Refining of nanopillars induced by Mn-doping in epitaxial Ba(Zr,Ti)O ₃ thin films

Microstructures of the epitaxially grown Ba(Zr,Ti)O ₃ (BZT) and Mn-doped Ba(Zr,Ti)O ₃ (Mn:BZT) thin films on (001) MgO substrate fabricated by pulsed laser deposition were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM. The XRD studies showed that both epitaxial thin film structures are c-axis oriented. TEM and high-resolution TEM studies demonstrated that both BZT and Mn:BZT films consist of a continuous epitaxial layer near the interface followed by the formation of twin-coupled nanopillars, united by sharing their {111} or {110} plane as a common plane. The microstructure evolution from the epilayer to nanopillars is accomplished by alternatively introducing {111} and {110} plane twin boundaries, resulting in gradual shrinking/enlarging of the lateral size of the epitaxial grains/twin-coupled nanopillars. The lateral size of the nanopillars in BZT films is about four times larger than that in the Mn:BZT films. The refining of the nanopillars in the Mn-doped films is attributed to enhanced twinning facilitated by the preferential presence of Mn ions on the {110} boundary planes.