Solid State Communications, Vol. 79, No. 10, pp. 839-841, 1991. Printed in Great Britain. 0038-1098191$3.00+.00 Pergamon Press plc TRANSPORT PROPERTIES OF EPITAXIAL BSCCO FILMS GROWN ON UNTWINNED NdGaO, SUBSTRATES G. Balestrino”), V. Fogliettr ‘(*), M. Marinelli@), E. Milanit3), A.Paolettir3’, P.Parolir’) (‘) Dipartimento di Fisica, Universita di Salerno, I-84100 Salerno, Italy r2) C.N.R.-I.E.S.S., Via Cineto Roman0 42, l-00158 Roma, Italy 13) Dipartimento di lngegneria Meccanica, Universith di Roma “Tor Vergata”, Via O.Raimondo 8, I-00173 Roma, Italy (‘) Dipartimento di Fisica, Universita della Calabna, Arcavacata di Rende, I-87036 Cosenza, Italy (Received 30 May 1991by M. Tosi) Epitaxial films of Bi2Sr2Ca,Cu20, have been grown on NdGaO,, twin-free substrates by liquid phase epitaxy. The films have high crystallographic quality and thickness of about 1 pm. The resistivity curve is metallic, with a sharp (2.9 K wide) resistive transition and zero resistivity at 84.5 K. The critical current density at 77.3 K is 10’ A/cm2, extrapolating to about 5 10s A/cm2 at 4.2 K. The latter value is more than one order of magnitude higher than that obtained using LaGaO, substrates, although lower than the one measured on films grown on SrTiO,. 1. Introduction The availability of good quality high T, superconducting (HTS) films capable of sustaining large critical currents is of course essential for the realization of superconducting devices working at liquid nitrogen temperature. It is therefore important, on one hand, to develope a convenient technique for the growth of HTS films, and on the other hand, to find the most useful substrate for that technique. Besides magnetron sputtering, laser ablation and chemical vapour deposition, liquid phase epitaxy (LPE) has been proved’ to be a simple and cheap technique for the growth of high quality Bi,Sr,Ca,CyO, (BSCCO) films. Using a substrate having good lattice-matching with the BSCCO ceil in the a-b plane, films with c-axis perpendicular to the film surface are routinely obtained which are superconducting as-grown. The films are truly epitaxia1203, that is, the a and b axes of the films are parallel to those of the substrate. The crystallographic, compositional and superconducting properties of the films are determined both by the growth parameters (melt composition, growth temperature etc.) and by the chosen substrate. A complete analysis of the influence of the growth parameters on the film properties will be published elsewhere’. In this paper we will present the structural and transport properties of epitaxial BSCCO films grown by LPE on twin-free NdGa03 substrates, and compare these results with those of films grown using the same technique on different substrates2”. Untwinned NdGaO, has been shown’ to have characteristics which make it an extremely interesting substrate for the growth of HTS films, especially in view of the realization of HTS devices. Y,Ba,Cu,O, (YBCO) films have been obtained on NdGaO, substrates by several groups’*‘, with very good results in terms of crystallographic quality and transport properties. 2. Results and Discussion Slices of NdGaO, cut perpendicularly to the (0 0 1) axis offer a good lattice match also with BSCCO compounds (a=5.43 zyxwvutsrqponmlkjihgfedcbaZY A, bz5.49 A for NdGaO,, a=5.40 A, bz5.42 A for BSCCO at room temperature) and are therefore suitable substrates for the growth of epitaxial BSCCO films by LPE. The BSCCO films (2212 phase) were grown following the method reported in Ref. 2, with a typical growth temperature of 810 ‘C. The melt composition was slightly enriched in Ca and Cu with respect to the one reported in Ref. 2 to avoid any contamination by the 2201 phase even growing at relatively low temperatures. Thick (1-2 pm), uniform films were obtained, having very high structural quality. X-ray diffraction spectra were taken using a Bragg-Brentano diffractometer with CuKa radiation. 839