Towards a low cost fully integrated IGZO TFT NO2 detection and quantification: A solution-processed approach

• Published in: Sensors and actuators. B, Chemical Chemical, 2021-03, Vol.331, p.129450, Article 129450
• Main Authors: Vijjapu, Mani Teja, Surya, Sandeep, Zalte, Maruti, Yuvaraja, Saravanan, Baghini, Maryam Shojaei, Salama, Khaled N.
• Format: Article
• Language: English
• Subjects: Air monitoring; Analog circuits; Analog to digital converters; Environmental monitoring; Gas sensing systems; Gas sensors; IGZO; Indicators; Indium gallium zinc oxide; Metal oxides; Nitrogen dioxide; Pollution monitoring; Room temperature; Room temperature gas sensor; Selectivity; Semiconductor devices; Sensors; Solution-processed gas sensor; TFT based system; Thin film transistors
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2021.129450

•A room temperature operable and solution-processed IGZO TFT based NO2 sensor is demonstrated.•In-situ characterization of the sensor is performed using kelvin probe force microscopy to study gas adsorption dynamics.•The gas sensor is re-generable and exhibits excellent sensitivity and selectivity to detect and monitor NO2 gas.•Fully integrated gas-sensitive indicators for sensing and quantifying NO2 concentration were demonstrated.•The measured limit of detection of sensors is ∼100 ppb. Semiconducting metal oxide gas sensors that are inexpensive, room temperature operable are imperative for toxic gas and air pollution monitoring. The heating or continuous light activation requirements are unavoidable for these types of gas sensors. This paper reports for the first time a room temperature operable solution-processed In-Ga-Zn-O thin-film transistor (TFT) gas sensor to detect NO2 without continuous light activation. The TFT sensor exhibits promising sensing and selectivity towards NO2. The devices are re-generable and require light activation only to recover after exposure to the gas. Kelvin probe force microscopy characterization studies are performed to understand in detail the sensing mechanism of the solution-processed TFT device. A novel solution-processed TFT based gas-sensitive digital indicators that yield digital output quantifying the NO2 concentration are demonstrated. One of the integrated gas-sensitive digital indicators is developed using only two InGaZnO TFTs incorporating a signal conditioning circuit and analog to digital converter. Furthermore, it paves the way for portable, compact, and inexpensive systems for various gas sensing applications, including smart cities and sustainable ecosystems.