Role of carbon and electronic structure effects in Al₂O₃:C OSL phosphor

Alumina has been investigated for thermoluminescent (TL) properties since the 1950s along with a large number of materials which were tested for dosimetric applications. Some natural alumina crystals were found to be more favourable than LiF for luminescence dosimetry applications. However later Alumina was abandoned in favour of other more promising materials. However in 1990s it was observed that TL and optically stimulated luminescence (OSL) in carbon doped Al₂O₃ enhances its use as dosimetric material increasing its applicability immensely. It was further observed that the performance of carbon doped alumina improved and remained linear over a large range of exposure to radiation. Also radiation trapped in the material remained localized and did not dissipate with time. This possibly could arise due to electronic states which are localised and with no hybridisation with other extended states of the host matrix. Furthermore the vibrations of the impurity atoms or vacancies also do not have any interaction with the host matrix resulting in absence of dissipation of stored energy form the localised states. The radiation induced defects responsible for OSL have been characterized. The aim of the present work is to theoretically investigate the role of carbon doping in enhancing defects in the material and also understand the origin of trap and recombination states in the material