Coating of TEM Specimen to Reduce Beam Damage & Sputtering
- Practical Electron Microscopy and Database -
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This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.

 

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The damage etching (also called sputtering) of TEM specimens is a surface process so that it can be delayed or prevented by coating the specimen a suitable material. To be practical in high-voltage TEMs, several factors are needed to be considered. First, the coating should be very thin in order to minimize additional electron scattering that reduces the contrast of EM images. Second, the coating should have high quality (e.g. amorphous) in order to avoid artifacts in the TEM images. Third, the coating should be stable in TEM thus we need a material of high atomic number of which sputtering threshold lies above the incident-beam energy.

To satisfy the first and third requirements, Egerton et al [1] had used tungsten coatings as the sputtering barrier of TEM specimens, however, it was not so successful most likely this layer was somewhat porous. The carbonaceous layer that builds up in the irradiated region of a specimen in the presence of hydrocarbon contamination can also satisfy the first and second requirements. For instance, Muller and Silcox [2] had irradiated their specimens to build a 5–10 nm polymerized layer before imaging or microanalysis under high-dose conditions and this layer was able to provide protection for up to one hour of microanalysis.

 

[1] R. F.Egerton, F. Wang, P. A. Crozier, Beam-induced damage to thin specimens in an intense electron probe, Microsc. Microanalysis 12 (2006) 65.
[2] D. A. Muller, J. Silcox, Phil. Mag. 71 (1995) 1375.

 

 

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