Local deformations quantified with the common sublattice method

Measurement of strain in epitaxial layers frequently faces the problem of localizing "perfectly" unstrained regions to use as a reference for the whole structure. Here, we develop a method for deducing such references in the unstrained substrate (with one crystal structure) to determine the local lattice deformations in the layer (with another crystal structure). The method works if there is a common sublattice in the layer and the substrate, so that the deviations from it may be used to interrelate the experimentally recorded data. The proof-of-concept is obtained using samples of cubic γ-Ga₂O₃ layers on a monoclinic β-Ga₂O₃ substrate, confirming that the new method overcomes several limitations of HRTEM-based methods. The precision of the method is ∼0.5% in strain values.