Search results for "Overlayer"
showing 6 items of 16 documents
Oxygen on Fe(110): magnetic properties of the adsorbate system
1999
Abstract Investigations concerning the electronic and magnetic properties of oxygen adsorbed on magnetized iron films were carried out by means of angle and spin resolving photoelectron spectroscopy. Iron(1 1 0), epitaxially grown on a W(1 1 0) crystal, served as the ferromagnetic substrate. Exchange splittings of the O 2p x derived level were detected demonstrating a magnetic coupling between the chemisorbate and the iron layer. This observation indicates the presence of an induced magnetic moment within the adsorbate overlayer. Variations of the exchange splitting occurred as a function of the oxygen coverage, energy of the exciting radiation, and detection angle of the emitted photoelect…
Photoemission of spinpolarized electrons from strained GaAsP
1996
Strained layer GaAs.95P.05 photo cathodes are presented, which emit electron beams spinpolarized to a degree of P = 75% typically. Quantum yields around QE = 0.4% are observed routinely. The figure of merit P2 × QE = 2.3 × 10−3 is comparable to that of the best strained layer cathodes reported in literature. The optimum wavelength of irradiating light around 830 nm is in convenient reach of Ti:sapphire lasers or diode lasers respectively. The cathodes are produced using MOCVD-techniques. A GaAs.55P.45-GaAs.85P.15 superlattice structure prevents the migration of dislocations from the substrate and bottom layers to the strained overlayer. The surface is protected by an arsenic layer so that n…
Chalcogen adsorption and surface magnetism
2000
Abstract Investigations concerning the electronic and magnetic properties of oxygen and sulfur adsorbed on magnetized surfaces were carried out by means of angle and spin resolving photoelectron spectroscopy. Iron(110), a polycrystalline iron alloy, and an amorphous metallic glass (Fe 79 B 16 Si 5 ) served as ferromagnetic substrates. Exchange splittings of the O 2p and S 3p derived levels could be detected, demonstrating a magnetic coupling between the chemisorbate and iron. This observation presents a prerequisite for an induced magnetic moment within the adsorbate overlayer. For sulfur an adsorbate-induced structure only in the minority spin channel near the Fermi level was observed whic…
Molecular dynamics simulation of epitaxial growth of the Si(001) surface
1988
Abstract Molecular beam epitaxy on a Si(100) substrate has been studied using a molecular dynamics method with the Stillinger-Weber model potential. At high substrate temperature, 800 K, well ordered crystalline layers are found to grow underneath an amorphous overlayer of approximately 5 A thick. A limiting temperature for epitaxial growth is found to be 480 K, below which the growth does not produce ordered layers. When the sample deposited below 480 K is heated up to 800 K and the deposition is started again the original adatoms start to form ordered atomic layers. Thus the collisions of the deposited atoms in addition to the substrate temperature seem to play an essential role in the gr…
MgO/Ag(100): confined vibrational modes in the limit of ultrathin films
2003
The vibrational modes of clean MgO films are investigated vs film thickness by means of high-resolution electron energy-loss spectroscopy. For thin films (20\char21{}30 monolayers) we observe, in accord with the literature, the Fuchs-Kliewer phonon at $677{\mathrm{cm}}^{\ensuremath{-}1}$ and the Wallis mode at $524{\mathrm{cm}}^{\ensuremath{-}1}.$ For ultrathin films standing wave optical phonons confined in the overlayer are present, whose frequencies depend strongly on film thickness. Comparison with theoretical calculations for MgO slabs on a perfect conductor shows that the experimental frequencies are lower than expected, indicating the presence of compressive stress. At and below one-…
Total Structure and Electronic Structure Analysis of Doped Thiolated Silver [MAg24(SR)18]2– (M = Pd, Pt) Clusters
2015
With the incorporation of Pd or Pt atoms, thiolated Ag-rich 25-metal-atom nanoclusters were successfully prepared and structurally characterized for the first time. With a composition of [PdAg24(SR)18](2-) or [PtAg24(SR)18](2-), the obtained 25-metal-atom nanoclusters have a metal framework structure similar to that of widely investigated Au25(SR)18. In both clusters, a M@Ag12 (M = Pd, Pt) core is capped by six distorted dimeric -RS-Ag-SR-Ag-SR- units. However, the silver-thiolate overlayer gives rise to a geometric chirality at variance to Au25(SR)18. The effect of doping on the electronic structure was studied through measured optical absorption spectra and ab initio analysis. This work d…