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Figure 8 | Nanoscale Research Letters

Figure 8

From: Ge/Si(001) heterostructures with dense arrays of Ge quantum dots: morphology, defects, photo-emf spectra and terahertz conductivity

Figure 8

TEM data for the five-layer Ge/Si heterostructures, T gr = 360℃. (a) to (c) h Ge = 9 Å; (d) to (i) h Ge = 10 Å; (a) domains of tensile strain in Si over Ge clusters are observed more or less distinctly near most clusters, but not around all; the surface is down; the mark equals 20 nm; (b), (c) zoom in two strained domains, no extended defects are observed; (d) strained domains are more pronounced, the strain is well recognized even under some clusters; (e) a magnified image of a strained domain; a strained lattice is well contrasted with the normal one; (f) zoom in the dilated lattice, a perfectly ordered lattice is observed; (g) a Si domain next to the Ge/Si interface near the cluster apex, a vacancy (‘V’) and disordered lattice (upper right corner) are revealed; letter ‘I’ indicates the direction to the interface along <11 1 ¯ >; (h) the same as in (g) but some farther from the interface, the lattice is perfect; (i) the Fourier transform of an image obtained from a strained domain demonstrates an enhanced lattice parameter (the strain varies from domain to domain, the estimated lattice period in the [001] direction sometimes reaches 5.6 Å).

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