New materials for extra thin computer chips

Increasingly smaller and more compact – this is the direction in which computer chips are developing, powered by the industry. This is the reason why so-called 2-D materials are considered the great hope: they are as thin as a material can be, in extreme cases they consist of a single layer of atoms. This makes it possible to produce novel electronic components with small dimensions, high speed and optimum efficiency.

However, there is a problem: electronic components always consist of more than one material. Two-dimensional materials can only be used effectively if they can be combined with suitable material systems, such as special insulating glass. If this is not considered, the advantage that 2D materials are supposed to offer is nullified. A team from the TU Wien Faculty of Electrical Engineering (Vienna) now presents these findings in the journal Nature’s Communications.

Reaching the end of the line on the atomic scale

“The semiconductor industry today is primarily based on silicon and silicon oxide,” says Professor Tibor Grasser of the TU Wien Institute for Microelectronics. “These are materials with very good electronic properties. For a long time, thinner layers of these materials were used to miniaturize electronic components. This worked well for a long time, but at some point we reached a natural limit.”

When the silicon layer is only a few nanometers thick, so that it only consists of a few atomic layers, the electronic properties of the material deteriorate very significantly. “The surface of a material behaves differently than most material, and if the entire object is practically made up of surfaces and no longer has a mass, it can have completely different material properties.”

Therefore, one has to switch to other materials to create ultrathin electronic components. And this is where so-called 2-D materials come into play: They combine excellent electronic properties with minimal thickness.

Thin layers need thin insulators

“However, it turns out that these 2-D materials are only the first half of the story,” says Tibor Grasser. “The materials have to be placed on the appropriate substrate, and an insulating layer is also needed on top, and this insulator also has to be extremely thin and of very good quality, otherwise you have gained nothing with 2-D materials “It is like driving a Ferrari in muddy terrain and wondering why a speed record is not set.”

Therefore, a team from TU Wien around Tibor Grasser and Yury Illarionov have discussed how to solve this problem. “Silicon dioxide, which is normally used in the industry as an insulator, is not suitable in this case,” says Tibor Grasser. “It has a very messy surface and many free and unsaturated bonds that interfere with the electronic properties in the 2-D material.”

It is better to look for a well-ordered structure: the team has already achieved excellent results with fluorides, a special class of crystals. A prototype transistor with a calcium fluoride insulator has already provided compelling data, and other materials are still being analyzed.

“New 2-D materials are currently being discovered. That is good, but with our results we want to demonstrate that this alone is not enough,” says Tibor Grasser. “These new two-dimensional semiconductor materials must also be combined with new types of insulators. Only then can we produce a new generation of efficient and powerful electronic components in miniature format.”