期刊
NEW JOURNAL OF PHYSICS
卷 23, 期 3, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1367-2630/abe3ac
关键词
small polarons; self-trapped excitons; unltrafst nonlinear optical spectroscopy; ferroelectrics; DFT; electric conductivity; atomistic simulations
资金
- Deutsche Forschungsgemeinschaft (DFG) [FOR5044, SA 1948/2-1, IM37/11-1, FR1301/32-1, INST 190/165-1 FUGG]
The investigation reveals some differences between LT and LN with respect to polaronic defects, optical response, and electrical conductivity. Despite fundamental similarities, discrepancies in structure, energy landscape, and temperature behavior between the two materials suggest potential for novel applications.
Different aspects of ferroelectric LiTaO3 (LT) such as polaronic defects, optical response and electrical conductivity are investigated by the most recent theoretical and experimental approaches. Comparing the results with the state-of-the-art knowledge of the widely studied LiNbO3 (LN), we evaluate the general assumption that there is little difference between the aforementioned properties of LT and LN. First-principles calculations reveal the existence of point defects in LT qualitatively compatible with the polaronic picture established in LN. Though, peculiar differences with respect to the individual binding energies and polaronic deformation can be revealed. Accordingly, (sub-)picosecond transient absorption measurements show pronounced differences in the kinetics in the sub-ps time domain of small polaron formation and, even more pronounced, in the long-term evolution identified with small polaron hopping. In contrast, (sub-)ps transient luminescence, attributed to the relaxation of self-trapped excitons in LN, shows very similar kinetics. Electrical conductivity measurements are performed in air as function of temperature. Up to about 600 degrees C they demonstrate similar temperature dependence for the two materials, from which rather comparable activation energies can be extracted. However, in the high-temperature range from about 600 degrees C to 920 degrees C both materials show noticeable differences. The results suggest that the fundamental microscopic understanding of LN can be in part transferred to LT. However, due to differences in structure, energetic landscape and temperature behavior, discrepancies between the two materials bear a striking potential for novel applications, even at high temperatures.
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