Highly Conductive and Conformal Poly(3,4-ethylenedioxythiophene)
(PEDOT) Thin Films via Oxidative Molecular Layer Deposition
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Abstract
This
work introduces oxidative molecular layer deposition (oMLD) as a chemical
route to synthesize highly conductive and conformal poly(3,4-ethylenedioxythiophene)
(PEDOT) thin films via sequential vapor exposures of molybdenum(V)
chloride (MoCl<sub>5</sub>, oxidant) and ethylene dioxythiophene (EDOT,
monomer) precursors. The growth temperature strongly affects PEDOT’s
crystalline structure and electronic conductivity. Films deposited
at ∼150 °C exhibit a highly textured crystalline structure,
with {010} planes aligned parallel with the substrate. Electrical
conductivity of these textured films is routinely above 1000 S cm<sup>–1</sup>, with the most conductive films exceeding 3000 S
cm<sup>–1</sup>. At lower temperatures (∼100 °C)
the films exhibit a random polycrystalline structure and display smaller
conductivities. Compared with typical electrochemical, solution-based,
and chemical vapor deposition techniques, oMLD PEDOT films achieve
high conductivity without the need for additives or postdeposition
treatments. Moreover, the sequential-reaction synthesis method produces
highly conformal coatings over high aspect ratio structures, making
it attractive for many device applications