Place: Kleiner Physik-Hörsaal, Geschwister-Scholl-Platz
Date: 11.12.09, Time: 15:30 h
Electron interference and spin-orbit coupling in semiconductor nanowires
Prof. Thomas Schaepers
Institute of Bio- and Nanosystems, FZ Jülich
Semiconductor nanowires fabricated by a bottom-up approach are versatile building blocks for the design of future electronic and spintronic devices. Among the many possible materials indium-based semiconductors, e.g. InN or InAs, are particularly interesting because of their low energy band gap and their high surface conductivity. At low temperatures electron interference effects often play an important role in the transport characteristics of nanostructures. In case that the characteristic phase-coherence length is in the order of the nanowire dimensions, interesting interference effects can be observed. Information on the phase-coherent transport is gained from measurements of universal conductance fluctuations. We find that at temperatures below 1 K phase-coherence is maintained in the complete wire structure. For InN nanowires with a very small diameter below 40 nm pronounced flux periodic oscillations in the magneto-conductance are observed, which can be attributed to the formation of coherent circular quantum states in the tube-like surface electron gas. For InN as well as for InAs nanowires the presence of spin-orbit coupling is verified by measuring the weak antilocalization effect. Spin-orbit coupling is relevant as a possible mechanism to control the spin orientation in spintronic devices.