Urbach tail and bandgap analysis in near stoichiometric LiNbO₃ crystals

Abstract

Energy of the indirect and direct optical bandgap of nearstoichiometric lithium niobate (nSLN) crystals is evaluated by optical absorption measurement. The value of the indirect bandgap (3.95 eV) is consistent with the earlier reports. However, the direct bandgap energy of 4.12 eV is higher than the previously reported experimental value (3.68 eV). The direct bandgap energy obtained here is closer to the recent theoretical value estimated by Thierfelder et al. [Phys. Status Solidi C 7, 362 (2010)] in comparison to the previously predicted value by Ching et al. [Phys. Rev. B 50, 1992(1994]. The phonons involved in the indirect allowed transitions have energies $85 meV (685 cm À1 ) and are identified as the E(TO9) and E(LO8) optical phonon modes from the Raman scattering measurement.

Control of Intrinsic Defects in Lithium Niobate Single Crystal for Optoelectronic Applications

“…For estimation, α 2 vs. energy (hν) is plotted for all the samples as shown in Figure 9. The steep rise of absorption and its linear fit at higher photon energy depict the direct allowed interband transition [93]. The intercept of the straight line at the energy axis (α 2 = 0) yields the direct optical band-gap (E g ) energies which are listed in Table 2.…”

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Synthesis of ammonium and sulfate ion-functionalized titanium dioxide for photocatalytic applications

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Structural, Optical and Photocatalytic Properties of Co-Tio2 Prepared by Sol-Gel Technique

“…The exciton absorption is at about 477 nm. The band gap energy has been determined using the Tauc relation 21 , which is given by:…”