Resistivity Measurements in Palladium Hydride Film Prepared by Low-Temperature Hydrogen Absorption Method

Ryoma Kato, Ten-ichiro Yoshida, Riku Iimori, Tai Zizhou, Masanobu Shiga, Yuji Inagaki, Takashi Kimura, and Tatsuya Kawae

We investigated the superconducting properties of a palladium hydride (PdHx; x = H=Pd) film with a thickness of
∼100nm prepared by a low-temperature hydrogen (H) absorption method. H atoms were loaded to a Pd film in H2 gas
pressure of ∼0.25 MPa at temperatures of T = 180 and 150 K. At T = 180 K, after the resistivity variation due to H
absorption was almost stopped, the PdHx film was cooled rapidly to low temperatures for the resistivity measurements. A
superconducting transition was observed at Tc ∼ 1.1 K, where the transition width is smaller than 0.1 K. This indicates
that a high-quality sample with a sharp transition can be obtained by providing sufficient time for H absorption. At
T = 150 K, although the resistivity variation remained, the film was cooled. The transition temperature Tc increased to
∼2.1 K, whereas the transition width increased owing to the inhomogeneity of the H concentration in the film. Curiously,
regardless of the H homogeneity, there remained a similar T-dependent residual resistivity in both films prepared at
T = 180 and 150K after the superconducting transition. This implies that the observed residual resistivity is essential for
the future of the system, although its origin is not clear.

J. Phys. Soc. Jpn. 93, 024703(2024)

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