Spray deposition and characterization of zirconium-oxide thin films

Zirconium oxide films were prepared by the pyrosol process using zirconium acetylacetonate as source material onto clear fused quartz and (100) silicon at sub;trate temperatures ranging from 300degreesC to 575degreesC. X-ray diffraction (XRD) measurements show that samples prepared at substrate temperatures lower than 425degreesC are amorphous. Films deposited at higher temperatures and short deposition times show a cubic crystalline structure. However, for long deposition times, the samples show monoclinic crystalline structure. A similar phase transformation is observed on samples deposited at short time if they are annealed at high temperature. The cubic and monoclinic phases of the corresponding samples were confirmed by infrared (IR) and Raman spectroscopy, respectively. The ZrO2 films with cubic phase show an almost stoichiometric chemical composition and refractive index values of the order of 2.1 with an energy band gap of 5.47 eV. The current-density electric-field characteristics of metal-oxide semiconductor (MOS) structures show a small ledge from 2 MV/cm to 4.5 MV/cm, indicating current injection and charge trapping. For higher electric fields, the current is associated with oxygen ion diffusion through the zirconium oxide film. The dielectric breakdown is observed at 6 MV/cm, which is a value higher than those observed in the monoclinic and tetragonal phases.