Organic thin film transistors with indium tin oxide bottom electrode

Organic thin film transistors (OTFTs) which employ indium tin oxide (ITO) as source and drain electrodes instead of gold are fabricated. A double gate dielectric layer was used, which consists of benzocyclobutane (BCB) and silicon nitride (SiNx). The pentacene TFT has lateral dimensions 192 μm×6 μm. The OTFT with the ITO bottom electrode shows a saturation mobility of 0.05~0.09 cm2 V−1 s−1 and an on-off current ratio of the order of 105 in a gate voltage span between 0 and −40 V. The TFT fabrication process steps had the beneficial side effect of changing the ITO surface from hydrophilic to hydrophobic. This change allows pentacene films with larger grains, observed up to 0.5 μm, to be grown on TFT compared to as-deposited ITO film onto which high quality films cannot be grown.