Graphene growth and properties on metal substrates

Effects of copper/graphene oxide core-shell nanoparticles on Rhipicephalus ticks and their detoxification enzymes

Nanopesticides have been recently introduced as novel pesticides to overcome the drawbacks of using traditional synthetic pesticides. The present study evaluated the acaricidal activity of Copper/Graphene oxide core-shell nanoparticles against two tick species, Rhipicephalus rutilus and Rhipicephalus turanicus. The Copper/Graphene oxide core-shell nanoparticles were synthetized through the solution plasma (SP) method under different conditions. The nanoparticles synthesized at 180 W and 45 min were highly toxic to Rh. rutilus and Rh. turanicus, with 50% lethal concentration (LC50) values of 248.1 and 195.7 mg ml-1, respectively, followed by those which were synthesized at 120 W/30 mins (LC50 = 581.5 and 526.5 mg ml-1), 120 W/15 mins (LC50 = 606.9 and 686.7 mg ml-1), and 100/45 mins (LC50 = 792.9 and 710.7 mg ml-1), after 24 h of application. The enzyme assays revealed that 180 W/45 min treatment significantly inhibited the activity of acetylcholinesterase (115 ± 0.81 and 123 ± 0.33 U/ mg protein/min) and superoxide dismutase (290 ± 0.18 and 310 ± 0.92 U/ mg protein/min) in Rh. rutilus and Rh. turanicus, respectively, as compared with the negative control. The results also revealed a significantly increased catalase activity (895 ± 0.37 and 870 ± 0.31 U/ mg protein/min) in Rh. rutilus and Rh. turanicus, respectively. The above results indicated that Copper/Graphene oxide core-shell nanoparticles could be a promising alternatives for the management of ticks.

Enhancing the Chemical Reactivity of Graphene through Substrate Engineering

Covalent functionalization of pristine graphene can modify its properties, enabling applications in optoelectronics, biomedical fields, environmental science, and energy. However, the chemical reactivity of pristine graphene is relatively low, and as such, methods have been developed to increase the reactivity of graphene. This review focuses on substrate engineering as an effective strategy to enhance the reactivity of graphene through strain and charge doping. Nanoparticles, metals with different crystal orientations, and stretchable polymers are employed to introduce strains in graphene, leading to enhanced chemical reactivity and increased degree of functionalization. Charge doping through orbital hybridization with metals and charge puddles induced by oxide substrates generally enhance the reactivity of graphene, while alkyl-modified surfaces and 2D materials often reduce graphene reactivity via charge screening and van der Waals interactions that increase the stability of the graphene layer, respectively. This review summarizes methods for creating and characterizing strains and charge doping in graphene and discusses their effects on the chemical functionalization of graphene in various reactions.

Measurement of the Induced Magnetic Polarisation of Rotated-Domain Graphene Grown on Co Film with Polarised Neutron Reflectivity

In this paper, we determine the magnetic moment induced in graphene when grown on a cobalt film using polarised neutron reflectivity (PNR). A magnetic signal in the graphene was detected by X-ray magnetic circular dichroism (XMCD) spectra at the C K-edge. From the XMCD sum rules an estimated magnetic moment of 0.3 μB/C atom, while a more accurate estimation of 0.49 μB/C atom was obtained by carrying out a PNR measurement at 300 K. The results indicate that the higher magnetic moment in Co is counterbalanced by the larger lattice mismatch between the Co-C (1.6%) and the slightly longer bond length, inducing a magnetic moment in graphene that is similar to that reported in Ni/graphene heterostructures.

STM Study of the Initial Stage of Gold Intercalation of Graphene on Ir(111)

In this paper, we present a study of the sub-monolayer gold intercalation of graphene on Ir(111) using scanning tunnelling microscopy (STM). We found that Au islands grow following different kinetics than growth on Ir(111) without graphene. Graphene appears to increase the mobility of Au atoms by shifting the growth kinetics of Au islands from dendritic to a more compact shape. Graphene on top of intercalated gold exhibits a moiré superstructure, with parameters significantly different from graphene on Au(111) but almost identical to graphene on Ir(111). The intercalated Au monolayer shows a quasi-herringbone reconstruction with similar structural parameters as on Au(111).

Determining the Proximity Effect-Induced Magnetic Moment in Graphene by Polarized Neutron Reflectivity and X-ray Magnetic Circular Dichroism

We report the magnitude of the induced magnetic moment in CVD-grown epitaxial and rotated-domain graphene in proximity with a ferromagnetic Ni film, using polarized neutron reflectivity (PNR) and X-ray magnetic circular dichroism (XMCD). The XMCD spectra at the C K-edge confirm the presence of a magnetic signal in the graphene layer, and the sum rules give a magnetic moment of up to ∼0.47 μ_B/C atom induced in the graphene layer. For a more precise estimation, we conducted PNR measurements. The PNR results indicate an induced magnetic moment of ∼0.41 μ_B/C atom at 10 K for epitaxial and rotated-domain graphene. Additional PNR measurements on graphene grown on a nonmagnetic Ni₉Mo₁ substrate, where no magnetic moment in graphene is measured, suggest that the origin of the induced magnetic moment is due to the opening of the graphene's Dirac cone as a result of the strong C p_z-Ni 3d hybridization.

The New Materials for Battery Electrode Prototypes

In this article, we present the performance of Copper (Cu)/Graphene Nano Sheets (GNS) and C-π (Graphite, GNS, and Nitrogen-doped Graphene Nano Sheets (N-GNS)) as a new battery electrode prototype. The objectives of this research are to develop a number of prototypes of the battery electrode, namely Cu/GNS//Electrolyte//C-π, and to evaluate their respective performances. The GNS, N-GNS, and primary battery electrode prototypes (Cu/GNS/Electrolyte/C-π) were synthesized by using a modified Hummers method; the N-doped sheet was obtained by doping nitrogen at room temperature and the impregnation or the composite techniques, respectively. Commercial primary battery electrodes were also used as a reference in this research. The Graphite, GNS, N-GNS, commercial primary batteries electrode, and battery electrode prototypes were analyzed using an XRD, SEM-EDX, and electrical multimeter, respectively. The research data show that the Cu particles are well deposited on the GNS and N-GNS (XRD and SEM-EDX data). The presence of the Cu metal and electrolytes (NH₄Cl and MnO₂) materials can increase the electrical conductivities (335.6 S cm^-1) and power density versus the energy density (4640.47 W kg^-1 and 2557.55 Wh kg^-1) of the Cu/GNS//Electrolyte//N-GNS compared to the commercial battery (electrical conductivity (902.2 S cm^-1) and power density versus the energy density (76 W kg^-1 and 43.95 W kg^-1). Based on all of the research data, it may be concluded that Cu/GNS//Electrolyte//N-GNS can be used as a new battery electrode prototype with better performances and electrical activities.

Self-Assembly of a Triphenylene-Based Electron Donor Molecule on Graphene: Structural and Electronic Properties

In this study, we report on the self-assembly of the organic electron donor 2,3,6,7,10,11-hexamethoxytriphenylene (HAT) on graphene grown epitaxially on Ir(111). Using scanning tunneling microscopy and low-energy electron diffraction, we find that a monolayer of HAT assembles in a commensurate close-packed hexagonal network on graphene/Ir(111). X-ray and ultraviolet photoelectron spectroscopy measurements indicate that no charge transfer between the HAT molecules and the graphene/Ir(111) substrate takes place, while the work function decreases slightly. This demonstrates that the HAT/graphene interface is weakly interacting. The fact that the molecules nonetheless form a commensurate network deviates from what is established for adsorption of organic molecules on metallic substrates where commensurate overlayers are mainly observed for strongly interacting systems.

Electronic and Magnetic Properties of the Graphene/Y/Co(0001) Interfaces: Insights from the Density Functional Theory Analysis

The effect of Y intercalation on the atomic, electronic, and magnetic properties of the graphene/Co(0001) interface is studied using state-of-the-art density functional theory calculations. Different structural models of the graphene/Y/Co(0001) interface are considered: (i) graphene/Y/Co(0001), (ii) graphene/1ML-YCo2/Co(0001), and (iii) graphene/bulk-like-YCo2(111). It is found that the interaction strength between graphene and the substrate is strongly affected by the presence of Y at the interface and the electronic structure of graphene (doping and the appearance of the energy gap) is defined by the Y concentration. For the Co-terminated interfaces between graphene and the metallic support in the considered systems, the electronic structure of graphene is strongly disturbed, leading to the absence of the linear dispersion for the graphene π band; in the case of the Y-terminated interfaces, a graphene layer is strongly n-doped, but the linear dispersion for this band is preserved. Our calculations show that the magnetic anisotropy for the magnetic atoms at the graphene/metal interface is strongly affected by the adsorption of a graphene layer, giving a possibility for one to engineer the magnetic properties of the graphene/ferromagnet systems.

Monolayer and Bilayer Graphene on Ru(0001): Layer-Specific and Moiré-Site-Dependent Phonon Excitations

Graphene phonons are excited by the local injection of electrons and holes from the tip of a scanning tunneling microscope. Despite the strong graphene-Ru(0001) hybridization, monolayer graphene unexpectedly exhibits pronounced phonon signatures in inelastic electron tunneling spectroscopy. Spatially resolved spectroscopy reveals that the strength of the phonon signal depends on the site of the moiré lattice with a substantial red-shift of phonon energies compared to those of free graphene. Bilayer graphene gives rise to more pronounced spectral signatures of vibrational quanta with energies nearly matching the free graphene phonon energies. Spectroscopy data of bilayer graphene indicate moreover the presence of a Dirac cone plasmon excitation.

Correlations in the Electronic Structure of van der Waals NiPS3 Crystals: An X-ray Absorption and Resonant Photoelectron Spectroscopy Study

The electronic structure of high-quality van der Waals NiPS₃ crystals was studied using near-edge X-ray absorption spectroscopy (NEXAFS) and resonant photoelectron spectroscopy (ResPES) in combination with density functional theory (DFT) approach. The experimental spectroscopic methods, being element specific, allow one to discriminate between atomic contributions in the valence and conduction band density of states and give direct comparison with the results of DFT calculations. Analysis of the NEXAFS and ResPES data allows one to identify the NiPS₃ material as a charge-transfer insulator. Obtained spectroscopic and theoretical data are very important for the consideration of possible correlated-electron phenomena in such transition-metal layered materials, where the interplay between different degrees of freedom for electrons defines their electronic properties, allowing one to understand their optical and transport properties and to propose further possible applications in electronics, spintronics, and catalysis.

Selecting 'convenient observers' to probe the atomic structure of CVD graphene on Ir(111) via photoelectron diffraction

CVD graphene grown on metallic substrates presents, in several cases, a long-range periodic structure due to a lattice mismatch between the graphene and the substrate. For instance, graphene grown on Ir(111), displays a corrugated supercell with distinct adsorption sites due to a variation of its local electronic structure. This type of surface reconstruction represents a challenging problem for a detailed atomic surface structure determination for experimental and theoretical techniques. In this work, we revisited the surface structure determination of graphene on Ir(111) by using the unique advantage of surface and chemical selectivity of synchrotron-based photoelectron diffraction. We take advantage of the Ir 4f photoemission surface state and use its diffraction signal as a probe to investigate the atomic arrangement of the graphene topping layer. We determine the average height and the overall corrugation of the graphene layer, which are respectively equal to 3.40 ± 0.11 Å and 0.45 ± 0.03 Å. Furthermore, we explore the graphene topography in the vicinity of its high-symmetry adsorption sites and show that the experimental data can be described by three reduced systems simplifying the moiré supercell multiple scattering analysis.

Graphene Layer Morphology as an Indicator of the Metal Alloy Formation at the Interface

The intercalation of different species in graphene-metal interfaces is widely used to stabilize the artificial phases of different materials, which in some cases leads to the formation of the surface alloys between atoms of the guest metal and the substrate. Here, the interfaces of graphene with Ru(0001) and Ir(111) were modified using intercalation of a thin Mn layer and investigated by means of scanning tunneling microscopy (STM) accompanied by density functional theory (DFT) calculations. It is found that Mn forms a pseudomorphic layer on Ru(0001) under a strongly buckled graphene layer. In the case of Mn intercalation in graphene/Ir(111), a buried thin layer of MnIr alloy is formed beneath the first Ir layer under a flat graphene layer. This unexpected observation is explained on the basis of phase diagram pictures for the Mn-Ru and Mn-Ir systems as well as via comparison of calculated total energies for the respective interfaces.

Intercalation of Mn in graphene/Cu(111) interface: insights to the electronic and magnetic properties from theory

The effect of Mn intercalation on the atomic, electronic and magnetic structure of the graphene/Cu(111) interface is studied using state-of-the-art density functional theory calculations. Different structural models of the graphene-Mn-Cu(111) interface are investigated. While a Mn monolayer placed between graphene and Cu(111) (an unfavorable configuration) yields massive rearrangement of the graphene-derived [Formula: see text] bands in the vicinity of the Fermi level, the possible formation of a [Formula: see text]Mn alloy at the interface (a favorable configuration) preserves the linear dispersion for these bands. The deep analysis of the electronic states around the Dirac point for the graphene/[Formula: see text]Mn/Cu(111) system allows to discriminate between contributions from three carbon sublattices of a graphene layer in this system and to explain the bands' as well as spins' topology of the electronic states around the Fermi level.

In situ synthesis of copper nanoparticles encapsulated by nitrogen-doped graphene at room temperature via solution plasma

Metal–carbon core–shell nanostructures have gained research interest due to their better performances in not only stability but also other properties, such as catalytic, optical, and electrical properties. However, they are limited by complicated synthesis approaches. Therefore, the development of a simple method for the synthesis of metal–carbon core–shell nanostructures is of great significance. In this work, a novel Cu–core encapsulated by a N-doped few-layer graphene shell was successfully synthesized in a one-pot in-liquid plasma discharge, so-called solution plasma (SP), to our knowledge for the first time. The synthesis was conducted at room temperature and atmospheric pressure by using a pair of copper electrodes submerged in a DMF solution as the precursor. The core–shell structure of the obtained products was confirmed by HR-TEM, while further insight information was explained from the results of XRD, Raman, and XPS measurements. The obtained Cu-core encapsulated by the N-doped few-layer graphene shell demonstrated relatively high stability in acid media, compared to the commercial bare Cu particles. Moreover, the stability was found to depend on the thickness of the N-doped few-layer graphene shell which can be tuned by adjusting the SP operating conditions.

An excellent corrosion protection for copper nanoparticles by nitrogen-doped few-layer graphene via solution plasma process.

Thermally Activated Processes for Ferromagnet Intercalation in Graphene-Heavy Metal Interfaces

The development of graphene (Gr) spintronics requires the ability to engineer epitaxial Gr heterostructures with interfaces of high quality, in which the intrinsic properties of Gr are modified through proximity with a ferromagnet to allow for efficient room temperature spin manipulation or the stabilization of new magnetic textures. These heterostructures can be prepared in a controlled way by intercalation through graphene of different metals. Using photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), we achieve a nanoscale control of thermally activated intercalation of a homogeneous ferromagnetic (FM) layer underneath epitaxial Gr grown onto (111)-oriented heavy metal (HM) buffers deposited, in turn, onto insulating oxide surfaces. XPS and STM demonstrate that Co atoms evaporated on top of Gr arrange in 3D clusters and, upon thermal annealing, penetrate through and diffuse below Gr in a 2D fashion. The complete intercalation of the metal occurs at specific temperatures, depending on the type of metallic buffer. The activation energy and the optimum temperature for the intercalation processes are determined. We describe a reliable method to fabricate and characterize in situ high-quality Gr-FM/HM heterostructures, enabling the realization of novel spin-orbitronic devices that exploit the extraordinary properties of Gr.

Hubbard excitons in two-dimensional nanomaterials

Excitons in two-dimensional nanomaterials are studied by solving the many-electron Hamiltonian with a configuration-interaction approach. It is shown that graphene or phosphorene nanoflakes can not accommodate any excitonic bound states if the long-range Coulomb interaction is suppressed when the systems are placed in a high-k dielectric environment or on a metal substrate. Hence it is revealed that an electron-hole pair created by an optical excitation does not always form an exciton even in a confined nanostructure. The negative exciton binding energy is found to exhibit distinct dependence on the strength of short-range Coulomb interaction as the system undergoes a phase transition from non-magnetic to anti-ferromagnetic. It is further shown that the electron-hole pair may form an exciton state only when the long-range Coulomb interaction is recovered in the nanoflakes.

Dirac Electron Behavior for Spin-Up Electrons in Strongly Interacting Graphene on Ferromagnetic Mn5Ge3

An elegant approach for the synthesis of graphene on the strong ferromagnetic (FM) material Mn₅Ge₃ is proposed via intercalation of Mn in the graphene-Ge(111) interface. According to the density functional theory calculations, graphene in this strongly interacting system demonstrates the large exchange splitting of the graphene-derived π band. In this case, only spin-up electrons in graphene preserve the Dirac-electron-like character in the vicinity of the Fermi level and the K point, whereas such behavior is not detected for the spin-down electrons. This unique feature of the studied gr-FM-Mn₅Ge₃ interface that can be prepared on the semiconducting Ge can lead to its application in spintronics.

Graphene as an Ideal Buffer Layer for the Growth of High-Quality Ultrathin Cr2O3 Layers on Ni(111)

Metal-oxide nanostructures play a fundamental role in a large number of technological applications, ranging from chemical sensors to data storage devices. As the size of the devices shrinks down to the nanoscale, it is mandatory to obtain sharp and good quality interfaces. Here, it is shown that a two-dimensional material, namely, graphene, can be exploited as an ideal buffer layer to tailor the properties of the interface between a metallic substrate and an ultrathin oxide. This is proven at the interface between an ultrathin film of the magnetoelectric antiferromagnetic oxide Cr₂O₃ and a Ni(111) single crystal substrate. The chemical composition of the samples has been studied by means of X-ray photoemission spectroscopy, showing that the insertion of graphene, which remains buried at the interface, is able to prevent the oxidation of the substrate. This protective action leads to an ordered and layer-by-layer growth, as revealed by scanning tunneling microscopy data. The structural analysis performed by low-energy electron diffraction indicates that the oxide layer grown on graphene experiences a significant compressive strain, which strongly influences the surface electronic structure observed by scanning tunneling spectroscopy.

Growth and electronic structure of 2D hexagonal nanosheets on a corrugated rectangular substrate

Graphene and h-BN are grown by chemical vapor deposition in ultra high vacuum conditions on the Pt(110) surface. Scanning tunneling microscopy measurements and low-energy electron diffraction data indicate that graphene forms a variety of differently oriented incommensurate domains although with a strong preference to align its [Formula: see text] direction with the [Formula: see text] direction of Pt. Meanwhile, h-BN exhibits a c(8 × 10) commensurate superstructure, which presents a high level of defectivity that implies local variation of the periodicity (i.e. mixed c(8 × 10) and c(8 × 12) patches) and the introduction of local defects. The combination of advanced photoemission spectroscopy data (angle-resolved photoemission spectroscopy from the valence band) and ab initio calculations indicates that both 2D materials interact weakly with the substrate: graphene exhibits neutral doping and is morphologically flat, even if it nucleates on the relatively highly corrugated rectangular (110) surface. In the case of h-BN, the interaction is slightly stronger and is characterized by a small electron transfer from surface Pt atoms to nitrogen atoms. The (110) termination of Pt is therefore a quite interesting surface for the growth of 2D materials because given its low symmetry, it may favor the growth of selectively oriented domains but does not affect their pristine electronic properties.

Size-Selective Carbon Clusters as Obstacles to Graphene Growth on a Metal

Chemical vapor deposition (CVD) on metals is so far the best suited method to produce high-quality, large-area graphene. We discovered an unprecedentedly large family of small size-selective carbon clusters that form together with graphene during CVD. Using scanning tunneling microscopy (STM) and density functional theory (DFT), we unambiguously determine their atomic structure. For that purpose, we use grids based on a graphene moiré and a dilute atomic lattice that unambiguously reveal the binding geometry of the clusters. We find that the observed clusters bind in metastable configurations on the substrate, while the thermodynamically stable configurations are not observed. We argue that the clusters are formed under kinetic control and establish that the evolution of the smallest clusters is blocked. They are hence products of surface reactions in competition with graphene growth, rather than intermediary species to the formation of extended graphene, as often assumed in the literature. We expect such obstacles to the synthesis of perfect graphene to be ubiquitous on a variety of metallic surfaces.

Sticking of atomic hydrogen on graphene

Recent years have witnessed an ever growing interest in the interactions between hydrogen atoms and a graphene sheet. Largely motivated by the possibility of modulating the electric, optical and magnetic properties of graphene, a huge number of studies have appeared recently that added to and enlarged earlier investigations on graphite and other carbon materials. In this review we give a glimpse of the many facets of this adsorption process, as they emerged from these studies. The focus is on those issues that have been addressed in detail, under carefully controlled conditions, with an emphasis on the interplay between the adatom structures, their formation dynamics and the electric, magnetic and chemical properties of the carbon sheet.

Water at the Interface Between Defective Graphene and Cu or Pt (111) Surfaces

The presence of defects in the graphenic layers deposited on metal surfaces modifies the nature of the interaction. Unsaturated carbon atoms, due to vacancies in the lattice, form strong organometallic bonds with surface metal atoms that highly enhance the binding energy between the two materials. We investigate by means of a wide set of dispersion-corrected density functional theory calculations how such strong chemical bonds affect both the electronic properties of these hybrid interfaces and the chemical reactivity with water, which is commonly present in the working conditions. We compare different metal substrates (Cu vs Pt) that present a different type of interaction with graphene and with defective graphene. This comparative analysis allows us to unravel the controlling factors of water reactivity, the role played by the carbon vacancies and by the confinement or "graphene cover effect". Water is capable of breaking the C-Cu bond by dissociating at the undercoordinated carbon atom of the vacancy, restoring the weak van der Waals type of interaction between the two materials that allows for an easy detachment of graphene from the metal, but the same is not true in the case of Pt, where C-Pt bonds are much stronger. These conclusions can be used to rationalize water reactivity at other defective graphene/metal interfaces.

Raman Spectroscopy of Lattice-Matched Graphene on Strongly Interacting Metal Surfaces

Regardless of the widely accepted opinion that there is no Raman signal from single-layer graphene when it is strongly bonded to a metal surface, we present Raman spectra of a graphene monolayer on Ni(111) and Co(0001) substrates. The high binding energy of carbon to these surfaces allows formation of lattice-matched (1 × 1) structures where graphene is significantly stretched. This is reflected in a record-breaking shift of the Raman G band by more than 100 cm^-1 relative to the case of freestanding graphene. Using electron diffraction and photoemission spectroscopy, we explore the aforementioned systems together with polycrystalline graphene on Co and analyze possible intercalation of oxygen at ambient conditions. The results obtained are fully supported by Raman spectroscopy. Performing a theoretical investigation of the phonon dispersions of freestanding graphene and stretched graphene on the strongly interacting Co surface, we explain the main features of the Raman spectra. Our results create a reliable platform for application of Raman spectroscopy in diagnostics of chemisorbed graphene and related materials.

Two-Dimensional Excitonic Photoluminescence in Graphene on a Cu Surface

Despite having outstanding electrical properties, graphene is unsuitable for optical devices because of its zero band gap. Here, we report two-dimensional excitonic photoluminescence (PL) from graphene grown on a Cu(111) surface, which shows an unexpected and remarkably sharp strong emission near 3.16 eV (full width at half-maximum ≤3 meV) and multiple emissions around 3.18 eV. As temperature increases, these emissions blue shift, displaying the characteristic negative thermal coefficient of graphene. The observed PL originates from the significantly suppressed dispersion of excited electrons in graphene caused by hybridization of graphene π and Cu d orbitals of the first and second Cu layers at a shifted saddle point 0.525(M+K) of the Brillouin zone. This finding provides a pathway to engineering optoelectronic graphene devices, while maintaining the outstanding electrical properties of graphene.

Universal classification of twisted, strained and sheared graphene moiré superlattices

Moiré superlattices in graphene supported on various substrates have opened a new avenue to engineer graphene's electronic properties. Yet, the exact crystallographic structure on which their band structure depends remains highly debated. In this scanning tunneling microscopy and density functional theory study, we have analysed graphene samples grown on multilayer graphene prepared onto SiC and on the close-packed surfaces of Re and Ir with ultra-high precision. We resolve small-angle twists and shears in graphene, and identify large unit cells comprising more than 1,000 carbon atoms and exhibiting non-trivial nanopatterns for moiré superlattices, which are commensurate to the graphene lattice. Finally, a general formalism applicable to any hexagonal moiré is presented to classify all reported structures.

Structural and electronic properties of graphene nanoflakes on Au(111) and Ag(111)

We investigate the electronic properties of graphene nanoflakes on Ag(111) and Au(111) surfaces by means of scanning tunneling microscopy and spectroscopy as well as density functional theory calculations. Quasiparticle interference mapping allows for the clear distinction of substrate-derived contributions in scattering and those originating from graphene nanoflakes. Our analysis shows that the parabolic dispersion of Au(111) and Ag(111) surface states remains unchanged with the band minimum shifted to higher energies for the regions of the metal surface covered by graphene, reflecting a rather weak interaction between graphene and the metal surface. The analysis of graphene-related scattering on single nanoflakes yields a linear dispersion relation E(k), with a slight p-doping for graphene/Au(111) and a larger n-doping for graphene/Ag(111). The obtained experimental data (doping level, band dispersions around E_F, and Fermi velocity) are very well reproduced within DFT-D2/D3 approaches, which provide a detailed insight into the site-specific interaction between graphene and the underlying substrate.

Phonon dynamics of graphene on metals

The study of surface phonon dispersion curves is motivated by the quest for a detailed understanding of the forces between the atoms at the surface and in the bulk. In the case of graphene, additional motivation comes from the fact that thermal conductivity is dominated by contributions from acoustic phonons, while optical phonon properties are essential to understand Raman spectra. In this article, we review recent progress made in the experimental determination of phonon dispersion curves of graphene grown on several single-crystal metal surfaces. The two main experimental techniques usually employed are high-resolution electron energy loss spectroscopy (HREELS) and inelastic helium atom scattering (HAS). The different dispersion branches provide a detailed insight into the graphene-substrate interaction. Softening of optical modes and signatures of the substrate's Rayleigh wave are observed for strong graphene-substrate interactions, while acoustic phonon modes resemble those of free-standing graphene for weakly interacting systems. The latter allows determining the bending rigidity and the graphene-substrate coupling strength. A comparison between theory and experiment is discussed for several illustrative examples. Perspectives for future experiments are discussed.

Restoring a nearly free-standing character of graphene on Ru(0001) by oxygen intercalation

Realization of a free-standing graphene is always a demanding task. Here we use scanning probe microscopy and spectroscopy to study the crystallographic structure and electronic properties of the uniform nearly free-standing graphene layers obtained by intercalation of oxygen monolayer in the “strongly” bonded graphene/Ru(0001) interface. Spectroscopic data show that such graphene layer is heavily p-doped with the Dirac point located at 552 meV above the Fermi level. Experimental data are understood within density-functional theory approach and the observed effects are in good agreement with the theoretical data.

Bottom-up fabrication of graphene nanostructures on Ru(1010)

Investigations on the bottom-up fabrication of graphene nanostructures with 10, 10'-dibromo-9, 9'-bianthryl (DBBA) as a precursor on Ru(1010) were carried out using scanning tunnelling microscopy (STM) and density functional theory (DFT) calculations. Upon annealing the sample at submonolayer DBBA coverage, N = 7 graphene nanoribbons (GNRs) aligned along the [1210] direction form. Higher DBBA coverage and higher annealing temperature lead to the merging of GNRs into ribbon-like graphene nanoflakes with multiple orientations. These nanoflakes show different Moiré patterns, and their structures were determined by DFT simulations. The results showed that GNRs possess growth preference on the Ru(1010) substrate with a rectangular unit cell, and GNRs with armchair and zigzag boundaries are obtainable. Further DFT calculations suggest that the interaction between graphene and the substrate controls the orientations of the graphene overlayer and the growth of graphene on Ru(1010).

Putting David Craig’s Legacy to Work in Nanotechnology and Biotechnology

David Craig (1919–2015) left us with a lasting legacy concerning basic understanding of chemical spectroscopy and bonding. This is expressed in terms of some of the recent achievements of my own research career, with a focus on integration of Craig’s theories with those of Noel Hush to solve fundamental problems in photosynthesis, molecular electronics (particularly in regard to the molecules synthesized by Maxwell Crossley), and self-assembled monolayer structure and function. Reviewed in particular is the relation of Craig’s legacy to: the 50-year struggle to assign the visible absorption spectrum of arguably the world’s most significant chromophore, chlorophyll; general theories for chemical bonding and structure extending Hush’s adiabatic theory of electron-transfer processes; inelastic electron-tunnelling spectroscopy (IETS); chemical quantum entanglement and the Penrose–Hameroff model for quantum consciousness; synthetic design strategies for NMR quantum computing; Gibbs free-energy measurements and calculations for formation and polymorphism of organic self-assembled monolayers on graphite surfaces from organic solution; and understanding the basic chemical processes involved in the formation of gold surfaces and nanoparticles protected by sulfur-bound ligands, ligands whose form is that of Au0-thiyl rather than its commonly believed AuI-thiolate tautomer.