Rules of thumb:

Whenever moving the stage, watch it so that the stage or sample do not contact anything else in the chamber. With the beam off, this is done through the viewing port. With the beam on, this can be done using the beam to image the stage. (It is usually easiest to figure out what your movement limits are before bringing up the beam, so you can move within that range without worry, but if there is any question, a very large field of view can be obtained by switching to SACP mode, moving the crossover point (''focus'') to 4mm working distance, and using the resultant image of the stage+chamber to see where things are. This doesn't work very well when your sample is close to the polepiece, however. Something that always works is to shut the beam down, look through the viewport, then start up again.)

Whenever moving the airlock exchange mechanism in or out of the chamber, make sure that the locking lever does not rub against the guide bars, as this will cause galling.

1. Before You begin:
• Check the pressure in the N₂ tank. If the supply pressure is below 300 psi, replace the tank and order another. (If preparing for a longer run, or if you plan on venting the chamber, replace the tank at ~400 psi.)
--> Always be aware of the supply pressure when venting the chamber, and if the supply pressure drops below ~100 psi, stop the venting cycle and replace the tank immediately! If the supply pressure drops too low, the gun isolation valve will open, killing the filament and causing arcing inside the gun.
• Turn on the console power.
• Sign in the logbook.
  
  
2. It is also a good idea to:
• Fill the l N₂ cold trap.
• Check for ground loops. There is a separate ground for the microscope, and if another piece of equipment is attached to the 'scope using a different ground, resolution can go to pot. (For example, this includes something like plugging something into a wall outlet, then attaching a signal cord from a device connected to the 'scope.)
• Make sure all connections are where you want them when operating the 'scope. (Unplug the ethernet line from the CPU before booting if you are going to use the framegrabber card, etc.)
• Check that the 'scope controls are where you want them. Common problems include: left in spot mode; left in SACP mode; BSE detector forming signal; left in beam profile mode...
• Prep your samples, stages, whatever, so they are ready to load.
• Check the glitch book for information on any modifications to or operating peculiarities of the microscope.
  
  
3. Loading the microscope:

If loading through the airlock:

1. Zero the stage.
2. Move the stage to the airlock exchange position.
3. Recheck all the axes.
4. Pump airlock. Wait until airlock pressure below ~5x10^-2 mbar.
5. Open inner airlock door.
6. Remove substage using the substage transfer mechanism.
7. Close inner airlock door.
8. Vent airlock.
9. Load sample onto substage. Make sure that the sample+substage profile fits within the circle of the outer airlock door. If it does not, or if you are unsure, replace the substage within the chamber without the sample and load through the main chamber door.
10. Replace outer airlock door. Pump the airlock (until pressure below ~5x10^-2 mbar.
11. Open inner airlock door.
12. Replace substage onto stage using the substage transfer mechanism.
13. Close inner airlock door.

 

If loading through the main chamber door:

1. Double check N₂ tank supply pressure--if it is below 300 psi, replace the N₂ tank before continuing.
2. Move the stage so that nothing will hit anything else when the chamber door swings open. Unless there is a large sample or stage mounted, the stage zero or airlock exchange positions are usually sufficient.
3. Make sure the chamber locking mechanism is not closed. Vent the chamber.
4. Open chamber door. Load stage or sample. Close chamber door.
5. Make sure the chamber vent cycle is finished before closing the chamber locking mechanism. Close the chamber locking mechanism and pump the chamber.
   
   
4. Starting the 'Scope and initial alignment:

Note: The gun isolation valve can be opened and closed at will to allow/deny the beam to the sample. If (for example) you are working with an uncoated polymer or ceramic, it might be a good idea not to hit your sample with the e^- beam until after you've brought the beam energy to the E₂ beam voltage.

Things like focusing, stigmation, contrast/brightness adjustment, etc. can (and should!) be done as needed throughout this process. Don't just follow the sheets!

1. Check that chamber pressure is below 2x10^-5 mbar, that the sample is positioned conveniently (under the polepiece), and that the view port cover is latched.
2. Check to ensure that the acceleration voltage knob setting is between 5kV-10kV (inclusive) before applying the acceleration voltage. Apply the acceleration voltage.
3. Slowly raise or lower the acceleration voltage to the desired setting. Do not change any faster than 1 click every 3+ seconds (or a slow count of 4, or 5 frames at the S2 scan rate.)
4. Go to beam profile mode.
5. Raise brightness until the screen starts to lighten, then back it off to black.
6. Raise the contrast until a spot is visible.
7. Set the C1+C2 control ("spot size") to position 5, then use C1 to make the spot ~3--5cm across.
8. Using the gun tilt controls, center the spot.
9. Exit beam profile mode; find some convenient feature on your sample to focus/align with. (Specks of dust <=1mm across are good for this, but the initial stages may require something larger.)
10. Turn on the beam wobbler (red button labeled w).
11. Adjust aperture so as to minimize apparent motion of feature as it goes in and out of focus. Back to beam profile mode.
12. Use gun tilt to center spot.
13. Iterate the last 4 steps until no further adjustment is required. These constitute the aperture alignment step.
14. Gun source alignment: (Optional, but usually needed to get maximum probe current and minimum probe size)
1. In beam profile mode, switch C1+C2 knob ("spot size") to position 4.
2. Use gun horizontal controls to re-center the spot.
3. Switch C1+C2 ("spot size") back to position 5.
4. Use gun tilt controls to re-center the spot.
5. Iterate a-d until the the spot is centered in both positions.
6. Check and re-align aperture, if necessary (usually re-alignment is required).
7. If aperture re-alignment was required, then re-align the gun source. Iterate everything until it is all happy.
15. Set your desired C1 and C2 settings.
16. Correct astigmatism.
17. Set eucentric height: (optional, but recommended if tilting is to be done)
1. At 0^o, find an easily identifiable, high contrast feature; center it on the screen at ~500X or so.
2. Tilt the sample, enough to see the feature move, but not enough to lose it completely. (Maybe 10^o or so.)
3. Without touching the x,y controls, use z' to re-center the feature.
4. Re-focus.
5. Tilt back to 0^o. If the previous step was less than 10^o, or if the feature moved significantly, repeat the previous 4 steps.
18. Have at it!!

written fall 2000 (Ben Simkin)

microscope room phone: (517)432-005