Inelastic deformability of nanopillar by focused-ion-beam chemical vapor deposition
Change about ratio of Young’s modulus, , of whole pillar to and volume fraction, , of Ga core diameter to whole pillar diameter. The whole Young’s modulus increases due to the thicker outer ring, because the modulus is larger than that of the Ga core. The outer ring becomes thicker due to the much confliction between the compound gas and dispersed secondary electrons.
Mechanism of growth of nanopillar consisting of and Ga core. For low-magnification ratio of FIB to get a thick pillar, the shallower crater due to the ion bombardment nucleates and the wider dispersion area of secondary electrons from the substrate is predicted. This may introduce the wider dissociation of compound gas by confliction.
Schematic view of bending test of the grown pillar onto Si substrate with initial length subjected to the lateral load using a cantilever tip of the usual atomic force microscope in SEM. The load can be estimated by the directly observed defection of the cantilever multiplied by the spring constant of the cantilever.
Relationship between load and maximum deflection at the free end of nanopillar. The linear response at the infinitesimal displacement is realized by the first loading denoted as the solid circles, and the inelastic behavior is obtained by the second loading until the finite deformation, denoted as the open circles. The nanopillar has a wide low-hardening region after linear response and then becomes extremely hardened; this behavior is almost identical to a polymer.
Three kinds of fundamental atomistic deformation styles of covalent bonding: bond stretching with central distance argument between two atoms, bond bending according to the angle between two bonds, and bond-torsional resistance, that is, bond-dihedral angular bending effect.
Loading history of vertically built pillar: pushing up, that is, from compressive state to bending; rotating around the fixed end, that is, torsional loading; and recovering.
Loading history of horizontally built pillar: pushing along axial direction, that is, from compression to bending until getting the maximum curvature; then recovering.
Summary on resonance frequency , calculated Young’s modulus and density , volume fraction of Ga core to whole pillar, and fabrication conditions of irradiation time and growth rate.
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