For decades scientists could move only single atoms across the flat surface of materials, usually under extreme cold and vacuum conditions. These slow processes limited what could be built. Now researchers at MIT and other institutions have created a new way to move tens of thousands of atoms inside a solid crystal in just minutes at ordinary room temperature. The advance makes it possible to design entirely new atomic arrangements that do not exist in nature.
The method uses a carefully controlled electron beam, a narrow stream of electrons fired through the material like a precise tool. Sophisticated computer instructions direct the beam to specific spots with accuracy measured in picometers, or one trillionth of a meter. As the beam traces a small oscillating path, it gently pushes entire columns of atoms to new positions, creating pairs of vacancies and displaced atoms known as quantum defects. These tiny structural changes give the material unusual quantum properties.
Creating custom atomic patterns
In experiments the researchers worked with a thin crystal of chromium sulfide bromide, a type of semiconductor material that can conduct electricity under certain conditions. They produced more than 40,000 quantum defects in about 40 minutes, forming different patterns across the three-dimensional atomic lattice, or regular grid of atoms that makes up the crystal. The resulting structures remain stable in ordinary air and do not require special laboratory conditions.
The ability to place atoms exactly where they are wanted inside a solid material could lead to better quantum computers, denser magnetic memory, atomic-scale logic devices, and improved sensors. It also allows scientists to study how groups of atoms interact in ways that were previously impossible. The new technique is expected to work in a range of other crystals and lays the groundwork for programmable matter that can be engineered for specific functions in future technologies.
This research is published in Nature.