Fabrication and formaldehyde gas-sensing property of ZnO–MnO2 coplanar gas sensor arrays

Nanostructured flat-type coplanar gas sensor arrays of ZnO with different MnO2 additive concentration were fabricated by a combination of screen-printing technology and solution growth process. The morphologies and crystal structures were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results showed that ZnO nanostructures were induced on the surface of gas sensor arrays through the solution growth process. The nanostructures were composed of nanowalls and nanosheets with the thickness of about 50–200 nm and length of about 1–2 μm. The resistance–temperature characteristic and the response to formaldehyde revealed that the solution growth process could effectively control the morphologies, change the aspect ratio of ZnO nanostructures and significantly improve the response of gas sensor arrays. In addition, the response to formaldehyde of ZnO sensors with 0.5 wt% and 1.0 wt% MnO2 additive was higher than that of pure ZnO sensor.