Thin Film Transistors Based On Single-Walled Carbon Nanotubes-Polyethylenimine Bilayer Film For No2 Gas Detection

In this paper, bottom contact organic thin film transistors (OTFTs) using SiO2 dielectric layer deposited on silicon wafer were fabricated for gas sensors application. Single-walled carbon nanotubes (SWNTs)-polyethylenimine(PEI) bilayer sensitive film was utilized as an active layer to test current-voltage characteristics and gas-sensing properties of the OTFT device. Due to PEI coating, the electronic characteristic of the active layer was turned from p-type (SWNTs film) into n-type (SWNTs-PEI bilayer film). When the gas sensor was exposed to NO2 of different concentrations at room temperature, the source-drain current changed within several minutes at appropriate gate and source-drain voltages. The selectivity and repeatability of gas sensor were investigated as well. The results showed that the gas sensor exhibited outstanding properties to NO2 gas. Moreover, the gas sensing mechanism of the sensitive film associated with the morphology analyzed by scanning electron microscope (SEM) was studied.