Piezoresponse in Ferroelectric PZT Thin Films
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0966-T07-02
Piezoresponse in Ferroelectric PZT Thin Films Dmitry Kiselev1, Igor Bdikin1, Alena Movchikova2, Andrei Kholkin1, Gunnar Suchaneck2, and Gerald Gerlach2 1 Dept. of Ceramics and Glass Engineering, University of Aveiro, Aveiro, 3810-193, Portugal 2 Institute for Solid State Electronics, Technische Universitaet Dresden, Dresden, 01069, Germany
ABSTRACT Poled ferroelectric lead zirconate titanate (PZT) films comprising a (111) texture on (100)Si/SiO2/(111)Pt substrates were investigated by piezoresponse force microscopy (PFM). Depending on the film thickness, the crystallite orientation varies from purely (111) (related to the Pt bottom electrode orientation) to a more random texture. By PFM, 90° domains with a width of 50 nm were obtained in an individual grain Pb(Pb0.10Zr0.21Ti0.69)O3 – PPZT (10/21/69). It was shown that the virgin (unpoled) films possess large piezoelectric activity comparable to that after local poling (self-polarization effect). This corresponds to a clear predominance of the domains with a polarization oriented from the bottom electrode to the free surface of the film. INTRODUCTION Lead zirconate titanate Pb(Zr1-xTix)O3 (PZT) has been extensively studied over the last fifty years due to its excellent ferroelectric, dielectric and piezoelectric properties. Many potential applications are now foreseen for PZT thin and thick films such as nonvolatile memory cells, as well as optical, sensing and microelectromechanical devices. With increasing Zr content, a rhombohedral-to-tetragonal phase transition occurs in PZT. Near the so-called morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases, the material exhibits exceptionally high dielectric and piezoelectric properties [1]. Recently, a new monoclinic phase has been observed in PZT at x∼0.5 [2,3]. This has stimulated a new wave of interest to this technologically important material. It is known that the properties of ferroelectric thin films are greatly influenced by their thickness and texture. Therefore, a great amount of studies has been dedicated to the thickness, composition and texture effects on the electrical properties (see, e.g., references [4-7]). Since the size of modern thin film devices is in the sub-µm range, local techniques to study ferroelectric and piezoelectric properties become increasingly important. One of these techniques, Piezoresponse Force Microscopy (PFM), has been successfully used to investigate the physical properties of ferroelectrics at the scale limited by only the size of the PFM tip (∼10 nm). In this work, local piezoelectric characteristics of PPZT films are accessed via PFM with the final aim to understand the relation between their microstructure and piezoelectric properties. EXPERIMENT In-situ crystallized Pb(Pb0.10Zr0.21Ti0.69)O3 - PPZT (10/21/69) thin films with a thickness of 500, 1000 and 1800 nm were deposited by multi-target reactive sputtering of metallic targets in an argon/oxygen atmosphere (0.02 to 0.04 mbar) at a substrate temperature of about 550°C
with a deposition
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