Wafer-scale floating-gate field effect transistor sensor built on carbon nanotubes film for Ppb-level NO2 detection

NO2 is served as an air pollutant and a specific biomarker for disease diagnosis, which becomes a major detection object in environmental protection and health medical fields. Transition metal dichalcogenides (TMDs) materials have attracted considerable attention for their ability to detect NO2 without heating conditions. The requirements in the above fields for the lower limit of NO2 concentration detection are as low as ppb-level, but the trace gas is difficult to cause the large electrical signal changes, which becomes the bottleneck for TMDS materials in NO2 detection. Moreover, TMDs-based conductance sensors are susceptible to humidity interference at room temperature, which also have challenges in device size, batch fabrication, and reproducibility. How to achieve miniaturization and integration of TMDs-based gas sensors will provide a boost to portable detection of NO2 in environmental protection and health medical fields. Herein, on the basis of the principle of top-gate field effect transistor (FET), a strategy of using gas-sensing materials as the floating-gate (FG) in FET sensor is proposed to realize the detection of trace gas. The channel, dielectric layer, and FG are formed by carbon nanotubes, Y2O3, and Pd/WS2 respectively. The unique amplification effect of carbon-based FET on the gas-sensing signal is utilized to achieve NO2 detection down to 20 ppb. Furthermore, visible-light-assisted detection mode is applied to the FG FET sensor, achieving stable anti-humidity property and 100% recoverability at 10%–70% RH. We expect our work can provide a significant approach to developing micro gas sensor chips for environmental detection and portable medical applications.