‘Writing’ with atoms could transform production of materials for quantum devices

The scientists who developed it say the new technology, which can continuously place individual atoms exactly where they are needed, could lead to new materials for devices that meet key needs in quantum computing and quantum communications and that cannot be made using conventional methods.

A research team at the Department of Energy’s Oak Ridge National Laboratory has created a novel, advanced microscope tool that can “write” with atoms—placing atoms exactly where they are needed to give a material new properties.

“By working at the atomic scale, we are also working at the scale where quantum properties emerge and persist naturally,” said Stephen Jesse, a materials scientist who led this research and directs the Nanomaterials Characterization Section in ORNL’s Center for Nanophase Materials Science (CNMS).

“Our goal is to use this improved access to quantum behavior as the basis for future devices that rely on unique quantum phenomena such as entanglement to improve computers, create more secure means of communication, and increase the sensitivity of detectors.”

To achieve better control over atoms, the research team created a tool they call a synthetiscope, which combines synthesis with advanced microscopy. Scientists use a scanning transmission electron microscope, or STEM, transformed into a platform for manipulating materials at the atomic scale.

Syntescope will advance the state of the art in manufacturing down to the level of individual building blocks of materials. This new approach allows researchers to place different atoms in a material in specific locations; new atoms and their locations can be selected to give the material new properties.

“Classical computers use bits that can be either 0 or 1, and they perform calculations by flipping those bits,” said ORNL materials scientist Ondrej Dyck, who contributed to the study. “Quantum computers use qubits that can be both 0 and 1 at the same time. 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 hard part is keeping these delicate qubits stable and working properly in the real world.

“One strategy for addressing these challenges is to build and operate at the scale where quantum mechanics exists more naturally—the atomic scale. We realized that if we had a microscope that could separate atoms, we might be able to use that same microscope to move atoms or modify materials with atomic precision. We also wanted to be able to add atoms to the structures we were building, so we needed a supply of atoms. The idea evolved into an atomic-scale synthesis platform—the synthoscope.”

This is important because the ability to tailor materials atom by atom could be used in many future technological applications in quantum information science, and more broadly in microelectronics and catalysis, as well as to gain a deeper understanding of materials synthesis processes. This work could facilitate atomic-scale manufacturing, which is notoriously difficult.

“Simply because we can now start putting atoms where we want them, we can think about creating arrangements of atoms that are precisely spaced close enough together that they can entangle and therefore share their quantum properties, which is key to making quantum devices more efficient than conventional ones,” Dyck said.

Such devices could include quantum computers, the proposed next generation of computers that could significantly outperform today’s fastest supercomputers; quantum sensors; and quantum communications devices, which require a single-photon source to create a secure quantum communications system.

“We’re not just moving atoms around,” Jesse said. “We’re showing that we can add different atoms to a material that weren’t there before and put them where we want them. Right now, there’s no technology that lets you put different elements exactly where you want them and have the right bonds and structure. With this technology, we could build structures from the atom up, designed for their electronic, optical, chemical or structural properties.”

The scientists, who are part of CNMS, a nanoscience research center and DOE Office of Science user center, detailed their research and vision in a series of four journal articles over the course of a year, starting with a proof of principle that the synthoscope could be realized. They have filed for a patent on the technology.

“With this work, we are changing the way electron-beam manufacturing at the atomic scale will look,” Dyck said. “Together, these manuscripts outline the direction we think atomic manufacturing technology will go in the near future, as well as the conceptual shift that is needed to advance the field.”

By using a beam of electrons, called an e-beam, to remove and deposit atoms, ORNL scientists were able to perform a direct writing procedure at the atomic level.

“The process is incredibly intuitive,” said ORNL’s Andrew Lupini, a STEM group leader and a member of the research team. “STEMs work by sending a high-energy beam of electrons through a material. The beam of electrons is focused to a point smaller than the distance between atoms and scans the material to create an atomic-resolution image. However, STEMs are notorious for damaging the very materials they image.”

Scientists realized that they could take advantage of this destructive “bug” and instead use it as a design feature and intentionally create holes. They could then place any atom in that hole, exactly where they made the defect. By intentionally damaging the material, they created a new material with different and useful properties.

“We’re exploring ways to create these defects on demand so we can put them where we want them,” Jesse said. “Because STEM has atomic-scale imaging capabilities, and we’re working with very thin materials that are just a few atoms thick, we can see every atom. So we’re manipulating matter on the atomic scale in real time. That’s the goal, and we’re actually achieving it.”

To demonstrate this method, the researchers moved a beam of electrons back and forth over a graphene lattice, creating tiny holes. They inserted tin atoms into these holes and achieved a continuous, atom-by-atom, direct writing process, thus filling the exact same places where the carbon atom had been with tin atoms.

“We believe that atomic-scale synthesis processes can become routine using relatively simple strategies. Combined with automated beam control and AI-based analysis and discovery, the synthescope concept offers a window into atomic-scale synthesis processes and a unique approach to atomic-scale manufacturing,” Jesse said.