Photoinduced charge injection from shallow point defects in diamond into water

TL;DR

This study demonstrates that engineered diamond surfaces with nitrogen-vacancy centers can generate photocurrent in water under visible light, expanding potential applications in photo-induced chemical and spin processes.

Contribution

It reveals that shallow NV centers in diamond enable visible-light-induced charge injection into water, overcoming the UV limitation of traditional diamond photocatalysis.

Findings

Photocurrent observed up to 594 nm in water with diamond surfaces.

NV centers dominate photocurrent response at high illumination intensities.

Surface defects and traps contribute to carrier injection.

Abstract

Thanks to its low or negative surface electron affinity and chemical inertness, diamond is attracting broad attention as a source material of solvated electrons produced by optical excitation of the solid-liquid interface. Unfortunately, its wide bandgap typically imposes the use of wavelengths in the ultra-violet range, hence complicating practical applications. Here we probe the photocurrent response of water surrounded by single-crystal diamond surfaces engineered to host shallow nitrogen-vacancy (NV) centers. We observe clear signatures of diamond-induced photocurrent generation throughout the visible range and for wavelengths reaching up to 594 nm. Experiments as a function of laser power suggest that NV centers and other co-existing defects - likely in the form of surface traps - contribute to carrier injection, though we find that NVs dominate the system response in the limit of high illumination intensities. Given our growing understanding of near-surface NV centers and adjacent point defects, these results open new perspectives in the application of diamond-liquid interfaces to photo-carrier-initiated chemical and spin processes in fluids.