Domain Formation in Nano-patterned PZT Thin Films
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Domain Formation in Nano-patterned PZT Thin Films Martin Waegner1, Mathias Schröder2, Gunnar Suchaneck1, Heinz Sturm3, Christiane Weimann3, Lukas M. Eng2, and Gerald Gerlach1 1
TU Dresden, Solid-State Electronics Laboratory, 01062 Dresden, Germany
2
TU Dresden, Institute of Applied Photophysics, 01062 Dresden, Germany
3
BAM – Federal Institute of Material Research and Testing, Div. Nanotribology and Nanostructuring of Surfaces, 12205 Berlin, Germany
ABSTRACT In this work, reactive magnetron-sputtered Pb(Zr,Ti)O3 thin films were used to fabricate well-ordered nanodot arrays by means of nanosphere lithography (NSL). NSL is based on a twostep etch process by means of, firstly adjusting the diameter of polystyrene spheres in the selfassembled polymeric nanosphere mask using reactive ion etching, and secondly transferring the mask to the substrate by ion milling with adjusted heights. Hence, structures with different aspect ratios can be fabricated. Piezoresponse force microscopy was used as the inspection tool on both non-patterned and patterned films. Both the topography and polarization out of plane and in plane was deduced in this mode. Grains of nanodots with low aspect ratio form domain structures comparable to domains in non-patterned films. In contrast to that, nanodots with a higher aspect ratio form particular structures. The in-plane amplitude images show mostly a bisectioned domain assembly, while the out-of-plane amplitude images show in some cases more complex structures like “c”-shaped domains or multi-domains around a center domain. The patterning of the ferroelectric material was shown to affect the formation of ferroelectric domains. The initial polycrystalline, randomly-ordered films are re-oriented and show domain structures depending on nanodisc diameter and aspect ratio. This may enable tailoring of ferroelectric materials in their piezoelectric and pyroelectric properties by patterning. INTRODUCTION Ferroelectric thin films and nanostructures are of large interest for sensor, actuator or memory applications. Already in 1954 Anliker et al. [1] reported on the characteristics of ferroelectric BaTiO3 nanoparticles. In the last decades the properties and the origin of sizeeffects in nano-patterned ferroelectric materials attracted the interest of research, first and foremost, to understand the behavior in shrinking memory devices [2]. But furthermore, taking advantage of their remarkable increased pyro- and piezoelectric coefficients near room temperature, high performance actuators and sensors could be designed. Exploiting these effects require the knowledge about the basics of domain formation affected also by nanostructuring. The domain formations in ferroelectric nanostructures such as ferroelectric dots or discs are still discussed controversially and are assumed to exist due to the changes in surface-to-volume ratio and the different boundary conditions compared to freestanding structures
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The question is if it is possible to influence the properties of the functional layer by nanopat
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