The Man Who Almost Saw Atoms

Abstract

ATOMIC IMAGING H einrich Rohrer and Gerd Binnig were not the first to spy on the world of atoms when the two IBM scientists invented the scanning tunneling microscope (STM) in the early 1980s. In the late 1950s, for example, Erwin Mueller at Pennsylvania State University had invented an atom-resolving device called the field ion microscope. In a vacuum chamber, a strong electric field tore charged atoms from the surface of a sample, sending them careening into a detector in positions that reflected their arrangement in the sample. Field ion microscopy, however, was limited to metal samples drawn into very sharp points. But in the late 1960s, one of Mueller's former students invented a device that could have anticipated the STM directly—if only he had completed it. Russell Young, then at the National Bureau of Standards (NBS, now the National Institute of Standards and Technology), called his instrument the “topografiner,” after a Greek word meaning to describe a place. And to STM aficionados, its basic scheme has a familiar ring. Piezoelectric elements scanned its fine metal tip across a surface, with feedback and control systems maintaining the tip at a constant height. Young and colleagues John Ward and Fredric Scire even measured tunneling currents—the basis of the STM—when they brought the topografiner's tip sufficiently close to a metal sample. They published reports claiming that the effect could, in principle, be used to measure a surface position to within about 0.3 nanometer, or about atomic resolution. “One can honestly say that the instrument developed [at NBS] and the instrument that achieved atomic resolution [at the IBM Zurich Research Center] looked very similar,” says Roland Wiesendanger of the University of Hamburg. But Young ran into technical and bureaucratic difficulties. Vibrations and other perturbations were preventing the topografiner from seeing atoms. In a 1972 paper in the Review of Scientific Instruments , the NBS researchers gave some sense of the difficulties by pointing out that they were able to achieve tunneling currents only by running experiments during odd hours when their building's air conditioner was off and by operating the instrument remotely so that their own movements would not generate resolution-killing disturbances. Binnig and Rohrer later solved these problems with multitiered isolation systems. Young never had a chance to try. In 1971, NBS management took him off the topografiner project in a resource-allocation decision. But Young never forgot that he was once on the verge of seeing atoms—and neither did the Royal Swedish Academy of Sciences. In awarding the 1986 Nobel Prize in physics to Binnig and Rohrer, the Nobel committee acknowledged Young's close approach to the STM and blamed his failure to beat Binnig and Rohrer on “exceptionally large experimental difficulties.”