On Fano effect in IR spectra of hydrogenated nanodiamonds
Andrei A. Shiryaev, Evgeni A. Ekimov
TLDR
This paper attributes the Fano effect in hydrogenated nanodiamond IR spectra to monohydride bending modes, not C-H stretch vibrations.
Key contributions
- Analyzed IR spectra of nanodiamonds (2.6-30 nm) exhibiting the Fano "transmission window."
- Showed C-H stretch vibrations of adsorbed groups are not responsible for the Fano resonance.
- Suggested monohydride bending modes on (111) faces couple with optical phonons, explaining the Fano effect.
Why it matters
This paper resolves a long-standing debate on the precise mechanism of Fano resonance in hydrogenated nanodiamonds. By identifying monohydride bending modes as the cause, it provides critical insights for tailoring nanodiamond surface properties. This understanding is vital for advanced material design and applications.
Original Abstract
Hydrogenated nanodiamonds may show a "transmission window" in infra-red spectra in the vicinity of diamond Raman frequency. This phenomenon is a manifestation of resonance coupling of incident photons with continuum states (Fano resonance). Hpwever, precise mechanism of appearence of the resonance and of related conductivity - surface hydrogenation or specific type of surface reconstruction - remains debatable. We present detailed analysis of infra-red spectra of nanodiamonds of different sizes (2.6-30 nm) possessing the "transmission window" and show that the C-H stretch vibrations of adsorbed functional groups cannot be responsible the the Fano resonance. At the same time, it is suggested that a bending mode of monohydride termination on nanodiamond (111) face may couple with diamond optical phonon, explaining the Fano resonance in some cases. The relative importance of the monohydride contribution and of the graphitic islets to the appearence of the "transmission window" and conductivity is likely dependent on dominating morphology and size distribution of nanodiamond grains.
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