A Molecular Dynamics Study of PDMS Stamp-Based Graphene Exfoliation

2017 ◽  
Vol 6 (1) ◽  
Author(s):  
Buddhika Jayasena ◽  
Shreyes N. Melkote
Keyword(s):  
Molecular Dynamics ◽  
Low Cost ◽  
Pyrolytic Graphite ◽  
Md Simulations ◽  
Process Conditions ◽  
Large Area ◽  
Pdms Stamp ◽  
Graphene Layers ◽  
Separation Force ◽  
Few Layer Graphene

Molecular dynamics (MD) simulations are used to gain insights into the process conditions that cause separation of graphene layers from a highly ordered pyrolytic graphite (HOPG) source in a polydimethylsiloxane (PDMS) stamp-assisted mechanical exfoliation process. Specifically, the effects of selected exfoliation process parameters and pre-existing defects, such as layer discontinuities in the graphite source, on the exfoliation process are investigated. The results show that exfoliation of individual and few layer graphene requires delicate control of the normal force applied to the HOPG by the PDMS stamp. The study also shows that defects (e.g., discontinuities) in the HOPG have a significant impact on the thickness of separated layers and the layer separation force. The insights derived from this study are expected to be very useful in the development of a low-cost, scalable, large area graphene production process.

Wedge Radius Effects in Mechanical Exfoliation of HOPG: A Molecular Simulation Study

2014 ◽  
Author(s):  
B. Jayasena ◽  
S. Subbiah ◽  
C. D. Reddy
Keyword(s):  
Molecular Dynamics ◽  
Pyrolytic Graphite ◽  
Single Layer ◽  
Layered Material ◽  
Critical Depth ◽  
Graphene Layers ◽  
Highly Ordered Pyrolytic Graphite ◽  
Single Sheet ◽  
Dynamics Simulations ◽  
Atomically Flat

We study the effects of wedge bluntness in mechanically exfoliating graphene layers from highly ordered pyrolytic graphite (HOPG), a layered material. Molecular dynamics simulations show that the layer initiation modes strongly depend on the wedge radius. Force and specific energy signatures are also markedly affected by the radius. Cleaving with a larger wedge radius causes buckling ahead of the wedge; larger the radius more the buckling. A critical depth of insertion of 1.6 A° is seen necessary to cleave a single layer; this is also found to be independent of wedge radius. Hence, with accurate positioning on an atomically flat HOPG surface it is possible to mechanically cleave, using a wedge, a single sheet of graphene even with a blunt wedge.

Diffusion of Epoxy Molecules on the Chemically Modified Graphene: A Molecular Dynamics Simulation Study

2015 ◽  
Vol 817 ◽  
pp. 803-808 ◽  
Author(s):  
Jian Wei Zhang ◽  
Cai Jiang ◽  
Gang Shi ◽  
Da Zhi Jiang
Keyword(s):  
Molecular Dynamics ◽  
Polymer Composites ◽  
Functional Groups ◽  
Md Simulations ◽  
Molecular Structures ◽  
Dynamics Simulation ◽  
Graphene Layers ◽  
Wall Structures ◽  
Modified Graphene ◽  
Main Factor

Buckypaper based polymer composites provides a new technical approach toward realizing conductive/structural multifunctional composites. Resin infiltration in the buckypaper is critical for the fabrication of buckypaper/polymer composites. To investigate the micro-infusion process of the polymer inside the paper, molecular dynamics (MD) simulations are conducted to study the diffusion behavior of epoxy molecules on the modified graphene and between graphene layers. The graphene molecular structures are constructed to represent the wall structures of the carbon nanotubes. Diffusion coefficients of the epoxy molecules on the graphene modified with different functionalization densities and interlayer distances are calculated. The results indicate that the functional groups increase the interfacial interactions between the epoxy molecules and graphene, however, largely decrease the diffusion speeds of the epoxy molecule. The simulations on the graphene layer systems indicate that, the viscous resistance of the resin is the main factor for retarding the diffusion of the epoxy molecules for the unmodified graphene layers; while for the modified graphene layers, functional groups are the main factor for retarding the resin diffusion

scholarly journals Atomic Level Insight into Wetting and Structure of Ag Droplet on Graphene Coated Copper Substrate—Molecular Dynamics versus Experiment

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1465
Author(s):  
Aleksandra Drewienkiewicz ◽  
Arkadiusz Żydek ◽  
Marcela E. Trybula ◽  
Janusz Pstruś
Keyword(s):  
Molecular Dynamics ◽  
Copper Substrate ◽  
Md Simulations ◽  
Atomic Level ◽  
Wetting Behavior ◽  
Graphene Layers ◽  
Metal Interactions ◽  
Metal Metal ◽  
Perfect Graphene ◽  
Pure Cu

Understanding the atomic-level phenomena occurring upon the wetting of graphene-coated Cu with liquid Ag is pivotal for the description of the wetting phenomenon and the role of graphene as a diffusion barrier. We have performed molecular dynamics (MD) simulations and confronted with our present experimental results to characterize wetting behavior of graphene coated Cu surfaces. Perfect and defected graphene layers covering Cu surface were wetted with liquid Ag droplet at 1273 K. Structural and topological aspects are discussed to characterize structure of the liquid Ag droplet and a product of wetting reaction occurring on Cu/Gn and Cu/Gndef substrates, also including perfect graphene layer and a pure Cu surface. The obtained results reveal the importance of defects in graphene structure, which play a key role in wetting mechanism and the formation of AgCu alloy. As a consequence, we observe a change of the wetting behavior and topology of both bulk and adsorbed Ag atoms by using Voronoi analysis (VA). Despite the differences in time scale, atomistic simulations allowed us to catch the early stages of wetting, which are important for explaining the final stage of wetting delivered from experiment. Our findings reveal also graphene translucency to metal-metal interactions, observed in previous papers.

Edge Forces in Contacting Graphene Layers

2015 ◽  
Vol 82 (10) ◽  
Author(s):  
Jianxin Li ◽  
Hongwei Zhang ◽  
Zhengrong Guo ◽  
Tienchong Chang ◽  
Huajian Gao
Keyword(s):  
Molecular Dynamics ◽  
Plane Deformation ◽  
Md Simulations ◽  
Graphene Layers ◽  
Out Of Plane ◽  
Edge Force ◽  
Edge Damage

Temperature- and stiffness-dependent edge forces offer new mechanisms of designing nanodevices driven by temperature and stiffness gradients. Here, we investigate the edge forces in a graphene nanolayer on a spring supported graphene substrate based on molecular dynamics (MD) simulations. The dependences of the edge forces on the temperature and stiffness of the substrate are discussed in detail. Special attention is paid to the effect of the out-of-plane deformation of the substrate on the constituent edge forces and the resultant edge force. The results show that the deformation may lead to a significant redistribution of the constituent edge forces but does not change the resultant edge force, suggesting that particular caution should be exercised in designing nanodevices based on sliding graphene layers to avoid potential edge damage.

Deformation Twinning of Molecular Dynamics Simulation in a Ternary Titanium Alloy under Nanoindentation

2016 ◽  
Vol 874 ◽  
pp. 328-332
Author(s):  
Si Ling Huang ◽  
Zhen Yu Zhang ◽  
Jun Feng Cui ◽  
Song Yang ◽  
Xiao Guang Guo
Keyword(s):  
Molecular Dynamics ◽  
Single Crystal ◽  
Md Simulations ◽  
Deformation Twinning ◽  
Dynamics Simulation ◽  
Single Element ◽  
Face Centered Cubic ◽  
Ti Alloy ◽  
Large Area ◽  
Face Centered

Nanotwinned (nt) metals exhibit excellent mechanical, electrical and thermal properties, and therefore attract much attentions. To fabricate large area nt surface, the fundamental mechanisms of deformation twinning induced by molecular dynamics (MD) are necessary to be explored. Nevertheless, MD of nt metals currently focus mainly on nt copper (Cu) and other single element metals with face-centered cubic (fcc) structure. In addition, MD simulations are usually performed on a built nt model, rather than from a single crystal, due to the difficulty of forming nanotwins. In this study, a single crystal is constructed in a ternary titanium (Ti) alloy with hexagonal closed-packed (hcp) lattice cell. Deformation twinning of MD simulation is performed in a ternary Ti alloy under nanoindentation from the built single crystal. Zonal structure is found during loading under nanoindentation, and nanograins transforms into nanotwins. Deformation twinning is significant to understanding the formation of nanotwins, as well as fabricating large area nt surface on a Ti alloy.

Simple, Fast and Cost-Effective Electrochemical Synthesis of Few Layer Graphene Nanosheets

NANO ◽  
2015 ◽  
Vol 10 (02) ◽  
pp. 1550019 ◽  
Author(s):  
Sumanta Kumar Sahoo ◽  
Archana Mallik
Keyword(s):  
Graphene Nanosheets ◽  
Pyrolytic Graphite ◽  
Cost Effective ◽  
Graphite Sheet ◽  
Graphene Layers ◽  
Force Microscopy ◽  
Green Approach ◽  
Atomic Force ◽  
Absorbance Peak ◽  
Few Layer Graphene

We report an efficient and green approach for mass production of few layered graphene nanosheets (FLGNSs) by intercalation and exfoliation of pyrolytic graphite sheet in a simple protic, H 2 SO 4 electrolyte. The as-prepared FLGNSs at the optimum intercalate concentration of 0.5 M H 2 SO 4 is able to produce large domain of lateral dimension of 11–26 μm consisting of 4–6 stacked graphene layers, as confirmed by field emission scanning electron microscopy and atomic force microscopy, respectively. Surface oxygenation and a characteristic absorbance peak at 228 nm are well observed for electrochemical exfoliated FLGNSs from Fourier transform infrared spectroscopy and UV–Vis spectra respectively. (002) planes of the obtained graphene sheets have been confirmed from X-ray diffraction pattern. The characteristic Raman bands have been observed at 1354 cm-1 and 1590 cm-1 in the exfoliated FLGNSs.

Computer simulation study about the dependence of amorphous silicon photonic waveguides efficiency on the material quality

2020 ◽  
Vol 90 (3) ◽  
pp. 30502
Author(s):  
Alessandro Fantoni ◽  
João Costa ◽  
Paulo Lourenço ◽  
Manuela Vieira
Keyword(s):  
Amorphous Silicon ◽  
High Throughput Screening ◽  
Simulation Analysis ◽  
Low Cost ◽  
Deposition Process ◽  
Large Area ◽  
Sidewall Roughness ◽  
Sensing Applications ◽  
Fabrication Defects ◽  
The Impact

Amorphous silicon PECVD photonic integrated devices are promising candidates for low cost sensing applications. This manuscript reports a simulation analysis about the impact on the overall efficiency caused by the lithography imperfections in the deposition process. The tolerance to the fabrication defects of a photonic sensor based on surface plasmonic resonance is analysed. The simulations are performed with FDTD and BPM algorithms. The device is a plasmonic interferometer composed by an a-Si:H waveguide covered by a thin gold layer. The sensing analysis is performed by equally splitting the input light into two arms, allowing the sensor to be calibrated by its reference arm. Two different 1 × 2 power splitter configurations are presented: a directional coupler and a multimode interference splitter. The waveguide sidewall roughness is considered as the major negative effect caused by deposition imperfections. The simulation results show that plasmonic effects can be excited in the interferometric waveguide structure, allowing a sensing device with enough sensitivity to support the functioning of a bio sensor for high throughput screening. In addition, the good tolerance to the waveguide wall roughness, points out the PECVD deposition technique as reliable method for the overall sensor system to be produced in a low-cost system. The large area deposition of photonics structures, allowed by the PECVD method, can be explored to design a multiplexed system for analysis of multiple biomarkers to further increase the tolerance to fabrication defects.

Efficient Treatment of Fixed and Induced Dipolar Interactions

2000 ◽  
Vol 653 ◽  
Author(s):  
Celeste Sagui ◽  
Thoma Darden
Keyword(s):  
Molecular Dynamics ◽  
Md Simulations ◽  
Lagrangian Formalism ◽  
Dipolar Interactions ◽  
Time Step ◽  
Efficient Treatment ◽  
Particle Mesh Ewald ◽  
Fixed Charges ◽  
Self Consistency ◽  
Induced Dipoles

AbstractFixed and induced point dipoles have been implemented in the Ewald and Particle-Mesh Ewald (PME) formalisms. During molecular dynamics (MD) the induced dipoles can be propagated along with the atomic positions either by interation to self-consistency at each time step, or by a Car-Parrinello (CP) technique using an extended Lagrangian formalism. The use of PME for electrostatics of fixed charges and induced dipoles together with a CP treatment of dipole propagation in MD simulations leads to a cost overhead of only 33% above that of MD simulations using standard PME with fixed charges, allowing the study of polarizability in largemacromolecular systems.

Split the Charge Difference in Two! a Rule of Thumb for Adding Proper Amounts of Ions in MD Simulations

2020 ◽  
Author(s):  
Matías R. Machado ◽  
Sergio Pantano
Keyword(s):  
Molecular Dynamics ◽  
Ionic Strength ◽  
Molecular Simulations ◽  
Md Simulations ◽  
Good Practices ◽  
Rule Of Thumb ◽  
Ionic Concentrations

<p> Despite the relevance of properly setting ionic concentrations in Molecular Dynamics (MD) simulations, methods or practical rules to set ionic strength are scarce and rarely documented. Based on a recently proposed thermodynamics method we provide an accurate rule of thumb to define the electrolytic content in simulation boxes. Extending the use of good practices in setting up MD systems is promptly needed to ensure reproducibility and consistency in molecular simulations.</p>

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