Electron microscopy
 
Techniques in Electron Microscopes
- Practical Electron Microscopy and Database -
- An Online Book -
Microanalysis | EM Book                                                                                   http://www.globalsino.com/EM/        


=================================================================================

 

 

i) Backscattered electron-scanning electron microscopy (BSE-SEM)
         Principle: Eelectrons (from the electron beam) are backscattered from samples.
         Signal: Electrons

ii) Transmission Electron Microscopy or STEM (scanning transmission electron microscope) 
         Signal: Electrons

iii) Electron diffractions 
         Signal: Electrons

iv) In Situ/Environmental TEM/STEM Observations 

v) Secondary electron-scanning electron microscopy (SE-SEM)
         Principle: Secondary electron (SE) emission from samples due to electron excitation.
         Signal: Electrons
         Special notes: Generation of secondary electron induces energy loss of the electron beam and thus, it is related to EELS measurement.

vi) EDS (Eenergy Dispersive X-ray Spectra) or Wavelength dispersive X-ray spectroscopy (WDXRF/WDS)
         Principle: This is one of the main ways that the excited or ionized atoms recover their fundamental-level state by emitting X-ray radiations. Due to the direct recombination of interband electrons, they transport the energy difference between the initial and final states.
         Signal: X-rays
         Special notes: Generation of X-rays induces energy loss of the electron beam and thus, it is related to EELS measurement.

vii) Auger electron spectroscopy (AES)
         Principle: This is also one of the main ways that the excited or ionized atoms recover their fundamental-level state by emitting radiations.
         Signal: Electrons
         Special notes: Generation of AES electrons induces energy loss of the electron beam and thus, it is related to EELS measurement.

viii) Cathodoluminescence
         Principle: Electron-hole (e-h) pairs are generated due to beam excitation. The electrons in semiconductors are recombined from the conduction band to the valence band, resulting in CL photons.
         Signal: photons
         Applications: Examines optical properties of electronic structures, e.g. providing information on local bandgap variations that may originate from strain, defects, impurities, alloy fluctuations, etc.
         Special notes: Generation of CL photons induces energy loss of the electron beam and thus, it is related to EELS measurement.

ix) Direct observation of grain growth due to beam-heating
         Principle: Phonon excitation (heat)
         Special notes: The beam-heating induces energy loss of the electron beam and thus, it is related to EELS measurement.

x) Electron beam induced current (EBIC)
         Principle: The generated current is formed by the separation of electron-hole pairs excited by the electron-beam irradiating on semiconductor devices.
         Applications: E.g. the distinction at cross-sectional surfaces between n- and n+ regions was observed on a Si wafer and EBIC measurements demonstrated that shallow states exist at Σ3 coincidence site lattice (CSL) grain boundaries.
         Special notes: Generation of electron-hole pairs induces energy loss of the electron beam and thus, it is related to EELS measurement.

xi) Electron beam absorbed current (EBAC)/resistive contrast imaging (RCI)
         Principle: Electron beam of SEM injects charges which is then absorbed by metal lines under the surface. Therefore, a current is induced and measured by a probe placed on the SEM sample
         Applications: To locate failures in metallization networks inside semiconductor devices.
         Special notes: Energy absorption from the electron beam induces energy loss of the electron beam and thus, it is related to EELS measurement.

xii) EELS (electron energy loss spectroscopy) and  EFTEM (Energy filtered transmission electron microscopy)
         xii.a) Phonon excitation (heat): a few 10 meV, which is not detectable with current EELS instruments.
         xii.b) Plasmons (outer shell scattering, collective excitations): 2 - 50 eV, which is longitudinal wave-like oscillations of weakly bound electron, reflecting free-electron density.
         xii.c) Inner shell scattering: some hundreds to thousands of electron volts (eV).
         Principle: Measures the spectral distribution of energy transferred from an incident electron beam into a specimen.
         Signal: Electrons
         Applications: Many applications, see details at page3168.

 

 

 

 

 

=================================================================================