"Happy accident" uncovers new transport process of atoms in 2D spaces

Written by
Wendy Plump, Chemistry
Nov. 29, 2023

Researchers from Princeton have discovered a surprising process that rapidly and uniformly disperses palladium and other metals over a confined, two dimensional space at a temperature far below its melting point.

The transport process also creates a stable new 2D crystalline material from the base metal palladium and the parent crystal. The resulting compounds are only a few atoms thick and were previously not known to exist.

palladium atoms dispersing across parent crystal

Palladium atoms (darker blue) dispersing across parent crystal. Watch video at Princeton Chemistry site. Image courtesy of the researchers

During experiments, the material uniformly blooms across the obtaining surface in defiance of well-known laws of diffusion; almost, scientists say, the way spilled ink saturates a piece of paper – except there are no liquids involved.

And they have no idea why.

Graduate student Yanyu Jia first observed the phenomenon using a scanning and transmission electron microscope in the Imaging and Analysis Center (IAC), where the team characterized and measured the palladium atoms moving across the parent crystal.

They assembled the device using nanolithography, a process that creates nanoscale patterns, and metal deposition to transfer patterned palladium onto a parent crystal surface.

“We worked in the cleanroom quite a lot,” said Jia, referring to Princeton Materials Institute’s Micro/Nanofabrication Center.

Leslie Schoop and Sanfeng Wu

As they seek to explain this phenomenon and explore applications of the new compounds, researchers extol the simplicity of this generalizable process that could have exciting implications for the synthesis of 2D materials and for unlocking new device functionalities. 

The paper, Surface-Confined Two Dimensional Mass Transport and Crystal Growth on a Monolayer, was published jointly by Associate Professor of Chemistry Leslie Schoop and Assistant Professor of Physics Sanfeng Wu in Nature Synthesis, who are both associated faculty in the materials institute.

The team is excited about future applications for this new method. “We are applying the approach for creating quantum structures and devices that were hard to imagine before,” said Wu. “Right now, this is an accident that solves several problems all at once.”