Effect of Surface Influenced Order on Thermal Expansivity of Polymer Thin Films

        Variations of the thermal expansion of thin polyimide films as a function of film thickness (40nm to 260nm) have been measured by monitoring film thickness as a function of temperature using x-ray reflectivity from samples of poly(pyromellitic dianhydride oxydianiline), (PMDA-ODA) films spin-cast onto silicon wafers. The effective expansion coefficient of the film decreases with decreasing thickness and is consistent with a bilayer model in which an interfacial region of constant thickness is formed for each film. The expansion coefficient of this surface or interfacial region is less than one third the coefficient of the interior of the films. A simple method is described whereby the thermal expansion coefficient may be determined by reflectivity.

By: C. Thompson (Polytechnic Univ.), R. F. Saraf and J. L. Jordan-Sweet

Published in: RC20693 in 1997

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