TEM STEM EDX EELS

Transmission Electron Microscopy or TEM allows a morphologic analysis, structural and chemical of solid samples at an atomic level. This technique is based on electrons interaction with the material and the electron detection which passed through the sample. Specimen which are analysed have to be made thinner before in order to be imperceptible to electrons. Biophy Research has for that purpose different techniques of preparation, like ultramicrotomy and FIB (Focused Ion Beam).

A huge amount of information can be obtained by TEM like the thickness of layers in complex stacks, materials morphology in cut, their structure, the nature of crystal defects, the crystal orientation, the grain size for polycrystal samples. The TEM added to a chemical analysis allows to access to the nature of thin layers and interfaces or the distribution of an element in a layer.

 

Applications

  • Observation of materials morphologie (composites and multilayers)
  • High resolution imaging (HRTEM)
  • Particles analysis : distribution in size of nanoparticles isolated or in a matrice
  • Thickness measurement of thin layers in multilayers samples
  • Determination of the structure and crystal orientation of a material
  • Study of structural defects
  • High resolution chemical imaging in STEM mode with annular dark field detector
  • Ponctual chemical analysis in STEM mode for determination of elementary composition at a nanometric level :
    • by detection of X-rays
    • by spectroscopy of electrons energy loss (EELS)
  • Imaging X (STEM-EDX) or imaging filtered in energie (EFTEM) for studies of elementary repartition.

TEM / TITAN / FEI

  • Imaging :
    • C-TEM (Conventional Transmission Electron Microscopy) : BF (Bright Field) / DF (Dark Field)
    • HRTEM (High-Resolution Transmission Electron Microscopy)
    • STEM (Scanning TEM) :  BF (Bright Field) / DF (Dark Field) / HAADF (High Angle Annular Dark Field Detector)
  • Diffraction of electrons :
    • SAED (Selected Area Electron Diffraction)
    • CBED (Convergent-Beam Electron Diffraction)
    • LACBED (Large-Angle Convergent-Beam Electron Diffraction)
  • Chemical Analysis on a nanometric scale, imaging or profile (STEM mode) :
    • EDX (Energy Dispersive X-ray spectroscopy)
    • EELS (Electron Energy Loss Spectroscopy)

Operational principles

The possibility of realising a microscope with electrons, meaning produce bigger images of items, is based on the combinaison of the following elements :
  • The wave nature of electrons. An electrons beam is equal to a radiation with wavelength l=h/mv where m and v are respectively the mass and the speed of electron, this last one being proportional to tension of acceleration V.
  • The existence of lens adapted to that type of radiation. It is possible to focalise a parallel beam of monocinetical electrons with the help of magnetic lens.
  • The existence of a system of emptyness allowing electrons to spread easily inside the column.
  • The existence of an electronic images acquisition system thanks to a CCD camera.
TEM STEM EDX EELS
multilayers on polymer

Documents for download

TRANSMISSION ELECTRON MICROSCOPY
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