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Spin-on Polymer Gate Dielectric for High Performance Organic Thin Film Transistors

Published online by Cambridge University Press:  10 February 2011

C.D. Sheraw
Affiliation:
Department of Electrical Engineering, Center for Thin Film Devices, and Electronics and Materials Processing Research Laboratory, The Pennsylvania State University, University Park, PA 16802
D.J. Gundlach
Affiliation:
Department of Electrical Engineering, Center for Thin Film Devices, and Electronics and Materials Processing Research Laboratory, The Pennsylvania State University, University Park, PA 16802
T.N. Jackson
Affiliation:
Department of Electrical Engineering, Center for Thin Film Devices, and Electronics and Materials Processing Research Laboratory, The Pennsylvania State University, University Park, PA 16802
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Abstract

We have investigated the polymeric insulators benzocyclobutene (BCB), parylene C and polyimide for use as gate dielectrics in pentacene organic thin film transistors (TFTs). Atomic force microscopy (AFM) was used to examine the surface roughness of the polymeric dielectrics and the morphology of pentacene films deposited onto them. X-ray diffraction was used to examine the molecular ordering of pentacene films deposited onto the polymeric dielectrics. We find a correlation between the surface roughness of the gate dielectric and the grain size in deposited pentacene films, with smooth surfaces yielding larger, more dendritic grains. Despite significant changes in film morphology, pentacene TFTs using BCB, parylene C, or polyimide as the gate dielectric have performance comparable to devices using SiO2 as the gate dielectric. These results suggest that there is not a strong correlation between pentacene film grain size and field-effect mobility for these devices. Pentacene TFTs using BCB as the gate dielectric had field-effect mobility as high as 0.7 cm2/V-s, on/off ratio > 107, subthreshold slope less than 2 V/decade, and negative threshold voltage, making them an attractive candidate for use in organic-based large-area electronic applications on flexible substrates.

Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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References

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