ABSTRACT
Deep-ultraviolet continuous-wave photoluminescence spectroscopy is performed for nano-polycrystalline diamond (NPD) synthesized by a high pressure high-temperature technique. NPD exhibits clear deep-ultraviolet emissions, which originate from intrinsic excitonic transitions assisted by a momentum-conserving phonon with a photon. Surprisingly, the peak emission energy is about 30 meV higher than that of the single-crystalline diamond. Raman scattering spectroscopy indicates that the energy difference should originate from the excitonic properties of the NPD and not the phonon. Hence, NPD has a large bandgap compared to single-crystalline diamond.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Ryota Ishii http://orcid.org/0000-0002-1413-4849
Fumitaro Ishikawa http://orcid.org/0000-0002-5632-056X