Thin film transistors based on single-walled carbon nanotubes-polyethylenimine bilayer film for NO_2 gas detection

摘要

In this paper, bottom contact organic thin film transistors (OTFTs) using SiO_2 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 NO_2 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 NO_2 gas. Moreover, the gas sensing mechanism of the sensitive film associated with the morphology analyzed by scanning electron microscope (SEM) was studied.