Scanning Electron microscope, a new type of electronic optical instrument. It is characterized by simple sample preparation, wide adjustable magnification range, high image resolution and large depth of field. For decades, SEM has been widely used in biology, medicine, metallurgy and other fields, promoting the development of related disciplines. Scanning Electron Microscope (SEM) is used to modulate the image by using various physical signals which are excited by the fine focusing electron beam scanning on the sample surface. The scanning electron microscope mainly includes vacuum system, electron beam system and imaging system.