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Interface induced crystal structures of dioctyl-terthiophene thin films
Oliver Werzer1, Nicolas Boucher, Johann P de Silva
1Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 810 Graz, Austria.
Langmuir : the ACS Journal of Surfaces and Colloids
|May 15, 2012
Summary
Investigations on semiconducting dioctyl-terthiophene thin films reveal surface-induced ordering and distinct bulk phases. Temperature changes alter these phases, impacting the material
Area of Science:
- Materials Science
- Organic Electronics
- Crystallography
Background:
- Semiconducting organic thin films are crucial for electronic devices.
- Understanding thin film structure and phase behavior is key to controlling material properties.
- Dioctyl-terthiophene (DOTT) is a relevant organic semiconductor.
Purpose of the Study:
- To investigate the temperature-dependent structural and morphological properties of DOTT thin films on silica.
- To elucidate the role of the silica interface in templating DOTT thin film phases.
- To explore the potential for tuning crystallographic and physical properties through interfacial control.
Main Methods:
- Thin film preparation of dioctyl-terthiophene (DOTT) on silica surfaces.
- Temperature-dependent X-ray diffraction (XRD) for structural analysis.
- Scanning force microscopy (SFM) for morphological investigations.
Main Results:
- DOTT thin films exhibit coexistence of surface-induced order and bulk polymorphs at room temperature.
- Distinct crystalline and liquid crystalline phases (crystal G, smectic F, smectic C) observed at elevated temperatures.
- An up-right standing molecular conformation of DOTT is maintained across all observed phases.
- A stable interfacial layer acts as a template for phase formation.
- Rapid cooling leads to a metastable crystalline state with an intermediate unit cell.
Conclusions:
- The silica-DOTT interface templated distinct structural phases in DOTT thin films.
- Temperature-induced phase transitions and molecular conformations were identified.
- Interfacial engineering offers a route to tune the properties of organic thin films.
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