A team of researchers at RMIT University in Melbourne have created two-dimensional sheets of materials using liquid metal. The materials have never been witnessed before in nature, and are no thicker than a few atoms.
School of Engineering Professor Kourosh Kalantar-zadeh and Dr. Torben Daeneke are heading the research. This is the culmination of their 18-month work on the project. The study, titled “A liquid metal reaction environment for the room-temperature synthesis of atomically thin metal oxides”, was published in ScienceJournal this month.
To achieve the results, the researchers synthesized the materials using a non-toxic gallium metal alloy. Daeneke explains the concept behind the experiment:
"When you write with a pencil, the graphite leaves very thin flakes called graphene, that can be easily extracted because they are naturally occurring layered structures," said Daeneke. "But what happens if these materials don’t exist naturally?"
"Here we found an extraordinary, yet very simple method to create atomically thin flakes of materials that don't naturally exist as layered structures."
To produce hafnium dioxide—a metal oxide which is often used as an electrical insulator—the researchers' powdered hafnium was dissolved inside of a gallium alloy at a low temperature.
Using traditional methods—to produce layers of about 10 atoms in thickness—metal is evaporated in a low-pressure chamber and thereafter forms condensation on the surface. Moreover, special equipment is needed, and the layers which are produced are not smooth, according to Professor Kalantar-zadeh. This condensation process usually ends with "islands" that form on the surface and then pool together to form the desired single layer.
This process does not happen smoothly, Kalantar-zadeh explains: "The edges, where the islands join, create boundaries that electrons [travelling through the metal oxide] bounce off [and become blocked]." The new technique allows the electrons to move around uninterrupted, which means greater efficiency in the overall process and the results. The differences are very striking: scientists created a material that was only two or three atoms thick.
A Shift in Electronics?
Another interesting aspect of this experiment is that the results were achieved using simple and relatively cost-effective methods, which surprised the team of researchers. The team did not even require additional special equipment—simply a stovetop and a small list of ingredients.
The great news also is that this method is quite versatile.
"We think the technique could be applied to a third of the periodic table," Daeneke expressed optimistically.
The most immediate impact this research could have is in the area of electronics: from smartphones to transistor radios, metal oxides are a critical part of the operation of a number of important electronic devices. This means that the thinner the layer of metal oxide researchers can create, the more energy efficient the electronic component is and faster it works. The results prove that “the liquid metal–based reaction route can be used to create 2D materials that were previously inaccessible with preexisting methods.”
Thanks to the important from this team of researchers, the future of electronics indeed looks very bright. This will affect the way the path of research and development for a number of industries will be mapped out.