Ya. B. Losovyj

Work function and implications of doped poly(3,4-ethylenedioxythiophene)-co-poly(ethylene glycol)

We report work function and conductivity measurements of the block copolymer poly(3,4-ethylenedioxythiophene)-co-poly(ethylene glycol) (PEDOT-PEG) doped with perchlorate or para-toluenesulfonate anions. The electronic and chemical properties of doped PEDOT-PEG are discussed in the context of the hole injection for organic light emitting diodes. We show that different dopants can result in significant differences in conductivity with only small alterations to the work function.

The anisotropic band structure of layered In4Se3(001)

There is discernable and significant band dispersion along both high symmetry directions for cleaved ordered surfaces of the layered In4Se3(001). The extent of dispersion of approximately 1 eV is observed along the surface chain rows, and about 0.5 eV perpendicular to the surface “furrows,” consistent with theoretical expectations. A possible surface state exists at the surface Brillouin zone edge, in the direction perpendicular to the chains, in a gap of the projected bulk band structure. Excluding the possible surface state, the experimental hole mass is 5.5 times greater along the chains than perpendicular to the chains, but the dispersion is easier to discern.

The electronic structure of surface chains in the layered semiconductor In4Se3(100)

The ordered (100) surface of layered In4Se3 single crystals is characterized by semiconducting quasi-one-dimensional indium (In) chains. A band with significant dispersion in the plane of the surface is observed near the valence band maximum. The band exhibits an anisotropic dispersion with ∼1eV band width along the In chain direction. The dispersion of this band is largely due to the hybridization of In-s and Se-p orbitals, but the hybridization between In-s and Se-p and In-p and Se-p orbitals is also critical in establishing the band gap.

Temperature dependent induced spin polarization in Cr2O3 overlayers on epitaxial CrO2 films

Abstract Spin-resolved inverse photoemission investigations show that the native Cr 2 O 3 surface is antiferromagnetically coupled to the CrO 2 thin film substrate, with a temperature dependent induced polarization. The Cr 2 O 3 exhibits the characteristic behavior of a rigid band/spin mixing behavior (non-Stoner) of a local moment paramagnet. The strong shifts of the conduction band edge from room temperature to low temperature suggests that the extent of the induced polarization of the Cr 2 O 3 oxide surface, by the CrO 2 substrate, may be partly related to Coulomb blockade effects identified in CrO 2 /Cr 2 O 3 /CrO 2 junctions.

Lattice-stiffening transition in gadolinium chains on furrowed (112) surfaces

Al attice-stiffening transition is observed near 230 K in corrugated ‘chain like’ gadolinium structures formed o nM o(112) and W(112). This transition is evident from the change in the effective Debye temperature. Below the transition temperature of 230 K the gadolinium overlayer lattice has much higher effective Debye temperature than that observed for higher temperatures (for the quasi-one-dimensional Gd sub-monolayer structures or for the higher coverage overlayers). From model studies, lateral dipole–dipole and indirect interactions as well as the interaction between the adatoms and the substrate play an important role in this transition.

The K-shell Auger electron spectrum of gadolinium obtained using neutron capture in a solid state device

Highly doped or alloyed Gd2O3 in HfO2 films form heterojunction diodes with silicon. Single neutron capture events can be identified with a Hf0.85Gd0.15O1.93 to n-type silicon heterojunction. With long pulse integration times and suppression of the smaller pulses, there is agreement between the key pulse height spectral features and those predicted by Monte Carlo simulations. The latter align very well with the decay channels of the Gd following neutron capture, particularly those involving the Gd K-shell Auger electron resonances.

Differences in the Surface Charging at the (100) and (110) Surfaces of Li 2 B 4 O 7

From angle resolved photoemission, the (100) surface termination of Li 2 B 4 O 7 is significantly more polar than the (110) surface termination although the accepted dipole orientation of this pyroelectric crystal is along (001). Consistent with the surface termination, the surface charging at the surface of (100) is significantly greater than observed at (110) and plays a role in the surface photovoltage effects. Because of the different interfaces formed, device properties likely depend upon crystal faces of lithium borate.

The structure of the CoS2 (100)-(1 ? 1) surface

Quantitative low-energy electron diffraction (LEED) has been used to determine the structure of the cubic CoS 2 (100)-(1 × 1) surface. The clearly favored structural model from the LEED analysis is the 1S-terminated (1 × 1) surface, in which the S–S dimer is intact and the terminal surface layer retains a complete S–Co–S sandwich structure. The surface S atoms move outwards towards the vacuum while the subsurface Co atoms move towards the bulk, by approximately 0.03 and 0.11 A, respectively. In addition, the S atoms in the third sublayer relax outwards by about 0.12 A, thus providing an indication of a stronger S–S dimer bond and a denser surface region. The complete atomic coordinates of the S–Co–S surface layers are determined in this analysis. Includes “Corrigendum” from J. Phys.: Condens. Matter 19 249001

The electron?phonon coupling at the Mo(112) surface

We investigated the electron-phonon coupling (EPC), in the vicinity of the Fermi level, for the surface-weighted states of Mo(112) from high resolution angle-resolved photoemission data taken parallel to the surface corrugation (i.e. [Formula: see text]). The surface-weighted bandwidth may be discussed in terms of electron-electron interactions, electron impurity scattering and electron-phonon coupling and exhibits a mass enhancement factor λ = 0.42, within the Debye model, determined from the experimentally derived self-energy. Gold overlayers suppress the mass enhancement of the Mo(112) surface-weighted band crossing the Fermi level at 0.54 Å(-1).

The surface stability of CoS2(100)

The stability of various possible terminations of the CoS2 (1 × 1) surface have been explored and theoretical expectations are found to agree with experiment. With extensive annealing, there is a phase separation at the (100) surface of CoS2. Sulfur segregation to the surface leads to a significant change in the largely sulfur bands due to changes in the hybridized bands, with cobalt. Resonant photoemission spectra indicate clearly that the hybridized cobalt and sulfur bands, characteristic of the CoS2 bulk, lie at higher binding energies than those of segregated sulfur layers. This is discussed in terms of the stability of various surface structures.