Defect centres in hBN as light emitters in visible spectral range.
Affiliation: NUS (Department of Materials Science and Engineering)
Host: Prof Antonio Castro Neto
Abstract Details: Luminescent defect centres in wide gap materials are known to play a crucial role in breakthrough developments in science and technology. Especially prominent examples of that notion may be found in photonic research. One of the first observations of population inversion, subsequently leading to creation of lasers, was possible through inspection of intrinsic transitions in Cr3+ ions acting as substitution for Al in Al2O3 crystals [1]. The efforts to fabricate and characterize nitrogen-vacancy defects in diamond inspired substantial progress in solid-state single photon emission [2] and sensing of local fields [3].
Even though undeniably important, well-controlled defect centres are rare and generally difficult to achieve. In this talk, I will present a road from uncovering emitting defect centres in hexagonal boron nitride (hBN) [4,5] of microscopically unknown origin to designing methods of intentional creation of stable carbon-related defects. Those new carbon-doped hBN specimen display a particular pattern of resonances seen in photoluminescence spectra under below-band-gap excitation. The optical response of carbon-doped hBN crystals, related to the physical character of the emitting states and radiative/non-radiative processes, is similar to other aforementioned emitting defects in solids. The strength of such findings comes from the omnipresence of hBN in the research of 2D materials, proving its compatibility with robust van der Waals technology. This opens up a path to obtain more intricate insight into the defect physics and introduce application-oriented developments in material science via methods applicable exclusively to 2D crystals.
References [1] T. H. Maiman, Stimulated optical radiation in ruby. Nature 187, 493-494 (1960). [2] R. Brouri, et al., Photon antibunching in the fluorescence of individual color centers in diamond. Opt. Lett. 25, 1294-1296 (2000). [3] R. Schirhagl, et al., Nitrogen-vacancy centers in diamond: nanoscale sensors for physics and biology. Annual Review of Physical Chemistry 65, 83-105 (2014). [4] T. T. Tran, et al., Quantum emission from hexagonal boron nitride monolayers. Nat. Nanotechnol. 11, 37 (2016). [5] M. Koperski, et al., Single photon emitters in boron nitride: More than a supplementary material. Opt. Commun. 411, 158-165 (2018).
About The Speaker: Dr. Maciej Koperski joined the Department of Materials Science and Engineering as an Assistant Professor in November 2019. He was born in 1988 in Slawno (Poland), a small town 30 km away from the south coast of the Baltic Sea. For the past two years, he was holding a post-doctoral position at the University of Manchester (UK) in the Condensed Matter Physics Group. After defending PhD dissertation on optical properties of transition metal dichalcogenides in High Magnetic Field Laboratory in Grenoble (France) in 2017, he shifted his research focus on explorations of novel phenomena related to magnetism in 2D, uncovering electronic properties of less understood materials (e. g., InSe) by combining optical and electrical investigations and devising novel methods of introducing light into other areas of low dimensional physics (optical detection of fluids/molecules in 2D channels/environments). The scientific interests of dr. Koperski currently gravitate towards excitonic physics in confined systems and properties of defect-related light emitting centres in solids.
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