Determination of charge trapping ability in doped α-alumina

The influence of Ag, Mg and Cr impurities on the charge trapping characteristics of α alumina single crystal is investigated. The penetration profiles, after diffusion annealing, are determined from S.I.M.S. analysis leading to the impurity concentration in doped samples. Charge trapping abilities are deduced, with new experimental conditions, from the Induction Charge Method (I.C.M) during successive injections of 5 pC performed with an electron beam in a Scanning Electron Microscope. This method consists in measuring the evolution of the absorbed current, induced by the trapped charges in the metallic sample holder, during injection. From the new experimental conditions (low injection doses and defocused beam) a classification in terms of charge trapping ability for the various impurities is obtained and the dependence of the nature of impurity on the charge trapping properties is discussed.