Surface-Treatment Effects on the Pentacene-Based Organic Field-Effect Transistors with Anodized Gate Dielectrics

The realization of low operating voltage organic field-effect transistors (OFETs) is technologically important with many methods having been proposed to achieve this goal. The use of anodized high-$k$ dielectrics is very promising in that the approach is applicable to obtaining gate dielectrics at low temperature. We report on the device characteristics and proper surface-treatment effects on low voltage OFETs with anodized Ta$_{2}$O$_{5}$ and SiO$_{2}$ gate dielectrics. Pentacene-based OFETs with anodized Ta$_{2}$O$_{5}$ gate dielectric obtained from an e-beam-evaporated and a sputtered Ta thin film layer exhibited the saturation mobility of 0.52 cm$^{2}$/Vs and 0.45 cm$^{2}$/Vs at $V_{ds}$ = -10V, respectively. Moreover, a hexamethyldisilazane (HMDS) and a mono-dodecyl phosphate surface treatment resulted in enhanced mobility and significantly reduced gate leakage current. In the case of anodized SiO$_{2}$ devices, an octadecyltrichlorosilane (OTS) treatment increased the saturation mobility from 0.38 cm$^{2}$/Vs to 0.88 cm$^{2}$/Vs at $V_{ds}$ = -10V. The OTS treatment also proved to reduce gate leakage current by more than 90{\%}. In related work, we will discuss the fabrication of all-organic dual-channel devices. These devices are promising because of their probable applications to organic sensing and CMOS transmission gates.