Pulsed Laser-Induced Rapid Surface Cooling and Amorphization

In this work, hybrid atomistic-macroscale simulation is conducted to explore the crystallization and amorphization of Si surface in the situation of fast melting and solidification induced by ultrafast laser heating and heat conduction. Our work is focused on investigating the relationship between the amorphization threshold (Ec) and the laser pulse width (tg). An empirical correlation Ec 1⁄4 448:76 tg is obtained to relate the critical fluence to the laser pulse width. By exploring the microstructure of the amorphous and crystalline state of Si, a sharp interface of about 0.6 nm thickness is observed between the amorphous layer and the crystalline Si. The relationship between the final thickness of amorphous layer and the fluence of the laser pulse is further studied in this work. Employing laser pulses with full width at half maximum (FWHM) equal to 6.67 ns, the formation and recrystallization processes of a 12-nm-thick amorphous layer is investigated. [DOI: 10.1143/JJAP.47.8113]