Search Results
Epitaxial hybrid ferromagnet-semiconductor structures: Growth, structural and magnetic properties
2004, Däweritz, L.
Ferromagnet-semiconductor heterostructures are promising materials for the integration of magnetic or spin related functions into semiconductor materials and devices. Fe-on-GaAs and MnAs-on-GaAs are canditates for potential room temperature applications. We review our recent results on growth, structural and magnetic properties of these materials, and their use as spin injectors. The most critical issue of Fe/GaAs heterostructures is the delicate interface formation during epitaxy and its possible modification during subsequent processing. The properties of the MnAs/GaAs heterostructures are intimately related to the phase transition between ferromagnetic and paramagnetic phases.
Oberflächenemitter auf der Basis von Gruppe-III-Nitriden - Verfahrensentwicklung, Herstellung und Bauelementecharakterisierung : Schlussbericht
2008, PDI
[no abstract available]
Elektronenkorrelation und Dissipationsprozesse in Halbleiterquantenstrukturen, Teilvorhaben: Quantendrähte und Quantenpunkte auf strukturierten, hochindizierten Substraten im Verbund mit metallischen, magnetischen Schichten : Abschlussbericht über das F+E Vorhaben im BMBF-Förderschwerpunkt
2005, Ploog, Klaus H., Herfort, Jens, Ramsteiner, Manfred, Trampert, Achim, Friedland, Klaus-Jürgen
[no abstract available]
Erforschung eines diodengepumpten (Multi-core) M-Profil-Faserlasers im Ultrakurzpulsbetrieb, Unterauftrag: Entwicklung eines Halbleiter-Bauelementes aus Bragg-Reflektoren, sättigbarem Absorber und 2-Photonen-Absorber : Abschlußbericht über das F&E-Vorhaben
2000, Däweritz, Lutz, Hey, Rudolf, Herfort, Jens
[no abstract available]
Enhanced spin coherence via mesoscopic confinement during acoustically induced transport
2008, Stotz, J.A.H., Hey, R., Santos, P.V., Ploog, K.H.
Long coherence lifetimes of electron spins transported using moving potential dots are shown to result from the mesoscopic confinement of the spin vector. The confinement condition to control electron spin dephasing is governed by the relation between the characteristic spin–orbit length of the electron spins and the dimensions of the dot potential, which governs the electron spin coherence lifetime. The spin–orbit length is a sample-dependent parameter determined by the Dresselhaus contribution to the spin–orbit coupling and can be predictably controlled by varying the sample geometry. We further show that the coherence lifetime of the electron spins is independent of the local carrier densities within each potential dot, which suggests the possibility of coherent, long-range transport of single electron spins.
Elektronenkorrelation und Dissipationsprozesse in Halbleiterquantenstrukturen, Teilvorhaben: Heteroepitaxie ferromagnetischer Materialien auf III-V Halbleiter für Spininjektion : Schlussbericht
2005, Ploog, Klaus H., Braun, Wolfgang, Kaganer, Vladimir M., Jenichen, Bernd, Satapathy, Dillip K.
[no abstract available]
Abschlußbericht über das F+E Vorhaben im BMBF-Förderschwerpunkt: Nanoelektronische Halbleiterstrukturen für die Quanteninformationstechnologie (nanoQUIT), Teilvorhaben: Ferromagnet/ Halbleiter-Heterostrukturen für die Magnetologik und Spintronik
2009, Herfort, Jens, Koch, Reinhold, Trampert, Achim
[no abstract available]
Nitrogen-enhanced indium segregation in (Ga,In)(N,As)/GaAs multiple quantum wells grown by molecular-beam epitaxy
2007, Luna, E., Trampert, A., Pavelescu, E.-M., Pessa, M.
Transmission electron microscopy (TEM) is used to determine the composition of quaternary (Ga,In)(N,As) quantum wells (QWs). Through a combined analysis of the chemically sensitive (002) dark-field (DF) images and the lattice-resolving high-resolution TEM images, the local distributions of nitrogen and indium in the growth direction are determined. In particular, we are able to directly detect the existence of indium segregation in (Ga,In)(N,As) QWs. A comparison with the indium distribution profile in the nitrogen-free (In,Ga)As QWs, grown under similar conditions, revealed that incorporating N into the alloy enhanced indium segregation.
Spininjektion, Spintransport, und Spinkohärenz für neuartige Spintronik-Bauelemente bei Raumtemperatur, Teilvorhaben: Hybridstrukturen aus Halbleitern und ferromagnetischen Materialien : Abschlussbericht für das F+E-Vorhaben im BMBF-Verbundprojekt
2005, Herfort, Jens, Ploog, Klaus H.
[no abstract available]
Ostwald ripening of faceted two-dimensional islands
2007, Kaganer, Vladimir, Braun, Wolfgang, Sabelfeld, Karl
We study Ostwald ripening of two-dimensional adatom and advacancy islands on a crystal surface by means of kinetic Monte Carlo simulations. At large bond energies the islands are square-shaped, which qualitatively changes the coarsening kinetics. The Gibbs--Thomson chemical potential is violated: the coarsening proceeds through a sequence of `magic' sizes corresponding to square or rectangular islands. The coarsening becomes attachment-limited, but Wagner's asymptotic law is reached only after a very long transient time. The unusual coarsening kinetics obtained in the Monte Carlo simulations are well described by the Becker--Döring equations of nucleation kinetics. These equations can be applied to a wide range of coarsening problems.