Infrared absorption studies of neutron-irradiated type Ib diamond

Infrared (IR) absorption measurements were performed at room temperature on neutron-irradiated type Ib diamonds which contain around 100 ppm substitutional nitrogen atoms in single form. It was observed that the 1332 cm−1 absorption peak appears by irradiation but vanishes again at the dose region higher than 2×1018 n/cm2. This phenomenon is explained by using two-step charge compensation model. Furthermore three remarkable peaks are observed at 1530 and 1570 cm−1 and at 1450 cm−1. Relations between absorption intensity and neutron dose of these peaks were studied. Intensity of these peaks increase linearly with dose; however, the 1450 cm−1 peak intensity saturates around 2×1017 n/cm2 in contrast with the others. These results are consistent with the interstitial models proposed previously.