Mechanical properties and mechanism of single crystal Cu pillar by in situ TEM compression and molecular dynamics simulation

In this study, we investigate the mechanical properties of single-crystal copper (Cu) nanopillars. Critical deformation variations of Cu-nanopillared structures are estimated using in situ transmission electron microscopy compression tests and molecular dynamics simulations. The Young's moduli of Cu nanopillars with diameters of 2-6 nmwere 90.20-124.47 GPa. The contact stiffnesses of the Cu nanopillars with diameters of 400 and 500 nmwere 1.33 and 3.86 Nm(-1), respectively; the Poisson's ratios for these nanopillars were 0.32 and 0.33. The yield strength of the nanopillars varied from 0.25 GPa at 500 nmto 0.42 GPa at 400 nm; the yield strength of single-crystal Cu nanopillars decreased with increasing diameter. The values of the indented hardness of the Cu block were 0.27 and 1.06 GPa, respectively. Through experimental work and molecular dynamics simulations, we demonstrate that Cu nanopillars exhibit internal stress transmission during compression. When compression reaches the maximum strain, it can be observed that Cu slips. Our results are useful for understanding the mechanical properties, contact, and local deformation of Cu nanopillars.