Orienting tetracene and pentacene thin films onto friction-transferred poly(tetrafluoroethylene) substrate

Oriented films of tetracene and pentacene have been obtained by high vacuum sublimation onto oriented poly(tetrafluoroethylene) (PTFE) substrates. Polymorphism, orientation, and morphology of the pentacene and tetracene films are studied as a function of deposition parameters [substrate temperature (T<sub>s</sub>), deposition time (t), and deposition rate (&tau;)] using X-ray and electron diffraction, transmission and scanning electron microscopies and atomic force microscopy (AFM). Oriented films of the triclinic structures reported by Campbell et al. have been obtained in well-defined T<sub>s</sub>-ranges. Oriented acene films of 50 nm consist of a continuous texture of flat-lying and terraced domains with a dense (001) contact plane and a high degree of in-plane orientation. Specific nucleation sites of pentacene on the PTFE substrate have been identified by AFM in the early stage of deposition. The similarity found in the growth phenomenology of tetracene and pentacene allows for identification of the mechanism responsible for oriented growth which involves (i) ledge-directed nucleation and (ii) confined growth of nanocrystals by the PTFE mesoscale relief, e.g. nanoscopic grooves between successive PTFE fibrils. In addition, various crystal defects, e.g. edge dislocations, have been identified by high-resolution TEM


Published in:
Journal Of Physical Chemistry B, 107, 38, 10531
Year:
2003
Publisher:
ACS
Keywords:
Note:
Inst. Charles Sadron, Strasbourg, France
Copyright 2004, IEE
8145978
1089-5647
orienting tetracene thin film
orienting pentacene thin film
friction-transferred poly(tetrafluoroethylene) substrate
vacuum sublimation
polymorphism
molecular morphology
deposition parameter
substrate temperature
deposition time
deposition rate
X-ray diffraction
electron diffraction
transmission electron microscopy
high-resolution TEM
scanning electron microscopy
atomic force microscopy
AFM
in-plane orientation
triclinic structure
growth phenomenology
ledge-directed nucleation
confined nanocrystal growth
nanoscopic groove
PTFE fibrils
crystal defect
edge dislocation
continuous texture
flat-lying domain
terraced domain
dense (001) contact plane
PTFE mesoscale relief
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Laboratories:




 Record created 2007-04-03, last modified 2018-03-17


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