Extended-gate structure for carbon-based field effect transistor type formaldehyde gas sensor

Field effect transistor (FET) type gas sensor plays a crucial role in real-time environmental monitoring, medical pre-diagnosis, and industrial control because of its trace hazardous gases detection capability, which can be attributed to the unique amplification of the electrical signal on its gate by FET. Limited by the nano-micro level manufacturing process, the controllable deposition of the tiny sensing gate composed of gas sensing materials and material selection limitations considering semiconductor process compatibility have become bottlenecks in developing FET-type gas sensors. Herein, based on a high-performance FET with semiconducting single-walled carbon nanotubes as the channel, a universal strategy of constructing an extended-gate structure by inkjet printing technology is proposed to realize the detection of trace gases. CuO widely used for HCHO detection is applied to this strategy, and the as-prepared EG-FET sensor has a limit of detection of 20 ppb for HCHO, good repeatability, long-term stability, and selectivity, which greatly improves the ability of conventional chemiresistive gas sensor to detect HCHO. The development of the EG structure makes the controlled deposition of gas sensing materials more accessible, and the introduction of inkjet printing expands the choices of sensing materials. In particular, it solves the issue of poor reproducibility in the fabrication of gas sensors from gas sensing materials and provides a feasible scheme for the reported excellent gas sensing materials from laboratory to application. We expect this work can provide a meaningful theoretical and experimental basis for the realization of high-performance trace gas sensors with the potential for on-chip integration.