Highly improved response and recovery characteristics of Si FET-type gas sensor using pre-bias

Abstract

By adopting a new pulse pre-bias (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pre</sub> ) scheme, the response and recovery characteristics is significantly improved in Si field-effect transistor (FET)-type gas sensor having ZnO film as a sensing layer. A target gas of NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , which is one of oxidizing gases, is detected by the FET-type sensor at various V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pre</sub> s. It is demonstrated that a negative V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pre</sub> (-3 V) improves the response by ~2.5 times and a positive V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pre</sub> (4 V) reduces the recovery time by ~9 times in 0.5 ppm NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ambience at 180 °C. The mechanism responsible for the pre-bias effect is explained using energy band diagram.