Atomistic investigation of process parameter variations on material deformation behavior in nanoimprint lithography of gold
A Gaikwad and J Odujole and S Desai, PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY, 64, 7-19 (2020).
Direct metal nanoimprint (NIL) of the gold substrate by silicon mold has been investigated through molecular dynamics simulations. The effects of different process parameters such as imprint temperature, mold velocity, and mold profile on the contact pressure, von Mises stresses, and dislocation behavior of the lattice structure was studied during the nanoimprinting process. Higher contact pressures were observed during the molding phases which further declined during the relaxation and demolding phases. The narrow mold geometry (aspect ratio = 2) had the highest contact pressure (6.61 GPa) at 1300 K and 50 m/s due to the lower cross-sectional area and incompressible nature of the gold atoms. The maximum von Mises stress (1.8 x 10(7) GPa) was observed under the mold tooth during the insertion phase at 298 K and 473 K. Further, the highest von Mises stress (1.32 x 10(7) GPa) was tracked at 1300 K due to the restraining effect of the mold on the expanding molten gold atoms. The lattice dislocation analysis using the polyhedral template matching (PTM) method revealed that the gold substrate maintains its face centered cubic (FCC) structure and consequent ductile nature after the NIL process at 298 K and 473 K, respectively. At 1300 K, for both mold profiles more than 60% of gold atoms remained with distorted structure after completion of NIL process due to the melting and rapid crystallization of the gold atoms. High-resolution imprints were achieved at the recrystallization temperature (473 K) of gold for both the mold geometries.
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