Acquiring a SIMS Alignment
To find out more about SIMS alignments, click here .
SIMS alignment tips:
When you are acquiring a SIMS alignment, you may change the Acceleration
voltage, Retard voltage, Ion voltage, and Focus voltage settings in real time. This
lets you see the effect that changes to these settings have on the data that
is acquired.
If your sample is non-conductive, charging may occur. This will appear as
unstable data and low count rates in the SIMS alignment. You can use your
electron gun to provide a source of electrons that will neutralize the positive
charge from the ion gun. Adjust the electron gun condenser and magnification until
the charging dissipates. Typically, when the sample charging is eliminated,
the data will “pop” back into the correct count rate and AMU position.
The more ion beam current that you use, the better the SIMS signal will be.
However, you will also sputter your sample at a higher rate.
For depth profiles, you will want to use a small beam size (condenser set to
5.00 on the 11-065) and a raster size of at least 1.5 X 1.5. Gating should be
turned on and should be set to 70% or more. This will ensure that the signal
that the SIMS optics sees is coming only from the center of the crater.
Note: For UTI SIMS systems, analyzer, gating, and polarity functions must be
controlled manually, so you need to adjust your procedure for acquiring data
accordingly. Note, however, that AugerScan will still record and display the
values placed in these fields so you can use them for bookkeeping.
For SIMS alignments, you’ll define two sets of settings in the Alignment Settings dialog box: one for
positive SIMS, one for negative SIMS. The Analyzer and Gating settings are used
as the default settings for all SIMS acquisition types.
- Perform an AES elastic peak alignment to ensure that the sample is at the focal point of the analyzer.
- Lower the SIMS optics nose to approximately ¼” from the sample. This is typically the correct distance at which the SIMS
optics obtain the most signal. Important: Remember to back out the SIMS nose when you are done acquiring SIMS data.
Otherwise, when you move your stage to another sample you may hit the SIMS nose
and possibly short out the focus lens.
- Set up your ion gun to normal operating conditions, including setting the
raster to SIMS.
- Set the technique to SIMS.
- Select the New Alignment command from the Acquisition menu (or click on the
appropriate toolbar button).
- Enter the values in the Alignment Settings dialog box. Use the What’s This Help to determine the appropriate values for each field.
- Acquire the SIMS alignment. SIMS peak(s) will be displayed.
- Mechanically adjust the SIMS optics for the highest count rate by turning the
large thumb screws on the 06-600 optics. Adjust the opposing screws
simultaneously (one axis at a time).
- While you are acquiring the alignment, the Real Time Alignment Settings dialog
is displayed to let you change the focus voltage, ion energy, and mass in real
time.
- Adjust the ion gun focus for maximum signal.
- You do not have to restart the alignment to center the peak mass, simply type
a new value for Peak Mass in the Real Time Alignment Settings dialog and center
mass will change on the next sweep.
- Repeat steps 8 through 11 until the signal is maximized.
You can now acquire SIMS data.
SIMS Acqusition Procedures