Influence of self-assembled monolayer chain length on modified gate dielectric pentacene thin-film transistors

Hill, I.; Weinert, C. M.; Kreplak, L.; van Zyl, B. P.
April 2009
Applied Physics A: Materials Science & Processing;Apr2009, Vol. 95 Issue 1, p81
Academic Journal
Self-assembled monolayers are widely used to modify the gate dielectric/semiconductor interface in organic thin-film transistors. By modifying the interaction between the molecular semiconductor and the substrate, thin-film ordering and the electronic properties of the semiconducting channel can be controlled. The modified semiconductor/dielectric properties result in macroscopically observed changes in the charge-carrier mobilities, threshold voltages, subthreshold swing and transfer characteristic hysteresis. The latter two are determined by the density of charge-trapping states at the interface. Here, we investigate the influence of the thickness of the self-assembled monolayer, via the alkyl chain length in n-alkyl phosphonic acid-based monolayers on SiO2, on the electronic properties of pentacene-based organic thin-film transistors. Rather than a monotonic increase or decrease in performance with increasing chain length, we have found that the optimum performance occurs with chains of 8–10 carbon atoms. Atomic force microscopy shows a correlation between pentacene crystalline grain size and transistor performance.


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