Abstract
Color centers in diamond have shown excellent potential for applications in quantum information processing, photonics, and biology. Here we report the optoelectronic investigation of shallow silicon vacancy (SiV) color centers in ultra-thin (7–40 nm) nanocrystalline diamond (NCD) films with variable surface chemistry. We show that hydrogenated ultra-thin NCD films exhibit no or lowered SiV photoluminescence (PL) and relatively high negative surface photovoltage (SPV) which is ascribed to non-radiative electron transitions from SiV to surface-related traps. Higher SiV PL and low positive SPV of oxidized ultra-thin NCD films indicate an efficient excitation—emission PL process without significant electron escape, yet with some hole trapping in diamond surface states. Decreasing SPV magnitude and increasing SiV PL intensity with thickness, in both cases, is attributed to resonant energy transfer between shallow and bulk SiV. We also demonstrate that thermal treatments (annealing in air or in hydrogen gas), commonly applied to modify the surface chemistry of nanodiamonds, are also applicable to ultra-thin NCD films in terms of tuning their SiV PL and surface chemistry.
Highlights
Diamond color centers have been attracting considerable attention due to their interesting optical properties [1]
We showed that silicon vacancy (SiV) PL is sensitive to nanocrystalline diamond (NCD) surface chemistry, in particular hydrogen-terminated NCD exhibited lower SiV PL intensity than oxygen-terminated NCD
By means of thickness and surface chemistry dependent Kelvin probe force microscopy (KPFM)/surface photovoltage (SPV) measurements we identified significant positive SPV and less pronounced negative SPV on hydrogen-terminated and oxygen-terminated NCD respectively
Summary
Diamond color centers have been attracting considerable attention due to their interesting optical properties [1]. Quantities of interest are magnetic fields, pressure, temperatures, as well as the presence of various biological species. The NV− centers have already been shown to be capable of detecting such quantities [2]. The sensing capabilities of the SiV centers have only been tested for a handful of these quantities. Optical studies have shown that both zero-phonon-line (ZPL) position and bandwidth changes as a function of the surrounding temperature [3,4]. Sensitivity to a magnetic field was demonstrated via the spectral splitting of energy levels at low temperature [5]
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