Secondary electrons are usually detected using a scintillator-photomultiplier tube detector (scintillator detector), while backscattered electrons are typically detected using an Electron Backscatter Diffraction (EBSD) detector.

The Secondary Electron Detector (SED) is a device used in Scanning Electron Microscopes (SEM) to detect and collect secondary electrons. Secondary electrons are low-energy electrons generated by inelastic scattering between incident electrons and the sample surface, which can reveal the surface morphology of the sample.

When a scanning electron microscope is in operation, the electron gun generates an electron beam that irradiates the sample to produce signals. The detector detects and collects these signals, which are then processed by a computer to obtain images and data, enabling the analysis of sample characteristics. Scanning electron microscopes typically require detecting signals including secondary electrons (SE) and backscattered electrons (BSE). Secondary electrons are usually detected using a scintillator-photomultiplier tube detector, while backscattered electrons are typically detected using an Electron Backscatter Diffraction (EBSD) detector.

The E-T detector (ETD) is a scintillator-photomultiplier tube detector, typically mounted on one side of the sample stage. During operation, secondary electrons first reach the scintillator and are converted into optical signals, which are then transmitted to the photomultiplier tube. After amplification, they are converted into electrical signals and finally sent to the computer for processing.

The signal intensity delivered by the E-T detector is directly proportional to the number of electrons detected. It has high signal collection efficiency, low delay, and low noise. It was developed in the 1960s. The E-T detector is the most common secondary electron detector product at this stage, and the secondary electron detector commonly referred to is the E-T detector.

In addition to the E-T detector, there is another type of optional secondary electron detector that is less common. Since it is usually installed inside the objective lens or the column, it is called an in-lens secondary electron detector or an in-column secondary electron detector. Its working principle is similar to that of the E-T detector. The in-lens secondary electron detector relies on the electromagnetic field of the objective lens to collect secondary electrons. Due to its close working distance, it has higher detection efficiency and higher resolution, which can further improve the imaging quality of scanning electron microscopes.

According to the "2024-2029 China Secondary Electron Detector (SED) Industry Market Depth Research and Development Prospect Forecast Report" released by the Xinsi Industry Research Center, in practical applications of secondary electron detectors, the E-T detector is the standard configuration in conventional scanning electron microscopes, while in high-resolution field emission scanning electron microscopes, both the E-T detector and the in-lens/in-column secondary electron detector are configured simultaneously. Scanning electron microscopes are important instruments for studying the three-dimensional surface structure of materials, with continuously expanding application fields and increasing demand. In 2023, the global market size reached US$3.66 billion, which is beneficial to the development of the secondary electron detector industry.

Industry analysts at Xinsi said that globally, the main producers of secondary electron detectors include ThermoFisher from the United States, Hitachi High-Technologies from Japan, Orsay Physics from France, and TESCAN from the Czech Republic. Overall, benefiting from the continuously expanding demand and increasing production and sales of scanning electron microscopes, secondary electron detectors, as an indispensable component, have a promising market prospect.