Characterization of PdO films for water vapour sensing

The functionality of interdigitated gold/aluminum electrodes on PdO films for water vapor (WV) sensing was studied. The characterization of the structure Au/Al/PdO/Al/Au was done at different temperatures introducing WV pulses in the test chamber under a continuous flow of N₂ to produce the desired moisture conditions. PdO films were obtained by thermal oxidation of Pd films at 650?C in air atmosphere. The Pd films were deposited by the electroless process on silicon (Si) substrates. The development of Pd/Si structures is important because it can be integrated with the microelectronic technology. Nanometric and micrometric thickness PdO films were studied. The electrical conduction limiting mechanisms of the Pd and PdO films were also determined. The response time, recovery time, and the sensitivity of structures was characterized in controlled humidity conditions. It was found that the response characteristics depend on the initial humidity condition of the PdO surface. When the structures were stored in environmental conditions the best operating parameters were observed. In contrast, when the structures were stored in dry atmosphere, the response resulted unstable with variations in the signal during extended measurement periods.