Influence of Platinum Thin Films on the Photophysical and Quantum Properties of Near-Surface NV Centers

Nitrogen-vacancy (NV) centers in diamond are optically addressable spin defects with great potential for nanoscale quantum sensing. A key application of NV centers is the detection of external spins at the diamond surface. Among metals, platinum thin films – widely used in spintronics, catalysis, and electrochemistry – provide a particularly interesting system for such studies. However, the interaction between NV centers and metals is known to affect their quantum sensing capabilities. In this work, five platinum-covered diamond samples containing shallow NVs created via nitrogen implantation with different energies (2.5–60 keV) are used to investigate the optical and quantum properties of NV ensembles beneath metal films. A substantial reduction of the photoluminescence lifetime and a pronounced decrease of the NV⁻ population are found for NV ensembles located near the diamond-platinum interface. As a result, optically detected magnetic resonance experiments could only be efficiently performed on diamonds implanted with at least 20 keV, where a strong increase in the T₂ coherence time beneath the platinum thin films is observed. The study describes the various processes affecting NV centers near diamond-platinum interfaces and provides guidance for the integration of thin metal films with near-surface NV centers.