Phase diagram of thin films of lutetium hydride — lutetium

Lutetium hydrides LuH_x thin films with x from 0 up to 3.2 were deposited on Si(001) substrates by laser ablating a 4N lutetium metal target in a vacuum or hydrogen environment. With x increasing, the hydride films undergo a phase transition at x ∼ 0.77 from hexagonal close-packed (hcp) to face-centered cubic (fcc) structures. The anomaly was found to emerge in temperature-dependent resistivity at ∼ 173 K in hcp-phase films but not in fcc-phase films. The sudden dramatic decrease in the amplitude of the anomaly once hydride enters the two-phase region from the hcp-phase side supports the idea that the formation of the hydrogen network in the a–b plane of the hcp-phase is the sole reason for the emergence of the anomaly.