Al₂O₃/TiO₂ nanolaminate gate dielectric films with enhanced electrical performances for organic field-effect transistors

Nanolamination has entered the spotlight as a novel process for fabricating highly dense nanoscale inorganic alloy films. OFET commercialization requires, above all, excellent dielectric properties of gate dielectric layer. Here, we describe the fabrication and characterization of Al-O-Ti (AT) nanolaminate gate dielectric films using a PEALD process, and their OFET applications. The AT films exhibited a very smooth surface (R_q < 0.3 nm), a high dielectric constant (17.8), and a low leakage current (8.6 × 10^-9 A/cm² at 2 MV/cm) compared to single Al₂O₃ or TiO₂ films. Importantly, a 50 nm thick AT film dramatically enhanced the value of μ_FET (0.96 cm²/V) on a pentacene device, and the high off-current level in a single TiO₂ film was effectively reduced. The nanolamination process removes the drawbacks inherent in each single layer so that the AT film provides excellent dielectric properties suitable for fabricating high-performance OFETs. Triethylsilylethynyl anthradithiophene (TES-ADT), a solution-processable semiconductor, was combined with the AT film in an OFET, and the electrical properties of the device were characterized. The excellent dielectric properties of the AT film render nanolamination a powerful strategy for practical OFET applications.