Aberration-corrected STEM of Cross-sectional View of Core-shell Nanowires

Aberration-corrected scanning transmission electron microscopy (AC-STEM) technique was used to investigate the interfacial structures of core-shell nanowires (NWs). The ultramicrotome technique was used to prepare cross-sectional samples of ZnO-Bi$_{\mathrm{2}}$O$_{\mathrm{3}}$ core-shell NWs. Thin layers Bi$_{\mathrm{2}}$O$_{\mathrm{3}}$ epitaxially grew onto the six \textbraceleft 11-20\textbraceright but not the six \textbraceleft 10-10\textbraceright nanoscale facets. Such selective growth can be explained by the differences in the interfacial energy between the two oxide phases. AC-STEM further revealed the interfacial reconstruction of the Bi$_{\mathrm{2}}$O$_{\mathrm{3}}$ layers, a consequence of minimizing the interfacial energy and to make the epilayer growth of the Bi$_{\mathrm{2}}$O$_{\mathrm{3}}$ possible. A model was proposed to understand the growth processes of Bi-containing phases onto ZnO NWs.