Synthesis and magnetic properties of manganite thin films on Si by polymer assisted (PAD) and pulsed laser deposition (P
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Synthesis and magnetic properties of manganite thin films on Si by polymer assisted (PAD) and pulsed laser deposition (PLD). J. M. Vila-Fungueiriño, B. Rivas-Murias, F. Rivadulla* Centro de Investigación en Química Biológica y Materiales Moleculares (CIQUS), C/Jenaro de la Fuente s/n, Campus Vida, Universidad de Santiago de Compostela, 15782-Santiago de Compostela, Spain. ABSTRACT We report the synthesis of polycrystalline films of La1-xCaxMnO3 in Si (111) by Polymer Assisted Deposition (PAD). An aqueous solution polyethyleneimine (PEI) and different metal ions stabilized with EDTA, was spin coated on hydrophilized Si substrates and subsequently annealed under different atmospheres. Homogeneous, dense polycrystalline films are obtained at optimized conditions of 950 ºC under flowing O2. The morphology and magnetic properties of the samples are compared with films obtained by Pulsed Laser Deposition. INTRODUCTION Manganites of general formula La1-x(Ca,Sr)xMnO3 (LCMO, LSMO) can be tuned to present a high Curie temperature, TC, and a large degree of spin-polarization [1,2] that makes them attractive for a large number of applications. For example, IR detectors or any other technology based on sensing a change in resistance in response to a temperature or magnetic field variation may be designed.[3] Also, they are being actively studied as polarized ferromagnetic (FM) electrodes for spin-injection in semiconductors. Particularly interesting in this regard is the direct deposition on Si, due to the long spin-coherence time of this semiconductor,[4] as well as to possibility of integrating the multifunctional oxide with this semiconductor. Different authors grew epitaxial thin films of LCMO and LSMO on Si through a buffer layer, by Pulsed Laser Depostion (PLD) and sputtering.[5] The nature of the buffer layer changes depending on the composition of the FM, and in some cases complex multilayer structures must be used between the FM and the semiconductor,[6,7] affecting the transport of charge carriers across the interface into Si. On the other hand, attempts to grow the FM oxide directly on Si are scarce. On the other hand, polycrystalline films of LSMO were deposited on Si by sputtering,[4] with magnetic properties similar to bulk manganites. Given the interest in de deposition of multifunctional, multicationic oxides directly on Si, we have considered the possibility of chemical solution deposition (CSD) and spin-coating based methods, as they are cost-effective approaches which could be competitive with sputtering and PLD in this case. This is an approach that has been shown to be successful to grow epitaxial LCMO and LSMO on STO and LAO substrates,[8,9,10] but it has not been extended to substrates with different structure, like Si. Here we report a comparison of the morphologic and magnetic properties of LCMO thin-films grown directly on Si by PAD [11] and PLD. The films deposited by PAD were subsequently annealed at different temperatures under different atmospheres to control their Curie temperature, TC, and magneti
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