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Dynamique et ingénierie de la photostriction dans des microdispositifs à base de films minces épitaxiés d'oxydes ferroélectriques

Abstract : Ferroelectric materials are good candidates for photostrictive actuators that deform under illumination. When illuminated above the bandgap energy, photoinduced charges will be separated by the internal electric field of the material, which depends on its remnant polarization. This separation leads to both a photoinduced modification of the electric field and a deformation since a ferroelectric material is also piezoelectric. In this thesis, the ferroelectric material Pb(ZrₓTi₁₋ₓ)O₃ (PZT) was chosen for its high piezoelectric coefficient. PZT thin films of high crystalline quality were grown by pulsed laser deposition (PLD), and integrated in a capacitance geometry between two metallic electrodes to enable the control of the material properties. First, the ferroelectric, dielectric and transport properties were studied to determine the influence of the electrode/ferroelectric interface. The photovoltaic behavior of PZT thin films was subsequently investigated, specifically its dependence on the incident wavelength and the polarization state. The results show that photoinduced response in PZT can be engineered. The choice of the electrodes and the incident energy were found to be particularly important in controlling the sign of the photoinduced current and voltage as well as the temporal stability of the device. Finally, the photoinduced deformation of a PZT thin film after a UV was studied by time-resolved X-ray diffraction. The novelty of this work comes from the in-situ control of the photostriction (both in sign and amplitude) by manipulating the polarization state. By considering the competition between the different components of the total electric field present in the sample, a model was proposed to determine the polarization’s contribution on the photostriction. In order to further control and optimize the photoinduced strain in devices, various approaches were studied, such as tuning the remnant polarization, the UV depth penetration and UV pulses frequency, and developing asymmetric electrodes, and all these approaches were found to affect dynamics and amplitude of photostriction.
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https://tel.archives-ouvertes.fr/tel-02102924
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Submitted on : Wednesday, April 17, 2019 - 6:23:07 PM
Last modification on : Tuesday, September 29, 2020 - 4:42:09 AM

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  • HAL Id : tel-02102924, version 1

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Loïc Guillemot. Dynamique et ingénierie de la photostriction dans des microdispositifs à base de films minces épitaxiés d'oxydes ferroélectriques. Science des matériaux [cond-mat.mtrl-sci]. Université Paris Saclay (COmUE), 2018. Français. ⟨NNT : 2018SACLS492⟩. ⟨tel-02102924⟩

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