Hochschullehre 2.0 zwischen Wunsch und Wirklichkeit

Entwicklung und Einsatz von Web-2.0-Technologien in verschiedenen Anwendungszusammenhängen führen zu einer Vielzahl von Veränderungen: Mit dem Rollenwechsel der Internet-Nutzenden von scheinbar passiven „consumern“ zu aktiven „prosumern“ geht die Veröffentlichung von zahlreichen selbst erstellten Inhalten im Web einher: Im Internetzeitalter bekommt die – erstmals 1980 von Alvin Toffler verwendete – Verbindung der Begriffe producer + consumer im Zusammenhang mit dem sog. user generated content nochmals eine neue Bedeutung. Dies stellt traditionelle Vorstellungen von Privatheit und Öffentlichkeit auf den Kopf – verspricht aber zugleich innovative und attraktive Einsatzmöglichkeiten. Dieser Beitrag widmet sich speziell der Frage, welche Potenziale Web-2.0-Werkzeuge für die Hochschullehre bergen. Zugleich wird untersucht, welche Anforderungen mit dem Einsatz der neuartigen Werkzeuge verbunden sind und inwiefern mit diesen Veränderungen ein – in der Literatur oft beschworener – „Wandel der Lernkultur“ einhergeht. (DIPF/ Orig.

Enhanced spin-orbit scattering length in narrow Al_xGa_{1-x}N/GaN wires

The magnetotransport in a set of identical parallel AlGaN/GaN quantum wire structures was investigated. The width of the wires was ranging between 1110 nm and 340 nm. For all sets of wires clear Shubnikov--de Haas oscillations are observed. We find that the electron concentration and mobility is approximately the same for all wires, confirming that the electron gas in the AlGaN/GaN heterostructure is not deteriorated by the fabrication procedure of the wire structures. For the wider quantum wires the weak antilocalization effect is clearly observed, indicating the presence of spin-orbit coupling. For narrow quantum wires with an effective electrical width below 250 nm the weak antilocalization effect is suppressed. By comparing the experimental data to a theoretical model for quasi one-dimensional structures we come to the conclusion that the spin-orbit scattering length is enhanced in narrow wires.Comment: 6 pages, 5 figure

Weak antilocalization in a polarization-doped AlxGa1-xN/GaN heterostructure with single subband occupation

Spin-orbit scattering in a polarization-doped Al0.30Ga0.70N/GaN two-dimensional electron gas with one occupied subband is studied at low temperatures. At low magnetic fields weak antilocalization is observed, which proves that spin-orbit scattering occurs in the two-dimensional electron gas. From measurements at various temperatures the elastic scattering time tau(tr), the dephasing time tau(phi), and the spin-orbit scattering time tau(so) are extracted. Measurements in tilted magnetic fields were performed, in order to separate spin and orbital effects

The State of Strain in Single GaN Nanocolumns As Derived from Micro-Photoluminescence Measurements

In the present paper, studies on the state of strain in single and ensembles of nanocolumns investigated by photoluminescence spectroscopy will be presented. The GaN nanocolumns were either grown in a bottom-up approach or prepared in a top-down approach by etching compact GaN layers grown on Si(111) and sapphire (0001) substrates. Experimental evidence for strain relaxation of the nanocolumns was found. The difference and development of the strain value for different nanocolumns could be verified by spatially resolved micro-photoluminescence on single nanocolumns separated from their substrate. A common D0X spectral position at 3.473 eV was found for all separated single GaN nanocolumns independent of the substrate or processing technique used, as expected for a relaxed system

Vorwort. Jubiläen und Zwischenbilanzen – Mit Lob und Kritik schon wieder zum Aufbruch?

Anlässlich des 50. Bandes der Buchreihe der Gesellschaft für Medien in der Wissenschaft ziehen die Autoren im Vorwort des Sammelwerkes zur Geschichte und zum Thema des E-Learning Zwischenbilanz. Unter den Schwerpunkten E-Learning-Förderung (1.), Didaktik (2.), Sicht der Anwender (3.), Institution Hochschule (4.) und Visionen fassen sie die Inhalte der einzelnen Beiträge des Buches zusammen. (DIPF/ ssch.

Spin dynamics in semiconductors

This article reviews the current status of spin dynamics in semiconductors which has achieved a lot of progress in the past years due to the fast growing field of semiconductor spintronics. The primary focus is the theoretical and experimental developments of spin relaxation and dephasing in both spin precession in time domain and spin diffusion and transport in spacial domain. A fully microscopic many-body investigation on spin dynamics based on the kinetic spin Bloch equation approach is reviewed comprehensively.Comment: a review article with 193 pages and 1103 references. To be published in Physics Reports