Raman investigation of femtosecond laser-induced graphitic columns in single-crystal diamond

Single-crystal chemical vapour deposition (scCVD) diamond is presently the reference wide bandgap semiconductor for the development of high-performance ionizing radiation detectors for medical and nuclear applications, due to its wide range of extreme properties (radiation hardness, chemical inertness and high thermal conductivity). Recently, it has been shown that the interaction with femtosecond laser pulses can induce a non-equilibrium phase transition from metastable sp3-bonded diamond to the stable sp2-bonded graphite. This makes possible to create inside the bulk material graphitic columns, through an accurate control of the laser interaction with the diamond lattice throughout the whole sample thickness. In this work, we performed a Raman investigation of fs-laser induced graphitic columns inside very high quality single-crystal diamond samples: by means of a proper choice of the experimental parameters, it is possible to improve the quality of the graphite columns in terms of reduction of diamond content and graphite degree of crystallinity.