31 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
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.
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.
Surface diffusion of Pb atoms on the Si(553)-Au surface in narrow quasi-one-dimensional channels
Electron transport through a strongly correlated monoatomic chain
We study transport properties of a strongly correlated monoatomic chain
coupled to metallic leads. Our system is described by tight binding
Hubbard-like model in the limit of strong on-site electron-electron
interactions in the wire. The equation of motion technique in the slave boson
representation has been applied to obtain analytical and numerical results.
Calculated linear conductance of the system shows oscillatory behavior as a
function of the wire length. We have also found similar oscillations of the
electron charge in the system. Moreover our results show spontaneous spin
polarization in the wire. Finally, we compare our results with those for
non-interacting chain and discuss their modifications due to the Coulomb
interactions in the system.Comment: 7 pages, 5 figure
Electron transport across a quantum wire in the presence of electron leakage to a substrate
We investigate electron transport through a mono-atomic wire which is tunnel
coupled to two electrodes and also to the underlying substrate. The setup is
modeled by a tight-binding Hamiltonian and can be realized with a scanning
tunnel microscope (STM). The transmission of the wire is obtained from the
corresponding Green's function. If the wire is scanned by the contacting STM
tip, the conductance as a function of the tip position exhibits oscillations
which may change significantly upon increasing the number of wire atoms. Our
numerical studies reveal that the conductance depends strongly on whether or
not the substrate electrons are localized. As a further ubiquitous feature, we
observe the formation of charge oscillations.Comment: 7 pages, 7 figure