The Effects Of Varying Plating Variables On The Morphology Of Palladium Nanostructures For Hydrogen Sensing Applications

Present state-of-the-art hydrogen sensors are limited by a number of defects such as poisoning effects, slow response, and/or the range of concentrations that can be detected. Thus, hydrogen sensors are currently under investigation. In the search for the ultimate sensor, a variety of materials have been employed as the sensing layer. One of these materials is palladium. Palladium is widely used for hydrogen sensing due to its high selectivity and property of spontaneously absorbing hydrogen. Thin and thick film palladium hydrogen sensors have been reported, as well as palladium nanostructures. Specifically, palladium nanowires for hydrogen sensing have had improved results relative to other types of sensors; these have been reported with a response time down to 75ms and do not suffer from poisoning effects. Additionally, the fabrication of these nanostructures via electrodeposition is simple and cost efficient. For this reason, palladium nanostructures were chosen as the front-end for a novel hydrogen sensor. The nanostructures were to be employed as the sensing front-end of a Surface Acoustic Wave (SAW) sensor. It was theorized that the response time would be vastly improved if these were used as opposed to a thin or thick palladium film due to the decreased hydrogen diffusion distance, which is a result of the structures being one-dimensional. Because it was theorized that the dimensions of the nanostructures play an integral role in the response time to hydrogen, control of the morphology was required. This control was achieved by varying the plating variables in the electrodeposition experiments. The plating variables investigated were deposition potential, time, and counter-electrode area. The dimensions of the resulting nanostructures were measured via Scanning Electron Microscopy (SEM) and correlated to the conditions of the electrodeposition experiments. Nanowires under 40nm were successfully fabricated