Hydrogenation of thin Y-Ba-Cu-O films: Electrical transport and structure properties of YBa₂Cu₃O₇ and YBa₂Cu₄O₈

c-axis-oriented YBa₂Cu₃O₇ (1:2:3) and YBa₂Cu₄O₈ (1:2:4) thin films were charged with hydrogen at 463 K and a H₂ pressure of 100 mbar. The hydrogen concentrations and depth profiles were measured with the ¹⁵N nuclear reaction method. In contrast to earlier studies on bulk samples where a constant T_c,onset is reported, we find in our 1:2:3 films that the superconducting transition temperature decreases continuously with increasing hydrogen concentration and that the transitions remain relatively sharp, e.g., T_c,onset=38 K and ΔT_c=6.2 K for [H]/cell≃0.6. The electrical resistivity and Hall-effect measurements in the normal state indicate that the main effect of hydrogen doping is a reduction of the charge carrier concentration, whereas the carrier mobility is not changed significantly. At an average hydrogen concentration of [H]/cell≃2 in both systems, a new hydride phase is observed, which for 1:2:3 is characterized by a c-axis expansion of 16% and for 1:2:4 by a c-axis expansion of 1.5%.