Structure and morphology of YBa2Cu3O7−x LPCVD layers

Thin films of YBa 2 Cu 3 O 7−x have been grown by chemical vapor deposition at 825 °C (5 Torr). The starting materials are tetramethylheptanedionates of Y, Ba and Cu. The superconducting properties of the films obtained on monocrystalline MgO have been studied by AC resistivity, AC susceptibility and magnetization measurements. Superconducting layers with zero resistance at 85 K and a transition width lower than 2 K are obtained. This communication will address more specifically the structural properties as well as the morphology of the layers. The films are highly orientated with their c-axis perpendicular to the substrate plane, and the pole figures show a very good in-plane orientation. The morphology of the layers has been investigated by scanning electron microscopy: we do observe a strong correlation between the roughness of the surface and the composition of the gas phase.