Resistive Hydrogen Sensor Based on Amorphous CuO Thin Film Covered With Pd Nanoparticles

Abstract

The sputtered copper oxide (CuO) film covered with palladium (Pd) nanoparticles (NPs) is employed to fabricate a high-performance p-type resistive hydrogen sensor. The metal NPs on the top layer of the sensor could accelerate the catalysis and expand the sensing surface area. When hydrogen is sensed at high temperature, the reaction between hydrogen molecules and oxygen ions on the surface of CuO thin film will form free electrons, which free electrons will release back to the conduction band of p-type CuO thin film. These holes recombined with the released free electrons on the CuO surface results in an increase of the surface-depletion depth of CuO thin film. This gives the reduction (increase) in the hole concentration (resistance) of p-type CuO. In addition, the sensing response ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S_R</i> ) rises to the highest when the operation temperature reaches 300 °C. It exhibits a high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S_R</i> of 13.22 at 1% H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /air and a low detection level of 50 ppb H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /air at 300 °C. The device takes the advantages of easy fabrication process, simple structure, high sensing response, and low cost, which provides a promise for the sensing of hydrogen at high temperature.