Electrical characterization of a graphite-diamond-graphite junction fabricated by MeV carbon implantation

Abstract The Deep Ion Beam Lithography technique has been extensively adopted in recent years for the fabrication of graphitic electrodes in bulk diamond with a wide range of technological applications. Particularly, it has been recently shown that a high current can be driven in devices consisting of micrometer-spaced sub-superficial graphitic electrodes. This effect has been exploited to stimulate electroluminescence from color centers placed in the active region of the device. A deep understanding of the conduction mechanisms governing charge transport in micro-regions of defective diamond comprised between graphitic electrodes is necessary in order to fully exploit the functionality of these opto-electronic devices, as well as to assess the ion-beam-micromachining of diamond as a convenient technique for the fabrication of solid-state micro-devices. In this work, a temperature-dependent characterization of the electrical properties of a sub-superficial graphite-diamond-graphite junction is presented and discussed. The ohmic behavior observed at low bias voltages is ascribed to a donor level with an activation energy of (0.217 ± 0.002) eV, a value compatible with previous reports on nitrogen-related defects. A transition to a high-current regime above a critical voltage V C was also observed, and interpreted in terms of the Space-Charge-Limited Current model. The temperature-dependent measurements allowed to investigate the role of charge trapping in the charge injection mechanism of the junction. By fitting the temperature dependence in the high-current regime it was possible to determine the relevant trap level of the associated Poole-Frenkel mechanism, leading to a value of (0.278 ± 0.001) eV from the conduction band. The Poole-Frenkel conduction model in high-current regime enabled also a preliminary investigation in the effects of ion implantation on the modification of the dc dielectric constant of diamond.