Study of the dynamics of the graphitization in diamond induced by high repetition rate fs laser.

In this paper, we studied the dynamics of the graphitization in diamond induced by high repetition rate fs laser. Unlike the dynamics in the case of employing low repetition rate fs laser, the graphitized region can grow both toward and along the laser beam. For surface processing, the experimental results have revealed that employing multi-scanning can effectively reduce the fluctuations of the thicknesses of the graphitization wire, but it is useless for fabricating a continuous graphitization wire inside diamond. There emerges a comb structure, which consists of an array of graphitization filaments. The growth of each filament in the comb structure can be classified by four growth regions, based on which we discussed the dynamics of the formation of this comb structure. Furthermore, we measured the magnetic properties of both surface-irradiated and inside-irradiated samples. The surface graphitized sample shows a common diamagnetism, but the internal graphitized sample exhibits an unusual superparamagnetism. • Dynamics of graphitization process is more complicated at high repetition fs laser. • Multiple scanning improves uniformity of graphitization wires on diamond surface. • The comb structure always emerges when laser repetition more than 100 kHz. • The formation of the comb structure is discussed based on filament growth dynamics. • The internal graphitized sample shows a rare superparamagnetism. [ABSTRACT FROM AUTHOR]