Heinrich Rohrer

Swiss physicist

• Born: June 6, 1933
• Birthplace: Buchs, St. Gallen, Switzerland
• Died: May 16, 2013

The collaborative research work of Rohrer and Gerd Binnig led to advancements in microscopy that enabled scientists to see objects as tiny as individual atoms. Their scanning tunneling microscope (STM) generated three-dimensional images of material surfaces that helped researchers determine the size and form of atoms and molecules, defects and abnormalities on surfaces, and how chemicals interact with materials. The STM soon became standard equipment in laboratories worldwide.

Primary field: Physics

Primary invention: Scanning tunneling microscope

Early Life

Heinrich Rohrer (HIN-rihk ROH-rur) was the third child born to Hans Heinrich and Katharina Ganpenbein Rohrer. His twin sister was born a half hour before him. His father worked as a distributer of manufactured products. Young Rohrer felt a special closeness to his mother, who always encouraged him to do his best and supported and assisted him when times were difficult.

Rohrer’s childhood was carefree and delightful. He enjoyed playing a variety of games with his siblings and friends, doing farm work, and attending school. When he turned thirteen years old, his family moved from the rural country setting of Buchs, Switzerland, to the urban lifestyle of Zurich.

During his school years, Rohrer developed a strong interest in classical languages and natural sciences, particularly physics and chemistry. After enrolling at the Swiss Federal Institute of Technology in Zurich in 1951, he decided to pursue a degree in physics and earned a bachelor of science in that discipline in 1955. During that time, he was taught and influenced by Nobel laureate Wolfgang Pauli, who had discovered the Pauli exclusion principle for electrons in atoms.

In the fall of 1955, Rohrer began work on a doctoral degree in physics at the institute. Under the direction of Jörgen Lykke Olsen, he made intricate measurements on materials at the critical point where superconductivity was induced by a magnetic field. Since the measurements made with mechanical transducers were so sensitive to the slightest vibrations, Rohrer had to do his work during the early morning hours when Zurich was quiet. As a member of the Swiss army, his Ph.D. work was occasionally interrupted as he participated in basic training in the mountain infantry. He earned his Ph.D. in experimental physics in 1960.

During 1960-1961, Rohrer worked as a research assistant at the Swiss Federal Institute of Technology. In the summer of 1961, he married Rose-Marie Egger, who helped him to settle down. For their honeymoon, they traveled to the United States, where Rohrer carried out postdoctoral research at Rutgers University for two years on the thermal conductivity of type-II superconductors.

Life’s Work

In 1963, Rohrer and his wife returned to Switzerland. Shortly thereafter, Rohrer was offered a research position with the recently founded International Business Machines (IBM) research laboratory in Rüschlikon, Switzerland, under the direction of Professor Ambros Speiser. His initial research work concentrated on changes in the thermal, electrical, and magnetic properties of nonmagnetic systems that contain small amounts of magnetic impurities. Such systems are referred to as Kondo systems. His focus was on Kondo systems exhibiting magnetoresistance in pulsed magnetic fields.

By 1969, Rohrer was working with Keith Blazey on optical experiments associated with antiferromagnets, which led him to the study of magnetic phase diagrams, phase transitions, and critical phenomena. During the 1974-1975 academic year, Rohrer took a sabbatical leave from IBM to do research on nuclear magnetic resonance with Alan King and Vince Jaccarino at the University of California, Santa Barbara. Prior to and following the sabbatical, Rohrer, his wife, and their two daughters, Doris and Ellen, took extended camping trips throughout the United States.

After returning to IBM, Rohrer became interested in the complex atomic structures of the surfaces of various materials. At the time, little was known about the nature of surface atoms. After German physicist Gerd Binnig joined IBM in 1978, he and Rohrer began exploring oxide layers on metal surfaces. Initially, they pursued the development of a spectroscopic probe to examine the surfaces. In the process, they invented a new type of microscope, the scanning tunneling microscope (STM), with the capability of examining the atomic structure of metal and semiconductor surfaces. Their idea was to scan the surface using the tip of a needle probe at a height of only a few atomic diameters above the surface.

In the development of their invention, Rohrer and Binnig encountered several problems. The most serious challenge was that the tip of the probe was very sensitive to any vibrations, a problem similar to that faced by Rohrer when he was collecting data during his Ph.D. research. Since the required magnification to see atoms was on the order of 100 million, any interference from vibration or noise would greatly distort the produced image. Using Rohrer’s previous experience, he and Binnig decided to shield the probe from disturbances by conducting their experiments on a heavy stone table set on top of inflated rubber tires and by resting the STM on copper plates positioned between magnets. Any movement of the copper plates in the magnetic field would produce an induced current in the copper, and the interaction between the current and the field generated a feedback effect that damped any motion of the plates. Vibrations were reduced to the point where a vertical resolution on the order of one-tenth the diameter of an atom was achieved. Rohrer and Binnig built their first STM in 1981.

After Binnig and Rohrer were awarded the Nobel Prize in Physics in 1986, along with Ernst Ruska, who had invented the electron microscope, Rohrer was appointed as an IBM fellow, the most prestigious technical position at IBM. In this position, Rohrer had the freedom to pursue whatever research projects he felt were most important for IBM. During 1986-1988, he managed the Physical Sciences Department of the IBM Rüschlikon research laboratory. By 1987, Rohrer’s research group had developed an STM the size of a human fingertip, with a resolution capability for seeing atomic-scale objects to within 1/25 the diameter of a typical-sized atom.

Rohrer retired from IBM in July, 1997. Afterward, he participated in research appointments at the Consejo Superior de Investigaciones Cientifcas (CSIC) in Madrid, Spain, and at the Riken Institute and Tohoku University in Japan. His research focus became nanoscience, how matter behaves at submicroscopic levels on the order of a billionth of a meter in size, and nanotechnology, research and technology development at the atomic and molecular levels that allows the ability to manipulate particles on the atomic scale. Rohrer has been instrumental in encouraging the use of the STM as a major tool in nanotechnology to control atoms and molecules to help modify and manufacture products at the nanoscale level.

Impact

Since the invention of the first microscope, scientists searched for improvements for exploring the microscopic world. Optical microscopes were limited by the wavelength of light, which is approximately two thousand times larger than the diameter of a typical atom. Electron microscopes achieved much higher resolution due to the shorter wavelength of electrons in forming images, but they could not resolve images smaller than about five times the diameter of a typical atom. Being very familiar with the field of microscopy, Rohrer set a goal to image microscopic particles. During his many years of research, he had developed both the theoretical and experimental foundations and insights that were necessary to be successful.

In 1978, Rohrer and Binnig began their quest to invent an atomic microscope. Displaying foresight and fierce tenacity, the two solved a number of significant problems, particularly vibrational and noise sensitivity of their imaging probe, in the development of their scanning tunneling microscope. After numerous changes and additions to their experimental setup and equipment, their invention came to fruition in 1981. Only five years later, they were awarded the Nobel Prize in Physics.

Rohrer’s practical abilities, inventive genius, and scientific contributions were rewarded with numerous prestigious awards in addition to the Nobel Prize. In 1984, Rohrer and Binnig received the King Faisal Prize and the Hewlett Packard Europhysics Prize for their invention of the STM. Rohrer was presented the Elliott Cresson Medal of the Franklin Institute in Philadelphia in 1987. In 1994, he was inducted into the United States National Inventors Hall of Fame. He has also been awarded numerous honorary doctorates by several universities throughout the world.

Bibliography

Chen, C. Julian. Introduction to Scanning Tunneling Microscopy. 2d ed. New York: Oxford University Press, 2007. This very readable book discusses the invention of the STM and the basic operating principles of scanning tunneling microscopy and atomic force microscopy. The theoretical basis and the relationship between tunneling and interaction energy are presented, along with the experimental facts. The use of the STM in biological research and its use in the manipulation of individual atoms in nanotechnology are presented. Bibliographical references and an index are included.

Dardo, Mauro. Nobel Laureates and Twentieth-Century Physics. New York: Cambridge University Press, 2004. Contains biographies and revealing personal anecdotes about the lives and events of the most famous physicists of the twentieth century. The work of Rohrer is presented and discussed by Dardo and by Rohrer himself. The significance of lasers, superconductivity, Bose-Einstein condensates, the STM, and other scientific breakthroughs of the twentieth century are highlighted. An index and bibliographical references are included.

Foster, Adam Stuart. Scanning Probe Microscopy: Atomic Scale Engineering by Forces and Currents. New York: Springer Science, 2006. Written in a tutorial style, the book explains the basic principles underlying atomic probe techniques that were pioneered by Rohrer and Binnig. Examples are presented of the theoretical concepts by using state-of-the-art simulations that allow comparisons with experimental data. Bibliographical references and an index are included.

Margulis, Lynn, and Eduardo Punset, eds. Mind, Life, and Universe: Conversations with Great Scientists of Our Time. White River Junction, Vt.: Chelsea Green, 2007. The authors interviewed thirty-six scientists, one of whom was Rohrer, about their thoughts and ideas regarding some of the most important concepts influencing their fields today. Rohrer gives insights into research in atomic and subatomic phenomena and applications to everyday uses. An index and bibliographical references are included.