Hysteresis and the single-phase metal-insulator transition in switchable YHx films

[摘要] Extraordinary large hysteresis effects in optical, electrical, and structural properties are observed in switchable mirrors based on thin yttrium hydride (YHx) films, deposited on quartz, glass or sapphire. The pressure-composition isotherms of the YHx system between x=2 and 3 for absorption and desorption, determined electrochemically, differ by approximately three orders of magnitude. The optical transmittance exhibits a distinct minimum when loading the films from the dihydride to the trihydride state; however, upon unloading this minimum is absent. The desorption data are in good agreement with literature data on bull; yttrium, but the absorption results show large deviations. Most important for the metal-insulator transition is that during hydrogen loading YHx remains in a single hcp phase for x>2.1. The hysteresis is discussed in terms of strains (and consequently stress) at the interface between fee dihydride and hcp trihydride.

[关键词] LANTHANUM HYDRIDE FILMS;OPTICAL-PROPERTIES;SEMICONDUCTOR TRANSITIONS;ELECTRONIC-STRUCTURE;HYDROGEN INSERTION;MIRRORS;YTTRIUM;TRANSMISSION;SPECTROSCOPY;DIFFRACTION