  Focused MeV ion beams with micrometric resolution are suitable tools for the
direct writing of conductive graphitic channels buried in an insulating diamond
bulk. Their effectiveness has been shown for the fabrication of multi-electrode
ionizing radiation detectors and cellular biosensors. In this work we
investigate such fabrication method for the electrical excitation of color
centers in diamond. Differently from optically-stimulated light emission from
color centers in diamond, electroluminescence (EL) requires a high current
flowing in the diamond subgap states between the electrodes. With this purpose,
buried graphitic electrode pairs with a spacing of 10 $\mu$m were fabricated in
the bulk of a single-crystal diamond sample using a 6 MeV C microbeam. The
electrical characterization of the structure showed a significant current above
an effective voltage threshold of 150V, which was interpreted according to the
theory of Space Charge Limited Current. The EL imaging allowed to identify the
electroluminescent regions and the residual vacancy distribution associated
with the fabrication technique. Measurements evidenced bright
electroluminescent emission from native neutrally-charged nitrogen-vacancy
centers ($NV^0$); the acquired spectra highlighted the absence of EL associated
with radiation damage.
