| Abstract
| - Ultrathin films of regioregular poly(3-hexyl thiophene) (RR-P3HT) were deposited through a dip-coatingtechnique and utilized as the semiconducting film in field-effect transistors (FETs). Proper selection of thesubstrate and solution concentration enabled the growth of a monolayer-thick RR-P3HT film. Atomic forcemicroscopy (AFM), UV−vis absorption spectroscopy, X-ray reflectivity, and grazing incidence diffractionwere used to study the growth mechanism, thickness and orientation of self-organized monolayer thickRR-P3HT films on SiO2 surfaces. Films were found to adopt a Stranski−Krastanov-type growth mode withformation of a very stable first monolayer. X-ray measurements show that the direction of π-stacking inthe films (the (010) direction) is parallel to the substrate, which is the preferred orientation for highfield-effect carrier mobilities. The field-effect mobilities in all ultrathin films prepared in this study arelower than those obtained for thicker films spun on similar substrates. However, monolayer FETs providea direct experimental system to study the charge transport at the charge accumulation layer.
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