High-angle angular dark field (HAADF) STEM images confirming that the quantum dot is perfectly positioned on the nanowire waveguide axis. Optimized contrast settings for visibility of nanowire (NW) core and shell are shown in (a) and for the quantum dot are shown in (b). The quantum dot is recognized along the black arrow in (b) by the contrast change from dark-to-bright regions along the nanowire. Scale bar: 20 nm. (c) Energy-dispersive X-ray spectroscopy line scan along the arrow in (b) confirming the presence of the quantum dot. The As concentration reaches a maximum of 12.5 atomic % (at. %) in the core only, thus resulting in a chemical composition for the quantum dot of InAs0.25P0.75.