Photoluminescence spectrum of divacancy in porous and nanocrystalline cubic silicon carbide

Csóré, András and Nain, Mukesh and Károlyházy, Gyula and Beke, Dávid and Gali, Adam (2022) Photoluminescence spectrum of divacancy in porous and nanocrystalline cubic silicon carbide. JOURNAL OF APPLIED PHYSICS, 131. No. 071102. ISSN 0021-8979

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Abstract

The divacancy in silicon carbide (SiC) is a prominent solid state defect quantum bit that bears a relatively strong fluorescence and optically detected magnetic resonance contrast (ODMR) at room temperature. These properties exemplify it for quantum sensing of biological molecules. To this end, we previously developed a top-down method to create divacancies in cubic SiC nanoparticles (NPs) as non-perturbative ODMR biomarkers. In this process, large SiC particles are synthesized and then stain etched to form porous SiC and then ultrasonication and filtering are applied to the solution to extract few nanometer diameter SiC NPs. We called this process no-photon exciton generation chemistry (NPEGEC). We showed that by adding aluminum to carbon and silicon in the synthesis process of cubic SiC, one can engineer divacancy defects in SiC NPs by NPEGEC. An alternative traditional way to introduce vacancies to the SiC lattice is irradiation. Here, we compare the fluorescence spectra of divacancies as created by neutron irradiation in porous cubic SiC and NPEGEC technique in SiC NPs, and the results are analyzed in detail by means of first principles calculations. We find that the irradiation technique produces a larger shift in the fluorescence spectrum with residual background fluorescence than that for divacancies in SiC NPs, which is most likely caused by the parasitic defects left after irradiation and annealing in the former sample. These results imply that the chemistry technique applied to prepare divacancies in few nanometer SiC NPs may preserve the bulk-like quality of divacancy quantum bits near the surface.

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