Band gap tuning of amorphous Al oxides by Zr alloying

Stela Canulescu, N. C. Jones, C. N. Borca, C. Piamonteze, Kristian Rechendorff, Visweswara Chakravarthy Gudla, Kirill Bordo, Lars Pleth Nielsen, Søren V. Hoffmann, K. P. Almtoft, Rajan Ambat, Jørgen Schou

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The optical band gap and electronic structure of amorphous Al-Zr mixed oxides, with Zr content ranging from4.8 to 21.9% were determined using vacuum ultraviolet (VUV) and X-ray absorption spectroscopy (XAS). Thelight scattering by the nano-porous structure of alumina at low wavelengths was estimated based on the Miescattering theory. The dependence of the optical band gap of the Al-Zr mixed oxides on Zr content deviatesfrom linearity and decreases from 7.3 eV for pure anodized Al2O3 to 6.45 eV for Al-Zr mixed oxide with Zrcontent of 21.9%. With increasing Zr content, the conduction band minimum changes non-linearly as well.Fitting of the energy band gap values resulted in a bowing parameter of 2 eV. The band gap bowing of themixed oxides is assigned to the presence of the Zr d-electron states localized below the conduction bandminimum of anodized Al2O3.
Original languageEnglish
Article number091902
JournalApplied Physics Letters
Number of pages4
Publication statusPublished - 2016

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Canulescu, S., Jones, N. C., Borca, C. N., Piamonteze, C., Rechendorff, K., Gudla, V. C., Bordo, K., Nielsen, L. P., Hoffmann, S. V., Almtoft, K. P., Ambat, R., & Schou, J. (2016). Band gap tuning of amorphous Al oxides by Zr alloying. Applied Physics Letters, 109, [091902].