A short history of Scanning Probe Microscopy
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1st-generation scanning tunneling microscope
3rd-generation STM |
1981-1986: Atomic resolution - really?
2nd-generation scanning tunneling microscope In the first few years after their invention, Binnig and Rohrer encountered disbelief and even some hostility. Given scientists' previous experience with phenomena on the atomic scale, and especially the quantum mechanical principle of uncertainty, the possibility of atomic resolution seemed remote if not theoretical impossible. The doubts were allayed only with the successful replication of STM measurements by other groups. This occurred after the development of the fourth generation: a simple, easy-to-use, and robust instrument that could be used not only in an ultra-high vacuum but in air and even liquid. More detail here.
4th-generation STM Image source: Binnig & Rohrer's first four generations were reproduced from IBM Journal of Research and Development, 30 (1986), 359. By permission of IBM Technical Journals. |
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After the Nobel Prize many researchers began to build their own STMs and to explore its capabilities in new fields. Binnig & Rohrer's fourth generation instrument was comparatively simple, so that some scientists (e.g. Erik Lægsgaard, and Vladimir Kirillovitch Nevolin) built one from scratch in a matter of weeks. Variants on the original STM, such as the Atomic Force Microscope were developed, now usually grouped under the heading of Scanning Probe Microscopy (SPM). With all these instruments, scientists still had to separate artifact from reality, but they no longer doubted it could be done. New enterprises sprang up manufacturing SPMs. Early examples include Digital Instruments, Park Scientific Instruments, and Hitachi Scientific Instruments, who were all selling to the US market by 1991. They testify to a lively market. An STM cost $30,000 to $200,000 in 1990. By 1992, the AFM alone had become an estimated $40 million a year business, and by mid-1993 DI claimed to have sold more than 1,000 of its Nanoscope SPMs. SPMs found application in ever more fields. As Ivan Stensgaard has put it: "One saw new phenomena almost regardless of what one studied". The STM was operated within electrochemical cells. Its first sibling, the AFM, could be used to image non-conducting surfaces, such as glasses. By 1992 several investigations were under way to image biological samples, such as viruses, bacilli, or DNA strands. The analog feedback circuit was replaced once computers became sufficiently fast to do the calculations. In fact, most scientific instruments were combined with electronic systems around 1990. The commercial SPMs were equipped with software, both guiding the scanning process and processing/imaging the data, and they usually included graphic workstations. This software was gradually rendered more user-friendly, for instance by automating sample loading and operating from a Microsoft Windows 3.1 platform (first advertised by Park Scientific Instruments). |
1987 - 1993:New uses and variations
The first STM built at DFM. Kim Carneiro points to the tip. |
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Sources (1987-1993):
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Early 1994 to now:becoming a part of the furniture
J. Garnaes and a Nanoscope at DFM. |
There is now an almost bewildering variety of SPMs. For instance, by making the tip out of a ferromagnetic material, the magnetic properties of the sample can be probed. Or by measuring the force as a function of distance, a measure of the sample's hardness is obtained. Using such tricks, measurable properties now include: roughness, stiffness, electrical effects, capacitance, adhesion. and friction. The instrument making industry developed more rugged and user-friendly SPMs. As a result they also became usable in semiconductor fabrication lines, where cost concerns demand a great degree of automation. Metrology now exists on the nanoscale. Speed and sample capacity continues to be improved upon, for instance by Calvin Quate of Stanford University. SPMs have also become much cheaper. NT-MDT, a Russian manufacturer, is currently making great inroads into the SPM market, primarily through very low prices. Many ways were found to investigate biosamples, but so far few biologists have accepted the technique. Significant success has been achieved within electrochemistry, such as the development of catalysts directly out of STM research. Furthermore, since 1995, the STM has been deployed to develop data storage devices of very great density. |
Cf. also our History of Scanning Probe Microscopy in Denmark.
This page was written and last updated on 19 July 2001 by Arne Hessenbruch.
