The effect of step-wise surface nitrogen doping in MPECVD grown polycrystalline diamonds (original) (raw)
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Journal of Materials Science: Materials in Electronics, 2019
Nitrogen-vacancy (NV) centres in diamonds are emerging quantum materials having applications in quantum computing and magnetic field sensing. The ability to synthesize polycrystalline diamond films from chemical vapour deposition technique offers a possibility to grow cheap diamonds with NV centres over large areas. Till date, extensive studies have not been carried out to understand the influence of nitrogen flow rate on the formation of NV centres in polycrystalline diamonds. In this study, we investigate the effect of nitrogen flow rate on the morphology, optical, and electrical properties of polycrystalline diamonds deposited at low pressure. Several samples were prepared in different nitrogen flow regimes using the microwave plasma chemical vapour deposition (MPCVD) technique. The films were characterized using Raman spectroscopy and scanning electron microscopy (SEM). The I-V characteristics of the samples were measured using a point contact method at room temperature. Results obtained showed the formation of both neutral and negatively charged NV centres at an optimum nitrogen flow rate of 10 sccm. An increase in nitrogen flow rate led to a decrease in the electrical resistivity of the films. Furthermore, nitrogen flow rates greater than 20 sccm results to a decrease in the reflectance spectra of samples and a depreciation in the crystalline quality of films. This study is important in benchmarking an optimal parameter space for the growth of nitrogen doped polycrystalline diamonds suitable for sensing applications.
arXiv (Cornell University), 2023
The negatively charged Nitrogen-Vacancy (NV-) center in diamond is one of the most versatile and robust quantum sensors suitable for quantum technologies, including magnetic field and temperature sensors. For precision sensing applications, densely packed NVcenters within a small volume are preferable due to benefiting from 1/√ sensitivity enhancement (N is the number of sensing NV centers) and efficient excitation of NV centers. However, methods for quickly and efficiently forming high concentrations of NVcenters are in development stage. We report an efficient, low-cost method for creating high-density NVcenters production from a relatively low nitrogen concentration based on high-energy photons from Ar + plasma. This study was done on type-IIa, single crystal, CVD-grown diamond substrates with an as-grown nitrogen concentration of 1 ppm. We estimate an NVdensity of ~ 0.57 ppm (57%) distributed homogeneously over 200 µm deep from the diamond surface facing the plasma source based on optically detected magnetic resonance and fluorescence confocal microscopy measurements. The created NVs have a spinlattice relaxation time (T1) of 5 ms and a spin-spin coherence time (T2) of 4 µs. We measure a DC magnetic field sensitivity of ~ 104 nT Hz-1/2 , an AC magnetic field sensitivity of ~ 0.12 pT Hz-1/2 , and demonstrate real-time magnetic field sensing at a rate over 10 mT s-1 using an active sample volume of 0.2 µm 3 .
Temperature dependent creation of nitrogen-vacancy centers in single crystal CVD diamond layers
Diamond and Related Materials, 2015
In this work, we explore the ability of plasma assisted chemical vapor deposition (PACVD) operating under high power densities to produce thin high-quality diamond layers with a controlled doping with negatively-charged nitrogen-vacancy (NV -) centers. This luminescent defect possesses specific physical characteristics that make it suitable as an addressable solid-state electron spin for measuring magnetic fields with unprecedented sensitivity. To this aim, a relatively large number of NVcenters (> 10 12 cm -3 ) should ideally be located in a thin diamond layer (a few tens of nm) close to the surface which is particularly challenging to achieve with the PACVD technique. Here we show that intentional temperature variations can be exploited to tune NVcreation efficiency during growth, allowing engineering complex stacking structures with a variable doping. Because such a temperature variation can be performed quickly and without any change of the gas phase composition, thin layers can be grown. Measurements show that despite the temperature variations, the luminescent centers incorporated using this technique exhibit spin coherence properties similar to those reached in ultrapure bulk crystals, which suggests that they could be successfully employed in magnetometry applications.
Detection of nitrogen in CVD diamond
Diamond and Related Materials, 1996
A series of CVD diamond films was analysed for their nitrogen content by high resolution elastic recoil detection (ERD) in order to investigate the incorporation of nitrogen from the gas phase in a CVD reactor into the growing diamond film. CVD diamond films were deposited from a mixture of 1.5% CH, in Hz and an admixture of nitrogen gas varying from 0.33% up to 67% [N]/[C]. The measurements revealed that the probability of nitrogen incorporation is only about 0.4% with respect to carbon. In addition, the morphology and texture of the polycrystalline films were investigated by scanning electron microscopy and X-ray texture analysis and showed a significant dependence on the nitrogen admixture.
Negatively Charged Nitrogen-Vacancy Centers in a 5 nm Thin 12C Diamond Film
Nano Letters, 2013
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 T 2 ∼ 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 T 2. The minimum detectable magnetic field estimated by this T 2 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.
Nitrogen-related dopant and defect states in CVD diamond
Physical Review B, 1996
Subbandgap absorption of chemical-vapor-deposition diamond films, with nitrogen contents varying from 10 to 132 ppm has been explored by the constant-photoconductivity method ͑CPM͒, photothermal-deflection spectroscopy ͑PDS͒ and electron spin resonance ͑ESR͒. The spectra measured by PDS increase monotonically and are structureless with increasing photon energies indicating absorption due to amorphous carbon and graphite. The CPM data show distinct features, with absorption bands at hϭ1.6, 4.0, and 4.7 eV in the nominally undoped film, and 2.4 and 4.7 eV in nitrogen-rich layers respectively. The CPM spectra of the doped films are comparable to photoconductivity data of synthetic Ib diamond. The defect densities involved increase with increasing nitrogen content. From ESR, a vacancy-related defect density (gϭ2.0028) is deduced. Paramagnetic nitrogen (gϭ2.0024) can be detected in the high-quality CVD layer or by illuminating the nitrogenrich samples with photon energies larger than the band gap. ͓S0163-1829͑96͒09535-5͔
Nitrogen Doping Effects on Electrical Properties of Diamond Films
Japanese Journal of Applied Physics, 1998
Chemical-vapor-deposited (CVD) diamond films with intentional nitrogen doping have been characterized by various standard techniques. Electrical resistance measurements demonstrate that the nitrogen doping significantly varies the surface conductivity of as-grown diamond films; the surface resistance of N-doped diamond films can reach as high as 1011 Ω, which is about six orders of magnitude higher than that of an undoped one. Such high surface resistance remains stable even after 8 hours of exposure to hydrogen plasma. It is also found that the photoemission threshold energy of N-doped diamond films is about 0.55 eV less than the diamond band-gap energy, which implies the existence of compensated surface gap states and possibly, negative electron affinity in the as-grown N-doped diamond films. The particular properties observed in the N-doped diamond films are discussed in relation to the fabrication of diode-type diamond electron emitters.
Luminescence study of polycrystalline CVD diamond films containing a small amount of nitrogen
Diamond and Related Materials, 2001
Polycrystalline diamond films were grown by the MPCVD method in a silica bell-jar chamber on 2-in. silicon substrates. UV Ž. Ž. Ž. argon laser 363.8 nm-induced photoluminescence PL at liquid helium temperature and cathodoluminescence CL at liquid nitrogen temperature were performed on the films. For the films containing varying amounts of nitrogen, PL spectra show a bright bluergreen luminescence and a broad band with sharp lines going from 550 to 650 nm attributed to nitrogen carbon Ž. vacancy N-V centers in different charge states. The intense bluergreen contribution extends from 2.65 to 2.3 eV, with a sequence of sharp bands peaking at 2.6538, 2.5803, 2.5504, 2.4238 and 2.3652 eV. The average value of their separation is Ž y1. approximately 74 meV ; 600 cm. CL spectra show a prominent complex, broad band-A luminescence peaking at 2.72 eV, on which was superimposed the above bluergreen lines. Deep UV emissions were also obtained for energies greater than 3.0 eV, up to near the band edge, depending on the samples.
Nitrogen in diamond thin films
Physica B: Condensed Matter, 1996
The local structure, dynamical properties and spin-lattice relaxation rate of nitrogen in diamond films produced by plasma-assisted chemical vapor deposition has been investigated by electron spin resonance in the temperature range 10-773 K. We find an isotropic 9-value 9 = 2.0024 and hyperfine interaction constants A N = 40.7 G and A l = 28.2 G consistent with an axial distortion along one of the four equivalent [-1 1 1] directions. The peak to peak line width is AHpp = 3.0 G and the spin concentration is of the order of N s = 9 × 1018 cm-3. The line shape has Lorentzian character in the center and Gaussian character in the wings. The high-temperature reorientation frequency was found to follow an Arrhenius-type behavior with v o = 3.2 × 1012 Hz and EjT = 0.69 eV. From the saturation behavior of the resonance line the spin-lattice relaxation time was found to be of the order of Tie ~ 1.0× 10-Ss at room temperature and Tie ~ 1.0x 10-3S at 10K.
Journal of Applied Physics, 1999
We found that very high concentrations (up to 20% vol) of nitrogen in the ethanol/hydrogen gas mixture do not prejudice the diamond quality as determined by Raman spectroscopy. Nitrogen addition also increases the diamond growth rate, as was previously reported at low nitrogen concentrations. We observed that after a second heating cycle in air at temperatures between 300 and 673 K the electrical resistance versus temperature curves of the as-grown films presented a bulk semiconductor behavior. This stabilization was due to the oxidation of the as-grown hydrogenated surface. The electrical ionization energy Ed was found to be in the range of 1.62–1.90 eV corresponding to films produced with 0 to 20% vol nitrogen in the feed. The room temperature photoluminescence spectra of films produced at low nitrogen concentration suggest that Ed results from pure electronic transitions in the nitrogen-vacancy neutral defects; for samples produced with nitrogen concentrations in the range 15–20%...