SEM cathodoluminescence studies of heat-treated MgO crystals

— The luminescence of MgO single crystals has been investigated using a scanning electron microscope (SEM) with a detection system for spectroscopic cathodoluminescence (CL) studies. The corrected CL spectrum of MgO consists of a large blue band with a maximum at 460 nm and a broad red emission with a dominant 722 nm peak. Annealing treatments in air, carbon monoxide or hydrogen change the spectra considerably. Oxidation divides the blue band into a number of peaks and shoulders and finally eliminates the deformation-induced peak entirely but has no effect on the shape or position of the red emission. In contrast, heating in Tiydrogen produces a sharpening of the broad red luminescence into six peaks, whilst the blue band remains unaffected. A similar effect was observed for carbon monoxide treatment except that very long annealing times completely eliminated the red peaks and replaced them by a new broad band at 645 nm.