Large-amplitude thermal oscillations in defected, tilted nanocolumns

Abstract

We consider the thermomechanical properties of highly defected, tilted copper nanocolumns grown via simulations of glancing angle deposition. The large defect density and compressive strain lead to ultra-low activation energies for plastic deformation via collective shear motion. As a result, the thermal oscillation amplitude is independent of temperature. This leads to a mechanism for large-amplitude thermally induced nanocolumn oscillation, in which the dynamics corresponds to a sequence of correlated activated events. V

Critical island size, scaling, and ordering in colloidal nanoparticle self-assembly

“…However, the ALA value for 4.9 nm NPs is not close to an expected critical island size, while both values are not consistent with our expectation of significant two-bond detachment for these NP sizes. In addition, the ALA value of i 1 for 8 nm NPs is not consistent with our expectation, based on estimates [36] of the prefactor and detachment barrier obtained using the Khan et al potential [15], that dimers are unstable even for 8 nm NPs. We also note that recent work [38] on the ALA model indicates that in many cases this may lead to an extended nucleation regime in which the island density only saturates at large coverage.…”

“…This is in contrast to previous theoretical [16] and simulation [18] results for the case of irreversible island growth (i = 1) with cluster diffusion and no barrier to island coalescence for the case D A ∼ A −μ (where D A is the mobility of an island of area A) with μ 1. On the other hand, recent simulation results [35,36] also indicate that for i 2 the ISD exhibits a well-defined peak near A/ A = 1, even in the presence of significant cluster diffusion and island coalescence. Thus, these results confirm our expectation, based on our analysis in Sec.…”

“…As a result, the effective critical island size is significantly larger than 6, while the effective value of χ is close to 1. In this connection, the effects of island diffusion and coalescence on the exponent χ (assuming D A ∼ A −μ where D A is the diffusion constant for an island of area A and 0 < μ < ∞) have been studied both for the case of irreversible growth with i = 1 [16][17][18]34] as well as more recently for higher values of i [35,36]. In all cases it has been found that, assuming no barrier to island coalescence, the effective value of χ ranges between a value of 1/2 for small μ and the standard prediction i/(i + 2) for large μ.…”