While much research into graphene for electronics applications has focused on ways to have it replace silicon, a research group at the University of Vienna is looking at ways to integrate graphene into current silicon-based technologies.
The Vienna researchers along with colleagues in Germany and in Russia took an approach to integrating silicon within graphene that involved building a semiconducting or an insulating buffer between graphene and a metallic substrate.
With this aim, the international team have successfully built a structure of high-quality metal silicides covered and protected underneath a graphene layer. Metal silicides, which are a compound of silicon with a more electropositive element, are used extensively in applications including complementary metal oxide semiconductor (CMOS) devices, thin film coatings and photovoltaics as interconnects and barriers.
The research published in Nature’s new open-access journal Scientific Reports (“Controlled assembly of graphene-capped nickel, cobalt and iron silicides”) used monocrystalline layers of films of nickel, cobalt and iron as the substrate on top of which high-quality graphene produced through chemical vapor deposition (CVD) was deposited. The resulting structure is protected against oxidation because of the graphene capping the metal silicide layers.
In the paper the researchers report: "Here, we demonstrate that intercalation of silicon atoms underneath the graphene top layer and a series of annealing cycles allow one to create a variety of metal silicides with different properties, all nicely covered and protected by graphene."
While the structure itself is interesting, the aim of the research was to reveal the basic properties of graphene/silicide interfaces. To accomplish this, the researchers employed angle-resolved photoemission spectroscopy (ARPES), which allowed the team to determine the angle under which the electrons escape from the material.
"Single-atom thick layers and hybrid materials made thereof allow us to study a wealth of novel electronic phenomena and continue to fascinate the community of material scientists,” said Alexander Grueneis and Nikolay Verbitskiy, members of the Electronic Properties of Materials Group at the University of Vienna and co-authors of the study, in a press release.
By applying the ARPES method, the researchers determined that the graphene layer has little interaction with the silicides it’s covering. It also revealed that the unique properties of graphene that make it so attractive in the first place are largely maintained.
The researchers believe that they demonstrated a way to integrate graphene into current metal silicide technologies. However, it would seem the main benefit of doing so would merely be to give the structure a new resistance to oxidation.
It’s not likely that this will be the ‘killer app’ for graphene in electronic applications that will see it “Conquer Silicon Valley” as the headlines tout. In addition to the application being somewhat underwhelming, the production of graphene through CVD is also a costly process and would struggle economically in being applied to any bulk, industrial scale application at this point.
Nonetheless, this research was only intended to demonstrate that this integration between graphene and metal silicides could be accomplished with good results. Graphene’s conquering of anything will have to wait for another day.
Image: Dr. Alexander Grueneis/University of Vienna