Electrical properties of sulfur-implanted cubic boron nitride thin films

Cubic boron nitride (c-BN) thin films were deposited on Si substrates by applying ion beam assisted deposition and then doped by S ion implantation. To produce a uniform depth profile of S ions in c-BN films, the implantation was carried out for the multiple energies. A slight degradation of c-BN crystallinity resulted from ion implantation can be recovered by thermal annealing, keeping the cubic phase content as high as 92 %. The resistance reduces from 10(10) Omega for the as-deposited c-BN film to 10(8) Omega after an S implantation of 5 x 10(14) ions cm(-2) and annealing at 1,173 K, suggesting an electrical doping effect of S dopant. The electrical resistance of the S-doped c-BN thin film decreases with increasing temperature, indicating semiconductor characteristics. The activation energy of S dopant is estimated to be 0.28 +/- A 0.01 eV from the temperature dependence of resistance.