Double CeO 2/YSZ buffer layer for the epitaxial growth of YBa 2Cu 3O 7 − δ films on Si (001) substrates

Abstract

Both single YSZ and double CeO 2/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). θ-2θ 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 c (zero resistance) of up to 88 K were obtained on YSZ/Si, ϕ-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 10 6 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.