If you think of a single atom as a grain of sand, then a wavelength of visible light—which is a thousand times larger than the atom’s width—is comparable to an ocean wave. The light wave can dwarf an atom, missing it entirely as it passes by. This gulf in size has long made it impossible for scientists to see and resolve individual atoms using optical microscopes alone.

Only recently have scientists found ways to break this “diffraction limit,” to see features that are smaller than the wavelength of light. With new techniques known as super-resolution microscopy, scientists can see down to the scale of a single molecule.

And yet, individual atoms have still been too small for optical microscopes —which are much simpler and less expensive than super-resolution techniques—to distinguish, until now.

Two-dimensional (2D) materials, which are only a few atoms thick, are known to exhibit unique electrical, mechanical and optical properties, which differ considerably from the properties of bulk materials. Some recent studies have also been probing these materials’ “transparency” to intermolecular interactions, such as van der Waals (vdW) forces—weak forces arising from fluctuating electrical charges, which prompt the attraction between molecules or surfaces.

Determining the extent to which these forces are screened by atomically thin materials could have important implications for the development of various technologies based on 2D materials.

Researchers at Peking University, Nanjing University of Aeronautics and Astronautics and Tsinghua University recently set out to shed light on whether 2D graphene systems fully transmit, partially screen or block vdW interactions.

For the first time, a team at BESSY II has succeeded in demonstrating the one-dimensional electronic properties of a material through a highly refined experimental process.

The samples consisted of short chains of phosphorus atoms that self-organize at specific angles on a silver substrate. Through sophisticated analysis, the team was able to disentangle the contributions of these differently aligned chains. This revealed that the electronic properties of each chain are indeed one-dimensional. Calculations predict an exciting phase transition to be expected as soon as these chains are more closely packed. While material consisting of individual chains with longer distances is semiconducting, a very dense chain structure would be metallic.

The work is published in the journal Small Structures.

Researchers at University of Tsukuba have successfully measured electric fields near the surfaces of two-dimensional layered materials with femtosecond temporal and nanometer spatial resolution. They employed a diamond containing a nitrogen-vacancy center—a lattice defect—as a probe within an atomic force microscope, enabling atomic-scale spatial precision.

When nitrogen is incorporated as an impurity in a diamond crystal, the absence of a neighboring carbon atom forms a nitrogen-vacancy (NV) center. Applying an electric field to diamond containing NV centers modifies its refractive index, a phenomenon known as the electro-optic (EO) effect. Notably, this effect has not been observed in pure diamond alone.

In previous work, the research team used a femtosecond laser to detect lattice vibrations in diamond with high sensitivity by measuring the EO effect in high-purity diamond containing NV centers. These results demonstrated that diamond can act as an ultrafast EO crystal and serve as a probe—termed a diamond NV probe—for measuring electric fields.