Optical properties of epitaxial Na0.5Bi0.5TiO3 lead-free piezoelectric thin films: Ellipsometric and theoretical studies
| Autor: | Tomasz Krzyzynski, Marie Bousquet, Marius Grundmann, Bohdan Andriyevsky, Krzysztof Dorywalski, N. Lemée, Michal Piasecki, Rüdiger Schmidt-Grund |
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| Rok vydání: | 2017 |
| Předmět: |
010302 applied physics
Materials science Condensed matter physics Absorption spectroscopy Band gap Analytical chemistry General Physics and Astronomy 02 engineering and technology Surfaces and Interfaces General Chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Semimetal Surfaces Coatings and Films Pulsed laser deposition Condensed Matter::Materials Science Absorption edge 0103 physical sciences Direct and indirect band gaps Thin film 0210 nano-technology Electronic band structure |
| Zdroj: | Applied Surface Science. 421:367-372 |
| ISSN: | 0169-4332 |
| DOI: | 10.1016/j.apsusc.2016.09.078 |
| Popis: | Ultra-thin Na 0.5 Bi 0.5 TiO 3 films were epitaxially deposited on (001)SrTiO 3 substrate by pulsed laser deposition. From the ellipsometric spectra collected in the photon energy range 2÷8.7 eV, real and imaginary parts of the complex dielectric function were determined. It was found, that the electronic transitions related to the fundamental absorption edge are of indirect type, which is confirmed by ab initio band structure calculations. This finding is in contradiction to previous theoretical studies but in agreement with the most recent experimental works. Based on their determined energies, phonons involved in the band gap transition can be primarily associated with vibrations involving oxygen atoms. Contributions to the VUV absorption spectra come mainly from the electronic transitions from the O 2 p valence band levels to Ti 3 d conduction band levels and a little to the Bi p levels. |
| Databáze: | OpenAIRE |
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