Heinrich Rohrer (1933–2013) Co-Inventor of the Scanning Tunnelling Microscope

Home , Ernst Ruska, Gerd Binnig, Heinrich Rohrer

COMMENT OBITUARY Heinrich Rohrer (1933–2013) Co-inventor of the scanning tunnelling microscope.

einrich Rohrer, Heini to those who contemplate a new device. By 1981, the eventually verified by other groups and knew him, helped to open the door pair had designed the world’s first scanning presented at a workshop on the STM in the to nanotechnology. With Gerd tunnelling microscope (STM). Austrian Alps in 1985. Devices such as the HBinnig, he produced a device that allowed Unlike conventional microscopes, the atomic force microscope (AFM) — a very researchers to image and measure atoms STM did not use lenses. Instead, a probe high resolution type of scanning microscope and molecules, and to manipulate them. sharpened to a single atom at the tip was that measures the atomic forces between the Rohrer, who died on 16 May, tip of a probe and the surface being three weeks before his 80th scanned — have their roots in this birthday, was born in 1933, half meeting. During the last night of an hour after his twin sister. He the workshop, the mountains were grew up in the village of Buchs in abuzz with crazy ideas about how eastern Switzerland. Rohrer stud- such microscopes might be used ied physics at the Swiss Federal in applications in all sorts of fields, Institute of Technology (ETH) from fundamental physics and — ZURICH IBM RESEARCH in Zurich, where he remained to chemistry to information tech- pursue a PhD. It was during his nology, quantum computing and PhD years that he first came into molecular electronics, as well as in contact with the nanometre scale, the life sciences. through studying the properties of In 1986, Rohrer and Binnig superconductors. shared half of the Nobel Prize in After receiving his PhD in Physics. The other half of the prize 1960, Rohrer pursued a two-year was given to the German physicist postdoctoral research fellowship Ernst Ruska for inventing the scan- at Rutgers University in New Jer- ning electron microscope, a device sey, working on superconductors that produces images of a sample and metals. At the end of 1963, he by scanning it with a focused beam joined the IBM Research Labora- of electrons. tory in Rüschlikon, Switzerland, With the emergence of scanning on the recommendation of various probe microscopes (the STM and peers including physicist Bruno Lüthi, who moved close enough to the surface of a the AFM are just two among many types of had worked alongside Rohrer at the ETH. conductive material, such as silicon or gold, these), the door to the nanoworld was pushed Towards the end of the 1960s, Rohrer for the electron wavefunctions of the atoms wide open. Today, such tools are still making a began working on an antiferromagnet called in the tip to overlap with those of the atoms tremendous impact on numerous disciplines. gadolinium aluminate (GdAlO3) in collabo- in the conductive surface. (Picture two over- An extraordinarily charismatic man, ration with Keith Blazey, another physicist lapping electron ‘clouds’.) When a voltage Heini went on to promulgate nanoscience at the IBM lab. Antiferromagnetism is a was applied to the tip, electrons started to and nanotechnology to upcoming genera- type of magnetic ordering that vanishes at a ‘tunnel’, or ‘leak’, through the vacuum gap, tions of researchers. I remember a lecture he certain temperature. The work brought causing a current to flow from the foremost gave in South Korea some years ago, which Rohrer into the field of critical phenomena atom of the tip into the surface. was attended by almost 4,000 high-school and led to crucial findings about magnetic Moving the tip by the diameter of a and university students. His captivating phase transitions. By this point, the group single atom changed the current by a factor description of the development of the STM at the IBM lab had established a world- of a thousand, giving the device its enormous was followed by thunderous applause. In renowned reputation in critical phenomena, resolution. As the tip was scanned back and fact, one of the attendees recently told me after K. Alex Müller — then head of physical forth, it followed the atomic structure of the that it was Heini’s talk that inspired him to science — had pioneered the field of struc- surface, extending and retracting over dips study physics and nanoscience. tural phase transitions. and bumps. Thus, for the first time, it was Heini will be deeply missed as a natural In the late 1970s, Rohrer’s interest shifted possible to get up close and personal with leader, a visionary, a stimulating scientist and towards the complex structure of surface atoms in three dimensions. a wonderful person. He is survived by his materials. In building ever-faster com- Nobody believed that Rohrer and Binnig’s wife Rose-Marie Egger, his two daughters puters, the semiconductor industry was experiments demonstrating quantum tun- Doris Rohrer Hansen and Ellen Rohrer, and rapidly approaching the design of chips on nelling could ever work. A tremendous two grandchildren. ■ the nanoscale. Yet few tools were available challenge was bringing the tip only 0.2 nano- to study the structure and properties of metres away from the surface (1 nanometre Christoph Gerber collaborated with materials at this scale. In 1978, Rohrer is 1 billionth of a metre). However, a clev- Rohrer at the IBM Research Laboratory for insisted that the IBM lab hire Gerd Binnig, erly designed mechanism using the forces of many years. He is at the Swiss Nanoscience a young German physicist from Frank- strong magnets did the trick. Institute, University of Basel, Switzerland. furt University, and the two started to Rohrer and Binnig’s initial results were e-mail: [email protected]