Scanning Electron Microscope (SEM)
A versatile technique for topographical and chemical characterisation of surfaces.
Intermetallic particles from an aluminium alloy extracted by the
Butanol method. EDS-spectrum of an aluminium-rich intermetallic phase.
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The technique: In a Scanning Electron Microscope (SEM), a focused electron beam sweeps over the surface of the sample. The beam induces an emission of two different types of electrons, Secondary Electrons (SE) and Back Scattered Electrons (BSE), and of X-rays that can be analysed by an Energy Dispersive Spectrometer (EDS). Thus it is possible to obtain both topographical and chemical information from the sample surface. The method is characterised by high depth of focus and high resolution, down to a few nanometer.
The instrument: A JEOL JSM-5900LV scanning electron microscope and an OXFORD Isis spectrometer with Germanium detector. The microscope can be run in the usual high vacuum mode, or a special low vacuum mode enabling the characterisation of non-conductive and delicate materials without having to coat the surface (only BSE-imaging). All elements with atomic number 6 (carbon) and above can be detected with the X-ray spectrometer, with a detection limit that usually lies under 1 weight percent.
Signal comparison:Signal | Secondary Electrons (SE) | Back Scattered Electrons (BSE) | X-ray (EDS) |
Lateral resolution | a few nm* | sub-µm to a few µm * | sub-µm to a few µm * |
Type of information | topography | atomic mass and topography | element composition |
* depending on composition and acquisition parameters
Sample requirements:Size | Typical lateral dimensions up to 125 mm x 100 mm, maximum 200 mm x 200 mm.
Maximum height 30 mm. |
Electrical properties | The sample must be electrically conductive. Non-conductive materials need to be coated
with a thin layer of gold or carbon for SE-imaging or EDS-measurements, respectively. |
Other | The material must withstand some vacuum and heat. |
The SEM instruments in Trondheim are located at the NTNU.
Contact persons:
Oslo: Joachim Moe Graff, phone: +47. 98 23 04 73
Trondheim: Wilhelm Dall, phone: +47 98283971
