The cathodoluminescence detector is an atomic microscope detector that obtains some properties of matter. In the following article, explanations are given about this detector.

Cathodoluminescence detector is the emission of light when a material is excited by an electron beam.

Cathodoluminescence in Scanning Electron Microscope (SEM) or Scanning Tunneling Electron Microscope (STEM) is a tool capable of characterizing composite, optical and electronic properties. Matter and relating them to morphology, microstructure and composition in micro and nanostructure dimensions.

This analysis is a powerful structural and compositional analysis technique that can reveal valuable information that cannot be obtained by secondary electron detector, backscatter, and X-ray spectroscopy. This information includes zonal composition, network structure and strain or damage to the material. Cathodoluminescence imaging based on electron microscopy has a much higher resolution compared to optical microscopy.

Cathodoluminescence imaging refers to the analysis of luminescence (emitted light or photon) from a material that is emitted due to excitation by an electron beam. Luminescence ranges from ultraviolet to infrared wavelengths.

Luminescence occurs when an energetic electron beam excites the sample, which emits photons (cathodeluminescence) to return to the ground state. In a semiconductor, this excitation process causes the transfer of an electron from the valence band to the conduction band, which leaves a hole in the valence band. So when this electron and hole recombine, a photon will be emitted from the semiconductor.

The energy of the photon (color) and the probability of photon emission depend on the material, its purity and defects. Therefore, to measure cathodoluminescence, almost all non-metallic materials can be examined. To investigate the band structure, semiconductors, insulators, ceramics, gemstones, minerals, and glasses can be examined in the same way. In metals, the excitation of the sample may increase the surface plasmon, and the decrease of this surface plasmon due to time can be seen in the form of cathodoluminescence photon emission.

The structure of the cathodoluminescence detector in the electron microscope:

Figure 2- Connecting the cathodoluminescence detector to the SEM

When the electron beam excites the sample, it causes the emission of luminescence from the areas near the surface of the sample. To collect this emitted cathodoluminescence, a mirror is placed above the sample, which is made in a special way to direct the light coming out of the sample, from the vacuum chamber to the spectrometer or photon detector. For thin samples such as TEM samples, usually mirrors are placed both above and below the sample to collect light from both sides of the sample. >

When the electron beam is scanned on the sample, it is possible to obtain an optical activity map of the sample.

The intensity of the emitted light from the sample may be very low and usually requires that as much as possible, all the emitted photons are directed to the detector. Even in samples that have a high efficiency in photon emission, the ability to collect and detect photons with minimal optical loss is needed to achieve the highest resolution.