  We report on a novel method for the fabrication of three-dimensional buried
graphitic micropaths in single crystal diamond with the employment of focused
MeV ions. The use of implantation masks with graded thickness at the
sub-micrometer scale allows the formation of conductive channels which are
embedded in the insulating matrix at controllable depths. In particular, the
modulation of the channels depth at their endpoints allows the surface
contacting of the channel terminations with no need of further fabrication
stages. In the present work we describe the sample masking, which includes the
deposition of semi spherical gold contacts on the sample surface, followed by
MeV ion implantation. Because of the significant difference between the
densities of pristine and amorphous or graphitized diamond, the formation of
buried channels has a relevant mechanical effect on the diamond structure,
causing localized surface swelling, which has been measured both with
interferometric profilometry and atomic force microscopy. The electrical
properties of the buried channels are then measured with a two point probe
station: clear evidence is given that only the terminal points of the channels
are electrically connected with the surface, while the rest of the channels
extends below the surface. IV measurements are employed also to qualitatively
investigate the electrical properties of the channels as a function of
implantation fluence and annealing.
