Scanning electron microscopy (SEM) is a high-resolution microscope that uses high-energy electron beams to scan the surface of a sample, and obtains surface morphology and composition information through signals generated by the interaction between electrons and matter. Here is a comprehensive guide to SEM from principle to operation:

1、 Working principle

The core components of SEM include electron gun, electromagnetic lens, scanning coil, sample chamber, and detector. The electron gun emits an electron beam, which is accelerated and focused to form a high-energy electron beam. The scanning coil controls the electron beam to perform grating scanning on the surface of the sample. After the interaction between the electron beam and the sample, signals such as secondary electrons, backscattered electrons, and characteristic X-rays are excited. These signals are received by the detector and converted into electrical signals, amplified and processed to form an image of the sample surface on the display screen.

2、 Operation steps

Sample preparation: The sample must be dry, conductive, and non-magnetic. For non-conductive samples, gold plating or carbon spraying treatment is required to increase conductivity.

Power on and initialization: Connect the power, start the vacuum system, wait for the vacuum degree to reach the required level, and then start the electron beam and computer system.

Sample placement: Fix the sample on the sample stage, adjust the height and position of the sample stage to ensure that the sample is within the scanning range of the electron beam.

Parameter settings: Set parameters such as acceleration voltage, beam current, scanning speed, and magnification based on sample characteristics and testing requirements.

Image observation and adjustment: Observe the surface image of the sample, adjust the brightness and contrast, move the sample stage to locate the area of interest, and perform focusing and astigmatic operations.

Image saving and processing: Capture and save images, and perform image processing and analysis if necessary.

Shutdown: Turn off the electron beam, vacuum system, and power supply in the order specified in the operation manual.

3、 Application Fields

SEM is widely used in fields such as materials science, biology, medicine, earth science, physics, and engineering to observe material surface morphology, analyze composition and structure, study fracture morphology and failure mechanisms.