61 research outputs found
Strong Electron Confinement By Stacking-fault Induced Fractional Steps on Ag(111) Surfaces
The electron reflection amplitude at stacking-fault (SF) induced
fractional steps is determined for Ag(111) surface states using a low
temperature scanning tunneling microscope. Unexpectedly, remains as high as
as energy increases from 0 to 0.5 eV, which is in clear contrast
to its rapidly decreasing behavior for monatomic (MA) steps [L. B{\"u}rgi et
al., Phys. Rev. Lett. \textbf{81}, 5370 (1998)]. Tight-binding calculations
based on {\em ab-initio} derived band structures confirm the experimental
finding. Furthermore, the phase shifts at descending SF steps are found to be
systematically larger than counterparts for ascending steps by . These results indicate that the subsurface SF plane significantly
contributes to the reflection of surface states
One-dimensional surface states on a striped Ag thin film with stacking fault arrays
One-dimensional (1D) stripe structures with a periodicity of 1.3 nm are
formed by introduction of stacking fault arrays into a Ag thin film. The
surface states of such striped Ag thin films are studied using a low
temperature scanning tunneling microscope. Standing waves running in the
longitudinal direction and characteristic spectral peaks are observed by
differential conductance (dI/dV) measurements, revealing the presence of 1D
states on the surface stripes. Their formation can be attributed to quantum
confinement of Ag(111) surface states into a stripe by stacking faults. To
quantify the degree of confinement, the effective potential barrier at the
stacking fault for Ag(111) surface states is estimated from independent
measurements. A single quantum well model with the effective potential barrier
can reproduce the main features of dI/dV spectra on stripes, while a
Kronig-Penney model fails to do so. Thus the present system should be viewed as
decoupled 1D states on individual stripes rather than as anisotropic 2D Bloch
states extending over a stripe array.Comment: 10 pages, 6 figure
ΠΠΈΠ΄ΡΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΠΊΠ° ΠΆΠΈΠ΄ΠΊΠΎΡΠ°Π·Π½ΠΎΠ³ΠΎ ΠΏΡΠΎΡΠ΅ΡΡΠ° Π°Π»ΠΊΠΈΠ»ΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π±Π΅Π½Π·ΠΎΠ»Π° ΠΏΡΠΎΠΏΠΈΠ»Π΅Π½ΠΎΠΌ
Improved electrical conductance through self-assembly of bioinspired peptides into nanoscale fibers
We investigated the electrical conductance of films consisting of bio-inspired peptide molecules and of their extended form, self-assembled nanoscale fibers. Here, the entirely natural and novel peptide sequence, GFPRFAGFP, was designed based on naturally occurring fibrous proteins. To attain electrical conductance, we implemented phenylalanine residues in the sequence such that the aromatic rings are present along face of the molecule. We confirmed self-assembly of nanoscale fibers in pure water after incubating the peptides at 37 Β°C by AFM. The morphology and conformation of the incubated peptide fibers were studied using AFM, fluorescence spectroscopy and circular dichroism spectroscopy. It was shown that very thin fibers with a single-molecule-level diameter form. The helical feature of the peptide backbone and enhanced stacking of aromatic residues were also investigated. This aromatic stacking is important to our electrical measurements as, even in vacuum environment, films of non-incubated GFPRFAGFP sometimes show apparent conductance while those containing self-assembled nanoscale fibers show stable and improved conductance. We propose that this effect may be due to extended stacking of aromatic residues providing Ο - Ο conjugation along the fiber
Macroscopic Superconducting Current through a Silicon Surface Reconstruction with Indium Adatoms: Si(111)-(R7R3)-In
Macroscopic and robust supercurrents are observed by direct electron
transport measurements on a silicon surface reconstruction with In adatoms
(Si(111)-(R7xR3)-In). The superconducting transition manifests itself as an
emergence of the zero resistance state below 2.8 K. characteristics
exhibit sharp and hysteretic switching between superconducting and normal
states with well-defined critical and retrapping currents. The two-dimensional
(2D) critical current density is estimated to be as high as
at 1.8 K. The temperature dependence of
indicates that the surface atomic steps play the role of strongly coupled
Josephson junctions.Comment: 4 pages, 3 figures; The error in the values of 2D critical current
density was corrected. In the old version, the numbers were
wrong by a factor of 100 due to a mechanical error. This does not affect the
following analysis and conclusio
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