3 Product and Functional Description | 3.2 Main Components
ZEISS
3.2.5.6 C2D Detector
Purpose
The cascade current detector (C2D) is a special type of detector that you can use instead of the SE
detector to create a secondary electron image under variable pressure conditions.
Function
On the surface of the specimen, secondary electrons are created. The secondary electrons acceler-
ate towards the C2D detector due to the potential that is applied to the detector electrode.
On their way to the detector, the secondary electrons collide with residual gas molecules (nitro-
gen, air molecules, or water). The collisions ionize the residual gas molecules and create additional
electrons, as well as cations. The additional electrons also accelerate towards the detector and
collide with further gas molecules, which are ionized.
The result is a charge cascade that amplifies the original SE signal by a factor of up to 1000.
The electrons that result from the charge cascade are all collected by the electrode of the C2D de-
tector and the current is further amplified by the detector.
The cations that result from the charge cascade neutralize any negative charge on the specimen
that may have been created by the primary electron beam.
3.2.5.7 Chamber CCD Camera
Purpose
The microscope contains a CCD camera (charge-coupled device camera) inside the specimen
chamber. It is referred to as the chamber CCD camera or chamberscope. It allows you to monitor
the position of the specimen stage and particularly the distance between the objective lens and
the specimen holder.
Position
The chamber CCD camera is located at the backside of the specimen chamber.
1
2
Fig. 38: Sample image from chamber
camera.
1
Objective lens
2
Specimen holder
52
Instruction Manual ZEISS SIGMA series | en-US | Rev. 7 | 352102-9344-006