Growth and structural characterization of orthorhombic and tetragonal SrCuO2 thin films

Epitaxial SrCuO2 thin films were grown on (0 0 1) SrTiO3 substrates by pulsed laser deposition using a stoichiometric target. X-ray diffraction indicated that the SrCuO2 films undergo a structural phase transition as a function of the substrate temperature. Films deposited at temperatures below 600 °C exhibit a tetragonal phase with the c-axis oriented along the growth direction while films deposited at temperatures above 700 °C exhibit an orthorhombic phase with the b-axis oriented along the growth direction. Atomic force microscopy indicated that the as-grown film surfaces are rather smooth and the roughness increases with increasing substrate temperature. Energy dispersive X-ray spectroscopy in agreement with X-ray diffraction intensity ratio data revealed that all films are non-stoichiometric and contain Sr vacancies (Sr/Cu ∼ 0.8). The influence of film-substrate lattice matching and substrate temperature on the structural phase transition is discussed.