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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 14: Poster: Interfaces and Thin Films

CPP 14.6: Poster

Monday, March 22, 2010, 16:30–18:00, Poster C

In situ measurements of polyelectrolyte multilayers using multiple angle ellipsometry: even-odd effects in layer thickness and refractive index — •Peter Nestler, Stephan Block, and Christiane A. Helm — Institut für Physik, Ernst-Moritz-Arndt Universität, Felix-Hausdorff-Str. 6, D-17489 Greifswald, Germany

We investigate in situ the growth of polyelectrolyte multilayers (PEMs) by sequential adsorption of poly(allyl amine)hydrochloride (PAH) and poly(styrene sulfonate) (PSS) using multiple angle ellipsometry within a liquid cell. The multilayers are built onto RCA cleaned and poly(ethylen imine) (PEI) coated silicon wafers using polyelectrolyte adsorption solutions, whose temperature is controlled between 22 °C and 55 °C and which additionally contain 1 M NaCl or 1 M KCl. After each adsorption step we determine the PEM thickness and index of refraction with high accuracy by measuring the ellipsometric parameters at several angles of incidence. We observe a PEM thickness which is increased by at least 40% with respect to X-Ray reflectrometry measurements performed after drying in air. Furthermore we find, that the increase in PEM thickness after an adsorption step shows an even-odd effect which is attributed to an unequal contribution of both polyelectrolytes to the thickness of one bilayer: at 22 °C PSS amounts to more than 60% to the average bilayer thickness, whereas at 55 °C this value reduces to 35%. A similar even-odd effect is observed in the refractive index of the PEM and allows an estimation of the refractive index of a single PSS or PAH layer within one bilayer.