Parameters - Datasheet

ADDITIONALLY, THE FOLLOWING ITEMS ARE NECESSARY:

• Dc power supply (for example 12 V / 0.5 A), if possible with adjustable current limit in the range between 20 mA and 100 mA
• Etching solution: 2 mol NaOH (ATTENTION: NaOH affect glass surfaces. Therefore, glass
• bottles with edge might be tightly closed after some time.)
• Pipette for etching solution
• bottle with distilled water
• Philips-tip screw driver No. 2
• Tweezer
• vessel for waste water
• tip holder boxes for etched tips

The current limit of the power supply should be set between 20 mA and 50 mA. If the power suppl yis switched on, bubbles inside the etching solution should be visible (solution looks milky white). The etching stops itself by dropping the lower part of the wire into the catcher. If the ecthing solution is used up (no bubbles anymore) before the tip is ready, remove the waste solution before you add new solution. Typical etching time: 2-4 min.

Tunneling tips can be prepared by simply cutting a thin metal wire (W or PtIr) with a wire cutter or by electrochemical etching (for W in NaOH). For the etching, the W-wire (Anode) is dipped into an etching solution in which a ring-like stainless steel or Pt-cathode is placed around the wire. If more than 1.4 V is applied between wire and counter electrode, the following reaction takes place:

At the surface of the NaOH, the etching speed is higher than in sode the solution. The tip radius achieved with electrochemical etching mainly depends on the time which the fully etched wire remains in the etching solution. If the tip is immediately removed after etching, the tips get sharper. While other etching methods use a electronic circuit to stop the etching when the current drops, the method used here stops itself when the lower part of the wire fall down due to its own weight into a catcher.