期刊
SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS
卷 16, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1468-6996/16/2/026002
关键词
epitaxial growth; ferroelectric nanofilms; optical properties
资金
- Academy of Finland [260361, 264961]
- Grant Agency of Czech Republic [P108/12/1941]
- Ministry of Education and Science of Russia [8516]
- European Research Council [ERC-2012-StG 307502-E-CONTROL]
- Academy of Finland (AKA) [264961, 264961] Funding Source: Academy of Finland (AKA)
Perovskite-type ferroelectric (FE) crystals are wide bandgap materials with technologically valuable optical and photoelectric properties. Here, versatile engineering of electronic transitions is demonstrated in FE nanofilms of KTaO3, KNbO3 (KNO), and NaNbO3 (NNO) with a thickness of 10-30 unit cells. Control of the bandgap is achieved using heteroepitaxial growth of new structural phases on SrTiO3 (001) substrates. Compared to bulk crystals, anomalous bandgap narrowing is obtained in the FE state of KNO and NNO films. This effect opposes polarization-induced bandgap widening, which is typically found for FE materials. Transmission electron microscopy and spectroscopic ellipsometry measurements indicate that the formation of higher-symmetry structural phases of KNO and NNO produces the desirable red shift of the absorption spectrum towards visible light, while simultaneously stabilizing robust FE order. Tuning of optical properties in FE films is of interest for nanoscale photonic and optoelectronic devices.
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