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A Review on Mechanics and Mechanical Properties of 2D Materials - Graphene and Beyond
Since the first successful synthesis of graphene just over a decade ago, a
variety of two-dimensional (2D) materials (e.g., transition
metal-dichalcogenides, hexagonal boron-nitride, etc.) have been discovered.
Among the many unique and attractive properties of 2D materials, mechanical
properties play important roles in manufacturing, integration and performance
for their potential applications. Mechanics is indispensable in the study of
mechanical properties, both experimentally and theoretically. The coupling
between the mechanical and other physical properties (thermal, electronic,
optical) is also of great interest in exploring novel applications, where
mechanics has to be combined with condensed matter physics to establish a
scalable theoretical framework. Moreover, mechanical interactions between 2D
materials and various substrate materials are essential for integrated device
applications of 2D materials, for which the mechanics of interfaces (adhesion
and friction) has to be developed for the 2D materials. Here we review recent
theoretical and experimental works related to mechanics and mechanical
properties of 2D materials. While graphene is the most studied 2D material to
date, we expect continual growth of interest in the mechanics of other 2D
materials beyond graphene
SciTech News Volume 71, No. 2 (2017)
Columns and Reports From the Editor 3
Division News Science-Technology Division 5 Chemistry Division 8 Engineering Division 9 Aerospace Section of the Engineering Division 12 Architecture, Building Engineering, Construction and Design Section of the Engineering Division 14
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Atomistic Boron-Doped Graphene Field Effect Transistors: A Route towards Unipolar Characteristics
We report fully quantum simulations of realistic models of boron-doped
graphene-based field effect transistors, including atomistic details based on
DFT calculations. We show that the self-consistent solution of the
three-dimensional (3D) Poisson and Schr\"odinger equations with a
representation in terms of a tight-binding Hamiltonian manages to accurately
reproduce the DFT results for an isolated boron-doped graphene nanoribbon.
Using a 3D Poisson/Schr\"odinger solver within the Non-Equilibrium Green's
Functions (NEGF) formalism, self-consistent calculations of the gate-screened
scattering potentials induced by the boron impurities have been performed,
allowing the theoretical exploration of the tunability of transistor
characteristics. The boron-doped graphene transistors are found to approach
unipolar behavior as the boron concentration is increased, and by tuning the
density of chemical dopants the electron-hole transport asymmetry can be finely
adjusted. Correspondingly, the onset of a mobility gap in the device is
observed. Although the computed asymmetries are not sufficient to warrant
proper device operation, our results represent an initial step in the direction
of improved transfer characteristics and, in particular, the developed
simulation strategy is a powerful new tool for modeling doped graphene
nanostructures.Comment: 7 pages, 5 figures, published in ACS Nan
Spatial dependence of the superexchange interactions for transition-metal trimers in graphene
This study examines the magnetic interactions between spatially-variable
manganese and chromium trimers substituted into a graphene superlattice. Using
density functional theory, we calculate the electronic band structure and
magnetic populations for the determination of the electronic and magnetic
properties of the system. To explore the super-exchange coupling between the
transition-metal atoms, we establish the magnetic magnetic ground states
through a comparison of multiple magnetic and spatial configurations. Through
an analysis of the electronic and magnetic properties, we conclude that the
presence of transition-metal atoms can induce a distinct magnetic moment in the
surrounding carbon atoms as well as produce an RKKY-like super-exchange
coupling. It hoped that these simulations can lead to the realization of
spintronic applications in graphene through electronic control of the magnetic
clusters.Comment: 6 pages, 5 Figur
Direct single-molecule dynamic detection of chemical reactions.
Single-molecule detection can reveal time trajectories and reaction pathways of individual intermediates/transition states in chemical reactions and biological processes, which is of fundamental importance to elucidate their intrinsic mechanisms. We present a reliable, label-free single-molecule approach that allows us to directly explore the dynamic process of basic chemical reactions at the single-event level by using stable graphene-molecule single-molecule junctions. These junctions are constructed by covalently connecting a single molecule with a 9-fluorenone center to nanogapped graphene electrodes. For the first time, real-time single-molecule electrical measurements unambiguously show reproducible large-amplitude two-level fluctuations that are highly dependent on solvent environments in a nucleophilic addition reaction of hydroxylamine to a carbonyl group. Both theoretical simulations and ensemble experiments prove that this observation originates from the reversible transition between the reactant and a new intermediate state within a time scale of a few microseconds. These investigations open up a new route that is able to be immediately applied to probe fast single-molecule physics or biophysics with high time resolution, making an important contribution to broad fields beyond reaction chemistry
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