Biaxial stress‐induced giant bandgap shift in BiFeO₃ epitaxial films

Abstract Thickness‐dependent stress relaxation and its influence on the bandgap of BiFeO₃ have been investigated. BiFeO₃ films with 15 at% Bi excess allow the control of lattice mismatch‐induced biaxial stress up to 10.8 GPa on SrTiO₃(001) substrates. Heteroepitaxy of such films follows the Stranski–Krastanov growth mode, as suggested by island formation on the wetting layer accompanied with stress relaxation. The bandgap is linearly decreased with the in‐plane compressive stress, and a large stress coefficient of 67 meV/GPa was extracted. A 0.7 eV red‐shift of the bandgap was observed in the fully epitaxially strained film. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)