ZEISS
3 Product and Functional Description | 3.2 Main Components
The efficiency of the InLens SE detector is mainly determined by the electric field of the electro-
static lens, which decreases exponentially with the distance.
Thus, the working distance (WD) is one of the most important factors affecting the signal-to-noise
ratio of the InLens SE detector.
As the tilt angle of the specimen surface affects the emission angle of the electrons, you should
avoid strong specimen tilting.
Info
The InLens SE detector can be used up to an acceleration voltage of 20 kV. At higher accelera-
tion voltages, the beam booster and thus the field of the electrostatic lens are switched off.
Without the field of the electrostatic lens, which attracts the secondary electrons, the effi-
ciency of the InLens SE detector is reduced.
3.2.5.3.1 Detector Efficiency and Working Distance
Working Distance
The efficiency of the InLens SE detector mainly depends on the electric field of the electrostatic
lens, which decreases exponentially with the distance. Thus, the working distance (WD) is one of
the most important factors tat affects the signal-to-noise ratio and therefore the efficiency of the
InLens SE detector.
For different imaging applications, the working distance needs to be selected depending on the
geometry of the specimen and depending on the acceleration voltage.
§
At acceleration voltages in the range of 1 kV to 5 kV, the working distance should be as low
as possible.
§
At very low interaction energies in the range of 100 V to 1 kV, the working distance should
not be greater than 4 mm. Often it is reasonable to set the working distance to 2 mm. This al-
lows the SE1 electrons to be efficiently attracted by the 8 kV voltage from the beam booster
towards the InLens SE detector.
Tilted Specimen
The signal from the InLens SE detector can also be affected by the direction of the specimen sur-
face. Large angles of specimen tilt affect the emission angle of the secondary electrons, and fewer
electrons are emitted in the direction of the final lens. This reduces the detection efficiency.
Large angles of specimen tilt also prevent the use of very short working distances.
It is therefore recommended to avoid large angles of tilt when using the InLens SE detector.
Fig. 17: Changed
distribution when using a tilted specimen
Instruction Manual ZEISS SIGMA series | en-US | Rev. 7 | 352102-9344-006
39
