Graphene-based Devices Research Articles

Application of digital twins for simulation based tailoring of laser induced graphene

In the era of man–machine interfaces, digital twins stand as a key technology, offering virtual representations of real-world objects, processes, and systems through computational models. They enable novel ways of interacting with, comprehending, and manipulating real-world entities within a virtual realm. The real implementation of graphene-based sensors and electronic devices remains challenging due to the integration complexities of high-quality graphene materials with existing manufacturing processes. To address this, scalable techniques for the in-situ fabrication of graphene-like materials are essential. One promising method involves using a CO2 laser to convert polyimide into graphene. Optimizing this graphitization process is hindered by complex parameter interactions and nonlinear terms. This article explores how these digital replicas can enhance the fabrication of laser-induced graphene (LIG) through laser simulation and machine learning methods to enable rapid single-step LIG patterning. This approach aims to create a universal simulation for all CO2 lasers, calculating optical energy flux and utilizing machine learning to control and predict LIG conductivity (ability to conduct current), morphology, and electrical resistance. The proposed procedure, integrating digital twins in the LIG production process, will avoid or reduce the preliminary tests required to determine the proper laser parameters to reach the desired LIG characteristics. Accordingly, this approach will reduce the time and costs associated with these tests and thus increase the efficiency and optimize the procedure.

Chasing Graphene-Based Anticancer Drugs: Where are We Now on the Biomedical Graphene Roadmap?

Graphene and graphene-based materials have attracted growing interest for potential applications in medicine because of their good biocompatibility, cargo capability and possible surface functionalizations. In parallel, prototypic graphene-based devices have been developed to diagnose, imaging and track tumor growth in cancer patients. There is a growing number of reports on the use of graphene and its functionalized derivatives in the design of innovative drugs delivery systems, photothermal and photodynamic cancer therapy, and as a platform to combine multiple therapies. The aim of this review is to introduce the latest scientific achievements in the field of innovative composite graphene materials as potentially applied in cancer therapy. The "Technology and Innovation Roadmap" published in the Graphene Flagship indicates, that the first anti-cancer drugs using graphene and graphene-derived materials will have appeared on the market by 2030. However, it is necessary to broaden understanding of graphene-based material interactions with cellular metabolism and signaling at the functional level, as well as toxicity. The main aspects of further research should elucidate how treatment methods (e.g., photothermal therapy, photodynamic therapy, combination therapy) and the physicochemical properties of graphene materials influence their ability to modulate autophagy and kill cancer cells. Interestingly, recent scientific reports also prove that graphene nanocomposites modulate cancer cell death by inducing precise autophagy dysfunctions caused by lysosome damage. It turns out as well that developing photothermal oncological treatments, it should be taken into account that near-infrared-II radiation (1000-1500 nm) is a better option than NIR-I (750-1000 nm) because it can penetrate deeper into tissues due to less scattering at longer wavelengths radiation.

Chemically doped-graphene FET photodetector enhancement via controlled carrier modulation with an iron(III)-chloride

Graphene is an excellent material among the family of 2D materials due to its electronic and optoelectronic properties. The intentional modification of its electronic structure via doping processes holds immense significance regarding tailoring its properties for specific applications. We comprehensively investigated p-type doping in few-layer graphene field-effect transistors (FETs) on SiO2/Si substrates by utilizing Iron(III)-chloride (FeCl3) dopant solutions with varying concentrations that range from 5 mM to 50 mM in this study. The successful doping was confirmed via a meticulous Raman spectroscopy analysis, which revealed notable shifts in the peak positions and peak broadening post-doping. Electrical measurements, which include transfer curves at a fixed biasing voltage, provided further confirmation, which demonstrates a distinctive shift in the Dirac point from −1 V to +25 V when the FeCl3 concentrations were changed from 5 mM to 50 mM. The impact of doping on the photoresponse of the graphene device was systematically explored. The device exhibited a significant increase in responsivity and external quantum efficiency following the p-type doping, which indicates an enhanced performance in photodetection. This research validates the successful p-type doping of graphene and underscores its implications regarding optimizing the electrical and optoelectronic properties of graphene-based devices, which confirms its potential for advanced applications for electronic and optoelectronic technologies.

Temperature-assisted electromagnetic surface modes in graphene-based temperature sensitive metafilms

Graphene has the potential to manipulate surface modes in frequency bands from THz to mid-IR regions. Typically, due to single-atom thickness and low charge-carrier density, the thermal response of graphene is ineffective. Temperature-sensitive materials (TSMs) can play an active role in enhancing the thermal response of graphene-based devices. In the present work, graphene-based temperature-sensitive metafilms have been proposed for thermally tunable propagation of electromagnetic surface modes. A detailed analytical and numerical solution for temperature-dependent electromagnetic surface (even and odd) modes supported by the graphene-based temperature-sensitive metafilm has been studied. The Kubo’s formulation has been used to model optical conductivity (σ g ) while the hybrid Drude’s model is implemented to realize the indium antimonide (InSb) as temperature-sensitive material. To simulate the metafilm, the waveguide modal analysis approach was implemented, while the realization of the graphene sheets was achieved by the use of impedance boundary conditions (IBCs). The propagation characteristics for even/odd surface modes were analyzed under different values of temperature (T), chemical potential (µ c ), and thickness of metafilm (d). Further, the numerical results for even and odd surface modes under two phases of InSb [Insulator phase (T = 200 K) and metallic phase (T = 300 K)] were compared under different values of chemical potential (µ c ) and TSM film thickness (d). It is concluded that the propagation characteristics of surface modes are sensitive to the external temperature and can be tailored by tuning the temperature, chemical potential (µ c ), and TSM film thickness (d). Moreover, the degeneracy of the even and odd modes can be controlled by varying the temperature and TSM film thickness. The work is suitable for designing temperature-assisted dual channel waveguides, THz optical switches, THz optical logic designs, and flexible thermal-optical sensors.

Engineering the flexibility and elastic modulus of graphene by heterojunctions

Graphene shows both superior flexibility and excellent mechanical strength. The fabricated graphene samples usually contain various defects like grain boundaries, which can either enhance or weaken the mechanical strength of graphene. So, exploring the effects of grain boundaries on the flexibility of graphene is useful in designing graphene-based flexible devices. Employing the first-principles calculation, flexibilities of graphene heterojunctions were studied, aiming to tailor the flexibility of graphene by heterojunctions. Here, by connecting armchair (AC) and zigzag (ZZ) graphene through grain boundaries, graphene heterojunctions with tunable AC to ZZ ratio were constructed. It was found that bending moduli, as well as Young’s moduli, of graphene heterojunctions are lower than the pristine graphene and can be further tailored by the AC to ZZ ratio, making graphene heterojunctions more flexible than graphene. Particularly, changing the AC to ZZ ratio can even alter the relative flexibility of graphene heterojunctions in different directions. Therefore, graphene heterojunction provides an approach to engineer the flexibility of graphene, which is helpful in understanding the mechanical properties of two-dimensional materials and designing the flexible devices.

Unveiling the electronic properties of BiP[formula omitted] triphosphide from bulk to graphene-based heterostructures by first-principles calculations

In our study, we conduct the structural and electronic properties of bismuth triphosphide (BiP3) in its bulk, few-layer, and monolayer forms. We found that BiP3 in bulk exhibits a metallic stable layered structure. The exfoliation energy of 1.07 J/m2 indicates ease exfoliation, comparable to other triphosphides. The band gap varies with thickness, transitioning from semiconductor—metal between four to five layers, influenced by interlayer coupling and quantum confinement. We also investigated the heterostructure created by depositing graphene (G) on few-layer BiP3. In monolayer (G/m-BiP3) and bilayer (G/2L-BiP3) forms, a metal–semiconductor junction is formed, characterized by weak vdW interactions at the interface and exhibiting p-type Schottky contacts. We observed that the Schottky Barrier Height (SBH) can be modulated by altering the interlayer distance between G and BiP3. This adjustment allows transitions between n-type and p-type Schottky contacts in G/m-BiP3 and the formation of an ohmic contact in G/2L-BiP3. Furthermore, applying an electric field affects the SBH, leading to similar transitions and the development of an ohmic contact. Additionally, our study shows that n-doping in graphene increases with the number of BiP3 layers and external electric field application. These properties position BiP3 few-layer as a promising material for nanoelectronic, optoelectronic, and graphene-based devices.

Broadband infrared polarizer of graphene wire grids with flat PER curves

Since 2004, the flourishing two-dimensional graphene has sparked extensive research on graphene-based optical and optoelectronic devices with high performance due to its ultra-fast photoelectric response, broadband, and tunable optical response. However, up until now, graphene-based wire grid polarizers have not been demonstrated to perform excellent characteristics with flat polarization extinction ratio (PER) curves, while they all exhibited narrow peak-shaped working bands. Here, we propose a broadband polarizer based on graphene wire grids with a flat PER curve of up to ∼84.5 dB in the ultrawide range of 1–10 μm. In the range of <4 μm, the graphene wire grid polarizer exhibits a strong plasmon resonance effect and outputs a linear-polarized state. Its performance is closely related to carrier density that is tuned by the Fermi level (EF) and thickness of graphene.

Large-Area Fabrication of Porous Graphene Networks on Carbon Fabric via Millisecond Photothermal Processing of Polyaniline for Supercapacitors.

Supercapacitors demonstrate promising potential for flexible, multi-functional energy storage devices; however, their widespread adoption is confronted by fabrication challenges. To access a combination of desirable device qualities such as flexibility, lightweight, structural stability, and enhanced electrochemical performance, carbon fiber (CF) can be utilized as a current collector, alongside graphene as an electrochemically active material. Yet achieving a cost-effective, large-scale graphene production, particularly on CF, remains challenging. Here, a rapid (<1min) photothermal approach is developed for the large-scale production of graphene directly onto CF, utilizing polyaniline (PANI) as a polymer precursor. The in situ electropolymerization of PANI on CF facilitates its rapid synthesis on large areas, followed by conversion into graphene networks, enabling the binder-free fabrication of supercapacitor devices. These devices exhibit an areal capacitance of 180mFcm-2 (at 2mAcm-2 in 1mH2SO4), an order of magnitude higher than other fabric-based devices. Moreover, the devised photothermal strategy allows for one-step preparation of supercapacitor devices on areas exceeding 100cm-2, yielding an absolute areal capacitance of 4.5F. The proportional increase in capacitance with device area facilitates scaling and indicates the commercial viability of this approach for low-cost, energy-efficient, and high-throughput production of lightweight, high-performance graphene-based multi-functional supercapacitor devices.

Far-Infrared Therapy Based on Graphene Ameliorates High-Fat Diet-Induced Anxiety-Like Behavior in Obese Mice via Alleviating Intestinal Barrier Damage and Neuroinflammation.

The consumption of a high-fat diet (HFD) has been implicated in the etiology of obesity and various neuropsychiatric disturbances, including anxiety and depression. Compelling evidence suggests that far-infrared ray (FIR) possesses beneficial effects on emotional disorders. However, the efficacy of FIR therapy in addressing HFD-induced anxiety and the underlying mechanisms remain to be elucidated. Here, we postulate that FIR emitted from a graphene-based therapeutic device may mitigate HFD-induced anxiety behaviors. The graphene-FIR modify the gut microbiota in HFD-mice, particularly by an enriched abundance of beneficial bacteria Clostridiaceae and Erysipelotrichaceae, coupled with a diminution of harmful bacteria Lachnospiraceae, Anaerovoracaceae, Holdemania and Marvinbryantia. Graphene-FIR also improved intestinal barrier function, as evidenced by the augmented expression of the tight junction protein occludin and G protein-coupled receptor 43 (GPR43). In serum level, we observed the decreased free fatty acids (FFA), lipopolysaccharides (LPS), diamine oxidase (DAO) and D-lactate, and increased the glucagon-like peptide-2 (GLP-2) levels in graphene-FIR mice. Simultaneously, inflammatory cytokines IL-6, IL-1β, and TNF-α manifested a decrease subsequent to graphene-FIR treatment in both peripheral and central system. Notably, graphene-FIR inhibited over expression of astrocytes and microglia. We further noticed that the elevated the BDNF and decreased TLR4 and NF-κB expression in graphene-FIR group. Overall, our study reveals that graphene-FIR rescued HFD-induced anxiety via improving the intestine permeability and the integrity of blood-brain barrier, and reduced inflammatory response by down regulating TLR4/NF-κB inflammatory pathway.

Sensitive Characterization of the Graphene Transferred onto Varied Si Wafer Surfaces via Terahertz Emission Spectroscopy and Microscopy (TES/LTEM).

Graphene shows great potential in developing the next generation of electronic devices. However, the real implementation of graphene-based electronic devices needs to be compatible with existing silicon-based nanofabrication processes. Characterizing the properties of the graphene/silicon interface rapidly and non-invasively is crucial for this endeavor. In this study, we employ terahertz emission spectroscopy and microscopy (TES/LTEM) to evaluate large-scale chemical vapor deposition (CVD) monolayer graphene transferred onto silicon wafers, aiming to assess the dynamic electronic properties of graphene and perform large-scale graphene mapping. By comparing THz emission properties from monolayer graphene on different types of silicon substrates, including those treated with buffered oxide etches, we discern the influence of native oxide layers and surface dipoles on graphene. Finally, the mechanism of THz emission from the graphene/silicon heterojunction is discussed, and the large-scale mapping of monolayer graphene on silicon is achieved successfully. These results demonstrate the efficacy of TES/LTEM for graphene characterization in the modern graphene-based semiconductor industry.

Active manipulation of the plasmonic induced asymmetric photonic spin Hall effect

The asymmetric photonic spin Hall effect (APSHE) induced by surface plasmon polaritons in a graphene-based structure is actively manipulated by external magnetic field and electric field. It is revealed that the spin-dependent splitting exhibits spatio-temporal asymmetric property due to the involvement of the anisotropic graphene. The peak of asymmetry degree in APSHE at the position of reflectance valley corresponds toward a smaller incident angle with the increase of magnetic field intensity or Fermi energy, which is attributed to the tunability of reflectance for the graphene-based structure. Based on the asymmetric splitting shift, a potential application is proposed for detecting low concentration gas molecules and the detection resolution can be dynamically tunable by changing the magnetic field intensity and Fermi energy. This study may provide a new reference in the fabrication of graphene-based plasmonic sensor devices.

Enhancing the Consistency and Performance of Graphene-Based Devices via Al Intermediate-Layer-Assisted Transfer and Patterning.

Graphene has garnered widespread attention, and its use is being explored for various electronic devices due to its exceptional material properties. However, the use of polymers (PMMA, photoresists, etc.) during graphene transfer and patterning processes inevitably leaves residues on graphene surface, which can decrease the performance and yield of graphene-based devices. This paper proposes a new transfer and patterning process that utilizes an Al intermediate layer to separate graphene from polymers. Through DFT calculations, the binding energy of graphene-Al was found to be only -0.48 eV, much lower than that of PMMA and photoresist with graphene, making it easier to remove Al from graphene. Subsequently, this was confirmed through XPS analysis. A morphological characterization demonstrated that the graphene patterns prepared using the Al intermediate layer process exhibited higher surface quality, with significantly reduced roughness. It is noteworthy that the devices obtained with the proposed method exhibited a notable enhancement in both consistency and sensitivity during electrical testing (increase of 67.14% in temperature sensitivity). The low-cost and pollution-free graphene-processing method proposed in this study will facilitate the further commercialization of graphene-based devices.

Modeling and Simulation of Graphene-Based Transducers in NEMS Accelerometers.

The mechanical characteristics of graphene ribbons with an attached proof mass that can be used as NEMS transducers have been minimally studied, which hinders the development of graphene-based NEMS devices. Here, we simulated the mechanical characteristics of graphene ribbons with an attached proof mass using the finite element method. We studied the impact of force, residual stress, and geometrical size on displacement, strain, resonant frequency, and fracture strength of graphene ribbons with an attached proof mass. The results show that the increase of width and thickness of graphene ribbons would result in a decrease of the displacement and strain but also an increase of resonant frequency. The increase of the length of graphene ribbons has an insignificant impact on the strain, but it could increase the displacement and decrease the resonant frequency. The increase of residual stress in the graphene ribbons decreases its strain and displacement. The estimated fracture strength of graphene shows limited dependence on its thickness, with an estimated value of around 148 GPa. These findings contribute to the understanding of the mechanical characteristics of graphene ribbons with an attached proof mass and lay the solid foundation for the design and manufacture of high-performance graphene-based NEMS devices such as accelerometers.

Comprehensive Study and Design of Graphene Transistor.

Graphene, renowned for its exceptional electrical, optical, and mechanical properties, takes center stage in the realm of next-generation electronics. In this paper, we provide a thorough investigation into the comprehensive fabrication process of graphene field-effect transistors. Recognizing the pivotal role graphene quality plays in determining device performance, we explore many techniques and metrological methods to assess and ensure the superior quality of graphene layers. In addition, we delve into the intricate nuances of doping graphene and examine its effects on electronic properties. We uncover the transformative impact these dopants have on the charge carrier concentration, bandgap, and overall device performance. By amalgamating these critical facets of graphene field-effect transistors fabrication and analysis, this study offers a holistic understanding for researchers and engineers aiming to optimize the performance of graphene-based electronic devices.

Photocarrier generation mechanism of graphene-based field effect device

The carrier generation in a photodetecting device plays a critical role in the enhancement of photocurrent. Here we perform photocurrent measurements on graphene-based photodetecting device and unveil three carrier generation mechanisms, namely, (I) thermally assisted- and (II) optically induced- excitation of in-gap defect state electron, and (III) inter-band optical absorption of bulk Si. We further determine their carrier supply strength defined as P = dn/dt, which are P(I) = 2.09×1010 /cm⋅2 s, P(II) = 2.15×1010 /cm⋅2s, and P(III) = 3.55×1011 /cm⋅2s, respectively. In addition, we show that the characteristic IV behavior induced by the gate voltage cycling can be interpreted in terms of the three carrier generation mechanisms. This study provides a useful guide to designing practical graphene-based photodetecting devices.

Hydrodynamic Electronic Transport

The “flow” of electric currents and heat in standard metals is diffusive with electronic motion randomized by impurities. However, for ultraclean metals, electrons can flow like water with their flow being described by the equations of hydrodynamics. While theoretically postulated, this situation was highly elusive for decades. In the past decade, several experimental groups have found strong indications for this type of flow, especially in graphene-based devices. In this review, we give an overview of some of the recent key developments, on both the theoretical and experimental sides.

Photo-thermoelectric effect-driven detection of optical communication light in graphene/hBN heterostructures

We report on the photodetection properties of high-quality graphene encapsulated by hexagonal boron nitride under illumination with optical communication light. We demonstrate a gate-tunable photocurrent and zero-bias switching cycle operation at RT. Through gate and temperature-dependent photocurrent measurements, we determine that the dominant photoresponse mechanism is the photo-thermoelectric effect. At low temperatures, the photocurrent in finite doping regions correlates with the Seebeck coefficient, while sharp peaks emerge near the charge neutrality point due to an edge-excited photocurrent. Our study provides guidelines for high-performance graphene-based optoelectronic devices.

Ultralow 1/f noise in epigraphene devices

We report the lowest recorded levels of 1/f noise for graphene-based devices, at the level of SV/V2=SI/I2=4.4×10−16 (1/Hz), measured at f = 10 Hz (SV/V2=SI/I2 &amp;lt; 10−16 1/Hz for f &amp;gt; 100 Hz) in large-area epitaxial graphene on silicon carbide (epigraphene) Hall sensors. This performance is made possible through the combination of high material quality, low contact resistance achieved by edge contact fabrication process, homogeneous doping, and stable passivation of the graphene layer. Our study explores the nature of 1/f noise as a function of carrier density and device geometry and includes data from Hall sensors with device area range spanning over six orders of magnitude, with characteristic device length ranging from L = 1 μm to 1 mm. In optimized graphene Hall sensors, we demonstrate arrays to be a viable route to improve further the magnetic field detection: a simple parallel connection of two devices displays record-high magnetic field sensitivity at room temperature, with minimum detectable magnetic field levels down to Bmin = 9.5 nT/√Hz. The remarkable low levels of 1/f noise observed in epigraphene devices hold immense capacity for the design and fabrication of scalable epigraphene-based sensors with exceptional performance.

Electrically tunable dual-channel absorber based on a graphene integrated slanted grating cavity

In this paper, we propose a tunable dual-channel absorber based on a monolayer of graphene combined with a slanted grating. A single-channel perfect absorption of a monolayer graphene structure at 850 nm was initially achieved in a Fabry-Perot cavity resonance. The absorption rate of graphene was enhanced by nearly 24.5 times. Furthermore, the symmetry of the grating is broken to excite the quasi-bound states in the continuum (quasi-BICs) resonance mode, resulting in another absorption channel at 878.8 nm, thus achieving a perfect dual-channel absorber. The absorption half-width and absorption wavelength can be adjusted by tuning the grating thickness and the electro-optical effect of the DAST material. Furthermore, adjusting the polarization angle of the incident light enables the transition between single- and dual-channel absorbers. The proposed device has potential applications in the fields of high-performance graphene-based optoelectronic devices and optical switching systems.

The quest for harnessing nuclear effects in graphene-based devices

The recent successes of superconducting qubits and the demonstration of quantum supremacy over classical bits herald a new era for information processing. Yet, the field is still in its infancy and there exist viable alternative candidates that can also store quantum information. In this review, we will highlight ideas, attempts, and the experimental progress to address nuclear spins in graphene, a readily available Dirac semimetal that consists of a single layer of carbon atoms. Carbon isotopes with a nuclear spin are rare in natural graphene. However, it is possible to enrich the spin-bearing 13C isotopes to produce large-scale graphene sheets, which constitute the testbed to store, transport, and retrieve spin information, or to engineer nanostructures. Here, the hyperfine interaction between the electron spins and the nuclear spins serves as an experimental control knob and mediator to address nuclear polarization and nuclear spin coherence times through electrical measurements. The exploitation of nuclear spins in graphene is thus an alluring perspective. We will discuss methods to synthesize 13C graphene and show experimental approaches and challenges to exploit the relatively weak hyperfine interaction in two-dimensional 13C graphene devices. The ultimate purpose, i.e., the exploitation of nuclear spins in graphene for information processing, is not within reach, but its potential for future applications merits a revisit of the current state-of-the-art.