Site selective laser spectroscopy study of defect equilibria in MgO:Cr 3+

Abstract

Aliovalent Cr 3+ dopants in MgO are compensated either locally or distantly by magnesium vacancies. The relative concentrations of the two Cr 3+ sites are measured as a function of dopant concentration by site selective laser spectroscopy. The locally compensated site concentration increases dramatically as the dopant concentration is raised. The increase can be described by a mass action relationship for the pairing equilibrium between the dopant and its charge compensation. This behavior is in marked contrast to the defect equilibria in fluorite compounds where the site concentrations do not follow simple mass action relationships.