The mineral mica, commonly found in granite, has been well-studied for its geological, chemical, and technical properties. However, researchers from the Vienna University of Technology have discovered the mineral by studying the distribution of potassium ions on the surface of mica at an atomic level. This information is significant for research on electronics made from 2D materials.

Currently, 2D materials, which are made up of atomically thin layers, are a highly researched topic in the field of materials science. Some examples of such materials include graphene and molybdenum disulfide, which have unique properties due to their single or few layers of atoms.

Mica: The Promising Mineral

Mica, a naturally occurring mineral, is also a form of 2D material as it is made up of atomically thin layers that can contain various atoms such as oxygen, silicon, potassium, and aluminum. The layered structure of mica also causes its distinctive sheen and can display a range of colors, similar to an oil slick on the water, as stated by Phys in a report.

Examining the outermost layer of mica is challenging as it easily gets contaminated by atoms and molecules from the air. To overcome this, researchers at the Vienna University of Technology used a new type of atomic force microscope in an ultra-high vacuum to image the surface of mica. According to the first author of the study, Giada Franceschi, they were able to observe the distribution of potassium ions on the surface and gain insights into the positions of aluminum ions under the surface layer, which is difficult to accomplish experimentally.

The study revealed that the potassium ions on the surface of mica are not randomly distributed, but instead are arranged in small patterns. These patterns could be predicted through computer simulations. This research could have significant implications for utilizing 2D materials, such as graphene, in electronic circuits as suitable insulators are required. Mica is a prime candidate for this purpose. As per Giada Franceschi, the surface properties of mica will be crucial for these electronic components.

Atomic structure of mica and a picture taken by an atomic force microscope.
(Photo : Vienna University of Technology)
Atomic structure of mica and a picture taken by an atomic force microscope.

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Previous Study on Muscovite mica

Mica, a widely recognized insulator, has been discovered to act as a semiconductor when reduced to a few molecular layers. Muscovite mica (MuM) is a highly stable mineral that is frequently used as an insulator, but the electrical properties of single-layer and few-layered MuM are not well understood. A group of researchers from Japan and India have previously found and explained unusually high conductivity in MuM flakes that are only a few molecular layers thick. Their discovery could lead to the development of two-dimensional electronic devices that are resistant to harsh environments.

In 2004, researchers from the University of Manchester developed a method to create sheets of single carbon atoms from graphite, called graphene, by using adhesive tape to pull them away. Graphene is a material that is 1000 times thinner than human hair but stronger than steel. This groundbreaking exfoliation technique opened the door for the creation of a diverse range of two-dimensional materials with unique electrical and physical properties for future electronic devices.

Muscovite mica (MuM) is a material that has attracted interest. These minerals have the formula KAl2(AlSi3O10)(F, OH)2 and have a layered structure made up of aluminum (Al), potassium (K), and silicon (Si). Similar to graphene, MuM has gained attention as a substrate for building flexible electronic devices due to its ultra-flat structure. However, unlike graphene, MuM is an insulator.

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