SPring-8, the large synchrotron radiation facility

Date : 16:00- November16, 2007

Place : SPring-8 "HOUKOUKAN"

Speaker : Dr. Harald Reichert

Affiliate : Max-Planck-Institute for Metals Research

Title : High Energy X-ray Diffraction for The Study of Confined Systems

Abstract :
Interfaces of confined systems such as thin films, nano-objects, or deeply buried interfaces are of fundamental interest in condensed matter physics. The availability of highly brilliant synchrotron radiation has boosted our understanding of the structure of such systems in the last decades. Most commonly, the structure of surfaces and interfaces or nano-objects is studied in surface scattering geometries (Grazing Angle Diffraction (GAD), Crystal Truncation Rod Diffraction (CTRD), and in specular and off-specular reflection geometry at typical photon energies around 15keV. These techniques are not applicable in the case of deeply buried interfaces. Conventional x-ray scattering geometries are often unable to separate the scattering signals from structurally modified thin layers at an interface from the large background of bulk-like scattering signals. Especially for deeply buried interfaces, the strong absorption of the incoming and scattered photons within the capping material producing very weak scattering signals on top of a large background from the penetrated solid. We have recently extended conventional diffraction techniques to high photon energies (E >> 50..100keV, using high energy microbeams) in a high resolution setup which allows us to resolve most of these problems. The technique has been implemented at a dedicated endstation (HEMD) at beamline ID15A at the ESRF (Grenoble, France). The instrument allows us to study free surfaces or thin films as well as buried interfaces. Examples from studies of combinatorial materials libraries [1] will be presented as well as examples of interfacial structures at deeply buried interfaces for a variety of materials like water/ice [2], metals [3] and organic liquids. The examples demonstrate the applicability of our methods for the nondestructive and in-situ characterization of a broad range of interfacial structures.

[1] D. A. Kukuruznyak et al., Appl. Phys. Lett. 91, 071916 (2007).
[2] S. Engemann et al., Phys. Rev. Lett. 90, 205701 (2004)
      M. Mezger et al., PNAS 103, 18401 (2006).
[3] H. Reichert et al., Phys. Rev. Lett. 98, 116101 (2007).
      H. Reichert et al., Nature 408, 839 (2000).

Organizer : MIZUKI (PHS 3902)