Group-IV Split Vacancy Nanodiamonds Synthesized via High-Pressure High-Temperature Techniques for Enhanced Quantum Sensing

Rapid strides in quantum sensing have necessitated the development of robust, scalable, and efficient nanodiamond materials with well-defined point-defect microstructure. This research presents a novel method to further this pursuit by synthesizing nanodiamonds doped with group-IV elements (Si, Pb, Sn, Ge), aiming to harness the unique properties of their split vacancies in nanodiamonds for a range of quantum sensing and quantum communication applications. A chemical bottom-up approach was employed, where 4.5 nM of tetraethylorthoxysilane (TEOS) and 4.5 nM of tetraphenylgermane (TPG) were added as the dopants for Si and Ge, respectively, while trace amounts of organometallic Sn and Pb were included in the processing of carbon aerogel target materials. The doped resorcinol-formaldehyde (RF) gels were pyrolyzed to obtain the group 4-doped carbon aerogels. Subsequent laser heating to 1260 K ± 10 K in high-pressure environments of 22 GPa ± 0.2GPa using diamond anvil cells yielded nanodiamond samples doped with group-IV point defects. Photoluminescence characterization showcased distinct zero-phonon lines (ZPLs) stemming from NV- (638 nm), SiV- (720 nm), SnV (620 nm), and Pb-related centers at ambient conditions. The observed shift in SiV ZPL with increasing pressure (0.85 meV/GPa) was in excellent alignment with existing density functional theory (DFT) calculations (0.83 meV/GPa). Further, we conducted lifetime measurements of the SiV centers at ambient conditions post nanodiamond recovery, resulting in a lifetime of ~1.25 ns ± 0.03 ns, which matches very closely with the literature. A significant advancement of this research lies in its potential to modulate the relative concentration of dopants, enabling the precise ratio control of various quantum sensors in the resultant nanodiamonds. This study contributes to the development of the synthesis of nanodiamonds with split vacancy without damage induced by ion implantation. With future development, these group-IV split vacancies hold promise for quantum sensing and quantum communication applications.