5 research outputs found
Cashew cultivation in Guinea-Bissau – risks and challenges of the success of a cash crop
Direct fabrication and IV characterization of sub-surface conductive channels in diamond with MeV ion implantation
Abstract. In the present work we report about the investigation of the conduction mechanism of sp2 carbon
micro-channels in single crystal diamond. The structures are fabricated with a technique which employs
a MeV focused ion-beam to damage diamond in conjunction with variable thickness masks. This process
changes significantly the structural properties of the target material, because the ion nuclear energy loss
induces carbon conversion from sp3 to sp2 state mainly at the end of range of the ions (few micrometers).
Furthermore, placing a mask with increasing thickness on the sample it is possible to modulate the channels
depth at their endpoints, allowing their electrical connection with the surface. A single-crystal HPHT
diamond sample was implanted with 1.8 MeV He+ ions at room temperature, the implantation fluence
was set in the range 2.1
× 10
16
−6.3 × 10
17
ions cm−2 , determining the formation of micro-channels with
a graded level of damage extending down to a depth of about 3 μm. After deposition of metallic contacts
at the channels’ endpoints, the electrical characterization was performed measuring the I -V curves at
variable temperatures in the 80
−690 K range. The Variable Range Hopping model was used to fit the
experimental data in the ohmic regime, allowing the estimation of characteristic parameters such as the
density of localized states at the Fermi level. A value of 5.5
× 10
17
states cm−3 eV−1 was obtained, in
satisfactory agreement with values previously reported in literature. The power-law dependence between
current and voltage is consistent with the space charge limited mechanism at moderate electric field