SPMwikiResharpening a tip by field emission 2017-06-18

A blunt tip could be repaired by field emission. And this method also can be used to clean a new tip. Here, I will make a brief introduction of conducting field emission to resharpen a SPM tip. I hope this would helpful to the future freshman in our lab.

Schematic


Set-up

  1. Approach the tip to cleaned metal single crystal surface.( Tunneling )
  2. ‘Tip-up’ and retract the tip using the Z-knob on the HV-amplifier. This step makes the tip slightly far away from the surface.
  3. Disconnect the pre-amplifier,and apply 100V to the tip and set the current to minimum (Fug powersupply). Remember to connect the 100kohm resistance for protecting the wires. All wire inside STM can only load a current less than 40mA!
  4. Connect a multimeter to the left-connect BNC or right-connect BNC and set the current range to 20uA.
  5. Slightly approach the tip to the surface by the Z-knob on the HV-amplifier (clockwise). Observe the current displaying on the multimeter and it should be stable and not overload.
  6. After finishing a full operation above, you can slightly retract the tip by the Z-knob and the coarse-motion on the software.( Just several steps, eg.-12V, 1 step, 20 clicks). Than move the tip to another cleaned place by XY oarse-motion on the software.
  7. repeat 5 until you can see a stable emission current from the multimeter, probably 600-800nA.
  8. When finished, retract the tip first,and switch off the power supply. Reconnet the pre-amlifier and other cables for scanning.
  9. Re-approach the tip the another place which is far away from the emission area and check the tip by scanning.

Notes

  • You will see the sparks from the CCD camera when the field-emission is roling.

  • You can also use 2450 source meter to power the emission and you can monitor the current from the 2450 directly.

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