Cathodoluminescence in a Scanning Transmission Electron Microscope: A Nanometer-Scale Counterpart of Photoluminescence for the Study of II–VI Quantum Dots

We report on nanometer-scale cathodoluminescence (nanoCL) experiments in a scanning transmission electron microscope on individual core–shell CdSe/CdS quantum dots (QDs). By performing combined photoluminescence (PL) and nanoCL experiments of the same individual QDs, we first show that both spectroscopies can be used equally well to probe the spectral properties of QDs. We then demonstrate that the spatial resolution of the nanoCL is only limited by the size of the QDs themselves by performing nanoCL experiments on QDs lying side by side. Finally, we show how nanoCL can be advantageous with respect to PL as it can rapidly and efficiently characterize the optical properties of a large set of individual QDs. These results contrast with pioneering CL works on II–VI QDs and pave the way to the characterization of any II–VI quantum-confined structure at the relevant scale.