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.