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DOE OSTI · 3375509

Engineering diamond interfaces free of dark spins

Yu, Xiaofei [Univ. of Chicago, IL (United States)] (ORCID:0000000233140937)·Villafranca, Evan J. [Univ. of Chicago, IL (United States)] (ORCID:000900001702156X)·Wang, Stella [Univ. of Chicago, IL (United States)] (ORCID:0000000346265875)·Jones, Jessica C. [Argonne National Laboratory (ANL), Lemont, IL (United States)] (ORCID:0000000174754620)·Xie, Mouzhe [Univ. of Chicago, IL (United States); Arizona State Univ., Tempe, AZ (United States)] (ORCID:000000022960644X)·Nagura, Jonah [Univ. of Chicago, IL (United States)] (ORCID:0000000223779702)·Chi-Durán, Ignacio [Univ. of Chicago, IL (United States)] (ORCID:0000000233272825)·Delegan, Nazar [Argonne National Laboratory (ANL), Lemont, IL (United States)] (ORCID:0000000212406409)·Martinson, Alex B.F. [Argonne National Laboratory (ANL), Lemont, IL (United States)] (ORCID:0000000339161672)·Flatté, Michael E. [Univ. of Iowa, Iowa City, IA (United States); Eindhoven Univ. of Technology (Netherlands)] (ORCID:0000000150931549)·Candido, Denis R. [Univ. of Iowa, Iowa City, IA (United States)] (ORCID:0000000267083280)·Galli, Giulia [Univ. of Chicago, IL (United States); Argonne National Laboratory (ANL), Lemont, IL (United States). Center for Molecular Engineering] (ORCID:0000000280015290)·Maurer, Peter C. [Univ. of Chicago, IL (United States); Argonne National Laboratory (ANL), Lemont, IL (United States). Center for Molecular Engineering; CZ Biohub Chicago, LLC, IL (United States)] (ORCID:0000000190335135)
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Abstract

Nitrogen-vacancy (NV) centers in diamond are utilized extensively as quantum sensors for imaging fields at the nanoscale. The ultrahigh sensitivity of NV magnetometers has enabled the detection and spectroscopy of individual electron spins, with potentially far-reaching applications in condensed matter physics, spintronics, and molecular biology. However, the surfaces of these diamond sensors naturally contain electron spins, which create a background signal that can be hard to differentiate from the signal of the target spins. In this study, we develop a surface modification approach that eliminates the unwanted signal of these so-called dark electron spins. Our surface passivation technique, based on coating diamond surfaces with a thin titanium oxide (Ti⁢O 2 ) layer, reduces the dark spin density. The observed reduction in dark spin density aligns with our findings on the electronic structure of the diamond-Ti⁢O 2 interface. The reduction, from a typical value of 2000 μm −2 to a value below that set by the detection limit of our NV sensors (200 μm −2 ), results in a twofold increase in Hahn-echo coherence time of near surface NV centers. Furthermore, we derive a comprehensive spin model that connects dark spin relaxation with NV coherence, providing additional insights into the mechanisms behind the observed spin dynamics. Our findings are directly transferable to other quantum platforms, including nanoscale solid-state qubits and superconducting qubits.

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74 ATOMIC AND MOLECULAR PHYSICSCoatingsElectron paramagnetic resonanceInterfacesNitrogen vacancy centers in diamondNuclear magnetic resonanceQuantum information with hybrid systemsQuantum sensingSample preparation

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Yu, Xiaofei [Univ. of Chicago, IL (United States)] (ORCID:0000000233140937), Villafranca, Evan J. [Univ. of Chicago, IL (United States)] (ORCID:000900001702156X), Wang, Stella [Univ. of Chicago, IL (United States)] (ORCID:0000000346265875), Jones, Jessica C. [Argonne National Laboratory (ANL), Lemont, IL (United States)] (ORCID:0000000174754620), Xie, Mouzhe [Univ. of Chicago, IL (United States); Arizona State Univ., Tempe, AZ (United States)] (ORCID:000000022960644X), Nagura, Jonah [Univ. of Chicago, IL (United States)] (ORCID:0000000223779702), Chi-Durán, Ignacio [Univ. of Chicago, IL (United States)] (ORCID:0000000233272825), Delegan, Nazar [Argonne National Laboratory (ANL), Lemont, IL (United States)] (ORCID:0000000212406409), Martinson, Alex B.F. [Argonne National Laboratory (ANL), Lemont, IL (United States)] (ORCID:0000000339161672), Flatté, Michael E. [Univ. of Iowa, Iowa City, IA (United States); Eindhoven Univ. of Technology (Netherlands)] (ORCID:0000000150931549), Candido, Denis R. [Univ. of Iowa, Iowa City, IA (United States)] (ORCID:0000000267083280), Galli, Giulia [Univ. of Chicago, IL (United States); Argonne National Laboratory (ANL), Lemont, IL (United States). Center for Molecular Engineering] (ORCID:0000000280015290), Maurer, Peter C. [Univ. of Chicago, IL (United States); Argonne National Laboratory (ANL), Lemont, IL (United States). Center for Molecular Engineering; CZ Biohub Chicago, LLC, IL (United States)] (ORCID:0000000190335135). 2026-03-03. Engineering diamond interfaces free of dark spins. https://doi.org/10.1103/3j8r-2kt6

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