Graphene-like Films Research Articles

Highly textured AlN film synthesized on a graphene-like undercoating

Piezoelectric properties of polycrystalline AlN films are strongly dependent on the texture of the material. For a number of applications, such as microelectromechanical systems (MEMS) and acoustic resonators, it is important to have a well-defined (002) orientation of the crystallites. Using an original method of selective deposition of graphene-like films (GLFs) followed by a simple, safe and efficient chemical vapor deposition (CVD) of AlN, we clearly demonstrate that the GLF sublayer does enhance the texture quality of AlN columnar structures. The improved crystal orientation along the (002) direction for AlN film grown on GLFs is locally visualized using a scanning electron microscope (SEM) and quantitatively reinforced using Raman spectroscopy.

Study of the Chemical Vapor Deposition of Nano-Sized Carbon Phases on {001} Silicon.

Different nano-sized phases were synthesized using chemical vapor deposition (CVD) processes. The deposition took place on {001} Si substrates at about 1150-1160 °C. The carbon source was thermally decomposed acetone (CH3)2CO in a main gas flow of argon. We performed experiments at two ((CH3)2CO + Ar)/Ar) ratios and observed that two visually distinct types of layers were deposited after a one-hour deposition process. The first layer type, which appears more inhomogeneous, has areas of SiO2 (about 5% of the surface area substrates) beside shiny bright and rough paths, and its Raman spectrum corresponds to diamond-like carbon, was deposited at a (CH3)2CO+Ar)/Ar = 1/5 ratio. The second layer type, deposited at (CH3)2CO + Ar)/Ar = a 1/0 ratio, appears homogeneous and is very dark brown or black in color and its Raman spectrum pointed to defect-rich multilayered graphene. The performed structural studies reveal the presence of diamond and diamond polytypes and seldom SiC nanocrystals, as well as some non-continuously mixed SiC and graphene-like films. The performed molecular dynamics simulations show that there is no possibility of deposition of sp3-hybridized on sp2-hybridized carbon, but there are completely realistic possibilities of deposition of sp2- on sp2- and sp3- on sp3-hybridized carbon under different scenarios.

N-Doped Graphene-like Film/Silicon Structures as Micro-Capacitor Electrodes.

Currently, the miniaturization of portable and autonomous devices is challenging for modern electronics. Graphene-based materials have recently emerged as one of the ideal candidates for supercapacitor electrodes, while Si is a common platform for direct component-on-chip integration. We have proposed the direct liquid-based CVD of N-doped graphene-like films (N-GLFs) on Si as a promising way to achieve solid-state on-chip micro-capacitor performance. Synthesis temperatures in the range from 800 °C to 1000 °C are investigated. Capacitances and electrochemical stability of the films are evaluated using cyclic voltammetry, as well as galvanostatic measurements and electrochemical impedance spectroscopy in 0.5 M Na2SO4. We have shown that N-doping is an efficient way to improve the N-GLF capacitance. 900 °C is the optimal temperature for the N-GLF synthesis with the best electrochemical properties. The capacitance rises with increasing film thickness which also has an optimum (about 50 nm). The transfer-free acetonitrile-based CVD on Si yields a perfect material for microcapacitor electrodes. Our best value of the area-normalized capacitance (960 mF/cm2) exceeds the world's achievements among thin graphene-based films. The main advantages of the proposed approach are the direct on-chip performance of the energy storage component and high cyclic stability.

Effect of pH and Concentration of Dopamine Solution on the Deposited Polydopamine Film and the Prepared Graphene-like Material

In this study, according to the acquired polydopamine deposition rates, polydopamine films with equal thickness were prepared under different conditions on SiO2 substrates. Subsequently, we investigated the influence of dopamine solution pH and concentration on the formation of surface aggregates of the deposited polydopamine films. Assumptions were made to explain how pH and concentration execute their effects. Based on the optimized parameters, a continuous and smooth polydopamine film with a thickness of about 14 nm and a roughness of 1.76 nm was fabricated on a silicon dioxide substrate, through the deposition for 20 minutes in a dopamine solution with a concentration of 1.5 mg/mL and a pH of 8.2. The prepared polydopamine film was then employed as a precursor and subjected to a high-temperature process for the carbonization and graphitization of the film. Raman spectroscopy analysis indicated that the resulting graphene-like film had fewer structural defects in comparison with previous works and the results of XPS indicated that most of the carbon atoms were bound into the cross-linked honeycomb lattice structure. The prepared graphene-like material also exhibited high electrical conductivity and satisfying mechanical elasticity.

In situ growth of lignin-based graphene-like films catalyzed by metal substrates

Biomass resource lignin was used to construct a large-scale and ordered lignin graphitization structure in a two-dimensional space through the catalytic graphitization process, forming a lignin-based graphene-like film with conductivity.

Local Natural Graphite as a Promising Raw Material for the Production of Thermally Reduced Graphene-Like Films

Local Natural Graphite as a Promising Raw Material for the Production of Thermally Reduced Graphene-Like Films

Insights into the Electrical Characterization of Graphene-like Materials from Carbon Black

A new class of graphene-related materials (GRMs) obtained as water suspensions through a two-step oxidation/reduction of a nanostructured carbon black, namely graphene-like (GL) materials, has recently emerged. GL materials undergo self-assembly in thin amorphous films after drying upon drop-casting deposition on different surfaces. The GL films, with thicknesses of less than a micron, were composed of clusters of nanoparticles each around 40 nm in size. The exploitation of the GL films for different options (e.g., bioelectronic, sensoristic, functional filler in composite) requires a deep characterization of the material in terms of their electric transport properties and their possible interaction with the surface on which they are deposited. In this work, a careful electrical characterization of GL films was performed at room temperature and the results were compared with those achieved on films of benchmark graphenic materials, namely graphene oxide (GO) materials, obtained by the exfoliation of graphite oxide, which differ both in morphology and in oxidation degree. The results indicate a non-linear current–voltage relationship for all the investigated films. The extrapolated dielectric constant (ε) values of the investigated GRMs (GL and GO materials) agree with the experimental and theoretically predicted values reported in the literature (ε~2–15). Because similar conductance values were obtained for the GL materials deposited on glass and silicon oxide substrates, no significant interactions of GL materials with the two different substrates were highlighted. These results are the starting point for boosting a feasible use of GL materials in a wide spectrum of applications, ranging from electronics to optics, sensors, membranes, functional coatings, and biodevices.

Synthesis of a flexible self-standing graphene-like graphite thin film and its application to anode materials for thin-film all-solid-state lithium-ion batteries

Synthesis of a flexible self-standing graphene-like graphite thin film and its application to anode materials for thin-film all-solid-state lithium-ion batteries

Superhydrophobic Graphene-Like Nanocarbon Film Formation on Arbitrary Surfaces through MgO Nanoparticle Catalysis: Advanced Coatings for Energy Storage and Nanocomposites

Superhydrophobic Graphene-Like Nanocarbon Film Formation on Arbitrary Surfaces through MgO Nanoparticle Catalysis: Advanced Coatings for Energy Storage and Nanocomposites

Synthesis of a flexible self-standing graphene-like graphite thin film and its application to anode materials for thin-film all-solid-state lithium-ion batteries

Synthesis of a flexible self-standing graphene-like graphite thin film and its application to anode materials for thin-film all-solid-state lithium-ion batteries

Anisotropic thermal conductivity and enhanced hardness of copper matrix composite reinforced with carbonized polydopamine

For thermal management applications, copper (Cu) metal matrixes reinforced by carbon are undoubtedly one of the most promising composites for heat spreaders In the frame of this work, hard Cu matrix composites having anisotropic thermal conductivity were fabricated by using Cu flakes coated with carbonized polydopamine. The flakes were coated by simply immersing them into a dopamine aqueous solution, then they were submitted to a thermal treatment under dihydrogen. This easy synthesis method results in a ≈10 nm thick N-doped graphene-like film surrounding the Cu flakes. The subsequently densified composites that contains about 0.23 wt % of C show an increase of hardness up 44% and 172% as compared to pure Cu in the parallel and perpendicular sintering direction, respectively. In addition an anisotropic thermal conductivity is obtained with an anisotropy ratio of 2.75.

Synergistic lubrication mechanisms of molybdenum disulfide film under graphene-oil lubricated conditions

Single solid or liquid lubricant cannot meet the ever-increasing lubricating performance of mechanical motion under extreme operating conditions. Solid-liquid synergistic lubrication could effectively solve the friction and wear problems due to the cooperation of solid and liquid lubricant. Herein, the solid–liquid composite coating was prepared via molybdenum disulfide (MoS2) film under graphene hybrid gear oil lubrication conditions. Its anti-friction and anti-wear abilities were reduced by 13.0% and 37.4% compared with gear oil lubricated MoS2 film, and 46.7% and 97.1% lower than those of only MoS2 film, respectively. More importantly, the graphene-like transfer film at frictional contact interfaces was formed. Hence, the excellent lubrication function of MoS2-based solid–liquid lubricating coating was attributed to not only the structural advantages of MoS2 and graphene, but also the solid–liquid synergism and transfer film, thereby enhancing the interfacial load-bearing capacity and anti-friction/wear behaviors.

Non-stoichiometric Mo6S9.5 films grown on graphene-like N-doped carbon films with high activity for hydrogen evolution reaction

Development of effective non-noble electrocatalysts for hydrogen evolution reaction (HER) is crucial for hydrogen production by water electrolysis. Herein, several composite catalysts of non-stoichiometric Mo6S9.5 films grown on graphene-like N-doped carbon films were prepared and evaluated for HER in 0.5 M H2SO4. The unique structure endowed the catalysts with highly exposed edge active sites, high specific surface area and prominently high activities for HER. The optimized catalyst exhibited a low overpotential of 113 mV at 10 mA/cm2, a low Tafel slope of 64 mV/dec, and a low charge transfer resistance of 40 Ω along with a highly catalytic stability.

Detection of free chlorine in water using graphene-like carbon based chemiresistive sensors.

Free chlorine is the most commonly used water disinfectant. Measuring its concentration during and after water treatment is crucial to ensure its effectiveness. However, many of the existing methods do not allow for continuous on-line monitoring. Here we demonstrate a solid state chemiresistive sensor using graphene-like carbon (GLC) that overcomes that issue. GLC films that were either bare or non-covalently functionalized with the redox-active phenyl-capped aniline tetramer (PCAT) were successfully employed to quantify aqueous free chlorine, although functionalized devices showed better performance. The response of the sensors to increasing concentrations of free chlorine followed a Langmuir adsorption isotherm in the two tested ranges: 0.01–0.2 ppm and 0.2–1.4 ppm. The limit of detection was estimated to be 1 ppb, permitting the detection of breaches in chlorine filters. The devices respond to decreasing levels of free chlorine without the need for a reset, allowing for the continuous monitoring of fluctuations in the concentration. The maximum sensor response and saturation concentration were found to depend on the thickness of the GLC film. Hence, the sensitivity and dynamic range of the sensors can be tailored to different applications by adjusting the thickness of the films. Tap water samples from a residential area were tested using these sensors, which showed good agreement with standard colorimetric measurement methods. The devices did not suffer from interferences in the presence of ions commonly found in drinking water. Overall, these sensors are a cost-effective option for the continuous automated monitoring of free chlorine in drinking water.

Electrical Properties of Selectively Deposited Graphene‐Like Film on Silicon Oxide/Silicon Structures Preirradiated with Low Energy Electrons

Graphene‐like films (GLFs) are selectively deposited on the silicon oxide/silicon structures preirradiated with electrons at various electron energies and irradiation doses. These films demonstrate high conductivity and are used as a gate material for metal‐oxide‐semiconductor (MOS)‐based devices. It is shown that high‐quality capacitance–voltage characteristics of the GLF‐gated MOS structures can be obtained if both an energy and a dose are carefully tuned. Using the GLF‐gated MOS as a pseudo‐field effect transistor structure, a notable current modulation in the selectively grown GLF is observed.

Golpar leaves extract application for construction of an effective anti-corrosion film for superior mild-steel acidic-induced corrosion mitigation at different temperatures

The application of bio-compatible organic compounds from Golpar leaves as a green source to establish a protective layer on the steel surface is the main target of this study. So herein, the effect of environmental-friendly and cost-effective Golpar leaves extract (GLE) on the corrosion retardation of the mild-steel (MS) substance in HCl aggressive solution (1 M) is reported. The Fourier transform infrared (FT-IR) and ultraviolet-visible (UV–vis) tests were conducted to recognize the GLE functional groups. The effect of GLE on the topology and morphology of the steel surface subjected to the GLE-HCl solution was investigated via atomic force microscopy (AFM) and field emission scanning electron microscopes (FE-SEM), respectively. Accordingly, the heterogeneity and roughness of the steel surface decreased in the presence of the GLE. The deposition of a graphene-like film that consists of GLE phytochemicals was examined by Raman spectroscopy ( I D / I G = 0.60). The grazing incidence X-Ray diffraction (GIXRD) indicated the formation of inhibitor and iron complex layers over the surface. The contact angle (CA) outcomes demonstrated 45° enhancement of the metal surface hydrophobicity in the presence of GLE. The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization spectroscopy (PDS), and weight loss measurements were utilized to survey the steel plates' corrosion resistance. The total resistance of 6.8, 8.1, 9.2, and 9.8 KΩ cm 2 was obtained at the concentrations of 400, 600, 800, and 1000 ppm, respectively. The results revealed that in the presence of 1000 ppm GLE, the inhibition activity was improved to up 91% after 10 h at 25 °C. The inhibition efficiency of GLE-contained solutions remained 90% even at 35 and 45 °C during 10 h of exposure, which is a significant number in comparison with most of the reported green inhibitors. According to the weight loss determinations, 90% surface coverage was attained after 5 h immersion in 1000 ppm GLE. Moreover, obeying Langmuir-isotherm the GLE organic compounds adsorbed on the steel substance and showed mixed (anodic/cathodic) corrosion inhibition activity. • The effect of GLE concentration on the MS corrosion protection in hydrochloric acid aqueous (1 M) solution was studied. • Addition of 1000 ppm GLE to the acidic media caused 91% inhibition efficiency and 92% surface coverage after 10 h of immersion. • Deposition of a hydrophobic and graphene-like film that consists of GLE phytochemicals was examined by Raman spectroscopy. • GLE acted as a mixed inhibitor in the acidic media and suppressed the corrosion reaction obeying Langmuir-isotherm.

Synthesis of pristine graphene-like behaving rGO thin film: Insights into what really matters

Despite the huge expansion of GO/rGO market, there is a clear lack of experimental studies on getting high quality, large scale GO and rGO nanosheets/thin films, which is a critical requirement for electronic applications. In this work, a detailed experimental study on the effect of lateral sheet size on properties of GO/rGO, supported by density functional theory (DFT) calculations, is presented for the first time, to help prepare pristine graphene-like rGO. Furthermore, we investigated the effect of thermal reduction at low temperature (200 °C), under ambient pressure, on the corresponding electronic properties of rGO. Current-voltage (I–V) analysis, optical and electron microscopy, atomic force microscopy, Raman, XPS, and quantitative 13C NMR spectroscopy were used to study and optimize rGO. The optimized rGO-field-effect transistor (rGO-FET) device exhibited the highest charge carrier mobilities, i.e. 2,962 (holes) and 2,183 (electrons) cm2/V.s. Furthermore, the transconductance characteristic curve of rGO-FET showed the ambipolar behavior of high-quality graphene, with Dirac point around zero. In addition, the optical band gap of rGO nanosheets (∼0.4 eV), prepared in this work, is among the smallest reported band gaps for rGO. These findings highlight the significance of our study for synthesizing large-scale graphene-like rGO thin film, for ultra-fast, low-power transistor applications.

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.

Effectively Regulating More Robust Amorphous Li Clusters for Ultrastable Dendrite-Free Cycling.

A disordered phase in Li‐deposit nanostructure is greatly attractive, but plagued by the uncontrollable and unstable growth, and the nanoscale characterization in the structure. Here, fully characterized in cryogenic transmission electron microscopy (cryo‐TEM), more robust amorphous‐Li (ALi) clusters are revealed and effectively regulated on heteroatom‐activating electronegative sites and an advanced solid electrolyte interphase (SEI) layer. Heteroatom‐activating electronegative sites capably enhance the electrostatic interaction of Li+ and heteroatom‐doping graphene‐like film (HDGs), meaning lower Li diffusion barrier and larger binding energy that is confirmed by small nucleation overpotentials of 13.9 and 10 mV at 0.1 mA cm−2 in the fluoroethylene carbonate‐adding ester‐based (FEC‐ester) and LiNO3‐adding ether‐based (LiNO3‐ether) electrolytes. Orderly multilayer SEI structure comprised of inorganic‐rich components enables fast ion transports and durable capabilities to construct highly reversible and long‐term plating/stripping cycling. ALi cluster anodes exhibit non‐crystalline morphologies and perform ultrastable dendrite‐free cycling over 2800 times. Stable ALi clusters are also grown in LiFePO4 (LFP) (LFP‐ALi‐HDGs‐N||LiFePO4 [LFP]) full cells with advantageous capacities up to 165.5 and 164.3 mAh g−1 in these optimized electrolytes at 0.1 C; the remarkable capacity retentions maintain to 93% and 91% after 150 cycles at 0.2 C. Structure viability, electrochemical reversibility, and excellent performance in ALi clusters are effectively regulated.

Microwave studies of reflective coatings based on natural graphene-like carbon

In this work, shielding coatings based on graphene-like carbon films have been investigated. To design the shielding, the Costas massif theory is applied. For microwave studies, the method of recording standing waves with a microwave interferometer was used. The resulting coatings are safe, durable, ecological and have an electromagnetic radiation reflection coefficient of 10-20 dB.