26 research outputs found
Detecting nitrogen-vacancy-hydrogen centers on the nanoscale using nitrogen-vacancy centers in diamond
In diamond, nitrogen defects like the substitutional nitrogen defect (Ns) or
the nitrogen-vacancy-hydrogen complex (NVH) outnumber the nitrogen vacancy (NV)
defect by at least one order of magnitude creating a dense spin bath. While
neutral Ns has an impact on the coherence of the NV spin state, the atomic
structure of NVH reminds of a NV center decorated with a hydrogen atom. As a
consequence, the formation of NVH centers could compete with that of NV centers
possibly lowering the N-to-NV conversion efficiency in diamond grown with
hydrogen-plasma-assisted chemical vapor deposition (CVD). Therefore, monitoring
and controlling the spin bath is essential to produce and understand engineered
diamond material with high NV concentrations for quantum applications. While
the incorporation of Ns in diamond has been investigated on the nano- and
mesoscale for years, studies concerning the influence of CVD parameters and the
crystal orientation on the NVH formation have been restricted to bulk N-doped
diamond providing high-enough spin numbers for electron paramagnetic resonance
and optical absorption spectroscopy techniques. Here, we investigate
sub-micron-thick (100)-diamond layers with nitrogen contents of (13.8 +- 1.6)
ppm and (16.7 +- 3.6) ppm, and exploiting the NV centers in the layers as local
nano-sensors, we demonstrate the detection of NVH- centers using
double-electron-electron-resonance (DEER). To determine the NVH- densities, we
quantitatively fit the hyperfine structure of NVH- and confirm the results with
the DEER method usually used for determining Ns0 densities. With our
experiments, we access the spin bath composition on the nanoscale and enable a
fast feedback-loop in CVD recipe optimization with thin diamond layers instead
of resource- and time-intensive bulk crystals.Comment: 7 pages, 3 figure
Charge stability and charge-state-based spin readout of shallow nitrogen-vacancy centers in diamond
Spin-based applications of the negatively charged nitrogen-vacancy (NV)
center in diamonds require efficient spin readout. One approach is the
spin-to-charge conversion (SCC), relying on mapping the spin states onto the
neutral (NV) and negative (NV) charge states followed by a subsequent
charge readout. With high charge-state stability, SCC enables extended
measurement times, increasing precision and minimizing noise in the readout
compared to the commonly used fluorescence detection. Nano-scale sensing
applications, however, require shallow NV centers within a few \si{\nano
\meter} distance from the surface where surface related effects might degrade
the NV charge state. In this article, we investigate the charge state
initialization and stability of single NV centers implanted \approx
\SI{5}{\nano \meter} below the surface of a flat diamond plate. We demonstrate
the SCC protocol on four shallow NV centers suitable for nano-scale sensing,
obtaining a reduced readout noise of 5--6 times the spin-projection noise
limit. We investigate the general applicability of SCC for shallow NV centers
and observe a correlation between NV charge-state stability and readout noise.
Coating the diamond with glycerol improves both charge initialization and
stability. Our results reveal the influence of the surface-related charge
environment on the NV charge properties and motivate further investigations to
functionalize the diamond surface with glycerol or other materials for
charge-state stabilization and efficient spin-state readout of shallow NV
centers suitable for nano-scale sensing.Comment: 9 pages, 5 figure
Precision temperature sensing in the presence of magnetic field noise and vice-versa using nitrogen-vacancy centers in diamond
We demonstrate a technique for precision sensing of temperature or the
magnetic field by simultaneously driving two hyperfine transitions involving
distinct electronic states of the nitrogen-vacancy center in diamond. Frequency
modulation of both driving fields is used with either the same or opposite
phase, resulting in the immunity to fluctuations in either the magnetic field
or the temperature, respectively. In this way, a sensitivity of 1.4 nT
Hz or 430 K Hz is demonstrated. The presented technique
only requires a single frequency demodulator and enables the use of
phase-sensitive camera imaging sensors. A simple extension of the method
utilizing two demodulators allows for simultaneous, independent, and
high-bandwidth monitoring of both the magnetic field and temperature.Comment: 5 pages, 4 figure
Contributed review: camera-limits for wide-field magnetic resonance imaging with a nitrogen-vacancy spin sensor
Sensitive, real-time optical magnetometry with nitrogen-vacancy centers in diamond relies on accurate imaging of small (≪10−2), fractional fluorescence changes across the diamond sample. We discuss the limitations on magnetic field sensitivity resulting from the limited number of photoelectrons that a camera can record in a given time. Several types of camera sensors are analyzed, and the smallest measurable magnetic field change is estimated for each type. We show that most common sensors are of a limited use in such applications, while certain highly specific cameras allow achieving nanotesla-level sensitivity in 1 s of a combined exposure. Finally, we demonstrate the results obtained with a lock-in camera that paves the way for real-time, wide-field magnetometry at the nanotesla level and with a micrometer resolution
Optimal frequency measurements with quantum probes
Precise frequency measurements are important in applications ranging from navigation and imaging to computation and
communication. Here we outline the optimal quantum strategies for frequency discrimination and estimation in the context of
quantum spectroscopy, and we compare the effectiveness of different readout strategies. Using a single NV center in diamond, we
implement the optimal frequency discrimination protocol to discriminate two frequencies separated by 2 kHz with a single 44 μs
measurement, a factor of ten below the Fourier limit. For frequency estimation, we achieve a frequency sensitivity of 1.6 µHz/Hz2 for
a 1.7 µT amplitude signal, which is within a factor of 2 from the quantum limit. Our results are foundational for discrimination and
estimation problems in nanoscale nuclear magnetic resonance spectroscopy
Chapter 9 Outdoor air pollutants sources, characteristics, and impact on human health and the environment
In this chapter, sources and characteristics of outdoor air pollutants are presented along with their effects on human health and the environment. In addition, emphasis is given to air pollutant monitoring by exploring the type of monitoring programs, sampling methods, and emission standards and by presenting the case of air pollution monitoring in the United Arab Emirates. Finally, the chapter explores the case of climate change by looking into its causes and economic and environmental impacts
Indirect overgrowth as a synthesis route for superior diamond nano sensors
Abstract The negatively charged nitrogen-vacancy ( NV - ) center shows excellent spin properties and sensing capabilities on the nanoscale even at room temperature. Shallow implanted NV - centers can effectively be protected from surface noise by chemical vapor deposition (CVD) diamond overgrowth, i.e. burying them homogeneously deeper in the crystal. However, the origin of the substantial losses in NV - centers after overgrowth remains an open question. Here, we use shallow NV - centers to exclude surface etching and identify the passivation reaction of NV to NVH centers during the growth as the most likely reason. Indirect overgrowth featuring low energy (2.5–5 keV) nitrogen ion implantation and CVD diamond growth before the essential annealing step reduces this passivation phenomenon significantly. Furthermore, we find higher nitrogen doses to slow down the NV–NVH conversion kinetics, which gives insight into the sub-surface diffusion of hydrogen in diamond during growth. Finally, nano sensors fabricated by indirect overgrowth combine tremendously enhanced T 2 and T 2 ∗ times with an outstanding degree of depth-confinement which is not possible by implanting with higher energies alone. Our results improve the understanding of CVD diamond overgrowth and pave the way towards reliable and advanced engineering of shallow NV - centers for future quantum sensing devices