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When a gecko moves on a ceiling it makes use of adhesion and stiction. Stiction--static friction--is experienced on microscopic and macroscopic scales and is related to adhesion and sliding friction (1). Although important for most locomotive processes, the concepts of adhesion, stiction and sliding friction are often only empirically correlated. A more detailed understanding of these concepts will, for example, help to improve the design of increasingly smaller devices such as micro- and nanoelectromechanical switches (2). Here we show how stiction and adhesion are related for a liquid drop on a hexagonal boron nitride monolayer on rhodium (3), by measuring dynamic contact angles in two distinct states of the solid-liquid interface: a corrugated state in the absence of hydrogen intercalation and an intercalation-induced flat state. Stiction and adhesion can be reversibly switched by applying different electrochemical potentials to the sample, causing atomic hydrogen to be intercalated or not. We ascribe the change in adhesion to a change in lateral electric field of in-plane two-nanometre dipole rings (4), because it cannot be explained by the change in surface roughness known from the Wenzel model (5). Although the change in adhesion can be calculated for the system we study (6), it is not yet possible to determine the stiction at such a solid-liquid interface using ab initio methods. The inorganic hybrid of hexagonal boron nitride and rhodium is very stable and represents a new class of switchable surfaces with the potential for application in the study of adhesion, friction and lubrication., Every object at rest sticks with some adhesion to its substrate. If this object is moved, then a force must act on it. This force has to overcome the stiction [...]

Over the past two decades, single-walled carbon nanotubes (SWCNTs) have received much attention because their extraordinary properties are promising for numerous applications (1,2). Many of these properties depend sensitively on SWCNT structure, which is characterized by the chiral index (n,m) that denotes the length and orientation of the circumferential vector in the hexagonal carbon lattice. Electronic properties are particularly strongly affected, with subtle structural changes switching tubes from metallic to semiconducting with various bandgaps. Monodisperse 'single-chirality' (that is, with a single (n,m) index) SWCNTs are thus needed to fully exploit their technological potential (1,2). Controlled synthesis through catalyst engineering (3-6), end- cap engineering (7) or cloning strategies (8,9), and also tube sorting based on chromatography (10,11), density-gradient centrifugation, electrophoresis and other techniques (12), have delivered SWCNT samples with narrow distributions of tube diameter and a large fraction of a predetermined tube type. But an effective pathway to truly monodisperse SWCNTs remains elusive. The use of template molecules to unambiguously dictate the diameter and chirality of the resulting nanotube (8,13-16) holds great promise in this regard, but has hitherto had only limited practical success (7,17,18). Here we show that this bottom-up strategy can produce targeted nanotubes: we convert molecular precursors into ultrashort singly capped (6,6) 'armchair' nanotube seeds using surface-catalysed cyclodehydrogenation on a platinum (111) surface, and then elongate these during a subsequent growth phase to produce single-chirality and essentially defect-free SWCNTs with lengths up to a few hundred nanometres. We expect that our on-surface synthesis approach will provide a route to nanotube-based materials with highly optimized properties for applications such as light detectors, photovoltaics, field-effect transistors and sensors (2)., Recent work has produced non-planar carbon-based nanostructures such as fullerenes, carbon pyramids, and buckybowls from their corresponding quasi-planar polycyclic aromatic hydrocarbon precursors through surface-catalysed cyclodehydrogenation (CDH) (19-21). We have extended [...]

The surface-supported corannulene (COR)-[C.sub.60] host-guest complexes are formed by deposition of [C.sub.60] onto a COR lattice on Cu(110). The studies have shown that the bistability has originated from a subtle interplay between homo- and heteromolecular interactions.

A newly developed adsorption process for a site- and orientation-selective anchoring of prototypical molecular building blocks on appropriate templates is described. The various data-sets obtained from the analysis shows that the specific adsorption angle observed is only due to the adsorption on the kink sites, as it requires the lowest energy.

[C.sub.60] nanostructures with long-range order and uniform size are prepared using a vicinal Au(11 12 12) surface, naturally patterned into a rectangular superlattice as a template. A two-dimensional long-range ordered superlattice of molecular nanochains is achieved at room temperature and at a coverage of 0.1 monolayer, which perfectly replicates the periodicity of the template surface.

The X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron diffraction (XPD) investigations are presented for the CuO thin films electrochemically deposited on an Au(001) single-crystal surface from a solution containing chiral tartaric acid (TA). The results have shown that the formation of chiral CuO surfaces through electrodeposition in a solution-based process is possible down to film thicknesses of a few nanometers.

Scalable substitutional doping of 2D transition metal dichalcogenides is a prerequisite to developing next-generation logic and memory devices based on 2D materials. To date, doping efforts are still nascent. Here, scalable growth and vanadium (V) doping of 2D WSe2 at front-end-of-line and back-end-of-line compatible temperatures of800 and 400 °C, respectively, is reported. A combination of experimental and theoretical studies confirm that vanadium atoms substitutionally replace tungsten in WSe2, which results in p-type doping via the introduction of discrete defect levels that lie close to the valence band maxima. The p-type nature of the V dopants is further verified by constructed field-effect transistors, where hole conduction becomes dominant with increasing vanadium concentration. Hence, this study presents a method to precisely control the density of intentionally introduced impurities, which is indispensable in the production of electronic-grade wafer-scale extrinsic 2D semiconductors. [ABSTRACT FROM AUTHOR]

A combined scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) is used for studying the surface-assisted assembly of the hexaiodo-substituted macrocycle cyclohexa-m-phenylene (CHP) toward covalently bonded polyphenylene networks on Cu(111), Au(111) and Ag(111) surfaces. Monte Carlo simulation has shown that different balances between diffusion and intermolecular coupling have determined the branched and compact polyphenylene networks on the Cu and Ag surface, which has shown that the choice of the substrate has played a vital role in the formation of two-dimensional polymers.

The self-assembly of the novel [C.sub.3] symmetric star-shaped molecule on an Au(111) surface at the submolecular level is studied by using scanning tunneling microscopy (STM). The coexistence of different honeycomb orders has highlighted the interplay of directional hydrogen bonding (HB) and less specific van der Waals interactions in determining two-dimensional crystal structures.

The self-assembly of extended polycyclic aromatic hydrocarbons with different symmetries on the Cu(111) surfaces is studied by low-temperature scanning tunneling microscopy. All molecules show a commensurate monolayer structure, with significant structural differences with respect to the unit cell of the molecular lattice and the orientational ordering and these are dominated by molecule-substrate interactions, while molecule-molecule interactions determine the molecular packing density through steric repulsion.