Physicists have measured the electronic properties of a single atom for the first time. Elke Scheer of the Universität Karlsruhe in Germany and colleagues measured the properties of lead, gold, aluminium and niobium atoms between metallic electrodes. The team used lithography, a technique common in the semiconductor industry, to create their devices (Nature 394 131). Such techniques might make it possible to design electronic circuits atom by atom and to exploit quantum phenomena in the development of ultrafast, ultrasensitive devices.
Scheer and colleagues used a scanning tunnelling microscope, a mechanically controlled break junction, and lithography to fabricate various simple electronic circuits. These devices measured the effect of passing a current through a single atom as they stretched the circuit to breaking point. They discovered that the current between the metal banks across the atom is equal to the number of valence orbitals in the atom. Their results prove that small quantum effects can effect conductance on macroscopic leads.
