Institute For Oberflachen Und Schichtanalytik Ifos

Kaiserslautern, Germany

Institute For Oberflachen Und Schichtanalytik Ifos

Kaiserslautern, Germany

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Gnaser H.,Institute For Oberflachen Und Schichtanalytik Ifos | Gnaser H.,University of Kaiserslautern | Gutsch S.,Albert Ludwigs University of Freiburg | Wahl M.,Institute For Oberflachen Und Schichtanalytik Ifos | And 5 more authors.
Journal of Applied Physics | Year: 2014

Silicon nanocrystals (SiNCs) embedded in a silicon oxide matrix were studied by 3D atom probe tomography (APT). The distribution of the SiNC diameter was found to have a mean value of 3.7 ± 0.8 nm. The elemental composition of these particles was determined by employing two different approaches: (i) The proximity histogram method and (ii) a cluster identification algorithm based on maximum-atom separations. Both approaches give very similar values in terms of the amount of P, O, and Si within the SiNCs: the mean atomic concentrations are cP = 0.77% ± 0.4%, cO = 12.3% ± 2.1%, and cSi = 85.3% ± 2.1%. A detailed cluster analysis implies that, on average, a 4.5-nm SiNC would contain around 30 P atoms, whereas a 2.0-nm SiNC would contain only around 3 P atoms. Radial concentration profiles obtained for these SiNCs indicate that the P content is inhomogeneous and possibly enhanced at the boundary as compared to the interior of the NCs. About 20% of the P atoms are found to be incorporated into the SiNCs, whereas roughly 30% are trapped within the interfacial layer (with a thickness of ∼ 0.8 nm); the remainder resides in the surrounding matrix. Cluster-size dependent P concentrations support the view of self-purification in the Si nanostructures. © 2014 AIP Publishing LLC.


Gutsch S.,Albert Ludwigs University of Freiburg | Gutsch S.,University of New South Wales | Laube J.,Albert Ludwigs University of Freiburg | Hiller D.,Albert Ludwigs University of Freiburg | And 7 more authors.
Applied Physics Letters | Year: 2015

We study the electronic properties of phosphorus doped Si nanocrystal/SiO2 superlattices and determine the carrier concentration by transient current analysis. This is achieved by encapsulating the multilayers between two electrical insulation layers and controlling the carrier mobility by a defined layer to layer separation. A saturation of the voltage dependent ionized carrier density is observed which indicates complete substitutional dopant ionization and allows to calculate the dopant induced charge carrier density. It is found that the doping efficiency of the superlattice is only 0.12% considering the full ionization regime which explains the unusual small dopant effect on transport characteristics. © 2015 AIP Publishing LLC.


Petkov C.,University of Kassel | Reintanz P.M.,University of Kassel | Kulisch W.,University of Kassel | Degenhardt A.K.,University of Kassel | And 7 more authors.
Applied Surface Science | Year: 2016

Phthalocyanine (Pc) derivatives containing different central metal atoms (Mn, Cu, Ti) and different peripheral chains were synthesized and comprehensively characterized. Their interaction with nanocrystalline diamond (NCD) films, as-grown by hot-filament chemical vapor deposition or after their modification with oxygen plasma to exchange the hydrogen termination with oxygen-containing groups, was studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The elemental composition as determined by XPS showed that the Pc were grafted on both as-grown and O-terminated NCD. Mn, Cu and Ti were detected together with N stemming from the Pc ring and S in case of the Ti-Pc from the peripheral ligands. The results for the elemental surface composition and the detailed study of the N 1s, S 2p and O 1s core spectra revealed that Ti-Pc grafted better on as-grown NCD but Cu-Pc and Mn-Pc on O-terminated films. Samples of Mn-Pc on as-grown and O-terminated NCD were further investigated by NEXAFS spectroscopy. The results showed ordering of the grafted molecules, laying flat on the H-terminated NCD surface while only the macrocycles were oriented parallel to the O-terminated surface with the peripheral chains perpendicular to it. © 2016 Elsevier B.V. All rights reserved.


Papaioannou E.T.,University of Kaiserslautern | Fuhrmann P.,University of Kaiserslautern | Jungfleisch M.B.,University of Kaiserslautern | Bracher T.,University of Kaiserslautern | And 4 more authors.
Applied Physics Letters | Year: 2013

We examine the influence of crystal growth on the spin-pumping induced inverse spin Hall effect in Fe/Pt bilayers. The morphology of the Fe/Pt interface influences the effective spin mixing conductance. The increase of growth temperature leads to smoother and larger grains at the interface that enhance the effective spin mixing conductance. The spin current injection efficiency into Pt, measured by the inverse spin Hall effect, is maximized by optimizing the epitaxy of Pt on Fe. In magnetic field dependent measurements, the presence of a strong magnetic anisotropy gives rise to two distinct inverse spin Hall effect voltage peaks. © 2013 AIP Publishing LLC.


Gnaser H.,Institute For Oberflachen Und Schichtanalytik Ifos | Gnaser H.,University of Kaiserslautern | Schiller R.,Institute For Oberflachen Und Schichtanalytik Ifos | Wahl M.,Institute For Oberflachen Und Schichtanalytik Ifos | Reuscher B.,Institute For Oberflachen Und Schichtanalytik Ifos
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2013

The displacement of atoms in a magnetic trilayer Fe (10 nm)/Cr (0.7 nm)/Fe (10 nm) system by 30 keV Ga+ ion irradiation was studied by 3D Atom Probe Tomography (APT). From APT, the positions of individual Cr and Fe atoms could be located with sub-nm spatial resolution, both before and after ion bombardment. In the pristine specimen the presence of the 0.7-nm Cr layer was identified and individual lattice planes with a distance of ∼0.15 nm were observed which would correspond to the monolayer spacing of the Fe lattice, in agreement with the growth process. Upon irradiation, the Cr layer broadens to ∼1.2 nm at a fluence of 3 ∓ 1014 Ga+/cm 2 and to ∼3.4 nm at 3 × 1015 Ga +/cm2. From this broadening the mean squared relocation distance of (Cr) atoms was derived, 〈r2〉 ∼0.4 nm 2. Computer simulations indicate that, at a fluence of 3 × 1014 Ga+/cm2, each Cr atom in the intermediate layer is displaced on average once in the collision processes. The distribution of implanted Ga ions appears to exhibit discontinuities at the Fe/Cr interfaces which might be caused by a demixing of Ga at the Cr layer. © 2013 Published by Elsevier B.V.


Gnaser H.,Institute For Oberflachen Und Schichtanalytik Ifos | Gnaser H.,University of Kaiserslautern
Surface and Interface Analysis | Year: 2014

Atomprobe tomography (APT) constitutes a rather unique analytical technique for the 3D elemental characterization of solidmaterials with potentially sub-nm spatial resolution. APT is, therefore, very well suited for the analysis of a nanostructured specimen such as matrix-embedded nanoparticles, ultra-thin films and junctions, grain boundaries, and others. This presentation will emphasize these capabilities, describing threemethods of datamining that can be used to fully exploit APT: (i) Visualization of atomic lattice planes in crystalline specimens, (ii) the determination of iso-concentration surfaces and proximity histograms derived thereof, and (iii) a cluster identification algorithm based on maximum-atom separations. These approaches will be illustrated by means of different types of samples: a crystalline tungsten specimen, a Fe/Cr/Fe multilayer system, Si nanocrystals embedded in a silicon oxidematrix, and Mg clustering in GaN. The results demonstrate clearly that sub-nm-sized structures can be characterized by APT. Copyright © 2014 John Wiley & Sons, Ltd.


Gnaser H.,University of Kaiserslautern | Gnaser H.,Institute For Oberflachen Und Schichtanalytik Ifos | Schiller R.,Institute For Oberflachen Und Schichtanalytik Ifos | Wahl M.,Institute For Oberflachen Und Schichtanalytik Ifos | And 6 more authors.
Journal of Physics D: Applied Physics | Year: 2012

Ion-bombardment effects in a magnetic trilayer Fe (10 nm)/Cr (0.7 nm)/Fe (10 nm) system have been studied by 3D atom probe tomography (APT). The films were bombarded by 30 keV Ga+ ions at low fluences. From APT, the positions of individual Cr and Fe atoms could be located with sub-nm spatial resolution, both before and after ion bombardment. In the pristine specimen the presence of the 0.7 nm Cr layer was verified and individual lattice planes with a spacing of ∼0.15 nm were identified which would correspond to the monolayer spacing of the Fe lattice, in agreement with the growth process. Upon irradiation, the Cr layer is broadened to ∼1.2 nm at a fluence of 3 × 1014 Ga+ cm-2 and to ∼3.4 nm at 3 × 1015 Ga+ cm-2. Computer simulations indicate that, at a fluence of 3 × 1014 Ga+ cm-2, each Cr atom in the intermediate layer is displaced on average once in the collision processes. © 2012 IOP Publishing Ltd.

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