Annealing-induced relief of compressive misfit strain in liquid phase epitaxial yttrium iron garnet films

Abstract

Films of yttrium iron garnet were grown on (111) gadolinium gallium garnet by liquid phase epitaxy from a PbO-B 2O 3 flux. Incorporation of Pb as a substitutional impurity produced an increase in film lattice parameter which resulted in initial compressive misfit strains in the films. The initial strains were relieved by annealing in O 2. The relief process was studied by X-ray double-crystal diffractometry and topography supplemented by optical and scanning electron microscopy. Strain relief was found to be associated with the occurrence of defects which were imaged in both film and substrate topographs. When the initial compressive misfit was sufficiently large, annealing eventually resulted in a tensile strain and the development of cracks which propagated through the films and into the substrates.