Micro Grazing Incidence SAXS of Gold Clusters

The image shows a microbeam grazing incidence small angle x-ray scattering ( mGISAXS) pattern obtained at ID13. The sample was a novel gradient multilayer consisting of a self-assembled nanometer-sized gold cluster layer on top of thin polymer layer on a silicon substrate. This class of samples plays a crucial role in biomedical analysis and anti-counterfeiting labels. The gradient was imposed on the gold cluster layer as a change in height of the clusters. The gradient was scanned with a 5 micron collimated beam and 50 micron stepsize.

Fig. 1 shows a comparison of a simulation with the mGISAXS pattern which was chosen as the title page of 24 March issue of Applied Physics Letters Vol. 82 (2003) [1]. The scattering pattern shows basically two phenomena: Minima in q_z along the line q_y=0 (middle of the picture, detector scan) and side maxima at finite q_y. These features indicate the 3D cluster shape, their height, in-plane radius and arrangement.

This new method mGISAXS was pioneered at ID13 and is now becoming a routine user mode. We can now investigate laterally inhomogeneous surfaces and interfaces with a two order-of-magnitude increase in spatial resolution compared to standard reflection setups and a ten-fold lower q_min compared to transmission geometry.

First experiments were performed on colloidal and polymeric surfaces [1,2].

Fig, 1: a) mGISAXS pattern (left) and comparison with simulation (right) using IsGISAXS [1,3]. This picture was chosen as title page on the 24 March issue of Appl. Phys. Lett., vol. 82 (2003). b) Detector coordinate system.

[1] S.V. Roth, M.Burghammer, C.Riekel, P.Müller-Buschbaum, A.Diethert, P.Panagiotou, Appl. Phys. Lett. 82 (2003) 1935-1937
[2] P.Müller-Buschbaum, S.V.Roth, M.Burghammer, A.Diethert, P.Panagiotou, C.Riekel, Europhys. Lett. 61 (2003) 639-644
[3] R. Lazzari, J. Appl. Cryst. 35 (2002) 406