2 research outputs found
Toward Optimized Surface δ‑Profiles of Nitrogen-Vacancy Centers Activated by Helium Irradiation in Diamond
The negatively charged nitrogen-vacancy
(NV) center in diamond has been shown recently as an excellent sensor
for external spins. Nevertheless, their optimum engineering in the
near-surface region still requires quantitative knowledge in regard
to their activation by vacancy capture during thermal annealing. To
this aim, we report on the depth profiles of near-surface helium-induced
NV centers (and related helium defects) by step-etching with nanometer
resolution. This provides insights into the efficiency of vacancy
diffusion and recombination paths concurrent to the formation of NV
centers. It was found that the range of efficient formation of NV
centers is limited only to approximately 10 to 15 nm (radius) around
the initial ion track of irradiating helium atoms. Using this information
we demonstrate the fabrication of nanometric-thin (δ) profiles
of NV centers for sensing external spins at the diamond surface based
on a three-step approach, which comprises (i) nitrogen-doped epitaxial
CVD diamond overgrowth, (ii) activation of NV centers by low-energy
helium irradiation and thermal annealing, and (iii) controlled layer
thinning by low-damage plasma etching. Spin coherence times (Hahn
echo) ranging up to 50 μs are demonstrated at depths of less
than 5 nm in material with 1.1% of <sup>13</sup>C (depth estimated
by spin relaxation (T<sub>1</sub>) measurements). At the end, the
limits of the helium irradiation technique at high ion fluences are
also experimentally investigated
DNA-Based Self-Assembly of Fluorescent Nanodiamonds
As
a step toward deterministic and scalable assembly of ordered
spin arrays we here demonstrate a bottom-up approach to position fluorescent
nanodiamonds (NDs) with nanometer precision on DNA origami structures.
We have realized a reliable and broadly applicable surface modification
strategy that results in DNA-functionalized and perfectly dispersed
NDs that were then self-assembled in predefined geometries. With optical
studies we show that the fluorescence properties of the nitrogen-vacancy
color centers in NDs are preserved during surface modification and
DNA assembly. As this method allows the nanoscale arrangement of fluorescent
NDs together with other optically active components in complex geometries,
applications based on self-assembled spin lattices or plasmon-enhanced
spin sensors as well as improved fluorescent labeling for bioimaging
could be envisioned