MICROSTRUCTURE OF EPITAXIAL POTASSIUM NIOBATE THIN-FILMS PREPARED BY METALORGANIC CHEMICAL-VAPOR-DEPOSITION

The microstructure of (001)(p)-oriented (subscript p indicates the cho ice of a pseudocubic unit cell) potassium niobate (KNbO3) thin films g rown by metalorganic chemical vapor deposition on (100)(p), lanthanum aluminate and having a large second-order nonlinear optical response i s examined. Transmission electron microscopy reveals the films to be e pitaxial and the film/substrate interface to be abrupt and semicoheren t. The strain between the film and substrate due to the 5% lattice con stant mismatch is accommodated by formation of an array of misfit disl ocations as well as 60 degrees and 120 degrees ferroelectric microdoma ins. The domains are located in a 20 nm thick region adjacent to the i nterface. Beyond the multidomain region, the film is free of significa nt defects. (C) 1996 American Institute of Physics.