Growth of Epitaxial LaVO 3 /(Pb,La)(Zr,Ti)O 3 /(La,Sr)CoO 3 Heterostructures
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Growth of Epitaxial LaVO3/(Pb,La)(Zr,Ti)O3/(La,Sr)CoO3 Heterostructures Woong Choi and Tim Sands Department of Materials Science & Engineering, University of California Berkeley, CA 94720 ABSTRACT Epitaxial semiconductor-ferroelectric-conductor LaVO3/(Pb,La)(Zr,Ti)O3/(La,Sr)CoO3 heterostructures were grown on (001) LaAlO3 single crystal substrates by pulsed laser deposition. A high degree of c-axis orientation and strong in-plane texture revealed by x-ray diffraction indicated the epitaxial crystallographic relationships between the layers. The capacitance measurement as a function of voltage revealed the modulation of the depletion layer in the semiconducting LaVO3 as well as the non-linear response of the (Pb,La)(Zr,Ti)O3 ferroelectric layer.
INTRODUCTION There has been increasing interest in growing epitaxial thin film heterostructures consisting of materials that have similar crystalline structures but possess remarkably different physical properties. Prime emphasis has been placed on perovskite oxides exhibiting wide ranges of electrical, magnetic and optical properties since the combination of such diverse materials offers attractive possibilities for novel device structures. One of the interesting devices using these epitaxial perovskite heterostructures is the ferroelectric field effect transistor (FET), which can be realized, in principle, with an epitaxial ferroelectric/semiconducting perovskite multilayer. [15] The ferroelectric FET permits a nonvolatile memory element with nondestructive readout because information can be stored as a polarization direction, which can be read out as a change in the conductance of the semiconductor channel. [6] However, the reliable performance of ferroelectric field effect transistors based on silicon has yet to be demonstrated mainly because of the screening of the field effect by the interface states between the ferroelectric thin film and the silicon. It is consequently of great interest to minimize the concentration of point and line defects at or near the interface to reveal the true unscreened field effect. The use of epitaxial oxide heterostructures has been suggested [1-5] as a way of circumventing the above problem. So far, epitaxial thin films of several semiconducting oxides have been used to build epitaxial heterostructures in a ferroelectric FET configuration. [1-5] Recently, it was shown that epitaxial thin films of LaVO3 could be grown on a perovskite substrate and that the films maintained the semiconducting property of the bulk. [7] In contrast to the semiconducting oxides used in previous studies, LaVO3 can be synthesized with a relatively low ionized hole concentration (~1018 /cm3) that could make the ferroelectric field effect more pronounced. [8] In this study, therefore, to demonstrate the feasibility of incorporating LaVO3 into a ferroelectric FET, epitaxial perovskite LaVO3/(Pb,La)(Zr,Ti)O3 (PLZT)/(La,Sr)CoO3 (LSCO) heterostructures were grown by pulsed laser deposition and characterized by x-ray diffraction and the electrical capacitance measurem
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