Surface Roughness Of Graphene Research Articles

Comparative Studies on Crystallinity, Thermal and Mechanical Properties of Polyketone Grown on Plasma Treated CVD Graphene.

In this work, we report a facile way to control crystalline structures of polyketone (PK) films by combining plasma surface treatment with chemical vapor deposition (CVD) technique. The crystalline structure of PKs grown on plasma-treated graphene and the resulting thermal and mechanical properties were systematically discussed. Every graphene sheet used in this work was produced by CVD method and the production of PKs having different crystallinity were performed on the O2- and N2-doped graphene sheets. It was evident that the CVD-grown graphene sheets acted as the nucleating agents for promoting the crystallization of β-form PK, while suppressing the growth of α-form PK crystals. Regardless of the increase in surface roughness of graphene, surface functionality of the CVD-grown graphene was found to be an important factor in determining the crystalline structure of PK. N2 plasma treatment of the CVD-grown graphene promoted growth of the β-form PK, whereas the O2 plasma treatment of CVD graphene led to transformation of the unoriented β-form PK into the oriented α-form PK. Thus, the resulting thermal and mechanical properties of the PKs were highly dependent on the surface functionality of the CVD graphene. The method of controlling crystalline structure of the PKs suggested in this study, is expected to be very effective in realizing the PK with good processability, heat resistance and mechanical properties.

Nanoscale Friction of Graphene

AbstractDespite being one of the oldest phenomena known to mankind and its vast use, there still are open questions about the frictional process between two surfaces, especially at the nanometer scale, such as the energy dissipation mechanism, the influence of the crystallographic orientation and the correlation between macroscopic and microscopic scales. In this work, we analyze the interaction between a sharp tip and graphene by friction force microscopy. The graphene surface roughness and adhesion forces with the microscope tip were measured. Neither roughness nor adhesion were observed to influence the friction forces. The scanning velocity dependence of friction was also measured for a different number of layers. The friction forces were observed to increase with the scanning velocity until a critical velocity is achieved by which we have estimated the effective interaction potential between the tip and the graphene surface.

Effects of substrate and graphene surface roughness on graphene sheet plasmons

Effects of substrate and graphene surface roughness on graphene sheet plasmons

Compaction of a copper film on graphene by argon-beam bombardment: Computer experiment

The process of Cu-film compaction on graphene under the action of Ar13 clusters hitting the surface with an energy of 5 eV is studied using the molecular-dynamics method. The horizontal and vertical components of the self-diffusion coefficient of a Cu film and graphene, the stresses on the horizontal Cu area, the Cu-graphene interaction energy, the radial distribution function of the film, and the graphene surface roughness under bombardment of a target by Ar13 clusters are calculated. Graphene exhibits some pliability, and traces of Cu film surface relief remain on it after total exposure under the impacts of Ar13 clusters.

In Situ Scanning Electron Microscope Peeling To Quantify Surface Energy between Multiwalled Carbon Nanotubes and Graphene

Understanding atomic interactions between constituents is critical to the design of high-performance nanocomposites. Here, we report an experimental-computational approach to investigate the adhesion energy between as-produced arc discharge multiwalled carbon nanotubes (MWCNTs) and graphene. An in situ scanning electron microscope (SEM) experiment is used to peel MWCNTs from graphene grown on copper foils. The force during peeling is obtained by monitoring the deflection of a cantilever. Finite element and molecular mechanics simulations are performed to assist the data analysis and interpretation of the results. A finite element analysis of the experimental configuration is employed to confirm the applicability of Kendall's peeling model to obtain the adhesion energy. Molecular mechanics simulations are used to estimate the effective contact width at the MWCNT-graphene interface. The measured surface energy is γ = 0.20 ± 0.09 J·m(-2) or γ = 0.36 ± 0.16 J·m(-2), depending on the assumed conformation of the tube cross section during peeling. The scatter in the data is believed to result from an amorphous carbon coating on the MWCNTs, observed using transmission electron microscopy (TEM), and the surface roughness of graphene as characterized by atomic force microscopy (AFM).

Rapid-thermal-annealing surface treatment for restoring the intrinsic properties of graphene field-effect transistors

Graphene field-effect transistors (GFETs) were fabricated by photolithography and lift-off processes, and subsequently heated in a rapid-thermal-annealing (RTA) apparatus at temperatures (TA) from 200 to 400 ° C for 10 min under nitrogen to eliminate the residues adsorbed on the graphene during the GFET fabrication processes. Raman-scattering, current–voltage (I–V), and sheet resistance measurements showed that, after annealing at 250 ° C, graphene in GFETs regained its intrinsic properties, such as very small intensity ratios of D to G and G to 2D Raman bands, a symmetric I–V curve with respect to ∼0 V, and very low sheet resistance. Atomic force microscopy images and height profiles also showed that the surface roughness of graphene was almost minimized at TA = 250 ° C. By annealing at 250 ° C, the electron and hole mobilities reached their maxima of 4587 and 4605 cm2 V−1 s−1, respectively, the highest ever reported for chemical-vapor-deposition-grown graphene. Annealing was also performed under vacuum or hydrogen, but this was not so effective as under nitrogen. These results suggest that the RTA technique is very useful for eliminating the surface residues of graphene in GFETs, in that it employs a relatively low thermal budget of 250 ° C and 10 min.