Channeling analysis of intrinsic and radiation-induced disorder in single crystalline high- Tc YBa 2Cu 3O 7 thin films
He ion channeling and backscattering spectroscopy was applied to analyze the crystalline quality and the surface preparation of SrTiO 3 single crystals which were used as substrates for the growth of large area single crystalline YBa 2Cu 3O 7 thin films. The analysis supported by Monte Carlo simulation calculations revealed a strain-free growth with the c-axis perpendicular to the substrate surface. The films reveal a mosaic structure with a standard deviation of 0.2° for the misoriented crystallites. The best minimum yield values of 0.12 are obtained for 1 MeV He ions. Energy dependent yield measurements indicate the existence of dislocations. He ion channeling and the resonant scattering at 3.04 MeV was used to determine the oxygen content and to study the damage production and annealing. After irradiation at 300 K the dechanneling yield of the metal atoms and the oxygen increases by about the same amount indicating that the same number of atoms are displaced in different sublattices. The displaced atom fraction is equal to the amorphous fraction as determined by X-ray diffraction.