PhD student, Noah Mendelson, was part of the team that discovered that carbon was the source of photons in ‘white graphene’ – a two-dimensional material that holds promise for use in emerging quantum technologies. One exciting aspect of this work was identifying that the carbon atom has spin, which means it can be manipulated for technological applications.

Prior to this work, we knew that white graphene or hexagonal boron nitride (hBN) was an excellent candidate material for quantum technologies due to its many favourable properties. However, despite extensive investigation, we did not understand the nature of the defects that emitted photons, hindering progress in the field.

The research, led by Professor Igor Aharonovich of the University of Technology Sydney was published in Nature Materials.

Noah explains the discovery from the lab at University of Technology Sydney.

“Confirming these defects carry spin opens up exciting possibilities for future quantum sensing applications, specifically with atomically thin materials.” Professor Aharonovich said.

“hBN single photon emitters display outstanding optical properties, among the best from any solid state material system, however, to make practical use of them we need to understand the nature of the defect and we have finally started to unravel this riddle,” said Mr Mendelson.

The team collaborated with national and international colleagues to solve this major challenge.

“Determining the structure of material defects is an incredibly challenging problem and requires experts from many disciplines. This is not something we could have done within our group alone. Only by teaming up with collaborators from across the world whose expertise lies in different materials growth techniques could we study this issue comprehensively. Working together were we finally able to provide the clarity needed for the research community as a whole,” said Professor Aharonovich.

“This is just the beginning, and we anticipate our findings will accelerate the deployment of hBN quantum emitters for a range of emerging technologies,” concludes Mr Mendelson.

Original Media Release: ‘Devil in the defect detail of quantum emissions unravelled’ by Marea Martlew

Identifying carbon as the source of visible single-photon emission from hexagonal boron nitride

Noah Mendelson, Dipankar Chugh, Jeffrey R. Reimers, Tin S. Cheng, Andreas Gottscholl, Hu Long, Christopher J. Mellor, Alex Zettl, Vladimir Dyakonov, Peter H. Beton, Sergei V. Novikov, Chennupati Jagadish, Hark Hoe Tan, Michael J. Ford, Milos Toth, Carlo Bradac & Igor Aharonovich

Nature Materials, 2nd November 2020 volume

Single-photon emitters (SPEs) in hexagonal boron nitride (hBN) have garnered increasing attention over the last few years due to their superior optical properties. However, despite the vast range of experimental results and theoretical calculations, the defect structure responsible for the observed emission has remained elusive. Here, by controlling the incorporation of impurities into hBN via various bottom-up synthesis methods and directly through ion implantation, we provide direct evidence that the visible SPEs are carbon related. Room-temperature optically detected magnetic resonance is demonstrated on ensembles of these defects. We perform ion-implantation experiments and confirm that only carbon implantation creates SPEs in the visible spectral range. Computational analysis of the simplest 12 carbon-containing defect species suggest the negatively charged VBC−NVBCN− defect as a viable candidate and predict that out-of-plane deformations make the defect environmentally sensitive. Our results resolve a long-standing debate about the origin of single emitters at the visible range in hBN and will be key to the deterministic engineering of these defects for quantum photonic devices.