Variations of the infrared transmission properties with the metal-insulator transition in thin films of the yttrium-hydride system

This work investigates the variations of the infrared transmission spectra of yttrium-hydride films YHx during the hydrogen loading process for the fr equency range 500-4000 cm(-1). The results indicate that the transmittance slightly decreases in the dihydride phase, followed by a significant increa se in the trihydride phase. In addition, the carrier concentration decrease s, whereas the carrier relaxation time increases with hydrogen content. The hydrogen vibration modes at interstitial sites are completely screened in the dihydride phase. The screening effect decreases as the system goes thro ugh the metal-insulator transition. Moreover, the screening effect can be c ontinuously tuned by simply varying the hydrogen content in the yttrium-hyd ride system. Analysis indicates that the absorption intensity of the vibrat ion mode depends on the carrier concentration. This effect can be used as a diagnostic tool for estimating the carrier concentration and hydrogen cont ent in rare-earth hydrides. (C) 2001 American Institute of Physics.