3 research outputs found
First-principles study of nucleation, growth, and interface structure of Fe/GaAs
We use density-functional theory to describe the initial stages of Fe film
growth on GaAs(001), focusing on the interplay between chemistry and magnetism
at the interface. Four features appear to be generic: (1) At submonolayer
coverages, a strong chemical interaction between Fe and substrate atoms leads
to substitutional adsorption and intermixing. (2) For films of several
monolayers and more, atomically abrupt interfaces are energetically favored.
(3) For Fe films over a range of thicknesses, both Ga- and As-adlayers
dramatically reduce the formation energies of the films, suggesting a
surfactant-like action. (4) During the first few monolayers of growth, Ga or As
atoms are likely to be liberated from the interface and diffuse to the Fe film
surface. Magnetism plays an important auxiliary role for these processes, even
in the dilute limit of atomic adsorption. Most of the films exhibit
ferromagnetic order even at half-monolayer coverage, while certain
adlayer-capped films show a slight preference for antiferromagnetic order.Comment: 11 two-column pages, 12 figures, to appear in Phys. Rev.
First Principles Calculations of Fe on GaAs (100)
We have calculated from first principles the electronic structure of 0.5
monolayer upto 5 monolayer thick Fe layers on top of a GaAs (100) surface. We
find the Fe magnetic moment to be determined by the Fe-As distance. As
segregates to the top of the Fe film, whereas Ga most likely is found within
the Fe film. Moreover, we find an asymmetric in-plane contraction of our
unit-cell along with an expansion perpendicular to the surface. We predict the
number of Fe 3d-holes to increase with increasing Fe thickness on -doped
GaAs.Comment: 9 pages, 14 figures, submitted to PR
RESONANCES IN NEAR-THRESHOLD X-RAY PHOTOABSORPTION OF INNER SHELLS
Nous avons mésuré au Laboratoire de Brookhaven (NSLS) et à Stanford (SSRL) des sections efficaces absolues de photoabsorption au moyen de rayonments de synchrotron près du seuil et pour un large éventail d'énergie (20 eV - 3 keV). Des données de transmissions receuillies pour des cibles multi-couches aux propriétés bien définies nous ont permis de déterminer les sections efficaces absolues avec une incertitude globale de l'ordre de 10 % et pour une résolution sur l'énergie meilleure que 0.2 %. Nous présentons quelques exemplaires de nos résultats.Synchrotron radiation measurements of near-threshold and broad-range (20 eV - 3 keV) absolute photoabsorption cross sections were made at the Brookhaven National Laboratory (NSLS) and at Stanford (SSRL). Transmission data for well-characterized multilayer foils provided absolute cross sections with 10 % overall uncertainties and better than 0.2 % energy resolution. Several examples of our results are presented