Preparation of high quality Bi2Sr2CaCu2O8+delta thin films on a MgO substrate by pulsed laser ablation and post-annealing - recrystallization of films accompanying in-plane rotation of a and b axes

摘要

A growth technique for bulk level superconducting transition temperature (T-c) and smooth surface Bi2Sr2CaCu2O8+delta (2212) thin films on MgO (0 0 1) single-crystal substrates has been developed by a combination of pulsed laser ablation and post-annealing. Films deposited at lower substrate temperatures show only the [100](2212)//[100](MgO) epitaxial relation. Although they have a unit-cell size level smooth surface, these films show superconductivity at considerably lower temperatures than bulk materials. After annealing, we have found that the inplane axes of the 2212 grains thoroughly rotate by 45 degrees, since only the [100](2212)//[1 1 0](MgO) epitaxial relation becomes observable. The T(c)s of these films are found to reach 75-80 K after the annealing without losing their surface flatness. We have successfully synthesized films, which have both atomically smooth-surface morphology and bulk level T(c)s. The key factor of this synthesis route is the in-plane rotational recrystallization. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 9]