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Scanning electron microscopy (SEM) is an advanced analytical tool that massively outstrips the capabilities of traditional light microscopy. Using visible wavelengths of light on the 400 – 700 nanometer (nm) range, the standard array of magnifying lenses in a compound microscope permits sample magnification by up to 1000x.
This allows analysts to optically resolve points in a specimen which are no nearer together than 200 nm. Topographical features, which are in closer proximity than the lower detection range, are unable to be distinguished with any degree of reliability.
As the requirement for nanoscale material characterization and elemental topography measurements became more prevalent worldwide, traditional microscopy’s wavelength range was a limiting factor. As a result, scanning electron microscopy was developed to supply novel techniques for sample imaging via electron scanning.
This article outlines the working principles and applications of scanning electron microscopy in further detail.
How Scanning Electron Microscopy Works
A high-energy electron source is at the heart of a scanning electron microscope which is positioned above a series of condenser lenses and apertures which focus these electrons into a beam.
Before the final lens aperture, the position of this beam is modified by sets of deflection or scanning coils. A sample is placed in the path of the electron beam which is deflected continuously into a raster scanning pattern by the deflection coils.
When electrons impact a surface, in addition to x-rays, they produce secondary and backscattered electrons (BSE). BSE and x-ray detectors in the sample chamber receive these signals, which are characteristic of the sample’s elemental composition, crystalline structure and morphology.
Subsequently, scanning electron microscopy can be employed to image the elemental composition of a sample surface and establish topographical sample features with a resolving power that is significantly increased.
Scanning electron microscopy produces 3D chemical surface maps of a sample with a magnifying capacity of up to 50,000x. This enables high lateral resolution ranging from millimeters to nanometres (>10 nm), while energy dispersive x-ray (EDX) analysis supplies chemical detection limits of 1000 – 3000 parts per million (ppm).
Applications of Scanning Electron Microscopy
Scanning electron microscopy is a robust analytical tool that has a wide scope of practical applications in the analytical, commercial, and industrial spaces. It is widely utilized for quality control (QC) and good-bad testing of pharmaceutical products, and it has proven useful for detecting and identifying unknown contaminants in manufactured goods.
Scanning Electron Microscopy with Jordi Labs
Jordi Labs specializes in expert analytical testing services for a wide variety of industries, from forensic samples to consumer products. It provides combinations of more than 60 different analytical methods for comprehensive testing of goods and products, including scanning electron microscopy with EDX capabilities.
This information has been sourced, reviewed and adapted from materials provided by Jordi Labs.
For more information on this source, please visit Jordi Labs.