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Operation of the S-2460N SEM This primer attempts to cover the procedures to follow for using the Hitachi SEM from the time you walk in the room until you finish for the day. Any and all comments or corrections or complements or complaints are welcome and will be used to make this a better tool.
Fig.1. Hitachi Scanning Electron Microscope Model S-2460N A -
Power Switch E - Digital Video Processor Figure 1 shows the user interface of the Hitachi S-2460N. In addition to this unit, there are three vacuum pumps that run 24-7-52 (24 hours and day-7 days a week-52 weeks a year) in the back room. Normally, when you attempt to use the SEM, the display power will be off (A), the column and sample stage will be under a high vacuum (B), and the vacuum pumps should be running (not shown). PROCEDURES 1. Enter your name, date, and the starting beam time into the record book. 2. Toggle ON the Display Power by your left knee (bottom left Fig.1 & Fig. 2). The EVAC POWER on the left must always be on as it controls the vacuum pumps which stay on all the time. In case of a power outage the SEM shuts itself down and powers up the vacuum pumps when the power comes back on.
Figure 3. The sample stage and column. A
- Stage X Control (-40 to 40 mm) 3. Make sure the stage (Fig. 3) is at the proper exchange settings. Especially knob E where the white "tabs" must be lined up!!! This ensures that the specimen stub is directly beneath the pole piece (where the beam comes out) AND it also ensures the sample is low enough not to hit the detector. 4. Since the vacuum is always on, we must allow air into the column in order to remove the sample holder. Press the AIR button (Fig. 4) and the vacuum will be released. Wait until the door can be opened (about 2 minutes).
Figure 4. Evacuating System Control Panel. The AIR/EVAC button is used to start/end the vacuum in the chamber. In the SEM mode, the meter should read ~10 Pa and NSEM mode ~20 Pa. The lights (HIGH/SE/BSE) will indicate when the vacuum is sufficient to saturate the filament. 5. At this point you should turn on the IR camera (Fig. 5, F in Fig. 3) to view the inside of the chamber and check out the status of the stub holder and whether samples are in the scope. Press the white button below. Each click will switch from chamber view to SEM mode.
6. If chamber looks clear, carefully open the STAGE DOOR and place a stub holder (Fig. 6) in the stage mount and check height of specimen so that it clears the pole piece and back scatter detector as the door is closed. If you set the stage height correctly in STEP 3, there should be no problem. ***Use the metal height plate to be sure***
Figure 6. The five sample holder we use quite a bit. Allows for five samples to be viewed. Knob C – the stage R Control (360 degrees) in Figure 3 rotates the sample under the beam. BE SURE THE FILAMENT KNOB IS SET TO ZERO PRIOR TO NEXT STEP !!!
Figure 7. The filament potentiometer. It is located under the "Secret Panel". Knob at the left is used to turn up the filament current to a saturated (optimum) level. The level is measured with the emission current meter and the raster image which comes up on the Raw Image CRT (Fig. 1). It must be at zero when you start. Generally if you set it to 1 o’clock you will be very close to the optimum (saturated) current level. 7. Be sure white chamber scope is set to SEM mode so you can see the screen. Use F2 on keyboard to choose your mode – SE/NSEM (Fig. 8). If you chose NSEM you must insert the Robinson detector into the chamber. Carefully release the pin and the vacuum will pull in the detector quickly!!! If using the SE mode, the Robinson detector should be out. It is tough but you can pull it out against the vacuum. Then use F8 to set the beam current to the range you want.
Figure 8. Keyboard. "F" keys across the top control functions on the scope. F1
after a photo, click F1 to reset image back to "live"
video. 8. Slide the stage door closed, press EVAC button. Wait for vacuum lights to change from low to high and red HIGH Kv lamp to burn steadily (2-3 minutes). The SE or NSEM light (Fig. 4) will glow also. When the READY LIGHT stops blinking, choose desired Accelerating Voltage by pressing the "up/down" buttons (Fig. 9) then turn on ACC. Voltage by pressing "ON/OFF" button.
Figure 9. The ready light indicates conditions are such that you can begin to saturate the filament (push the ON/OFF switch). One must set the accelerating voltage (UP/DOWN) prior to saturating the filament. As you turn up the current to the filament, a color bar will form on the emission current meter . 10. Saturate the filament using the static waveform. Push waveform button twice (Fig. 10, upper right corner) slowly turn filament knob clockwise (Fig. 7 UNDER THE SECRET COMPARTMENT) until the waveform reaches its highest level (post HV button must be turned on for SE mode). Once set, you can view the sample image by pressing one of the span speed buttons (Fig. 10, top row). We usually use the computer enhanced "live" mode (leftmost button). Click it twice to get computer smoothed image.
Figure 10. Upper panel shows the scanning speed buttons on left. The open box is "real-time" video [The computer takes the scanned image and makes it appear as a steady "TV" image]. The middle ones: you see the scan across the image, last one: this makes a small box on screen to help with focus. Waveform buttons in upper right corner are used to obtain waveform image on the Raw Image CRT (Fig. 1) so you can saturate the filament. Lower panel right shows the focus controls. THEY ARE MISLABELED: The bottom two buttons allow you to coarse focus (up and down) and the knob is the fine focus. 11. Set the brightness and contrast to AUTO and then Press ABC (Fig. 11). This will automatically (or at least try to) set these parameters. You might need to go to manual.
Figure 11. Upper - brightness and contrast knobs. In the AUTO mode pressing the ABC will allow the computer to best determine the best settings (sometimes it gets worse than your settings). In manual setting you spin the knobs with your finger to adjust the image to your liking. Lower – Stigmator knobs fix astigmatism. At high magnification and in the SE mode, the image may be "out of round" so you need to adjust it. AUTO works OK but generally manual settings gives a better image. 12. Set desired working distance with knob E (Fig. 3). Working distance can be monitored by pressing the down arrows focus button once and it will read out at the magnification LED. Minimum W.D. : BSE 10mm with the Robinson detector in 13. Focus image (Fig. 10). One can set the focus to AUTO and press either button and the computer will try to focus on your sample OR one can focus manually with coarse buttons and fine knob. Increase/decrease the magnification with the magnification buttons on far right of Panel F (see Fig. 12. You will do this a lot!!! 14. Move the sample using the controls on the STAGE (Fig 3) or for small small movement, the IMAGE SHIFT (Fig. 9). At his point you will likely "PLAY" with the brightness/contrast/focus/magnification, etc…to get the best picture. This is where the ART of SEM comes in. Bottom line: Focus your sample at the highest mag you can and then capture image at lower mag……. Finally you have the perfect image !!!! 15. Shoot a picture. Pick a scan speed (1/2/3) in the PHOTO system (Fig. 12) to view the best image of your sample. Once you like the image, capture the image by pressing the PHOTO button. A fine image will slowly appear as the computer collects lots-o-data which produces a high res image.
Figure 12. The upper panel shows the photo system. After getting the best image possible in the "real-time" mode one then sets the time of scanning with the speed switch and then depresses the PHOTO button which starts the very slow scanning needed to develop the best still image. The lower panel shows the magnification buttons. Use up and down zoom in and out……. 16. Print a picture with the VIDEO PROCESSOR.
A
- Power Switch Fig. 13. Digital Video Processor. Move switch D down to print position when ready to print. Press C or use remote print switch to print the picture after it is captured using the PHOTO button above the keyboard (Figure 9). This is a digital printer so the "film" (paper) is NOT ruined when exposed to light. 17. Once you have printed the picture, press F1 to unfreeze the image so you can look around some more, take some pictures, whatever……. To exchange specimens:
To take a break: Turn down the filament, leave everything else as is…turn up filament when you come back. To end your session:
Figure 14. Single sample stud holder along with black conductive stub two-sided tape. Simply peel the circles off the paper and apply to the stub. When your sample is ready, peel off the upper black cover and apply sample to the stub. Process the sample and view. Photographing Condition Setting
1: 40 sec/frame
Direct photo procedure
Notes: 1. IN the course of recording, all switches except for ACC VOLTAGE ON/OFF will not function. 4. Once scan has covered two thirds of the screen after start of recording, its cancellation cannot be accepted.
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Support
for equipment was provided by the National Science Foundation,
Division of Undergraduate Education (UNDERGRADUATE INSTRUMENTATION
AND LAB IMPROVEMENT GRANT #9451930) to The Department of Biology,
Wartburg College.
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Fig. 5. Chamberscope IR camera located above Keyboard G.
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Blvd. - Waverly, IA 50677 - (800) 772-2085