Analysis of misfit relaxation in heteroepitaxial BaTiO3 thin films

The misfit relaxation mechanism of BaTiO3 thin films of different thicknesses grown two-dimensionally on SrTiO3(100) substrates by pulsed laser deposition was analysed using X-ray diffraction and transmission electron microscopy. Major defects in partially relaxed films are misfit dislocations with Burgers vectors of type a[100], threading dislocations connected to those dislocations, and inclined threading dislocations with Burgers vectors of type a[110]. Misfit and threading dislocations with equivalent Burgers vectors of type a[100] constitute half-loops, a[110] threading dislocations are formed by the kinetic reaction between these half-loops. In addition, two types of dislocation dissociation in a[100] misfit dislocations and a[110] threading dislocations are found by high-resolution observation. The dissociation of this misfit dislocation takes place with increasing film thickness and generates stacking faults with displacement vectors of type 1/2a[101]. Misfit relaxation depends on the half-loop misfit segment and fused threading dislocation, not upon the a[100] threading segment of the half-loop.