Shallow Nitrogen Vacancy Color Centers in Diamond by Ion Implantation

Recent advancements in quantum technologies are fueled by the ability to engineer materials with specific quantum properties, enabling various applications. The nitrogen-vacancy (NV) center in diamond is a key system for nanoscale sensors, capable of detecting weak magnetic fields with nanotesla-range sensitivity. To achieve high spatial resolution and sensitivity, NV centers must be placed near the diamond surface. This study investigates the creation of NV defects in a pure chemical vapor deposition (CVD) diamond single crystal via broad-beam ion implantation. The implantations are performed through thin (100 nm) SiO2 layers deposited by plasma-enhanced CVD (PECVD). Both normal and oblique ion beam incidences are used, with the oblique incidence chosen to reduce the nitrogen ion penetration depth. Simulations show a subsurface NV center distribution, with the highest concentration near the surface; the expected trends are confirmed by angle-resolved X-ray photoelectron spectroscopy (ARXPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). This distribution extends to a depth of 30 nm. By adjusting the ion beam incidence angle, NV center density can be modulated. This work contributes to optimizing the fabrication process for shallow color centers through ion implantation using a screening layer.