Microstructural study of growth of a YBa2Cu3O7−x/LaAlO3/YBa2Cu3O7−x trilayered film by pulsed laser deposition

Abstract

The growth process of a YBCO/LaAlO3/YBCO trilayered film made by pulsed laser deposition has been studied by high resolution transmission electron microscopy (HRTEM). The high resolution images of the cross-section samples have shown that a 7 nm layer of LaAlO3 has been grown epitaxially between c-axis oriented YBCO layers having the nominal thickness of 250 nm. A stacking fault in the LaAlO3 layer may introduce a stacking fault into the YBCO layer, which may form nucleation sites for α-axis oriented grains. A second phase had been formed at the interface between the LaAlO3 layer and the lower YBCO layer, which has been identified by image simulation and energy dispersive x-ray (EDX) analysis as a new tetragonal La–Al–Cu–O phase based on LaAlO3 in which some of Al atoms have been replaced by Cu. The approximate lattice parameters of the new phase are a = 0.38 nm and c = 0.76 nm. However, no second phase was found at the interface between the lower YBCO layer and the LaAlO3 substrate.