  Color centers in diamond are widely explored for applications in quantum
sensing, computing, and networking. Their optical, spin, and charge properties
have been extensively studied, while their interactions with itinerant carriers
are relatively unexplored. Here we show that NV centers situated within 10 nm
of the diamond surface can be converted to the neutral charge state via hole
capture. By measuring the hole capture rate, we extract the capture cross
section, which is suppressed by proximity to the diamond surface. The distance
dependence is consistent with a carrier diffusion model, indicating that the
itinerant carrier lifetime can be long, even at the diamond surface. Measuring
dynamics of near-surface NV centers offers a new tool for characterizing the
diamond surface and investigating charge transport in diamond devices.
