Molecular dynamics study on compressive strength of monocrystalline, nanocrystalline and amorphous Si mold for nanoimprint lithography

Molecular dynamics studies are carried out to investigate the compressive strengths and the failure mechanisms of monocrystalline, nanocrystalline and amorphous Si molds for nanoimprint lithography. The stress-strain characteristics and the stress distributions are analyzed for the three types of Si molds. The stress-strain characteristics show that the strength of the monocrystalline Si mold is the greatest among the three types of Si molds. The strength of the nanocrystalline Si mold decreases as the grain size decreases. This shows the Hall-Petch effect does not hold true in the grain size of nanometer order. The visualization of the stress distribution shows that the monocrystalline, nanocrystalline and amorphous Si mold fail due to the slipping of the specific atomic plane, the sliding in the grain boundaries and the nonlocal plastic deformation, respectively. As a result, the monocrystalline Si mold is the most suitable for nanoimprint lithography among the three types of Si molds in the nanoscale regime.