Materials Research Activities

Overview of Binnig & Rohrer's publications 1981-1986

Introduction to Binnig and Rohrer's 10 publications, 1981-1986

Gerd Binnig and Heinrich Rohrer submitted their first publication on the Scanning Tunneling Microscope (STM) in September 1981. In 1986 they received the Nobel Prize. The following account describes their publications in this period as a first guide to the early history of the STM.

What was the nature of their publications in this period? It was primarily an endeavour to 'sell' the STM. Binnig and Rohrer had several tasks that fall under the rubric of 'selling', that is to say: they had to convince their colleagues that their new instrument was useful. These were the tasks:

  • get consistent results (make the STM a stable tool that yielded replicable experimental results)
  • make the STM more user-friendly
  • show the utility of STM (get interesting results analyzing, say, the surface of a silicon crystal)
In fact, there were scientists who refused to believe that one could possibly do what Binnig and Rohrer claimed: to scan a surface yielding information with a finer resolution than ever before: so fine that individual atoms showed up. Some scientists thought the STM a hoax and others accused Binnig and Rohrer with fraud. And so, they had a very basic task:
  • convince other scientists that their results were trustworthy

Binnig and Rohrer pursued the first three tasks and through this they eventually managed to achieve the fourth, basic task. The Nobel Prize clearly indicates that they had succeeded in convincing the world at large. It is striking how quickly the recognition came. Until 1984, noone outside Binnig and Rohrer's lab at IBM Zurich had replicated an STM experiment. And the first trickle of reports of replication came from their immediate circle of colleagues, such as scientists at other IBM labs. Nonetheless, by 1986 Binnig & Rohrer published an article in Scientific American and the trickle became a flood. Only a year later, they received the ultimate recognition. Clearly Binnig & Rohrer's publications in the period from 1981 to 1986 completed the tasks in the above list.

The following account asks specific questions that we would like to have answered. But anyone reading this is invited to respond in any matter they please. The purpose of this website is to elicit criticism and to respond to it wherever appropriate. For example, readers are welcome to criticise the conclusions and the emphases made. Go to discussions.

The following describes 10 publications by Binnig and Rohrer between 1981 when they began to publish on tunneling microscopy and 1986 when they received the Nobel Prize. Very general issues can be examined using this early STM history. 1981-1986 is an extraordinarily short time span for 'product development'. One may thus well ponder such issues as innovation and acceptance of novelty, technology transfer, and the role of replication and of robustness. The aspiration in the following pages could be described as preparatory: to get a grip on the historical development in order to build a solid platform from which the more general questions may be fruitfully posed.

Binnig and Rohrer's first publication, submitted in 1981, presented the basic principles of tunneling in a vacuum, particularly that the tunneling current could be used as a highly sensitive measure of the miniscule distance between tip and sample. In the following paragraphs, their argument will be rehearsed. It is well to remember that they did not simply report

their findings but that they had an interpretation. It was important for them that other scientists accepted their interpretation and so they put their best arguments forward. In order to understand Binnig and Rohrer's endeavour it is necessary also to establish why other scientists might have been disinterested, sceptic, or even hostile. Binnig and Rohrer give some clues in this regard in our interview with them (members may click here), their Nobel speech, and in Binnig's book, Aus dem Nichts: 'People came to our laboratory and angrily called us liars. We also received a lot of abusive letters describing us as frauds.' [pp. 128-9]

In almost all their publications in this period, Binnig and Rohrer had to explain their new tool. And yet, they did not pretend to completely understand it themselves. For example, in 1984 they stated that finally the STM had matured from an art to a technique and that a development from the experimentalist's wishful thinking to a fundamental theoretical understanding had taken place. One could call this retrospective modesty as a result of new-found confidence.

Even the basics were contested. The STM works by scanning a tip across a sample surface, noticing the hills and valleys in the surface topography. 'Noticing' here refers to a tunneling current. If the tip is very close to the surface and a small voltage is applied, then a small current will jump across from sample to tip (or in the opposite direction). Normally, a current does not flow through air and so the gap between tip and sample can be regarded as an insulator. Binnig and Rohrer sometimes carried out the scanning in a vacuum which is an even better insulator than air. But a current does flow when the distance between sample and tip is very small, due to a quantum effect called tunneling. For tunneling to occur, the distance has to be very small indeed: of atomic dimensions. This means that you have to be able to position the tip within the distance of one atom or less from the sample. In fact, the tunneling current depends not merely on the distance between tip and sample but rather on the overlap between wavefunctions of the atoms of tip and sample.

Reproduced from Scientific American, August 1985, p. 53, by permission of Ian Worpole.

To many the positioning of an object within the distance of one atom will have sounded like an impossibility. For much of the 20th century, quantum mechanics had taught that many of our common sense notions do not apply at the atomic scale. For example, the common sense notions related to the mechanics of billiard balls does not apply. The semi-classical notion of electrons orbiting the nucleus does not actually apply. All you can justifiably talk about is wavefunctions (electron 'clouds'), the distribution of which will yield a probability of finding an electron there upon measurement.

Reproduced from Physica B, Vol 127., Binnig et al, "Scanning tunneling microscopy", 37-45, Copyright 1984, with permission from Elsevier Science.

You cannot simultaneously measure with absolute precision the momentum and position of a particle at the atomic level. And the measurement (which might involve sending a light particle in to collide with an electron and then to subsequently detect the scatter) will disturb the atomic system. In other words, anyone having imbibed quantum mechanics has learned that common sense notions applied with impunity to macroscopic phenomena may not be so applied at the atomic level. Hence, the claim that one could position a tip within a distance of one atom from a sample and that one can measure a current across such a distance sounded suspect from the very beginning. And on a more mundane level, thermal movement, mechanical and acoustical vibrations would render such precision positioning illusory anyway. Binnig and Rohrer were told that in principle the STM could not work and their first attempt at publication failed (Nobel talk, p. 389 and 397). In our interview with the two Nobel Laureates, much light is thrown on these issues. (Members may click here.) Binnig and Rohrer's attitude to manageability at the atomic level was unusual. Heinrich Rohrer points to an important lesson of his PhD work (on length changes of superconductors at the magnetic-field-induced superconducting transition): that he lost all respect for angstroms (Nobel talk, p. 387).
  • Introduction to Binnig & Rohrer's 1981-1986 publications (you are here)
  • Paper 1 (Applied Physics Letters 1982)
  • Paper 2 (Physical Review Letters 1982)
  • Paper 3 (Surface Science 1982)
  • Paper 4 (Helvetica Physica Acta 1983)
  • Paper 5 (Surface Science Letters 1983)
  • Paper 6 (Physica 1984)
  • Paper 7 (Surface Science 1984)
  • Paper 8 (Surface Science Letters 1985)
  • Paper 9 (Europhysics Letters 1986)
  • Paper10 (Scientific American 1986)

This page was written and last updated on 15 July 2001 by Arne Hessenbruch.