Increased band A cathodoluminescence after carbon ion implantation and annealing of diamond

Abstract

Carbon ions have been used to modify a high-purity type IIa diamond by means of the cold implantation-rapid annealing (CIRA) method. A low dose of 5 × 10 12cm −2 was chosen in order to limit the introduction of macrostrain into the implanted diamond layer. After implantation, consecutive anneals were performed at 500, 1200 and 1600 °C, and the associated changes which occurred in the implanted diamond layer were monitored using cathodoluminescence measurements. The anneal at 1200 °C generated a broad UV band at 4 eV. During anneals at 1600 °C, this band disappeared and the intensity of the blue band A at about 2.9 eV, typically found in type IIa diamonds, increased to a higher value than had been measured before implantation. By repeating the same CIRA step consecutively on the diamond, it was found that the intensities of both the 4 eV UV band and the blue band A increased with the accumulated ion dose. A model is proposed in which it is postulated that the two centres are different manifestations of vacancy clusters in diamond; the 4 eV centres have a more random arrangement of vacancies which gives them donor-like properties, and the band A centres have a more periodic arrangement of vacancies which, in this case, leads to acceptor-like behaviour.