1 Tescan MIRA3 SEM w/ EDAX EDS and EBSD Nicholas G. Rudawski [email protected](805) 252-4916 DISCLAIMER: the intent of this instrument is for performing EDS and/or EBSD and this operating procedure is written accordingly; currently, it is not suitable for high-resolution work due to environmental instabilities, which cause image distortions at high magnifications. If you need to perform high-resolution imaging, ask about appropriate alternative instruments. 1. Sample preparation/mounting 1.1. Specimens should be conductive. If your specimen is not conductive, it can be given a very thin C coat to help avoid charging. If performing EBSD, specimens should also be flat with a damage-free smooth surface. 1.2. Specimens can be mounted on any type of pin stub as long as the pin height = 8 mm and the pin diameter = 3.2 mm. 1.3. Mounting of specimens to stubs should be done using conductive tape; do not use any type of paint to mount a specimen to a stub as this can increase the risk of contamination. 2. Specimen loading 2.1. Open the MIRA3 control software and then log in.
Transcript
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Tescan MIRA3 SEM w/ EDAX EDS and EBSD Nicholas G. Rudawski [email protected] (805) 252-4916 DISCLAIMER: the intent of this instrument is for performing EDS and/or EBSD and this operating procedure is written accordingly; currently, it is not suitable for high-resolution work due to environmental instabilities, which cause image distortions at high magnifications. If you need to perform high-resolution imaging, ask about appropriate alternative instruments. 1. Sample preparation/mounting
1.1. Specimens should be conductive. If your specimen is not conductive, it can
be given a very thin C coat to help avoid charging. If performing EBSD, specimens should also be flat with a damage-free smooth surface.
1.2. Specimens can be mounted on any type of pin stub as long as the pin height = 8 mm and the pin diameter = 3.2 mm.
1.3. Mounting of specimens to stubs should be done using conductive tape; do
not use any type of paint to mount a specimen to a stub as this can increase the risk of contamination.
2. Specimen loading
2.1. Open the MIRA3 control software and then log in.
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2.2. In the “Vacuum” panel, select “VENT” to vent the chamber; the panel will indicated when venting is finished.
2.3. Open the chamber door and load your specimen(s) into the carousel. If you intend on performing any EBSD, only 1 specimen stub may be loaded at a time and must be inserted in the “7” position. Otherwise, there are no restrictions on the number of stubs and/or stub positions. Under no circumstances are specimens to be directly mounted on the carousel.
2.4. Close the chamber door and select “PUMP” to evacuate the chamber; the vacuum panel will indicate “Vacuum ready” when the vacuum level is satisfactory.
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3. Turning on the beam
3.1. Select “BEAM ON” in the “Electron Beam” panel to turn on the beam. The instrument is preconfigured for operation at 1, 5, 10, and 20 kV; if operation at a voltage different from that indicated is needed, this can be adjusted via the pull-down menu in the same panel.
3.2. The SEM scanning window will come up after the beam is turned on; the bottom of the window indicates several instrument parameters while the column of icons to the right are used to adjust the image and align the beam. Middle mouse clicking on a point in the image will move the stage to center that point in the image. Double left clicking on the image will reduce the scan area (shown at right).
3.3. To adjust probe current, select (beam intensity) from the column of icons and adjust using the “Pad” panel. Higher beam intensity will result in more probe current, but at the expense of a larger beam. Generally speaking, it is usually best to use high beam intensity for performing EDS and/or EBSD to maximize signal.
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3.4. To adjust the magnification of the image, select from the column of icons and then use the trackball; the magnification will update on the bottom of the scanning window. Alternatively, you can also directly input a desired magnification into the “Pad” panel.
4. Setting the WD
4.1. If only EDS is to be performed, then the optimal WD is 15 mm. If EBSD or TEAM is to be performed, the optimal WD is 20 mm. With the stage still
in the bottom position, focus the image using . Then incrementally
lower the WD in the “Stage Control” panel via . Observe the stage movement via “Chamber View”; be prepared to stop the stage movement using “Stop” if any collision appears imminent.
4.2. Once the stage movement is complete, adjust the focus again using ; the updated WD should be quite close to the value you just input. If not, adjust again using the “Stage Control” panel and refocus.
5. Beam alignment
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5.1. Find an area of interest on the specimen surface and center it in the scanning
window; then increase the magnification to ~5000 X. Select
(beam centering) from the column of icons; select in the “Manual Centering Wizard” to turn on wobbling. Use the trackball to minimize shifting of the image during wobbling. It usually helps to use a reduced scan area and a region with distinct features when doing this.
5.2. Select (stigmation) from the column of icons. Use the trackball to adjust the image so it is sharp. By holding down F11 or F12, the trackball will only adjust the X or Y stigmators. Again, it usually helps to do this using a reduced scan area with distinct features.
5.3. Note that alignment depends strongly on three factors: beam voltage,
beam intensity, and WD; if any of these parameters is changed, the alignment will need to be readjusted. Additionally, if magnifications higher than ~5000X are to be used, alignment should probably be performed again at the higher magnification.
6. Detector selection
6.1. In the “SEM Detectors & Mixer” panel, SE and BSE detectors can be selected
from the “Channel A” pull-down menu. Since the BSE signal will decrease rapidly at high stage tilts, the SE detector should be selected If EBSD or combined EDS/EBSD is to be performed.
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6.2. If the BSE detector is selected, it must be manually inserted as shown below in “Chamber View”.
7. Setting specimen tilt (if performing EBSD or TEAM)
7.1. Make sure the region of interest is centered in the scanning window and
make sure is checked in the “Stage Control” panel (this keeps the area of interest at the same WD after tilting). Ideally, the region of interest should be far away from any specimen edges.
7.2. Using the “Stage Control” panel, tilt the stage to –70° (negative 70°); after tilting, the “Chamber View” should look similar to that indicated below.
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7.3. OPTIONAL: if performing only EDS, specimen tilt doesn’t need to be adjusted for this to be effective. However, as the tilt angle decreases from 0 to –35° (negative 35°), the takeoff angle will decrease to 0°, which will reduce the path the generated X-rays must travel through the specimen to reach the detector (assuming a flat specimen).
7.4. OPTIONAL: in the “Geometric Transformations” panel, enter in the specimen
tilt in ; this ensures the focus is uniform across the specimen surface; again, this assumes a flat specimen.
7.5. Set the magnification to the desired value for performing your analysis
and focus the image . Any magnification can be used, but if performing EBSD, the magnification should be set so that if the magnification is reduced by 50%, no specimen edges are present in the image.
8. Image acquisition (as needed)
8.1. Select (acquire image) to acquire a slow scan still image. The default image size of 768 X 768 with an acquisition time of 16 s is usually sufficient. If different acquisition parameters are desired, select “SEM” along the top menu bar and then “Image Parameters” and adjust accordingly.
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Staring TEAM
8.2. Open the TEAM software.
8.3. The following box will pop up as the hardware is initialized (listen for the motor on the EBSD camera to turn on).
8.4. Log in to the TEAM software; select “EDS” if only performing EDS, “EBSD” if only performing EBSD and “TEAM” if performing simultaneous EDS and EBSD. Only one option can be selected at a time.
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9. Before performing EDS (for performing EDS or TEAM)
9.1. The EDS detector uses a Peltier cooler, which is not actively turned on unless the detector is actively in use. Select the “Advanced Properties” tab on the right and then select “EDS Detectors”.
9.2. Select “Octane Pro” and then “Det 1 – Detector Status”. Select “Cooling Off” to turn on the cooling; the button will turn green and indicate “Cooling On” when cooling is complete.
9.3. “Chamber View” must be turned off prior to performing EDS or the system will
not function properly. Select from the “Main Toolbar” panel to turn off “Chamber View”, if necessary.
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10. Performing EDS in “Spectrum Only” mode
10.1. “Spectrum Only” mode is used to provide a general qualitative survey of the elements present in the area being scanned; it is not used for mapping and
the resulting data cannot be saved. Select along the top
row of buttons and then to acquire a spectrum. 11. Performing EDS in “Point Analysis” mode
11.1. “Point Analysis” mode is used to collect spectra from specific points or
defined regions. Select from the top row of buttons and
then select to acquire an SEM image.
11.2. Once the image is acquired, desired points for analysis can be selected by clicking on the image. Clicking and dragging on the image can also define finite-sized regions for analysis. Once the points and/or regions are defined,
select to start collecting the spectra.
12. Performing EDS in “Mapping” mode
12.1. “Mapping” mode is used to map the EDS signal as a function of two
dimensions. Select from the top row of buttons and then
to acquire an SEM image.
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12.2. The default setting is to collect a map over the whole image (shown at left); to adjust this area, click and drag the corners of the defining box and move it as
desired (right). Select to start collecting the map.
12.3. A phase map that updates in real time will begin to appear. In a phase map, all regions of identical composition will appear as the same color.
12.4. Alternatively, an element map can be displayed by selecting “E2P” from the wheel on the lower left corner (also indicates total time required for mapping).
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12.5. The map will run for a specific number of sweeps as determined by the software such that a sufficient signal can be generated. However, you can
also stop mapping at any time by selecting .
12.6. Select to save the map. 13. Performing EDS in “Line Scan” mode
13.1. “Line Scan” mode is used to map the EDS signal as a function of one
dimension. Select along the top row of buttons and then
to acquire an SEM image.
13.2. Reposition the line in the acquired SEM image as desired; select
to start collecting the line scan. The line scan will update in real time and run for a specific number of sweeps as determined by the software such that a sufficient signal is generated.
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13.3. Select to save the line scan.
14. Inserting the EBSD camera (for performing EBSD or TEAM)
14.1. The area of interest must be at WD = 20 mm with a stage tilt of –70° (negative 70°) prior to insertion of the EBSD camera. Insertion of the camera under any other conditions may cause a collision of the camera with the specimen or stage.
14.2. Select the “Advanced Properties” tab and then “Camera Position”. Select “Insert” to insert the camera. Be sure to monitor the insertion process in the “Chamber View” panel and be prepared to select “Stop” if any collision appears imminent. The “Chamber View” panel should look similar to below after insertion is complete.
15. EBSD camera optimization
15.1. “Chamber View” must be turned off prior to camera optimization and
performing EBSD or the system will not function properly. Select from the “Main Toolbar” panel to turn off “Chamber View”, if necessary.
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15.2. Select “EBSD Camera”; make sure “Binning” is set to “4x4” ,
“Optimize” is set to “Manual” , and “Image Processing” is set
to “None”
15.3. Adjust “Gain” and “Exposure” so the max counts reads 0.8 – 0.9.
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15.4. Next to “Capture Bkg”, select “Smart” to capture the background; when finished, set “Image Processing” to “Standard”
. 16. Performing EBSD in “Survey” mode
16.1. “Survey” mode allows the user to take control of the electron beam to obtain a
real time EBSD pattern from any point on the SEM image; it cannot be used
to record any data or perform any mapping. Select from
the top row of buttons and then to acquire an SEM image.
16.2. Select and then to take control of the beam. The small cursor (green circle) on the image can then be moved around the SEM image and a live EBSD pattern from the cursor position will
be shown under .
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17. Performing EBSD in “Point Analysis” mode
17.1. “Point Analysis” mode is used to collect EBSD patterns from individual points.
Select from the top row of buttons and then
to acquire an SEM image.
17.2. Hover over the button to expand the options. Select
and select the prospective phases that you believe are present in the specimen. The system cannot index the patterns unless at least one phase is specified.
17.3. The system can be set up to analyze single or multiple points on the imaged
area by hovering over and changing
accordingly. Click on the image to select the point(s) for
analysis and select to start acquiring the data. An indexed EBSD pattern (based on the phase(s) you input) from each point will pop up after analysis of each point is complete.
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18. Performing EBSD in “Mapping” mode
18.1. “Mapping” mode is used to collect a two-dimensional crystal orientation map
(COM). Select from the top row of buttons and then
to acquire an SEM image. 18.2. If not done previously in “Point Analysis” mode, hover over the
button to expand the options, select , and select the prospective phases you believe are present. A COM cannot be produced unless at least one phase is selected.
18.3. Similarly to EDS mapping, the default setting is to collect a map over the
whole image (shown at left); to adjust this area, click and drag the corners of
the defining box and move it as desired (right). Select to start collecting the map.
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18.4. A COM will be generated as the beam is scanned from top to bottom. In a COM, regions of similar color will have similar crystallographic orientation as indicated by the color-coded inverse pole figure.
18.5. Select when the map is complete to save the map.
19. Performing TEAM
19.1. TEAM is used for the simultaneous collection of EDS an EBSD maps. For performing TEAM, the area of interest must be at WD = 20 mm with a stage tilt of –70° (negative 70°). As described previously, make sure the EDS detector is cooled, the EBSD camera is inserted, “Chamber View” is turned off, and the EBSD camera properly optimized.
19.2. Select to acquire an SEM image; the size/position of the analysis area can again be adjusted similarly to performing EDS and EBSD
mapping. Hover over the button to expand the
options and select ; if not done previously,
select , and select the prospective phases you believe are present. TEAM cannot be performed unless at least one phase is selected.
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19.3. Select to start collecting the maps. A single sweep of the beam from top to bottom on the image will be performed (similar to EBSD mapping) rather than several sweeps. The software will automatically determine the time needed to generate sufficient EDS and EBSD signals. The map can be changed between EDS and IPF (COM) via the wheel in the lower left corner.
19.4. Select when the map is complete to save the map.
20. Finishing the session
20.1. If EDS was performed, the detector cooling must be turned off prior to closing TEAM; do not vent the chamber with the detector in a cooled state. From the “Advanced Properties” tab, select “EDS Detectors”, then “Octane Pro”, then “Det 1 – Detector Status” and turn off cooling (the “Ok to Vent” light will turn green)
20.2. If EBSD was performed, retract the camera by going to the “Advanced Properties” tab, selecting “Camera Position”, and then selecting “Retract”;
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verify retraction of the camera using “Chamber View”; do not attempt any stage tilting with the camera inserted.
20.3. Close the TEAM software.
20.4. In the “Electron Beam” panel, select “BEAM ON” to turn off the beam.
20.5. Retract the BSE detector (if necessary).
20.6. In the “Stage Control” panel, select “Calibrate” to calibrate the stage and return it to the home position; “Chamber View” should look similar to shown below after homing.
20.7. In the “Vacuum” panel, select “VENT” to start venting the chamber
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20.8. When venting is complete, remove your specimens, then close the chamber
door, and select “PUMP” to return the chamber to vacuum.
20.9. Exit the MiraTC software; when the system asks to go to “STANDBY” mode, select “No” (this ensures the column is still actively being pumped).
