Sign in

Preparation Stage for STM Tips


Stable and clean tungsten tips for scanning tunneling microscopy (STM) applications require in situ annealing. Thermally emitted electrons from a tungsten filament are accelerated towards the positive potential (100-500V) applied to the STM tip. An emission current of in the micro Ampere range is sufficient to heat up the STM tip to annealing temperature where absorbed molecules are removed from the tips surface. Additional annealing of the tip under partial pressure of oxygen helps to remove carbon from the tips surface. With a spherical electrode mounted on the same stage field emission tests can be performed on the annealed STM tip. A stable field emission characteristic is a measure for the quality of STM tips and indicates its capability to achieve high resolution when doing STM later.

The proposed tip preparation stage must either be mounted on an accurate positioning device such as our AX40 manipulator or the tip should be positioned with sufficient precision instead. A stable distance between the tip and the spherical electrode is important for comparable emission results. For this reason the miniature linear rotary feed through is equipped with a manually actuated high precision spindle drive. Coarse positioning is done by turning the hand wheel. The precision scale on the hand wheel (with a readout of at least 0.05mm) allows the user for a precise adjustment of the optimal annealing position.

Additional information on the subject of STM tip preparation was found in: The master thesis of Stefan Ernst (Optimization 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).

Specifications: Preparation Stage for STM Tips

length configuration: ≤ 500mm

MD16-DRVMD Manipulator with Tip Preparation stage TIPEBFE2.

  • Manipulator with linear travel: 100mm, 150mm, 200mm, 250mm, 300mm or customized length
  • mounting flange DN 40CF
  • MD16-Manipulator with manually actuated high precision spindle drive
  • different spindle pitches available
  • Millimeter scale for coarse positioning
  • precision scale for fine positioning (0.05mm)
  • 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 optional
  • bakeout temperature: 150deg C max.
  • pressure range 1E-11mbar to 1000mbar
  • fully UHV compatible materials
  • Typical filament current 2A
  • Typical tip - ball distance: 0.5-2mm
  • Typical tip bias: 150-500V

    download drawing

Ferrovac Gmbh | Thurgauerstrasse 72 | CH-8050 Zürich | | | TEL +41 44 273 16 38 | FAX +41 44 273 16 30
© Ferrovac GmbH 2018 | © vogy GmbH 2018