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Unformatted text preview: MSE 2020 3/1/2011 Page 1 of 5 SE M (Cont) Depth of focus distance between the crossover point of the beams and the object itself o How deep into the material can you maintain focus? o = ~ - ( ) Dobject 20 200 nm very limiting o o = tan rD o lim 0tan = = D r o , = If r then D Area that you are going to map is magnification o Spot is projected onto 1 pixel o Magnification comes from scanning coils o = M p2r o = D p2M o Higher magnification, higher resolution, lower depth of focus (compromise) MSE 2020 3/1/2011 Page 2 of 5 o is on the order of nms for SEM better special resolution lower accelerating voltage can also measure the electrons that flow through the sample (transmitted) o gives a negative of the image from the backscattered/secondary electrons o the larger the amount of backscattering/secondary electrons, the smaller the amount of transmitted electrons electron yield varies with atomic number (pseudo linear function)...
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This note was uploaded on 09/12/2011 for the course MSE 2020 taught by Professor Alamgir during the Spring '09 term at Georgia Institute of Technology.
- Spring '09