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Scanning Electron Microscopy

Since October 2014, we have a new FEG-SEM with many different detectors (EDS, EBSD, CL, BSE, SE) attached with several software packages (MAPS, Bruker, iDiscover/iMeasure for QEMSCAN) to allow for many techniques to be employed to fully explore and interrogate a given sample.

Quanta 650F SEM

1.  Academic Staff Member:  Dr Richard Harrison

2.  Contact: Please email the lab managers or come find us in our offices.

            (office M9)

            (office N029)

Peak demand for the laboratory typically occurs from October to January. At other times of the year, the SEM is usually over-subscribed and waiting times are typically 2-5 weeks.  Please do talk to us if you have an urgent requirement. 

3. Location:   East Wing - Ground floor Room N029 

4.  Quick overview of different techniques

The SEM is a fully equipped instrument that can be run at high vacuum, low vacuum or environmental mode.  This allows for imaging/chemically analysing samples with or without a conductive (carbon and/or gold) coat.

Examples of these techniques will be uploaded at a later date.

Imaging

  1. Secondary Electron (SE) – A common imaging technique that collects low energy (<50 eV) secondary electrons that are ejected from the k-shell in the sample by inelastic scattering interactions with the incident beam electrons.  They originate from within a few nanometres from the sample surface, thus providing an excellent, high resolution, depth of field image.  This is typically used for imaging structures and topography of samples.
  2. Back Scattered Electrons (BSE) – These electrons vary directly as a function of composition by virtue of the atomic number (Z) through inelastic interactions in the specimen.  Provides an invaluable imaging tool to rapidly discriminate phases that have different mean Z values.
  3. Cathodluminescence (CL) – A signal produced upon the promotion of a valence band electron to the conduction band.  The resulting photon emission of electromagnetic radiation is within the visible light region.

All three of these signals can be obtained of large areas of a given sample using a stage mapping software, MAPS.

Chemical/Phase Analysis

  1. Energy Dispersive X-Ray Spectroscopy (EDS) Spot Analysis and Mapping – Using characteristic X-rays for elemental analysis or chemical characterisation of a given sample.  This is a relatively simple and easy technique for major and some minor elemental analysis.
  2. Quantitative Evaluation of Minerals by SCANning electron microscopy (QEMSCAN) – Using EDS detectors for X-Ray analysis in combination with the BSE detector for the back-scattered electron (BSE) brightness and into mineral phases.  The method aids in phase mapping, modal proportion analysis, particle and mineral grain size and shape among other things using the iDiscover software package.
  3. Electron Back Scattered Diffraction (EBSD) – Is a technique that uses electron diffraction signal to characterise the texture of polycrystalline material.  Typically it is used to explore texture at the millli- to micrometer scale, grain morphology and strain deformation.

Other features of the SEM allow for Beam deceleration mode, charge contrast imaging (CCI) and Environmental SEM (ESEM) mode options.