GROWTH OF KNBO3 THIN-FILMS ON MGO BY PULSED-LASER DEPOSITION

Crystalline and stoichiometric KNbO3 thin films have been grown on (10 0) oriented MgO substrates by pulsed laser deposition technique. Elect ron microprobe analysis and Rutherford backscattering spectroscopy of the films show a progressive loss of K with increasing substrate-targe t distance. To compensate for this K loss the ceramic KNbO3 targets we re enriched with K2CO3 powder, pressed at room temperature, and sinter ed at 650-degrees-C. For a substrate-target distance of 6 cm, targets with [K]/[Nb] molar ratio = 2.85 yield stoichiometric KNbO3 films. A p artial oxygen pressure of 2 X 10(-2) mbar was optimum for growing tran sparent films. Films grown between 650 and 700-degrees-C show the KNbO 3 crystalline phase with its (110) axis preferentially oriented perpen dicular to the surface of the substrate. At these temperatures KNbO3 d iffusion into the MgO substrate is observed. Films grown from KNbO3 si ngle crystal targets only contain a Mg4Nb2O9 crystalline layer.