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(Color) Images of the bilayer wrinkle film. (a) Optical microscopy image showing the periodical wrinkle pattern at large scale. (b) AFM image of the wrinkle pattern. Dark color corresponds to the shallow trench. Bright color indicates the wrinkle pattern with a lateral depth of . The orange color is the area of bonded SiGe film. The tilted three-dimensional image in the inset shows the decrease of wrinkle height along the direction.
(Color online) Spatial variation of the wrinkle pattern. (a) Along the direction, at the free edge, the height varies periodically with a characterized wavelength of . (b) In the direction, the wrinkle has a maximum height at the free edge and decreases gradually toward the bonded area.
(Color) UV micro-Raman mapping of the wrinkle pattern. It exhibits a similar shape as that of AFM image (bright color) due to the strain variation. Red color corresponds to the shallow trench. Green color indicates the wrinkle pattern.
(Color online) Family of micro-Raman spectrum recorded along the direction. The peak position shifts to lower energy continuously from the bonded area to the free edge as indicated by the dashed arrow line. The shift reflects a strain relaxation due to the detachment.
Raman shift together with the spatial height and a schematic side view of the lattice structure. (a) Raman shift measured across a spatial pattern along the edge. Solid squares are the Raman data and the solid line is a guide for the eye. Dashed line is the spatial height taken from Fig. 2. It shows that the strain varies periodically as that of spatial height with a reversed relationship. (b) Schematic side view of the local lattice structure of the flat bilayer freestanding film. (c) Schematic side view of the local lattice structure of the bilayer wrinkle film.
Lattice constant, strain, and Raman shift.
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