Radiation-induced electronic and ionic charge storage and release in sapphire

Abstract

Radiation-induced thermally stimulated relaxation (TSR) processes in the reduced f -Al 2 O 3 (sapphire) crystal were investigated at 290-650 v K by means of the TS current (TSC), ionic depolarisation current (TSDC) and electron emission (TSEE) techniques. After thermal (ionic) polarisation of sapphire wide (∼75 v K) and asymmetric ionic dipolar TSDC peak at T max , 590 v K (disorientation of the anion vacancy-related dipoles) was detected. This peak correlates with the wide TSEE peak at T max , 615 v K, the radiation-induced electrical degradation (RIED) yield rise above 550 v K ( T max , 745 v K) and the chromium emission line broadening in ruby. Above 450-500 v K the anion vacancy hopping (migration) starts. This can lead to lattice dynamic disordering and anion vacancy diffusion-controlled processes in sapphire (especially in vacuo near the sample surface, grain boundaries, dislocations) in various TSR (TSC, TSDC, TS heat release and bleaching) and RIED phenomena. Surface structure and impurity content, surrounding atmosphere (vacuum or air) and electric fields determine these phenomena.