Study of charging phenomena in MgO single crystal: effect of polishing, annealing temperature and crystallographic orientation

Several experiments have shown that dielectric improvement of ceramics could be partially explained by the decrease of the trapped charge density. To carry out the study of charged dielectrics through to a successful conclusion, preliminary analyses are necessary to establish standard norms of utilisation of ceramics. Through recent studies, it was admitted that a trapping phenomenon is taking place on specific sites: point defects (impurities, vacancies…), lattice distortion and extended defects (grain boundaries, dislocations…) etc. Model of impurities states and Anderson states can analyse respectively the trapping and the diffusion of charges in ceramics. The aim of this paper is to outline the polishing effect on the charge trapping phenomena in a single crystal of magnesium oxide (MgO). In this way, using a scanning electron microscope (SEM), the charging phenomena was characterised for MgO as polished or post-annealed. In addition the role of the crystallographic orientation was studied. The amount of trapped charge is determined using the mirror method associated with the absorbed current method.