Ultra-thin films of GdBa2Cu3O7–δ grown by pulsed laser deposition on NdGaO3 (001) and SrTiO3 (001) were studied by grazing incidence X-ray diffraction. The critical thickness was found to be 50nm on SrTiO3 (001). On NdGaO3 (001), the shear distortion introduced by the substrate was released in 2 stages at 15 and 40nm thickness by the formation of disclinations with orthogonal pseudo-Burgers vectors. A twin structure formed in the films in the first stage of strain relief and, as a consequence, the twin boundaries were aligned unidirectionally. Calculated values for the critical thickness were too small for GdBCO/STO suggesting the existence of other mechanisms of strain relief, which was corroborated by the experimental findings.

Strain Release and Twin Structure in GdBa2Cu3O7–δ Films on (001) SrTiO3 and NdGaO3. L.X.Cao, T.L.Lee, F.Renner, Y.Su, R.L.Johnson, J.Zegenhagen: Physical Review B, 2002, 65[11], 113402 (4pp)