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A theory is presented for the amplification of a surface acoustic wave (SAW) due to its interaction with conduction electrons in gate-controlled epitaxial graphene (epigraphene) on a SiC substrate. It is assumed that the SAW is launched onto the substrate in the direction of an external dc electric field applied to the graphene sample and causing the conduction electrons to drift at a speed greater than the speed of the SAW. The wavelength of the SAW is assumed to be shorter than the mean free path of the electrons, so that the quantum regime of interaction of those electrons with the SAW is realized. The Green's function method is used to calculate the SAW gain as a function of the electron concentration in epigraphene and the external dc electric field strength. It is shown that the substrate-induced band gap in the electronic spectrum of epigraphene leads to a significant (at least an order of magnitude) increase in the SAW gain as compared to the case of gapless graphene. In addition, the opening of the band gap results in a non-monotonic dependence of the SAW gain on the electron concentration, controlled by the gate voltage applied to the graphene sample. This dependence is characterized by the presence of a distinct maximum at a certain value of electron concentration (of about 2 × 10 12 cm−2 for typical values of the other parameters involved), which distinguishes it from the monotonic concentration dependence of the SAW gain in gapless graphene. [ABSTRACT FROM AUTHOR]

Emergent electronic phenomena, from superconductivity to ferroelectricity, magnetism, and correlated many-body band gaps, have been observed in domains created by stacking and twisting atomic layers of Van der Waals materials. In graphene, emergent properties have been observed in ABC stacking domains obtained by exfoliation followed by expert mechanical twisting and alignment with the desired orientation, a process very challenging and nonscalable. Here, conductive atomic force microscopy shows in untwisted epitaxial graphene grown on SiC the surprising presence of striped domains with dissimilar conductance, a contrast that demonstrates the presence of ABA and ABC domains since it matches exactly the conductivity difference observed in ABA/ABC domains in twisted exfoliated graphene and calculated by density functional theory. The size and geometry of the stacking domains depend on the interplay between strain, solitons crossing, and shape of the three-layer regions. Interestingly, we demonstrate the growth of three-layer regions in which the ABA/ABC stacking domains self-organize in stable stripes of a few tens of nanometers. The growth-controlled production of isolated and stripe-shaped ABA/ABC domains open the path to fabricate quantum devices on these domains. These findings on self-assembly formation of ABA/ABC epitaxial graphene stripes on SiC without the need of time-consuming and nonscalable graphene exfoliation, alignment, and twisting provide different potential applications of graphene in electronic devices. [ABSTRACT FROM AUTHOR]

In this study, we explore the substrate-mediated control of self-assembly behavior in diboron molecules (C12H8B2O4, B2Cat2) using scanning tunneling microscopy (STM). The structural transformation of B2Cat2 molecules from one-dimensional (1D) molecular chains to two-dimensional (2D) molecular arrays was achieved by changing the substrate from Au(111) to bilayer graphene (BLG), highlighting the key role of substrate interactions in determining the assembly structure. Notably, the B-B bond in the molecular arrays on BLG is distinctly pronounced, reflecting a more refined molecular resolution with distinct electronic states than that on Au(111). Density functional theory (DFT) calculations confirm the weak interaction between B2Cat2 molecules and the BLG substrate, which facilitates the formation of 2D molecular arrays on BLG. This work demonstrates how controlling substrate properties enables the formation of 1D chains and 2D arrays, providing valuable insights for the design of next-generation molecular electronics and catalysis systems. [ABSTRACT FROM AUTHOR]

Nickel nanoparticles (Ni NPs) combined with carbon nanomaterials are of significant interest due to their wide range of applications, including catalysis, hydrogen storage, and sensor technologies. However, it is challenging to develop an efficient process to produce small and stable Ni NPs ideal for functionalizing graphene or substrates with complex geometries. For this purpose, a rapid, simple, and cost‐effective method is presented for synthesizing uniformly small Ni NPs. The process involves cooling aqueous solutions of Ni(OAc)2 and cetyltrimethylammonium bromide (CTAB) to ≈1 °C, followed by the rapid addition of NaBH4. Crucial parameters, such as temperature and stirring rate, are precisely controlled to ensure uniform particle growth, with the reaction completing in just a few minutes. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) characterizations reveal spherical NPs with an average diameter of ≈11 nm and a narrow size distribution. Additionally, epitaxial graphene (EG) samples are functionalized with the synthesized NPs and their arrangement on the surface and their stability upon thermal annealing are investigated. X‐ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) measurements demonstrate the degradation of CTAB, along with the recovery of Ni(0) under mild conditions (below 350 °C), with the NPs maintaining structural stability up to approximately 550 °C. [ABSTRACT FROM AUTHOR]

Here, we report the selective detection of biotinylated interleukin-6 receptor (IL-6R) protein using both chemical vapor deposition (CVD) and epitaxial graphene (EG) based electrochemical sensors and their reusability. Detection was based on the principle of avidin-biotin technology, which was widely used in different types of sensor technology. Following the characterization of graphene, the CVD and EG on SiC were fabricated with gold nanoparticles using our recently developed technique. The CVD graphene-based device was made by transferring the CVD graphene onto an interdigitated array electrode (IDA). In contrast, the EG-based device was made by photolithography by fabricating interdigital electrodes on EG on SiC. The detection of IL-6R was monitored by real-time two-terminal current measurements at fixed voltages, while the IL-6R protein was injected into avidin-immobilized graphene-based devices. Drops of the current (Ids) upon injection of as low as 50 pg/ml of IL-6R solution confirm the detection of IL-6R with ultra-high sensitivity. The specificity of the device was confirmed by a chicken egg white solution in PBS, which contains a variety of biomolecules. The EG on a SiC-based device can also be used to detect biomolecules with high sensitivity. The EG on the SiC-based device was found to be reusable after the physical cleaning procedure. The present study is expected to be exploited in the development of reusable ultra-sensitive point-of-care biosensors.

The direct epitaxial growth of graphene on semi‐insulating SiC presents significant potential for a variety of technologically important applications, including next‐generation electronics, photonics, and quantum metrology. However, this approach also poses a competitive disadvantage in terms of quality and cost, primarily due to the uncontrollable and time‐consuming nature of the annealing process. Herein, a thermal shock annealing (TSA) method is reported that enables kinetics‐controlled epitaxial growth of graphene on SiC within 10 s, which efficiently fulfills the requirements for producing high‐quality, few‐layer, and low‐cost graphene on SiC. The epitaxial graphene (EG) grown on both β‐SiC nanoparticles (SiC@EG NPs) and centimeter‐scale α‐SiC wafer (EG/SiC) exhibits mono‐ or bi‐layer features with negligible structural defects. Moreover, the findings indicate that the TSA method can efficiently mitigate the persistent issue of step bunching conundrum and improve the flatness of EG/SiC. As an application demonstration, the significant enhancement of surface‐enhanced infrared absorption (SEIRA) by SiC@EG NPs is exhibited. The graphene plasmon arising on SiC@EG NPs enables SEIRA detection sensitivity of up to a monolayer of p‐nitrobenzenethiol (p‐NTP). Consequently, the precise regulation and comprehensive comprehension of TSA afford an exceedingly desirable approach to produce cost‐effective, high‐quality EG growth on SiC for diverse emerging application scenarios. [ABSTRACT FROM AUTHOR]

This paper presents a dataset offering profound insights into the formation and physical properties of two-dimensional (2D) noble metals under various configurations, with a primary focus on their role as catalysts for the hydrogen evolution reaction (HER). These data are of significant value to catalysis researchers, materials scientists, and computational chemists, providing them with a detailed understanding of 2D noble metals' behavior as catalysts and enabling advancements in their respective studies. The dataset, thoughtfully structured and meticulously documented, comprises five primary sections, each housing distinct content and analyses. It offers a comprehensive view of the substrate-mediated stabilization and physical properties of 2D noble metals, including silver (Ag), gold (Au), iridium (Ir), osmium (Os), palladium (Pd), platinum (Pt), rhodium (Rh), and ruthenium (Ru). The substrates utilized include bare Si-face 4H-SiC, buffer layer (BuL), and monolayer epitaxial graphene (MEG). The data collection process involves the use of the SIESTA code for density functional theory (DFT) calculations. The vdW-BH functional is consistently applied in conjunction with a double-ζ polarized (DZP) basis set, known for its reliability in capturing nuanced interactions with noble metals. Parameters such as an energy shift of 200 meV and a force tolerance of 0.02 eV/Å are meticulously configured for accurate results. In-depth structural information, including optimized structures in top and side views and Cartesian coordinates for various substrate-metal configurations, is a central component of the dataset. These structural details are pivotal for comprehending the physical properties of 2D noble metals. Furthermore, the dataset encompasses results from charge density difference (CDD) analyses, including cube files, planar-averaged CDD curves, and 3D CDD maps. These analyses provide essential data for understanding the electronic properties of these materials. The dataset also includes outcomes from charge population analyses utilizing Hirshfeld and Voronoi schemes. These analyses offer insights into structural parameters, Hirshfeld charge magnitudes on 2D metal layers, and various energy-related metrics, further enhancing the dataset's richness. In addition to structural data, the dataset presents atomic structures in top and side views of free-standing and substrate-supported 2D noble metals after hydrogen adsorption, along with corresponding Cartesian coordinates. Gibbs free energy (ΔGH*) data for hydrogen adsorption on both free-standing and substrate-supported 2D noble metals contribute to the dataset's depth. This meticulously curated dataset not only serves as a valuable resource for researchers exploring the properties and behaviors of 2D noble metals but also holds significant reuse potential. Researchers can employ this dataset to validate their computational methods and models in catalysis research, enhancing the quality and reliability of their simulations. Furthermore, it serves as a possible educational tool, fostering hands-on learning for students and emerging researchers in the field of computational materials science and catalysis, thereby promoting methodological consistency within the scientific community.

Finite element methods based numerical simulations and experiments are conducted to systematically investigate the influence of temperature distribution and working gas flow to the growth of epitaxial graphene on SiC. It demonstrates the key role of temperature uniformity on the sample, which determines the coverage rate and quality of the grown graphene, as well as Ar flow for regulating the silicon partial vapour pressure. An optimized crucible was designed accordingly, which is successfully applied to prepare high coverage epitaxial graphene on the (0001) facet of SiC with great uniformity. Those insights might benefit the large-area high-quality epi-graphene growth for future industrial applications. [ABSTRACT FROM AUTHOR]

We report a reliable and scalable fabrication method for producing electrical contacts to two-dimensional (2D) materials based on the tri-layer resist system. We demonstrate the applicability of this method in devices fabricated on epitaxial graphene on silicon carbide (epigraphene) used as a scalable 2D material platform. For epigraphene, data on nearly 70 contacts result in median values of the one-dimensional (1D) specific contact resistances ρc ∼ 67 Ω·μm and follow the Landauer quantum limit ρc ∼ n–1/2, consistently reaching values ρc < 50 Ω·μm at high carrier densityn. As a proof of concept, we apply the same fabrication method to the transition metal dichalcogenide (TMDC) molybdenum disulfide (MoS2). Our edge contacts enable MoS2 field-effect transistor (FET) behavior with an ON/OFF ratio of >106 at room temperature (>109 at cryogenic temperatures). The fabrication route demonstrated here allows for contact metallization using thermal evaporation and also by sputtering, giving an additional flexibility when designing electrical interfaces, which is key in practical devices and when exploring the electrical properties of emerging materials. [ABSTRACT FROM AUTHOR]

The availability of accurate and reliable dry sensors for electroencephalography (EEG) is vital to enable large-scale deployment of brain–machine interfaces (BMIs). However, dry sensors invariably show poorer performance compared to the gold standard Ag/AgCl wet sensors. The loss of performance with dry sensors is even more evident when monitoring the signal from hairy and curved areas of the scalp, requiring the use of bulky and uncomfortable acicular sensors. This work demonstrates three-dimensional micropatterned sensors based on a subnanometer-thick epitaxial graphene for detecting the EEG signal from the challenging occipital region of the scalp. The occipital region, corresponding to the visual cortex of the brain, is key to the implementation of BMIs based on the common steady-state visually evoked potential paradigm. The patterned epitaxial graphene sensors show efficient on-skin contact with low impedance and can achieve comparable signal-to-noise ratios against wet sensors. Using these sensors, we have also demonstrated hands-free communication with a quadruped robot through brain activity. [ABSTRACT FROM AUTHOR]

Graphene‐based materials are among the most promising candidates for studying superconductivity arising from reduced dimensionality. Apart from doping by twisted stacking, superconductivity can also be achieved by metal‐intercalation of stacked graphene sheets, where the properties depend on the choice of the metal atoms and the number of graphene layers. Many different and even unconventional pairing mechanisms and symmetries are predicted in the literature for graphene monolayers and few‐layers. However, those theoretical predictions have yet to be verified experimentally. Here, it is shown that potassium‐intercalated epitaxial bilayer graphene is a superconductor with a critical temperature of Tc = 3.6 ± 0.1 K. By scanning‐tunneling microscopy and angle‐resolved photoelectron spectroscopy, the physical mechanisms are analyzed in great detail, using laboratory equipment. The data demonstrate that electron–phonon coupling is the driving force enabling superconductivity. Although the consideration of an s‐wave pairing symmetry is sufficient to explain the experimental data, evidence is found for the existence of multiple energy gaps. Furthermore, it is shown that low‐dimensional effects are most likely the cause of a gap ratio of 6.1 ± 0.2 that strongly exceeds the Bardeen‐Cooper‐Schrieffer (BCS) value of 3.52 for conventional superconductors. These results highlight the importance of reduced dimensionality yielding unusual superconducting properties of K‐intercalated epitaxial bilayer graphene. [ABSTRACT FROM AUTHOR]

Using first‐principles and analytical potential atomistic simulations, production of defects in epitaxial graphene (EG) on SiC upon ion irradiation for ion types and energies accessible in helium‐ion microscope is studied. Graphene‐SiC systems consisting of the buffer (zero) graphene layer and SiC substrate, as well as one (monolayer) and two (bilayer) additional graphene layers, are focused on. The probabilities for single, double, and more complex vacancies to appear upon impacts of energetic ions in each graphene layer as functions of He‐ and Ne‐ion energies are calculated and the data are compared with those obtained for free‐standing graphene. The results indicate that the role of the substrate is minimal for He‐ion irradiation with energies above 5 keV, which can be associated with a low sputtering yield from this system upon ion irradiation, as compared with the common Si/SiO2 substrate. In contrast, SiC substrate has a significant effect on defect production upon Ne‐ion irradiation. The results can serve as a guide to the experiments on ion irradiation of EG to choose the optimum ion beam parameters for defect‐mediated engineering of such systems, for example, for creating nucleation centers to grow other 2D materials, such as h‐BN, on top of the irradiated EG. [ABSTRACT FROM AUTHOR]

We describe the annealing, geometry, storage, and lifespan of graphite crucibles for the growth of epitaxial graphene on SiC. We monitor residual gas content during the annealing of the as-manufactured graphite crucible before the growth of the first graphene samples. The high-temperature evolution of carbon monoxide points towards the reaction of solid carbon and residual water. Therefore, we propose a procedure consisting of four annealing cycles to eliminate this reaction. The residual gas evolution after long-term storage of well-baked crucibles in the air shows a similar increase in water and carbon monoxide as that in unbaked crucibles. Hence, we propose the crucible storage in argon ambient. Further, we discuss the role of the crucible shape on graphene quality. Namely, we compare the cylindrical semi-closed crucible to the flat opened crucibles. The flow-aided gas exchange in the opened crucible is more beneficial for graphene growth than the diffusion-driven gas exchange in the semi-closed cylindrical crucibles. The flow-aided gas exchange leads to more efficient removal of outgassed residual contaminants, thus outperforming the advantage of increased silicon vapor pressure in the semi-closed cylindrical crucible. We also study the graphite crucible lifespan, showing that the aged crucible leads to the enhanced inhomogeneous strain in graphene. • We show the role of graphite crucible on the growth of epitaxial graphene on SiC. • Annealing of manufactured crucibles is described, including in-situ chemistry. • Cylindrical semi-closed, and flat opened crucible designs are compared. • The crucible storage recommendations are provided. • The crucible aging and graphene quality degradation is described. [ABSTRACT FROM AUTHOR]

The intercalation of graphene with suitable atomic species is one of the most frequently applied methods to decouple the graphene layer from the substrate in order to establish the classical electronic properties of graphene. In this context, we studied the bismuth (Bi) intercalation of the $\left(6\sqrt{3}\times6\sqrt{3}\right)R30^\circ$ reconstructed so-called ‘zeroth layer graphene’ on SiC $\left(0001\right)$ . As reported earlier by Sohn et al (2021 J. Korean Phys. Soc. 78 157) two phases are formed depending on the amount of intercalated Bi, which in turn is controlled by the annealing temperature: The α phase, showing a $(1\times1)$ periodicity with respect to the substrate, and, at higher temperatures, the $(\sqrt{3}\times\sqrt{3})$ reconstructed β phase. We characterise both phases and the transformation from the α to the β phase by photoelectron spectroscopy, normal incidence x-ray standing waves, electron diffraction and electron microscopy. We clearly see an almost complete intercalation of the graphene layers in both phases, with strong (covalent) interaction between the topmost Si atoms of the substrate and the Bi intercalant, but only weak (van der Waals) interaction between Bi and the graphene layer. The n-doping of the graphene found for the α phase decreases continuously during the phase transformation, in agreement with a reduced density of the Bi intercalating layer. Missing core level shifts of the surface species as well as the normal incidence x-ray standing waves results indicate that all surface Si atoms remain saturated during the transition and no dangling bonds are formed. Low energy electron microscopy and diffraction reveal the coexistance of both phases after annealing to intermediate temperatures and allow a quantitative analysis of island sizes and numbers.

Abstract Graphene‐based materials are among the most promising candidates for studying superconductivity arising from reduced dimensionality. Apart from doping by twisted stacking, superconductivity can also be achieved by metal‐intercalation of stacked graphene sheets, where the properties depend on the choice of the metal atoms and the number of graphene layers. Many different and even unconventional pairing mechanisms and symmetries are predicted in the literature for graphene monolayers and few‐layers. However, those theoretical predictions have yet to be verified experimentally. Here, it is shown that potassium‐intercalated epitaxial bilayer graphene is a superconductor with a critical temperature of Tc = 3.6 ± 0.1 K. By scanning‐tunneling microscopy and angle‐resolved photoelectron spectroscopy, the physical mechanisms are analyzed in great detail, using laboratory equipment. The data demonstrate that electron–phonon coupling is the driving force enabling superconductivity. Although the consideration of an s‐wave pairing symmetry is sufficient to explain the experimental data, evidence is found for the existence of multiple energy gaps. Furthermore, it is shown that low‐dimensional effects are most likely the cause of a gap ratio of 6.1 ± 0.2 that strongly exceeds the Bardeen‐Cooper‐Schrieffer (BCS) value of 3.52 for conventional superconductors. These results highlight the importance of reduced dimensionality yielding unusual superconducting properties of K‐intercalated epitaxial bilayer graphene.

Silicon carbide (SiC) is one of the hardest known materials. Its exceptional mechanical properties combined with its high thermal conductivity make it a very attractive material for a variety of technological applications. Recently, it is discovered that two‐layer epitaxial graphene films on SiC can undergo a pressure activated phase transition into a sp3 diamene structure at room temperature. Here, it is shown that epitaxial graphene films grown on SiC can increase the hardness of SiC up to 100% at low loads (up to 900 µN), and up to 30% at high loads (10 mN). By using a Berkovich diamond indenter and nanoindentation experiments, it is demonstrated that the 30% increase in hardness is present even for indentations depths of 175 nm, almost three hundred times larger than the graphene film thickness. The experiments also show that the yield point of SiC increases up to 77% when the SiC surface is coated with epitaxial graphene. These improved mechanical properties are explained with the formation of diamene under the indenter's pressure. [ABSTRACT FROM AUTHOR]

Condensation of moisture on the epitaxial graphene on 6H-SiC was observed below room temperature despite continuous nitrogen flow on the graphene surface. Raman peaks associated with ice were observed. A combination of peaks in the frequency range of 500–750 cm−1, along with a broad peak centered at ~1327 cm−1, were also observed and were assigned to airborne contaminants. The latter is more important since its position is in the frequency range where the defect-associated D band of graphene appears. This band can be easily misunderstood to be the D band of graphene, particularly when the Raman spectrum is taken below room temperature. This peak was even observed after the sample was brought back to room temperature due to water stains. This work highlights the importance of careful Raman investigation of graphene below room temperature and its proper insulation against moisture. [ABSTRACT FROM AUTHOR]

Graphene epitaxy on the Si face of a SiC wafer offers monolayer graphene with unique crystal orientation at the wafer-scale. However, due to carrier scattering near vicinal steps and excess bilayer stripes, the size of electrically uniform domains is limited to the width of the terraces extending up to a few microns. Nevertheless, the origin of carrier scattering at the SiC vicinal steps has not been clarified so far. A layer-resolved graphene transfer (LRGT) technique enables exfoliation of the epitaxial graphene formed on SiC wafers and transfer to flat Si wafers, which prepares crystallographically single-crystalline monolayer graphene. Because the LRGT flattens the deformed graphene at the terrace edges and permits an access to the graphene formed at the side wall of vicinal steps, components that affect the mobility of graphene formed near the vicinal steps of SiC could be individually investigated. Here, we reveal that the graphene formed at the side walls of step edges is pristine, and scattering near the steps is mainly attributed by the deformation of graphene at step edges of vicinalized SiC while partially from stripes of bilayer graphene. This study suggests that the two-step LRGT can prepare electrically single-domain graphene at the wafer-scale by removing the major possible sources of electrical degradation.

Electron emission from quasi-freestanding bilayer epitaxial graphene (QFEG) on a silicon carbide substrate is reported, demonstrating emission currents as high as 8.5 μ A, at ∼200 °C, under 0.3 Torr vacuum. Given the significantly low turn-on temperature of these QFEG devices, ∼150°C, the electron emission is explained by phonon-assisted electron emission, where the acoustic and optical phonons of QFEG causes carrier acceleration and emission. Devices of differing dimensions and shapes are fabricated via a simple and scalable fabrication procedure and tested. Variations in device morphology increase the density of dangling bonds, which can act as electron emission sites. Devices exhibit emission enhancement at increased temperatures, attributed to greater phonon densities. Devices exhibit emission under various test conditions, and a superior design and operating methodology are identified. [ABSTRACT FROM AUTHOR]

Novel two-dimensional materials (2DMs) with balanced electrical conductivity and lithium (Li) storage capacity are desirable for next-generation rechargeable batteries as they may serve as high-performance anodes, improving output battery characteristics. Gaining an advanced understanding of the electrochemical behavior of lithium at the electrode surface and the changes in interior structure of 2DM-based electrodes caused by lithiation is a key component in the long-term process of the implementation of new electrodes into to a realistic device. Here, we showcase the advantages of bilayer-patched epitaxial graphene on 4H-SiC (0001) as a possible anode material in lithium-ion batteries. The presence of bilayer graphene patches is beneficial for the overall lithiation process because it results in enhanced quantum capacitance of the electrode and provides extra intercalation paths. By performing cyclic voltammetry and chronoamperometry measurements, we shed light on the redox behavior of lithium at the bilayer-patched epitaxial graphene electrode and find that the early-stage growth of lithium is governed by the instantaneous nucleation mechanism. The results also demonstrate the fast lithium-ion transport (~4.7–5.6 × 10−7 cm2∙s−1) to the bilayer-patched epitaxial graphene electrode. Raman measurements complemented by in-depth statistical analysis and density functional theory calculations enable us to comprehend the lithiation effect on the properties of bilayer-patched epitaxial graphene and ascribe the lithium intercalation-induced Raman G peak splitting to the disparity between graphene layers. The current results are helpful for further advancement of the design of graphene-based electrodes with targeted performance. [ABSTRACT FROM AUTHOR]

Layered molybdenum disulphide (MoS2) crystals in combination with graphene create the opportunity for the development of heterostructures with tailored surface and structural properties for energy storage applications. Herein, 2D heterostructures are developed by growing MoS2 on epitaxial and self‐standing nanoporous graphene (NPG) using chemical vapor deposition (CVD). The effect of substrate as well as different CVD growth parameters such as temperature, amount of sulfur and MoO3 precursors, and argon flow on the growth of MoS2 is systematically investigated. Interestingly, various structures of MoS2 such as monolayer triangular islands, spirals, standing sheets, and irregular stacked multilayered MoS2 are successfully developed. The growth mechanism is proposed using different advanced characterization techniques. The formation of a continuous wetting layer with grain boundaries over the surface prior to formation of any other structures is detected. As a proof of principle, MoS2/NPG is employed for the first time as anode material in potassium ion battery. The electrode delivers a specific capacity of 389 mAh g−1 with over 98% stability after 200 cycles. The porous structures clearly facilitate the ion transport which is beneficial for the ion battery. These encouraging results open new opportunities to develop hierarchical heterostructures of 2D‐materials for next‐generation energy storage technologies. [ABSTRACT FROM AUTHOR]

Magnesium intercalated "quasi‐freestanding" bilayer graphene on 6H‐SiC(0001) (Mg‐QFSBLG) has many favorable properties (e.g., highly n‐type doped, relatively stable in ambient conditions). However, intercalation of Mg underneath monolayer graphene is challenging, requiring multiple intercalation steps. Here, these challenges are overcome and the rate of Mg intercalation is significantly increased by laser patterning (ablating) the graphene to form micron‐sized discontinuities. Low energy electron diffraction is then used to verify Mg‐intercalation and conversion to Mg‐QFSBLG, and X‐ray photoelectron spectroscopy to determine the Mg intercalation rate for patterned and non‐patterned samples. By modeling Mg intercalation with the Verhulst equation, it is found that the intercalation rate increase for the patterned sample is 4.5 ± 1.7. Since the edge length of the patterned sample is ≈5.2 times that of the non‐patterned sample, the model implies that the increased intercalation rate is proportional to the increase in edge length. Moreover, Mg intercalation likely begins at graphene discontinuities in pristine samples (not step edges or flat terraces), where the 2D‐like crystal growth of Mg‐silicide proceeds. The laser patterning technique may enable the rapid intercalation of other atomic or molecular species, thereby expanding upon the library of intercalants used to modify the characteristics of graphene, or other 2D materials and heterostructures. [ABSTRACT FROM AUTHOR]

Condensation of moisture on the epitaxial graphene on 6H-SiC was observed below room temperature despite continuous nitrogen flow on the graphene surface. Raman peaks associated with ice were observed. A combination of peaks in the frequency range of 500–750 cm−1, along with a broad peak centered at ~1327 cm−1, were also observed and were assigned to airborne contaminants. The latter is more important since its position is in the frequency range where the defect-associated D band of graphene appears. This band can be easily misunderstood to be the D band of graphene, particularly when the Raman spectrum is taken below room temperature. This peak was even observed after the sample was brought back to room temperature due to water stains. This work highlights the importance of careful Raman investigation of graphene below room temperature and its proper insulation against moisture.

The control of carrier transport by electrical, chemical, or optical Fermi level tuning is central to graphene electronics. Here, an optical pump—terahertz (THz) probe spectroscopy—is applied to investigate ultrafast sheet conductivity dynamics in various epitaxially grown graphene layers representing a large variety of carbon allotropes, including H2 intercalated films. The graphene layers display a prominent plasmonic response connected with induced THz transparency spectra on ultrashort timescale. It is generally believed that the plasmonic excitations appear due to wrinkles, and substrate terraces that bring about natural confinement potentials. It is shown that these potentials act within micrometer‐sized domains with essentially isotropic character. The measured ultrafast dynamics are entirely controlled by the quasi‐Fermi level of laser‐excited carriers through their temperature. The photocarriers undergo a disorder‐enabled super‐collision cooling process with an initial picosecond transfer of the optically deposited heat to the lattice followed by a sub‐nanosecond relaxation governed by the lattice cooling. The transient spectra is described by a two‐temperature Drude‐Lorentz model revealing the ultrafast evolution of the carrier temperature and chemical potential and providing crucial material parameters such as Fermi energy, carrier mobility, carrier confinement length, and disorder mean free path. [ABSTRACT FROM AUTHOR]

Due to weak light-matter interaction, standard chemical vapor deposition (CVD)/exfoliated single-layer graphene-based photodetectors show low photoresponsivity (on the order of mA/W). However, epitaxial graphene (EG) offers a more viable approach for obtaining devices with good photoresponsivity. EG on 4H–SiC also hosts an interfacial buffer layer (IBL), which is the source of electron carriers applicable to quantum optoelectronic devices. We utilize these properties to demonstrate a gate-free, planar EG/4H–SiC-based device that enables us to observe the positive photoresponse for (405–532) nm and negative photoresponse for (632–980) nm laser excitation. The broadband binary photoresponse mainly originates from the energy band alignment of the IBL/EG interface and the highly sensitive work function of the EG. We find that the photoresponsivity of the device is > 10 A/W under 405 nm of power density 7.96 mW/cm2 at 1 V applied bias, which is three orders of magnitude greater than the obtained values of CVD/exfoliated graphene and higher than the required value for practical applications. These results path the way for selective light-triggered logic devices based on EG and can open a new window for broadband photodetection. [Display omitted] [ABSTRACT FROM AUTHOR]

Metal-Graphene-Metal (MGM) UV photodetectors have been fabricated by using an Epitaxial Graphene (EG)/SiC junction on a semi-insulating 4H–SiC. The migration of carriers in the EG/SiC photodetectors under 365 nm light irradiation is clarified by introducing a top gate electrode. Besides, it is found that the response performance of EG/SiC photodetectors is affected by the geometric parameters of the graphene channel. When the graphene channel of the detector is reduced from multi-layer to single-layer and its aspect ratio (AR) is increased from 15 to 100, the detector shows a faster response under illumination that its rise time (t r) is reduced from about 20 s to 5 m s, and its decay time (t d) reduced from far more than 20 s to 15 m s at a bias of 10 V. At the same time, the responsivity of the detector has been increased to 189.7 mA/V, its External Quantum Efficiency (EQE) has been increased to 66.6 % and its response signal becomes more stable. After systematic analysis, the geometric parameters of the graphene channel are proved to determine the number of carriers in it, the correlation between the response performance of EG/SiC photodetectors and the number of carriers in graphene is found out. [Display omitted] [ABSTRACT FROM AUTHOR]

Understanding the interaction between noble metals (NMs) and epitaxial graphene is essential for the design and fabrication of novel devices. Within this framework, a combined experimental and theoretical investigation of the effect of vapor‐deposited NM (silver [Ag] and gold [Au]) nanostructures on the vibrational and electronic properties of monolayer epitaxial graphene (MLG) on 4H‐SiC is presented. Large sets of Raman scattering data are analyzed using supervised classification and statistical methods. This analysis enables identification of the specific Raman fingerprints of Au‐ and Ag‐decorated MLG originating from different dispersion interactions and charge transfer at the metal nanostructure/MLG interface. It is found that Raman scattering spectra of Au‐decorated MLG feature a set of allowed phonon modes similar to those in pristine MLG, whereas the stronger Ag physisorption triggers an activation of defect‐related phonon modes and electron doping of MLG. A principal component analysis (PCA) and linear discriminant analysis (LDA) are leveraged to highlight the features in phonon dispersion of MLG that emanate from the NM deposition process and to robustly classify large‐scale Raman spectra of metal‐decorated graphene. The present results can be advantageous for designing highly selective sensor arrays on MLG patches decorated with different metals. [ABSTRACT FROM AUTHOR]

Defects in graphene are important nanoscale pathways for metal atoms to enter the interface between epitaxial graphene and SiC in order to form stable ultrathin metal layers with new exotic physical properties. However, the atomic-scale details of defects that mainly govern the intercalation process remain modest. In this work, we present the first atomic investigation of point defects generated by oxygen plasma treatment on epitaxial graphene grown on SiC using low-temperature scanning tunneling microscopy, corroborated by density functional theory calculations. We found a broad spectrum of point defects that varies in size, shape, and symmetry and is dominated by triangular species. Tunneling spectroscopy identified defect-induced states in the vicinity of the Fermi level that significantly perturb the graphene electronic properties at the defect site. Based on the well-defined defect symmetry, we simulated the local density of states of the triangular defects and their corresponding scanning tunneling microscopy images which further helped us to identify the exact atomic configurations of monovacancy defects. The combination of atomic-scale scanning tunneling microscopy experiments and reliable density functional theory simulations provides ultimate microscopic details and opens a new way to identify the atomic configurations of defects in oxygen plasma-treated graphene. Our work might shed light on precise control of defect engineering in graphene for metal intercalation by controlling the defect types based on a deep understanding of each configuration. [Display omitted] [ABSTRACT FROM AUTHOR]

We report the direct mapping of photo-transport properties of relativistic carriers generated on terrace-surface and terrace-edge structures of epitaxial graphene grown on silicon carbide. In this method, a conductive probe made a direct contact with epitaxial graphene and scanned the surface, allowing us to map the topography, current, and noise of graphene with nanoscale resolutions via a scanning noise microscopy. The maps were further analyzed by a two-dimensional network model to obtain the sheet-conductance (S □) and noise-source density (n eff) distributions of epitaxial graphene. The topography image showed the formation of terraces, which could be attributed to the different decomposition rate of silicon atoms during the graphene growth. The terraces of graphene exhibited uniform S □ , being separated by one-dimensional terrace-edges. Interestingly, terrace-edges exhibited a rather large n eff with a power-law relationship of S □ ∝ n eff −0.5, indicating a typical hopping conduction. However, in terrace-surfaces, sheet-conductance was nearly independent on n eff , which was attributed to the relativistic nature of charge carriers unaffected by charge-trapping potential. Notably, under illumination, we observed the relativistic behavior of photocarriers in overall graphene terraces, presumably because photocarriers were generated through charge-transfer complexes formation at epitaxial graphene/substrate interface without the participation of noise-sources. Interestingly, we observed nearly homogeneous photoconductance and n eff , which could be possibly due to the merger of one-dimensional edge-states into two-dimensional surface-states. The mapping of photoconductance and photo-traps provides valuable insights into the generation of relativistic photocarriers in epitaxial graphene. [Display omitted] • A conductive nanoprobe is utilized to map carrier transports of epitaxial graphene. • Epitaxial graphene grown on SiC-substrate has terrace structures, separated by edges. • Sheet-conductance and noise-source density maps show 2D surface and 1D edge states. • Carriers show relativistic and hopping transports in surface and edge, respectively. • In light, carriers in edge exhibit transition from hopping to relativistic transport. [ABSTRACT FROM AUTHOR]

A new type of graphene-based quantum Hall standards is tested for electrical quantum metrology applications at alternating current (ac) and direct current (dc). The devices are functionalized with Cr(CO)3 to control the charge carrier density and have branched Hall contacts based on NbTiN superconducting material. The work is an in-depth study about the characteristic capacitances and related losses in the ac regime of the devices and about their performance during precision resistance measurements at dc and ac. [ABSTRACT FROM AUTHOR]

A hybrid nanomaterial, a single layer of C60 molecules sandwiched between single-layer graphene and a metal substrate, is considered. Formulas for the specific energy of interaction of C60 fullerene molecules with single-layer graphene and a thick substrate are derived using the Lennard–Jones potential. The specific adhesion energy of graphene and the equilibrium parameters of the structure under consideration are calculated. The theoretical results obtained in the study are consistent with available experimental data. [ABSTRACT FROM AUTHOR]

Material growth on a dangling-bond-free interface such as graphene is a challenging technological task, which usually requires additional surface pre-treatment steps (functionalization, seed layer formation) to provide enough reactive sites. Being one of the most promising and adaptable graphene-family materials, epitaxial graphene on SiC, due to its internal features (substrate-induced n-doping, compressive strain, terrace-stepped morphology, bilayer graphene nano-inclusions), may provide pre-conditions for the enhanced binding affinity of environmental species, precursor molecules, and metal atoms on the topmost graphene layer. It makes it possible to use untreated pristine epitaxial graphene as a versatile platform for the deposition of metals and insulators. This mini-review encompasses relevant aspects of magnetron sputtering and electrodeposition of selected metals (Au, Ag, Pb, Hg, Cu, Li) and atomic layer deposition of insulating Al2O3 layers on epitaxial graphene on 4H-SiC, focusing on understanding growth mechanisms. Special deliberation has been given to the effect of the deposited materials on the epitaxial graphene quality. The generalization of the experimental and theoretical results presented here is hopefully an important step towards new electronic devices (chemiresistors, Schottky diodes, field-effect transistors) for environmental sensing, nano-plasmonics, and biomedical applications. [ABSTRACT FROM AUTHOR]

The friction coefficients of single-layer epitaxial graphene grown on the Si-terminated and C-terminated faces of Silicon Carbide (SiC) substrate were measured under ambient conditions using Friction Force Microscope (FFM). The lateral friction force measurements acquired in the applied normal force range between 4.0 and 16.0 nN showed that the friction coefficient of graphene on the C-terminated face of SiC is about two times smaller than the one grown on its Si-terminated face. The lateral friction was found to be decreased as the average of root mean square roughness increases suggesting the observed difference in the friction coefficients cannot be related to the roughness of the graphene layers. DFT calculations demonstrated that the altered periodicity of charge distribution on graphene due to the specific interactions with two distinct polar faces of SiC substrate might explain the observed difference in the friction coefficients. [Display omitted] [ABSTRACT FROM AUTHOR]

Iron–platinum (Fe–Pt) compounds are well known for their interesting magnetic and electrocatalytic properties. However, iron segregation and iron oxides formation under oxidative conditions may influence the characteristics of Fe–Pt systems. Several approaches are used to protect the Fe–Pt compounds from oxidation, the most promising of which involves covering the material with a protective graphitic layer. By performing model‐type ultrahigh vacuum (UHV) studies, it is shown that a layer of epitaxial graphene (Gr) grown on a [111]‐oriented single‐crystal platinum substrate with thermally dissolved iron (Fe–Pt(111) surface alloy) effectively blocks iron segregation and iron oxides formation under oxidative conditions, while still allowing for the adsorption of oxygen atoms underneath the carbon layer. The oxidation is monitored in real time and at the micrometer scale using low energy electron microscopy (LEEM) and local diffraction (μLEED). Notably, a similar result is obtained for a poorly ordered Gr‐like carbon layer grown directly on a Fe–Pt(111) substrate. The findings are rationalized in terms of a locally lowered partial oxygen pressure and inhibited iron oxide growth in a confined space between the carbon layer and the metal support. [ABSTRACT FROM AUTHOR]

The aim of this Special Issue is to provide a scientific platform for recognized experts in the field of epitaxial graphene on SiC to present their recent studies towards a deeper comprehension of growth mechanisms, property engineering and device processing. This Special Issue gives readers the possibility to gain new insights into the nature of buffer layer formation, control of electronic properties of graphene and usage of epitaxial graphene as a substrate for deposition of different substances, including metals and insulators. We believe that the papers published within the current Special Issue develop cumulative knowledge on matters related to device-quality epaxial graphene on SiC, bringing this material closer to realistic practical applications. [ABSTRACT FROM AUTHOR]

The crystallinity of graphene flakes and their orientation with respect to the Cu(111) substrate are investigated by means of low‐energy electron microscopy (LEEM). The interplay between graphene and the metal substrate during chemical vapor deposition (CVD) introduces a restructuring of the metal surface into surface facets, which undergo a step bunching process during the growth of additional layers. Moreover, the surface facets introduce strain between the successively nucleated layers that follow the topography in a carpet‐like fashion. The strain leads to dislocations in between domains of relaxed Bernal stacking. After the transfer onto an epitaxial buffer layer, the imprinted rippled structure of even monolayer graphene as well as the stacking dislocations are preserved. A similar behavior might also be expected for other CVD grown 2D materials such as hexagonal boron nitride or transition metal dichalcogenides, where stacking relations after transfer on a target substrate or heterostructure could become important in future experiments. [ABSTRACT FROM AUTHOR]

GaN is proven as the most important modern semiconductor with many potential applications. Although GaN growth is matured enough, unfortunately, it is still very difficult to obtain this material with the same quality as the Si crystal, either in heteroepitaxy or homoepitaxy. GaN has recently been proposed to grow on two-dimensional (2D) layered material. This paper reports the van der Waals epitaxy (vdWE) and orientation control of GaN on epitaxial graphene (EG) by means of RF-MBE. A single crystalline GaN with a smooth surface on the EG is successfully obtained. It is found that the incorporation of an AlN intermediate layer on the EG surface significantly improves the GaN on EG. The AlN/EG structure can control the a-axis orientation of the nitride growth layer and improve the epitaxial layer quality. The GaN layers fabricated on the AlN/EG structure are also found to be free from interfacial stress. The quality of the GaN layer obtained on the AlN/EG structure is comparable to that of the GaN layer on the sapphire substrate. This research paves the way for the expansion of high-quality GaN on EG.

A graphene quantized Hall resistance (QHR) device fabricated at the National Institute of Standards and Technology, Gaithersburg, MD, USA, was measured alongside a GaAs QHR device fabricated by the National Research Council of Canada, Ottawa, ON, Canada, by comparing them to a 1- $\text{k}\Omega $ standard resistor using a cryogenic current comparator. The two devices were mounted in a custom developed dual probe that was then assessed for its viability as a suitable apparatus for precision measurements. The charge carrier density of the graphene device exhibited controllable tunability when annealed after Cr(CO)3 functionalization. These initial measurement results suggest that making resistance comparisons is possible with a single- probe wired for two types of quantum standards—GaAs, the established material, and graphene - the newer material that may promote the development of more user-friendly equipment. [ABSTRACT FROM AUTHOR]

In this work a comprehensive study is presented for the analysis of epitaxial graphene layers using Raman spectroscopy. A wide range of graphene types is covered, from defective/polycrystalline single layer graphene to multilayer graphene with low defect density. On this basis the influence of strain type, Fermi level and number of layers on the Raman spectrum of graphene is investigated. A detailed view on the 2 D / G dispersion and the respective slopes of uniaxially and biaxially strained graphene is given and its implications on the asymmetry of the G peak analyzed. A linear dependency of the phonon mode asymmetry on uniaxial strain is presented in addition to the known Fermi level dependence. Additional impacts on the asymmetry are found to be arising from the defect density and transfer doping of adsorbates. The discovered transfer doping mechanism is contrary to pure phonon excitation through excitons and exhibits increasing asymmetry with increasing Fermi level. A new characteristic correlation between the 2 D mode line width and the inverse I(D)/I(G) ratio is introduced that allows the determination of the strain type and layer number and explains the difference between Raman line widths of monolayer graphene on different substrates. Image 1 • Analysis of epitaxial graphene by Raman spectroscopy regarding the parameters strain, Fermi level and layer number. • 2D/G phonon dispersion of biaxially strained graphene is proven to exhibit a slope of 2.2. • Asymmetry of the G mode exhibits contributions from strain and Fermi level (e.g. transfer doping or adsorbate-induced). • The correlation of the 2 D line width with the I(G)/I(D) ratio is found as a new characteristic for strain type determination. [ABSTRACT FROM AUTHOR]

Nanodevices based on hybrid graphene–superconductor structures have recently attracted much attention owing to both fundamental and application aspects. However, atomic‐level investigations of proximity‐induced superconductivity in graphene, especially on technologically relevant substrates remain rare. Here, the atomic‐scale study of electronic properties and the superconducting proximity effect in hydrogen‐intercalated single‐layer graphene on SiC decorated with epitaxial lead (Pb) islands is reported. The graphene layer is thoroughly characterized by means of Landau level spectroscopy which confirms its quasi‐free‐standing nature. Scanning tunneling spectroscopy performed at 1.8 K on the graphene layer in the vicinity of Pb islands shows a reduced superconducting gap of Δgr=0.20(1) meV, which points to a graphene/superconductor junction of moderate transparency. The variations of the proximity‐induced superconducting gap on graphene are measured as function of spatial position as well as of magnetic field strength. Spatially resolved measurements yield a coherence length of about 175 nm in the graphene monolayer. The study provides a foundation for realization of graphene–superconductor heterostructures on large‐scale SiC(0001) wafers suitable for future technological applications. [ABSTRACT FROM AUTHOR]

The nucleation and growth mechanism of aluminum oxide (Al 2 O 3) in the early stages of atomic layer deposition (ALD) on monolayer epitaxial graphene (EG) on silicon carbide (4H–SiC) has been investigated by atomic force microscopy (AFM), conductive-atomic force microscopy (C-AFM) and Raman spectroscopy. Differently than for other types of graphene, a large and uniform density of nucleation sites was observed in the case of EG and ascribed to the presence of the buffer layer at EG/SiC interface. The deposition process was characterized by Al 2 O 3 island growth in the very early stages, followed by the formation of a continuous Al 2 O 3 film (∼2.4 nm thick) after only 40 ALD cycles due to the islands coalescence, and subsequent layer-by-layer growth. The electrical insulating properties of the deposited ultrathin Al 2 O 3 films were demonstrated by nanoscale current mapping with C-AFM. Raman spectroscopy analyses showed low impact of the ALD process on the defect's density of EG. The EG strain was also almost unaffected by the deposition in the regime of island growth and coalescence, whereas a significant increase was observed after the formation of a compact Al 2 O 3 film. The obtained results can have important implications for device applications of epitaxial graphene requiring ultra-thin high-k insulators. Image 1 [ABSTRACT FROM AUTHOR]

The functionalization of graphene is a well-established route for modulating its optoelectronic properties for a wide range of applications. Here, we studied, using photoemission spectroscopies and synchrotron radiation, the band structure upon evaporation of a p-type dopant tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) molecules and determined the work function (WF) shift over a large area of epitaxial graphene grown on a 4H-SiC (0001) silicon carbide substrate. This system exhibits peculiar nanostructures composed of mono and multilayers, notably at the step edges where the electronic properties differ from the terraces. We observed, owing to the high spatial resolution of photoemission electron microscopy (PEEM), that after the adsorption of F4-TCNQ, multilayer graphene on step edges was subjected to less charge transfer compared to the monolayer graphene on terraces, making their final WF smaller. We calculated the thermoelectric properties of this functionalized graphene system by using density functional theory and Boltzmann transport formalism within the range of the Fermi level (EF), and the carrier concentration, which was experimentally determined. We show that the Seebeck coefficient (S) on the nanofacets is 25% larger than on the monolayer terraces, and the maximum power factor (PF) is on the order of 10−2 W/K2m. This order of magnitude is comparable to the PF of commercial thermoelectric materials such as bulk bismuth telluride. [ABSTRACT FROM AUTHOR]

The electronic and transport properties of epitaxial graphene are dominated by the interactions the material makes with its surroundings. Based on the transport properties of epitaxial graphene on SiC and 3C-SiC/Si substrates reported in the literature, we emphasize that the graphene interfaces formed between the active material and its environment are of paramount importance, and how interface modifications enable the fine-tuning of the transport properties of graphene. This review provides a renewed attention on the understanding and engineering of epitaxial graphene interfaces for integrated electronics and photonics applications. [ABSTRACT FROM AUTHOR]

Graphene layers grown on the C‐face SiC exhibit quite different structural and electronic properties compared with those grown on the Si‐face SiC. Herein, the growth and structural properties of graphene on the off‐axis C‐face 3C‐SiC(1¯1¯1¯) are studied. The as‐grown 4° off‐axis 3C‐SiC(1¯1¯1¯) exhibits highly periodic steps with step height of ≈0.75 nm and terrace width of ≈50 nm. After annealing at 1800 °C under 850 mbar argon atmosphere, relatively uniform large graphene domains can be grown. The low‐energy electron microscopy (LEEM) results demonstrate that one monolayer (ML) to four‐ML graphene domains are grown over several micrometers square, which enables us to measure micro low‐energy electron diffraction (μ‐LEED) on the single graphene domain. The μ‐LEED pattern collected on the monolayer domain mainly exhibits four sets of graphene (1 × 1) spots, indicating the presence of graphene grains with different azimuthal orientations in the same graphene sheet. Raman spectra collected on the graphene domains show rather small D peaks, indicating the presence of less defects and higher crystalline quality of the graphene layers grown on the C‐face off‐axis 3C‐SiC(1¯1¯1¯). [ABSTRACT FROM AUTHOR]

Featured Application: Graphene-based electronics and sensing. Due to its excellent physical properties and availability directly on a semiconductor substrate, epitaxial graphene (EG) grown on the (0001) face of hexagonal silicon carbide is a material of choice for advanced applications in electronics, metrology and sensing. The deposition of ultrathin high-k insulators on its surface is a key requirement for the fabrication of EG-based devices, and, in this context, atomic layer deposition (ALD) is the most suitable candidate to achieve uniform coating with nanometric thickness control. This paper presents an overview of the research on ALD of high-k insulators on EG, with a special emphasis on the role played by the peculiar electrical/structural properties of the EG/SiC (0001) interface in the nucleation step of the ALD process. The direct deposition of Al2O3 thin films on the pristine EG surface will be first discussed, demonstrating the critical role of monolayer EG uniformity to achieve a homogeneous Al2O3 coverage. Furthermore, the ALD of several high-k materials on EG coated with different seeding layers (oxidized metal films, directly deposited metal-oxides and self-assembled organic monolayers) or subjected to various prefunctionalization treatments (e.g., ozone or fluorine treatments) will be presented. The impact of the pretreatments and of thermal ALD growth on the defectivity and electrical properties (doping and carrier mobility) of the underlying EG will be discussed. [ABSTRACT FROM AUTHOR]