Chapter 1: The Dawn of Atomic Engineering

Recent breakthroughs in manipulating individual atoms using electron beams have been achieved by researchers from MIT and the University of Vienna, signaling the advent of atomic engineering.

This illustration depicts the precise relocation of a phosphorus atom within a graphite layer, facilitated by an electron beam, as demonstrated by the research team. (Image courtesy of the researchers)

Achieving unparalleled control over materials at the atomic level could enable the construction of devices with exceptional precision. Scientists at MIT, the University of Vienna, and other institutions have developed a technique that allows them to reposition atoms using a finely focused electron beam. This method not only dictates the precise locations of the atoms but also the orientation of their bonds.

The implications of this research could revolutionize the creation of quantum computing devices and sensors, heralding a new era of "atomic engineering," according to the research team.

Ju Li, a professor at MIT specializing in nuclear science and engineering, states: “We’re employing numerous nanotechnology tools.” This new approach, published in the journal Science Advances, leverages these tools to manage processes that operate on a scale significantly smaller than before.

Li elaborates: “Our objective is to control one to a few hundred atoms, regulating their positions, charge states, and electronic and nuclear spin states.”

Historically, scientists have successfully manipulated individual atoms, even arranging them in neat circles. This earlier method involved mechanically picking up single atoms with a scanning tunneling microscope and positioning them, a process that was notably slow.

The current method employs a relativistic electron beam within a scanning transmission electron microscope (STEM). This setup eliminates the need for mechanical components, as the beam is directed using magnetic lenses, potentially accelerating the process and broadening its practical applications.

Li mentions that with the integration of electronic controls and artificial intelligence, they anticipate being able to manipulate atoms within microseconds. “This is many orders of magnitude quicker than our current mechanical manipulation methods. Furthermore, we could potentially utilize several electron beams simultaneously on the same material.”

Professor Toma Susi of the University of Vienna describes this approach as “an exciting new paradigm for atom manipulation.”

Traditional computer chip fabrication involves “doping” silicon crystals with other atoms to impart specific electrical attributes, resulting in “defects” that disrupt the orderly crystalline structure of silicon. Li notes that this existing technique lacks the atomic precision that the new system offers.

The research illustrates that a single, narrowly focused electron beam can displace an atom from one location to another. By measuring the beam's angle, the researchers can confirm the new position of the atom, ensuring it was relocated accurately.

While positioning is based on probabilities and isn't completely accurate, the capability to ascertain the actual position enables the selection of configurations that meet the desired criteria.

Li humorously compares this process to a game of soccer: “We aim to use the beam to nudge atoms, essentially dribbling them across a graphene field to their intended 'goal' position. Like soccer, it’s not deterministic, but you can manipulate the probabilities. The objective remains to advance toward the goal.”

In their experiments, the team primarily utilized phosphorus atoms, a common dopant, embedded in a graphene sheet—a two-dimensional structure of carbon atoms arranged in a honeycomb formation. The phosphorus atoms substitute for carbon atoms in this lattice, influencing the material’s electronic, optical, and other properties based on their positions.

The goal is to maneuver multiple atoms in intricate patterns. Li adds, “We aspire to use the electron beam to effectively position these dopants to create a pyramid or a complex defect where we can accurately determine the placement of each atom.”

This represents the first instance of electronically distinct dopant atoms being manipulated within graphene. As Professor Susi notes, “While we’ve previously worked with silicon impurities, phosphorus is particularly intriguing due to its electrical and magnetic properties, and we’ve now discovered it behaves in surprisingly diverse ways. Each element may reveal new possibilities and insights.”

However, the method comes with challenges. Precise control over the beam’s angle and energy is crucial. Susi cautions: “We sometimes encounter unintended outcomes if we’re not meticulous. For instance, a carbon atom meant to remain in place might become displaced, or a phosphorus atom could become locked within the lattice, making it impossible to alter its position regardless of beam adjustments.”