Change of cathodoluminescence spectra of diamond with irradiation of low energy electron beam followed by annealing

We have reported previously that cathodoluminescence (CL) spectra of type II diamond change with irradiation of 20 kV electron beam using a scanning electron microscope (SEM), although it is known that diamond has high resistance against radiation beams. Following the previous paper, the diamond irradiated with the electron beam was annealed at 500 °C, and the CL spectra were measured. It was found from the annealed sample that the CL spectra which changed with the irradiation are partially recovered, namely, the lines at 420 nm and 540 nm formed with the irradiation are annealed out, and the lines at 485 nm, 535 nm and 545 nm which disappeared with the irradiation are recovered. However the 420 nm broad band that appeared with the irradiation does not change with the heat treatment. The effect of the heat treatment suggests that the CL peaks which changed with the irradiation are related to ionization of defects.