| Scope and Method of Study. The objective of this study is to investigate the point defects in single crystals of undoped LiNbO(,3), undoped LiTaO(,3), and Mg-doped LiNbO(,3). Optical absorption, electron spin resonance (ESR), and thermal luminescence techniques were used to study the point defects produced by x-irradiation and reduction in these materials.; Findings and Conclusions. Radiation-induced defects in undoped LiNbO(,3) and LiTaO(,3) include a trapped hole center and an electron trapped on either a Nb('5+) ion or on a Ta('5+) ion. The Ta('4+) ion in LiTaO(,3) was identified by ESR as a self-trapped electron. A different electron trap, assigned to a Mg('+) complex, was observed after x-irradiation in certain Mg-doped LiNbO(,3) crystals, depending on the Mg-doping level and the stoichiometry.; Oxygen vacancies, produced by reduction, were identified in LiNbO(,3) and LiTaO(,3). Spectroscopic evidence for F to F('+) conversion at 77 K was observed in both materials. The F('+) centers decay in the 100 K to 150 K region. Oxygen vacancies are formed in Mg-doped LiNbO(,3), but the F('+) centers are stable at room temperature. An electron from the vacancy is trapped at a Mg('2+) complex and is assigned to a 1200 nm optical absorption band. |
