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Radio-luminescence spectral features and fast emission in hafnium dioxide nanocrystals

Abstract

In this work, we investigate the optical properties of hafnium dioxide nanocrystals, upon X-ray irradiation, looking for spectral evolutions following thermal treatments in air up to 1000 °C that modify the crystal size as well as their point defects concentrations. Radio-luminescence measurements from 10 K up to room temperature reveal a rich and evolving picture of the optical features. A complete spectral analysis of the broad luminescence spectra reveals the presence of several emission components in the visible and UV regions. The lower energy components peaking at 2.1, 2.5, and 2.9 eV are characterized by a thermal quenching energy of 0.08 eV, while the corresponding value for the UV bands at 4.1 and 4.7 eV is close to 0.23 eV. We tentatively assign the components ranging from 2 to 3 eV to the presence of optically active defects of intrinsic nature, together with the occurrence of titanium impurities; conversely, the bands at higher energies are likely to be of excitonic nature. The comparison with previous photo-luminescence studies allows to evidence characteristic differences between the features of luminescence emissions caused by intra-centre excitation and those occurring under ionizing irradiation. Finally, scintillation measurements in the visible range reveal the existence of a fast decay in the nanosecond time scale for the smallest hafnia nanocrystals. This study offers a clear description of HfO2 luminescence characteristics upon excitation by X-rays and can lead to a better comprehension of the structure–property relationship at nanoscale in metal oxides.  

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Publication details

The article was received on 23 Feb 2018, accepted on 14 May 2018 and first published on 14 May 2018


Article type: Paper
DOI: 10.1039/C8CP01230J
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Radio-luminescence spectral features and fast emission in hafnium dioxide nanocrystals

    I. Villa, A. Lauria, F. Moretti, M. Fasoli, C. Dujardin, M. Niederberger and A. Vedda, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP01230J

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