O2-exposure and light-irradiation properties of picene thin film field-effect transistor: A new way toward O2 gas sensor

Transistor characteristics and O2 gas sensing properties are investigated for picene thin film field-effect transistors (FETs) with ZrO2, Ta2O5, HfO2 and BaxSr1−xTiO3 (x = 0.4). The low-voltage operation is achieved using the above oxides with high gate dielectric constant, contrary to SiO2 gate dielectric. The O2 gas sensing is achieved at 11 s intervals without any bias stress by an application of pulse drain and gate voltages (VD and VG), in contrast to previous result in which the O2 gas sensing was performed at least at 1 h step because of bias stress effect. The actual O2 sensing-speed in the picene thin film FET was ∼10 s for 3.8 Torr O2, and the O2 sensing limit was concluded to be 0.15–0.38 Torr. Furthermore, it has been found that the O2 sensing properties are observed only under irradiation of light with wavelength below 400 nm. From the result, we have presented two scenarios for O2 sensing mechanism in picene thin film FET.