Creation, Control, and Modeling of NV Centers in Nanodiamonds

TL;DR

This paper advances the control and modeling of NV centers in nanodiamonds by exploring surface chemistry, proton irradiation effects, and developing a predictive model for NV center formation and charge state management.

Contribution

It introduces a novel mathematical model for predicting NV center formation and charge states, validated through systematic experiments with surface treatments and proton irradiation.

Findings

Proton irradiation fluences effectively control NV center concentration.

Surface chemistry influences NV charge state ratios.

The new model predicts NV center efficiencies across various ion-beam conditions.

Abstract

Sensing based on Nitrogen-Vacancy (NV) centers in nanodiamonds (NDs) offers significant potential across various applications. However, optimizing their quantum-optical properties remains challenging. This study focuses on enhancing and controlling the optical properties of NV centers in NDs through surface chemistry tuning and proton beam irradiation. Systematic thermal oxidations were performed to investigate the evolution of surface chemical groups using IR spectroscopy and their influence on optical properties using photoluminescence spectroscopy and PL decay measurements. Proton irradiation was explored over a wide range of fluences (10^14 to 10^17 cm^-2) to precisely control the NV center concentration, identifying conditions that maximize creation and emission intensity. Furthermore, NV center charge state control was achieved by analyzing the NV-/NV0 ratio with varying surface terminations and NV center concentrations. A novel predictive mathematical model was developed to evaluate the efficiencies of forming NV- and NV0. Although tested specifically with proton-irradiated NDs, this model has broad applicability, representing a significant advancement in predicting the outcomes of ion-beam-based color center generation in diamond.