David A. Keller

Control of the 2D/3D transition of the growth mechanism in the YBCO/Ce1-xLaxO2-x/2/SrTiO3 system

Abstract Yba 2 Cu 3 O 7− δ thin films have been deposited by pulsed laser-assisted deposition (PLD) on (001) SrTiO 3 substrates coated by a lattice-matching buffer layer. The buffer layer, deposited by PLD prior to the YBCO film, consisted of a graded La-doped CeO 2 layer, having the composition Ce (1− x ) La x O 2− x /2 , the La content x being decreased from 0.3 (substrate side) to 0.15 (YBCO film side) in order to achieve lattice matching at the substrate and at the film sides, respectively. It was found that this system permitted the growth of YBCO films with large-sized grains, by a quasi layer-by-layer mechanism up to thickness values in excess of 150 nm. The outcome of this preliminary study suggests that the achievement of high quality YBCO films aimed at microwave devices—smooth and having grains strongly coupled by Josephson coupling—entirely grown by a quasi layer-by-layer mechanism, may be within reach. The stake of this study is in the possible application of the lattice-matching concept to cost effective systems such as YBCO/MgO or YBCO/Al 2 O 3 .

Nucleation of YBa2Cu3O7−δ films on MgO substrates by pulsed laser deposition

Abstract YBa 2 Cu 3 O 7−δ ultra-thin films, grown on MgO (001) substrates using the in-situ pulsed laser deposition technique, were studied by high-resolution transmission electron microscopy and by atomic force microscopy. This work reports on the influence of the substrate surface rugosity on the film growth process at fixed temperature and oxygen partial pressure.

Nucleation and growth mechanisms of YBa2Cu3O7-δ thin films driven by substrate temperature on MgO and SrTiO3 substrates

Abstract This study gives an overview of nucleation/growth mechanisms of YBCO films on MgO and SrTiO3 substrates, and evidences conditions for the fabrication of films with a low roughness.