Roughness of manganite-based thin films and superlattice interfaces

J. C. ROJAS SÁNCHEZ; M. GRANADA; J. GUIMPEL; I. MAZZARO; D. H. MOSCA; L.B. STEREN

S.C. de Bariloche, Argentina

Conferencia; 13th International Conference on Solid Films and Surfaces; 2006

The roughness at the interfaces of magnetoresistive (MR) devices essentially determined diffusive scattering parameters. A careful determination of the roughness of MR superlattices could help to understand the transport properties of the samples. In this work, we present a structural characterization of La0.75Sr0.25Mn03 (LSMO) thin films and (La0.75Sr0.25Mn03/LaNiO3)x15 superlattices (LSMO/LNO). The samples were grown on (001) SrTiO3 at 700ºC using a multi-target dc magnetron sputtering. The deposition rate of the LSMO was typically 13.3 Å/min while that of the LNO layers was 20 Å/min. The samples thickness were calibrated with a profilometer. The structural characterization of the samples was performed by X-ray diffraction spectroscopy (XRD). Measurements of X-rays reflectometry at low angles were performed in a four-circle P3 Nicolet-Siemens diffractometer. These experiments serve to determine the LSMO films thickness that have a nominal value of t = 200Å. The deduced value, t =208Å, is in very good agreement with the nominal value. The roughness of the films has been studied by Atomic Force Microscopy. It was not possible to resolve the reflectometry at low angles because the high value of total thickness of the superlattices. In fact, the nominal thickness of a bilayer LSMO/LNO is 250 Å while the total thickness of the samples is 3750Å. So, the distance between the low-angle peaks fall within the experimental resolution. The roughness of the superlattice was calculated using the Suprex program [1]. This program allows us to determine also the thickness and the lattice parameter of the individual layer. The program fit the q -2q XRD pattern of two elements A/B superlattices, adjusting these parameters. The program was modified in order to be able to fit the XRD pattern of our superlattice LSMO/LNO.