Electrical properties of surface conductive layers of homoepitaxial diamond films

The electrical properties of surface conductive layers of the undoped diamond films via various subsequent treatments and of the as-grown N-doped diamond films have been investigated in the present study. Hall effect measurements reveal that the sheet carrier density of the surface conductive layers almost remains constant with varying temperature, and the temperature dependence of sheet resistivity is mainly determined by that of the Hall mobility, which varies exponentially with reciprocal temperature. The activation energies deduced for the mobility are demonstrated to monotonously decrease when increasing the sheet carrier densities. Based on these experimental results, the origin of the surface conductive layers is discussed. (C) 1999 American Institute of Physics. [S0021-8979(99)02612-2].