Epitaxial Non c-Axis Twin-Free Bi2Sr2CaCu2O8+ Thin Films for Future THz Devices

Thin films of (117) Bi2Sr2Ca2CuO8+ (Bi-2212) were grown by Molecular Organic Chemical Vapor Deposition (MOCVD) on (110) SrTiO3 and (110) LaAlO3 substrates. Substrates were vicinal with off angles up to 20 degrees. Films are 3D epitaxial and X-ray diffraction phi- scans demonstrate that, while the films grown on a flat substrate are composed of twinned grains, the films on vicinal substrate are twin-free. A higher quality is obtained if growth is performed at two temperatures: Growth starts at 550-600 degrees C and continues at 700-750 degrees C. The twin-free film grown by the two-temperature method shows a zero-resistance critical temperature of 37 and 32 K when the measuring current is applied in-plane parallel and perpendicular to [001] direction of the substrate. Twin-free non c-axis thin films are promising for fabrication of novel planar THz devices.