Direct observation of graphenic nanostructures inside femtosecond-laser modified diamond

In this paper we report on the study of the buried laser-modified region produced inside single crystal diamond by femtosecond laser irradiation. The cross-section of the modified region was prepared via precise mechanical polishing to investigate its intrinsic structure with Raman spectroscopy, scanning electron microscopy and scanning spreading resistance microscopy. It is found that the opaque laser-modified region is pierced by 40-100 nm thick sheets of graphenic carbon united into a single conductive network, while the gaps between the sheets are filled by diamond. Only small part of the irradiated diamond volume (∼16 vol. %) is transformed into the sp2 phase. The results obtained are consistent with the model of laser-induced crack-assisted phase transition in diamond bulk proposed earlier.