Ames Laboratory

Ames Laboratory and Northeastern University developed and validated a model that predicts the shape of metal nanoparticles blanketed by 2D material. The top blanket of graphene resists deformation, "squeezing" downward on the metal nanoparticle and forcing it to be extremely low and wide.

In a collaboration between the U.S. Department of Energy's Ames Laboratory and Northeastern University, scientists have developed a model for predicting the shape of metal nanocrystals or "islands" sandwiched between or below two-dimensional (2-D) materials such as graphene. The advance moves 2-D quantum materials a step closer to applications in electronics.

Ames Laboratory scientist are experts in 2-D materials, and recently discovered a first-of-its-kind copper and graphite combination, produced by depositing copper on ion-bombarded graphite at high temperature and in an ultra-high vacuum environment. This produced a distribution of copper islands, embedded under an ultra-thin "blanket" consisting of a few layers of graphene.

"Because these metal islands can potentially serve as electrical contacts or heat sinks in electronic applications, their shape and how they reach that shape are important pieces of information in controlling the design and synthesis of these materials," said Pat Thiel, an Ames Laboratory scientist and Distinguished Professor of Chemistry and Materials Science and Engineering at Iowa State University.

Ames Laboratory scientists used scanning tunneling microscopy to painstakingly measure the shapes of more than a hundred nanometer-scale copper islands. This provided the experimental basis for a theoretical model developed jointly by researchers at Northeastern University's Department of Mechanical and Industrial Engineering and at Ames Laboratory. The model served to explain the data extremely well. The one exception, concerning copper islands less than 10 nm tall, will be the basis for further research.