Using the STM

Cámara: FlyCap2 (software)

STM: SPM Controller

 

Dosers:

 

 

1. Connect water.

2. Connect filament and doser power supplies (Delta and FUG).

3. Check that minus output of doser power supply is grounded.

4. Check that shutter is closed.

5. Turn on doser power supply.

6. Apply required high voltage.

7. Make sure filament current is 0 A.

8. Turn on filament power supply.

9. Increase filament current until required emission.

10. Leave some time warming (5-15 min, depending on doser).

11. Heat sample during warming time *

12. Open shutter for a given time. Record emission current (and HV voltage), background pressure, filament current and voltage, sample temperature.

 

 

* Heating Ru sample:

 

1. Connect sample bias to ground.

2. Check that FUG HV power supply has outputs connected to transparent box.

3. Connect thermocouple to Keithley microvoltmeter.

4. Connect sample filament to transparent box.

5. Turn on sample high-voltage power supply (FUG), set output to 1000V, current limit to 100mA.

6. Pull cord up in transparent box.

7. Check temperature with pyrometer. If it goes above 1450ºC, stop heating manually by pulling cord down, reduce filament current a bit for next time (should be around 1.9 A).

8. After flash ends automatically, pull cord down in transparent box.

9. Turn off output in the sample HV power supply.

 

Retracted STM

 

To start STM:

 

  1. Check the valve between the chamber and turbo pump. It must be closed.

  2. Check that doser water is closed.

  3. Check the RGA system. It must be OFF.

  4. Close the valve between the turbo pump and the “roughing” pump station (Pfeiffer).

  5. Stop the turbo pump (Varian) and the “roughing” pump station (Pfeiffer).

  6. Disconnect the fan and the controller of turbo pump (Varian).

  7. Connect sample bias to STM electronics. Usually it is connected.

  8.  

    Pneumatic legs valve

    Lower STM head onto sample holder, making sure the glass balls sit in the kinematic mount.

  9. Disengage STM base using the lower linear drives.

  10. Inflate pneumatic legs (open valve attached to chamber frame).

  12. Turn ON the Omicron controller and the Nanonis controller.

  13. Turn ON the HV OUT X/Y and Z in the Nanonis controller. Multiplier is usually at x10.

  14. Disconnect the PC network cable (gray cable) and start the SPM controller software.

  15. Reconnect the network cable.

  16. Start the FlyCap2 software and adjust the camera in order to observe the STM tip.

  17.  

    Illustration 1: Nanonis electronics, showing detail of HV switches

    Turn on light. Approach by hand until end of tip reflection overlaps with sapphire tube (on Omicron MSCU controller, F2(+) is up and F2(-) is down). Turn off light.

  18. Set the session directory in the SPM controller software.

  19. Set the external control in the Omicron controller using the remote control (press up/down buttons until remote screen).

  20. Set the Current (1nA) and Bias (+2V) value.

  21. Set the Proportional (100pm) and Time constant (70us) value.

  22. Approach the tip using the SPM software (TOOLS>AUTO-APPROACH).

  23. Start the STM measurements.

To stop STM:

  1. Set the manual control in the Omicron remote controller.

  3. Turn on light. Retract manually until space can be seen between tip reflection and end of sapphire tube (F2(+) for moving up). Turn off light.

  4. Turn off the HV OUT X/Y and Z in the Nanonis controller.

2. Turn off STM software and electronics (Omicron and Nanonis).

3. Deflate pneumatic legs.

5. Engage STM holder using the lower linear drives and move up the STM head.

6. Turn on turbo (Varian) and the “roughing” station (Pfeiffer).

  1. Open the valve between the turbo and the “roughing” pump only when the pumps are accelerated.

  2. Turn on turbo gauge controller.

  3. Reconnect the turbo pump fan.

 

 

Base of STM

 

 

 

 

Ru Cleaning sample at end of day:

1. Follow steps 1-5 of “Heating sample" above.

2. Flash sample to ~1400ºC.

3. Turn off HV power supply.

4. Wait for sample to cool down below dull red.

5. Open and close O2 cylinder.

6. Open leak valve so as to fill the chamber with O2 to 1x10-7 Torr.

7. Wait 20 s.

tip in tunneling position

8. Close leak valve.

9. Wait for pressure to go below 2x10-9 Torr. If too much O2 has been let in, turn on sublimator.

10. Redo 5 times.