CAN N-TYPE DOPING OF DIAMOND BE ACHIEVED BY LI OR NA ION-IMPLANTATION

The electrical conductivity of Na- and Li-implanted diamond is investigated. The highest conductivities are obtained for high dose implantations followed by thermal graphitization Of the heavily damaged layer and chemical removal of the graphitized layer. The temperature dependence of the resistivity is measured, yielding activation energies of 0.2 eV for Li (400 < T < 680 K) and for Na 0.13 eV (220 < T < 400 K) and 0.21 eV (415 < T < 670 K). Analysis of the data shows that the conduction may be understood in terms of variable range hopping between implant sites in the crystal rather than due to thermal activation.