Electric energy harvesting with ferroelectric nano-structures using mechanical deformations

• Applicants: Professor Dr.-Ing. Horst Hahn, since 11/2015; Professor Dr.-Ing. Ingo Münch
• Subject Area: Synthesis and Properties of Functional Materials ; Experimental Condensed Matter Physics
• Term: from 2012 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 227613316

• Final Report Year: 2019

Final Report Abstract

High-quality ferroelectric and epitaxial thin films of BTO were successfully grown by pulsed laser deposition after a careful adjustment of the deposition conditions and involved materials (buffer layers and substrates). Patterning of the surface of BTO devices via electron beam and laser lithography was deleterious for the ferroelectric properties. Alternative strategies are currently being investigated to identify an appropriate tool to prepare the interdigitated metallic electrodes expected in the final nanogenerator design. A manuscript concerning the optimization of the ferroelectric properties of BTO/LSMO/STO heterostructures and difficulties related to the patterning of top electrodes via lithographic methods is currently under preparation. The final aim is to test the idea of energy harvesting by applying an external strain to the substrate and concurrently measuring the voltage produced between the electrodes onto the BTO surface. With help of our simulation model we obtained good insight into the working principle of the preferential energy harvesting system and optimized some design parameters as geometry of the top electrodes and voltage of the outer electric circuit at the working point. We fully developed the enhanced Finite Element phase field formulation into 3D, added element formulations for the elastic interaction between ferroelectric film, substrate, and top electrodes. Finally, the electric potential outside the solid object was taken into account. We published articles onto the enhanced phase field model, the formulation of periodic boundary conditions for ferroelectric phase field models, the principle of ferroelectric energy harvesting at the nanoscale, and the simulation of leakage effects in BTO. In the second period Franziska Wöhler attended the experiments and learned how to obtain, interprete and transfer experimental results into our simulation model. We have prepared a joint paper to bring together simulation and experimental results. However, we often have been relying onto results from the literature to perform the theoretical part of the work program. In hindsight we would schedule the workflow between experimental and theoretical work differently. Additionally, we have underestimated the difficulty to grow good quality BTO thin films on a conductive buffer layer. Moreover, keeping a complex instrument as the pulsed laser deposition unit in constant efficient working conditions has represented another time-consuming task. It is also obvious that we have not been able to measure the performance of the energy harvesting system since the patterning of top electrodes has not been completed as yet. The work group of Prof. Hahn continues to fabricate new BTO/LSMO/STO samples and to test alternative lithographic methods with the final aim to realize interdigitated top electrodes giving satisfactory ferroelectric characteristics.

Publications

• (2018) Leakage current and polarization domains in ferroelectric nanogenerators for energy harvesting. Proc. Appl. Math. Mech. (PAMM) 18 (1)
  Wöhler, Franziska; Muench, Ingo; Wagner, Werner
  
• Error measurement and FEM benchmark for phase field modeling. Proc. Appl. Math. Mech. 15, 2015
  Münch, I.
  
• A selective enhanced FE-method for phase field modeling of ferroelectric materials, Computational Mechanics 57(1), 2016
  Krauß, M., Münch, I.
  
• Gradient based enhanced finite element formulation for diffuse phase interfaces. Proc. Appl. Math. Mech. 16, 2016
  Krauß, M., Münch, I.
  
• Nanoscale periodic domain patterns in tetragonal ferroelectrics: a phase-field study, Physical Review B 93(17), 2016
  Balakrishna, A.R., Huber, J.E., Münch, I.
  
• Electric leakage current density in phase field simulations for nanogenerator concepts. Proc. Appl. Math. Mech., 17, 2017
  Wöhler, F.J., Münch, I., Wagner, W.
  
• Entwurf und Finite-Elemente-Modellierung ferroelektrischer Nanostrukturen zur Transformation mechanischer Deformationen in elektrische Energie, Dissertation, Institut für Baustatik, KIT, ISBN 978-3-935322-23-2, 2017
  Krauß, M.
  
• Leakage currents in nanogenerator concepts in phase field simulations, Proceedings of the 7th GACM Colloquium on Computational Mechanics for Young Scientists from Academia and Industry, 731-734, 2017
  Wöhler, F., Münch, I. Wagner, W.
  
• Periodic boundary conditions for the simulation of 3D domain patterns in tetragonal ferroelectric material, Archive of Applied Mechanics, 2018
  Münch, I., Balakrishna, A.R., Huber, J.E.