Substrate temperature dependence of the structure of polythiophene thin films obtained by Matrix Assisted Pulsed Laser Evaporation (MAPLE)

Issue		Eur. Phys. J. Appl. Phys. Volume 48, Number 1, October 2009


Article Number		10505
Number of page(s)		8
Section		Surfaces, Interfaces and Films
DOI		10.1051/epjap/2009130
Published online		21 July 2009

Eur. Phys. J. Appl. Phys. 48, 10505 (2009)
DOI: 10.1051/epjap/2009130

Substrate temperature dependence of the structure of polythiophene thin films obtained by Matrix Assisted Pulsed Laser Evaporation (MAPLE)

V. Califano¹, F. Bloisi^{1, 2}, L. Vicari^{1, 2}, M. Barra^{1, 2}, A. Cassinese^{1, 2}, E. Fanelli³, R. Buzio⁴, U. Valbusa⁴, A. Carella⁵ and A. Roviello⁵

¹ CNR-INFM Coerenthia c/o Università degli Studi di Napoli Federico II, Piazzale Tecchio 80, 80125 Napoli, Italy
² Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II, Piazzale Tecchio 80, 80125 Napoli, Italy
³ Department of Materials and Production Engineering, Università degli Studi di Napoli Federico II, Piazzale Tecchio 80, 80125 Napoli, Italy
⁴ Nanomed Labs, Department of Physics, Università of Genova and Advanced Biotechnology Center, Via Dodecaneso 33, 16146 Genova, Italy
⁵ Department of Chemistry, Università degli Studi di Napoli Federico II, Via Cinthia, 80124 Napoli, Italy

valeriacalifano@hotmail.com

Received: 13 March 2009 / Accepted: 11 May 2009 / Published online: 21 July 2009

Abstract
Thin films of head-tail (H-T) regio-regular poly[3-(4-octyloxyphenyl) thiophene] (POOPT) were grown using the MAPLE (Matrix Assisted Pulsed Laser Evaporation) technique in which the target is a frozen solution of the polymer in chloroform. Target evaporation was obtained by laser irradiation at 1064 nm and substrates were kept at different temperatures. Information concerning the preservation of the polymer local chemical structure following laser irradiation was obtained by FTIR (Fourier Transform InfraRed) spectroscopy. Based on FTIR data, the chemical structure of the deposited polymer seemed to undergo little or no damage. From UV-Visible spectroscopic analysis, it turned out that the degree of order of the film is strongly affected by the substrate temperature: the polymer was deposited in a disordered form on the substrate at room temperature whereas on the hot surface we locally obtained the $\pi$ -stacked structure characteristic of polythiophenes. Atomic force microscopy (AFM) images showed that the polymer formed aggregates of different dimensions (<1 $\mu$ m to 5 $\mu$ m) with a columnar shape and showed micrometric domains with sharp and apparently regular edges for the film grown on a hot substrate. Electrical measurements performed by a standard two-probe technique confirm that the structural order degree strongly affects the film charge transport properties.

PACS
78.20.-e - Optical properties of bulk materials and thin films.
78.40.Me - Organic compounds and polymers.
61.80.Ba - Ultraviolet, visible, and infrared radiation effects.
81.15.Fg - Laser deposition.

© EDP Sciences 2009

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