Scientists Create Atomically Thin Metallic Boron

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A team of scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory, Northwestern University and Stony Brook University has, for the first time, created a two-dimensional sheet of boron – a material known as borophene.

Scientists have been interested in two-dimensional materials for their unique characteristics, particularly involving their electronic properties. Borophene is an unusual material because it shows many metallic properties at the nanoscale even though three-dimensional, or bulk, boron is nonmetallic and semiconducting. 

Because borophene is both metallic and atomically thin, it holds promise for possible applications ranging from electronics to photovoltaics, said Argonne nanoscientist Nathan Guisinger, who led the experiment. “No bulk form of elemental boron has this metal-like behavior.”

Like its periodic table neighbor carbon, which appears in nature in forms ranging from humble graphite to precious diamond, boron wears a number of different faces, called allotropes.  But that’s where the similarities end.  While graphite is composed of stacks of two-dimensional sheets that can be peeled off one at a time, there is no such analogous process for making two-dimensional boron.

“Borophenes are extremely intriguing because they are quite different from previously studied two-dimensional materials,” Guisinger said. “And because they don’t appear in nature, the challenge involved designing an experiment to produce them synthetically in our lab.”

Although at least 16 bulk allotropes of boron are known, scientists had never before been able to make a whole sheet, or monolayer, of borophene. “It’s only in the recent past that researchers have been able to make tiny bits of boron at the nanoscale,” said Andrew Mannix, a Northwestern graduate student and first author of the study. “This is a brand new material with exciting properties that we are just beginning to investigate.”

“Boron has a rich and storied history and a very complicated chemistry,” added Mark Hersam, professor of materials science and engineering at Northwestern’s McCormick School of Engineering, who helped advise Mannix. “This is something that could have easily not worked, but Andy had the courage and persistence to make it happen.”

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