Researchers have been able to make a silicon-based transistor for the first time. This material is seen as a ‘silicon alternative’ to graphene, but silicene did not seem stable enough to actually be used for transistors.
Graphene consists of a single layer of carbon atoms in a kind of chicken wire lattice. The material was seen as a promising successor to silicon for use in transistors, but the band gap turned out to be too small; roughly said: graphene cannot be turned off. Silicene had to offer a solution by combining the advantages of silicon and graphene; the material consists of a layer of silicon atoms with a chicken wire structure, albeit with a somewhat more bent and thus more complex arrangement. Silicene, in turn, suffers from stability problems. The material reacts quickly with oxygen under almost all conditions and then decomposes.
Researchers at the University of Texas have nevertheless succeeded in making a transistor from the material by using a new method in which silicene is barely exposed to air. To this end, they had hot vapor of silicon atoms condense on a crystalline structure of silver in a vacuum chamber.
This created a layer of silicene, protected by a thin silver layer, to which they added aluminum oxide as an extra protective layer. Then they were able to carefully scrape off the silver to create two islands that could act as source and drain, with the strip of silicene in between. Thus, at room temperature, the result behaved like a field-effect transistor.
The team will now investigate new structures and methods, in the hope that the material can eventually be used for economical and fast computer chips. One of the properties to be further investigated is that the electrical conductivity of the silicene in the production method used was much lower than expected. It is unclear how the research result relates to the claim of the University of Twente that silicene cannot be stably produced in meaningful quantities because crystalline silicon structures ‘eat’ the silicene.
The University of Texas research was published this week in the scientific journal Nature Nanotechnology.