SANDiE Partner P02

Katholieke Universiteit Leuven, Belgium

The KU Leuven is the oldest university in the Low Countries, and the largest in Belgium (30 000 students). The Laboratorium voor Vaste-Stoffysica en Magnetisme (VSM) is the largest solid-state physics laboratory in Belgium. It currently consists of more than fifty researchers, plus a dozen technicians and two secretarial staff. VSM is involved in a number of national and international collaborative projects, many of which are funded by the EC, and coordinated the successful NANOMAT project of the FP5 GROWTH programme on self-assembled semiconductor nanostructures. The main activity of the laboratory is the research of low-dimensional and nanoscale materials physics. A wide range of semiconducting, superconducting and magnetic materials are investigated using state-of-the-art sample preparation, characterization and measurement techniques. Two groups, Pulsed Fields - Low Dimensional Semiconductors and Scanning Probe Microscopy (SPM) will contribute to the project, integrating 6 researchers and 4 doctoral students into the network.

VSM's expertise and unique facilities for the optical spectroscopy of low-dimensional semiconductor systems will be exploited during the project. The main work will be centered around the photoluminescence (PL) facility in the Pulsed Field Group headed by Prof. Victor Moshchalkov. Pulsed magnetic fields allow the study of self-assembled nanostructured materials in a regime where the magnetic length is smaller than the confining length scale, and is a unique method for obtaining important spectroscopic information about carrier confinement. KU Leuven is the world's leading institution in the use of pulsed fields for the study of semiconductor nanostructures and has the unique possibility to these systems in the crucial 900 to 1700 nm range relevant for most applications. Current research includes InP/GaInP2 and inverted GaAs/AlGaAs quantum dots (QDs) in collaboration with P23 (MPI-FKF), InAs/GaAs QDs in collaboration with P09 (UNOTT), GaSb/GaAs QDs in collaboration with P04 (TUB) and InAs/InP quantum wires in collaboration with P22 (CS1C). There is a long-standing collaboration with the theory group at P03 (UA). Presently, fields of up to 50 T are available, with 60 T expected shortly.

In the SPM Group headed by Prof. Chris Van Haesendonck, who is also the administrative head of the VSM laboratory, the focus is on studying the structural, electrical and magnetic properties at the nanometer scale using scanning probes combined with high-resolution electrical transport measurements. Powerful and up-to-date facilities were developed for scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) in a controlled atmosphere, in ultra-high vacuum (UHV) and at low temperatures. SPM is an important technique to analyse the growth surface after formation of self-assembled nanostructures. With this technique one obtains information on the location, concentration and shape of the self-assembled nanostructures. The unique low-temperature SPM techniques available at Leuven, (i) an STM with an in situ cleavage mechanism, and (ii) an AFM based on piezoresistive force detection, will allow the study of crystal surfaces with atomic resolution. Both the STM and the AFM are able to operate in the presence of a magnetic field. Using the cleavage technique atomically flat surfaces that remain perfectly clean for several weeks can be obtained, allowing to measure in detail the electronic properties of the cleaved surfaces with atomic resolution by means of scanning tunnelling spectroscopy (STS). An advanced low-temperature STM-UHV system became available in 2004.

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last update: 28 February 2019, A. Weber