¿Solo un material ordinario? Los últimos misterios de la mica

La mica es un mineral natural comúnmente utilizado en la industria electrónica por sus propiedades aislantes. Es bien conocido tanto por su capacidad para soportar altas temperaturas como por su resistencia a las interferencias eléctricas.

Un conocido mineral vuelve a estar en el punto de mira gracias a sus aplicaciones en la electrónica: la Universidad Tecnológica de Viena demuestra que la mica todavía tiene algunas sorpresas guardadas.

A primera vista, la mica parece bastante ordinaria: es un mineral frecuente en materiales como el granito y que ha sido objeto de un extenso examen desde el punto de vista geológico, químico y técnico.

Al principio puede parecer que no hay nada innovador que descubrir sobre un material tan mundano. Sin embargo, un equipo de la Universidad Tecnológica de Viena publicó recientemente un estudio en graphene and molybdenum disulfide, consist of only one or a few layers of atoms, which frequently leads to 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, often potassium or aluminum as well. The layer structure of the mica is also the reason for its characteristic sheen – you can often see a spectrum of colors, similar to a thin layer of oil on a puddle of water.

Florian Mittendorfer, Giada Franceschi, Michael Schmid and Andrea Conti

Florian Mittendorfer, first author Giada Franceschi, Michael Schmid, and Andrea Conti (left to right). Credit: Vienna University of Technology

Potassium ions in ultra-high vacuum

The outermost layer of mica is difficult to examine because it is quickly contaminated by atoms and molecules from the air. It has now been possible to image the surface of mica in ultra-high vacuum, however, using a new type of atomic force microscope at the Vienna University of Technology. “We were able to see how the potassium ions are distributed on the surface,” says Giada Franceschi, the first author of the current paper, who works in Prof. Ulrike Diebold’s team. “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 from the Vienna University of Technology 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.

Matching insulator for 2D electronics

This work could be important, among other things, for attempts to use 2D materials such as graphene for electronic circuits. One also needs suitable insulators for this – and mica is a very obvious candidate. “The surface properties of mica will play a crucial role in such electronic components,” says Giada Franceschi.

Reference: “Resolving the intrinsic short-range ordering of K+ ions on cleaved muscovite mica” by Giada Franceschi, Pavel Kocán, Andrea Conti, Sebastian Brandstetter, Jan Balajka, Igor Sokolović, Markus Valtiner, Florian Mittendorfer, Michael Schmid, Martin Setvín and Ulrike Diebold, 13 January 2023, Nature Communications.
DOI: 10.1038/s41467-023-35872-y

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