Fig. 1. (Color online) (a)−(d) Schematic illustration of the growth process of embedded GaAs_1−xSb_x quantum dots. (a) Ga droplets formed on the Si (111) substrate; (b) GaAs nanowires grown on the Si (111) substrate; (c) GaAs_1−xSb_x quantum dots grown on the top of GaAs nanowires; (d) upper GaAs nanowires grown on the top of GaAs_1−xSb_x quantum dots; (e) and (f) side-view SEM images of GaAs nanowires and GaAs nanowires with embedded GaAs_1−xSb_x quantum dots, respectively.

Fig. 2. (Color online) (a) TEM image of an embedded GaAs_0.8Sb_0.2 quantum dot grown at 590 °C. The rectangles highlight the regions where the HRTEM images were recorded; (b) HAADF-STEM image and the corresponding EDS line scan; (c)−(e) false color EDS maps of the GaAs_0.8Sb_0.2 quantum dot; (f) HRTEM image of the bottom GaAs (blue rectangular in panel (a)); (g) the corresponding FFT image of panel (f); (h) HRTEM image of the GaAs/GaAs_0.8Sb_0.2/GaAs (red rectangular in panel (a)); (i) HRTEM image of the GaAs_0.8Sb_0.2 quantum dot (green rectangular in panel (a)); (j) the corresponding FFT image of panel (i); (k) HRTEM image of the upper GaAs (orange rectangular in panel (a)); (l) the corresponding FFT image of panel (k); compared to the panel (a), panel (f), (h), (i) and (k) were rotated 90 degrees.

Fig. 3. (Color online) (a)−(d) Schematic illustration of the growth process of embedded GaAs_1−xSb_x quantum dots covered with spontaneous GaAs passivation layers. (a) Ga droplets formed on the Si (111) substrate; (b) GaAs nanowires grown on the Si (111) substrate; (c) GaAs_1−xSb_x quantum dots grown on the top of GaAs nanowires; (d) the upper GaAs nanowires and spontaneous GaAs passivation layers grown simultaneously on the GaAs_1−xSb_x quantum dots; (e) and (f) side-view SEM images of nanowires with GaAs_1−xSb_x quantum dots grown at 510 and 530 °C, respectively.

Fig. 4. (Color online) (a) TEM image of an embedded GaAs_0.58Sb_0.42 quantum dot covered with a spontaneous GaAs passivation layer grown at 530 °C. The rectangles in Fig. 4(a) highlight the regions where the HRTEM images were recorded; (b) HAADF-STEM image and the corresponding EDS line scan; (c)−(e) false color EDS maps of the GaAs_0.58Sb_0.42 quantum dot; (f) HRTEM image of the bottom GaAs (blue rectangular in panel (a)); (g) the corresponding FFT image of panel (f); (h) HRTEM image of the GaAs/GaAs_0.58Sb_0.42/GaAs (red rectangular in panel (a)); (i) HRTEM image of the GaAs/GaAs_0.58Sb_0.42/GaAs (green rectangular in panel (h)); (j) HRTEM image of the upper GaAs (orange rectangular in panel (a)); (k) the corresponding FFT image of panel (j); compared to the panel (a), panel (f), (h), (i) and (j) were rotated 90 degrees.