Contact: Prof. Philipp Aebi

Team fall 2003

X-ray photoelectron diffraction and Fermi surface mapping on a thin ferroelectric film (left) and a charge density wave compound (right), respectively

Geometrical and Electronic Structure at and Near Surfaces of Materials with Novel Electronic Properties
The aim of our research is to understand the electronic structure and the interplay between electronic degrees of freedom and the geometrical arrangement of atoms in materials with novel electronic properties. Since our experiments are based on photoemission (and in the future also on scanning probe microscopy) we are sensitive to materials properties in an area close to the surface defined by the escape depth of the electrons.

Angle-resolved photoemission is applied in two distinct energy regimes, either using ultraviolet photons to map valence bands and Fermi surfaces or by exciting core electrons with soft X-rays to obtain local, real-space information on the geometrical structure around the emitting atom (X-ray photoelectron diffraction).
Materials are on the one hand produced within MaNEP, e.g., charge density wave compounds (CDW’s) (H. Berger, EPFL) and thin ferroelectric films (J.-M. Triscone, Geneva) and on the other by in situ evaporation on single crystal surfaces. For the CDW’s the main interest is the driving mechanism behind the CDW formation, whereas for the thin ferroelectric films we explore the minimal thickness necessary to still exhibit ferroelectricity. In situ evaporation of thin films has been used to study hydrogen concentration induced switching optical properties.

References:
[1] J. Hayoz et al., Phys. Rev. Lett. 90, 196804 (2003).
[2] M. Bovet, et al., Phys. Rev. B 67, 125105 (2003).