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Preparation Station for STM Tips


Stable and clean tungsten tips for scanning tunneling microscopy (STM) applications require in-situ annealing. A simple and effective way for annealing is to place the tip in front of a small tungsten filament. Put enough current through the filament to achieve thermal emission (~2A through the electrical connector next to the blue arrow in the last picture below). Apply a positive potential (100-500V at the electrical connectors next to the red arrow in the last picture below) to the tip while carefully monitoring the emission current. Around 2-5 microamps is sufficient, too much bluntens (melts) the actual tip. You can now perform cycles of annealing and after every cycle, check field emission treshold level at a given current of a few nanoamps by placing the spherical electrode in front of the tip (measure the field emission current between the contacts next to the red and yellow arrow in the last picture below). This gives you a good indication of tip sharpness, but you can also check if the tip is clean, because only a clean tip will give you a stable emission current. Tips prepared in this way do normally produce good STM images on the first go. A reproducable distance between the tip and the spherical electrode is a must for comparable emission results. The ESFC adjustment ring on the MD16-manipulator blocks the movement always on the same place in front of the tip. Adjustment of the distance between tip and electrode is possible with the threaded stop ring of the ESFC. The device has no scale for absolute positioning. This feature is available with our more advanced preparation stage HSASM40-TIPEBFE2-MD16(TS)-DRVMD. The proposed tip preparation stage (or the tip itself) must be mounted to a fairly accurate positioning device such as our AX40 manipulator. Additional information on the subject was found in: The master thesis of Stefan Ernst (Optimisation of the preparation process for tips used in scanning tunneling microscopy, TU Dresden 2006) and the master Thesis of Anne-Sophie Lucier (Preparation and Characterization of Tungsten Tips Suitable for Molecular Electronics Studies, McGill University 2004). A more advanced tip preparation stage is also available (look up the product code "HSASM40-TIPEBFE2-MD16(TS)-DRVMD" on the Ferrovac Website)

Specifications: Preparation Station for STM Tips

linear travel X >= 10mm AND <= 750mm; standard 150mm
retracted length Y >= 100mm AND <= 250mm; standard 100mm

MD16(TS)-ESFC Manipulator with a mounted Tip Preparation stage TIPEBFE2.

  • linear travel: customized length (short distances only such as 20mm)
  • mounting flange DN 40CF
  • MS-Type feedthrough DN16CF,4 pin (EFMA0192(4)CF)for filament heating current
  • Airside connector without cable for MS-Type feedthrough DN16CF,4 pin (EFMA0192(4)CF) is included
  • Electrical connector CFH-ELFEED-DN16CF-500V-BNC (EFMA0237(1)CF)for field emission measuring
  • Airside connector without cable for CFH-ELFEED-DN16CF-500V-BNC is included
  • Customer specific cable set for both connectors is an option
  • bakeout temperature: 150°C max.
  • pressure range 1E-11mbar to 1000mbar
  • fully UHV compatible materials
  • Required current for the filament is around 2Amps
  • Typical tip - ball distance: 0.5-2mm
  • Typical tip bias: 150-500V

    download drawing

Possibly an end-user certificate (EUC) is required from purchaser.
Export licence from the State Secretariat for Economic Affairs (SECO) or Swiss Federal Office of Energy (SFOE) may be required

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