High-Performance Pentacene Organic Thin-Film Transistor by Using Nd₂O₃ Gate Dielectric Doped with Nb

Pentacene organic thin-film transistors (OTFTs) using high-k Nd_xNb_(1−x)O gate dielectric with different Nb contents (x = 1, 0.950, 0.908, and 0.877) are fabricated. The best OTFT has x = 0.950, achieving a high carrier mobility of 1.95 cm² V⁻¹ s⁻¹, small threshold voltage of −1.57 V, small sub-threshold swing of 0.13 V dec⁻¹, and small hysteresis of 0.13 V. Atomic force microscopy and X-ray photoelectron spectroscopy measurements reveal that the Nb doping can suppress the hygroscopicity of Nd oxide to produce a smoother dielectric surface, on which larger pentacene grains are grown to result in higher carrier mobility. The hysteresis of the OTFTs is attributed to donor-like traps associated with the hydroxide formed in Nd₂O₃ after absorbing moisture and also acceptor-like traps (in the form of oxygen vacancies) induced by Nb incorporation.