Self-assembled growth of Ce O 2 nanostructures on sapphire
Self-assembled growth of Ce O 2 nanostructures on sapphire
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DOI：
10.1103/physrevb.70.195421
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发表时间：
2004-11
影响因子：
3.7
通讯作者：
J. Nie;H. Yamasaki;Y. Mawatari
中科院分区：
文献类型：
--
作者：
J. Nie;H. Yamasaki;Y. Mawatari
Experimental evidence of a self-assembly process was obtained where high-temperature ${\mathrm{O}}_{2}$ annealing $(1025\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ induced a surface reorganization in $\mathrm{Ce}{\mathrm{O}}_{2}$ deposited on $R$-cut sapphire substrates. Based on observation using atomic force microscopy and transmission electron microscopy, when the $\mathrm{Ce}{\mathrm{O}}_{2}$ film was thin $(l10\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$, a highly ordered phase was formed as large three-dimensional islands of $\mathrm{Ce}{\mathrm{O}}_{2}$ with sapphire surface exposed. When the $\mathrm{Ce}{\mathrm{O}}_{2}$ film thickness exceeded a critical value $(\ensuremath{\sim}10\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$, an atomically-flat surface was formed by the reorganization. An energetics model based on these results was developed in which the formation energy of the island was calculated based on the observed facet configuration, taking into account the surface and interface energies, elastic strain, and short-range energy of edges. The energy minimization calculation showed that the calculated lateral and vertical dimensions agreed well with the observed shape of the islands. Based on the experimental evidence and these energy minimization calculations, we demonstrated that increasing the film thickness induces the important phase transition from large islands to an atomically-flat surface.
Experimental evidence of a self-assembly process was obtained where high-temperature ${\mathrm{O}}_{2}$ annealing $(1025\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ induced a surface reorganization in $\mathrm{Ce}{\mathrm{O}}_{2}$ deposited on $R$-cut sapphire substrates. Based on observation using atomic force microscopy and transmission electron microscopy, when the $\mathrm{Ce}{\mathrm{O}}_{2}$ film was thin $(l10\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$, a highly ordered phase was formed as large three-dimensional islands of $\mathrm{Ce}{\mathrm{O}}_{2}$ with sapphire surface exposed. When the $\mathrm{Ce}{\mathrm{O}}_{2}$ film thickness exceeded a critical value $(\ensuremath{\sim}10\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$, an atomically-flat surface was formed by the reorganization. An energetics model based on these results was developed in which the formation energy of the island was calculated based on the observed facet configuration, taking into account the surface and interface energies, elastic strain, and short-range energy of edges. The energy minimization calculation showed that the calculated lateral and vertical dimensions agreed well with the observed shape of the islands. Based on the experimental evidence and these energy minimization calculations, we demonstrated that increasing the film thickness induces the important phase transition from large islands to an atomically-flat surface.