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

Transistor characteristics and O-2 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 O-2 gas sensing is achieved at 11 s intervals without any bias stress by an application of pulse drain and gate voltages (V-D and V-G), in contrast to previous result in which the O-2 gas sensing was performed at least at 1 h step because of bias stress effect. The actual O-2 sensing-speed in the picene thin film FET was similar to 10 s for 3.8 Torr O-2, and the O-2 sensing limit was concluded to be 0.15-0.38 Torr. Furthermore, it has been found that the O-2 sensing properties are observed only under irradiation of light with wavelength below 400 nm. From the result, we have presented two scenarios for O-2 sensing mechanism in picene thin film FET. (C) 2012 Elsevier B.V. All rights reserved.