Optical defects and their depth penetration in 200 keV electron irradiated IIa diamond

Abstract

Diamond is a wide bandgap semiconducting material, and electron irradiation is a good modification method for diamond. When the diamond with a thickness of 0.1 mm is irradiated with MeV electrons, the irradiation defects will be evenly distributed in the crystal. However, when the electron irradiation energy is 200 keV, the situation is different. The distribution of irradiation defects is not uniform, so these distributions cannot be ignored. In this work, the low-temperature photoluminescence method is employed to study the optical defects and their depth penetration in 200 keV electron irradiated IIa diamond. With the increase of depth penetration, the intensities of 2.091 eV emission and GR1 emission decrease accompanied by the enhancement of nitrogen vacancy (NV) intensity. The attenuation coefficients are 0.068 μm−1 for 2.091 eV emission and 0.045 μm−1 for GR1 emission, respectively. However, the enhancement coefficient is 0.02 μm−1 for the NV center, which is quite close to the difference of attenuation coefficient between 2.091 eV and GR1 emissions. The results indicated that the 2.091 eV emission is possibly related to self-interstitials and during the irradiation, the self-interstitials annihilate with the vacancies in the structure of nitrogen-vacancy defects. Furthermore, the 2.091 eV emission has a larger migration distance of about 65 μm, which is greater than GR1 emission (50 μm). This work also concludes that vacancy-related optical defects more accurately characterize the actual penetration of radiation damage in diamonds than interstitial-related optical defects.