Electrical and Raman-imaging characterization of laser-made electrodes for 3D diamond detectors

Pulsed laser writing of graphitic electrodes in diamond is a promising technique for innovative particle detectors. Although of great relevance in 3D fabrication, the processes involved in sub-bandgap bulk irradiation are still not well understood. In this work, Raman imaging is exploited to correlate resistivity and graphitic content in 5-10 pm-thick electrodes, obtained both in the domains of femtoseconds and of nanoseconds of pulse duration. A wide interval of resistivities (60-900 m Omega cm), according to the irradiation technique employed, are correlated with an sp(2) content of the modified material ranging over a factor 2.5. The stress distribution (maximum of about 10 GPa) and the presence of nanostructured sp(3) material around the graphitic columns have also been studied by Raman spectroscopy, and a rationale for the conductive behavior of the material is presented in terms of the thermodynamics of the process. (C) 2014 Elsevier B.V. All rights reserved.