We have observed a surface magnetic phase transition on Cr(100) using angle-resolved photoelectron spectroscopy. The temperature dependence of resonance indicates 780\ifmmode\pm\else\textpm\fi{}50 K. This is consistent with theoretical predictions ferromagnetic surface. room-temperature exchange potential estimated to be 0.8\ifmmode\pm\else\textpm\fi{}0.1 eV, an associated moment (2.4\ifmmode\pm\else\textpm\fi{}0.3)${\ensuremath{\mu}}_{B}$.

We present valence and core-level photoemission measurements from vacuum-fractured, single-crystal barium titanate. These results resolve contradictory in the literature which have employed other methods of sample surface preparation. The valence-shell electronic structure is compared with previously published band cluster calculations. Resonant used to probe covalent coupling between titanium oxygen cubic tetragonal phases this ionic compound. Photoelectron spectra Ti 2p O 1s core levels...

Angle-resolved photoemission extended fine structure from adsorbate core levels yields complete, accurate surface structures without resort to trial-and-error comparisons theory. Scattering peaks individual substrate atoms were observed with use of $\mathrm{S}(1s)$ $c(2\ifmmode\times\else\texttimes\fi{}2)\mathrm{S}/\mathrm{Ni}(001)$ and $p(2\ifmmode\times\else\texttimes\fi{}2)\mathrm{S}/\mathrm{Cu}(001)$, along [011]. Fourfold-hollow site geometries found for both systems, interatomic...

When clean, vacuum-fractured surfaces of ${\mathrm{BaTiO}}_{3}$ are analyzed using ultraviolet and x-ray photoelectron spectroscopy (UPS XPS), more than one set barium core levels is observed. Sputtering the surface with ions removes lower-binding-energy intensity within line shapes in UPS spectra while little change noted XPS. also causes band bending creation band-gap states Ti 3d character. From a comparison XPS Ba 4d from surface, component assigned to 12-fold oxygen coordination...

We describe our procedures for deducing adsorbate geometry from angle-resolved core-level photoemission measurements as they are applied to c(2\ifmmode\times\else\texttimes\fi{}2)S/Ni(001). Extracting the energy-dependent, oscillating part of sulfur (1s) partial cross section gives angle-resolved-photoemission extended fine structure (ARPEFS). Fourier transformation ARPEFS yields peaks at distances characteristic local site and in most cases closely related geometrical path-length...

Donor–acceptor interfaces are critical for the operation of organic photovoltaic devices. Exciton dynamics at these play a significant role in determining efficiency and controlling open circuit voltage (VOC), short current (JSC), or fill factor (FF). These fundamental interfacial dynamical processes dependent on electronic molecular structure. In this report we use time-resolved two-photon photoemission (TR-2PPE) to investigate exciton dissociation, recombination, relaxation occurring...

High-resolution angle-resolved photoelectron spectra have been obtained from the (111) face of an Ag crystal for normal electron emission. These made it possible to determine experimentally valence-band structure along high-symmetry line \ensuremath{\Lambda} with better accuracy than previously [P. S. Wehner et al., Phys. Rev. B 19, 6164 (1979)], and also revealed a second flat band near point \ensuremath{\Gamma} in conduction bands 23 eV above Fermi level. The new binding energies at points...

We have measured the adsorption geometry for (2\ifmmode\times\else\texttimes\fi{}2)S/Cu(001) surface, including reconstruction and relaxation of copper substrate. Multiple-scattering spherical-wave calculations were compared with angle-resolved-photoemission extended-fine-structure data these results then a Fourier analysis data. The sulfur atoms are located in fourfold hollow site, S--Cu bond distance 2.26(1) A\r{}. With (1/4) monolayer ``p(2\ifmmode\times\else\texttimes\fi{}2)'' coverage...

Pentacene deposited onto a Ag(111) surface at 300 K is studied using scanning tunneling microscopy temperatures of and 50 K, providing structural insight into its unusual growth habit. At room temperature, an unexpectedly high pentacene coverage needed to nucleate ordered islands, which appear surrounded by disordered phase. These temperature nuclei are revealed as bilayer structures from their coverage-dependent size evolution molecularly resolved images domain boundaries, recorded K. this...

An angle-resolved photoelectron spectroscopy (ARPES) study of Cr(001) near-surface electronic structure is presented. Measurements are reported for energy-band dispersions along the [010] direction parallel to crystal surface. The periodicity these band indicates that valence electrons experience and self-consistently establish antiferromagnetism in layers Cr(001). We also present highly-surface-sensitive ARPES measurements [001] normal results suggest surface magnetic moments, which couple...

Angle-resolved photoemission was used to investigate the valence-band structure of metal overlayer system $c(10\ifmmode\times\else\texttimes\fi{}2)\frac{\mathrm{Ag}}{\mathrm{Cu}(001)}$. At 1-2-monolayer coverages, Ag adlayer exhibited $d$-band spectral behavior characteristic two-dimensional dispersion. Evaporation progressively more onto substrate produced a series surfaces which by 3-5-monolayer exposures were converging toward three-dimensional valence electronic bulk, Ag(111)-like system.

One- and two-photon photoelectron spectroscopies were used to determine the electronic structure around Fermi level for self-assembled monolayers of a prototypical "molecular wire", 4,4'-(ethynylphenyl)-1-benzenethiol (C6H5−C≡C−C6H4−C≡C−C6H5−SH), on Au. One−photon ultraviolet spectroscopy indicated separation between peak occupied delocalized π levels 1.9 eV, thus providing representative value hole injection barrier. Two states identified in measurements corresponding excitation lowest...

The metal overlayer system c(10\ifmmode\times\else\texttimes\fi{}2)Ag/Cu(001) was studied at coverages near one monolayer with angle-resolved photoemission. observed spectroscopic features indicate a two-dimensional d-band electronic structure that can be interpreted the use of model planar, hexagonal symmetry in which crystal-field effects dominate over spin-orbit effects.

Synchrotron-radiation-excited angle-resolved photoelectron spectra of the Ge(001)-(2 \ifmmode\times\else\texttimes\fi{} 1) reconstructed surface reveal two states 0.6 and 1.3 eV below bulk valence-band maximum at $\ensuremath{\Gamma}$ point Brillouin zone. These are similar to those observed previously for Si(001) GaAs(001) surfaces. The dispersion Ge bands with ${k}_{\ensuremath{\parallel}}$ is qualitatively in agreement calculations Chadi using his asymmetric dimer model Si(001)-(2 1).

Measurements of the extended fine structure in photoemission intensity from S(1s) core level were performed for a c(2\ifmmode\times\else\texttimes\fi{}2) overlayer S on Ni(011). Four experimental geometries employed, making this most complete angle-resolved-photoemission extended-fine-structure (ARPEFS) study to date. Surface structural information was extracted ARPEFS using combination Fourier-transform techniques and comparisons multiple-scattering calculations. The results analysis are...

The ultrafast dynamics at a well-characterized $\text{CuPc}/{\text{C}}_{60}$ organic photovoltaic heterojunction have been directly measured with time-resolved two-photon photoemission (TR-2PPE). Phthalocyanine/${\text{C}}_{60}$ donor-acceptor interfaces, characterized in detail via scanning tunneling microscopy, provide model systems for studies of critical charge separation and recombination processes that determine device performance. TR-2PPE copper phthalocyanine...

The unoccupied electronic structure of C${}_{60}$ layers on Ag(111) was investigated with two-photon photoemission (2PPE) and scanning tunneling spectroscopy (STS). focus, in addition to providing level assignments for monolayers, is identifying signatures superatom molecular orbitals (SAMOs), diffuse levels weakly bound by the spherical potential fullerene shell, two complementary techniques. s-SAMO identified 3.3 eV above Fermi 2PPE at a bias 3.5 STS. Possible contributions from $p$-SAMO...

The molecular organization of a polar phthalocyanine, titanyl phthalocyanine (TiOPc), on the Ag(110) surface was studied with scanning tunneling microscopy (STM). In addition to intermolecular hydrogen bonding and electrostatic interactions that guide structure for nonpolar Pc's, we find evidence impact dipole layer TiOPc/Ag(110). TiOPc molecules adsorb tilted orientation contrasts flat-lying typically observed phthalocyanines. At highest coverages, consists neighboring opposing tilts. Close...

Changes induced in the electronic structure of ${\mathrm{BaTiO}}_{3}$ by substitutions R=Y, La, or Nd for Ba to form mixed oxides ${\mathit{R}}_{\mathit{x}}$${\mathrm{Ba}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{TiO}}_{3\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ have been investigated using ultraviolet photoelectron spectroscopy. Substitution formally ${\mathit{R}}^{3+}$ ions ${\mathrm{Ba}}^{2+}$ leads introduction filled states band gap that are shown...

Photoelectron spectroscopy was used to explore changes in Fermi level alignment, within the pi-pi* gap, arising from modifications coupling chemistry of conjugated phenylene ethynylene oligomers Au surface. Self-assembled monolayers were formed employing either thiol (4,4'-ethynylphenyl-1-benzenethiol or OPE-T) isocyanide (4,4'-ethynylphenyl-1-benzeneisocyanide OPE-NC) coupling. The electronic density states valence region two systems are nearly identical with exception a shift higher...

Using monochromatic synchrotron radiation over the energy range of 6--32 eV, development valence-band electronic structure Ag overlayers on Cu(001) was followed with angle-resolved photoelectron spectroscopy. The d-band observed to be two dimensional for a single adlayer c(10\ifmmode\times\else\texttimes\fi{}2)Ag/Cu(001). With five layers coverage, silver bulklike, three-dimensional, and very similar that Ag(111).

The adsorption of ${\mathrm{C}}_{60}$ on a bilayer film pentacene Ag(111) is studied with scanning tunneling microscopy and spectroscopy. At low coverage, molecules form extended linear structures due to the templating effect bilayer. in chains adsorb at bridge sites between two neighboring molecules. transport gap chain measured be $4.5\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ using constant-current distance-voltage magnitude correlated uniquely coordination...

A review of in situ x‐ray photoelectron spectroscopy studies fluorine‐based plasma etching induced surface modifications several electronic materials, but primarily single‐crystal silicon, is presented. Post‐plasma analysis vacuum‐transferred etched specimens has been conducted an ultra‐high vacuum chamber connected via a load‐lock to the chamber. The achievement etch selectivity because different formation rates passivating fluorocarbon film which controls behavior and general substrate...

Scanning tunneling microscopy observations of the initial growth stages first layer pentacene on a monolayer film C60 Ag(111) are presented. Pentacene films nucleate and grow with molecules standing up at pentacene:C60 interface similar to thin phases observed weakly interacting substrates such as SiO2. Unlike reported phases, those 1 C60/Ag(111) exhibit striated morphology domains 4 nm nominal width. This long range pattern periodic displacements relative substrate is response stress...