(Left to right) Florian Mittendorfer, Giada Franceschi, Michael Schmid and Andrea Conti in their laboratory at TU Wien. Photo: TU Wien.
(Left to right) Florian Mittendorfer, Giada Franceschi, Michael Schmid and Andrea Conti in their laboratory at TU Wien. Photo: TU Wien.

At first glance, mica is quite ordinary: it is a common mineral, found in rocks like granite, and has been extensively studied from geological, chemical and technical perspectives.

One might think nothing new could be discovered about such an everyday material. But now, in a paper in Nature Communications, a team from Vienna University of Technology (TU Wien) in Austria report new information about the distribution of potassium ions on the surface of mica. The physical surface details of mica had never before been studied on an atomic scale, and these novel findings could be important for research on electronics that utilize two-dimensional (2D) materials.

Atomically thin 2D materials are currently one of the most researched topics in materials science: Certain materials, such as graphene and molybdenum disulfide, consist of only one or a few layers of atoms, giving them unusual properties.

In a sense, mica is a naturally occurring 2D material. It consists of atomically thin layers that can contain different atoms depending on the type of mica: oxygen is always present, often silicon, and often potassium or aluminum as well. The layered structure of mica is also the reason for its characteristic sheen, which can generate a spectrum of colors, similar to a thin layer of oil on a puddle of water.

The outermost layer of mica is difficult to examine because it is quickly contaminated by atoms and molecules from the air. Now, however, using a new type of atomic force microscope (AFM), the TU Wien team has managed to image the surface of mica in an ultra-high vacuum.

"We were able to see how the potassium ions are distributed on the surface," says Giada Franceschi, the first author of the paper. "We were also able to gain insights into the positions of the aluminum ions under the surface layer – this is a particularly difficult task experimentally."

The images generated by the AFM show that the potassium ions are not randomly distributed on the surface, as previously assumed, but are arranged in tiny patterns. These distributions could also be calculated with the help of computer simulations.

This work could prove important for the use of 2D materials such as graphene in electronic circuits, because this requires suitable insulators– and mica is a very obvious candidate. “The surface properties of mica will play a crucial role in such electronic components,” says Franceschi.

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