Schematic representation of the fabrication process from upper to lower: Si1−xGex relaxed buffer layer/Si(001) substrate; FIB milling of Si1−xGex wires (200 nm < ϕ < 300 nm). (c) RTO of the wires; (d) chemical oxide removal. The two last steps (oxidation/etching) produce the Ge pile up on the shell of the NWs.
Evolution of the wires shape with the milling conditions. After the first milling step at 0°, a second step was performed from left to right: at normal incidence (0°), 33° from normal or 38° from normal. Directions of milling are indicated by arrows.
SEM image of the periodic array of NWs with an aspect ratio about ∼1 obtained by a two step FIB milling (at 0° and 38°) of a fully relaxed Si0.8Ge0.2 pseudo-substrate capped with a Pt layer before milling.
TEM cross-section images of SiO2/Ge/SiO2/Ge/Si1−xGex NWs produced by the combination of FIB milling and condensation process. The core-shell configuration was produced by two thermal oxidation/etching cycles with RTO performed at 1000 °C for 2 min.
TEM cross-section images of the NWs after RTO at 750 °C during 120 min: (a) large view image of NWs periodicity and size homogeneity; (b) higher magnification image and corresponding EDS filtered image of the Ge-L23 edge.
TEM cross-sectional images of periodic array of NWs perfectly homogeneous in size. The nanofabrication process involves mainly two steps: (i) LMAIS-FIB milling and (ii) a thermal oxidation/etching cycle with RTO performed at 750 °C for 120 min. (a) Gives an overall view of the NWs. The inset gives an EELS filtered image of the Ge distribution; (b) gives a higher magnification image of one NW which evidences the reproducible SiO2/Ge/Si0.8Ge0.2 core-shell configuration.
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