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Ferroelectric thin films

Updated on November 30, 2009
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Ferroelectric thin films Student: A. Bartasyte  Objectives  The objective of this activity was to study the strain engineering in thin ferroelectric films. The final aim of such studies would be, by controlling the deformation of a thin ferroelectric film with an applied voltage, to modify the properties of the subsequent layer due to interfacial strain. We started first to synthesize high quality PbTiO3 (PTO) epitaxial thin films and performed than in details the stressstrain behavior analysis of these typical ferroelectric films. Main results Raman spectroscopy, X-ray diffraction (XRD) and Transmission Electron Microscopy were used to investigate the origin and stress effects on phase transitions in PbTiO3 (PTO) epitaxial thin films. A thickness series of epitaxial PTO films were deposited on substrates inducing compressive (SrTiO3 and LaAlO3) and tensile (MgO) misfit stresses to vary the stress level in the films. The combination of all the mentioned characterisation techniques was very useful to understand in details the phase transitions in PTO under stress. Concerning Raman spectroscopy, we have shown that the VH polarization configuration is essential for the investigation of residual stress in PTO thin films, as oblique modes are absent. we have also shown that the E(3TO) hard mode is the unique reliable mode. In order to obtain information about the dominant c domains in PTO, the Raman spectra must be collected on the film cross section. The residual stress in PTO originates not only from misfit stresses, but also from thermal and phase transformation stresses. Phase transitions and domain state transformations were also investigated. It was found that the ferroelectric cluster size in the high temperature phase is increased and that Tc is higher in highly stressed films. Collaborations Uni. Vilnius, ICMAB Barcelona, ICMCB Bordeaux, CRISMAT Caen Funding French Ambassy, EIFFEL grant, NoE FAME, GDR ferroelectriques
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Date of update November 30, 2009

Staff

F. Weiss M. Boudard

Collaboration

SPCS group O. Chaix-Pulchery J. Kreisel

Engineering and technical support

C. Jimenez L . Rapenne-Homand
Univ. Grenoble Alpes