Characterization of Nanocrystalline Conductive a-C as the Electrode Used in the Bottom-Gated Structure of a Pentacene-Based Organic Thin Film Transistor

Abstract

Nanocrystalline amorphous carbon (nc a-C) films recently prepared in our laboratory exhibited very low resistivity (< 1 momega x cm) and good conductivity without any dopant. They also showed properties such as good adhesion to glass and plastic substrates, smooth surface, low friction coefficient, thermal stability, and high transparency. We applied nc a-C films to the bottom-gated electrodes of organic thin film transistors (OTFTs). In this work, we describe the characterization of conductive nc a-C films synthesized by closed-field unbalanced magnetron (CFUBM) sputtering and fabricate OTFTs of a bottom gate structure using pentacene as the active layer and polyvinylphenol (PVP) as the gate dielectric on the nc a-C gate electrode. We investigated the surface and electrical properties of each layer using an AFM method and estimated the device properties of OTFTs including I(D)-V(D), I(D)-V(G), threshold voltage V(T), on/off ratio, and field effect mobility.