Anisotropy on the a, b-plane of c-axis orientated almost twin-free YBCO films on NdGaO3

Crossover between fractal and nonfractal flux penetration in high-temperature superconducting thin films

“…33 Due to the so-called Cu-O chains of YBa 2 Cu 3 O 7Ϫx , which run along the b axis, the electronic structure is anisotropic, leading to, e.g., anisotropy in the resistivity above T c . 35,42 Anisotropy of j c can thus be expected. However, isotropic YBa 2 Cu 3 O 7Ϫx films on NdGaO 3 substrates have been also obtained.…”

“…The film thickness is only 80 nm to prevent strain in the film. 33,42 The YBa 2 Cu 3 O 7Ϫx films are grown with the c axis perpendicular to the substrate and due to crystallographic anisotropy of the substrate surface, the a and b axes of the YBa 2 Cu 3 O 7Ϫx film have the same orientation over the whole substrate surface. This is verified using Rutherford backscattering and x-ray texture analysis.…”

Twinning and domain structure of epitaxial YBa2Cu3Ox films studies by X-ray diffraction methods

“…Similar to single crystals, twinning in c-oriented YBCO films occurs in accordance with the {1 1 0}//1 1 0S scheme with an angle of twinning of about 11 [1,2]. The type of twinning structure of YBCO films correlates with the structure of the substrate.…”

The origin of preferential twinning in YBa2Cu3O7−δ thin films deposited on the (0 0 1) NdGaO3 substrate

“…Efforts to detwin these films have centered around suspending a portion of the film to remove the constraining effects of the substrate 1 or by using the unique straining properties associated with the orthorhombic crystal structure of the ͑0 0 1͒ NdGaO 3 ͑NGO͒ substrate. [2][3][4][5][6][7][8][9][10][11] The latter method, however, is controversial as there have been reports of detwinned films [2][3][4][5][6][7] as well as studies that show bidirectional twinning, 8 preferential twinning, [9][10][11] as well as the assertion that a detwinned film is inherently impossible in this system. 9 The transformation from a microtwinned state to a twinfree state will give rise to a film exhibiting anisotropy in the optical and transport properties.…”