Solid-Phase Silicon Homoepitaxy via Shear-Induced Amorphization and Recrystallization.

Thomas Reichenbach,Michael Moseler,Lars Pastewka,Gianpietro Moras

doi:10.1103/physrevlett.127.126101

Thomas Reichenbach, Michael Moseler + Show 2 more

Open Access

https://doi.org/10.1103/physrevlett.127.126101

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Abstract

We study mechanically induced phase transitions at tribological interfaces between silicon crystals using reactive molecular dynamics. The simulations reveal that the interplay between shear-driven amorphization and recrystallization results in an amorphous shear interface with constant thickness. Different shear elastic responses of the two anisotropic crystals can lead to the migration of the amorphous interface normal to the sliding plane, causing the crystal with lowest elastic energy density to grow at the expense of the other one. This triboepitaxial growth can be achieved by crystal misorientation or exploiting elastic finite-size effects, enabling the direct deposition of homoepitaxial silicon nanofilms by a crystalline tip rubbing against a substrate.

Highlights

Silicon crystals have intriguing, size-dependent, anisotropic mechanical properties with diverse brittle and ductile deformation mechanisms [1,2,3,4,5] that are responsible for the failure of micro- and nanodevices but can be harnessed to improve their manufacturing and performance
We study mechanically induced phase transitions at tribological interfaces between silicon crystals using reactive molecular dynamics
The simulations reveal that the interplay between shear-driven amorphization and recrystallization results in an amorphous shear interface with constant thickness

Summary

Published by the American Physical Society

Direction with v 1⁄4 10 ms−1. (b) After shearing at Pn 1⁄4 8 GPa for a sliding distance s 1⁄4 300 nm. An a-Si layer forms [snapshot in Fig. 1(b)] at the interface between the two crystals It entirely accommodates the plastic shear deformation of the system [10], and its thickness Δhðs; PnÞ increases with sliding distance s and with applied normal pressure Pn [Fig. 1(c) for Pn 1⁄4 0–9 GPa; see Supplemental Material [20] for details of Δh computation]. An arbitrary steady-state configuration from the MD trajectory in Fig. 1(f) is selected and relaxed to τ 1⁄4 0 GPa and T 1⁄4 0 K (Supplemental Material [20]) This provides the starting structure for a quasistatic shear simulation where a finite shear stress τq > 0 is imposed by a stepwise displacement of the upper rigid layer in the lateral direction while continuously relaxing the atomic positions. The elastic energy density in a crystal under shear stress τ is given by

GÃ is the effective shear

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