Scientists at the Department of Energy’s Oak Ridge National Laboratory have developed a groundbreaking advanced microscopy tool that can precisely place individual atoms, enabling the creation of new materials with unique properties for quantum computing and communication devices that cannot be produced by conventional methods.
“By working at the atomic scale, we also work at the scale where quantum properties naturally emerge and persist,” said Stephen Jesse, a materials scientist who leads this research and heads the Nanomaterials Characterizations section at ORNL’s Center for Nanophase Materials Sciences, or CNMS. “We aim to use this improved access to quantum behavior as a foundation for future devices that rely on uniquely quantum phenomena, like entanglement, for improving computers, creating more secure communications and enhancing the sensitivity of detectors.”
To accomplish improved control over atoms, the research team created a tool they call a synthescope for combining synthesis with advanced microscopy. The researchers used a scanning transmission electron microscope, or STEM, transformed into an atomic-scale material manipulation platform. The synthescope will advance the state of the art in fabrication down to the level of the individual building blocks of materials. This new approach allows researchers to place different atoms into a material at specific locations; the new atoms and their locations can be selected to give the material new properties.
“Classical computers use bits, which can be either 0 or 1, and do calculations by flipping these bits,” said ORNL’s Ondrej Dyck, a materials scientist contributing to the research. “Quantum computers use qubits, which can be both 0 and 1 at the same time. The qubits can also become entangled, with one qubit connected to the state of another. This entangled system of qubits can be used to solve certain problems much faster than classical computers. The tricky part is keeping these delicate qubits stable and working correctly in the real world.
“One strategy to tackle these challenges is to build and operate at the scale where quantum mechanics exist more naturally—at the atomic scale. We realized that if we have a microscope that can resolve atoms, we may be able to use the same microscope to move atoms or alter materials with atomic precision. We also want to be able to add atoms to the structures we create, so we need a supply of atoms. The idea morphed into an atomic-scale synthesis platform—the synthescope.”
That is important because the ability to tailor materials atom-by-atom can be applied to many future technological applications in quantum information science, and more broadly in microelectronics and catalysis, and for gaining a deeper understanding of materials synthesis processes. This work could facilitate atomic-scale manufacturing, which is notoriously challenging.
“Simply by the fact that we can now start putting atoms where we want, we can think about creating arrays of atoms that are precisely positioned close enough together that they can entangle, and therefore share their quantum properties, which is key to making quantum devices more powerful than conventional ones,” Dyck said.
Such devices might include quantum computers — a proposed next generation of computers that may vastly outpace today’s fastest supercomputers; quantum sensors; and quantum communication devices that require a source of a single photon to create a secure quantum communications system.
By using an electron beam, or e-beam, to remove and deposit the atoms, the ORNL scientists could accomplish a direct writing procedure at the atomic level.
“The process is remarkably intuitive,” said ORNL’s Andrew Lupini, STEM group leader and a member of the research team. “STEMs work by transmitting a high-energy e-beam through a material. The e-beam is focused to a point smaller than the distance between atoms and scans across the material to create an image with atomic resolution. However, STEMs are notorious for damaging the very materials they are imaging.”
The scientists realized they could exploit this destructive “bug” and instead use it as a constructive feature and create holes on purpose. Then, they can put whatever atom they want in that hole, exactly where they made the defect. By purposely damaging the material, they create a new material with different and useful properties.
“We’re exploring methods to create these defects on demand so we can place them where we want to,” Jesse said. “Since STEMs have atomic-scale imaging capabilities, and we work with very thin materials that are only a few atoms in thickness, we can see every atom. So, we are manipulating matter at the atomic scale in real time. That’s the goal, and we are actually achieving it.”
For more information: Nano Letters
Image: This artistic rendering shows a way to make materials atom-by-atom. The electron beam ejects a carbon atom from graphene, and a different atom bonds at the vacancy.
