Nanoscale Sensing Using Point Defects in Single-Crystal Diamond: Recent Progress on Nitrogen Vacancy Center-Based Sensors

Individual, luminescent point defects in solids so called color centers are atomic-sized quantum systems enabling sensing and imaging with nanoscale spatial resolution. In this overview, we introduce nanoscale sensing based on individual nitrogen vacancy (NV) centers in diamond. We discuss two central challenges of the field: First, the creation of highly-coherent, shallow NV centers less than 10 nm below the surface of single-crystal diamond. Second, the fabrication of tip-like photonic nanostructures that enable efficient fluorescence collection and can be used for scanning probe imaging based on color centers with nanoscale resolution.Comment: Overview paper on sensing with defects in diamond, we focus on creation of shallow NV centers and nanostructures, Final Version published in Crystal

Resolved sidebands in a strain-coupled hybrid spin-oscillator system

We report on single electronic spins coupled to the motion of mechanical resonators by a novel mechanism based on crystal strain. Our device consists of single-crystalline diamond cantilevers with embedded Nitrogen-Vacancy center spins. Using optically detected electron spin resonance, we determine the unknown spin-strain coupling constants and demonstrate that our system resides well within the resolved sideband regime. We realize coupling strengths exceeding ten MHz under mechanical driving and show that our system has the potential to reach strong coupling. Our novel hybrid system forms a resource for future experiments on spin-based cantilever cooling and coherent spin-oscillator coupling.Comment: 4 pages, 4 figures and supplementary information. Comments welcome. Further information under http://www.quantum-sensing.physik.unibas.ch

Photophysics of single silicon vacancy centers in diamond: implications for single photon emission

Single silicon vacancy (SiV) color centers in diamond have recently shown the ability for high brightness, narrow bandwidth, room temperature single photon emission. This work develops a model describing the three level population dynamics of single SiV centers in diamond nanocrystals on iridium surfaces including an intensity dependent de-shelving process. Furthermore, we investigate the brightness and photostability of single centers and find maximum single photon rates of 6.2 Mcps under continuous excitation. We investigate the collection efficiency of the fluorescence and estimate quantum efficiencies of the SiV centers.Comment: 15 pages, 7 figures, version 2 accepted for publication in Optics Expres

Silicon vacancy color centers in chemical vapor deposition diamond : new insights into promising solid state single photon sources

This work extensively investigates single silicon vacancy (SiV) color centers in diamond which are promising candidates for solid state single photon sources. The SiV centers are hosted by synthetic chemical vapor deposition diamonds in which they are created during the growth due to the incorporation of silicon impurities. The SiV centers display outstanding spectral properties including bright zero-phonon-lines (ZPLs, wavelengths mostly between 736 nm and 746 nm) with linewidths as narrow as 0.7 nm together with a distinct concentration of the fluorescence (approx. 70%) in the ZPL. With single photon count rates up to 6.2 Mcps under continuous excitation, SiV centers are the brightest single color centers at present. Intensity auto-correlation measurements reveal three level population dynamics including a shelving state from which the SiV center can be reactivated by the excitation laser. Besides the ZPL, we identify previously unobserved electronic transitions in the spectral range between 820 nm and 840 nm. Using polarization spectroscopy, we investigate for the first time the transition dipole(s) for a single SiV center and find a single <110>-oriented dipole enabling fully linearly polarized single photon emission. Spectroscopy at cryogenic temperature for the first time reveals the ZPL fine structure of a single SiV center as well as mostly temperature independent population dynamics.In dieser Arbeit werden einzelne Silizium-Fehlstellen (SiV) Farbzentren in Diamant untersucht. Diese sind vielversprechende Kandidaten für festkörperbasierte Einzelphotonenquellen. Die SiV Zentren entstehen während des Wachstums in synthetischen, durch Gasphasenabscheidung hergestellten Diamanten aus Silizium-Verunreinigungen. SiV Zentren zeigen herausragende spektrale Eigenschaften darunter eine intensive Null-Phononen (NP) Linie (Wellenlänge meist zwischen 736 nm und 746 nm) mit einer Breite von minimal nur 0.7 nm zusammen mit einer ausgeprägten Konzentration der Fluoreszenz (ca. 70%) in der NP Linie. SiV Zentren sind mit Einzelphotonenraten bis zu 6.2 Mcps bei kontinuierlicher Anregung die hellsten einzelnen Farbzentren zum jetzigen Zeitpunkt. Intensitäts-Autokorrelationsmessungen zeigen eine Drei-Niveau Besetzungsdynamik mit einem Shelving Zustand, aus dem das SiV Zentrum durch den Anregungslaser reaktiviert werden kann. Neben der NP Linie werden erstmals elektronische Übergänge zwischen 820 nm und 840 nm identifiziert. Mit Hilfe von Polarisationsspektroskopie wird die Dipolausrichtung einzelner SiV Zentren untersucht und ein einzelner Dipol in <110> Kristallrichtung identifiziert. Tieftemperaturspektroskopie liefert erstmals die Feinstruktur der NP Linie eines einzelnen SiV Zentrums und zeigt eine weitgehend temperaturunabhängige Besetzungsdynamik

Reliable Nanofabrication of Single-Crystal Diamond Photonic Nanostructures for Nanoscale Sensing

In this manuscript, we outline a reliable procedure to manufacture photonic nanostructures from single-crystal diamond (SCD). Photonic nanostructures, in our case SCD nanopillars on thin (<1 µm) platforms, are highly relevant for nanoscale sensing. The presented top-down procedure includes electron beam lithography (EBL) as well as reactive ion etching (RIE). Our method introduces a novel type of inter-layer, namely silicon, that significantly enhances the adhesion of hydrogen silsesquioxane (HSQ) electron beam resist to SCD and avoids sample charging during EBL. In contrast to previously used adhesion layers, our silicon layer can be removed using a highly-selective RIE step, which is not damaging HSQ mask structures. We thus refine published nanofabrication processes to ease a higher process reliability especially in the light of the advancing commercialization of SCD sensor devices

Nanoscale Sensing Using Point Defects in Single-Crystal Diamond: Recent Progress on Nitrogen Vacancy Center-Based Sensors

Individual, luminescent point defects in solids, so-called color centers, are atomic-sized quantum systems enabling sensing and imaging with nanoscale spatial resolution. In this overview, we introduce nanoscale sensing based on individual nitrogen vacancy (NV) centers in diamond. We discuss two central challenges of the field: first, the creation of highly-coherent, shallow NV centers less than 10 nm below the surface of a single-crystal diamond; second, the fabrication of tip-like photonic nanostructures that enable efficient fluorescence collection and can be used for scanning probe imaging based on color centers with nanoscale resolution

Reliable Nanofabrication of Single-Crystal Diamond Photonic Nanostructures for Nanoscale Sensing

In this manuscript, we outline a reliable procedure to manufacture photonic nanostructures from single-crystal diamond (SCD). Photonic nanostructures, in our case SCD nanopillars on thin (< 1$\mu$m) platforms, are highly relevant for nanoscale sensing. The presented top-down procedure includes electron beam lithography (EBL) as well as reactive ion etching (RIE). Our method introduces a novel type of inter-layer, namely silicon, that significantly enhances the adhesion of hydrogen silsesquioxane (HSQ) electron beam resist to SCD and avoids sample charging during EBL. In contrast to previously used adhesion layers, our silicon layer can be removed using a highly-selective RIE step which is not damaging HSQ mask structures. We thus refine published nanofabrication processes to ease a higher process reliability especially in the light of the advancing commercialization of SCD sensor devices.Comment: v2: accepted for publication in Micromachines 2019, 10(11), 718; https://doi.org/10.3390/mi1011071