High-Mobility Pentacene Organic Thin-Film Transistor with LaxNb(1-x) Oy Gate Dielectric Fabricated on Vacuum Tape

Pentacene organic thin-film transistors (OTFTs) using LaxNb(1-x)Oy as gate dielectric with x = 1, 0.946, 0.850, and 0.648 have been fabricated on vacuum tape at a temperature of 200 degrees C. Among them, the OTFT with La0.850Nb0.150Oy as gate dielectric has the highest carrier mobility of 4.63 cm(2)V(-1)s(-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)Oy that can result in the largest grain size and, hence, the highest carrier mobility.