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New Properties of Boron-Doped Diamonds Open Doors for Advanced Technologies

Diamonds are not only prized for their brilliance and durability; they have become valuable in the realms of high-power electronics and cutting-edge quantum optics. Recent advancements reveal that when boron is used as a dopant, diamonds can achieve electrical conductivity comparable to that of metals.

Researchers from Case Western Reserve University and the University of Illinois Urbana-Champaign have unveiled a compelling trait of boron-doped diamonds—these diamonds demonstrate plasmonic characteristics. This discovery, detailed in a recent publication in Nature Communications, may significantly influence the development of innovative biomedical applications and quantum optical devices, promising higher speed and efficiency beyond the capabilities of traditional technologies.

The study highlights that boron-doped diamonds can support plasmonic waves—groups of electrons that are activated by incident light. This property enables the manipulation of electric fields on an incredibly small scale, which is essential for enhancing advanced sensors, nanoscale optical instruments, and improving solar energy absorption in quantum devices. While prior research confirmed the electrical conductivity and superconductive properties of boron-doped diamonds, their potential for plasmonic activity was largely unexplored. Distinctively, boron-doped diamonds maintain their optical clarity, unlike metals or many other semiconductor materials.

Giuseppe Strangi, a physics professor at Case Western Reserve, remarked, “Diamond continues to shine both literally and metaphorically as a pillar of scientific progress. Each finding carries us closer to tapping into the profound possibilities that arise from manipulating materials at the most basic level.”

Mohan Sankaran, a professor in nuclear, plasma, and radiological engineering at the University of Illinois, emphasized the importance of understanding doping mechanisms in altering the optical properties of semiconductors like diamonds. “This knowledge transforms how we perceive these materials,” he noted.

The fascination with plasmonic materials is not new; humans have been intrigued by their light-manipulating capabilities for centuries. A prime example can be seen in medieval glass-making, where the interplay of light and metal nanoparticles created the vivid colors that adorn stained-glass windows. When light interacts with these particles, it generates plasmons responsible for the striking hues: gold produces a rich red, while silver yields a bright yellow. This historical connection underscores the modern relevance of nanotechnology and optics in creating functional and aesthetic technologies.

Diamonds, which are made up of crystalline carbon, can be synthesized with traces of boron due to their adjacent positions on the periodic table. Boron, which has one less electron than carbon, can accept electrons, creating a “hole” that enhances electrical conductivity. The resulting boron-doped diamond retains its transparency, often exhibiting a blue tint—a characteristic seen in the famed Hope Diamond, attributed to its boron content.

Due to their intrinsic properties, including chemical inertness and biological compatibility, boron-doped diamonds have the potential to be utilized in fields where other materials might fall short, such as in advanced medical imaging techniques, ultra-sensitive biosensors, or molecular detectors.

The low-pressure synthesis of diamonds was first pioneered by John Angus at Case Western Reserve in 1968. Angus was also the first to document the electrical conductivity of boron-doped diamonds and passed away in 2023.

Strangi and Sankaran’s research involved a collaborative effort with graduate student Souvik Bhattacharya, who served as the lead author, alongside Jonathan Boyd from Case Western Reserve, as well as researchers from the University of Luxembourg and Marseilles University. Their work received support from the National Science Foundation, exemplifying the commitment to advancing scientific understanding and technological innovation.

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