Low power hydrogen sensors using electrodeposited PdNi–Si Schottky diodes

The use of electrodeposited PdNi–Si Schottky barriers as low power Hydrogen sensors is investigated. The Palladium content of the film causes the Hydrogen molecules to dissociate and be absorbed by the film, changing the metal work function and Schottky barrier current. In this work we show that electrodeposited Pd(Ni)–Si Schottky barriers exhibit very low reverse bias currents compared to evaporated Schottky diodes. The Schottky diodes were fabricated on 0.5–1.5 Ω cm (100) n-type Si by electrodeposition of PdNi followed by evaporation of aluminium contact pads. Electrical measurements at different Hydrogen pressures were performed on back-to-back Schottky diodes in a vacuum chamber using pure nitrogen and a 5% hydrogen–nitrogen mixture. Very low currents of ∼1 nA were measured in the absence of hydrogen. Large increases in the currents, up to a factor of 100, were observed upon exposure to different hydrogen partial pressures. A back-to-back configuration forms a device that draws extremely low power when idle. The low idle current, simplicity of the fabrication process and ability to easily integrate with conventional electronics proves the suitability of electrodeposited PdNi–Si Schottky barriers as low power hydrogen sensors.