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PubMed Journals Articles About "Phase Imaging Nanoscale Energy Dissipation Supported Graphene Using" RSS

13:34 EDT 26th April 2018 | BioPortfolio

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Showing "Phase imaging nanoscale energy dissipation supported graphene using" PubMed Articles 1–25 of 22,000+

Phase imaging and nanoscale energy dissipation of supported graphene using amplitude modulation atomic force microscopy.

We investigate phase imaging of supported graphene using amplitude modulation atomic force microscopy (AFM), so called, tapping mode. The phase contrast between graphene and neighbouring substrate grows at hard tapping conditions and the contrast is enhanced compared to the topographic one. Therefore, the phase measurements could enable a high contrast imaging of graphene and related two dimensional materials and heterostructures, not achievable with conventional AFM based topographic measurements. Obtained...


Phase imaging and nanoscale energy dissipation of supported graphene using amplitude modulation atomic force microscopy.

We investigate the phase imaging of supported graphene using amplitude modulation atomic force microscopy (AFM), the so-called tapping mode. The phase contrast between graphene and the neighboring substrate grows in hard tapping conditions and the contrast is enhanced compared to the topographic one. Therefore, phase measurements could enable the high-contrast imaging of graphene and related two-dimensional materials and heterostructures, which is not achievable with conventional AFM based topographic measu...

Thermal Transport in Supported Graphene Nanomesh.

Graphene is considered as a promising candidate material to replace silicon for the next generation nanoelectronics due to its superb carrier mobility. To evaluate its thermal dissipation capability as electronic materials, the thermal transport in monolayer graphene was extensively explored over the past decade. However, the supported chemical vapor deposition (CVD) grown monolayer graphene with submicron structures were seldom studied, which is important for practical nanoelectronics. Here we investigate ...


Measuring and Manipulating the Adhesion of Graphene.

We present a technique to precisely measure the surface energies between two dimensional materials and substrates that is simple to implement and allows exploration of spatial and chemical control of adhesion at the nanoscale. As an example, we characterize the delamination of single-layer graphene from monolayers of pyrene tethered to glass in water and maximize the work of separation between these surfaces by varying the density of pyrene groups in the monolayer. Control of this energy scale enables high-...

Energy dissipation mapping of cancer cells.

The purpose of this study is to map the energy dissipation of Jurkat cells using a single 60 nanosecond pulse electric field (NsPEF), primarily through atomic force microscopy (AFM). The phase shift is generated by the sample elements that do not have a heterogeneous surface. Monitoring and manipulating the phase shift is a powerful way for determining the dissipated energy and plotting the topography. The dissipated energy is a relative value, so the silica wafer and cover slip are given a set reference wh...

Probing plasma fluorinated graphene via spectromicroscopy.

Plasma fluorination of graphene is studied using a combination of spectroscopy and microscopy techniques, giving insight into the yield and fluorination mechanism for functionalization of supported graphene with both CF4 and SF6 gas precursors. Ion acceleration during fluorination is used to probe the effect on grafting functionalities. Adatom clustering, which occurs with CF4 plasma treatment, is suppressed when higher kinetic energy is supplied to the ions. During SF6 plasma functionalization, the sulfur ...

Optical imaging and spectroscopic characterization of self-assembled environmental adsorbates on graphene.

Topographic studies using scanning probes have found that graphene surfaces are often covered by micron-scale domains of periodic stripes with a 4 nm pitch. These stripes have been variously interpreted as structural ripples or as self-assembled adsorbates. We show that the stripe domains are optically anisotropic by imaging them using a polarization-contrast technique. Optical spectra between 1.1 and 2.8 eV reveal that the anisotropy in the in-plane dielectric function is predominantly real, reaching 0.6 f...

Core Level Spectra of Organic Molecules Adsorbed on Graphene.

We perform first principle calculations based on density functional theory to investigate the effect of the adsorption of core-excited organic molecules on graphene. We simulate Near Edge X-ray absorption Fine Structure (NEXAFS) and X-ray Photoemission Spectroscopy (XPS) at the N and C edges for two moieties: pyridine and the pyridine radical on graphene, which exemplify two different adsorption characters. The modifications of molecular and graphene energy levels due to their interplay with the core-level ...

Graphene oxide assisted template-free synthesis of nanoscale splode-like NiCo2O4 hollow microsphere with superior lithium storage properties.

A facile template-free Ostwald ripening method is developed for the preparation of the reduced graphene oxide supported splode-like NiCo2O4 hollow microsphere (SNHM/rGO). The graphene oxide used in the reaction mixture is found to play a crucial role in the formation of the SNHM/rGO. It promotes the formation of the NiCo-glycerol microspheres suitable for the Ostwald ripening to form the reduced graphene oxide supported hollow NiCo-glycerol microspheres, which is important for the subsequent calcination to ...

Optical Forging of Graphene into Three-Dimensional Shapes.

Atomically thin materials, such as graphene, are the ultimate building blocks for nanoscale devices. But although their synthesis and handling today are routine, all efforts thus far have been restricted to flat natural geometries, since the means to control their three-dimensional (3D) morphology has remained elusive. Here we show that, just as a blacksmith uses a hammer to forge a metal sheet into 3D shapes, a pulsed laser beam can forge graphene sheet into controlled 3D shapes in the nanoscale. The forgi...

Band-Gap Engineering of Graphene Heterostructures via Substitutional Doping with B3N3.

We investigated the energetics and electronic structures of B3N3-doped graphene using the density functional theory with the generalized gradient approximation. Our calculations showed that all of the B3N3-doped graphene structures were semiconductors, irrespective of the periodicity of the B3N3 embedded into the graphene network, in contrast to graphene nanomeshes which are either semiconductors or metals depending on the mesh arrangement. The B3N3-doped graphene has small effective masses for both electro...

Wrinkling formation in simply-supported graphenes under tension and compression loadings.

Wrinkles in supported graphenes can be formed either by uniaxial compression or uniaxial tension beyond a certain critical load depending on the mode of loading. In the first case, the wrinkling direction is normal to the compression axis whereas in tension, wrinkles of the same pattern are formed parallel to the loading direction due to Poisson's (lateral) contraction. Herein we show by direct AFM observations that in simply-supported graphenes such instabilities appear as periodic wrinkles over existing s...

Electron microscopy of polyoxometalate ions on graphene by electrospray ion beam deposition.

Aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM) has enabled atomically resolved imaging of molecules adsorbed on low-dimensional materials like carbon nanotubes, graphene oxide and few-layer-graphene. However, conventional methods for depositing molecules onto such supports lack selectivity and specificity. Here, we describe the chemically selective preparation and deposition of molecules-like polyoxometalate (POM) anions [PWO]using electrospray ion-beam deposition (ES-IBD) ...

The Effect of Thickness and Chemical Reduction of Graphene Oxide on Nanoscale Friction.

The tribological properties of two-dimensional (2D) atomic layers are quite different from three-dimensional (3D) continuum materials because of the unique mechanical responses of 2D layers. It is known that friction on graphene shows a remarkable decreasing behavior as the number of layers increases, which is caused by the puckering effect. On other graphene derivatives, such as graphene oxide (GO) or reduced graphene oxide (rGO), the thickness dependence of friction is important because of the possibiliti...

The Effects of Graphene Stacking on the Performance of Methane Sensor: A First-Principles Study on the Adsorption, Band Gap and Doping of Graphene.

The effects of graphene stacking are investigated by comparing the results of methane adsorption energy, electronic performance, and the doping feasibility of five dopants (i.e., B, N, Al, Si, and P) via first-principles theory. Both zigzag and armchair graphenes are considered. It is found that the zigzag graphene with Bernal stacking has the largest adsorption energy on methane, while the armchair graphene with Order stacking is opposite. In addition, both the Order and Bernal stacked graphenes possess a ...

Temperature Measurement by a Nanoscale Electron Probe Using Energy Gain and Loss Spectroscopy.

Heat dissipation in integrated nanoscale devices is a major issue that requires the development of nanoscale temperature probes. Here, we report the implementation of a method that combines electron energy gain and loss spectroscopy to provide a direct measurement of the local temperature in the nanoenvironment. Loss and gain peaks corresponding to an optical-phonon mode in boron nitride were measured from room temperature to ∼1600  K. Both loss and gain peaks exhibit a shift towards lower energies as...

Low-Temperature Copper Bonding Strategy with Graphene Interlayer.

The reliability of lead-free Cu bonding technology is often limited by high bonding temperature and perpetual growth of intermetallic compounds between Sn solder and Cu substrate. Here, we report a low-bonding-temperature and highly-reliable Cu bonding strategy with the use of graphene as an interlayer. By integrating nanoscale graphene/Cu composite on the Cu substrate prior to thermocompression bonding, we observe a macro-scale phenomenon where reliable Sn-Cu joints can be fabricated at a bonding temperatu...

Two-dimensional Cu2Si sheet: A promising electrode material for nanoscale electronics.

Building electronic devices on top of two dimensional (2D) materials has become one of most interesting topics recently in nanoelectronics. Finding high-performance 2D electrode materials is one central issue in 2D nanoelectronics. In current study, based on first principles calculations, we compare the electronic and transport properties of two nanoscale devices. One device consists of two single-atom-thick planar Cu2Si electrodes and a nickel-phthalocyanine (NiPc) molecule in middle. The other one is made...

Log-Normal Turbulence Dissipation in Global Ocean Models.

Data from turbulent numerical simulations of the global ocean demonstrate that the dissipation of kinetic energy obeys a nearly log-normal distribution even at large horizontal scales O(10  km). As the horizontal scales of resolved turbulence are larger than the ocean is deep, the Kolmogorov-Yaglom theory for intermittency in 3D homogeneous, isotropic turbulence cannot apply; instead, the down-scale potential enstrophy cascade of quasigeostrophic turbulence should. Yet, energy dissipation obeys approxim...

Orientation-Dependent Strain Relaxation and Chemical Functionalization of Graphene on a Cu(111) Foil.

Epitaxial graphene grown on single crystal Cu(111) foils by chemical vapor deposition is found to be free of wrinkles and under biaxial compressive strain. The compressive strain in the epitaxial regions (0.25-0.40%) is higher than regions where the graphene is not epitaxial with the underlying surface (0.20-0.25%). This orientation-dependent strain relaxation is through the loss of local adhesion and the generation of graphene wrinkles. Density functional theory calculations suggest a large frictional forc...

Controlled electrochemical doping of graphene-based 3D nanoarchitecture electrodes for supercapacitors and capacitive deionisation.

Chemically-doped graphenes are promising electrode materials for energy storage and electrosorption applications. Here, an affordable electrochemical green process is introduced to dope graphene with nitrogen. The process is based on reversing the polarity of two identical graphene oxide (GO) electrodes in molten KCl-LiCl-Li3N. During the cathodic step, the oxygen functional groups on the GO surface are removed through direct electro-deoxidation reactions or a reaction with the deposited lithium. In the ano...

Contributions of kinetic energy and viscous dissipation to airway resistance in pulmonary inspiratory and expiratory airflows in multiscale symmetric airway models with various bifurcation angles.

The aim of this study was to investigate and quantify contributions of kinetic energy and viscous dissipation to airway resistance during inspiration and expiration at various flow-rates in airway models of different bifurcation angles. We employed symmetric airway models up to the 20th generation with the following five different bifurcation angles at a tracheal flow-rate of 20 L/min: 15, 25, 35, 45 and 55 degrees. Thus, a total of 10 CFD simulations for both inspiration and expiration were conducted. Furt...

Evaluation of Graphene/WO3 and Graphene/CeO x Structures as Electrodes for Supercapacitor Applications.

The combination of graphene with transition metal oxides can result in very promising hybrid materials for use in energy storage applications thanks to its intriguing properties, i.e., highly tunable surface area, outstanding electrical conductivity, good chemical stability, and excellent mechanical behavior. In the present work, we evaluate the performance of graphene/metal oxide (WO3 and CeO x ) layered structures as potential electrodes in supercapacitor applications. Graphene layers were grown by chemic...

Observation of the Mott insulator to superfluid crossover of a driven-dissipative Bose-Hubbard system.

Dissipation is ubiquitous in nature and plays a crucial role in quantum systems such as causing decoherence of quantum states. Recently, much attention has been paid to an intriguing possibility of dissipation as an efficient tool for the preparation and manipulation of quantum states. We report the realization of successful demonstration of a novel role of dissipation in a quantum phase transition using cold atoms. We realize an engineered dissipative Bose-Hubbard system by introducing a controllable stren...

Energy Dissipation in Fluid Coupled Nanoresonators: The Effect of Phonon-Fluid Coupling.

Resonant nanomechanical systems find numerous sensing applications both in the vacuum and in the fluid environment but their performance is degraded by different dissipation mechanisms. In this work, we study dissipation mechanisms associated with high frequency axial excitation of a single-walled carbon nanotube (CNT) filled with argon, which is a representative fluid coupled resonator system. By performing molecular dynamics simulations, we identify two dissipative processes associated with the axial exci...


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