Intervalence Plasmons in Boron-Doped Diamond

• Main Authors: Bhattacharya, Souvik, Boyd, Jonathan, Reichardt, Sven, Talebi, Amir Hossein, Maccaferri, Nicolò, Shenderova, Olga, Wirtz, Ludger, Strangi, Giuseppe, Sankaran, R. Mohan
• Format: Journal Article
• Language: English
• Published: 18-03-2024
• Subjects: Physics - Materials Science; Physics - Optics
• DOI: 10.48550/arxiv.2403.12221

Doped semiconductors are capable of exhibiting metallic-like properties
ranging from superconductivity to tunable localized surface plasmon resonances.
Diamond is a wide-bandgap semiconductor that is rendered electronically active
by incorporating a hole dopant, boron. While the effects of boron doping on the
electronic band structure of diamond are well-studied, any link between charge
carriers and plasmons, which could facilitate optical applications, has never
been shown. Here, we report intervalence plasmons in boron-doped diamond,
defined as collective electronic excitations between the valence subbands,
opened up by the presence of holes. Evidence for these low energy excitations
is provided by scanning transmission electron microscope-valence electron
energy loss spectroscopy and photoinduced force infrared spectroscopy. The
measured loss and absorbance spectra are subsequently reproduced by
first-principles calculations based on the contribution of intervalence band
transitions to the dielectric function. Remarkably, the calculations also
reveal that the real part of the dielectric function exhibits a resonance
characteristic of metallicity (narrow-banded negative values of the dielectric
function). The energy of the zero-crossing and the position of the loss peak
are found to coincide, and both increase with the carrier density. Our results
provide insight into a new mechanism for inducing plasmon-like behavior in
doped semiconductors from intervalence band transitions, and the possibility of
attaining such properties in diamond, a key emerging material for biomedical
and quantum information technologies.