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Graphene on SiO2enables fabrication of Si-technology-compatible devices, but a transfer of these devices from other substrates and direct growth have severe limitations due to a relatively small grain size or device-contamination. Here, we show an efficient, transfer-free way to integrate centimeter-scale, single-crystal graphene, of a quality suitable for electronic devices, on an insulating SiO2film. Starting with single-crystal graphene grown epitaxially on Ru(0001), a SiO2film is grown under the graphene by stepwise intercalation of silicon and oxygen. Thin (∼1 nm) crystalline or thicker (∼2 nm) amorphous SiO2has been produced. The insulating nature of the thick amorphous SiO2is verified by transport measurements. The device-quality of the corresponding graphene was confirmed by the observation of Shubnikov-de Haas oscillations, an integer quantum Hall effect, and a weak antilocalization effect within in situfabricated Hall bar devices. This work provides a reliable platform for applications of large-scale, high-quality graphene in electronics.

Pristine graphene is known to be nonmagnetic due to its π-conjugated electron system. However, we find that localized magnetic moments can be generated by chemically attaching boron atoms to the graphene sheets. Such spin-polarized states are evidenced by the spin-split of the density of states (DOS) peaks near the Fermi level in scanning tunneling spectroscopy (STS). In the vicinity of several coadsorbed boron atoms, the Coulomb repulsion between multiple spins leads to antiferromagnetic coupling for the induced spin states in the graphene lattice, manifesting itself as an increment of spin-down state at specific regions. Experimental observations and interpretations are rationalized by extensive density functional theory (DFT) simulations.

In biomineralization, inorganic materials are formed with remarkable control of the shape and morphology. Chirality, as present in the biomolecular world, is therefore also common for biominerals. Biomacromolecules, like proteins and polysaccharides, are in direct contact with the mineral phase and act as modifiers during nucleation and crystal growth. Owing to their homochirality—they exist only as one of two possible mirror-symmetric isomers—their handedness is often transferred into the macroscopic shape of the biomineral crystals, but the way in which handedness is transmitted into achiral materials is not yet understood at the atomic level. By using the submolecular resolution capability of scanning tunnelling microscopy, supported by photoelectron diffraction and density functional theory, we show how the chiral ‘buckybowl’ hemibuckminsterfullerene arranges copper surface atoms in its vicinity into a chiral morphology. We anticipate that such new insight will find its way into materials synthesis techniques.

The mechanism of attachment of nanocrystals (NCs) to curved carbonaceous species such as graphene nanoribbons and carbon nanotubes (CNTs) is of current scientific interest. In addition, we have observed anisotropic growth patterns of titania NCs from carbonaceous materials, for which there is no theoretical explanation. In this work, we use density functional theory (DFT) calculations for calculating the energy of adsorption of titania nanostructures to both armchair metallic and zigzag semiconducting single-walled carbon nanotubes (SWCNTs) in their pure and functionalized forms. Several adsorption sites are considered including top, bridge, and hollow sites for pure SWCNTs, while for functionalized SWCNTs epoxy, alcohol, and carboxylate are examined. Results from binding energy calculations were found to predict favorable adsorption of TiO2NCs on the chemical adsorption sites of functionalized SWCNTs compared to the physical adsorption sites of pure SWCNTs. The rotation of anatase and rutile titania species on the physical adsorption sites showed interesting behavior particularly regarding binding strength and growth direction predictions. Partial density of states (PDOS) calculations examined the electronic structure of the assemblies. Charge density maps showed the importance of chemisorption sites for interactions between titania structures and SWCNTs. Electronic local potentials showed the difference in binding strengths for anatase titania on SWCNT physical adsorption sites. These results provide new theoretical evidence for controlled and oriented growth mechanisms on curved carbon-based substrates that have applications in various emerging applications from photovoltaic devices to nanomedicine.

Graphene substrates are known to have randomly located functional groups on their surface, particularly at their edges, including carboxylate, carbonyl, epoxy, and alcohol functionalities. However, the detailed interactions of these graphene functionalities with metal oxide nanoclusters are unexplored. This work examined the interaction of titania nanostructures with both graphene and functionalized graphene nanoribbons (GNRs) using density functional theory (DFT) calculations. The interactions of TiO2(anatase, rutile, and molecular) with graphene were found to favor the physisorption of rutile titania. The interactions of TiO2with GNRs were found to considerably improve the strength of the nanostructure binding to the substrate with rutile and anatase showing similar chemisorption. Charge density maps showed the importance of the electron distribution in the interaction between titania and graphene with chemisorption sites. Valuable information on the strength of the binding energies was determined by studying the electronic structure using partial density of states (PDOS) of the TiO2/graphene systems at specific adsorption sites. These results show the potential for controlled and oriented growth mechanisms that have applications in next generation photovoltaic and photocatalytic devices.

By precise control of substrate temperature, two kinds of structures (structure I and structure II) of coronene on Ag(110) are alternatingly observed by in situ molecular beam epitaxy−low energy electron diffraction. This series of alternating structural transition is confirmed by scanning tunneling microscopy images and density functional theory calculations. As the substrate temperature increases after the molecular monolayer growth at 250 K, the first transition from structure I to structure II occurs around 335 K, which is due to the different vibrational contributions of structures I and II to their free energy. The second transition from structure II to structure I around 367 K is due to the molecule−molecule repulsion, at that temperature the molecular island dissociation and the molecular desorption are dramatically activated and thus the molecule−molecule interaction becomes the dominant effect to the molecular structure. Comprehension of the underlying physics processes behind this alternating structural transition helps establish an understanding of the structural evolution and thermal stability of functional molecular thin films.

Kopf oder Zahl?Die Entwicklung der strukturellen und elektronischen Eigenschaften von Zinn‐Phthalocyanin‐Filmen wurde von einer Submonoschicht‐ bis zu einer Multischichtbedeckung mithilfe der Niedertemperatur‐Rastertunnelmikroskopie analysiert. Zwei Molekülkonformationen wurden beobachtet: zufällig verteilt in der ersten Schicht und als Inseln mit einer einzigen Konformation in den folgenden Schichten.

Heads or tails?The evolution of structural and electronic properties of tin–phthalocyanine films has been analyzed for sub‐monolayer to multilayer coverage using low‐temperature scanning tunneling microscopy. Two molecular conformations are observed: randomly dispersed for the first layer, and islands with a single conformation in subsequent layers.

A change of solvent provides a means to modulate the intermetallic distance of the Ag ion chains in solvated structures of [AgI(cytidine-5′-monophosphate)], a 3D coordination polymer which features the less common O2,N3-binding mode for the nucleobase. Though the shortest Ag···Ag separation is within 5% of that in the metallic element, the coordination polymer is not electrically conducting, as shown by oriented single-crystal I/Vmeasurements. Band structure calculations for the isolated coordination chain ([Ag-(O2,N3-Cyt)]+)nalso support this. Additionally, we demonstrate that these AgIion chains are retained when crystalline MOF samples are processed as dispersions in the liquid phase by ultrasonication, yielding well-defined bilayer nanosheets through cleavage of phosphoester O–Ag bonds.