Rutherford backscattering and channeling studies on epitaxial YBa2Cu3O7-x thin films

We have conducted ion-backscattering and channeling experiments on epitaxial c-axis oriented YBa2Cu3O7-x(YBCO) thin films (Tc∝90 K, Jc≥106 A cm-2) grown onto (001)MgO and MgO buffered (1anti 102)Al2O3 substrates. From our results on films with a range of compositions around 1:2:3 stoichiometry we infer that a film, with metal ratios (Y:Ba:Cu): 1.25:1.78:2.97 (film A), has a minimum channeling yield χmin,Ba of 8% compared with a value of 14% obtained on a film with metal ratios: 1.03:2.22:2.74 (film B). Angular-yield profiles for film A in the <001> and <101> MgO substrate directions along the {010} plane demonstrate that full epitaxy of the YBCO film on (001)MgO is achieved. This film (3300 A thick) is relaxed as expected, with the <103> direction in the film being at an angle of 44.6deg to the <001> film direction. Backscattering and channeling data on a YBCO film (Tc ≅ 88 K, Jc≥106 A cm-2) on MgO buffered Al2O3 show a χmin.Ba of 25%, the beam becoming about 90% dechanneled in the MgO buffer layer and Al2O3/MgO interface. The interlayer reaction between MgO and Al2O3 is at a minimum. (orig.)