Correlated growth in ultrathin pentacene films on silicon oxide: effect of deposition rate

Understanding the growth mechanism in molecular organic thin films is fundamental to their applications in organic electronics. We present an extensive study of the growth mechanism of pentacene thin films on silicon dioxide (SiO<sub>2</sub>) using atomic force microscopy. For a fixed substrate temperature T<sub>s</sub>, the deposition rate &kappa; is found to be a key parameter in controlling the nucleation density in the submonolayer regime and hence transport properties in the first layer of the organic field effect transistors. At a fixed T<sub>s</sub>=338 K the maximum number of pentacene islands per unit area N follows the scaling law N&prop;&kappa;<sup>&delta;</sup> with &delta;=1.16&plusmn;0.10. A mechanism of homogeneous nucleation followed by diffusive growth accounts for this behavior and allows us to estimate the critical nucleus size of the pentacene islands. The results obtained from a statistical analysis of the island size distribution are fully consistent with a phenomenological capture zone model. The validity of this model depends on the extent of reevaporation of pentacene admolecules during deposition, which is moderated by the deposition rate. We demonstrate that the rate dependence of island nucleation has important implications for the density of grain boundaries, which may play an important role in the transport mechanism

Published in:
Physical Review B (Condensed Matter and Materials Physics), 69, 16, 165201
APS through AIP
Inst. Charles Sadron CNRS, Strasbourg, France
Copyright 2004, IEE
ultrathin pentacene films
silicon oxide
deposition rate
growth mechanism
molecular organic thin films
organic electronics
atomic force microscopy
substrate temperature
nucleation density
submonolayer regime
transport properties
organic field effect transistors
diffusive growth
scaling law
statistical analysis
island size distribution
phenomenological capture zone model
pentacene admolecules
grain boundaries
338 K
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 Record created 2007-04-03, last modified 2018-03-17

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