Scanning Electron Microscopy (SEM) is a powerful imaging technique used to observe the surface structure and composition of samples at very high magnifications. Unlike traditional optical microscopy, which uses visible light to form an image, SEM uses a focused beam of electrons to scan the surface of a specimen.
Here’s how it works:
- Electron Beam: An electron gun emits a beam of electrons, which is focused into a fine spot using electromagnetic lenses.
- Sample Interaction: The electron beam is directed onto the sample surface. As the electrons interact with the atoms of the sample, various signals are produced, including secondary electrons, backscattered electrons, and X-rays.
- Signal Detection: Detectors collect these signals to create an image. The most commonly detected signals are secondary electrons, which provide high-resolution surface details.
- Imaging: The collected signals are processed to create detailed, high-resolution images of the sample’s surface, with magnifications ranging from 10x to over 1,000,000x.
SEM provides detailed, 3D-like images, which is useful for examining surface topography, texture, and composition of a wide variety of materials, from biological samples to metals and nanomaterials. Additionally, it can be combined with other techniques, like Energy-Dispersive X-ray Spectroscopy (EDS), to analyze the elemental composition of the sample.
