Short answer: Hexagonal boron nitride, a two-dimensional material, hosts defects that emit single photons at room temperature. A 2016 Nature Nanotechnology paper reported room-temperature, polarized, ultrabright emission from a colour centre in hBN, a 2024 paper reports a stable emitter with a low Huang-Rhys factor of 0.6, and a 2025 Science Advances paper reports emitters in carbon-doped hBN films with a g2(0) of 0.015. These are laboratory results on emitters that remain hard to control.
The starting point
The 2016 abstract says room-temperature quantum emitters had been observed in wide-bandgap semiconductors such as diamond and silicon carbide, nanocrystal quantum dots, and carbon nanotubes, while single-photon emission from two-dimensional materials had been reported only at cryogenic temperatures. The authors demonstrate room-temperature, polarized and ultrabright single-photon emission from a colour centre in hexagonal boron nitride. Density functional theory calculations suggest vacancy-related defects are a probable source. They say the results show the potential of van der Waals crystals for nanophotonics and quantum information.
2024: a stable, isolated emitter
The 2024 abstract says stable, bright room-temperature emitters from atomic defects in hBN flakes are promising, but that creating and detecting isolated, stable emitters with high emission rates and very low Huang-Rhys factor remains a challenge. The authors discuss a single, isolated, stable emitter with a high emission rate and a Huang-Rhys factor of 0.6 with an uncertainty of 0.2 at room temperature. A scanning confocal image shows a zero-phonon line near 578 nm with a separated phonon sideband at 626 nm. The second-order correlation shows an anti-bunching dip of about 0.25, with an emission lifetime of 2.46 nanoseconds with an uncertainty of 0.1. They stress that low-energy electron beam irradiation followed by annealing is important for stable, reproducible emitters.
2025: centimeter-scale films
The Science Advances abstract says improving emitter purity, stability and scalability remains a challenge. The authors grow carbon-doped, centimeter-scale hBN thin films directly by pulsed laser deposition and report highly pure and stable emitters. They operate at room temperature with polarized emission and report a g2(0) value of 0.015, which they describe as among the lowest reported for room-temperature emitters and the lowest for hBN. They also report a brightness of about 0.5 million counts per second, stability during continuous operation over 15 minutes, and a Debye-Waller factor of 45%. First-principles calculations point to particular carbon defects as responsible. They say the method is effective for large-scale production of high-purity emitters, which is their claim.
Limits
An anti-bunching dip of 0.25 in 2024 and a g2(0) of 0.015 in 2025 come from different samples and methods, so they are not a single progression. The stability reported in 2025 is over 15 minutes of operation. The abstracts do not show a deterministic, scalable source integrated into a device, and the origin of the defects is described through calculation.
FAQ
Why is hBN interesting?
It emits single photons at room temperature from defects in a two-dimensional material.
How pure was the best emission?
A g2(0) of 0.015 in the 2025 paper, as reported by the authors.
What is the Huang-Rhys factor?
A measure of coupling to lattice vibrations. A low value, here 0.6 with an uncertainty of 0.2, means more of the light is in the sharp zero-phonon line.
What causes the emission?
The authors point to vacancy-related and carbon defects, based on calculations.
Can they be made at scale?
The 2025 authors say their film method is suited to large-scale production. Control of individual emitters is still a challenge.
All field notes