Molecular dynamics simulation of heat conduction in Si nano-films induced by ultrafast laser heating

• Thin films heated by ultrafast lasers are studied via molecular dynamics simulation.
• Thermal waves are observed and related to local stress and net heat development.
• Oscillation of displacements is consistent with the static pressure fluctuation.
• Oscillation period and fast Fourier heat wave speed are obtained.

Molecular dynamics simulations are carried out to study the thermal and mechanical phenomena of heat conduction induced by ultrafast laser heating of nanoscale Si films. A distribution of internal heat source obeying Beer–Lambda law is applied to model the laser energy deposition in the film and to calculate the induced temperature and stress distributions. Thermal waves are observed from the local temperature temporal variations and spatial distributions. The developments of averaged static pressure and local displacement in the film show a consistent periodicity. The time evolutions of both the local pressure and net heat flux fluctuate strongly, but show similar trends between these two local physical quantities, demonstrating a close relationship between the stress and the net heat flow.