Strain-induced structural changes in thin YBa2Cu3O7-x films on SrTiO3 substrates

High-energy synchrotron radiation is used to obtain reciprocal space maps of thin YBa2Cu3O7−x films grown by pulsed laser deposition on (001) SrTiO3 substrates. The films show a transition from a tetragonal to an orthorhombic structure with increasing film thickness. The critical thickness is found to be 11.5±0.6 nm, whereas the thickness characterizing the tetragonal-to-orthorhombic transition is estimated to be 23±1 nm. Furthermore, it is shown that for miscut angles of the vicinal substrates up to approximately 1.2°, the films grow parallel to the optical surface-normal, rather than to the crystallographic c-axis of the substrates. The feasibility of using high energy X-rays allows for the use of complicated sample chambers, needed for in-situ studies of the growth and behaviour of thin films under controlled atmosphere and at elevated temperatures