A new type of nitrogen dioxide (NO2 ) gas sensor based on copper phthalocyanine (CuPc) thin film transistors (TFTs) with a simple, low-cost UV-ozone (UVO)-treated polymeric gate dielectric is reported here. The NO2 sensitivity of these TFTs with the dielectric surface UVO treatment is ≈400× greater for [NO2 ] = 30 ppm than for those without UVO treatment. Importantly, the sensitivity is ≈50× greater for [NO2 ] = 1 ppm with the UVO-treated TFTs, and a limit of detection of ≈400 ppb is achieved with this sensing platform. The morphology, microstructure, and chemical composition of the gate dielectric and CuPc films are analyzed by atomic force microscopy, grazing incident X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, revealing that the enhanced sensing performance originates from UVO-derived hydroxylated species on the dielectric surface and not from chemical reactions between NO2 and the dielectric/semiconductor components. This work demonstrates that dielectric/semiconductor interface engineering is essential for readily manufacturable high-performance TFT-based gas sensors.
Keywords: UV-ozone; interface trap; nitrogen dioxide sensors; organic thin-film transistors.
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