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3 Product and Functional Description | 3.2 Main Components
ZEISS
The effects of the acceleration voltage also are dependent on the atomic number of the material:
Fig. 22: Comparison of surface information at 1 kV and 5 kV – low atomic number. 1 kV acceleration voltage (left):
Good surface imaging. 5 kV acceleration voltage (right): Transparent surface due to increased penetration depth
Fig. 23: Comparison of surface information at 1 kV and 15 kV – high atomic number, 1 kV acceleration voltage (left):
Good surface-sensitive imaging. 15 kV acceleration voltage (right): Transparent surface due to increased penetration
depth
Charging Effects
Another reason to use low acceleration voltages is to minimize and compensate the local charg-
ing on the surface of the specimen. If electrons hit a non-conducting or a partially-conducting
specimen, they accumulate on the surfaces and cannot discharge. Generated local charges affect
the electron beam and can significantly reduce the image quality. It is possible to reduce or com-
pensate for this effect by reducing the primary energy of the electrons and reducing the probe
current (aperture size).
Fig. 24: Compensation for charging using lower acceleration voltage. 7 kV acceleration voltage (left): Poor image
quality due to charging effects. 1 kV acceleration voltage (right): No charging effects.
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Instruction Manual ZEISS SIGMA series | en-US | Rev. 7 | 352102-9344-006