Evaluating Brightness and Stability of Cathodoluminescence from Colloidal Semiconductor Nanocrystals

Cathodoluminescence promises correlation of atomic structure and electronic structure at the level of individual nanoparticles or even defects. Despite 10-year-old reports of individual nanoparticle cathodoluminescence, cathodoluminescence of colloidal semiconductor materials remains challenging due to material instability. To clarify the roadblocks for cathodoluminescence analysis of colloidal nanocrystals, this work undertakes a comprehensive study of the cathodoluminescence of semiconductor quantum shells. CdS/CdSe/CdS quantum shells have bright and durable radioluminescence (up to 100 ph/keV). Comparative quantum yield measurements are designed to assess the brightness of semiconductor nanocrystal films, which show that the quantum shells are much less bright under electron irradiation compared to X-ray photons. Through a series of voltage, current, dwell time, and atmospheric pressure experiments, cathodobleaching is assigned to charging of the samples─and not thermal effects or irreversible chemical changes. The results outline potential approaches for improved measurement of colloidal materials and other beam sensitive materials.