Piezoresponse Force Microscopy Studies on (100), (110) and (111) Epitaxially Growth BiFeO 3 Thin Films
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PIEZORESPONSE FORCE MICROSCOPY STUDIES ON (100), (110) AND (111) EPITAXIALLY GROWTH BiFeO3 THIN FILMS R. P. Fernandes1, L. Batista2, A. C. G. Castro 3, L. Salamanca-Riba4, M. P. Cruz5, F. J. EspinozaBeltrán3, S. Hirsekorn2, U. Rabe2, J. Muñoz-Saldaña3, G. A. Schneider1 1 Institute of Advanced Ceramics, Hamburg University of Technology, Denickstr. 15, 21073 Hamburg, Germany, 2 Fraunhofer Institute for Nondestructive Testing (IZFP), Campus E3.1, 66123 Saarbrücken, Germany, 3 Centro de Investigación y de Estudios Avanzados del I.P.N., Lib. Norponiente No. 2000, Fracc. Real de Juriquilla, C.P. 76230, Santiago de Querétaro, Qro., México, 4 Materials Science and Engineering Department, University of Maryland, MD, USA, 5 Universidad Nacional Autónoma de México, CNyN, Ensenada, B.C., México C.P. 22860 ABSTRACT Bismuth ferrite (BiFeO3) is a magnetoelectric, multiferroic material with coexisting ferroelectric and magnetic orderings. It is considered as a candidate for the next generation of ferroelectric random-access memory devices because BiFeO3, in contrast to industrial ferroelectrics used today, does not contain the toxic element lead. Furthermore, its polarization values are higher than those of lead-based ferroelectrics. The magnitude of the polarization of a BiFeO3 film is dependent on its orientation and is related to the domain structure. This contribution presents and discusses the preparation of epitaxial BiFeO3 (BFO) thin films grown on SrRuO3/SrTiO3 substrates by pulsed laser deposition (PLD) and their characterization, especially by piezo force microscopy (PFM) and atomic force acoustic microscopy (AFAM). The thickness of an individual BFO film varies between 100 and 200 nm. The epitaxial nature of films in the crystallographic (100), (110), and (111) directions was confirmed by x-ray diffraction (XRD). Thin SrRuO3 layers, also prepared by PLD, were used as bottom electrode for the ferroelectric hysteresis measurements. Low frequency PFM measurements showed a monodomain structure for the as-grown (110) and (111) oriented samples. In BFO (100) films, different polarization variants were observed by ultrasonic piezo force microscopy (UPFM). The domain structure is reproduced from minimization of the electrostatic and elastic energies. Switching experiments using standard PFM as well as UPFM were carried out on the three samples with the objective of testing the coercive field and domain stability. The AFAM technique was used to map the elastic properties of the BFO thin-films at the micro- and nanoscale. INTRODUCTION In the last decade, extensive research has been devoted to multiferroic materials, in particular to multiferroic magnetoelectrics [1,2,3]. This is due to the fascinating physics behind their response to external fields as well as to the potential applications for industry. More important than the usual ferromagnetism or ferroelectricity response is the coupling of the two effects which gives rise to a wide spectrum of new applications, e.g. memory elements with electric as well as magnetic data stora
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