Single atom in silicon crystal enables working transistor

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Researchers have developed a working transistor consisting of a single atom placed precisely in a silicon crystal, paving the way for future quantum computers.

To develop the electronic device, physicists from the University of New South Wales used an individual phosphorus atom patterned between atomic scale electrodes and electrostatic control gates as an active component. According to the researchers, this is the first time anyone has shown control of a single atom in a substrate with this level of precise accuracy. The tiny device has visible markers etched onto its surface so metal contacts can be connected and a voltage applied. UNSW researcher, Dr Martin Fuechsle, said: "Our group has proved that it is really possible to position one phosphorus atom in a silicon environment – exactly as we need it – with near atomic precision, and at the same time register gates." A scanning tunnelling microscope was used to manipulate atoms at the surface of the crystal inside an ultra high chamber. Using a lithographic process, phosphorus atoms were patterned into functional devices on the crystal. These were then covered with a non-reactive layer of hydrogen. Hydrogen atoms were removed selectively in precisely defined regions with the metal tip of the microscope and a controlled chemical reaction then incorporated phosphorus atoms into the silicon surface. The structure was then encapsulated with a silicon layer and the device contacted electrically using a system of alignment markers on the silicon chip to align metallic connects. According to the researchers, the electronic properties of the device were in excellent agreement with theoretical predictions for a single phosphorus atom transistor. The researchers findings have been published in nature nanotechnology.