Growth of pentacene on clean and modified gold surfaces
- Physikalische Chemie I, Ruhr-Universitaet Bochum, 44780 Bochum (Germany)
The growth and evolution of pentacene films on gold substrates have been studied. By combining complementary techniques including scanning tunneling microscopy, atomic force microscopy, scanning electron microscopy, near-edge x-ray-absorption fine structure, and x-ray diffraction, the molecular orientation, crystalline structure, and morphology of the organic films were characterized as a function of film thickness and growth parameters (temperature and rate) for different gold substrates ranging from Au(111) single crystals to polycrystalline gold. Moreover, the influence of precoating the various gold substrates with self-assembled monolayers (SAM's) of organothiols with different chemical terminations has been studied. On bare gold the growth of pentacene films is characterized by a pronounced dewetting while the molecular orientation within the resulting crystalline three-dimensional islands depends distinctly on the roughness and cleanliness of the substrate surface. After completion of the first wetting layer where molecules adopt a planar orientation parallel to the surface the molecules continue to grow in a tilted fashion: on Au(111) the long molecular axis is oriented parallel to the surface while on polycrystalline gold it is upstanding oriented and thus parallels the crystalline orientation of pentacene films grown on SiO{sub 2}. On SAM pretreated gold substrates the formation of a wetting layer is effectively suppressed and pentacene grows in a quasi-layer-by-layer fashion with an upstanding orientation leading to rather smooth films. The latter growth mode is observed independently of the chemical termination of the SAM's and the roughness of the gold substrate. Possible reasons for the different growth mechanism as well as consequences for the assignment of spectroscopic data of thin pentacene film are discussed.
- OSTI ID:
- 20976714
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 75, Issue 8; Other Information: DOI: 10.1103/PhysRevB.75.085309; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
ABSORPTION SPECTROSCOPY
ATOMIC FORCE MICROSCOPY
COATINGS
GOLD
LAYERS
ORGANIC SEMICONDUCTORS
PENTACENE
ROUGHNESS
SCANNING ELECTRON MICROSCOPY
SCANNING TUNNELING MICROSCOPY
SILICA
SILICON OXIDES
SUBSTRATES
SURFACE TREATMENTS
SURFACES
THIN FILMS
THREE-DIMENSIONAL CALCULATIONS
X RADIATION
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY