Kazuhiro Endo

(119) Bi-2223 thin films grown by MOCVD on (100) NdGaO3 and (110) SrTiO3

In high temperature superconductors (HTS) the coherence length along non-c axis directions is longer. This feature can be useful wh en designing electronics devices based on HTS. Therefore growth and characterization of non-c axis oriented thin HTS films is of great interest. In this paper we present a short review of our data regarding (119) Bi-2223 thin films grown by MOCVD on (100) NdGaO3 and (110) SrTiO3. The emphasis is made on improvement and control of the quality of the films by the two-temperature technological approach and/or use of the vicinal substrates. Phase and morphology evolution for different processing conditions, substrates type and off-angle are presented. The highest critical temperatures of Tc0=67.2 K and Tc0=74 K for the single and two-temperature routes were obtained on vicinal SrTiO3 with the off-angle of 20°. A higher off-angle promoted the formation of a specific step-like morphology with lower roughness. For the films grown on flat substrates the morphology was of mountain-range shape. Surface morphology as a result of two types of growth mechanisms (two-dimensional (2D), assisted by a so-called twin-growth and step-flow growth) for the (119)Bi-2223 filmes are discussed.

AFM and TEM observation of surface morphology of Bi-2223 superconducting thin films by MOCVD

Abstract Using atomic force microscopy and transmission electron microscopy, we examined the surface morphology of Bi-2223 superconducting thin films grown by metalorganic chemical vapor deposition, which is closely related to the growth mechanism of Bi-2223 films. As a result, we found an anisotropic in-plane growth. The growth rate along the a -axis is larger than that along the b -axis. Finally, we report on the fabrication of c -axis oriented Bi-2223 films with a roughness less than half a unit cell.

Orientation Control of HTS Thin Films

The preparation of non c -axis oriented HTS films with longer coherence length is one of key technologies toward realisation of viable Josephson devices. We reports on the successful growth of (119)Bi-2223 films by MOCVD using a two-step growth temperature procedure and on AFM observation of the film surface. This temperature procedure was found to be effective for orientation control and phase control in comparison with a fixed growth temperature procedure. As a result, superconducting properties were much improved. The surface morphology observed by AFM showed a mountain-range-shaped one, which strongly reflects the epitaxial relationship between the (119)Bi-2223 film and (110) SrTiO 3 substrate.