Unlocking Brilliance: Groundbreaking Discoveries in Diamond Semiconductor Properties

Researchers from Case Western Reserve University and the University of Illinois Urbana-Champaign have recently uncovered another fascinating characteristic of diamonds with added boron, referred to as boron-doped diamonds. Their discoveries could usher in novel types of biomedical and quantum optical apparatus — swifter, more efficient, and capable of processing information in manners that traditional technologies cannot. Their findings are published today in Nature Communications.

The investigators determined that boron-doped diamonds demonstrate plasmons — electron waves that propagate when illuminated — enabling electric fields to be controlled and amplified on a nanoscale level. This feature is significant for advanced biosensors, nanoscale optical apparatus, and for enhancing solar cells and quantum devices. Previously, it was recognized that boron-doped diamonds could conduct electricity and achieve superconductivity, but they lacked known plasmonic characteristics. In contrast to metals or other doped semiconductors, boron-doped diamonds remain optically transparent.

“Diamond continues to radiate,” proclaimed Giuseppe Strangi, professor of physics at Case Western Reserve, “both literally and as a guiding light for scientific and technological progress. As we delve deeper into the realm of quantum computing and communication, discoveries like this bring us closer to harnessing the complete potential of materials at their most fundamental level.”

“Comprehending how doping alters the optical reaction of semiconductors like diamond transforms our perception of these materials,” remarked Mohan Sankaran, professor of nuclear, plasma and radiological engineering at Illinois Grainger College of Engineering.

Plasmonic materials, which influence light at the nanoscale, have fascinated humans for centuries, even before their scientific properties were grasped. The striking colors found in medieval stained-glass windows are the result of metal nanoparticles embedded within the glass. As light passes through, these particles produce plasmons that yield specific colors. Gold nanoparticles appear ruby red, while silver nanoparticles exhibit a vivid yellow. This ancient artistry underscores the interaction between light and matter, inspiring contemporary advancements in nanotechnology and optics.

Diamonds, consisting of transparent crystals of carbon, can be created with trace amounts of boron, which is adjacent to carbon in the periodic table. Boron possesses one less electron than carbon, permitting it to accept electrons. Essentially, boron introduces a periodic electronic “hole” within the material, enhancing its capacity to conduct electricity. The lattice of boron-doped diamonds maintains its transparency, featuring a blue tint. (The renowned Hope Diamond is blue due to its trace amounts of boron).

Thanks to its additional unique traits — it is also chemically inert and biologically compatible — boron-doped diamond could potentially be utilized in applications where other materials might fall short, such as in medical imaging or for high-sensitivity biochips or molecular sensors.

Diamonds synthesized under low pressure were first developed at Case Western Reserve (then Case Institute of Technology) in 1968 by faculty member John Angus, who passed away in 2023. Angus was also the first to report on the electrical conductivity of boron-doped diamond.

Strangi and Sankaran worked alongside Souvik Bhattacharya, the lead author and a graduate student at Illinois; Jonathan Boyd, Case Western Reserve; Sven Reichardt and Ludger Wirtz, University of Luxembourg; Vallentin Allard, Aude Lereu, and Amir Hossein Talebi, Marseilles University; and Nicolo Maccaferri, Umeå University, Sweden.

The research received support from the National Science Foundation.