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

•Fabrication of superficial and buried graphitic structures in diamond by means of ns- and fs-pulsed laser radiation•Quantitative 2-dimensional maps of the phase composition and of the stress conditions were obtained by micro-Raman imaging.•A correlation between electrical conductivity and graphitic content was assessed.•A rationale for the different composition of phases obtained in different condition has been found.

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 μm-thick electrodes, obtained both in the domains of femtoseconds and of nanoseconds of pulse duration. A wide interval of resistivities (60–900 mΩcm), according to the irradiation technique employed, are correlated with an sp2 content of the modified material ranging over a factor 2.5. The stress distribution (maximum of about 10 GPa) and the presence of nanostructured sp3 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.