Scanning electron microscopy (SEM) is an advanced analytical tool that vastly outstrips the capabilities of traditional light microscopy. The standard array of magnifying lenses in a compound microscope enables sample magnification by up to 1000x, using visible wavelengths of light on the 400 – 700 nanometer (nm) range. This enables analysts to optically resolve points in a specimen that are no closer together than 200nm. Topographical features in closer proximity than this lower detection range cannot be distinguished with any degree of reliability.
Traditional microscopy’s wavelength range was a limiting factor as the need for nanoscale material characterization and elemental topography measurements became increasingly prevalent worldwide. Scanning electron microscopy was developed as a result, providing novel methods of sample imaging via electron scanning.
This blog post will explore the working principles and applications of scanning electron microscopy in more detail.
How Scanning Electron Microscopy Works
At the heart of a scanning electron microscope is a high-energy electron source positioned above a series of condenser lenses and apertures which focus these electrons into a beam. The position of this beam is altered by sets of deflection or scanning coils before the final lens aperture. A sample is placed in the path of the electron beam which is continuously deflected into a raster scanning pattern by the deflection coils.
When electrons impact a surface, they generate secondary and backscattered electrons (BSE), as well as x-rays. BSE and x-ray detectors in the sample chamber acquire these signals, which are characteristic of the sample’s elemental composition, morphology, and crystalline structure. Scanning electron microscopy can subsequently be used for imaging the elemental composition of a sample surface and determining topographical sample features with a significantly increased resolving power.
Scanning electron microscopy can generate 3D chemical surface maps of a sample with a magnifying capacity of up to 50,000x. This offers high lateral resolution ranging from millimeters to nanometres (>10nm), while energy dispersive x-ray (EDX) analysis provides chemical detection limits of 1000 – 3000 parts per million (ppm).
Applications of Scanning Electron Microscopy
Scanning electron microscopy is a robust analytical tool with a broad range of practical applications in the commercial, analytical, and industrial spaces. It is broadly used for quality control (QC) and good-bad testing of pharmaceutical products and has proven useful for detecting and identifying unknown contaminants in manufactured goods.
If you would like to learn more about the applications of scanning electron microscopy, read our previous blog posts:
- Particulates and Residue Analysis with Jordi Labs
- Identifying Particulates and Residue in Pharmaceuticals
Scanning Electron Microscopy with Jordi Labs
Jordi Labs specializes in expert analytical testing services for a broad range of industries, from consumer products to forensic samples. We offer combinations of over 60 different analytical techniques for comprehensive testing of goods and products, including scanning electron microscopy with EDX capabilities.