Single-electron transistor allows for nanoscale ‘Etch A Sketch’ designs of ultra-dense memories

April 19, 2011
Single Electron

An atomic-scale depiction of the SketchSET shows three wires (green bars) converging on the central island (center green area), which can house up to two electrons. Electrons tunnel from one wire to another through the island. Conditions on the third wire can result in distinct conductive properties. (Credit: U. Pittsburgh)

A University of Pittsburgh-led team has created a 1.5 nanometer single-electron transistor that provides a building block for ultra-dense computer memories, advanced electronic materials, and the basic components of quantum computers.

The SketchSET (sketch-based single-electron transistor) is the first single-electron transistor made entirely of oxide-based materials, and consists of an island formation that can house up to two electrons. The number of electrons on the central island can be 0, 1, or 2. Wires extending from the transistor carry additional electrons across the island.

The SketchSET works like a microscopic Etch A Sketch drawing toy.  Using the sharp conducting probe of an atomic force microscope, the researchers can create electronic devices such as wires and transistors of nanometer dimensions at the interface of a crystal of strontium titanate and a 1.2 nanometer thick layer of lanthanum aluminate. The electronic devices can then be erased and the interface used anew.

A property of the oxide materials is ferroelectricity, which allows the transistor to act as a solid-state memory. The ferroelectric state can, in the absence of external power, control the number of electrons on the island, which in turn can be used to represent the 1 or 0 state of a memory element.

A computer memory based on ferroelectric state would be able to retain information even when the processor itself is powered down.

In addition, the tiny central island could be used as an artificial atom for developing new classes of artificial electronic materials, such as exotic superconductors with properties not found in natural materials.

The research was funded by the U.S. Air Force Office of Scientific Research’s Multi-University Research Initiative, and also supported in part by grants from the U.S. Defense Advanced Research Projects Agency (DARPA), the U.S. Army Research Office, the National Science Foundation, and the Fine Foundation.

Ref.: Gilberto Medeiros-Ribeiro & Jeremy Levy et al., Sketched oxide single-electron transistor, Nature Nanotechnology, April 17, 2011