Investigation of hydrogen sensing properties and aging effects of Schottky like Pd/porous Si

We prepared porous silicon samples coated by continuous palladium layer in electroless process. Scanning electron microscopy (SEM) showed cauliflower-shape Pd clusters on the surface. I–V curves of Schottky like Pd/porous Si samples were measured in air and in hydrogen. These measurements showed a metal–interface–semiconductor configuration rather than an ideal Schottky diode. Variations of the electrical current in the presence of diluted hydrogen at room temperature revealed that the samples can sense hydrogen in a wide range of concentration (100–40,000 ppm) without any saturation behavior. Hydrogen sensing properties of these samples were investigated at room temperature for a duration of nine months. Sample sensitivity (response time) decreased (increased) to a saturated value after 45 days. We discussed sensing and Schottky contact properties of the fresh and aged Pd/porous Si samples by variation of structure and chemical composition using SEM, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) data.