Ion-beam-induced transformation of diamond

Abstract

The ion-beam-induced transformation of insulating diamond to a conducting form of carbon is explored by performing measurements of the electrical conductivity of diamond subject to ion damage. A wide range of implantation temperatures (150--690 K) with both Xe (320 keV) and C (100 keV) ions are employed. The dose dependence of the conductivity, R(D), is found to scale with the nuclear energy deposited in the irradiated volume, thus demonstrating that it is the density of collisionally induced defects that governs the electrical conductivity. The data are analyzed in terms of a model that proposes that the passage of an ion through the solid leaves in its wake conducting spheres of varying radii. The average radius of these spheres is found to decrease from about 2.05 nm for irradiation at 150 K with 320-keV Xe ions to zero for implantation at about 815 K. At critical doses ${\mathit{D}}_{\mathit{c}}$, which depend on the implantation temperature and the ion species, these spheres overlap to form a continuous conductive pathway through the irradiated diamond. In some cases this transition is sharp enough to be well accounted for by a simple percolation theory. Below ${\mathit{D}}_{\mathit{c}}$, R(D) displays complicated nonmonotonic behavior, which is explained as being due to the competition of the contribution of different types of defects to the observed electrical conductivity. Remarkable similarities between the conductivity induced in diamond and fused quartz implanted with C ions under identical conditions are reported.