High-Performance Polymer-Alumina Nanocomposite Dielectrics for Low-Voltage Organic Thin-Film Transistors

Dielectric materials are essential in thin-film transistors (TFTs) and capacitive devices, with polymer-ceramic composites offering a promising alternative to traditional inorganic dielectrics. In the present work, spin-coated thin films of poly(methyl methacrylate) (PMMA), incorporating varying concentrations of alumina nanoparticles, both as received and annealed, were fabricated for applications in organic TFTs (OTFTs). The structural, morphological, elemental, and dielectric properties of the nanocomposite films were investigated by using XRD, SEM, AFM, and electrical characterization techniques. The impact of curing temperatures on the dielectric performance was also investigated. The optimized nanocomposite exhibited a dielectric constant of 5.2 at 100 Hz, with a film thickness of approximately 180 nm. The leakage current density was 1.5 nA/cm2 at a 100 kV/cm field, demonstrating excellent insulating properties. The thin-film devices showed high repeatability and reproducibility (RSD < 1.9% and <2.3%, respectively), along with superior stability with voltage bias, time, and temperature fluctuations. OTFTs, prepared using the optimized nanocomposite as the dielectric layer, with graphene oxide (GO) and multiwalled carbon nanotubes (MWCNTs) as semiconducting channel materials, show a distinct gating effect at low applied voltages (±3 V). The GO-TFT exhibited p-type characteristics with a mobility of 8.1 × 10–3 and cm2/V-s, whereas the MWCNT-TFT exhibited ambipolar nature with mobility between 3.26 and 3.30 × 102 cm2/V-s. The PMMA-Al2O3 nanocomposite provides an excellent balance of smooth morphology, dielectric constant, and leakage current, making it a suitable dielectric material for low-power organic electronics.