Oxide transistors produced by Combustion Synthesis: Influence of the PVP on the properties of the insulator

Abstract

Solution processing of amorphous metal oxides has been used as an option to implement in flexible electronics, allowing to reduce the associated costs, when compared with vacuum processes. Recent research has been more focused on the semiconductor layer; however, the dielectric layer is equally important since its responsible for the stability and electric performance of the device. This work aims to evaluate hybrid dielectric thin films, using aluminium oxide and different types of polyvinylpyrrolidone (PVP), both obtained by solution process using solution combustion synthesis (SCS), to study the influence of the amount of organic material used in the insulator layer, as well as to study the influence of the hybrid insulator obtained in oxide thin film transistors (TFTs) using indium-gallium-zinc-oxide (IGZO) and zinc-tin-oxide (ZTO) as semiconductor layer. The insulator layer was obtained using aluminium nitrate nonahydrate and polyvinylpyrrolidone (PVP) with different molecular weights (10000 and 40000) and different percentages as precursor solutions, using urea as fuel and 2-methoxyethanol as solvent. The best hybrid dielectric was obtained with 0.8 % PVP 40000 (weight per volume), showing a breakdown voltage of 1.1 MV/cm, low density leakage current of 9.6 × 10-5 A/cm2, capacitance per area of 123 nF/cm2, thickness of 49.35 nm, annealed at 200 °C for 30 minutes. Moreover, the roughness study obtained using atomic force microscopy showed highly smooth surface, resulting in improvement dielectric-semiconductor interface, while still maintaining an amorphous nature. These characteristics allowed this hybrid dielectric, lead to enhanced TFTs electrical properties. The best performing thin films were applied in IGZO TFTs as hybrid dielectrics. The optimized TFTs show good reproducibility with an average mobility of 40.24 ± 1.1 cm2∙V-1∙s-1, subthreshold slope of 0.169 ± 0.012 V∙dec-1, a turn-on voltage of 0.078 ± 0.004 V and a low operating voltage (maximum 2 V).