ANNEALING-INDUCED ENHANCEMENT IN THE ACTIVATION-ENERGY OF HEAVILY BORON-DOPED POLYCRYSTALLINE DIAMOND

We show that the electrical properties of heavily boron-doped polycrys talline chemical vapor-deposited diamond films are modified by post-de position thermal annealing with slow heating and cooling rates. We fou nd that the boron effective activation energy increased after heating and cooling cycles in the temperature range of 300-673 K. The improvem ent also depends on the doping level. Samples with a resistivity of 6. 41 m Omega.cm, 3.84 m Omega.cm and 0.826 m Omega.cm showed improvement s of 6.4, 11.5 and 205%, respectively. Scanning tunneling microscopy ( STM) images show that there were no exceptional changes in film morpho logy produced by the annealing processes, only an apparent cleaning of the surface at the nanometer scale. (C) 1998 Elsevier Science S.A.