Improved performance of Pd/WO<inf>3</inf>/SiC schottky-diode hydrogen gas sensor by using fluorine plasma treatment

Abstract

A high-performance Pd/WO<inf>3</inf>/SiC Schottky-diode hydrogen gas sensor was fabricated by using fluorine plasma treatment on the WO<inf>3</inf> film. From the electrical measurements under various hydrogen concentrations and temperatures, the plasma-treated sensor exhibited a maximum barrier-height change of 279meV and a static gas sensitivity of more than 30000, which is 30 times higher than that of the untreated sensor. This significant improvement is attributed to the larger adsorption area caused by the plasma-roughened WO<inf>3</inf> film and the lower baseline leakage current induced by fluorine passivation of oxide traps. Additionally, the kinetics analysis and hydrogen coverage of the devices were studied to demonstrate the temperature dependence of the gas sensing behaviors. The hydrogen adsorption enthalpy at the Pd-WO<inf>3</inf> interface significantly decreased from -31.2kJ/mol to -57.6kJ/mol after the plasma treatment. Therefore, the adsorption process on the plasma-treated sample is much easier and the suppression of sensing properties is more obvious at elevated temperatures above 423K.