Atomically thin materials with microprocessors built on them could result in a quantum leap for conventional processors. It could also be a giant step forward in new applications in the flexible electronics field.
Two-dimensional (2D) materials are exceptionally versatile because they are made up of just a few layers of atoms, or even only one. The best-known 2D material is graphene. A layer consisting of sulphur and molybdenum atoms (molybdenum disulphide) is only three atoms thick and falls in the 2D category. Unlike graphene though, molybdenum disulphide has semiconductor properties.
Dr Thomas Mueller from the Photonics Institute at TU Wien is conducting research into 2D materials with his team. They see 2D materials as a promising alternative for the future production of both microprocessors and other integrated circuits.
Microprocessors are indispensable and a universal component in today’s world. Without their constant development, most of the things we all experience as an integral part of our normal lives these days would not be possible at all. This includes mobile phones, computers and the internet.
Although silicon has always been used in the manufacturing of microprocessors, it is slowly but surely reaching its physical limits. 2D materials such as molybdenum disulphide have the potential to become potential replacements for silicon.
Transistors are the most basic components of every digital circuit. Since graphene was first discovered in 2004, research into individual transistors produced from 2D materials has been ongoing. Achieving success in producing structures that are more complex than transistors has however been very difficult. Up to now, it has only been possible to produce individual digital components using a few transistors. Circuits that are much more complex are however required to achieve a microprocessor that operates independently. In addition, these circuits need to interact flawlessly.
Mueller’s team has now managed to achieve this for the first time. The outcome is a 1-bit microprocessor that can run simple programs. The microprocessor consists of 115 transistors over a surface area of around 0.6 mm2. Stefan Wachter, a doctoral student in Mueller’s team notes that although this seems modest when compared to the industry standards achieved with silicon, it is however a major breakthrough within this field of research. Now that the proof of concept has been achieved, there is no reason in principle that prevents further developments.
Mueller explained that not only the choice of material resulted in the success of the project. Careful consideration was given to the size of the individual transistors. To be able to create and cascade units that are more complex, the exact relationships between the transistor geometries within a basic circuit component is a crucial factor.
For this technology to be applied practically, much more complex and powerful circuits with thousands or even millions of transistors will be needed. The biggest challenges currently facing this field of research is reproducibility, with the yield in the production of the transistors used coming in a close second.
Both the production of 2D materials and the methods for processing them further are still at the very early stages of research. Mueller added that the circuits were manufactured by hand in the lab, because such complex designs are currently beyond their capability. Before the processor will be able to work as a whole, every single transistor has to function as planned.
Mueller also stressed that huge demands are placed on state of the art electronics. The researchers are however convinced that over the next few years, industrial methods could open up new fields of application for this technology. Flexible electronics that are required for flexible displays and medical sensors would be one example. 2D materials are much more suitable for these type of applications than the silicon traditionally used, because of their significantly superior mechanical flexibility.