Correlation Between Thermally Stimulated Exoelectron Emission (TSEE) Glow Curves and Optical Absorption (OA) Spectra for MgO Single Crystal

Abstract

Abstract TSEE glow curves of MgO single crystals, heat treated at 1000 oC for 30 min and X irradiated, showed prominent peaks at 190 oC(peak I) and 430 oC(peak II). OA spectra of samples, heat treated under the same conditions and exposed to 60Co ? radiation, showed bands at 540, 285, 250 and 220 nm. Submitting the samples to successive heat treatments from room temperature (RT) up to 1000 oC, caused: (i) the 540 nm band to disappear after annealing at 100 oC for 30 min; (ii) a slow decay of the other bands with successive annealing up to 410 oC; (iii) with the 525 oC annealing the 220 nm almost to disappear; (iv) the 650 oC annealing to eliminate completely the 285 nm band while the 250 nm band became clearly resolved. The 220 and 285 nm bands have been associated with Fe3+ present in the crystal. While the band at 220 nm started to decrease after annealing at 410 oC, the TSEE peak II had its maximum at 430 oC, indicating that this TSEE peak is formed at the expense of the centres that give rise to the 220 nm band.