The effect of target crystallography on the growth of Pb(Mg 1/3 Nb 2/3 )O 3 thin films using pulsed laser deposition
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The effect of target crystallography on the growth of Pb(Mg1/3 Nb2/3 )O3 thin films using pulsed laser deposition M. H. Corbett, G. Catalan, R. M. Bowman,a) and J. M. Gregg Condensed Matter Physics and Materials Science Research Division, School of Mathematics and Physics, The Queen’s University of Belfast, Belfast BT7 1NN, United Kingdom (Received 7 July 1998; accepted 17 February 1999)
Pulsed laser deposition has been used to make two sets of lead magnesium niobate thin films grown on single-crystal 兵100其 MgO substrates. One set was fabricated using a perovskite-rich target while the other used a pyrochlore-rich target. It was found that the growth conditions required to produce almost 100% perovskite Pb(Mg1/3 Nb2/3 )O3 (PMN) films were largely independent of target crystallography. Films were characterized crystallographically using x-ray diffraction and plan view transmission electron microscopy, chemically using energy dispersive x-ray analysis, and electrically by fabricating a planar thin film capacitor structure and monitoring capacitance as a function of temperature. All characterization techniques indicated that perovskite PMN thin films had been successfully fabricated.
Lead magnesium niobate [Pb(Mg1/3 Nb2/3 )O3 — PMN] is a well-known perovskite relaxor ferroelectric that has received recent attention for its potential in capacitors1 and mechanical actuator and transducer applications.2 Interest has been driven by the large and relatively temperature independent dielectric constant and electrostrictive response shown by the materials.3 As with many relaxor ceramics, PMN tends to exist as a mixture of crystalline structures—perovskite and in various pyrochlore phases.4,5 The occurrence of the pyrochlore phase drastically reduces the electrical poling performance of the material.4 Minimization of pyrochlore is a challenge in itself, and the synthesis of bulk material requires complex multistage processing, e.g., the columbite and wolframite methods.4,6 These processing routes are both tedious and sensitive to changes in preparation parameters. This has contributed to a reluctance to use PMN for large-scale industrial applications despite its attractive properties. As bulk preparation of perovskite PMN is cumbersome, the target fabrication required for sputter, laser, or ion beam deposition becomes significant. This has led to few reports on the growth of perovskite phase PMN thin films.7 The most frequently used approach to obtain perovskite PMN has been to prepare a PMN–PbTiO3 target8 ; however, a residue of PbTiO3 can remain in the PMN film if conditions are not precisely controlled. In this letter the authors report single-stage growth of high quality PMN thin films with almost 100% perovskite content using pulsed laser deposition (PLD). Significantly, we demonstrate that growth of perovskite
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Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 14, No. 6, Jun 1999
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