This image shows the semi-transparent structure of germanium manganese oxide, one of the newly discovered 2D materials, superimposed on its surface magnetic structure. The color pattern depicts regions in the vicinity of magnetic ions where the magnetization points out of the plane (red) or into the plane (blue). The strong spatial variation in the magnetic information could prove useful for data storage applications. Image: HZDR/Rico Friedrich.
This image shows the semi-transparent structure of germanium manganese oxide, one of the newly discovered 2D materials, superimposed on its surface magnetic structure. The color pattern depicts regions in the vicinity of magnetic ions where the magnetization points out of the plane (red) or into the plane (blue). The strong spatial variation in the magnetic information could prove useful for data storage applications. Image: HZDR/Rico Friedrich.

Two-dimensional (2D) materials possess extraordinary properties. They usually consist of atomic layers that are only a few nanometers thick, and are particularly good at conducting heat and electricity, for instance.

To the astonishment of many scientists, it was recently discovered that certain metal oxides can exist as 2D materials. These oxides are of great interest for areas such as nanoelectronics. Now, a German-American research team, led by researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), has succeeded in using data-driven methods to predict 28 representatives of this new class of 2D materials.

There is a substantial difference between conventional 2D materials such as graphene and the novel 2D materials that can be synthesized from metal oxides such as ilmenite and chromite. The latter do not form weak interactions – what are known as van der Waals forces – in their crystal structure, but instead form stronger ionic bonds that point in all directions. For this reason, only a few experiments have so far succeeded in detaching 2D versions of these metal oxides from their three-dimensional bulk versions.

The results of this study, reported in a paper in Nano Letters, can now lead to success in further experiments of this type. Using theoretical methods, the research team has predicted which compounds are actually worthwhile for experimental research.

“With our data driven method, we built upon the first available information from the initial experiments,” explains Rico Friedrich from the HZDR Institute of Ion Beam Physics and Materials Research, who led the study. “From this information, we developed structural prototypes and then ran them through a huge materials database as a filter criterion. The main challenge was figuring out why these materials form 2D systems so easily with particular oxides. From this information, we were able to develop a valid generalized search criterion and could systematically characterize the identified candidates according to their properties.”

For this purpose, the researchers primarily applied what is known as ‘density functional theory’, a practical computational method for electronic structures that is widely used in quantum chemistry and condensed matter physics. They collaborated with several German high-performance data centers for the necessary computing stages. A decisive factor was determining the exfoliation energy, which defines how much energy must be expended to remove a 2D layer from the surface of a bulk material.

The study also utilized the AFLOW (Automatic Flow for Materials Discovery) database, which has been developed for more than 20 years by Stefano Curtarolo at Duke University, who is an author of the paper. AFLOW is regarded as one of the largest materials science databases and classifies approximately 3.5 million compounds with more than 700 million calculated material properties.

Together with the associated software, this database not only provided the researchers with the chemical composition of 28 2D-capable materials, but it also allowed them to study their properties, which are remarkable in electronic, magnetic and topological respects. According to Friedrich, the specific magnetic surface structures of these 2D materials could make them particularly attractive for spintronic applications, such as data storage in computers and smartphones.

“I’m certain that we can find additional 2D materials of this kind,” he says. “With enough candidates, perhaps even a dedicated database could be created entirely specialized in this new class of materials.”

Together with partners in Germany and the US, Friedrich and his colleagues plan to pursue further study of the most promising 2D materials.

This story is adapted from material from Helmholtz-Zentrum Dresden-Rossendorf, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.