Systems of spins engineered with tunable density and reduced dimensionality
enable a number of advancements in quantum sensing and simulation. Defects in
diamond, such as nitrogen-vacancy (NV) centers and substitutional nitrogen (P1
centers), are particularly promising solid-state platforms to explore. However,
the ability to controllably create coherent, two-dimensional spin systems and
characterize their properties, such as density, depth confinement, and
coherence is an outstanding materials challenge. We present a refined approach
to engineer dense (≳1 ppm⋅nm), 2D nitrogen and NV layers in
diamond using delta-doping during plasma-enhanced chemical vapor deposition
(PECVD) epitaxial growth. We employ both traditional materials techniques, e.g.
secondary ion mass spectrometry (SIMS), alongside NV spin decoherence-based
measurements to characterize the density and dimensionality of the P1 and NV
layers. We find P1 densities of 5-10 ppmâ‹…nm, NV densities between 1 and
3.5 ppmâ‹…nm tuned via electron irradiation dosage, and depth confinement
of the spin layer down to 1.6 nm. We also observe high (up to 42%)
conversion of P1 to NV centers and reproducibly long NV coherence times,
dominated by dipolar interactions with the engineered P1 and NV spin baths