Neutron transmutation of 10B doped diamond

Free standing {sup 10}B isotope doped diamond films deposited by chemical vapor deposition in a microwave chamber were irradiated to thermal neutron fluence values of 0.32 x 10{sup 19}, 0.65 x 10{sup 19}, 1.3 x 10{sup 19}, and 2.6 x 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 x 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 x 10{sup 19} n/cm{sup 2} indicating that the sample reached a temperature of 300 C 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 neutronmore » irradiation to a fluence of 2.6 x 10{sup 19} n/cm{sup 2} was well below 650 C 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 x 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.« less