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Scanning Electron Microscopy (SEM)

Scanning electron microscopy (SEM) is a surface imaging technique that achieves nanometer-scale resolution: orders of magnitude smaller than is possible with optical microscopy.

In addition to standard SEM detectors, all Covalent instruments are also outfitted with energy dispersive spectroscopy (EDS) detectors to capture quantitative elemental composition measurements, as well as 2D elemental maps, alongside conventional SEM images.


  • Top-down or cross-section imaging with nm- resolution
  • Sub-nm resolution possible; see ‘high resolution’ technique variant
  • Multimodal morphology characterization of surface or subsurface features


  • Specimen damage can occur during imaging

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Sample Requirements

Example Outputs

Top-down image of spherical nanoparticles and aggregates grown on silicon substrate

From: Center for Advanced Materials Analysis in Oregon

SEM-EDS Map of elemental distribution across a battery electrode cross-section.

Instruments Used

ThermoFisher Scientific Helios 5 UC (x3)

ThermoFisher Scientific Helios 5 UC (x3)

  • Maximum Horizontal Field Width: 2.3 mm at 4 mm WD
  • Electron Beam:
    • Resolution Limit: 0.7 nm at 1 kV
    • Current Range: 0.8 pA to 100 nA
    • Accelerating Voltage Range: 350 V to 30 kV
  • Ion Beam
    • Resolution Limit: 4.0 nm at 30 kV using preferred statistical method
    • Current Range: 1 pA to 100 nA
    • Accelerating Voltage Range: 500 V to 30kV
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Thermo Scientific Scios

Thermo Scientific Scios

  • Powerful charge neutralization
  • Enables analysis on magnetic samples
  • Able to operate above vacuum pressure
JEOL JSM-IT800 SHL - Schottky Field Emission Microscope

JEOL JSM-IT800 SHL - Schottky Field Emission Microscope

  • Versatile electromagnetic/electrostatic hybrid lens design for outstanding imaging and analysis performance
  • NEOENGINE – intelligent automated electron beam control
  • Advanced auto functions including beam alignment, focus, and stigmation
  • In-lens field emission gun
  • Aperture Angle Control Lens (ACL) for superb resolution at any kV or probe current
  • Beam Deceleration (BD) mode reduces effects of lens aberrations at the sample
  • Large specimen chamber with multiple ports
  • Montage images and elemental maps
  • Smile View Lab for data management and report generation
  • Live Analysis with integrated JEOL EDS elemental screening
  • High spatial resolution imaging and analysis of nanostructures

How SEM Works

To generate electron images – called micrographs – a highly focused electron beam is scanned over the surface of a specimen. As it scans, the beam interacts with the sample to produce several detectable signals (different types of photons and electrons) through elastic and inelastic scattering events.

The intensities of these signals depend predominantly on the atomic number of the scattering atom, and the adjacent surface topography. Each signal is affected by these factors slightly differently, and the SEM can be calibrated to detect one or two signals at a time.

As the electron beam is scanned, the active detector(s) measure the intensity of the selected signal(s) at each pixel, and correlate these to a grayscale value.

When the scan is complete, the system outputs an image that captures topographical (and sometimes relative atomic number) information.