Hydrogen in thin epitaxial Nb films

• Published in: Journal of alloys and compounds Vol. 293; pp. 476 - 479
• Main Authors: Song, G, Remhof, A, Labergerie, D, Sutter, C, Zabel, H
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20-12-1999
• Subjects: Hydrogen absorption/desorption; Nb-film; Thin epitaxial film; X-ray scattering isotherms; X-ray scattering isotherms; Hydrogen absorption/desorption; Nb; Thin epitaxial film; Nb-film
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/S0925-8388(99)00468-5

The solubility isotherms of hydrogen in epitaxial Nb(100) films have been determined via in situ X-ray lattice-parameter measurements. The Nb films were grown by molecular-beam epitaxial techniques on R-Al
2O
3 substrates with different thicknesses varying from 34 to 204 nm. Similar to Nb(110) films, the maximum out-of-plane lattice expansion scales inversely with Nb(100) film thickness. Furthermore, the critical temperature
T
c for the α-α′ phase transition as derived from the solubility isotherms depends strongly on the film thickness. For both orientations we determine similar
T
c’s but for film thicknesses below 30 nm,
T
c in Nb(100) films are higher by about 80 K as compared to Nb(110) films. The influence of finite size scaling and adhesion of the films to the substrates on the solubility isotherms will be discussed.