Chemin, A.; Levine, I.; Rusu, M.; Vaujour, R.; Knittel, P.; Reinke, P.; Hinrichs, K.; Unold, T.; Dittrich, T.; Petit, T.: Surface-Mediated Charge Transfer of Photogenerated Carriers in Diamond. Small Methods 7 (2023), p. 2300423/1-11
10.1002/smtd.202300423
Open Access Version
Abstract:
Solvated electrons are highly reductive chemical species whose chemicalproperties remain largely unknown. Diamond materials are proposed as apromising emitter of solvated electrons and visible light excitation wouldenable solar-driven CO2or N2reductions reactions in aqueous medium. Butsub-bandgap excitation remains challenging. In this work, the role of surfacestates on diamond materials for charge separation and emission in bothgaseous and aqueous environments from deep UV to visible light excitation iselucidated. Four different X-ray and UV–vis spectroscopy methods are appliedto diamond materials with different surface termination, doping andcrystallinity. Surface states are found to dominate sub-bandgap chargetransfer. However, the surface charge separation is drastically reduced forboron-doped diamond due to a very high density of bulk defects. In a gaseousatmosphere, the oxidized diamond surface maintains a negative electronaffinity, allowing charge emission, due to remaining hydrogenated andhydroxylated groups. In an aqueous electrolyte, a photocurrent forillumination down to 3.5 eV is observed for boron-doped nanostructureddiamond, independent of the surface termination. This study opens newperspectives on photo-induced interfacial charge transfer processes frommetal-free semiconductors such as diamonds