MSEN 360 Materials Characterization - Scanning Electron Microscopy

Flashcards covering key vocabulary and concepts related to Scanning Electron Microscopy (SEM), including beam generation, electron scattering, detection schemes, imaging modes, and factors affecting resolution and image quality.

Thermionic Guns

Thermionic guns provide thermal kinetic energy for a beam of primary electrons to escape the filament surface, generating an e-beam.

Field Emission (FE) Guns

Field emission guns produce an e-beam by tunneling effects and operate colder than thermionic guns, producing a brighter light source.

Electromagnetic Lenses

Condense the e-beam to a nanoscale probe for imaging a surface.

Deflection System

Used for scanning the e-probe over the sample surface in a raster pattern.

Primary Electrons (PEs)

Electrons generated from the e-beam interacting with the atoms of the sample.

Secondary Electrons (SEs)

Generated by inelastic scattering.

Backscattered Electrons (BSEs)

Generated by elastic scattering.

Evarhart-Thornley (E-T) Detector

Commonly used to detect secondary electrons (SEs) and is placed at a low angle relative to the sample.

Backscattered Electrons (BSEs)

Have more energy and are detected using a detector in the path of the electrons (higher angle relative to the sample).

Secondary Electron (SE) Imaging Mode

The most commonly used mode of imaging and provides topographic contrast.

Magnification (M) of an SEM

Dependent on the area scanned by the probe (a) and the size of the projector onto which this image is projected.

Working Distance

Impacts the convergence angle and thus affects both depth of field and resolution.

Backscattered Electrons (BSE)

Inform us about the compositional differences in a sample and are sensitive to atomic number.

Yield of Secondary Electron

Depends on the element type (due to changes in work function).