Understanding femtosecond laser internal scribing of diamond by atomic simulation: Phase transition, structure and property

Abstract

Micro-nano complex structures of carbon allotrope inside the diamond has strong application potential in optoelectronic devices. Femtosecond laser direct writing is an effective method for processing ultra-high hardness diamonds and has the ability to modify the internal structure of diamonds, but the related mechanism is still unclear. This study investigates the effects of femtosecond laser internal scribing on the localized changes in microstructure, phase transition, stress/strain distribution and mechanical property using molecular dynamics simulation. The statistical analysis of the modified lattice shows that diamond is transformed into amorphous diamond with C–C sp3 bond and dislocations, which was verified by Raman spectra after experiment. These structures allow the modified zone to maintain the same strength as the diamond crystal without losing mechanical strength. The local high temperature and high pressure induced by femtosecond laser are the reasons for the phase transition. The type of dislocation was mainly 1/6<112>. However, the increase of laser energy density induces a large amount of 1/2<110> dislocation in the focal spot area. The femtosecond laser pulse induced stress wave results in increase of dislocation density. Femtosecond laser-induced microstructure evolution can provide guidance for the fabrication of diamond devices with desired electro-optical properties.