FEI Quanta FEG 250, User'S Operation Manual

Page: 163 / 228

System Options: Optional Detectors
9-15
DIRECTIONAL BACKSCATTERED DETECTOR –
CONCENTRIC BACKSCATTERED DETECTOR
(CBS)
The CBS uses concentric segmentation of the detector diode to
distinguish between BS electrons scattered close to the beam axis –
inner segment (preferentially compositional contrast) and electrons
scattered far from the beam axis – outer segment (more topography
signal). Z-contrast mode provides signal collection from all detector
segments.
FIGURE 9-9 DIRECTIONAL BACKSCATTERED DETECTOR
Detector Settings
Select the CBS from the Detector Settings module / Detector list
box. Choose the required Mode from the list box, where there are
several preset segment combinations.
Distribution of electrons collected by detector segments changes with
setting of working distance, lens mode and Beam Deceleration mode.
The Custom mode is used to define the segments to be used for
detecting. Right-click over particular segment and select Add (yellow
color) / Substract (blue color) to add / substract the segment signal or
Turn Off (grey color) to switch the segment off.
It is also possible to set different azimuthal segments in particular
quads and thereafter to use the
Enhanced Image module / Mix 3 or
Mix 4 tab to mix color coded signals to create color images (see
Chapter 5).
Inserting and Retracting CBS Detector
Follow the instructions for the vCD detector (see above).