Software control: Microscope Control
3-31
C O N F I D E N T I A L
– limited rights
User Manual
Revision A
Feb 2018
2. Column module
contains the controls for setting the electron beam conditions:
Beam On button
switches the accelerating voltage on (orange background) / off
(gray button). If the source is not started (empty progress bar),
this button starts the electron source first (green progress bar).
Beam current / Spot size adjuster
enables adjusting the electron
Beam
current
/
Spot size
with adjustable accuracy (see the
Preferences
/
General
section). The actual value (from the factory preset list) is shown in the adjuster text area, toolbar and imaging
databar (if selected). Only values applicable for actual imaging conditions are shown.
Note
The Spot size influences both the focused electron beam area and the Beam Current: the smaller the Spot size, the lower
the Beam Current.
High voltage adjuster
enables adjusting the overall electron beam accelerating voltage (from 200 V to 30 kV) either continuously or
using the pre-set values (see the
Preferences
/
Presets
section). The actual High Voltage value is shown in the
adjuster text area, toolbar and imaging databar (if selected).
3. Magnification module
The adjuster offers a variety of ways to control imaging
magnification. The magnification range changes dynamically
according to the working distance and can also be controlled with
the use of other tools.
Magnification control
•
Clicking on the
end right
/
left arrow
increases / decreases magnification by
5%
.
•
Clicking between
the right
/
left end arrow
and the
button
increases / decreases magnification by
20%
.
4. Compound Lens Filter module
The compound lens filter uses the advantages of the compound
final lens, that combines the magnetic final lens inside the pole
piece, the immersion magnetic lens and the electrostatic lens
formed by the potential at the T1 detector. Main function of the
compound final lens is to focus the primary electron beam to the sample. However, independent control of these
three lenses together with continuous control of the immersion lens enables to filter back-scattered (BS) electrons
reaching the T1 detector. The compound lens filter behaves as a chromatic sensitive lens, which focuses the low
energy BS electrons into the aperture of the annular T1 detector. The high energy BS electrons are less sensitive to
the magnetic field and reach the T1 detector. Secondary electrons also pass through the aperture in the T1 and are
collected further in the column by the T2 and T3 detectors.
The compound lens filter is available in the
OptiPlan
and
Immersion
Use cases with or without the Beam
Deceleration. The main goal of the compound lens filter is the enhancement of the compositional contrast of the
sample. Besides that, it can be successfully used for imaging of insulating samples without charging - secondary
and low energy BS electrons which are most sensitive to charge are filtered out from the T1.
When clicking the
On
button the
Threshold Energy
slider becomes active to define threshold energy of BS electrons
– energies lower than threshold are filtered out and don't contribute to the T1 signal, energies higher than threshold
contribute to the T1 signal. The filter functionality is also visible within the image databar via the
Treshold
item and
via the
Detector type
item – T1.
The compound lens filter works ideally at low landing energies – 5 keV and less. Typical imaging conditions are:
WD = 4 mm / Landing Energy = 1 keV / Beam current = 100 pA / Threshold Energy = 500 eV
Start imaging with the T1 detector with the OptiPlan Use case, activate the filter and gradually increase the
Threshold Energy
– T1 imaging gets dark as the lower energy backscattered electrons are filtered out of the detector
surface. The filter can be applied also with the
Immersion
Use case; in this case the starting
Threshold Energy
is
maximal.
Caution!
Magnetic samples must not be used (see
Sample exchange
above), otherwise it can be torn away from the holder and
stuck to the final lens pole.
