New radiation induced defects in HPHT synthetic diamonds

Narrow symmetric IR absorption bands at 872.0 and 713.8 cm−1 were observed in HPHT synthetic diamonds that had been grown in metal-carbon systems with titanium as a nitrogen getter and irradiated with 3 MeV 2×1017 cm−2 electrons. As the irradiation dose was increased, the intensities of the 872.0 and 713.8 cm−1 bands increased also. When the irradiation dose reached 6×1017 cm−2 the band intensities reached 3.9 and 1.8 cm−1, respectively. In addition, another narrow band at 847.9 cm−1 with an intensity of 0.3 cm−1 was noted on the shoulder of the 872.0 cm−1 band. On subsequent annealing the band intensity in the samples reached its maximum at 200 °C then sharply decreased reaching zero at 600 °C. It is suggested that the bands could be attributed to titanium ions that entered into the lattice during diamond synthesis.