A Low-Voltage, Self-Oriented Organic Polymer Nanocomposite-Based Flexible TFT for Ammonia Gas Sensing at Room Temperature

Abstract

This study includes the fabrication and characterization of a novel, low-voltage, flexible organic thin film transistor (OTFT) for ammonia sensing at room temperature (RT 25 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> C). The device fabrication process uses a hybrid (inorganic oxide/polymer) dielectric layer as a gate oxide and a polymer/2-D nanocomposite as an active layer. The UV-cured synthesized hybrid dielectric layer of ZrO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\textit{x}}$</tex-math> </inline-formula> /poly(methyl methacrylate) (PMMA)/poly melamine co-formaldehyde (PMCF) passes with a very smooth film (rms roughness-0.388 nm) (thickness-55 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 4 nm), the high areal capacitance of 310 nF/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text{2}}$</tex-math> </inline-formula> , a dielectric constant of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 20, low leakage current density of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-\text{9}}$</tex-math> </inline-formula> A/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text{2}}$</tex-math> </inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 2 V, and a high band gap of 5.27 eV. A uniform thickness of 35 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 4 nm polymer nanocomposite layer, deposited by the solution-casted floating film transfer (FTM) technique, has been used to investigate the electrical characteristics of the flexible sensor in terms of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{I}$</tex-math> </inline-formula> / <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}$</tex-math> </inline-formula> plot, subthreshold swing (SS), mobility, etc. The bending test of the device has been performed over the curved holder and shows a reliable performance with solution-processed hybrid dielectric and polymer nanocomposite film. Using polymer/2-D nanocomposite material as a sensing layer offers a low detection limit of 500 ppb, a sensing response of 69%, and a fast response/recovery time of 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 0.5/36 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 4 s over 20 ppm ammonia gas. The fabricated flexible device, therefore, has a potential application in the area of low voltage operated OTFT for ammonia sensing application.