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Low-dimensional structures
Low dimensional structures show several interesting
effects due to the breaking of the bulk symmetry and confinement.
Resonances induced by surface states and surface phonons can enhance
signals by two orders of magnitude or make signals appear at
forbidden energies.
Self-organized formation is the main method to form
the low-dimensional structures. To understand and concequently to
influence the mechanism of self-organized formation of quantuum dots
in III-V semicondutors in Metal-Organic Vapour Phase Epitaxy (MOVPE)
is one of the major research topics in our group. Other related
topics are step-bunching or the formation of quantuum wires.
Microstructures are also formed during the adsorption
of adsorbates on clean surfaces in Ultra-High Vaccum. Here the focus
lies on Raman scattering, together with electron diffraction. Even
clean surfaces can have detectable surface phonons at energies
different from bulk phonons. Currently the surface phonons of
low-dimensional structures such as 1D-In nanowires on Si are studied
in more detail.
Using a new setup all available optical techniques
(Raman, Reflectance Anisotropy
Spectroscopy (RAS), Ellipsometry) work between high (1000K) and
low temperatures (20K) on the same surface in the same machine. This
allows us to investigate phase transitions such as charge density
waves in the quasi-1D-Structures. Ex-situ the surfaces are
characterized by Atomic Force Microscopy (AFM), Electron Microscopy,
Photoluminescence, and Angle Resolved ligh Scattering (ARS).
AFM
image of quantum dots aligned along macrossteps from step bunching.
Contact:
- Stefan Weeke (MOVPE, quantum dot formation)
- Karsten Fleischer (UHV, nanowire formation, RAS, Raman)
- Sandhya Chandola (UHV, nanowire formation, RAS)
Collaboration:
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