# Electric noise spectra of a near-surface nitrogen vacancy center diamond with a protective layer

## TL;DR

This study investigates how different surface protective layers influence electric noise spectra in near-surface nitrogen vacancy diamond sensors, revealing key parameters that affect noise reduction and guiding material choice for improved device performance.

## Contribution

It provides a detailed analysis of how various surface layer materials impact electric noise spectra, identifying critical parameters and offering insights for optimizing NV diamond sensor design.

## Key findings

- Surface layers can reduce electric noise in NV diamond sensors.
- Four parameters significantly influence the noise spectrum: relaxation time, loss tangent, power law exponent, and layer thickness.
- Material choice for surface layers depends on the device's operational frequency range.

## Abstract

Surface noise is a detrimental issue for sensing devices based on shallow nitrogen vacancy (NV) color center diamonds. A recent experiment indicates that electric field noise is significant compared to magnetic field noise. They also found that the electric field noise can be reduced with a protective surface layer, though the mechanism of noise reduction is not well understood. We examine the effect of a protective surface layer on the noise spectrum, which is caused by surface charge fluctuations. We use the fluctuation-dissipation theorem to calculate and analyze the noise spectrum for six different surface layer materials typically used for NV center diamond devices. We find that four parameters largely affect the noise spectrum: effective relaxation time, effective loss tangent, power law exponent of the noise spectrum, and layer thickness. Our results suggest that a surface covering layer is indeed useful for decreasing surface noise, but which material is most suitable depends on the device operational frequency range.