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Research Papers

Peeling Silicene From Model Silver Substrates in Molecular Dynamics Simulations

[+] Author and Article Information
Zhao Qin

Laboratory for Atomistic and
Molecular Mechanics (LAMM),
Department of Civil and Environmental Engineering,
Massachusetts Institute of Technology,
77 Massachusetts Avenue,
Cambridge, MA 02139
Center for Computational Engineering,
Massachusetts Institute of Technology,
77 Massachusetts Avenue,
Cambridge, MA 02139
e-mail: qinzhao@mit.edu

Zhiping Xu

Applied Mechanics Laboratory,
Department of Engineering Mechanics and
Center for Nano and Micro Mechanics,
Tsinghua University,
Beijing 100084, China

Markus J. Buehler

Laboratory for Atomistic and
Molecular Mechanics (LAMM),
Department of Civil and Environmental Engineering,
Massachusetts Institute of Technology,
77 Massachusetts Avenue,
Cambridge, MA 02139
Center for Computational Engineering,
Massachusetts Institute of Technology,
77 Massachusetts Avenue,
Cambridge, MA 02139

1Corresponding author.

Contributed by the Applied Mechanics Division of ASME for publication in the JOURNAL OF APPLIED MECHANICS. Manuscript received April 28, 2015; final manuscript received June 20, 2015; published online July 10, 2015. Editor: Yonggang Huang.

J. Appl. Mech 82(10), 101003 (Jul 10, 2015) (6 pages) Paper No: JAM-15-1213; doi: 10.1115/1.4030888 History: Received April 28, 2015

Silicene is a two-dimensional (2D) allotrope of silicon with a rippled or corrugated honeycomb structure in analogy to graphene. Its semiconducting properties make it attractive for developing future nano-electronic devices. However, it has been challenging to obtain its naked form by using a mechanical exfoliation method as what has been applied to graphene. Here, we use fully atomistic simulations with an effective potential for the silver substrate derived from first-principles calculations to investigate possible ways of peeling silicene solely by mechanical force. We find that the peeling direction is critical for exfoliating silicene and the peeling at a 45 deg angle with the substrate is the most efficient one to detach silicene. Our study could help to understand the mechanics of silicene on substrates and guide the technology of isolation of silicene from the substrate on which it is synthesized.

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Figures

Grahic Jump Location
Fig. 1

The top view (a) and side view (b) of the DFT simulation system of silicene layer (with golden particles for silicon atoms) on the top of Ag (111) surface (with gray particles for silver atoms) at equilibrium. The frame in the two snapshots highlights the supercell used in the interfacial energy calculations.

Grahic Jump Location
Fig. 2

Peeling silicene from Ag surface is difficult and cannot follow the same way as preparing graphene. (a) Simulation snapshots of the deformation and displacement (d) of silicene under peeling, with panels i to v corresponding to the d value given in (c). (b) Number of Si–Si bond (NSi–Si, a bond is judged to form if the Si–Si interatomic distance < 2.8 Å) for all the silicon atoms between the two initial notches as a function of the moving distance of the fix boundary. (c) The total loading force (F) and forces in y (Fy) and z (Fz) directions recorded during the silicene peeling, solid curves are results of moving average for every 2 Å in displacement.

Grahic Jump Location
Fig. 3

Strength of silicene under interfacial confinements. (a) Snapshots of the deformation of a silicene ribbon under a uniaxial tensile load, with panels (a-i) to (a-v) corresponding to (c). For (a-ii), the atoms and bonds are colored by out-of-plane displacement as given by the legend. (b) The stress–strain (σ–ε) curves of the silicene ribbons confined by different cohesive energy (γ, with γ = 8.82 eV/nm2 for interaction with Ag (111) surface) with the interface. (c) Summary of the rupture strength (σC) of the silicene ribbon as a function of the cohesive energy. The asymptotic value of silicene strength is 9.0 ± 0.1 N/m as indicated by the dashed line.

Grahic Jump Location
Fig. 4

Strength of silicene with defects. (a) The stress–strain (σ–ε) curves of the silicene ribbons with different ratio of missing atoms (p) as defects. (b) Summary of the rupture strength (σC) of the silicene ribbon as a function of the ratio of missing atoms. In the two sets of simulations, the defected silicene is subjected to different interactions with the substrate as γ = 0 and γ = 8.82 eV/nm2 for the effective Ag substrate. The exponential decay fit has the function of σC = 6.4exp(-p/0.126) for simulations with γ = 0 and σC = 6.7exp(-p/0.134) for simulations with γ = 8.82 eV/nm2.

Grahic Jump Location
Fig. 5

Silicene ribbon can be obtained by peeling in 45 deg. (a) The total area (A) of silicene been peeled from the substrate as a function of the two times of the peeling angel (2θ), which corresponds to the angle between the silicene been peeled off and the substrate as illustrated by the inserted schematic figures. (b) The apex angle φ of the wedgelike silicene ribbon after peeling as a function of 2θ, where θ = 45 deg yields the smallest φ. (c) Simulation snapshots of the silicene under peeling with a peeling angle of 45 deg. (d) Side view of the snapshots in (c) with the pictures overlaid.

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