Monitoring the deleterious gases presented in breath or indoor has become a promising candidate as a suitable approach for healthcare. To detect the harmful gases, extensive efforts are conducted by nanostructures with metal additives or hetero-junctions on the basis of three basic factors (transducer function, utility factor and receptor function). Generally, porous nanostructures as a sensing material are synthesized by solution or chemical based methods, but have limitations such as uniformity, productivity and reproducibility in practical application. In order to overcome these drawbacks, we studied the synthesis of nanostructures without nano-template or chemical additives based on RF sputtering or glancing angle deposition (GLAD) method via e-beam evaporator. By controlling the incident angle of vapor flux, orientation of the substrate, vacuum level, deposition rate and size of electrodes, morphological and electrical properties are effectively tailored.
In this presentation, the recent several developed metal oxide gas sensors are introduced. We successfully fabricated Rh-decorated WO3nanorods using GLAD (glancing angle deposition) method. Interestingly, morphological evolution characterized by anomalous surface with numerous resgions of negatie curvature were observed upon decorating the bare WO3nanorods with metallic Rh, which were systematically investigated on the basis of impeded surface diffusion and trapping effects. The improvements of gas sensing properties were demonstrated to be a stepwise process involving the transition of Rh on the WO3 surface. Furthermore, SnO2nanorods based gas sensors were investigated for room-temperature operation. Underlying sensing mechanism was interpreted by complex impedance spectroscopy (CIS) and in-situ X-ray photoelectron spectroscopy (XPS). We believe that these results provide new insight into the synthesis of effective nanostructures, and contributes to a variety of applications including battery, solar water splitting, sensor devices, and so on.