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

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 $\sim1000$~m/s {\it particle-reflection} dominates. At increased speeds the partial onset in the nanosphere of a $\beta$-tin phase on the approach followed by $a$-Si phase on the recoil is an efficient dissipative route that promotes {\it 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. \\[3pt] [1] M. Suri and T. Dumitric\u{a}, {\it Efficient Sticking of Surface-Passivated Si Nanospheres via Phase-Transition Plasticity}, Physical~Review~B [Rapid~Communication] {\bf 78}, 081405 (2008). \\[0pt] [2] P. Valentini and T. Dumitric\u{a}, {\it Microscopic Theory for Nanoparticle-Surface Collisions in Crystalline Silicon}, Physical Review B {\bf 75}, 224106 (2007).