Method of producing diamond structure with nitrogen-vacancy defects

FIELD: chemistry.

SUBSTANCE: invention can be used in magnetometry, quantum optics, biomedicine and information technology. Cleaned detonation nanodiamonds are sintered in a chamber at pressure 5-7 GPa and temperature 750-1200°C for a period time ranging from several seconds to several minutes. The obtained powder of diamond aggregates is exposed to laser radiation with wavelength smaller than 637 nm and diamond aggregates with high concentration of nitrogen-vacancy (NV) defects are selected based on the bright characteristic luminescence in the red spectral region. In the obtained diamond structure, about 1% of carbon atoms are substituted with NV defects and about 1% of carbon atoms are substituted with single nitrogen donors.

EFFECT: aligned blocks of nanodiamonds obtained using the invention have quasi-crystalline properties, which makes investigation and identification thereof easier; the aggregates can also be ground to obtain diamond nanocrystals having NV defects.

2 cl, 5 dwg

The invention relates to microelectronics and can be used in magnetometry, quantum optics, Biomedicine, as well as in information technology, based on the quantum properties of spins and single photons.

Nitrogen-vacancy defects (NV defects) represent the position of C (V), in the nearest coordination sphere which one of the four carbon atoms are replaced by nitrogen atom (N). After opening a unique emitting properties of NV defects in diamond, allowing optical record magnetic resonance in the ground state of NV defects at room temperature until the registration of magnetic resonance on single defect (see A.Gruber, A.Drabenstedt, C.Tietz, L.Fleury, J.Wrachtrup, C.Von Borczyskowski, Scanning Confocal Optical Microscopy and Magnetic Resonance on Single Defect Centers, Science 1997, 276, 2012-2014; J.Wrachtrup, F.Jelezko, Processing quantum information in diamond, J. Phys.: Condens. Matter 18, S807, 2006), started a fantastic script, which can be achieved absolute miniaturization of the element base of micro - and optoelectronics up to the device on the basis of a single defect, which opens up opportunities for the application of NV defects in such promising areas as magnetometry, quantum optics, Biomedicine, as well as for the development of new information technologies, based on the quantum properties of spins and single photons.

Known SP is a way to get purple diamond with NV-color centers (NV defects) based on synthetic diamond (see patent US 4950463, IPC B28D 5/00; C30B 33/00; C01B 031/06 published 21.08.1990), in which the synthetic diamond of type Ib nitrogen in the form of isolated atoms substitution (defects) in the concentration range of 8·10¹⁷to 1.4·10¹⁹at/cm³(or from 4.5 to 80 ppm) is irradiated with the electron flow in the range of 5·10¹⁶-2·10¹⁸cm^-2at an energy of 2-4 MeV, followed by annealing in a vacuum of not less than 10^-2Torr at a temperature of 800-1100°C for more than 20 hours In the irradiation process, a large number of primary radiation defects: vacancies and Midwesterner atoms. Subsequent high-temperature annealing in vacuum assures a robust NV color centers in the capture of vacancies nitrogen atoms (P-centers). Such defects have absorption in the red region of the spectrum at wavelengths less than 640 nm, and cause different intensity of red color of the diamond crystals. Get the purple crystals of the diamond NV-color centers having absorption in the range 500-640 nm at the peak of 570 nm.

The disadvantage of this method is the need for a source of high-energy electron irradiation, which is inevitably accompanied by the formation of additional defects that negatively affect the characteristics of the NV defect. Moreover, the penetration depth of electrons in the diamond is what I uneven, which leads to uneven distribution of NV defects on the sample. In addition subsequent operations type of mechanical grinding and chemical effects on the crystals already containing NV defects, has a negative impact on the properties of NV defects.

There is a method of creating a light-emitting nanoparticles of diamond NV defects (see application EP 1990313, IPC C01B 31/06, published 12.11.2008), which outlines a way of turning on an industrial scale synthetic diamond microcrystals containing a light-emitting NV defects in spatially isolated ultra-low doped NV defects in diamond nanoparticles, showing a stable luminescence, not subjected to bleaching. The output of the nanoparticles of diamond is approximately 15% of the mass of the initial particles of synthetic diamond. NV defects created in the source powder microelisa by irradiating the electron beam 10¹⁷-2·10¹⁹cm^-2with energy more than 7 MeV with subsequent annealing at temperatures above 700°C for more than 1 hour, grinding and chemical processing.

The disadvantage of this method is the need for a source of high-energy electron irradiation which is inevitably accompanied by the formation of additional defects that negatively affect the characteristics of the NV defect. The depth of printroleselector in diamond is uneven, which leads to uneven distribution of NV defects on the sample.

Known method for improving the optical properties of the crystal diamond obtained by chemical deposition from the gas phase, NV defects (see PCT application WO 2010048607, IPC C01B 31/06, published 29.04.2010), including annealing of diamond doped with nitrogen at a temperature above 2200°C and a pressure of 300 Torr. It is shown that annealing at temperatures below 1700°C the intensity of the photoluminescence of NV defects in two charge States increases approximately 5-fold, whereas annealing at temperatures above 1700°C leads to a decrease of the intensity of the photoluminescence of NV defects. Also it is shown that annealing at high pressure leads to the decrease or disappearance of the concentration of NV defects.

The disadvantages of this method is the low initial concentration of NV defects in diamond compared to the received radiation, which increase five times during the annealing does not lead to a sufficient concentration for most applications. Also in diamond there are two charge state of NV defects in similar concentrations, while the NV defects in the neutral state are undesirable, because their properties are not of interest for applications.

A method of obtaining diamonds with sustainable NV-color centers, absorbing in the wavelength range 400-640 nm (see patent RU2237113, IPC C30B 33/04, published 26.06.2003), by irradiating the electron beam and annealing at temperatures of at least 1100°C in vacuum. In a known way using natural diamond type Ia and in its crystal lattice form isolated nitrogen atoms in positions of substitution - the defects by high-temperature treatment in a high pressure chamber at a temperature of more than 2150°C for stabilizing the pressure 6,0-7,0 HPa carried out before irradiation high-energy stream of electrons with a dose of 5·10¹⁵-5·10¹⁸cm^-2when 2-4 MeV. Used diamonds with defects And nitrogen pairs), or irradiated with high natural diamonds high-energy stream of electrons with a dose of more than 10¹⁹cm^-2containing more than 800 ppm of nitrogen in the form of defects or B1 (four nitrogen).

The disadvantage of this method is the necessity of using natural diamonds, which makes the procedure expensive for technical applications. In addition, the concentration of NV defects is relatively low and does not exceed 5 ppm.

Known method of preparing the luminescent nanodiamonds containing NV defects (see J.-P.Boudou, P.A.Curmi, F.Jelezko, J.Wrachtrup, P.Aubert, M.Sennour, G.Balasubramanian, R.Reuter, A.Thorel and E.Gaffet, High yield fabrication of fluorescent nanodiamond, Nantechnology 20, 235602, 2009), in which at the initial stage of NV defects create synthetic powder is ke of microelisa by irradiation by electrons with energy of 10 MeV and a current of 8 mA at 24 hours and subsequent annealing for 2 hours at 800°C in vacuum. Then, the fluorescence powder mechanically crushed and treated with chemicals in the form of heat in the mixture of acids HF/NGO₃accompanied placed in a centrifuge and the unnecessary separation of fractions from the main powder in the form of nanodiamonds containing NV defects.

The disadvantage of this method is the need for a source of high-energy electron irradiation, which is inevitably accompanied by the formation of additional defects that negatively affect the characteristics of the NV defect. The penetration depth of electrons in diamond is uneven, resulting in uneven distribution of NV defects on the sample.

There is a method of creation of NV defects (see Y.Mitra, Change of absorption spectra in type-Ib diamond with heavy neutron irradiation, Phys. Rev. 53, 11360, 1996) in the bulk diamond crystals, as well as in micro - and nanodiamonds by irradiation with neutrons for the formation of vacancies and subsequent annealing at temperatures of 800-900°C, resulting in the movement of vacancies and capture them in the diamond isolated nitrogen atoms with the formation of nitrogen-vacancy NV defect.

The disadvantage of this method is the necessity of using source neutron irradiation, which is inevitably accompanied by the formation of large amounts of undesirable defects, which does not allow to increase the dose of irradiation is placed above 10 ¹⁸cm^-2and neutron irradiation leads to the formation of radioactive elements, which requires, as a rule, a long process of decontamination. Since the formation of vacancies is statistical, it is almost impossible to control their education, as well as the efficiency of formation of vacancies in the nanocrystals with size less than 20 nm is practically zero.

There is a method of creation of NV defects (see B.R.Smith, D.W.Inglis, .Sandnes, J.R.Rabeau, A.V.Zvyagin, D.Gruber, C.J.Noble, R.Vogel, E.Osawa, and T.Plakhotnik, Five-Nanometer Diamond dial with Luminescent Nitrogen-Vacancy Defect Centers, Small 5, 1649, 2009) directly in the detonation nanodiamonds (BOTTOM) by irradiation by electrons with energies above the threshold (above 1 MeV) for the formation of vacancies and subsequent annealing at temperatures of 800-900°C, resulting in the movement of vacancies and capture them in the diamond isolated nitrogen atoms with the formation of nitrogen-vacancy defect NV.

The disadvantage of this method is the necessity of using high-energy source of electron irradiation in fact, due to the statistical nature of the process of formation of vacancies, it is almost impossible to control their education. In addition, the efficiency of formation of vacancies in the nanocrystals with size less than 20 nm is practically zero (see I.Vlasov, O.Shenderova, S.Turner, O.I.Lebedev, A.A.Basov, I.Sildos, M.Rähn, A.A.Shiryaev, and G.Van Tendeloo, Ntrogen and Luminescent Nitrogen-Vacancy Defects in Detonation Nanodiamond, Small 6, 687, 2010).

There is a method of creation of NV defects by ion implantation of nitrogen in ultrapure diamond with subsequent annealing at 800°-900°C. the Implanted isotope¹⁵N, to be able to share implanted nitrogen atoms from those that were present in the source material (see J.R.Rabeau, P.Reichart, G.Tamanyan, D.N.Jamieson, S.Prawer, F.Jelezko, T.Gaebel, I.Popa, M.Domhan and J.Wrachtrup, Implantation of labelled single nitrogen vacancy centers in diamond using 15N, Appl. Phys. Lett. 88, 023113, 2006). Also NV defects can be manufactured in nanodiamond by implantation annealing.

The drawback is a very limited depth of penetration of the nitrogen ions and the production of large samples using this technique appears to be an elusive task. In the case of implantation in nanodiamonds depth of penetration of nitrogen is limited to a few millimeters.

There is a method of creation of NV defects with the use of the method of deposition of diamond from the vapor phase (chemical vapor deposition - CVD) (see J.R.Rabeau, A.Stacey, A.Rabeau, S.Prawer, F.Jelezko, I.Mirza, and J.Wrachtrup, Single Nitrogen Vacancy Centers in Chemical Vapor Deposited Diamond Nanocrystals, Nano Lett. 7, 3433, 2007). The diamond nanocrystals were grown on quartz substrates using a 1.2 kW microwave plasma reactor for CVD. The chamber pressure was set to 40 mbar with 0.7% SN₄in N₂the gas mixture. The temperature of the substrate during growth was 800°C. the Nitrogen is not specifically dobavlyali is, but was present in the background, corresponding to the ratio N/C equal to 0.15.

The disadvantage of this method is the very low probability of creating nitrogen-vacancy defects in nanodiamonds obtained by CVD method: only one defect with 100% probability is generated for crystals with a diameter of 110 nm. When reducing the size of the crystal, the probability of creating at least one defect is significantly reduced, and for nanodiamond size of 60-70 nm the probability of NV defects drops to 2%.

There is a method of creation of NV defects, coinciding with the inventive solution for the greatest number of significant features and adopted for the prototype (see .Bradac, .Gaebel, N.Naidoo, M.J.Sellars, J.Twamley, L.J.Brown, A.S.Barnard, T.Plakhotnik, A.V.Zvyagin and J.R.Rabeau, Nature Nanotech., on-line publication (doi: 10.1038/nnano. 2010.56, 2010). In the method prototype is shown that NV defects can be created in the detonation nanodiamonds (BOTTOM) without irradiation. To obtain isolated BOTTOM approximately 5 nm from the conglomerates of micron size were conducted following procedures. The BOTTOM is mixed with sulfuric acid (98%, 8 ml) and nitric acid (70%, 1 ml) and then incubated for 3 days at 70°C. the Mixture was placed in a centrifuge and subjected to ultrasonic impact, then again heated in a mixture of acids, after which it was washed. All procedures were repeated 3 times. As a result, separate analyze, which was significantly reduced graphite shell. These nanodiamonds were then covered with a polyvinyl film.

The disadvantage of the prototype method is the very low efficiency of education NV defects. In addition, the properties of these defects significantly differ from those obtained in the bulk diamond crystals due to the influence gratituesday shell nanocrystal and internal stresses, and these samples could not even watch besporodnye line luminescence.

The task of the claimed invention to provide such a method of producing a diamond structure with a nitrogen-vacancy defects, which would ensure the creation of large concentrations of NV defects in nanodiamonds and microelisa.

The problem is solved in that a method of obtaining a diamond structure with a nitrogen-vacancy defects includes sintering the treated detonation nanodiamonds in the chamber at a pressure of 5-7 GPA and a temperature of 750-1200°C in a period of time from several seconds to several minutes. The obtained powder of diamond aggregates influence of laser radiation with a wavelength of less than 637 nm and diamond select aggregates with a high concentration of NV defects characterized by a bright luminescence in the red region of the spectrum.

Sintering typically used purified detonation nanodiamond size of al is asnyk grains of 4.5-5 nm. During sintering of the samples carried out at temperatures of 750-850°C and a pressure of 5-7 GPA over time from several seconds to several minutes in the high-pressure chamber "toroid"is self-organization of nanodiamonds in large (micron size) oriented diamond aggregates with quasicrystalline properties. During sintering is the movement of vacancies in the diamond with the subsequent capture them on the nitrogen atoms (P-centers) and the formation of NV defects. The average size of the diamond crystallites in the sintered powder BOTTOM, determined from the integral of the half-width of the reflex x-ray diffraction, is 5.8 nm. After sintering the powder is a separate aggregates with a linear size of about 10 microns, in which under the microscope there is a certain order with planes and steps. The concentration of NV defects in the resulting diamond aggregates is determined by the characteristic of the NV defect intensity of the red luminescence, the same way produce the selection of individual units with a high concentration of NV defects.

The concentration of NV defects and isolated nitrogen atoms N⁰you can determine the signal intensity of electron paramagnetic resonance (EPR).

During sintering of detonation nanodiamonds in the chamber at a pressure less 6 HPa, is graphitization nanodiamond particles. On pecanje detonation nanodiamonds under pressure, greater than 7 GPA, imposed technical limitations of the used cameras sintering associated with their destruction.

Sintering at a temperature less than 750°C does not change the structure and properties of detonation nanodiamond due to the lack of adhesion processes and vzaimodeistvie nanodiamond particles.

Sintering temperatures, large 1200°C leads to enhanced diffusion of vacancies and destruction of nitrogen-vacancy defects in the sintered aggregates of detonation diamonds.

Lower limit of the sintering procedure (10) is determined by the time of the establishment of a uniform field of temperature and pressure on the sample volume. When the duration of the sintering procedure more than 5 minutes is graphitization detonation nanodiamond particles. Sintering of more than 3 minutes impractical from an economic point of view due to accelerated destruction camera sintering.

When using the proposed method, the concentration of NV defects in the sintering was increased by many orders of magnitude up to a concentration of 1% or 10⁴ppm. However, unlike the prototype method, was observed classical NV defect luminescence with a pronounced bisphenol line.

An important advantage of the proposed method is to obtain oriented arrays of nanodiamonds with quasicrystalline properties that significantly about what agchat their research, identification and use of the fixed structures, such as magnetometers or for biomedical applications. Also, you receive the possibility of subsequent crushing of aggregates mechanically or chemically with the aim of obtaining diamond nanocrystals containing NV defects.

The claimed technical solution is illustrated by drawings, where

figure 1 shows the luminescence of several aggregates of micron size sintered nanodiamonds containing high concentrations of NV defects;

figure 2 shows the luminescence spectrum at room temperature for a single diamond unit, surrounded by a circle in figure 1;

figure 3 presents the spectra of the luminescence of NV defects, registered at low temperature for 2 To a single diamond unit, surrounded by a circle in figure 1;

figure 4 shows the spectra of optically detected magnetic resonance registered at a temperature of 2 K for a single diamond unit, luminescence intensity, are presented in figure 3;

figure 5 shows the orientation dependence of the EPR spectrum recorded by electron spin echo (ESE) at a frequency of 94 GHz at room temperature in the diamond unit, obtained by sintering the BOTTOM at T=800°C and P=6 GPA. Points correspond to experimental data, the solid and dotted Lin and are the result of calculations using the spin Hamiltonian the dashed lines correspond to the twins.

The inventive method of obtaining a diamond structure with a nitrogen-vacancy defects is as follows. Pre-BOTTOM purified from metallic impurities, and then the powder of the purified BOTTOM with the size of the diamond grains 4-5 nm is placed in a high pressure chamber with controlled temperature, produce sintering BOTTOM at high pressure 5-7 GPA and temperatures in the range of 750-1200°C in a period of time from several seconds to several minutes, in which there is movement of vacancies in diamond, and self-organization of nanodiamonds in large oriented micron size aggregates. Then produce a selection of diamond aggregates of the powder sintered nanodiamonds with a high concentration of NV defects characterized by a bright luminescence in the red region when excited with their laser with a wavelength shorter than bisphenol line NV defects equal to 637 nm, for example, a typical solid-state laser with a wavelength of 532 nm. Output yarkovytsya aggregates with sizes in the field of 1-15 μm with quasicrystalline properties reaches 50%. To determine the concentration of NV defects in diamond aggregates and the degree of orientation of these units are placed in the spectrometer, electron paramagnetic resonance (EPR) and recorded EPR spectra of NV defects in anatoy temperature, then determine the concentration of NV defects or by comparing with a reference signal with a known concentration of spins, or the ratio signal/noise using passport data on the sensitivity of the EPR spectrometer.

The inventive method is illustrated for the manufacture of diamond aggregates with a high concentration of emitting NV defects and control the process of their formation and concentration methods photoluminescence, optical detection of magnetic resonance and electron paramagnetic resonance. The purified powder of the BOTTOM with the size of the diamond grains 4-5 nm were placed in a special high-pressure chamber with controlled temperature, then made sintering BOTTOM at high pressure of 6 GPA and a temperature of 800°C for 11 seconds. Then made a selection of diamond powder aggregates with a high concentration of NV defects characterized by a bright luminescence in the red region when excited with their laser with a wavelength of 532 nm. Y at room temperature microaggregate nd shown in figure 1, which is a real photograph taken through an optical microscope, the luminescence spectrum recorded at room temperature for a single diamond unit, circled in figure 1, is shown in figure 2. Output yarkovytsya units the dimensions in the field of 1-15 μm with quasicrystalline properties reached 50%. During sintering the BOTTOM at high pressure P=6 GPA and a temperature of 1530°C for 11 seconds in the powders of diamond aggregates characteristic luminescence in the red region when excited by a laser with a wavelength of 532 nm was absent, and EPR spectra were no signals of NV defects.

To determine the concentration of NV defects in diamond aggregates and the degree of orientation of these units were placed in the spectrometer, electron paramagnetic resonance (EPR) and recorded the EPR spectra of NV defects at room temperature.

Figure 5 shows the orientation dependence of the EPR spectrum recorded by electron spin echo (ESE) at a frequency of 94 GHz at room temperature in the sample obtained by sintering the BOTTOM at T=800°C and P=6 GPA for 11 seconds. Points correspond to experimental data, the solid and dashed lines are the result of calculations using the spin Hamiltonian, the dashed lines correspond to the twins. Orientational dependence of EPR spectra clearly indicate quasicrystalline properties of the diamond system, i.e. almost perfect orientation of this system also recorded the presence of twins. Then determined the concentration of NV defects of the ratio signal/noise using passport data on the sensitivity spec is romera EPR. The sensitivity of the instrument was ~5×10⁹spins when the line width of the 1 Gauss. Given the width of individual lines and the signal-to-noise ratio for each line related to the defect, received that recorded the number of spins NV-defects was ~2.8×10¹²the spins. The linear size of the diamond unit was ~10 μm (volume ~10³μm³). Thus, given that the concentration of NV-defects was 2.8×10²¹cm^-3. Conducting a similar evaluation for single-donor nitrogen, can be obtained that the concentration of N⁰centres close to the concentration of NV-defects and is ~3×10²¹cm^-3. The concentration of carbon atoms in the crystalline diamond is 1.76×10²³atoms/cm³. Thus, micro-size particles in the aggregate, obtained by sintering without radiation, discovered a giant concentration of NV defects. First obtained oriented diamond system, which ~1% of carbon atoms are substituted NV defects and ~1% of carbon atoms are replaced by a single donor of nitrogen.

1. A method of obtaining a diamond structure with a nitrogen-vacancy (NV) defects, including effects on purified detonation nanodiamonds physical factor, wherein the purified detonation nanodiamonds is sintered in the chamber at a pressure of 5-7 GPA and a temperature of 750-1200°C during the time from which escolca seconds to several minutes, affect the obtained powder of diamond aggregates of laser radiation with a wavelength of less than 637 nm and diamond select aggregates with a high concentration of NV defects characterized by a bright luminescence in the red region of the spectrum.

2. The method according to claim 1, characterized in that the concentration of NV defects in diamond aggregates is determined by the signal intensity of electron paramagnetic resonance.