Fig. 6: HRTEM images of SnGe microdots annealed at 350 °C.

a A SnGe microdot with a “trapezoid” morphology dominated by α-Sn. b A SnGe microdot with a “dome” morphology dominated by β-Sn. c A zoomed-in HRTEM image of a pure α-Sn region in the SnGe microdot shown in Figure a. To show the crystal planes more clearly, the boxed region in c is highlighted in d by converting the brightness contrast into color contrast, i.e., red for brighter and blue for darker regions. Panel e shows a Fourier transform of d in order to obtain the d spacing and the corresponding Miller indices, as labeled in d and e. Panels f–h zoomed into an α/β overlapped region of Figure a, showing Moiré fringes due to vertical overlapping of α-Sn planes with β-Sn(200) planes. Panels i–k correspond to a pure β-Sn microdot.