Scanning electron microscopy (SEM) is a type of electron microscopy that uses a beam of electrons to create a detailed three-dimensional image of the surface of a sample. SEM involves scanning the surface of a sample with a focused beam of electrons, and collecting the scattered or emitted electrons to create an image of the sample’s surface.
The basic steps involved in SEM are as follows:
- Sample preparation: The sample is prepared by coating it with a thin layer of conductive material, such as gold or carbon. This allows the sample to conduct electrons and prevents the accumulation of electrical charge on the surface during imaging.
- Electron beam generation: An electron beam is generated in the electron source and focused onto the surface of the sample using a series of electromagnetic lenses.
- Scanning of the sample: The electron beam is scanned across the surface of the sample in a grid pattern. As the beam scans across the sample, it interacts with the atoms on the surface, causing some of the electrons to be scattered or emitted from the surface.
- Collection of the scattered or emitted electrons: The scattered or emitted electrons are collected by a detector, which can be either a fluorescent screen or a digital camera. The collected electrons create an image of the sample’s surface.
- Image processing: The collected electron signals are processed by computer software to create a final image. This may involve adjusting the contrast, brightness, and other parameters of the image.
SEM can provide high-resolution images of the surface of a sample, allowing for the visualization of the topography, shape, and texture of the sample. It is widely used in many fields of science, including materials science, biology, and geology. In materials science, SEM can be used to study the structure and properties of materials at the nanoscale, while in biology, it can be used to study the surface structure of cells, tissues, and other biological structures.