Evolution of nano-fingers in epitaxial Mn-doped Ba(Zr,Ti)O3 thin films driven by {110} twin boundaries

We report on the evolution of twin-coupled nanofinger structures in epitaxial Mn-doped Ba(Zr,Ti)O₃ films on a (001) MgO substrate. XRD studies showed that the films are highly c-axis oriented epitaxial films. TEM and high-resolution TEM studies showed that Mn:BZT films present a pseudo-cubic perovskite structure composed of an epitaxial layer near the interface followed by the formation of twin-coupled nanofingers. The epitaxial grains and the twin-couple domains coexist by sharing their {111} or {110} plane as a common plane. The transition from the epilayer to nanofingers is accomplished by alternatively introducing {111} and {110} plane twin boundaries. This particular process results in gradual reduction of the lateral size of the epitaxial grains and eventually drives the epitaxial structure into twin-coupled nanofingers. The possible atomic structure models for the {110} plane twin boundary are discussed.