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Schrodinger's Sharpener is the world's most popular instrument for the fabrication of probe tips for scanning tunneling microscopy (STM).
The quality of micrograms having atomic resolution depends stringly on proper tip fabrication. STM tip fabrication remains one of the most difficult aspect of the art. Numerous fabrication methods have been reported, the vast majority of which involve electrochemical etching of a metal needle to the point where the needle just breaks. At this point the etching current is stopped resulting (theoretically) in a tip of atomic size. It has recently been discovered that if the etching is halted within about 100 ns before the tip breaks, tips of higher quality and greater reproducibility can be formed. However, this poses great technical difficulty.
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| Tungsten STM tip fabricated with Schrodinger's Sharpener |
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- First, one must monitor the derivative of the current in addition to the current itself.
- Second, the sensitivity of the circuit must be adjustable so the user can fine tune the stopping point of his/her application.
- Third, the triggering circuit must be ultra fast and highly sensitive, but at the same time be immune to false triggering due to noise.
- Fourth, the electrochemical circuitry must operate reliable over a wide rage of voltages and in solutions of greatly varying composition.
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| Thus, the electronics must be carefully designed for speed and sensitivity and have a high level of noise immunity, a difficult combination of requirements.We therefore designed Schrodinger's Sharpener as an affordable solution to the dilemma of making one's own STM probes. The instrument operates in DC and pulsed modes, and can fabricate high quality STM tips from a variety of metal wires, including tungsten and platinum/iridium. The Model SS02 is also capable of micropolishing of cut wires, a technique known to provide STM probes of the highest quality. |
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To address the growing need in the STM community for tips of various metals, Obbligato Objectives replaced the SS01C with an upgrade, the Model SS02. The SS02 uses the same sophisticated algorithm, however contains an internal computer, so there is no need for connection to a host computer. Moreover, the SS02 has a number of improvements including a wider etching voltage range and the ability to perform electrochemical micropolishing. Thus, the SS02 can reliably fabricate atomic resolution STM probes from virtually any metal. Although the Model SS01C is no longer available, Obbligato Objectives still offers software support for our existing customers. |
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| Ag(001) surface taken with Schrodinger's Sharpener tungsten tip (courtesy Prof. Sylvie Morin, York University) |
STM image of iodine atoms on nickel using a Schrodinger's Sharpener Pt tip (courtesy Prof. Ursala Mazur, Washington State University) |
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| SOURCES FOR METAL WIRES |
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