Low-temperature electrical conductivity of heavily boron-doped diamond single crystals

Single crystal diamonds 0.2-0.7 cm large doped with boron concentration 10 19 -10 20 cm -3 were grown by temperature gradient method on the seed under pressure P = 5.5 GPa, temperature T= 1650 K. Temperature dependence of electrical resistance had been measured in the range of 0.5-297 K. Boltzmann activation type of conductivity and Mott's VRH law observed in samples in the temperature ranges -200-297 K and -70-297 K respectively. The temperature rise of conductivity in the range of -0.5-50 K for most heavily doped crystals was proportional to T 1/2 . This rule indicates the vicinity of the electronic system to metal-insulator transition.