Chemical vapour deposition diamond single crystals with nitrogen-vacancy centres: a review of material synthesis and technology for quantum sensing applications

Abstract

Diamond is a host for a wide variety of colour centres that have demonstrated outstanding optical and spin properties. Among them, the nitrogen-vacancy (NV) centre is by far the most investigated owing to its superior characteristics, which promise the development of highly sophisticated quantum devices, in particular for sensing applications. Nevertheless, harnessing the potential of these centres mainly relies on the availability of high quality and purity diamond single crystals that need to be specially designed and engineered for this purpose. The plasma assisted Chemical Vapour Deposition (CVD) has become a key enabling technology in this field of research. Nitrogen can indeed be directly in-situ doped into a high crystalline quality diamond matrix in a controlled way allowing the production of single isolated centres or ensembles that can potentially be integrated into a device.In this paper we will provide an overview on the requirements for synthesizing "quantum-grade" diamond films by CVD. These include the reduction of impurities and surrounding spins that limit coherence times, the control of NV density in a wide range of concentrations as well as their spatial localization within the diamond. Enhancing the charge state and preferential orientation of the colour centres is also discussed. These improvements in material fabrication have contributed to position diamond as one of the most promising solid-state quantum system and the first industrial applications in sensing are just starting to emerge.

Is a Quantum Biosensing Revolution Approaching? Perspectives in NV‐Assisted Current and Thermal Biosensing in Living Cells

“…the paramagnetic 13 C isotopes, whose natural abundance is about 1.1%). [170][171][172] It is important to note that the NV density increase will necessary worsen the coherence time of the NVs themselves, because of their mutual interaction. Consequently, an optimal trade-offs between these parameters must be sought.…”

Benchmark for Synthesized Diamond Sensors Based on Isotopically Engineered Nitrogen‐Vacancy Spin Ensembles for Magnetometry Applications

“…However, this comes at the cost of lattice damages implying low coherence times and the loss of preferential orientation. [19,20] Another subtle approach is to tune the growth parameters in order to improve the NV incorporation during crystal growth. In this regard, a recent study shows the temperature dependence of NV incorporation in a ⟨113⟩-oriented diamond substrate while retaining preferential orientation.…”

Self-activated photoblinking of nitrogen vacancy centers in nanodiamonds (sandSTORM): A method for rapid single molecule localization microscopy with unlimited observation time

“…Direct ionization of NVrequires photon energies higher than 2.6 eV which is not possible using the 561 nm illumination in the work here, corresponding to ‚ 2.21 eV. However, ionization may occur via a 2 photon absorption process in which one photon induces a transition to the excited state of the defect while the second photon excites the electron to the conduction band of the diamond [43]. Blinking on the microsecond time scale has been ascribed to a photoconversion process of the NV itself between the NVand NV o state whilst blinking occurring at the millisecond time scale has been linked with a two photon charge state conversion process.…”

“…Collectively the experimental results suggest the chemical environment local to NVs strongly affects photoblinking and it is hypothesized that this may arise from a combination of effects including changes in radiative and nonradiative decay paths and lifetimes along with ligand induced shifts in the energies of the dark and bright exciton states [44]. It is further noted that blinking arising from charge state conversion between NVand NV o via two photon process, initiated by long term photoionization, is liable to be affected by the local chemical environment owing to inhibited recombination in the presence of charge traps near to and within the ND that prevents an efficient diffusion of charge carriers [43]. Moreover, electronic interactions between the NVs and surrounding molecules, including bond-building/breaking and charge transfer, will strongly affect the NV electronic states and correspondingly photoblinking [45].…”