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Epitaxial Graphene Sensors Combined with 3D Printed Microfluidic Chip for Heavy Metals Detection
摘要： Two-dimensional materials may constitute key elements in the development of a sensing platform where extremely high sensitivity is required, since even minimal chemical interaction can generate appreciable changes in the electronic state of the material. In this work, we investigate the sensing performance of epitaxial graphene on Si-face 4H-SiC (EG/SiC) for liquid-phase detection of heavy metals (e.g., Pb). The integration of preparatory steps needed for sample conditioning is included in the sensing platform, exploiting fast prototyping using a 3D printer, which allows direct fabrication of a microfluidic chip incorporating all the features required to connect and execute the Lab-on-chip (LOC) functions. It is demonstrated that interaction of Pb2+ ions in water-based solutions with the EG enhances its conductivity exhibiting a Langmuir correlation between signal and Pb2+ concentration. Several concentrations of Pb2+ solutions ranging from 125 nM to 500 μM were analyzed showing good stability and reproducibility over time.
关键词： heavy metals detection,3D printed flow cell,reusable lab-on-chip,epitaxial graphene,high sensitivity
更新于2025-09-23 15:23:52
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Homogeneous Large-area Quasi-freestanding Monolayer and Bilayer Graphene on SiC
摘要： In this study, we first show that the argon flow during epitaxial graphene growth is an important parameter to control the quality of the buffer and the graphene layer. Atomic force microscopy (AFM) and low-energy electron diffraction (LEED) measurements reveal that the decomposition of the SiC substrate strongly depends on the Ar mass flow rate while pressure and temperature are kept constant. Our data are interpreted by a model based on the competition of the SiC decomposition rate, controlled by the Ar flow, with a uniform graphene buffer layer formation under the equilibrium process at the SiC surface. The proper choice of a set of growth parameters allows the growth of defect-free, ultra-smooth and coherent graphene-free buffer layer and bilayer-free monolayer graphene sheets which can be transformed into large-area high-quality quasi-freestanding monolayer and bilayer graphene by hydrogen intercalation. AFM, scanning tunneling microscopy, Raman spectroscopy and electronic transport measurements underline the excellent homogeneity of the resulting quasi-freestanding layers. Electronic transport measurements in four-point probe configuration reveal a homogeneous low resistance anisotropy on both μm- and mm scales.
关键词： SiC terrace steps,polymer assisted sublimation growth,Epitaxial graphene,freestanding bilayer graphene,argon gas flow,graphene buffer layer,monolayer graphene,resistance anisotropy,large-scale graphene growth,freestanding monolayer graphene
更新于2025-09-23 15:22:29
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Laser-induced growth of large-area epitaxial graphene with low sheet resistance on 4H-SiC(0001)
摘要： Multilayer graphene on SiC is a promising material due to its compatibility with modern electronics technology. Herein, we demonstrate the growth of large-area (~10 × 5 mm2), high-quality (D/G area ratio: ~0.03) epitaxial graphene on 4H-SiC(0001) using a high-power continuous laser with an extremely fast heating rate of 500 °C/s. As the growth temperature rises from 1550 °C to 1780 °C, the number of graphene layers increases from three to more than ten. The obtained graphene/SiC samples are highly conductive, with a sheet resistance of as low as ~0.43 Ω/sq. The high power and fast heating rate of the laser contribute to the formation of large-area and low-sheet-resistance graphene. The high conductivity makes graphene/SiC a very promising material for applications in conductive films. The growth mechanism of graphene and the influence of the structural properties of graphene on the conductivity are also discussed.
关键词： Sheet resistance,Large-area,4H-SiC,Continuous laser,Epitaxial graphene
更新于2025-09-23 15:21:01
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Bismuth mediated defect engineering of epitaxial graphene on SiC(0001)
摘要： Structural defects are commonly undesirable in materials, however, atomic-level defect engineering is promising to improve the electronic, mechanical and chemical properties of graphene, if the density and types of defects could be well controlled. Herein, bismuth-mediated defect engineering method for epitaxial graphene (EG) grown on SiC(0001) is demonstrated. It is found that single defects and defect clusters could be facilitated by evaporating Bi atoms on SiC(0001) substrate before the standard EG preparation and, Bi atoms could be thoroughly cleaned away from the EG and the unwanted doping effects of Bi will be avoided by post-annealing at higher temperature. Scanning tunneling microscopy/spectroscopy characterization reveals the atomic structures, the electronic states and the Fermi level shift of flower-like, tube-like and point defects. This study sheds light on the metal-mediated formation of defects in graphene, and provides a practical defect engineering method.
关键词： Defect engineering,Scanning tunneling microscopy/spectroscopy.,Epitaxial graphene (EG)
更新于2025-09-19 17:15:36
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Atomically thin half-van der Waals metals enabled by confinement heteroepitaxy
摘要： Atomically thin two-dimensional (2D) metals may be key ingredients in next-generation quantum and optoelectronic devices. However, 2D metals must be stabilized against environmental degradation and integrated into heterostructure devices at the wafer scale. The high-energy interface between silicon carbide and epitaxial graphene provides an intriguing framework for stabilizing a diverse range of 2D metals. Here we demonstrate large-area, environmentally stable, single-crystal 2D gallium, indium and tin that are stabilized at the interface of epitaxial graphene and silicon carbide. The 2D metals are covalently bonded to SiC below but present a non-bonded interface to the graphene overlayer; that is, they are ‘half van der Waals’ metals with strong internal gradients in bonding character. These non-centrosymmetric 2D metals offer compelling opportunities for superconducting devices, topological phenomena and advanced optoelectronic properties. For example, the reported 2D Ga is a superconductor that combines six strongly coupled Ga-derived electron pockets with a large nearly free-electron Fermi surface that closely approaches the Dirac points of the graphene overlayer.
关键词： 2D metals,superconductivity,epitaxial graphene,quantum devices,silicon carbide
更新于2025-09-19 17:13:59
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Epitaxial Graphene p-n Junctions
摘要： We report the fabrication and measurement of top gated epitaxial graphene p-n junctions where exfoliated hexgonal boron nitride (hBN) is used as the gate dielectric. The four terminal longitudinal resistance across a single junction is well quantized at RK?90 (= 25812.807 ?) with a relative uncertainty of 10?7. Our work opens the possibility to realize programmable electrical resistance standards using external gating.
关键词： resistance standard,quantum Hall effect,graphene p-n junction,Epitaxial graphene
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - A Table-Top Graphene Quantized Hall Standard
摘要： We report the performance of a quantum standard based on epitaxial graphene maintained in a 5 T table-top cryocooler system. The ν = 2 resistance plateau, with a value of RK-90/2, is used to scale to 1 k? using a binary cryogenic current comparator (BCCC) bridge. The preliminary uncertainties achieved with the BCCC are like those obtained in state-of-the-art measurements using GaAs-based devices. This quantum standard requires no liquid He and can operate continuously, allowing year-round accessibility to traceable resistance measurements.
关键词： binary cryogenic current comparator,epitaxial graphene,quantized Hall resistance,direct current comparator,standard resistor
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Epitaxial Graphene for High-Current QHE Resistance Standards
摘要： We report the growth of large-area monolayer graphene on the centimeter scale using an optimized growth process and morphology improvements. Magneto-transport measurements on graphene quantum Hall effect devices demonstrate the applicability for high-current quantum resistance metrology.
关键词： polymer-assisted growth (PASG),face-to-graphite (FTG),epitaxial graphene,quantum resistance metrology
更新于2025-09-10 09:29:36
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Towards epitaxial graphene p-n junctions as electrically programmable quantum resistance standards
摘要： We report the fabrication and measurement of top gated epitaxial graphene p-n junctions where exfoliated hexagonal boron nitride (h-BN) is used as the gate dielectric. The four-terminal longitudinal resistance across a single junction is well quantized at the von Klitzing constant RK with a relative uncertainty of 10?7. After the exploration of numerous parameter spaces, we summarize the conditions upon which these devices could function as potential resistance standards. Furthermore, we offer designs of programmable electrical resistance standards over six orders of magnitude by using external gating.
关键词： p-n junctions,quantum resistance standards,gate dielectric,hexagonal boron nitride,epitaxial graphene
更新于2025-09-09 09:28:46