Different Types Of Oxygen Vacancies Research Articles

Oxygen defects ordering in ?-Bi2O3: LMTO-ASA and FPLMTO calculations

Using the Full-Potential LMTO and LMTO-ASA methods we have carried out the calculations of electronic structure and chemical bonding for different types of oxygen vacancies ordering in δ-Bi2O3. Nonlinear changes of cohesive energy with the variation of vacancy concentration was found. The lattice with two vacancies per cell appears to be the most stable one with vacancies ordered along the 〈111〉 direction. The semiconducting gap formation is analyzed, and the suggestion is made that the gap corresponds to the structure with uniform distribution of oxygen atoms over all possible oxygen crystal lattice site. © 1995 John Wiley & Sons, Inc.

Photoluminescence and optical absorption studies of the effects of heat treatment on cuprous oxide

The defects responsible for the short-wave (720 nm) and medium-wave (820 nm) luminescence in cuprous oxide can be created by annealing the crystal at a temperature of 1050 °C under low oxygen pressures. The annihilation of these defects has been observed from the photoluminescence and optical absorption measurements after the crystal has been subjected to a second annealing in the temperature range of about 750 °C under a reducing atmosphere. From the photoluminescence measurements, the density of these defects is found to decrease exponentially as a function of annealing time, as manifested by the reduction in the luminescent intensity. The rate of reduction in intensity is also found to increase with annealing temperature.Because the defects responsible for the luminescence are ascribed to various forms of oxygen vacancies, we believe the decrease in luminescence is due to a reduction in the oxygen vacancies resulting from the formation of copper precipitates in the crystal. The short-wave and medium-wave emissions, which are ascribed to different types of oxygen vacancies, are found to have different activation energies of diffusion.