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

The electrical conductivity of Na- and Li-implanted diamond is investi gated. The highest conductivities are obtained for high dose implantat ions followed by thermal graphitization Of the heavily damaged layer a nd chemical removal of the graphitized layer. The temperature dependen ce 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 conduct ion may be understood in terms of variable range hopping between impla nt sites in the crystal rather than due to thermal activation.