Two-Dimensional MoS₂ Based Field Effect Transistors as Gas Nano-Sensors

Nowadays, sensor technology is very important in our society to monitor the environment, detecting toxic gases relevant to healthcare, environmental pollution, and air quality. Some mature gas sensing technologies include semiconductor-based, electrochemical, photoionization, and infrared adsorption. The main figures of merit to identify the best technology for broad applications are sensitivity, selectivity, cost, and compactness. Recent advancements in the field of gas nano-sensors are mostly focused on sensitivity performance, while selectivity remains the main weakness for the development of innovative sensors. The most promising solution for the next generation sensors with enhanced selectivity is the exploitation of 2D materials as gas sensing elements, having high surface area to volume ratio and mechanical flexibility. We use molybdenum disulfide (MoS₂) as conducting channels in back-gated field effect transistors. The gate terminal in FET provides an extra knob for controlling the carrier mobilities, which helps to achieve a higher sensitivity compared to other devices. In particular, we investigated the effect of pressure, electric stress, gas type on the electrical characteristic of the transistor. The electrical conductivity shows a clear response to the presence of different gas molecules. The presence of defects and point vacancies in the MoS₂ crystal structure facilitates the adsorption of gas molecules, which strongly affect the transistor's electrical characteristics. We systematically investigate how different gases modify the transistor behaviour and the correlation with the adsorption energy onto the MoS₂ surface. Finally, we consider the possibility of using the electrical noise generated in gas sensor as a useful signal for improving the sensor's selectivity, the microscopic, random fluctuation phenomena in physical systems being rich sources of information. Our results can pave the way to realize environmental gas nano-sensors, for air pollution monitoring, with enhanced selectivity through fluctuation spectroscopy, in which 2D materials are exploited as the conductive channels in nanometric back-gated FET. This activity is performed within the framework of the project PRIN 2022 PNRR, 2DEGAS “Development of two-dimensional environmental gas nano-sensors with enhanced selectivity through fluctuation spectroscopy”.<br/><br/>References:<br/>Di Bartolomeo, A., et al, (2023) Materials Today Nano, 24, 100382.<br/>Kumar, A., et al, (2023) Journal of Physics and Chemistry of Solids, 179, 111406.<br/>Pelella, A., et al, (2021) Advanced Electronic Materials, 7 (2), 2000838.<br/>Pelella, A., et al, (2020) ACS Applied Materials and Interfaces, 12 (36), pp. 40532-40540.<br/>Giubileo, F., et al, (2019) Journal of Physical Chemistry C, 123 (2), pp. 1454-1461.<br/>Urban, F., et al, (2019) 2D Materials, 6 (4), art. no. 045049.<br/>Di Bartolomeo, A., et al, (2018) Advanced Functional Materials, 28, 1800657.