Coordination chemistry relies on harnessing active metal sites within organic matrices. Polynuclear complexes-where organic ligands bind to several metal atoms-are relevant due to their ...electronic/magnetic properties and potential for functional reactivity pathways. However, their synthesis remains challenging; few geometries and configurations have been achieved. Here, we synthesise-via supramolecular chemistry on a noble metal surface-one-dimensional metal-organic nanostructures composed of terpyridine (tpy)-based molecules coordinated with well-defined polynuclear iron clusters. Combining low-temperature scanning probe microscopy and density functional theory, we demonstrate that the coordination motif consists of coplanar tpy's linked via a quasi-linear tri-iron node in a mixed (positive-)valence metal-metal bond configuration. This unusual linkage is stabilised by local accumulation of electrons between cations, ligand and surface. The latter, enabled by bottom-up on-surface synthesis, yields an electronic structure that hints at a chemically active polynuclear metal centre, paving the way for nanomaterials with novel catalytic/magnetic functionalities.
Hydrogen-terminated diamond possesses due to transfer doping a quasi-two-dimensional (2D) hole accumulation layer at the surface with a strong, Rashba-type spin–orbit coupling that arises from the ...highly asymmetric confinement potential. By modulating the hole concentration and thus the potential using an electrostatic gate with an ionic-liquid dielectric architecture the spin–orbit splitting can be tuned from 4.6–24.5 meV with a concurrent spin relaxation length of 33–16 nm and hole sheet densities of up to 7.23 × 1013 cm–2. This demonstrates a spin–orbit interaction of unprecedented strength and tunability for a 2D hole system at the surface of a wide band gap semiconductor. With a spin relaxation length that is experimentally accessible using existing nanofabrication techniques, this result suggests that hydrogen-terminated diamond has great potential for the study and application of spin transport phenomena.
Atomic force microscopy, Kelvin probe force microscopy, and scanning photoluminescence spectroscopy image the progressive postgrowth hydroxylation and hydration of atomically flat Al2O3(0001) under ...monolayer MoS2, manifested in large work function shifts (100 mV) due to charge transfer (>1013 cm–2) from the substrate and changes in PL intensity, energy, and peak width. In contrast, trapped water between exfoliated graphene and Al2O3(0001) causes surface potential and doping changes one and two orders of magnitude smaller, respectively, and MoS2 grown on hydrophobic hexagonal boron nitride is unaffected by water exposure.
The stability of the surface of vacuum-cleaved topological insulator Bi2Se3 single crystals is investigated with high-resolution synchrotron-based photoelectron spectroscopy. While the surface is ...stable at room temperature in vacuum, a Bi2 layer always forms at the surface of Bi2Se3 upon even brief (5 min) exposure to atmosphere. This is accompanied by a depletion of selenium in the near surface region and a 1.4 eV decrease in work function. The Bi2 surface is found to be stable upon return to ultrahigh vacuum conditions but is unstable with prolonged exposure to air, ultimately resulting in two possible different reconstructed surfaces, explaining previous contradictory results on long-term atmosphere exposure of Bi2Se3.
Making monolayer superconductors creates interesting effects, but often decreases the transition temperature compared to 3D materials. Instead, intercalating molecules into a layered superconductor ...tailors the superconductivity with fewer trade-offs.
Hydrogenated diamond possesses a unique surface conductivity as a result of transfer doping by surface acceptors. Yet, despite being extensively studied for the past two decades, little is known ...about the system at low temperature, particularly whether a two-dimensional hole gas forms at the diamond surface. Here we report that (100) diamond, when functionalized with hydrogen, supports a p-type spin-3/2 two-dimensional surface conductivity with a spin–orbit interaction of 9.74 ± 0.1 meV through the observation of weak antilocalization effects in magneto-conductivity measurements at low temperature. Fits to 2D localization theory yield a spin relaxation length of 30 ± 1 nm and a spin-relaxation time of ∼0.67 ± 0.02 ps. The existence of a 2D system with spin orbit coupling at the surface of a wide band gap insulating material has great potential for future applications in ferromagnet–semiconductor and superconductor–semiconductor devices.
•Total and methylmercury were sampled in feathers of Canadian Arctic marine birds.•Species in higher trophic positions had higher mercury concentrations.•Ivory gulls had exceptionally high mercury, ...especially in primary feathers.•The proportion of mercury as methylmercury in feathers varied across species.
Mercury (Hg) concentrations are a concern in the Canadian Arctic, because they are relatively high compared to background levels and to similar species farther south, and are increasing in many wildlife species. Among marine birds breeding in the Canadian Arctic, Hg concentrations have been monitored regularly in eggs and intermittently in livers, but feathers have generally not been used as an indicator of Hg exposure or burden. We examined Hg concentrations in six marine bird species in the Canadian Arctic. Ivory gull Pagophila eburnea, feather Hg was exceptionally high, while glaucous gull Larus hyperboreus feather Hg was unexpectedly low, and ratios of feather THg to egg THg varied across species. The proportion of total Hg that was comprised of methyl Hg in ivory gull feathers was lower than in other species, and may be related to photo-demethylation or keratin breakdown in semi-opaque feather tissue.
Photoelectron emission from lithiated diamond O'Donnell, Kane M.; Martin, Tomas L.; Edmonds, Mark T. ...
Physica status solidi. A, Applications and materials science,
October 2014, Letnik:
211, Številka:
10
Journal Article
Recenzirano
This paper reviews electron emission from negative electron affinity (NEA) diamond and gives account of the recent developments in alternatives to hydrogen‐termination for producing NEA diamond ...surfaces, particularly using lithium on oxygen‐terminated diamond. We discuss the background and motivation for using alkali metals and present both experimental and computational results that cover structure, electronic properties, photoemission, and total photoyield. Secondary yield enhancement of over 200 × is demonstrated over a reference surface with positive electron affinity.
One of the incredible properties of diamond is negative electron affinity: electrons excited in diamond can escape with no barrier to emission. In this Feature Article, the authors discuss a new way of generating negative electron affinity on diamond using lithium and present a summary of the work that was done to understand lithiated diamond surfaces.
Abstract 2D topological insulators promise novel approaches towards electronic, spintronic, and quantum device applications. This is owing to unique features of their electronic band structure, in ...which bulk-boundary correspondences enforces the existence of 1D spin–momentum locked metallic edge states—both helical and chiral—surrounding an electrically insulating bulk. Forty years since the first discoveries of topological phases in condensed matter, the abstract concept of band topology has sprung into realization with several materials now available in which sizable bulk energy gaps—up to a few hundred meV—promise to enable topology for applications even at room-temperature. Further, the possibility of combining 2D TIs in heterostructures with functional materials such as multiferroics, ferromagnets, and superconductors, vastly extends the range of applicability beyond their intrinsic properties. While 2D TIs remain a unique testbed for questions of fundamental condensed matter physics, proposals seek to control the topologically protected bulk or boundary states electrically, or even induce topological phase transitions to engender switching functionality. Induction of superconducting pairing in 2D TIs strives to realize non-Abelian quasiparticles, promising avenues towards fault-tolerant topological quantum computing. This roadmap aims to present a status update of the field, reviewing recent advances and remaining challenges in theoretical understanding, materials synthesis, physical characterization and, ultimately, device perspectives.
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