Tuesday, December 11, 2012

Transfer rod to Prep Manipulator


  1. Set manipulator position:
    1. Top (vertical motion) micrometer: 11.05 mm
    2. Z (horizontal insertion) screw: 105 mm (scale ends at 100, engraved on one support rod) There is also a red sharpie mark on the support rods
    3. Rotary motion 300 degrees (red mark on top of support)
    4. These positions are approximate, adjustment may be required to engage sample.
  2. To transfer the sample to the stage: Slide the transfer rod forward until the long pins engage the rectangular hole in the side of the manipulator stage. 
    1. If there is any resistance, adjust the height, insertion, rotation until the motion is easy.
  3. The sample plate should slide into the dock on the manipulator.
    1. If there is any resistance, adjust the height, insertion, rotation until the motion is easy.
    2. Insert the sample plate fully, until the metal part of the transfer rod touches the dock, then rotate the transfer rod handle to open the jaws.
    3. Now retract the transfer rod, leaving the sample plate on the manipulator dock.

Sample Introduction and Airlock

Here is the procedure to transfer samples from air to the long transfer rod in the prep chamber. From there samples can be moved either to the prep manipulator or to the parking carousel in the analysis chamber.

  1. Start the "Prep" turbo pump, if it is not running already (see Turbo Pumps how to for details)
    1. Start PV TurboViewer software on Auger-pxi. 
      1. click connection wizard, set find multiple devices to 3 and click button, software should find three pumps. Drag window taller and click arrange. Click on speed display to toggle between rpm/Hz/% for speed. 
      2. pump 001 is nano, 002 is prep/sample intro, 003 is ion gun
    2. Prep turbo should reach 100% within a minute or two, power < 20 Watts, foreline pressue (push down arrow on ion gauge controller to see fore pressure) < 0.1 mBar.
  2. Vent airlock
    1. Close airlock pumping valve (large black plastic handle) and bypass pumping (small green valve handle). 
    2. Open N2 vent supply valve (small green valve below table)
    3. Turn off air lock ion gauge if on.
    4. Open airlock vent valve (below airlock). You should hear gas flowing. Airlock pirani gauge should read about 780 torr (slightly above atmosphere).
    5. Open air lock door. Do not let glass door fall open. 
  3. Load samples
    1. Up to 3 samples can be loaded. Use gloves and clean sample plates.
    2. Normally sample surface is to the right as you face airlock. 
    3. VT double-plate holders must face right
    4. If flat sample plates will be heated on prep manipulator, load upside down (facing left) so sample surface faces heater after transfer.
  4. Pump airlock
    1. Close N2 vent valve

Gun Arc at 30 kV


  • On Thursday 12/6/12 low-level radiation group requested SEM be operated at max voltage and current.
  • I set the beam voltage to 30 kV. The system had not be operated above 10 kV for some time. Just as the voltage reached 30 kV I heard the "snap" of an arc. The gun went off, there were no error messages.
  • I had trouble restarting the gun, I got "EHT Vac not ready" (see previous notes). Raising pressure, restarting PC no help. After putting electronics to standby and back to run, EHT Vac was good, gun started.
  • Emission current almost doubled, from ~ 107 uA to ~ 170 uA. I was afraid filament had been damaged during arc, however the same feature was centered in the field of view, and it was possible to get similar image quality. 
  • Robert Ribay from Zeiss happened to be working on the Supra, he looked at the image quality, did a quick alignment, and did not see serious problems.

Friday, December 7, 2012

pBN VT heater test

Test of VT pBN heater plate


  • Remove old sample, re-attach top plate, verify thickness of assembly and heater brushes
    • 7.6 mm total, 2.9-3.0 from top of brush to bottom of top plate
    • 17 ohm left brush (seen from handle) to ground. Right brush grounded.
  • Sample Heating Selector to "Direct Current"
    • Initial 1.6 V at 0.16 A (10 ohm), gentle pressure rise, manipulator TC increases linearly with time 22 to 28 C over 6 minutes, 0.25 W
    • Next 3.24 V 0.40 A 1.3 W 8.1 Ohm
    • 4.49 V 0.65 A 2.96 W 6.7 Ohm, temp rises slowly with time
    • 5.73 V, 1.04 A, 5.96 W 5.7 Ohm, current rises to 1.18, pressure low 1e7 outgassing
  • More tests
    • Set 6.26 V 1.05 A Monday 9:23 am
    • by 10:14 current limited at 1.49 A, 5.7s C 8.5 W, stage at 270 C
    • pressure rose to 1e-7 then down to 2e-9
    • increase current to 2.01 A, initial 7.43 V drops to 7.23 steady state, 14.5 W
    • stage steady state 332 C. pBN heater uniform "cherry red" 
      • contact bars also hot, darker red
      • heat shield, top plate, sample straps do not glow
      • pressure has dropped to 1e-9
    • Set 1.49 A, 5.55 V increases to 5.70, initially 3.72 Ohm -> 3.83
      • heater "incipient red" just at visible glow threshold
      • steady state base 280 C
      • 8.5 W
Photo of heater at 14.5 Watts, pBN "cherry red"


Approximate sample temp vs power for pBN VT holders


Prep chamber heater hints


  • Prep chamber manipulator heater powered by TDK-Lambda power supply (60 V, 12.5 A) under system controller.
    • push small button on far right under digital displays "out" to enable output
    • adjust current and voltage knobs. Depending on load either current or voltage limit will control. Green LED near knobs shows which is limiting. 
  • Set Sample Heating/Bias Selector switch to "Resistive" to connect the TDK supply to the pBN heater built in to the prep manipulator.
  • This heater is ~ 30 Ohm cold, 5 A max current, 100 W max output
    • Increase and decrease heater power slowly to avoid thermal shocks
    • 1.45 A requires 27.6 V for 40 W, R ~ 19 Ohm (lower when hot). This gave ~ 525 C at thermocouople, sufficient to dewet Au/Si film at ~ 600 C
  • There is a thermocouple attached to the sample plate dock. This temperature will be lower than the actual sample temp, and the difference will be greater when radiation is important, > 500 C.
    • temperature will depend on sample properties such as emissivity since heating is by radiation coupling

Estimated temperatures for stage and sample vs power
  • The side of the sample plate facing the heater must be flat (no sample, screws, clips, wires, etc.
  • For simple plates with the sample mounted below, the sample can face the heater
    • For this to work, put the sample in the airlock "reversed" or upside down. 
    • The sample can be heated
    • transfer to the carousel in the analysis chamber upside down. Then use the wobble stick to flip the sample over for inserting in the Auger/STM stage.
    • Do not heat samples mounted with spring clips to high temp (> ~ 200 C) as this will anneal and damage the springs. Mount samples with spot welding for high T.
  • VT double plates with direct or pBN heating may be inserted in the manipulator stage face up. 
    • The plates can be heated using the manipulator pBN heater, or by using the VT heater since the  "fingers" on the manipulator contact the heating terminal.
    • Set the selector switch to "direct current" to use the VT heaters.
    • The top of the VT heating contact must be 3.6 to 3.7 mm above the bottom of the VT assembly, also the total thickness should be 7.6 mm
    • adjust the VT plate if these distances are not correct. Using a badly set VT plate will bend the contact springs.

Wednesday, December 5, 2012

SEM Chiller problem

Chiller was much more noisy that normal in pump room. Disconnect brass pump head from motor. Motor quiet, pump hard to turn manually, "rusty" crud in pump. Must be failing

Pump failed once before, shortly after installation, was replaced by Thermo under warranty.

Ed will order new pump, for now run chiller only when SEM in use, not 24/7

On Thursday, took 3 tries to get chiller to run without alarming for low pressure

Pump replaced Wednesday 12/12/12. Old pump had damaged impeller blades. We also ordered a spare pump.

AuSi experiments Nov 30 12

Introduce two new samples on large-circle holders

  • AS121130F - 670 C tube furnace, quenched, air, older holder no faraday hole
  • AS121130D - 655 C, newer holder with FC hole
Transfer samples to carousel, look at F sample, rather low carbon, can find denuded zones, shadow zone clearly visible in Auger images near O KLL at 3 kV.

Get nice LVV Si and NVV Au at 3 kV. Record auger map images with smart sem 14 bit. Switch to 10 kV for Si KLL and Au MNN.

Need to readjust max current gun align, escecially at 3 kV.