Redistribution and Redistribution Rate of Secondary Electrons
- 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 SE signal current (IS) received by SEM detector is approximately equal to the current (ISE) of emitted SEs minus the current (IRE) of SEs pulled back to the specimen surface by the local surface potential due to charging. Therefore, IS is given by,

          SE signal current ----------------------------- [3827a]

The process of which SEs return to the surface is called redistribution of SEs. The redistribution rate α is the ratio of the amount of SEs collected by the surface and the amount of emitted SEs, given by,

          Redistribution Rate of Secondary Electrons ----------------------------- [3827b]

The incident current (Ip) of primary electrons is given by,

          incident current (Ip) of primary electrons ----------------------------- [3827c]

where,
          δ -- SE yield (emission coefficient) 

Substituting Equations 3827b and 3827c into Equation 3827a, therefore, the SE signal current (IS) can be obtained and given by,

          SE signal current ----------------------------- [3827d]

For certain observation conditions in SEM, Ip and δ are constant and thus, the redistribution rate α is the only factor for determining the signal current as well as the local contrast.

 

 

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