The structure of epitaxially grown thin films: a study of niobium on sapphire

Abstract

The x-ray scattering from epitaxially grown films of niobium on sapphire has been measured as the thickness of niobium was varied. For thicknesses d larger than 80 Å, the mean square displacements perpendicular to the growth planes increase as where , and the correlation length for these displacements increases as with . A model is put forward to account for these results in terms of the strains when the film thickness is larger than the distance between the misfit dislocations.