SEM Quick Start
Revision No.2
May 2014
Page 14 of 16
switching to the TV detector channel (Section 1.3.1), open the
Stage
Points List
tool and double click the stage point labelled
$STEM_SAFE_ZONE
. The stage will move to an area in the chamber
that is safe for detector arm insertion.
Once the stage is in the safe zone, the STEM detector arm can be
inserted using the
STEM Control
tool. To open this tool, open the
docking sidebar and double-click the tool labelled
STEM Control
. The
arm can now be inserted by clicking the button labelled
STEM -> IN
. The
STEM stage can now be moved into position using either the
Stage
Navigation
tool (Section 1.3.3), or the
Stage Points List
tool.
Finally, the STEM detector can be displayed in the viewing
window by selecting the STEM channel in the
Detectors
tab (Section
1.3.1). It is important to note that since the STEM detector is detecting
electrons that are transmitted through the sample, better results are often
observed at higher accelerating voltages.
1.4.2
Imaging Modes
The STEM detector is composed of both dark-field and bright-field
components which are assigned labels called quadrants. The bright-field
component of the detector is located directly in line with the electron beam
and is responsible for detecting electrons that are either completely
transmitted, or weakly deflected by the sample. This field is labelled Q1
(for quadrant 1). There are two dark-field components that form a
perimeter around the bright-field component which are responsible for
detecting electrons that are scattered to a certain degree with respect to the
electron beam. These components are labelled Q2 and Q3.
Different quadrants, and thus different fields, can be set to three
different modes independently from one another (with the modes being
3
normal, inverted, and off). The sum of these permutations yield 27 (i.e. 3 )
distinct field modes, with several modes often being visually
indistinguishable from one another. Experimentation with different
combinations of field modes is encouraged given that different
combinations usually lead to very different images. Changing the modes
STEM detector quadrants is accomplished with the
STEM Control
tool
found in the docking sidebar (Section 1.4.1).