INFLUENCE OF THE CRYSTALLINE-STRUCTURE ON THE ELECTRICAL-PROPERTIES OF CVD DIAMOND FILMS

[100], [110] and non-textured polycrystalline diamond films were depos ited by microwave plasma enhanced chemical vapour deposition. Resistiv e devices with coplanar and sandwich electrical contacts were made to characterise and compare these films towards their use as radiation de tector. Current-voltage measurements in the dark and under UV light an d X-ray radiation were carried out. The crystalline structure of the f ilm is shown to have a significant influence on its electrical propert ies and on their sensitivity to UV and X-ray radiation. Film bulk resi stivities range from 1 x 10(12) for the [100] textured films to 5 x 10 (14) Omega cm for the [110] textured films. We found that the [100] te xtured film has the highest carrier drift length before trapping (mu t au E, where mu and tau are the carrier mobility and lifetime and E is the applied electric field) while the non-textured film has the lowest mu tau E. The presence of nitrogen in a [100] textured film is shown to increase its resistivity by more than two orders of magnitude owing to compensation effect, but it reduces the carrier drift length befor e trapping by a factor of 2.