properties of the film. It was observed that the as-deposited ZrO2 thin films at temperature below 500 °C were smooth, dense, and structurally amorphous - while the ZrO2 thin film deposited at 500 °C are poorly crystalline. As confirmed by Raman and X-ray diffraction peak deconvolution, ZrO2 tetragonal phase was predominant in the film upon annealing at 500 °C, and the monoclinic phase favoured after annealing at 800 °C. As-deposited ZrO2 thin film are optically transparent (above 80% in the visible region) with a slight decrease in transmittance upon annealing at higher temperature. The optical band gap of ZrO2 film was in the range 5.39-5.68 eV and the dielectric constant (k) in the range 4.3-13.0, depending on the deposition temperature.