Hafnium oxide thin films studied by time differential perturbed angular correlations

Abstract

We report on the study of hafnium oxide thin films grown by pulsed laser deposition at various partial oxygen pressures by Time Differential Perturbed Angular Correlations using the nuclear probe 181Hf(β−)181Ta to determine the nuclear quadrupole interaction (NQI), and by x-ray diffraction. The samples were neutron activated and measured at room temperature as received as well as after annealing in air. All spectra exhibited two to three inequivalent probe sites, even after annealing. At 0.3 mbar oxygen partial pressure and annealing for 5 hs at 1073 K the majority (88%) of the sites exhibited NQI parameters as reported for the bulk monoclinic phase [ωQ = 125.4(2) Mrad/s, η = 0.335(5)]. We can exclude amorphous as well as cubic and tetragonal hafnium oxide phases in the annealed samples. There was no indication of room-temperature ferromagnetism.