Atomic and electronic structures of amorphous ZrO2 and HfO2 films

Atomic and electronic structures of ZrO2 and HfO2 films deposited using sputtering technique were studied by X-ray diffraction (XRD), EXAFS spectroscopy, photoemission (with X-ray and ultraviolet excitation sources) and electron energy loss spectroscopy (EELS). XRD results indicated that the as-deposited films were amorphous and a monoclinic phase was detected after annealing them in ambient at 800 °C. Photoemission results indicated that the ZrO2 valence band consists of two bands separated by an ionic gap of 6 eV. The lower band of 10 eV width is occupied mainly by O 2s states. EELS results indicated that the bandgap of ZrO2 and HfO2 films are 4.7 and 5.7 eV, respectively.