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Novel single-electron device formed, claims NIST

Posted: 07 Feb 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Peter Clarke? NTT? silicon transistor? electron? National Institute of Standards and Technology?

Engineers from NTT Corp. have produced a novel design of silicon transistor that is controlled by the motion of individual electrons, according to the National Institute of Standards and Technology (NIST), which tested devices.

The devices are experimental but may find application in next-generation integrated circuits for logic operationsas opposed to memoryNIST said. At negative voltage, the transistor is off; at higher voltage, the transistor is turned on and individual electrons file through the circuit, as opposed to thousands at a time in a conventional device.

The transistors, described in the Jan. 30, 2006, issue of Applied Physics Letters, have been dubbed "single-electron tunneling" (SET) devices and are typically made with a metal wire interrupted by insulating barriers that offer the means to control electron flow. Particular voltage levels are applied across the barriers, to manipulate charge, as a means of encouraging or impeding electron flow.

A great deal of single electron device work was done at Cambridge University's Cavendish laboratory and at Hitachi Central Research Laboratories. Early work concentrated on compound semiconductor material and required temperatures close to absolute zero. Silicon-based devices would allow fabrication using standard semiconductor technologym but until NTT's work no silicon SET transistor designs have been reported that are reproducible and controllable, NIST asserted.

NTT made five uniform, working silicon transistors with tunable barriers. Each device consists of a silicon channel 360 nanometers long and 30-nanometers wide, with three gates crossing the channel. The gates have two levels; the upper level turns the current on and off, while the lower level controls electron flow in small local areas, the NIST report said. The team was able to tune gate conductance properties over a wide range, by more than three orders of magnitude.

- Peter Clarke
EE Times

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