The manufacturing of scanning electron microscope is based on the interaction between electrons and matter. When a beam of high-energy incident electrons bombards the surface of matter, the excited area will produce secondary electrons, Auger electrons, characteristic X-rays and continuum X-rays. Rays, backscattered electrons, transmitted electrons, and electromagnetic radiation generated in the visible, ultraviolet, and infrared light regions. At the same time, electron-hole pairs, lattice vibrations (phonons), and electron oscillations (plasma) can also be generated. In principle, using the interaction between electrons and matter, information on various physical and chemical properties of the sample itself, such as morphology, composition, crystal structure, electronic structure, and internal electric or magnetic fields, can be obtained.
The actual imaging process is that the electron gun emits an electron beam with an energy up to 30keV, which is narrowed and focused by the converging lens and the objective lens, and an electron beam with a certain energy, intensity, and spot diameter is formed on the surface of the sample. Under the action of the magnetic field of the scanning coil, the incident electron beam will scan the surface of the sample according to a certain time and space in a raster-like manner point by point. Due to the interaction between the incident electrons and the surface of the sample, secondary electronic. Due to the function of the secondary electron collector, the secondary electrons emitted in all directions can be collected, and then accelerated by the accelerator to the scintillator to be transformed into an optical signal, and then reach the photomultiplier tube through the light guide, so that the optical signal can be converted again. for electrical signals. This electrical signal is amplified by the video amplifier and output to the grid of the picture tube to modulate the brightness of the picture tube, so a secondary electron image reflecting the surface fluctuation of the sample is displayed on the fluorescent screen. The transmission electron microscope imaging uses magnetic lens imaging and completes it at one time, which is completely different from its imaging principle.
The scanning electron microscope is mainly composed of electron optical system, scanning system, signal detection system, display system, power supply and vacuum system. Its structure diagram is shown in the figure. The scanning electron microscope is the most widely used in adhesive testing.
