Strains and rotations in thin deposited films

Abstract

Thin films deposited on misfitting substrates exhibit distortions produced by the superposition of coherency strains and the elastic fields of interfacial defects. These distortions become homogeneous strains, ϵ, and rotations, φ, beyond a characteristic distance from the interface, z, and are partitioned between the film and substrate. Residual strain arises when the density of interfacial defects is insufficient to compensate the intrinsic coherency strain, and is partitioned in a manner depending on the relative thicknesses of the two layers, d. However, rotations are not partitioned in this way. Expressions for the magnitude and partitioning of ϵ and φ are derived for the case of elastically isotropic materials. Calculated values are shown to be in excellent agreement with experimental measurements for a variety of technologically relevant cases.

Keywords:

• dislocation theory
• epitaxy
• thin film
• interfacial structure
• strained layer
• topological theory of defects