Cathodoluminescence

Cathodoluminescence (CL) is the luminescent emission produced when a material is excited by energetic electrons, typically in an electron microscope. The incident electrons transfer energy to electronic states or defects, and radiative recombination yields photons. The emitted light reflects the electronic structure, defect content, and dopant distribution of the material.

In practice, CL is observed in scanning electron microscopes (SEMs) and transmission electron microscopes (TEMs) equipped with light detectors. Detectors such as photomultiplier tubes, cooled CCDs, or spectrometers collect and spectrally analyze the emitted photons. CL can be recorded as spectra or as spatially resolved maps, providing compositional and microstructural information at submicron to nanometer scales, especially in TEM where the electron probe is highly localized.

Applications: In geology and mineralogy, CL helps identify minerals and reveal zoning, weathering, and radiation damage; in materials science, CL characterizes semiconductors, phosphors, oxides, and gemstones, revealing dopant distributions, defects, phase boundaries, and strain effects. Time-resolved CL can measure luminescence lifetimes, informing on recombination dynamics.

Factors: The CL yield depends on accelerating voltage, beam current, material thickness, and the presence of non-radiative centers; beam damage and heating can alter the signal. Resolution is governed by electron interaction volume and detector optics; spectral interpretation requires calibration and control experiments.

Relation to other techniques: CL is complementary to photoluminescence, offering higher spatial resolution in an electron microscope, but generally requires vacuum and can induce damage.