CEITEC scientists uncovered a novel mode of tuning graphene


Graphene: the wonder-material


Graphene (source: Image by seagul from Pixabay) 


Graphene is a 2-dimensional honeycomb pane of carbon atoms, equipped with extraordinary properties in terms of strength, heat, and electrical conductivity.


It is a dream-substance for a material scientist, with myriads of applications in the ranges of sensors, electronics, membranes & coatings, energy harvesting or biotechnology.


Especially, in the electronics industry with the increasing need for low-dimensional but competent semiconductors, the planar mono-atom thick graphene is an ideal candidate. The material science arena is thriving to modify the characters of this wonder-material to their desires. 



Doping of graphene


In material science, ‘doping’ implies the addition of impurities (aka dopants, supplying e.g. electrons) to provide a material of the desired property (e.g. better electrical conductance).


The field of graphene doping is evolving with time, and the research group of Jan Čechal at CEITEC BUT has taken a strong stride at this end. They are studying graphene and trying to fine-tune its electronic properties by applying varied dopants. Recently, by means of low energy electron beams as a doping agent, they set forth a doping model for graphene with efficient versatility (1). 


Dr. Jan Čechal (Photography by Emil Gallík)


“We couldn’t believe our eyes at the beginning when we were checking the graphene resistance,” said Dr. Čechal, “you could see the huge change in resistance under X-ray irradiation, but when we turned the irradiation off, the resistance peak did not come back to base, but kept climbing farther.”


“But, after many repetitions using varied ranges of voltage, we disentangled and realized about the substrate effect; and the process was not less than a detective story,” stated Dr. Čechal.


With an aim to protect the graphene and ensure that only low energy electrons are transferred, the researchers covered the graphene with a layer of aluminum oxide/alumina. This appeared to be a key part of their approach. 


In the future, this novel doping procedure could also be used on other materials, apart from graphene. The future applications are aplenty: “it can be used in the field of adaptive electronics, where you can produce any kind of chip you want,” said Dr. Čechal, “imagine a research base on Mars, where you have no semiconductor factories, this new doping technique can help you to fabricate chips modifying the universal chips, with varied replacement parts you desire.”   


Graphene characterization (Photography by Emil Gallík)


Dr. Čechal adds, “The knowledge would be especially beneficial for universities and research institutes to assess their electronic prototypes quickly. But, most importantly, the research outcome has refined our expertise on how to characterize graphene.”



It is analogous to LEGO!


Nonetheless, the main focus of Dr. Čechal’s research is molecular self-assembly.


He explains, “We use single molecules to fabricate complex nanostructure. If you modify their chemical form, different structures can be created." 


"The idea is quite similar to LEGO, where you can use all different bricks and build something unique. However, it would be impractical to put brick by brick to make the structure.  Fortunately, we can follow the processes in the living nature, letting them assemble organically into more complex structures with defined functionality” states Dr. Čechal.


The process needs a lot of tweaking and we are excited to do that!” Dr. Čechal expressed eagerly.


Using dissimilar substrates, graphene would behave differently. Therefore, as an imminent aspiration, the Čechal lab would like to employ graphene doping to steer the self-assembly process and functionally refine the self-assembled nanostructures.

 


References

V. Stará, P. Procházka, D. Mareček, T. Šikola, and J. Čechal, “Ambipolar remote graphene doping by low-energy electron beam irradiation”. Nanoscale, 10(37), 17520–17524 (2018).

 

 

Written by Somsuvro Basu


Publication date: 01.07.2019