27-07-2018 | By Rob Coppinger
Faster transistors for higher speed electronics are possible with a new two-dimensional semiconductor, Tellurene, made from the element Tellurium.
Researchers fabricated Tellurene transistors that exhibited stable performance at ambient room temperatures and operated for more than two months. Electrons can travel more quickly through Tellurene enabling faster computation. Tellurene is stable at room temperature and can be made in large quantities to compete with the volumes of today’s silicon transistors. A challenge for the researchers was to avoid creating a Tellurene wire, which has been the outcome of earlier work because Tellurium’s crystalline structure has a tendency to grow in chains.
“For the past 20 years of trying to synthesis Tellurium nanostructures, researchers ended up with one dimensional nanowires or rods,” said Wenzhuo Wu, an assistant professor in Purdue’s School of Industrial Engineering. “No one has reported these two-dimensional, sheet like, paper like, 2D Tellurene. We are the first to experimentally achieve that.” A two-dimensional material is like a piece of paper. One dimensional is a wire or rod and three-dimensional is material in bulk.
Created in a solution, the 2D Tellurene can be produced in flakes that are 100 microns in length and width and can have a thickness of tens of nanometres. The precise thickness can be controlled during production. To make the flakes in larger quantities, the container for the solution just needs to be larger. Tellurene can be used with any substrate, another reason it can be utilised for electronic devices. “We could 3D print Tellurene onto any substrate,” Wu explained. Wu and his fellow researchers believe that Tellurene could also be used for flexible printed devices that convert mechanical vibrations, or heat, into electricity.
A small quantity of two-dimensional tellurene, derived from the rare element tellurium, can make computer chip transistors both more scalable and efficient.
Credit: Purdue University image/Vincent Walter
Other two-dimensional semiconductors, such as graphene, black phosphorus and silicene, either are not stability at room temperature, requiring colder conditions, or their manufacturing methods cannot achieve the volumes needed for mass production. Black phosphrous, for example, is made using the chemical vapour deposition process which uses a vacuum and it can only produce small quantities at a time.
Discovered in the 19th century, Tellurium is a semimetallic, lustrous, crystalline, brittle, silver-white element that is relatively rare. There are eight naturally occurring isotopes of Tellurium, of which three are radioactive. Tellurium is among the rarest stable solid elements in the Earth's crust. At 0.005 parts per million, it is comparable to platinum in abundance. It can be alloyed with some metals to improve their machinability.
The 2D Tellurene work began about two years ago, and Wu teased further advances in upcoming scientific papers. “We intend to publish more results soon,” he added. That work is not how to design a Tellurene transistor, rather it is studying the fundamental properties of this new material. The research is being supported by the United States (US) government’s National Science Foundation, Oak Ridge Associated Universities, the US Air Force Office of Scientific Research, the US Army Research Office and the Semiconductor Research Corporation.