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

Na0.5K0.5NbO3 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 degrees. 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 de bias applied. The loss decreased further with increasing de bias. For lower temperatures, the capacitance exhibited a broad maximum at similar to 200 K, which is possibly linked to a phase transformation of the Na0.5K0.5NbO3 film. (C) 1998 American Institute of Physics.