Deposition Of Graphene Research Articles

Direct graphene synthesis on Si(1 0 0) by inductively coupled plasma beam source

The graphene was synthesized directly on the Si(100) substrate by an Inductively Coupled Plasma Beam Source without any catalyst. Plasma power, methane gas flow, hydrogen gas flow, temperature and time effects on graphene layers number and flake size, defects density, and surface morphology were studied. Prevailing defects type was considered. Boundary defects dominated in most samples due to the polycrystalline nature of the directly synthesized graphene. However, high methane gas flows, low synthesis times, and low synthesis temperatures were beneficial for the hydrogenation of the growing graphene. On-site defects prevailed in these samples. It was found that synthesis power, temperature, and time should be optimized to avoid out-of-plane graphene growth. An additional hydrogen gas flow effectively controlled graphene layers number. D + D‘ and D + D“ peaks were explored. It was supposed that the D + D‘ peak is mainly related to the on-site defects associated with a hydrogen atom bonded to the carbon atom in the graphene sheet. The line-of-sight graphene deposition was demonstrated. The main graphene growth-related physical and chemical processes were considered. The observed results were explained by a competition between graphene growth, hydrogen etching, hydrogenation, and thermal stress release.

Growth of Graphene on a Liquified Copper Skin at Submelting Temperatures.

In chemical vapor deposition of graphene, crossing over the melting temperature of the bulk catalyst is an effective approach to heal the defects and thus improve the crystallinity of the lattice. Here, electromagnetic absorption (the capability of metals to absorb radiated thermal energy) yields a thin skin of liquid metal catalyst at submelting temperatures, allowing the growth of high quality graphene. In fact, a chromium film initially deposited on one side of a copper foil absorbs the thermal energy radiated from a heating stage several times more effectively than a plain copper foil. The resulting migration of the chromium grains to the other side of the foil locally melts the copper, improving the crystalline quality of the growing graphene, confirmed by Raman spectroscopy. The process duration is therefore dramatically minimized, and the crystallinity of the graphene is maximized. Remarkably, the usual annealing step is no more necessary prior to the growth which together with unlocking the direct healing of defects in the growing graphene, will unify growth strategies between a range of catalysts.

Fabrication of flexible microheater with tunable heating capabilities by direct laser writing and selective electrodeposition

Flexible microheaters are useful in a variety of fields, such as portable medical instruments, wearable electronic devices, aircraft, and many more. The microheaters that can provide thermal stimuli in a series of small regions have received considerable attention in recent years. In this work, we present a novel manufacturing process for flexible microheaters with designed heating patterns. Such flexible microheaters with customized heating patterns are fabricated using a hybrid manufacturing process that combines direct laser writing, 3D printing, and selective electrodeposition to control the deposition of graphene and copper on a polyimide film. Based on a given heating pattern, a laser-induced graphene (LIG) structure is utilized as the active heating material, and selectively electrodeposited copper defined by 3D-printed masks is used as the electrode material to connect LIG. The width of the heating line can be as small as 60 μm. The total processing time of a typical 60 mm × 30 mm microheater was within 20 min. When connected to electricity, the fabricated microheaters have tunable heating temperatures at designed heating areas. The heating temperature can reach up to 150 °C. Moreover, the microheaters have shown quick heating and stable thermal performance when subjected to bending, twisting, and folding. Compared with the existing microheater fabrication methods, the newly developed manufacturing process is simple to operate and has the advantages of high accuracy (up to 60 μm heating line width), flexible tunability, and low cost (within $5) compared with other conventional microfabrication methods.

Aerosol Jet Printing of Graphene and Carbon Nanotube Patterns on Realistically Rugged Substrates.

Direct-write additive manufacturing of graphene and carbon nanotube (CNT) patterns by aerosol jet printing (AJP) is promising for the creation of thermal and electrical interconnects in (opto)electronics. In realistic application scenarios, this however often requires deposition of graphene and CNT patterns on rugged substrates such as, for example, roughly machined and surface-oxidized metal block heat sinks. Most AJP of graphene/CNT patterns has thus far however concentrated on flat wafer- or foil-type substrates. Here, we demonstrate AJP of graphene and single walled CNT (SWCNT) patterns on realistically rugged plasma-electrolytic-oxidized (PEO) Al blocks, which are promising heat sink materials. We show that AJP on the rugged substrates offers line resolution of down to ∼40 μm width for single AJP passes, however, at the cost of noncomplete substrate coverage including noncovered μm-sized pores in the PEO Al blocks. With multiple AJP passes, full coverage including coverage of the pores is, however, readily achieved. Comparing archetypical aqueous and organic graphene and SWCNT inks, we show that the choice of the ink system drastically influences the nanocarbon AJP parameter window, deposit microstructure including crystalline quality, compactness of deposit, and inter/intrapass layer adhesion for multiple passes. Simple electrical characterization indicates aqueous graphene inks as the most promising choice for AJP-deposited electrical interconnect applications. Our parameter space screening thereby forms a framework for rational process development for graphene and SWCNT AJP on application-relevant, rugged substrates.

Direct fabrication and characterization of vertically stacked Graphene/h-BN/Graphene tunnel junctions

We have used a lithography free technique for the direct fabrication of vertically stacked two-dimensional (2D) material-based tunnel junctions and characterized by Raman, AFM, XPS. We fabricated Graphene/h-BN/Graphene devices by direct deposition of graphene (bottom layer), h-BN (insulating barrier) and graphene (top layer) sequentially using a plasma enhanced chemical vapor deposition on Si/SiO2 substrates. The thickness of the h-BN insulating layer was varied by tuning the plasma power and the deposition time. Samples were characterized by Raman, AFM, and XPS. The I-V data follows the barrier thickness dependent quantum tunneling behavior for equally doped graphene layers. The resonant tunneling behavior was observed at room temperature for oppositely doped graphene layers where hydrazine and ammonia were used for n-doping of one of the graphene layers. The resonance with negative differential conductance occurs when the band structures of the two electrodes are aligned. The doping effect of the resonant peak is observed for varying doping levels. The results are explained according to the Bardeen tunneling model.

Preparation and Evaluation of the Polyethylene Film Deposited With a Multilayer Graphene Membrane for Tensile Properties

This study aims to improve the tensile properties of the polyethylene film deposited with a multilayer graphene membrane, in order to establish the understanding of the influence of the methane to hydrogen ratio on the tensile properties of the multilayer graphene membrane. Multilayer graphene membranes were prepared using the chemical vapor deposition method. Four types of multilayer graphene membranes were prepared with different ratios of methane to hydrogen before depositing a membrane on the polyethylene film. Experiments showed that the tensile strength of the polyethylene films with multilayer graphene deposition increased 7 times and the Young’s modulus 5 times more than that of pure polyethylene films, when the ratio of methane to hydrogen was set to 35/100 sccm. A compromise between hydrogen and methane mixture is required to achieve uniform growth of graphene. Insufficient hydrogen cannot activate the surface bound carbon that is necessary for continuous growth. Continuous and well-defined multilayer graphene was synthesized when the ratio of methane to hydrogen reached up a proper value.

Atmospheric Pressure Catalytic Vapor Deposition of Graphene on Liquid In and Cu-In Alloy Substrates

Liquid substrates are great candidates for the growth of high-quality graphene using chemical vapour deposition (CVD) due to their atomically flat and defect free surfaces. A detailed study of graphene growth using atmospheric pressure CVD (APCVD) on liquid indium (In) was conducted. It was found that the effect of the growth parameters on the quality of the graphene produced is highly dependent on the properties of the substrate used. A short residence time of 6.8 sec for the reactive gases led to a high graphene quality, indicating the good catalytic behaviour of In. The role of hydrogen partial pressure was found to be crucial, with monolayer and bilayer graphene films with a low defect density obtained at low PH2 (38.6 mbar), whilst more defective, thicker graphene films with a partial coverage being obtained at high PH2 (74.3 mbar). The graphene deposition was insensitive to growth time as the graphene growth on liquid In was found to self-limit to bilayer. For further investigation, five compositions of Cu-In alloys were made by arc-melting. Graphene was then grown using the optimum conditions for In and the quality of the graphene was found to degrade with increasing Cu wt.%. This work will aid the future optimisation of the growth conditions based upon the substrate’s properties.

Hydrogen permeation behavior and mechanism of multi-layered graphene coatings and mitigation of hydrogen embrittlement of pipe steel

A method for in situ deposition of multi-layered graphene (MLG) coatings is demonstrated to mitigate hydrogen embrittlement of the X70 pipe steel. Carbon is implanted into the nickel catalytic layer pre-deposited by electroplating on the surface of the pipe steel, followed by annealing to segregate and form MLG. The MLG coatings are investigated systematically with respect to the surface morphology, phase structure, hydrogen resistance, corrosion resistance, and molecular dynamics simulation. In the stacked MLG structure, the in situ grown graphene layers interpenetrate each other to boost the coating adhesion and hydrogen resistance. Diffusion and the solid solution formed between the Ni coating and substrate improve the adhesion strength after annealing. The diffusion coefficient and permeability are reduced by 123 times and 48 times, respectively. Slow strain rate tests demonstrate outstanding resistance against hydrogen embrittlement because the MLG coatings inhibit hydrogen evolution, extend the diffusion path, decrease the permeation area, and enhance hydrogen adsorption. Moreover, electrochemical tests indicate that the MLG coatings have better corrosion resistance. These results reveal a viable strategy to use graphene to protect commercial steels from hydrogen embrittlement.

A Heat Transfer Model for Graphene Deposition on Ni and Cu Foils in a Roll-to-Roll Plasma Chemical Vapor Deposition System

Abstract High-throughput production is a major bottleneck for integration of graphene-based technologies in existing and future applications. Here, a semi-empirical heat transfer model is developed to optimize large-scale deposition of graphene on Ni and Cu foils in a roll-to-roll (R2R) plasma chemical vapor deposition (CVD) system. Temperature distributions in Ni and Cu foils during deposition are recorded with in situ temperature measurements using near-IR optical emission spectroscopy. The model indicates that foil movement significantly affects the temperature distribution and the cooling rate of the foil. Consequently, graphene growth on Cu is limited to lower web speeds for which the foil temperature is higher, and the residence time in the plasma is longer. On the other hand, graphene can be deposited on Ni at relatively higher web speeds due to moderately high diffusion rate of carbon in Ni and increased cooling rates up to 20 K/s with higher web speed. Critical limitations in the production rates of graphene using R2R CVD process exist due to significant effects of web speed on the temperature distribution of the substrate. The thermal analysis approach reported here is expected to aid in enhancing the throughput of graphene production in R2R CVD systems.

Thermodynamic analysis of graphene CVD grown on liquid metal: Growth on liquid metallic gallium or solid gallium oxide skin?

A number of recent publications have reported liquid gallium to have an extraordinary catalytic activity for chemical vapor deposition (CVD) of graphene, enabling the growth of high-quality graphene on its surface even below 600 K. Our presented thermodynamic analysis however, indicates that during several of these experiments, an atomically thin gallium oxide layer should have covered the liquid gallium. This means that graphene should have actually grown on the solid oxide skin rather than on the liquid metal. This suggests a more complex mechanism for graphene growth on liquid gallium than what is currently considered in the community.

Acetone and isopropanol – a new liquid precursor for the controllable transfer- and lithography-free CVD of graphene-like films

Liquid precursors are of high practical interest for the chemical vapor deposition (CVD) of graphene and related materials. In terms of cost, safety and technological operability, the liquids are significantly more attractive than the conventional gas precursors. Another challenge to the technology is the direct deposition of carbon films on dielectric substrates without the transfer procedure. In the present work, we study the synthesis of graphene-like films (GLFs) on sapphire and SiO2/Si from two liquid precursors: acetone and isopropanol. GLFs in this work are defined as multi-layer graphene films with a crystallite size of several tens of nm. The films synthesized by CVD at different temperatures were characterized by the optical transmittance and sheet resistance; the structure of the films was studied by Raman spectroscopy. We show that such films have superior characteristics as compared to most literature data on direct CVD deposition from oxygen-containing liquid precursors. The films can be grown selectively on exposed areas of the e-beam pre-patterned substrate at specific deposition conditions. We demonstrate this by selectively growing a Hall bar microstructure for carrier mobility measurements.

Wear behavior of electrodeposited nickel/graphene composite coating

The agglomeration of the doped graphene powder during electrochemical deposition and non-uniform dispersion in the nickel coating matrix are problems to be solved urgently. In order to solve these problems, a graphite flake was used for the anode, and on the basis of Watt's type electroplating solution, sulfuric acid was introduced to strip the graphite. Since the electroplating solution can peel graphene, the anodic peeling and cathodic deposition of graphene can be realized simultaneously, and the nickel/graphene composite coating can be obtained. The results showed that the exfoliated graphene (EG) was uniformly dispersed in the coating without agglomeration, which exhibited a typical wrinkled double-layer structure. The addition of graphene changed the preferred orientation of nickel from (200) to (111), the crystal grains were refined, and the performance was significantly improved. The microhardness of the nickel coating was increased from 186 HV to 330 HV, the friction coefficient was reduced to 0.16, and the wear rate was only 3.2 × 10−5 mm3 (N·m)−1. This research provides a new idea to solve the problem of graphene agglomeration and uniform dispersion in the electrolyte and coating and offers a new solution for the efficient preparation of nickel/graphene composite coatings with uniform graphene dispersion.

Antibiofouling Activity of Graphene Materials and Graphene-Based Antimicrobial Coatings.

Microbial adhesion and biofilm formation is a common, nondesirable phenomenon at any living or nonliving material surface in contact with microbial species. Despite the enormous efforts made so far, the protection of material surfaces against microbial adhesion and biofilm formation remains a significant challenge. Deposition of antimicrobial coatings is one approach to mitigate the problem. Examples of such are those based on heparin, cationic polymers, antimicrobial peptides, drug-delivering systems, and other coatings, each one with its advantages and shortcomings. The increasing microbial resistance to the conventional antimicrobial treatments leads to an increasing necessity for new antimicrobial agents, among which is a variety of carbon nanomaterials. The current review paper presents the last 5 years’ progress in the development of graphene antimicrobial materials and graphene-based antimicrobial coatings that are among the most studied. Brief information about the significance of the biofouling, as well as the general mode of development and composition of microbial biofilms, are included. Preparation, antibacterial activity, and bactericidal mechanisms of new graphene materials, deposition techniques, characterization, and parameters influencing the biological activity of graphene-based coatings are focused upon. It is expected that this review will raise some ideas for perfecting the composition, structure, antimicrobial activity, and deposition techniques of graphene materials and coatings in order to provide better antimicrobial protection of medical devices.

Chemical vapor deposition of graphene by ethanol decomposition and its smooth transfer

Chemical vapor deposition of graphene by ethanol decomposition and its smooth transfer

Polymer-Compatible Low-Temperature Plasma-Enhanced Chemical Vapor Deposition of Graphene on Electroplated Cu for Flexible Hybrid Electronics.

Flexible hybrid electronics and fan-out redistribution layers rely on electroplating Cu on polymers. In this work, direct low-temperature plasma-enhanced chemical vapor deposition (PECVD) of graphene on electroplated Cu over polyimide substrates is demonstrated, and the deposition of graphene is found to passivate and strengthen the electroplated Cu circuit. The effect of the H2/CH4 ratio on the PECVD graphene growth is also investigated, which is shown to affect not only the quality of graphene but also the durability of Cu. 100,000 cycles of folding with a bending radius of 2.5 mm and the corresponding resistance tests are carried out, revealing that Cu circuits covered by graphene grown with a higher H2/CH4 ratio can sustain many more bending cycles. Additionally, graphene coverage is shown to suppress the formation of copper oxides in ambient environment for at least 8 weeks after the PECVD process.

Predicting Graphene Growth on Cu: Universal Kinetic Growth Model and Its Experimental Verification.

The kinetics of the chemical vapor deposition (CVD) of graphene on Cu in CH4 + H2 were investigated by monitoring the graphene flake size as a function of CVD growth time. A growth model was set up which relates the CVD parameters to the mass action constant Qexp of the methane decomposition reaction toward graphene at a given temperature T. Graphene growth was shown to proceed from pre-equilibrated adsorbed carbon (Cad) within a wide CVD parameter range. The model not only leads to the correct scaling relation of the growth kinetics but quantitatively determines how far the CVD parameters deviate from thermal equilibrium and correctly predicts the absolute flake size increase per time. Fitting experimental data delivers the energy barrier for carbon detachment from the graphene island edge (Edet = 4.7 ± 0.3 eV) and the methane decomposition entropy toward Cad on Cu (ΔdecS° = 260 ± 20 J mol-1 K-1). The latter value is used to estimate the vanishingly small Cad equilibrium concentration of 3 × 10-10 monolayers at 1045 °C. The universal validity of the model is proven by comparison with literature data providing the correct order of magnitude growth velocities up to 1000 μm/h. The performed reactor experiments deliver data that match the predicted flake growth velocity with a precision of about 50%. The obtained results can be used to calibrate any hot wall CVD reactor setup for the methane decomposition reaction toward graphene on Cu. The description can be directly applied for any hydrocarbon in the gas feed, and the technique can be easily applied for other catalytic support surfaces.

Preparation and tribological characteristics of graphene/triangular copper nanoplate composites as grease additive

PurposeThis study aims to the preparation and tribological characteristics of graphene/triangular copper nanoplate composites (abbreviated as GN/Cu nanoplates) as grease additive and clarifies the growth mechanism and tribological mechanism of GN/Cu nanoplates by different analysis methods. In this paper, it is expected to alleviate the problems of easy aggregation and poor dispersion stability of graphene in lubricants and provide theoretical support for the application of graphene and its composites in the tribology field.Design/methodology/approachIn this study, the GN/Cu nanoplates have been successfully prepared by the electrostatic self-assembly method. The structural characteristics of GN/Cu nanoplates were analyzed via transmission electron microscopy and X-ray diffraction. Then the tribological properties of GN/Cu nanoplates were investigated under different loads with SRV-IV [Schwingung, Reibung, Verschleiß (German); oscillating, friction, wear (English translation)] tribotester. White-light interferometry was applied to quantify the wear loss of the disk. The element chemical state on worn surfaces was analyzed by an X-ray photoelectron spectroscope to clarify the tribological mechanism of graphene composites.FindingsThe electrostatic force between the negative charge of graphene and the positive charge of triangular copper nanoplates promotes the self-assembly of GN/Cu nanoplates. With the addition of GN/Cu nanoplates, the wear loss and average friction coefficient under the load of 200 N have been decreased by 72.6% and 18.3%, respectively. It is concluded that the combined action of graphene deposition film and the copper melting film formed on the worn surface could effectively improve the antiwear ability and friction reduction performance of the grease.Originality/valueThis manuscript fulfills a new approach for the preparation of GN/Cu nanoplates. At the same time, its tribological properties and mechanism as a lubricating additive were studied which provide theoretical support for the application of graphene and its composites in the tribology field.

Chemical Vapor Deposition of N-Doped Graphene through Pre-Implantation of Nitrogen Ions for Long-Term Protection of Copper.

Nitrogen-doped graphene (NG) was synthesized through the chemical vapor deposition (CVD) of graphene on Cu substrates, which were pre-implanted with N ions by the ion implantation method. The pre-implanted N ions in the Cu substrate could dope graphene by the substitution of C atoms during the CVD growth of graphene, forming NG. Based on this, NG’s long-term protection properties for Cu were evaluated by ambient exposure for a corrosion test. The results showed that NG can obviously reduce the natural oxidation of Cu in the long-term exposure compared with the case of pristine graphene (PG) coated on Cu. Moreover, with the increase in pre-implanted N dose, the formed NG’s long-term protection for Cu improved. This indicates that the modification of graphene by N doping is an effective way to improve the corrosion resistance of the PG coating owing to the reduction in its conductivity, which would inhibit galvanic corrosion by cutting off electron transport across the interface in their long-term protection. These findings provide insight into corrosion mechanisms of the graphene coating and correlate with its conductive nature based on heteroatoms doping, which is a potential route for improving the corrosion resistance of graphene as an effective barrier coating for metals.

Preventing colour fading in artworks with graphene veils.

Modern and contemporary art materials are generally prone to irreversible colour changes upon exposure to light and oxidizing agents. Graphene can be produced in thin large sheets, blocks ultraviolet light, and is impermeable to oxygen, moisture and corrosive agents; therefore, it has the potential to be used as a transparent layer for the protection of art objects in museums, during storage and transportation. Here we show that a single-layer or multilayer graphene veil, produced by chemical vapour deposition, can be deposited over artworks to protect them efficiently against colour fading, with a protection factor of up to 70%. We also show that this process is reversible since the graphene protective layer can be removed using a soft rubber eraser without causing any damage to the artwork. We have also explored a complementary contactless graphene-based route for colour protection that is based on the deposition of graphene on picture framing glass for use when the direct application of graphene is not feasible due to surface roughness or artwork fragility. Overall, the present results are a proof of concept of the potential use of graphene as an effective and removable protective advanced material to prevent colour fading in artworks.

Preparation of polyvinylidene fluoride composite ultrafiltration membrane for micro-polluted surface water treatment

Blending modification of graphene oxide (GO) and deposition of silver carbonate (Ag2CO3) on the membrane surface by suction filtration was used to prepare polyvinylidene fluoride (PVDF) composite ultrafiltration (UF) membranes (denoted as PGA membranes). The effect of this strategy on the morphology and performance of the pure PVDF membrane was investigated. Owing to an increased hydrophilicity and the formation of a more open pore, the pollution resistance and permeability of the PGA membrane were improved. The pure water flux of the PGA-3 membrane (254 LMH) was increased to more than 2-fold compared to that of the neat PVDF membrane (126 LMH). In addition, the results of antifouling experiments showed that the flux recovery rate, flux decay rate, and antibacterial performance of the PGA-3 membrane was superior to those of the other membranes synthesized in this study. Finally, after conducting multi-cycle filtration experiments with lake water, the flux and recovery rate of the PGA-3 membrane was observed to be the highest, and the water quality of the lake water filtered by the PGA-3 membrane was the best. Thus, the above results indicate that this membrane modification strategy is extraordinarily effective in improving the antifouling properties and permeability of the PVDF UF membranes in practical applications.