[Image above] Bird’s eye view of the subject areas covered for synthesis, properties, and applications of borophene. Credit: Kumar et al., Progress in Materials Science (CC BY 4.0)

 

This year marks the 10th anniversary since borophene made its debut on the experimental stage. First predicted by theory in the mid-1990s, this 2D sheet of boron atoms has made a name for itself among the Xenes due to its metallic character, impressive Young’s moduli (surpassing graphene), and exceptional electron mobility and thermal conductivity.

The tendency of borophene to rapidly oxidize in air and form clusters has presented hurdles to commercialization. But researchers have found ways to overcome these challenges and successfully use borophene in energy, sensing, and biomedical applications.

As borophene continues to find new applications in various fields, the amount of literature on this material is growing fast. In response, a group of researchers from Australia and India published an open-access review article to provide a “bird’s eye view” of borophene’s journey to date and discuss future opportunities. Highlights from the 52-page review article are below.

Borophene properties: Structural origins and dopant possibilities

In contrast to other Xenes, borophene exhibits numerous crystallographic phases. These phases all form distinct “ridges” of closely spaced boron atoms along the surface of a borophene sheet, which significantly impacts the material’s electronic and chemical properties.

This structural variability provides opportunities to tune borophene’s properties without the need for dopants, which is fortunate because “strong in-plane boron–boron bonds make doping challenging,” the researchers write. However, microwave doping, which uses microwave irradiation to achieve homogeneous volumetric heating and uniform distribution of dopants, provides an amicable and facile approach for doping of borophene.

Recently, density functional theory has become a popular method to explore the effect of structure and composition on borophene’s properties. Examples of such studies are available here and here.

Borophene-based heterostructures and hybrids

As noted above, borophene has the tendency to rapidly oxidize in air. Integrating borophene with other functional components to form heterostructures and hybrids can stabilize the material for application.

Examples of successful borophene-based heterolayers and hybrids:

Applications of borophene

Thanks to its unique properties, borophene can find application in a wide variety of fields. The last section of the review paper provides examples from each of these fields, including electronics, magnetism, superconductivity, sensing, catalysis, energy storage, triboelectric and piezoelectric nanogenerators, and biomedical applications.

Hurdles to commercialization

Borophene still faces several significant hurdles to commercialization.

Synthesis challenges: Molecular beam epitaxy and atomic layer deposition methods are reliable but expensive. Conversely, chemical vapor deposition synthesis is affordable, but more work is needed for large-scale production with high reproducibility.

Device integration challenges: Researchers are working to overcome poor interface quality and contact resistances of borophene with devices. Clean transfer techniques for borophene from its native substrate to an arbitrary destination substrate also require further development, as well as ways to prevent oxidation.

Fundamental knowledge challenges: Our understanding of surface and interface chemistry in borophene is currently limited. Additionally, explorations are needed on the role of crystal defects and the impact of intentionally induced post-growth defects on physical properties.

Despite these hurdles, the structural design engineering offered by borophene is “unmatched” and thus provides impetus to “address such concerns” and “realize its potential,” the researchers conclude.

The open-access paper, published in Progress in Materials Science, is “The rise of borophene” (DOI: 10.1016/j.pmatsci.2024.101331).

Author

Lisa McDonald

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