Low temperature processing of Al2O3-GPTMS-PMMA hybrid films with applications to high-performance ZnO thin-film transistors

Abstract

In this work we evaluate the synthesis of inorganic-organic Al2O3-GPTMS-PMMA hybrid films using a low temperature sol-gel process and their use as gate dielectric for thin film transistors (TFTs). The hybrid films were deposited by dip coating process and then annealed at 150 °C in air. The analysis of the hybrid films was performed by UV–VIS spectroscopy, FTIR, AFM, SEM, C-V and I-V measurements. The optical transparency above 85% in the visible range and homogeneity of the hybrid films support the proper link between inorganic and organic phases with strong bonds. At microscopic level, the hybrid films have uniform surface roughness lower than 1 nm. The C-V and I-V measurements performed on MIM structures showed leakage current density in the order of 10−7 A/cm2 at 104 kV/cm electric field. Capacitance and dielectric constant measured at 1 kHz were 20.4 pF and of 6.2, respectively. TFTs were fabricated using bottom gate and aluminium top contacts to obtain mobilities of 4.5 cm2/Vs, threshold voltage of 0.7 V and Ion/Ioff ratio of 107, while mantaining operating voltage under 8 V.