Development of a highly sensitive porous Si-based hydrogen sensor using Pd nano-structures

A novel, resistance-based porous silicon sensor with Pd nano-structures as hydrogen sensing layer is presented. The sensor operates at room temperature. p-Type Si substrate is subjected to porous Si etching. The substrate is then coated with a thin layer of Pd and annealed at 900 °C. This results in some Pd getting oxidized on porous Si and a thin PdO layer forms on the surface of the substrate. The sensor was tested in the range of 0-1.5% hydrogen. The sensor responded in real time. Unlike conventional thin film-based resistive hydrogen sensors this sensor showed an inverse relationship between increased hydrogen concentration versus resistance. The mechanism driving the changed output is discussed.