ABSTRACT
Ferroelectric KTa0.65Nb0.35O3 thin films were grown by pulsed laser deposition on R-plane sapphire substrates. The potassium enriched ceramic targets were used for compensating potassium losses. In order to improve the KTa0.65Nb0.35O3 film growth on sapphire, a thin KNbO3 layer was introduced as seed layer. The experimental results show that the crystalline quality is lowered when increasing the K-excess. Simultaneously, phase purity, orientation and crystalline quality of perovskite (h00)-oriented KTa0.65Nb0.35O3 are greatly improved by the use of the KNbO3 seed layer. In particular, the presence of the latter effectively suppresses any pyrochlore secondary phase formation.
ACKNOWLEDGMENTS
This work was partially supported by Region Bretagne (PRIR DISCOTEC). One of us (W. Peng) acknowledges University of Rennes 1 for a post-doctoral grant. SEM was performed at CMEBA in University of Rennes 1. S. Weber and A. Dauscher (LMP, Nancy) are warmly acknowledged for SNMS. Thanks also to Prof. O. Bonnaud and Dr. N. Coulon for giving access to ellipsometry measurements.