Suppression Effects of Oxygen Deficient on Ultrathin Indium Oxide Electrochemical Transistors-Based Biosensors

Abstract

Recently, the necessity of real-time and non-invasive detection-based biosensors has been increasing by using electrical device platforms. Metal oxide semiconductors-based electrochemical transistors (MOECTs) have many advantages, such as easy processing, good chemical resistance, high sensitivity, and universal surface complexation for biomolecule detection for continuous healthcare monitoring. A specific pH in each organ is required to maintain health and the health problems or diseases can be predicted by pH changes. Thus, high sensitivity of biosensors is essential to apply real-time sensor platforms. Here, we proposed solution-processed ultrathin indium oxide-based ECTs, which had an ultrathin metal oxide semiconductor of ~4 nm thick. This platform shows a high sensitivity for the pH variations but intrinsic surface defects (i.e., oxygen deficient) influences the sensitivity. In order to reduce these effect, we studied the surface defect passivation effect of Ga doped In2O3 (GIO)-based ECTs by using solution process. The change of sensitivity and reliability of GIO-based ECTs were confirmed clearly at the range of 2-12 pH for the different gallium contents (5-40%). As an increase of gallium contents, the oxygen deficient of GIO films was gradually reduced and the sensitivity of the device was improved. However, excessive Ga added In2O3-based ECTs showed poor sensitivity for the pH variations. As a result, we found that optimal gallium doping concentration is an important factor to construct high sensitivity and reliability of MOECTs under diverse physiological environment.