CHARACTERIZATION OF ULTRATHIN RIGID-ROD POLYIMIDE FILMS PREPARED BY THE LANGMUIR-BLODGETT METHOD

Svetlana Goloudina¹, Victor Luchinin¹, Vyacheslav Pasyuta¹, Valentina Sklizkova², Vladislav Kudryavtsev², Vladimir Rozanov³, Alexandr Levin⁴, Dirk Meyer⁴, Peter Paufler⁴

¹St.Petersburg State Electrotechnical University, St.Peterburg,  Russia

²Institute of Macromolecular Compounds, Russian Academy of Sciences, St.Petersburg,  Russia

³Institute for Analytical Instrumentation, Russian Academy of Sciences, St.Petersburg, Russia

⁴Institut fur Strukturphysik, Technische Universitat Dresden, Dresden, Germany

Ultrathin films of various substances on the solid surface are important for modern micro- and nanotechnology. Rigid-chain polyimides are of considerable interest for these purposes because this type of polyimides exhibits the highest thermal stability among polyimides (up to 560°C), good dielectric properties, and low thermal expansion coefficient, which provides good compatibility with the substrate used in microelectronics.

In the present work polyimide films were obtained by the thermal imidization of Langmuir-Blodgett films of precursor (alkylammonium salts of tert-amine o, o', o''- trihexadecanoyltriethanolamine  and a polyamic acid (PAA) based on dianhydride of 3, 3', 4, 4'- biphenyltetracarboxylic acid and o-tolidine (BPDA-oTD)). The precursor Langmuir-Blodgett films on silicon substrate consisted of 7, 11 and 29 monolayers. The polyimide films prepared were examined by using atomic-force microscopy (AFM), X-ray reflectivity and ellipsometry.

The results of an X-ray reflection analysis have shown that the polyimide films are homogeneous, and the thickness of films is linearly proportional to the number of precursor monolayers.

It was shown that film thickness increasing within the range from 3.3 nm to 13.6 nm is correlated  with an increase of the roughness (from 1.6 nm to 2.6 nm) of the film surface and with a decrease of the film density (from 1.39 g/sm³ to 1.00 g/sm³). The AFM images show a micro-domain structure of the polyimide films. The size of domains depends on the polyimide film thickness and alters from 30-50 nm to ~ 100 nm. Values of the thickness of ultra-thin films as determined by different methods were found  to agree well. The same applies to values of the roughness.

This work was supported in part by the RFBI (project N 05-03-33194) and Sci.Sch.-1824.2003.3

Svetlana Goloudina, Victor Luchinin, Vyacheslav Pasyuta, Valentina Sklizkova, Vladislav Kudryavtsev, Vladimir Rozanov, Alexandr Levin, Dirk Meyer, Peter Paufler Characterization of ultrathin rigid-rod polyimide films prepared by the Langmuir-Blodgett method // 5^th International Symposium «Molecular Mobility and Order in Polymer Systems». Saint Petersburg , june 20-24, 2005 . Book of Abstracts, P-152.

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