cathodoluminescence

**CL** (Cathodoluminescence) is a **technique that detects light emitted from a material when excited by an electron beam** — the emitted photon energy, intensity, and spatial distribution reveal band gap, defects, composition, and stress at the nanoscale. **How Does CL Work?** - **Excitation**: The SEM/STEM electron beam creates electron-hole pairs in the sample. - **Recombination**: Some carriers recombine radiatively, emitting photons with characteristic energies. - **Detection**: A parabolic mirror + spectrometer collects and analyzes the emitted light. - **Modes**: Panchromatic (total intensity), monochromatic (single wavelength), or spectral (full spectrum at each pixel). **Why It Matters** - **Band Gap Mapping**: Maps local band gap variations in semiconductors and quantum structures. - **Defect Identification**: Non-radiative defects appear as dark spots (killed luminescence). - **Spatial Resolution**: ~50-100 nm in SEM, sub-nm in STEM — orders of magnitude better than photoluminescence. **CL** is **making materials glow with electrons** — using the electron beam to excite luminescence that reveals band structure, defects, and composition at the nanoscale.