ISSN:
1077-3118
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Symmetric superlattice structures consisting of alternating atomic-scale layers of KTaO3 and KNbO3 with variable periodicity were grown on KTaO3 substrates by pulsed laser deposition. The in-plane structure of KNbO3 closely matches that of the KTaO3 substrate, resulting in KTaO3/KNbO3 heterostructures that are uniformly strained in-plane without misfit dislocations. This strain imposes an in-plane KNbO3 lattice spacing identical to that of the KTaO3 substrate for the temperature range 30 °C〈T〈700 °C, and a tetragonal-to-tetragonal transition is observed whose phase transition temperature Tc depends on the KNbO3 layer thickness. The in-plane strain results in a significant increase in this ferroelectric-paraelectric Tc for superlattices with relatively thick KNbO3 layers (Tc=535 °C for a 17 nm thick layer, as compared to 435 °C for bulk KNbO3) and for K(Nb0.5Ta0.5)O3 random-alloy thin films. As the superlattice period decreases, a reduction of Tc is observed. For superlattices with periodicities of 50 Å or less, the Curie temperature is identical to that of the K(Ta0.5Nb0.5)O3 random-alloy film, indicating significant long-range ferroelectric coupling across the KTaO3 layers. © 1998 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.121411
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