The effects of thermal annealing on the concentration of cationic vacancies in p-type semiconducting NiO thin films have been studied by x-ray absorption spectroscopy at the O 1s threshold. This technique proves to be very sensitive to the amount of Ni vacancies through the intensity of a prepeak observed below the absorption threshold, associated with Ni ions in a high oxidation state. Samples with different vacancy concentrations were obtained by radio frequency magnetron sputtering with different O2/Ar ratios in the plasma. Thermal effects have been studied both during thin film growth and after postprocessing annealing. In both cases, the observed effects were very similar, showing a depletion of cationic vacancies with temperature. By changing the surface sensibility of the x-ray absorption spectroscopy measurements, the authors could find out that the transition to stoichiometric NiO begins at the surface.
Thermal induced depletion of cationic vacancies in NiO thin films evidenced by x-ray absorption spectroscopy at the O 1s threshold
Alejandro Gutiérrez, Guillermo Domínguez-Cañizares, Stefan Krause, Daniel Díaz-Fernández, Leonardo Soriano; Thermal induced depletion of cationic vacancies in NiO thin films evidenced by x-ray absorption spectroscopy at the O 1s threshold. J. Vac. Sci. Technol. A 1 May 2020; 38 (3): 033209. https://doi.org/10.1116/6.0000080
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