Laser excited photoluminescence of InSe single crystal shows three peaks at 1.311, 1.272, and 1.227 eV. The relative intensity of these peaks variation from point to point on the surface of the crystal. The high-energy peak is assigned to impurity to band transitions, the 1.277 eV to donor-acceptor type transition and 1.227 eV to transition within an impurity vacancy complex. From these peak positions and the known band gap, the donor and acceptor levels associated with these centers are estimated to be approximately 41 and 40 meV, respectively.
Infrared absorption study of the annealing behavior of defects in neutron transmutation-doped silicon is reported in this paper. Infrared absorption measurements were carried out in the region 10 000–400 cm−1. This has shown the presence of extended band edge tailing, divacancy associated bands (5882, 2900, and 2760 cm−1) and higher order bands (1300–700 cm−1) at different stages of isochronal annealing from 423 to 873 K. The study of higher order bands under illumination with monochromatic light of wavelength varying from 0.5 to 1.5 μm has helped in understanding the nature of the transitions responsible for higher order bands. These bands disappear on annealing at 873 K, and no new bands appear on further annealing the sample to 1223 K. By correlating the present results with our earlier electron paramagnetic resonance results, we have postulated the formation of voids at higher temperatures of isochronal annealing.
Infrared absorption spectrum of NaCl crystals doped with Ni(CN)42− shows the presence of this complex in the crystal in C4v and C2v site symmetry corresponding to the cation vacancy in the 〈100〉 direction above the plane of the ion and along 〈110〉 direction in the plane of the ion, respectively. X irradiation of these crystals produces Ni(CN)4n−, where n=3,4, and 5, giving rise to Ni ion in 1+, 0+, and 1− charge states, as shown by the new set of infrared bands. The infrared absorption from heat treated crystals give evidence for the migration of cation vacancies.
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