The lattice damage in a diamond crystal irradiated with 9-MeV carbon ions has been studied as a function of fluence and layer depth by Raman and photoluminescence micro-spectroscopies. In the irradiated layers, formation of neutral vacancies and interstitial defects was observed, as well as a disordering of the lattice. The damage increases with fluence and reaches a maximum at the stopping layer, which becomes amorphous for fluences well above 1016 ions/cm2. After annealing for 1 h at 1000oC the lattice damage partially recovers, leaving some residual damage that increases with increasing fluence. However, for higher fluences recrystallization of the amorphous layers dramatically reduces the residual damage producing high-quality diamond layers.
Therefore, it has been shown that in deeply-buried layers of irradiated diamond, graphitization can be avoided after annealing. Furthermore, when annealed at temperatures around 1000oC, layers irradiated at fluences of about 5x1016 ions/cm2 can recrystallize into high-quality diamond, paving the way for the implantation of diamond at high fluences for diamond device applications in photonics or electronics. [Full article]