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Dynamics of Monolayer–Island Transitions in 2,7-Dioctyl-benzothienobenzthiophene Thin Films

Authors

  • Michael Dohr,

    1. Institut für Festkörperphysik, Technische Universität Graz, Petersgasse 16, 8010 Graz (Austria)
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  • Dr. Oliver Werzer,

    1. Institut für Pharmazeutische Wissenschaften, Karl-Franzens Universität Graz Mozartgasse 3, 8010 Graz (Austria)
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  • Quan Shen,

    1. Institut für Physik, Montanuniversität Leoben Franz-Josef-Straße 18, 8700 Leoben (Austria)
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  • Dr. Ingo Salzmann,

    1. Institut für Physik, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 6, 12489 Berlin (Germany)
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  • Prof. Dr. Christian Teichert,

    1. Institut für Physik, Montanuniversität Leoben Franz-Josef-Straße 18, 8700 Leoben (Austria)
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  • Dr. Christian Ruzié,

    1. Laboratoire de Chimie des Polymères, Faculté des Sciences, Université Libre de Bruxelles CP 206/01, Campus de la Plaine,1050 Bruxelles (Belgium)
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  • Dr. Guillaume Schweicher,

    1. Laboratoire de Chimie des Polymères, Faculté des Sciences, Université Libre de Bruxelles CP 206/01, Campus de la Plaine,1050 Bruxelles (Belgium)
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  • Prof. Dr. Yves Henri Geerts,

    1. Laboratoire de Chimie des Polymères, Faculté des Sciences, Université Libre de Bruxelles CP 206/01, Campus de la Plaine,1050 Bruxelles (Belgium)
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  • Prof. Dr. Michele Sferrazza,

    Corresponding author
    1. Département de Physique, Faculté des Sciences, Université Libre de Bruxelles CP223, Campus de la Plaine, 1050 Bruxelles (Belgium)
    • Département de Physique, Faculté des Sciences, Université Libre de Bruxelles CP223, Campus de la Plaine, 1050 Bruxelles (Belgium)
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  • Prof. Dr. Roland Resel

    Corresponding author
    1. Institut für Festkörperphysik, Technische Universität Graz, Petersgasse 16, 8010 Graz (Austria)
    • Institut für Festkörperphysik, Technische Universität Graz, Petersgasse 16, 8010 Graz (Austria)
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Abstract

The order in molecular monolayers is a crucial aspect for their technological application. However, the preparation of defined monolayers by spin-coating is a challenge, since the involved processes are far from thermodynamic equilibrium. In the work reported herein, the dynamic formation of dioctyl-benzothienobenzothiophene monolayers is explored as a function of temperature by using X-ray scattering techniques and atomic force microscopy. Starting with a disordered monolayer after the spin-coating process, post-deposition self-reassembly at room temperature transforms the initially amorphous layer into a well-ordered bilayer structure with a molecular herringbone packing, whereas at elevated temperature the formation of crystalline islands occurs. At the temperature of the liquid-crystalline crystal–smectic transition, rewetting of the surface follows resulting in a complete homogeneous monolayer. By subsequent controlled cooling to room temperature, cooling-rate-dependent kinetics is observed; at rapid cooling, a stable monolayer is preserved at room temperature, whereas slow cooling causes bilayer structures. Increasing the understanding and control of monolayer formation is of high relevance for achieving ordered functional monolayers with defined two-dimensional packing, for future applications in the field of organic electronics.

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