Depth dependent decoherence caused by surface and external spins for NV centers in diamond

TL;DR

This study investigates how the proximity of NV centers in diamond to the surface affects their decoherence, revealing a depth-dependent pattern influenced by surface and external spins, with a characteristic depth for maximum decoherence.

Contribution

It introduces a method to analyze depth-dependent decoherence in NV centers by systematically varying their depth and measuring coherence ratios, highlighting the influence of surface and external spins.

Findings

Decoherence ratios vary non-monotonically with depth.

A characteristic depth exists where decoherence from external spins peaks.

Surface and external spins significantly impact NV center coherence.

Abstract

By efficient nanoscale plasma etching, the nitrogen-vacancy (NV) centers in diamond were brought to the sample surface step by step successfully. At each depth, we used the relative ratios of spin coherence times before and after applying external spins on the surface to present the decoherence, and investigated the relationships between depth and ratios. The values of relative ratios declined and then rised with the decreasing depth, which was attributed to the decoherence influenced by external spins, surface spins, discrete surface spin effects and electric field noise. Moreover, our work revealed a characteristic depth at which the NV center would experience relatively the strongest decoherence caused by external spins in consideration of inevitable surface spins. And the characteristic depth was found depending on the adjacent environments of NV centers and the density of surface spins.