Formation of graphitic micro-channels on boron-doped diamond electrodes via femtosecond laser irradiation: A Route for controlled sp2 functionalization

Diamond is a promising material for electrodes in the field of electrochemical analysis, biosensing, and energy storage. However, the diamond has to be doped with charge carriers like boron to make it a p-type semiconductor material. Creating highly localized and geometrically confined sp 2 graphitic columns in boron-doped diamonds can improve the electrocatalytic properties of the electrode. In this work, graphitic columns were created on boron-doped diamond using 100 fs laser pulses at 800 nm wavelength. The laser fluence of 8.85–––44.2 J/cm 2 and the scanning speed of 0.1–1 mm/s were found to be suitable for graphitization. Microstructural analysis of the samples was done using scanning electron microscopy and Raman spectroscopy techniques. The Raman results showed that a suitable fluence of 22.1 J/cm 2 and graphitization speed of 0.5 mm/s improves the crystallinity of the graphitic column and suppresses the residual diamond content. A four-probe resistivity measurement was done on the graphitic columns to evaluate the resistivity difference. A minimum resistance of 66.39 Ω/sq was observed at a preferred laser fluence of 22.1 J/cm 2 ; with an increase in laser fluence, an increase in the resistivity was observed.