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The quest for scalable integration of monolayer graphene into functional composites confronts the bottleneck of high-fidelity transfer onto substrates, crucial for unlocking graphene's full potential in advanced applications. Addressing this, our research introduces the camphor-assisted transfer (CAT) method, a novel approach that surmounts common issues of residue and structural deformation endemic to existing techniques. Grounded in the sublimation dynamics of camphor, the CAT method achieves a clean, contiguous transfer of centimeter-scale monolayer graphene onto an array of polymer films, including ultra-thin polyethylene films. The resultant ultrathin graphene-polyethylene (gPE) films, characterized by their exceptional transparency and conductivity, reveal the CAT method's unique ability to preserve the pristine quality of graphene, underscoring its practicality for preparing flexible transparent electrodes by monolayer graphene. In-depth mechanism investigation into the camphor sublimation during CAT has led to a pivotal realization: the porosity of the target polymer substrate is a determinant in achieving high-quality graphene transfer. Ensuring that camphor sublimates initially from the polymer side is crucial to prevent the formation of wrinkles or delamination of graphene. By extensive examination of CAT on a spectrum of commonly used polymer films, including PE, PP, PTFE, PI and PET, we have confirmed this important conclusion. This discovery offers crucial guidance for fabricating monolayer graphene-polymer composite films using methods akin to CAT, underscoring the significance of substrate selection in the transfer process. [ABSTRACT FROM AUTHOR]

First-principles simulations are conducted to explore the structural stability, electronic properties, and optical responses of pristine and boron- or nitrogen-doped monolayers graphene. The computed electronic density of states revealed that the substitutional doping of boron impurity atoms on monolayer graphene (MLG) shifts the Dirac point upward, although the substitution of nitrogen impurity atoms in graphene pushes the Dirac point downward the Fermi level. This could exhibit that upon the doping of MLG with boron or nitrogen, respectively, p-type or n-type semimetal is acquired. The overall optical spectral properties of the substituted graphene with boron or nitrogen atoms are simulated and compared with the optical spectra results of pure graphene. The optical features of pristine and doped MLG are determined by taking the interband and intra-band transitions into account ranging from the far-infrared to the ultraviolet regime of the electromagnetic radiation. A remarkable red shift in the optical spectra of the doped MLG towards the visible regime of radiation is established. An enhanced reflectivity illustrated that concentration-dependent optical properties of boron and nitrogen-doped MLG happen at lower electromagnetic radiation regimes. In addition, we explored the thermoelectric behaviors of the pristine/doped graphene monolayers with 4 × 4 supercells. We found a significant improvement in the electrical conductivity of graphene when doped with boron or nitrogen impurities. However, an increase in the electrical conductivity has textured a decrease in the Seebeck coefficients. Improvement in the electrical conductivity is attributed to an interesting effect on the graphene monolayers' power factor (PF). These findings indicate a positive impact of the dopants on the thermoelectric properties of graphene monolayers and reveal that they are potential materials for thermoelectric applications and nanodevices. [ABSTRACT FROM AUTHOR]

We study the electron–phonon and Rashba spin–orbit coupling effects on thermodynamic properties of a monolayer graphene under magnetic field. We propose a diagonalization procedure to solve the Fröhlich-type Hamiltonian based on the Lee–Low–Pines theory. The study reveals that, the cyclotron frequency, Debye cut-off wavenumber (DCOW) and Rashba spin–orbit coupling (RSOC) modulate the thermodynamic properties through Tsallis formalism for different substrates. It is also found that RSOC induce a gap formation while dropping the disorder thus rising up the potential application. [ABSTRACT FROM AUTHOR]

Two‐dimensional materials have been widely used to tune the growth and energy‐level alignment of perovskites. However, their incomplete passivation and chaotic usage amounts are not conducive to the preparation of high‐quality perovskite films. Herein, we succeeded in obtaining higher‐quality CsPbBr3 films by introducing large‐area monolayer graphene as a stable physical overlay on top of TiO2 substrates. Benefiting from the inert and atomic smooth graphene surface, the CsPbBr3 film grown on top by the van der Waal epitaxy has higher crystallinity, improved (100) orientation, and an average domain size of up to 1.22 μm. Meanwhile, a strong downward band bending is observed at the graphene/perovskite interface, improving the electron extraction to the electron transport layers (ETL). As a result, perovskite film grown on graphene has lower photoluminescence (PL) intensity, shorter carrier lifetime, and fewer defects. Finally, a photovoltaic device based on epitaxy CsPbBr3 film is fabricated, exhibiting power conversion efficiency (PCE) of up to 10.64% and stability over 2000 h in the air. [ABSTRACT FROM AUTHOR]

Abstract This study systematically explores the influence of charged impurities on static screening in monolayer graphene and extends the investigation to AA-stacked and AB-stacked bilayer graphene (BLG). Applying the random phase approximation (RPA), monolayer graphene displays unique beating Friedel oscillations (FOs) in inter-valley and intra-valley channels. Shifting to BLG, the study emphasizes layer-specific responses on each layer by considering self-consistent field interactions between layers. It also explores the derived multimode FOs, elucidating distinctions from monolayer behavior. In AA-stacked BLG, distinct metallic screening behaviors are revealed, uncovering unique oscillatory patterns in induced charge density, providing insights into static Coulomb scattering effects between two Dirac cones. The exploration extends to AB-stacked BLG, unveiling layer-specific responses of parabolic bands in multimode FOs with increasing Fermi energy. This comprehensive investigation, integrating RPA considerations, significantly advances our understanding of layer-dependent static screening in the broader context of FOs in graphene, providing valuable contributions to the field of condensed matter physics.

This study systematically explores the influence of charged impurities on static screening in monolayer graphene and extends the investigation to AA-stacked and AB-stacked bilayer graphene (BLG). Applying the random phase approximation (RPA), monolayer graphene displays unique beating Friedel oscillations (FOs) in inter-valley and intra-valley channels. Shifting to BLG, the study emphasizes layer-specific responses on each layer by considering self-consistent field interactions between layers. It also explores the derived multimode FOs, elucidating distinctions from monolayer behavior. In AA-stacked BLG, distinct metallic screening behaviors are revealed, uncovering unique oscillatory patterns in induced charge density, providing insights into static Coulomb scattering effects between two Dirac cones. The exploration extends to AB-stacked BLG, unveiling layer-specific responses of parabolic bands in multimode FOs with increasing Fermi energy. This comprehensive investigation, integrating RPA considerations, significantly advances our understanding of layer-dependent static screening in the broader context of FOs in graphene, providing valuable contributions to the field of condensed matter physics. [ABSTRACT FROM AUTHOR]

Graphene/carbon fiber composite laminates were prepared by vacuum assisted resin transfer molding process. The effects of different structural forms of graphene with different mass fractions on the tensile properties of carbon fiber composite laminates were investigated. First, the graphene monolayer and multilayer graphene were distributed evenly into epoxy resin by ultrasonic dispersion. Then, single-layer and multilayer graphene/carbon fiber composite laminates were prepared by vacuum assisted resin transfer molding process. Finally, tensile testing machine was used to test the tensile properties of composite laminates. The results show that when the mass fraction of graphene is 0.03%~0.10%, the tensile properties of the specimens are gradually improved with the increase of the mass fraction of graphene. When the mass fraction of multilayer graphene is 0.03%~0.10%, the tensile properties of the specimens gradually decrease with the increase of the mass fraction of multilayer graphene. [ABSTRACT FROM AUTHOR]

We investigate Coulomb drag resistivity in a double-layer system consisting of two parallel monolayer graphene sheets. In calculations, we employ the random-phase approximation to determine the polarizability functions of the graphene layers and the frequency-dependent dielectric function of the structure, taking into account inhomogeneity effects of the background dielectric. Our numerical calculations reveal that Coulomb drag resistivity in double-layer graphene systems steadily increases with increasing temperature but quickly decreases as the interlayer separation increases. The drag resistivity between the two layers in the case of an inhomogeneous background dielectric is substantially larger than that in the case of a homogeneous one. In addition, both the value and the imbalance in carrier density in the layers lead to noticeable changes in Coulomb drag resistivity in the system. Our study results are useful in graphene-based structure applications.

Experimental realizations of graphene-based stadium-shaped quantum dots (QDs) have been few and have been incompatible with scanned probe microscopy. Yet, the direct visualization of electronic states within these QDs is crucial for determining the existence of quantum chaos in these systems. We report the fabrication and characterization of electrostatically defined stadium-shaped QDs in heterostructure devices composed of monolayer graphene (MLG) and bilayer graphene (BLG). To realize a stadium-shaped QD, we utilized the tip of a scanning tunneling microscope to charge defects in a supporting hexagonal boron nitride flake. The stadium states visualized are consistent with tight-binding-based simulations but lack clear quantum chaos signatures. The absence of quantum chaos features in MLG-based stadium QDs is attributed to the leaky nature of the confinement potential due to Klein tunneling. In contrast, for BLG-based stadium QDs (which have stronger confinement) quantum chaos is precluded by the smooth confinement potential which reduces interference and mixing between states.

We successfully fabricated a pair of microgap monolayer graphene electrodes (MMGEs), in which the basal planes of two monolayer graphenes are arranged in parallel facing each other across a small gap of 20 μm, without using a microfabrication process. We measured the redox cycling in the MMGEs using (ferrocenylmethyl) trimethylammonium bromide and observed an excellent redox cycling under low-speed scanning conditions of 0.005 V/s. The collection efficiency reached 97% and was almost independent of the scan rate. [ABSTRACT FROM AUTHOR]

Phase-contrast transmission electron microscopy (TEM) is a powerful tool for imaging the local atomic structure of materials. TEM has been used heavily in studies of defect structures of two-dimensional materials such as monolayer graphene due to its high dose efficiency. However, phase-contrast imaging can produce complex nonlinear contrast, even for weakly scattering samples. It is, therefore, difficult to develop fully automated analysis routines for phase-contrast TEM studies using conventional image processing tools. For automated analysis of large sample regions of graphene, one of the key problems is segmentation between the structure of interest and unwanted structures such as surface contaminant layers. In this study, we compare the performance of a conventional Bragg filtering method with a deep learning routine based on the U-Net architecture. We show that the deep learning method is more general, simpler to apply in practice, and produces more accurate and robust results than the conventional algorithm. We provide easily adaptable source code for all results in this paper and discuss potential applications for deep learning in fully automated TEM image analysis.

Within the maximum entropy principle, we present a general theory able to describe in a dynamical context the transport properties of hot carriers in monolayer graphene under electric fields of arbitrary strength. Therefore, we obtain a closed extended hyperbolic system of hydrodynamic (HD) equations in which all the unknown constitutive functions are completely determined. In particular, we consider the different scattering mechanisms used in the literature in the kinetic approaches. The closed extended HD system is applied to monolayer graphene at 300 K and is validated by comparing numerical calculations with ensemble Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

Polyurethane (PU) has the advantages of green and environmental protection, It is often used as a coating on the surface of objects, but Us hardness and such performance need to be greatly improved to meet the high-end requirements. Due to the particularity of the coating, t as difficult to meet the requirements of high hardness and high light transmittance at the same time by general modification methods. Monolayer graphene has excellent mechanical properties and fight transmission. In this paper, t as selected to modify polyurethane. Firstly, monolayer graphene oxide (GO) was prepared and dispersed in the polyurethane system to obtain the polyurethane-monolayer graphene oxide coating, and then the Ugh hardness and transparent polyurethane-graphene coating was obtained by reduction. The effects of GO content and reduction on scratch resistance and light transmittance of the coating were studied. The results show that the crosslinking network between GO and polyurethane can improve the dispensability of GO and the mechanical properties of the polyurethane matrix, and the mechanical properties of coating were further improved after reduction to graphene. When the amount of GO reached 0.05wt%o, the penal hardness of the coating was increased by 3-5 orders of magnitude compared with the pure polyurethane coating, and the fight transmittance of the polyurethane-graphene coating was reduced within 10% compared with the pure polyurethane coating. [ABSTRACT FROM AUTHOR]

While charge transport in the horizontal plane of graphene has been widely studied, there is only limited understanding about the transport across a stack of films that include graphene sheets. In this report, a model of a metal–graphene–metal stack was produced and investigated via detailed analysis of experimental dependences of electrical current on applied external voltage. Scanning probe microscopy (SPM) was used to measure the dependences of the local tunneling current on the voltage under fixed compressing force. The SPM platinum probe produced the compressing force on gold-supported graphene in the metal–graphene–metal system. The experimental results were explained by a model that included the pinning of the Fermi level of graphene to platinum and the related changes in the parameters of the potential barrier for the electron flow. It was demonstrated that low-voltage and high-voltage intervals can be identified in the charge transport across the metal–graphene–metal stack. In the high-voltage interval (approximately > |±0.7| V in the tested stack), the history of the current measurement was detected due to the charge accumulation. In the low-voltage interval, the current was determined by the electronic states near the Fermi level. In this interval, the graphene layer can function as a blocking gate for the electron transport in the metal–graphene–metal system. [ABSTRACT FROM AUTHOR]

Monolayer graphene has attracted enormous attention owing to its unique electronic and optical properties. However, achieving an effective approach without applying electrical bias for manipulating the charge transfer based on graphene is elusive to date. Herein, we realized the manipulation of excitons' transition from emitter to the graphene surface with plasmonic engineering nanostructures and firstly obtained large enhancements for photon emission on the graphene surface. The localized plasmons generated from the plasmonic nanostructures of shell-isolated nanoparticle coupling to ultra-flat Au substrate would dictate a consistent junction geometry while enhancing the optical field and dominating the electron transition pathways, which may cause obvious perturbations for molecular radiation behaviors. Additionally, the three-dimensional finite-difference time-domain and time-dependent density functional theory were also carried out to simulate the distributions of electromagnetic field and energy levels of hybrid nanostructure respectively and the results agreed well with the experimental data. Therefore, this work paves a novel approach for tunning graphene charge/energy transfer processes, which may hold great potential for applications in photonic devices based on graphene. [ABSTRACT FROM AUTHOR]

This study aims to explore bond capacity between monolayer graphene and cementitious composites for the first time through a pullout test. The low-pressure chemical vapor deposition method was used to synthesize monolayer graphene on the copper substrate to be embedded in the mortar made by the briquette mold. The bond capacity between them was higher than the tensile strength of the copper sheet with as-grown monolayer graphene on the surface since all specimens failed in fracture with embedment length of more than 30 mm. The monolayer graphene enhanced the copper tensile fracture stress and normalized energy during the test as the copper sheet width increased. This short communication explores a new path to quantify the bond between the monolayer graphene and the mortar to promote the understanding of the behavior of graphene-enhanced cementitious composites.

Graphene, known for its high carrier mobility and broad spectral response range, has proven to be a promising material in photodetection applications. However, its high dark current has limited its application as a high-sensitivity photodetector at room temperature, particularly for the detection of low-energy photons. Our research proposes a new approach for overcoming this challenge by designing lattice antennas with an asymmetric structure for use in combination with high-quality monolayers of graphene. This configuration is capable of sensitive detection of low-energy photons. The results show that the graphene terahertz detector-based microstructure antenna has a responsivity of 29 V·W−1 at 0.12 THz, a fast response time of 7 μs, and a noise equivalent power of less than 8.5 pW/Hz1/2. These results provide a new strategy for the development of graphene array-based room-temperature terahertz photodetectors. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) is generally observed by the excitation of surface plasmon polaritons on the metal (Au/Ag) surface. In order to utilize the SPR phenomenon for sensing application, the metal surface is functionalized with suitable ligands. Although such functionalization can enhance the specific adsorption capability of the sensor however due to the large thickness of the ligands, the plasmonic field of the metal surface becomes less sensitive towards the adsorption of analytes. In the next generation SPR-based sensor, graphene can be utilized not only as plasmonic material but also as a suitable ligand for attracting analytes through π-π interaction. In this article, we present our theoretical simulation studies on the observation of the SPR phenomenon using graphene monolayer (MLG), bilayer graphene (BLG), and in-plane twisted layers of BLG (T-BLG) as plasmonic materials deposited over zinc-selenide substrate. The Kretschmann configuration under wavelength interrogation setup was simulated, and SPR wavelength for graphene systems/water interface was estimated. The bio-sensing simulation was performed, and the sensing parameters viz. sensitivity, figure-of-merit (FOM), and plasmonic field for different graphene systems were obtained. Interestingly, the excellent sensing parameters were found in T-BLG system with relative in-plane twist angle near to magic angle viz. 1°. The enhancement is due to strong coupling between the layers twisted at the magic angle. This study demonstrates that the MLG, BLG and T-BLG can be employed as a standalone layer system for not only the generation of plasmonic fields but also enhanced sensing due to its intrinsic interactions with bio-analytes. [ABSTRACT FROM AUTHOR]

A near-perfect narrow-band graphene-based absorber was fabricated using a resonant system integrated with an asymmetric meta-grating at a wavelength of 1550 nm. By optimizing the gap between the two grating strips, the absorption of monolayer graphene can be increased to 99.6% owing to the strong field confinement of the bottom zero-contrast grating (ZCG). The position of the absorption spectrum could be adjusted by tailoring the grating period or the thickness of the waveguide layer. Interestingly, absorption spectrum linewidth can be tailored by changing the thickness of the spacer layer. The accidental bound states in the continuum (BICs) are then demonstrated in the structure. Moreover, the designed structure realizes the dynamic adjustment of the absorption efficiency at a specific wavelength, which has excellent potential in integrated optical devices and systems. [ABSTRACT FROM AUTHOR]

Two-dimensional materials are easily affected by radiation. So far, there is no work to predict the neutron irradiation effects of AA bilayer graphene. Furthermore, the differences and comparisons of various properties between monolayer graphene and AA bilayer graphene after irradiation in the approximately same neutron environment have not been reported. In this study, the neutron irradiation processes on monolayer graphene and AA bilayer graphene were simulated in ab initio molecular dynamics. The mechanical, and optoelectronic properties of monolayer and AA bilayer systems before and after irradiation were calculated using the method based on density functional theory. The results indicate that the AA bilayer system is more resistant to neutron irradiation than the monolayer system. The bandgap of the monolayer (bilayer) system after irradiation will reach the order of 0.1 eV. This article has important value in exploring the methods of radiation reinforcement technology for carbon-based devices. [ABSTRACT FROM AUTHOR]

High‐quality customized monolayer graphene structures are a prerequisite for various applications such as electronics, optoelectronics, and energy devices. Top‐down photolithography is the main method for graphene patterning, but it is greatly affected by complex manufacturing processes and residual photoresist. Recently, bottom‐up methods based on catalyst or precursor patterning have been developed. Although these methods can achieve high‐resolution graphene patterns, it is difficult to control the number of graphene layers and has a high defect density. Here, the authors propose a selective area reconstruction method for in‐situ growth of high‐quality monolayer graphene structures on copper substrates. The method utilizes selective oxidation and high‐temperature reduction technologies, which can effectively regulate the surface characteristics of the copper substrate, thereby precisely controlling the nucleation and growth behavior of the customized graphene structure. The feature size of the fabricated graphene structure is less than 1 µm and it has high monolayer coverage and extremely low defect density. The performance of the photoluminescence device and photodetector based on the customized monolayer graphene structure is characterized. The method provides a new approach for the direct growth of high‐quality, scalable, and high‐precision functional graphene structures, which is expected to have great potential in the optoelectronic applications. [ABSTRACT FROM AUTHOR]

Magnons have demonstrated enormous potential for next‐generation information technology, namely the ability to build quasiparticle low‐power integrated circuits without the moving of electrons. An experimental bosonic magnon transistor with multifunction, low‐loss, and full‐wavelength control of propagating spin waves (magnon current) is developed in this work. Using a monolayer of graphene as the high‐efficiency thermal phonon source and a low‐loss electrically insulating ferrimagnetic single‐crystalline yttrium iron garnet film as the propagating spin‐wave channel, the presented transistor has three functioning regions of spin‐wave modulation at full wavelength: prominent amplification, complete cut‐off, and linear phase shift. The magnon‐phonon‐mediated nonequilibrium state created by the temperature gradient in this transistor works in two ways: when the thermal phonon flow is small, the positive thermal spin‐torque induced by the longitudinal spin‐Seebeck effect amplifies spin waves; when the thermal phonon flow is large, the magnon–magnon interaction due to nonequilibrium thermal magnon injection greatly contributes to spin‐wave cut‐off. Furthermore, linear adjustment of the spin‐wave phase by creating a thermal phonon bath is demonstrated. These findings reveal that the numerous magnon–phonon coupling mechanisms in magnetic insulators offer a promising platform for the implementation of reconfigurable magnonic transistors. [ABSTRACT FROM AUTHOR]

The selection of photoactive materials and the design of device structures are critical to the photoelectronic performance of photodetectors. This study reports on a vertically structured photodetector device with rapid, stable, and efficient photoelectric performance across the UV-visible broadband range based on the Si ++ /SiO 2 /Au/single-layer graphene/CsPbI 3 quantum dots (QDs) configuration. In this specific device structure, a relatively high conductivity Si ++ /SiO 2 wafer was used as the substrate, a CsPbI 3 QD film with high light absorption was used as the photoactive layer, and a monolayer graphene with high conductivity was inserted between the substrate and the CsPbI 3 QD film to form a heterojunction with the QD film. Based on the Frenkel-Poole emission effect arising from the high trap state density within the SiO 2 layer, the device exhibited excellent photoelectric performances. Especially at a wavelength of 365 nm, a photocurrent responsivity of 2319 A/W, a specific detectivity of 1.15 × 10 14 Jones, an external quantum efficiency of 7883%, and an on/off time of 39/36 ms at a Si ++ terminal voltage of -80 V and an optical power density of 84.03 nW/cm 2 can be achieved.

The dynamically switchable triple-band absorption enhancement over 96% of monolayer graphene in the visible to the near-infrared range is achieved by a simple configuration consisting of subwavelength grating and periodically distributed Bragg reflectors. The isolated optical field distribution enabled by the optical Tamm state (OTS), guided mode resonance (GMR) and Fabry–Perot (FP) mode allows each graphene layer to selectively absorb the incident light in different wavelengths at different parts of the structure, creating favorable conditions for the independent extraction of multi-channel signals. Moreover, the continuous regulation of the absorption wavelength is futher realized by varying the geometrical parameters and dielectric permittivity. Also, the electrical tunability of graphene allows the independent step modulation of the absorption efficiency of three eigenmodes, resulting in the real-time dynamic switching of the system's triple-band/dual-band/single-band operation modes. The proposed structure can be integrated as a dynamic component into other graphene-based multifunctional and switchable optoelectronic devices.

Inverted planar perovskite solar cells (PSCs) have intrigued great promise in negative hysteresis, simple fabrication process, and flexible substrate implementation, in which the shared hole transport materiel is NiOx. However, the low‐temperature solution processing of the NiOx film is usually accompanied by defect formation, which deteriorates the perovskite quality and device performance. Meanwhile, the energy‐level offset between the NiOx and perovskite films is relatively large, limiting the interfacial charge transport. To suppress those setbacks, a defect‐free monolayer graphene sheet is transferred onto the NiOx film surface as a template for van der Waals epitaxial growth of perovskite films for the first time, leading to enhancing crystallinity with a large grain size of perovskite layer, 0.20 eV energy level offset drop, and accelerating charge transfer for the devices. Finally, the power conversion efficiency of 19.21% without hysteresis is achieved, exceeding 18.35% of the control device. [ABSTRACT FROM AUTHOR]

Monolayer graphene (1LG) is frequently unpredictably modified by supporting material so that it limits development of devices. Van der Waals interaction is dominant in the models describing the in-plane processes, including the electrical charge transport. However, the current flow perpendicular to the plane of the graphene is still less understood. This report analysed specific aspect of the perpendicular current and disclosed an original way to create transport bridges perpendicular to the plane across the 1LG. The most extraordinary finding is that the electron transport between two parallel metal surfaces can be shut down and opened if the metals are separated by the 1LG. The electron transmission can be intentionally varied in this metalâ€"1LGâ€"metal (Mâ€"Gâ€"M) system by pressure. In the experimental study the AFM force curve and tunnelling current measurements were combined when the external load force (0â€"1200 nN) and electrical potential (âˆ'1.5 V to +1.5 V) were used. It is proved that for low voltages (<±9 mV) a bridge is opened perpendicular to the graphene across the Mâ€"Gâ€"M systems by the external force, if the compression dependent Fermi level crosses electronic states in the interfaces and graphene. The localised bridges with diameter about 10â€"40 nm can be opened and kept continuously by the stabilised force in separated points of the system. However, the predictable changes can be produced in the system if the voltage and the force exceeded critical magnitudes. A combined model was proposed acceptable to explain the bridging and predictably modify the characteristics. [ABSTRACT FROM AUTHOR]

Graphene devices are susceptible to the surrounding environment. For example, the substrate in contact with graphene influences the device performance because the carriers are confined in two-dimensional (2D) atomic thickness. However, 2D van der Waals dielectric materials used as an interface modifier can provide a path to improve the device quality. In this paper, we report enhanced mobility of up to 540 000 cm2 V–1 s–1 in monolayer graphene sandwiched between two layers of a CrOCl insulator through a dielectric shielding effect. The Shubnikov–de Haas quantum oscillation is also observed with the amplitude linearly decreasing with increasing temperature, consistent with the standard Lifshitz–Kosevich theory. More strikingly, this oscillation persists to a temperature as high as 100 K because of this enhanced mobility. Our work paves a way to improve the mobility of graphene and realize the nontrivial quantum states at high temperatures for the exploration of low-power-consumption device applications in electronics. [ABSTRACT FROM AUTHOR]

Graphene is an excellent piezoresistive material. The gauge factor of graphene mirrors the sensitivity of electromechanical devices. This paper mainly studies the gauge factors of different layers of graphene under different deformation conditions. Specifically, a theoretical model was combined with linearized Boltzmann transport equation, and the density function theory (DFT) to explore how the layer number of graphene affects sensitivity. The results show that monolayer graphene is slightly more sensitive than two-layer graphene, and significantly more sensitive than three-layer graphene and fourlayer graphene. In particular, monolayer graphene remains highly sensitive under large deformation conditions, which gives monolayer graphene a significant advantage over other layers of graphene. Furthermore, a microelectromechanical system (MEMS) pressure sensor was proposed with monolayer graphene, and compared with previous similar sensors with multilayer graphene in terms of sensitivity. [ABSTRACT FROM AUTHOR]

Abstarct: An ultra-narrow-band perfect absorber based on collective resonances in an Ag nanoring period array is theoretically proposed for the absorption enhancement of monolayer graphene, where the absorptivity can reach as high as 99.4% with the full-width-half-maximum as narrow as 3.6 nm in the visible band. This outstanding absorptive characteristic can be attributed to the excitation of surface lattice resonance modes by Ag nanoring periodic array. The as-designed structure possesses high refractive-index sensitivity, reaching 557.9 nm RIUâˆ'1 with its figure of merit attaining 155 RIUâˆ'1. This work provides promising guidance for developing high-performance graphene-based photonic devices. [ABSTRACT FROM AUTHOR]

This paper investigates a sub-wavelength multilayer dielectric grating structure based on a simple metasurface, achieving dynamically switchable four-band absorption enhancement. This enhancement spans the visible to near-infrared (NIR) range, with absorption exceeding 90%, representing nearly a 40-fold increase over the intrinsic absorption of a single graphene layer. The contributions of guided-mode resonance (GMR), optical Tamm state (OTS), and photonic crystal defect cavity resonance to the absorption spectra are analyzed separately, offering a method for independent multi-channel signal extraction. Additionally, we explore the impact of structural parameters on the absorption response and examine the broad-spectrum multiband detection mechanism. This mechanism, explained through the integration of resonant cavity perturbation theory and the dynamic tuning of absorption efficiency via graphene's Fermi energy levels, results in an independently tunable optical system for four key operating bands. These properties make the structure suitable for applications such as multiband biomedical photodetectors or components in optoelectronic devices with multiple operating bands. • Tunable four band absorption enhancement is achieved by a subwavelength grating structure. • The effects of excitation of GMR, OTS, and photonic crystal defect cavity resonance on the absorption are analyzed. • The influence of structural parameters on absorption is explored. [ABSTRACT FROM AUTHOR]

We theoretically study how to greatly improve the near-infrared light absorption of monolayer graphene through the excitation of magnetic resonance in metamaterials. The absorption maximum of monolayer graphene is able to reach up to about 77% at the communication wavelength of 1550 nm. The conventionally defined absorption bandwidth, i.e., the full width at half maximum (FWHM), is nearly 160 nm. Thanks to the localization nature of magnetic resonance, the broadband high-efficiency absorption of monolayer graphene is insensitive to the incident angle and the light polarization. The absorption maximum, the absorption bandwidth, and the resonance position all have almost no change, when the incident angle is increased to even 60 degrees for both p and s polarizations. By applying an external bias voltage to change Fermi energy, the absorption in graphene can be completely modulated, with a nearly 100% modulation depth. Furthermore, the graphene absorption has an abrupt and large change around the interband transition, which exhibits an electrical switching property. Our work may find potential applications in graphene-based optoelectronic devices such as photodetector and modulator.

In this study, we developed a monolayer graphene/nanostructured cobalt oxide (MLG/Co 3 O 4) composite for asymmetric supercapacitor and electrochemical sensor applications. The MLG was grown by chemical vapor deposition process and the Co 3 O 4 nanostructures were electrodeposited on the MLG surface. Scanning electron microscopy proved that there were flower-like nanostructured Co 3 O 4 densely electrodeposited on the MLG surface. At a current density of 3 mA cm−2, the MLG/Co 3 O 4 composite produced an areal capacitance of 3.73 F cm−2. After 10,000 cycles, the composite electrode still had 93.6 % of its initial capacitance at 5 mA cm−2. The asymmetric system displayed an areal capacitance of 929 mF cm−2 at 4 mA cm−2 with good cycle stability. The asymmetric electrode produced a specific energy of 51 μWh cm−2 and a specific power of 11.1 mW cm−2. Cyclic voltammetric measurements demonstrated that the composite showed redox peaks at 0.48 eV and 0.09 eV toward the determination of CA. With a sensitivity of 0.13 µA/µM/cm2 and a limit of detection of 0.009 µM, the composite showed CA concentrations, ranging from 0.5 to 480 M. The composite displayed excellent selectivity and the current produced for the interfering compounds was exceedingly low. Using the composite electrode, the spiked CA in red wine and green tea samples recovered remarkably effectively. • Fabrication of Co 3 O 4 /CVD-grown monolayer graphene composite. • The composites showed an areal capacitance of 3.73 F cm−2 at 3 mA cm−2. • The electrode lost only 6.4 % of its original capacitance after 10,000 cycles. • The asymmetrical supercapacitor exhibited an energy density of 51 μWh cm−2. • The composite showed a sensitivity of 0.13 µA/µM/cm2 and a LOD of 0.009 µM. [ABSTRACT FROM AUTHOR]

We study the supercontinuum (SC) generation from a passively mode-locked erbium-doped fiber laser (ML-EDFL) using two different samples of monolayer graphene saturable absorber (SA) onto the side-polished surface of a D-shaped fiber, characterized with 98% and 65% polarization dependent loss (PDL), respectively. By using the first 98% PDL graphene SA (setup-1), output pulse spectral profile with 11.6 nm bandwidth was obtained from the ML-EDFL and subsequently amplified using an erbium-doped fiber amplifier (EDFA) to pump 2-m highly nonlinear fiber (HNLF) and 5-m ZBLAN lengths, both fibers operating at the normal dispersion regime, which resulted in individual SC generation of 350 and 245 nm, respectively. Furthermore, the EDFA was spectrally characterized by observing their SC blue shift of the central wavelength, reaching a value of 6.9 nm at 12 dB due to dispersion gain. With the second 65% PDL graphene SA (setup-2), we could generate SC with 227 and 351 nm bandwidths using 0.5 and 2 m HNLF lengths, respectively. Because the two SC setups were highly dependent on the polarization state of the input pulse, we optimized the SC generation from setup-2 using an external polarization controller (PC), which allowed us to adjust both the spectral brightness and the broadening of the SC. • SC generation using two samples of monolayer graphene on D-shaped fibers as SA. • SC generation seeded by both different solitons profiles and polarization states. • The two previous SC generation studies were analyzed using HNLF and ZBLAN fibers. [ABSTRACT FROM AUTHOR]

Emerging high-entropy alloy (HEA) films achieve high strength but generally show ineludible brittle fractures, strongly restricting their micro/nano-mechanical and functional applications. Nanolayered (NL) CoCrFeNi/graphene composites are elaborately fabricated via magnetron sputtering and the transfer process. It is uncovered that NL CoCrFeNi/graphene composite pillars exhibit a simultaneous ultra-high strength of 4.73 GPa and considerable compressive plasticity of over 20%. Detailed electron microscope observations and simulations reveal that the monolayer graphene interface can effectively block the crack propagation and stimulate dislocations to accommodate further deformation. Our findings open avenues for the fabrication of high-performance, HEA-based composites, thereby addressing the challenges and unmet needs in flexible electronics and mechanical metamaterials. [ABSTRACT FROM AUTHOR]

We report an ultra-broadband and compact TM-pass polarizer based on graphene-buried polymer waveguides. The characteristic parameters of the polarizer were carefully designed and optimized. The standard microfabrication processes were employed to fabricate the device. The presented polarizers exhibit high polarization-dependent transmission imposing a TE mode cutoff while leaving the TM mode almost unaffected. We experimentally demonstrated the polarizer that has an ultra-high extinction ratio of more than 22.9 dB and 41.9 dB for the monolayer graphene film placed on the surface of core layer and buried in the center of core layer, respectively, and as low insertion loss as ~4.0 dB for the TM mode with the bandwidth over 110 nm. The presented polarizer has the advantages of high extinction ratio, ultra-broadband, low cost, and easy integration with other polymer-based planar lightwave devices. [ABSTRACT FROM AUTHOR]

In this paper, the eigenstates and energy levels of carriers confined in quantum rings (QRs) in single-layer graphene under an applied magnetic field are calculated analytically. Extensive (Shannon) and non-extensive (Tsallis) formalisms are then used to determine the entropy, specific heat, and susceptibility of the system. Specifically, by using the Tsallis entropy formalism, the entropy, specific heat, and magnetic susceptibility of this system are investigated. We also compare these quantities for QR monolayer graphene in two statistical mechanics regimes: extensive (Shannon entropy) and non-extensive (Tsallis entropy). Our findings show that the thermodynamic quantities in the Shannon entropy have periodic behavior with increasing external magnetic field, and the properties obtained by the Tsallis formalism show a peak structure. In particular, the specific heat calculated by the Tsallis formalism shows a Schottky anomaly effect. The results obtained in this work can serve as a good starting point for future experimental works. [ABSTRACT FROM AUTHOR]

We investigate the plasmonic excitations and the broadening functions of the plasmon dispersions in multilayer structures consisting of four parallel monolayer graphene (4-MLG) sheets on an inhomogeneous background dielectric within the random-phase approximation. By finding the zeroes of the frequency-dependent dielectric function, we determine one optical and three acoustic plasmon modes in the system. We observed that the dependence of plasmon properties in the inhomogeneous 4-MLG system on the parameters differs significantly from that in the homogeneous one. Once the inhomogeneity of the background dielectric is taken into account, the plasmon frequencies get smaller values, compared to those in the homogeneous situation as well as in the MLG at the same parameters. As the interlayer separation increases, the plasmon branches in the inhomogeneous system move downward while only the optical branch in the homogeneous one does this, the acoustic plasmon branches shift to the opposite direction. With the efficiently large separations, plasmon lines in the homogeneous case become identical while those in the inhomogeneous case separate from each other in the large momentum region. For homogeneous 4-MLG systems, the decrease in carrier density leads to the decrease in plasmon frequency, but for inhomogeneous 4-MLG structures, the decrease in the doping density of the first graphene layer increases remarkably the frequencies of all plasmon branches. Finally, the broadening function of the plasmon dispersions gets the larger values as plasmon lines go far away from the inter single-particle excitation boundary. [ABSTRACT FROM AUTHOR]

Graphene, known for its high carrier mobility and broad spectral response range, has proven to be a promising material in photodetection applications. However, its high dark current has limited its application as a high-sensitivity photodetector at room temperature, particularly for the detection of low-energy photons. Our research proposes a new approach for overcoming this challenge by designing lattice antennas with an asymmetric structure for use in combination with high-quality monolayers of graphene. This configuration is capable of sensitive detection of low-energy photons. The results show that the graphene terahertz detector-based microstructure antenna has a responsivity of 29 V·W−1 at 0.12 THz, a fast response time of 7 μs, and a noise equivalent power of less than 8.5 pW/Hz1/2. These results provide a new strategy for the development of graphene array-based room-temperature terahertz photodetectors.

Graphene is a promising candidate for the thermal management of downscaled microelectronic devices owing to its exceptional electrical and thermal properties. Nevertheless, a comprehensive understanding of the intricate electrical and thermal interconversions at a nanoscale, particularly in field-effect transistors with prevalent gate operations, remains elusive. In this study, nanothermometric imaging is used to examine a current-carrying monolayer graphene channel sandwiched between hexagonal boron nitride dielectrics. It is revealed for the first time that beyond the expected Joule heating, the thermoelectric Peltier effect actively plays a significant role in generating hotspots beneath the gated region. With gate-controlled charge redistribution and a shift in the Dirac point position, an unprecedented systematic evolution of thermoelectric hotspots, underscoring their remarkable tenability is demonstrated. This study reveals the field-effect Peltier contribution in a single graphene-material channel of transistors, offering valuable insights into field-effect thermoelectrics and future on-chip energy management., (© 2024 Wiley‐VCH GmbH.)

Cacti, a common drought-tolerant plant, enable the directional transport of droplets from the tip of the spikes to the roots in order to collect moisture from the air, creating conditions for cactus survival in arid areas. Inspired by this interesting natural phenomenon, a novel design for a monolayer graphene-covered nanocone (GNC) is proposed to realize ultrafast water droplet transport from the tip to the end of the GNC. The results show that the self-driving speed of a water droplet can reach ∼80 m sâˆ'1 driven by the Youngâ€"Laplace pressure difference. The rule of energy change during the droplet self-driving process indicates that the potential energy of the droplet and the interaction energy between the droplet and the GNC undergo cooperation and competition successively, resulting in the droplet first speeding up and then slowing down to a steady moving state. A larger droplet can extend the high-speed stage, which is beneficial to long-distance self-driving of droplets in a water-harvesting process. Continuum theory in the self-driving of a droplet at a microscale is used to describe the steady moving process, in order to further understand the rule in GNC-based water transport. The findings will open a broad range of novel perspectives for spontaneous droplet transport and water harvesting by graphene-covered functional surfaces. [ABSTRACT FROM AUTHOR]

Electron-electron interactions (EEI) play a pivotal role in the transport behavior of carriers confined in a two-dimensional system. The strength of the interaction can be tuned by changing carrier concentration in a conventional two-dimensional system, while it expectedly cannot be controlled in monolayer graphene with a linear dispersion relation since the interaction parameter is not related to carrier concentration. Here, an anomalous carrier-concentration dependence of the EEI is observed in epitaxial graphene on SiC. From quantum transport measurement, a logarithmic temperature dependence of the Hall coefficient is obtained, which is a manifestation of the EEI. From the logarithmic temperature dependence, the EEI-related factor K e e is extracted. Unexpectedly, the extracted K e e shows an increase on increasing carrier concentration, which is further confirmed by analyzing logarithmic correction to the Drude conductivity. This can be attributed to the carrier-concentration dependence of Fermi-liquid constant F 0 σ due to gas absorption, which offers a route to control the EEI in graphene. [Display omitted] [ABSTRACT FROM AUTHOR]

A near-perfect narrow-band graphene-based absorber was fabricated using a resonant system integrated with an asymmetric meta-grating at a wavelength of 1550 nm. By optimizing the gap between the two grating strips, the absorption of monolayer graphene can be increased to 99.6% owing to the strong field confinement of the bottom zero-contrast grating (ZCG). The position of the absorption spectrum could be adjusted by tailoring the grating period or the thickness of the waveguide layer. Interestingly, absorption spectrum linewidth can be tailored by changing the thickness of the spacer layer. The accidental bound states in the continuum (BICs) are then demonstrated in the structure. Moreover, the designed structure realizes the dynamic adjustment of the absorption efficiency at a specific wavelength, which has excellent potential in integrated optical devices and systems.

The excellent thermal and chemical stability of monolayer graphene makes it an ideal material for separations at high temperatures and in harsh organic solvents. Here, based on understanding of solvent permeation through nanoporous graphene via molecular dynamics simulation, a resistance model was established to guide the design of a defect-tolerant graphene composite membrane consisting of monolayer graphene on a porous supporting substrate. Guided by the model, we experimentally engineered polyimide (PI) supporting substrates with appropriate pore size, permeance, and excellent solvent resistance and investigated transport across the resulting graphene-covered membranes. The cross-linked PI substrate could effectively mitigate the impacts of leakage through defects across graphene to allow selective transport without defect sealing. The graphene-covered membrane showed pure solvent permeance of 24.1 L m-2 h-1 bar-1 and stable rejection (~90%) of Allura Red AC (496.42 g mol-1) in a harsh polar solvent, dimethylformamide (DMF), at 100 °C for 10 d. [ABSTRACT FROM AUTHOR]

Large-area graphene synthesized by a chemical vapor deposition (CVD) method is promising for a flexible, stretchable transparent electrode but suffers from structural defects such as grain boundaries, which causes to degrade its physical properties. Recently, preparation methods of large-scale growth templates for single-crystalline graphene (SCG) were reported, but the macroscopic properties of SCG have not been adequately examined yet. Here, an SCG-based flexible, stretchable graphene transparent electrode is successfully demonstrated, which shows superior optoelectrical, electromechanical, and barrier properties compared to polycrystalline graphene (PCG)-based transparent electrodes. The result exhibits the grain boundary effect of graphene on soft substrates on a macroscopic scale and a great promise toward realizing a tremendous performance improvement of graphene-based flexible transparent electrodes on a large scale. [Display omitted] • The macroscopic properties of SCG and PCG related to transparent electrode application are examined. • SCG and PCG were synthesized and confirmed with various methods both in microscopic and macroscopic scale. • According to the scaling law, graphene without GBs may not have advantages in its physical properties. • The graphene GBs highly affect electromechanical and barrier properties, as well as electrical conductivity. • Using SCG instead of PCG for flexible transparent electrodes is worth it for its improved long-term stability. [ABSTRACT FROM AUTHOR]