Press release: The 1986 Nobel Prize in Physics

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   Tunnelling works for you every day: Esaki's diode, the microscope that sees atoms and the flash memory in your phone all live on it. It is also a wall for ever-smaller transistors, through which electrons start to leak.

   Press release: The 1986 Nobel Prize in Physics · 1986

   The microscope sees atoms and flash memory keeps data because tunnelling depends enormously on distance and voltage.

   The first invention came in 1957. Leo Esaki, a young researcher at the Japanese company that would become Sony, made a diode (a part that lets current pass only one way) with an extremely thin separating layer. The current crossed the layer by tunnelling, and the diode behaved strangely: at a certain voltage, if you pushed harder, the current went down. That made it very fast. The Esaki diode earned him the 1973 Nobel Prize in Physics, together with Ivar Giaever and Brian Josephson. The second: the scanning tunnelling microscope, built in 1981 by Gerd Binnig and Heinrich Rohrer at IBM's laboratory in Zurich. A needle sharpened down to a single atom at its tip moves over a surface without touching it, at a distance of about two atoms. Electrons tunnel between the needle and the surface. Because the chance of getting through falls very fast with distance, the current changes about tenfold if the needle rises or falls by a tenth of a nanometre. By holding the current steady and following how the needle moves up and down, you can draw the surface atom by atom. The Nobel came in 1986. In 1989, at IBM, Don Eigler and Erhard Schweizer used such a needle to move 35 xenon atoms and spell the letters I, B and M. The third is in your pocket: the flash memory in your phone and on USB sticks. Each bit is a tiny island of conductor buried in an insulator. To write, you apply a high voltage and electrons tunnel through the insulator onto the island. Without the voltage, the insulator is thick enough for them to stay there for years, with the phone switched off. The same tunnelling is also a problem: when the insulator in transistors shrank to a few atoms thick, electrons began leaking through it, and the industry had to switch to other materials.

   “An electrical potential between the tip of the stylus and the surface causes an electric current to flow between them despite the fact that they are not in contact. […] Recording the vertical movement of the stylus makes it possible to study the structure of the surface atom by atom.”

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