Synthesis and characterization of hafnium oxide films for thermo and photoluminescence applications

Hafnium oxide (HfO₂) films were deposited by the ultrasonic spray pyrolysis process. The films were synthesized from hafnium chloride as raw material in deionized water as solvent and were deposited on corning glass substrates at temperatures from 300 to 600 °C. For substrate temperatures lower than 400 °C the deposited films were amorphous, while for substrate temperatures higher than 450 °C, the monoclinic phase of HfO₂ appeared. Scanning electron microscopy showed that the film's surface resulted rough with semi-spherical promontories. The films showed a chemical composition close to HfO₂, with an Hf/O ratio of about 0.5. UV radiation was used in order to achieve the thermoluminescent characterization of the films; the 240 nm wavelength induced the best response. In addition, preliminary photoluminescence spectra, as a function of the deposition temperatures, are shown.