7 research outputs found
Two-domains bulklike Fermi surface of Ag films deposited onto Si(111)-(7x7)
Thick metallic silver films have been deposited onto Si(111)-(7x7) substrates
at room temperature. Their electronic properties have been studied by using
angle resolved photoelectron spectroscopy (ARPES). In addition to the
electronic band dispersion along the high-symmetry directions, the Fermi
surface topology of the grown films has been investigated. Using ARPES, the
spectral weight distribution at the Fermi level throughout large portions of
the reciprocal space has been determined at particular perpendicular
electron-momentum values. Systematically, the contours of the Fermi surface of
these films reflected a sixfold symmetry instead of the threefold symmetry of
Ag single crystal. This loss of symmetry has been attributed to the fact that
these films appear to be composed by two sets of domains rotated 60 from
each other. Extra, photoemission features at the Fermi level were also
detected, which have been attributed to the presence of surface states and
\textit{sp}-quantum states. The dimensionality of the Fermi surface of these
films has been analyzed studying the dependence of the Fermi surface contours
with the incident photon energy. The behavior of these contours measured at
particular points along the Ag L high-symmetry direction puts forward
the three-dimensional character of the electronic structure of the films
investigated.Comment: 10 pages, 12 figures, submitted to Physical Review
Atomic-scale structure of dislocations revealed by scanning tunneling microscopy and molecular dynamics
Selective area, synchrotron radiation induced, delta doping of silicon
We have used broadband synchrotron radiation to induce selective area surface doping of boron into silicon. The source of the boron was nido-decaborane (B10H14) adsorbed on Si(111) at 100 K. Irradiation caused decomposition of the adsorbed molecule which lead to an enhanced concentration of free boron in the irradiated area. Using Si 2p core level photoelectron spectroscopy, the surface chemical composition and Fermi level position in both the irradiated and unirradiated regions were determined. The downward movement of the Fermi level was greater in the irradiated region than in the unirradiated region, and greater for n-type than for p-type Si
Mismatch dislocations caused by preferential sputtering of a platinum-nickel alloy surface
Transient mobility mechanisms of deposited metal atoms on insulating surfaces: Pd on MgO (100)
The importance and mechanisms of transient mobility of atoms and molecules adsorbing at surfaces have been a subject of controversy for many years. We used classical molecular dynamics simulations to examine transient mobility of Pd atoms adsorbing on the MgO (100) surface with incident kinetic energies not exceeding 0.4 eV. The calculations show that deposited Pd atoms exhibit high mobility at temperatures below 80 K where the contribution from thermal diffusion processes should be negligible. For our selected deposition conditions, aimed at simulation of Pd cluster growth experiments, an estimated 76 of the impinging Pd atoms are expected to travel up to 20 à away from the collision site before capture on a 5 K surface. We find that mobility of metal atoms on oxide surfaces is expected to decrease with decreasing incident energy and increase with decreasing incident angle. Comparison with prior studies highlights similarities and differences with other surface diffusion processes, such as long jumps. At higher surface temperatures, the observed mobility will mainly be due to thermally activated processes rather than transient mobility mechanisms. Atoms that exhibit transient mobility upon deposition may quickly migrate to surface features and defects affecting kinetics of growth and structures of nanoclusters and surface layers. © 2012 American Chemical Society