Humidity sensors based on Aurivillius type Bi2MO6 (M = W, Mo) oxide films

Humidity sensors based on Aurivillius type Bi2MO6 (M = W or Mo) materials have been fabricated using the “Doctor Blade” method. The structure and morphology of the fabricated films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The sensing properties were investigated with respect to both impedance and capacitance characteristics. The humidity sensing tests displayed ultrahigh sensitivities with impedance changes of 4–5 orders of magnitude with the increase of the relative humidity (RH) from 11 to 95%. The Bi2MO6 materials furthermore revealed a rapid response and recovery time with good reproducibility. The sensing properties of the Bi2WO6 sample are superior to those of the Bi2MoO6 materials due to their larger surface-to-volume ratio and different degrees of hydrophilicity. In addition, the sensing mechanism of the Bi2MO6 based sensors is discussed. These results open up promising applications of Aurivillius type oxides in electronic devices for highly sensitive environmental monitoring and humidity control.