Effect of film thickness, type of buffer layer, and substrate temperature on the morphology of dicyanovinyl-substituted sexithiophene films

Journal article

The influence of film thickness, type of buffer underlayer, and deposition substrate temperature on the crystal structure, microstructure, and morphology of the films of dicyanovinyl-substituted sexithiophene with four butyl-chains (DCV6T-Bu₄) is investigated by means of X-ray diffraction (XRD) and X-ray reflectivity methods. A neat Si wafer or a Si wafer covered by a 15 nm buffer underlayer of fullerene C₆₀ or 9,9-Bis[4-(N,N-bis-biphenyl-4- yl-amino)phenyl]-9H-fluorene (BPAPF) is used as a substrate. The crystalline nature and ordered molecular arrangement of the films are recorded down to 6 nm film thickness. By using substrates heated up to 90 °C during the film deposition, the size of the DCV6T-Bu₄ crystallites in direction perpendicular to the film surface increases up to value of the film thickness. With increasing deposition substrate temperature or film thickness, the DCV6T-Bu₄ film relaxes, resulting in reducing the interplane distances closer to the bulk values. For the films of the same thickness deposited at the same substrate temperature, the DCV6T-Bu₄ film relaxes for growth on Si to BPAPF to C₆₀. Thicker films grown at heated substrates are characterized by smaller density, higher roughness and crystallinity and better molecular ordering. A thin (up to about 6 nm-thick) intermediate layer with linear density-gradient is formed at the C₆₀/DCV6T-Bu₄ interface for the films with buffer C₆₀ layer. The XRD pattern of the DCV6T-Bu₄ powder is indexed using triclinic unit cell parameters. © 2011 Elsevier B.V. All rights reserved.

Authors: Levin, A; Levichkova, M; Hildebrandt, D; Klisch, M; Weiss, A

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Thin Solid Films
• Volume: 520
• Issue: 7
• Pages: 2479-2487
• Publication date: 2012-01-31
• DOI: 10.1016/j.tsf.2011.10.022
• ISSN: 0040-6090
• Language: English
• Keywords: Sexithiophene; Crystallite; Organic semiconductor; X-ray reflectivity; X-ray diffraction