ELSEVIER Physica C 269 (1996) 124-130 PHYSICA ® Double CeO2/YSZ buffer layer for the epitaxial growth of YBa2Cu307_ films on Si (001)substrates Laurence M~chin ~'*, Jean-Claude Vill~gier a, Guy Rolland b, Frederic Laugier a D~partement de Recherche Fondamentale sur la Mati~re Condens~e, SPSMS/LCP, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 9, France b LETI. D£partement d'Optronique, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 9, France Received 29 June 1996 Abstract Both single YSZ and double CeO2/YSZ buffer layers were considered for the epitaxial growth of YBaCuO films on silicon (001) substrates. The paper reports on the influence of YSZ and CeO 2 layer thicknesses on in-plane epitaxial relationships and superconducting properties of YBaCuO films. All the films were grown by pulsed laser ablation. The thickness and interface quality was deduced from grazing X-ray reflectivity and optical spectroscopic ellipsometry measurements. The structural properties have been characterized by X-ray diffraction analysis (XRD). 0-20 scan XRD spectra showed that, in appropriate conditions, both YSZ and CeO 2 films have (001) orientation on Si (001) and YSZ/Si (001) substrates respectively. C-axis textured YBaCuO films were obtained on each buffer layer. A single YSZ buffer layer was considered first. Even when critical temperatures T~ (zero resistance) of up to 88 K were obtained on YSZ/Si, q~-scan XRD spectra indicated that two different in-plane orientations exist in the YBaCuO films. With the introduction of an intermediate 10 nm thick CeO 2 layer on a 70 nm thick YSZ layer, the total YBaCuO in-plane alignment was obtained. YSZ and CeO 2 films were cube on cube aligned, whereas YBaCuO films were totally 45 ° rotated, around the c-axis, with respect to the Si (001) substrate. Critical temperatures T c (R = 0) of 88.5 K and critical current densities above 106 A/cm 2 at 77 K confirm the high quality of the 40 nm thick YBaCuO films. The films are stable upon aging and thermal cycling as proved by their successful use for the realization of sensitive suspended YBaCuO microbolometers. Keywords: YBaCuO; Silicon substrate; Epitaxial growth; Thickness of buffer layers I. Introduction The development of high-temperature supercon- ducting electronics first requires the processing of thin epitaxial YBaCuO films. The choice of the substrate is then an important material issue. In a * Corresponding author. Fax: + 33 76 88 50 96. first approach, the criteria are of a material nature: lattice matching, small difference of thermal coeffi- cients with respect to YBaCuO, chemical inertia, compatibility with the deposition process [1]. How- ever, the specific application envisaged often im- poses the choice of the substrate. In our case, the choice of substrate was determined by the possibility of removing the substrate underneath the YBaCuO film in order to fabricate very sensitive suspended YBaCuO edge-bolometers [2-5]. Although it does 0921-4534/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved PH S0921-4534(96)00435-2