Optical characterization by variable angle spectroscopic ellipsometry of nitrogen-doped Mg Zn1−O thin films prepared by the plasma-assisted reactive evaporation method

Autor: Shigeki Chiba, Takami Abe, Kouichi Tsutsumi, K. Aota, Yasube Kashiwaba, Michiko Nakagawa, Y. Kashiwaba, Hiroshi Osada, T. Ojima, Masahiro Daibo, Tetsuya Chiba, Tamiya Fujiwara, Ikuo Niikura, Akira Nakagawa, Shuzo Takahashi, Michio Suzuki
Rok vydání: 2014
Předmět:
Zdroj: Thin Solid Films. 571:615-619
ISSN: 0040-6090
DOI: 10.1016/j.tsf.2014.02.091
Popis: Non-doped Mg x Zn 1 − x O films (Mg x Zn 1 − x O films) and nitrogen-doped Mg x Zn 1 − x O films (Mg x Zn 1 − x O:N films) were grown epitaxially on Zn faces of ZnO single crystal substrates by the plasma-assisted reactive evaporation (PARE) method using ZnMg alloys. Optical parameters, refractive index n , extinction coefficient k , and absorption coefficient α of these films and ZnO substrate were easily estimated by variable angle spectroscopic ellipsometry. The k values of these films abruptly increased with increase in photon energy near the absorption edge region. Dispersions of n of these films were sharper with larger peak values than that of a ZnO substrate. Mg x Zn 1 − x O films and Mg x Zn 1 − x O:N films grown on a ZnO substrate by the PARE method are of high quality with less defects than those of a ZnO substrate. Maximum value of α of these films calculated from k was about 2 × 10 5 cm − 1 . The values of intercepts on photon energy hν axis of ( αhν ) 2 ‐ hν plots for these films and the ZnO substrate agree with peak energy of PL spectra, the origin of which is free excitons. These results indicate that absorption in those materials is dominated by exciton absorption.
Databáze: OpenAIRE
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