47 research outputs found
Tuning fulleride electronic structure and molecular ordering via variable layer index
C60 fullerides are uniquely flexible molecular materials that exhibit a rich
variety of behavior, including superconductivity and magnetism in bulk
compounds, novel electronic and orientational phases in thin films, and quantum
transport in a single-C60 transistor. The complexity of fulleride properties
stems from the existence of many competing interactions, such as
electron-electron correlations, electron-vibration coupling, and intermolecular
hopping. The exact role of each interaction is controversial due to the
difficulty of experimentally isolating the effects of a single interaction in
the intricate fulleride materials. Here we report a unique level of control of
the material properties of KxC60 ultra-thin films through well-controlled
atomic layer indexing and accurate doping concentrations. Using STM techniques,
we observe a series of electronic and structural phase transitions as the
fullerides evolve from two-dimensional monolayers to quasi-threedimensional
multilayers in the early stages of layer-by-layer growth. These results
demonstrate the systematic evolution of fulleride electronic structure and
molecular ordering with variable KxC60 film layer index, and shed new light on
creating novel molecular structures and devices.Comment: 16 pages, 4 figures, to appear in Nature Material
ELECTRONIC-STRUCTURE OF MGO STUDIED BY ANGLE-RESOLVED ULTRAVIOLET PHOTOELECTRON-SPECTROSCOPY
We report on the electronic structure of MgO using angle-resolved ultraviolet photoelectron spectroscopy. The commonly catastrophic charging effects have been managed by means of an electron flood-gun. Features in the spectra, taken from the MgO(100) surface, can be assigned to a superposition of angle-integrated bulk transitions and direct bulk transitions. The results are in accordance with ab-initio bulk band-structure calculations
ANGLE OF INCIDENCE DEPENDENCE OF ELECTRON-BEAM INDUCED CRYSTAL CURRENT FROM AG(100) AND AG(111) SURFACES
We have examined the variation of medium energy ( ∼ 3 keV) electron beam induced crystal current from Ag(100) and Ag(111) surfaces, as a function of the polar and azimuthal angle of incidence. The results are interpreted in terms of a dynamical two-beam model, based on the variation of electron absorption as a function of the diffraction conditions. This model allows the determination of complex Fourier components of the one-electron potential in Ag, with which anisotropies in both elastic and inelastic scattering processes can be described. These anisotropies could be of importance in the interpretation of angle dependent X-ray photoelectron spectroscopy, angle dependent Auger electron spectroscopy, angle dependent inverse photoemission and various backscattered electron diffraction experiments
RELATIONSHIP BETWEEN ATOMIC AND ELECTRONIC-STRUCTURE OF CLEAN AND OXYGEN COVERED COPPER (110) SURFACE
We described the electronic band-structure of the clean and oxygen covered Cu(110) surface using a tight-binding method in a recursive layer by layer scheme. These are compared to angle-resolved ultraviolet photoelectron and angle-resolved inverse photoemission data. Good agreement for all (except image potential) surface states for the clean surface is obtained and also for the oxygen covered surface if the “ buckled-row” reconstruction is assumed, where alternate 〈001〉 copper rows are displaced outwardly by 0.6± 0.2 Å from the first layer and the oxygen atoms are located 0.1 ± 0.2 Å below these copper atoms. From this we conclude that the room temperature Cu(110)-p2 × 1-O superstructure is the result of a “buckled-row” reconstruction. The possibility of a “missing-row” reconstruction for the high temperature Cu(110)-p2 × 1-O superstructure is discussed