Ba2-xSrxCuO₂CO₃:  A Series of Oxycarbonate Thin Films Grown by Pulsed Laser Deposition on NdGaO₃ Substrates

Monophasic thin films of the oxycarbonates Ba 2- x Sr x CuO 2 CO 3 have been grown by pulsed laser deposition on [110]-oriented NdGaO 3 substrates for x = 2, 1.6, 0.9, 0.4, and 0.3. A systematic study of these films by X-ray diffraction and transmission electron microscopy shows that the film orientation varies from a -axis or [110] orientation (copper layers perpendicular to the substrate) to a c -axis or [001] orientation (copper layers parallel to the substrate) as x decreases. Sr 2 CuO 2 CO 3 ( x = 2) is indeed a -axis oriented, whereas for 0.4 < x < 1.6 these films have a [110] orientation, and finally for x = 1.6−1.7 the films exhibit c -axis, [110]- and [11̄0]-oriented domains. The factors which influence the orientation of these films are discussed.