SEM Practice 2
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smallest separation at which two points can be seen as distinct entities
_______ the d-value, the better the resolution
If the sample is not transparent, can it still be detected under SEM?
Yes, because SEM only scans the surface through using electrons not photon
what is the electron source in SEM?
Where is scanning Coils located?
located in optical column
How does diffusion pump work?
- Electric heater heats oil and oil vapour rises up the chimney
- Vapor is condensed in chimney by cooling coils and it takes air molecules from the top of the pump to the bottom
Can Diffusion pump used directly?
No, First Mechanical pump has to be used until the pressure gets to 10-2 , then Diffusion pump can be used
Primary Electron ( used for flat surfaces) gives _________ while secondary electron gives__________ about the sample
- atomic number
- Surface information
What is Electrical Bias?
Electrical field which bends the electron towards the detector
Column maintained at _______ vaccum, and sample chamber at ______- vaccume
Wet sample ( non-conductive) can be observed using SE and BSE detection. (T/F)
What element is used for cooling SEM?
Depth of field
extent of the focus through the depth of the image
Speed the electron running down the column (KV)
Distance between aperture and sample
How big of spot we are hitting on the sample
What parameters causes an increase in resolution?
- Increase accelerating voltage(KV)
- Lowering working distance
- smaller aperture size
- lower the beam current
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