Neutron transmutation of 10{sup left}B doped diamond

摘要

Free standing 10{sup left}B isotope doped diamond films deposited by chemical vapor deposition in a microwave chamber were irradiated to thermal neutron fluence values of 0.32 × 10{sup}19, 0.65 × 10{sup}19, 1.3 × 10{sup}19, and 2.6 × 10{sup}19 n/cm{sup}2. Cooling of the diamond films was maintained during irradiation. In a separate experiment, neutron irradiation to a total fluence of 2.4 × 10{sup}20 n/cm{sup}2 with equal fast and thermal neutrons was also performed on a diamond epilayer without cooling during irradiation. The formation of defects in the diamond films was characterized using Raman, FTIR, photoluminescence, electron paramagnetic resonance spectroscopy, and X-ray diffraction. It was found that defect configurations in diamond responsible for an increase in continuum background in the one-phonon region of Raman spectrum were absent in the films that have been cooled. The FTIR peak at 1530 cm{sup}(-1) annealed in the sample irradiated to a fluence of 2.6 × 10{sup}19 n/cm{sup}2 indicating that the sample reached a temperature of 300℃ during irradiation. Absence of characteristic infrared absorption peaks that were observed only upon annealing neutron irradiated diamond is used to conclude that the temperature of the sample during neutron irradiation to a fluence of 2.6 × 10{sup}19 n/cm{sup}2 was well below 650℃ needed for mobility of defects and accumulation of stable unrecoverable damage. On the other hand, results from diamond epilayer subjected to equal thermal and fast neutron fluence of 2.4 × 10{sup}20 n/cm{sup}2 and without cooling showed that defects formed from displaced carbon atoms became mobile and formed complex configurations of irrecoverable damage. Electrical conductance of the unirradiated and irradiated diamond samples was measured as a function of temperature to determine the compensation of the p-type by the n-type charge carriers.