The conduction path in as-grown undoped diamond films deposited by chemical
vapor deposition has been investigated by employing impedance spectroscopy
, electroplating and electroetching. The thickness- and direction-dependenc
ies of electrical resistivity did not agree with the previously known surfa
ce conduction model. The Cu electroplating and Ag electroetching results sh
owed that the current path followed the grain boundaries within the diamond
films. The Cu electroplating of diamond film with an insulating surface la
yer also showed that the grain boundaries within the films were the main co
nduction path in undoped polycrystalline films. (C) 2001 Elsevier Science B
.V. All rights reserved.