Growth and structure of Mg-Al spinel nanodonut-decorated MgO nanowires

We report the growth of MgO nanowires surrounded by a donut-shaped spinel in a periodic way at a particular growth temperature of 1,000 °C. We examined the samples by means of scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and X-ray diffraction. At a lower temperature 950 °C, regular MgO nanowires grow. In contrast, at a higher temperature of 1,050 °C, spinel of (Mg_0.4Al_0.6)Al_1.8O₄ nanowires grow. From the absence of tip nanoparticles, we suggest that the synthesis of nanowires in the present study is dominated by a base-growth process. Based on the thermochemistry calculations, we propose that the absence of spinel in samples equilibrated at 950 °C is due to the catalytic-like behaviors of the silicon substrate which promotes the formation of MgO. In terms of choosing appropriate source materials, the technique reported here can be extended and exploited to produce various combinations of nanowire backbone structure with a surrounded nano-scale disk.