Effect of Inserting Teflon as a Surface Modification Layer on Bottom-Contact Pentacene-Based Organic Thin-Film Transistors

This study reports the effect of poly(tetrafluoroethylene) (Teflon) as a surface modification layer, which was deposited on the surface of gate insulator and source/drain (S/D) electrodes, on bottom-contact pentacene-based organic thin-film transistors (OTFTs). The inserted 1.5-nm-thick Teflon layer can enhance the device performance because of the improved molecular orientation in pentacene film and reduced contact resistance (R-C) between the pentacene film and the S/D electrodes. The improved molecular orientation of pentacene film is caused by the hydrophobic and smooth Teflon layer surface. The reduced R-C is a result of the tunneling process at the Au/pentacene interface. This study also found that the device performance decreased as the Teflon layer increased in thickness. This is because of the increased R-C and decreased carrier injection efficiency between the pentacene film and the S/D electrodes. Compared to devices without a Teflon layer, the drain current and field-effect mobility of devices with a 1.5-nm-thick Teflon layer increased by 93 and 105%, respectively. (C) 2012 The Japan Society of Applied Physics