Controlled Surface Modification to Revive Shallow NV^– Centers

Abstract

Near-surface negatively charged nitrogen vacancy (NV) centers hold excellent promise for nanoscale magnetic imaging and quantum sensing. However, they often experience charge-state instabilities, leading to strongly reduced fluorescence and NV coherence time, which negatively impact magnetic imaging sensitivity. This occurs even more severely at 4 K and ultrahigh vacuum (UHV, p = 2 × 10 −10 mbar). We demonstrate that in situ adsorption of H 2 O on the diamond surface allows the partial recovery of the shallow NV sensors. Combining these with bandbending calculations, we conclude that controlled surface treatments are essential for implementing NV-based quantum sensing protocols under cryogenic UHV conditions.

Investigating the initialization and readout of relative populations of NV− and NV0 defects in diamond

“…, where the terms in the restricted sum iterate through the timescales for the sequence of effective defects of increasing numbers of physical point defects that ultimately culminates in equilibrium within the entire collection of N point defects in the least time. In this manner, vacancies 86 and other defects occurring in the dopant formation process could be considered. Thus, given a population of N point defects in thermodynamic equilibrium, the charge state of that population could be initialized by allowing that population to decay in the presence of an additional dopant or an additional effective dopant for the length of time prescribed above, generalizing the notion of donoracceptor pair quantum technologies.…”

Stability of Near-Surface Nitrogen Vacancy Centers Using Dielectric Surface Passivation

“…The most general diamond surface composition involves nondiamond (sp 2 ) carbon, functional groups (C-X n ), dangling bonds, metallic traces, and adsorbed environmental species. , Among these, many surface constituents have been identified as a source of local charge traps (e.g., sp 2 carbon is known to form the double potential well as an electronic trap state) leading to fluctuating electric and magnetic fields which would degrade the properties of proximal NV centers. − NV-diamond quantum sensing protocols typically use high-power nonresonant laser excitation (∼532 nm), which can lead to significant heating, NV spectral diffusion, ionization of nitrogen atoms (P1 centers), and excitation of various surface constituents. − To improve the stability of near-surface NV centers under ambient conditions, numerous atomic functionalization and organic species have been applied on the surface. ,− The effects of band bending and formation of inter-band gap states due to different surface terminations , on stability of proximal NVs have been explored using density functional theory (DFT) simulations. Ultrahigh vacuum (UHV) and cryogenic conditions have been reported to degrade the properties of single NV centers in diamond nanopillar structures, while their stability was partially improved upon surface passivation with ultrapure water . The exact origin of NV degradation near the surface and under different environmental conditions remains unclear and requires attention in order to develop effective mitigation strategies.…”

“…Ultrahigh vacuum (UHV) and cryogenic conditions have been reported to degrade the properties of single NV centers in diamond nanopillar structures, while their stability was partially improved upon surface passivation with ultrapure water. 35 The exact origin of NV degradation near the surface and under different environmental conditions remains unclear and requires attention in order to develop effective mitigation strategies.…”

First-Principles Investigation of Near-Surface Divacancies in Silicon Carbide

“…A prerequisite to reach effective nanostructuring and materials’ integration is the investigation of spin-defects in the proximity of surfaces and interfaces. While studies of near surface defects in diamond, for example the nitrogen vacancy (NV) center, have been reported in several recent papers, − in SiC the stability and electronic properties of spin-defects at surfaces are mostly unexplored …”