2 research outputs found
Plasmon-assisted electron-electron collisions at metallic surfaces
We present a theoretical treatment for the ejection of a secondary electron
from a clean metallic surface induced by the impact of a fast primary electron.
Assuming a direct scattering between the incident, primary electron and the
electron in a metal, we calculate the electron-pair energy distributions at the
surfaces of Al and Be. Different models for the screening of the
electron-electron interaction are examined and the footprints of the surface
and the bulk plasmon modes are determined and analyzed. The formulated
theoretical approach is compared with the available experimental data on the
electron-pair emission from Al.Comment: 30 pages, 9 figure
Instability, Intermixing and Electronic Structure at the Epitaxial LaAlO3/SrTiO3(001) Heterojunction
The question of stability against diffusional mixing at the prototypical
LaAlO3/SrTiO3(001) interface is explored using a multi-faceted experimental and
theoretical approach. We combine analytical methods with a range of
sensitivities to elemental concentrations and spatial separations to
investigate interfaces grown using on-axis pulsed laser deposition. We also
employ computational modeling based on the density function theory as well as
classical force fields to explore the energetic stability of a wide variety of
intermixed atomic configurations relative to the idealized, atomically abrupt
model. Statistical analysis of the calculated energies for the various
configurations is used to elucidate the relative thermodynamic stability of
intermixed and abrupt configurations. We find that on both experimental and
theoretical fronts, the tendency toward intermixing is very strong. We have
also measured and calculated key electronic properties such as the presence of
electric fields and the value of the valence band discontinuity at the
interface. We find no measurable electric field in either the LaAlO3 or SrTiO3,
and that the valence band offset is near zero, partitioning the band
discontinuity almost entirely to the conduction band edge. Moreover, we find
that it is not possible to account for these electronic properties
theoretically without including extensive intermixing in our physical model of
the interface. The atomic configurations which give the greatest electrostatic
stability are those that eliminate the interface dipole by intermixing, calling
into question the conventional explanation for conductivity at this interface -
electronic reconstruction. Rather, evidence is presented for La indiffusion and
doping of the SrTiO3 below the interface as being the cause of the observed
conductivity