REVERSIBLE LOADING OF EPITAXIAL Y(00.1) FILMS WITH HYDROGEN

Yttrium can be loaded with hydrogen up to high concentrations causing dramatic structural and electronic changes of the host lattice. We rep ort on the reversibility of hydrogen loading in thin, monocrystalline Y films grown by molecular beam epitaxy on Nb/sapphire substrates. Dur ing hydrogen loading, the Y film undergoes structural transitions from the cubic dihydrid phase to the hexagonal trihydrid phase, while the structural coherence is maintained. The transition from YH2 to YH3 occ urs at room temperature at a hydrogen pressure of 10 mbar and is compl etely reversible.