Highly enhanced gas sensing in single-walled carbon nanotube-based thin-film transistor sensors by ultraviolet light irradiation

Single-walled carbon nanotube (SWCNT) random networks are easily fabricated on a wafer scale, which provides an attractive path to large-scale SWCNT-based thin-film transistor (TFT) manufacturing. However, the mixture of semiconducting SWCNTs and metallic SWCNTs (m-SWCNTs) in the networks significantly limits the TFT performance due to the m-SWCNTs dominating the charge transport. In this paper, we have achieved a uniform and high-density SWCNT network throughout a complete 3-in. Si/SiO(2) wafer using a solution-based assembly method. We further utilized UV radiation to etch m-SWCNTs from the networks, and a remarkable increase in the channel current on/off ratio (I(on)/I(off)) from 11 to 5.6 × 10(3) was observed. Furthermore, we used the SWCNT-TFTs as gas sensors to detect methyl methylphosphonate, a stimulant of benchmark threats. It was found that the SWCNT-TFT sensors treated with UV radiation show a much higher sensitivity and faster response to the analytes than those without treatment with UV radiation.