Temperature dependent optical properties of pentacene films on zinc oxide

Journal Article · Mon Nov 21 00:00:00 EST 2011 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.3663863· OSTI ID:22027817

Helzel, J; Jankowski, S; El Helou, M; Witte, G; Heimbrodt, W ^[1]

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1. Department of Physics and Material Sciences Center, Philipps-University Marburg, Renthof 5, D-35032 Marburg (Germany)

The optical transitions of pentacene films deposited on ZnO have been studied by absorption spectroscopy as a function of temperature in the range of room temperature down to 10 K. The pentacene films were prepared with thicknesses of 10 nm, 20 nm, and 100 nm on the ZnO-O(000-1) surface by molecular beam deposition. A unique temperature dependence has been observed for the two Davydov components of the excitons for different film thicknesses. At room temperature, the energetic positions of the respective absorption bands are the same for all films, whereas the positions differ more than 20 meV at 10 K caused by the very different expansion coefficients of pentacene and ZnO. Although the pentacene is just bonded via van der Waals interaction to the ZnO substrate, the very first pentacene monolayer (adlayer) is forced to keep the initial position on the ZnO surface and suffering, therefore, a substantial tensile strain. For all the subsequent pentacene monolayers, the strain is reduced step by step resulting electronically in a strong potential gradient at the interface.

• OSTI ID: 22027817
• Journal Information: Applied Physics Letters, Vol. 99, Issue 21; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTROSCOPY
CRYSTAL GROWTH
ENERGY BEAM DEPOSITION
EXCITONS
INTERFACES
LAYERS
MOLECULAR BEAM EPITAXY
OPTICAL PROPERTIES
ORGANIC SEMICONDUCTORS
PENTACENE
STRAINS
SUBSTRATES
SURFACES
TEMPERATURE DEPENDENCE
THICKNESS
THIN FILMS
VAN DER WAALS FORCES
ZINC OXIDES