Spectroscopic studies of carbon-13 synthetic diamond

Identification of Pink-Coloured CVD Synthetic Diamonds from Huzhou Sino-C Semiconductor Co. in China

In recent years, increasing numbers of pink-coloured CVD synthetic diamonds have appeared on the market. One of the major sources is Huzhou SinoC Semiconductor Science and Technology Co., Ltd., Zhejiang province of China. In this article, seven pink-coloured CVD-grown diamonds produced in the last two years by Huzhou have been investigated and identified, including their gemological and spectroscopic characteristics. In DiamondView, they fluoresced orange–red, with an obscure striated growth structure, which is common for CVD synthetics. The mid-IR absorption spectra of these samples showed some single nitrogen and hydrogen-related features (1130, 1344, 3123, 3323 cm−1), which indicated that the diamonds were type Ib and were CVD-grown diamonds. The H1a defect annealed out at approximately 1400 °C, whereas the 3107 cm−1 defect was produced by annealing above 1700 or 1800 °C. This implied that the samples had undergone two separate heat treatments: first, a high-temperature anneal (possibly an HPHT treatment to reduce any brown colour), which would have produced the 3107 cm−1 defects and a small number of A centres, followed by irradiation, followed by annealing above 800 °C to make the vacancies mobile. The UV–Vis–NIR absorption spectra showed distinct NV-related features (575 and 637 nm), the main reason for the pink colour. Photoluminescence spectra obtained at liquid nitrogen temperature recorded radiation-related emissions (388.9, 503.5 nm), a strong N-V centre, H3 and H2 defects, and many unassigned emissions. These pink CVD products can be separated from natural and treated pink-coloured diamonds by a combination of optical spectroscopic properties, such as fluorescence colour, and absorption features in the infrared and UV–Vis regions.

Orientation Dependence of Cathodoluminescence and Photoluminescence Spectroscopy of Defects in Chemical-Vapor-Deposited Diamond Microcrystal

Point defects, impurities, and defect–impurity complexes in diamond microcrystals were studied with the cathodoluminescence (CL) spectroscopy in the scanning electron microscope, photoluminescence (PL), and Raman spectroscopy (RS). Such defects can influence the directions that microcrystals are grown. Micro-diamonds were obtained by a hot-filament chemical vapor deposition (HF CVD) technique from the methane–hydrogen gas mixture. The CL spectra of diamond microcrystals taken from (100) and (111) crystallographic planes were compared to the CL spectrum of a (100) oriented Element Six diamond monocrystal. The following color centers were identified: 2.52, 2.156, 2.055 eV attributed to a nitrogen–vacancy complex and a violet-emitting center (A-band) observed at 2.82 eV associated with dislocation line defects, whose atomic structure is still under discussion. The Raman studies showed that the planes (111) are more defective in comparison to (100) planes. What is reflected in the CL spectra as (111) shows a strong band in the UV region (2.815 eV) which is not observed in the case of the (100) plane.

Nanodiamonds enable adaptive-optics enhanced, super-resolution, two-photon excitation microscopy

Particles of diamond in the 5-100 nm size range, known as nanodiamond (ND), have shown promise as robust fluorophores for optical imaging. We demonstrate here that, due to their photostability, they are not only suitable for two-photon imaging, but also allow significant resolution enhancement when combined with computational super-resolution techniques. We observe a resolution of 42.5 nm when processing two-photon images with the Super-Resolution Radial Fluctuations algorithm. We show manipulation of the point-spread function of the microscope using adaptive optics. This demonstrates how the photostability of ND can also be of use when characterizing adaptive optics technologies or testing the resilience of super-resolution or aberration correction algorithms.

Spatially controlled fabrication of a bright fluorescent nanodiamond-array with enhanced far-red Si-V luminescence

We demonstrate a novel approach to precisely pattern fluorescent nanodiamond-arrays with enhanced far-red intense photostable luminescence from silicon-vacancy (Si-V) defect centers. The precision-patterned pre-growth seeding of nanodiamonds is achieved by a scanning probe 'dip-pen' nanolithography technique using electrostatically driven transfer of nanodiamonds from 'inked' cantilevers to a UV-treated hydrophilic SiO2 substrate. The enhanced emission from nanodiamond dots in the far-red is achieved by incorporating Si-V defect centers in a subsequent chemical vapor deposition treatment. The development of a suitable nanodiamond ink and mechanism of ink transport, and the effect of humidity and dwell time on nanodiamond patterning are investigated. The precision patterning of as-printed (pre-CVD) arrays with dot diameter and dot height as small as 735 nm ± 27 nm and 61 nm ± 3 nm, respectively, and CVD-treated fluorescent ND-arrays with consistently patterned dots having diameter and height as small as 820 nm ± 20 nm and, 245 nm ± 23 nm, respectively, using 1 s dwell time and 30% RH is successfully achieved. We anticipate that the far-red intense photostable luminescence (~738 nm) observed from Si-V defect centers integrated in spatially arranged nanodiamonds could be beneficial for the development of next generation fluorescence-based devices and applications.

Optical superradiance from nuclear spin environment of single-photon emitters

We show that superradiant optical emission can be observed from the polarized nuclear spin ensemble surrounding a single-photon emitter such as a single quantum dot or nitrogen-vacancy center. The superradiant light is emitted under optical pumping conditions and would be observable with realistic experimental parameters.

Prediction and measurement of the size-dependent stability of fluorescence in diamond over the entire nanoscale

Fluorescent defects in noncytotoxic diamond nanoparticles are candidates for qubits in quantum computing, optical labels in biomedical imaging, and sensors in magnetometry. For each application these defects need to be optically and thermodynamically stable and included in individual particles at suitable concentrations (singly or in large numbers). In this Letter, we combine simulations, theory, and experiment to provide the first comprehensive and generic prediction of the size, temperature, and nitrogen-concentration-dependent stability of optically active N-V defects in nanodiamonds.

13C NMR Investigations of Spin-Lattice Relaxation in 99% 13C-Enriched Diamonds

The paper is devoted to investigations of spin-lattice relaxation processes in 99% 13C-enriched diamonds. Relaxation time measurements were performed as a function of orientation, magnetic field, and temperature. Both experimental results and theoretical discussion are presented. Multiexponential behavior of nuclear magnetization recovery was observed. There was found no significant influence of the diamond orientation on the nuclear spin-lattice relaxation. The field dependence of the spin-lattice relaxation time was found to be proportional to the second power of the magnetic field. The temperature measurements showed a weak increase of the spin-lattice relaxation time with decreasing temperature. Possible mechanisms of impurity relaxation are considered and compared with the experimental data. Copyright 1998 Academic Press. Copyright 1998 Academic Press