PERCOLATIVE TRANSITION IN CARBON-ION IMPLANTED TYPE IIA DIAMOND

Experimental data for the conductivity of type IIa diamond specimens i mplanted at low temperatures with carbon ions, followed by high temper ature annealing, have been analyzed using hopping and percolation theo ries in the vicinity of the insulator-metal transition. Near the trans ition it appears that conductivity occurs via sp(2)-bonded graphitic c lusters which are randomly distributed in the sp(3)-bonded diamond mat rix. A conductivity crossover between the Mott and Efros-Shklovskii VR H laws has been observed on the insulating side of the transition.