EFFECT OF THIN KNbO₃ SEED LAYERS ON PULSED LASER DEPOSITED FERROELECTRIC KTa_0.65Nb_0.35O₃ FILMS FOR MICROWAVE TUNABLE APPLICATION

ABSTRACT

Ferroelectric KTa_0.65Nb_0.35O₃ 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 KTa_0.65Nb_0.35O₃ 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 KTa_0.65Nb_0.35O₃ 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.

Keywords:

• Potassium tantalate niobate
• PLD
• seed layer
• pyrochlore phase

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.