|
Specimen preparation |
|
Some
materials can be examined in the Field Emission Scanning
Electron Microscope, with virtually no specimen preparation (e.g. metals).
Specimen thickness is not a consideration, unlike transmission
electron microscopy.
But the sample preparation is often necessary. This preparation is function of the material (biological,
ceramic, metal) and it is highly dependent on the type of information we are attempting to derive. |
To generalize the following fundamentals must be taken in
consideration:
1- Because the signal detection is influenced by the surface topography, it is highly recommended to polish the sample surface.
For fracture studies, the sample should be in an unaltered state.
3-
Foreign substance can be deposit at the specimen surface (usually
carbonaceous material derived from breakdown of a hydrocarbon. This phenomenon
is called contamination.
To avoid it is necessary to ensure that the specimen is properly clean and
thoroughly degreased and dried.
4-
If the material is an insulator it must be coated, providing a path to release the
absorbed electrons in the specimen.
5-
When any kind of mounting is used, although the specimen it self may
be a conductor an appropriate connection must be created to avoid the charging.
6-
In case of non conductive material, the recommended coating is carbon
if you are planning to do an energy dispersive spectroscopy (EDS).
7- The specimen size is limited by considerations of accommodation in the specimen stage.
8- To prepare biological samples there is a common protocol that must be follow.