Ammonia Gas Sensing Properties of 6,13-Bis(tri-isopropylsilyethynyl) Pentacene Based Field-Effect Transistor

Abstract

The ammonia (NH3) gas sensing properties of pentacene and 6,13-Bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) based field-effect transistors (FETs) were investigated. The pentacene and TIPS-pentacene thin films were deposited by the thermal evaporation process using a shadow mask. The electrical properties of pentacene and TIPS-pentacene such as field-effect mobility, subthreshold slope, threshold voltage, on/off current ratio have been observed as 5.6 x 10(-2) and 3.9 x 10(-2) cm(2)/Vs, 0.83 and 1.74 V/dec, 1.7 and 3.2 V, and 10(6) (for both), respectively. We observed the responsivity to 1 ppm ammonia gas at room temperature, and it was confirmed that pentacene FET hardly reacts. On the other hand, the TIPS-pentacene FET exhibits high reactivity to even low ammonia gas concentrations. It was also confirmed that this phenomenon occurs due to the increased surface gas adsorption rate through the rough surface of TIPS-pentacene film. The electrons in the NH3 adsorbed surface react with the holes of the organic semiconductor to reduce the overall positive charge. As a result, TIPS-pentacene based FET can increase the gas surface adsorption rate, confirming that gas detection is possible even at low concentrations. It is expected that these organic FET-based gas sensors can be integrated into sensor systems that can effectively detect harmful gases in the future.