UV-Induced Change in the Electronic Structure of SrTiO3 at Low Temperature Probed by Resonant X-ray Emission Spectroscopy
Both Ti $L$ and $K\beta$ resonant x-ray emission spectra (RXES) of SrTiO 3 were measured at low temperature, $T\leq 40$ K. Regardless of the $d^{0}$-ness of a Ti 4+ ion, a $dd$ excitation peak in Ti $L$ RXES is irreversibly created by UV irradiation, directly indicating a mixture of the $d^{1} L $ e...
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| Published in: | Journal of the Physical Society of Japan Vol. 82; no. 5; pp. 053701 - 053701-4 |
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| Main Authors: | , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
The Physical Society of Japan
01-05-2013
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| Online Access: | Get full text |
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| Summary: | Both Ti $L$ and $K\beta$ resonant x-ray emission spectra (RXES) of SrTiO 3 were measured at low temperature, $T\leq 40$ K. Regardless of the $d^{0}$-ness of a Ti 4+ ion, a $dd$ excitation peak in Ti $L$ RXES is irreversibly created by UV irradiation, directly indicating a mixture of the $d^{1} L $ electronic configuration under reduced symmetry around a Ti 4+ ion, where $ L $ denotes an oxygen hole. This mixture can also be evidenced by the UV-induced change in the relative intensity of two charge-transfer peaks observed in Ti $K\beta$ RXES. A similar change is reported for a cubic-to-tetragonal ferroelectric phase transition in BaTiO 3 . We therefore conclude that the local ferroelectric moment, i.e., displacement of a Ti 4+ ion in an oxygen octahedron, is induced in SrTiO 3 by UV irradiation at low temperature. |
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| Bibliography: | (Color online) (a) Ti $L$ RXES spectrum of an STO single crystal at low temperature. The excitation energy corresponds to that of the Ti $L_{3} e_{g}$ absorption edge shown by a tick mark in the inset (b). The detail of the solid framed area is shown in Fig. . (c) Intensity plot of Ti $L$ RXES spectra. The horizontal and vertical axes are excitation energy and emission energy, respectively. Two white dashed lines indicate Raman peaks and correspond to two features indicated by arrows in (a). (Color online) UV dependence of the $dd$ excitation peaks in the Ti $L$ RXES of STO. The spectrum of an electron-doped STO (La-5%-doped STO) is shown as a reference (gray [dashed] line). Under UV irradiation, the $dd$ peak of pure STO is observed at the same energy as that of LSTO. (Color online) Ti $K\beta$ RXES spectrum of an STO single crystal at low temperature. The excitation energy is set to the edge jump of the Ti $K$ XAS spectrum of STO powders, which is indicated by a tick mark in the inset. (Color online) UV dependence of CT peaks shown in the dashed frame in Fig. . The vertical axis is displayed with a logarithmic scale. Under UV irradiation, the intensity of CT2 becomes slightly enhanced with the relative decrease in the intensity of CT1 (blue [thick] line). |
| ISSN: | 0031-9015 1347-4073 |
| DOI: | 10.7566/JPSJ.82.053701 |