ZURUECK HOCH VOR INHALT SUCHEN

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Proposing Institution

Fakultät für angewandte Naturwissenschaften und Mechatronik,
Project Manager

Prof. Dr. Alfred Kersch
Lothstr. 8
80335 München
Abstract
The aim of this project is to investigate the piezoelectric properties of the thin Hf/ZrO2 films. We are mainly interested in so called giant piezoelectric effect which is well known for perovskites [Liu]. In Hf/ZrO2 systems this effect may emerge, when the tetragonal crystal phase P42c/nmc undergoes a field induced phase transition into ferroelectric crystal phase Pca21. If the volumes of the both phases are substantially different, the giant piezoelectric effect may overcome the conventional piezoelectric effect by an order of magnitude.Incipient ferroelectricity is known to occur in perovskites such as SrTiO3, KTaO3, and CaTiO3. Recently, ferroelectric properties have been found in thin HfO2 and ZrO2 based thin films. The ferroelectric phase is not related to perovskites but is similarly induced from perturbations of the crystal lattice caused by dopants and stress [Park1]. The ferroelectric properties of the modified Hf/ZrO2 based thin films yield high potential for various ferroelectric, piezoelectric, and pyroelectric applications: the material is lead free and fully compatible with silicon process technology.From RWTH Aachen, a project partners in the Inferox DFG-funding project, first values for piezoelectric coefficients of about 10pm/V have been obtained from laser interferometric measurements (compared with 300 pm/V for PZT). These results are promising, because the investigated materials have not been optimized for piezoelectric FOM [Star][Inferox].Besides the collaboration with Namlab Dresden, RWTH Aachen in Inferox II, there is cooperation with Fraunhofer IPMS which investigates piezoelectric micro-harvester experimentally containing (non-optimized) piezoelectric hafnia [Wein].Large volume differences of crystal cells between tetragonal and orthorhombic phases can be achieved via doping, different alloy composition in HfxZr1-xO2 oxide and different crystal morphology [Park2]. The tetragonal phase as well as the orthorhombic phase are not favorable phases under usual conditions [Mate]. Two further phases, the monoclinic P21/c and cubic Fm-3m occur in bulk materials at low and high temperatures respectively. Hence, the further condition must be proven while the survey, that monoclinic and cubic phases are energetically suppressed, for instance, via doping by tetragonal and orthorhombic phases.For investigation of piezoelectric properties of the oxide system of our interest we are going to use two DFT codes, FHI AIMS [AIMS] and Quantum Espresso [QEsp], for calculation of the ground state of cells of different phases in order to determine their volumes or rather lattice constants.[Liu] T.Liu, C.S.Lynch, “Energy analysis of field induced phase transitions in relaxor based piezo- and ferroelectric crystals”, in: Ed. Z.G. Ye, Handbook of Advanced Dielectric, Piezoelectric and Ferroelectric Materials[Park1] M. Park, Y. Lee, H. Kim, Y. Kim, T. Moon, K. Kim, J. Müller, A. Kersch, U. Schroeder, T. Mikolajick, and C. Hwang, Ferroelectricity and Antiferroelectricity of Doped Thin HfO2-Based Films, Advanced Materials 27, 1811 (2015)[Inferox] Projektbericht zur 1. Förderperiode und Beschreibung des Vorhabens zur 2. Förderperiode “Inzipiente Ferroelektrika auf der Basis von Hafniumoxid”[Star] S. Starschich, T. Schenk, U. Schroeder, and U. Boettger, “Ferroelectric and piezoelectric properties of Hf1-xZrxO2 and pure ZrO2 films “, Appl. Phys. Lett. 110, 182905 (2017)[Wein] http://www.ipms.fraunhofer.de/en/press-media/press/2017/2017-03-08.html[Park2] M. H. Park, T. Schenk, C. M. Fancher, E. D. Grimley, C. Zhou, C. Richter, J. M. LeBeau, J. L. Jones, T. Mikolajicka and U. Schroeder, “A comprehensive study on the structural evolution of HfO2 thin films doped with various dopants”, Journal of Materials Chemistry C, 2017[Mate] R. Materlik, C. Künneth, and A. Kersch, The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model, Journal of Applied Physics 117, 134109 (2015)[AIMS] V. Blum, R. Gehrke, F. Hanke, P. Havu, V. Havu, X. Ren, K. Reuter, and M. Scheffler, "Ab initio molecular simulations with numeric atom-centered orbitals", Computer Physics Communications 180, 2175-2196 (2009)[Qesp] P. Giannozzi, S. Baroni, N. Bonini, M. Calandra, R. Car, C. Cavazzoni, D. Ceresoli, G. L. Chiarotti, M. Cococcioni, I. Dabo, A. Dal Corso, S. Fabris, G. Fratesi, S. de Gironcoli, R. Gebauer, U. Gerstmann, C. Gougoussis, A. Kokalj, M. Lazzeri, L. Martin-Samos, N. Marzari, F. Mauri, R. Mazzarello, S. Paolini, A. Pasquarello, L. Paulatto, C. Sbraccia, S. Scandolo, G. Sclauzero, A. P. Seitsonen, A. Smogunov, P. Umari, R. M. Wentzcovitch, J.Phys.:Condens.Matter 21, 395502 (2009), http://arxiv.org/abs/0906.2569

Impressum, Conny Wendler