X-rays reveal electrons holding layers together

Synchrotron x-ray data has outlined the fragile bonds that hold together two-dimensional materials such as graphene. 

A team from the University of Tsukuba and Aarhus University x-rayed the layered 2D material, titanium disulfide, showing for the first time the distribution of electrons between the layers in high resolution.

The layers are held together by fluctuations in electron clouds that result in weak binding, known as Van der Waals forces. Unlike the covalent binding forces within the layers, the weak chemical Van der Waals forces between the titanium and sulfur atoms are difficult to model with the current method, Density Functional Theory (DFT). 

While the experiments showed good agreement with DFT calculations for the intralayer bonds, they found discrepancies in the interlayer bonds. For example — the bonds between the sulfur atoms were stronger than predicted.

“Our experiments are the first to reveal the true nature of the interactions that make 2D materials so interesting, and we hope they will underpin many future developments in this area,” says the University of Tsukuba’s, Hidetaka Kasai, first author of the study.