Paper eintragenEpitaxial thin films of various thicknesses were deposited onto monocrystalline substrates of MgO and SrTiO3, with nominally (001) surface orientations. The films were examined by using scanning tunnelling and atomic force microscopy, and this revealed the development of the surface topography. It was shown that the films on MgO exhibited Volmer-Weber island growth, while those on SrTiO3 grew in a 2-dimensional Frank-van der Merwe manner. In both systems, spiral growth features were seen only for films that were greater than a critical thickness; thus indicating that they were formed at emergent threading segments of dislocation half-loops that were introduced by misfit. In the case of films on SrTiO3, the thickness at which this occurred corresponded well with the critical thickness for dislocation half-loop nucleation which was predicted by Matthews’ model. In films on MgO, the first spirals arose at a similar thickness; thus indicating that the residual misfit was similar to the total misfit for Cu3Ba2YO7/SrTiO3. In both systems, the spiral density increased (with deposit thickness) to a peak value. It then fell to a background level. The form of these variations corresponded well to the variation in threading dislocation density that was expected for dislocation half-loop introduction; followed by the mutual annihilation of adjacent threading segments with Burgers vector components that were parallel to [001] in opposite senses.

M.Yeadon, M.Aindow, F.Wellhöfer, J.S.Abell: Journal of Crystal Growth, 1997, 172, 145-55