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Designed Organophosphonate Self-Assembled Monolayers Enhance Device Performance of Pentacene-Based Organic Thin-Film Transistors (DMR 0819860) IRG-B: K.-C. Liao, A. G. Ismail, L. Kreplak, J. Schwartz and I. G. Hill.
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IRG-B: K.-C. Liao, A. G. Ismail, L. Kreplak, J. Schwartz and I. G. Hill
Organic thin-film transistors (OTFTs) are compatible with large area fabrication techniques, and they may yield new paradigms for manufacturing that would reduce device costs for large area circuits. Pentacene-based OTFTs are well studied; yet they can be compromised with regard to critical device parameters: on/off ratios, carrier mobilities, sub-threshold performance, and threshold voltages. Surface treatments for the SiO2 gate dielectric can be
effective; typically, however, improvement is realized in only one ofthese critical areas, often to the detriment of the others. We showed that systematic structural modification of self-assembled monolayers of phosphonates (SAMPs) fabricated on SiO2 gate dielectrics can yield pentacene-based devices in which all four critical parameters are enhanced simultaneously. We hypothesize that phosphonate structural motifs enable twodimensionalSAMP surface coverage to translate to a threedimensional one through controlled lateral spacing between vertically oriented acene units, which can affect crystallization of vapor-deposited pentacene. AFM shows that the morphology of the deposited pentacene depends solely on the structure of the underlying SAMP; a simple (anthracene)-phosphonate gives rise to the AFM shown at the left, and a naphthyl-substituted
(anthracene)phosphonate gives rise to the AFM shown in the center. Especially high mobilities (average saturation mobility 2.5cm2/Vs) were recorded for transistors based on the latter SAMP;the cartoon at the right suggests how that SAMP could template
K.-C. Liao, A. G. Ismail, L. Kreplak, J. Schwartz, I. G. Hill, Adv. Mater. 2010, in press.