title: Optimizing pentacene thin-film transistor performance: Temperature and surface condition induced layer growth modification.
abstract: In this work we presentin situelectrical and surface analytical, as well asex situatomic force microscopy (AFM) studies on temperature and surface condition induced pentacene layer growth modifications, leading to the selection of optimized deposition conditions and entailing performance improvements. We prepared p++-silicon/silicon dioxide bottom-gate, gold bottom-contact transistor samples and evaluated the pentacene layer growth for three different surface conditions (sputtered, sputtered + carbon and unsputtered + carbon) at sample temperatures during deposition of 200 K, 300 K and 350 K. The AFM investigations focused on the gold contacts, the silicon dioxide channel region and the highly critical transition area. Evaluations of coverage dependent saturation mobilities, threshold voltages and corresponding AFM analysis were able to confirm that the first 3-4 full monolayers contribute to the majority of charge transport within the channel region. At high temperatures and on sputtered surfaces uniform layer formation in the contact-channel transition area is limited by dewetting, leading to the formation of trenches and the partial development of double layer islands within the channel region instead of full wetting layers. By combining the advantages of an initial high temperature deposition (well-ordered islands in the channel) and a subsequent low temperature deposition (continuous film formation for low contact resistance) we were able to prepare very thin (8 ML) pentacene transistors of comparably high mobility.
authors.affiliation: Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Lassnig
authors.affiliation: Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Hollerer
authors.affiliation: MATERIALS-Institute for Surface Technologies and Photonics, Joanneum Research Forschungsgesellschaft mbH, Franz-Pichler-Straße 30, A-8160 Weiz, Austria.
authors.forename: B
authors.initials: B
authors.lastname: Striedinger
authors.affiliation: MATERIALS-Institute for Surface Technologies and Photonics, Joanneum Research Forschungsgesellschaft mbH, Franz-Pichler-Straße 30, A-8160 Weiz, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Fian
authors.affiliation: MATERIALS-Institute for Surface Technologies and Photonics, Joanneum Research Forschungsgesellschaft mbH, Franz-Pichler-Straße 30, A-8160 Weiz, Austria.
authors.forename: B
authors.initials: B
authors.lastname: Stadlober
authors.affiliation: Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Winkler
keywords: Atomic force microscopy; Carrier mobility; Dewetting; Diffusion; Organic thin-film transistor; Pentacene