A novel technique that nudges single atoms to switch places within an atomically thin material could bring scientists another step closer to realizing theoretical physicist Richard Feynman’s vision of building tiny machines from the atom up.
A significant push to develop materials that harness the quantum nature of atoms is driving the need for methods to build atomically precise electronics and sensors. Fabricating nanoscale devices atom by atom requires delicacy and precision, which has been demonstrated by a microscopy team at the Department of Energy’s Oak Ridge National Laboratory.
They used a scanning transmission electron microscope, or STEM, at the lab’s Center for Nanophase Materials Sciences to introduce silicon atoms into a single-atom-thick sheet of graphene. As the electron beam scans across the material, its energy slightly disrupts the graphene’s molecular structure and creates room for a nearby silicon atom to swap places with a carbon atom.
“We observed an electron beam-assisted chemical reaction induced at a single atom and chemical bond level, and each step has been captured by the microscope, which is rare,” said ORNL’s Ondrej Dyck, co-author of a study published in the journal Small that details the STEM demonstration.
Using this process, the scientists were further able to bring two, three and four silicon atoms together to build clusters and make them rotate within the graphene layer. Graphene is a two-dimensional, or 2D, the layer of carbon atoms that exhibits unprecedented strength and high electrical conductivity. Dyck said he selected graphene for this work, because “it is robust against a 60-kilovolt electron beam.”
“We can look at graphene for long periods of time without hurting the sample, compared with other 2D materials such as transition metal dichalcogenide monolayers, which tend to fall apart more easily under the electron beam,” he added.
STEM has emerged in recent years as a viable tool for manipulating atoms in materials while preserving the sample’s stability. Ondrej Dyck/Oak Ridge National Laboratory, U.S. Dept. of Energy
With a STEM microscope, ORNL’s Ondrej Dyck brought two, three and four silicon atoms together to build clusters and make them rotate within a layer of graphene, a two-dimensional layer of carbon atoms that exhibits unprecedented strength and high electrical conductivity. Credit: Ondrej Dyck/Oak Ridge National Laboratory, U.S. Dept. of Energy
Dyck and ORNL colleagues Sergei Kalinin, Albina Borisevich and Stephen Jesse are among few scientists learning to control the movement of single atoms in 2D materials using the STEM. Their work supports an ORNL-led initiative coined The Atomic Forge, which encourages the microscopy community to reimagine STEM as a method to build materials from scratch.
thumbnail courtesy of ornl.gov