The outstanding properties of graphene make it a top candidate for replacing silicon in future electronic devices. However, for technological applications, graphene must be synthesized on the surface of wide-gap semiconductors. In this review, we focus on graphene synthesized on single-crystalline cubic-SiC thin films epitaxially grown on standard silicon wafers. These low-cost substrates are commercially available and fully compatible with existing silicon technologies. The results obtained in recent years demonstrate that few-layer graphene synthesized on cubic-SiC substrates possesses the atomic structure and electronic properties of quasi-free-standing graphene. However, according to data obtained by various techniques, few-layer graphene on cubic-SiC consists of nanodomains connected to one another through nanodomain boundaries. After optimization of the preparation procedures, such a nanostructured graphene overlayer can represent a very promising system for the development of new graphene-based electronic devices. In particular, recent works demonstrate that continuous few-layer graphene with self-aligned nanodomain boundaries can be synthesized on vicinal SiC(0 0 1) substrates. Electrical measurements show the opening of a transport gap in nanostructured trilayer graphene synthesized on SiC/2°-off Si(0 0 1) wafers. This development may lead to new tunable electronic nanostructures made from graphene on cubic-SiC, opening up opportunities for a wide range of applications.

The structural and chemical composition of the surface layer (100–140 nm) of niobium radiofrequency cavities operating at cryogenic temperature has enormous impact on their superconducting characteristics. During the last years, cavities treated with a new thermal processing recipe, so-called nitrogen infusion, have demonstrated an increased efficiency and high accelerating gradients. The role and importance of nitrogen gas has been a topic of many debates. In the present work we employ variable-energy synchrotron x-ray photoelectron spectroscopy (XPS), to study the niobium surface subjected to the following treatments: vacuum annealing at 800 °C, nitrogen infusion, and vacuum heat treatment as for the infusion process but without nitrogen supply. Careful analysis of XPS energy-distribution curves revealed a slightly increased thickness of the native oxide Nb 2 O 5 for the infused samples (∼3.8 nm) as compared to the annealed one (∼3.5 nm) which indicates insignificant oxygen incorporation into niobium during 120 °C baking and no effect of nitrogen on the formation of oxides or other niobium phases. By conducting an additional in-situ annealing experiment and analyzing the niobium after the failed infusion process, we conclude that the vacuum furnace hygiene particularly during the high-temperature stage is the prerequisite for success of any treatment recipe.

Few-layer graphene on β-SiC(001) functionalized with phenazine dye Neutral Red by means of diazonium chemistry has been studied using X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure, photoemission electron microscopy, scanning tunneling microscopy, and density functional theory calculations. The experimental data reveal the formation of a composite phenazine dye/graphene structure with a large energy gap. The molecules in this structure can be oriented both parallel and perpendicular to the graphene surface. According to scanning tunneling spectroscopy and theoretical calculations, the density of electron states in different surface areas depends on the local short-range order and the molecules’ environment. On the other hand, the photoemission spectroscopy study shows that the bottom layers of the few-layer graphene remain intact, which inherently makes the synthesized layered composite a low-dimensional metal/semiconductor heterostructure. In addition, photoemission electron microscopy imaging shows a high homogeneity of the dye-modified graphene on a micrometer scale.

The studies of the properties of graphene synthesized on the surface of epitaxial films of cubic single-crystal silicon carbide preliminarily grown on Si(001) wafers have been reviewed. These studies were supported by the Russian Foundation for Basic Research, project no. 17-02-01139. The results of these studies demonstrate that graphene layers synthesized on β-SiC/Si(001) substrates have the atomic structure and electronic properties of a quasi-freestanding graphene sheet. Continuous graphene layers with a preferential direction of nanodomain boundaries, which is determined by the orientation of steps on the initial surface, can be synthesized on vicinal SiC(001) substrates. The possibility of controlled growth of mono-, bi-, and trilayer graphene on β-SiC/Si(001) wafers has been demonstrated. The studies have shown the opening of a transport gap and a high positive magnetoresistance in a parallel magnetic field in an ordered system of graphene nanoribbons on the vicinal SiC(001) surface. It has been shown that the functionalization of graphene with organic compounds changes the electronic properties of graphene on SiC(001), modifying it to a semiconductor with given properties, which allows applications in modern micro- and nanoelectronics.

We study the in-situ growth of a nanocomposite material consisting of a thin CuPcF4 film and multiphase/multidimensional indium nanoparticles, self-organizing on the surface and in the bulk, at various stages of thermal deposition of metal on an organic film under ultrahigh vacuum conditions. The analysis of high-resolution transmission electron microscopy (HR-TEM) images provided valuable information about the evolution of morphology, size, density, and distribution of indium nanoparticles upon indium deposition. These 2D/3D ultra-small nano-objects turned out to have not only body-centered tetragonal (bct) crystal structure, typical for bulk indium, but also unusual face-centered cubic (fcc) one. Using a synchrotron facility, the study of the electronic structure of the hybrid nanocomposite on variable stages of metal deposition was performed by XPS and NEXAFS. Core-level spectra related to the organics indicated reasonably weak chemical interaction of indium with CuPcF4 molecules, which is not the case for a number of metal/organic semiconductor systems, while valence band spectra have shown a considerable change of the material electronic properties. The energy level diagrams, derived from the experiment, can be applied for the creation of new prototypes of metal-organic memory devices.

We present the fabrication and investigation of the properties of nanocomposite structures consisting of two-dimensional (2D) and three-dimensional (3D) metallic nano-objects self-organized on the surface and inside of organic molecular thin-film copper tetrafluorophthalocyanine (CuPcF4). Metallic atoms, deposited under ultrahigh vacuum (UHV) conditions onto the organic ultrathin film, diffuse along the surface and self-assemble into a system of 2D metallic overlayers. At the same time, the majority of the metal atoms diffuse into the organic matrix and self-organize into 3D nanoparticles (NPs) in a well-defined manner. The evolution of the morphology and electronic properties of such structures as a function of nominal metal content is studied under UHV conditions using transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), and photoelectron spectroscopy (PES) techniques. Using HR-TEM, we have observed the periodicity of atomic planes of individual silver NPs. The steady formation of agglomerates from individual single nanocrystallites with intercrystallite boundaries is observed as well. PES reveals generally weak chemical interactions between silver and the organic matrix and n-doping of CuPcF4 at the initial stages of silver deposition, which is associated with charge transfer from the 2D wetting layer on the basis of core-level spectra shift analysis.

The purpose of this work is the synthesis and study of the properties of nanocomposite structures created by noble metal (silver) nanoparticles (NP's), an exciting class of materials with unique properties differ from both bulk and atomic behavior, which are self-organize in a thin organic film of copper phthalocyanine (CuPc). The structure and morphology of this material, depending on the amount of deposited silver, was studied in ultrahigh vacuum using transmission electron microscopy (TEM) and photoelectron spectroscopy (PES). Metallic atoms deposited on the surface of an organic substrate diffuse into the substrate, forming NPs with a narrow size distribution, which correlates with the content of the deposited metal. With the help of high-resolution TEM, the distance between the atomic planes of individual silver nanoparticles was determined and the steady gathering of individual nanoparticles into agglomerates and then into nanocrystals with inter-crystallite boundaries was observed. PES revealed a generally weak interaction between silver NPs and the organic matrix. However, a strong band bending in the organic film at small coatings with metal atoms was observed.

Few-layer graphene exhibits exceptional properties that are of interest for fundamental research and technological applications. Nanostructured graphene with self-aligned domain boundaries and ripples is one of very promising materials because the boundaries can reflect electrons in a wide range of energies and host spin-polarized electronic states. In this chapter, we discuss the ultra-high vacuum synthesis of few-layer graphene on the technologically relevant semiconducting β-SiC/Si(001) wafers. Recent experimental results demonstrate the possibility of controlling the preferential domain boundary direction and the number of graphene layers in the few-layer graphene synthesized on the β-SiC/Si(001) substrates. Both these goals can be achieved utilizing vicinal silicon wafers with small miscuts from the (001) plane. This development may lead to fabricating new tunable electronic nanostructures made from graphene on β-SiC, opening up opportunities for new applications.

This chapter contains sections titled: Introduction Graphene on β-SiC/Si Wafers Atomic and Electronic Structure of Few-Layer Graphene Synthesized on β-SiC/Si(001) Growth of Few-Layer Graphene on SiC(001)/Si(001) Wafers in UHV Self-Aligned Graphene Nanoribbons Synthesized on Vicinal SiC(001) Surfaces: Atomic Structure and Transport Properties Magnetic Properties of Graphene/SiC(001) Conclusions Acknowledgments

Herein, we report a simple method for a covalent modification of surface supported graphene with photoactive dyes. Graphene was fabricated on cubic-SiC/Si(001) wafers due to their low cost and suitability for mass-production of continuous graphene fit for electronic applications on millimetre scale. Functionalisation of the graphene surface was carried out in solution via white light induced photochemical generation of phenazine radicals from phenazine diazonium salt. The resulting covalently bonded phenazine-graphene hybrid structure was characterised by scanning tunnelling microscopy (STM) and spectroscopy (STS), Raman spectroscopy and density functional theory (DFT) calculations. It was found that phenazine molecules form an overlayer, which exhibit a short range order with a rectangular unit cell on the graphene surface. DFT calculations based on STM results reveal that molecules are standing up in the overlayer with the maximum coverage of 0.25 molecules per graphene unit cell. Raman spectroscopy and STM results show that the growth is limited to one monolayer of standing molecules. STS reveals that the phenazine-graphene hybrid structure has a band gap of 0.8 eV.

The mechanism of few-layer graphene growth on the technologically relevant cubic-SiC/Si(001) substrate is uncovered using high-resolution core-level and angle-resolved photoelectron spectroscopy, low-energy electron microscopy, and microspot low-energy electron diffraction. The thickness of the graphitic overlayer supported on the silicon carbide substrate and related changes in the surface structure are precisely controlled by monitoring the progress of the surface graphitization in situ during high-temperature graphene synthesis, using a combination of microspectroscopic techniques. The experimental data reveal gradual changes in the preferential graphene lattice orientations at the initial stages of the few-layer graphene growth on SiC(001) and can act as reference data for controllable growth of single-, double-, and triple-layer graphene on silicon carbide substrates.

Graphene supports long spin lifetimes and long diffusion lengths at room temperature, making it highly promising for spintronics. However, making graphene magnetic remains a principal challenge despite the many proposed solutions. Among these, graphene with zig-zag edges and ripples are the most promising candidates, as zig-zag edges are predicted to host spin-polarized electronic states, and spin–orbit coupling can be induced by ripples. Here we investigate the magnetoresistance of graphene grown on technologically relevant SiC/Si(001) wafers, where inherent nanodomain boundaries sandwich zig-zag structures between adjacent ripples of large curvature. Localized states at the nanodomain boundaries result in an unprecedented positive in-plane magnetoresistance with a strong temperature dependence. Our work may offer a tantalizing way to add the spin degree of freedom to graphene.