47 research outputs found
High resolution scanning tunneling spectroscopy of ultrathin Pb on Si(111)-(6x6) substrate
The electronic structure of Si(111)-(6x6)Au surface covered with submonolayer
amount of Pb is investigated using scanning tunneling spectroscopy. Already in
small islands of Pb with thickness of 1 ML Pb and with the diameter
of only about 2 nm we detected the quantized electronic state with energy 0.55
eV below the Fermi level. Similarly, the I(V) characteristics made for the
Si(111)-(6x6)Au surface reveal a localized energy state 0.3 eV below the Fermi
level. These energies result from fitting of the theoretical curves to the
experimental data. The calculations are based on tight binding Hubbard model.
The theoretical calculations clearly show prominent modification of the I(V)
curve due to variation of electronic and topographic properties of the STM tip
apex.Comment: 7 pages, 7 figures, accepted for publication in Surface Scienc
Quantum statistics of ideal gases in confined space
In this paper, the effects of boundary and connectivity on ideal gases in
two-dimensional confined space and three-dimensional tubes are discussed in
detail based on the analytical result. The implication of such effects on the
mesoscopic system is also revealed.Comment: 7 pages, Late
Anomalous thickness dependence of the Hall effect in ultrathin Pb layers on Si(111)
The magnetoconductive properties of ultrathin Pb films deposited on Si(111)
are measured and compared with density-functional electronic band-structure
calculations on two-dimensional, free-standing, 1 to 8 monolayers thick Pb(111)
slabs. A description with free-standing slabs is possible because it turned out
that the Hall coefficient is independent of the substrate and of the
crystalline order in the film. We show that the oscillations in sign of the
Hall coefficient observed as a function of film thickness can be explained
directly from the thickness dependent variations of the electronic
bandstructure at the Fermi energy.Comment: 4 pages incl. 3 figures, RevTeX, to appear in Phys. Rev.
Thermoelectric effects in STM tunneling through a monoatomic chain
We study thermoelectric properties of the system composed of a monoatomic
chain on a surface and additional electrode coupled to the chain, which can be
an STM tip. In particular, we are interested in thermopower, electric and
thermal conductance, Wiedemann-Franz relation and thermoelectric figure of
merit, which is a direct measure of the usefulness of the system for
applications. We discuss the modifications of the STM wire topography due to
temperature gradient between the electrodes. Finally, we also make connection
to STM experiment, in which the thermopower has been directly measured, showing
different structure, not visible in topography spectra.Comment: 5 pages, 3 eps figure
Surface diffusion of Pb atoms on the Si(553)-Au surface in narrow quasi-one-dimensional channels
The one-dimensional diffusion of individual Pb atoms on the Si(553)-Au surface has been investigated by a combination of scanning tunneling microscopy (STM), spectroscopy (STS), and first-principles density functional theory. The obtained results unambiguously prove that the diffusion channels are limited to a narrow region between Au chains and step edges of the surface. Much wider channels observed in STM and STS data have electronic origin and result from an interaction of Pb with surface atoms. The length of the channels is determined by a distance between defects at step edges of the Si(553)-Au surface. The defects can act as potential barriers or potential wells for Pb atoms, depending on their origin
Double non-equivalent chain structure on vicinal Si(557)-Au surface
We study electronic and topographic properties of the vicinal Si(557)-Au
surface using scanning tunneling microscopy and reflection of high energy
electron diffraction technique. STM data reveal double wire structures along
terraces. Moreover behavior of the voltage dependent STM tip - surface distance
is different in different chains. While the one chain shows oscillations of the
distance which are sensitive to the sign of the voltage bias, the oscillations
in the other chain remain unchanged with respect to the positive/negative
biases. This suggests that one wire has metallic character while the other one
- semiconducting. The experimental results are supplemented by theoretical
calculations within tight binding model suggesting that the observed chains are
made of different materials, one is gold and the other one is silicon chain.Comment: 9 pages, 12 figures, accepted for publication in Phys. Rev.
Template driven self-assembly of the pentacene structure on the Si(553)-Pb surface
The self-assembly of the pentacene molecules on the Pb-ordered Si(553) surface is studied with scanning tunneling microscopy and density functional theory methods. Within the surface coverage up to a single monolayer, pentacene was found to form two different chain-like structures. They vary in molecular density, but both exhibit long-range, one-dimensional ordering with longer molecular axes aligned along step edges. The low-density phase consists of single discontinuous molecular rows and adapts the template surface periodicity, while the high-density phase features triple molecular chains with the unit cell determined by the length of the pentacene molecules. Such an arrangement of the molecules is controlled by a subtle balance between moleculeâmolecule and moleculeâsubstrate interactions
Scanning tunneling microscopy of monoatomic gold chains on vicinal Si(335) surface: experimental and theoretical study
We study electronic and topographic properties of the Si(335) surface,
containing Au wires parallel to the steps. We use scanning tunneling microscopy
(STM) supplemented by reflection of high energy electron diffraction (RHEED)
technique. The STM data show the space and voltage dependent oscillations of
the distance between STM tip and the surface which can be explained within one
band tight binding Hubbard model. We calculate the STM current using
nonequilibrium Keldysh Green function formalism.Comment: 6 pages, 4 figure
Electrical conductance at initial stage in epitaxial growth of Pb on modified Si(111) surface
The electrical conductance and RHEED intensities as a function of the
coverage have been measured during Pb depositions at 105 K on Si(111)-(6x6)Au
with up to 4.2 ML of annealed Pb. The experiments show the strong influence of
used substrates on the behavior of the conductance during the epitaxy of Pb
atoms, especially for very initial stage of growth. Oscillations of the
conductance during the layer-by-layer growth are correlated with RHEED
intensity oscillations. The analysis of the conductance behavior is made
according to the theory described by Trivedi and Aschcroft (Phys.Rev.B 38,12298
(1988)).Comment: 5 pages, 3 figures. Surf. Sci. - accepte