From the lab into a computer

When I started my PhD in the lovely city of Toulouse I already knew that an increasingly large portion of the solid-state physics community was focusing on the study of 2D materials. Graphene was already well known even outside the scientific community and everyone was describing it as the miraculous material of the future. That was one of the reasons why I started looking for a position in this field.


What I’m actually working on different 2D crystals which, contrary to Graphene, act like semiconductors. This family is called Transition Metal Dichalcogenides (TMDs) and in this Spin-NANO blog you will find a lot of details about them: the description of their properties, the possibilities they open up in the creation of new devices or in improving existing ones as well as the challenges in the way. That’s why today I’m not focusing on all of this but I’ll prefer doing something different.


I was just checking my newsfeed on Facebook when I saw a post of one of my former colleagues, who just got a permanent position at École Polytechnique in Paris. It was a Nature Communications paper whose title immediately caught my attention: A microprocessor based on a two-dimensional semiconductor. I already knew that in 2011 a MoS2  monolayer based Field Effect Transistor (FET) was built and proven to be operational. However, this paper appeared to talk about a more complex and integrated device, a full microprocessor. I read it as soon as I could.


Unfortunately, because of my limited knowledge of microprocessor logic and operation, I didn’t grasp every detail about the device but I was still fascinated by the overall message. The team at the Institute of Photonics at Vienna University of Technology replaced the silicon in the FETs channel with MoS2 bilayer achieving a microprocessor made of 115 transistors which is able to execute user-defined programs, perform operations and communicate the result to outer devices.


Microscope image of the TMD transistor microprocessor.


One intriguing property of this device is the fact that the substrate can be bendable, opening up the possibility of having flexible electronic devices. However, the most obvious advantage of replacing silicon in transistors with 2D crystals comes from the better geometric scaling and less power consumption that these materials will provide. Which ultimately results in smaller devices with long lasting batteries!


Obviously, this prototype microprocessor is still far from the performances of its commercially available counterparts but this is not diminishing my interest on this result as it represents a proof of concept. These devices are doable and making them even more efficient than the ones which are available is just a technological challenge and thus just a question of time.


I’m talking about this topic because I work on the other side of the research process: the fundamental research. My aim is principally the understanding of the intrinsic properties of these crystals, and this kind of study is mainly performed for a sense of curiosity rather than for reaching an application goal. It is thus easier to lose the connection between what I’m actually studying and why so many people are working around the world are working on these materials. It’s true that in the introduction of every paper on TMDs you can read how many applications will be possible when our control over them will be good enough, but these often appear distant. Reading that paper instead reminded me how close we are to turn those world into reality.


By Marco Manca, PhD student at LPCNO laboratory in Toulouse, France


Wachter, S. et al. A microprocessor based on a two-dimensional semiconductor. Nat. Commun. 8, 14948 doi: 10.1038/ncomms14948 (2017)



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