X-Ray diffraction line broadening by stacking faults in SrBi2Nb2O9/SrTiO3 epitaxial thin films

SrBi2Nb2O9 thin films were deposited on (001) SrTiO3 substrate by sol-gel s pin coating. A previous study showed that the him crystallizes with the c-a xis normal to the surface. Those epitaxial films are studied by means of X- ray diffraction (XRD) line profile analysis as a function of thermal anneal ing duration. The line profile analysis of the diffraction patterns collect ed in omega -2 theta scan mode, gives detailed information on the coherentl y diffracting domain size and microstrains along a given direction. For low annealing duration the width of the (001) diffraction lines reaches values of approximately 1 degrees. In accordance with a recent study, integral br eadth and Fourier analysis suggest the presence of stacking faults separate d by a mean distance of 5 nm. The profiles exhibit a marked Lorentzian char acter as expected from a faulted crystal. In addition to faulting, both fin ite: grain size and microstrains contribute to the observed width. When hea t treatment time is increased, the breadth and Lorentzian content of the (0 01) diffraction lines decrease attesting that the stacking fault density is lowered. For a 500-h treatment at 700 degreesC the calculated domain size equals the films thickness. This indicates that stacking faults have almost disappeared: the SBN crystallites of the film have reached an equilibrium state. (C) 2001 Elsevier Science B.V. All rights reserved.