Structure, radiation damage and annealing effects in diamond implanted with a high fluence of a few MeV carbons

Crystallinity of the type-Ib single crystal diamond damaged with 3 MeV carbon ions to a fluence of 2 × 1016 cm−2 and subsequent post-implantation anneal at 1200 °C in a hydrogen plasma atmosphere was investigated. The annealed sample had very low optical transmission, suggesting occurrence of graphitization due to an excess introduction of radiation defects and the following post-implantation annealing. In this optical transmission spectrum, an interference pattern was also observed. Combination of such an interference pattern with a TRIM simulation demonstrated that a thin highly defective layer was formed around the depth of ∼1.6 μm, whereas the optical transparent diamond is preserved as an over-layer in the depth region from the surface to ∼1.6 μm. In the photoluminescence (PL) spectra of such a residual thin diamond over-layer, a very broad luminescent band appeared in the spectral range 1.4-2.3 eV. The data of time-resolved PL measurements allowed one to resolve this broadband to two types of bands peaking at ∼1.6 eV and ∼1.9 eV. The ∼1.6 eV band is probably the “B-band” originated from the radiation defects introduced by the ion-implantation. It seems that the ∼1.9 eV band consists of phonon sidebands of zero phonon lines (around 2.1-2.3 eV) of two types of optical centers, but the further studies are required for detailed identifications of these optical centers.