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

Area of Science:

• Quantum Optics
• Materials Science
• Surface Chemistry

Background:

• Nitrogen vacancy (NV) centers in diamond are promising for quantum sensing applications.
• The photophysical stability of NV centers is critical for reliable sensor performance.
• Surface conditions significantly influence NV center charge state and stability.

Purpose of the Study:

• To investigate the photophysical stability of near-surface NV centers in diamond under varying environmental conditions (air vs. vacuum).
• To understand the mechanisms behind NV center charge state switching and degradation.
• To evaluate the effectiveness of alumina coatings in enhancing NV center stability.

Main Methods:

• Optically detected magnetic resonance (ODMR) measurements to assess NV center contrast.
• X-ray photoelectron spectroscopy (XPS) for surface characterization and chemical state analysis.
• Photoluminescence spectroscopy to confirm NV charge state dynamics.
• Deposition of alumina (Al2O3) coatings on diamond surfaces.

Main Results:

• NV center stability showed opposing trends in air (increase in contrast) and vacuum (decrease in contrast) under illumination.
• Surface reconstruction, influenced by oxygen adsorption/desorption, was identified as the cause of NV charge state switching (NV- in air, NV0 in vacuum).
• A ~2 nm alumina coating effectively stabilized the NV charge state in both environments, preventing degradation.

Conclusions:

• Surface chemistry plays a critical role in the photophysical stability of NV centers.
• Alumina coatings provide a robust method for stabilizing NV centers against environmental influences and illumination.
• Alumina-coated diamond surfaces offer a promising pathway for developing resilient and high-performance NV-based quantum sensors.