Designing ZrO₂-blended nanocomposite MIM capacitors for future OFET applications and their characterizations

Organic field-effect transistors (OFETs) have been exploited as sensors for a variety of applications due to their excellent advantages over diodes and other electronic devices. Capacitors are one of the key components of the OFET designs that consist of a dielectric layer sandwiched between two parallel metal plates. The dielectric layer should be thin and/or have a high k constant value to achieve a high capacitance value (C-i, areal capacitance), so more charge carriers can be accumulated at the interface between the dielectric and the organic semiconductor, for OFETs to operate under low voltage (< 3 V). In this study, high-k nanocomposites (NCs) of ZrO2 metal oxide ceramic nanoparticles (NPs) in varying concentrations blended in two different polymer matrixes, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and cyanoethyl cellulose (CEC) have been utilised as the dielectric layer in metal-insulator-metal (MIM) capacitors. The physical and electrical properties of fabricated MIM capacitors were evaluated. The measured areal capacitance, C-i, values demonstrated a gradual rise with increasing ZrO2 metal oxide content in both polymer matrixes. ZrO2-PVDF-HFP-based capacitors exhibited a two-fold increase in C-i, 91.86 +/- 6.1 nF/cm(2) (a 140 % increase) for 10 wt % NP content. Similarly, areal capacitance values of 76 +/- 3.03 nF/cm(2) (a 45 % rise) was measured on MIMs using CZ10 dielectric layer. High average dielectric constant (k) values of 28.61 and 35.68 for CZ5 and PZ5, respectively) were obtained. As expected, leakage current density increased for higher NP % in polymer matrixes. Nevertheless, all MIMs yielded average leakage current density < 1.75 x 10(-6) (A/cm(2)) at 2 V. Therefore, the reported nanocomposites are suitable dielectric layers for OFETs and as platforms for gas, chemical and photoactivated sensing devices.