Step bunching-induced vertical lattice mismatch and crystallographic tilt in vicinal BiFeO3(001) films

摘要

Epitaxial (001) BiFeO3 thin films grown on vicinal SrTiO3 substrates areunder large anisotropic stress from the substrates. The variations of thecrystallographic tilt angle and the c lattice constant, caused by the latticemismatch, along the film thickness were analyzed quantitatively using the X-raydiffraction technique. By generalizing the Nagai model, we estimated how stepbunching resulted in the vertical lattice mismatch between adjacent BiFeO3layers, which induced the strain relaxation and crystallographic tilt. The stepbunching was confirmed by the increased terrace width on the BiFeO3 surface.