Peter Busch
Department of Materials Science & Engineering, Cornell University
Abstract:
Due the chemical
connectivity of incompatible polymers block copolymers tend to phase
separate into highly ordered structures on length scales smaller than 100
nm, which is of great interest for thin film technology. However, knowledge
about their structure and their orientation in the thin films is mandatory
to design films with specific properties. For the investigation of the
structure of block copolymers in bulk, small angle X-ray scattering (SAXS)
in transmission geometry has been emerged as a routine technique. For thin
films on supported substrates SAXS in transmission geometry is difficult
because of the low scattering volume as well as the high absorption of the
substrate. For this reason SAXS in reflection geometry has emerged as an
alternative in the last few years. If an X-ray beam impinges under a very
small incident angle onto the surface of a film, most of the intensity is
reflected, but a small part is scattered due to the internal structure of
the thin film. Because of the very small incident angles this technique is
called grazing incidence small angle X-ray scattering (GISAXS). The
resulting scattering patterns differ slightly from traditional transmission
SAXS, as the image below demonstrates. The talk will unravel the
peculiarities of this technique by discussing the contributions of
refraction at the film surface and reflection from the substrate to the
resulting scattering patterns on selected examples from recent experiments.
2008 Run
Nov 19th - Dec 22nd
