Keitaro Kago

Characterization of Thin Polymer Films by X-ray Reflectometry with Synchrotron Radiation

X-ray reflectivity (XR) measurements with a synchrotron radiation source were carried out for thin polymer films on a glass plate. From the XR data, the film thickness and surface and interface roughnesses could be determined. In addition, the appropriate conditions and precision for measurements were also discussed. Kiessig fringes were observed clearly for specular XR measurements of poly(methylmethacrylate) thin film. Analysis of the XR data allowed the determination of the film thickness very precisely. By a curve-fitting procedure of the XR profile, the film-surface roughness and film-substrate interface roughnesses were determined. A Fourier transform of the XR data was performed as an alternative method of evaluating the film thickness. The values for the film thickness obtained by the curve-fitting procedure and Fourier-transform procedure were slightly different from each other. One possibility for the cause of this difference may be an integral error and/or cut-off effect in the Fourier-transform procedure. The XR technique with synchrotron radiation is a very powerful tool for structural characterization of thin polymer films.

X-ray reflectivity study of fine structure of thin polymer films and polymer assembly at interface

Abstract For the purpose of studying the surfaces of both thin films and monolayers on water surface, an apparatus for X-ray reflectometry (XR) has been newly constructed by modification of a theta–theta goniometer. At the sample position, the specially designed LB trough was set for water surface measurements. In the case of a thin poly(vinyl alcohol) film on a glass plate prepared by the spin-coating method, a lot of sharp and clear Kiessig fringes (at least 34th) are observed, indicating an extremely high resolution of our XR apparatus. Similar experiments were also performed for thin multilayer films composed of different kinds of polymers, and the fine structures of these films were precisely determined. XR profiles of distearoylphosphatidylcholine (DSPC), a phospholipid, monolayer on water surface were measured at three different surface pressures. The fringe positions shifted towards the lower angle direction with increasing surface pressure, indicating that the monolayer thickness increases with the increase of surface pressure.