Sensing Characteristics of Polymer-Based Thin Films for Extended-Gate Field-Effect Transistor (Egfet) Ph Sensors

This work presents the sensing performance of extended gate field effect transistor (EGFET) pH sensors utilizing polymer-based thin films, with a focus on advancing miniaturized and nanoelectronic sensor technologies. Polyaniline (PANI), Polyvinyl butyral (PVB) and Polyvinyl pyrrolidone (PVP) thin films were employed as sensing electrodes, deposited on indium tin oxide (ITO)-coated substrates via a simple and scalable sol-gel spin-coating method. The resulting films exhibited ultrathin layers of approximately <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$20-40$</tex> nanometers, aligning well with the dimensional requirements of nanoelectronic devices. Among the materials studied, PANI demonstrated the highest sensitivity (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$64.2 \text{mV} / \text{pH}$</tex>) and high linearity (0.9938), followed by PVB (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{5 8. 0 ~ m V / p H, ~ 0. 9 9 7 2) ~ a n d ~ P V P ~ (~} \mathbf{5 0. 6 ~ m V / p H, ~ 0. 9 8 5 8). ~}$</tex> The SEM images reveal that small particles were discovered undistributed on the sample's surfaces, indicating the presence of microstructures caused by polymer development during the deposition process. The elemental analysis of the thin films identified by EDS analysis was also discussed. This study represents the first comparative analysis of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{p H}$</tex> sensitivity among PANI, PVB, and PVP polymer thin films, offering new insights into their electrochemical performance for sensing applications. The findings underscore the potential of polymerbased films in the development of next-generation miniaturized pH sensors, particularly within the growing field of nanoelectronics.