Correlation between hydrogen absorption, electrical resistivity and optical properties in La28.9Ni67.5Si3.6 thin film

Hydrogen intercalation changes both the electrical and the optical properties of the thin film. Discovery of electrical and optical switching in yttrium and lanthanum hydride thin film has triggered large scale investigations of rare earth hydride thin films. In this paper, electrical resistance and optical measurements on hydrogenated La28.9Ni67.5Si3.6 thin film in the temperature and pressure range 25⩽T⩽200∘C and 10-5⩽P⩽760torr, respectively, are presented. Thin film sample was characterized by the means of XRD. The films were prepared in a high vacuum chamber by flash evaporation method and hydrogenated by exposing hydrogen in the chamber. It is found that the resistance of film increases with the absorption of hydrogen and decreases with desorption of hydrogen. The amount of hydrogen absorbed by the film increases with the number of charging/discharging cycle and after four cycles the sample becomes saturated with hydrogen. Transmittance spectra of thin metallic film show that the films switch reversibly from their initial reflecting state to visually transparent states when exposed to gaseous hydrogen.