Structural and electrical properties of LaNiO 3 thin films grown on (100) and (001) oriented SrLaAlO 4 substrates by che
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Structural and electrical properties of LaNiO3 thin films grown on (100) and (001) oriented SrLaAlO4 substrates by chemical solution deposition method D. S. L. Pontes1, F. M Pontes2*, Marcelo A. Pereira-da-Silva3,4, O. M. Berengue5, A. J. Chiquito5, E. Longo1,6 1 LIEC – Department of Chemistry, Universidade Federal de São Carlos, Via Washington Luiz, Km 235,P.O. Box 676, 13565-905, São Carlos, São Paulo,Brazil 2 Department of Chemistry, Universidade Estadual Paulista - Unesp, P.O. Box 473, 17033-360, Bauru, São Paulo,Brazil 3 Institute of Physics of São Carlos, USP, São Carlos, 13560-250, São Paulo, Brazil 4 UNICEP, São Carlos, 13563-470, São Paulo, Brazil 5 NanO LaB – Department of Physics, Universidade Federal de São Carlos, Via Washington Luiz, Km 235, P.O. Box 676, 13565-905, São Carlos, São Paulo,Brazil 6 Institute of Chemistry, Universidade Estadual Paulista – Unesp, Araraquara, São Paulo - Brazil
ABSTRACT LaNiO3 thin films were deposited on SrLaAlO4 (100) and SrLaAlO4 (001) single crystal substrates by a chemical solution deposition method and heat-treated in oxygen atmosphere at 700oC in tube oven. Structural, morphological, and electrical properties of the LaNiO3 thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and electrical resistivity as temperature function (Hall measurements). The X-ray diffraction data indicated good crystallinity and a structural preferential orientation. The LaNiO3 thin films have a very flat surface and no droplet was found on their surfaces. Samples of LaNiO3 grown onto (100) and (001) oriented SrLaAlO4 single crystal substrates reveled average grain size by AFM approximately 15-30 and 20-35 nm, respectively. Transport characteristics observed were clearly dependent upon the substrate orientation which exhibited a metal-to-insulator transition. The underlying mechanism is a result of competition between the mobility edge and the Fermi energy through the occupation of electron states which in turn is controlled by the disorder level induced by different growth surfaces.
1 Introduction Metal-to-insulator transitions (MIT) has been studied in a large variety of systems. These transitions are normally driven by typical parameters such as doping, pressure, temperature and dimensionality (thickness). Metallic perovskites oxides such as La0.5Sr0.5CoO3 (LSCO) [1], LaNiO3 (LNO) [2,3] and SrRuO3 (SRO) [4] are examples of excellent candidates to explore basic science regarding MIT. These materials can be characterized as strongly electron correlated interactions due to their metallic behavior which in turn is highly dependent upon the dimensionality of the system. Among these materials, the entire class of rare-earth nickelates RNiO3 is known to display MIT which
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is usually associated with a variation of the unit cell volume as a function of temperature and the radius of the rare-earth material. Of these materials, rare-earth nickelate LaNiO3 is the most interesting, and, surprisingly, LaNiO
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