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Modification of band gap in lithium niobate caused by indium incorporation

Authors

  • J. Castillo-Torres

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    • Instituto de Física y Matemáticas, Universidad Tecnológica de la Mixteca, Huajuapan de León, Oaxaca, Mexico
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Corresponding author: e-mail jaimec@mixteco.utm.mx, Phone: +52 01 953 5320214, ext: 290, Fax: +52 01 953 5320399

Abstract

Measurements on transition energies near the optical absorption band edge for lithium niobate samples doped with indium at several concentrations are presented. Indirect and direct optical absorption processes were analyzed. It was found that the energies for these transitions are larger than those corresponding to undoped lithium niobate, suggesting that the energy band structure was modified by the presence of indium. For an indium concentration between 0 and 4 mol%, a value of energy of 3.8 eV was measured for indirect transition, and a range of 3.9–4.0 eV was determined for direct transition energy; whereas 3.6 and 3.8 eV were obtained, respectively, for the corresponding values of pure lithium niobate. In addition, Urbach and phonon energies were also calculated for the same indium-doped lithium niobate samples which values are lesser than those obtained for pure lithium niobate. Both behaviors remain unaltered regardless of whether the indium concentration is above or below the optical damage threshold value. Substitution of only lithium vacancies and antisite defects by indium atoms for any concentration of doping may explain the results.

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