Discover how electron microscopy reveals fine surface details, internal structures, and material differences at micro- and nanoscale. Learn the basic principles behind image formation, the differences between Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Scanning Transmission Electron Microscopy (STEM), and what key signals can tell us about a sample’s morphology and composition.
Introduction
Electron microscopy makes it possible to study structures that are too small to be seen clearly with the naked eye or a conventional light microscope. By using electrons instead of visible light, it reveals fine surface details, internal structures, and material differences at micro- and nanoscale.
In this guide, you will learn:
- What is electron microscopy and how it works
- The difference between SEM, TEM, and STEM
- How electron microscope images are created
- What signals are generated during imaging and what information they provide
Whether you are new to electron microscopy or simply want to revisit the basics, this overview offers a clear introduction to the fundamental principles.
What is electron microscopy?
Electron microscopy is a group of imaging techniques that uses a beam of electrons to examine a sample. Instead of visible light and glass lenses, electron microscopes use electron sources, electromagnetic lenses, and detectors that collect signals created when electrons interact with matter. This enables highly detailed imaging and provides valuable information about a specimen.
What is resolution in electron microscopy?
Resolution describes how much detail a microscope can reveal. More precisely, it is the smallest distance between two points at which they can still be seen as separate. In practice, resolution is influenced not only by electron wavelength, but also by factors such as diffraction and lens aberrations, so image quality depends on both the instrument and how well it is set up and optimized.
Why does electron microscopy offer higher resolution than light microscopy?
Electron microscopy offers higher resolution because electrons have much shorter wavelengths than visible light. This allows electron microscopes to distinguish much smaller features than optical microscopes can. Modern transmission electron microscopes can routinely reach sub-nanometer or atomic-scale imaging, while scanning electron microscopes are typically used for nanometer-scale surface detail.
How does an electron microscope work?
An electron microscope starts with an electron source that emits electrons into a column under vacuum. Electromagnetic lenses shape and focus the beam, which is then directed onto or through the sample. As electrons interact with the specimen, detectors collect signals that are processed into an image or analytical output. In scanning systems, the image is built point by point as the beam moves across the selected area of interest.
Why is vacuum necessary in electron microscopy?
Vacuum is essential because gas molecules would scatter the electron beam and reduce image quality. Keeping the column and chamber under vacuum allows the beam to travel to the sample in a controlled way and helps protect the electron source from contamination, contributing to stable microscope performance. Some instruments can also work in lower-vacuum or variable-pressure modes for specific sample types, but this usually involves trade-offs in image quality or resolution.
What affects image quality in electron microscopy?
Image quality depends on several factors, including:
- Beam energy
- Focusing
- Detector choice
- Diffraction
- Lens aberrations
Spherical aberration, chromatic aberration, and astigmatism can all reduce sharpness or distort the image. That is why correct beam alignment and optical setup are essential for getting clear, reliable results.
What are the main types of electron microscopy and what is the difference between them?
The three main types of electron microscopy are:
Applications include:
- Scanning Electron Microscopy (SEM)
- Transmission Electron Microscopy (TEM)
- Scanning Transmission Electron Microscopy (STEM)
They differ significantly in how they create images and what kind of information they provide:
- Scanning Electron Microscopy (SEM) is mainly used to study the surface of a sample. It detects signals generated when the electron beam interacts with the outer part of the specimen and is especially useful for revealing surface topography and morphology (3D-like images).
- Transmission Electron Microscopy (TEM) is used to examine internal structures by detecting electrons transmitted through an ultra-thin sample. It provides 2D-projected high-resolution images of features inside the specimen.
- Scanning Transmission Electron Microscopy (STEM) also works with thin samples, but combines a scanning approach with transmitted-electron detection. This makes it useful for high-resolution imaging of internal structure while using the beam in scanning mode.
What signals can electron microscopes detect?
Electron microscopes can detect several different signals, and each one gives different information about the sample.
Common examples include:
- Secondary electrons
- Backscattered electrons
- Transmitted electrons
- X-rays
- Cathodoluminescence (light emitted from the sample)
Together, these signals help users reveal topography, composition, internal structure, and elemental information.
What do secondary electrons show?
Secondary electrons are especially useful for imaging fine surface topography. Because they come from the near-surface region of the sample, they help reveal texture, shape, and small surface details. They are often used when the goal is to produce highly detailed surface images.
WWhat do backscattered electrons show?
Backscattered electrons are valuable for compositional contrast. Heavier elements usually produce a stronger backscattered signal and appear brighter in the image, while lighter elements appear darker. This makes backscattered electron imaging useful when the aim is to distinguish between different materials or phases within a sample.
Why is electron microscopy so important today?
Electron microscopy gives researchers and engineers access to structural and compositional information at very small scales. That makes it a key tool across materials science, nanotechnology, life sciences, and many industrial applications (semiconductors, batteries) where fine detail and precise analysis matter.
New product releases, application insights, and event updates.
Delivered as a quarterly newsletter with product news, insights, and events.
