Stabilized switchable “black state” in Mg2NiH4 /Ti/Pd thin films for optical hydrogen sensing

Abstract

A triple layer thin film (30 nm Mg2Ni/100 nm Ti/10 nm Pd sputtered on glass) switches reversibly from a shiny metallic to a “black” state upon exposure to moderate hydrogen pressure (=5.103 Pa). This black state resembles that obtained in thick Mg2NiHx layers and has the great advantage of being stable and easily controlled. Both the reversible high optical contrast (Rreflective /Rblack=10 in the red wavelength range) and the fast kinetics of hydrogen absorption and desorption make this material interesting for applications as optical hydrogen sensors.