Fig. 4

a Cross-sectional [110] HAADF-STEM image of the interface GaAsBi/GaAs of sample S2, capturing a Bi cluster of about 12 nm in size, next to the GaAsBi/GaAs interface. b Low-filtered image of the HAADF-STEM image shows two areas with different contrast in the GaAsBi layer, a Bi-rich zone is faceted along {111} and (001) planes, surrounded by a lower Bi-rich one. c Coloured map representing the R values around group V columns depicting a graded Bi distribution around the cluster. d The corresponding Fourier transformation from the selected areas marked with red rectangles in Fig. 1a. Additional spots matching {102} planes related to rh-Bi phase are detected in the highest contrast cluster region