Optical absorption and electron paramagnetic resonance studies of chemically reduced congruent lithium niobate

Dutt, David A.; Feigl, F. J.; DeLeo, Gary G.

doi:10.1016/0022-3697(90)90175-f

Cited by 36 publications

(21 citation statements)

References 28 publications

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“…The observation that the EPR signal disappears for high doping concentrations of Mg [24] supports this interpretation, because the Mg atoms are assumed to occupy Li sites and thus to prevent the formation of Nb Li antisites [26], which are supposed to give rise to bound rather than free polarons [14]. However, the most striking argument for this scenario is the fact that the optical absorption at 1.7 eV and the EPR signal anneal simultaneously in the temperature range of 100-200 K, suggesting bound polarons as a common origin [27].…”

Section: Introductionmentioning

confidence: 94%

Free and defect-bound (bi)polarons inLiNbO3: Atomic structure and spectroscopic signatures fromab initiocalculations

Schmidt

Kozub

Biktagirov

et al. 2020

Phys. Rev. Research

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Polarons in dielectric crystals play a crucial role for applications in integrated electronics and optoelectronics. In this work, we use density-functional theory and Green's function methods to explore the microscopic structure and spectroscopic signatures of electron polarons in lithium niobate (LiNbO 3). Total-energy calculations and the comparison of calculated electron paramagnetic resonance data with available measurements reveal the formation of bound polarons at Nb Li antisite defects with a quasi-Jahn-Teller distorted, tilted configuration. The defect-formation energies further indicate that (bi)polarons may form not only at Nb Li antisites but also at structures where the antisite Nb atom moves into a neighboring empty oxygen octahedron. Based on these structure models, and on the calculated charge-transition levels and potential-energy barriers, we propose two mechanisms for the optical and thermal splitting of bipolarons, which provide a natural explanation for the reported two-path recombination of bipolarons. Optical-response calculations based on the Bethe-Salpeter equation, in combination with available experimental data and new measurements of the optical absorption spectrum, further corroborate the geometries proposed here for free and defect-bound (bi)polarons.

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Section: Introductionmentioning

confidence: 94%

Free and defect-bound (bi)polarons inLiNbO3: Atomic structure and spectroscopic signatures fromab initiocalculations

Schmidt

Kozub

Biktagirov

et al. 2020

Phys. Rev. Research

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“…This fact makes it difficult to control the reduction process and may lead to arbitrarily different results for slightly altered experimental conditions. [6][7][8][9] Since the dependence of bipolaron concentration on the reduction conditions in nominally pure LiNbO 3 is not generally known, the most convenient characterization is given by the properties of the bipolaron band itself. According to Ref.…”

Section: Samples Characterictics and Experimental Techniquesmentioning

confidence: 99%

Z-scan study of nonlinear absorption in reduced LiNbO3 crystals

Кострицкий

Aillerie

2012

Journal of Applied Physics

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Bipolaron recombination in conjugated polymers J. Chem. Phys. 135, 074902 (2011) Correlation effects on the dynamics of bipolarons in nondegenerate conjugated polymers J. Chem. Phys. 130, 234908 (2009) Acidification of three-dimensional emeraldine polymers: Search for minimum energy paths from base to salt J. Chem. Phys. 128, 234903 (2008) Transformation of polarons to bipolarons in disordered matter Appl. Phys. Lett. 92, 222108 (2008) A suitable model for emeraldine salt J. Chem. Phys. 128, 174706 (2008) Additional information on J. Appl. Phys. The nonlinear absorption (NLA) was studied by open-aperture Z-scan experiments in the chemically reduced nominally pure LiNbO 3 crystals at cw-illumination with the red (644 nm) and green (514.5 nm) laser beams. The magnitude of the measured NLA is considerably different from the reported Z-scan results obtained in as-grown LiNbO 3 . The positive sign of NLA obtained with the red light has been related to the generation of the small bound polarons absorbing in red and near-IR ranges. Application of green light results in the light-induced transparency, i.e., the Z-scan traces show negative sign of NLA. Intensity dependence of Z-scan traces allows for conclusion that the photo-induced dissociation of small Nb Li 4þ :Nb Nb 4þ bipolarons and sequent generation of small polarons gives the dominating contribution to the nonlinear optical absorption in reduced crystals with a large bipolarons concentration. V C 2012 American Institute of Physics.

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“…The blackening of LN is a well known effect caused by the chemical reduction (i.e., oxygen outdiffusion) of the material under vacuum annealing [6,7]. A direct correlation has been found [8] between the optical absorption and the concentration of Nb 4+ centers forming bipolarons. The light absorbing bipolaron is made from two Nb atoms, where one exists as antisite defect Nb 4+ Li (i.e.…”

Section: Resultsmentioning

confidence: 94%

“…The dependence corresponds to that of a semiconductor. As given above, [8] near the oxygen vacancy when each of Nb atoms traps one electron from the (2e) O defect. However, the plasma surface of our samples reveals a significant drop of Li concentration, see Fig.…”

Section: Resultsmentioning

confidence: 99%

Sheet resistance of LiNbO3 wafers processed in radio-frequency plasma of hydrogen

et al. 2000

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Radio-frequency discharge of 13.56 MHz in hydrogen was used for processing single domain crystalline LiNbO3 wafers under an electrodeless capacitive coupling. At a pressure of 0.5 torr and RF input power of 250 W a surface layer of approx. 0.5 μm on the LiNbO3 wafers was created in which the niobate structure was strongly injured. The Li concentration dropped almost to zero at the very surface and only niobium oxides remained there. After the surface modification the wafers lost their insulating properties and became electrically conducting. The sheet resistance was measured and revealed a semiconducting character. We discuss possible mechanisms of the charge carriers creation in the material during the plasma processing. The nuclear method NDP (Neutron Depth Profiling) has been used for the lithium depth profiling and the four-point probe technique for the sheet resistance measurements.

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Optical absorption and electron paramagnetic resonance studies of chemically reduced congruent lithium niobate

Cited by 36 publications

References 28 publications

Free and defect-bound (bi)polarons inLiNbO3: Atomic structure and spectroscopic signatures fromab initiocalculations

Free and defect-bound (bi)polarons inLiNbO3: Atomic structure and spectroscopic signatures fromab initiocalculations

Z-scan study of nonlinear absorption in reduced LiNbO3 crystals

Sheet resistance of LiNbO3 wafers processed in radio-frequency plasma of hydrogen

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