Nano-to-micro diamond formation by nanosecond pulsed laser annealing

Here, we report the synthesis and characterization of nano-, micro-, twinned, and lonsdaleite diamonds, which are formed after melting and quenching of amorphous carbon or Q-carbon essentially at room temperature and atmospheric pressure. These conversions depend on the degree of undercooling, which is controlled by the laser parameters and thermal conductivities of the amorphous carbon and the substrate. The laser melting and undercooling provide liquid-phase packing of atoms similar to high-pressure, which facilitate the conversion of amorphous carbon into diamond or Q-carbon without using any catalyst. By changing the nucleation and growth rates, we have synthesized a wide range of sizes (4 nm to 3 mu m) of diamond crystals. The formation of twinned and lonsdaleite diamonds is controlled by the quenching rate. Therefore, we have created a factory of diamonds at ambient conditions by nanosecond laser annealing, which will pave the pathway to design high-speed mechanical and electrical devices.