Nitrogen Impurities In Diamond Research Articles

Study on the synergistic mechanism of N[sbnd]H[sbnd]S[sbnd]O co-doping in diamonds

Nitrogen impurity remains a crucial focus in diamond impurity research. To address difficulties associated with excessive nitrogen impurities during the synthesis of high-quality diamonds under high-pressure and high-temperature conditions and to increase the proportion of aggregated nitrogen impurities in diamonds, we explored the multi-element growth environment of natural diamonds. In this study, we used N–H–S–O multi-component co-doping to increase the proportion of aggregated nitrogen impurities in diamond. Through Fourier-transform infrared spectroscopy characterization, we successfully used the synergistic mechanism of N–H–S–O co-doping to achieve a 47.9% proportion of aggregated nitrogen impurities in diamond in a single synthesis and successfully synthesized the type IaA + Ib diamond. Raman tests revealed a lower residual stress in the high-quality large single-crystal diamond synthesized. Moreover, we comprehensively analyzed the mechanism of N–H–S–O co-doping to increase the proportion of nitrogen impurities in diamond aggregates and proposed an optimal ratio principle based on the experimental results. This study presents a method for synthesizing diamonds with a high proportion of aggregated nitrogen impurities and provides valuable guidance for elucidating the origin of natural diamonds and synthesizing multi-doped functional diamonds.

A review on forms and concentrations of nitrogen impurities in diamond

A review on forms and concentrations of nitrogen impurities in diamond

Demonstration of NV-detected ESR spectroscopy at 115 GHz and 4.2 T

High frequency electron spin resonance (ESR) spectroscopy is an invaluable tool for identification and characterization of spin systems. Nanoscale ESR using the nitrogen-vacancy (NV) center has been demonstrated down to the level of a single spin. However, NV-detected ESR has exclusively been studied at low magnetic fields, where the spectral overlap prevents clear identification of spectral features. In this work, we demonstrate NV-detected ESR measurements of single-substitutional nitrogen impurities in diamond at a NV Larmor frequency of 115 GHz and the corresponding magnetic field of 4.2 T. The NV-ESR measurements utilize a double electron-electron resonance sequence and are performed using both ensemble and single NV spin systems. In the single NV experiment, chirp pulses are used to improve the population transfer and for NV-ESR measurements. This work provides the basis for NV-based ESR measurements of external spins at high magnetic fields.

Probing Dynamics of an Electron-Spin Ensemble via a Superconducting Resonator

We study spin relaxation and diffusion in an electron-spin ensemble of nitrogen impurities in diamond at low temperature (0.25-1.2K) and polarizing magnetic field (80-300mT). Measurements exploit field-controlled coupling of the ensemble to two modes of a transmission-line resonator. The observed temperature-independent spin relaxation time indicates that spin outdiffusion across the mode volume dominates over spin-lattice relaxation. Depolarization of one hyperfine-split subensemble by pumping of another indicates fast cross relaxation, with implications for the use of subensembles as independent quantum memories.

Pulsed electron paramagnetic resonance spectroscopy powered by a free-electron laser

Electron paramagnetic resonance (EPR) spectroscopy interrogates unpaired electron spins in solids and liquids to reveal local structure and dynamics; for example, EPR has elucidated parts of the structure of protein complexes that other techniques in structural biology have not been able to reveal. EPR can also probe the interplay of light and electricity in organic solar cells and light-emitting diodes, and the origin of decoherence in condensed matter, which is of fundamental importance to the development of quantum information processors. Like nuclear magnetic resonance, EPR spectroscopy becomes more powerful at high magnetic fields and frequencies, and with excitation by coherent pulses rather than continuous waves. However, the difficulty of generating sequences of powerful pulses at frequencies above 100 gigahertz has, until now, confined high-power pulsed EPR to magnetic fields of 3.5 teslas and below. Here we demonstrate that one-kilowatt pulses from a free-electron laser can power a pulsed EPR spectrometer at 240 gigahertz (8.5 teslas), providing transformative enhancements over the alternative, a state-of-the-art ∼30-milliwatt solid-state source. Our spectrometer can rotate spin-1/2 electrons through π/2 in only 6 nanoseconds (compared to 300 nanoseconds with the solid-state source). Fourier-transform EPR on nitrogen impurities in diamond demonstrates excitation and detection of EPR lines separated by about 200 megahertz. We measured decoherence times as short as 63 nanoseconds, in a frozen solution of nitroxide free-radicals at temperatures as high as 190 kelvin. Both free-electron lasers and the quasi-optical technology developed for the spectrometer are scalable to frequencies well in excess of one terahertz, opening the way to high-power pulsed EPR spectroscopy up to the highest static magnetic fields currently available.

A quantum memory intrinsic to single nitrogen–vacancy centres in diamond

A nitrogen impurity in diamond—where two of the carbon atoms are replaced by a nitrogen atom and a vacant lattice site—is seen as a valuable qubit. The spin of an electron localized to the nitrogen-vacancy centre is commonly used for processing. Researchers now show that this electron spin state can be transferred to the nitrogen nuclear spin, where it can be stored until needed.

Quenching Spin Decoherence in Diamond through Spin Bath Polarization

We experimentally demonstrate that the decoherence of a spin by a spin bath can be completely eliminated by fully polarizing the spin bath. We use electron paramagnetic resonance at 240 GHz and 8 T to study the electron-spin coherence time T2 of nitrogen-vacancy centers and nitrogen impurities in diamond from room temperature down to 1.3 K. A sharp increase of T2 is observed below the Zeeman energy (11.5 K). The data are well described by a suppression of the flip-flop induced spin bath fluctuations due to thermal electron-spin polarization. T2 saturates at approximately 250 micros below 2 K, where the polarization of the electron-spin bath exceeds 99%.

Two-photon-excited luminescence spectra in diamond nanocrystals

Two-photon-excited luminescence (TEL) spectra have been recorded in the blue (400–500 nm) and near-ultraviolet (300–400 nm) ranges for diamond particles with 4 nm average size, which were obtained by detonation synthesis from explosives. The observed TEL bands are attributed, by comparing the obtained spectra with the impurity luminescence spectra in large diamond crystals, to N2 and N3 defects associated with the presence of nitrogen impurities in diamond. The TEL spectra presented are found to have certain distinguishing features: short-wavelength shift of the maximum and changes in the shape and width of the spectral bands for ultradispersed diamond compared with the spectrum in bulk crystals.

Core excitons and vibronic coupling in diamond and graphite.

The C 1s exciton in diamond is studied by soft x-ray emission excited with high resolution monochromatic photons. A strong phonon sideband of 5 eV wide is observed in the exciton recombination spectrum. With the phonon contribution, the exciton binding energy is estimated to be 1.5 eV. The excited atoms is suggested to undergo Jahn-Teller relaxation similar to that of the nitrogen impurities in diamond. A similar exciton is observed at the ${\mathrm{\ensuremath{\sigma}}}^{\mathrm{*}}$-band threshold in graphite. These results provide new insights to the understanding of the core exciton and the donor problem in diamond and other systems.

First-principles supercell studies of the nitrogen impurity in diamond.

We have used a first-principles, local-orbital computational scheme to study the electronic structure of a substitutional N donor impurity in cubic diamond. The calculations were carried out in a supercell framework, using three different supercells with increasing impurity-impurity separation. Comparison of the results from all three supercells allows a reliable extrapolation to the isolated-impurity limit; we find that the N impurity level falls at ${\mathit{E}}_{\mathit{c}}$-0.8 eV, where ${\mathit{E}}_{\mathit{c}}$ is the conduction-band edge. Analysis of the impurity wave function for the three supercells shows that, while the calculated energies indicate a deep donor level, the impurity wave function is nonetheless surprisingly long ranged. The implications of this for the interpretation of recent findings on magnetic multilayers are briefly discussed.

First principles cluster investigation of electronic structure and hyperfine interaction for nitrogen in diamond

The self-consistent field Unrestricted Hartree-Fock cluster procedure has been used to study the location, electronic structure and hyperfine properties of nitrogen impurity in diamond. From the analysis of the potential energy curve for nitrogen along the axis, it was found that nitrogen is located at a position 0.3A away from the substitutional site towards the plane formed by the three nearest neighbour carbon atoms. The calculated values of the magnetic hyperfine constants and nuclear quadrupole coupling constants for14N agree very well with values obtained from electron paramagnetic resonance and electronnuclear double resonance measurements.

Reorientation of Nitrogen in Type-IbDiamond by Thermal Excitation and Tunneling

The rate of anneal of stress-induced ordering of isolated substitutional nitrogen impurities in diamond, measured in the temperature range $78 \mathrm{K}lTl200 \mathrm{K}$, shows large deviations from Arrhenius-type behavior. It is concluded that in the temperature range considered, reorientation of the centers occurs by tunneling between thermally populated excited vibrational states. Two parameters serve to describe reorientations by thermal activation, by tunneling, and by the combined process.

Nonmetallic crystals with high thermal conductivity

Nonmetallic crystals transport heat primarily by phonons at room temperature and below. There are only a few nonmetallic crystals which can be classed as high thermal conductivity solids, in the sense of having a thermal conductivity of > 1 W/cmK at 300K. Thermal conductivity measurements on natural and synthetic diamond, cubic BN, BP and AIN confirm that all of them are high thermal conductivity solids. Studies have been made of the effect on the thermal conductivity of nitrogen impurities in diamond, and oxygen impurities in AIN. The nitrogen impurities scatter phonons mostly from the strain field, the oxygen impurities scatter phonons mostly from the mass defects caused by aluminum vacancies. Pure A1N as well as pure SiC, BeO, BP and BeS conduct heat almost as well as does copper at room temperature, while pure natural and synthetic diamonds conduct heat five times better than copper. All of the nonmetallic solids that are known to possess high thermal conductivity have either the diamond-like, boron carbide, or graphite crystal structure. There are twelve different diamond-like crystals, a few boron carbide-type crystals, and two graphite structure crystals that have high thermal conductivity. Analyses of the rock-salt, fluorite, quartz, corundum and other structures show no candidates for this class. The four rules for finding crystals with high thermal conductivity are that the crystal should have (1) low atomic mass, (2) strong bonding, (3) simple crystal structure, and (4) low anharmonicity. The prime example of such a solid is diamond, which has the highest known thermal conductivity at 300K.

New lines in the electron spin resonance spectrum of substitutional nitrogen donors in diamond

The electron spin resonance lines of nitrogen impurity in diamond found by Smith, Sorokin, Gelles and Lasher have been re-examined in special samples and at low energy densities. The new spectral lines found have been analysed into three new systems: (i) Two more pairs of weak lines were found nearer to the main nitrogen lines. These lines are attributed to 13C atoms in some of the next nearest neighbour positions to the substitutional nitrogen. The principal hyperfine axes of the lines attributed by Smith et al. to the 13C atoms basal to the nitrogen of the N-C bond are found to be approximately parallel to the nitrogen hyperfine axes. (ii) Weak lines occur half-way between the main nitrogen lines. They are shown to be due to the interaction of the small quadrupole moment of the nitrogen with the electric field gradient. (iii) The lines due to the 15N with a nuclear spin of I = ½ have also been identified.