79 research outputs found
Diffraction from disordered vicinal surfaces with alternating terraces
Vicinal surfaces with terraces of alternating stress develop inhomogeneous distributions of terrace sizes which sometimes leads even to the formation of double steps. Both vicinal Si(001) and vicinal Ge(001) are typical examples for this behavior. However, vicinal surfaces of some alloys show this effect, too. It is well established that average terrace sizes can be evaluated from the splitting of peaks in surface sensitive diffraction experiments. More parameters, however, are necessary to obtain an improved characterization of the morphology of the vicinal surface. Therefore, we present a detailed analysis of diffraction patterns from alternating vicinal surfaces to extract more statistical data, e.g., standard deviations of the terrace size distributions, step rms widths, step correlation lengths, and kink densities. This analysis considers both profiles of (split) diffraction peaks and the profile of the diffuse scattering. In addition, the diffraction analysis is applied to vicinal Ge(001) to characterize the morphology in full detail. © 2007 The American Physical Society
Formation routes and structural details of the CaF1 layer on Si(111) from high-resolution noncontact atomic force microscopy data
We investigate the CaF1/Si(111) interface using a combination of high-resolution scanning tunnelling and noncontact atomic force microscopy operated at cryogenic temperature as well as x-ray photoelectron spectroscopy. Submonolayer CaF1 films grown at substrate temperatures between 550 and 600 ◦C on Si(111) surfaces reveal the existence of two island types that are distinguished by their edge topology, nucleation position, measured height, and inner defect structure. Our data suggest a growth model where the two island types are the result of two reaction pathways during CaF1 interface formation. A key difference between these two pathways is identified to arise from the excess species during the growth process, which can be either fluorine or silicon. Structural details as a result of this difference are identified by means of high-resolution noncontact atomic force microscopy and add insights into the growth mode of this heteroepitaxial insulator-on-semiconductor system
Static magnetic proximity effect in Pt/NiFe bilayers investigated by x-ray resonant magnetic reflectivity
We present x-ray resonant magnetic reflectivity (XRMR) as a very sensitive
tool to detect proximity induced interface spin polarization in Pt/Fe,
Pt/NiFe, Pt/NiFe (permalloy), and Pt/Ni bilayers.
We demonstrate that a detailed analysis of the reflected x-ray intensity gives
insight in the spatial distribution of the spin polarization of a non-magnetic
metal across the interface to a ferromagnetic layer. The evaluation of the
experimental results with simulations based on optical data from ab initio
calculations provides the induced magnetic moment per Pt atom in the spin
polarized volume adjacent to the ferromagnet. We find the largest spin
polarization in Pt/Fe and a much smaller magnetic proximity effect in Pt/Ni.
Additional XRMR experiments with varying photon energy are in good agreement
with the theoretical predictions for the energy dependence of the magnetooptic
parameters and allow identifying the optical dispersion and absorption
across the Pt L3-absorption edge
Static Magnetic Proximity Effect in Pt Layers on Sputter-Deposited NiFe2O4 and on Fe of Various Thicknesses Investigated by XRMR
The longitudinal spin Seebeck effect is detected in sputter-deposited NiFe2O4
films using Pt as a spin detector and compared to previously investigated
NiFe2O4 films prepared by chemical vapor deposition. Anomalous Nernst effects
induced by the magnetic proximity effect in Pt can be excluded for the
sputter-deposited NiFe2O4 films down to a certain limit, since x-ray resonant
magnetic reflectivity measurements show no magnetic response down to a limit of
0.04 {\mu}B per Pt atom comparable to the case of the chemicallydeposited
NiFe2O4 films. These differently prepared films have various thicknesses.
Therefore, we further studied Pt/Fe reference samples with various Fe
thicknesses and could confirm that the magnetic proximity effect is only
induced by the interface properties of the magnetic material.Comment: 4 pages, 4 figure
Step and kink correlations on vicinal Ge(100) surfaces investigated by electron diffraction
Using spot profile analysis in low-energy electron diffraction, we have investigated vicinal Ge(100) surfaces, which were miscut by 2.7° and 5.4°, respectively, in [011] direction with respect to the surface normal. Within the kinematic approximation the morphology was evaluated quantitatively both perpendicular and parallel to the step edge direction. In contrast to vicinal Si(100) surfaces with similar miscut angles, the Ge(100) surfaces still show an alternating configuration of (2×1) and (1×2) reconstructed (100) terraces, which are separated by steps of single atomic height. From the spot profiles and their energy dependence we extracted the morphological parameters such as the average terrace width, the variance of the terrace size distribution, and the average kink separation. Furthermore, step energies on the vicinal Ge(100) surfaces were estimated. These turn out to be significantly lower than for Si(100) and lead to the formation of the observed double domain structure. © 2002 The American Physical SocietyDFGK+S Grupp
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