8 CHIMIA 2012, 66, No. 1/2 30 Years scanning Tunneling MicroscopY

doi:10.2533/chimia.2012.8 Chimia 66 (2012) 8–9 © Schweizerische Chemische Gesellschaft “Oh yes, oh yes, these are the atoms!” A Personal Recollection from the Times of the Invention of the STM

Karl-Heinz Rieder*

Abstract: The scanning tunneling microscope, invented and developed in the 1980s in the IBM research laboratory in Rüschlikon, has become the dominent scientific tool in surface science and together with its younger brother the atomic force microscope, is widely used also in many other modern research areas. This account contains very personal anecdotal memories from a colleague who worked in a neighboring lab in Rüschlikon describing some events at the periphery of the development of this ingenious instrument.

Keywords: Physics Nobel Prize 1986 · STM invention · Surface science

From 1975 to 1986 I was research staff These surfaces had been investigated with member at IBM Research Laboratories various methods without conclusive re- in Rüschlikon near Zürich. There I got to sults. Together with these problems I also know Gerd Binnig as he joined the group of provided my well-prepared single crystals. Heini Rohrer, a renowned expert for phase Because of its relative large corrugation, I transitions and critical phenomena in mag- proposed to try the (1×2)-reconstructed netic materials. Heini and Gerd wanted to gold(110) surface first. Previous helium move into a new area of research, namely, scattering experiments suggested either a vacuum electron tunneling. Their original symmetric missing-row or an asymmetric intention was a new spectroscopic method saw-tooth reconstruction. Before returning with a high lateral resolution. Gerd Binnig that crystal to me in form of a solidified showed his talent not only in the labora- droplet, Binnig had succeeded in imaging tory, but also in our IBM music band. We the (1×2)-Au(110) structure. put a lot of effort into practicing and per- I recall that I returned from a confer- forming some of his songs (Fig. 1). ence late one evening and found the cor- After having measured successfully the responding STM line scans on my desk exponential current–voltage characteristics (Fig. 2). In order to document his success, for tunneling in vacuum, which meant that Binnig had left this ‘STM image’ there for they had already solved serious mechani- me. I realized instantly from the symmetric cal damping problems, Binnig and Rohrer shape of line scans, that gold(110) is miss- started to scan the counter electrode, the ing-row reconstructed. I remember vividly that I kept looking at this image literally for Fig. 1. Gerd Binnig’s composition named hours, desperately trying to find any rea- ‘Diabolo’. son for which helium scattering might be

tunneling tip, over surfaces. Surprisingly they quickly were able to ‘see’ atomic steps with their first STM, and already these results attracted considerable inter- est. After showing these step corrugations to me, it immediately came to my mind that they were now in a position to look at some longstanding problems in surface science with their new instrument. The structure *Correspondence: Prof. Dr. K.-H. Rieder of surfaces has intrigued me for a long Nanoscale Materials Science time, and I used helium atom diffraction Empa, Swiss Federal Laboratories for Materials Science and Technology in order to study clean surfaces or adsor- Überlandstrasse 129 bate structures.[1] So I suggested to Binnig CH-8600 Dübendorf and Rohrer to study reconstructed gold Tel.: + 41 58 765 4629 and silicon surfaces, which were known to Fax: + 41 58 765 4034 Fig. 2. The first STM image of the (1×2) miss- E-mail: [email protected] deviate from the bulk-derived structures. ing-row reconstructed Au(110) surface. 30 Years scanning Tunneling MicroscopY CHIMIA 2012, 66, No. 1/2 9

good for in the future. I came to the conclu- many times Christoph Gerber, a member of IBM Rüschlikon in great excitement, be- sion that Binnig and Rohrer’s new method Binnig and Rohrer’s team and co-inventor cause Binnig and Rohrer had received the would make helium scattering only valu- of the STM, explaining results to visitors phone call from Stockholm. I immediately able for studying structures of insulating and emphasizing “Oh yes, oh yes, we see walked up to them to congratulate the new surfaces. But Binnig, Gerber and Quate’s the atoms!” laureates. Binnig’s comment to me was: invention of the atomic force microscope The final breakthrough, convincing “But I’ll get only one quarter!” Completely five years later made my favorite investiga- the entire scientific community, came by stunned with this reply, I told him that in tion technique basically obsolete. solving the structure of the reconstructed the future his name would stand in a row Binnig went on to investigate the com- (7×7) silicon(111) surface. This estab- together with such famous physicists as plex reconstruction ofAu(100) and showed lished STM as a powerful surface science Einstein, Planck, Dirac and Feynman. But that single atoms could be resolved with tool and added another melted crystal to Gerd replied dryly: “It’s nevertheless only STM – before melting this crystal as well. my collection. one quarter!” Numerous scientists from all over the Soon it became clear that the inven- world now came to visit our laboratory, tion of the STM had a good chance to Received: December 11, 2011 but often expressed doubts about these be awarded the Nobel Prize. On October th novel STM results. The inventors, how 15 1986 I came to the laboratory in the [1] K.-H. Rieder, T. Engel, Phys. Rev. Lett. 1980, ever, were absolutely confident and I heard early afternoon and found the whole 45, 824.