We report successful introduction of negatively charged nitrogen-vacancy (NV(-)) centers in a 5 nm thin, isotopically enriched ([(12)C] = 99.99%) diamond layer by CVD. The present method allows for the formation of NV(-) in such a thin layer even when the surface is terminated by hydrogen atoms. NV(-) centers are found to have spin coherence times of between T2 ~ 10-100 μs at room temperature. Changing the surface termination to oxygen or fluorine leads to a slight increase in the NV(-) density, but not to any significant change in T2. The minimum detectable magnetic field estimated by this T2 is 3 nT after 100 s of averaging, which would be sufficient for the detection of nuclear magnetic fields exerted by a single proton. We demonstrate the suitability for nanoscale NMR by measuring the fluctuating field from ~10(4) proton nuclei placed on top of the 5 nm diamond film.

We report on a microwave planar ring antenna specifically designed for optically-detected magnetic resonance (ODMR) of nitrogen-vacancy (NV) centers in diamond. It has the resonance frequency at around 2.87 GHz with the bandwidth of 400 MHz, ensuring that ODMR can be observed under external magnetic fields up to 100 G without the need of adjustment of the resonance frequency. It is also spatially uniform within the 1-mm-diameter center hole, enabling the magnetic-field imaging in the wide spatial range. These features facilitate the experiments on quantum sensing and imaging using NV centers at room temperature.

We have investigated photoinduced spectral changes of excitons in inorganic-organic layered semiconductors, ͑C 6 H 5 C 2 H 4 NH 3 ͒ 2 PbI 4 ͑PhE-PbI 4 ͒ and ͑C 6 H 13 NH 3 ͒ 2 PbI 4 ͑C6-PbI 4 ͒, by means of the subpicosecond pump-probe spectroscopy. The two semiconductors consist of the same inorganic layers and different organic layers. In the two substances, the blueshift and the bleaching of the exciton are observed. It is found that both of the blueshift and the bleaching are considerably stronger in C6-PbI 4 than in PhE-PbI 4 . The weight of the blueshift relative to the bleaching is larger in PhE-PbI 4 than in C6-PbI 4 . These differences are qualitatively explained in terms of the stronger dielectric confinement in C6-PbI 4 than in PhE-PbI 4 due to the lower dielectric constant of the organic layers in C6-PbI 4 than in PhE-PbI 4 . Delay time dependences of the blueshift and the bleaching and their polarization dependences are understood as being due to the exciton relaxation in the angular momentum space with rates of 2.7 and 4.1 ps −1 for PhE-PbI 4 and C6-PbI 4 , respectively.

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We investigated the photoluminescence of individual air-suspended single-walled carbon nanotubes (SWNTs) from 6 to 300 K. Time-resolved and antibunching measurements over the telecommunication wavelength range were performed using a superconducting single-photon detector. We detected moderate temperature independent antibunching behavior over the whole temperature range studied. To investigate the exciton dynamics, which is responsible for the antibunching behavior, we measured excitation-power and temperature dependence of the photoluminescence spectra and lifetime decay curves. These measurements suggested an exciton confinement effect that is likely caused by high-dielectric amorphous carbon surrounding the SWNTs. These results indicate that SWNTs are good candidates for light sources in quantum communication technologies operating in the telecommunication wavelength range and at room temperature.