EFFECT OF THIN KNbO3 SEED LAYERS ON PULSED LASER DEPOSITED FERROELECTRIC KTa0.65Nb0.35O3 FILMS FOR MICROWAVE TUNABLE APPLICATION

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.