By Josh Perry, Editor
A team of researchers from Rice University (Houston, Texas), Argonne National Laboratory (Lemont, Ill.), and Northwestern University (Evanston, Ill.) demonstrated that boron atoms placed in a bath of gold heated by a furnace will form 2-D layers of borophene on the surface of the gold when it is cooled.
Scientists at Rice, Northwestern and the Argonne National Laboratory created islands of highly conductive borophene, the atom-flat form of boron, on gold. (Rice University)
According to a report from Rice, the researchers found that, at high enough heat and in a high vacuum environment, boron atoms placed in the furnace will sink into the gold bath. When the bath is cooled, one square nanometer islands of borophene form on the surface of the gold.
“This is distinct from most other 2D materials made by feeding gases into a furnace,” the article explained. “In standard chemical vapor deposition, the atoms settle onto a substrate and connect with each other. They typically don’t disappear into the substrate.”
Researchers believe that changing the substrate could lead to borophene with different properties, such as borophene’s wavy features when made with silver. It took significantly more boron to form borophene in gold than it did in silver, which was an indication that the boron was sinking into the material rather than settling on the surface. This occurred at around 550°C.
The research was recently published in ACS Nano. The abstract stated:
“Borophene (the first two-dimensional (2D) allotrope of boron) is emerging as a groundbreaking system for boron-based chemistry and, more broadly, the field of low-dimensional materials. Exploration of the phase space for growth is critical because borophene is a synthetic 2D material that does not have a bulk layered counterpart and thus cannot be isolated via exfoliation methods.
“Herein, we report synthesis of borophene on Au(111) substrates. Unlike previously studied growth on Ag substrates, boron diffuses into Au at elevated temperatures and segregates to the surface to form borophene islands as the substrate cools. These observations are supported by ab initiomodeling of interstitial boron diffusion into the Au lattice.
“Borophene synthesis also modifies the surface reconstruction of the Au(111) substrate, resulting in a trigonal network that templates growth at low coverage. This initial growth is composed of discrete borophene nanoclusters, whose shape and size are consistent with theoretical predictions. As the concentration of boron increases, nanotemplating breaks down and larger borophene islands are observed.
“Spectroscopic measurements reveal that borophene grown on Au(111) possesses a metallic electronic structure, suggesting potential applications in 2D plasmonics, superconductivity, interconnects, electrodes, and transparent conductors.”