Figure 4: Structural and compositional analysis of individual spheres.
From: Silicon-in-silica spheres via axial thermal gradient in-fibre capillary instabilities
(a) Selected area electron diffraction pattern, from the region indicated by the dashed circle on the inset, confirming that the core is composed of multiple diamond cubic Silicon grains. Indexed {400}, {022} and {111} spots highlight three distinct grains within the selected region. The inset shows cross-sectional bright-field TEM image of Si sphere prepared using focused ion beam. (b) Dark-field STEM image of the Si sphere cross-section with overlaid EDX line scan. EDX is unable to detect increased oxygen concentration in the Si-core or at the grain boundary (indicated by flame-coloured arrows) visible in the inset of a (scale bar, 100 nm). Labels indicate deposited protective layers (1: Pt, 2: C, 3: Au and Pd) and four: voids milled by focused ion beam. (c) Bright-field TEM image of a Si sphere, which reveals the core-shell structure (scale bar, 100 nm). (d) Zoomed view of the shell section showing individual Si ‘fingers’ (scale bar, 20 nm). Inset: high-resolution TEM of Si fingers (scale bar, 2 nm). FFT confirms crystallinity and detects multiple grains of diamond cubic Silicon oriented on the [110] zone axis. The measured lattice constant is (0.538±0.008) nm, which is consistent with the literature value 0.543 nm (ref. 29).
