Growth and field dependent dielectric properties of epitaxial Na0.5K0.5NbO3 thin films

Na 0.5 K 0.5 NbO 3 thin films have been grown on LaAlO3(001) substrates using rf magnetron sputtering from a Na and K enriched target. X-ray diffraction showed that the films are epitaxial with mosaic broadening as narrow as 0.044°. Interdigital Au finger electrodes were photolithographically defined on the film surfaces. The dielectric properties of these interdigital capacitors were measured at 1 MHz from room temperature down to 50 K. The capacitor showed 35% tunability at room temperature and a loss tangent of 0.007 without dc bias applied. The loss decreased further with increasing dc bias. For lower temperatures, the capacitance exhibited a broad maximum at ∼200 K, which is possibly linked to a phase transformation of the Na0.5K0.5NbO3 film.