UNSW physicists were able to use a single phosphorus atom as a transistor that was placed between "atomic-scale electrodes and electrostatic control gates". To exactly position atoms on a chip is a critical ability to build quantum computers, the scientists said.
The team used a scanning tunnelling microscope to monitor and move atoms on the surface of a silicon crystal that was put in an ultra-high vacuum chamber. The phosphorus atoms were positioned via a lithography process and then covered with a non-reactive layer of hydrogen. The researchers then removed the hydrogen atoms in specific locations using the microscope tip. The placement of the phosphorus atoms on the silicon surface was achieved via a chemical reaction. The researchers completed the transistor with a silicon layer and "alignment markers" that enabled them to apply an electrical charge.
The researchers said that the "electronic properties of the device were in excellent agreement with theoretical predictions for a single phosphorus atom transistor."
So far, it has not been possible to target a specific location and position an atom in that specific spot. "This device is perfect", said Michelle Simmons, group leader and director of the ARC Centre for Quantum Computation and Communication at UNSW. "This is the first time anyone has shown control of a single atom in a substrate with this level of precise accuracy." Previously scientists hoped that an atom would be present in the location they needed it.
Intel will be rolling out processors built in 22 nm this year. Transistors that reach an atom level are expected to be built in the 2020 time frame.