Efficient sticking of surface-passivated Si nanospheres via phase-transition plasticity

Abstract

Large-scale atomistic simulations considering a 5 nm in radius H-passivated Si nanosphere that impacts with relatively low energies onto a H-passivated Si substrate reveal a transition between two fundamental collision modes. At impacting speeds of less than ϳ1000 m / s particle-reflection dominates. At increased speeds the partial onset in the nanosphere of a ␤-tin phase on the approach followed by a-Si phase on the recoil is an efficient dissipative route that promotes particle capture. In spite of significant deformation, the integrity of the deposited nanosphere is retained. Our result explains the efficient fabrication of nanoparticulate films by hypersonic impaction, where the nanoparticle impact velocities equal 1000-2000 m / s.

Accretion in Protoplanetary Disks by Collisional Fusion

“…Moreover, the process occurs in silicon, which melts at ∼1690 K, and where the range of collisional fusion speeds is ΔV c ∼ 100-1000 m s −1 , as seen in the recent molecular Vol. 719 dynamics simulations of Suri & Dumitricǎ (2008). Finally, bodies of inhomogenous composition can fuse in this manner.…”

“…The molecular dynamics simulations of Suri & Dumitricǎ (2008) provide an excellent example of damage-induced polyamorphism and fusion in Si which experimentally melts at ∼1690 K. They find that in high-speed and hence high-pressure collisions the β-tin phase forms in an interfacial region followed by picosecond annealing to the a-Si phase. While the particles in their study are sufficiently small that were they in the inner nebula they would be strongly coupled to the gas phase, their work demonstrates the basic effect of low-speed rebound (V c ∼ 900 m s −1 ) and high-speed (V c ∼ 1640 m s −1 ) damage-induced fusion.…”

“…While the particles in their study are sufficiently small that were they in the inner nebula they would be strongly coupled to the gas phase, their work demonstrates the basic effect of low-speed rebound (V c ∼ 900 m s −1 ) and high-speed (V c ∼ 1640 m s −1 ) damage-induced fusion. Clearly too, perhaps using simulations such as those on silicon (Suri & Dumitricǎ 2008), it is important to microscopically examine the role of the depth of disorder/liquidity necessary to fuse particles. While here material with laboratory determined properties is used, it is understood that agglomeration of micron scale particles can create highly porous "preplanetesimals" in experiments and simulations (Blum & Wurm 2008;Güttler et al 2010).…”

Simulation of cohesive head-on collisions of thermally activated nanoclusters

“…For example, it has been demonstrated that hydrogen coated Si nanoparticles exhibit the weak attraction by H atoms on the surface. [34,35] We believe that our model captures the essence of such a system. For realistic simulations, we may need to carry out another simulation of the collision of H-passivated Si clusters by introducing suitable empirical potentials.…”

“…It is known that the instability of the spherical shape and the plastic deformation in a cluster cause the increase of the internal temperature of the cluster. [33,34] We numerically performed free flights of cluster by the use of C 1055 to check the time evolution of the internal temperature of the cluster. Figure 11(b) shows the time evolution of the temperature inside the cluster C 1055 after giving the translational speed V = 0.07 ǫ/m and the initial temperature T = 0.02ǫ.…”