Low-Temperature Solution-Processed Amorphous Indium Tin Oxide Field-Effect Transistors

Abstract

Amorphous indium tin oxide (ITO)-based thin-film transistors (TFTs) were fabricated on various dielectrics [SiO₂ and self-assembled nanodielectrics (SANDs)] by spin-coating an ITO film precursor solution consisting of InCl₃ and SnCl₄ as the sources of In³⁺ and Sn⁴⁺, respectively, methoxyethanol (solvent), and ethanolamine (base). These films can be annealed at temperatures T_a ≤ 250 °C and afford devices with excellent electrical characteristics. The optimized [In³⁺]/[In³⁺ + Sn⁴⁺] molar ratio (0.7) and annealing temperature (T_a = 250 °C) afford TFTs exhibiting electron mobilities of ∼2 and ∼10−20 cm² V⁻¹ s⁻¹ with SiO₂ and SAND, respectively, as the gate dielectric. Remarkably, ITO TFTs processed at 220 °C still exhibit electron mobilities of >0.2 cm² V⁻¹ s⁻¹, which is encouraging for processing on plastic substrates.