Too small to see By P. Weiss Varying the voltage of the gate, an electrode in the ultrasmall vacuum tube shown in this diagram, adjusts the current zipping from a cathode pillar to the anode.
Insulating material appears in magenta.
In the lilliputian realm of modern electronics, old-style vacuum tubes have all the charm of hulking Gullivers. They hope to exploit ways in which vacuum tubes outperform semiconductor devices. A team in England has now developed a vacuum tube whose size rivals that of transistors in today's microcircuits. The evacuated hollow in the so-called nanotriode occupies only about a billionth the volume of a grain of salt, says Haroon Ahmed, whose group describes the device in the Nov. 1 Applied Physics Letters . Alexander A.G. Driskill-Smith, David G. Hasko, and Ahmed, all of the University of Cambridge, fabricated the prototype device from alternating layers of metals and insulators.