Crystal structure effects on the Co-sputtered p-type Fe2-xSnxO3 hydrogen gas sensors

Abstract

Fe2-xSnxO3 structures grown by RF-DC magnetron co-sputtering. The band gap of Fe2O3, SnO2, Fe2-xSnxO3 structure was calculated as 2.86, 4.06, 2.77 eV, respectively. The Fe2O3 thin film has shown a tetragonal as well as the SnO2 structure, however, the Fe2-xSnxO3 (0 < x < 1) has shown rhombohedral structure. XPS measurements have shown change in binding energy which is due to the electron exchange of tin-iron with oxygen, and iron - tin oxide structure. This binding energy increases slightly with the chemical environment effect. The films were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM). In AFM images was seen that the iron oxide structure was pyramidal and the tin oxide structure was spherical, similar to the SEM image. The response of the film to hydrogen gas was measured at flow values of 100, 500 and 1000 ppm at 300 °C. Fe2O3 thin films show 46%, SnO2 61% and, Fe2-xSnxO3 6.5% response to 1000 ppm H2 gas. It is seen that the gas sensor response was affected by the morphological and structural features of the grown film.