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Growth of KNbO3 thin films on MgO by pulsed laser deposition
C.Zaldo*, D.S.Gill and R.W.Eason
Department of Physics and Optoelectronics Research Centre, University of Southampton, UK
Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Campus Universitario de Cantoblanco C-IV. 28049 Madrid, Spain.
School of Mathematical and Physical Sciences, University of Sussex, Brighton BN1 9QH, UK
* Permanent address: Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Campus Universitario de Cantoblanco C-IV, 28049 Madrid. Spain.
Crystalline and stoichiometric KNbO3 thin films have been grown on (100) oriented MgO substrates by pulsed laser deposition technique. Electron microprobe analysis and Rutherford backscattering spectroscopy of the films show a progressive loss of K with increasing substrate-target distance. To compensate for this K loss the ceramic KNbO3 targets were enriched with K2CO3 powder, pressed at room temperature and sintered at 650°C. For a substrate-target distance of 6 cm, targets with [K]/[Nbl molar ratio = 2.85 yield stoichiometric KNbO3 films. A partial oxygen pressure of 2 x mbar was optimum for growing transparent films. Films grown between 650 and 700 °C show the KNbO3 crystalline phase with its (110) axis preferentially oriented perpendicular to the surface of the substrate. At these temperatures KNbO3 diffusion into the MgO substrate is observed. Films grown from KNbO3 single crystal targets only contain a Mg4Nb2O9 crystalline layer.
Applied Physics Letters (1994) Vol.65(4) pp.502-504
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