Channelling behaviour of expitaxial YBa₂Cu₃O₇ films with various orientations

Thin films of YBa₂Cu₃O₇ were deposited on (100) and (110) SrTiO₃ substrates by magnetron sputtering. Films were produced with c axis, a axis, (110) and mixed (110)/(013) orientations depending on substrate orientation and on substrate temperatures, as determined by X-ray diffraction. Helium ion channelling was applied to analyse the films. In all cases single crystalline growth was detected. The best minimum yield values X_min of c axis and a axis oriented films on (100) SrTiO₃ were 15% and 25% respectively, whereas those of (110) and (110)/(013) oriented films on (110) SrTiO₃ were about 50% for 2 MeV helium ions. The X_min values of the films were found to depend strongly on the substrate quality whereas only a weak dependence of X_min on the film thickness between 130 and 3000 Å was observed.