High-Mobility Pentacene Organic Thin-Film Transistor with La_xNb_(1-x)O_yGate Dielectric Fabricated on Vacuum Tape

Pentacene organic thin-film transistors (OTFTs) using LaxNb(1-x)Oyas gate dielectric with x= 1, 0.946, 0.850, and 0.648 have been fabricated on vacuum tape at a temperature of 200 °C. Among them, the OTFT with La0.850Nb0.150Oyas gate dielectric has the highest carrier mobility of 4.63 cm2V-1s-1, negligible hysteresis of -0.032 V, small subthreshold swing of 0.174 V/decade, and small threshold voltage of -1.90 V. AFM and X-ray photoelectron spectroscopy reveal that Nb incorporation can alleviate the hygroscopicity of La oxide, resulting in a smoother dielectric surface. Pentacene grain size first increases with Nb content due to smoother dielectric surface, and then decreases due to Nb-induced traps acting as nucleation sites for the growth of pentacene grains on the dielectric surface. Therefore, there exists an optimal Nb content in LaxNb(1-x)Oythat can result in the largest grain size and, hence, the highest carrier mobility.