X-ray diffuse scattering from thin polystyrene films

ORAL

Abstract

Diffuse x-ray scattering from silicon supported polystyrene films has been measured as a function of thickness. An x-ray standing wave method was used to distinguish scattering from the surface and scattering from density fluctuations within the interior of the film. The former is a measure of surface roughness, while the latter yields the compressibility, $\kappa { }_T$. Films thicker than $h \quad \sim $100 nm had bulk values for $\kappa { }_T$, while thinner films showed the empirical relation $\kappa { }_T(h)=\kappa _T^{bulk} \left( {1+\alpha \mathord{\left/ {\vphantom {\alpha h}} \right. \kern-\nulldelimiterspace} h} \right)^\delta $ with \textit{$\alpha $} = 20 ($\pm $1) nm and \textit{$\delta $ }= 1.6 ($\pm $1). The surface component of the scattering agreed with capillary wave theory for small $q$, but excess scattering appeared at larger $q, $which followed a power law, $S^\ast \sim \,q^{1 \mathord{\left/ {\vphantom {1 \upsilon }} \right. \kern-\nulldelimiterspace} \upsilon }$. We attribute the excess scattering to static roughness from chain ends and loops near the surface.

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Authors

  • Mrinmay Mukhopadhyay

    • University of California, San Diego, CA 92093
    • Department of Physics, University of California at San Diego

  • Zhang Jiang

    • University of California, San Diego, CA 92093
    • Department of Physics, University of California at San Diego
    • Sogang University

  • Sunil Sinha

    • University of California, San Diego, CA 92093
    • Department of Physics, University of California, San Diego, La Jolla, CA-92093, USA.
    • Dept. of Physics, Univ. of California San Diego, La Jolla, CA 92093
    • Department of Physics, University of California at San Diego
    • University of California, San Diego
    • Department of Physics, University of California San Diego, La Jolla, CA 92093
    • University of California, San Diego and Los Alamos National Laboratory

  • Laurence B. Lurio

    • Northern Illinois University, DeKalb, IL 60115

  • Jarett Stark

    • Northern Illinois University, DeKalb, IL 60115

  • Xuesong Jiao

    • Advanced Photon Source, Argonne, IL 60439

  • Suresh Narayanan

    • Advanced Photon Source, Argonne, IL 60439
    • X-ray Science Division, Argonne National Lab, Argonne, IL 60439
    • Argonne National Laboratory
    • Advanced Photon Source, Argonne National Lab
    • X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439
    • Argonne National Lab

  • Alec Sandy

    • Advanced Photon Source, Argonne, IL 60439
    • Advanced Photon Source, Argonne National Laboratory, Argonne, IL-60439, USA.
    • Advanced Photon Source, Argonne National Lab