Luminescent centres F and F+ in α-alumina detected by cathodoluminescence technique

Abstract α-Al 2 O 3 (0 0 0 1) single crystals have been investigated using cathodoluminescence (CL) technique and Auger electron spectroscopy (AES). The main luminescent centres such as F, F + or Cr 3+ activated during the irradiation of crystals by electrons of 4 keV energy were detected and discussed. CL intensity is shown to be highly dependent on both synthesis conditions and thermal annealing treatments. The air-annealing treatments at high temperature (1700 °C) reduce considerably the concentration of defects inducing a constant evolution of CL-signal of the band located at 330 nm attributed to F + defects. On the contrary, crystals not annealed enough display a large increase of the F + CL-signal during the electron irradiation. The F + emission is also observed to be very sensitive to electron dose.