Structure and role of carbon-related defects in yttrium aluminum garnet

Abstract This paper presents ab-initio calculations of composition and energy structure of carbon-related defects in carbon-doped yttrium aluminum garnet, Y3Al5O12. Defect formation energies are considered for isolated point defects and their combinations in case of O-poor atmosphere, which is inherent to crystal growth under Ar + CO gas conditions, and O-rich atmosphere used at post-growth annealing. The point CAl and complex carbon-related defects, such as Ci-VAl, and CAl-VO with lower formation energies should play a role of electron acceptors that compete with oxygen vacancies for electron capture. These results are discussed in conjunction with specific properties of carbon-doped garnets, in particular, no F-type center formation in annealed crystals, even under high irradiation doses.