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A team of researchers from Korea and Japan have had a breakthrough with a semiconductor material that they claim could be a candidate to replace silicon in future electronics. In the 7 August issue of Science they report the creation of a transistor where the channel consists of layers of a two-dimensional material molybdenum ditelluride (MoTe2).

Everyone’s on the lookout for a replacement for silicon, because, great as it is, it has two drawbacks:  its electronic properties degrade when the silicon layer is thinned to just one or a few atoms thick, and its indirect bandgap make it difficult to use silicon in optoelectronics.

One class of candidate materials that researchers have been examining is transition metal dichacogenides, which include molybdenum disulfide and tungsten diselenide. But making good electrical connections between these materials and metal contacts has been a problem.

This is the first metal-semiconductor junction in the same 2-D material

Molybdenum ditelluride, synthesized for the first time in the 1960s was little investigated because it could not be obtained in a pure form that could be used in electronics. Last year things changed when Yang and his colleagues at Sungkyunkwan University obtained a very pure form of molybdenum ditelluride, and made a surprising discovery. "I was studying MoTe2 and we were using a technique called Raman spectroscopy.  Each time we measured we obtained results that were different. I got quite disappointed because I really didn’t understand why. As we have a solid, it should have produced the same Raman spectrum for each measurement," says Yang.