WorldWideScience

Sample records for nitrogen-vacancy color center

  1. Generation of Nitrogen-Vacancy Centers in Diamond with Ion Implantation

    International Nuclear Information System (INIS)

    Cui Jin-Ming; Chen Xiang-Dong; Gong Zhao-Jun; Sun Fang-Wen; Han Zheng-Fu; Guo Guang-Can; Fan Le-Le; Zou Chong-Wen

    2012-01-01

    Nitrogen-vacancy defect color centers are created in a high purity single crystal diamond by nitrogen-ion implantation. Both optical spectrum and optically detected magnetic resonance are measured for these artificial quantum emitters. Moreover, with a suitable mask, a lattice composed of nitrogen-vacancy centers is fabricated. Rabi oscillation driven by micro-waves is carried out to show the quality of the ion implantation and potential in quantum manipulation. Along with compatible standard lithography, such an implantation technique shows high potential in future to make structures with nitrogen-vacancy centers for diamond photonics and integrated photonic quantum chip

  2. Efficiency of Cathodoluminescence Emission by Nitrogen-Vacancy Color Centers in Nanodiamonds.

    Science.gov (United States)

    Zhang, Huiliang; Glenn, David R; Schalek, Richard; Lichtman, Jeff W; Walsworth, Ronald L

    2017-06-01

    Correlated electron microscopy and cathodoluminescence (CL) imaging using functionalized nanoparticles is a promising nanoscale probe of biological structure and function. Nanodiamonds (NDs) that contain CL-emitting color centers are particularly well suited for such applications. The intensity of CL emission from NDs is determined by a combination of factors, including particle size, density of color centers, efficiency of energy deposition by electrons passing through the particle, and conversion efficiency from deposited energy to CL emission. This paper reports experiments and numerical simulations that investigate the relative importance of each of these factors in determining CL emission intensity from NDs containing nitrogen-vacancy (NV) color centers. In particular, it is found that CL can be detected from NV-doped NDs with dimensions as small as ≈40 nm, although CL emission decreases significantly for smaller NDs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Optical determination and magnetic manipulation of a single nitrogen-vacancy color center in diamond nanocrystal

    International Nuclear Information System (INIS)

    Diep Lai, Ngoc; Zheng, Dingwei; Treussart, François; Roch, Jean-François

    2010-01-01

    The controlled and coherent manipulation of individual quantum systems is fundamental for the development of quantum information processing. The nitrogen-vacancy (NV) color center in diamond is a promising system since its photoluminescence is perfectly stable at room temperature and its electron spin can be optically read out at the individual level. We review here the experiments currently realized in our laboratory concerning the use of a single NV color center as the single photon source and the coherent magnetic manipulation of the electron spin associated with a single NV color center. Furthermore, we demonstrate a nanoscopy experiment based on the saturation absorption effect, which allows to optically pin-point a single NV color center at sub-λ resolution. This offers the possibility to independently address two or multiple magnetically coupled single NV color centers, which is a necessary step towards the realization of a diamond-based quantum computer

  4. Nitrogen-Vacancy color center in diamond-emerging nanoscale applications in bioimaging and biosensing.

    Science.gov (United States)

    Balasubramanian, Gopalakrishnan; Lazariev, Andrii; Arumugam, Sri Ranjini; Duan, De-Wen

    2014-06-01

    Nitrogen-Vacancy (NV) color center in diamond is a flourishing research area that, in recent years, has displayed remarkable progress. The system offers great potential for realizing futuristic applications in nanoscience, benefiting a range of fields from bioimaging to quantum-sensing. The ability to image single NV color centers in a nanodiamond and manipulate NV electron spin optically under ambient condition is the main driving force behind developments in nanoscale sensing and novel imaging techniques. In this article we discuss current status on the applications of fluorescent nanodiamonds (FND) for optical super resolution nanoscopy, magneto-optical (spin-assisted) sub-wavelength localization and imaging. We present emerging applications such as single molecule spin imaging, nanoscale imaging of biomagnetic fields, sensing molecular fluctuations and temperatures in live cellular environments. We summarize other current advances and future prospects of NV diamond for imaging and sensing pertaining to bio-medical applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Multiphoton-Excited Fluorescence of Silicon-Vacancy Color Centers in Diamond

    Science.gov (United States)

    Higbie, J. M.; Perreault, J. D.; Acosta, V. M.; Belthangady, C.; Lebel, P.; Kim, M. H.; Nguyen, K.; Demas, V.; Bajaj, V.; Santori, C.

    2017-05-01

    Silicon-vacancy color centers in nanodiamonds are promising as fluorescent labels for biological applications, with a narrow, nonbleaching emission line at 738 nm. Two-photon excitation of this fluorescence offers the possibility of low-background detection at significant tissue depth with high three-dimensional spatial resolution. We measure the two-photon fluorescence cross section of a negatively charged silicon vacancy (Si -V- ) in ion-implanted bulk diamond to be 0.74 (19 )×10-50 cm4 s /photon at an excitation wavelength of 1040 nm. Compared to the diamond nitrogen-vacancy center, the expected detection threshold of a two-photon excited Si -V center is more than an order of magnitude lower, largely due to its much narrower linewidth. We also present measurements of two- and three-photon excitation spectra, finding an increase in the two-photon cross section with decreasing wavelength, and we discuss the physical interpretation of the spectra in the context of existing models of the Si -V energy-level structure.

  6. Electron spin resonance of nitrogen-vacancy centers in optically trapped nanodiamonds

    Science.gov (United States)

    Horowitz, Viva R.; Alemán, Benjamín J.; Christle, David J.; Cleland, Andrew N.; Awschalom, David D.

    2012-01-01

    Using an optical tweezers apparatus, we demonstrate three-dimensional control of nanodiamonds in solution with simultaneous readout of ground-state electron-spin resonance (ESR) transitions in an ensemble of diamond nitrogen-vacancy color centers. Despite the motion and random orientation of nitrogen-vacancy centers suspended in the optical trap, we observe distinct peaks in the measured ESR spectra qualitatively similar to the same measurement in bulk. Accounting for the random dynamics, we model the ESR spectra observed in an externally applied magnetic field to enable dc magnetometry in solution. We estimate the dc magnetic field sensitivity based on variations in ESR line shapes to be approximately . This technique may provide a pathway for spin-based magnetic, electric, and thermal sensing in fluidic environments and biophysical systems inaccessible to existing scanning probe techniques. PMID:22869706

  7. Improved generation of single nitrogen-vacancy centers in diamond by ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Naydenov, Boris; Beck, Johannes; Steiner, Matthias; Balasubramanian, Gopalakrishnan; Jelezko, Fedor; Wrachtrup, Joerg [3. Institute of Physics, University of Stuttgart (Germany); Richter, Vladimir; Kalish, Rafi [Solid State Institute, Technion City, Haifa (Israel); Achard, Jocelyn [Laboratoire d' Ingenieurie des Materiaux et des Hautes Pressions, CNRS, Villetaneuse (France)

    2010-07-01

    Nitrogen-vacancy (NV) centers in diamond have recently attracted the attention of many research groups due to their possible application as quantum bits (qubits), ultra low magnetic field sensors and single photon sources. These color centers can be produced by nitrogen ion implantation, although the yield is usually below 5 % at low ion energies. Here we report an increase of the NV production efficiency by subsequently implanting carbon ions in the area of implanted nitrogen ions. This method improves the production yield by more than 50 %. We also show that very low nitrogen concentration (below 0.1 ppb) in diamond can be determined by converting the intrinsic nitrogen atoms to single NV centers and detecting the latter using a confocal microscope.

  8. Stimulated emission depletion microscopy resolves individual nitrogen vacancy centers in diamond nanocrystals.

    OpenAIRE

    Arroyo Camejo, S.; Adam, M.; Besbes, M.; Hugonin, J.; Jaques, V.; Greffet, J.; Roch, J.; Hell, S.; Treussart, F.

    2013-01-01

    Nitrogen-vacancy (NV) color centers in nanodiamonds are highly promising for bioimaging and sensing. However, resolving individual NV centers within nanodiamond particles and the controlled addressing and readout of their spin state has remained a major challenge. Spatially stochastic super-resolution techniques cannot provide this capability in principle, whereas coordinate-controlled super-resolution imaging methods, like stimulated emission depletion (STED) microscopy, have been predicted ...

  9. Perfect alignment and preferential orientation of nitrogen-vacancy centers during chemical vapor deposition diamond growth on (111) surfaces

    International Nuclear Information System (INIS)

    Michl, Julia; Zaiser, Sebastian; Jakobi, Ingmar; Waldherr, Gerald; Dolde, Florian; Neumann, Philipp; Wrachtrup, Jörg; Teraji, Tokuyuki; Doherty, Marcus W.; Manson, Neil B.; Isoya, Junichi

    2014-01-01

    Synthetic diamond production is a key to the development of quantum metrology and quantum information applications of diamond. The major quantum sensor and qubit candidate in diamond is the nitrogen-vacancy (NV) color center. This lattice defect comes in four different crystallographic orientations leading to an intrinsic inhomogeneity among NV centers, which is undesirable in some applications. Here, we report a microwave plasma-assisted chemical vapor deposition diamond growth technique on (111)-oriented substrates, which yields perfect alignment (94% ± 2%) of as-grown NV centers along a single crystallographic direction. In addition, clear evidence is found that the majority (74% ± 4%) of the aligned NV centers were formed by the nitrogen being first included in the (111) growth surface and then followed by the formation of a neighboring vacancy on top. The achieved homogeneity of the grown NV centers will tremendously benefit quantum information and metrology applications

  10. Electron Spin Resonance Shift and Linewidth Broadening of Nitrogen-Vacancy Centers in Diamond as a Function of Electron Irradiation Dose

    OpenAIRE

    Kim, Edwin; Acosta, Victor M.; Bauch, Erik; Budker, Dmitry; Hemmer, Philip R.

    2009-01-01

    A high-nitrogen-concentration diamond sample was subject to 200-keV electron irradiation using a transmission electron microscope. The optical and spin-resonance properties of the nitrogen-vacancy (NV) color centers were investigated as a function of the irradiation dose up to 6.4\\times1021 e-/cm2. The microwave transition frequency of the NV- center was found to shift by up to 0.6% (17.1 MHz) and the linewidth broadened with increasing electron-irradiation dose. Unexpectedly, the measured ma...

  11. Silicon-Vacancy Color Centers in Nanodiamonds: Cathodoluminescence Imaging Marker in the Near Infrared

    OpenAIRE

    Zhang, Huiliang; Aharonovich, Igor; Glenn, David R.; Schalek, R.; Magyar, Andrew P.; Lichtman, Jeff W.; Hu, Evelyn L.; Walsworth, Ronald L.

    2013-01-01

    We demonstrate that nanodiamonds fabricated to incorporate silicon-vacancy (Si-V) color centers provide bright, spectrally narrow, and stable cathodoluminescence (CL) in the near-infrared. Si-V color centers containing nanodiamonds are promising as non-bleaching optical markers for correlated CL and secondary electron microscopy, including applications to nanoscale bioimaging.

  12. Chip-integrated plasmonic cavity-enhanced single nitrogen-vacancy center emission

    DEFF Research Database (Denmark)

    Siampour, Hamidreza; Kumar, Shailesh; Bozhevolnyi, Sergey I.

    2017-01-01

    High temporal stability and spin dynamics of individual nitrogen-vacancy (NV) centers in diamond crystals make them one of the most promising quantum emitters operating at room temperature. We demonstrate a chip-integrated cavity-coupled emission into propagating surface plasmon polariton (SPP...

  13. Generation of Nitrogen-Vacancy Center Pairs in Bulk Diamond by Molecular Nitrogen Implantation

    International Nuclear Information System (INIS)

    Zhao-Jun Gong; Xiang-Dong Chen; Cong-Cong Li; Shen Li; Bo-Wen Zhao; Fang-Wen Sun

    2016-01-01

    The coupled negatively charged nitrogen-vacancy (NV − ) center system is a promising candidate for scalable quantum information techniques. In this work, ionized nitrogen molecules are implanted into bulk diamond to generate coupled NV − center pairs. The two-photon autocorrelation measurement and optically detected magnetic resonance measurement are carried out to confirm the production of the NV − center pair. Also, both 1.3 μs decoherence time and 4.9 kHz magnetic coupling strength of the NV − center pair are measured by controlling and detecting the spin states. Along with nanoscale manipulation and detection methods, such coupled NV − centers through short distance dipole-dipole interaction would show high potential in scalable quantum information processes. (paper)

  14. Stimulated emission depletion microscopy resolves individual nitrogen vacancy centers in diamond nanocrystals.

    Science.gov (United States)

    Arroyo-Camejo, Silvia; Adam, Marie-Pierre; Besbes, Mondher; Hugonin, Jean-Paul; Jacques, Vincent; Greffet, Jean-Jacques; Roch, Jean-François; Hell, Stefan W; Treussart, François

    2013-12-23

    Nitrogen-vacancy (NV) color centers in nanodiamonds are highly promising for bioimaging and sensing. However, resolving individual NV centers within nanodiamond particles and the controlled addressing and readout of their spin state has remained a major challenge. Spatially stochastic super-resolution techniques cannot provide this capability in principle, whereas coordinate-controlled super-resolution imaging methods, like stimulated emission depletion (STED) microscopy, have been predicted to fail in nanodiamonds. Here we show that, contrary to these predictions, STED can resolve single NV centers in 40-250 nm sized nanodiamonds with a resolution of ≈10 nm. Even multiple adjacent NVs located in single nanodiamonds can be imaged individually down to relative distances of ≈15 nm. Far-field optical super-resolution of NVs inside nanodiamonds is highly relevant for bioimaging applications of these fluorescent nanolabels. The targeted addressing and readout of individual NV(-) spins inside nanodiamonds by STED should also be of high significance for quantum sensing and information applications.

  15. Vector magnetic field microscopy using nitrogen vacancy centers in diamond

    NARCIS (Netherlands)

    Maertz, B.J.; Wijnheijmer, A.P.; Fuchs, G.D.; Nowakowski, M.E.; Awschalom, D.D.

    2010-01-01

    The localized spin triplet ground state of a nitrogen vacancy (NV) center in diamond can be used in atomic-scale detection of local magnetic fields. Here we present a technique using ensembles of these defects in diamond to image fields around magnetic structures. We extract the local magnetic field

  16. Coupling nitrogen-vacancy centers in diamond to superconducting flux qubits

    DEFF Research Database (Denmark)

    Marcos, D.; Wubs, Martijn; Taylor, J.M.

    2010-01-01

    We propose a method to achieve coherent coupling between nitrogen-vacancy (NV) centers in diamond and superconducting (SC) flux qubits. The resulting coupling can be used to create a coherent interaction between the spin states of distant NV centers mediated by the flux qubit. Furthermore......, the magnetic coupling can be used to achieve a coherent transfer of quantum information between the flux qubit and an ensemble of NV centers. This enables a long-term memory for a SC quantum processor and possibly an interface between SC qubits and light....

  17. Coupling of nitrogen-vacancy centers in a nanodiamond to a silver nanocube

    DEFF Research Database (Denmark)

    Andersen, Sebastian Kim Hjælm; Kumar, Shailesh; Bozhevolnyi, Sergey I.

    2016-01-01

    Spontaneous emission (SE) of nitrogen-vacancy centers (NV-centers), which are contained in a single nanodiamond (ND), placed near a silver nanocube, is investigated both experimentally and theoretically. The ND-cube system is assembled with an atomic force microscope, allowing us to directly...... from randomly oriented electric dipoles, allowing us to reveal the underlying physics of the investigated configuration....

  18. Scalable Quantum Information Transfer between Individual Nitrogen-Vacancy Centers by a Hybrid Quantum Interface

    International Nuclear Information System (INIS)

    Pei Pei; He-Fei Huang; Yan-Qing Guo; He-Shan Song

    2016-01-01

    We develop a design of a hybrid quantum interface for quantum information transfer (QIT), adopting a nanomechanical resonator as the intermedium, which is magnetically coupled with individual nitrogen-vacancy centers as the solid qubits, while capacitively coupled with a coplanar waveguide resonator as the quantum data bus. We describe the Hamiltonian of the model, and analytically demonstrate the QIT for both the resonant interaction and large detuning cases. The hybrid quantum interface allows for QIT between arbitrarily selected individual nitrogen-vacancy centers, and has advantages of the scalability and controllability. Our methods open an alternative perspective for implementing QIT, which is important during quantum storing or processing procedures in quantum computing. (paper)

  19. Excitation of surface plasmon polariton modes with multiple nitrogen vacancy centers in single nanodiamonds

    DEFF Research Database (Denmark)

    Kumar, Shailesh; Larsen Lausen, Jens; García Ortíz, César Eduardo

    2016-01-01

    Nitrogen-vacancy (NV) centers in diamonds are interesting due to their remarkable characteristics that are well suited to applications in quantum-information processing and magnetic field sensing, as well as representing stable fluorescent sources. Multiple NV centers in nanodiamonds (NDs) are es...

  20. Nanophotonic quantum interface for nitrogen vacancy centers in diamond

    International Nuclear Information System (INIS)

    Yiwen Chu

    2014-01-01

    Nitrogen vacancy (NV) centers in diamond have emerged as a promising solid-state platform for quantum communication, quantum information processing and nanoscale sensing with optical read-out. Engineering light-matter interactions is crucial for the practical realization of these systems. I will present our work toward realizing individual NV centers embedded in nanofabricated hybrid photonic crystal cavities consisting of single crystal diamond and PMMA based Bragg structures. Devices with quality factors up to 3,000 coupled to NV centers have been implemented, leading to substantial Purcell enhancement of zero-phonon line. We investigate the optical coherence properties of NV centers inside these nanoscale structures and report on first cavity QED experiments with such systems. Applications of diamond nanophotonic devices for quantum networks and nonlinear optics with single photons will be discussed. (author)

  1. Creation of high density ensembles of nitrogen-vacancy centers in nitrogen-rich type Ib nanodiamonds

    International Nuclear Information System (INIS)

    Su, Long-Jyun; Fang, Chia-Yi; Chang, Yu-Tang; Chang, Huan-Cheng; Chen, Kuan-Ming; Yu, Yueh-Chung; Hsu, Jui-Hung

    2013-01-01

    This work explores the possibility of increasing the density of negatively charged nitrogen-vacancy centers ([NV − ]) in nanodiamonds using nitrogen-rich type Ib diamond powders as the starting material. The nanodiamonds (10–100 nm in diameter) were prepared by ball milling of microdiamonds, in which the density of neutral and atomically dispersed nitrogen atoms ([N 0 ]) was measured by diffuse reflectance infrared Fourier transform spectroscopy. A systematic measurement of the fluorescence intensities and lifetimes of the crushed monocrystalline diamonds as a function of [N 0 ] indicated that [NV − ] increases nearly linearly with [N 0 ] at 100–200 ppm. The trend, however, failed to continue for nanodiamonds with higher [N 0 ] (up to 390 ppm) but poorer crystallinity. We attribute the result to a combined effect of fluorescence quenching as well as the lower conversion efficiency of vacancies to NV − due to the presence of more impurities and defects in these as-grown diamond crystallites. The principles and practice of fabricating brighter and smaller fluorescent nanodiamonds are discussed. (paper)

  2. Creation of high density ensembles of nitrogen-vacancy centers in nitrogen-rich type Ib nanodiamonds.

    Science.gov (United States)

    Su, Long-Jyun; Fang, Chia-Yi; Chang, Yu-Tang; Chen, Kuan-Ming; Yu, Yueh-Chung; Hsu, Jui-Hung; Chang, Huan-Cheng

    2013-08-09

    This work explores the possibility of increasing the density of negatively charged nitrogen-vacancy centers ([NV(-)]) in nanodiamonds using nitrogen-rich type Ib diamond powders as the starting material. The nanodiamonds (10-100 nm in diameter) were prepared by ball milling of microdiamonds, in which the density of neutral and atomically dispersed nitrogen atoms ([N(0)]) was measured by diffuse reflectance infrared Fourier transform spectroscopy. A systematic measurement of the fluorescence intensities and lifetimes of the crushed monocrystalline diamonds as a function of [N(0)] indicated that [NV(-)] increases nearly linearly with [N(0)] at 100-200 ppm. The trend, however, failed to continue for nanodiamonds with higher [N(0)] (up to 390 ppm) but poorer crystallinity. We attribute the result to a combined effect of fluorescence quenching as well as the lower conversion efficiency of vacancies to NV(-) due to the presence of more impurities and defects in these as-grown diamond crystallites. The principles and practice of fabricating brighter and smaller fluorescent nanodiamonds are discussed.

  3. Vacancy-impurity centers in diamond: prospects for synthesis and applications

    Science.gov (United States)

    Ekimov, E. A.; Kondrin, M. V.

    2017-06-01

    The bright luminescence of impurity-vacancy complexes, combined with high chemical and radiation resistance, makes diamond an attractive platform for the production of single-photon emitters and luminescent biomarkers for applications in nanoelectronics and medicine. Two representatives of this kind of defects in diamond, silicon-vacancy (SiV) and germanium-vacancy (GeV) centers, are discussed in this review; their similarities and differences are demonstrated in terms of the more thoroughly studied nitrogen-vacancy (NV) complexes. The recent discovery of GeV luminescent centers opens a unique opportunity for the controlled synthesis of single-photon emitters in nanodiamonds. We demonstrate prospects for the high-pressure high-temperature (HPHT) technique to create single-photon emitters, not only as an auxiliary to chemical vapor deposition (CVD) and ion-implantation methods but also as a primary synthesis tool for producing color centers in nanodiamonds. Besides practical applications, comparative studies of these two complexes, which belong to the same structural class of defects, have a fundamental importance for deeper understanding of shelving levels, the electronic structure, and optical properties of these centers. In conclusion, we discuss several open problems regarding the structure, charge state, and practical application of these centers, which still require a solution.

  4. Ultrabright Linearly Polarized Photon Generation from a Nitrogen Vacancy Center in a Nanocube Dimer Antenna

    DEFF Research Database (Denmark)

    Andersen, Sebastian Kim Hjælm; Kumar, Shailesh; Bozhevolnyi, Sergey I.

    2017-01-01

    We demonstrate an exceptionally bright photon source based on a single nitrogen-vacancy center (NV center) in a nanodiamond (ND) placed in the nanoscale gap between two monocrystalline silver cubes in a dimer configuration. The system is operated near saturation at a stable photon rate of 850 kcps...

  5. Deterministic fabrication of dielectric loaded waveguides coupled to single nitrogen vacancy centers in nanodiamonds

    DEFF Research Database (Denmark)

    Siampour, Hamidreza; Kumar, Shailesh; Bozhevolnyi, Sergey I.

    We report on the fabrication of dielectric-loaded-waveguides which are excited by single-nitrogen-vacancy (NV) centers in nanodiamonds. The waveguides are deterministically written onto the pre-characterized nanodiamonds by using electron beam lithography of hydrogen silsesquioxane (HSQ) resist...... on silver-coated silicon substrate. Change in lifetime for NV-centers is observed after fabrication of waveguides and an antibunching in correlation measurement confirms that nanodiamonds contain single NV-centers....

  6. Enhanced photoluminescence from single nitrogen-vacancy defects in nanodiamonds coated with phenol-ionic complexes

    Science.gov (United States)

    Bray, Kerem; Previdi, Rodolfo; Gibson, Brant C.; Shimoni, Olga; Aharonovich, Igor

    2015-03-01

    Fluorescent nanodiamonds are attracting major attention in the field of bio-sensing and bio-labeling. In this work we demonstrate a robust approach to achieve an encapsulation of individual nanodiamonds with phenol-ionic complexes that enhance the photoluminescence from single nitrogen vacancy (NV) centers. We show that single NV centres in the coated nanodiamonds also exhibit shorter lifetimes, opening another channel for high resolution sensing. We propose that the nanodiamond encapsulation reduces the non-radiative decay pathways of the NV color centers. Our results provide a versatile and assessable way to enhance photoluminescence from nanodiamond defects that can be used in a variety of sensing and imaging applications.Fluorescent nanodiamonds are attracting major attention in the field of bio-sensing and bio-labeling. In this work we demonstrate a robust approach to achieve an encapsulation of individual nanodiamonds with phenol-ionic complexes that enhance the photoluminescence from single nitrogen vacancy (NV) centers. We show that single NV centres in the coated nanodiamonds also exhibit shorter lifetimes, opening another channel for high resolution sensing. We propose that the nanodiamond encapsulation reduces the non-radiative decay pathways of the NV color centers. Our results provide a versatile and assessable way to enhance photoluminescence from nanodiamond defects that can be used in a variety of sensing and imaging applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07510b

  7. Entangling separate nitrogen-vacancy centers in a scalable fashion via coupling to microtoroidal resonators

    International Nuclear Information System (INIS)

    Chen Qiong; Yang Wanli; Feng Mang; Du Jiangfeng

    2011-01-01

    We propose a potentially practical scheme to entangle negatively charged nitrogen-vacancy (N-V) centers in distant diamonds. Each diamond is supposed to be fixed on the exterior surface of a microtoroidal resonator, and the single-photon input-output process - a currently available technique - could entangle separate N-V centers in a scalable fashion. The feasibility of our scheme and the experimental challenge are discussed by considering currently available techniques for qualified N-V centers and cavities.

  8. Alignment of the diamond nitrogen vacancy center by strain engineering

    Energy Technology Data Exchange (ETDEWEB)

    Karin, Todd [Department of Physics, University of Washington, Seattle, Washington 98195 (United States); Dunham, Scott [Department of Electrical Engineering, University of Washington, Seattle, Washington 98195 (United States); Fu, Kai-Mei [Department of Physics, University of Washington, Seattle, Washington 98195 (United States); Department of Electrical Engineering, University of Washington, Seattle, Washington 98195 (United States)

    2014-08-04

    The nitrogen vacancy (NV) center in diamond is a sensitive probe of magnetic field and a promising qubit candidate for quantum information processing. The performance of many NV-based devices improves by aligning the NV(s) parallel to a single crystallographic direction. Using ab initio theoretical techniques, we show that NV orientation can be controlled by high-temperature annealing in the presence of strain under currently accessible experimental conditions. We find that (89 ± 7)% of NVs align along the [111] crystallographic direction under 2% compressive biaxial strain (perpendicular to [111]) and an annealing temperature of 970 °C.

  9. Orbital State Manipulation of a Diamond Nitrogen-Vacancy Center Using a Mechanical Resonator

    Science.gov (United States)

    Chen, H. Y.; MacQuarrie, E. R.; Fuchs, G. D.

    2018-04-01

    We study the resonant optical transitions of a single nitrogen-vacancy (NV) center that is coherently dressed by a strong mechanical drive. Using a gigahertz-frequency diamond mechanical resonator that is strain coupled to a NV center's orbital states, we demonstrate coherent Raman sidebands out to the ninth order and orbital-phonon interactions that mix the two excited-state orbital branches. These interactions are spectroscopically revealed through a multiphonon Rabi splitting of the orbital branches which scales as a function of resonator driving amplitude and is successfully reproduced in a quantum model. Finally, we discuss the application of mechanical driving to engineering NV-center orbital states.

  10. Strain cupling of a nitrogen-vacancy center spin to a diamond mechanical oscillator

    OpenAIRE

    Teissier, J.; Barfuss, A.; Appel, P.; Neu, E.; Maletinsky, P.

    2014-01-01

    We report on single electronic spins coupled to the motion of mechanical resonators by a novel mechanism based on crystal strain. Our device consists of single-crystal diamond cantilevers with embedded nitrogen-vacancy center spins. Using optically detected electron spin resonance, we determine the unknown spin-strain coupling constants and demonstrate that our system resides well within the resolved sideband regime. We realize coupling strengths exceeding 10 MHz under mechanical driving and ...

  11. Little bits of diamond: Optically detected magnetic resonance of nitrogen-vacancy centers

    Science.gov (United States)

    Zhang, Haimei; Belvin, Carina; Li, Wanyi; Wang, Jennifer; Wainwright, Julia; Berg, Robbie; Bridger, Joshua

    2018-03-01

    We give instructions for the construction and operation of a simple apparatus for performing optically detected magnetic resonance measurements on diamond samples containing high concentrations of nitrogen-vacancy (NV) centers. Each NV center has a spin degree of freedom that can be manipulated and monitored by a combination of visible and microwave radiation. We observe Zeeman shifts in the presence of small external magnetic fields and describe a simple method to optically measure magnetic field strengths with a spatial resolution of several microns. The activities described are suitable for use in an advanced undergraduate lab course, powerfully connecting core quantum concepts to cutting edge applications. An even simpler setup, appropriate for use in more introductory settings, is also presented.

  12. Noise-Resilient Quantum Computing with a Nitrogen-Vacancy Center and Nuclear Spins.

    Science.gov (United States)

    Casanova, J; Wang, Z-Y; Plenio, M B

    2016-09-23

    Selective control of qubits in a quantum register for the purposes of quantum information processing represents a critical challenge for dense spin ensembles in solid-state systems. Here we present a protocol that achieves a complete set of selective electron-nuclear gates and single nuclear rotations in such an ensemble in diamond facilitated by a nearby nitrogen-vacancy (NV) center. The protocol suppresses internuclear interactions as well as unwanted coupling between the NV center and other spins of the ensemble to achieve quantum gate fidelities well exceeding 99%. Notably, our method can be applied to weakly coupled, distant spins representing a scalable procedure that exploits the exceptional properties of nuclear spins in diamond as robust quantum memories.

  13. Observation of Diamond Nitrogen-Vacancy Center Photoluminescence under High Vacuum in a Magneto-Gravitational Trap

    Science.gov (United States)

    Ji, Peng; Hsu, Jen-Feng; Lewandowski, Charles W.; Dutt, M. V. Gurudev; D'Urso, Brian

    2016-05-01

    We report the observation of photoluminescence from nitrogen-vacancy (NV) centers in diamond nanocrystals levitated in a magneto-gravitational trap. The trap utilizes a combination of strong magnetic field gradients and gravity to confine diamagnetic particles in three dimensions. The well-characterized NV centers in trapped diamond nanocrystals provide an ideal built-in sensor to measure the trap magnetic field and the temperature of the trapped diamond nanocrystal. In the future, the NV center spin state could be coupled to the mechanical motion through magnetic field gradients, enabling in an ideal quantum interface between NV center spin and the mechanical motion. National Science Foundation, Grant No. 1540879.

  14. Enhanced photoluminescence from single nitrogen-vacancy defects in nanodiamonds coated with phenol-ionic complexes.

    Science.gov (United States)

    Bray, Kerem; Previdi, Rodolfo; Gibson, Brant C; Shimoni, Olga; Aharonovich, Igor

    2015-03-21

    Fluorescent nanodiamonds are attracting major attention in the field of bio-sensing and bio-labeling. In this work we demonstrate a robust approach to achieve an encapsulation of individual nanodiamonds with phenol-ionic complexes that enhance the photoluminescence from single nitrogen vacancy (NV) centers. We show that single NV centres in the coated nanodiamonds also exhibit shorter lifetimes, opening another channel for high resolution sensing. We propose that the nanodiamond encapsulation reduces the non-radiative decay pathways of the NV color centers. Our results provide a versatile and assessable way to enhance photoluminescence from nanodiamond defects that can be used in a variety of sensing and imaging applications.

  15. Experimental identification of nitrogen-vacancy complexes in nitrogen implanted silicon

    Science.gov (United States)

    Adam, Lahir Shaik; Law, Mark E.; Szpala, Stanislaw; Simpson, P. J.; Lawther, Derek; Dokumaci, Omer; Hegde, Suri

    2001-07-01

    Nitrogen implantation is commonly used in multigate oxide thickness processing for mixed signal complementary metal-oxide-semiconductor and System on a Chip technologies. Current experiments and diffusion models indicate that upon annealing, implanted nitrogen diffuses towards the surface. The mechanism proposed for nitrogen diffusion is the formation of nitrogen-vacancy complexes in silicon, as indicated by ab initio studies by J. S. Nelson, P. A. Schultz, and A. F. Wright [Appl. Phys. Lett. 73, 247 (1998)]. However, to date, there does not exist any experimental evidence of nitrogen-vacancy formation in silicon. This letter provides experimental evidence through positron annihilation spectroscopy that nitrogen-vacancy complexes indeed form in nitrogen implanted silicon, and compares the experimental results to the ab initio studies, providing qualitative support for the same.

  16. Live-cell thermometry with nitrogen vacancy centers in nanodiamonds

    Science.gov (United States)

    Jayakumar, Harishankar; Fedder, Helmut; Chen, Andrew; Yang, Liudi; Li, Chenghai; Wrachtrup, Joerg; Wang, Sihong; Meriles, Carlos

    The ability to measure temperature is typically affected by a tradeoff between sensitivity and spatial resolution. Good thermometers tend to be bulky systems and hence are ill-suited for thermal sensing with high spatial localization. Conversely, the signal resulting from nanoscale temperature probes is often impacted by noise to a level where the measurement precision becomes poor. Adding to the microscopist toolbox, the nitrogen vacancy (NV) center in diamond has recently emerged as a promising platform for high-sensitivity nanoscale thermometry. Of particular interest are applications in living cells because diamond nanocrystals are biocompatible and can be chemically functionalized to target specific organelles. Here we report progress on the ability to probe and compare temperature within and between living cells using nanodiamond-hosted NV thermometry. We focus our study on cancerous cells, where atypical metabolic pathways arguably lead to changes in the way a cell generates heat, and thus on its temperature profile.

  17. Tutorial: Magnetic resonance with nitrogen-vacancy centers in diamond—microwave engineering, materials science, and magnetometry

    Science.gov (United States)

    Abe, Eisuke; Sasaki, Kento

    2018-04-01

    This tutorial article provides a concise and pedagogical overview on negatively charged nitrogen-vacancy (NV) centers in diamond. The research on the NV centers has attracted enormous attention for its application to quantum sensing, encompassing the areas of not only physics and applied physics but also chemistry, biology, and life sciences. Nonetheless, its key technical aspects can be understood from the viewpoint of magnetic resonance. We focus on three facets of this ever-expanding research field, to which our viewpoint is especially relevant: microwave engineering, materials science, and magnetometry. In explaining these aspects, we provide a technical basis and up-to-date technologies for research on the NV centers.

  18. Broadband, large-area microwave antenna for optically detected magnetic resonance of nitrogen-vacancy centers in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Kento; Monnai, Yasuaki; Saijo, Soya; Fujita, Ryushiro; Ishi-Hayase, Junko; Itoh, Kohei M., E-mail: kitoh@appi.keio.ac.jp; Abe, Eisuke, E-mail: e-abe@keio.jp [School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Watanabe, Hideyuki [Correlated Electronics Group, Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

    2016-05-15

    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.

  19. On-Demand Generation of Neutral and Negatively Charged Silicon-Vacancy Centers in Diamond

    Science.gov (United States)

    Dhomkar, Siddharth; Zangara, Pablo R.; Henshaw, Jacob; Meriles, Carlos A.

    2018-03-01

    Point defects in wide-band-gap semiconductors are emerging as versatile resources for nanoscale sensing and quantum information science, but our understanding of the photoionization dynamics is presently incomplete. Here, we use two-color confocal microscopy to investigate the dynamics of charge in type 1b diamond hosting nitrogen-vacancy (NV) and silicon-vacancy (SiV) centers. By examining the nonlocal fluorescence patterns emerging from local laser excitation, we show that, in the simultaneous presence of photogenerated electrons and holes, SiV (NV) centers selectively transform into the negative (neutral) charge state. Unlike NVs, 532 nm illumination ionizes SiV- via a single-photon process, thus hinting at a comparatively shallower ground state. In particular, slower ionization rates at longer wavelengths suggest the latter lies approximately ˜1.9 eV below the conduction band minimum. Building on the above observations, we demonstrate on-demand SiV and NV charge initialization over large areas via green laser illumination of variable intensity.

  20. Electron spin contrast of Purcell-enhanced nitrogen-vacancy ensembles in nanodiamonds

    Science.gov (United States)

    Bogdanov, S.; Shalaginov, M. Y.; Akimov, A.; Lagutchev, A. S.; Kapitanova, P.; Liu, J.; Woods, D.; Ferrera, M.; Belov, P.; Irudayaraj, J.; Boltasseva, A.; Shalaev, V. M.

    2017-07-01

    Nitrogen-vacancy centers in diamond allow for coherent spin-state manipulation at room temperature, which could bring dramatic advances to nanoscale sensing and quantum information technology. We introduce a method for the optical measurement of the spin contrast in dense nitrogen-vacancy (NV) ensembles. This method brings insight into the interplay between the spin contrast and fluorescence lifetime. We show that for improving the spin readout sensitivity in NV ensembles, one should aim at modifying the far-field radiation pattern rather than enhancing the emission rate.

  1. Effect of low-damage inductively coupled plasma on shallow nitrogen-vacancy centers in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Fávaro de Oliveira, Felipe; Momenzadeh, S. Ali; Wang, Ya; Denisenko, Andrej, E-mail: a.denisenko@physik.uni-stuttgart.de [3. Institute of Physics, Research Center SCoPE and IQST, University of Stuttgart, 70569 Stuttgart (Germany); Konuma, Mitsuharu [Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany); Markham, Matthew; Edmonds, Andrew M. [Element Six Innovation, Harwell Oxford, Didcot, Oxfordshire OX11 0QR (United Kingdom); Wrachtrup, Jörg [3. Institute of Physics, Research Center SCoPE and IQST, University of Stuttgart, 70569 Stuttgart (Germany); Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany)

    2015-08-17

    Near-surface nitrogen-vacancy (NV) centers in diamond have been successfully employed as atomic-sized magnetic field sensors for external spins over the last years. A key challenge is still to develop a method to bring NV centers at nanometer proximity to the diamond surface while preserving their optical and spin properties. To that aim we present a method of controlled diamond etching with nanometric precision using an oxygen inductively coupled plasma process. Importantly, no traces of plasma-induced damages to the etched surface could be detected by X-ray photoelectron spectroscopy and confocal photoluminescence microscopy techniques. In addition, by profiling the depth of NV centers created by 5.0 keV of nitrogen implantation energy, no plasma-induced quenching in their fluorescence could be observed. Moreover, the developed etching process allowed even the channeling tail in their depth distribution to be resolved. Furthermore, treating a {sup 12}C isotopically purified diamond revealed a threefold increase in T{sub 2} times for NV centers with <4 nm of depth (measured by nuclear magnetic resonance signal from protons at the diamond surface) in comparison to the initial oxygen-terminated surface.

  2. Coupling a single nitrogen-vacancy center with a superconducting qubit via the electro-optic effect

    Science.gov (United States)

    Li, Chang-Hao; Li, Peng-Bo

    2018-05-01

    We propose an efficient scheme for transferring quantum states and generating entangled states between two qubits of different nature. The hybrid system consists of a single nitrogen-vacancy (NV) center and a superconducting (SC) qubit, which couple to an optical cavity and a microwave resonator, respectively. Meanwhile, the optical cavity and the microwave resonator are coupled via the electro-optic effect. By adjusting the relative parameters, we can achieve high-fidelity quantum state transfer as well as highly entangled states between the NV center and the SC qubit. This protocol is within the reach of currently available techniques, and may provide interesting applications in quantum communication and computation with single NV centers and SC qubits.

  3. Strain coupling between nitrogen vacancy centers and the mechanical motion of a diamond optomechanical crystal resonator

    Science.gov (United States)

    Cady, J. V.; Lee, K. W.; Ovartchaiyapong, P.; Bleszynski Jayich, A. C.

    Several experiments have recently demonstrated coupling between nitrogen vacancy (NV) centers in diamond and mechanical resonators via crystal strain. In the strong coupling regime, such devices could realize applications critical to emerging quantum technologies, including phonon-mediated spin-spin interactions and mechanical cooling with the NV center1. An outstanding challenge for these devices is generating higher strain coupling in high frequency devices while maintaining the excellent coherence properties of the NV center and high mechanical quality factors. As a step toward these objectives, we demonstrate single-crystal diamond optomechanical crystal resonators with embedded NV centers. These devices host highly-confined GHz-scale mechanical modes that are isolated from mechanical clamping losses and generate strain profiles that allow for large strain coupling to NV centers far from noise-inducing surfaces.

  4. Localized chemical switching of the charge state of nitrogen-vacancy luminescence centers in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Shanley, Toby W.; Martin, Aiden A.; Aharonovich, Igor, E-mail: Igor.Aharonovich@uts.edu.au; Toth, Milos, E-mail: Milos.Toth@uts.edu.au [School of Physics and Advanced Materials, University of Technology, Sydney, P.O. Box 123, Broadway, New South Wales 2007 (Australia)

    2014-08-11

    We present a direct-write chemical technique for controlling the charge state of near-surface nitrogen vacancy centers (NVs) in diamond by surface fluorination. Fluorination of H-terminated diamond is realized by electron beam stimulated desorption of H{sub 2}O in the presence of NF{sub 3} and verified with environmental photoyield spectroscopy (EPYS) and photoluminescence (PL) spectroscopy. PL spectra of shallow NVs in H- and F-terminated nanodiamonds show the expected dependence of the NV charge state on their energetic position with respect to the Fermi-level. EPYS reveals a corresponding difference between the ionization potential of H- and F-terminated diamond. The electron beam fluorination process is highly localized and can be used to fluorinate H-terminated diamond, and to increase the population of negatively charged NV centers.

  5. Spin properties of dense near-surface ensembles of nitrogen-vacancy centers in diamond

    Science.gov (United States)

    Tetienne, J.-P.; de Gille, R. W.; Broadway, D. A.; Teraji, T.; Lillie, S. E.; McCoey, J. M.; Dontschuk, N.; Hall, L. T.; Stacey, A.; Simpson, D. A.; Hollenberg, L. C. L.

    2018-02-01

    We present a study of the spin properties of dense layers of near-surface nitrogen-vacancy (NV) centers in diamond created by nitrogen ion implantation. The optically detected magnetic resonance contrast and linewidth, spin coherence time, and spin relaxation time, are measured as a function of implantation energy, dose, annealing temperature, and surface treatment. To track the presence of damage and surface-related spin defects, we perform in situ electron spin resonance spectroscopy through both double electron-electron resonance and cross-relaxation spectroscopy on the NV centers. We find that, for the energy (4 -30 keV) and dose (5 ×1011-1013ions/cm 2 ) ranges considered, the NV spin properties are mainly governed by the dose via residual implantation-induced paramagnetic defects, but that the resulting magnetic sensitivity is essentially independent of both dose and energy. We then show that the magnetic sensitivity is significantly improved by high-temperature annealing at ≥1100 ∘C . Moreover, the spin properties are not significantly affected by oxygen annealing, apart from the spin relaxation time, which is dramatically decreased. Finally, the average NV depth is determined by nuclear magnetic resonance measurements, giving ≈10 -17 nm at 4-6 keV implantation energy. This study sheds light on the optimal conditions to create dense layers of near-surface NV centers for high-sensitivity sensing and imaging applications.

  6. Time-Resolved Luminescence Nanothermometry with Nitrogen-Vacancy Centers in Nanodiamonds

    Science.gov (United States)

    Tsai, Pei-Chang; Chen, Oliver Y.; Tzeng, Yan-Kai; Liu, Hsiou-Yuan; Hsu, Hsiang; Huang, Shaio-Chih; Chen, Jeson; Yee, Fu-Ghoul; Chang, Huan-Cheng; Chang, Ming-Shien

    2016-05-01

    Measuring thermal properties with nanoscale spatial resolution either at or far from equilibrium is gaining importance in many scientific and engineering applications. Although negatively charged nitrogen-vacancy (NV-) centers in diamond have recently emerged as promising nanometric temperature sensors, most previous measurements were performed under steady state conditions. Here we employ a three-point sampling method which not only enables real-time detection of temperature changes over +/-100 K with a sensitivity of 2 K/(Hz)1/2, but also allows the study of nanometer scale heat transfer with a temporal resolution of better than 1 μs with the use of a pump-probe-type experiment. In addition to temperature sensing, we further show that nanodiamonds conjugated with gold nanorods, as optically-activated dual-functional nanoheaters and nanothermometers, are useful for highly localized hyperthermia treatment. We experimentally demonstrated time-resolved fluorescence nanothermometry, and the validity of the measurements was verified with finite-element numerical simulations. The approaches provided here will be useful for probing dynamical thermal properties on nanodevices in operation.

  7. DFT study of anisotropy effects on the electronic properties of diamond nanowires with nitrogen-vacancy center.

    Science.gov (United States)

    Solano, Jesús Ramírez; Baños, Alejandro Trejo; Durán, Álvaro Miranda; Quiroz, Eliel Carvajal; Irisson, Miguel Cruz

    2017-09-26

    In the development of quantum computing and communications, improvements in materials capable of single photon emission are of great importance. Advances in single photon emission have been achieved experimentally by introducing nitrogen-vacancy (N-V) centers on diamond nanostructures. However, theoretical modeling of the anisotropic effects on the electronic properties of these materials is almost nonexistent. In this study, the electronic band structure and density of states of diamond nanowires with N-V defects were analyzed through first principles approach using the density functional theory and the supercell scheme. The nanowires were modeled on two growth directions [001] and [111]. All surface dangling bonds were passivated with hydrogen (H) atoms. The results show that the N-V introduces multiple trap states within the energy band gap of the diamond nanowire. The energy difference between these states is influenced by the growth direction of the nanowires, which could contribute to the emission of photons with different wavelengths. The presence of these trap states could reduce the recombination rate between the conduction and the valence band, thus favoring the single photon emission. Graphical abstract Diamond nanowires with nitrogen-vacancy centerᅟ.

  8. Laser polarization dependent and magnetically control of group velocity in a dielectric medium doped with nanodiamond nitrogen vacancy centers

    Energy Technology Data Exchange (ETDEWEB)

    Asadpour, Seyyed Hossein; Rahimpour Soleimani, H., E-mail: Rahimpour@guilan.ac.ir

    2014-03-01

    In this paper, group velocity control of Gaussian beam in a dielectric medium doped with nanodiamond nitrogen vacancy (NV) centers under optical excitation is discussed. The shape of transmitted and reflected pulses from dielectric can be tuned by changing the intensity of magnetic field and polarization of the control beam. The effect of intensity of control beam on group velocity is also investigated.

  9. Microwave plasma-assisted photoluminescence enhancement in nitrogen-doped ultrananocrystalline diamond film

    Directory of Open Access Journals (Sweden)

    Yu Lin Liu

    2012-06-01

    Full Text Available Optical properties and conductivity of nitrogen-doped ultrananocrystal diamond (UNCD films were investigated following treatment with low energy microwave plasma at room temperature. The plasma also generated vacancies in UNCD films and provided heat for mobilizing the vacancies to combine with the impurities, which formed the nitrogen-vacancy defect centers. The generated color centers were distributed uniformly in the samples. The conductivity of nitrogen-doped UNCD films treated by microwave plasma was found to decrease slightly due to the reduced grain boundaries. The photoluminescence emitted by the plasma treated nitrogen-doped UNCD films was enhanced significantly compared to the untreated films.

  10. Loading an Optical Trap with Diamond Nanocrystals Containing Nitrogen-Vacancy Centers from a Surface

    Science.gov (United States)

    Hsu, Jen-Feng; Ji, Peng; Dutt, M. V. Gurudev; D'Urso, Brian R.

    2015-03-01

    We present a simple and effective method of loading particles into an optical trap. Our primary application of this method is loading photoluminescent material, such as diamond nanocrystals containing nitrogen-vacancy (NV) centers, for coupling the mechanical motion of the trapped crystal with the spin of the NV centers. Highly absorptive material at the trapping laser frequency, such as tartrazine dye, is used as media to attach nanodiamonds and burn into a cloud of air-borne particles as the material is swept near the trapping laser focus on a glass slide. Particles are then trapped with the laser used for burning or transferred to a second laser trap at a different wavelength. Evidence of successful loading diamond nanocrystals into the trap presented includes high sensitivity of the photoluminecscence (PL) to the excitation laser and the PL spectra of the optically trapped particles

  11. Bragg superlattice for obtaining individual photoluminescence of diamond color centers in dense 3D ensembles

    Science.gov (United States)

    Kukushkin, V. A.

    2017-10-01

    A way to significantly increase the spatial resolution of the color center photoluminescence collection in chemically vapor-deposited (CVD) diamond at a fixed exciting beam focal volume is suggested. It is based on the creation of a narrow waveguide for the color center photoluminescence with a small number of allowed vertical indices of guided modes. The waveguide is formed between the top surface of a CVD diamond film and an underlaid mirror—a Bragg superlattice made of interchanging high- and low boron-doped layers of CVD diamond. The guided color center photoluminescence is extracted through the top surface of a CVD diamond film with the frustrated total internal reflection method. According to the results of simulation made for a case when color centers are nitrogen-vacancy (NV) centers, the suggested way allows to increase the maximal value of the NV center concentration still compatible with selective collection of their photoluminescence by several times at a fixed exciting beam focal volume. This increase is provided without the deterioration of the NV center photoluminescence collection efficiency.

  12. Quantum Control of a Nitrogen-Vacancy Center using Surface Acoustic Waves in the Resolved Sideband Limit

    Science.gov (United States)

    Golter, David; Oo, Thein; Amezcua, Maira; Wang, Hailin

    Micro-electromechanical systems research is producing increasingly sophisticated tools for nanophononic applications. Such technology is well-suited for achieving chip-based, integrated acoustic control of solid-state quantum systems. We demonstrate such acoustic control in an important solid-state qubit, the diamond nitrogen-vacancy (NV) center. Using an interdigitated transducer to generate a surface acoustic wave (SAW) field in a bulk diamond, we observe phonon-assisted sidebands in the optical excitation spectrum of a single NV center. This exploits the strong strain sensitivity of the NV excited states. The mechanical frequencies far exceed the relevant optical linewidths, reaching the resolved-sideband regime. This enables us to use the SAW field for driving Rabi oscillations on the phonon-assisted optical transition. These results stimulate the further integration of SAW-based technologies with the NV center system.

  13. Vector magnetometer based on synchronous manipulation of nitrogen-vacancy centers in all crystal directions

    Science.gov (United States)

    Zhang, Chen; Yuan, Heng; Zhang, Ning; Xu, Lixia; Zhang, Jixing; Li, Bo; Fang, Jiancheng

    2018-04-01

    Negatively charged nitrogen vacancy (NV‑) centers in diamond have been extensively studied as high-sensitivity magnetometers, showcasing a wide range of applications. This study experimentally demonstrates a vector magnetometry scheme based on synchronous manipulation of NV‑ center ensembles in all crystal directions using double frequency microwaves (MWs) and multi-coupled-strip-lines (mCSL) waveguide. The application of the mCSL waveguide ensures a high degree of synchrony (99%) for manipulating NV‑ centers in multiple orientations in a large volume. Manipulation with double frequency MWs makes NV‑ centers of all four crystal directions involved, and additionally leads to an enhancement of the manipulation field. In this work, by monitoring the changes in the slope of the resonance line consisting of multi-axes NV‑ centers, measurement of the direction of the external field vector was demonstrated with a sensitivity of {{10}\\prime}/\\sqrt{Hz} . Based on the scheme, the fluorescence signal contrast was improved by four times higher and the sensitivity to the magnetic field strength was improved by two times. The method provides a more practical way of achieving vector sensors based on NV‑ center ensembles in diamond.

  14. Learning nitrogen-vacancy electron spin dynamics on a silicon quantum photonic simulator

    NARCIS (Netherlands)

    Wang, J.; Paesani, S.; Santagati, R.; Knauer, S.; Gentile, A. A.; Wiebe, N.; Petruzzella, M.; Laing, A.; Rarity, J. G.; O'Brien, J. L.; Thompson, M. G.

    2017-01-01

    We present the experimental demonstration of quantum Hamiltonian learning. Using an integrated silicon-photonics quantum simulator with the classical machine learning technique, we successfully learn the Hamiltonian dynamics of a diamond nitrogen-vacancy center's electron ground-state spin.

  15. Single-nitrogen-vacancy-center quantum memory for a superconducting flux qubit mediated by a ferromagnet

    Science.gov (United States)

    Lai, Yen-Yu; Lin, Guin-Dar; Twamley, Jason; Goan, Hsi-Sheng

    2018-05-01

    We propose a quantum memory scheme to transfer and store the quantum state of a superconducting flux qubit (FQ) into the electron spin of a single nitrogen-vacancy (NV) center in diamond via yttrium iron garnet (YIG), a ferromagnet. Unlike an ensemble of NV centers, the YIG moderator can enhance the effective FQ-NV-center coupling strength without introducing additional appreciable decoherence. We derive the effective interaction between the FQ and the NV center by tracing out the degrees of freedom of the collective mode of the YIG spins. We demonstrate the transfer, storage, and retrieval procedures, taking into account the effects of spontaneous decay and pure dephasing. Using realistic experimental parameters for the FQ, NV center and YIG, we find that a combined transfer, storage, and retrieval fidelity higher than 0.9, with a long storage time of 10 ms, can be achieved. This hybrid system not only acts as a promising quantum memory, but also provides an example of enhanced coupling between various systems through collective degrees of freedom.

  16. Deterministic Electrical Charge-State Initialization of Single Nitrogen-Vacancy Center in Diamond

    Directory of Open Access Journals (Sweden)

    Y. Doi

    2014-03-01

    Full Text Available Apart from applications in classical information-processing devices, the electrical control of atomic defects in solids at room temperature will have a tremendous impact on quantum devices that are based on such defects. In this study, we demonstrate the electrical manipulation of individual prominent representatives of such atomic solid-state defects, namely, the negative charge state of single nitrogen-vacancy defect centers (NV^{−} in diamond. We experimentally demonstrate, deterministic, purely electrical charge-state initialization of individual NV centers. The NV centers are placed in the intrinsic region of a p-i-n diode structure that facilitates the delivery of charge carriers to the defect for charge-state switching. The charge-state dynamics of a single NV center were investigated by time-resolved measurements and a nondestructive single-shot readout of the charge state. Fast charge-state switching rates (from negative to neutrally charged defects, which are greater than 0.72 ± 0.10  μs^{−1}, were realized. Furthermore, in no-operation mode, the realized charge states were stable for presumably much more than 0.45 s. We believe that the results obtained are useful not only for ultrafast electrical control of qubits, long T_{2} quantum memory, and quantum sensors associated with single NV centers but also for classical memory devices based on single atomic storage bits working under ambient conditions.

  17. Micro-concave waveguide antenna for high photon extraction from nitrogen vacancy centers in nanodiamond

    Science.gov (United States)

    Rajasekharan, Ranjith; Kewes, Günter; Djalalian-Assl, Amir; Ganesan, Kumaravelu; Tomljenovic-Hanic, Snjezana; McCallum, Jeffrey C.; Roberts, Ann; Benson, Oliver; Prawer, Steven

    2015-01-01

    The negatively charged nitrogen-vacancy colour center (NV− center) in nanodiamond is an excellent single photon source due to its stable photon generation in ambient conditions, optically addressable nuclear spin state, high quantum yield and its availability in nanometer sized crystals. In order to make practical devices using nanodiamond, highly efficient and directional emission of single photons in well-defined modes, either collimated into free space or waveguides are essential. This is a Herculean task as the photoluminescence of the NV centers is associated with two orthogonal dipoles arranged in a plane perpendicular to the NV defect symmetry axis. Here, we report on a micro-concave waveguide antenna design, which can effectively direct single photons from any emitter into either free space or into waveguides in a narrow cone angle with more than 80% collection efficiency irrespective of the dipole orientation. The device also enhances the spontaneous emission rate which further increases the number of photons available for collection. The waveguide antenna has potential applications in quantum cryptography, quantum computation, spectroscopy and metrology. PMID:26169682

  18. Process of optical excitation and relaxation of color center in synthetic diamond and its application to optoelectronics

    International Nuclear Information System (INIS)

    Nishida, Yoshio

    1989-01-01

    Irradiation of high-pressure synthesized diamond is carried out by using a nuclear reactor or a linac. Then, the effect of annealing on the color centers is observed. A study is made to identify different color centers and to provide techniques to control their introduction. Investigations cover the relation of color center formation with annealing temperature, dependence of color center formation on radiation dose, migration of H3 center and hydrogen, and applicability of five different color centers to optoelectronics. Next, a study is made of the formation and relaxation of the nitrogen vacancy (NV) center in a metastable excited state produced by optical excitation. An optical gain is essential to provide laser. Optical amplification is measured at the vibronic emission band of the NV center. An increase in absorption is detected, indicating that the NV center will not provide laser. In the optical excitation-relaxation process, the relaxation proceeds via a metastable state. Finally, hole burning of ZPL of the NV center is observed in the temperature range from 20K to 80K, and some of its features are described. (N.K.)

  19. Motion Control and Optical Interrogation of a Levitating Single Nitrogen Vacancy in Vacuum.

    Science.gov (United States)

    Conangla, Gerard P; Schell, Andreas W; Rica, Raúl A; Quidant, Romain

    2018-05-24

    Levitation optomechanics exploits the unique mechanical properties of trapped nano-objects in vacuum to address some of the limitations of clamped nanomechanical resonators. In particular, its performance is foreseen to contribute to a better understanding of quantum decoherence at the mesoscopic scale as well as to lead to novel ultrasensitive sensing schemes. While most efforts have focused so far on the optical trapping of low-absorption silica particles, further opportunities arise from levitating objects with internal degrees of freedom, such as color centers. Nevertheless, inefficient heat dissipation at low pressures poses a challenge because most nano-objects, even with low-absorption materials, experience photodamage in an optical trap. Here, by using a Paul trap, we demonstrate levitation in vacuum and center-of-mass feedback cooling of a nanodiamond hosting a single nitrogen-vacancy center. The achieved level of motion control enables us to optically interrogate and characterize the emitter response. The developed platform is applicable to a wide range of other nano-objects and represents a promising step toward coupling internal and external degrees of freedom.

  20. Hybrid quantum gates between flying photon and diamond nitrogen-vacancy centers assisted by optical microcavities

    Science.gov (United States)

    Wei, Hai-Rui; Lu Long, Gui

    2015-01-01

    Hybrid quantum gates hold great promise for quantum information processing since they preserve the advantages of different quantum systems. Here we present compact quantum circuits to deterministically implement controlled-NOT, Toffoli, and Fredkin gates between a flying photon qubit and diamond nitrogen-vacancy (NV) centers assisted by microcavities. The target qubits of these universal quantum gates are encoded on the spins of the electrons associated with the diamond NV centers and they have long coherence time for storing information, and the control qubit is encoded on the polarizations of the flying photon and can be easily manipulated. Our quantum circuits are compact, economic, and simple. Moreover, they do not require additional qubits. The complexity of our schemes for universal three-qubit gates is much reduced, compared to the synthesis with two-qubit entangling gates. These schemes have high fidelities and efficiencies, and they are feasible in experiment. PMID:26271899

  1. Tapered fiber coupling of single photons emitted by a deterministically positioned single nitrogen vacancy center

    Energy Technology Data Exchange (ETDEWEB)

    Liebermeister, Lars, E-mail: lars.liebermeister@physik.uni-muenchen.de; Petersen, Fabian; Münchow, Asmus v.; Burchardt, Daniel; Hermelbracht, Juliane; Tashima, Toshiyuki [Fakultät für Physik, Ludwig-Maximilians-Universität München, 80799 München (Germany); Schell, Andreas W.; Benson, Oliver [Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin (Germany); Meinhardt, Thomas; Krueger, Anke [Institut für Organische Chemie, Universität Würzburg, 97074 Würzburg (Germany); Wilhelm Conrad Roentgen Research Center for Complex Materials Systems, Universität Würzburg, 97074 Würzburg (Germany); Stiebeiner, Ariane; Rauschenbeutel, Arno [Atominstitut, Technische Universität Wien, 1020 Wien (Austria); Weinfurter, Harald; Weber, Markus, E-mail: markusweber@lmu.de [Fakultät für Physik, Ludwig-Maximilians-Universität München, 80799 München (Germany); Max-Planck-Institut für Quantenoptik, 85748 Garching (Germany)

    2014-01-20

    A diamond nano-crystal hosting a single nitrogen vacancy (NV) center is optically selected with a confocal scanning microscope and positioned deterministically onto the subwavelength-diameter waist of a tapered optical fiber (TOF) with the help of an atomic force microscope. Based on this nano-manipulation technique, we experimentally demonstrate the evanescent coupling of single fluorescence photons emitted by a single NV-center to the guided mode of the TOF. By comparing photon count rates of the fiber-guided and the free-space modes and with the help of numerical finite-difference time domain simulations, we determine a lower and upper bound for the coupling efficiency of (9.5 ± 0.6)% and (10.4 ± 0.7)%, respectively. Our results are a promising starting point for future integration of single photon sources into photonic quantum networks and applications in quantum information science.

  2. A statistical correlation investigation for the role of surface spins to the spin relaxation of nitrogen vacancy centers

    Energy Technology Data Exchange (ETDEWEB)

    Song, Xuerui; Zhang, Jian; Feng, Fupan; Wang, Junfeng; Zhang, Wenlong; Lou, Liren; Zhu, Wei; Wang, Guanzhong, E-mail: gzwang@ustc.edu.cn [Hefei National Laboratory for Physical Science at Microscale, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026 (China)

    2014-04-15

    We investigated the influence of spins on surface of nanodiamonds (NDs) to the longitudinal relaxation time (T{sub 1}) and transverse relaxation time (T{sub 2}) of nitrogen vacancy (NV) centers in ND. A spherical model of the NDs was suggested to account for the experimental results of T{sub 1} and T{sub 2}, and the density of surface spins was roughly estimated based on the statistical analysis of experimental results of 72 NDs containing a single NV center. For NDs studied here, the T{sub 1} of NV center inside is highly dependent to the surface spins of the NDs. However, for the T{sub 2} of NV center, intrinsic contributions must be much pronounced than that by surface spins. In other words, T{sub 1} of an NV center in NDs is more sensitive to the change of the surface spin density than T{sub 2}.

  3. A statistical correlation investigation for the role of surface spins to the spin relaxation of nitrogen vacancy centers

    Directory of Open Access Journals (Sweden)

    Xuerui Song

    2014-04-01

    Full Text Available We investigated the influence of spins on surface of nanodiamonds (NDs to the longitudinal relaxation time (T1 and transverse relaxation time (T2 of nitrogen vacancy (NV centers in ND. A spherical model of the NDs was suggested to account for the experimental results of T1 and T2, and the density of surface spins was roughly estimated based on the statistical analysis of experimental results of 72 NDs containing a single NV center. For NDs studied here, the T1 of NV center inside is highly dependent to the surface spins of the NDs. However, for the T2 of NV center, intrinsic contributions must be much pronounced than that by surface spins. In other words, T1 of an NV center in NDs is more sensitive to the change of the surface spin density than T2.

  4. Efficient Extraction of Light from a Nitrogen-Vacancy Center in a Diamond Parabolic Reflector.

    Science.gov (United States)

    Wan, Noel H; Shields, Brendan J; Kim, Donggyu; Mouradian, Sara; Lienhard, Benjamin; Walsh, Michael; Bakhru, Hassaram; Schröder, Tim; Englund, Dirk

    2018-04-03

    Quantum emitters in solids are being developed for a range of quantum technologies, including quantum networks, computing, and sensing. However, a remaining challenge is the poor photon collection due to the high refractive index of most host materials. Here we overcome this limitation by introducing monolithic parabolic reflectors as an efficient geometry for broadband photon extraction from quantum emitter and experimentally demonstrate this device for the nitrogen-vacancy (NV) center in diamond. Simulations indicate a photon collection efficiency exceeding 75% across the visible spectrum and experimental devices, fabricated using a high-throughput gray scale lithography process, demonstrating a photon extraction efficiency of (41 ± 5)%. This device enables a raw experimental detection efficiency of (12 ± 1)% with fluorescence detection rates as high as (4.114 ± 0.003) × 10 6 counts per second (cps) from a single NV center. Enabled by our deterministic emitter localization and fabrication process, we find a high number of exceptional devices with an average count rate of (3.1 ± 0.9) × 10 6 cps.

  5. Circularly polarized microwaves for magnetic resonance study in the GHz range: Application to nitrogen-vacancy in diamonds

    International Nuclear Information System (INIS)

    Mrózek, M.; Rudnicki, D. S.; Gawlik, W.; Mlynarczyk, J.

    2015-01-01

    The ability to create time-dependent magnetic fields of controlled polarization is essential for many experiments with magnetic resonance. We describe a microstrip circuit that allows us to generate strong magnetic field at microwave frequencies with arbitrary adjusted polarization. The circuit performance is demonstrated by applying it to an optically detected magnetic resonance and Rabi nutation experiments in nitrogen-vacancy color centers in diamond. Thanks to high efficiency of the proposed microstrip circuit and degree of circular polarization of 85%; it is possible to address the specific spin states of a diamond sample using a low power microwave generator. The circuit may be applied to a wide range of magnetic resonance experiments with a well-controlled polarization of microwaves

  6. Strong coupling between a single nitrogen-vacancy spin and the rotational mode of diamonds levitating in an ion trap

    Science.gov (United States)

    Delord, T.; Nicolas, L.; Chassagneux, Y.; Hétet, G.

    2017-12-01

    A scheme for strong coupling between a single atomic spin and the rotational mode of levitating nanoparticles is proposed. The idea is based on spin readout of nitrogen-vacancy centers embedded in aspherical nanodiamonds levitating in an ion trap. We show that the asymmetry of the diamond induces a rotational confinement in the ion trap. Using a weak homogeneous magnetic field and a strong microwave driving we then demonstrate that the spin of the nitrogen-vacancy center can be strongly coupled to the rotational mode of the diamond.

  7. Excitation of surface plasmon polariton modes with multiple nitrogen vacancy centers in single nanodiamonds

    International Nuclear Information System (INIS)

    Kumar, Shailesh; Lausen, Jens L; Andersen, Sebastian K H; Roberts, Alexander S; Radko, Ilya P; Bozhevolnyi, Sergey I; Garcia-Ortiz, Cesar E; Smith, Cameron L C; Kristensen, Anders

    2016-01-01

    Nitrogen-vacancy (NV) centers in diamonds are interesting due to their remarkable characteristics that are well suited to applications in quantum-information processing and magnetic field sensing, as well as representing stable fluorescent sources. Multiple NV centers in nanodiamonds (NDs) are especially useful as biological fluorophores due to their chemical neutrality, brightness and room-temperature photostability. Furthermore, NDs containing multiple NV centers also have potential in high-precision magnetic field and temperature sensing. Coupling NV centers to propagating surface plasmon polariton (SPP) modes gives a base for lab-on-a-chip sensing devices, allows enhanced fluorescence emission and collection which can further enhance the precision of NV-based sensors. Here, we investigate coupling of multiple NV centers in individual NDs to the SPP modes supported by silver surfaces protected by thin dielectric layers and by gold V-grooves (VGs) produced via the self-terminated silicon etching. In the first case, we concentrate on monitoring differences in fluorescence spectra obtained from a source ND, which is illuminated by a pump laser, and from a scattering ND illuminated only by the fluorescence-excited SPP radiation. In the second case, we observe changes in the average NV lifetime when the same ND is characterized outside and inside a VG. Fluorescence emission from the VG terminations is also observed, which confirms the NV coupling to the VG-supported SPP modes. (paper)

  8. Excitation of surface plasmon polariton modes with multiple nitrogen vacancy centers in single nanodiamonds

    Science.gov (United States)

    Kumar, Shailesh; Lausen, Jens L.; Garcia-Ortiz, Cesar E.; Andersen, Sebastian K. H.; Roberts, Alexander S.; Radko, Ilya P.; Smith, Cameron L. C.; Kristensen, Anders; Bozhevolnyi, Sergey I.

    2016-02-01

    Nitrogen-vacancy (NV) centers in diamonds are interesting due to their remarkable characteristics that are well suited to applications in quantum-information processing and magnetic field sensing, as well as representing stable fluorescent sources. Multiple NV centers in nanodiamonds (NDs) are especially useful as biological fluorophores due to their chemical neutrality, brightness and room-temperature photostability. Furthermore, NDs containing multiple NV centers also have potential in high-precision magnetic field and temperature sensing. Coupling NV centers to propagating surface plasmon polariton (SPP) modes gives a base for lab-on-a-chip sensing devices, allows enhanced fluorescence emission and collection which can further enhance the precision of NV-based sensors. Here, we investigate coupling of multiple NV centers in individual NDs to the SPP modes supported by silver surfaces protected by thin dielectric layers and by gold V-grooves (VGs) produced via the self-terminated silicon etching. In the first case, we concentrate on monitoring differences in fluorescence spectra obtained from a source ND, which is illuminated by a pump laser, and from a scattering ND illuminated only by the fluorescence-excited SPP radiation. In the second case, we observe changes in the average NV lifetime when the same ND is characterized outside and inside a VG. Fluorescence emission from the VG terminations is also observed, which confirms the NV coupling to the VG-supported SPP modes.

  9. Impact of Surface Functionalization on the Quantum Coherence of Nitrogen-Vacancy Centers in Nanodiamonds.

    Science.gov (United States)

    Ryan, Robert G; Stacey, Alastair; O'Donnell, Kane M; Ohshima, Takeshi; Johnson, Brett C; Hollenberg, Lloyd C L; Mulvaney, Paul; Simpson, David A

    2018-04-18

    Nanoscale quantum probes such as the nitrogen-vacancy (NV) center in diamonds have demonstrated remarkable sensing capabilities over the past decade as control over fabrication and manipulation of these systems has evolved. The biocompatibility and rich surface chemistry of diamonds has added to the utility of these probes but, as the size of these nanoscale systems is reduced, the surface chemistry of diamond begins to impact the quantum properties of the NV center. In this work, we systematically study the effect of the diamond surface chemistry on the quantum coherence of the NV center in nanodiamonds (NDs) 50 nm in size. Our results show that a borane-reduced diamond surface can on average double the spin relaxation time of individual NV centers in nanodiamonds when compared to thermally oxidized surfaces. Using a combination of infrared and X-ray absorption spectroscopy techniques, we correlate the changes in quantum relaxation rates with the conversion of sp 2 carbon to C-O and C-H bonds on the diamond surface. These findings implicate double-bonded carbon species as a dominant source of spin noise for near surface NV centers. The link between the surface chemistry and quantum coherence indicates that through tailored engineering of the surface, the quantum properties and magnetic sensitivity of these nanoscale systems may approach that observed in bulk diamond.

  10. High density nitrogen-vacancy sensing surface created via He{sup +} ion implantation of {sup 12}C diamond

    Energy Technology Data Exchange (ETDEWEB)

    Kleinsasser, Ed E., E-mail: edklein@uw.edu [Department of Electrical Engineering, University of Washington, Seattle, Washington 98195-2500 (United States); Stanfield, Matthew M.; Banks, Jannel K. Q. [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States); Zhu, Zhouyang; Li, Wen-Di [HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen 518000 (China); Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong (China); Acosta, Victor M. [Department of Physics and Astronomy, Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87106 (United States); Watanabe, Hideyuki [Correlated Electronics Group, Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8565 (Japan); Itoh, Kohei M. [School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Fu, Kai-Mei C., E-mail: kaimeifu@uw.edu [Department of Electrical Engineering, University of Washington, Seattle, Washington 98195-2500 (United States); Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States)

    2016-05-16

    We present a promising method for creating high-density ensembles of nitrogen-vacancy centers with narrow spin-resonances for high-sensitivity magnetic imaging. Practically, narrow spin-resonance linewidths substantially reduce the optical and RF power requirements for ensemble-based sensing. The method combines isotope purified diamond growth, in situ nitrogen doping, and helium ion implantation to realize a 100 nm-thick sensing surface. The obtained 10{sup 17 }cm{sup −3} nitrogen-vacancy density is only a factor of 10 less than the highest densities reported to date, with an observed 200 kHz spin resonance linewidth over 10 times narrower.

  11. Creation of quantum entanglement with two separate diamond nitrogen vacancy centers coupled to a photonic molecule

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Siping [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Physics and Electronic Engineering, Hubei University of Arts and Science, Xiangyang 441053 (China); Yu, Rong, E-mail: rong-yu2013@163.com [School of Science, Hubei Province Key Laboratory of Intelligent Robot, Wuhan Institute of Technology, Wuhan 430073 (China); Li, Jiahua, E-mail: huajia-li@163.com [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Key Laboratory of Fundamental Physical Quantities Measurement of Ministry of Education, Wuhan 430074 (China); Wu, Ying [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2013-12-28

    We explore the entanglement generation and the corresponding dynamics between two separate nitrogen-vacancy (NV) centers in diamond nanocrystal coupled to a photonic molecule consisting of a pair of coupled photonic crystal (PC) cavities. By calculating the entanglement concurrence with readily available experimental parameters, it is found that the entanglement degree strongly depends on the cavity-cavity hopping strength and the NV-center-cavity detuning. High concurrence peak and long-lived entanglement plateau can be achieved by properly adjusting practical system parameters. Meanwhile, we also discuss the influence of the coupling strength between the NV centers and the cavity modes on the behavior of the concurrence. Such a PC-NV system can be employed for quantum entanglement generation and represents a building block for an integrated nanophotonic network in a solid-state cavity quantum electrodynamics platform. In addition, the present theory can also be applied to other similar systems, such as two single quantum emitters positioned close to a microtoroidal resonator with the whispering-gallery-mode fields propagating inside the resonator.

  12. Observation and control of blinking nitrogen-vacancy centres in discrete nanodiamonds.

    Science.gov (United States)

    Bradac, C; Gaebel, T; Naidoo, N; Sellars, M J; Twamley, J; Brown, L J; Barnard, A S; Plakhotnik, T; Zvyagin, A V; Rabeau, J R

    2010-05-01

    Nitrogen-vacancy colour centres in diamond can undergo strong, spin-sensitive optical transitions under ambient conditions, which makes them attractive for applications in quantum optics, nanoscale magnetometry and biolabelling. Although nitrogen-vacancy centres have been observed in aggregated detonation nanodiamonds and milled nanodiamonds, they have not been observed in very small isolated nanodiamonds. Here, we report the first direct observation of nitrogen-vacancy centres in discrete 5-nm nanodiamonds at room temperature, including evidence for intermittency in the luminescence (blinking) from the nanodiamonds. We also show that it is possible to control this blinking by modifying the surface of the nanodiamonds.

  13. Charge Dynamics in near-Surface, Variable-Density Ensembles of Nitrogen-Vacancy Centers in Diamond.

    Science.gov (United States)

    Dhomkar, Siddharth; Jayakumar, Harishankar; Zangara, Pablo R; Meriles, Carlos A

    2018-06-13

    Although the spin properties of superficial shallow nitrogen-vacancy (NV) centers have been the subject of extensive scrutiny, considerably less attention has been devoted to studying the dynamics of NV charge conversion near the diamond surface. Using multicolor confocal microscopy, here we show that near-surface point defects arising from high-density ion implantation dramatically increase the ionization and recombination rates of shallow NVs compared to those in bulk diamond. Further, we find that these rates grow linearly, not quadratically, with laser intensity, indicative of single-photon processes enabled by NV state mixing with other defect states. Accompanying these findings, we observe NV ionization and recombination in the dark, likely the result of charge transfer to neighboring traps. Despite the altered charge dynamics, we show that one can imprint rewritable, long-lasting patterns of charged-initialized, near-surface NVs over large areas, an ability that could be exploited for electrochemical biosensing or to optically store digital data sets with subdiffraction resolution.

  14. Dependence of high density nitrogen-vacancy center ensemble coherence on electron irradiation doses and annealing time

    Science.gov (United States)

    Zhang, C.; Yuan, H.; Zhang, N.; Xu, L. X.; Li, B.; Cheng, G. D.; Wang, Y.; Gui, Q.; Fang, J. C.

    2017-12-01

    Negatively charged nitrogen-vacancy (NV-) center ensembles in diamond have proved to have great potential for use in highly sensitive, small-package solid-state quantum sensors. One way to improve sensitivity is to produce a high-density NV- center ensemble on a large scale with a long coherence lifetime. In this work, the NV- center ensemble is prepared in type-Ib diamond using high energy electron irradiation and annealing, and the transverse relaxation time of the ensemble—T 2—was systematically investigated as a function of the irradiation electron dose and annealing time. Dynamical decoupling sequences were used to characterize T 2. To overcome the problem of low signal-to-noise ratio in T 2 measurement, a coupled strip lines waveguide was used to synchronously manipulate NV- centers along three directions to improve fluorescence signal contrast. Finally, NV- center ensembles with a high concentration of roughly 1015 mm-3 were manipulated within a ~10 µs coherence time. By applying a multi-coupled strip-lines waveguide to improve the effective volume of the diamond, a sub-femtotesla sensitivity for AC field magnetometry can be achieved. The long-coherence high-density large-scale NV- center ensemble in diamond means that types of room-temperature micro-sized solid-state quantum sensors with ultra-high sensitivity can be further developed in the near future.

  15. Luminescence properties of engineered nitrogen vacancy centers in a close surface proximity

    Czech Academy of Sciences Publication Activity Database

    Petráková, V.; Nesládek, M.; Taylor, Andrew; Fendrych, František; Cígler, Petr; Ledvina, Miroslav; Vacík, Jiří; Štursa, Jan; Kučka, Jan

    2011-01-01

    Roč. 208, č. 9 (2011), s. 2051-2056 ISSN 1862-6300 R&D Projects : GA AV ČR KAN200100801; GA AV ČR KAN301370701; GA AV ČR(CZ) KAN400480701; GA MŠk(CZ) LD11076 EU Projects : European Commission(XE) 245122 - DINAMO Grant - others:GA MŠk(CZ) LD11078; European RD projects (XE) 238201-MATCON Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z10100520; CEZ:AV0Z10480505 Keywords : diamond * luminescence properties * nitrogen-vacancy * surface proximity Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.463, year: 2011

  16. Ultrathin Nanocrystalline Diamond Films with Silicon Vacancy Color Centers via Seeding by 2 nm Detonation Nanodiamonds.

    Science.gov (United States)

    Stehlik, Stepan; Varga, Marian; Stenclova, Pavla; Ondic, Lukas; Ledinsky, Martin; Pangrac, Jiri; Vanek, Ondrej; Lipov, Jan; Kromka, Alexander; Rezek, Bohuslav

    2017-11-08

    Color centers in diamonds have shown excellent potential for applications in quantum information processing, photonics, and biology. Here we report chemical vapor deposition (CVD) growth of nanocrystalline diamond (NCD) films as thin as 5-6 nm with photoluminescence (PL) from silicon-vacancy (SiV) centers at 739 nm. Instead of conventional 4-6 nm detonation nanodiamonds (DNDs), we prepared and employed hydrogenated 2 nm DNDs (zeta potential = +36 mV) to form extremely dense (∼1.3 × 10 13 cm -2 ), thin (2 ± 1 nm), and smooth (RMS roughness < 0.8 nm) nucleation layers on an Si/SiO x substrate, which enabled the CVD growth of such ultrathin NCD films in two different and complementary microwave (MW) CVD systems: (i) focused MW plasma with an ellipsoidal cavity resonator and (ii) pulsed MW plasma with a linear antenna arrangement. Analytical ultracentrifuge, infrared and Raman spectroscopies, atomic force microscopy, and scanning electron microscopy are used for detailed characterization of the 2 nm H-DNDs and the nucleation layer as well as the ultrathin NCD films. We also demonstrate on/off switching of the SiV center PL in the NCD films thinner than 10 nm, which is achieved by changing their surface chemistry.

  17. Color centers in heavily irradiated CsI(Tl) crystals

    International Nuclear Information System (INIS)

    Yakovlev, V.; Meleshko, A.; Trefilova, L.

    2008-01-01

    The absorption and luminescence properties of CsI(Tl) crystals colored by irradiation are studied by the method of the time-resolved spectroscopy. The scheme of the electron transitions in CsI(Tl) crystal is suggested to explain the appearance of the color centers under exposure to the near-UV light. It is established that either of the two types activator color centers holds the charge carrier with opposite sign. The model of the hole Tl 2+ v c - activator color center is suggested. According to the model the positive charge of Tl 2+ ion is compensated by the negative charge of a close cation vacancy v c - . The color center emission reveals in the cathode-luminescence spectrum of the colored CsI(Tl) crystal. The high-dose irradiation of CsI(Tl) crystal results in the reduction of the decay time of the near-thallium self-trapped excitons (STE) emission. The decay kinetics of Tl 2+ v c - emission contains the time components typical for the decay kinetics of near-thallium STE emission. The reason of the observed effects is the energy transfer from the near-thallium STE excitons to the color centers via the inductive-resonant mechanism

  18. Near-surface layer radiation color centers in lithium fluoride nanocrystals: Luminescence and composition

    Energy Technology Data Exchange (ETDEWEB)

    Voitovich, A.P., E-mail: voitovich@imaph.bas-net.by; Kalinov, V.S.; Stupak, A.P.; Novikov, A.N.; Runets, L.P.

    2015-01-15

    Lithium fluoride nanocrystals are irradiated by gamma quanta at 77 K. The radiation color centers formed in a near-surface layer of nanocrystals are studied. Absorption, luminescence and luminescence excitation spectra of the surface defects have been measured. It has been found that the luminescence excitation spectra for aggregated surface centers consist of two or three bands with not very much different intensities. Reactions of the surface centers separately with electrons and with anion vacancies have been investigated. Numbers of anion vacancies and electrons entering into the centers composition have been established and it has been found that F{sub S1}, F{sub S1}{sup −}, F{sub S2}, F{sub S2}{sup −}, F{sub S3}{sup +} and F{sub S3} types of the surface centers are formed. The degree of luminescence polarization has been defined and it has been determined that the polarization degree for F{sub S2}{sup +} centers changes sign under transition from one excitation band to another. It has been shown that during irradiation at 77 K radiation-induced defects are formed more efficiently on the surface than in the bulk. - Highlights: • Radiative color centers were fabricated in lithium fluoride nanocrystals. • The unique absorption and luminescence characteristics are inherent in the centers. • The reactions of these centers with electrons and anion vacancies were studied. • The degree of luminescence polarization was defined. • Numbers of anion vacancies and electrons forming the centers were established.

  19. Size-controlled fluorescent nanodiamonds: A facile method of fabrication and color-center counting

    KAUST Repository

    Mahfouz, Remi

    2013-01-01

    We present a facile method for the production of fluorescent diamond nanocrystals (DNCs) of different sizes and efficiently quantify the concentration of emitting defect color centers (DCCs) of each DNC size. We prepared the DNCs by ball-milling commercially available micrometer-sized synthetic (high pressure, high temperature (HPHT)) diamonds and then separated the as-produced DNCs by density gradient ultracentrifugation (DGU) into size-controlled fractions. A protocol to enhance the uniformity of the nitrogen-vacancy (NV) centers in the diamonds was devised by depositing the DNCs as a dense monolayer on amino-silanized silicon substrates and then subjecting the monolayer to He+ beam irradiation. Using a standard confocal setup, we analyzed the average number of NV centers per crystal, and obtained a quantitative relationship between the DNC particle size and the NV number per crystal. This relationship was in good agreement with results from previous studies that used more elaborate setups. Our findings suggest that nanocrystal size separation by DGU may be used to control the number of defects per nanocrystal. The efficient approaches described herein to control and quantify DCCs are valuable to researchers as they explore applications for color centers and new strategies to create them. © 2013 The Royal Society of Chemistry.

  20. Role of nitrogen vacancies in cerium doped aluminum nitride

    Energy Technology Data Exchange (ETDEWEB)

    Majid, Abdul, E-mail: abdulmajid40@yahoo.com [Department of Physics, University of Gujrat, Gujrat (Pakistan); Department of Adaptive Machine Systems, Osaka University, Osaka (Japan); Asghar, Farzana [Department of Physics, University of Gujrat, Gujrat (Pakistan); Rana, Usman Ali; Ud-Din Khan, Salah [Sustainable Energy Technologies Center, College of Engineering, King Saud University, PO-Box 800, Riyadh 11421 (Saudi Arabia); Yoshiya, Masato [Department of Adaptive Machine Systems, Osaka University, Osaka (Japan); Hussain, Fayyaz [Physics Department, Bahauddin Zakarya University, Multan (Pakistan); Ahmad, Iftikhar [Department of Mathematics, University of Gujrat, Gujrat (Pakistan)

    2016-08-15

    In this report, a systematic density functional theory based investigation to explain the character of nitrogen vacancies in structural, electronic and magnetic properties of Ce doped wurtzite AlN is presented. The work demonstrates the modification in the properties of the material upon doping thereby addressing dopant concentration and inter-dopant distance. The presence of anionic vacancy reveals spin polarization and introduction of magnetic character in the structure. The doping produced the magnetic character in the material which was of ferromagnetic nature in most cases except the situation when dopants separated by largest distance of 5.873 Å. The calculated values of total energy and exchange energy suggested the configuration including Ce{sub Al}–V{sub N} complex is more favorable and exhibits ferromagnetic ordering. - Highlights: • Ce doped AlN with and without nitrogen vacancy. • Dopant at nearest neighbor site introduce ferromagnetism. • Ce{sub Al}–V{sub N} complex is favorable in Ce:AlN.

  1. Role of nitrogen vacancies in cerium doped aluminum nitride

    International Nuclear Information System (INIS)

    Majid, Abdul; Asghar, Farzana; Rana, Usman Ali; Ud-Din Khan, Salah; Yoshiya, Masato; Hussain, Fayyaz; Ahmad, Iftikhar

    2016-01-01

    In this report, a systematic density functional theory based investigation to explain the character of nitrogen vacancies in structural, electronic and magnetic properties of Ce doped wurtzite AlN is presented. The work demonstrates the modification in the properties of the material upon doping thereby addressing dopant concentration and inter-dopant distance. The presence of anionic vacancy reveals spin polarization and introduction of magnetic character in the structure. The doping produced the magnetic character in the material which was of ferromagnetic nature in most cases except the situation when dopants separated by largest distance of 5.873 Å. The calculated values of total energy and exchange energy suggested the configuration including Ce Al –V N complex is more favorable and exhibits ferromagnetic ordering. - Highlights: • Ce doped AlN with and without nitrogen vacancy. • Dopant at nearest neighbor site introduce ferromagnetism. • Ce Al –V N complex is favorable in Ce:AlN.

  2. Optical properties of implanted Xe color centers in diamond

    Science.gov (United States)

    Sandstrom, Russell; Ke, Li; Martin, Aiden; Wang, Ziyu; Kianinia, Mehran; Green, Ben; Gao, Wei-bo; Aharonovich, Igor

    2018-03-01

    Optical properties of color centers in diamond have been the subject of intense research due to their promising applications in quantum photonics. In this work we study the optical properties of Xe related color centers implanted into nitrogen rich (type IIA) and an ultrapure, electronic grade diamond. The Xe defect has two zero phonon lines at ∼794 nm and 811 nm, which can be effectively excited using both green and red excitation, however, its emission in the nitrogen rich diamond is brighter. Near resonant excitation is performed at cryogenic temperatures and luminescence is probed under strong magnetic field. Our results are important towards the understanding of the Xe related defect and other near infrared color centers in diamond.

  3. Interaction of nitrogen with vacancy defects in N+-implanted ZnO studied using a slow positron beam

    International Nuclear Information System (INIS)

    Chen, Z.Q.; Maekawa, M.; Kawasuso, A.; Suzuki, R.; Ohdaira, T.

    2005-01-01

    ZnO crystals were implanted with N + , O + , and Al + , and co-implanted with O + /N + and Al + /N + ions. Positron annihilation measurements indicate introduction of vacancy clusters upon implantation. In the N + -implanted and Al + /N + co-implanted samples, these vacancy clusters are only partially annealed at 800 deg. C, as compared with their entire recovery in the O + - and Al + -implanted samples at 800-900 deg. C, suggesting a strong interaction between nitrogen and vacancy clusters. However, in the O + /N + co-implanted sample, most vacancy clusters disappear at 800 deg. C. Probably oxygen scavenges nitrogen to enhance the annealing of the vacancy clusters. Upon further annealing at 1000-1100 deg. C, nitrogen also forms stable complexes with thermally generated vacancies. These nitrogen-related vacancy complexes need high-temperature annealing at 1200-1250 deg. C to be fully removed

  4. Fast nanoscale addressability of nitrogen-vacancy spins via coupling to a dynamic ferromagnetic vortex

    Science.gov (United States)

    Wolf, M. S.; Badea, R.; Berezovsky, J.

    2016-01-01

    The core of a ferromagnetic vortex domain creates a strong, localized magnetic field, which can be manipulated on nanosecond timescales, providing a platform for addressing and controlling individual nitrogen-vacancy centre spins in diamond at room temperature, with nanometre-scale resolution. Here, we show that the ferromagnetic vortex can be driven into proximity with a nitrogen-vacancy defect using small applied magnetic fields, inducing significant nitrogen-vacancy spin splitting. We also find that the magnetic field gradient produced by the vortex is sufficient to address spins separated by nanometre-length scales. By applying a microwave-frequency magnetic field, we drive both the vortex and the nitrogen-vacancy spins, resulting in enhanced coherent rotation of the spin state. Finally, we demonstrate that by driving the vortex on fast timescales, sequential addressing and coherent manipulation of spins is possible on ∼100 ns timescales. PMID:27296550

  5. Counting vacancies and nitrogen-vacancy centers in detonation nanodiamond† †Electronic supplementary information (ESI) available: (1) DND synthesis; (2) HRTEM and EELS characterization methods; (3) EELS simulation method; (4) supporting figures of EELS simulations; (5) soft-X-ray K-edge spectra of the DND; and (6) ab initio N-V center modeling method. See DOI: 10.1039/C6NR01888B Click here for additional data file.

    Science.gov (United States)

    Barnard, Amanda S.; Dwyer, Christian; Boothroyd, Chris B.; Hocking, Rosalie K.; Ōsawa, Eiji

    2016-01-01

    Detonation nanodiamond particles (DND) contain highly-stable nitrogen-vacancy (N-V) centers, making it important for quantum-optical and biotechnology applications. However, due to the small particle size, the N-V concentrations are believed to be intrinsically very low, spawning efforts to understand the formation of N-V centers and vacancies, and increase their concentration. Here we show that vacancies in DND can be detected and quantified using simulation-aided electron energy loss spectroscopy. Despite the small particle size, we find that vacancies exist at concentrations of about 1 at%. Based on this experimental finding, we use ab initio calculations to predict that about one fifth of vacancies in DND form N-V centers. The ability to directly detect and quantify vacancies in DND, and predict the corresponding N-V formation probability, has a significant impact to those emerging technologies where higher concentrations and better dispersion of N-V centres are critically required. PMID:27147128

  6. Enhanced photoluminescence from single nitrogen-vacancy defects in nanodiamonds coated with metal-phenolic networks

    OpenAIRE

    Bray, Kerem; Previdi, Rodolfo; Gibson, Brant C.; Shimoni, Olga; Aharonovich, Igor

    2015-01-01

    Fluorescent nanodiamonds are attracting major attention in the field of bio-sensing and biolabeling. In this work we demonstrate a robust approach to surface functionalize individual nanodiamonds with metal-phenolic networks that enhance the photoluminescence from single nitrogen vacancy (NV) centers. We show that single NV centres in the coated nanodiamonds also exhibit shorter lifetimes, opening another channel for high resolution sensing. We propose that the nanodiamond encapsulation suppr...

  7. Magnetic Field Sensing with Nitrogen-Vacancy Color Centers in Diamond

    Science.gov (United States)

    2013-05-01

    8217d from r.haracteristic time of the der.ay enwlop<’. as shown in Figm<’ 1.7(b). For an ensemble of NV centers , inhomogeneities stemming from the...Backgnmnd a initialization detection optical _.J:.D ____. __________ __._n....__ b 350 "E 300 ~ 250 (jj §, 200 Cll Ŕ 150 l!l ~ 100 ~ 50 0...Free Precession Time-r (J.IS) II) ---(ij c .2’ (/) Cll (J c :!l e 0 ::J u: 0 0.5 15 2 Static Magnetic Field B (G) Figurr A. 2

  8. Efficient coupling of a single diamond color center to propagating plasmonic gap modes

    DEFF Research Database (Denmark)

    Kumar, Shailesh; Huck, Alexander; Andersen, Ulrik L

    2013-01-01

    We report on coupling of a single nitrogen-vacancy (NV) center in a nanodiamond to the propagating gap mode of two parallel placed chemically grown silver nanowires. The coupled NV-center nanowire system is made by manipulating nanodiamonds and nanowires with the tip of an atomic force microscope...

  9. Optical and microwave control of germanium-vacancy center spins in diamond

    Science.gov (United States)

    Siyushev, Petr; Metsch, Mathias H.; Ijaz, Aroosa; Binder, Jan M.; Bhaskar, Mihir K.; Sukachev, Denis D.; Sipahigil, Alp; Evans, Ruffin E.; Nguyen, Christian T.; Lukin, Mikhail D.; Hemmer, Philip R.; Palyanov, Yuri N.; Kupriyanov, Igor N.; Borzdov, Yuri M.; Rogers, Lachlan J.; Jelezko, Fedor

    2017-08-01

    A solid-state system combining a stable spin degree of freedom with an efficient optical interface is highly desirable as an element for integrated quantum-optical and quantum-information systems. We demonstrate a bright color center in diamond with excellent optical properties and controllable electronic spin states. Specifically, we carry out detailed optical spectroscopy of a germanium-vacancy (GeV ) color center demonstrating optical spectral stability. Using an external magnetic field to lift the electronic spin degeneracy, we explore the spin degree of freedom as a controllable qubit. Spin polarization is achieved using optical pumping, and a spin relaxation time in excess of 20 μ s is demonstrated. We report resonant microwave control of spin transitions, and use this as a probe to measure the Autler-Townes effect in a microwave-optical double-resonance experiment. Superposition spin states were prepared using coherent population trapping, and a pure dephasing time of about 19 ns was observed at a temperature of 2.0 K.

  10. Bright and photostable nitrogen-vacancy fluorescence from unprocessed detonation nanodiamond.

    Science.gov (United States)

    Reineck, P; Capelli, M; Lau, D W M; Jeske, J; Field, M R; Ohshima, T; Greentree, A D; Gibson, B C

    2017-01-05

    Bright and photostable fluorescence from nitrogen-vacancy (NV) centers is demonstrated in unprocessed detonation nanodiamond particle aggregates. The optical properties of these particles is analyzed using confocal fluorescence microscopy and spectroscopy, time resolved fluorescence decay measurements, and optically detected magnetic resonance experiments. Two particle populations with distinct optical properties are identified and compared to high-pressure high-temperature (HPHT) fluorescent nanodiamonds. We find that the brightness of one detonation nanodiamond particle population is on the same order as that of highly processed fluorescent 100 nm HPHT nanodiamonds. Our results may open the path to a simple and up-scalable route for the production of fluorescent NV nanodiamonds for use in bioimaging applications.

  11. An efficient fluorescent single-particle position tracking system for long-term pulsed measurements of nitrogen-vacancy centers in diamond

    Science.gov (United States)

    Kim, Kiho; Yun, Jiwon; Lee, Donghyuck; Kim, Dohun

    2018-02-01

    A simple and convenient design enables real-time three-dimensional position tracking of nitrogen-vacancy (NV) centers in diamond. The system consists entirely of commercially available components (a single-photon counter, a high-speed digital-to-analog converter, a phase-sensitive detector-based feedback device, and a piezo stage), eliminating the need for custom programming or rigorous optimization processes. With a large input range of counters and trackers combined with high sensitivity of single-photon counting, high-speed position tracking (upper bound recovery time of 0.9 s upon 250 nm of step-like positional shift) not only of bright ensembles, but also of low-photon-collection-efficiency single to few NV centers (down to 103 s-1) is possible. The tracking requires position modulation of only 10 nm, which allows simultaneous position tracking and pulsed measurements in the long term. Therefore, this tracking system enables measuring a single-spin magnetic resonance and Rabi oscillations at a very high resolution even without photon collection optimization. The system is widely applicable to various fields related to NV center quantum manipulation research such as NV optical trapping, NV tracking in fluid dynamics, and biological sensing using NV centers inside a biological cell.

  12. Effective implantation of light emitting centers by plasma immersion ion implantation and focused ion beam methods into nanosized diamond

    International Nuclear Information System (INIS)

    Himics, L.; Tóth, S.; Veres, M.; Tóth, A.; Koós, M.

    2015-01-01

    Highlights: • Characteristics of nitrogen implantation of nanodiamond using two low ion energy ion implantation methods were compared. • Formation of complex nitrogen-related defect centers was promoted by subsequent helium implantation and heat treatments. • Depth profiles of the implanted ions and the generated vacancies were determined using SRIM calculations. • The presence of nitrogen impurity was demonstrated by Fourier-transform infrared spectroscopic measurements. • A new nitrogen related band was detected in the photoluminescence spectrum of the implanted samples that was attributed to the N3 color center in nanodiamond. - Abstract: Two different implantation techniques, plasma immersion ion implantation and focused ion beam, were used to introduce nitrogen ions into detonation nanodiamond crystals with the aim to create nitrogen-vacancy related optically active centers of light emission in near UV region. Previously samples were subjected to a defect creation process by helium irradiation in both cases. Heat treatments at different temperatures (750 °C, 450 °C) were applied in order to initiate the formation of nitrogen-vacancy related complex centers and to decrease the sp 2 carbon content formed under different treatments. As a result, a relatively narrow and intensive emission band with fine structure at 2.98, 2.83 and 2.71 eV photon energies was observed in the light emission spectrum. It was assigned to the N3 complex defect center. The formation of this defect center can be expected by taking into account the relatively high dose of implanted nitrogen ions and the overlapped depth distribution of vacancies and nitrogen. The calculated depth profiles distribution for both implanted nitrogen and helium by SRIM simulation support this expectation

  13. Native and induced triplet nitrogen-vacancy centers in nano- and micro-diamonds: Half-field electron paramagnetic resonance fingerprint

    Energy Technology Data Exchange (ETDEWEB)

    Shames, A. I., E-mail: sham@bgu.ac.il [Department of Physics, Ben-Gurion University of the Negev, Be' er-Sheva 84105 (Israel); Osipov, V. Yu.; Vul’, A. Ya. [Ioffe Physical-Technical Institute, Polytechnicheskaya 26, 194021 St. Petersburg (Russian Federation); Bardeleben, H.-J. von [Institut des Nano Sciences de Paris-INSP, Université Pierre et Marie Curie/UMR 7588 au CNRS, 7500 Paris (France); Boudou, J.-P.; Treussart, F. [Laboratoire Aimé Cotton, CNRS, Université Paris-Sud and ENS Cachan, 91405 Orsay (France)

    2014-02-10

    Multiple frequency electron paramagnetic resonance (EPR) study of small (4–25 nm) nanodiamonds obtained by various dynamic synthesis techniques reveals systematic presence in the half-field (HF) region a distinctive doublet fingerprint consisting of resolved g{sub HF1} = 4.26 and g{sub HF2} = 4.00 signals. This feature is attributed to “forbidden” ΔM{sub S} = 2 transitions in EPR spectra of two native paramagnetic centers of triplet (S = 1) origin designated as TR1 and TR2, characterized by zero field splitting values D{sub 1} = 0.0950 ± 0.002 cm{sup −1} and D{sub 2} = 0.030 ± 0.005 cm{sup −1}. Nanodiamonds of ∼50 nm particle size, obtained by crushing of Ib type nitrogen rich synthetic diamonds, show only HF TR2 signal whereas the same sample undergone high energy (20 MeV) electron irradiation and thermal annealing demonstrates rise of HF TR1 signal. The same HF TR1 signals appear in the process of fabrication of fluorescent nanodiamonds from micron-size synthetic diamond precursors. Results obtained allow unambiguous attribution of the half-field TR1 EPR signals with g{sub HF1} = 4.26, observed in nano- and micron-diamond powders, to triplet negatively charged nitrogen-vacancy centers. These signals are proposed as reliable and convenient fingerprints in both qualitative and quantitative study of fluorescent nano- and micron-diamonds.

  14. Native and induced triplet nitrogen-vacancy centers in nano- and micro-diamonds: Half-field electron paramagnetic resonance fingerprint

    International Nuclear Information System (INIS)

    Shames, A. I.; Osipov, V. Yu.; Vul’, A. Ya.; Bardeleben, H.-J. von; Boudou, J.-P.; Treussart, F.

    2014-01-01

    Multiple frequency electron paramagnetic resonance (EPR) study of small (4–25 nm) nanodiamonds obtained by various dynamic synthesis techniques reveals systematic presence in the half-field (HF) region a distinctive doublet fingerprint consisting of resolved g HF1  = 4.26 and g HF2  = 4.00 signals. This feature is attributed to “forbidden” ΔM S  = 2 transitions in EPR spectra of two native paramagnetic centers of triplet (S = 1) origin designated as TR1 and TR2, characterized by zero field splitting values D 1  = 0.0950 ± 0.002 cm −1 and D 2  = 0.030 ± 0.005 cm −1 . Nanodiamonds of ∼50 nm particle size, obtained by crushing of Ib type nitrogen rich synthetic diamonds, show only HF TR2 signal whereas the same sample undergone high energy (20 MeV) electron irradiation and thermal annealing demonstrates rise of HF TR1 signal. The same HF TR1 signals appear in the process of fabrication of fluorescent nanodiamonds from micron-size synthetic diamond precursors. Results obtained allow unambiguous attribution of the half-field TR1 EPR signals with g HF1  = 4.26, observed in nano- and micron-diamond powders, to triplet negatively charged nitrogen-vacancy centers. These signals are proposed as reliable and convenient fingerprints in both qualitative and quantitative study of fluorescent nano- and micron-diamonds

  15. Marshak Lectureship: Vibrational properties of isolated color centers in diamond

    Science.gov (United States)

    Alkauskas, Audrius

    In this talk we review our recent work on first-principles calculations of vibrational properties of isolated defect spin qubits and single photon emitters in diamond. These properties include local vibrational spectra, luminescence lineshapes, and electron-phonon coupling. They are key in understanding physical mechanisms behind spin-selective optical initialization and read-out, quantum efficiency of single-photon emitters, as well as in the experimental identification of as yet unknown centers. We first present the methodology to calculate and analyze vibrational properties of effectively isolated defect centers. We then apply the methodology to the nitrogen-vacancy and the silicon-vacancy centers in diamond. First-principles calculations yield important new insights about these important defects. Work performed in collaboration with M. W. Doherty, A. Gali, E. Londero, L. Razinkovas, and C. G. Van de Walle. Supported by the Research Council of Lithuania (Grant M-ERA.NET-1/2015).

  16. Theoretical study of hyperfine interactions and optically detected magnetic resonance spectra by simulation of the C291[NV]-H172 diamond cluster hosting nitrogen-vacancy center

    International Nuclear Information System (INIS)

    Nizovtsev, A P; Ya Kilin, S; Pushkarchuk, A L; Pushkarchuk, V A; Jelezko, F

    2014-01-01

    Single nitrogen-vacancy (NV) centers in diamond coupled to neighboring nuclear spins are promising candidates for room-temperature applications in quantum information processing, quantum sensing and metrology. Here we report on a systematic density functional theory simulation of hyperfine coupling of the electronic spin of the NV center to individual 13 C nuclear spins arbitrarily disposed in the H-terminated C 291 [NV] - H 172 cluster hosting the NV center. For the ‘families’ of equivalent positions of the 13 C atom in diamond lattices around the NV center we calculated hyperfine characteristics. For the first time the data are given for a system where the 13 C atom is located on the NV center symmetry axis. Electron paramagnetic resonance transitions in the coupled electron–nuclear spin system 14 NV- 13 C are analyzed as a function of the external magnetic field. Previously reported experimental data from Dréau et al (2012 Phys. Rev. B 85 134107) are described using simulated hyperfine coupling parameters. (paper)

  17. Modulation of nitrogen vacancy charge state and fluorescence in nanodiamonds using electrochemical potential.

    Science.gov (United States)

    Karaveli, Sinan; Gaathon, Ophir; Wolcott, Abraham; Sakakibara, Reyu; Shemesh, Or A; Peterka, Darcy S; Boyden, Edward S; Owen, Jonathan S; Yuste, Rafael; Englund, Dirk

    2016-04-12

    The negatively charged nitrogen vacancy (NV(-)) center in diamond has attracted strong interest for a wide range of sensing and quantum information processing applications. To this end, recent work has focused on controlling the NV charge state, whose stability strongly depends on its electrostatic environment. Here, we demonstrate that the charge state and fluorescence dynamics of single NV centers in nanodiamonds with different surface terminations can be controlled by an externally applied potential difference in an electrochemical cell. The voltage dependence of the NV charge state can be used to stabilize the NV(-) state for spin-based sensing protocols and provides a method of charge state-dependent fluorescence sensing of electrochemical potentials. We detect clear NV fluorescence modulation for voltage changes down to 100 mV, with a single NV and down to 20 mV with multiple NV centers in a wide-field imaging mode. These results suggest that NV centers in nanodiamonds could enable parallel optical detection of biologically relevant electrochemical potentials.

  18. Modulation of nitrogen vacancy charge state and fluorescence in nanodiamonds using electrochemical potential

    Science.gov (United States)

    Karaveli, Sinan; Gaathon, Ophir; Wolcott, Abraham; Sakakibara, Reyu; Shemesh, Or A.; Peterka, Darcy S.; Boyden, Edward S.; Owen, Jonathan S.; Yuste, Rafael; Englund, Dirk

    2016-04-01

    The negatively charged nitrogen vacancy (NV-) center in diamond has attracted strong interest for a wide range of sensing and quantum information processing applications. To this end, recent work has focused on controlling the NV charge state, whose stability strongly depends on its electrostatic environment. Here, we demonstrate that the charge state and fluorescence dynamics of single NV centers in nanodiamonds with different surface terminations can be controlled by an externally applied potential difference in an electrochemical cell. The voltage dependence of the NV charge state can be used to stabilize the NV- state for spin-based sensing protocols and provides a method of charge state-dependent fluorescence sensing of electrochemical potentials. We detect clear NV fluorescence modulation for voltage changes down to 100 mV, with a single NV and down to 20 mV with multiple NV centers in a wide-field imaging mode. These results suggest that NV centers in nanodiamonds could enable parallel optical detection of biologically relevant electrochemical potentials.

  19. Wide-Field Imaging Using Nitrogen Vacancies

    Science.gov (United States)

    Englund, Dirk Robert (Inventor); Trusheim, Matthew Edwin (Inventor)

    2017-01-01

    Nitrogen vacancies in bulk diamonds and nanodiamonds can be used to sense temperature, pressure, electromagnetic fields, and pH. Unfortunately, conventional sensing techniques use gated detection and confocal imaging, limiting the measurement sensitivity and precluding wide-field imaging. Conversely, the present sensing techniques do not require gated detection or confocal imaging and can therefore be used to image temperature, pressure, electromagnetic fields, and pH over wide fields of view. In some cases, wide-field imaging supports spatial localization of the NVs to precisions at or below the diffraction limit. Moreover, the measurement range can extend over extremely wide dynamic range at very high sensitivity.

  20. Nanodiamond-based nanostructures for coupling nitrogen-vacancy centres to metal nanoparticles and semiconductor quantum dots.

    Science.gov (United States)

    Gong, Jianxiao; Steinsultz, Nat; Ouyang, Min

    2016-06-08

    The ability to control the interaction between nitrogen-vacancy centres in diamond and photonic and/or broadband plasmonic nanostructures is crucial for the development of solid-state quantum devices with optimum performance. However, existing methods typically employ top-down fabrication, which restrict scalable and feasible manipulation of nitrogen-vacancy centres. Here, we develop a general bottom-up approach to fabricate an emerging class of freestanding nanodiamond-based hybrid nanostructures with external functional units of either plasmonic nanoparticles or excitonic quantum dots. Precise control of the structural parameters (including size, composition, coverage and spacing of the external functional units) is achieved, representing a pre-requisite for exploring the underlying physics. Fine tuning of the emission characteristics through structural regulation is demonstrated by performing single-particle optical studies. This study opens a rich toolbox to tailor properties of quantum emitters, which can facilitate design guidelines for devices based on nitrogen-vacancy centres that use these freestanding hybrid nanostructures as building blocks.

  1. Contributed review: camera-limits for wide-field magnetic resonance imaging with a nitrogen-vacancy spin sensor

    DEFF Research Database (Denmark)

    Wojciechowski, Adam M.; Karadas, Mürsel; Huck, Alexander

    2018-01-01

    Sensitive, real-time optical magnetometry with nitrogen-vacancy centers in diamond relies on accurate imaging of small (≪10−2), fractional fluorescence changes across the diamond sample. We discuss the limitations on magnetic field sensitivity resulting from the limited number of photoelectrons t......-level sensitivity in 1 s of a combined exposure. Finally, we demonstrate the results obtained with a lock-in camera that paves the way for real-time, wide-field magnetometry at the nanotesla level and with a micrometer resolution....

  2. Amplified Sensitivity of Nitrogen-Vacancy Spins in Nanodiamonds Using All-Optical Charge Readout.

    Science.gov (United States)

    Hopper, David A; Grote, Richard R; Parks, Samuel M; Bassett, Lee C

    2018-04-23

    Nanodiamonds containing nitrogen-vacancy (NV) centers offer a versatile platform for sensing applications spanning from nanomagnetism to in vivo monitoring of cellular processes. In many cases, however, weak optical signals and poor contrast demand long acquisition times that prevent the measurement of environmental dynamics. Here, we demonstrate the ability to perform fast, high-contrast optical measurements of charge distributions in ensembles of NV centers in nanodiamonds and use the technique to improve the spin-readout signal-to-noise ratio through spin-to-charge conversion. A study of 38 nanodiamonds with sizes ranging between 20 and 70 nm, each hosting a small ensemble of NV centers, uncovers complex, multiple time scale dynamics due to radiative and nonradiative ionization and recombination processes. Nonetheless, the NV-containing nanodiamonds universally exhibit charge-dependent photoluminescence contrasts and the potential for enhanced spin readout using spin-to-charge conversion. We use the technique to speed up a T 1 relaxometry measurement by a factor of 5.

  3. On investigation of optical and spin properties of NV centers in aggregates of detonation nanodiamonds

    Science.gov (United States)

    Bolshedvorskii, S. V.; Vorobyov, V. V.; Soshenko, V. V.; Zeleneev, A.; Sorokin, V. N.; Smolyaninov, A. N.; Akimov, A. V.

    2018-02-01

    Quickly developing application of nitrogen-vacancy color centers in diamond sets demands on cheap and high optical and spin properties nanodiamonds. Among other types, detonation nanodiamonds are easiest for production but often show no NV color centers inside. In this work we show, that aggregates of detonation nanodiamonds could be as good, or even better in terms of brightness and spin properties, than more expensive single crystal nanodiamonds. This way aggregates of detonation nanodiamonds could efficiently serve as cheap and bright source of single photon radiation or sensitive element of biocompatible sensor.

  4. Formation of H a - hydrogen centers upon additive coloration of alkaline-earth fluoride crystals

    Science.gov (United States)

    Radzhabov, E. A.; Egranov, A. V.; Shendrik, R. Yu.

    2017-06-01

    The mechanism of coloration of alkaline-earth fluoride crystals CaF2, SrF2, and BaF2 in calcium vapors in an autoclave with a cold zone is studied. It was found that the pressure in the autoclave upon constant evacuation by a vacuum pump within the temperature range of 500-800°C increases due to evaporation of metal calcium. In addition to the optical-absorption bands of color centers in the additively colored undoped crystals or to the bands of divalent ions in the crystals doped with rare-earth Sm, Yb, and Tm elements, there appear intense bands in the vacuum ultraviolet region at 7.7, 7.0, and 6.025 eV in CaF2, SrF2, and BaF2, respectively. These bands belong to the Ha - hydrogen centers. The formation of hydrogen centers is also confirmed by the appearance of the EPR signal of interstitial hydrogen atoms after X-ray irradiation of the additively colored crystals. Grinding of the outer edges of the colored crystals leads to a decrease in the hydrogen absorption-band intensity with depth to complete disappearance. The rate of hydrogen penetration inside the crystal is lower than the corresponding rate of color centers (anion vacancies) by a factor of tens. The visible color density of the outer regions of the hydrogen-containing crystals is several times lower than that of the inner region due to the competition between the color centers and hydrogen centers.

  5. Detection of the ODMR signal of a nitrogen vacancy centre in nanodiamond in propagating surface plasmons

    Science.gov (United States)

    Al-Baiaty, Zahraa; Cumming, Benjamin P.; Gan, Xiaosong; Gu, Min

    2018-02-01

    We demonstrate that the optically detected magnetic resonance (ODMR) signal of a nitrogen vacancy (NV) centre can be coupled to propagating surface plasmons for the detection of the NV centre spin states, and of external magnetic fields. By coupling the spin dependent luminescence signal of a NV centre in a nanodiamond (ND) to a chemically synthesized silver nanowire, we demonstrate the readout of the ODMR signal as a reduction in the surface plasmon polariton intensity, with improved contrast in comparison to the emission from the NV centre. Furthermore, on the application of a permanent magnetic field from zero to 13 G, we demonstrate that the Zeeman splitting of the magnetic spin states of the nitrogen vacancy centre ground states can also be detected in the coupled surface plasmons. This is an important step in the development of a compact on-chip information processing system utilizing the nitrogen vacancy in nanodiamond as an on-chip source with efficient magnetometry sensing properties.

  6. Statistical inference with quantum measurements: methodologies for nitrogen vacancy centers in diamond

    Science.gov (United States)

    Hincks, Ian; Granade, Christopher; Cory, David G.

    2018-01-01

    The analysis of photon count data from the standard nitrogen vacancy (NV) measurement process is treated as a statistical inference problem. This has applications toward gaining better and more rigorous error bars for tasks such as parameter estimation (e.g. magnetometry), tomography, and randomized benchmarking. We start by providing a summary of the standard phenomenological model of the NV optical process in terms of Lindblad jump operators. This model is used to derive random variables describing emitted photons during measurement, to which finite visibility, dark counts, and imperfect state preparation are added. NV spin-state measurement is then stated as an abstract statistical inference problem consisting of an underlying biased coin obstructed by three Poisson rates. Relevant frequentist and Bayesian estimators are provided, discussed, and quantitatively compared. We show numerically that the risk of the maximum likelihood estimator is well approximated by the Cramér-Rao bound, for which we provide a simple formula. Of the estimators, we in particular promote the Bayes estimator, owing to its slightly better risk performance, and straightforward error propagation into more complex experiments. This is illustrated on experimental data, where quantum Hamiltonian learning is performed and cross-validated in a fully Bayesian setting, and compared to a more traditional weighted least squares fit.

  7. Color center annealing and ageing in electron and ion-irradiated yttria-stabilized zirconia

    International Nuclear Information System (INIS)

    Costantini, Jean-Marc; Beuneu, Francois

    2005-01-01

    We have used X-band electron paramagnetic resonance (EPR) measurements at room-temperature (RT) to study the thermal annealing and RT ageing of color centers induced in yttria-stabilized zirconia (YSZ), i.e. ZrO 2 :Y with 9.5 mol% Y 2 O 3 , by swift electron and ion-irradiations. YSZ single crystals with the orientation were irradiated with 2.5 MeV electrons, and implanted with 100 MeV 13 C ions. Electron and ion beams produce the same two color centers, namely an F + -type center (singly ionized oxygen vacancy) and the so-called T-center (Zr 3+ in a trigonal oxygen local environment) which is also produced by X-ray irradiations. Isochronal annealing was performed in air up to 973 K. For both electron and ion irradiations, the defect densities are plotted versus temperature or time at various fluences. The influence of a thermal treatment at 1373 K of the YSZ single crystals under vacuum prior to the irradiations was also investigated. In these reduced samples, color centers are found to be more stable than in as-received samples. Two kinds of recovery processes are observed depending on fluence and heat treatment

  8. Photonics and electronics for nitrogen vacancy control

    International Nuclear Information System (INIS)

    Shaun Ho

    2014-01-01

    Deterministic indistinguishable single photon sources are one of the key requirements for the realisation of Optical Quantum Computing. Recent low temperature experiments have shown the potential of the negatively charged nitrogen vacancy (NV-) centre as a source of indistinguishable photons. Furthermore its ground state spin structure with extensional decoherence time and spin dependent transitions means it can be harnessed as a spin-photon interface. However, development of these potential applications requires exquisite control of te electronic and spin states via Stark and Zeeman shifting, as well as enhanced photon collection through photonic structures. Here we present the integration of micro-fabricated solid immersion lenses with lithographically defined gold electrodes for control and spin manipulation. (author)

  9. Splitting of photoluminescent emission from nitrogen–vacancy centers in diamond induced by ion-damage-induced stress

    International Nuclear Information System (INIS)

    Olivero, P; Bosia, F; Fairchild, B A; Gibson, B C; Greentree, A D; Spizzirri, P; Prawer, S

    2013-01-01

    We report a systematic investigation on the spectral splitting of negatively charged, nitrogen–vacancy (NV − ) photoluminescent emission in single-crystal diamond induced by strain engineering. The stress fields arise from MeV ion-induced conversion of diamond to amorphous and graphitic material in regions proximal to the centers of interest. In low-nitrogen sectors of a high-pressure–high-temperature diamond, clearly distinguishable spectral components in the NV − emission develop over a range of ∼4.8 THz corresponding to distinct alignment of sub-ensembles which were mapped with micron spatial resolution. This method provides opportunities for the creation and selection of aligned NV − centers for ensemble quantum information protocols. (paper)

  10. Creation of nitrogen-vacancy centres in diamond with high resolution

    Energy Technology Data Exchange (ETDEWEB)

    Pezzagna, Sebastien; Meijer, Jan [Rubion, Ruhr-Universitaet Bochum (Germany); Wildanger, Dominik; Hell, Stefan W. [Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Goettingen (Germany); Mazarov, Paul; Wieck, Andreas D. [Lehrstuhl fuer Angewandte Festkoerperphysik, Ruhr-Universitaet Bochum (Germany); Naydenov, Boris; Jelezko, Fedor; Wrachtrup, Joerg [3. Institute of Physics, University of Stuttgart (Germany)

    2010-07-01

    Nowadays, diamond and the nitrogen-vacancy (NV) colour centres constitute the best solid-state system in view of quantum-computing applications. It has also been shown recently that single NV centres could be used as nanoscale magnetic sensors. Such applications require the creation of single NV centres with very high resolution and with a high efficiency. The nano-implanter at the university of Bochum provides low energy nitrogen ions which can be implanted through a hole pierced in the tip of an atomic force microscope. Ultrapure diamond samples have been implanted with spot sizes of 50nm and less. Stimulated Emission Depletion (STED) microscopy has been used to characterise and resolve the implanted spots.

  11. Fiber-Optic Magnetometry and Thermometry Using Optically Detected Magnetic Resonance With Nitrogen-Vacancy Centers in Diamond

    Science.gov (United States)

    Blakley, Sean Michael

    Nitrogen--vacancy diamond (NVD) quantum sensors are an emerging technology that has shown great promise in areas like high-resolution thermometry and magnetometry. Optical fibers provide attractive new application paradigms for NVD technology. A detailed description of the fabrication processes associated with the development of novel fiber-optic NVD probes are presented in this work. The demonstrated probes are tested on paradigmatic model systems designed to ascertain their suitability for use in challenging biological environments. Methods employing optically detected magnetic resonance (ODMR) are used to accurately measure and map temperature distributions of small objects and to demonstrate emergent temperature-dependent phenomena in genetically modified living organisms. These methods are also used to create detailed high resolution spatial maps of both magnetic scalar and magnetic vector field distributions of spatially localized weak field features in the presence of a noisy, high-field background.

  12. Photoluminescent properties of single crystal diamond microneedles

    Science.gov (United States)

    Malykhin, Sergey A.; Ismagilov, Rinat R.; Tuyakova, Feruza T.; Obraztsova, Ekaterina A.; Fedotov, Pavel V.; Ermakova, Anna; Siyushev, Petr; Katamadze, Konstantin G.; Jelezko, Fedor; Rakovich, Yury P.; Obraztsov, Alexander N.

    2018-01-01

    Single crystal needle-like diamonds shaped as rectangular pyramids were produced by combination of chemical vapor deposition and selective oxidation with dimensions and geometrical characteristics depending on the deposition process parameters. Photoluminescence spectra and their dependencies on wavelength of excitation radiation reveal presence of nitrogen- and silicon-vacancy color centers in the diamond crystallites. Photoluminescence spectra, intensity mapping, and fluorescence lifetime imaging microscopy indicate that silicon-vacancy centers are concentrated at the crystallites apex while nitrogen-vacancy centers are distributed over the whole crystallite. Dependence of the photoluminescence on excitation radiation intensity demonstrates saturation and allows estimation of the color centers density. The combination of structural parameters, geometry and photoluminescent characteristics are prospective for advantageous applications of these diamond crystallites in quantum information processing and optical sensing.

  13. Identification of nickel-vacancy defects by combining experimental and ab initio simulated photocurrent spectra

    Science.gov (United States)

    Londero, E.; Bourgeois, E.; Nesladek, M.; Gali, A.

    2018-06-01

    There is a continuous search for solid state spin qubits operating at room temperature with excitation in the infrared communication bandwidth. Recently, we have introduced the photoelectric detection of magnetic resonance (PDMR) to read the electron spin state of nitrogen-vacancy (NV) centers in diamond, a technique which is promising for applications in quantum information technology. By measuring the photoionization spectra on a diamond crystal, we found two ionization thresholds of unknown origin. On the same sample we also observed absorption and photoluminescence signatures that were identified in the literature as Ni-associated defects. We performed ab initio calculations of the photoionization cross section of the nickel split-vacancy complex (NiV) and N-related defects in their relevant charge states and fitted the concentration of these defects to the measured photocurrent spectrum, which led to a surprising match between experimental and calculated spectra. This study enabled us to identify the two unknown ionization thresholds with the two acceptor levels of NiV. Because the excitation of NiV is in the infrared, the photocurrent detected from the paramagnetic NiV color centers is a promising way towards the design of electrically readout qubits.

  14. Determination of the nitrogen vacancy as a shallow compensating center in GaN doped with divalent metals.

    Science.gov (United States)

    Buckeridge, J; Catlow, C R A; Scanlon, D O; Keal, T W; Sherwood, P; Miskufova, M; Walsh, A; Woodley, S M; Sokol, A A

    2015-01-09

    We report accurate energetics of defects introduced in GaN on doping with divalent metals, focusing on the technologically important case of Mg doping, using a model that takes into consideration both the effect of hole localization and dipolar polarization of the host material, and includes a well-defined reference level. Defect formation and ionization energies show that divalent dopants are counterbalanced in GaN by nitrogen vacancies and not by holes, which explains both the difficulty in achieving p-type conductivity in GaN and the associated major spectroscopic features, including the ubiquitous 3.46 eV photoluminescence line, a characteristic of all lightly divalent-metal-doped GaN materials that has also been shown to occur in pure GaN samples. Our results give a comprehensive explanation for the observed behavior of GaN doped with low concentrations of divalent metals in good agreement with relevant experiment.

  15. Determination of the Nitrogen Vacancy as a Shallow Compensating Center in GaN Doped with Divalent Metals

    Science.gov (United States)

    Buckeridge, J.; Catlow, C. R. A.; Scanlon, D. O.; Keal, T. W.; Sherwood, P.; Miskufova, M.; Walsh, A.; Woodley, S. M.; Sokol, A. A.

    2015-01-01

    We report accurate energetics of defects introduced in GaN on doping with divalent metals, focusing on the technologically important case of Mg doping, using a model that takes into consideration both the effect of hole localization and dipolar polarization of the host material, and includes a well-defined reference level. Defect formation and ionization energies show that divalent dopants are counterbalanced in GaN by nitrogen vacancies and not by holes, which explains both the difficulty in achieving p -type conductivity in GaN and the associated major spectroscopic features, including the ubiquitous 3.46 eV photoluminescence line, a characteristic of all lightly divalent-metal-doped GaN materials that has also been shown to occur in pure GaN samples. Our results give a comprehensive explanation for the observed behavior of GaN doped with low concentrations of divalent metals in good agreement with relevant experiment.

  16. Double vacancy on BN layer: A natural trap for Hydrogen Molecule

    International Nuclear Information System (INIS)

    Arellano, J S

    2015-01-01

    A pair of vacancies, one of boron and other of nitrogen atom at a flat layer becomes a natural trap to capture a hydrogen molecule at the center of the cavity defined by the empty space left by the lack of a nitrogen and a boron atom at the perfect BN layer formed by 16 N atoms and 16 B atoms. The adsorption of the hydrogen molecule is compared with the equivalent graphene layer with a pair of carbon vacancies. The little increase in the BN cell parameter respect to the graphene cell parameter, besides the differences between N, B and C atoms helps to explain the easier adsorption on the defective BN layer

  17. V color centers in electrolytically colored hydroxyl-doped sodium chloride crystals

    International Nuclear Information System (INIS)

    Gu Hongen; Song Cuiying; Han Li

    2006-01-01

    Hydroxyl-doped sodium chloride crystals were successfully colored electrolytically by using pointed anode and flat cathode at various temperatures and under various electric field strengths. V 2 and V 3 color centers were produced in the colored crystals. Current-time curves for the electrolytic colorations were given, and activation energy for the V 2 and V 3 color center migration was determined. Production of the V 2 and V 3 color centers and formation of current zones for the electrolytic colorations of the hydroxyl-doped sodium chloride crystals are explained

  18. Contributed Review: Camera-limits for wide-field magnetic resonance imaging with a nitrogen-vacancy spin sensor

    Science.gov (United States)

    Wojciechowski, Adam M.; Karadas, Mürsel; Huck, Alexander; Osterkamp, Christian; Jankuhn, Steffen; Meijer, Jan; Jelezko, Fedor; Andersen, Ulrik L.

    2018-03-01

    Sensitive, real-time optical magnetometry with nitrogen-vacancy centers in diamond relies on accurate imaging of small (≪10-2), fractional fluorescence changes across the diamond sample. We discuss the limitations on magnetic field sensitivity resulting from the limited number of photoelectrons that a camera can record in a given time. Several types of camera sensors are analyzed, and the smallest measurable magnetic field change is estimated for each type. We show that most common sensors are of a limited use in such applications, while certain highly specific cameras allow achieving nanotesla-level sensitivity in 1 s of a combined exposure. Finally, we demonstrate the results obtained with a lock-in camera that paves the way for real-time, wide-field magnetometry at the nanotesla level and with a micrometer resolution.

  19. Atom-Photon Coupling from Nitrogen-vacancy Centres Embedded in Tellurite Microspheres

    Science.gov (United States)

    Ruan, Yinlan; Gibson, Brant C.; Lau, Desmond W. M.; Greentree, Andrew D.; Ji, Hong; Ebendorff-Heidepriem, Heike; Johnson, Brett C.; Ohshima, Takeshi; Monro, Tanya M.

    2015-06-01

    We have developed a technique for creating high quality tellurite microspheres with embedded nanodiamonds (NDs) containing nitrogen-vacancy (NV) centres. This hybrid method allows fluorescence of the NVs in the NDs to be directly, rather than evanescently, coupled to the whispering gallery modes of the tellurite microspheres at room temperature. As a demonstration of its sensing potential, shifting of the resonance peaks is also demonstrated by coating a sphere surface with a liquid layer. This new approach is a robust way of creating cavities for use in quantum and sensing applications.

  20. The vacancy-interstitial model of DX centers

    International Nuclear Information System (INIS)

    Morgan, T.N.

    1989-01-01

    Recent DLTS (deep level transient spectroscopy) studies of 'DX' centers in dilute Al x Ga 1-x As alloys agree with a model of the deep neutral state in which the donor has moved into an adjacent interstitial site leaving behind a vacancy. The enthalpy and entropy of these states, which depend on the number (0 to 3) of Al atoms adjacent to the donors, have been obtained by fitting the data. This model, which also predicts the large potential barriers between the centered and relaxed states, thus accounting for PPC (persistent photoconductivity), is an extension to large displacement of the displaced donor model proposed earlier. It is equivalent to recent model of the EL2 metastable state based on displaced antisite double-donors. (author) 9 refs., 3 figs., 1 tab

  1. Continuous wave protocol for simultaneous polarization and optical detection of P1-center electron spin resonance

    Science.gov (United States)

    Kamp, E. J.; Carvajal, B.; Samarth, N.

    2018-01-01

    The ready optical detection and manipulation of bright nitrogen vacancy center spins in diamond plays a key role in contemporary quantum information science and quantum metrology. Other optically dark defects such as substitutional nitrogen atoms (`P1 centers') could also become potentially useful in this context if they could be as easily optically detected and manipulated. We develop a relatively straightforward continuous wave protocol that takes advantage of the dipolar coupling between nitrogen vacancy and P1 centers in type 1b diamond to detect and polarize the dark P1 spins. By combining mutual spin flip transitions with radio frequency driving, we demonstrate the simultaneous optical polarization and detection of the electron spin resonance of the P1 center. This technique should be applicable to detecting and manipulating a broad range of dark spin populations that couple to the nitrogen vacancy center via dipolar fields, allowing for quantum metrology using these spin populations.

  2. Excitation of nanowire surface plasmons by silicon vacancy centers in nanodiamonds

    DEFF Research Database (Denmark)

    Kumar, Shailesh; Davydov, Valery A.; Agafonov, Viatcheslav N.

    2017-01-01

    Silicon vacancy (SiV) centers in diamonds have emerged as a very promising candidate for quantum emitters due to their narrow emission line resulting in their indistinguishability. While many different quantum emitters have already been used for the excitation of various propagating plasmonic modes......, the corresponding exploitation of SiV centers has remained so far uncharted territory. Here, we report on the excitation of surface plasmon modes supported by silver nanowires using SiV centers in nanodiamonds. The coupling of SiV center fluorescence to surface plasmons is observed, when a nanodiamond situated...

  3. Charged dopants in neutral supercells through substitutional donor (acceptor): nitrogen donor charging of the nitrogen-vacancy center in diamond

    Science.gov (United States)

    Löfgren, Robin; Pawar, Ravinder; Öberg, Sven; Larsson, J. Andreas

    2018-02-01

    Charged defects are traditionally computed by adding (subtracting) electrons for negative (positive) impurities. When using periodic boundary conditions this results in artificially charged supercells that also require a compensating background charge of the opposite sign, which makes slab supercells problematic because of an arbitrary dependence on the vacuum thickness. In this work, we test the method of using neutral supercells through the use of a substitutional electron donor (acceptor) to describe charged systems. We use density functional theory (DFT) to compare the effects of charging the well-studied NV-center in diamond by a substitutional donor nitrogen. We investigate the influence of the donor-N on the NV-center properties as a function of the distance between them, and find that they converge toward those obtained when adding an electron. We analyze the spin density and conclude that the donor-N has a zero magnetic moment, and thus, will not be seen in electron spin resonance. We validate our DFT energies through comparison to GW simulations. Charging the NV-center with a substitutional donor-N enables accurate calculations of slabs, without the ambiguity of using charged supercells. Implantation of donor-N atoms opens up the possibility to engineer NV-centers with the desired charge state for future ICT and sensor applications.

  4. Silicon vacancy-related centers in non-irradiated 6H-SiC nanostructur

    Czech Academy of Sciences Publication Activity Database

    Bagraev, N.T.; Danilovskii, E.Yu.; Gets, D.S.; Kalabukhova, E.N.; Klyachkin, L.E.; Koudryavtsev, A.A.; Malyarenko, A.M.; Mashkov, V.A.; Savchenko, Dariia; Shanina, B.D.

    2015-01-01

    Roč. 49, č. 5 (2015), 649-657 ISSN 1063-7826 R&D Projects: GA ČR GP13-06697P; GA MŠk(CZ) LM2011029 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : electron spin resonance * 6H-SiC nanostructures * silicon vacancy related centers * NV centers Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.701, year: 2015

  5. Identification and tunable optical coherent control of transition-metal spins in silicon carbide

    NARCIS (Netherlands)

    Bosma, Tom; Lof, Gerrit J. J.; Gilardoni, Carmem M.; Zwier, Olger V.; Hendriks, Freddie; Ellison, Alexandre; Magnusson, Björn; Gällström, Andreas; Ivanov, Ivan G.; Son, N. T.; Havenith, Remco W. A.; Wal, Caspar H. van der

    2018-01-01

    Color centers in wide-bandgap semiconductors are attractive systems for quantum technologies since they can combine long-coherent electronic spin and bright optical properties. Several suitable centers have been identified, most famously the nitrogen-vacancy defect in diamond. However, integration

  6. Feasibility and resolution limits of opto-magnetic imaging of neural network activity in brain slices using color centers in diamond

    DEFF Research Database (Denmark)

    Karadas, Mürsel; Wojciechowski, Adam M.; Huck, Alexander

    2018-01-01

    We suggest a novel approach for wide-field imaging of the neural network dynamics of brain slices that uses highly sensitivity magnetometry based on nitrogen-vacancy (NV) centers in diamond. Invitro recordings in brain slices is a proven method for the characterization of electrical neural activi...... cell. Our results suggest that imaging of slice activity will be possible with the upcoming generation of NV magnetic field sensors, while single-shot imaging of planar cell activity remains challenging....

  7. Shape and crystallographic orientation of nanodiamonds for quantum sensing

    NARCIS (Netherlands)

    Ong, S. Y.; Chipaux, M.; Nagl, A.; Schirhagl, R.

    2017-01-01

    Nanodiamonds with dimensions down to a few tens of nanometers containing nitrogen-vacancy (NV) color centers have revealed their potential as powerful and versatile quantum sensors with a unique combination of spatial resolution and sensitivity. The NV centers allow transducing physical properties,

  8. Photoluminescence excitation spectroscopy of SiV- and GeV- color center in diamond

    Science.gov (United States)

    Häußler, Stefan; Thiering, Gergő; Dietrich, Andreas; Waasem, Niklas; Teraji, Tokuyuki; Isoya, Junichi; Iwasaki, Takayuki; Hatano, Mutsuko; Jelezko, Fedor; Gali, Adam; Kubanek, Alexander

    2017-06-01

    Color centers in diamond are important quantum emitters for a broad range of applications ranging from quantum sensing to quantum optics. Understanding the internal energy level structure is of fundamental importance for future applications. We experimentally investigate the level structure of an ensemble of few negatively charged silicon-vacancy (SiV-) and germanium-vacancy (GeV-) centers in bulk diamond at room temperature by photoluminescence (PL) and excitation (PLE) spectroscopy over a broad wavelength range from 460 to 650 {nm} and perform power-dependent saturation measurements. For SiV- our experimental results confirm the presence of a higher energy transition at ˜ 2.31 {eV}. By comparison with detailed theoretical simulations of the imaginary dielectric function we interpret the transition as a dipole-allowed transition from {}2{E}g-state to {}2{A}2u-state where the corresponding a 2u -level lies deeply inside the diamond valence band. Therefore, the transition is broadened by the diamond band. At higher excitation power of 10 {mW} we indicate signs of a parity-conserving transition at ˜ 2.03 {eV} supported by saturation measurements. For GeV- we demonstrate that the PLE spectrum is in good agreement with the mirror image of the PL spectrum of the zero-phonon line. Experimentally we do not observe a higher lying energy level up to a transition wavelength of 460 {nm}. The observed PL spectra are identical, independent of excitation wavelength, suggesting a rapid decay to {}2{E}u excited state and followed by optical transition to {}2{E}g ground state. Our investigations convey important insights for future quantum optics and quantum sensing experiments based on SiV--center and GeV--center in diamond.

  9. Nitrogen vacancies as a common element of the green luminescence and nonradiative recombination centers in Mg-implanted GaN layers formed on a GaN substrate

    Science.gov (United States)

    Kojima, Kazunobu; Takashima, Shinya; Edo, Masaharu; Ueno, Katsunori; Shimizu, Mitsuaki; Takahashi, Tokio; Ishibashi, Shoji; Uedono, Akira; Chichibu, Shigefusa F.

    2017-06-01

    The photoluminescences of ion-implanted (I/I) and epitaxial Mg-doped GaN (GaN:Mg) are compared. The intensities and lifetimes of the near-band-edge and ultraviolet luminescences associated with a MgGa acceptor of I/I GaN:Mg were significantly lower and shorter than those of the epilayers, respectively. Simultaneously, the green luminescence (GL) became dominant. These emissions were quenched far below room temperature. The results indicate the generation of point defects common to GL and nonradiative recombination centers (NRCs) by I/I. Taking the results of positron annihilation measurement into account, N vacancies are the prime candidate to emit GL and create NRCs with Ga vacancies, (VGa) m (VN) n , as well as to inhibit p-type conductivity.

  10. Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles

    DEFF Research Database (Denmark)

    El-Ella, Haitham; Ahmadi, Sepehr; Wojciechowski, Adam

    2017-01-01

    transitions, we experimentally show that when the ratio between the hyperfine linewidth and their separation is ≥ 1=4, square-wave based frequency modulation generates the steepest slope at modulation depths exceeding the separation of the hyperfine lines, compared to sine-wave based modulation. We formulate......Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional...... to the derivative of the optical magnetic resonance lock-in spectrum, which is in turn dependant on the lock-in modulation parameters. Here we study the dependence of the lock-in spectral slope on the modulation of the spin-driving microwave field. Given the presence of the intrinsic nitrogen hyperfine spin...

  11. Dynamical nuclear polarization using multi-colour control of color centers in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Pengcheng [Huazhong University of Science and Technology, School of Physics, Wuhan (China); Huazhong University of Science and Technology, Center for Quantum Optical Science, Wuhan (China); Plenio, Martin B. [Universitaet Ulm, Institut fuer Theoretische Physik, Ulm (Germany); Universitaet Ulm, Center for Integrated Quantum Science and Technology, Ulm (Germany); Cai, Jianming [Huazhong University of Science and Technology, School of Physics, Wuhan (China); Huazhong University of Science and Technology, Center for Quantum Optical Science, Wuhan (China); Universitaet Ulm, Institut fuer Theoretische Physik, Ulm (Germany); Universitaet Ulm, Center for Integrated Quantum Science and Technology, Ulm (Germany)

    2016-12-15

    Dynamical nuclear polarization (DNP) transfers the polarization of electron spins at cryogenic temperatures to achieve strong nuclear polarization for applications in nuclear magnetic resonance. Recently introduced approaches employ optical pumping of nitrogen-vacancy (NV) centers in diamond to achieve DNP even at ambient temperatures. In such schemes microwave radiation is used to establish a Hartmann-Hahn condition between the NV electron spin and proximal nuclear spins to facilitate polarization transfer. For a single monochromatic microwave driving field, the Hartmann-Hahn condition cannot be satisfied for an ensemble of NV centers due to inhomogeneous broadening and reduces significantly the overall efficiency of dynamical nuclear polarization using an ensemble of NV centers. Here, we adopt generalized Hartmann-Hahn type dynamical nuclear polarization schemes by applying microwave driving fields with (multiple) time-modulated frequencies. We show that it is possible to enhance the effective coupling between an ensemble of NV center spins with inhomogeneous broadening and nuclear spins, thereby improving significantly the overall efficiency of dynamical nuclear polarization. This approach can also be used to achieve dynamical nuclear polarization of an ensemble of nuclei with a distribution of Larmor frequencies, which would be helpful in magnetic resonance spectroscopy using a single NV spin sensor. (orig.)

  12. Excited-state lifetime measurement of silicon vacancy centers in diamond by single-photon frequency upconversion

    Science.gov (United States)

    Rong, Youying; Ma, Jianhui; Chen, Lingxiao; Liu, Yan; Siyushev, Petr; Wu, Botao; Pan, Haifeng; Jelezko, Fedor; Wu, E.; Zeng, Heping

    2018-05-01

    We report a method with high time resolution to measure the excited-state lifetime of silicon vacancy centers in bulk diamond avoiding timing jitter from the single-photon detectors. Frequency upconversion of the fluorescence emitted from silicon vacancy centers was achieved from 738 nm to 436 nm via sum frequency generation with a short pump pulse. The excited-state lifetime can be obtained by measuring the intensity of upconverted light while the pump delay changes. As a probe, a pump laser with pulse duration of 11 ps provided a high temporal resolution of the measurement. The lifetime extracted from the pump–probe curve was 0.755 ns, which was comparable to the timing jitter of the single-photon detectors.

  13. First-principles study on the interaction of nitrogen atom with α–uranium: From surface adsorption to bulk diffusion

    International Nuclear Information System (INIS)

    Su, Qiulei; Deng, Huiqiu; Xiao, Shifang; Li, Xiaofan; Hu, Wangyu; Ao, Bingyun; Chen, Piheng

    2014-01-01

    Experimental studies of nitriding on uranium surfaces show that the modified layers provide considerable protection against air corrosion. The bimodal distribution of nitrogen is affected by both its implantation and diffusion, and the diffusion of nitrogen during implantation is also governed by vacancy trapping. In the present paper, nitrogen adsorption, absorption, diffusion, and vacancy trapping on the surface of and in the bulk of α–uranium are studied with a first-principles density functional theory approach and the climbing image nudged elastic band method. The calculated results indicate that, regardless of the nitrogen coverage, a nitrogen atom prefers to reside at the hollow1 site and octahedral (Oct) site on and below the surface, respectively. The lowest energy barriers for on-surface and penetration diffusion occur at a coverage of 1/2 monolayer. A nitrogen atom prefers to occupy the Oct site in bulk α–uranium. High energy barriers are observed during the diffusion between neighboring Oct sites. A vacancy can capture its nearby interstitial nitrogen atom with a low energy barrier, providing a significant attractive nitrogen-vacancy interaction at the trapping center site. This study provides a reference for understanding the nitriding process on uranium surfaces

  14. Nanodiamonds with silicon vacancy defects for nontoxic photostable fluorescent labeling of neural precursor cells.

    Science.gov (United States)

    Merson, Tobias D; Castelletto, Stefania; Aharonovich, Igor; Turbic, Alisa; Kilpatrick, Trevor J; Turnley, Ann M

    2013-10-15

    Nanodiamonds (NDs) containing silicon vacancy (SiV) defects were evaluated as a potential biomarker for the labeling and fluorescent imaging of neural precursor cells (NPCs). SiV-containing NDs were synthesized using chemical vapor deposition and silicon ion implantation. Spectrally, SiV-containing NDs exhibited extremely stable fluorescence and narrow bandwidth emission with an excellent signal to noise ratio exceeding that of NDs containing nitrogen-vacancy centers. NPCs labeled with NDs exhibited normal cell viability and proliferative properties consistent with biocompatibility. We conclude that SiV-containing NDs are a promising biomedical research tool for cellular labeling and optical imaging in stem cell research.

  15. Radiation color and electron-hole centers of serpentines

    International Nuclear Information System (INIS)

    Lyutoev, V.P.; Yukhtanov, P.P.

    1999-01-01

    Radiation-induced coloring of serpentine (Mg 3 [Si 2 O 5 ](OH) 4 ), gamma radiation dose being 30 Mrad, is studied by the ESR and absorption spectroscopy methods. It is ascertained that ionizing radiation gives rise to formation of radiation centers on the mineral basic structural elements. paramagnetic centers and coloring centers, relating to radiation centers, stem from the same type of defects - O - oxygen centers, formed as a result of radiation-induced break of OH-bonds [ru

  16. Radiation Induced Color Centers in a La Doped PWO Crystal

    CERN Document Server

    Deng, Qun

    1998-01-01

    This report presents result of a study on radiation induced color center densities in a La doped lead tungstate ( PWO) crystal. The creation and annihilation constants of radiation induced color centers were determined by using transmittance data measured for a PWO sample before and during Co-60 gamma ray irradiation at a dose rate of 15 rad/hr. Following a model of color center kinetics, these constants were used to calculate color center densities under irradiations at 100 rad/hr. The result was found to be in a good agreement with experimental data, indicating that this model of color center kinetics can be used to predict behavior of PWO crystals under irradiation.

  17. Quantifying the number of color centers in single fluorescent nanodiamonds by photon correlation spectroscopy and Monte Carlo simulation

    International Nuclear Information System (INIS)

    Hui, Y.Y.; Chang, Y.-R.; Lee, H.-Y.; Chang, H.-C.; Lim, T.-S.; Fann Wunshain

    2009-01-01

    The number of negatively charged nitrogen-vacancy centers (N-V) - in fluorescent nanodiamond (FND) has been determined by photon correlation spectroscopy and Monte Carlo simulations at the single particle level. By taking account of the random dipole orientation of the multiple (N-V) - fluorophores and simulating the probability distribution of their effective numbers (N e ), we found that the actual number (N a ) of the fluorophores is in linear correlation with N e , with correction factors of 1.8 and 1.2 in measurements using linearly and circularly polarized lights, respectively. We determined N a =8±1 for 28 nm FND particles prepared by 3 MeV proton irradiation

  18. Semiconductor color-center structure and excitation spectra: Equation-of-motion coupled-cluster description of vacancy and transition-metal defect photoluminescence

    Science.gov (United States)

    Lutz, Jesse J.; Duan, Xiaofeng F.; Burggraf, Larry W.

    2018-03-01

    Valence excitation spectra are computed for deep-center silicon-vacancy defects in 3C, 4H, and 6H silicon carbide (SiC), and comparisons are made with literature photoluminescence measurements. Optimizations of nuclear geometries surrounding the defect centers are performed within a Gaussian basis-set framework using many-body perturbation theory or density functional theory (DFT) methods, with computational expenses minimized by a QM/MM technique called SIMOMM. Vertical excitation energies are subsequently obtained by applying excitation-energy, electron-attached, and ionized equation-of-motion coupled-cluster (EOMCC) methods, where appropriate, as well as time-dependent (TD) DFT, to small models including only a few atoms adjacent to the defect center. We consider the relative quality of various EOMCC and TD-DFT methods for (i) energy-ordering potential ground states differing incrementally in charge and multiplicity, (ii) accurately reproducing experimentally measured photoluminescence peaks, and (iii) energy-ordering defects of different types occurring within a given polytype. The extensibility of this approach to transition-metal defects is also tested by applying it to silicon-substituted chromium defects in SiC and comparing with measurements. It is demonstrated that, when used in conjunction with SIMOMM-optimized geometries, EOMCC-based methods can provide a reliable prediction of the ground-state charge and multiplicity, while also giving a quantitative description of the photoluminescence spectra, accurate to within 0.1 eV of measurement for all cases considered.

  19. Diamond nanophotonics

    Directory of Open Access Journals (Sweden)

    Katja Beha

    2012-12-01

    Full Text Available We demonstrate the coupling of single color centers in diamond to plasmonic and dielectric photonic structures to realize novel nanophotonic devices. Nanometer spatial control in the creation of single color centers in diamond is achieved by implantation of nitrogen atoms through high-aspect-ratio channels in a mica mask. Enhanced broadband single-photon emission is demonstrated by coupling nitrogen–vacancy centers to plasmonic resonators, such as metallic nanoantennas. Improved photon-collection efficiency and directed emission is demonstrated by solid immersion lenses and micropillar cavities. Thereafter, the coupling of diamond nanocrystals to the guided modes of micropillar resonators is discussed along with experimental results. Finally, we present a gas-phase-doping approach to incorporate color centers based on nickel and tungsten, in situ into diamond using microwave-plasma-enhanced chemical vapor deposition. The fabrication of silicon–vacancy centers in nanodiamonds by microwave-plasma-enhanced chemical vapor deposition is discussed in addition.

  20. Synergistic effect of oxygen vacancy and nitrogen doping on enhancing the photocatalytic activity of Bi{sub 2}O{sub 2}CO{sub 3} nanosheets with exposed {0 0 1} facets for the degradation of organic pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yafei [School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062 (China); Zhu, Gangqiang, E-mail: zgq2006@snnu.edu.cn [School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062 (China); Hojamberdiev, Mirabbos [School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062 (China); Department of Natural and Mathematic Sciences, Turin Polytechnic University in Tashkent, Kichik Halqa Yo’li 17, Tashkent 100095 (Uzbekistan); Gao, Jianzhi [School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062 (China); Hao, Jing [Xi' an Rejee Industry Development Co., Ltd., Xi’an 710016 (China); Zhou, Jianping; Liu, Peng [School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062 (China)

    2016-05-15

    Highlights: • Nitrogen-doped Bi{sub 2}O{sub 2}CO{sub 3} flower-like microstructures were synthesized by hydrothermal method. • Surface oxygen vacancy were obtained by irradiating the nitrogen-doped Bi{sub 2}O{sub 2}CO{sub 3} with UV light. • Photocatalytic activity was studied by degrading Rhodamine B. • A synergistic effect between oxygen vacancy and nitrogen doping in Bi{sub 2}O{sub 2}CO{sub 3}. - Abstract: Single-crystalline bare Bi{sub 2}O{sub 2}CO{sub 3} (BOC) nanosheets with exposed {0 0 1} facets and nitrogen-doped Bi{sub 2}O{sub 2}CO{sub 3} (NBOC) flower-like microstructures were synthesized by a simple hydrothermal method. The nitrogen-doped Bi{sub 2}O{sub 2}CO{sub 3} flower-like microstructures with oxygen vacancy (UV-NBOC) were obtained by irradiating the NBOC microstructures with UV light for 2 h in ethanol. The UV–vis diffuse reflectance spectra showed that the NBOC and UV-NBOC nanosheets exhibit an obvious red shift in light absorption band compared with the pure BOC nanosheets. Rhodamine B (RhB) was chosen as a model organic pollutant to verify the influence of oxygen vacancy and nitrogen doping on the photocatalytic activity of Bi{sub 2}O{sub 2}CO{sub 3} under simulated solar light irradiation. Judging from the kinetics of RhB photodegradation over the synthesized samples, a synergistic effect between oxygen vacancy and nitrogen doping was found with a remarkable increase (more than 10 and 2 times) in the photocatalytic activity of UV-NBOC compared with BOC and NBOC, respectively. Moreover, the UV-NBOC also exhibited an excellent cyclability and superior photocatalytic activity toward degradation of other organic pollutants (methylene blue, Congo red, Bisphenol A) under simulated solar light irradiation.

  1. Oxygen vacancy rich Cu2O based composite material with nitrogen doped carbon as matrix for photocatalytic H2 production and organic pollutant removal.

    Science.gov (United States)

    Lu, Lele; Xu, Xinxin; Yan, Jiaming; Shi, Fa-Nian; Huo, Yuqiu

    2018-02-06

    A nitrogen doped carbon matrix supported Cu 2 O composite material (Cu/Cu2O@NC) was fabricated successfully with a coordination polymer as precursor through calcination. In this composite material, Cu 2 O particles with a size of about 6-10 nm were dispersed evenly in the nitrogen doped carbon matrix. After calcination, some coordinated nitrogen atoms were doped in the lattice of Cu 2 O and replace oxygen atoms, thus generating a large number of oxygen vacancies. In Cu/Cu2O@NC, the existence of oxygen vacancies has been confirmed by electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS). Under visible light irradiation, Cu/Cu2O@NC exhibits excellent H 2 production with the rate of 379.6 μmol h -1 g -1 . Its photocatalytic activity affects organic dyes, such as Rhodamine B (RhB) and methyl orange (MO). In addition to photocatalysis, Cu/Cu2O@NC also exhibits striking catalytic activity in reductive conversion of 4-nitrophenol to 4-aminophenol with in presence of sodium borohydride (NaBH 4 ). The conversion efficiency reaches almost 100% in 250 s with the quantity of Cu/Cu2O@NC as low as 5 mg. The outstanding H 2 production and organic pollutants removal are attributed to the oxygen vacancy. We expect that Cu/Cu2O@NC will find its way as a new resource for hydrogen energy as well as a promising material in water purification.

  2. Photoluminescence related to Gd3+:N-vacancy complex in GaN:Gd multi-quantum wells

    International Nuclear Information System (INIS)

    Almokhtar, Mohamed; Emura, Shuichi; Koide, Akihiro; Fujikawa, Takashi; Asahi, Hajime

    2015-01-01

    Highlights: • We grew Gd-doped GaN multi-quantum wells (MQWs) with quantum layer thickness of one nm by MBE. • The X-ray absorption near edge structure spectra observed at Gd LIII-edge indicate a nitrogen vacancy adjacent to Gd substituting the Ga ion in Gd-doped GaN MQW. • The photoluminescence of the samples is discussed considering the formation of a Gd 3+ :Nitrogen-vacancy complex. • A model is presented considering exciton-polaron formation trapped in defect sites around the Gd 3+ :N-vacancy complex in Gd-doped GaN MQWs. - Abstract: The photoluminescence of Gd-doped GaN multi-quantum wells (MQWs) is presented and discussed considering the formation of a Gd 3+ :Nitrogen-vacancy (N-vacancy) complex. A lower energy photoluminescence peak was observed for the Gd-doped GaN MQW sample with respect to the main peak assigned to a neutral donor bound exciton (D 0 X) of the undoped GaN MQW sample. The X-ray absorption near edge structure spectrum observed at Gd L III -edge indicates a nitrogen vacancy adjacent to the Gd substituting the Ga ion in Gd-doped GaN MQW sample. Local stresses around the Gd dopants in Gd-doped GaN matrix generated due to the larger diameter of the Gd 3+ ion with respect to the Ga 3+ ion can be relieved by the creation of vacancies. The lower formation energy of N-vacancies in GaN matrix introduce them as a preferred candidate to relieve the generated stresses. A Gd 3+ :N-vacancy complex consisting of a Gd 3+ ion and the created nitrogen vacancy adjacent to the Gd 3+ dopant is likely to form in GaN:Gd matrix. The lower photoluminescence peak energy observed in the Gd-doped GaN MQW sample is assigned to the recombination of an exciton captured at the Gd 3+ :N-vacancy complex forming a small polaron-like state. A model is presented considering the small exciton-polaron population in defect sites captured around the Gd 3+ ions in the Gd-doped GaN

  3. All-Optical Nanoscale Thermometry using Silicon-Vacancy Centers in Diamond

    Science.gov (United States)

    Nguyen, Christian; Evans, Ruffin; Sipahigil, Alp; Bhaskar, Mihir; Sukachev, Denis; Lukin, Mikhail

    2017-04-01

    Accurate thermometry at the nanoscale is a difficult challenge, but building such a thermometer would be a powerful tool for discovering and understanding new processes in biology, chemistry and physics. Applications include cell-selective treatment of disease, engineering of more efficient integrated circuits, or even the development of new chemical and biological reactions. In this work, we study how the bulk properties of the Silicon Vacancy center (SiV) in diamond depend on temperature, and use them to measure temperature with 100mK accuracy. Using SiVs in 200 nm nanodiamonds, we measure the temperature with 100 nm spatial resolution over a 10 μm area.

  4. Identification and quantification of oxygen vacancies in CeO{sub 2} nanocrystals and their role in formation of F-centers

    Energy Technology Data Exchange (ETDEWEB)

    Jaffari, G.Hassnain, E-mail: hassnain@qau.edu.pk [Department of Physics, Quaid-i-Azam University Islamabad (Pakistan); Imran, Ali [Department of Physics, Quaid-i-Azam University Islamabad (Pakistan); Bah, M. [Department of Materials Science and Engineering, University of Delaware, 19716, Newark, DE (United States); Ali, Awais; Bhatti, Arshad S. [Centre for Micro and Nano Devices, Department of Physics, COMSATS Institute of Information Technology, Park Road, Islamabad, 44000 (Pakistan); Qurashi, Umar Saeed [Department of Physics, Quaid-i-Azam University Islamabad (Pakistan); Ismat Shah, S. [Department of Materials Science and Engineering, University of Delaware, 19716, Newark, DE (United States); Department of Physics, University of Delaware, 19716, Newark, DE (United States)

    2017-02-28

    Highlights: • Detail crystal and electronic structural analysis was employed to quantify oxygen vacancies. • The Raman F{sub 2g} mode shifted towards lower wave number, exhibiting mode softening with broader and asymmetric peak. • Observation of absorption edge revealed presence of 4f band within the band gap. • PL emission studies revealed presence of F-centers with corresponding energy level located below 4f band. • Transitions associated by the F-center are mainly associated with 4f{sup 0} to 4f{sup 1}, F{sup ++} to 4f{sup 1} and 4f{sup 0} to F{sup +}. - Abstract: In this work we present synthesis and extensive characterization of Cerium oxide (CeO{sub 2}) nanocrystals. Comparison between the properties of as-prepared and air annealed nanoparticles has been carried out, with a goal to clearly identify the effect of oxygen vacancies on crystal, electronic and band structure. Detail crystal and electronic structural analysis was employed to quantify oxygen vacancies. Structural analysis confirmed that the formation of single phase cubic Fluorite structure for both as-prepared and annealed samples. Crystal and electronic structural studies confirmed that Ce ions exists in two oxidation states, Ce{sup +3} and Ce{sup +4}. Concentration of oxygen vacancies was larger in as-synthesis nanocrystal. A drastic decrease in oxygen vacancy concentration was observed for the sample annealed in air at 550 °C. For the as-prepared sample, the Raman allowed F{sub 2g} mode shifted towards lower wavenumber, exhibiting mode softening with broader and asymmetric peak. Observation of absorption edge revealed presence of 4f band within the band gap. Absorption with different band edge, confirmed different energy position of 4f level for the sample possessing oxygen vacancies. Blue shift of the band edge for as-prepared sample has been discussed in terms of increase in lattice parameter, formation of Ce{sup +3} ions, quantum confinement effect etc. Photoluminescence emission

  5. Color center formation in plutonium electrorefining residues

    International Nuclear Information System (INIS)

    Morris, D.E.; Eller, P.G.; Hobart, D.E.; Eastman, M.P.; McCurry, L.E.

    1989-01-01

    Plutonium electrorefining residues containing Pu(III) in KCl exhibit dramatic reversible, light-induced color changes. Similar color changes were observed in Ln-doped (Ln = La, Nd, Gd, and Lu) and undoped KCl samples which were subjected to intense gamma irradiation. Diffuse reflectance electronic and electron paramagnetic resonance spectroscopies were used to show conclusively that Pu(III) is present in both the bleached and unbleached plutonium-bearing residues and the spectacular color changes are the result of color center formation and alternation by visible light. (orig.)

  6. Study of Tl0(1) and In0(1) defects in alkaline halides: prototype of a color center as active laser medium

    International Nuclear Information System (INIS)

    Vieira Junior, N.D.

    1986-01-01

    The optical properties of the Tl 0 (1) and In 0 (1) centers in Kcl crystals in cation sites of the crystal lattice, perturbed by an adjacent anion vacancy. Emphasis is given to the lowest energy levels. Using a tagging optical absorption technique, the absorption bands were identified. The laser action of Tl 0 (1) center in KCl by pumping with Nd: YAG laser in the lowest energy absorption band was obtained. A simple way to achieve continuous single frequency laser operation using a grating as the sole tuning element is described. It is shown that, by proper choice of cavity parameters, the competing hole burning modes can be completely supressed. Experiments were carried out using Tl 0 (1) centers in KCl as the gain medium. The production of pulses via synchronous pumping of Tl 0 (1) color center in KCl are reported. (author) [pt

  7. Effect of pond depth and lining plastic color on growth and nitrogen ...

    African Journals Online (AJOL)

    Thus, this study evaluated the effect of pond depth and lining plastic colors on nitrogen fixing capacity of Anabaena species strain E3. Factorial combinations of four pond lining plastic colors and two depths were laid out in a complete randomized design with three replications. The ANOVA results revealed that the 20 cm ...

  8. The negatively charged nitrogen-vacancy centre in diamond: the electronic solution

    International Nuclear Information System (INIS)

    Doherty, M W; Hollenberg, L C L; Manson, N B; Delaney, P

    2011-01-01

    The negatively charged nitrogen-vacancy centre is a unique defect in diamond that possesses properties highly suited to many applications, including quantum information processing, quantum metrology and biolabelling. Although the unique properties of the centre have been extensively documented and utilized, a detailed understanding of the physics of the centre has not yet been achieved. Indeed, there persist a number of points of contention regarding the electronic structure of the centre, such as the ordering of the dark intermediate singlet states. Without a detailed model of the centre's electronic structure, the understanding of the system's unique dynamical properties cannot effectively progress. In this work, the molecular model of the defect centre is fully developed to provide a self-consistent model of the complete electronic structure of the centre. The application of the model to describe the effects of electric, magnetic and strain interactions, as well as the variation of the centre's fine structure with temperature, provides an invaluable tool to those studying the centre and a means of designing future empirical and ab initio studies of this important defect.

  9. Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles.

    Science.gov (United States)

    El-Ella, Haitham A R; Ahmadi, Sepehr; Wojciechowski, Adam M; Huck, Alexander; Andersen, Ulrik L

    2017-06-26

    Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional to the derivative of the optical magnetic resonance lock-in spectrum, which is in turn dependant on the lock-in modulation parameters. Here we study the dependence of the lock-in spectral slope on the modulation of the spin-driving microwave field. Given the presence of the intrinsic nitrogen hyperfine spin transitions, we experimentally show that when the ratio between the hyperfine linewidth and their separation is ≳ 1/4, square-wave based frequency modulation generates the steepest slope at modulation depths exceeding the separation of the hyperfine lines, compared to sine-wave based modulation. We formulate a model for calculating lock-in spectra which shows excellent agreement with our experiments, and which shows that an optimum slope is achieved when the linewidth/separation ratio is ≲ 1/4 and the modulation depth is less then the resonance linewidth, irrespective of the modulation function used.

  10. Within-field Corn Nitrogen Response Related to Aerial Photograph Color

    Science.gov (United States)

    Precision agriculture management of nitrogen (N) using aerial imagery of corn [Zea mays L.] canopy color has been a proposed strategy to understand crop N health and base within-season N fertilizer application rates. The objective of this study was to evaluate at field scale the relationship between...

  11. Optical properties of color centers in calcium-stabilized gadolinium gallium garnets

    International Nuclear Information System (INIS)

    Pogatshnik, G.J.; Cain, L.S.; Chen, Y.; Evans, B.D.

    1991-01-01

    The addition of small amounts of calcium during the crystal growth of large-diameter, gadolinium gallium garnet (GGG) crystals creates color centers that absorb in the near-uv region of the spectrum. Ultraviolet and γ-ray irradiation of the crystals produced changes in the intensities of the uv color-center bands along with a broad absorption throughout the visible spectrum. The color center that gives rise to an absorption band at 350 nm serves as a photoionizable donor center so that uv excitation results in a visible coloration of the crystals. The effects of oxidation and reduction treatments on the strength of the color-center bands and on the radiation response of the material were examined. Photoluminescence bands were observed in both reduced GGG crystals as well as crystals that were irradiated with neutrons. Visible coloration is likely to occur during flashlamp pumping of laser rods that utilize large-diameter GGG crystals as the laser host. The changes in the optical properties of the material under uv excitation indicate that the addition of small amounts of calcium to assist in the growth of large-diameter crystals is likely to result in the degradation of laser performance

  12. Vacancy clustering and acceptor activation in nitrogen-implanted ZnO

    Science.gov (United States)

    Børseth, Thomas Moe; Tuomisto, Filip; Christensen, Jens S.; Monakhov, Edouard V.; Svensson, Bengt G.; Kuznetsov, Andrej Yu.

    2008-01-01

    The role of vacancy clustering and acceptor activation on resistivity evolution in N ion-implanted n -type hydrothermally grown bulk ZnO has been investigated by positron annihilation spectroscopy, resistivity measurements, and chemical profiling. Room temperature 220keV N implantation using doses in the low 1015cm-2 range induces small and big vacancy clusters containing at least 2 and 3-4 Zn vacancies, respectively. The small clusters are present already in as-implanted samples and remain stable up to 1000°C with no significant effect on the resistivity evolution. In contrast, formation of the big clusters at 600°C is associated with a significant increase in the free electron concentration attributed to gettering of amphoteric Li impurities by these clusters. Further annealing at 800°C results in a dramatic decrease in the free electron concentration correlated with activation of 1016-1017cm-3 acceptors likely to be N and/or Li related. The samples remain n type, however, and further annealing at 1000°C results in passivation of the acceptor states while the big clusters dissociate.

  13. The negatively charged nitrogen-vacancy centre in diamond: the electronic solution

    Energy Technology Data Exchange (ETDEWEB)

    Doherty, M W; Hollenberg, L C L [School of Physics, University of Melbourne, Melbourne, Victoria 3010 (Australia); Manson, N B [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Delaney, P, E-mail: marcuswd@unimelb.edu.au [School of Mathematics and Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom)

    2011-02-15

    The negatively charged nitrogen-vacancy centre is a unique defect in diamond that possesses properties highly suited to many applications, including quantum information processing, quantum metrology and biolabelling. Although the unique properties of the centre have been extensively documented and utilized, a detailed understanding of the physics of the centre has not yet been achieved. Indeed, there persist a number of points of contention regarding the electronic structure of the centre, such as the ordering of the dark intermediate singlet states. Without a detailed model of the centre's electronic structure, the understanding of the system's unique dynamical properties cannot effectively progress. In this work, the molecular model of the defect centre is fully developed to provide a self-consistent model of the complete electronic structure of the centre. The application of the model to describe the effects of electric, magnetic and strain interactions, as well as the variation of the centre's fine structure with temperature, provides an invaluable tool to those studying the centre and a means of designing future empirical and ab initio studies of this important defect.

  14. NV-centers in nanodiamonds: How good they are

    Science.gov (United States)

    Plakhotnik, Taras; Aman, Haroon

    2018-02-01

    This paper presents a method for determination of the size distribution for diamond nanocrystals containing luminescent nitrogen-vacancy (NV) centers using the luminescence intensity only. We also revise the basic photo physical properties of NV centers and conclude that the luminescence quantum yield of such centers is significantly smaller than the frequently stated 100\\%. The yield can be as low as 5\\% for centers embedded in nanocrystals and depends on their shape and the refractive index of the surrounding medium. The paper also addresses the value of the absorption cross-section of NV centers.

  15. Detection and identification of nitrogen defects in nanodiamond as studied by EPR

    Energy Technology Data Exchange (ETDEWEB)

    Soltamova, A.A.; Ilyin, I.V. [Ioffe Physical Technical Institute, Politechnicheskaya, 26, St. Petersburg 194021 (Russian Federation); Baranov, P.G., E-mail: pavel.baranov@mail.ioffe.r [Ioffe Physical Technical Institute, Politechnicheskaya, 26, St. Petersburg 194021 (Russian Federation); Vul' , A.Ya.; Kidalov, S.V.; Shakhov, F.M. [Ioffe Physical Technical Institute, Politechnicheskaya, 26, St. Petersburg 194021 (Russian Federation); Mamin, G.V.; Orlinskii, S.B.; Silkin, N.I.; Salakhov, M.Kh. [Kazan State University, Federal Center of Shared Usage for Physicochemical Measurements, Kazan 420008 (Russian Federation)

    2009-12-15

    Electron paramagnetic resonance (EPR) and electron spin echo (ESE) at X-band and at high-frequency W-band (95 GHz) have been used to study defects in natural diamond nanocrystals, detonation nanodiamond (ND) with a size of approx4.5 nm and detonation ND after high-temperature, high-pressure sintering with a size of approx8.5 nm. Atomic nitrogen centers N{sup 0} and nitrogen pairs N{sub 2}{sup +} have been detected and identified and their structure has been unambiguously determined by means of the high frequency EPR and ESE in natural diamond nanocrystals. In detonation ND and detonation ND after sintering atomic nitrogen centers N{sup 0} have been discovered in nanodiamond core. In addition EPR signal of multi-vacancy centers with spin 3/2 seems to be observed in diamond core of detonation ND.

  16. Single spin stochastic optical reconstruction microscopy

    OpenAIRE

    Pfender, Matthias; Aslam, Nabeel; Waldherr, Gerald; Wrachtrup, Jörg

    2014-01-01

    We experimentally demonstrate precision addressing of single quantum emitters by combined optical microscopy and spin resonance techniques. To this end we utilize nitrogen-vacancy (NV) color centers in diamond confined within a few ten nanometers as individually resolvable quantum systems. By developing a stochastic optical reconstruction microscopy (STORM) technique for NV centers we are able to simultaneously perform sub diffraction-limit imaging and optically detected spin resonance (ODMR)...

  17. Radiation-induced color centers in La-doped PbWO sub 4 crystals

    CERN Document Server

    Deng, Q; Zhu, R Y

    1999-01-01

    This report presents the result of a study on radiation-induced color center densities in La-doped lead tungstate (PbWO sub 4) crystals. The creation and annihilation constants of radiation-induced color centers were determined by using transmittance data measured for a PbWO sub 4 sample before and during sup 6 sup 0 Co gamma-ray irradiation at a dose rate of 15 rad/h. Following a model of color center kinetics, these constants were used to calculate color center densities under irradiations at 100 rad/h. The result was found to be in good agreement with experimental data, indicating that the behaviour of PbWO sub 4 crystals under irradiation can be predicted according to this model.

  18. Vacancy complexes induce long-range ferromagnetism in GaN

    KAUST Repository

    Zhang, Zhenkui

    2014-11-14

    By means of density functional theory, we argue that ferromagnetism in GaN can be induced by vacancy complexes. Spin polarization originates from the charge compensation between neutral N and Ga vacancies. Defect formation energy calculations predict that a vacancy complex of two positively charged N vacancies and one doubly negative Ga vacancy is likely to form. This defect complex induces a net moment of 1 μB, which is localized around the negative Ga center and exhibits pronounced in-plane ferromagnetic coupling. In contrast to simple Ga vacancy induced ferromagnetism, the proposed picture is in line with the fact that N vacancies have a low formation energy. Formation energies indicate mutual stabilization of the intrinsic defects in GaN.

  19. Vacancy complexes induce long-range ferromagnetism in GaN

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhenkui; Schwingenschlögl, Udo, E-mail: Udo.Schwingenschlogl@kaust.edu.sa, E-mail: Iman.Roqan@kaust.edu.sa; Roqan, Iman S., E-mail: Udo.Schwingenschlogl@kaust.edu.sa, E-mail: Iman.Roqan@kaust.edu.sa [Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia)

    2014-11-14

    By means of density functional theory, we argue that ferromagnetism in GaN can be induced by vacancy complexes. Spin polarization originates from the charge compensation between neutral N and Ga vacancies. Defect formation energy calculations predict that a vacancy complex of two positively charged N vacancies and one doubly negative Ga vacancy is likely to form. This defect complex induces a net moment of 1 μ{sub B}, which is localized around the negative Ga center and exhibits pronounced in-plane ferromagnetic coupling. In contrast to simple Ga vacancy induced ferromagnetism, the proposed picture is in line with the fact that N vacancies have a low formation energy. Formation energies indicate mutual stabilization of the intrinsic defects in GaN.

  20. Vacancy complexes induce long-range ferromagnetism in GaN

    KAUST Repository

    Zhang, Zhenkui; Schwingenschlö gl, Udo; Roqan, Iman S.

    2014-01-01

    By means of density functional theory, we argue that ferromagnetism in GaN can be induced by vacancy complexes. Spin polarization originates from the charge compensation between neutral N and Ga vacancies. Defect formation energy calculations predict that a vacancy complex of two positively charged N vacancies and one doubly negative Ga vacancy is likely to form. This defect complex induces a net moment of 1 μB, which is localized around the negative Ga center and exhibits pronounced in-plane ferromagnetic coupling. In contrast to simple Ga vacancy induced ferromagnetism, the proposed picture is in line with the fact that N vacancies have a low formation energy. Formation energies indicate mutual stabilization of the intrinsic defects in GaN.

  1. Optical bistability and multistability driven by external magnetic field in a dielectric slab doped with nanodiamond nitrogen vacancy centres

    Science.gov (United States)

    Nasehi, R.; Norouzi, F.

    2016-08-01

    The theoretical investigation of controlling the optical bistability (OB) and optical multistability (OM) in a dielectric medium doped with nanodiamond nitrogen vacancy centres under optical excitation are reported. The shape of the OB curve from dielectric slab can be tuned by changing the external magnetic field and polarization of the control beam. The effect of the intensity of the control laser field and the frequency detuning of probe laser field on the OB and OM behaviour are also discussed in this paper. The results obtained can be used for realizing an all-optical bistable switching or development of nanoelectronic devices.

  2. Color centers in KCN: a structural analysis of crystalline domains

    International Nuclear Information System (INIS)

    Carmo, L.C.S. do.

    1976-03-01

    Pure singlecrystals of KCN exposed to X-rays showed several color centers detected by EPR. The F center was identified through the correlation of its optical absorption band which satisfies the Ivey law for the KCN lattice parameter and the EPR spectrum typical of a center in an anionic site. Two other color centers were identified: N - 2 and HCN - . Two centers assigned to hydrogen atoms have their models proposed: U 2 and U 3 centers. Two other centers remain unidentified: an anionic and an extrinsic centers. The orthorhombic character of the N - 2 center EPR parameters allowed an structural analysis of the crystal line domains in the orthorhombic phase. The optical absorption spectrum of the HCN - center in KCl matrix was investigated and showed a set of resolved bands with a constant energy splitting; this splitting was associated to a vibrational mode of the excited state of this molecular ion. (author) [pt

  3. Probing condensed matter physics with magnetometry based on nitrogen-vacancy centres in diamond

    Science.gov (United States)

    Casola, Francesco; van der Sar, Toeno; Yacoby, Amir

    2018-01-01

    The magnetic fields generated by spins and currents provide a unique window into the physics of correlated-electron materials and devices. First proposed only a decade ago, magnetometry based on the electron spin of nitrogen-vacancy (NV) defects in diamond is emerging as a platform that is excellently suited for probing condensed matter systems; it can be operated from cryogenic temperatures to above room temperature, has a dynamic range spanning from direct current to gigahertz and allows sensor-sample distances as small as a few nanometres. As such, NV magnetometry provides access to static and dynamic magnetic and electronic phenomena with nanoscale spatial resolution. Pioneering work has focused on proof-of-principle demonstrations of its nanoscale imaging resolution and magnetic field sensitivity. Now, experiments are starting to probe the correlated-electron physics of magnets and superconductors and to explore the current distributions in low-dimensional materials. In this Review, we discuss the application of NV magnetometry to the exploration of condensed matter physics, focusing on its use to study static and dynamic magnetic textures and static and dynamic current distributions.

  4. Investigation of the oxygen-vacancy (A-center) defect complex profile in neutron irradiated high resistivity silicon junction particle detectors

    International Nuclear Information System (INIS)

    Li, Zheng; Kraner, H.W.; Verbitskaya, E.; Eremin, V.; Ivanov, A.; Rubinelli, F.A.; Fonash, S.J.

    1992-02-01

    Distributions of the A-center (oxygen-vacancy) in neutron silicon detectors have been studied using Deep Level Transient Spectroscopy. A-centers have been found to be nearly uniformly distributed in the silicon water depth for medium resistivity (0.1 - 0.2 kΩ-cm) silicon detectors. A positive filling pulse was needed to detect the A-centers in high resistivity (>4 kΩ-cm) silicon detectors, and this effect was found to be dependent on the oxidation temperature. A discussion of this effect is presented. 16 refs

  5. Creating nitrogen–vacancy ensembles in diamond for coupling with flux qubit

    International Nuclear Information System (INIS)

    Zheng Ya-Rui; Xing Jian; Chang Yan-Chun; Yan Zhi-Guang; Deng Hui; Wu Yu-Lin; Lü Li; Pan Xin-Yu; Zhu Xiao-Bo; Zheng Dong-Ning

    2017-01-01

    Hybrid quantum system of negatively charged nitrogen−vacancy (NV − ) centers in diamond and superconducting qubits provide the possibility to extend the performances of both systems. In this work, we numerically simulate the coupling strength between NV − ensembles and superconducting flux qubits and obtain a lower bound of 10 16 cm −3 for NV − concentration to achieve a sufficiently strong coupling of 10 MHz when the gap between NV-ensemble and flux qubit is 0. Moreover, we create NV − ensembles in different types of diamonds by 14 N + and 12 C + ion implantation, electron irradiation, and high temperature annealing. We obtain an NV − concentration of 1.05 × 10 16 cm −3 in the diamond with 1-ppm nitrogen impurity, which is expected to have a long coherence time for the low nitrogen impurity concentration. This shows a step toward performance improvement of flux qubit-NV − hybrid system. (paper)

  6. Controlling composition and color characteristics of Monascus pigments by pH and nitrogen sources in submerged fermentation.

    Science.gov (United States)

    Shi, Kan; Song, Da; Chen, Gong; Pistolozzi, Marco; Wu, Zhenqiang; Quan, Lei

    2015-08-01

    Submerged fermentations of Monascus anka were performed with different nitrogen sources at different pH in 3 L bioreactors. The results revealed that the Monascus pigments dominated by different color components (yellow pigments, orange pigments or red pigments) could be selectively produced through pH control and nitrogen source selection. A large amount of intracellular pigments dominated by orange pigments and a small amount of water-soluble extracellular yellow pigments were produced at low pH (pH 2.5 and 4.0), independently of the nitrogen source employed. At higher pH (pH 6.5), the role of the nitrogen source became more significant. In particular, when ammonium sulfate was used as nitrogen source, the intracellular pigments were dominated by red pigments with a small amount of yellow pigments. Conversely, when peptone was used, intracellular pigments were dominated by yellow pigments with a few red pigments derivatives. Neither the presence of peptone nor ammonium sulfate promoted the production of intracellular orange pigments while extracellular pigments with an orangish red color were observed in both cases, with a higher yield when peptone was used. Two-stage pH control fermentation was then performed to improve desirable pigments yield and further investigate the effect of pH and nitrogen sources on pigments composition. These results provide a useful strategy to produce Monascus pigments with different composition and different color characteristics. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  7. A Facile Approach to Prepare Black TiO2 with Oxygen Vacancy for Enhancing Photocatalytic Activity

    Science.gov (United States)

    Chen, Shihao; Xiao, Yang; Hu, Zhengfa; Zhao, Hui; Xie, Wei

    2018-01-01

    Black TiO2 has triggered worldwide research interest due to its excellent photocatalytic properties. However, the understanding of its structure–property relationships and a more effective, facile and versatile method to produce it remain great challenges. We have developed a facile approach to synthesize black TiO2 nanoparticles with significantly improved light absorption in the visible and infrared regions. The experimental results show that oxygen vacancies are the major factors responsible for black coloration. More importantly, our black TiO2 nanoparticles have no Ti3+ ions. These oxygen vacancies could introduce localized states in the bandgap and act as trap centers, significantly decreasing the electron–hole recombination. The photocatalytic decomposition of both rhodamine B and methylene blue demonstrated that, under ultraviolet light irradiation, better photocatalytic performance is achieved with our black TiO2 nanoparticles than with commercial TiO2 nanoparticles. PMID:29659500

  8. Color centers in KCN: ferro-elastic alignment and free optical absorption of phonons

    International Nuclear Information System (INIS)

    Grillo, M.L.N.

    1983-01-01

    Some color centers in KCN pure and KCL or KOH doped are studied. The used tecniques for detection of these color centers were optical absorption and electron paramagnetic resonance (EPR). To obtain this color centers crystals were always exposed to X-rays. With an optical absorption technique, one color center was analysed after X-ray irradiation followed by a suitable photochemical process. Throught the EPR technique the F center and three other centers produced by radiation damage were observed through several KCN solid phases. As in the orthorhombic and ferroelastic phase (temperatures between 168K and 83K), the crystals of KCN present one multidomain structure responsable for strong light scattering on the optical absorption spectra and EPR spectra that does not present the resolved lines formed above 168K, one system of aligned domains was obtained through mechanical stress built specifically to be capable of reducing the number of distinct domain, and this allowed us to observe of partially resolved EPR lines. (Auhtor) [pt

  9. Modeling of the structure and properties of oxygen vacancies in amorphous silica

    International Nuclear Information System (INIS)

    Mukhopadhyay, Sanghamitra; Sushko, Peter V.; Stoneham, A. Marshall; Shluger, Alexander L.

    2004-01-01

    We used an embedded cluster method to predict and characterize possible structural types of neutral and positively charged oxygen vacancies in amorphous silica. Defects were treated at 70 different oxygen sites of continuous random network amorphous structure generated using classical molecular dynamics. The neutral vacancies are characterized by a wide distribution of formation energies and structural parameters. Our modeling predicts the two major structural types of positively charged vacancies (E ' centers): dimer and dangling bond centers. The local structure of both types of centers depends on the medium range structure of the surrounding amorphous network. The majority of the dangling bond centers are unpuckered. We used structural 'fingerprints' derived from similar calculations of oxygen vacancy type centers in quartz and from experiment to find two other structural types of dangling bond centers: the puckered configuration and the back-projected configuration of E ' centers. In each case we find a distribution of both structural and EPR parameters. However, the average values of the EPR parameters for all dangling bond configurations are very similar. The structural criteria which favor the formation of different types of centers in the original amorphous structure are formulated in terms of the average Si-O distance of oxygen ion with its two neighboring silicon ions

  10. Effect of elimination of nitrogen and/or hypoxia or restricted visual environment on color vision and range of accommodation

    Science.gov (United States)

    Wolbarsht, M. L.; White, C. W.; Anderson, W. B., Jr.

    1973-01-01

    The effects upon range of accommodation and color vision of reduced atmospheric pressure, at partial and complete elimination of nitrogen, of hypoxia, and of exposure for varying periods of time to restricted visual environment, have been studied alone or in various combinations. Measurements were made on the electroretinogram, the electrooculogram, and the diameter of the retinal vessels as an indicator of blood flow to the retina at the time of total elimination of nitrogen. An objective method was used to test range of accommodation. In the color vision test the flicker colors of a Benham's top were matched with a colorimeter.

  11. Infrared defect dynamics—Nitrogen-vacancy complexes in float zone grown silicon introduced by electron irradiation

    Science.gov (United States)

    Inoue, Naohisa; Kawamura, Yuichi

    2018-05-01

    The interaction of nitrogen and intrinsic point defects, vacancy (V) and self-interstitial (I), was examined by infrared absorption spectroscopy on the electron irradiated and post-annealed nitrogen doped float zone (FZ) silicon crystal. Various absorption lines were observed, at 551 cm-1 in as-grown samples, at 726 and 778 cm-1 in as-irradiated samples (Ir group), at 689 cm-1 after post-annealing at 400 °C and above (400 °C group), at 762 and 951 cm-1 after annealing at 600 °C (600 °C group), and at 714 cm-1 up to 800 °C (800 °C group). By irradiation, a part of N2 was changed into the Ir group. VN2 is the candidate for the origin of the Ir group. By the post annealing at 400 and 600 °C, a part of N2 and the Ir group were changed into the 400 °C group, to less extent at 600 °C. V2N2 is the candidate for the origin of the 400 °C group. By annealing at 600 °C, most of the Ir group turned into 400 °C and 600 °C groups. By annealing at 800 °C, N2 recovered almost completely, and most other complexes were not observed. Recently, lifetime degradation has been observed in the nitrogen doped FZ Si annealed at between 450 and 800 °C. The N-V interaction in the same temperature range revealed here will help to understand the lifetime degradation mechanism. The behavior of the 689 cm-1 line corresponded well to the lifetime degradation.

  12. Study of vacancy-type defects by positron annihilation in ultrafine-grained aluminum severely deformed at room and cryogenic temperatures

    International Nuclear Information System (INIS)

    Su, L.H.; Lu, C.; He, L.Z.; Zhang, L.C.; Guagliardo, P.; Tieu, A.K.; Samarin, S.N.; Williams, J.F.; Li, H.J.

    2012-01-01

    Commercial-purity aluminum was processed by equal-channel angular pressing (ECAP) at room temperature (RT-ECAP) and cryogenic temperature (CT-ECAP) with liquid nitrogen cooling between two successive passes. It was found that the RT-ECAPed samples showed equiaxed microstructure after 4 and 8 ECAP passes, while the CT-ECAPed samples displayed slightly elongated microstructure and slightly smaller grain size. Moreover, the CT-ECAPed samples had higher hardness values than the RT-ECAPed samples subjected to the same amount of deformation. Positron annihilation lifetime spectroscopy (PALS) was used to investigate the evolution of vacancy-type defects during the ECAP deformation process. The results showed that three types of defects existed in the ECAPed samples: vacancies associated with dislocations, bulk monovacancies and bulk divacancies. The CT-ECAPed samples had a higher fraction of monovacancies and divacancies. These two types of defects are the major vacancy-type defects that can work as dislocation pinning centers and induce hardening, resulting in higher hardness values in the CT-ECAPed samples. A quantitative relationship between material hardness and the defect concentration and defect diffusion coefficient has been established.

  13. Color centers inside crystallic active media

    Science.gov (United States)

    Mierczyk, Zygmunt; Kaczmarek, Slawomir M.; Kopczynski, Krzysztof

    1995-03-01

    This paper presents research results on color centers induced by radiation of a xenon lamp in non doped crystals of yttrium aluminum garnet Y3Al5O12 (YAG), strontium- lanthanum aluminate SrLaAlO4 (SLAO), strontium-lanthanum gallate SrLaGa3O7 (SLGO), and in doped crystals: Nd:YAG, Cr, Tm, Ho:YAG (CTH:YAG), Nd:SLAO and Nd:SLGO. In all these investigated crystals under the influence of intensive exposure by xenon lamp radiation additional bands connected with centers O-2, O2 and centers F came up near the short-wave absorption edge. In the case of doped crystals the observed processes are much more complicated. In crystals CTH:YAG the greatest perturbations in relation to basic state are present at the short-wave absorption edge, as well as on areas of absorption bands of ions Cr+3 and Tm+3 conditioning the sensibilization process of ions Ho+3. These spectral structure disturbances essentially influence the efficiency of this process, as proven during generating investigations. In the case of SrLaGa3O7:Nd+3 under the influence of exposure substantial changes of absorption spectrum occurred on spectral areas 346 divided by 368 nm, 429 divided by 441 nm and 450 divided by 490 nm. Those changes have an irreversible character. They disappear not before the plate is being held at oxidizing atmosphere. Investigations of laser rods Nd:SLGO, CTH:YAG, and Nd:YAG in a free generation demonstrated that the color centers of these crystals are induced by pomp radiation from the spectral area up to 450 nm.

  14. Effect of impurities on vacancy migration energy in Fe-based alloys

    International Nuclear Information System (INIS)

    Hashimoto, N.; Sakuraya, S.; Tanimoto, J.; Ohnuki, S.

    2014-01-01

    Effects of impurities, such as carbon, nitrogen, helium and hydrogen, on microstructural evolution in pure iron were investigated by means of a multi-beam electron microscope. Growth rate of dislocation loops were measured to calculate vacancy migration energies. In all irradiation temperature conditions, both the size and the number density of dislocation loops were increased as a function of dose. Irradiation with more impurities showed an increase in the temperature dependence of the dislocation loop growth rate compared to irradiation with little impurities. The in situ experiment indicated that the net migration energy of vacancies could be increased due to trapping by impurities, and the effect of C and N on the migration energy of vacancy would be larger than that of W, V, Ta. Furthermore, H and He would increase vacancy migration energy greater than C and N, as well as W, V, Ta. The density functional theory (DFT), applied to the atomic models of BCC iron, indicated an increase in vacancy migration energy by the trapping of impurity atoms, that is a good agreement with this in situ experiment

  15. Vacancies in transition metals

    International Nuclear Information System (INIS)

    Allan, G.; Lannoo, M.

    1976-01-01

    A calculation of the formation energy and volume for a vacancy in transition metals is described. A tight-binding scheme is used for the d band and a Born-Mayer type potential to account for the repulsive part of the energy at small distances. The results show that the relaxation energy is small in all cases, less than 0.1 eV. This seems to be coherent with the good agreement obtained for the theoretical and experimental values of the formation energy Esub(F)sup(V) of the vacancy, without including relaxation. The center of the transitional series is found to give a contraction (Formation volume of order -0.4 at.vol.) whereas the edges are found to produce dilations. (author)

  16. Origin of the nitrogen over- and understoichiometry in Ti0.5Al0.5N thin films

    International Nuclear Information System (INIS)

    Baben, Moritz to; Raumann, Leonard; Music, Denis; Schneider, Jochen M

    2012-01-01

    To identify the origin of the experimentally observed nitrogen over- and understoichiometry in TiAlN thin films, various point defect configurations were studied by ab initio calculations in terms of formation energies, equilibrium volume and elastic moduli. From formation energies and comparison to existing experimental equilibrium volume and elasticity data, it is shown that nitrogen vacancies and metal vacancies are responsible for nitrogen understoichiometry and overstoichiometry, respectively. Irrespective of the type of vacancies, the bulk modulus is decreased by approximately 7% as the nitrogen concentration is increased or decreased by 3 at.%. (paper)

  17. Plasmonic enhancement of a silicon-vacancy center in a nanodiamond crystal

    Science.gov (United States)

    Meng, Xiang; Liu, Shang; Dadap, Jerry I.; Osgood, Richard M.

    2017-06-01

    This work reports a rigorous and comprehensive three-dimensional electromagnetic computation to investigate and design photoluminescence enhancement from a single silicon-vacancy center (SVC) in a nanodiamond crystal embedded in various metallic nanoantennae, each having a different geometry. The study demonstrates how each antenna design enhances the photoluminescence of SVCs in diamond. In particular, our report discusses how the 2D or 3D curvature of the nanoantenna and the control of the local environment of the SVC can lead to significant field enhancement of its optical field. Our calculated optimal photoluminescence for each design enhances the emission intensity by 15 -300 × that of a single SVC without antenna. The enhancement mechanisms are investigated using four representative structures that can be fabricated under feasible and realistic growth conditions, i.e., spherical-, nanorod-, nanodisk-dimer, and bow-tie nanoantennae. These results demonstrate a method for rationally designing arbitrary metallic nanoantenna/emitter assemblies to achieve optimal SVC photoluminescence.

  18. The double luminescence of Color Centers

    International Nuclear Information System (INIS)

    Baldacchini, Giuseppe

    2015-01-01

    An experiment on the luminescence of Color Centers (CCs) carried out in 1987 at the ENEA Laboratories in Frascati had a negative result, but subsequent investigations showed that it was not a failure but rather a discovery of a new phenomenon. Since the coming of lasers, CCs in alkali halides have been successfully used as optically active materials, in particular FA Centers. One of these centers, well known for its medium infrared laser emission at 77 K, cooled further to 2 K emitted in the near infrared and without laser effect. Further investigations showed that the double luminescence was a fundamental property unknown until that time. This important discovery was achieved in Frascati because of the existence since 1973 of a solid and extensive expertise in the field of CCs, which continued over time and later on applied to the modern miniaturized photonic devices [it

  19. Moderate plasma treatment enhances the quality of optically detected magnetic resonance signals of nitrogen-vacancy centres in nanodiamonds

    Science.gov (United States)

    Sotoma, Shingo; Igarashi, Ryuji; Shirakawa, Masahiro

    2016-05-01

    We demonstrate that a moderate plasma treatment increases the quality of optically detected magnetic resonance (ODMR) signals from negatively charged nitrogen-vacancy centres in nanodiamonds (NDs). We measured the statistics of the ODMR spectra of 50-nm-size NDs before and after plasma treatment. We then evaluated each ODMR spectrum in terms of fluorescence and ODMR intensities, line width and signal-to-noise (SN) ratio. Our results showed that plasma treatment for more than 10 min contributes to higher-quality ODMR signals, i.e. signals that are brighter, stronger, sharper and have a higher SN ratio. We showed that such signal improvement is due to alteration of the surface chemical states of the NDs by the plasma treatment. Our study contributes to the advancement of biosensing applications using ODMR of NDs.

  20. Excitation of surface plasmon polariton modes with multiple nitrogen vacancy centers in single nanodiamonds

    DEFF Research Database (Denmark)

    Kumar, Shailesh; Lausen, Jens L.; Garcia-Ortiz, Cesar E.

    2016-01-01

    ) are especially useful as biological fluorophores due to their chemical neutrality, brightness and room-temperature photostability. Furthermore, NDs containing multiple NV centers also have potential in high-precision magnetic field and temperature sensing. Coupling NV centers to propagating surface plasmon...

  1. Cooperative effects between color centers in diamond: applications to optical tweezers and optomechanics

    Science.gov (United States)

    Bradac, Carlo; Prasanna Venkatesh, B.; Besga, Benjamin; Johnsson, Mattias; Brennen, Gavin; Molina-Terriza, Gabriel; Volz, Thomas; Juan, Mathieu L.

    2017-08-01

    Since the early work by Ashkin in 1970,1 optical trapping has become one of the most powerful tools for manipulating small particles, such as micron sized beads2 or single atoms.3 Interestingly, both an atom and a lump of dielectric material can be manipulated through the same mechanism: the interaction energy of a dipole and the electric field of the laser light. In the case of atom trapping, the dominant contribution typically comes from the allowed optical transition closest to the laser wavelength while it is given by the bulk polarisability for mesoscopic particles. This difference lead to two very different contexts of applications: one being the trapping of small objects mainly in biological settings,4 the other one being dipole traps for individual neutral atoms5 in the field of quantum optics. In this context, solid state artificial atoms present the interesting opportunity to combine these two aspects of optical manipulation. We are particularly interested in nanodiamonds as they constitute a bulk dielectric object by themselves, but also contain artificial atoms such as nitrogen-vacancy (NV) or silicon-vacancy (SiV) colour centers. With this system, both regimes of optical trapping can be observed at the same time even at room temperature. In this work, we demonstrate that the resonant force from the optical transition of NV centres at 637 nm can be measured in a nanodiamond trapped in water. This additional contribution to the total force is significant, reaching up to 10%. In addition, due to the very large density of NV centres in a sub-wavelength crystal, collective effects between centres have an important effect on the magnitude of the resonant force.6 The possibility to observe such cooperatively enhanced optical force at room temperature is also theoretically confirmed.7 This approach may enable the study of cooperativity in various nanoscale solid-state systems and the use of atomic physics techniques in the field of nano-manipulation and opto-mechanics.

  2. Enhanced extraction of silicon-vacancy centers light emission using bottom-up engineered polycrystalline diamond photonic crystal slabs

    Czech Academy of Sciences Publication Activity Database

    Ondič, Lukáš; Varga, Marián; Hruška, Karel; Fait, J.; Kapusta, Peter

    2017-01-01

    Roč. 11, č. 3 (2017), s. 2972-2981 ISSN 1936-0851 R&D Projects: GA ČR GJ16-09692Y; GA MŠk LD15003; GA ČR(CZ) GBP208/12/G016 Institutional support: RVO:68378271 ; RVO:61388955 Keywords : photonic crystal * diamond * silicon vacancy center Subject RIV: BM - Solid Matter Physics ; Magnetism; CF - Physical ; Theoretical Chemistry (UFCH-W) OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.); Physical chemistry (UFCH-W) Impact factor: 13.942, year: 2016

  3. Room-temperature single-photon sources with definite circular and linear polarizations based on single-emitter fluorescence in liquid crystal hosts

    International Nuclear Information System (INIS)

    Winkler, Justin M; Lukishova, Svetlana G; Bissell, Luke J

    2013-01-01

    Definite circular and linear polarizations of room-temperature single-photon sources, which can serve as polarization bases for quantum key distribution, are produced by doping planar-aligned liquid crystal hosts with single fluorescence emitters. Chiral 1-D photonic bandgap microcavities for a single handedness of circularly polarized light were prepared from both monomeric and oligomeric cholesteric liquid crystals. Fluorescent emitters, such as nanocrystal quantum dots, nitrogen vacancy color centers in nanodiamonds, and rare-earth ions in nanocrystals, were doped into these microcavity structures and used to produce circularly polarized fluorescence of definite handedness. Additionally, we observed circularly polarized resonances in the spectrum of nanocrystal quantum dot fluorescence at the edge of the cholesteric microcavity's photonic stopband. For this polarization we obtained a ∼4.9 enhancement of intensity compared to the polarization of the opposite handedness that propagates without photonic bandgap microcavity effects. Such a resonance is indicative of coupling of quantum dot fluorescence to the cholesteric microcavity mode. We have also used planar-aligned nematic liquid crystal hosts to align DiI dye molecules doped into the host, thereby providing a single-photon source of linear polarization of definite direction. Antibunching is demonstrated for fluorescence of nanocrystal quantum dots, nitrogen vacancy color centers, and dye molecules in these liquid crystal structures.

  4. Enhancing the brightness of electrically driven single-photon sources using color centers in silicon carbide

    Science.gov (United States)

    Khramtsov, Igor A.; Vyshnevyy, Andrey A.; Fedyanin, Dmitry Yu.

    2018-03-01

    Practical applications of quantum information technologies exploiting the quantum nature of light require efficient and bright true single-photon sources which operate under ambient conditions. Currently, point defects in the crystal lattice of diamond known as color centers have taken the lead in the race for the most promising quantum system for practical non-classical light sources. This work is focused on a different quantum optoelectronic material, namely a color center in silicon carbide, and reveals the physics behind the process of single-photon emission from color centers in SiC under electrical pumping. We show that color centers in silicon carbide can be far superior to any other quantum light emitter under electrical control at room temperature. Using a comprehensive theoretical approach and rigorous numerical simulations, we demonstrate that at room temperature, the photon emission rate from a p-i-n silicon carbide single-photon emitting diode can exceed 5 Gcounts/s, which is higher than what can be achieved with electrically driven color centers in diamond or epitaxial quantum dots. These findings lay the foundation for the development of practical photonic quantum devices which can be produced in a well-developed CMOS compatible process flow.

  5. Photoconversion and dynamic hole recycling process in anion vacancies in neutron-irradiated MgO crystals

    International Nuclear Information System (INIS)

    Monge, M.A.; Gonzalez, R.; Munoz Santiuste, J.E.; Pareja, R.; Chen, Y.; Kotomin, E.A.; Popov, A.I.

    1999-01-01

    Optical spectroscopy and theory demonstrate that photon excitation of the positively charged anion vacancies (F + centers) at 5.0 eV in neutron-irradiated MgO crystals releases holes that are subsequently trapped at V-type centers, which are cation vacancies charge compensated by impurities, such as Al 3+ , F - , and OH - ions. The concentration of trapped-hole centers was found to exceed that of available anion vacancies. The disproportionately large amount of holes produced is attributed to a dynamic recycling process, by which the F + center serves to release a hole to the V-type centers and subsequently trap a hole from an Fe 3+ ion. The net effect was the increase of V-type centers mostly at the expense of Fe 3+ ions. It was also shown that concurrently there was a component which distributed holes directly from Fe 3+ to the V-type centers. copyright 1999 The American Physical Society

  6. Color center lasers passively mode locked by quantum wells

    International Nuclear Information System (INIS)

    Islam, M.N.; Soccolich, C.E.; Bar-Joseph, I.; Sauer, N.; Chang, T.Y.; Miller, B.I.

    1989-01-01

    This paper describes how, using multiple quantum well (MQW) saturable absorbers, the authors passively mode locked a NaCl color center laser to produce 275 fs transform-limited, pedestal-free pulses with as high as 3.7 kW peak power. The pulses are tunable from λ = 1.59 to 1.7 μm by choosing MQW's with different bandgaps. They shortened the output pulses from the laser to 25 fs using the technique of soliton compression in a fiber. The steady-state operation of the laser requires the combination of a fast saturable absorber and gain saturation. In addition to the NaCl laser, they passively mode locked a Tl 0 (1):KCl color center laser and produced -- 22 ps pulses. Although the 275 fs pulses from the NaCl laser are Gaussian, when broadened, the pulses acquire an asymmetric spectrum because of carrier-induced refractive index changes

  7. Ionizing acceleration of color center transformation in the low radiation dose range

    International Nuclear Information System (INIS)

    Mamontov, A.P.; Starodubtsev, V.A.; Chernov, I.P.

    1985-01-01

    The purpose of the study is investigation of annealing and colour centers transformation of known nature in lithium fluoride crystals at the γ-irradiation low doses. The controlled colour centers have been introduced by LiF monocrystal samples irradiation by protons with 6 MeV energy. The γ-radiation dose rate constitutes 25 Grxssup(-1). The variation of absorption spectra caused by proton and γ-irradiation in initial crystals and in the sample being twice exposed has been studied. It is shown that for LiF monocrystals in the γ-radiation low dose range (below 5 kGr) anomalous dependences of concentration of F-aggregate colour centers on the irradiation dose are observed. High efficiency in defects transformation can be caused by the chain of self-sustaining reactions. The observed N-type dependences caused defects decay and competition of the processes of capture of anionic vacancies by F- and F-aggregate centers

  8. First principles investigation of nitrogenated holey graphene

    Science.gov (United States)

    Xu, Cui-Yan; Dong, Hai-Kuan; Shi, Li-Bin

    2018-04-01

    The zero band gap problem limits the application of graphene in the field of electronic devices. Opening the band gap of graphene has become a research issue. Nitrogenated holey graphene (NHG) has attracted much attention because of its semiconducting properties. However, the stacking orders and defect properties have not been investigated. In this letter, the structural and stacking properties of NHG are first investigated. We obtain the most stable stacking structure. Then, the band structures for bulk and multilayer NHG are studied. Impact of the strain on the band gaps and bond characteristics is discussed. In addition, we investigate formation mechanism of native defects of carbon vacancy (VC), carbon interstitial (Ci), nitrogen vacancy (VN), and nitrogen interstitial (Ni) in bulk NHG. Formation energies and transition levels of these native defects are assessed.

  9. Preferred skin color enhancement for photographic color reproduction

    Science.gov (United States)

    Zeng, Huanzhao; Luo, Ronnier

    2011-01-01

    Skin tones are the most important colors among the memory color category. Reproducing skin colors pleasingly is an important factor in photographic color reproduction. Moving skin colors toward their preferred skin color center improves the color preference of skin color reproduction. Several methods to morph skin colors to a smaller preferred skin color region has been reported in the past. In this paper, a new approach is proposed to further improve the result of skin color enhancement. An ellipsoid skin color model is applied to compute skin color probabilities for skin color detection and to determine a weight for skin color adjustment. Preferred skin color centers determined through psychophysical experiments were applied for color adjustment. Preferred skin color centers for dark, medium, and light skin colors are applied to adjust skin colors differently. Skin colors are morphed toward their preferred color centers. A special processing is applied to avoid contrast loss in highlight. A 3-D interpolation method is applied to fix a potential contouring problem and to improve color processing efficiency. An psychophysical experiment validates that the method of preferred skin color enhancement effectively identifies skin colors, improves the skin color preference, and does not objectionably affect preferred skin colors in original images.

  10. Spin-dependent recombination involving oxygen-vacancy complexes in silicon

    OpenAIRE

    Franke, David P.; Hoehne, Felix; Vlasenko, Leonid S.; Itoh, Kohei M.; Brandt, Martin S.

    2014-01-01

    Spin-dependent relaxation and recombination processes in $\\gamma$-irradiated $n$-type Czochralski-grown silicon are studied using continuous wave (cw) and pulsed electrically detected magnetic resonance (EDMR). Two processes involving the SL1 center, the neutral excited triplet state of the oxygen-vacancy complex, are observed which can be separated by their different dynamics. One of the processes is the relaxation of the excited SL1 state to the ground state of the oxygen-vacancy complex, t...

  11. Photoluminescence of magnesium-associated color centers in LiF crystals implanted with magnesium ions

    Science.gov (United States)

    Nebogin, S. A.; Ivanov, N. A.; Bryukvina, L. I.; V. Shipitsin, N.; E. Rzhechitskii, A.; Papernyi, V. L.

    2018-05-01

    In the present paper, the effect of magnesium nanoparticles implanted in a LiF crystal on the optical properties of color centers is studied. The transmittance spectra and AFM images demonstrate effective formation of the color centers and magnesium nanoparticles in an implanted layer of ∼ 60-100 nm in thickness. Under thermal annealing, a periodical structure is formed on the surface of the crystal and in the implanted layer due to self-organization of the magnesium nanoparticles. Upon excitation by argon laser with a wavelength of 488 nm at 5 K, in a LiF crystal, implanted with magnesium ions as well as in heavily γ-irradiated LiF: Mg crystals, luminescence of the color centers at λmax = 640 nm with a zero-phonon line at 601.5 nm is observed. The interaction of magnesium nanoparticles and luminescing color centers in a layer implanted with magnesium ions has been revealed. It is shown that the luminescence intensity of the implanted layer at a wavelength of 640 nm is by more than two thousand times higher than that of a heavily γ-irradiated LiF: Mg crystal. The broadening of the zero-phonon line at 601.5 nm in the spectrum of the implanted layer indicates the interaction of the emitting quantum system with local field of the surface plasmons of magnesium nanoparticles. The focus of this work is to further optimize the processing parameters in a way to result in luminescence great enhancement of color centers by magnesium nanoparticles in LiF.

  12. Multi-scale modeling of interaction between vacancies and alloying elements in ferritic alloys

    International Nuclear Information System (INIS)

    Barouh, Caroline

    2015-01-01

    This PhD thesis is devoted to the study of interaction between vacancies and alloying elements in Oxide Dispersion Strengthened (ODS) steels, which are promising candidate materials for future nuclear reactors. This work is based on multi-scale modeling of a simplified system composed by oxygen, yttrium and titanium atoms and vacancies in an α-iron lattice. We particularly focused on the role of vacancies which are created in excess during the fabrication of these steels. The stability and mobility of vacancy-solute clusters have been examined using ab initio calculations for oxygen, on one hand, which has been systematically compared to carbon and nitrogen, interstitial solutes frequently present in iron-based materials, and, on the other hand, for substitutional solutes: titanium and yttrium. The three interstitial solutes show very similar energetic and kinetic behaviors. The impact of small mobile vacancy-solute clusters has been verified using a cluster dynamics model based on our ab initio results. It has been thus demonstrated that with over-saturation of vacancies, diffusion of interstitial solutes may be accelerated, while substitutional solutes do not become necessarily faster. These conclusions are consistent with existing experimental observations. All these results have been then used to complete our understanding of nano-clusters formation mechanisms. It appeared that the relative mobility of yttrium and titanium, as well as the number of potential nuclei to form nanoparticles strongly depend on the total vacancy concentration in the system. (author) [fr

  13. Electron color centers in SrF2-Na crystals

    International Nuclear Information System (INIS)

    Kachan, S.I.; Chornij, Z.P.

    2006-01-01

    A radiation-induced memory effect in SrF 2 -Na crystals is studied. It was shown that optical bleaching of M + A color centers at 80 K in SrF 2 -Na crystals causes the core of an M + A -center to transform into the V + a Me + V + a configuration, in which all three point defects are arranged diagonally in the cube cell. Reirradiation of an optically bleached crystal by X-rays generates F D centers in it. The F D →M + A transformation in SrF 2 -Na crystals occurs at T = 135 K, in contrast to the F A →M + A transformations, which take place at T > 200 K [ru

  14. Beyond the Cahn-Hilliard equation: a vacancy-based kinetic theory

    International Nuclear Information System (INIS)

    Nastar, M.

    2011-01-01

    A Self-Consistent Mean Field (SCMF) kinetic theory including an explicit description of the vacancy diffusion mechanism is developed. The present theory goes beyond the usual local equilibrium hypothesis. It is applied to the study of the early time spinodal decomposition in alloys. The resulting analytical expression of the structure function highlights the contribution of the vacancy diffusion mechanism. Instead of the single amplification rate of the Cahn-Hillard linear theory, the linearized SCMF kinetic equations involve three constant rates, first one describing the vacancy relaxation kinetics, second one related to the kinetic coupling between local concentrations and pair correlations and the third one representing the spinodal amplification rate. Starting from the same vacancy diffusion model, we perform kinetic Monte Carlo simulations of a Body Centered Cubic (BCC) demixting alloy. The resulting spherically averaged structure function is compared to the SCMF predictions. Both qualitative and quantitative agreements are satisfying. (authors)

  15. Influence of chromium ions on the color center formation in crystals with garnet structure

    International Nuclear Information System (INIS)

    Ashurov, M.Kh.; Zharikov, E.V.; Laptev, V.V.

    1985-01-01

    The in fluence of chromium ions on the color center formation in crystals of yttrium-aluminium garnet, gadolinium-gallium garnet, gadolinium-scandium-gallium garnet, and yttrium-scandium-gallium garnet is studied. In addition to basic activator ions these crystals were coactivated also by chromium ions with two wide bands of fundamental absorption within the range of pump tube radiation with maximas close to 450 and 650 nm. The color centers for γ-irradiated samples were observed at 300 K by measuring the adsorption spectra within the 300-800 nm range. Temperature of destruction of the charge trapping sites was determined by the method of thermoluminescence measuring in the 100-500 K temperature range. Detection of recombination center luminescence was accomplished within the 200-1600 nm wavelength range. Chromium ions are found to hinder the formation of color centers as a result of γ-irradiation at room and higher temperatures within the wavelength range over 300 nm; i.e. Cr 3+ ions increase radiation resistance of all the investigated crystals

  16. Memristive behaviour of Si-Al oxynitride thin films: the role of oxygen and nitrogen vacancies in the electroforming process

    Science.gov (United States)

    Blázquez, O.; Martín, G.; Camps, I.; Mariscal, A.; López-Vidrier, J.; Ramírez, J. M.; Hernández, S.; Estradé, S.; Peiró, F.; Serna, R.; Garrido, B.

    2018-06-01

    The resistive switching properties of silicon-aluminium oxynitride (SiAlON) based devices have been studied. Electrical transport mechanisms in both resistance states were determined, exhibiting an ohmic behaviour at low resistance and a defect-related Poole‑Frenkel mechanism at high resistance. Nevertheless, some features of the Al top-electrode are generated during the initial electroforming, suggesting some material modifications. An in-depth microscopic study at the nanoscale has been performed after the electroforming process, by acquiring scanning electron microscopy and transmission electron microscopy images. The direct observation of the devices confirmed features on the top electrode with bubble-like appearance, as well as some precipitates within the SiAlON. Chemical analysis by electron energy loss spectroscopy has demonstrated that there is an out-diffusion of oxygen and nitrogen ions from the SiAlON layer towards the electrode, thus forming silicon-rich paths within the dielectric layer and indicating vacancy change to be the main mechanism in the resistive switching.

  17. Si-related color centers in nanocrystalline diamond thin films

    Czech Academy of Sciences Publication Activity Database

    Potocký, Štěpán; Holovský, Jakub; Remeš, Zdeněk; Müller, Martin; Kočka, Jan; Kromka, Alexander

    2014-01-01

    Roč. 251, č. 12 (2014), s. 2603-2606 ISSN 0370-1972 R&D Projects: GA TA ČR TA01011740; GA ČR(CZ) GA14-04790S; GA MŠk LH12186 Institutional support: RVO:68378271 Keywords : chemical vapor deposition * color center * diamond * photoluminescence * plasma Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.489, year: 2014

  18. Characterization of color centers in quartz induced by gamma irradiation

    International Nuclear Information System (INIS)

    Guttler, Rainer A.S.

    2009-01-01

    The availability of gamma ray irradiators in Brazil increased the possibilities of treatments of gemstones for color enhancements. One of the minerals with a very high potential of these treatments is quartz, a very widespread mineral with much colored commercial varieties. Quartz occurs in Brazil mainly in two geological environments, called pegmatitic and hydrothermal. The detailed mechanism of color center formation of these two types of quartz will be investigated by spectroscopic and chemical analysis. Until yet, it can be shown that due to chemical differences of the nature of mineral forming fluids, the two types behave differently. All quartzes contain mainly traces of Iron, Aluminum, Lithium and some amounts of Water. The quartz of hydrothermal origin incorporated much structurally bound water, and despite some similarities with the chemical composition of pegmatitic quartz, this high water content is the reason for the formation of Silanol radicals, giving the green color to the quartz. The main difference in chemical composition of pegmatitic quartz is the presence of higher amounts of Al and Li , responsible for the brownish and yellowish colors formed by irradiation. Since each pegmatite is different, the quartz will behave differently. This explains the formation of the famous 'Green Gold' of quartz from Sao Jose da Safira , and the more yellowish, Citrine type, color of quartz from the Coluna deposit, near Itamarandiba, Minas Gerais. (author)

  19. Characterization of color centers in quartz induced by gamma irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Guttler, Rainer A.S., E-mail: rainersg@usp.b [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Geociencias; Enokihara, Cyro T.; Rela, Paulo R., E-mail: prela@ipen.b, E-mail: cteiti@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    The availability of gamma ray irradiators in Brazil increased the possibilities of treatments of gemstones for color enhancements. One of the minerals with a very high potential of these treatments is quartz, a very widespread mineral with much colored commercial varieties. Quartz occurs in Brazil mainly in two geological environments, called pegmatitic and hydrothermal. The detailed mechanism of color center formation of these two types of quartz will be investigated by spectroscopic and chemical analysis. Until yet, it can be shown that due to chemical differences of the nature of mineral forming fluids, the two types behave differently. All quartzes contain mainly traces of Iron, Aluminum, Lithium and some amounts of Water. The quartz of hydrothermal origin incorporated much structurally bound water, and despite some similarities with the chemical composition of pegmatitic quartz, this high water content is the reason for the formation of Silanol radicals, giving the green color to the quartz. The main difference in chemical composition of pegmatitic quartz is the presence of higher amounts of Al and Li , responsible for the brownish and yellowish colors formed by irradiation. Since each pegmatite is different, the quartz will behave differently. This explains the formation of the famous 'Green Gold' of quartz from Sao Jose da Safira , and the more yellowish, Citrine type, color of quartz from the Coluna deposit, near Itamarandiba, Minas Gerais. (author)

  20. Properties of the generation of radiation in the near infrared part of the spectrum with a sapphire crystal laser having radiation-induced color centers

    International Nuclear Information System (INIS)

    Voitovich, A.P.; Grinkevich, V.E.; Kononov, V.A.; Kromskii, G.I.

    1986-01-01

    This paper investigates the spectral stability of the color centers in sapphire and the energy of lasers in which the active elements were colored with various techniques. Color centers were produced by neutron irradiation. The absorption spectra of the color centers are shown. The transformation of the spectra shows that the mutual conversions of color centers takes place during the thermal annealing of the sapphire; most of the color centers formed have luminescence. Generation or radiation with a tunable frequency was obtained in the case of transverse or quasi-longitudinal excitation by a ruby laser. The results show that ways for increasing the stability of the energy generated by a sapphire laser with color centers can be found

  1. Formation and transformation of the radiation-induced nearsurface color centers in sodium and lithium fluorides nanocrystals

    Science.gov (United States)

    Novikov, A. N.; Kalinov, V. S.; Radkevich, A. V.; Runets, L. P.; Stupak, A. P.; Voitovich, A. P.

    2017-11-01

    Near-surface color centers in sodium fluoride nanocrystals have been formed. At pre-irradiation annealing of sodium and lithium fluorides samples at temperatures of 623 K and above, the near-surface color centers in them have not been found after γ-irradiation. Annealing lithium fluoride nanocrystals with the near-surface defects leads to their transformation into bulk ones of the same composition.

  2. Fluorescent nanodiamonds and their use in biomedical research

    Science.gov (United States)

    Suarez-Kelly, Lorena P.; Rampersaud, Isaac V.; Moritz, Charles E.; Campbell, Amanda R.; Hu, Zhiwei; Alkahtani, Masfer H.; Alghannam, Fahad S.; Hemmer, Phillip; Carson, William E.; Rampersaud, Arfaan A.

    2016-03-01

    Nanodiamonds containing color-centers produce non-quenching fluorescence that is easily detected. This makes them useful for cellular, proteomic and genomic applications. However, fluorescent nanodiamonds have yet to become popular in the biomedical research community as labeling reagents. We discuss production of nanodiamonds with distinct color-centers and assess their biocompatibility and techniques for bioconjugation. Fluorescent diamonds were fabricated by electron irradiation of high-pressure, high-temperature micron-sized diamonds which generated diamonds with vacancy-related defects (V). These diamonds were annealed to create nitrogen vacancy (NV)-centers then following a milling step were fractionated into nanoparticle sizes of 30, 60, and 95 nm. Optical characterization of Vand NV-center diamonds demonstrated fluorescence in two distinct green and red channels, respectively. In vitro studies demonstrated that these nanodiamonds are biocompatible and readily taken up by murine macrophage cells. Quantification of NV-center nanodiamond uptake by flow cytometry, showed that uptake was independent of nanodiamond size. Confocal microscopy demonstrated that NV-center nanodiamonds accumulate within the cytoplasm of these cells. NV-center nanodiamonds were then conjugated with streptavidin using a short polyethylene chain as linker. Conjugation was confirmed via a catalytic assay employing biotinylated-horseradish peroxidase. We present a technique for large-scale production of biocompatible conjugated V- or NV-center nanodiamonds. Functional testing is essential for standardization of fluorescent nanodiamond bioconjugates and quality control. Large-scale production of bioconjugated fluorescent nanodiamonds is crucial to their development as novel tools for biological and medical applications.

  3. Quantum optics with single nanodiamonds flying over gold films: Towards a Robust quantum plasmonics

    Energy Technology Data Exchange (ETDEWEB)

    Mollet, O.; Drezet, A.; Huant, S. [Institut Néel, CNRS and Université Joseph Fourier, BP 166, F-38042 Grenoble (France)

    2013-12-04

    A nanodiamond (ND) hosting nitrogen-vacancy (NV) color centers is attached on the apex of an optical tip for near-field microscopy. Its fluorescence is used to launch surface plasmon-polaritons (SPPs) in a thin polycrystalline gold film. It is shown that the quantum nature of the initial source of light is preserved after conversion to SPPs. This opens the way to a deterministic quantum plasmonics, where single SPPs can be injected at well-defined positions in a plasmonic device produced by top-down approaches.

  4. Proteomic Analysis Reveals the Leaf Color Regulation Mechanism in Chimera Hosta "Gold Standard" Leaves.

    Science.gov (United States)

    Yu, Juanjuan; Zhang, Jinzheng; Zhao, Qi; Liu, Yuelu; Chen, Sixue; Guo, Hongliang; Shi, Lei; Dai, Shaojun

    2016-03-08

    Leaf color change of variegated leaves from chimera species is regulated by fine-tuned molecular mechanisms. Hosta "Gold Standard" is a typical chimera Hosta species with golden-green variegated leaves, which is an ideal material to investigate the molecular mechanisms of leaf variegation. In this study, the margin and center regions of young and mature leaves from Hosta "Gold Standard", as well as the leaves from plants after excess nitrogen fertilization were studied using physiological and comparative proteomic approaches. We identified 31 differentially expressed proteins in various regions and development stages of variegated leaves. Some of them may be related to the leaf color regulation in Hosta "Gold Standard". For example, cytosolic glutamine synthetase (GS1), heat shock protein 70 (Hsp70), and chloroplastic elongation factor G (cpEF-G) were involved in pigment-related nitrogen synthesis as well as protein synthesis and processing. By integrating the proteomics data with physiological results, we revealed the metabolic patterns of nitrogen metabolism, photosynthesis, energy supply, as well as chloroplast protein synthesis, import and processing in various leaf regions at different development stages. Additionally, chloroplast-localized proteoforms involved in nitrogen metabolism, photosynthesis and protein processing implied that post-translational modifications were crucial for leaf color regulation. These results provide new clues toward understanding the mechanisms of leaf color regulation in variegated leaves.

  5. Electronic structure of vacancies and vacancy clusters in simple metals

    International Nuclear Information System (INIS)

    Manninen, M.; Nieminen, R.M.

    1978-05-01

    The self-consistent density functional approach has been applied in a study of electronic properties of vacancies and vacancy clusters in simple metals. The electron density profiles and potentials have been obtained for spherical voids of varying size. The formation energies and residual resistivities have been calculated for vacancies using both perturbational and variational inclusion of discrete lattice effects. The relation of the void properties to the plane surface ones is studied, and the inadequacy of the jellium-based methods to high-index faces is demonstrated. (author)

  6. Creation and characterization of He-related color centers in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Forneris, J., E-mail: forneris@to.infn.it [Istituto Nazionale di Fisica Nucleare (INFN), Sez. Torino, via P. Giuria 1, 10125 Torino (Italy); Physics Department and “NIS” Inter-departmental Centre - University of Torino, 10125 Torino (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Sez. Torino, Torino (Italy); Tengattini, A.; Tchernij, S. Ditalia [Physics Department and “NIS” Inter-departmental Centre - University of Torino, 10125 Torino (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sez. Torino, via P. Giuria 1, 10125 Torino (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Sez. Torino, Torino (Italy); Picollo, F. [Istituto Nazionale di Fisica Nucleare (INFN), Sez. Torino, via P. Giuria 1, 10125 Torino (Italy); Physics Department and “NIS” Inter-departmental Centre - University of Torino, 10125 Torino (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Sez. Torino, Torino (Italy); Battiato, A. [Physics Department and “NIS” Inter-departmental Centre - University of Torino, 10125 Torino (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sez. Torino, via P. Giuria 1, 10125 Torino (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Sez. Torino, Torino (Italy); Traina, P.; Degiovanni, I.P.; Moreva, E.; Brida, G. [Istituto Nazionale di Ricerca Metrologica (INRiM), Strada delle Cacce 91, 10135 Torino (Italy); Grilj, V.; Skukan, N.; Jakšić, M. [Ruđer Bošković Institute, Bijenicka 54, P.O. Box 180, 10002 Zagreb (Croatia); and others

    2016-11-15

    Diamond is a promising material for the development of emerging applications in quantum optics, quantum information and quantum sensing. The fabrication and characterization of novel luminescent defects with suitable opto-physical properties is therefore of primary importance for further advances in these research fields. In this work we report on the investigation in the formation of photoluminescent (PL) defects upon MeV He implantation in diamond. Such color centers, previously reported only in electroluminescence and cathodoluminescence regime, exhibited two sharp emission lines at 536.5 nm and 560.5 nm, without significant phonon sidebands. A strong correlation between the PL intensities of the above-mentioned emission lines and the He implantation fluence was found in the 10{sup 15}–10{sup 17} cm{sup −2} fluence range. The PL emission features were not detected in control samples, i.e. samples that were either unirradiated or irradiated with different ion species (H, C). Therefore, the PL features are attributed to optically active defects in the diamond matrix associated with He impurities. The intensity of the 536.5 nm and 560.5 nm emission lines was investigated as a function of the annealing temperature of the diamond substrate. The emission was observed upon annealing at temperatures higher than 500 °C, at the expenses of the concurrently decreasing neutral-vacancy-related GR1 emission intensity. Therefore, our findings indicate that the luminescence originates from the formation of a stable lattice defect. Finally, photoluminescence from He-related defects was observed under different laser excitations wavelengths (i.e. 532 nm and 405 nm), thus providing promising evidence of a broad spectral range for optical stimulation. - Highlights: • Creation of luminescent defects in single-crystal diamond upon He implantation. • First observation of photoluminescent emission from two sharp emission lines at 536.5 and 560.5 nm. • Attribution of the

  7. Creation and characterization of He-related color centers in diamond

    International Nuclear Information System (INIS)

    Forneris, J.; Tengattini, A.; Tchernij, S. Ditalia; Picollo, F.; Battiato, A.; Traina, P.; Degiovanni, I.P.; Moreva, E.; Brida, G.; Grilj, V.; Skukan, N.; Jakšić, M.

    2016-01-01

    Diamond is a promising material for the development of emerging applications in quantum optics, quantum information and quantum sensing. The fabrication and characterization of novel luminescent defects with suitable opto-physical properties is therefore of primary importance for further advances in these research fields. In this work we report on the investigation in the formation of photoluminescent (PL) defects upon MeV He implantation in diamond. Such color centers, previously reported only in electroluminescence and cathodoluminescence regime, exhibited two sharp emission lines at 536.5 nm and 560.5 nm, without significant phonon sidebands. A strong correlation between the PL intensities of the above-mentioned emission lines and the He implantation fluence was found in the 10 15 –10 17 cm −2 fluence range. The PL emission features were not detected in control samples, i.e. samples that were either unirradiated or irradiated with different ion species (H, C). Therefore, the PL features are attributed to optically active defects in the diamond matrix associated with He impurities. The intensity of the 536.5 nm and 560.5 nm emission lines was investigated as a function of the annealing temperature of the diamond substrate. The emission was observed upon annealing at temperatures higher than 500 °C, at the expenses of the concurrently decreasing neutral-vacancy-related GR1 emission intensity. Therefore, our findings indicate that the luminescence originates from the formation of a stable lattice defect. Finally, photoluminescence from He-related defects was observed under different laser excitations wavelengths (i.e. 532 nm and 405 nm), thus providing promising evidence of a broad spectral range for optical stimulation. - Highlights: • Creation of luminescent defects in single-crystal diamond upon He implantation. • First observation of photoluminescent emission from two sharp emission lines at 536.5 and 560.5 nm. • Attribution of the emission lines to

  8. Many-electron states of the N2 and N3 color centers in diamond: A first- principles and many-body study

    Energy Technology Data Exchange (ETDEWEB)

    Babamoradi, Mohsen, E-mail: babamoradi@iust.ac.ir [Department of Physics, Iran University of Science and Technology, Narmak,16846-13114 Tehran (Iran, Islamic Republic of); Asgari, Sussan [Department of Physics, Iran University of Science and Technology, Narmak,16846-13114 Tehran (Iran, Islamic Republic of); Ranjbar, Ahmad [Computational Materials Science Research Team, RIKEN Advanced Institute for Computational Science, Kobe, Hyogo 650-0047 (Japan); Belosludov, Rodion V. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Yunoki, Seiji [Computational Materials Science Research Team, RIKEN Advanced Institute for Computational Science, Kobe, Hyogo 650-0047 (Japan); Computational Condensed Matter Physics Laboratory, RIKEN, Wako, Saitama 351-0198 (Japan); Computational Quantum Matter Research Team, RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198 (Japan)

    2017-01-15

    A new model is applied to calculate the many-body properties of the neutral N3 color center in diamond. This model is based on the first-principles density functional theory (DFT) and cluster method, which is combined with the generalized Hubbard model. In contrast to the previous models for N3 centers, our model does not require the configuration interaction (CI) and molecular orbital (MO) techniques. The N3 defect in diamond is simulated with an empty site next to three substitutional nitrogen atoms in the center of a hydrogen-terminated diamond cluster. The method is shown to be highly accurate for describing the symmetries and spin properties of the ground state and the first dipole-allowed excited state for the N3 center. We obtain the transition energy as 412 nm for the first dipole-allowed transition, which is in good agreement with the corresponding experimental value as 415 nm. We assigned the dipole-allowed transition between the first and second excited states as the N2 optical peak, and evaluated the N2 optical peak to be 463 nm, which is close to the experimental value as 478 nm.

  9. Spin-dependent recombination involving oxygen-vacancy complexes in silicon

    Science.gov (United States)

    Franke, David P.; Hoehne, Felix; Vlasenko, Leonid S.; Itoh, Kohei M.; Brandt, Martin S.

    2014-05-01

    Spin-dependent relaxation and recombination processes in γ-irradiated n-type Czochralski-grown silicon are studied using continuous wave (cw) and pulsed electrically detected magnetic resonance (EDMR). Two processes involving the SL1 center, the neutral excited triplet state of the oxygen-vacancy complex, are observed which can be separated by their different dynamics. One of the processes is the relaxation of the excited SL1 state to the ground state of the oxygen-vacancy complex, the other a charge transfer between 31P donors and SL1 centers forming close pairs, as indicated by electrically detected electron double resonance. For both processes, the recombination dynamics is studied with pulsed EDMR techniques. We demonstrate the feasibility of true zero-field cw and pulsed EDMR for spin-1 systems and use this to measure the lifetimes of the different spin states of SL1 also at vanishing external magnetic field.

  10. Luminescence of color centers in MgF2 crystals

    International Nuclear Information System (INIS)

    Vakhidov, Sh.A.; Nuritdinov, I.; Musaeva, M.A.

    1999-01-01

    The photoluminescence characteristics of the proper radiation color centers of the MgF 2 crystals are studied. The samples were irradiated by the 60 Co source γ-rays up to the dose 10 7 Gy. The bands with the maxima in the area of 420, 460, 550 and 620 nm were identified, which are excited correspondingly in the bands with the maxima of 370, 320, 410 and 480 nm

  11. Role of oxygen vacancies in anodic TiO2 thin films

    International Nuclear Information System (INIS)

    Tit, N.; Halley, J.W.

    1992-05-01

    Defects play an important role in the electronic and optical properties of amorphous solids in general. Here we present both experimental and theoretical investigations on the nature and origin of defect states in anodic rutile TiO 2 thin films (of thickness 5nm to 20nm). There is experimental evidence that the observed gap state at 0.7eV below the edge of conduction-band is due to an oxygen vacancy. For this reason, oxygen vacancies are used in our model. A comparison of the calculated bulk-photoconductivity to photospectroscopy experiment reveals that the films have bulk-like transport properties. On the other hand a fit of the surface density of states to the scanning tunneling microscopy (STM) on the (001) surfaces has suggested a surface defect density of 5% of oxygen vacancies. To resolve this discrepancy, we calculated the dc-conductivity where localization effects are included. Our results show an impurity band formation at about p c =9% of oxygen vacancies. We concluded that the gap states seen in STM are localized and the oxygen vacancies are playing the role of trapping centers (deep levels) in the studied films. (author). 15 refs, 5 figs

  12. Elastic atomic displacements and color center creation in LiF crystals irradiated with 3-, 9- and 12-MeV Au ions

    International Nuclear Information System (INIS)

    Sorokin, M.V.; Papaleo, R.M.; Schwartz, K.

    2009-01-01

    Creation of color centers in LiF under irradiation with 3-12-MeV Au ions was studied. Comparison of experimental data of color center creation with computer simulation of the energy deposition and elastic atomic displacements reveals the role of elastic collisions in defect creation by these ions, which have comparable magnitudes of electronic and elastic stopping. The experimentally measured efficiency of color center creation and that predicted by the simulation of elastic displacements have a similar dependence on the projectile energy. Thus, the color center creation is mainly associated with the elastic collisions, despite the relatively large values of the electronic stopping power for these ions. (orig.)

  13. The effect of ions on the magnetic moment of vacancy for ion-implanted 4H-SiC

    Science.gov (United States)

    Peng, B.; Zhang, Y. M.; Dong, L. P.; Wang, Y. T.; Jia, R. X.

    2017-04-01

    The structural properties and the spin states of vacancies in ion implanted silicon carbide samples are analyzed by experimental measurements along with first-principles calculations. Different types and dosages of ions (N+, O+, and B+) were implanted in the 4H-silicon carbide single crystal. The Raman spectra, positron annihilation spectroscopy, and magnetization-magnetic field curves of the implanted samples were measured. The fitting results of magnetization-magnetic field curves reveal that samples implanted with 1 × 1016 cm-2 N+ and O+ ions generate paramagnetic centers with various spin states of J = 1 and J = 0.7, respectively. While for other implanted specimens, the spin states of the paramagnetic centers remain unchanged compared with the pristine sample. According to the positron annihilation spectroscopy and first-principles calculations, the change in spin states originates from the silicon vacancy carrying a magnetic moment of 3.0 μB in the high dosage N-implanted system and 2.0 μB in the O-doped system. In addition, the ratio of the concentration of implanted N ions and silicon vacancies will affect the magnetic moment of VSi. The formation of carbon vacancy which does not carry a local magnetic moment in B-implanted SiC can explain the invariability in the spin states of the paramagnetic centers. These results will help to understand the magnetic moments of vacancies in ion implanted 4H-SiC and provide a possible routine to induce vacancies with high spin states in SiC for the application in quantum technologies and spintronics.

  14. Reducing RN Vacancy Rate: A Nursing Recruitment Office Process Improvement Project.

    Science.gov (United States)

    Hisgen, Stephanie A; Page, Nancy E; Thornlow, Deirdre K; Merwin, Elizabeth I

    2018-06-01

    The aim of this study was to reduce the RN vacancy rate at an academic medical center by improving the hiring process in the Nursing Recruitment Office. Inability to fill RN positions can lead to higher vacancy rates and negatively impact staff and patient satisfaction, quality outcomes, and the organization's bottom line. The Model for Improvement was used to design and implement a process improvement project to improve the hiring process from time of interview through the position being filled. Number of days to interview and check references decreased significantly, but no change in overall time to hire and time to fill positions was noted. RN vacancy rate also decreased significantly. Nurse manager satisfaction with the hiring process increased significantly. Redesigning the recruitment process supported operational efficiencies of the organization related to RN recruitment.

  15. Electron spin resonance from NV centers in diamonds levitating in an ion trap

    International Nuclear Information System (INIS)

    Delord, T; Nicolas, L; Schwab, L; Hétet, G

    2017-01-01

    We report observations of the electron spin resonance (ESR) of nitrogen vacancy centers in diamonds that are levitating in an ion trap. Using a needle Paul trap operating under ambient conditions, we demonstrate efficient microwave driving of the electronic spin and show that the spin properties of deposited diamond particles measured by the ESR are retained in the Paul trap. We also exploit the ESR signal to show angle stability of single trapped mono-crystals, a necessary step towards spin-controlled levitating macroscopic objects. (paper)

  16. Large-scale production of graphitic carbon nitride with outstanding nitrogen photofixation ability via a convenient microwave treatment

    International Nuclear Information System (INIS)

    Ma, Huiqiang; Shi, Zhenyu; Li, Shuang; Liu, Na

    2016-01-01

    Highlights: • Microwave method for synthesizing g-C_3N_4 with N_2 photofixation ability is reported. • Nitrogen vacancies play the important role on the nitrogen photofixation ability. • The present process is a convenient method for large-scale production of g-C_3N_4. - Abstract: A convenient microwave treatment for synthesizing graphitic carbon nitride (g-C_3N_4) with outstanding nitrogen photofixation ability under visible light is reported. X-ray diffraction (XRD), N_2 adsorption, UV–vis spectroscopy, SEM, N_2-TPD, EPR, photoluminescence (PL) and photocurrent measurements were used to characterize the prepared catalysts. The results indicate that microwave treatment can form many irregular pores in as-prepared g-C_3N_4, which causes the increased surface area and separation rate of electrons and holes. More importantly, microwave treatment causes the formation of many nitrogen vacancies in as-prepared g-C_3N_4. These nitrogen vacancies not only serve as active sites to adsorb and activate N_2 molecules but also promote interfacial charge transfer from catalysts to N_2 molecules, thus significantly improving the nitrogen photofixation ability. Moreover, the present process is a convenient method for large-scale production of g-C_3N_4 which is significantly important for the practical application.

  17. Color Fundus Photography versus Fluorescein Angiography in Identification of the Macular Center and Zone in Retinopathy of Prematurity

    Science.gov (United States)

    Patel, Samir N.; Klufas, Michael A.; Ryan, Michael C.; Jonas, Karyn E.; Ostmo, Susan; Martinez-Castellanos, Maria Ana; Berrocal, Audina M.; Chiang, Michael F.; Chan, R.V. Paul

    2016-01-01

    Purpose To examine the utility of fluorescein angiography (FA) in identification of the macular center and the diagnosis of zone in patients with retinopathy of prematurity (ROP). Design Validity and reliability analysis of diagnostic tools Methods 32 sets (16 color fundus photographs; 16 color fundus photographs paired with the corresponding FA) of wide-angle retinal images obtained from 16 eyes of eight infants with ROP were compiled on a secure web site. 9 ROP experts (3 pediatric ophthalmologists; 6 vitreoretinal surgeons) participated in the study. For each image set, experts identified the macular center and provided a diagnosis of zone. Main Outcome Measures (1) Sensitivity and specificity of zone diagnosis (2) “Computer facilitated diagnosis of zone,” based on precise measurement of the macular center, optic disc center, and peripheral ROP. Results Computer facilitated diagnosis of zone agreed with the expert’s diagnosis of zone in 28/45 (62%) cases using color fundus photographs and in 31/45 (69%) cases using FA. Mean (95% CI) sensitivity for detection of zone I by experts as compared to a consensus reference standard diagnosis when interpreting the color fundus images alone versus interpreting the color fundus photographs and FA was 47% (35.3% – 59.3%) and 61.1% (48.9% – 72.4%), respectively, (t(9) ≥ (2.063), p = 0.073). Conclusions There is a marginally significant difference in zone diagnosis when using color fundus photographs compared to using color fundus photographs and the corresponding fluorescein angiograms. There is inconsistency between traditional zone diagnosis (based on ophthalmoscopic exam and image review) compared to a computer-facilitated diagnosis of zone. PMID:25637180

  18. Electrically active induced energy levels and metastability of B and N vacancy-complexes in 4H–SiC

    Science.gov (United States)

    Igumbor, E.; Olaniyan, O.; Mapasha, R. E.; Danga, H. T.; Omotoso, E.; Meyer, W. E.

    2018-05-01

    Electrically active induced energy levels in semiconductor devices could be beneficial to the discovery of an enhanced p or n-type semiconductor. Nitrogen (N) implanted into 4H–SiC is a high energy process that produced high defect concentrations which could be removed during dopant activation annealing. On the other hand, boron (B) substituted for silicon in SiC causes a reduction in the number of defects. This scenario leads to a decrease in the dielectric properties and induced deep donor and shallow acceptor levels. Complexes formed by the N, such as the nitrogen-vacancy centre, have been reported to play a significant role in the application of quantum bits. In this paper, results of charge states thermodynamic transition level of the N and B vacancy-complexes in 4H–SiC are presented. We explore complexes where substitutional N/N or B/B sits near a Si (V) or C (V) vacancy to form vacancy-complexes (NV, NV, NV, NV, BV, BV, BV and BV). The energies of formation of the N related vacancy-complexes showed the NV to be energetically stable close to the valence band maximum in its double positive charge state. The NV is more energetically stable in the double negative charge state close to the conduction band minimum. The NV on the other hand, induced double donor level and the NV induced a double acceptor level. For B related complexes, the BV and BV were energetically stable in their single positive charge state close to the valence band maximum. As the Fermi energy is varied across the band gap, the neutral and single negative charge states of the BV become more stable at different energy levels. B and N related complexes exhibited charge state controlled metastability behaviour.

  19. Clustering and segregation of small vacancy clusters near tungsten (0 0 1) surface

    Science.gov (United States)

    Duan, Guohua; Li, Xiangyan; Xu, Yichun; Zhang, Yange; Jiang, Yan; Hao, Congyu; Liu, C. S.; Fang, Q. F.; Chen, Jun-Ling; Luo, G.-N.; Wang, Zhiguang

    2018-01-01

    Nanoporous metals have been shown to exhibit radiation-tolerance due to the trapping of the defects by the surface. However, the behavior of vacancy clusters near the surface is not clear which involves the competition between the self-trapping and segregation of small vacancy clusters (Vn) nearby the surface. In this study, we investigated the energetic and kinetic properties of small vacancy clusters near tungsten (0 0 1) surface by combining molecular statics (MS) calculations and object Kinetic Monte Carlo (OKMC) simulations. Results show that vacancies could be clustered with the reduced formation energy and migration energy of the single vacancy around a cluster as the respective energetic and kinetic driving forces. The small cluster has a migration energy barrier comparable to that for the single vacancy; the migration energy barriers for V1-5 and V7 are 1.80, 1.94, 2.17, 2.78, 3.12 and 3.11 eV, respectively. Clusters and become unstable near surface (0 0 1) and tend to dissociate into the surface. At the operation temperature of 1000 K, the single vacancy, V2, 2 V 3 V3 and V4 were observed to segregate to the surface within a time of one hour. Meanwhile, larger clusters survived near the surface, which could serve as nucleating center for voids near the surface. Our results suggest that under a low radiation dose, surface (0 0 1) could act as a sink for small vacancy clusters, alleviating defect accumulation in the material under a low radiation dose. We also obtained several empirical expressions for the vacancy cluster formation energy, binding energy, and trapping radius as a function of the number of vacancies in the cluster.

  20. Silicon-vacancy centre as an artificial atom in diamond

    International Nuclear Information System (INIS)

    Lachlan Rogers

    2014-01-01

    A transition at 738 nm in diamond has been attributed to the silicon vacancy (SiV) colour centre. Much less is known about this defect site than the famous nitrogen-vacancy centre, but it appears to have advantages for some applications It is particularly promising as a single-photon source, due to a bright optical transition which has most of its intensity in the zero-phonon-line and only a small phonon sideband. A number of results will be reported for single SiV sites in bulk diamond, complementing recent activity on SiV in nanodiamonds. Individual SiV sites in the low-strain environment of bulk diamond show almost no variation in photoluminescence spectra. By fabricating a solid-immersion lens in the diamond over a SiV site we have enhanced the photon collection rate by nearly a factor of ten. In order to identify whether the SiV centre could be useful for broader quantum information processing application, it is first necessary to establish its electronic structure. Recent experimental developments in this direction will be discussed. (author)

  1. Ordering of vacancies on Si(001)

    NARCIS (Netherlands)

    Zandvliet, Henricus J.W.

    1997-01-01

    Missing dimer vacancies are always present on the clean Si(001) surface. The vacancy density can be increased by ion bombardment (Xe+, Ar+), etching (O2, Br2, I2, etc.) or Ni contamination. The equilibrium shape at low vacancy concentrations (<0.2¿0.3 monolayers) of these vacancy islands is

  2. Vacancy behavior in a compressed fcc Lennard-Jones crystal

    International Nuclear Information System (INIS)

    Beeler, J.R. Jr.

    1981-12-01

    This computer experiment study concerns the determination of the stable vacancy configuration in a compressed fcc Lennard-Jones crystal and the migration of this defect in a compressed crystal. Isotropic and uniaxial compression stress conditions were studied. The isotropic and uniaxial compression magnitudes employed were 0.94 less than or equal to eta less than or equal to 1.5, and 1.0 less than or equal to eta less than or equal to 1.5, respectively. The site-centered vacancy (SCV) was the stable vacancy configuration whenever cubic symmetry was present. This includes all of the isotropic compression cases and the particular uniaxial compression case (eta = √2) that give a bcc structure. In addition, the SCV was the stable configuration for uniaxial compression eta 1.20, the SV-OP is an extended defect and, therefore, a saddle point for SV-OP migration could not be determined. The mechanism for the transformation from the SCV to the SV-OP as the stable form at eta = 1.29 appears to be an alternating sign [101] and/or [011] shear process

  3. Modification of Color Centers by Electron Bombardment: Final Report CRADA No. TC-0460-93-A

    Energy Technology Data Exchange (ETDEWEB)

    Van Bibber, Karl [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Alger, Don M. [Quali-Tech, Inc., Columbia, MO (United States)

    2000-11-30

    The purpose of the project was to: Identify those electron beam irradiation parameters most relevant to process quality and efficiency, to producing and modifying color centers in topaz. Develop and test improved radiation processing techniques, and evaluate their potential applicability to other types of semi-precious gems. Develop an optimized data base for the process and procedures for identifying and characterizing material from new and diverse sources. Transfer new processing technology to the private sector, and, until they are implemented industrially, to perform radiation dosing to partially satisfy existing excess demand. We planned to define the interaction between sample purity level, the physics of irradiation to achieve color cent-er modification on a reproducible basis and demonstration of the resulting process on a commercially viable basis. The primary deliverable was the increased knowledge base in terms of expanded understanding of the systematics of color center modification in materials, and an extensive database of electron beam parameters which would optimize the efficiency and quality of radiation processing of topaz from diverse sources. The radiation processing of these stones constitutes a deliverable to Quali-Tech by LLNL.

  4. Room-temperature vacancy migration in crystalline Si from an ion-implanted surface layer

    DEFF Research Database (Denmark)

    Larsen, Arne Nylandsted; Christensen, Carsten; Petersen, Jon Wulff

    1999-01-01

    Migration of vacancies in crystalline, n-type silicon at room temperature from Ge+-implanted (150 keV, 5×109–1×1011 cm–2) surface layers was studied by tracing the presence of P–V pairs (E centers) in the underlying layer using deep level transient spectroscopy (DLTS). Under the conditions we have......–Et[approximate]0.15 eV that has donor character. It is argued that the center associated with this line is most probably the P2–V complex; it anneals at about 550 K. A lower limit of the RT-diffusion coefficient of the doubly charged, negative vacancy is estimated to be 4×10–11 cm2/s. ©1999 American Institute...

  5. Super-resolution from single photon emission: toward biological application

    Science.gov (United States)

    Moreva, E.; Traina, P.; Forneris, J.; Ditalia Tchernij, S.; Guarina, L.; Franchino, C.; Picollo, F.; Ruo Berchera, I.; Brida, G.; Degiovanni, I. P.; Carabelli, V.; Olivero, P.; Genovese, M.

    2017-08-01

    Properties of quantum light represent a tool for overcoming limits of classical optics. Several experiments have demonstrated this advantage ranging from quantum enhanced imaging to quantum illumination. In this work, experimental demonstration of quantum-enhanced resolution in confocal fluorescence microscopy will be presented. This is achieved by exploiting the non-classical photon statistics of fluorescence emission of single nitrogen-vacancy (NV) color centers in diamond. By developing a general model of super-resolution based on the direct sampling of the kth-order autocorrelation function of the photoluminescence signal, we show the possibility to resolve, in principle, arbitrarily close emitting centers. Finally, possible applications of NV-based fluorescent nanodiamonds in biosensing and future developments will be presented.

  6. Positron lifetime in vacancy clusters. Application to the study of vacancy-impurity interactions

    International Nuclear Information System (INIS)

    Corbel, C.

    1986-02-01

    Positron lifetime measurements are used to study the vacancy recovery (77-650 K) in 20 K electron irradiated dilute gold or iron alloys in stainless steels. Positron lifetimes in clusters of various shapes and structures are calculated to precise the information obtained by measuring the positron lifetime in a vacancy cluster of unknown size and configuration. From the calculations, we have drawn the following conclusions: - the minimal size of an unknown cluster can be deduced from the measurement of the positron lifetime in the cluster; - a decrease of the positron lifetime when the structure of the cluster evolves, means either a decrease of the size of the cluster, or, the appearance of a relaxed configuration. - The positron lifetime is very useful to discriminate between a spatial planar or relaxed configuration and a tri-dimensional one. In AuGe, AuSb, AuTn alloys, vacancy clusters decorated by solute atoms appear at 250 K. Their configurations are different from those in pure Au. Mobile vacancy-solutes complexes are involved in the clustering process in AuGe, AuSb. The clusters are probably decorated by several solute atoms in AuGe and AuSb where the resistivity evidences a clustering of solute atoms. In AuFe, vacancy-single or multi-complexes stable up to 670 K prevent cluster formation. In FeTi, FeSb, FeAu, vacancy migration is hindered by the formation of vacancy-solute complexes up to 315 K (Ti), up to 670 K (Sb), up to 700 K (Au). In FeSi, FeCu, FeAg, tri-dimensional clusters grow less easily than Fe. This is likely due to the formation of several kinds of small decorated clusters with relaxed or planar configurations. They are peculiarly stable, surviving up to 700 K at least. In Si (resp. Ti) doped 59Fe25Ni16Cr, solute atoms retain the vacancies up to 300 K (resp. 320 K) [fr

  7. Nitrogen terminated diamond

    Czech Academy of Sciences Publication Activity Database

    Stacey, A.; O'Donnell, K.M.; Chou, J.P.; Schenk, A.; Tadich, A.; Dontschuk, N.; Červenka, Jiří; Pakes, C.; Gali, A.; Hoffman, A.; Prawer, S.

    2015-01-01

    Roč. 2, č. 10 (2015), s. 1500079 ISSN 2196-7350 Institutional support: RVO:68378271 Keywords : vacancy centers * surface * sensors * xps Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.365, year: 2015

  8. Large-scale production of graphitic carbon nitride with outstanding nitrogen photofixation ability via a convenient microwave treatment

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Huiqiang [College of Chemistry, Chemical Engineering, and Environmental Engineering, Liaoning Shihua University, Fushun 113001 (China); College of Environment and Resources, Key Lab of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021 (China); Shi, Zhenyu; Li, Shuang [College of Chemistry, Chemical Engineering, and Environmental Engineering, Liaoning Shihua University, Fushun 113001 (China); Liu, Na, E-mail: Naliujlu@163.com [College of Environment and Resources, Key Lab of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021 (China)

    2016-08-30

    Highlights: • Microwave method for synthesizing g-C{sub 3}N{sub 4} with N{sub 2} photofixation ability is reported. • Nitrogen vacancies play the important role on the nitrogen photofixation ability. • The present process is a convenient method for large-scale production of g-C{sub 3}N{sub 4}. - Abstract: A convenient microwave treatment for synthesizing graphitic carbon nitride (g-C{sub 3}N{sub 4}) with outstanding nitrogen photofixation ability under visible light is reported. X-ray diffraction (XRD), N{sub 2} adsorption, UV–vis spectroscopy, SEM, N{sub 2}-TPD, EPR, photoluminescence (PL) and photocurrent measurements were used to characterize the prepared catalysts. The results indicate that microwave treatment can form many irregular pores in as-prepared g-C{sub 3}N{sub 4}, which causes the increased surface area and separation rate of electrons and holes. More importantly, microwave treatment causes the formation of many nitrogen vacancies in as-prepared g-C{sub 3}N{sub 4}. These nitrogen vacancies not only serve as active sites to adsorb and activate N{sub 2} molecules but also promote interfacial charge transfer from catalysts to N{sub 2} molecules, thus significantly improving the nitrogen photofixation ability. Moreover, the present process is a convenient method for large-scale production of g-C{sub 3}N{sub 4} which is significantly important for the practical application.

  9. Positron annihilation study of vacancy-type defects in fast-neutron-irradiated MgO·nAl2O3

    Science.gov (United States)

    Rahman, Abu Zayed Mohammad Saliqur; Li, Zhuoxin; Cao, Xingzhong; Wang, Baoyi; Wei, Long; Xu, Qiu; Atobe, Kozo

    2014-09-01

    The positron lifetimes of fast-neutron-irradiated MgO·nAl2O3 single crystals were measured to investigate the formation of cation vacancies. Al monovacancy was possibly observed in samples irradiated by fast neutrons at ultra-low temperatures. Additionally, vacancy-oxygen complex centers were possibly observed in samples irradiated at higher temperatures and fast neutron fluences. Coincidence Doppler broadening (CDB) spectra were measured to obtain information regarding the vicinity of vacancy-type defects. A peak at approximately 11 × 10-3 m0c was observed, which may be due to the presence of oxygen atoms in the neighborhood of the vacancies.

  10. Cathodoluminescence microscopy and spectroscopy of micro- and nanodiamonds: an implication for laboratory astrophysics.

    Science.gov (United States)

    Gucsik, Arnold; Nishido, Hirotsugu; Ninagawa, Kiyotaka; Ott, Ulrich; Tsuchiyama, Akira; Kayama, Masahiro; Simonia, Irakli; Boudou, Jean-Paul

    2012-12-01

    Color centers in selected micro- and nanodiamond samples were investigated by cathodoluminescence (CL) microscopy and spectroscopy at 298 K [room temperature (RT)] and 77 K [liquid-nitrogen temperature (LNT)] to assess the value of the technique for astrophysics. Nanodiamonds from meteorites were compared with synthetic diamonds made with different processes involving distinct synthesis mechanisms (chemical vapor deposition, static high pressure high temperature, detonation). A CL emission peak centered at around 540 nm at 77 K was observed in almost all of the selected diamond samples and is assigned to the dislocation defect with nitrogen atoms. Additional peaks were identified at 387 and 452 nm, which are related to the vacancy defect. In general, peak intensity at LNT at the samples was increased in comparison to RT. The results indicate a clear temperature-dependence of the spectroscopic properties of diamond. This suggests the method is a useful tool in laboratory astrophysics.

  11. First-principles study on migration of vacancy in tungsten

    International Nuclear Information System (INIS)

    Oda, Yasuhiro; Ito, Atsushi M.; Takayama, Arimichi; Nakamura, Hiroaki

    2014-03-01

    We calculated di-vacancy binding energies and migration energies of mono-vacancy and di-vacancy in tungsten material using DFT calculation. The mono-vacancy diffuses in [111] direction easily rather than in [001] direction. The migration energies of di-vacancies are almost the same value of the mono-vacancy. The migration of di-vacancy is approximately the same as the migration of mono-vacancy. The di-vacancy binding energies are almost zero or negative. The interactions between two vacancies in tungsten material are repulsive from the second to fifth nearest-neighbor. The vacancies are difficult to aggregate since di-vacancy is less stable than mono-vacancy. (author)

  12. First-Principles Study on the Structural and Electronic Properties of N Atoms Doped-Rutile TiO2 of Oxygen Vacancies

    Directory of Open Access Journals (Sweden)

    Zhong-Liang Zeng

    2015-01-01

    Full Text Available For the propose of considering the actual situation of electronic neutral, a simulation has been down on the basis of choosing the position of dual N and researching the oxygen vacancy. It is found that the reason why crystal material gets smaller is due to the emergence of impurity levels. By introducing the oxygen vacancy to the structure, the results show that while the oxygen vacancy is near the two nitrogen atoms which have a back to back position, its energy gets the lowest level and its structure gets the most stable state. From its energy band structure and density, the author finds that the impurity elements do not affect the migration of Fermi level while the oxygen vacancy has been increased. Instead of that, the conduction band of metal atoms moves to the Fermi level and then forms the N-type semiconductor material, but the photocatalytic activity is not as good as the dual N-doping state.

  13. Diurnal variability in carbon and nitrogen pools within Chesapeake Bay and northern Gulf of Mexico: implications for future ocean color satellite sensors

    Science.gov (United States)

    Mannino, A.; Novak, M. G.; Tzortziou, M.; Salisbury, J.

    2016-02-01

    Relative to their areal extent, estuaries and coastal ocean ecosystems contribute disproportionately more to global biogeochemical cycling of carbon, nitrogen and other elements compared to the open ocean. Applying ocean color satellite data to study biological and biogeochemical processes within coastal ecosystems is challenging due to the complex mixtures of aquatic constituents derived from terrestrial, anthropogenic, and marine sources, human-impacted atmospheric properties, presence of clouds during satellite overpass, fine-scale spatial gradients, and time-varying processes on diurnal scales that cannot be resolved with current sensors. On diurnal scales, biological, photochemical, and biogeochemical processes are regulated by the variation in solar radiation. Other physical factors, such as tides, river discharge, estuarine and coastal ocean circulation, wind-driven mixing, etc., impart further variability on biological and biogeochemical processes on diurnal to multi-day time scales. Efforts to determine the temporal frequency required from a NASA GEO-CAPE ocean color satellite sensor to discern diurnal variability C and N stocks, fluxes and productivity culminated in field campaigns in the Chesapeake Bay and northern Gulf of Mexico. Near-surface drogues were released and tracked in quasi-lagrangian space to monitor hourly changes in community production, C and N stocks, and optical properties. While only small diurnal changes were observed in dissolved organic carbon (DOC) and colored dissolved organic matter (CDOM) absorption in Chesapeake Bay, substantial variation in particulate organic carbon (POC) and nitrogen (PN), chlorophyll-a, and inorganic nitrogen (DIN) were measured. Similar or greater diurnal changes in POC, PN, chlorophyll-a and DIN were found in Gulf of Mexico nearshore and offshore sites. These results suggest that satellite observations at hourly frequency are desirable to capture diurnal variability in carbon and nitrogen stocks, fluxes

  14. Positron probing of open vacancy volume of phosphorus-vacancy complexes in float-zone n-type silicon irradiated by 0.9-MeV electrons and by 15-MeV protons

    Energy Technology Data Exchange (ETDEWEB)

    Arutyunov, Nikolay [Department of Physics, Martin Luther University Halle (Germany); Ioffe Physico-Technical Institute, St. Petersburg (Russian Federation); Institute of Ion-Plasma and Laser Technologies (Institute of Electronics), Tashkent (Uzbekistan); Emtsev, Vadim; Oganesyan, Gagik [Ioffe Physico-Technical Institute, St. Petersburg (Russian Federation); Elsayed, Mohamed [Department of Physics, Martin Luther University Halle (Germany); Faculty of Science, Department of Physics, Minia University (Egypt); Krause-Rehberg, Reinhard [Department of Physics, Martin Luther University Halle (Germany); Abrosimov, Nikolay [Leibniz Institute for Crystal Growth, Berlin (Germany); Kozlovski, Vitalii [St. Petersburg State Polytechnical University (Russian Federation)

    2017-07-15

    For the first time the samples, cut from the same wafer of crystals of float-zone silicon, n-FZ-Si(P) and n-FZ-Si(Bi), were subjected to irradiation with 0.9-MeV electrons and 15-MeV protons at RT for studying them by low-temperature positron annihilation lifetime spectroscopy. Measurements of Hall effect have been used for the materials characterization. The discussion is focused on the open vacancy volume (V{sub op}) of the thermally stable group-V-impurity-vacancy complexes comprising the phosphorus atoms; the bismuth-related vacancy complexes are briefly considered. The data of positron probing of PV pairs (E-centers), divacancies, and the thermally stable defects in the irradiated n-FZ-Si(P) materials are compared. Beyond a reliable detecting of the defect-related positron annihilation lifetime in the course of isochronal annealing at ∝ 500 C, the recovery of concentration of phosphorus-related shallow donor states continues up to ∝650-700 C. The open vacancy volumes V{sub op} to be characterized by long positron lifetimes Δτ{sub 2} ∝271-289 ps in (gr.-V-atom)-V{sub op} complexes are compared with theoretical data available for the vacancies, τ(V{sub 1}), and divacancies, τ(V{sub 2}). The extended semi-vacancies, 2V{sub s-ext}, and relaxed vacancies, 2V{sub inw}, are proposed as the open volume V{sub op} in (gr.-V-atom)-V{sub op} complexes. It is argued that at high annealing temperature the defect P{sub s}-V{sub op}-P{sub s} is decomposed. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Solute-vacancy binding in aluminum

    International Nuclear Information System (INIS)

    Wolverton, C.

    2007-01-01

    Previous efforts to understand solute-vacancy binding in aluminum alloys have been hampered by a scarcity of reliable, quantitative experimental measurements. Here, we report a large database of solute-vacancy binding energies determined from first-principles density functional calculations. The calculated binding energies agree well with accurate measurements where available, and provide an accurate predictor of solute-vacancy binding in other systems. We find: (i) some common solutes in commercial Al alloys (e.g., Cu and Mg) possess either very weak (Cu), or even repulsive (Mg), binding energies. Hence, we assert that some previously reported large binding energies for these solutes are erroneous. (ii) Large binding energies are found for Sn, Cd and In, confirming the proposed mechanism for the reduced natural aging in Al-Cu alloys containing microalloying additions of these solutes. (iii) In addition, we predict that similar reduction in natural aging should occur with additions of Si, Ge and Au. (iv) Even larger binding energies are found for other solutes (e.g., Pb, Bi, Sr, Ba), but these solutes possess essentially no solubility in Al. (v) We have explored the physical effects controlling solute-vacancy binding in Al. We find that there is a strong correlation between binding energy and solute size, with larger solute atoms possessing a stronger binding with vacancies. (vi) Most transition-metal 3d solutes do not bind strongly with vacancies, and some are even energetically strongly repelled from vacancies, particularly for the early 3d solutes, Ti and V

  16. Towards single photon generation using NV centers in diamond coupled to thin layer optical waveguides

    International Nuclear Information System (INIS)

    Toshiyuki Tashima

    2014-01-01

    Single photon emitters like the nitrogen-vacancy (NV) center in diamond are important for quantum communication such as quantum cryptography and quantum metrology. In this context, e.g. tapered optical nano-fibers are a promising approach as they allow efficient coupling of single photons into a single spatial mode. Yet, integration of such fibers in a compact integrated quantum circuit is demanding. Here we propose a NV defect center in diamond as a single photon emitter coupled to a thin layer photonic waveguide. The benefit is to allow smaller size devices while having a similar strong evanescent field like tapered nano-optical fibers. We present numerical simulations and fabrication steps of such structures. (author)

  17. Towards quantum superposition of a levitated nanodiamond with a NV center

    Science.gov (United States)

    Li, Tongcang

    2015-05-01

    Creating large Schrödinger's cat states with massive objects is one of the most challenging goals in quantum mechanics. We have previously achieved an important step of this goal by cooling the center-of-mass motion of a levitated microsphere from room temperature to millikelvin temperatures with feedback cooling. To generate spatial quantum superposition states with an optical cavity, however, requires a very strong quadratic coupling that is difficult to achieve. We proposed to optically trap a nanodiamond with a nitrogen-vacancy (NV) center in vacuum, and generate large spatial superposition states using the NV spin-optomechanical coupling in a strong magnetic gradient field. The large spatial superposition states can be used to study objective collapse theories of quantum mechanics. We have optically trapped nanodiamonds in air and are working towards this goal.

  18. Enrichment of ODMR-active nitrogen-vacancy centres in five-nanometre-sized detonation-synthesized nanodiamonds: Nanoprobes for temperature, angle and position.

    Science.gov (United States)

    Sotoma, Shingo; Terada, Daiki; Segawa, Takuya F; Igarashi, Ryuji; Harada, Yoshie; Shirakawa, Masahiro

    2018-04-03

    The development of sensors to estimate physical properties, and their temporal and spatial variation, has been a central driving force in scientific breakthroughs. In recent years, nanosensors based on quantum measurements, such as nitrogen-vacancy centres (NVCs) in nanodiamonds, have been attracting much attention as ultrastable, sensitive, accurate and versatile physical sensors for quantitative cellular measurements. However, the nanodiamonds currently available for use as sensors have diameters of several tens of nanometres, much larger than the usual size of a protein. Therefore, their actual applications remain limited. Here we show that NVCs in an aggregation of 5-nm-sized detonation-synthesized nanodiamond treated by Krüger's surface reduction (termed DND-OH) retains the same characteristics as observed in larger diamonds. We show that the negative charge at the NVC are stabilized, have a relatively long T 2 spin relaxation time of up to 4 μs, and are applicable to thermosensing, one-degree orientation determination and nanometric super-resolution imaging. Our results clearly demonstrate the significant potential of DND-OH as a physical sensor. Thus, DND-OH will raise new possibilities for spatiotemporal monitoring of live cells and dynamic biomolecules in individual cells at single-molecule resolution.

  19. Ultrathin nanocrystalline diamond films with silicon vacancy color centers via seeding by 2 nm detonation nanodiamonds

    Czech Academy of Sciences Publication Activity Database

    Stehlík, Štěpán; Varga, Marián; Štenclová, Pavla; Ondič, Lukáš; Ledinský, Martin; Pangrác, Jiří; Vaňek, O.; Lipov, J.; Kromka, Alexander; Rezek, Bohuslav

    2017-01-01

    Roč. 9, č. 44 (2017), s. 38842-38853 ISSN 1944-8244 R&D Projects: GA MŠk(CZ) LD15003; GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:68378271 Keywords : detonation nanodiamond * surface chemistry * hydrogenation * zeta potential * nucleation density * nanocrystalline diamond * SiV center Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 7.504, year: 2016

  20. Relaxometry imaging of superparamagnetic magnetite nanoparticles at ambient conditions

    Science.gov (United States)

    Finkler, Amit; Schmid-Lorch, Dominik; Häberle, Thomas; Reinhard, Friedemann; Zappe, Andrea; Slota, Michael; Bogani, Lapo; Wrachtrup, Jörg

    We present a novel technique to image superparamagnetic iron oxide nanoparticles via their fluctuating magnetic fields. The detection is based on the nitrogen-vacancy (NV) color center in diamond, which allows optically detected magnetic resonance (ODMR) measurements on its electron spin structure. In combination with an atomic-force-microscope, this atomic-sized color center maps ambient magnetic fields in a wide frequency range from DC up to several GHz, while retaining a high spatial resolution in the sub-nanometer range. We demonstrate imaging of single 10 nm sized magnetite nanoparticles using this spin noise detection technique. By fitting simulations (Ornstein-Uhlenbeck process) to the data, we are able to infer additional information on such a particle and its dynamics, like the attempt frequency and the anisotropy constant. This is of high interest to the proposed application of magnetite nanoparticles as an alternative MRI contrast agent or to the field of particle-aided tumor hyperthermia.

  1. Resonance fluorescence and quantum interference of a single NV center

    Science.gov (United States)

    Ma, Yong-Hong; Zhang, Xue-Feng; Wu, E.

    2017-11-01

    The detection of a single nitrogen-vacancy center in diamond has attracted much interest, since it is expected to lead to innovative applications in various domains of quantum information, including quantum metrology, information processing and communications, as well as in various nanotechnologies, such as biological and subdiffraction limit imaging, and tests of entanglement in quantum mechanics. We propose a novel scheme of a single NV center coupled with a multi-mode superconducting microwave cavity driven by coherent fields in squeezed vacuum. We numerically investigate the spectra in-phase quadrature and out-of-phase quadrature for different driving regimes with or without detunings. It shows that the maximum squeezing can be obtained for optimal Rabi fields. Moreover, with the same parameters, the maximum squeezing is greatly increased when the detunings are nonzero compared to the resonance case.

  2. Sn doped TiO{sub 2} nanotube with oxygen vacancy for highly efficient visible light photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jinliang; Xu, Xingtao [Engineering Research Center for Nanophotonics & Advanced Instrument, Ministry of Education, Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, Department of Physics, East China Normal University, Shanghai 200062 (China); Liu, Xinjuan [Institute of Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018 (China); Yu, Caiyan; Yan, Dong; Sun, Zhuo [Engineering Research Center for Nanophotonics & Advanced Instrument, Ministry of Education, Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, Department of Physics, East China Normal University, Shanghai 200062 (China); Pan, Likun, E-mail: lkpan@phy.ecnu.edu.cn [Engineering Research Center for Nanophotonics & Advanced Instrument, Ministry of Education, Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, Department of Physics, East China Normal University, Shanghai 200062 (China)

    2016-09-15

    Sn doped TiO{sub 2} nanotube with oxygen vacancy (V{sub o}-Sn−TiO{sub 2}) was successfully synthesized via a facile hydrothermal process and subsequent annealing in nitrogen atmosphere. The morphology, structure and photocatalytic performance of V{sub o}-Sn−TiO{sub 2} in the degradation of nitrobenzene were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, UV–vis absorption spectroscopy, nitrogen adsorption-desorption and electrochemical impedance spectra, respectively. The inner diameter, outer diameter and specific surface area of V{sub o}-Sn−TiO{sub 2} are about 5 nm, 15 nm and 235.54 m{sup 2} g{sup −1}, respectively. The experimental results show that the V{sub o}-Sn−TiO{sub 2} exhibits excellent photocatalytic performance with a maximum degradation rate of 92% in 300 min for nitrobenzene and 94% in 100 min for Rhodamine B and corresponding mineralization rates of 68% and 70% under visible light irradiation. The improved photocatalytic performance is ascribed to the enhanced light absorption and specific surface area as well as the reduced electron-hole pair recombination with the presence of oxygen vacancy and Sn doping in the TiO{sub 2} nanotube. - Highlights: • Photocatalysis is an environmental-friendly technology for nitrobenzene removal. • Sn doped TiO{sub 2} nanotube with oxygen vacancy is fabricated for the first time. • It exhibits excellent photocatalytic performance in degradation of nitrobenzene. • A high degradation rate of 92% is achieved under visible light irradiation.

  3. The influence of excess vacancy generation on the diffusion of ion implanted phosphorus into silicon

    International Nuclear Information System (INIS)

    Bakowski, A.

    1985-01-01

    The diffusion of ion implanted phosphorus in silicon has been studied. It was found that the diffusion coefficient is not only dependent on the phosphorus surface concentration (the concentration effect) but also on the conditions at the silicon surface (the surface effect). The phosphorus diffusion coefficient is considerably lower when the silicon surface during annealing is covered with a CVD oxide layer. It is suggested that excess vacancies generated at the surface are reponsible for both the concentration and surface effects. Enhanced phosphorus diffusion is attributed to the disturbance of thermodynamic equilibrium in the crystal through phosphorus-vacancy part formation by vacancies introduced into silicon at the surface. On the basis of the data presented, it can be concluded that two mechanisms for excess vacancy generation are involved. Assuming that phosphorus diffuses via E-centers, calculations of the concentration profiles and the diffusion coefficient were performed for different concentrations and surface conditions. (orig.)

  4. First-principles study of intrinsic vacancy defects in Sr2MgSi2O7 phosphorescent host material

    Science.gov (United States)

    Duan, H.; Dong, Y. Z.; Huang, Y.; Hu, Y. H.; Chen, X. S.

    2016-01-01

    Electronic structures of intrinsic vacancy defects in Sr2MgSi2O7 phosphorescent host material are investigated using first-principles calculations. Si vacancies are too high in energy to play any role in the persistent luminescence of Sr2MgSi2O7 phosphor. Mg vacancies form easier than Sr vacancies as a result of strain relief. Among all the vacancies, O1 vacancies stand out as a likely candidate because they are the most favorable in energy and introduce an empty triply degenerate state just below the CBM and a fully-occupied singlet state at ~1 eV above the VBM, constituting in this case effective hole trap level and electron trap levels, respectively. Mg vacancies are unlikely to explain the persistent luminescence because of its too shallow electron trap level but they may compensate the hole trap associated with O1 vacancies. We yield consistent evidence for the defect physics of these vacancy defects on the basis of the equilibrium properties of Sr2MgSi2O7, total-energy calculations, and electronic structures. The persistent luminescence mechanism of Sr2MgSi2O7:Eu2+, Dy3+ phosphor is also discussed based on our results for O1 vacancies trap center. Our results provide a guide to more refined experiments to control intrinsic traps, whereby probing synthetic strategies toward new improved phosphors.

  5. Slow recombination centers in cadmium selenide monocrystalline films

    International Nuclear Information System (INIS)

    Smyntyna, V.A.

    1983-01-01

    As a result of annealing when concentration of selenium Vacancies decreases due to their diffusion towards the surface, show recombination K-centers begin to influence the photoelectric properties of monocrystalline cadmium selenide layers. Energy levels of K-centers are located by 0.23-0.25 eV over the valent zone ceiling. The nature of K-centers is determined by the presence in the cadmium selenide layer structure of intrisic defects-cadmium vacancies in contrast to r-centers of slow recombination which are bound with impurities in a semiconductor material

  6. Coupling of single nitrogen-vacancy defect centers in diamond nanocrystals to optical antennas and photonic crystal cavities

    Energy Technology Data Exchange (ETDEWEB)

    Wolters, Janik; Kewes, Guenter; Schell, Andreas W.; Aichele, Thomas; Benson, Oliver [Humboldt-Universitaet zu Berlin, Institut fuer Physik, Berlin (Germany); Nuesse, Nils; Schoengen, Max; Loechel, Bernd [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Berlin (Germany); Hanke, Tobias; Leitenstorfer, Alfred [Department of Physics and Center for Applied Photonics, Universitaet Konstanz, Konstanz (Germany); Bratschitsch, Rudolf [Department of Physics and Center for Applied Photonics, Universitaet Konstanz, Konstanz (Germany); Technische Universitaet Chemnitz, Institut fuer Physik, Chemnitz (Germany)

    2012-05-15

    We demonstrate the ability to modify the emission properties and enhance the interaction strength of single-photon emitters coupled to nanophotonic structures based on metals and dielectrics. Assembly of individual diamond nanocrystals, metal nanoparticles, and photonic crystal cavities to meta-structures is introduced. Experiments concerning controlled coupling of single defect centers in nanodiamonds to optical nanoantennas made of gold bowtie structures are reviewed. By placing one and the same emitter at various locations with high precision, a map of decay rate enhancements was obtained. Furthermore, we demonstrate the formation of a hybrid cavity quantum electrodynamics system in which a single defect center is coupled to a single mode of a gallium phosphite photonic crystal cavity. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Vacancies in thermal equilibrium in Nb

    International Nuclear Information System (INIS)

    Nielsen, B.; Lynn, K.G.; Hurst, J.; Vehanen, A.; Schultz, P.J.

    1985-06-01

    We have measured the diffusion of positrons in Nb(110) in the temperature range from 300K to 2450K utilizing a variable energy positron beam. The purpose was to study the vacancy formation. However, no significant sign of vacancy trapping was observed. This could be due to a high detrapping rate caused by a low positron binding energy or due to a high vacancy formation enthalpy H/sub IV//sup F/. The last possibility is consistent with recent studies of the vacancy migration and with calculation of the positron binding energy. In this case we find the H/sub IV//sup F/ > 3 eV

  8. 7 CFR 1221.105 - Vacancies.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS... INFORMATION ORDER Sorghum Promotion, Research, and Information Order Sorghum Promotion, Research, and Information Board § 1221.105 Vacancies. To fill any vacancy occasioned by the death, removal, resignation, or...

  9. Photocatalytic Conversion of Nitrogen to Ammonia with Water on Surface Oxygen Vacancies of Titanium Dioxide.

    Science.gov (United States)

    Hirakawa, Hiroaki; Hashimoto, Masaki; Shiraishi, Yasuhiro; Hirai, Takayuki

    2017-08-09

    Ammonia (NH 3 ) is an essential chemical in modern society. It is currently manufactured by the Haber-Bosch process using H 2 and N 2 under extremely high-pressure (>200 bar) and high-temperature (>673 K) conditions. Photocatalytic NH 3 production from water and N 2 at atmospheric pressure and room temperature is ideal. Several semiconductor photocatalysts have been proposed, but all suffer from low efficiency. Here we report that a commercially available TiO 2 with a large number of surface oxygen vacancies, when photoirradiated by UV light in pure water with N 2 , successfully produces NH 3 . The active sites for N 2 reduction are the Ti 3+ species on the oxygen vacancies. These species act as adsorption sites for N 2 and trapping sites for the photoformed conduction band electrons. These properties therefore promote efficient reduction of N 2 to NH 3 . The solar-to-chemical energy conversion efficiency is 0.02%, which is the highest efficiency among the early reported photocatalytic systems. This noble-metal-free TiO 2 system therefore shows a potential as a new artificial photosynthesis for green NH 3 production.

  10. Studies on color-center formation in glass utilizing measurements made during 1 to 3 MeV electron irradiation

    International Nuclear Information System (INIS)

    Swyler, K.J.; Levy, P.W.

    1976-01-01

    The coloring of NBS 710 glass has been studied using a new facility for making optical absorption measurements during and after electron irradiation. The induced absorption contains three Gaussian shaped bands. The color center growth curves contain two saturating exponential and one linear components. After irradiation the coloring decays and can be described by three decreasing exponentials. At room temperature both the coloring curve plateau and coloring rate increase with increasing dose rate. Coloring measurements made at a fixed dose rate but at increasing temperature indicate: (1) the coloring curve plateau decreases with increasing temperature and coloring has not been observed at 400 0 C; (2) the plateau is reached more rapidly as the temperature increases; (3) the decay occurring after irradiation cannot be described by Arrhenius kinetics. At each temperature the coloring can be explained by simple kinetics. The temperature dependence of the decay can be explained if it is assumed that the thermal untrapping is controlled by a distribution of activation energies

  11. Study of the fluorescence blinking behavior of single F2 color centers in LiF crystal

    International Nuclear Information System (INIS)

    Boichenko, S V; Koenig, K; Zilov, S A; Dresvianskiy, V P; Rakevich, A L; Kuznetsov, A V; Bartul, A V; Martynovich, E F; Voitovich, A P

    2014-01-01

    Using confocal fluorescence microscopy technique, we observed experimentally the luminescence of single F 2 color centers in LiF crystal. It is disclosed that the fluorescence shows blinking behavior. It is shown that this phenomenon is caused by the F 2 center reorientation occurring during the experiment. The ratio of luminescence intensities of differently oriented centers is assessed theoretically for two different experiment configurations. The calculated ratios are in fine agreement with experimental result

  12. The role of ion-implantation in the realization of spintronic devices in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Kalish, Rafi, E-mail: kalish@si-sun1.technion.ac.il [Physics Department and Solid State Institute, Technion-Israel Institute of Technology, Haifa 32000 (Israel)

    2012-02-01

    The application of single photons emitted by specific quantum systems is promising for quantum computers, cryptography and for other future nano-applications. These heavily rely on ion implantation both for selective single ion implantations as well as for the introduction of controlled damage with specific properties. Of particular promise is the negatively charged nitrogen-vacancy (NV{sup -}) defect center in diamond. This center has many desirable luminescence properties required for spintronic devices operational at room temperature, including a long relaxation time of the color center, emission of photons in the visible and the fact that it is produced in diamond, a material with outstanding mechanical and optical properties. This center is usually realized by nitrogen and/or vacancy producing ion implantations into diamond which, following annealing, leads to the formation of the desired NV{sup -} center. The single photons emitted by the decay of this center have to be transported to allow their exploitation. This can be best done by realizing very thin wave guides in single crystal diamond with/or without nano-scale cavities in the same diamond in which NV centers are produced. For this, advantage is taken of the unique property of heavily ion-damaged diamond to be converted, following annealing, to etchable graphite. Thus a free standing submicron thick diamond membrane containing the NV center can be obtained. If desirable, specific photonic crystal structures can be realized in them by the use of FIB. The various ion-implantation schemes used to produce NV centers in diamond, free standing diamond membranes, and photonic crystal structures in them are reviewed. The scientific problems and the technological challenges that have to be solved before actual practical realization of diamond based spintronic devices can be produced are discussed.

  13. Cooling the center-of-mass motion of a diamond nanocrystal in a magneto-gravitational trap

    Science.gov (United States)

    Hsu, Jen-Feng

    A magneto-gravitational trap for micro/nanometer sized diamagnetic particles, such as diamond nanocrystals, is tested and characterized. After exploring various other systems, such as a suspended graphene beam and an optical trap, this magneto-gravitational nanomechanical trapping system for diamond with nitrogen-vacancy (NV) centers presents unique advantages for experiments in fundamental quantum mechanics. Those include, for example, the generation of large quantum superposition states and tests of quantum gravity. Features are demonstrated for this system, such as stable and passive levitation from atmospheric pressure to high vacuum, low resonant frequencies and damping rates, and cooling of the center-of-mass motions to below 1 K. The construction of the trap, vacuum system, optics, and motion detection electronics are described in detail.

  14. Controlled coupling of NV defect centers to plasmonic and photonic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Barth, Michael, E-mail: michael.barth@physik.hu-berlin.d [Institute of Physics, Humboldt-Universitaet zu Berlin, Hausvogteiplatz 5-7, D-10117 Berlin (Germany); Schietinger, Stefan; Schroeder, Tim; Aichele, Thomas; Benson, Oliver [Institute of Physics, Humboldt-Universitaet zu Berlin, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)

    2010-09-15

    Nitrogen-vacancy (NV) defect centers in diamond have recently emerged as promising candidates for a number of applications in the fields of quantum optics and quantum information, such as single photon generation and spin qubit operations. The performance of these defect centers can strongly be enhanced through coupling to plasmonic and photonic nanostructures, such as metal particles and optical microcavities. Here, we demonstrate the controlled assembly of such hybrid structures via manipulation with scanning near-field probes. In particular, we investigate the plasmonic enhancement of the single photon emission through coupling to gold nanospheres as well as the coupling of diamond nanocrystals to the optical modes of microsphere resonators and photonic crystal cavities. These systems represent prototypes of fundamental nanophotonic/plasmonic elements and provide control on the generation and coherent transfer of photons on the level of a single quantum emitter.

  15. Effect of annealing ambience on the formation of surface/bulk oxygen vacancies in TiO2 for photocatalytic hydrogen evolution

    Science.gov (United States)

    Hou, Lili; Zhang, Min; Guan, Zhongjie; Li, Qiuye; Yang, Jianjun

    2018-01-01

    The surface and bulk oxygen vacancy have a prominent effect on the photocatalytic performance of TiO2. In this study, TiO2 possessing different types and concentration of oxygen vacancies were prepared by annealing nanotube titanic acid (NTA) at various temperatures in air or vacuum atmosphere. TiO2 with the unitary bulk single-electron-trapped oxygen vacancies (SETOVs) formed when NTA were calcined in air. Whereas, TiO2 with both bulk and surface oxygen vacancies were obtained when NTA were annealed in vacuum. The series of TiO2 with different oxygen vacancies were systematically characterized by TEM, XRD, PL, XPS, ESR, and TGA. The PL and ESR analysis verified that surface oxygen vacancies and more bulk oxygen vacancies could form in vacuum atmosphere. Surface oxygen vacancies can trap electron and hinder the recombination of photo-generated charges, while bulk SETOVs act as the recombination center. The surface or bulk oxygen vacancies attributed different roles on the photo-absorbance and activity, leading that the sample of NTA-A400 displayed higher hydrogen evolution rate under UV light, whereas NTA-V400 displayed higher hydrogen evolution rate under visible light because bulk SETOVs can improve visible light absorption because sub-band formed by bulk SETOVs prompted the secondary transition of electron excited.

  16. Dissipation Assisted Quantum Memory with Coupled Spin Systems

    Science.gov (United States)

    Jiang, Liang; Verstraete, Frank; Cirac, Ignacio; Lukin, Mikhail

    2009-05-01

    Dissipative dynamics often destroys quantum coherences. However, one can use dissipation to suppress decoherence. A well-known example is the so-called quantum Zeno effect, in which one can freeze the evolution using dissipative processes (e.g., frequently projecting the system to its initial state). Similarly, the undesired decoherence of quantum bits can also be suppressed using controlled dissipation. We propose and analyze the use of this generalization of quantum Zeno effect for protecting the quantum information encoded in the coupled spin systems. This new approach may potentially enhance the performance of quantum memories, in systems such as nitrogen-vacancy color-centers in diamond.

  17. Dynamic strain-mediated coupling of a single diamond spin to a mechanical resonator

    OpenAIRE

    Ovartchaiyapong, Preeti; Lee, Kenneth W.; Myers, Bryan A.; Jayich, Ania C. Bleszynski

    2014-01-01

    The development of hybrid quantum systems is central to the advancement of emerging quantum technologies, including quantum information science and quantum-assisted sensing. The recent demonstration of high quality single-crystal diamond resonators has led to significant interest in a hybrid system consisting of nitrogen-vacancy center spins that interact with the resonant phonon modes of a macroscopic mechanical resonator through crystal strain. However, the nitrogen-vacancy spin-strain inte...

  18. First-principles calculations of vacancy effects on structural and electronic properties of TiCx and TiNx

    International Nuclear Information System (INIS)

    Dridi, Z.; Bouhafs, B.; Ruterana, P.; Aourag, H.

    2002-01-01

    First-principles calculations have been used to study the effect of vacancies on the structural and electronic properties in substoichiometric TiC x and TiN x . The effect of vacancies on equilibrium volumes, bulk moduli, electronic band structures and density of states of the substoichiometric phases was studied using a full-potential linear augmented plane-wave method. A model structure of eight-atom supercells with ordered vacancies within the carbon and nitrogen sublattices is used. We find that the lattice parameters of the studied stoichiometries in both TiC x and TiN x are smaller than that of ideal stoichiometric TiC and TiN. Our results for the variation of the lattice parameters and the bulk moduli for TiC x are found to be in good agreement with experiment. The variation of the energy gaps with the atomic concentration ratio shows that these compounds present the same trends. Results for TiC x are compared to a recent full-potential calculation with relaxed 16-atom supercells

  19. Diffusion in a pure, high-vacancy-content crystal

    International Nuclear Information System (INIS)

    McKee, R.A.

    1981-01-01

    The idea that vacancies can follow a nonrandom walk in a solid has been developed and put into a quantitative form for diffusion in a pure, high-vacancy-content crystal. Intrinsic and tracer diffusion in a metal have been analyzed, and the electrical mobility in an ionic solid has been expressed in terms of the tracer diffusion coefficient and the separate correlation factors for atoms and vacancies. The description uses classical methods of diffusion theory, and generalized results that account for nonrandom vacancy walk have been shown to reduce to those obtained by Howard and Lidiard in a system where the vacancy moves randomly as an isolated point defect. Experimental data for carbon diffusion in fcc iron have been examined to illustrate an interstitial-vacancy analogy that was used in this analysis, and the general result has been applied specifically to discuss vacancy diffusion in Fe/sub 1-x/S

  20. Effect of Pre-Irradiation Annealing and Laser Modification on the Formation of Radiation-Induced Surface Color Centers in Lithium Fluoride

    Science.gov (United States)

    Voitovich, A. P.; Kalinov, V. S.; Novikov, A. N.; Radkevich, A. V.; Runets, L. P.; Stupak, A. P.; Tarasenko, N. V.

    2017-01-01

    It is shown that surface color centers of the same type are formed in the surface layer and in regions with damaged crystal structure inside crystalline lithium fluoride after γ-irradiation. Results are presented from a study of the effect of pre-irradiation annealing on the efficiency with which surface centers are formed in lithium fluoride nanocrystals. Raising the temperature for pre-irradiation annealing from room temperature to 250°C leads to a substantial reduction in the efficiency with which these centers are created. Surface color centers are not detected after γ-irradiation for pre-irradiation annealing temperatures of 300°C and above. Adsorption of atmospheric gases on the crystal surface cannot be regarded as a necessary condition for the formation of radiation-induced surface centers.

  1. Neutral Silicon-Vacancy Center in Diamond: Spin Polarization and Lifetimes

    Science.gov (United States)

    Green, B. L.; Mottishaw, S.; Breeze, B. G.; Edmonds, A. M.; D'Haenens-Johansson, U. F. S.; Doherty, M. W.; Williams, S. D.; Twitchen, D. J.; Newton, M. E.

    2017-09-01

    We demonstrate optical spin polarization of the neutrally charged silicon-vacancy defect in diamond (SiV0 ), an S =1 defect which emits with a zero-phonon line at 946 nm. The spin polarization is found to be most efficient under resonant excitation, but nonzero at below-resonant energies. We measure an ensemble spin coherence time T2>100 μ s at low-temperature, and a spin relaxation limit of T1>25 s . Optical spin-state initialization around 946 nm allows independent initialization of SiV0 and NV- within the same optically addressed volume, and SiV0 emits within the telecoms down-conversion band to 1550 nm: when combined with its high Debye-Waller factor, our initial results suggest that SiV0 is a promising candidate for a long-range quantum communication technology.

  2. HYDROGEN VACANCY INTERACTION IN TUNGSTEN

    NARCIS (Netherlands)

    FRANSENS, [No Value; ELKERIEM, MSA; PLEITER, F

    1991-01-01

    Hydrogen-vacancy interaction in tungsten was investigated by means of the perturbed angular correlation technique, using the isotope In-111 as a probe. Hydrogen trapping at an In-111-vacancy cluster manifests itself as a change of the local electric field gradient, which gives rise to an observable

  3. Spin and Optical Characterization of Defects in Group IV Semiconductors for Quantum Memory Applications

    Science.gov (United States)

    Rose, Brendon Charles

    This thesis is focused on the characterization of highly coherent defects in both silicon and diamond, particularly in the context of quantum memory applications. The results are organized into three parts based on the spin system: phosphorus donor electron spins in silicon, negatively charged nitrogen vacancy color centers in diamond (NV-), and neutrally charged silicon vacancy color centers in diamond (SiV0). The first part on phosphorus donor electron spins presents the first realization of strong coupling with spins in silicon. To achieve this, the silicon crystal was made highly pure and highly isotopically enriched so that the ensemble dephasing time, T2*, was long (10 micros). Additionally, the use of a 3D resonator aided in realizing uniform coupling, allowing for high fidelity spin ensemble manipulation. These two properties have eluded past implementations of strongly coupled spin ensembles and have been the limiting factor in storing and retrieving quantum information. Second, we characterize the spin properties of the NV- color center in diamond in a large magnetic field. We observe that the electron spin echo envelope modulation originating from the central 14N nuclear spin is much stronger at large fields and that the optically induced spin polarization exhibits a strong orientation dependence that cannot be explained by the existing model for the NV- optical cycle, we develop a modification of the existing model that reproduces the data in a large magnetic field. In the third part we perform characterization and stabilization of a new color center in diamond, SiV0, and find that it has attractive, highly sought-after properties for use as a quantum memory in a quantum repeater scheme. We demonstrate a new approach to the rational design of new color centers by engineering the Fermi level of the host material. The spin properties were characterized in electron spin resonance, revealing long spin relaxation and spin coherence times at cryogenic

  4. Measurable position-sensitive wide-angle interference effects of single photons radiated by a nitrogen-vacancy center in diamond

    International Nuclear Information System (INIS)

    Sandor Varro

    2014-01-01

    Single-photon wide-angle interference phenomena have been studied theoretically for glass-diamond-oil (air) layered structures. As a single optical radiator, one NV-center has been assumed close to the upper surface of a diamond plate, and it was represented by a Hertzian dipole of arbitrary orientation. It has been shown that the far-field interference pattern (of 3/5 or 100% visibility) is sensitive to the vertical position of the NV-center, to that extent that ∼2 nm difference in distance from the upper surface of the diamond results in ∼0.01 degree shift of the pattern, which should be a measurable effect. (author)

  5. Quantum Properties of Dichroic Silicon Vacancies in Silicon Carbide

    Science.gov (United States)

    Nagy, Roland; Widmann, Matthias; Niethammer, Matthias; Dasari, Durga B. R.; Gerhardt, Ilja; Soykal, Öney O.; Radulaski, Marina; Ohshima, Takeshi; Vučković, Jelena; Son, Nguyen Tien; Ivanov, Ivan G.; Economou, Sophia E.; Bonato, Cristian; Lee, Sang-Yun; Wrachtrup, Jörg

    2018-03-01

    Although various defect centers have displayed promise as either quantum sensors, single photon emitters, or light-matter interfaces, the search for an ideal defect with multifunctional ability remains open. In this spirit, we study the dichroic silicon vacancies in silicon carbide that feature two well-distinguishable zero-phonon lines and analyze the quantum properties in their optical emission and spin control. We demonstrate that this center combines 40% optical emission into the zero-phonon lines showing the contrasting difference in optical properties with varying temperature and polarization, and a 100% increase in the fluorescence intensity upon the spin resonance, and long spin coherence time of their spin-3 /2 ground states up to 0.6 ms. These results single out this defect center as a promising system for spin-based quantum technologies.

  6. The effect of alloying elements on the vacancy defect evolution in electron-irradiated austenitic Fe-Ni alloys studied by positron annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Druzhkov, A.P. [Institute of Metal Physics, Ural Branch RAS, 18 Kovalevskaya St., 620041 Ekaterinburg (Russian Federation)], E-mail: druzhkov@imp.uran.ru; Perminov, D.A.; Davletshin, A.E. [Institute of Metal Physics, Ural Branch RAS, 18 Kovalevskaya St., 620041 Ekaterinburg (Russian Federation)

    2009-01-31

    The vacancy defect evolution under electron irradiation in austenitic Fe-34.2 wt% Ni alloys containing oversized (aluminum) and undersized (silicon) alloying elements was investigated by positron annihilation spectroscopy at temperatures between 300 and 573 K. It is found that the accumulation of vacancy defects is considerably suppressed in the silicon-doped alloy. This effect is observed at all the irradiation temperatures. The obtained results provide evidence that the silicon-doped alloy forms stable low-mobility clusters involving several Si and interstitial atoms, which are centers of the enhanced recombination of migrating vacancies. The clusters of Si-interstitial atoms also modify the annealing of vacancy defects in the Fe-Ni-Si alloy. The interaction between small vacancy agglomerates and solute Al atoms is observed in the Fe-Ni-Al alloy under irradiation at 300-423 K.

  7. Non-Invasive Imaging Method of Microwave Near Field Based on Solid State Quantum Sensing

    OpenAIRE

    Yang, Bo; Du, Guanxiang; Dong, Yue; Liu, Guoquan; Hu, Zhenzhong; Wang, Yongjin

    2018-01-01

    In this paper, we propose a non-invasive imaging method of microwave near field using a diamond containing nitrogen-vacancy centers. We applied synchronous pulsed sequence combined with charge coupled device camera to measure the amplitude of the microwave magnetic field. A full reconstruction formulation of the local field vector, including the amplitude and phase, is developed by measuring both left and right circular polarizations along the four nitrogen-vacancy axes. Compared to the raste...

  8. Vacancy defects and defect clusters in alkali metal ion-doped MgO nanocrystallites studied by positron annihilation and photoluminescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sellaiyan, S.; Uedono, A. [University of Tsukuba, Division of Applied Physics, Tsukuba, Ibaraki (Japan); Sivaji, K.; Janet Priscilla, S. [University of Madras, Department of Nuclear Physics, Chennai (India); Sivasankari, J. [Anna University, Department of Physics, Chennai (India); Selvalakshmi, T. [National Institute of Technology, Nanomaterials Laboratory, Department of Physics, Tiruchirappalli (India)

    2016-10-15

    Pure and alkali metal ion (Li, Na, and K)-doped MgO nanocrystallites synthesized by solution combustion technique have been studied by positron lifetime and Doppler broadening spectroscopy methods. Positron lifetime analysis exhibits four characteristic lifetime components for all the samples. Doping reduces the Mg vacancy after annealing to 800 C. It was observed that Li ion migrates to the vacancy site to recover Mg vacancy-type defects, reducing cluster vacancies and micropores. For Na- and K-doped MgO, the aforementioned defects are reduced and immobile at 800 C. Coincidence Doppler broadening studies show the positron trapping sites as vacancy clusters. The decrease in the S parameter is due to the particle growth and reduction in the defect concentration at 800 C. Photoluminescence study shows an emission peak at 445 nm and 498 nm, associated with F{sub 2} {sup 2+} and recombination of higher-order vacancy complexes. Further, annealing process is likely to dissociate F{sub 2} {sup 2+} to F{sup +} and this F{sup +} is converted into F centers at 416 nm. (orig.)

  9. Vacancy defects and defect clusters in alkali metal ion-doped MgO nanocrystallites studied by positron annihilation and photoluminescence spectroscopy

    Science.gov (United States)

    Sellaiyan, S.; Uedono, A.; Sivaji, K.; Janet Priscilla, S.; Sivasankari, J.; Selvalakshmi, T.

    2016-10-01

    Pure and alkali metal ion (Li, Na, and K)-doped MgO nanocrystallites synthesized by solution combustion technique have been studied by positron lifetime and Doppler broadening spectroscopy methods. Positron lifetime analysis exhibits four characteristic lifetime components for all the samples. Doping reduces the Mg vacancy after annealing to 800 °C. It was observed that Li ion migrates to the vacancy site to recover Mg vacancy-type defects, reducing cluster vacancies and micropores. For Na- and K-doped MgO, the aforementioned defects are reduced and immobile at 800 °C. Coincidence Doppler broadening studies show the positron trapping sites as vacancy clusters. The decrease in the S parameter is due to the particle growth and reduction in the defect concentration at 800 °C. Photoluminescence study shows an emission peak at 445 nm and 498 nm, associated with F2 2+ and recombination of higher-order vacancy complexes. Further, annealing process is likely to dissociate F2 2+ to F+ and this F+ is converted into F centers at 416 nm.

  10. Vacancy defects and defect clusters in alkali metal ion-doped MgO nanocrystallites studied by positron annihilation and photoluminescence spectroscopy

    International Nuclear Information System (INIS)

    Sellaiyan, S.; Uedono, A.; Sivaji, K.; Janet Priscilla, S.; Sivasankari, J.; Selvalakshmi, T.

    2016-01-01

    Pure and alkali metal ion (Li, Na, and K)-doped MgO nanocrystallites synthesized by solution combustion technique have been studied by positron lifetime and Doppler broadening spectroscopy methods. Positron lifetime analysis exhibits four characteristic lifetime components for all the samples. Doping reduces the Mg vacancy after annealing to 800 C. It was observed that Li ion migrates to the vacancy site to recover Mg vacancy-type defects, reducing cluster vacancies and micropores. For Na- and K-doped MgO, the aforementioned defects are reduced and immobile at 800 C. Coincidence Doppler broadening studies show the positron trapping sites as vacancy clusters. The decrease in the S parameter is due to the particle growth and reduction in the defect concentration at 800 C. Photoluminescence study shows an emission peak at 445 nm and 498 nm, associated with F_2 "2"+ and recombination of higher-order vacancy complexes. Further, annealing process is likely to dissociate F_2 "2"+ to F"+ and this F"+ is converted into F centers at 416 nm. (orig.)

  11. Electrolytic coloration of air-grown sodium fluoride crystals

    International Nuclear Information System (INIS)

    Gu Hongen; Han Li; Song Cuiying; Guo Meili; Wang Na

    2007-01-01

    Air-grown sodium fluoride crystals were colored electrolytically by using a pointed cathode at various temperatures and electric field strengths, which should mainly benefit appropriate coloration temperatures and electric field strengths. O 2 - , F, M, N 1 , N 2 color centers and O 2- -F + complexes were produced in the colored crystals. Current-time curves for the electrolytic colorations were given, and activation energy for the V color center migration was determined. The formation of the color centers was explained

  12. Oxygen vacancy chain and conductive filament formation in hafnia

    Science.gov (United States)

    Xue, Kan-Hao; Miao, Xiang-Shui

    2018-04-01

    The stability and aggregation mechanisms of oxygen vacancy chains are studied for hafnia using self-energy corrected density functional theory. While oxygen vacancies tend not to align along the c-axis of monoclinic HfO2, oxygen vacancy chains along a-axis and b-axis are energetically favorable, with cohesive energies of 0.05 eV and 0.03 eV per vacancy, respectively. Nevertheless, with an increase of the cross section area, intensive oxygen vacancy chains become much more stable in hafnia, which yields phase separation into Hf-clusters and HfO2. Compared with disperse single vacancy chains, intensive oxygen vacancy chains made of 4, 6, and 8 single vacancy chains are energetically more favorable by 0.17, 0.20, and 0.30 eV per oxygen vacancy, respectively. On the other hand, while a single oxygen vacancy chain exhibits a tiny electronic energy gap of around 0.5 eV, metallic conduction emerges for the intensive vacancy chain made of 8 single vacancy chains, which possesses a filament cross section area of ˜0.4 nm2. This sets a lower area limit for Hf-cluster filaments from metallic conduction point of view, but in real hafnia resistive RAM devices the cross section area of the filaments can generally be much larger (>5 nm2) for the sake of energy minimization. Our work sets up a bridge between oxygen vacancy ordering and phase separation in hafnia, and shows a clear trend of filament stabilization with larger dimensions. The results could explain the threshold switching phenomenon in hafnia when a small AFM tip was used as the top electrode, as well as the undesired multimode operation in resistive RAM cells with 3 nm-thick hafnia.

  13. Vacancy decay in endohedral atoms

    International Nuclear Information System (INIS)

    Amusia, M. Ya.; Baltenkov, A. S.

    2006-01-01

    It is demonstrated that the fullerene shell dramatically affects the radiative and Auger vacancy decay of an endohedral atom A-C 60 . The collectivized electrons of the C 60 shell add new possibilities for radiative and nonradiative decays similar to that in ordinary atoms where the vacancies in the initial and final state almost always belong to different subshells. It is shown that the smallness of the atomic shell radii as compared to that of the fullerene shell provides an opportunity to derive the simple formulas for the probabilities of the electron transitions. It is shown that the radiative and Auger (or Koster-Kronig) widths of the vacancy decay due to electron transition in the atom A in A-C 60 acquire an additional factor that can be expressed via the polarizability of the C 60 at transition energy. It is demonstrated that due to an opening of the nonradiative decay channel for vacancies in subvalent subshells the decay probability increases by five to six orders of magnitude

  14. Photo darkening characterization and mechanisms

    DEFF Research Database (Denmark)

    Mattsson, Kent Erik

    2010-01-01

    + formation. The color center becomes hereby either neutral oxygen vacancies that have received an electron to form E’ type color centers or by capture of a hole on surrounding anions such as (AlO4/20) reported for smoky quartz. In this presentation a phenomenological model for PD is suggested...... and the mechanism both of color center formation and the physics of the color center is described. Experimentally the induced PD is found to be either partially or fully reversed through temperature annealing or exposure to UV and/or visible light. Even bleach by the 915 nm pump power gives this possibility...

  15. Positron annihilation study of vacancy-type defects in fast-neutron-irradiated MgO·nAl2O3

    International Nuclear Information System (INIS)

    Rahman, Abu Zayed Mohammad Saliqur; Li, Zhuoxin; Cao, Xingzhong; Wang, Baoyi; Wei, Long; Xu, Qiu; Atobe, Kozo

    2014-01-01

    Highlights: •Detection of Al monovacancy by positron lifetime spectroscopy in fast neutron-irradiated MgO·nAl 2 O 3 (n=2). •Concentration of defects is also estimated for Al monovacancy. •O atom peak was observed by using coincidence Doppler broadening spectroscopy. -- Abstract: The positron lifetimes of fast-neutron-irradiated MgO·nAl 2 O 3 single crystals were measured to investigate the formation of cation vacancies. Al monovacancy was possibly observed in samples irradiated by fast neutrons at ultra-low temperatures. Additionally, vacancy-oxygen complex centers were possibly observed in samples irradiated at higher temperatures and fast neutron fluences. Coincidence Doppler broadening (CDB) spectra were measured to obtain information regarding the vicinity of vacancy-type defects. A peak at approximately 11 × 10 −3 m 0 c was observed, which may be due to the presence of oxygen atoms in the neighborhood of the vacancies

  16. Content-Based Image Retrieval Benchmarking: Utilizing color categories and color distributions

    NARCIS (Netherlands)

    van den Broek, Egon; Kisters, Peter M.F.; Vuurpijl, Louis G.

    From a human centered perspective three ingredients for Content-Based Image Retrieval (CBIR) were developed. First, with their existence confirmed by experimental data, 11 color categories were utilized for CBIR and used as input for a new color space segmentation technique. The complete HSI color

  17. Silicon-Vacancy Spin Qubit in Diamond: A Quantum Memory Exceeding 10 ms with Single-Shot State Readout

    Science.gov (United States)

    Sukachev, D. D.; Sipahigil, A.; Nguyen, C. T.; Bhaskar, M. K.; Evans, R. E.; Jelezko, F.; Lukin, M. D.

    2017-12-01

    The negatively charged silicon-vacancy (SiV- ) color center in diamond has recently emerged as a promising system for quantum photonics. Its symmetry-protected optical transitions enable the creation of indistinguishable emitter arrays and deterministic coupling to nanophotonic devices. Despite this, the longest coherence time associated with its electronic spin achieved to date (˜250 ns ) has been limited by coupling to acoustic phonons. We demonstrate coherent control and suppression of phonon-induced dephasing of the SiV- electronic spin coherence by 5 orders of magnitude by operating at temperatures below 500 mK. By aligning the magnetic field along the SiV- symmetry axis, we demonstrate spin-conserving optical transitions and single-shot readout of the SiV- spin with 89% fidelity. Coherent control of the SiV- spin with microwave fields is used to demonstrate a spin coherence time T2 of 13 ms and a spin relaxation time T1 exceeding 1 s at 100 mK. These results establish the SiV- as a promising solid-state candidate for the realization of quantum networks.

  18. Entanglement transfer from microwaves to diamond NV centers

    Science.gov (United States)

    Gomez, Angela V.; Rodriguez, Ferney J.; Quiroga, Luis

    2014-03-01

    Strong candidates to create quantum entangled states in solid-state environments are the nitrogen-vacancy (NV) defect centers in diamond. By the combination of radiation from different wavelength (optical, microwave and radio-frequency), several protocols have been proposed to create entangled states of different NVs. Recently, experimental sources of non-classical microwave radiation have been successfully realized. Here, we consider the entanglement transfer from spatially separated two-mode microwave squeezed (entangled) photons to a pair of NV centers by exploiting the fact that the spin triplet ground state of a NV has a natural splitting with a frequency on the order of GHz (microwave range). We first demonstrate that the transfer process in the simplest case of a single pair of spatially separated NVs is feasible. Moreover, we proceed to extend the previous results to more realistic scenarios where 13C nuclear spin baths surrounding each NV are included, quantifying the degradation of the entanglement transfer by the dephasing/dissipation effects produced by the nuclear baths. Finally, we address the issue of assessing the possibility of entanglement transfer from the squeezed microwave light to two nuclear spins closely linked to different NV center electrons. Facultad de Ciencias Uniandes.

  19. Nanoscale quantum gyroscope using a single 13C nuclear spin coupled with a nearby NV center in diamond

    Science.gov (United States)

    Song, Xuerui; Wang, Liujun; Feng, Fupan; Lou, Liren; Diao, Wenting; Duan, Chongdi

    2018-03-01

    Developing gyroscopes based on quantum systems are important for inertial sensing applications, and its underlying physics is of fundamental interest. In this paper, we proposed a new type of gyroscope based on the Berry phase generated during rotation of the quantum system by using a single 13C nuclear spin coupled with a nearby nitrogen-vacancy center in diamond. Due to the atom-scale size of the quantum system, rotation information can be obtained with high spatial resolution. The gyroscope can be manipulated at room temperature and without the need for a strong magnetic field, which is also beneficial to its further applications.

  20. Effect of vacancy loops on swelling of metals under irradiation

    International Nuclear Information System (INIS)

    Golubov, S.I.

    1981-01-01

    Subsequent analysis of vacancy loops formation in metals under irradiation is carried out and effect of vacancy loops on vacancy porosity is studied. Expression for quasistationary function of vacancy loops distribution according to sizes taking into consideration two mechanisms of their initiation-cascade and fluctuational ones - is obtained. It is shown that rate of vacancy absorption and interstitials by vacancy loops in quasiequilibrium state is similar and depends only on summary length of loops, for its calculations the self-coordinated procedure is formulated. For the rate of metal swelling under irradiation obtained is the expression taking into consideration the presence of vacancy loops [ru

  1. Ultrabright and efficient single-photon generation based on nitrogen-vacancy centres in nanodiamonds on a solid immersion lens

    International Nuclear Information System (INIS)

    Schroeder, Tim; Gaedeke, Friedemann; Banholzer, Moritz Julian; Benson, Oliver

    2011-01-01

    Single photons are fundamental elements for quantum information technologies such as quantum cryptography, quantum information storage and optical quantum computing. Colour centres in diamond have proven to be stable single-photon sources and thus essential components for reliable and integrated quantum information technology. A key requirement for such applications is a large photon flux and a high efficiency. Paying tribute to various attempts to maximize the single-photon flux, we show that collection efficiencies of photons from colour centres can be increased with a rather simple experimental setup. To do so, we spin-coated nanodiamonds containing single nitrogen-vacancy (N-V) colour centres on the flat surface of a ZrO 2 solid immersion lens. We found stable single-photon count rates of up to 853 kcts s -1 at saturation under continuous wave excitation while having access to more than 100 defect centres with count rates from 400 to 500 kcts s -1 . For a blinking defect centre, we found count rates up to 2.4 Mcts s -1 for time intervals of several tens of seconds. It seems to be a general feature that very high rates are accompanied by blinking behaviour. The overall collection efficiency of our setup of up to 4.2% is the highest yet reported for N-V defect centres in diamond. Under pulsed excitation of a stable emitter of 10 MHz, 2.2% of all pulses caused a click on the detector adding to 221 kcts s -1 thus, opening the way towards diamond-based on-demand single-photon sources for quantum applications.

  2. Controlled manipulation of oxygen vacancies using nanoscale flexoelectricity

    Energy Technology Data Exchange (ETDEWEB)

    Das, Saikat [Inst. for Basic Science (IBS), Seoul (Republic of Korea). Center for Correlated Electron Systems; Seoul National University (SNU), Seoul (Republic of Korea). Dept. of Physics and Astronomy; Wang, Bo [Pennsylvania State Univ., University Park, PA (United States).Dept. of Materials Science and Engineering; Cao, Ye [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Inst. for; Rae Cho, Myung [Inst. for Basic Science (IBS), Seoul (Republic of Korea). Center for Correlated Electron Systems; Seoul National University (SNU), Seoul (Republic of Korea). Dept. of Physics and Astronomy; Jae Shin, Yeong [Inst. for Basic Science (IBS), Seoul (Republic of Korea). Center for Correlated Electron Systems; Seoul National University (SNU), Seoul (Republic of Korea). Dept. of Physics and Astronomy; Mo Yang, Sang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Sookmyung Women' s Univ., Seoul (Republic of Korea). Dept. of Physics; Wang, Lingfei [Inst. for Basic Science (IBS), Seoul (Republic of Korea). Center for Correlated Electron Systems; Seoul National University (SNU), Seoul (Republic of Korea). Dept. of Physics and Astronomy; Kim, Minu [Inst. for Basic Science (IBS), Seoul (Republic of Korea). Center for Correlated Electron Systems; Seoul National University (SNU), Seoul (Republic of Korea). Dept. of Physics and Astronomy; Kalinin, Sergei V. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Inst. for Functional Imaging of Materials; Chen, Long-Qing [Pennsylvania State Univ., University Park, PA (United States).Dept. of Materials Science and Engineering; Noh, Tae Won [Inst. for Basic Science (IBS), Seoul (Republic of Korea). Center for Correlated Electron Systems; Seoul National University (SNU), Seoul (Republic of Korea). Dept. of Physics and Astronomy

    2017-09-20

    Oxygen vacancies, especially their distribution, are directly coupled to the electromagnetic properties of oxides and related emergent functionalities that have implications for device applications. Here using a homoepitaxial strontium titanate thin film, we demonstrate a controlled manipulation of the oxygen vacancy distribution using the mechanical force from a scanning probe microscope tip. By combining Kelvin probe force microscopy imaging and phase-field simulations, we show that oxygen vacancies can move under a stress-gradient-induced depolarisation field. When tailored, this nanoscale flexoelectric effect enables a controlled spatial modulation. In motion, the scanning probe tip thereby deterministically reconfigures the spatial distribution of vacancies. Finally, the ability to locally manipulate oxygen vacancies on-demand provides a tool for the exploration of mesoscale quantum phenomena and engineering multifunctional oxide devices.

  3. Efficient Visible Light Nitrogen Fixation with BiOBr Nanosheets of Oxygen Vacancies on the Exposed {001} Facets.

    Science.gov (United States)

    Li, Hao; Shang, Jian; Ai, Zhihui; Zhang, Lizhi

    2015-05-20

    Even though the well-established Haber-Bosch process has been the major artificial way to "fertilize" the earth, its energy-intensive nature has been motivating people to learn from nitrogenase, which can fix atmospheric N2 to NH3 in vivo under mild conditions with its precisely arranged proteins. Here we demonstrate that efficient fixation of N2 to NH3 can proceed under room temperature and atmospheric pressure in water using visible light illuminated BiOBr nanosheets of oxygen vacancies in the absence of any organic scavengers and precious-metal cocatalysts. The designed catalytic oxygen vacancies of BiOBr nanosheets on the exposed {001} facets, with the availability of localized electrons for π-back-donation, have the ability to activate the adsorbed N2, which can thus be efficiently reduced to NH3 by the interfacial electrons transferred from the excited BiOBr nanosheets. This study might open up a new vista to fix atmospheric N2 to NH3 through the less energy-demanding photochemical process.

  4. The hydrogen interaction in an FCC FePd alloy with a vacancy

    Energy Technology Data Exchange (ETDEWEB)

    Ardenghi, S [Instituto de AstronomIa y Fisica del Espacio (IAFE), CC 67-Suc 28 (C1428ZAA) Ciudad Autonoma de Buenos Aires (Argentina); Gonzalez, E; Jasen, P; Juan, A [Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253 BahIa Blanca (8000) (Argentina)], E-mail: cajuan@uns.edu.ar

    2009-04-15

    The absorption of hydrogen in the ordered face-centered cubic FePd alloy is investigated using a density functional calculation method. Changes in the electronic structure and bonding after introducing an Fe or Pd vacancy are analysed. H locates close to a tetrahedral site and the H-metal bond is achieved at the expense of the interfacial Fe-Pd bond.

  5. All-Optical dc Nanotesla Magnetometry Using Silicon Vacancy Fine Structure in Isotopically Purified Silicon Carbide

    Directory of Open Access Journals (Sweden)

    D. Simin

    2016-07-01

    Full Text Available We uncover the fine structure of a silicon vacancy in isotopically purified silicon carbide (4H-^{28}SiC and reveal not yet considered terms in the spin Hamiltonian, originated from the trigonal pyramidal symmetry of this spin-3/2 color center. These terms give rise to additional spin transitions, which would be otherwise forbidden, and lead to a level anticrossing in an external magnetic field. We observe a sharp variation of the photoluminescence intensity in the vicinity of this level anticrossing, which can be used for a purely all-optical sensing of the magnetic field. We achieve dc magnetic field sensitivity better than 100  nT/sqrt[Hz] within a volume of 3×10^{-7}mm^{3} at room temperature and demonstrate that this contactless method is robust at high temperatures up to at least 500 K. As our approach does not require application of radio-frequency fields, it is scalable to much larger volumes. For an optimized light-trapping waveguide of 3  mm^{3}, the projection noise limit is below 100  fT/sqrt[Hz].

  6. Photoconversion of F+ centers in neutron-irradiated MgO

    International Nuclear Information System (INIS)

    Monge, M.A.; Gonzalez, R.; Munoz Santiuste, J.E.; Pareja, R.; Chen, Y.; Kotomin, E.A.; Popov, A.I.

    2000-01-01

    In neutron-irradiated MgO crystals, experiments and theory demonstrate that photon excitation of the positively charged anion vacancies (F + centers) at 5.0 eV releases holes that are subsequently trapped at V-type centers, which are cation vacancies charge-compensated by impurities, such as Al 3+ , F - , and OH - ions. A photoconversion mechanism occurs very likely via electron transfer to F + centers from the quasi-local states which are induced in the valence band. INDO quantum chemical simulations of F + centers confirmed the appearance of two induced quasi-local states located at 1.2 and 2.0 eV below the top of the valence band

  7. Dynamics of vacancies in two-dimensional Lennard-Jones crystals

    Science.gov (United States)

    Yao, Zhenwei; Olvera de La Cruz, Monica

    2015-03-01

    Vacancies represent an important class of crystallographic defects, and their behaviors can be strongly coupled with relevant material properties. We report the rich dynamics of vacancies in two-dimensional Lennard-Jones crystals in several thermodynamic states. Specifically, we numerically observe significantly faster diffusion of the 2-point vacancy with two missing particles in comparison with other types of vacancies; it opens the possibility of doping 2-point vacancies into atomic materials to enhance atomic migration. In addition, the resulting dislocations in the healing of a long vacancy suggest the intimate connection between vacancies and topological defects that may provide an extra dimension in the engineering of defects in extensive crystalline materials for desired properties. We thank the financial support from the U.S. Department of Commerce, National Institute of Standards and Technology, the Office of the Director of Defense Research and Engineering (DDR&E) and the Air Force Office of Scientific Research.

  8. In Situ Observation of Oxygen Vacancy Dynamics and Ordering in the Epitaxial LaCoO3 System.

    Science.gov (United States)

    Jang, Jae Hyuck; Kim, Young-Min; He, Qian; Mishra, Rohan; Qiao, Liang; Biegalski, Michael D; Lupini, Andrew R; Pantelides, Sokrates T; Pennycook, Stephen J; Kalinin, Sergei V; Borisevich, Albina Y

    2017-07-25

    Vacancy dynamics and ordering underpin the electrochemical functionality of complex oxides and strongly couple to their physical properties. In the field of the epitaxial thin films, where connection between chemistry and film properties can be most clearly revealed, the effects related to oxygen vacancies are attracting increasing attention. In this article, we report a direct, real-time, atomic level observation of the formation of oxygen vacancies in the epitaxial LaCoO 3 thin films and heterostructures under the influence of the electron beam utilizing scanning transmission electron microscopy (STEM). In the case of LaCoO 3 /SrTiO 3 superlattice, the formation of the oxygen vacancies is shown to produce quantifiable changes in the interatomic distances, as well as qualitative changes in the symmetry of the Co sites manifested as off-center displacements. The onset of these changes was observed in both the [100] pc and [110] pc orientations in real time. Additionally, annular bright field images directly show the formation of oxygen vacancy channels along [110]pc direction. In the case of 15 u.c. LaCoO 3 thin film, we observe the sequence of events during beam-induced formation of oxygen vacancy ordered phases and find them consistent with similar processes in the bulk. Moreover, we record the dynamics of the nucleation, growth, and defect interaction at the atomic scale as these transformations happen. These results demonstrate that we can track dynamic oxygen vacancy behavior with STEM, generating atomic-level quantitative information on phase transformation and oxygen diffusion.

  9. Nitrogen determination on tomato ( Lycopersicon esculentum Mill ...

    African Journals Online (AJOL)

    In order to investigate the effectiveness of a new method based on color image analysis and the Minolta SPAD-502 chlorophyll meter for the diagnosis of nitrogen deficiencies of tomato seedlings, a field experiment was conducted. In this study, five levels of nitrogen fertilization were established so as to induce nitrogen ...

  10. Double ionization of nitrogen molecules in orthogonal two-color femtosecond laser fields

    Science.gov (United States)

    Song, Qiying; Li, Hui; Wang, Junping; Lu, Peifen; Gong, Xiaochun; Ji, Qinying; Lin, Kang; Zhang, Wenbin; Ma, Junyang; Li, Hanxiao; Zeng, Heping; He, Feng; Wu, Jian

    2018-04-01

    Double ionization of nitrogen molecules in orthogonally polarized two-color femtosecond laser fields is investigated by varying the relative intensity between the fundamental wave (FW) and its second harmonic (SH) components. The yield ratios of the double ionization channels, i.e., the non-dissociative {{{{N}}}2}2+ and Coulomb exploded (N+, N+), to the singly charged N2 + channel exhibit distinct dependences on the relative strength between the FW and SH fields. As the intensity ratio of SH to FW increases, the yield ratio of (N+, N+)/N2 + gradually increases, while the ratio of {{{{N}}}2}2+/N2 + first descends and then increases constituting a valley shape which is similar to the behavior of Ar2+/Ar+ observed in the same experimental condition. Based on the classical trajectory simulations, we found that the different characteristics of the two doubly ionized channels stem from two mechanisms, i.e., the {{{{N}}}2}2+ is mostly accessed by the (e, 2e) impact ionization while the recollision-induced excitation with subsequent ionization plays an important role in producing the (N+, N+) channel.

  11. Zinc vacancy and oxygen interstitial in ZnO revealed by sequential annealing and electron irradiation

    Science.gov (United States)

    Knutsen, K. E.; Galeckas, A.; Zubiaga, A.; Tuomisto, F.; Farlow, G. C.; Svensson, B. G.; Kuznetsov, A. Yu.

    2012-09-01

    By combining results from positron annihilation and photoluminescence spectroscopy with data from Hall effect measurements, the characteristic deep level emission centered at ˜1.75 eV and exhibiting an activation energy of thermal quenching of 11.5 meV is associated with the zinc vacancy. Further, a strong indication that oxygen interstitials act as a dominating acceptor is derived from the analysis of charge carrier losses induced by electron irradiation with variable energy below and above the threshold for Zn-atom displacement. We also demonstrate that the commonly observed green emission is related to an extrinsic acceptorlike impurity, which may be readily passivated by oxygen vacancies.

  12. Effect of nitrogen addition on the structural, electrical, and optical properties of In-Sn-Zn oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Junjun, E-mail: jia@chem.aoyama.ac.jp [Graduate School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo, Sagamihara, Kanagawa 252-5258 (Japan); Torigoshi, Yoshifumi; Suko, Ayaka; Nakamura, Shin-ichi [Graduate School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo, Sagamihara, Kanagawa 252-5258 (Japan); Kawashima, Emi; Utsuno, Futoshi [Advanced Technology Research Laboratories, Idemitsu Kosan Co., Ltd., Sodegaura, Chiba 299-0293 (Japan); Shigesato, Yuzo, E-mail: yuzo@chem.aoyama.ac.jp [Graduate School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo, Sagamihara, Kanagawa 252-5258 (Japan)

    2017-02-28

    Highlights: • Nitrogen addition induces the structure of ITZO film change from amorphous phase to a c-axis oriented InN polycrystalline phase. • Nitrogen addition suppressed the formation of oxygen-related vacancies in ITZO films. • A red-shift in the optical band edge for ITZO films was observed as the nitrogen flow ratio increased, which was due to the generation of InN crystallites. - Abstract: Indium-tin-zinc oxide (ITZO) films were deposited at various nitrogen flow ratios using magnetron sputtering. At a nitrogen flow ratio of 40%, the structure of ITZO film changed from amorphous, with a short-range-ordered In{sub 2}O{sub 3} phase, to a c-axis oriented InN polycrystalline phase, where InN starts to nucleate from an amorphous In{sub 2}O{sub 3} matrix. Whereas, nitrogen addition had no obvious effect on the structure of indium-gallium-zinc oxide (IGZO) films even at a nitrogen flow ratio of 100%. Nitrogen addition also suppressed the formation of oxygen-related vacancies in ITZO films when the nitrogen flow ratio was less than 20%, and higher nitrogen addition led to an increase in carrier density. Moreover, a red-shift in the optical band edge was observed as the nitrogen flow ratio increased, which could be attributed to the generation of InN crystallites. We anticipate that the present findings demonstrating nitrogen-addition induced structural changes can help to understand the environment-dependent instability in amorphous IGZO or ITZO based thin-film transistors (TFTs).

  13. Vacancy clusters at nanoparticle surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Xu, J.; Moxom, J.; Somieski, B.; White, C.W. [Oak Ridge National Lab., TN (United States); Mills, A.P. Jr. [Bell Labs., Lucent Technologies, Murray Hill, NJ (United States); Suzuki, R.; Ishibashi, S. [Electrotechnical Lab., Tsukuba, Ibaraki (Japan); Ueda, A.; Henderson, D. [Physics Dept., Fisk Univ., Nashville, TN (United States)

    2001-07-01

    We detect vacancy clusters at Au nanoparticle surfaces using a combination of positron lifetime spectroscopy, 1- detector, and 2-detector measurements of Doppler broadening of annihilation radiation. Gold nanoparticles are formed by MeV implantation of gold ions into MgO (100) followed by annealing. Clusters of two Mg and two O vacancies (v{sub 4}) are attached to the gold nanoparticle surfaces within the projected range (R{sub p}). (orig.)

  14. Vacancy clusters at nanoparticle surfaces

    International Nuclear Information System (INIS)

    Xu, J.; Moxom, J.; Somieski, B.; White, C.W.; Mills, A.P. Jr.; Suzuki, R.; Ishibashi, S.; Ueda, A.; Henderson, D.

    2001-01-01

    We detect vacancy clusters at Au nanoparticle surfaces using a combination of positron lifetime spectroscopy, 1- detector, and 2-detector measurements of Doppler broadening of annihilation radiation. Gold nanoparticles are formed by MeV implantation of gold ions into MgO (100) followed by annealing. Clusters of two Mg and two O vacancies (v 4 ) are attached to the gold nanoparticle surfaces within the projected range (R p ). (orig.)

  15. Defining and Measuring Job Vacancies in a Dynamic Perspective

    NARCIS (Netherlands)

    P.A. Donker van Heel (Peter)

    2015-01-01

    textabstractWhat is the best definition for job vacancies, what is the best method to measure job vacancies, and what further research is needed to gain a better insight into job vacancies in a dynamic perspective?

  16. Examination of the Potential for Adaptive Chirality of the Nitrogen Chiral Center in Aza-Aspartame

    Directory of Open Access Journals (Sweden)

    Samir H. Bouayad-Gervais

    2013-11-01

    Full Text Available The potential for dynamic chirality of an azapeptide nitrogen was examined by substitution of nitrogen for the α-carbon of the aspartate residue in the sweetener S,S-aspartame. Considering that S,S- and R,S-aspartame possess sweet and bitter tastes, respectively, a bitter-sweet taste of aza-aspartame 9 could be indicative of a low isomerization barrier for nitrogen chirality inter-conversion. Aza-aspartame 9 was synthesized by a combination of hydrazine and peptide chemistry. Crystallization of 9 indicated a R,S-configuration in the solid state; however, the aza-residue chiral center was considerably flattened relative to its natural amino acid counterpart. On tasting, the authors considered aza-aspartame 9 to be slightly bitter or tasteless. The lack of bitter sweet taste of aza-aspartame 9 may be due to flattening from sp2 hybridization in the urea as well as a high barrier for sp3 nitrogen inter-conversion, both of which may interfere with recognition by taste receptors.

  17. Examination of the potential for adaptive chirality of the nitrogen chiral center in aza-aspartame.

    Science.gov (United States)

    Bouayad-Gervais, Samir H; Lubell, William D

    2013-11-28

    The potential for dynamic chirality of an azapeptide nitrogen was examined by substitution of nitrogen for the α-carbon of the aspartate residue in the sweetener S,S-aspartame. Considering that S,S- and R,S-aspartame possess sweet and bitter tastes, respectively, a bitter-sweet taste of aza-aspartame 9 could be indicative of a low isomerization barrier for nitrogen chirality inter-conversion. Aza-aspartame 9 was synthesized by a combination of hydrazine and peptide chemistry. Crystallization of 9 indicated a R,S-configuration in the solid state; however, the aza-residue chiral center was considerably flattened relative to its natural amino acid counterpart. On tasting, the authors considered aza-aspartame 9 to be slightly bitter or tasteless. The lack of bitter sweet taste of aza-aspartame 9 may be due to flattening from sp2 hybridization in the urea as well as a high barrier for sp3 nitrogen inter-conversion, both of which may interfere with recognition by taste receptors.

  18. Vacancy supersaturations produced by high-energy ion implantation

    International Nuclear Information System (INIS)

    Venezia, V.C.; Eaglesham, D.J.; Jacobson, D.C.; Gossmann, H.J.

    1998-01-01

    A new technique for detecting the vacancy clusters produced by high-energy ion implantation into silicon is proposed and tested. This technique takes advantage of the fact that metal impurities, such as Au, are gettered near one-half of the projected range (1/2 R p ) of MeV implants. The vacancy clustered region produced by a 2 MeV Si + implant into silicon has been labeled with Au diffused in from the front surface. The trapped Au was detected by Rutherford backscattering spectrometry (RBS) to profile the vacancy clusters. Cross section transmission electron microscopy (XTEM) analysis shows that the Au in the region of vacancy clusters is in the form of precipitates. By annealing MeV implanted samples prior to introduction of the Au, changes in the defect concentration within the vacancy clustered region were monitored as a function of annealing conditions

  19. Vacancy-type defects in InxGa1−xN grown on GaN templates probed using monoenergetic positron beams

    International Nuclear Information System (INIS)

    Uedono, Akira; Watanabe, Tomohito; Kimura, Shogo; Zhang, Yang; Lozac'h, Mickael; Sang, Liwen; Sumiya, Masatomo; Ishibashi, Shoji; Oshima, Nagayasu; Suzuki, Ryoichi

    2013-01-01

    Native defects in In x Ga 1−x N layers grown by metalorganic chemical vapor deposition were studied using monoenergetic positron beams. Measurements of Doppler broadening spectra of the annihilation radiation and lifetime spectra of positrons for a 200-nm-thick In 0.13 Ga 0.87 N layer showed that vacancy-type defects were introduced by InN alloying, and the major species of such defects was identified as complexes between a cation vacancy and nitrogen vacancies. The presence of the defects correlated with lattice relaxation of the In 0.13 Ga 0.87 N layer and the increase in photon emissions from donor-acceptor-pair recombination. The species of native defects in In 0.06 Ga 0.94 N layers was the same but its concentration was decreased by decreasing the InN composition. With the layer thickness increased from 120 nm to 360 nm, a defect-rich region was introduced in the subsurface region (<160 nm), which can be associated with layer growth with the relaxation of compressive stress

  20. Liquid nitrogen or phenolization for giant cell tumor of bone?: a comparative cohort study of various standard treatments at two tertiary referral centers.

    Science.gov (United States)

    van der Heijden, Lizz; van der Geest, Ingrid C M; Schreuder, H W Bart; van de Sande, Michiel A J; Dijkstra, P D Sander

    2014-03-05

    The rate of recurrence of giant cell tumor of bone is decreased by use of adjuvant treatments such as phenol, liquid nitrogen, or polymethylmethacrylate (PMMA) during curettage. We assessed recurrence and complication rates and functional outcome after curettage with use of phenol and PMMA, liquid nitrogen and PMMA, and liquid nitrogen and bone grafts. We retrospectively compared the relative effectiveness of treatment of giant cell tumors of bone at two tertiary centers with a regional function from 1990 to 2010. The 132 (of 201) patients who met the inclusion criteria had a mean age of thirty-three years (range, eleven to sixty-nine years). Treatment assignment depended purely on the center, with primary treatment consisting of curettage with use of phenol and PMMA (n = 82) at one center and with use of either liquid nitrogen and PMMA (n = 26) or liquid nitrogen and bone grafts (n = 24) at the other center. Recurrence and complication rates were determined, and functional outcome was assessed on the basis of the Musculoskeletal Tumor Society (MSTS) score. The mean duration of follow-up was eight years (range, two to twenty-two years). Recurrence rates were comparable among the groups (28% for phenol and PMMA, 31% for liquid nitrogen and PMMA, and 38% for liquid nitrogen and bone grafts; p = 0.52). Soft-tissue extension increased the recurrence risk (hazard ratio [HR] = 2.1, 95% confidence interval [CI] = 1.1 to 4.0, p = 0.024). The complication rate was 33% after use of liquid nitrogen and bone grafts, 27% after liquid nitrogen and PMMA, and 11% after phenol and PMMA (p = 0.019); complications included osteoarthritis, infection, postoperative fracture, nonunion, transient nerve palsy, and PMMA leakage. The complication risk was increased by the presence of a pathologic fracture (HR = 4.1, 95% CI = 1.7 to 9.5, p = 0.001) and use of liquid nitrogen (HR = 3.9, 95% CI = 1.5 to 10, p = 0.006 for liquid nitrogen and bone grafts; HR = 3.1, 95% CI = 1.1 to 8.6, p = 0

  1. Magnetometry with Ensembles of Nitrogen Vacancy Centers in Bulk Diamond

    Science.gov (United States)

    2015-10-23

    the ESR curve. Any frequency components of the photodetector signal which are not close to the reference frequency, are filtered out. This mitigates ...indicating that we have not yet run up against thermal or flicker noise for these time scales. 5.3 Details of frequency modulation circuit In order

  2. Non-flipping 13C spins near an NV center in diamond: hyperfine and spatial characteristics by density functional theory simulation of the C510[NV]H252 cluster

    Science.gov (United States)

    Nizovtsev, A. P.; Kilin, S. Ya; Pushkarchuk, A. L.; Pushkarchuk, V. A.; Kuten, S. A.; Zhikol, O. A.; Schmitt, S.; Unden, T.; Jelezko, F.

    2018-02-01

    Single NV centers in diamond coupled by hyperfine interaction (hfi) to neighboring 13C nuclear spins are now widely used in emerging quantum technologies as elements of quantum memory adjusted to a nitrogen-vacancy (NV) center electron spin qubit. For nuclear spins with low flip-flop rate, single shot readout was demonstrated under ambient conditions. Here we report on a systematic search for such stable NV-13C systems using density functional theory to simulate the hfi and spatial characteristics of all possible NV-13C complexes in the H-terminated cluster C510[NV]-H252 hosting the NV center. Along with the expected stable ‘NV-axial-13C’ systems wherein the 13C nuclear spin is located on the NV axis, we found for the first time new families of positions for the 13C nuclear spin exhibiting negligible hfi-induced flipping rates due to near-symmetric local spin density distribution. Spatially, these positions are located in the diamond bilayer passing through the vacancy of the NV center and being perpendicular to the NV axis. Analysis of available publications showed that, apparently, some of the predicted non-axial near-stable NV-13C systems have already been observed experimentally. A special experiment performed on one of these systems confirmed the prediction made.

  3. 24 CFR 983.352 - Vacancy payment.

    Science.gov (United States)

    2010-04-01

    ... PROJECT-BASED VOUCHER (PBV) PROGRAM Payment to Owner § 983.352 Vacancy payment. (a) Payment for move-out month. If an assisted family moves out of the unit, the owner may keep the housing assistance payment... 24 Housing and Urban Development 4 2010-04-01 2010-04-01 false Vacancy payment. 983.352 Section...

  4. Fractal kinetics of radiation-induced point-defect formation and decay in amorphous insulators: Application to color centers in silica-based optical fibers

    Science.gov (United States)

    Griscom, David L.

    2001-11-01

    Formalisms have been developed to express the time evolution of bimolecular processes taking place in fractal spaces. These ``stretched-second-order'' solutions are specifically applicable to radiation-induced electron-hole pairs and/or vacancy-interstitial pairs in insulating glasses. Like the analogous Kohlrausch-type (stretched-first-order) expressions, the present solutions are functions of (kt)β, where 0the new second-order formalism and the familiar Kohlrausch approach have been used to fit experimental data (induced optical absorptions in silica-based glasses monitored at selected wavelengths) that serve as proxies for the numbers of color centers created by γ irradiation and/or destroyed by processes involving thermal, optical, or γ-ray activation. Two material systems were investigated: (1) optical fibers with Ge-doped-silica cores and (2) fibers with low-OH/low-chloride pure-silica cores. Successful fits of the growth curves for the Ge-doped-silica-core fibers at four widely separated dose rates were accomplished using solutions for color-center concentrations, N[(kt)β], which approach steady-state values, Nsat, as t-->∞. The parametrization of these fits reveals some unexpected, and potentially useful, empirical rules regarding the dose-rate dependences of β, k, and Nsat in the fractal regime (0the pure-silica-core fibers as well. In both material systems, there appear to be fractal classical phase transitions at certain threshold values of dose rate, below which the dose-rate dependencies of k and Nsat revert to those specified by classical (β=1) first- or second-order kinetics. For ktthe first- and second-order fractal kinetic growth curves become identical, i.e., N((kt)β)~Atβ, where the coefficient A depends on dose rate but not kinetic order. It is found empirically that A depends on the 3β/2 power of dose rate in both first- and second-order kinetics, thus ``accidentally'' becoming linearly proportional to dose rate in cases where β~2

  5. Positron annihilation lifetime in float-zone n-type silicon irradiated by fast electrons: a thermally stable vacancy defect

    International Nuclear Information System (INIS)

    Arutyunov, Nikolay; Emtsev, Vadim; Oganesyan, Gagik; Krause-Rehberg, Reinhard; Elsayed, Mohamed; Kozlovskii, Vitalii

    2016-01-01

    Temperature dependency of the average positron lifetime has been investigated for n-type float-zone silicon, n-FZ-Si(P), subjected to irradiation with 0.9 MeV electrons at RT. In the course of the isochronal annealing a new defect-related temperature-dependent pattern of the positron lifetime spectra has been revealed. Beyond the well known intervals of isochronal annealing of acceptor-like defects such as E-centers, divacancies and A-centers, the positron annihilation at the vacancy defects has been observed in the course of the isochronal annealing from ∝ 320 C up to the limit of reliable detecting of the defect-related positron annihilation lifetime at ≥ 500 C. These data correlate with the ones of recovery of the concentration of the charge carriers and their mobility which is found to continue in the course of annealing to ∝ 570 C; the annealing is accomplished at ∝650 C. A thermally stable complex consisting of the open vacancy volume and the phosphorus impurity atom, V_o_p-P, is suggested as a possible candidate for interpreting the data obtained by the positron annihilation lifetime spectroscopy. An extended couple of semi-vacancies, 2V_s_-_e_x_t, as well as a relaxed inwards a couple of vacancies, 2V_i_n_w, are suggested as the open vacancy volume V_o_p to be probed with the positron. It is argued that a high thermal stability of the V_s_-_e_x_t PV_s_-_e_x_t (or V_i_n_wPV_i_n_w_.) configuration is contributed by the efficiency of PSi_5 bonding. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Vacancy dynamic in Ni-Mn-Ga ferromagnetic shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Merida, D., E-mail: david.merida@ehu.es [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); García, J. A. [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); BC Materials (Basque Centre for Materials, Application and Nanostructures), 48040 Leioa (Spain); Sánchez-Alarcos, V.; Pérez-Landazábal, J. I.; Recarte, V. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Plazaola, F. [Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain)

    2014-06-09

    Vacancies control any atomic ordering process and consequently most of the order-dependent properties of the martensitic transformation in ferromagnetic shape memory alloys. Positron annihilation spectroscopy demonstrates to be a powerful technique to study vacancies in NiMnGa alloys quenched from different temperatures and subjected to post-quench isothermal annealing treatments. Considering an effective vacancy type the temperature dependence of the vacancy concentration has been evaluated. Samples quenched from 1173 K show a vacancy concentration of 1100 ± 200 ppm. The vacancy migration and formation energies have been estimated to be 0.55 ± 0.05 eV and 0.90 ± 0.07 eV, respectively.

  7. Ultrabright and efficient single-photon generation based on nitrogen-vacancy centres in nanodiamonds on a solid immersion lens

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Tim; Gaedeke, Friedemann; Banholzer, Moritz Julian; Benson, Oliver, E-mail: tim.schroeder@physik.hu-berlin.de [Humboldt-Universitaet zu Berlin, Institut fuer Physik, AG Nano Optics Newtonstrasse 15, 12489 Berlin (Germany)

    2011-05-15

    Single photons are fundamental elements for quantum information technologies such as quantum cryptography, quantum information storage and optical quantum computing. Colour centres in diamond have proven to be stable single-photon sources and thus essential components for reliable and integrated quantum information technology. A key requirement for such applications is a large photon flux and a high efficiency. Paying tribute to various attempts to maximize the single-photon flux, we show that collection efficiencies of photons from colour centres can be increased with a rather simple experimental setup. To do so, we spin-coated nanodiamonds containing single nitrogen-vacancy (N-V) colour centres on the flat surface of a ZrO{sub 2} solid immersion lens. We found stable single-photon count rates of up to 853 kcts s{sup -1} at saturation under continuous wave excitation while having access to more than 100 defect centres with count rates from 400 to 500 kcts s{sup -1}. For a blinking defect centre, we found count rates up to 2.4 Mcts s{sup -1} for time intervals of several tens of seconds. It seems to be a general feature that very high rates are accompanied by blinking behaviour. The overall collection efficiency of our setup of up to 4.2% is the highest yet reported for N-V defect centres in diamond. Under pulsed excitation of a stable emitter of 10 MHz, 2.2% of all pulses caused a click on the detector adding to 221 kcts s{sup -1} thus, opening the way towards diamond-based on-demand single-photon sources for quantum applications.

  8. Radiation-Induced Color Centers in LiF for Dosimetry at High Absorbed Dose Rates

    DEFF Research Database (Denmark)

    McLaughlin, W. L.; Miller, Arne; Ellis, S. C.

    1980-01-01

    Color centers formed by irradiation of optically clear crystals of pure LiF may be analyzed spectrophotometrically for dosimetry in the absorbed dose range from 102 to 107 Gy. Routine monitoring of intense electron beams is an important application. Both 6LiF and 7LiF forms are commercially...... available, and when used with filters as albedo dosimeters in pairs, they provide discrimination of neutron and gamma-ray doses....

  9. Predicting Soil Organic Carbon and Total Nitrogen in the Russian Chernozem from Depth and Wireless Color Sensor Measurements

    Science.gov (United States)

    Mikhailova, E. A.; Stiglitz, R. Y.; Post, C. J.; Schlautman, M. A.; Sharp, J. L.; Gerard, P. D.

    2017-12-01

    Color sensor technologies offer opportunities for affordable and rapid assessment of soil organic carbon (SOC) and total nitrogen (TN) in the field, but the applicability of these technologies may vary by soil type. The objective of this study was to use an inexpensive color sensor to develop SOC and TN prediction models for the Russian Chernozem (Haplic Chernozem) in the Kursk region of Russia. Twenty-one dried soil samples were analyzed using a Nix Pro™ color sensor that is controlled through a mobile application and Bluetooth to collect CIEL*a*b* (darkness to lightness, green to red, and blue to yellow) color data. Eleven samples were randomly selected to be used to construct prediction models and the remaining ten samples were set aside for cross validation. The root mean squared error (RMSE) was calculated to determine each model's prediction error. The data from the eleven soil samples were used to develop the natural log of SOC (lnSOC) and TN (lnTN) prediction models using depth, L*, a*, and b* for each sample as predictor variables in regression analyses. Resulting residual plots, root mean square errors (RMSE), mean squared prediction error (MSPE) and coefficients of determination ( R 2, adjusted R 2) were used to assess model fit for each of the SOC and total N prediction models. Final models were fit using all soil samples, which included depth and color variables, for lnSOC ( R 2 = 0.987, Adj. R 2 = 0.981, RMSE = 0.003, p-value < 0.001, MSPE = 0.182) and lnTN ( R 2 = 0.980 Adj. R 2 = 0.972, RMSE = 0.004, p-value < 0.001, MSPE = 0.001). Additionally, final models were fit for all soil samples, which included only color variables, for lnSOC ( R 2 = 0.959 Adj. R 2 = 0.949, RMSE = 0.007, p-value < 0.001, MSPE = 0.536) and lnTN ( R 2 = 0.912 Adj. R 2 = 0.890, RMSE = 0.015, p-value < 0.001, MSPE = 0.001). The results suggest that soil color may be used for rapid assessment of SOC and TN in these agriculturally important soils.

  10. Mobility and stability of large vacancy and vacancy-copper clusters in iron: An atomistic kinetic Monte Carlo study

    Energy Technology Data Exchange (ETDEWEB)

    Castin, N., E-mail: ncastin@sckcen.be [Studiecentrum voor Kernenergie - Centre d' Etudes de l' energie Nucleaire (SCK-CEN), Nuclear Materials Science Institute, Unit Structural Materials Modelling and Microstructure-Boeretang 200, B2400 Mol (Belgium); Pascuet, M.I., E-mail: pascuet@cnea.gov.ar [Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Av. Rivadavia 1917, C1033AAJ Buenos Aires (Argentina); Malerba, L. [Studiecentrum voor Kernenergie - Centre d' Etudes de l' energie Nucleaire (SCK-CEN), Nuclear Materials Science Institute, Unit Structural Materials Modelling and Microstructure-Boeretang 200, B2400 Mol (Belgium)

    2012-10-15

    The formation of Cu-rich precipitates under irradiation is a major cause for changes in the mechanical response to load of reactor pressure vessel steels. In previous works, it has been shown that the mechanism under which precipitation occurs is governed by diffusion of vacancy-copper (VCu) complexes, also in the absence of irradiation. Coarse-grained computer models (such as object kinetic Monte Carlo) aimed at simulating irradiation processes in model alloys or steels should therefore explicitly include the mobility of Cu precipitates, as a consequence of vacancy hops at their surface. For this purpose, in this work we calculate diffusion coefficients and lifetimes for a large variety of VCu complexes. We use an innovative atomistic model, where vacancy migration energies are calculated with little approximations, taking into account all effects of static relaxation and long-range chemical interaction as predicted by an interatomic potential. Our results show that, contrary to what intuition might suggest, saturation in vacancies tend to slow down the transport of Cu atoms.

  11. Vacancies and defect levels in III–V semiconductors

    KAUST Repository

    Tahini, H. A.

    2013-08-13

    Using electronic structure calculations, we systematically investigate the formation of vacancies in III-V semiconductors (III = Al, Ga, and In and V = P, As, and Sb), for a range of charges ( −3≤q≤3 ) as a function of the Fermi level and under different growth conditions. The formation energies were corrected using the scheme due to Freysoldt et al. [Phys. Rev. Lett. 102, 016402 (2009)] to account for finite size effects. Vacancy formation energies were found to decrease as the size of the group V atom increased. This trend was maintained for Al-V, Ga-V, and In-V compounds. The negative-U effect was only observed for the arsenic vacancy in GaAs, which makes a charge state transition from +1 to –1. It is also found that even under group III rich conditions, group III vacancies dominate in AlSb and GaSb. For InSb, group V vacancies are favoured even under group V rich conditions.

  12. Vacancies and defect levels in III–V semiconductors

    KAUST Repository

    Tahini, H. A.; Chroneos, Alexander; Grimes, R. W.; Murphy, S. T.; Schwingenschlö gl, Udo

    2013-01-01

    Using electronic structure calculations, we systematically investigate the formation of vacancies in III-V semiconductors (III = Al, Ga, and In and V = P, As, and Sb), for a range of charges ( −3≤q≤3 ) as a function of the Fermi level and under different growth conditions. The formation energies were corrected using the scheme due to Freysoldt et al. [Phys. Rev. Lett. 102, 016402 (2009)] to account for finite size effects. Vacancy formation energies were found to decrease as the size of the group V atom increased. This trend was maintained for Al-V, Ga-V, and In-V compounds. The negative-U effect was only observed for the arsenic vacancy in GaAs, which makes a charge state transition from +1 to –1. It is also found that even under group III rich conditions, group III vacancies dominate in AlSb and GaSb. For InSb, group V vacancies are favoured even under group V rich conditions.

  13. Ordered array of CoPc-vacancies filled with single-molecule rotors

    Science.gov (United States)

    Xie, Zheng-Bo; Wang, Ya-Li; Tao, Min-Long; Sun, Kai; Tu, Yu-Bing; Yuan, Hong-Kuan; Wang, Jun-Zhong

    2018-05-01

    We report the highly ordered array of CoPc-vacancies and the single-molecule rotors inside the vacancies. When CoPc molecules are deposited on Cd(0001) at low-temperature, three types of molecular vacancies appeared randomly in the CoPc monolayer. Annealing the sample to higher temperature leads to the spontaneous phase separation and self-organized arrangement of the vacancies. Highly ordered arrays of two-molecule vacancies and single-molecule vacancies have been obtained. In particular, there is a rotating CoPc molecule inside each single-molecule vacancy, which constitutes the array of single-molecule rotors. These results provide a new routine to fabricate the nano-machines on a large scale.

  14. Simulation of vacancy migration energy in Cu under high strain

    International Nuclear Information System (INIS)

    Sato, K.; Yoshiie, T.; Satoh, Y.; Xu, Q.; Kiritani, M.

    2003-01-01

    The activation energy for the migration of vacancies in Cu under high strain was calculated by computer simulation using static methods. The migration energy of vacancies was 0.98 eV in the absence of deformation. It varied with the migration direction and stress direction because the distance between a vacancy and its neighboring atoms changes by deformation. For example, the migration energy for the shortest migration distance was reduced to 9.6 and 39.4% of its initial value by 10% compression and 20% elongation, respectively, while that for the longest migration distance was raised to 171.7 by 20% elongation. If many vacancies are created during high-speed deformation, the lowering of migration energy enables vacancies to escape to sinks such as surfaces, even during the shorter deformation period. The critical strain rate above which the strain rate dependence of vacancy accumulation ceases to exist increases with the lowering of vacancy migration energy

  15. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Education Center Oculofacial Plastic Surgery Center Laser Surgery Education Center Redmond Ethics Center Global Ophthalmology Guide Eye Health ... Leer en Español: Peligros asociados con los lentes de contacto de color Sep. 26, ...

  16. Effect of air annealing on the color center in Yb:Y3Al5O12 transparent ceramics with MgO as sintering additive

    Science.gov (United States)

    Lu, Zhongwen; Lu, Tiecheng; Wei, Nian; Zhang, Wei; Ma, Benyuan; Qi, Jianqi; Guan, Yongbing; Chen, Xingtao; Wu, Huajun; Zhao, Yu

    2015-09-01

    High quality Yb:Y3Al5O12 (YAG) transparent ceramics were fabricated by vacuum sintering with MgO as sintering aids. The Yb:YAG samples were annealed at 1250-1450 °C for 20 h in air. The experimental results showed that the transparency of Yb:YAG samples declined markedly with the annealing temperatures of 1250-1450 °C. The samples became increasingly orange-yellow in color with the increase of annealing temperature. The potential reasons of discoloration were discussed for the first time. It was attributed to the complex color center [Mg2+F+] formed during the annealing, which was evidenced by optical absorption in the range of 300-500 nm wavelength and the presence of an electron spin resonance (ESR) line at g = 1.9806. The formation mechanism of the complex color center was explained in detail. The complex color center can be eliminated after post-HIP (hot isostatic pressing). And by air annealing and post-HIP, the transmittance of the samples increased from 80.3% to 83.4%.

  17. Positron annihilation study of vacancy-type defects in fast-neutron-irradiated MgO·nAl{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Abu Zayed Mohammad Saliqur, E-mail: zayed82000@yahoo.com [Key Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquanlu Shijingshan District, Beijing 100049 (China); Li, Zhuoxin; Cao, Xingzhong; Wang, Baoyi; Wei, Long [Key Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquanlu Shijingshan District, Beijing 100049 (China); Xu, Qiu [Reactor Research Institute, Kyoto University 2, Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan); Atobe, Kozo [Nuclear Safety Technology Center, 9-15, 1-chome, Utsubohonmachi, Nishi Ku, Osaka 550-0004 (Japan)

    2014-09-15

    Highlights: •Detection of Al monovacancy by positron lifetime spectroscopy in fast neutron-irradiated MgO·nAl{sub 2}O{sub 3}(n=2). •Concentration of defects is also estimated for Al monovacancy. •O atom peak was observed by using coincidence Doppler broadening spectroscopy. -- Abstract: The positron lifetimes of fast-neutron-irradiated MgO·nAl{sub 2}O{sub 3} single crystals were measured to investigate the formation of cation vacancies. Al monovacancy was possibly observed in samples irradiated by fast neutrons at ultra-low temperatures. Additionally, vacancy-oxygen complex centers were possibly observed in samples irradiated at higher temperatures and fast neutron fluences. Coincidence Doppler broadening (CDB) spectra were measured to obtain information regarding the vicinity of vacancy-type defects. A peak at approximately 11 × 10{sup −3} m{sub 0}c was observed, which may be due to the presence of oxygen atoms in the neighborhood of the vacancies.

  18. Single-spin stochastic optical reconstruction microscopy.

    Science.gov (United States)

    Pfender, Matthias; Aslam, Nabeel; Waldherr, Gerald; Neumann, Philipp; Wrachtrup, Jörg

    2014-10-14

    We experimentally demonstrate precision addressing of single-quantum emitters by combined optical microscopy and spin resonance techniques. To this end, we use nitrogen vacancy (NV) color centers in diamond confined within a few ten nanometers as individually resolvable quantum systems. By developing a stochastic optical reconstruction microscopy (STORM) technique for NV centers, we are able to simultaneously perform sub-diffraction-limit imaging and optically detected spin resonance (ODMR) measurements on NV spins. This allows the assignment of spin resonance spectra to individual NV center locations with nanometer-scale resolution and thus further improves spatial discrimination. For example, we resolved formerly indistinguishable emitters by their spectra. Furthermore, ODMR spectra contain metrology information allowing for sub-diffraction-limit sensing of, for instance, magnetic or electric fields with inherently parallel data acquisition. As an example, we have detected nuclear spins with nanometer-scale precision. Finally, we give prospects of how this technique can evolve into a fully parallel quantum sensor for nanometer resolution imaging of delocalized quantum correlations.

  19. Soft X-ray imaging by optically stimulated luminescence from color centers in lithium fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Bonfigli, F. [ENEA, C.R. Frascati, Via E. Fermi, 45, 00044 Frascati (Rome) (Italy)], E-mail: bonfigli@frascati.enea.it; Almaviva, S.; Baldacchini, G.; Bollanti, S.; Flora, F.; Lai, A.; Montereali, R.M. [ENEA, C.R. Frascati, Via E. Fermi, 45, 00044 Frascati (Rome) (Italy); Nichelatti, E. [ENEA, C.R. Casaccia, Via Anguillarese 301, 00060 S.Maria di Galeria (Rome) (Italy); Tomassetti, G.; Ritucci, A.; Reale, L. [Universita de L' Aquila e INFN, Dip. di Fisica, Coppito, L' Aquila (Italy); Faenov, A. Ya.; Pikuz, T.A. [MISDC of VNIIFTRI Mendeleevo, Moscow region, 141570 (Russian Federation); Larciprete, R. [ISC-CNR, Sezione Montelibretti, Via Salaria, Km. 29.3, 00016 Monterotondo Scalo (Rome) (Italy); Gregoratti, L.; Kiskinova, M. [Sincrotrone Trieste, S. S. 14, Km. 163.5, 34012 Basovizza (TS) (Italy)

    2007-07-15

    An innovative X-ray imaging detector based on Optically Stimulated Luminescence from color centers in lithium fluoride is presented. Regular photoluminescent patterns produced on LiF samples by different intense X-ray sources, like synchrotrons, laser plasma sources and a capillary discharge laser have been investigated by a Confocal Laser Scanning Microscope. The use of a LiF-based imaging plate for X-ray microscopy is also discussed showing microradiographies of small animals.

  20. Vacancy defect and defect cluster energetics in ion-implanted ZnO

    Science.gov (United States)

    Dong, Yufeng; Tuomisto, F.; Svensson, B. G.; Kuznetsov, A. Yu.; Brillson, Leonard J.

    2010-02-01

    We have used depth-resolved cathodoluminescence, positron annihilation, and surface photovoltage spectroscopies to determine the energy levels of Zn vacancies and vacancy clusters in bulk ZnO crystals. Doppler broadening-measured transformation of Zn vacancies to vacancy clusters with annealing shifts defect energies significantly lower in the ZnO band gap. Zn and corresponding O vacancy-related depth distributions provide a consistent explanation of depth-dependent resistivity and carrier-concentration changes induced by ion implantation.

  1. On the stability and mobility of di-vacancies in tungsten

    Science.gov (United States)

    Heinola, K.; Djurabekova, F.; Ahlgren, T.

    2018-02-01

    Properties of small vacancy clusters in tungsten were studied with first-principles calculations. The binding and formation energies of the vacancy clusters increase with the cluster size. Dynamic characteristics of a di-vacancy were specified between room temperature and 700 K with lattice kinetic Monte Carlo calculations, which were parametrised with the present first-principles results for the dissociation barriers. An Arrhenius fit for the di-vacancy diffusion yielded \

  2. Double K-vacancy production by x-ray photoionization

    International Nuclear Information System (INIS)

    Southworth, S. H.; Dunford, R. W.; Kanter, E. P.; Krassig, B.; Young, L.; Armen, G. B.; Levin, J. C.; Chen, M. H.; Ederer, D. L.

    2002-01-01

    We have studied double K-shell photoionization of Ne and Mo (Z = 10 and 42) at the Advanced Photon Source. Double K-vacancy production in Ne was observed by recording the KK-KLL Auger hypersatellite spectrum. Comparison is made with calculations using the multiconfiguration Dirac-Fock method. For Mo, double K-vacancy production was observed by recording the Kα, β fluorescence hypersatellite and satellite x rays in coincidence. From the intensities of the Auger or x-ray hypersatellites relative to diagram lines, the probabilities for double K-vacancy production relative to single K-vacancies were determined. These results, along with reported measurements on other atoms, are compared with Z-scaling calculations of the high-energy limits of the double-to-single K-shell photoionization ratio

  3. Engineering of Fermi level by nin diamond junction for control of charge states of NV centers

    Science.gov (United States)

    Murai, T.; Makino, T.; Kato, H.; Shimizu, M.; Murooka, T.; Herbschleb, E. D.; Doi, Y.; Morishita, H.; Fujiwara, M.; Hatano, M.; Yamasaki, S.; Mizuochi, N.

    2018-03-01

    The charge-state control of nitrogen-vacancy (NV) centers in diamond is very important toward its applications because the NV centers undergo stochastic charge-state transitions between the negative charge state (NV-) and the neutral charge state (NV0) of the NV center upon illumination. In this letter, engineering of the Fermi level by a nin diamond junction was demonstrated for the control of the charge state of the NV centers in the intrinsic (i) layer region. By changing the size (d) of the i-layer region between the phosphorus-doped n-type layer regions (nin) from 2 μm to 10 μm, we realized the gradual change in the NV- charge-state population in the i-layer region from 60% to 80% under 532 nm excitation, which can be attributed to the band bending in the i-layer region. Also, we quantitatively simulated the changes in the Fermi level in the i-layer region depending on d with various concentrations of impurities in the i-layer region.

  4. Efficient coherent driving of NV centers in a YIG-nanodiamond hybrid platform

    Science.gov (United States)

    Andrich, Paolo; de Las Casas, Charles F.; Liu, Xiaoying; Bretscher, Hope L.; Nealey, Paul F.; Awschalom, David D.; Heremans, F. Joseph

    The nitrogen-vacancy (NV) center in diamond is an ideal candidate for room temperature quantum computing and sensing applications. These schemes rely on magnetic dipolar interactions between the NV centers and other paramagnetic centers, imposing a stringent limit on the spin-to-spin separation. For instance, creating multi-qubit entanglement requires two NV centers to be within a few nanometers of each other, limiting the possibility for individual optical and microwave (MW) control. Moreover, to sense spins external to the diamond lattice the NV centers need to be within few nanometers from the surface, where their coherence properties are strongly reduced. In this work, we address these limitations using a hybrid YIG-nanodiamond platform where propagating spin-waves (SWs) are used to mediate the interaction between a MW source and a NV center ensemble, thereby relaxing the requirements imposed by dipolar interactions. In particular, we show that SWs can be used to amplify a MW signal detected by the NV centers by more than two orders of magnitude, allowing us to obtain ultra-low energy SW-driven coherent control of the NV centers. These results demonstrate the potentials of YIG-ND hybrid systems for the realization of enhanced quantum sensing and scalable computing devices. This work is supported by the ARO MURI program and the AFOSR.

  5. Shape and crystallographic orientation of nanodiamonds for quantum sensing.

    Science.gov (United States)

    Ong, S Y; Chipaux, M; Nagl, A; Schirhagl, R

    2017-05-03

    Nanodiamonds with dimensions down to a few tens of nanometers containing nitrogen-vacancy (NV) color centers have revealed their potential as powerful and versatile quantum sensors with a unique combination of spatial resolution and sensitivity. The NV centers allow transducing physical properties, such as strain, temperature, and electric or magnetic field, to an optical transition that can be detected in the single photon range. For example, this makes it possible to sense a single electron spin or a few nuclear spins by detecting their magnetic resonance. The location and orientation of these defects with respect to the diamond surface play a crucial role in interpreting the data and predicting their sensitivities. Despite its relevance, the geometry of these nanodiamonds has never been thoroughly investigated. Without accurate data, spherical models have been applied to interpret or predict results in the past. With the use of High Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), we investigated nanodiamonds with an average hydrodynamic diameter of 25 nm (the most common type for quantum sensing) and found a flake-like geometry, with 23.2 nm and 4.5 nm being the average lateral and vertical dimensions. We have also found evidence for a preferred crystallographic orientation of the main facet in the (110) direction. Furthermore, we discuss the consequences of this difference in geometry on diamond-based applications. Shape not only influences the creation efficiency of nitrogen-vacancy centers and their quantum coherence properties (and thus sensing performance), but also the optical properties of the nanodiamonds, their interaction with living cells, and their surface chemistry.

  6. Electrically active induced energy levels and metastability of B and N vacancy-complexes in 4H-SiC.

    Science.gov (United States)

    Igumbor, E; Olaniyan, O; Mapasha, R E; Danga, H T; Omotoso, E; Meyer, W E

    2018-05-10

    Electrically active induced energy levels in semiconductor devices could be beneficial to the discovery of an enhanced p or n-type semiconductor. Nitrogen (N) implanted into 4H-SiC is a high energy process that produced high defect concentrations which could be removed during dopant activation annealing. On the other hand, boron (B) substituted for silicon in SiC causes a reduction in the number of defects. This scenario leads to a decrease in the dielectric properties and induced deep donor and shallow acceptor levels. Complexes formed by the N, such as the nitrogen-vacancy centre, have been reported to play a significant role in the application of quantum bits. In this paper, results of charge states thermodynamic transition level of the N and B vacancy-complexes in 4H-SiC are presented. We explore complexes where substitutional N[Formula: see text]/N[Formula: see text] or B[Formula: see text]/B[Formula: see text] sits near a Si (V[Formula: see text]) or C (V[Formula: see text]) vacancy to form vacancy-complexes (N[Formula: see text]V[Formula: see text], N[Formula: see text]V[Formula: see text], N[Formula: see text]V[Formula: see text], N[Formula: see text]V[Formula: see text], B[Formula: see text]V[Formula: see text], B[Formula: see text]V[Formula: see text], B[Formula: see text]V[Formula: see text] and B[Formula: see text]V[Formula: see text]). The energies of formation of the N related vacancy-complexes showed the N[Formula: see text]V[Formula: see text] to be energetically stable close to the valence band maximum in its double positive charge state. The N[Formula: see text]V[Formula: see text] is more energetically stable in the double negative charge state close to the conduction band minimum. The N[Formula: see text]V[Formula: see text] on the other hand, induced double donor level and the N[Formula: see text]V[Formula: see text] induced a double acceptor level. For B related complexes, the B[Formula: see text]V[Formula: see text] and B[Formula: see text

  7. Coupling of Quantum Emitters in Nanodiamonds to Plasmonic Structures

    DEFF Research Database (Denmark)

    Kumar, Shailesh

    This PhD thesis describes work towards the enhancement and efficient channeling of photons emitted from a single photon emitter. The emitter used is a defect center, the Nitrogen-Vacancy (NV) center, in diamond. The NV-center has many unique properties, such as long coherence time of its electron...

  8. Moessbauer effect and vacancy diffusion

    International Nuclear Information System (INIS)

    Gunther, L.

    1976-01-01

    A dynamical theory of vacancy diffusion which was motivated by the need to explain recent experimental results for the Moessbauer spectra of Fe in Cu, Fe in Au and Fe in Al is presented. Diffusion in these systems is dominated by the vacancy mechanism, which involves strong correlations between successive jumps. The theory developed by Singwi and Sjoelander for the Moessbauer spectrum of a diffusing nucleus is therefore not applicable. The inverse of the normalized Moessbauer spectrum evaluated at zero frequency is introduced as a useful means of comparing experimental with theoretical spectral widths

  9. F-center mechanism of long-term relaxation in lead zirconate-titanate-based piezoelectric ceramics. 1. After-heating relaxation

    Directory of Open Access Journals (Sweden)

    V. M. Ishchuk

    2015-12-01

    The oxygen vacancies-based model for description of the long-time relaxation processes is suggested. The model takes into account oxygen vacancies on the sample’s surface ends, their conversion into F+- and F0-centers under external effects (due to the liberation of the pyroelectric charge and subsequent relaxation of these centers into the simple oxygen vacancies after the actions termination. The initial sample’s state is electroneutrality one. F-center formation leads to the violation of the original sample’s electroneutrality, and generates DC electric field into the sample. Relaxation of F-centers is accompanied by decreasing of electric field, induced by them, and dielectric constant relaxation as consequent effect.

  10. DNA-Based Self-Assembly of Fluorescent Nanodiamonds.

    Science.gov (United States)

    Zhang, Tao; Neumann, Andre; Lindlau, Jessica; Wu, Yuzhou; Pramanik, Goutam; Naydenov, Boris; Jelezko, Fedor; Schüder, Florian; Huber, Sebastian; Huber, Marinus; Stehr, Florian; Högele, Alexander; Weil, Tanja; Liedl, Tim

    2015-08-12

    As a step toward deterministic and scalable assembly of ordered spin arrays we here demonstrate a bottom-up approach to position fluorescent nanodiamonds (NDs) with nanometer precision on DNA origami structures. We have realized a reliable and broadly applicable surface modification strategy that results in DNA-functionalized and perfectly dispersed NDs that were then self-assembled in predefined geometries. With optical studies we show that the fluorescence properties of the nitrogen-vacancy color centers in NDs are preserved during surface modification and DNA assembly. As this method allows the nanoscale arrangement of fluorescent NDs together with other optically active components in complex geometries, applications based on self-assembled spin lattices or plasmon-enhanced spin sensors as well as improved fluorescent labeling for bioimaging could be envisioned.

  11. Study of the spectral and energy characteristics of lasing in the green spectral region by lithium fluoride with radiation color centers

    Energy Technology Data Exchange (ETDEWEB)

    Voitovich, A.P.; Kalinov, V.S.; Mikhnov, S.A.; Ovseichuk, S.I.

    1987-06-01

    The spectral and energy characteristics of lasers utilizing lithium fluoride with F2 and F3(+) color centers in transverse and longitudinal pumping schemes are studied. The feasibility of obtaining stable narrow-band radiation in the 510-570 nm range using a selective resonator is demonstrated. Consideration is given to the effect of lithium-fluoride crystal processing by excimer laser radiation at a wavelength of 308 nm on the spectroscopic and lasing characteristics of the F3(+) color center. After this processing, the laser efficiency in the green spectral region increases by more than a factor of two (reaching an efficiency of 14 percent). 7 references.

  12. Rapid estimation of organic nitrogen in oil shale wastewaters

    Energy Technology Data Exchange (ETDEWEB)

    Jones, B.M.; Harris, G.J.; Daughton, C.G.

    1984-03-01

    Many of the characteristics of oil shale process wastewaters (e.g., malodors, color, and resistance to biotreatment) are imparted by numerous nitrogen heterocycles and aromatic amines. For the frequent performance assessment of waste treatment procsses designed to remove these nitrogenous organic compounds, a rapid and colligative measurement of organic nitrogen is essential.

  13. Advanced treatment technique for swine wastewater using two agents: Thermally polymerized amorphous silica and hydrated lime for color and phosphorus removal and sulfur for nitrogen removal.

    Science.gov (United States)

    Hasegawa, Teruaki; Kurose, Yohei; Tanaka, Yasuo

    2017-10-01

    The efficacy of advanced treatment of swine wastewater using thermally polymerized, modified amorphous silica and hydrated lime (M-CSH-lime) for color and phosphorus removal and sulfur for nitrogen removal was examined with a demonstration-scale treatment plant. The color removal rate was approximately 78% at M-CSH-lime addition rates of > 0.055 wt/v%. The PO43--P removal rate exceeded 99.9% with > 0.023 wt/v%. pH of the effluent from the M-CSH-lime reactor increased with the addition rate till a maximum value of 12.7, which was effective in disinfection. The recovered M-CSH-lime would be suitable as a phosphorus fertilizer because the total P 2 O 5 content was approximately 10%. The nitrogen oxide (NOx-N) removal rate by sulfur denitrification increased to approximately 80% when the NOx-N loading rate was around 0.1 kg-N/ton-S/day. It was suggested that the combination of the two processes would be effective in the advanced treatment of swine wastewater. © 2017 Japanese Society of Animal Science.

  14. Improving surface and defect center chemistry of fluorescent nanodiamonds for imaging purposes--a review.

    Science.gov (United States)

    Nagl, Andreas; Hemelaar, Simon Robert; Schirhagl, Romana

    2015-10-01

    Diamonds are widely used for jewelry owing to their superior optical properties accounting for their fascinating beauty. Beyond the sparkle, diamond is highly investigated in materials science for its remarkable properties. Recently, fluorescent defects in diamond, particularly the negatively charged nitrogen-vacancy (NV(-)) center, have gained much attention: The NV(-) center emits stable, nonbleaching fluorescence, and thus could be utilized in biolabeling, as a light source, or as a Förster resonance energy transfer donor. Even more remarkable are its spin properties: with the fluorescence intensity of the NV(-) center reacting to the presence of small magnetic fields, it can be utilized as a sensor for magnetic fields as small as the field of a single electron spin. However, a reproducible defect and surface and defect chemistry are crucial to all applications. In this article we review methods for using nanodiamonds for different imaging purposes. The article covers (1) dispersion of particles, (2) surface cleaning, (3) particle size selection and reduction, (4) defect properties, and (5) functionalization and attachment to nanostructures, e.g., scanning probe microscopy tips.

  15. VACANCIES AND THE RECRUITMENT OF NEW EMPLOYEES

    NARCIS (Netherlands)

    VANOURS, J; RIDDER, G

    Little is known about the search strategy that employers use in their efforts to fill job vacancies. In this article, we analyze unique micro data to study this search strategy. We conclude that almost all vacancies are filled from a pool of applicants that is formed shortly after the posting of the

  16. Using clinical simulation centers to test design interventions: a pilot study of lighting and color modifications.

    Science.gov (United States)

    Gray, Whitney Austin; Kesten, Karen S; Hurst, Stephen; Day, Tama Duffy; Anderko, Laura

    2012-01-01

    The aim of this pilot study was to test design interventions such as lighting, color, and spatial color patterning on nurses' stress, alertness, and satisfaction, and to provide an example of how clinical simulation centers can be used to conduct research. The application of evidence-based design research in healthcare settings requires a transdisciplinary approach. Integrating approaches from multiple fields in real-life settings often proves time consuming and experimentally difficult. However, forums for collaboration such as clinical simulation centers may offer a solution. In these settings, identical operating and patient rooms are used to deliver simulated patient care scenarios using automated mannequins. Two identical rooms were modified in the clinical simulation center. Nurses spent 30 minutes in each room performing simulated cardiac resuscitation. Subjective measures of nurses' stress, alertness, and satisfaction were collected and compared between settings and across time using matched-pair t-test analysis. Nurses reported feeling less stressed after exposure to the experimental room than nurses who were exposed to the control room (2.22, p = .03). Scores post-session indicated a significant reduction in stress and an increase in alertness after exposure to the experimental room as compared to the control room, with significance levels below .10. (Change in stress scores: 3.44, p = .069); (change in alertness scores: 3.6, p = .071). This study reinforces the use of validated survey tools to measure stress, alertness, and satisfaction. Results support human-centered design approaches by evaluating the effect on nurses in an experimental setting.

  17. Strain Relaxation and Vacancy Creation in Thin Platinum Films

    International Nuclear Information System (INIS)

    Gruber, W.; Chakravarty, S.; Schmidt, H.; Baehtz, C.; Leitenberger, W.; Bruns, M.; Kobler, A.; Kuebel, C.

    2011-01-01

    Synchrotron based combined in situ x-ray diffractometry and reflectometry is used to investigate the role of vacancies for the relaxation of residual stress in thin metallic Pt films. From the experimentally determined relative changes of the lattice parameter a and of the film thickness L the modification of vacancy concentration and residual strain was derived as a function of annealing time at 130 deg. C. The results indicate that relaxation of strain resulting from compressive stress is accompanied by the creation of vacancies at the free film surface. This proves experimentally the postulated dominant role of vacancies for stress relaxation in thin metal films close to room temperature.

  18. Dissociative diffusion mechanism in vacancy-rich materials according to mass action kinetics

    Directory of Open Access Journals (Sweden)

    N. J. Biderman

    2016-05-01

    Full Text Available Two sets of diffusion-reaction numerical simulations using a finite difference method (FDM were conducted to investigate fast impurity diffusion via interstitial sites in vacancy-rich materials such as Cu(In,GaSe2 (CIGS and Cu2ZnSn(S, Se4 (CZTSSe or CZTS via the dissociative diffusion mechanism where the interstitial diffuser ultimately reacts with a vacancy to produce a substitutional. The first set of simulations extends the standard interstitial-limited dissociative diffusion theory to vacancy-rich material conditions where vacancies are annihilated in large amounts, introducing non-equilibrium vacancy concentration profiles. The second simulation set explores the vacancy-limited dissociative diffusion where impurity incorporation increases the equilibrium vacancy concentration. In addition to diffusion profiles of varying concentrations and shapes that were obtained in all simulations, some of the profiles can be fitted with the constant- and limited-source solutions of Fick’s second law despite the non-equilibrium condition induced by the interstitial-vacancy reaction. The first set of simulations reveals that the dissociative diffusion coefficient in vacancy-rich materials is inversely proportional to the initial vacancy concentration. In the second set of numerical simulations, impurity-induced changes in the vacancy concentration lead to distinctive diffusion profile shapes. The simulation results are also compared with published data of impurity diffusion in CIGS. According to the characteristic properties of diffusion profiles from the two set of simulations, experimental detection of the dissociative diffusion mechanism in vacancy-rich materials may be possible.

  19. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are considering buying approved by the ... Service For Advertisers For Media Ophthalmology Job Center © American ...

  20. Unraveling the oxygen vacancy structures at the reduced Ce O2(111 ) surface

    Science.gov (United States)

    Han, Zhong-Kang; Yang, Yi-Zhou; Zhu, Beien; Ganduglia-Pirovano, M. Verónica; Gao, Yi

    2018-03-01

    Oxygen vacancies at ceria (Ce O2 ) surfaces play an essential role in catalytic applications. However, during the past decade, the near-surface vacancy structures at Ce O2(111 ) have been questioned due to the contradictory results from experiments and theoretical simulations. Whether surface vacancies agglomerate, and which is the most stable vacancy structure for varying vacancy concentration and temperature, are being heatedly debated. By combining density functional theory calculations and Monte Carlo simulations, we proposed a unified model to explain all conflicting experimental observations and theoretical results. We find a novel trimeric vacancy structure which is more stable than any other one previously reported, which perfectly reproduces the characteristics of the double linear surface oxygen vacancy clusters observed by STM. Monte Carlo simulations show that at low temperature and low vacancy concentrations, vacancies prefer subsurface sites with a local (2 × 2) ordering, whereas mostly linear surface vacancy clusters do form with increased temperature and degree of reduction. These results well explain the disputes about the stable vacancy structure and surface vacancy clustering at Ce O2(111 ) , and provide a foundation for the understanding of the redox and catalytic chemistry of metal oxides.

  1. Use of Color in Child Care Environments: Application of Color for Wayfinding and Space Definition in Alabama Child Care Environments.

    Science.gov (United States)

    Read, Marilyn A.

    2003-01-01

    Compared the use of color in physical design features associated with the exterior and interior designs of 101 child care centers in Alabama. Found that color was evidenced on the exterior of the centers at just over half of the sample. The interior environments had warm colors and bright accents in the setting; however, the majority of centers…

  2. Generation and Controlled Routing of Single Plasmons on a Chip

    DEFF Research Database (Denmark)

    Kumar, Shailesh; Israelsen, Niels Møller; Huck, Alexander

    2014-01-01

    We demonstrate the excitation of single surface plasmon polaritons on a silver nanowire using a nitrogen vacancy center and the subsequent controlled coupling to a second silver nanowire. The coupling efficiency and thus the splitting ratio between the nanowires is controlled by adjusting the gap...... size between the wires with an atomic force microscope. By numerical methods, we estimate the splitting ratios for different gap sizes, and the results support the values obtained in the experiment.......We demonstrate the excitation of single surface plasmon polaritons on a silver nanowire using a nitrogen vacancy center and the subsequent controlled coupling to a second silver nanowire. The coupling efficiency and thus the splitting ratio between the nanowires is controlled by adjusting the gap...

  3. ATR/OTR-SY Tank Camera Purge System and in Tank Color Video Imaging System

    International Nuclear Information System (INIS)

    Werry, S.M.

    1995-01-01

    This procedure will document the satisfactory operation of the 101-SY tank Camera Purge System (CPS) and 101-SY in tank Color Camera Video Imaging System (CCVIS). Included in the CPRS is the nitrogen purging system safety interlock which shuts down all the color video imaging system electronics within the 101-SY tank vapor space during loss of nitrogen purge pressure

  4. The Correlation Between Dislocations and Vacancy Defects Using Positron Annihilation Spectroscopy

    Science.gov (United States)

    Pang, Jinbiao; Li, Hui; Zhou, Kai; Wang, Zhu

    2012-07-01

    An analysis program for positron annihilation lifetime spectra is only applicable to isolated defects, but is of no use in the presence of defective correlations. Such limitations have long caused problems for positron researchers in their studies of complicated defective systems. In order to solve this problem, we aim to take a semiconductor material, for example, to achieve a credible average lifetime of single crystal silicon under plastic deformation at different temperatures using positron life time spectroscopy. By establishing reasonable positron trapping models with defective correlations and sorting out four lifetime components with multiple parameters, as well as their respective intensities, information is obtained on the positron trapping centers, such as the positron trapping rates of defects, the density of the dislocation lines and correlation between the dislocation lines, and the vacancy defects, by fitting with the average lifetime with the aid of Matlab software. These results give strong grounds for the existence of dislocation-vacancy correlation in plastically deformed silicon, and lay a theoretical foundation for the analysis of positron lifetime spectra when the positron trapping model involves dislocation-related defects.

  5. Molecular dynamics simulations of oxygen vacancy diffusion in SrTiO3

    International Nuclear Information System (INIS)

    Schie, Marcel; Marchewka, Astrid; Waser, Rainer; Müller, Thomas; De Souza, Roger A

    2012-01-01

    A classical force-field model with partial ionic charges was applied to study the behaviour of oxygen vacancies in the perovskite oxide strontium titanate (SrTiO 3 ). The dynamical behaviour of these point defects was investigated as a function of temperature and defect concentration by means of molecular dynamics (MD) simulations. The interaction between oxygen vacancies and an extended defect, here a Σ3(111) grain boundary, was also examined by means of MD simulations. Analysis of the vacancy distribution revealed considerable accumulation of vacancies in the envelope of the grain boundary. The possible clustering of oxygen vacancies in bulk SrTiO 3 was studied by means of static lattice calculations within the Mott-Littleton approach. All binary vacancy-vacancy configurations were found to be energetically unfavourable.

  6. Molecular dynamics simulations of oxygen vacancy diffusion in SrTiO3.

    Science.gov (United States)

    Schie, Marcel; Marchewka, Astrid; Müller, Thomas; De Souza, Roger A; Waser, Rainer

    2012-12-05

    A classical force-field model with partial ionic charges was applied to study the behaviour of oxygen vacancies in the perovskite oxide strontium titanate (SrTiO(3)). The dynamical behaviour of these point defects was investigated as a function of temperature and defect concentration by means of molecular dynamics (MD) simulations. The interaction between oxygen vacancies and an extended defect, here a Σ3(111) grain boundary, was also examined by means of MD simulations. Analysis of the vacancy distribution revealed considerable accumulation of vacancies in the envelope of the grain boundary. The possible clustering of oxygen vacancies in bulk SrTiO(3) was studied by means of static lattice calculations within the Mott-Littleton approach. All binary vacancy-vacancy configurations were found to be energetically unfavourable.

  7. Quantum transport in defective phosphorene nanoribbons: Effects of atomic vacancies

    Science.gov (United States)

    Li, L. L.; Peeters, F. M.

    2018-02-01

    Defects are almost inevitably present in realistic materials and defective materials are expected to exhibit very different properties than their nondefective (perfect) counterparts. Here, using a combination of the tight-binding approach and the scattering matrix formalism, we investigate the electronic transport properties of defective phosphorene nanoribbons (PNRs) containing atomic vacancies. We find that for both armchair PNRs (APNRs) and zigzag PNRs (ZPNRs), single vacancies can create quasilocalized states, which can affect their conductance. With increasing vacancy concentration, three different transport regimes are identified: ballistic, diffusive, and Anderson localized ones. In particular, ZPNRs that are known to be metallic due to the presence of edge states become semiconducting: edge conductance vanishes and transport gap appears due to Anderson localization. Moreover, we find that for a fixed vacancy concentration, both APNRs and ZPNRs of narrower width and/or longer length are more sensitive to vacancy disorder than their wider and/or shorter counterparts, and that for the same ribbon length and width, ZPNRs are more sensitive to vacancy disorder than APNRs.

  8. Total K-vacancy production in Ne (10 MeV) traversing Al

    International Nuclear Information System (INIS)

    Groeneveld, K.O.; Kolb, B.; Schader, J.; Sevier, K.D.

    1976-01-01

    Deexcitation of projectile inner shell vacancies created while traversing a solid foil may take place via competing processes: a) vacancy sharing with foil atoms in close impacts, b) radiative and non-radiative electron capture, and c) such X-ray and Auger electron transitions are possible in the heavy ion projectile. The change in K-vacancy creation with foil thickness can be investigated by measuring either projectile or target X-rays where the vacancies are created by Coulomb excitation and process a. In the system Ne (10 MeV) on Al, detecting Al K X-rays, the Ne K-vacancy production probability has been determined. (orig.) [de

  9. Radiation induced color in topaz crystals

    International Nuclear Information System (INIS)

    Castagnet, A.C.; Rocca, H.C.C.; Rostilato, M.E.C.M.

    1989-08-01

    The presence of defects and impurities in the crystal lattice alters the eletric field distribution within the crystal, allowing the electrons to occupy energy levels in the forbbiden band. Ionizing radiation supply the required energy to permit the electrons originaly bound to lattice atoms, to occupy effectively those intermediate levels, forming color centers. Dependig upon the nature and energy of the radiation, it is possible to produce defects in regions of the crystal, generating color centers. Based on these premises, a technique to induce color in originally colorless topaz, by using the IEA-R1 nuclear reactor, was developed at Engineering and Industrial Application Department (TE). Samples were irradiated inside iron capsules coated with cadmium foils. The iron, and principaly the cadmium, absorb the thermal neutrons that could activate crystal impurities generating long-lived radioisotopes. The epithermal neutrons that overpass the iron and cadmium barriers interact with the crystal atoms, causing lattice defects which give rise to color center, by subsequent ionization processes. The procedure used at TE induces permanent blue color, in natural colorless topaz. (author) [pt

  10. Reconstruction of mono-vacancies in carbon nanotubes: Atomic relaxation vs. spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Berber, S. [Institute of Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8571 (Japan)]. E-mail: berber@comas.frsc.tsukuba.ac.jp; Oshiyama, A. [Institute of Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8571 (Japan)

    2006-04-01

    We have investigated the reconstruction of mono-vacancies in carbon nanotubes using density functional theory (DFT) geometry optimization and electronic structure calculations, employing a numerical basis set. We considered mono-vacancies in achiral nanotubes with diameter range {approx}4-9A. Contrary to previous tight-binding calculations, our results indicate that mono-vacancies could have several metastable geometries, confirming the previous plane-wave DFT results. Formation energy of mono-vacancies is 4.5-5.5eV, increasing with increasing tube diameter. Net magnetic moment decreases from ideal mono-vacancy value after reconstruction, reflecting the reduction of the number of dangling bonds. In spite of the existence of a dangling bond, ground state of mono-vacancies in semiconducting tubes have no spin polarization. Metallic carbon nanotubes show net magnetic moment for most stable structure of mono-vacancy, except for very small diameter tubes.

  11. Reconstruction of mono-vacancies in carbon nanotubes: Atomic relaxation vs. spin polarization

    International Nuclear Information System (INIS)

    Berber, S.; Oshiyama, A.

    2006-01-01

    We have investigated the reconstruction of mono-vacancies in carbon nanotubes using density functional theory (DFT) geometry optimization and electronic structure calculations, employing a numerical basis set. We considered mono-vacancies in achiral nanotubes with diameter range ∼4-9A. Contrary to previous tight-binding calculations, our results indicate that mono-vacancies could have several metastable geometries, confirming the previous plane-wave DFT results. Formation energy of mono-vacancies is 4.5-5.5eV, increasing with increasing tube diameter. Net magnetic moment decreases from ideal mono-vacancy value after reconstruction, reflecting the reduction of the number of dangling bonds. In spite of the existence of a dangling bond, ground state of mono-vacancies in semiconducting tubes have no spin polarization. Metallic carbon nanotubes show net magnetic moment for most stable structure of mono-vacancy, except for very small diameter tubes

  12. Electronic structure and formation energy of a vacancy in aluminum

    International Nuclear Information System (INIS)

    Chakraborty, B.; Siegel, R.W.

    1981-11-01

    The electronic structure of a vacancy in Al was calculated self-consistently using norm-conserving ionic pseudopotentials obtained from ab initio atomic calculations. A 27-atom-site supercell containing 1 vacancy and 26 atoms was used to simulate the environment of the vacancy. A vacancy formation energy of 1.5 eV was also calculated (cf. the experimental value of 0.66 eV). The effects of the supercell and the nature of the ionic potential on the resulting electronic structure and formation energy are discussed. Results for the electronic structure of a divacancy are also presented. 3 figures

  13. Tracking Oxygen Vacancies in Thin Film SOFC Cathodes

    Science.gov (United States)

    Leonard, Donovan; Kumar, Amit; Jesse, Stephen; Kalinin, Sergei; Shao-Horn, Yang; Crumlin, Ethan; Mutoro, Eva; Biegalski, Michael; Christen, Hans; Pennycook, Stephen; Borisevich, Albina

    2011-03-01

    Oxygen vacancies have been proposed to control the rate of the oxygen reduction reaction and ionic transport in complex oxides used as solid oxide fuel cell (SOFC) cathodes [1,2]. In this study oxygen vacancies were tracked, both dynamically and statically, with the combined use of scanned probe microscopy (SPM) and scanning transmission electron microscopy (STEM). Epitaxial films of La 0.8 Sr 0.2 Co O3 (L SC113) and L SC113 / LaSrCo O4 (L SC214) on a GDC/YSZ substrate were studied, where the latter showed increased electrocatalytic activity at moderate temperature. At atomic resolution, high angle annular dark field STEM micrographs revealed vacancy ordering in L SC113 as evidenced by lattice parameter modulation and EELS studies. The evolution of oxygen vacancy concentration and ordering with applied bias and the effects of bias cycling on the SOFC cathode performance will be discussed. Research is sponsored by the of Materials Sciences and Engineering Division, U.S. DOE.

  14. [Diagnoses of rice nitrogen status based on characteristics of scanning leaf].

    Science.gov (United States)

    Zhu, Jin-Xia; Deng, Jin-Song; Shi, Yuan-Yuan; Chen, Zhu-Lu; Han, Ning; Wang, Ke

    2009-08-01

    In the present research, the scanner was adopted as the digital image sensor, and a new method to diagnose the status of rice based on image processing technology was established. The main results are as follows: (1) According to the analysis of relations between leaf percentage nitrogen contents and color parameter, the sensitive color parameters were abstracted as B, b, b/(r+g), b/r and b/g. The leaf position (vertical spatial variation) effects on leaf chlorophyll contents were investigated, and the third fully expanded leaf was selected as the diagnosis leaf. (2) Field ground data such as ASD were collected simultaneously. Then study on the relationships between scanned leaf color characteristics and hyperspectral was carried out. The results indicated that the diagnosis of nitrogen status based on the scanned color characteristic is able to partly reflect the hyperspectral properties. (3) The leaf color and shape features were intergrated and the model of diagnosing the status of rice was established with calculated at YIQ color system. The distinct accuracy of nitrogen status was as follows: N0: 74.9%; N1 : 52%; N2 : 84.7%; N3 : 75%. The preliminary study showed that the methodology has been proved successful in this study and provides the potential to monitor nitrogen status in a cost-effective and accurate way based on the scanned digital image. Although, some confusion exists, with rapidly increasing resolution of digital platform and development of digital image technology, it will be more convenient for larger farms that can afford to use mechanized systems for site-specific nutrient management. Moreover, deeper theory research and practice experiment should be needed in the future.

  15. Molecular dynamics simulations of ferroelectric domain formation by oxygen vacancy

    Science.gov (United States)

    Zhu, Lin; You, Jeong Ho; Chen, Jinghong; Yeo, Changdong

    2018-05-01

    An oxygen vacancy, known to be detrimental to ferroelectric properties, has been investigated numerically for the potential uses to control ferroelectric domains in films using molecular dynamics simulations based on the first-principles effective Hamiltonian. As an electron donor, an oxygen vacancy generates inhomogeneous electrostatic and displacement fields which impose preferred polarization directions near the oxygen vacancy. When the oxygen vacancies are placed at the top and bottom interfaces, the out-of-plane polarizations are locally developed near the interfaces in the directions away from the interfaces. These polarizations from the interfaces are in opposite directions so that the overall out-of-plane polarization becomes significantly reduced. In the middle of the films, the in-plane domains are formed with containing 90° a 1/a 2 domain walls and the films are polarized along the [1 1 0] direction even when no electric field is applied. With oxygen vacancies placed at the top interface only, the films exhibit asymmetric hysteresis loops, confirming that the oxygen vacancies are one of the possible sources of ferroelectric imprint. It has been qualitatively demonstrated that the domain structures in the imprint films can be turned on and off by controlling an external field along the thickness direction. This study shows qualitatively that the oxygen vacancies can be utilized for tuning ferroelectric domain structures in films.

  16. Electrolytic coloration and spectral properties of hydroxyl-doped potassium chloride single crystals

    International Nuclear Information System (INIS)

    Gu Hongen; Wu Yanru

    2011-01-01

    Hydroxyl-doped potassium chloride single crystals are colored electrolytically at various temperatures and voltages using a pointed cathode and a flat anode. Characteristic OH - spectral band is observed in the absorption spectrum of uncolored single crystal. Characteristic O - , OH - , U, V 2 , V 3 , O 2- -V a + , F, R 2 and M spectral bands are observed simultaneously in absorption spectra of colored single crystals. Current-time curve for electrolytic coloration of hydroxyl-doped potassium chloride single crystal and its relationship with electrolytic coloration process are given. Production and conversion of color centers are explained. - Highlights: → Expanded the traditional electrolysis method. → Hydroxyl-doped potassium chloride crystals were colored electrolytically for the first time. → Useful V, F and F-aggregate color centers were produced in colored crystals. → V color centers were produced directly and F and F-aggregate color centers indirectly.

  17. Observation of Zn vacancies in ZnO grown by chemical vapor transport

    Energy Technology Data Exchange (ETDEWEB)

    Tuomisto, F.; Saarinen, K. [Laboratory of Physics, Helsinki University of Technology, P.O. Box 1100, 02015 TKK (Finland); Grasza, K.; Mycielski, A. [Institute of Physics, Polish Academy of Sciences, Lotnikow 32/46, 02-668 Warsaw (Poland)

    2006-03-15

    We have used positron annihilation spectroscopy to study the vacancy defects in ZnO crystals grown by both the conventional and contactless chemical vapor transport (CVT and CCVT). Our results show that Zn vacancies or Zn vacancy related defects are present in as-grown ZnO, irrespective of the growth method. Zn vacancies are observed in CVT-grown undoped ZnO and (Zn,Mn)O. The Zn vacancies present in undoped CCVT-ZnO are the dominant negatively charged point defect in the material. Doping the material with As introduces also Zn vacancy-related defect complexes with larger open volume. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Vacancies and negative ions in GaAs

    International Nuclear Information System (INIS)

    Corbel, C.

    1991-01-01

    We use positron lifetime studies performed in GaAs materials to show the defect properties which can be investigated by implanting positive positrons in semiconductors. The studies concern native and electron irradiation induced defects. These studies show that vacancy charge state and vacancy ionization levels can be determined from positron annihilation. They show also that positrons are trapped by negative ions and give information on their concentration

  19. Vacancies in quantal Wigner crystals near melting

    International Nuclear Information System (INIS)

    Barraza, N.; Colletti, L.; Tosi, M.P.

    1999-04-01

    We estimate the formation energy of lattice vacancies in quantal Wigner crystals of charged particles near their melting point at zero temperature, in terms of the crystalline Lindemann parameter and of the static dielectric function of the fluid phase near freezing. For both 3D and 2D crystals of electrons our results suggest the presence of vacancies in the ground state at the melting density. (author)

  20. A quantum-chemical study of oxygen-vacancy defects in PbTiO3 crystals

    International Nuclear Information System (INIS)

    Stashans, Arvids; Serrano, Sheyla; Medina, Paul

    2006-01-01

    Investigation of an oxygen vacancy and F center in the cubic and tetragonal lattices of PbTiO 3 crystals is done by means of quantum-chemical simulations. Displacements of defect-surrounding atoms, electronic and optical properties, lattice relaxation energies and some new effects due to the defects presence are reported and analyzed. A comparison with similar studies is made and conclusions are drawn on the basis of the obtained results

  1. Optimizing Chemical-Vapor-Deposition Diamond for Nitrogen-Vacancy Center Ensemble Magnetrometry

    Science.gov (United States)

    2017-06-01

    excited state sublevels. The NV system cannot optically cycle while in the 1 singlet state (with an average lifetime of about 250 ns [28]), hence...it is dark during this time period. Since the |0⟩ state decays mainly through optical cycling (average excited state lifetime of 12 ns [29]), it is...times: a /2 pulse that creates an equal superposition of the |0⟩ and | − 1⟩ spin states, a pulse that inverts the spin state from |0⟩ to | − 1

  2. Electrolytic coloration and spectral properties of hydroxyl-doped potassium bromide single crystals

    International Nuclear Information System (INIS)

    Qi, Lan; Song, Cuiying; Gu, Hongen

    2013-01-01

    Hydroxyl-doped potassium bromide single crystals are colored electrolytically at various temperatures and voltages by using a pointed cathode and a flat anode. The characteristic OH − spectral band is observed in absorption spectrum of uncolored single crystal. The characteristic O − , OH − , U, V 2 , O 2− −V a + , M L1 , F and M spectral bands are observed simultaneously in absorption spectra of colored single crystals. Current–time curve for electrolytic coloration of hydroxyl-doped potassium bromide single crystal and its relationship with electrolytic coloration processes are given. Production and conversion of color centers are explained. - Highlights: ► We expanded the traditional electrolysis method. ► Hydroxyl-doped potassium bromide crystals were colored electrolytically for the first time. ► Useful V, F and F-aggregate color centers were produced in colored crystals. ► V color centers were produced directly and F as well as F-aggregate color centers indirectly.

  3. Direct detection of light dark matter and solar neutrinos via color center production in crystals

    OpenAIRE

    Budnik, Ranny; Cheshnovsky, Ori; Slone, Oren; Volansky, Tomer

    2018-01-01

    We propose a new low-threshold direct-detection concept for dark matter and for coherent nuclear scattering of solar neutrinos, based on the dissociation of atoms and subsequent creation of color center type defects within a lattice. The novelty in our approach lies in its ability to detect single defects in a macroscopic bulk of material. This class of experiments features ultra-low energy thresholds which allows for the probing of dark matter as light as O(10) MeV through nuclear scattering...

  4. Formation of vacancy clusters in tungsten crystals under hydrogen-rich condition

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Daiji, E-mail: kato.daiji@nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292 (Japan); Iwakiri, Hirotomo, E-mail: iwakiri@edu.u-ryukyu.ac.jp [University of the Ryukyus, Okinawa 903-0213 (Japan); Morishita, Kazunori, E-mail: morishita@iae.kyoto-u.ac.jp [Institute of Advanced Energy, Kyoto University, Kyoto 611-0011 (Japan)

    2011-10-01

    Di-vacancy formation assisted by hydrogen trapping is studied in terms of nucleation free-energies evaluated with density functional theory. Calculations give binding energies for single hydrogen atom as first- and second-nearest-neighbor of di-vacancies of 1.80 and 2.15 eV, respectively, which are significantly larger than that for mono-vacancies. At elevated atomic concentrations of interstitial hydrogen atoms, evaluated nucleation free-energies indicate that the hydrogen assisted di-vacancy formation becomes more favorable. It is suggested that the formation would be preceded by VH cluster formation.

  5. Formation of vacancy clusters in tungsten crystals under hydrogen-rich condition

    International Nuclear Information System (INIS)

    Kato, Daiji; Iwakiri, Hirotomo; Morishita, Kazunori

    2011-01-01

    Di-vacancy formation assisted by hydrogen trapping is studied in terms of nucleation free-energies evaluated with density functional theory. Calculations give binding energies for single hydrogen atom as first- and second-nearest-neighbor of di-vacancies of 1.80 and 2.15 eV, respectively, which are significantly larger than that for mono-vacancies. At elevated atomic concentrations of interstitial hydrogen atoms, evaluated nucleation free-energies indicate that the hydrogen assisted di-vacancy formation becomes more favorable. It is suggested that the formation would be preceded by VH cluster formation.

  6. A Color-Opponency Based Biological Model for Color Constancy

    Directory of Open Access Journals (Sweden)

    Yongjie Li

    2011-05-01

    Full Text Available Color constancy is the ability of the human visual system to adaptively correct color-biased scenes under different illuminants. Most of the existing color constancy models are nonphysiologically plausible. Among the limited biological models, the great majority is Retinex and its variations, and only two or three models directly simulate the feature of color-opponency, but only of the very earliest stages of visual pathway, i.e., the single-opponent mechanisms involved at the levels of retinal ganglion cells and lateral geniculate nucleus (LGN neurons. Considering the extensive physiological evidences supporting that both the single-opponent cells in retina and LGN and the double-opponent neurons in primary visual cortex (V1 are the building blocks for color constancy, in this study we construct a color-opponency based color constancy model by simulating the opponent fashions of both the single-opponent and double-opponent cells in a forward manner. As for the spatial structure of the receptive fields (RF, both the classical RF (CRF center and the nonclassical RF (nCRF surround are taken into account for all the cells. The proposed model was tested on several typical image databases commonly used for performance evaluation of color constancy methods, and exciting results were achieved.

  7. Vacancy-type defects in In{sub x}Ga{sub 1−x}N grown on GaN templates probed using monoenergetic positron beams

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Watanabe, Tomohito; Kimura, Shogo; Zhang, Yang; Lozac' h, Mickael [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Sang, Liwen; Sumiya, Masatomo [Wide Bandgap Material Group, National Institute for Materials Science, Tsukuba 305-0044 (Japan); Ishibashi, Shoji [Nanosystem Research Institute (NRI) “RICS,” National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Oshima, Nagayasu; Suzuki, Ryoichi [Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

    2013-11-14

    Native defects in In{sub x}Ga{sub 1−x}N layers grown by metalorganic chemical vapor deposition were studied using monoenergetic positron beams. Measurements of Doppler broadening spectra of the annihilation radiation and lifetime spectra of positrons for a 200-nm-thick In{sub 0.13}Ga{sub 0.87}N layer showed that vacancy-type defects were introduced by InN alloying, and the major species of such defects was identified as complexes between a cation vacancy and nitrogen vacancies. The presence of the defects correlated with lattice relaxation of the In{sub 0.13}Ga{sub 0.87}N layer and the increase in photon emissions from donor-acceptor-pair recombination. The species of native defects in In{sub 0.06}Ga{sub 0.94}N layers was the same but its concentration was decreased by decreasing the InN composition. With the layer thickness increased from 120 nm to 360 nm, a defect-rich region was introduced in the subsurface region (<160 nm), which can be associated with layer growth with the relaxation of compressive stress.

  8. Radiation-induced defects in LiAlO{sub 2} crystals: Holes trapped by lithium vacancies and their role in thermoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Holston, M.S.; McClory, J.W.; Giles, N.C. [Department of Engineering Physics, Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433 (United States); Halliburton, L.E., E-mail: Larry.Halliburton@mail.wvu.edu [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States)

    2015-04-15

    Electron paramagnetic resonance (EPR) is used to identify the primary hole trap in undoped lithium aluminate (LiAlO{sub 2}) crystals. Our interest in this material arises because it is a candidate for radiation detection applications involving either optically stimulated luminescence (OSL) or thermoluminescence (TL). During an x-ray irradiation at room temperature, holes are trapped at oxygen ions adjacent to lithium vacancies. Large concentrations of these lithium vacancies are introduced into the crystal during growth. With the magnetic field along the [001] direction, the EPR spectrum from these trapped-hole centers consists of eleven lines, evenly spaced but with varying intensities, caused by nearly equal hyperfine interactions with two {sup 27}Al nuclei (I=5/2, 100% abundant). The g matrix is determined from the angular dependence of the EPR spectrum and has principal values of 2.0130, 2.0675, and 2.0015. These g shifts strongly support the model of a hole in a p orbital on an oxygen ion. The adjacent lithium vacancy stabilizes the hole on the oxygen ion. A sequence of pulsed thermal anneals above room temperature shows that the EPR spectrum from the holes trapped adjacent to the lithium vacancies disappears in the 90–120 °C range. The thermal decay of these hole centers directly correlates with an intense TL peak near 105 °C. Signals at lower magnetic field in the 9.4 GHz EPR spectra suggest that the electron trap associated with this TL peak at 105 °C may be a transition-metal-ion impurity, most likely Fe, located at a cation site. Additional less intense TL peaks are observed near 138, 176, and 278 °C. - Highlights: • Undoped LiAlO{sub 2} crystals are irradiated at room temperature with x-rays. • EPR is used to identify holes trapped at oxygen ions adjacent to lithium vacancies. • Thermal decay of the EPR spectrum correlates with an intense TL peak at 105 °C.

  9. Vacancy defects in electron irradiated RPV steels studied by positron lifetime

    Energy Technology Data Exchange (ETDEWEB)

    Moser, P; Li, X H [CEA Centre d` Etudes de Grenoble, 38 (France). Dept. de Recherche Fondamentale sur la Matiere Condensee; Akamatsu, M; Van Duysen, J C [Electricite de France (EDF), 77 - Ecuelles (France)

    1994-12-31

    Specimens of French RPV (reactor pressure vessels) steels at different rates of segregation have been irradiated at 150 and 288 deg C with 3 MeV electrons (irradiation dose: 4*10{sup 19} e-/cm{sup 2}). Vacancy defects are studied by positron lifetime measurements before and after irradiation and at each step of isochronal annealing. After 150 deg C irradiation, a recovery step is observed in both specimens, for annealing treatments in the range 220-370 deg C and is attributed to the dissociation of vacancy-impurity complexes. The size of vacancy clusters never overcome 10 empty atomic volumes. If ``fresh`` dislocations are created just before irradiation, big vacancy clusters could be formed. After 288 deg C irradiation, small vacancy cluster of 4-10 empty atomic volumes are observed. (authors). 3 figs., 7 refs.

  10. Optical characterization of single-crystal diamond grown by DC arc plasma jet CVD

    Science.gov (United States)

    Hei, Li-fu; Zhao, Yun; Wei, Jun-jun; Liu, Jin-long; Li, Cheng-ming; Lü, Fan-xiu

    2017-12-01

    Optical centers of single-crystal diamond grown by DC arc plasma jet chemical vapor deposition (CVD) were examined using a low-temperature photoluminescence (PL) technique. The results show that most of the nitrogen-vacancy (NV) complexes are present as NV- centers, although some H2 and H3 centers and B-aggregates are also present in the single-crystal diamond because of nitrogen aggregation resulting from high N2 incorporation and the high mobility of vacancies under growth temperatures of 950-1000°C. Furthermore, emissions of radiation-induced defects were also detected at 389, 467.5, 550, and 588.6 nm in the PL spectra. The reason for the formation of these radiation-induced defects is not clear. Although a Ni-based alloy was used during the diamond growth, Ni-related emissions were not detected in the PL spectra. In addition, the silicon-vacancy (Si-V)-related emission line at 737 nm, which has been observed in the spectra of many previously reported microwave plasma chemical vapor deposition (MPCVD) synthetic diamonds, was absent in the PL spectra of the single-crystal diamond prepared in this work. The high density of NV- centers, along with the absence of Ni-related defects and Si-V centers, makes the single-crystal diamond grown by DC arc plasma jet CVD a promising material for applications in quantum computing.

  11. Ion-bombardment-induced reduction in vacancies and its enhanced effect on conductivity and reflectivity in hafnium nitride films

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Zhiqing; Wang, Jiafu; Hu, Chaoquan; Zhang, Xiaobo; Dang, Jianchen; Gao, Jing; Zheng, Weitao [Jilin University, School of Materials Science and Engineering, Key Laboratory of Mobile Materials, MOE, and State Key Laboratory of Superhard Materials, Changchun (China); Zhang, Sam [Nanyang Technological University, School of Mechanical and Aerospace Engineering, Singapore (Singapore); Wang, Xiaoyi [Chinese Academy of Sciences, Key Laboratory of Optical System Advanced Manufacturing Technology, Changchun Institute of Optics, Fine Mechanics and Physics, Changchun (China); Chen, Hong [Jilin University, Department of Control Science and Engineering, Changchun (China)

    2016-08-15

    Although the role of ion bombardment on electrical conductivity and optical reflectivity of transition metal nitrides films was reported previously, the results were controversial and the mechanism was not yet well explored. Here, we show that proper ion bombardment, induced by applying the negative bias voltage (V{sub b}), significantly improves the electrical conductivity and optical reflectivity in rocksalt hafnium nitride films regardless of level of stoichiometry (i.e., in both near-stoichiometric HfN{sub 1.04} and over-stoichiometric HfN{sub 1.17} films). The observed improvement arises from the increase in the concentration of free electrons and the relaxation time as a result of reduction in nitrogen and hafnium vacancies in the films. Furthermore, HfN{sub 1.17} films have always much lower electrical conductivity and infrared reflectance than HfN{sub 1.04} films for a given V{sub b}, owing to more hafnium vacancies because of larger composition deviation from HfN exact stoichiometry (N:Hf = 1:1). These new insights are supported by good agreement between experimental results and theoretical calculations. (orig.)

  12. Ordered perovskites with cationic vacancies. 7. Structural investigations on Ba/sub 2/Zrsub(3/4)vacantsub(1/4)SbO/sub 6/

    Energy Technology Data Exchange (ETDEWEB)

    Treiber, U; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

    1980-11-01

    The ochre coloured Ba/sub 2/Zrsub(3/4)vacantsub(1/4)SbO/sub 6/ belongs to the group of oxygen perovskites with an ordered distribution of the vacancies. It crystallizes tetragonal (a = 11.68/sub 5/ A; c = 16.60/sub 6/ A) with 16 formula units in the cell: Ba/sub 32/Zr/sub 12/vacant/sub 4/Sb/sub 16/O/sub 96/. For the space group P 4/mmm intensity calculations on powder data gave a refined, intensity related R' value of 4.8%. In the structure the Zr and Ba atoms are ordered (1:1 order); the four cationic vacancies are located in a face centered arrangement in the zirconium sublattice. The Ba atoms are displaced by approximately 0.20 A in direction of the neighbouring vacancy, while the other cations maintain their ideal positions.

  13. High-temperature interaction of low niobium oxides with carbon and nitrogen

    International Nuclear Information System (INIS)

    Lyubimov, V.D.; Alyamovskij, S.I.; Askarova, L.Kh.

    1980-01-01

    Presented are the results of investigation on the process of high-temperature interaction (1200-1300 deg C) of NbO 2 and NbO with carbon (in the helium medium) and nitrogen. The reaction between NbO 2 and carbon is successfully realized at 1300 deg C and involves two stages, viz. reduction of oxide by the mechanism of direct reduction and subsequent insertion of metalloid into the oxygen vacancies formed. As a result, on the base of the initial oxide a cubic phase is formed, its final composition at 1300 deg C corresponding to the formula NbCsub(0.74)Osub(0.28). Neither NbO monoxide, nor metal is detected in the reaction products under these conditions. Interaction of NbO 2 with carbon and nitrogen proceeds in the similar way. In this case, the oxygen vacancies formed are occupied by the atoms of the two metalloids the end-product of the reaction at 1300 deg C being oxycarbonitride NbCsub(0.30)Nsub(0.66)Osub(0.66). Intermediate products of the reaction between NbO and metalloids involve oxycarbide, oxynitride, or oxycarbonitride and dioxide of niobium, while the end products contain only a cubic phase [ru

  14. Molecular dynamics simulation on mechanical properties of crystalline CoSb3 with vacancy defect

    International Nuclear Information System (INIS)

    Yang Xuqiu; Zhai Pengcheng; Liu Lisheng; Zhang Qingjie

    2012-01-01

    The present work has investigated the tensile mechanical behavior of the skutterudite CoSb 3 single-crystal in the presence of antimony vacancies, since the antimony atoms in CoSb 3 are active and are usually easy to lose in practice. The molecular dynamics simulation method is employed. The vacancy atoms, whose fraction is limited up to 5%, are chosen randomly. The virtual uniaxial tension is carried out by strain controlling along a principal crystallographic direction at 300 K. The specimens with vacancies show similar stress-strain response features to there of the perfect crystal. However, the effective Young's modulus decreases linearly with the increase of the vacancy content, and the ultimate strength drops substantially from no vacancy to even a small vacancy fraction. Temperature dependence of the simulation results is also considered. Both Young's modulus and the ultimate strength exhibit an approximately linear reduction with increasing temperature for a specific vacancy fraction, and moreover, the reduction rate is comparable for different vacancy fractions. The Vacancy distribution effect is briefly discussed as well. As the vacancy concentration becomes uniform, the ultimate strength of the material would be promoted significantly.

  15. Gold fillings unravel the vacancy role in the phase transition of GeTe

    Science.gov (United States)

    Feng, Jinlong; Xu, Meng; Wang, Xiaojie; Lin, Qi; Cheng, Xiaomin; Xu, Ming; Tong, Hao; Miao, Xiangshui

    2018-02-01

    Phase change memory (PCM) is an important candidate for future memory devices. The crystalline phase of PCM materials contains abundant intrinsic vacancies, which plays an important role in the rapid phase transition upon memory switching. However, few experimental efforts have been invested to study these invisible entities. In this work, Au dopants are alloyed into the crystalline GeTe to fill the intrinsic Ge vacancies so that the role of these vacancies in the amorphization of GeTe can be indirectly studied. As a result, the reduction of Ge vacancies induced by Au dopants hampers the amorphization of GeTe as the activation energy of this process becomes higher. This is because the vacancy-interrupted lattice can be "repaired" by Au dopants with the recovery of bond connectivity. Our results demonstrate the importance of vacancies in the phase transition of chalcogenides, and we employ the percolation theory to explain the impact of these intrinsic defects on this vacancy-ridden crystal quantitatively. Specifically, the threshold of amorphization increases with the decrease in vacancies. The understanding of the vacancy effect sheds light on the long-standing puzzle of the mechanism of ultra-fast phase transition in PCMs. It also paves the way for designing low-power-consumption electronic devices by reducing the threshold of amorphization in chalcogenides.

  16. Strain engineering of magnetic state in vacancy-doped phosphorene

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Jie [Hunan Provincial Key Laboratory of Micro–Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, Hunan (China); Zhang, Chunxiao, E-mail: zhangchunxiao@xtu.edu.cn [Hunan Provincial Key Laboratory of Micro–Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, Hunan (China); Li, Jin [Hunan Provincial Key Laboratory of Micro–Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, Hunan (China); Guo, Zhixin [Department of Physics, Xiangtan University, Xiangtan 411105, Hunan (China); Xiao, Huaping, E-mail: hpxiao@xtu.edu.cn [Hunan Provincial Key Laboratory of Micro–Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, Hunan (China); Zhong, Jianxin [Hunan Provincial Key Laboratory of Micro–Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, Hunan (China)

    2016-09-23

    Inducing and manipulating the magnetism in two-dimensional materials play an important role for the development of the next-generation spintronics. In this letter, the effects of the biaxial strain on magnetic properties of vacancy-doped phosphorene are investigated using first-principles calculation. We find although only SV956 doping induces magnetism for unstrained phosphorene, the biaxial strain induces nonzero magnetic moment for SV5566 and DVa doped phosphorene. The biaxial strain also modulates the magnetic state for SV956, SV5566 and DVa doped phosphorene. The local magnetic moment derives from the spin polarization of the dangling bonds near the vacancy. The biaxial strain influences the local bonding configuration near the vacancy which determines the presence of dangling bonds, and then modulates the magnetic state. Our findings promise the synergistic effect of strain engineering and vacancy decoration is an effective method for the operation of phosphorene-based spintronic devices. - Highlights: • Investigation of the magnetic moment of vacancy-doped phosphorene by DFT calculation. • The modulation of the magnetic moment by the biaxial strain. • The analysis of the bonding configuration with the biaxial strain. • The analysis of the electronic structures to explain the evolution of the magnetic moment. • The effects of the biaxial strain on the band gap and doping levels.

  17. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... MD, professor of ophthalmology at Case Western Reserve University in Cleveland. "This is far from the truth." ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are considering buying approved by the ... Service For Advertisers For Media Ophthalmology Job Center © American ...

  18. 7 CFR 924.26 - Vacancies.

    Science.gov (United States)

    2010-01-01

    ... an alternate member of the committee to qualify, or in the event of the death, removal, resignation... vacancy without regard to nominations, which selection shall be made on the basis of representation...

  19. Nanodiamonds as multi-purpose labels for microscopy

    NARCIS (Netherlands)

    Hemelaar, S. R.; de Boer, P.; Chipaux, M.; Zuidema, W.; Hamoh, T.; Martinez, F. Perona; Nagl, A.; Hoogenboom, J. P.; Giepmans, B. N. G.; Schirhagl, R.

    2017-01-01

    Nanodiamonds containing fluorescent nitrogen-vacancy centers are increasingly attracting interest for use as a probe in biological microscopy. This interest stems from (i) strong resistance to photobleaching allowing prolonged fluorescence observation times; (ii) the possibility to excite

  20. Effect of vacancies on the mechanical properties of phosphorene nanotubes

    Science.gov (United States)

    Sorkin, V.; Zhang, Y. W.

    2018-06-01

    Using density functional tight-binding method, we studied the mechanical properties, deformation and failure of armchair (AC) and zigzag (ZZ) phosphorene nanotubes (PNTs) with monovacancies and divacancies subjected to uniaxial tensile strain. We found that divacancies in AC PNTs and monovacancies in ZZ PNTs possess the lowest vacancy formation energy, which decreases with the tube diameter in AC PNTs and increases in ZZ PNTs. The Young’s modulus is reduced, while the radial and thickness Poisson’s ratios are increased by hosted vacancies. In defective AC PNTs, deformation involves fracture of the intra-pucker bonds and formation of the new inter-pucker bonds at a critical strain, and the most stretched bonds around the vacancy rupture first, triggering a sequence of the structural transformations terminated by the ultimate failure. The critical strain of AC PNTs is reduced significantly by hosted vacancies, whereas their effect on the critical stress is relatively weaker. Defective ZZ PNTs fail in a brittle-like manner once the most stretched bonds around a vacancy rupture, and vacancies are able to significantly reduce the failure strain but only moderately reduce the failure stress of ZZ PNTs. The understandings revealed here on the mechanical properties and the deformation and failure mechanisms of PNTs provide useful guidelines for their design and fabrication as building blocks in nanodevices.

  1. E centers in ternary Si1−x−yGexSny random alloys

    KAUST Repository

    Chroneos, Alexander; Bracht, H.; Grimes, R. W.; Jiang, C.; Schwingenschlö gl, Udo

    2009-01-01

    Density functional theory calculations are used to study the association of arsenic (As) atoms to lattice vacancies and the formation of As-vacancy pairs, known as E centers, in the random Si0.375Ge0.5Sn0.125 alloy. The local environments are described by 32-atom special quasirandom structures that represent random Si1−x−yGexSny alloys. It is predicted that the nearest-neighbor environment will exert a strong influence on the stability of E centers in ternary Si0.375Ge0.5Sn0.125.

  2. E centers in ternary Si1−x−yGexSny random alloys

    KAUST Repository

    Chroneos, Alexander

    2009-09-14

    Density functional theory calculations are used to study the association of arsenic (As) atoms to lattice vacancies and the formation of As-vacancy pairs, known as E centers, in the random Si0.375Ge0.5Sn0.125 alloy. The local environments are described by 32-atom special quasirandom structures that represent random Si1−x−yGexSny alloys. It is predicted that the nearest-neighbor environment will exert a strong influence on the stability of E centers in ternary Si0.375Ge0.5Sn0.125.

  3. A comparison of nitrogen-doped sonoelectrochemical and chemical graphene nanosheets as hydrogen peroxide sensors.

    Science.gov (United States)

    Wu, Yi-Shan; Liu, Zhe-Ting; Wang, Tzu-Pei; Hsu, Su-Yang; Lee, Chien-Liang

    2018-04-01

    Nitrogen-doped graphene nanosheet (N-SEGN) with pyrrolic nitrogen and 5-9 vacancy defects has been successfully prepared from a hydrothermal reaction of tetra-2-pyridinylpyrazine and sonoelectrochemistry-exfoliated graphene nanosheet, with point defects. Additionally, based on the same reaction using chemically reduced graphene oxide, nitrogen-doped chemically reduced graphene oxide (N-rGO) with graphitic nitrogen was prepared. The N-SEGN and N-rGO were used as a non-enzymatic H 2 O 2 sensors. The sensitivity of the N-SEGN was 231.3 μA·mM -1 ·cm -2 , much greater than 57.3 μA·mM -1 ·cm -2 of N-rGO. The N-SEGN showed their potential for being a H 2 O 2 sensor. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Effect of the melting conditions on the properties of radiation color centers in lanthanum phosphate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Karapetyan, G.O.; Rusan, V.V.; Yashchurzhinskaya, O.A.

    1986-01-01

    The authors investigate the spatial effects of ionizing radiation on the radiation processes in phosphate glasses to make a comparative estimate of the radiation yield from the radiation color centers (RCC) of different types. A study is made of their behavior under thermal decoloration. The results of a comparison of the integrated intensities of the ESR signal from trapping centers are given. The ESR spectrum of the glasses are presented--one differs slightly from the others. On the basis of the result of processing the ESR and optical spectra of gamma-irradiated lanthanum phosphate glasses synthesized under various conditions, the radiation yield of the RCC and the behavior of the intensity of their absorption under thermodecoloration are significantly affected by the conditions of synthesis of the glass.

  5. Localized versus itinerant states created by multiple oxygen vacancies in SrTiO3

    Science.gov (United States)

    Jeschke, Harald O.; Shen, Juan; Valentí, Roser

    2015-02-01

    Oxygen vacancies in strontium titanate surfaces (SrTiO3) have been linked to the presence of a two-dimensional electron gas with unique behavior. We perform a detailed density functional theory study of the lattice and electronic structure of SrTiO3 slabs with multiple oxygen vacancies, with a main focus on two vacancies near a titanium dioxide terminated SrTiO3 surface. We conclude based on total energies that the two vacancies preferably inhabit the first two layers, i.e. they cluster vertically, while in the direction parallel to the surface, the vacancies show a weak tendency towards equal spacing. Analysis of the nonmagnetic electronic structure indicates that oxygen defects in the surface TiO2 layer lead to population of Ti {{t}2g} states and thus itinerancy of the electrons donated by the oxygen vacancy. In contrast, electrons from subsurface oxygen vacancies populate Ti eg states and remain localized on the two Ti ions neighboring the vacancy. We find that both the formation of a bound oxygen-vacancy state composed of hybridized Ti 3eg and 4p states neighboring the oxygen vacancy as well as the elastic deformation after extracting oxygen contribute to the stabilization of the in-gap state.

  6. Memory and neural networks on the basis of color centers in solids.

    Science.gov (United States)

    Winnacker, Albrecht; Osvet, Andres

    2009-11-01

    Optical data recording is one of the most widely used and efficient systems of memory in the non-living world. The application of color centers in this context offers not only systems of high speed in writing and read-out due to a high degree of parallelism in data handling but also a possibility to set up models of neural networks. In this way, systems with a high potential for image processing, pattern recognition and logical operations can be constructed. A limitation to storage density is given by the diffraction limit of optical data recording. It is shown that this limitation can at least in principle be overcome by the principle of spectral hole burning, which results in systems of storage capacities close to the human brain system.

  7. 7 CFR 920.26 - Vacancies.

    Science.gov (United States)

    2010-01-01

    ... member or as an alternate member of the committee to qualify, or in the event of the death, removal... vacancy without regard to nominations, which selection shall be made on the basis of representation...

  8. Nanodiamonds as multi-purpose labels for microscopy

    NARCIS (Netherlands)

    Hemelaar, S. R.; de Boer, P.; Chipaux, M.; Zuidema, W.; Hamoh, T.; Perona Martinez, F.; Nagl, A.; Hoogenboom, J.P.; Giepmans, B. N.G.; Schirhagl, R.

    2017-01-01

    Nanodiamonds containing fluorescent nitrogen-vacancy centers are increasingly attracting interest for use as a probe in biological microscopy. This interest stems from (i) strong resistance to photobleaching allowing prolonged fluorescence observation times; (ii) the possibility to excite

  9. 78 FR 7399 - Application(s) for Duty-Free Entry of Scientific Instruments

    Science.gov (United States)

    2013-02-01

    ... Solenoid Superconducting Magnet. Manufacturer: Leiden Cryogenics, the Netherlands. Intended Use: The...-lived localized states (nitrogen- vacancy centers) and delocalized states (superconducting resonators... the natural tendency of SrTiO 3 to become superconducting to develop superconducting structures with...

  10. Influence of Agricultural Management on Phytochemicals of Colored Corn Genotypes ( Zea mays L.). Part 1: Nitrogen Fertilization.

    Science.gov (United States)

    Giordano, Debora; Beta, Trust; Vanara, Francesca; Blandino, Massimo

    2018-05-02

    In this study, the influence of nitrogen (N) fertilization (170 versus 300 kg of N/ha) on the content of bioactive compounds of whole-meal flour of 10 different colored corn genotypes was investigated. Considerable differences in antioxidant capacity and phytochemical concentrations were observed among genotypes. Higher N fertilization rates significantly ( p < 0.05) increased the content of both total cell-wall-bound phenolics and xanthophylls (lutein and zeaxanthin). Nevertheless, the main phenolic acids (ferulic, p-coumaric, and sinapic acids) as well as the antioxidant capacity and content of β-cryptoxanthin, β-carotene, and total anthocyanins did not show significant differences as far as the N fertilization rate is concerned. For corn cultivation, the application of high N fertilization rates, generally carried out to obtain higher grain yields, could positively influence the content of some bioactives particularly in years characterized by high rainfall levels responsible for N leaching from the soil.

  11. A quantum-chemical study of oxygen-vacancy defects in PbTiO{sub 3} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Stashans, Arvids [Laboratorio de Fisica, Escuela de Electronica y Telecomunicaciones, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)]. E-mail: arvids@utpl.edu.ec; Serrano, Sheyla [Centro de Investigacion en Fisica de Materia Condensada, Corporacion de Fisica Fundamental y Aplicada, Apartado 17-12-637, Quito (Ecuador); Escuela de Ingenierias, Universidad Politecnica Salesiana, Campus Sur, Rumichaca s/n y Moran Valverde, Apartado 17-12-536, Quito (Ecuador); Medina, Paul [Centro de Investigacion en Fisica de Materia Condensada, Corporacion de Fisica Fundamental y Aplicada, Apartado 17-12-637, Quito (Ecuador)

    2006-05-31

    Investigation of an oxygen vacancy and F center in the cubic and tetragonal lattices of PbTiO{sub 3} crystals is done by means of quantum-chemical simulations. Displacements of defect-surrounding atoms, electronic and optical properties, lattice relaxation energies and some new effects due to the defects presence are reported and analyzed. A comparison with similar studies is made and conclusions are drawn on the basis of the obtained results.

  12. Hybridizing Differential Evolution with a Genetic Algorithm for Color Image Segmentation

    Directory of Open Access Journals (Sweden)

    R. V. V. Krishna

    2016-10-01

    Full Text Available This paper proposes a hybrid of differential evolution and genetic algorithms to solve the color image segmentation problem. Clustering based color image segmentation algorithms segment an image by clustering the features of color and texture, thereby obtaining accurate prototype cluster centers. In the proposed algorithm, the color features are obtained using the homogeneity model. A new texture feature named Power Law Descriptor (PLD which is a modification of Weber Local Descriptor (WLD is proposed and further used as a texture feature for clustering. Genetic algorithms are competent in handling binary variables, while differential evolution on the other hand is more efficient in handling real parameters. The obtained texture feature is binary in nature and the color feature is a real value, which suits very well the hybrid cluster center optimization problem in image segmentation. Thus in the proposed algorithm, the optimum texture feature centers are evolved using genetic algorithms, whereas the optimum color feature centers are evolved using differential evolution.

  13. Zero-phonon lines and electron–phonon interaction characteristics of near-surface layer radiation color centers in lithium fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Voitovich, A.P., E-mail: voitovich@ifanbel.bas-net.by [Institute of Physics, National Academy of Sciences of Belarus, 68 Nezavisimosti Avenue, 220072 Minsk (Belarus); Kalinov, V.S. [Institute of Physics, National Academy of Sciences of Belarus, 68 Nezavisimosti Avenue, 220072 Minsk (Belarus); Mudryi, A.V. [Scientific-Practical Materials Research Center, National Academy of Sciences of Belarus, 19 Brovka Street, 220072 Minsk (Belarus); Pavlovskii, V.N.; Runets, L.P.; Svitsiankou, I.E. [Institute of Physics, National Academy of Sciences of Belarus, 68 Nezavisimosti Avenue, 220072 Minsk (Belarus)

    2016-04-15

    Zero-phonon lines have been registered in photoluminescence spectra of near-surface layer radiation color centers in lithium fluoride nanocrystals. They have been assigned to transitions of the definite types centers. The frequencies of phonons participating in the transitions of the different type centers located both in the near-surface layer and in the crystal bulk have been measured and compared. The Huang-Rhys parameters for the transitions of these centers have been determined. It has been found that the Huang-Rhys parameters for the studied transitions in the near-surface layer centers of the certain composition are less than for those in the crystal bulk centers of the same composition. This feature is connected with the difference of the electron density distribution in defects. Temperature dependences of the zero-phonon lines widths and shifts have been measured. It has been determined that both widths and shifts grow faster with the increase of a temperature for the defects transitions with the lesser Huang-Rhys parameters. Phonons lifetimes are estimated from the experimental data.

  14. Zero-phonon lines and electron–phonon interaction characteristics of near-surface layer radiation color centers in lithium fluoride

    International Nuclear Information System (INIS)

    Voitovich, A.P.; Kalinov, V.S.; Mudryi, A.V.; Pavlovskii, V.N.; Runets, L.P.; Svitsiankou, I.E.

    2016-01-01

    Zero-phonon lines have been registered in photoluminescence spectra of near-surface layer radiation color centers in lithium fluoride nanocrystals. They have been assigned to transitions of the definite types centers. The frequencies of phonons participating in the transitions of the different type centers located both in the near-surface layer and in the crystal bulk have been measured and compared. The Huang-Rhys parameters for the transitions of these centers have been determined. It has been found that the Huang-Rhys parameters for the studied transitions in the near-surface layer centers of the certain composition are less than for those in the crystal bulk centers of the same composition. This feature is connected with the difference of the electron density distribution in defects. Temperature dependences of the zero-phonon lines widths and shifts have been measured. It has been determined that both widths and shifts grow faster with the increase of a temperature for the defects transitions with the lesser Huang-Rhys parameters. Phonons lifetimes are estimated from the experimental data.

  15. 24 CFR 990.145 - Dwelling units with approved vacancies.

    Science.gov (United States)

    2010-04-01

    ... 24 Housing and Urban Development 4 2010-04-01 2010-04-01 false Dwelling units with approved vacancies. 990.145 Section 990.145 Housing and Urban Development Regulations Relating to Housing and Urban...; Computation of Eligible Unit Months § 990.145 Dwelling units with approved vacancies. (a) A PHA is eligible to...

  16. Mechanism of dopant-vacancy association in α-quartz GeO2

    KAUST Repository

    Wang, Hao; Chroneos, Alexander; Schwingenschlö gl, Udo

    2013-01-01

    Improving the electron mobility of devices such as Ge metal oxide semiconductor field effect transistors requires good Ge/dielectric interfaces. GeO2 thus is reconsidered as a passivation layer for Ge. However, O-vacancies need to be controlled as they have a deleterious impact on the properties. We employ electronic structure calculations to investigate the introduction of trivalent ions (Al, Y, and La) in α-quartz GeO2. The binding energies of the dopant-vacancy pairs reveal that dopants can be used to control the O-vacancies and reduce the induced dangling bonds. It is proposed that the introduction of Al will limit the concentration of O-vacancies at low Fermi energy.

  17. Mechanism of dopant-vacancy association in α-quartz GeO2

    KAUST Repository

    Wang, Hao

    2013-02-28

    Improving the electron mobility of devices such as Ge metal oxide semiconductor field effect transistors requires good Ge/dielectric interfaces. GeO2 thus is reconsidered as a passivation layer for Ge. However, O-vacancies need to be controlled as they have a deleterious impact on the properties. We employ electronic structure calculations to investigate the introduction of trivalent ions (Al, Y, and La) in α-quartz GeO2. The binding energies of the dopant-vacancy pairs reveal that dopants can be used to control the O-vacancies and reduce the induced dangling bonds. It is proposed that the introduction of Al will limit the concentration of O-vacancies at low Fermi energy.

  18. Experimental investigation of vector static magnetic field detection using an NV center with a single first-shell 13C nuclear spin in diamond

    Science.gov (United States)

    Jiang, Feng-Jian; Ye, Jian-Feng; Jiao, Zheng; Jiang, Jun; Ma, Kun; Yan, Xin-Hu; Lv, Hai-Jiang

    2018-05-01

    We perform a proof-of-principle experiment that uses a single negatively charged nitrogen–vacancy (NV) color center with a nearest neighbor 13C nuclear spin in diamond to detect the strength and direction (including both polar and azimuth angles) of a static vector magnetic field by optical detection magnetic resonance (ODMR) technique. With the known hyperfine coupling tensor between an NV center and a nearest neighbor 13C nuclear spin, we show that the information of static vector magnetic field could be extracted by observing the pulsed continuous wave (CW) spectrum. Project supported by the National Natural Science Foundation of China (Grant Nos. 11305074, 11135002, and 11275083), the Key Program of the Education Department Outstanding Youth Foundation of Anhui Province, China (Grant No. gxyqZD2017080), and the Education Department Natural Science Foundation of Anhui Province, China (Grant No. KJHS2015B09).

  19. 7 CFR 1210.324 - Vacancies.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE WATERMELON RESEARCH AND PROMOTION PLAN Watermelon Research and Promotion Plan National Watermelon Promotion Board § 1210.324 Vacancies...

  20. Learning color receptive fields and color differential structure

    NARCIS (Netherlands)

    ter Haar Romenij, B.M.

    2016-01-01

    In this paper we study the role of brain plasticity, and investigate the emergence and self-emergence of receptive fields from scalar and color natural images by principal component analysis of image patches. We describe the classical experiment on localized PCA on center-surround weighted patches

  1. Migration mechanisms and diffusion barriers of vacancies in Ga2O3

    Science.gov (United States)

    Kyrtsos, Alexandros; Matsubara, Masahiko; Bellotti, Enrico

    2017-06-01

    We employ the nudged elastic band and the dimer methods within the standard density functional theory (DFT) formalism to study the migration of the oxygen and gallium vacancies in the monoclinic structure of β -Ga2O3 . We identify all the first nearest neighbor paths and calculate the migration barriers for the diffusion of the oxygen and gallium vacancies. We also identify the metastable sites of the gallium vacancies which are critical for the diffusion of the gallium atoms. The migration barriers for the diffusion of the gallium vacancies are lower than the migration barriers for oxygen vacancies by 1 eV on average, suggesting that the gallium vacancies are mobile at lower temperatures. Using the calculated migration barriers we estimate the annealing temperature of these defects within the harmonic transition state theory formalism, finding excellent agreement with the observed experimental annealing temperatures. Finally, we suggest the existence of percolation paths which enable the migration of the species without utilizing all the migration paths of the crystal.

  2. Quantum corrections to conductivity in graphene with vacancies

    Science.gov (United States)

    Araujo, E. N. D.; Brant, J. C.; Archanjo, B. S.; Medeiros-Ribeiro, G.; Alves, E. S.

    2018-06-01

    In this work, different regions of a graphene device were exposed to a 30 keV helium ion beam creating a series of alternating strips of vacancy-type defects and pristine graphene. From magnetoconductance measurements as function of temperature, density of carriers and density of strips we show that the electron-electron interaction is important to explain the logarithmic quantum corrections to the Drude conductivity in graphene with vacancies. It is known that vacancies in graphene behave as local magnetic moments that interact with the conduction electrons and leads to a logarithmic correction to the conductance through the Kondo effect. However, our work shows that it is necessary to account for the non-homogeneity of the sample to avoid misinterpretations about the Kondo physics due the difficulties in separating the electron-electron interaction from the Kondo effect.

  3. Vacancy-rearrangement theory in the first Magnus approximation

    International Nuclear Information System (INIS)

    Becker, R.L.

    1984-01-01

    In the present paper we employ the first Magnus approximation (M1A), a unitarized Born approximation, in semiclassical collision theory. We have found previously that the M1A gives a substantial improvement over the first Born approximation (B1A) and can give a good approximation to a full coupled channels calculation of the mean L-shell vacancy probability per electron, p/sub L/, when the L-vacancies are accompanied by a K-shell vacancy (p/sub L/ is obtained experimentally from measurements of K/sub α/-satellite intensities). For sufficiently strong projectile-electron interactions (sufficiently large Z/sub p/ or small v) the M1A ceases to reproduce the coupled channels results, but it is accurate over a much wider range of Z/sub p/ and v than the B1A. 27 references

  4. A Variable Single Photon Plasmonic Beamsplitter

    DEFF Research Database (Denmark)

    Israelsen, Niels Møller; Kumar, Shailesh; Huck, Alexander

    Plasmonic structures can both be exploited for scaling down optical components beyond the diffraction limit and enhancing andcollecting the emission from a single dipole emitter. Here, we experimentally demonstrate adiabatic coupling between two silvernanowires using a nitrogen vacancy center as ...

  5. Trapping of positron in gallium arsenide: evidencing of vacancies and of ions with a negative charge

    International Nuclear Information System (INIS)

    Pierre, F.

    1989-12-01

    Vacancy type defects in Ga As as grown and irradiated by electrons are characterized by lifetime of positrons. Positron lifetime increases from 230 ps to 258 and 295 ps in presence of native vacancies in n type Ga As. Configuration of native vacancies changes when Fermi level crosses energy levels localized in the forbidden zone at 0.035eV and at 0.10eV from the bottom of the conduction band. Native vacancies are identified to arsenic vacancies with or without other point defects. Positron lifetime increases from 230 to 260 ps in presence of vacancies produced by low temperature irradiation negative ions are also produced. In irradiated Ga As, these ions trap positrons in competition with vacancies produced by irradiation, showing they have a negative charge. Two annealing zones between 180-300K and 300-600K are presented by vacancies. Ions do not anneal below ambient temperature. Vacancies and negative ions are identified respectively to gallium vacancies and gallium antisite [fr

  6. Characterisation and modelling of vacancy dynamics in Ni–Mn–Ga ferromagnetic shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Merida, D., E-mail: david.merida@ehu.es [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); García, J.A. [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); BC Materials (Basque Centre for Materials, Application and Nanostructures), 48040 Leioa (Spain); Sánchez-Alarcos, V. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Pérez-Landazábal, J.I.; Recarte, V. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Institute for Advanced Materials (INAMAT), Universidad Pública de Navarra, Campus de Arrosadía, 31006 Pamplona (Spain); Plazaola, F. [Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain)

    2015-08-05

    Highlights: • We study the dynamics of vacancies for three different Ni–Mn–Ga alloy samples. • The formation and migration energies have been obtained experimentally. • The entropic factor and the distance a vacancy has to reach a sink are measured. • We present a theoretical model to explain the dynamics of vacancies. • Results are applicable for any thermal treatment and extensible to other alloys. - Abstract: The dynamics of vacancies in Ni–Mn–Ga shape memory alloys has been studied by positron annihilation lifetime spectroscopy. The temperature evolution of the vacancy concentration for three different Ni–Mn–Ga samples, two polycrystalline and one monocrystalline, have been determined. The formation and migration energies and the entropic factors are quite similar in all cases, but vary slightly according to composition. However, the number of jumps a vacancy has to overtake to reach a sink is five times higher in the single crystal. This is an expected result, due to the role that surfaces and grain boundaries should play in balancing the vacancy concentration. In all cases, the initial vacancy concentration for the samples quenched from 1173 K lies between 1000 ppm and 2000 ppm. A phenomenological model able to explain the dynamics of vacancies has been developed in terms of the previous parameters. The model can reproduce the vacancy dynamics for any different kind of thermal history and can be easily extended to other alloys.

  7. Plasmon resonance enhanced temperature-dependent photoluminescence of Si-V centers in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Shaoheng [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Song, Jie; Wang, Qiliang; Liu, Junsong; Li, Hongdong, E-mail: hdli@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Zhang, Baolin [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China)

    2015-11-23

    Temperature dependent optical property of diamond has been considered as a very important factor for realizing high performance diamond-based optoelectronic devices. The photoluminescence feature of the zero phonon line of silicon-vacancy (Si-V) centers in Si-doped chemical vapor deposited single crystal diamond (SCD) with localized surface plasmon resonance (LSPR) induced by gold nanoparticles has been studied at temperatures ranging from liquid nitrogen temperature to 473 K, as compared with that of the SCD counterpart in absence of the LSPR. It is found that with LSPR the emission intensities of Si-V centers are significantly enhanced by factors of tens and the magnitudes of the redshift (width) of the emissions become smaller (narrower), in comparison with those of normal emissions without plasmon resonance. More interestingly, these strong Si-V emissions appear remarkably at temperatures up to 473 K, while the spectral feature was not reported in previous studies on the intrinsic Si-doped diamonds when temperatures are higher than room temperature. These findings would lead to reaching high performance diamond-based devices, such as single photon emitter, quantum cryptography, biomarker, and so forth, working under high temperature conditions.

  8. Vacancies in functional materials for clean energy storage and harvesting: the perfect imperfection.

    Science.gov (United States)

    Li, Guowei; Blake, Graeme R; Palstra, Thomas T M

    2017-03-21

    Vacancies exist throughout nature and determine the physical properties of materials. By manipulating the density and distribution of vacancies, it is possible to influence their physical properties such as band-gap, conductivity, magnetism, etc. This can generate exciting applications in the fields of water treatment, energy storage, and physical devices such as resistance-change memories. In this review, we focus on recent progress in vacancy engineering for the design of materials for energy harvesting applications. A brief discription of the concept of vacancies, the way to create and control them, as well as their fundamental properties, is first provided. Then, emphasis is placed on the strategies used to tailor vacancies for metal-insulator transitions, electronic structures, and introducing magnetism in non-magnetic materials. Finally, we present representative applications of different structures with vacancies as active electrode materials of lithium or sodium ion batteries, catalysts for water splitting, and hydrogen evolution.

  9. Color centers of a borosilicate glass induced by 10 MeV proton, 1.85 MeV electron and 60Co-γ ray

    International Nuclear Information System (INIS)

    Du, Jishi; Wu, Jiehua; Zhao, Lili; Song, Lixin

    2013-01-01

    Optical absorption spectra, electron paramagnetic resonance (EPR) spectra, Raman spectra of a borosilicate glass after irradiation by 10 MeV proton, 1.85 MeV electron and 60 Co-γ ray were studied. The process of irradiation inducing color centers in the glass was discussed. The band gap of the glass before and after 60 Co-γ ray irradiation was studied using Mott and Davis's theory, and it was found that calculated change of the band gap introduced a paradox, because Mott and Davis's theory on the band gap cannot be adopted in the study on the irradiated glass. - Highlights: ► All the three types of irradiation induce the same types of color centers. ► Calculated change of the band gap introduced a paradox. ► Mott and Davis's theory on band gap cannot be adopted in the irradiated glass

  10. 7 CFR 1260.146 - Vacancies.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BEEF PROMOTION AND RESEARCH Beef Promotion and Research Order Cattlemen's Beef Promotion and Research Board § 1260.146 Vacancies. To fill any...

  11. 7 CFR 1207.324 - Vacancies.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill any...

  12. Fracture of vacancy-defected carbon nanotubes and their embedded nanocomposites

    International Nuclear Information System (INIS)

    Xiao Shaoping; Hou Wenyi

    2006-01-01

    In this paper, we investigate effects of vacancy defects on fracture of carbon nanotubes and carbon nanotube/aluminum composites. Our studies show that even a one-atom vacancy defect can dramatically reduce the failure stresses and strains of carbon nanotubes. Consequently, nanocomposites, in which vacancy-defected nanotubes are embedded, exhibit different characteristics from those in which pristine nanotubes are embedded. It has been found that defected nanotubes with a small volume fraction cannot reinforce but instead weaken nanocomposite materials. Although a large volume fraction of defected nanotubes can slightly increase the failure stresses of nanocomposites, the failure strains of nanocomposites are always decreased

  13. Origin of Nanobubbles Electrochemically Formed in a Magnetic Field: Ionic Vacancy Production in Electrode Reaction

    Science.gov (United States)

    Aogaki, Ryoichi; Sugiyama, Atsushi; Miura, Makoto; Oshikiri, Yoshinobu; Miura, Miki; Morimoto, Ryoichi; Takagi, Satoshi; Mogi, Iwao; Yamauchi, Yusuke

    2016-07-01

    As a process complementing conventional electrode reactions, ionic vacancy production in electrode reaction was theoretically examined; whether reaction is anodic or cathodic, based on the momentum conservation by Newton’s second law of motion, electron transfer necessarily leads to the emission of original embryo vacancies, and dielectric polarization endows to them the same electric charge as trans- ferred in the reaction. Then, the emitted embryo vacancies immediately receive the thermal relaxation of solution particles to develop steady-state vacancies. After the vacancy production, nanobubbles are created by the collision of the vacancies in a vertical magnetic field.

  14. Impurity decoration of native vacancies in Ga and N sublattices of gallium nitride

    OpenAIRE

    Hautakangas, Sami

    2005-01-01

    The effects of impurity atoms as well as various growth methods to the formation of vacancy type defects in gallium nitride (GaN) have been studied by positron annihilation spectroscopy. It is shown that vacancy defects are formed in Ga or N sublattices depending on the doping of the material. Vacancies are decorated with impurity atoms leading to the compensation of the free carriers of the samples. In addition, the vacancy clusters are found to be present in significant concentrations in n-...

  15. Contribution to the study of vacancies in silver and uranium (1962); Contribution a l'etude des lacunes dans l'argent et l'uranium (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Quere, Y [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-12-15

    In metals, high temperature vacancies can be retained by quenching. Results are given for the quenching of uranium (in liquid helium) and of silver (in liquid nitrogen). In this last case the energy of formation (1.06 eV) and the energy of mobility (0.86 eV) of the vacancies have been measured as well as the energy of mobility of the divacancies (0.58 eV). If the quenching is slow, it is shown that it is possible to trap the vacancies on the impurities of the metal. This leads to increases in the electrical resistivity observed by annealing after quenching, the vacancies being released before disappearing into sinks. The vacancy-impurity binding energy (the impurity being probably oxygen which is present in the silver used at a concentration of 20 ppm. atom.) can thus be estimated to be 0.4 eV. (author) [French] Dans un metal, les lacunes de haute temperature peuvent etre retenues par trempe. On presente des experiences de trempe d'uranium (dans l'helium liquide) et d'argent (dans l'azote liquide). Dans ce dernier cas, on mesure l'energie de formation (1,06 eV) et l'energie de mobilite (0,86 eV) des lacunes ainsi que l'energie de mobilite des bilacunes (0,58 eV). Si la trempe est lente, on montre que l'on peut pieger des lacunes sur les impuretes du metal. On interprete de cette facon des augmentations de resistivite electrique observees par recuit apres trempe, les lacunes se depiegeant avant de disparaitre dans des puits. L'energie de liaison lacune-impurete (l'impurete etant probablement l'oxygene dont l'argent utilise contient 20 ppm. atom.) peut alors etre evalue 0,4 eV. (auteur)

  16. Heat-induced chemical and color changes of extractive-free Black Locust (Rosinia Pseudoacacia) wood

    Science.gov (United States)

    Yao Chen; Jianmin Gao; Yongming Fan; Mandla A. Tshabalala; Nicole M. Stark

    2012-01-01

    To investigate chemical and color changes of the polymeric constituents of black locust (Robinia pseudoacacia) wood during heat treatment, extractive-free wood flour was conditioned to 30% initial moisture content (MC) and heated for 24 h at 120 °C in either an oxygen or nitrogen atmosphere. The color change was measured using the CIELAB color system. Chemical changes...

  17. Mechanism of vacancy formation induced by hydrogen in tungsten

    Directory of Open Access Journals (Sweden)

    Yi-Nan Liu

    2013-12-01

    Full Text Available We report a hydrogen induced vacancy formation mechanism in tungsten based on classical molecular dynamics simulations. We demonstrate the vacancy formation in tungsten due to the presence of hydrogen associated directly with a stable hexagonal self-interstitial cluster as well as a linear crowdion. The stability of different self-interstitial structures has been further studied and it is particularly shown that hydrogen plays a crucial role in determining the configuration of SIAs, in which the hexagonal cluster structure is preferred. Energetic analysis has been carried out to prove that the formation of SIA clusters facilitates the formation of vacancies. Such a mechanism contributes to the understanding of the early stage of the hydrogen blistering in tungsten under a fusion reactor environment.

  18. Vacancies and atomic processes in intermetallics - From crystals to quasicrystals and bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Hans-Eckhardt [Institute of Theoretical and Applied Physics, Stuttgart University, Pfaffenwaldring 57, 70569 Stuttgart (Germany); Baier, Falko [Voith Turbo Comp., Alexanderstr. 2, 89552 Heidenheim (Germany); Mueller, Markus A. [GFT Technologies A. G., Filderhauptstr. 142, 70599 Stuttgart (Germany); Reichle, Klaus J. [Philipp-Matthaeus-Hahn School, Jakob-Beutter-Str. 15, 72336 Balingen (Germany); Reimann, Klaus [NXP Semiconductors, Central Research and Development, High Tech Campus 4, 5656 AE Eindhoven (Netherlands); Rempel, Andrey A. [Institute of Solid State Chemistry, Russian Academy of Sciences, Ul. Pervomaiskaya 91, 620041 Ekaterinburg (Russian Federation); Sato, Kiminori [Tokyo Gakugei University, Nukuikita 4-1-1, Koganei, Tokyo 184-8501 (Japan); Ye, Feng [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, 30 Xue Yuan Road, Beijing 100083 (China); Zhang, Xiangyi [Yanshan University, Qinhuangdao 066004 (China); Sprengel, Wolfgang [Institute of Materials Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria)

    2011-10-15

    A review is given on atomic vacancies in intermetallic compounds. The intermetallic compounds cover crystalline, quasicrystalline, and bulk metallic glass (BMG) structures. Vacancies can be specifically characterized by their positron lifetimes, by the coincident measurement of the Doppler broadening of the two quanta emitted by positron-electron annihilation, or by time-differential dilatometry. By these techniques, high concentrations and low mobilities of thermal vacancies were found in open-structured B2 intermetallics such as FeAl or NiAl, whereas the concentrations of vacancies are low and their mobilities high in close-packed structure as, e.g., L1{sub 2}-Ni{sub 3}Al. The activation volumes of vacancy formation and migration are determined by high-pressure experiments. The favorable sublattice for vacancy formation is found to be the majority sublattice in Fe{sub 61}Al{sub 39} and in MoSi{sub 2}. In the icosahedral quasicrystal Al{sub 70}Pd{sub 21}Mn{sub 9} the thermal vacancy concentration is low, whereas in the BMG Zr{sub 57}Cu{sub 15.4}Ni{sub 12.6}Nb{sub 3}Al{sub 10} thermal vacancies are found in high concentrations with low mobilities. This may determine the basic mechanisms of the glass transition. Making use of the experimentally determined vacancy data, the main features of atomic diffusion studies in crystalline intermetallics, in quasicrystals, and in BMGs can be understood. Manfred Faehnle and his group have substantially contributed to the theoretical understanding of vacancies and diffusion mechanisms in intermetallics. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. 7 CFR 1280.205 - Vacancies.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Vacancies. 1280.205 Section 1280.205 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS... INFORMATION ORDER Lamb Promotion, Research, and Information Order Lamb Promotion, Research, and Information...

  20. 7 CFR 1215.25 - Vacancies.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Vacancies. 1215.25 Section 1215.25 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS... CONSUMER INFORMATION Popcorn Promotion, Research, and Consumer Information Order Popcorn Board § 1215.25...

  1. A new method for skin color enhancement

    Science.gov (United States)

    Zeng, Huanzhao; Luo, Ronnier

    2012-01-01

    Skin tone is the most important color category in memory colors. Reproducing it pleasingly is an important factor in photographic color reproduction. Moving skin colors toward their preferred skin color center improves the skin color preference on photographic color reproduction. Two key factors to successfully enhance skin colors are: a method to detect original skin colors effectively even if they are shifted far away from the regular skin color region, and a method to morph skin colors toward a preferred skin color region properly without introducing artifacts. A method for skin color enhancement presented by the authors in the same conference last year applies a static skin color model for skin color detection, which may miss to detect skin colors that are far away from regular skin tones. In this paper, a new method using the combination of face detection and statistical skin color modeling is proposed to effectively detect skin pixels and to enhance skin colors more effectively.

  2. Evaluation of the energetics of copper-vacancy clusters in Fe

    Energy Technology Data Exchange (ETDEWEB)

    Morishita, Kazunori, E-mail: morishita@iae.kyoto-u.ac.jp; Nakasuji, Toshiki; Ruan, Xiaoyong

    2017-02-15

    Highlights: • Thermodynamics evaluation of the nucleation process of copper-vacancy clusters in Fe is performed. • Nucleation free energy of copper-vacancy clusters in Fe is formulated. • With this energetics, two different nucleation paths of clusters are found as a function of the damage rate. - Abstract: A theoretical study is conducted to evaluate the nucleation free energy of copper-vacancy clusters in Fe as a function of the numbers of copper atoms and of vacancies in a cluster. Using this free energy value, cluster nucleation processes during irradiation are investigated. The results clearly show that there are two different types of cluster nucleation paths on the free energy surface; one is the formation of empty voids by jumping over the ridge of the free energy surface, and the other corresponds to a path for the formation of copper clusters by going around the ridge. The dependence of easy nucleation paths on the damage rate is discussed.

  3. Structure of compensating centers in neutron irradiated n-type germanium

    International Nuclear Information System (INIS)

    Erchak, D.P.; Kosobutskij, V.S.; Stel'makh, V.F.

    1989-01-01

    Structural model of one of the main compensating defects of Ge-M1, Ge-M5, Ge-M6 in neutron irradiated (10 18 -10 20 cm -2 ) germanium, strongly alloyed (2x10 18 -3x10 19 cm -3 ) with antimony, phosphorus and arsenic respectively, is suggested. The above mentioned compensating centers are paramagnetic in a positive charge state and represent a vacancy, two nearby germanium atoms of which are replaced with two atoms of corresponding fine donor impurity. It is mainly contributed (63%- for Ge-M5 centers, 56% - for Ge-M6 centers) by orbitals of two germanium atoms neighbouring the vacancy. The angle of the bonds of each of two mentioned germanium atoms with its three neighbours and orientation of maximum electron density of hybride orbital, binding both germanium atoms, is approximately by 5 deg greater the tetrahedral one

  4. Color in present culture of European architecture

    Science.gov (United States)

    Schindler, Verena M.

    2002-06-01

    The influential architect Le Corbusier (1887 - 1965) was also involved in the adventure of contemporary painting, and color occupied half of his day, during twenty years, as he revealed in a study entitled 'Architectural Polychromy' written in the early thirties and recently published in 1997. In the present, contemporary architects in Central Europe are dealing with color in quite a different and exceptional way: most of them engage the artist to collaborate with them in their architectural projects. If painting is concerned with the interaction of color in the two-dimensional plane, architecture is deeply dependent on light and space, and deals entirely with the three- dimensional environment and its human perception. In the 1990s, the way architects and artists employed color in architecture was so striking that color offered a key to larger discussions and opened up an interesting aspect of architectural practice. It must be remembered that recent housing projects, such as the housing estate Pilotengasse in Vienna, Gigon & Guyer's Broelberg in Kilchberg (with Harald F. Muller), next to Zurich, and their Sport Center in Davos (with Adrian Schiess), Jean Nouvel's Cultural and Congress Center in Lucerne, or Sauerbruch & Hutton's Photonic Center and their GSW office building in Berlin have all been contributing to free color from its unconscious and dormant role. These works all impart qualities to color in architecture that were hitherto reserved to other materials and fields: they define the aspects of the interaction of visual and physical space, of materialization of volumes, and of the expression of wealth and luxury.

  5. Hydrogen vacancies facilitate hydrogen transport kinetics in sodium hydride nanocrystallites

    NARCIS (Netherlands)

    Singh, S.; Eijt, S.W.H.

    2008-01-01

    We report ab initio calculations based on density-functional theory, of the vacancy-mediated hydrogen migration energy in bulk NaH and near the NaH(001) surface. The estimated rate of the vacancy mediated hydrogen transport, obtained within a hopping diffusion model, is consistent with the reaction

  6. Demonstration of a variable plasmonic beam splitter

    DEFF Research Database (Denmark)

    Kumar, Shailesh; Israelsen, Niels Møller; Andersen, Ulrik Lund

    2014-01-01

    In this contribution, we excite surface plasmon polaritons propagating along a silver nano-wire by a single nitrogen-vacancy center located in a diamond nano-crystal. By using the tip of an atomic force microscope, a second nano-wire is brought into the evanescent field of the first wire such tha......In this contribution, we excite surface plasmon polaritons propagating along a silver nano-wire by a single nitrogen-vacancy center located in a diamond nano-crystal. By using the tip of an atomic force microscope, a second nano-wire is brought into the evanescent field of the first wire...... such that surface plasmons can evanescently couple. In our experiment, we are able to tune the coupling strength from one nano-wire to another by adjusting the gap with the aid of the atomic force microscope. Numerical calculations of the coupling strength are carried out, which support the values found...

  7. Attempt at interpreting some optical absorption bands in X-ray irradiated fluorine

    International Nuclear Information System (INIS)

    Allain, Yves

    1959-01-01

    According to the results of one of our experiments, the 575 mμ absorption band of fluorine irradiated with X-Rays seams due to F - ion vacancies. Our goal has been to find a color centers model in fluorine colored in various conditions. Reprint of a paper published in Comptes rendus des seances de l'Academie des Sciences, t. 248, p. 2318-2320, sitting of Aril 20, 1959 [fr

  8. 2014 - Color & Infrared - Northeastern Vermont (0.5m)

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) This metadata record describes the acquisition and production of natural color and color infrared digital ground orthoimagery covering a portion...

  9. Determination of the vacancy formation enthalpy for high purity Ni

    International Nuclear Information System (INIS)

    Lynn, K.G.; Snead, C.L. Jr.; Hurst, J.J.; Farrell, K.

    1979-01-01

    Positron-annihilation lifetime measurements have been made on Ni over a temperature range of 4.2 to 1700 K. We find a small change in the lifetime from 4.2 to 900 K indicating a very small thermal-expansion effect. A small precursor effect is observed before the onset of significant vacancy trapping. A monovacancy formation enthalpy of 1.54/sub +0.2//sup -0.1/ eV is extracted without taking divacancies into consideration in the analysis. No detrapping from mono-vacancies is observed even at the higher temperatures. The vacancy formation enthalpy extracted from the lifetime data is compared to values obtained by Doppler-broadening and angular-correlation techniques

  10. Determination of the vacancy formation enthalpy for high purity Ni

    International Nuclear Information System (INIS)

    Lynn, K.G.; Snead, C.L. Jr.; Hurst, J.J.; Farrell, K.

    1979-01-01

    Positron-annihilation lifetime measurements have been made on Ni over a temperature range of 4.2 to 1700 K. We find a small change in the lifetime from 4.2 - 900 K indicating a very small thermal-expansion effect. A small precursor effect is observed before the onset of significant vacancy trapping. A monovacancy formation enthalpy of 1.54sub(+0.2)sup(-0.1) eV is extracted without taking divacancies into consideration in the analysis. No detrapping from mono-vacancies is observed even at the higher temperatures. The vacancy formation enthalpy extracted from the lifetime data is compared to values obtained by Doppler-broadening and angular-correlation techniques. (author)

  11. Exchange and Dzyaloshinskii-Moriya interactions in bulk FeGe: Effects of atomic vacancies

    Science.gov (United States)

    Loh, G. C.; Gan, C. K.

    2017-05-01

    We examine the effects of atomic vacancies on the (1) spin interaction, and (2) electronic character in the cubic B20 chiral magnet FeGe. For the former, Heisenberg exchange and Dzyaloshinskii-Moriya (DM) interactions are studied. The latter is done via a particular Wannier flavor of the Hamiltonian in the form of maximally-localized Wannier functions (MLWFs). Using first-principles calculations based on full-potential linearized augmented plane-wave (FLAPW)-based density functional theory (DFT), the spin order of bulk FeGe, in its pristine form, and with a Fe (Fe75%Ge100%) or Ge vacancy (Fe100%Ge75%) is investigated. Despite the presence of vacancies, the ground state of FeGe remains helimagnetic, i.e. spin spirals in FeGe are fairly robust. The energetic stability of FeGe increases in the presence of the vacancies. The spiral size is increased by approximately 40%, suggesting that vacancies can be introduced to manipulate the chiral order. The vacancies lift the band degeneracy in the valence manifold of the Wannier-interpolated band structures. Only the spin-down Fermi surfaces are substantially different between the pristine and defective FeGe; it is electron-like in the pristine case, but largely hole-like in the defective ones. The Ge vacancy splits the Fermi surface more than the Fe vacancy. The Heisenberg exchange between nearest Fe pairs is ferromagnetic in pristine FeGe. This Fe-Fe interaction remains ferromagnetic, albeit a slight decrease in strength, in the presence of a Fe vacancy. In contrast, a Ge vacancy in FeGe induces anti-ferromagnetism between nearest Fe pairs. By including spin-orbit coupling effects, we find that the DM interaction of defective FeGe is reversed in sign, and it is more uniform in strength along the three highly symmetric directions, relative to that in pristine FeGe. All in all, the versatility of FeGe makes it an excellent functional material, especially in data storage and spintronics applications.

  12. Valence and atomic size dependent exchange barriers in vacancy-mediated dopant diffusion

    International Nuclear Information System (INIS)

    Nelson, J.S.; Schultz, P.A.; Wright, A.F.

    1998-01-01

    First-principles pseudopotential calculations of dopant-vacancy exchange barriers indicate a strong dependency on dopant valence and atomic size, in contrast to current models of vacancy-mediated dopant diffusion. First-row elements (B, C, N) are found to have exchange barriers which are an order of magnitude larger than the assumed value of 0.3 eV (the Si vacancy migration energy). copyright 1998 American Institute of Physics

  13. Correlated lifetimes of free paraexcitons and excitons trapped at oxygen vacancies in cuprous oxide

    International Nuclear Information System (INIS)

    Koirala, Sandhaya; Naka, Nobuko; Tanaka, Koichiro

    2013-01-01

    We have studied transients of luminescence due to free excitons and excitons trapped at oxygen vacancies in cuprous oxide. We find that both trapped and free paraexcitons have lifetime dependent on temperature and on the oxygen concentration. By using samples containing much less copper vacancies relative to oxygen vacancies, we find out the direct correlation between the free paraexciton lifetime and trapped exciton lifetime. - Highlights: ► We have investigated trapping of free excitons at oxygen vacancies in cuprous oxide. ► Lifetimes of free and trapped excitons exhibit correlative temperature dependence. ► Four-level model with the activation energy of 33 meV well explains the observation. ► Comparison is made using the four samples with different vacancy concentrations. ► We clarified the crucial role of the oxygen vacancy in shortening the lifetimes.

  14. Detection of current-induced vacancies in thin aluminum endash copper lines using positrons

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; OBrien, K.; Lynn, K.G.; Simpson, P.J.; Rodbell, K.P.

    1996-01-01

    In situ depth-resolved positron annihilation spectroscopy (PAS) is used to show dynamic formation of vacancies in 1 μmx1 μm Al-0.5 wt% Cu lines under current flow. We show that the number of vacancies in these lines increases when a dc current (8x10 4 A/cm 2 ) is applied. This increase in vacancy concentration is substantially greater than that due to thermal vacancy generation alone (4x10 18 cm -3 versus 3x10 17 cm -3 ). Isothermal measurements (with no current flow) yield a vacancy formation energy of 0.60±0.02 eV. These results show that PAS can be used to examine the initial stages of interconnect damage due to electromigration. copyright 1996 American Institute of Physics

  15. Agglomeration Versus Localization Of Hydrogen In BCC Fe Vacancies

    International Nuclear Information System (INIS)

    Simonetti, S.; Juan, A.; Brizuela, G.; Simonetti, S.

    2006-01-01

    Severe embrittlement can be produced in many metals by small amounts of hydrogen. The interactions of hydrogen with lattice imperfections are important and often dominant in determining the influence of this impurity on the properties of solids. The interaction between four-hydrogen atoms and a BCC Fe structure having a vacancy has been studied using a cluster model and a semiempirical method. For a study of sequential absorption, the hydrogen atoms were positioned in their energy minima configurations, near to the tetrahedral sites neighbouring the vacancy. VH 2 and VH 3 complexes are energetically the most stables in BCC Fe. The studies about the stability of the hydrogen agglomeration gave as a result that the accumulation is unfavourable in complex vacancy-hydrogen with more than three atoms of hydrogen. (authors)

  16. Understanding the presence of vacancy clusters in ZnO from a kinetic perspective

    Science.gov (United States)

    Bang, Junhyeok; Kim, Youg-Sung; Park, C. H.; Gao, F.; Zhang, S. B.

    2014-06-01

    Vacancy clusters have been observed in ZnO by positron-annihilation spectroscopy (PAS), but detailed mechanisms are unclear. This is because the clustering happens in non-equilibrium conditions, for which theoretical method has not been well established. Combining first-principles calculation and kinetic Monte Carlo simulation, we determine the roles of non-equilibrium kinetics on the vacancies clustering. We find that clustering starts with the formation of Zn and O vacancy pairs (VZn - Vo), which further grow by attracting additional mono-vacancies. At this stage, vacancy diffusivity becomes crucial: due to the larger diffusivity of VZn compared to VO, more VZn-abundant clusters are formed than VO-abundant clusters. The large dissociation energy barriers, e.g., over 2.5 eV for (VZn - Vo), suggest that, once formed, it is difficult for the clusters to dissociate. By promoting mono-vacancy diffusion, thermal annealing will increase the size of the clusters. As the PAS is insensitive to VO donor defects, our results suggest an interpretation of the experimental data that could not have been made without the in-depth calculations.

  17. Probing color-singlet exchange at D0

    International Nuclear Information System (INIS)

    Abbott, B.; Abolins, M.; Acharya, B.S.

    1997-07-01

    We present latest preliminary results on hard color-singlet exchange in proton-antiproton collisions. The fraction of dijet events produced via color-singlet exchange is measured as a function of jet transverse energy, dijet pseudorapidity separation, and proton-antiproton center-of-mass energy. These results are qualitatively consistent with a color-singlet fraction that increases with increasing quark-initiated processes

  18. Photoionization and vacancy decay of endohedral atoms

    International Nuclear Information System (INIS)

    Amusia, M. Ya.

    2007-01-01

    We demonstrate the role played by the fullerenes shell in the photoionization and vacancy decay of endohedral atoms A-C 60 . It is shown, partly in the frame of a rather simple model that describes the fullerene shell, partly using only the assumption on the smallness of the atom A in comparison to the size of C 60 that it affects photoionization and the vacancy decay of A-C 60 profoundly. Namely, it leads to a number of new resonances in photoionization cross-section and other photoionization characteristics as well as strong modifications of the vacancy decay probabilities and to opening of new decay channels. We will discuss the problem of photon propagation through the C 60 shell and conclude that at any considered frequency ω, 0 ≤ ω ≤ 60 eV the C 60 enhances the incoming radiation. This shows non-metallic dielectric behavior of the 240 collectivized electrons in C 60 . We also discuss the effects of C 60 upon the fast electron inelastic scattering. The results obtained are valid qualitatively also for other than C 60 molecules, e.g. for C 70 or C 76

  19. Photoionization and vacancy decay of endohedral atoms

    Energy Technology Data Exchange (ETDEWEB)

    Amusia, M. Ya. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); A.F. Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation)], E-mail: amusia@vms.huji.ac.il

    2007-10-15

    We demonstrate the role played by the fullerenes shell in the photoionization and vacancy decay of endohedral atoms A-C{sub 60}. It is shown, partly in the frame of a rather simple model that describes the fullerene shell, partly using only the assumption on the smallness of the atom A in comparison to the size of C{sub 60} that it affects photoionization and the vacancy decay of A-C{sub 60} profoundly. Namely, it leads to a number of new resonances in photoionization cross-section and other photoionization characteristics as well as strong modifications of the vacancy decay probabilities and to opening of new decay channels. We will discuss the problem of photon propagation through the C{sub 60} shell and conclude that at any considered frequency {omega}, 0 {<=} {omega} {<=} 60 eV the C{sub 60} enhances the incoming radiation. This shows non-metallic dielectric behavior of the 240 collectivized electrons in C{sub 60}. We also discuss the effects of C{sub 60} upon the fast electron inelastic scattering. The results obtained are valid qualitatively also for other than C{sub 60} molecules, e.g. for C{sub 70} or C{sub 76}.

  20. First-principles calculations of vacancy formation in In-free photovoltaic semiconductor Cu2ZnSnSe4

    International Nuclear Information System (INIS)

    Maeda, Tsuyoshi; Nakamura, Satoshi; Wada, Takahiro

    2011-01-01

    To quantitatively evaluate the formation energies of Cu, Zn, Sn, and Se vacancies in kesterite-type Cu 2 ZnSnSe 4 (CZTSe), first-principles pseudopotential calculations using plane-wave basis functions were performed. The formation energies of neutral Cu, Zn, Sn and Se vacancies were calculated as a function of the atomic chemical potentials of constituent elements. The obtained results were as follows: (1) the formation energy of Cu vacancy was generally smaller than those of the other Zn, Sn and Se vacancies, (2) under the Cu-poor and Zn-rich condition, the formation energy of Cu vacancy was particularly low, (3) the formation energy of Zn vacancy greatly depended on the chemical potentials of the constituent elements and under the Zn-poor and Se-rich condition, the formation energy of Zn vacancy was smaller than that of Cu vacancy, and (4) the formation energy of Sn vacancy did not greatly depend on the chemical potentials of the constituent elements and was much larger than those of Cu, Zn, and Se vacancies. These results indicate that Cu vacancy is easily formed under Cu-poor and Zn-rich conditions, but Zn vacancy is easily formed under the Zn-poor and Se-rich conditions.

  1. Electroluminescence from a diamond device with ion-beam-micromachined buried graphitic electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Forneris, J., E-mail: jacopo.forneris@unito.it [Physics Department and NIS Interdepartmental Centre, University of Torino, Torino (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sez. Torino, Torino (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Sez. Torino, Torino (Italy); Battiato, A.; Gatto Monticone, D. [Physics Department and NIS Interdepartmental Centre, University of Torino, Torino (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sez. Torino, Torino (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Sez. Torino, Torino (Italy); Picollo, F. [Istituto Nazionale di Fisica Nucleare (INFN), Sez. Torino, Torino (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Sez. Torino, Torino (Italy); Physics Department and NIS Interdepartmental Centre, University of Torino, Torino (Italy); Amato, G.; Boarino, L.; Brida, G.; Degiovanni, I.P.; Enrico, E.; Genovese, M.; Moreva, E.; Traina, P. [Istituto Nazionale di Ricerca Metrologica (INRiM), Torino (Italy); Verona, C.; Verona Rinati, G. [Department of Industrial Engineering, University of Roma “Tor Vergata”, Roma (Italy); Olivero, P. [Physics Department and NIS Interdepartmental Centre, University of Torino, Torino (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sez. Torino, Torino (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), Sez. Torino, Torino (Italy)

    2015-04-01

    Focused MeV ion microbeams are suitable tools for the direct writing of conductive graphitic channels buried in an insulating diamond bulk, as demonstrated in previous works with the fabrication of multi-electrode ionizing radiation detectors and cellular biosensors. In this work we investigate the suitability of the fabrication method for the electrical excitation of color centers in diamond. Differently from photoluminescence, electroluminescence requires an electrical current flowing through the diamond sub-gap states for the excitation of the color centers. With this purpose, buried graphitic electrodes with a spacing of 10 μm were fabricated in the bulk of a detector-grade CVD single-crystal diamond sample using a scanning 1.8 MeV He{sup +} micro-beam. The current flowing in the gap region between the electrodes upon the application of a 450 V bias voltage was exploited as the excitation pump for the electroluminescence of different types of color centers localized in the above-mentioned gap. The bright light emission was spatially mapped using a confocal optical microscopy setup. The spectral analysis of electroluminescence revealed the emission from neutrally-charged nitrogen-vacancy centers (NV{sup 0}, λ{sub ZPL} = 575 nm), as well as from cluster crystal dislocations (A-band, λ = 400–500 nm). Moreover, an electroluminescence signal with appealing spectral features (sharp emission at room temperature, low phonon sidebands) from He-related defects was detected (λ{sub ZPL} = 536.3 nm, λ{sub ZPL} = 560.5 nm); a low and broad peak around λ = 740 nm was also observed and tentatively ascribed to Si-V or GR1 centers. These results pose interesting future perspectives for the fabrication of electrically-stimulated single-photon emitters in diamond for applications in quantum optics and quantum cryptography.

  2. Evidence for vacancy migration in stage III for copper

    International Nuclear Information System (INIS)

    Antesberger, G.; Sonnenberg, K.; Wienhold, P.; Coltman, R.R.; Klabunde, C.E.; Williams, J.M.

    1975-01-01

    Specimens doped with interstitial clusters and single vacancies have been annealed isochronally through the temperature range of stage III. Combining this annealing with a test irradiation after each annealing step reactions of mobile single test interstitials with the doping defects were studied. These reactions provide information about the variation of the doping defect structure during annealing. The experimental results suggest that vacancy clusters are formed in stage III

  3. Coupling of single quantum emitters to plasmons propagating on mechanically etched wires

    DEFF Research Database (Denmark)

    Kumar, Shailesh; Huck, Alexander; Lu, Ying-Wei

    2013-01-01

    We demonstrate the coupling of a single nitrogen vacancy center in a nanodiamond to propagating plasmonic modes of mechanically etched silver nanowires. The mechanical etch is performed on single crystalline silver nanoplates by the tip of an atomic force microscope cantilever to produce wires...

  4. Single Photon, Spin, and Charge in Diamond Semiconductor at room temperature

    International Nuclear Information System (INIS)

    Yuki Doi

    2014-01-01

    The nitrogen-vacancy (NV) center in diamond is a promising candidate for a qubit driven at room temperature. In order to derive potential of NV center, manipulation of their charge state is a very important topic. Here we succeeded to electrically control between single NV-/NV0 by means of current injection. This method allows us to very stable charge state control. (author)

  5. Stability enhancement of Cu2S against Cu vacancy formation by Ag alloying

    Science.gov (United States)

    Barman, Sajib K.; Huda, Muhammad N.

    2018-04-01

    As a potential solar absorber material, Cu2S has proved its importance in the field of renewable energy. However, almost all the known minerals of Cu2S suffer from spontaneous Cu vacancy formation in the structure. The Cu vacancy formation causes the structure to possess very high p-type doping that leads the material to behave as a degenerate semiconductor. This vacancy formation tendency is a major obstacle for this material in this regard. A relatively new predicted phase of Cu2S which has an acanthite-like structure was found to be preferable than the well-known low chalcocite Cu2S. However, the Cu-vacancy formation tendency in this phase remained similar. We have found that alloying silver with this structure can help to reduce Cu vacancy formation tendency without altering its electronic property. The band gap of silver alloyed structure is higher than pristine acanthite Cu2S. In addition, Cu diffusion in the structure can be reduced with Ag doped in Cu sites. In this study, a systematic approach is presented within the density functional theory framework to study Cu vacancy formation tendency and diffusion in silver alloyed acanthite Cu2S, and proposed a possible route to stabilize Cu2S against Cu vacancy formations by alloying it with Ag.

  6. Nitrogen Removal from Milking Center Wastewater via Simultaneous Nitrification and Denitrification Using a Biofilm Filtration Reactor

    Directory of Open Access Journals (Sweden)

    Seung-Gun Won

    2015-06-01

    Full Text Available Milking center wastewater (MCW has a relatively low ratio of carbon to nitrogen (C/N ratio, which should be separately managed from livestock manure due to the negative impacts of manure nutrients and harmful effects on down-stream in the livestock manure process with respect to the microbial growth. Simultaneous nitrification and denitrification (SND is linked to inhibition of the second nitrification and reduces around 40% of the carbonaceous energy available for denitrification. Thus, this study was conducted to find the optimal operational conditions for the treatment of MCW using an attached-growth biofilm reactor; i.e., nitrogen loading rate (NLR of 0.14, 0.28, 0.43, and 0.58 kg m−3 d−1 and aeration rate of 0.06, 0.12, and 0.24 m3 h−1 were evaluated and the comparison of air-diffuser position between one-third and bottom of the reactor was conducted. Four sand packed-bed reactors with the effective volume of 2.5 L were prepared and initially an air-diffuser was placed at one third from the bottom of the reactor. After the adaptation period of 2 weeks, SND was observed at all four reactors and the optimal NLR of 0.45 kg m−3 d−1 was found as a threshold value to obtain higher nitrogen removal efficiency. Dissolved oxygen (DO as one of key operational conditions was measured during the experiment and the reactor with an aeration rate of 0.12 m3 h−1 showed the best performance of NH4-N removal and the higher total nitrogen removal efficiency through SND with appropriate DO level of ~0.5 mg DO L−1. The air-diffuser position at one third from the bottom of the reactor resulted in better nitrogen removal than at the bottom position. Consequently, nitrogen in MCW with a low C/N ratio of 2.15 was successfully removed without the addition of external carbon sources.

  7. First-principles study of vacancy formation and migration in clean and Re-doped γ'-Ni3Al

    International Nuclear Information System (INIS)

    Zhang Xu; Wang Chongyu

    2009-01-01

    Using density functional theory calculations in conjunction with the climbing images nudged elastic band method, we studied the vacancy formation and migration in clean and Re-doped Ni 3 Al. Both the chemical potential of the species and the magnetic effect are considered to determine the vacancy formation energy. We also simulated the vacancy migration in a complete set of migration paths. The evaluated vacancy formation energy and activation energy for the motion of vacancy compared well with the experimental results. Also, the obtained migration ways for the diffusion of Ni and Al atoms are consistent with previous theoretical predictions and experimental observations. Magnetism is found to influence both the vacancy formation and migration. Our results reveal that Re doping can inhibit the formation of Ni vacancies but facilitate the formation of Al vacancies, and can also inhibit the migration of neighboring vacancies. While the doped Re atom on the Al site is stable, the Re atom on the Ni site can diffuse within the Ni-sublattice mediated by Ni vacancies

  8. Vacancy identification in Co+ doped rutile TiO2 crystal with positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Ma Minyang; Qin Xiubo; Wang Baoyi; Wu Weiming

    2013-01-01

    Background: Room temperature Diluted Magnetic Semiconductor (DMS) is a critical path in the study of spin-electronic devices, but there are many disputes in the intrinsic properties and origin of the room temperature ferromagnetism. Positron annihilation spectroscopy (PAS) is a powerful technique for evaluating vacancy-type defects. Purpose: We aim to establish the relationship between the defect structure and ferromagnetism of the materials by analyzing the parameters of positron annihilation. Methods: Co-doped rutile TiO 2 films were synthesized by ion implantation and extensively studied by variable energy positron annihilation Doppler broadening spectroscopy (DBS) and coincidence Doppler broadening (CDB) measurements with variable energy slow positron beam for identification of the vacancies. Results: The results of DBS showed that a newly formed type of vacancy could be concluded by the S-W plot and the CDB results indicated that the oxygen vacancy (Vo) complex Ti-Co-Vo and/or Ti-Vo were formed with Co ions implantation and the vacancy concentration increased with increasing dopant dose. Conclusion: We identify that the generation of Ti-Vo and/or Ti-Co-Vo vacancy complex are induced by the existence of excess Ti 3d electrons around the oxygen vacancy. (authors)

  9. Vacancy identification in Co+ doped rutile TiO2 crystal with positron annihilation spectroscopy

    Science.gov (United States)

    Qin, X. B.; Zhang, P.; Liang, L. H.; Zhao, B. Z.; Yu, R. S.; Wang, B. Y.; Wu, W. M.

    2011-01-01

    Co-doped rutile TiO2 films were synthesized by ion implantation. Variable energy positron annihilation Doppler broadening spectroscopy and coincidence Doppler broadening measurements were performed for identification of the vacancies. A newly formed type of vacancy can be concluded by the S-W plot and the CDB results indicated that the oxygen vacancy (VO) complex Ti-Co-VO and/or Ti-VO are formed with Co ions implantation and the vacancy concentration is increased with increase of dopant dose.

  10. Energetic, structural and electronic properties of metal vacancies in strained AlN/GaN interfaces.

    Science.gov (United States)

    Kioseoglou, J; Pontikis, V; Komninou, Ph; Pavloudis, Th; Chen, J; Karakostas, Th

    2015-04-01

    AlN/GaN heterostructures have been studied using density-functional pseudopotential calculations yielding the formation energies of metal vacancies under the influence of local interfacial strains, the associated charge distribution and the energies of vacancy-induced electronic states. Interfaces are built normal to the polar direction of the wurtzite structure by joining two single crystals of AlN and GaN that are a few atomic layers thick; thus, periodic boundary conditions generate two distinct heterophase interfaces. We show that the formation energy of vacancies is a function of their distance from the interfaces: the vacancy-interface interaction is found repulsive or attractive, depending on the type of the interface. When the interaction is attractive, the vacancy formation energy decreases with increasing the associated electric charge, and hence the equilibrium vacancy concentration at the interface is greater. This finding can reveal the well-known morphological differences existing between the two types of investigated interfaces. Moreover, we found that the electric charge is strongly localized around the Ga vacancy, while in the case of Al vacancies is almost uniformly distributed throughout the AlN/GaN heterostructure. Crucially, for the applications of heterostructures, metal vacancies introduce deep states in the calculated bandgap at energy levels from 0.5 to 1 eV above the valence band maximum (VBM). It is, therefore, predicted that vacancies could initiate 'green luminescence' i.e. light emission in the energy range of 2.5 eV stemming from electronic transitions between these extra levels, and the conduction band, or energy levels, due to shallow donors.

  11. Vacancy-type defects induced by grinding of Si wafers studied by monoenergetic positron beams

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Yoshihara, Nakaaki [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Mizushima, Yoriko [Devices and Materials Labs Fujitsu Laboratories Ltd., Atsugi, Kanagawa 243-0197 (Japan); ICE Cube Center, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Kim, Youngsuk [ICE Cube Center, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Disco Corporation, Ota, Tokyo 143-8580 (Japan); Nakamura, Tomoji [Devices and Materials Labs Fujitsu Laboratories Ltd., Atsugi, Kanagawa 243-0197 (Japan); Ohba, Takayuki [ICE Cube Center, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Oshima, Nagayasu; Suzuki, Ryoichi [Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

    2014-10-07

    Vacancy-type defects introduced by the grinding of Czochralski-grown Si wafers were studied using monoenergetic positron beams. Measurements of Doppler broadening spectra of the annihilation radiation and the lifetime spectra of positrons showed that vacancy-type defects were introduced in the surface region (<98 nm), and the major defect species were identified as (i) relatively small vacancies incorporated in dislocations and (ii) large vacancy clusters. Annealing experiments showed that the defect concentration decreased with increasing annealing temperature in the range between 100 and 500°C. After 600–700°C annealing, the defect-rich region expanded up to about 170 nm, which was attributed to rearrangements of dislocation networks, and a resultant emission of point defects toward the inside of the sample. Above 800°C, the stability limit of those vacancies was reached and they started to disappear. After the vacancies were annealed out (900°C), oxygen-related defects were the major point defects and they were located at <25 nm.

  12. Room temperature ferromagnetism and absorption red-shift in nitrogen-doped TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Gómez-Polo, C.; Larumbe, S.; Monge, M.

    2014-01-01

    Highlights: • N-doped TiO 2 anatase nanoparticles were obtained by sol–gel. • The nanoparticle size, controlled by the N doping, determines lattice parameters. • Correlation between room temperature ferromagnetism and absorption red-shift. • Oxygen vacancies reinforce both phenomena. • Metal transition impurities contribute to the room temperature ferromagnetism. - Abstract: In this work, room-temperature ferromagnetism and the red-shift of the optical absorption is analyzed in nitrogen doped TiO 2 semiconductor nanoparticles. The nanoparticles were synthesized by the sol–gel method using urea as the nitrogen source. Titanium Tetraisopropoxide (TTIP) was employed as the alkoxyde precursor and dissolved in ethanol. The as prepared gels were dried and calcined in air at 300 °C. Additionally, post-annealing treatments under vacuum atmosphere were performed to modify the oxygen stoichiometry of the samples. The anatase lattice parameters, analyzed by means of powder X-ray diffractometry, depend on the nanometer grain size of the nanoparticles (increase and decrease, respectively, of the tetragonal a and c lattice parameters with respect to the bulk values). The diffuse reflectance ultraviolet–visible (UV–Vis) absorbance spectra show a clear red-shift as consequence of the nitrogen and the occurrence of intragap energy levels. The samples display ferromagnetic features at room temperature that are reinforced with the nitrogen content and after the post annealings in vacuum. The results indicate a clear correlation between the room temperature ferromagnetism and the shift of the absorbance spectrum. In both phenomena, oxygen vacancies (either induced by the nitrogen doping or by the post vacuum annealings) play a dominant role. However, we conclude the existence of very low concentration of diluted transition metal impurities that determine the room ferromagnetic response (bound magnetic polaron BMP model). The contraction of the c soft axis of the

  13. HYDROGEN VACANCY INTERACTION IN MOLYBDENUM

    NARCIS (Netherlands)

    Abd El Keriem, M.S.; van der Werf, D.P.; Pleiter, F

    1993-01-01

    Vacancy-hydrogen interaction in molybdenum was investigated by means of the perturbed angular correlation technique, using the isotope In-111 as a probe. The complex InV2 turned out to trap up to two hydrogen atoms: trapping of a single hydrogen atom gives rise to a decrease of the quadrupole

  14. Understanding the presence of vacancy clusters in ZnO from a kinetic perspective

    International Nuclear Information System (INIS)

    Bang, Junhyeok; Zhang, S. B.; Kim, Youg-Sung; Park, C. H.; Gao, F.

    2014-01-01

    Vacancy clusters have been observed in ZnO by positron-annihilation spectroscopy (PAS), but detailed mechanisms are unclear. This is because the clustering happens in non-equilibrium conditions, for which theoretical method has not been well established. Combining first-principles calculation and kinetic Monte Carlo simulation, we determine the roles of non-equilibrium kinetics on the vacancies clustering. We find that clustering starts with the formation of Zn and O vacancy pairs (V Zn  − Vo), which further grow by attracting additional mono-vacancies. At this stage, vacancy diffusivity becomes crucial: due to the larger diffusivity of V Zn compared to V O , more V Zn -abundant clusters are formed than V O -abundant clusters. The large dissociation energy barriers, e.g., over 2.5 eV for (V Zn  − Vo), suggest that, once formed, it is difficult for the clusters to dissociate. By promoting mono-vacancy diffusion, thermal annealing will increase the size of the clusters. As the PAS is insensitive to V O donor defects, our results suggest an interpretation of the experimental data that could not have been made without the in-depth calculations.

  15. Radiation induced coloring of glasses measured during and after electron irradiation

    International Nuclear Information System (INIS)

    Swyler, K.J.; Hardy, W.H. II; Levy, P.W.

    1975-01-01

    The growth of color centers during irradiation, and the decay after irradiation, were studied in two glasses using recently developed equipment for making optical absorption and luminescence measurements during and after electron irradiation. The glasses studied were NBS 710, a soda-lime silicate glass, and NBS 711, a lead silicate glass. Both glasses exhibit similar coloring characteristics. The radiation-induced absorption spectra consists of a weak gaussian shaped band in the visible, a stronger gaussian band in the ultraviolet, and a band edge ''shift'' which may be accurately approximated by a third gaussian band. For all absorption bands, the color center vs dose (or irradiation time) curves can be accurately resolved into two saturating exponential and one linear component. The decay curves obtained after the irradiation is terminated can be accurately expressed by three exponential components. Coloring and decay curves made at different dose rates indicate that the processes responsible for decay after irradiation and electron hole recombination during irradiation play important roles in determining the rate and extent of coloring. Results are qualitatively in agreement with some very simple kinetic treatments for color center formation. In some, but not all, respects the quantitative agreement is also good. Lastly, the results indicate that it is necessary to make measurements during irradiation to establish the formation kinetics of color centers that are unstable at the bombardment temperature. (U.S.)

  16. Formation and properties of metallic nanoparticles in lithium and sodium fluorides with radiation-induced color centers

    Science.gov (United States)

    Bryukvina, L. I.; Martynovich, E. F.

    2012-12-01

    The specific features of light- and temperature-induced formation of metallic nanoparticles in γ-irradiated LiF and NaF crystals have been investigated. Atomic force microscope images of nanoparticles of different sizes and in different locations have been presented. The relation between the crystal processing regimes and properties of the nanoparticles formed has been revealed. The optical properties of the processed crystals have been analyzed. The thermo- and light-stimulated processes underlying the formation of metallic nanoparticles in aggregation of the color centers and their decay due to the recovery of the crystal lattice have been studied.

  17. Stability and electronic structure of iron nanoparticle anchored on defective hexagonal boron nitrogen nanosheet: A first-principle study

    International Nuclear Information System (INIS)

    Lin, Sen; Huang, Jing; Ye, Xinxin

    2014-01-01

    Highlights: • Fe 13 nanoparticle strongly interacts with the monovacancy of h-BN nanosheet. • Significant charges are transferred from Fe 13 to the defective h-BN nanosheet. • The upshift of d-band center makes the surface Fe atoms of supported Fe 13 with higher reactivity. - Abstract: By first-principle methods, we investigate the stability and electronic structures of Fe 13 nanoparticles anchored on hexagonal boron nitrogen nanosheets (h-BNNSs) with monovacancy defect sites. It is found that the defect sites such as boron and nitrogen vacancy significantly increase the adsorption energies of Fe 13 , suggesting that the supported Fe 13 nanoparticles should be very stable against sintering at high temperatures. From the calculated density of states, we testify that the strong interaction is attributed to the coupling between the 3d orbitals of Fe atoms with the sp 2 dangling bonds at the defect sites. The Bader charge and differential charge density analyses reveal that there is significant charge redistribution at the interface between Fe 13 and the substrates, leading to positive charges located on most of the Fe atoms. Additionally, our results show that the strong binding of the nanoparticle results in the upshift of d-band center of Fe 13 toward the Fermi level, thus making the surface Fe atoms with higher reactivity. This work gives a detailed understanding the interaction between Fe 13 nanoparticle and defective h-BNNS and will provide helpful instructions in the design and synthesis of supported Fe-based catalysts in heterogeneous catalysis

  18. Preparation of fluorescent nanodiamond suspensions using bead-assisted ultrasonic disintegration

    Science.gov (United States)

    Głowacki, Maciej J.; Gardas, Mateusz; Ficek, Mateusz; Sawczak, Mirosław; Bogdanowicz, Robert

    2017-08-01

    Nitrogen-vacancy (N-V) centers are the most widely studied crystallographic defect in the diamond lattice since their presence causes strong and stable fluorescence. The negative charge state of the defect (NV-) is especially desired because of its potential for quantum information processing. In this study, fluorescent suspensions of diamond particles have been produced by microbead-assisted ultrasonic disintegration of commercially obtained diamond powder containing N-V color centers. Zirconium dioxide ZrO2 was chosen as an abrasive and a mixture of deionized water and dimethyl sulfoxide (DMSO) was used as a solvent. Raman spectrum of the starting material has been obtained and the resulting liquids have been measured in terms of photoluminescence. Moreover, thin layer of the diamond particles has been deposited on a silicon substrate and examined using scanning electron microscopy (SEM). During the course of the experiment a new method, which uses sodium chloride NaCl as an abrasive, has been proposed. The results of fluorescence measurements of the suspension prepared using this technique are highly promising.

  19. Anaerobic Nitrogen Fixers on Mars

    Science.gov (United States)

    Lewis, B. G.

    2000-07-01

    The conversion of atmospheric nitrogen gas to the protein of living systems is an amazing process of nature. The first step in the process is biological nitrogen fixation, the transformation of N2 to NH3. The phenomenon is crucial for feeding the billions of our species on Earth. On Mars, the same process may allow us to discover how life can adapt to a hostile environment, and render it habitable. Hostile environments also exist on Earth. For example, nothing grows in coal refuse piles due to the oxidation of pyrite and marcasite to sulfuric acid. Yet, when the acidity is neutralized, alfalfa and soybean plants develop root nodules typical of symbiotic nitrogen fixation with Rhizobium species possibly living in the pyritic material. When split open, these nodules exhibited the pinkish color of leghemoglobin, a protein in the nodule protecting the active nitrogen-fixing enzyme nitrogenase against the toxic effects of oxygen. Although we have not yet obtained direct evidence of nitrogenase activity in these nodules (reduction of acetylene to ethylene, for example), these findings suggested the possibility that nitrogen fixation was taking place in this hostile, non-soil material. This immediately raises the possibility that freeliving anaerobic bacteria which fix atmospheric nitrogen on Earth, could do the same on Mars.

  20. Oxygen vacancies dependent phase transition of Y{sub 2}O{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Pengfei; Zhang, Kan [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun 130012 (China); Huang, Hao [Titanium Alloys Lab. Beijing Institute of Aeronautical Materials, Beijing 81-15 100095 (China); Wen, Mao, E-mail: Wenmao225@jlu.edu.cn [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun 130012 (China); Li, Quan; Zhang, Wei; Hu, Chaoquan [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun 130012 (China); Zheng, Weitao, E-mail: WTZheng@jlu.edu.cn [Department of Materials Science, State Key Laboratory of Automotive Simulation and Control and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun 130012 (China)

    2017-07-15

    Highlights: • Oxygen vacancies for Y{sub 2}O{sub 3} films increase monotonously with increasing T{sub s}. • Oxygen vacancies can promote the nucleation of monoclinic phase. • That monoclinic phase with oxygen deficiency is not thermodynamic stable at high temperature. • Phase transition from monoclinic to oxygen defective occurs at high concentrations of oxygen vacancies. • High hardness just appears in Y{sub 2}O{sub 3} films with mixed phase configurations. - Abstract: Y{sub 2}O{sub 3} films have great application potential in high-temperature metal matrix composite and nuclear engineering, used as interface diffusion and reaction barrier coating owing to their excellent thermal and chemical stability, high melting point and extremely negative Gibbs formation energy, and thus their structural and mechanical properties at elevated temperature are especially important. Oxygen vacancies exist commonly in yttrium oxide (Y{sub 2}O{sub 3}) thin films and act strongly on the phase structure and properties, but oxygen vacancies dependent phase transition at elevated temperature has not been well explored yet. Y{sub 2}O{sub 3} thin films with different oxygen vacancy concentrations have been achieved by reactive sputtering through varying substrate temperature (T{sub s}), in which oxygen vacancies increase monotonously with increasing T{sub s}. For as-deposited Y{sub 2}O{sub 3} films, oxygen vacancies present at high T{sub s} can promote the nucleation of monoclinic phase, meanwhile, high T{sub s} can induce the instability of monoclinic phase. Thus their competition results in forming mixed phases of cubic and monoclinic at high T{sub s}. During vacuum annealing at 1000 °C, a critical oxygen vacancy concentration is observed, below which phase transition from monoclinic to cubic takes place, and above which phase transfer from monoclinic to the oxygen defective phase (ICDD file no. 39-1063), accompanying by stress reversal from compressive to tensile and

  1. A Unifying Perspective on Oxygen Vacancies in Wide Band Gap Oxides.

    Science.gov (United States)

    Linderälv, Christopher; Lindman, Anders; Erhart, Paul

    2018-01-04

    Wide band gap oxides are versatile materials with numerous applications in research and technology. Many properties of these materials are intimately related to defects, with the most important defect being the oxygen vacancy. Here, using electronic structure calculations, we show that the charge transition level (CTL) and eigenstates associated with oxygen vacancies, which to a large extent determine their electronic properties, are confined to a rather narrow energy range, even while band gap and the electronic structure of the conduction band vary substantially. Vacancies are classified according to their character (deep versus shallow), which shows that the alignment of electronic eigenenergies and CTL can be understood in terms of the transition between cavity-like localized levels in the large band gap limit and strong coupling between conduction band and vacancy states for small to medium band gaps. We consider both conventional and hybrid functionals and demonstrate that the former yields results in very good agreement with the latter provided that band edge alignment is taken into account.

  2. Zinc Vacancy Formation and its Effect on the Conductivity of ZnO

    Science.gov (United States)

    Khan, Enamul; Weber, Marc; Langford, Steve; Dickinson, Tom

    2010-03-01

    Exposing single crystal ZnO to 193-nm ArF excimer laser radiation can produce metallic zinc nanoparticles along the surface. The particle production mechanism appears to involve interstitial-vacancy pair formation in the near-surface bulk. Conductivity measurements made with one probe inside the laser spot and the other outside show evidence for rectifying behavior. Positron annihilation spectroscopy confirms the presence of Zn vacancies. We suggest that Zn vacancies are a possible source of p-type behavior in irradiated ZnO. Quadrupole mass spectroscopy shows that both oxygen and zinc are emitted during irradiation. Electron-hole pair production has previously been invoked to account for particle desorption from ZnO during UV illumination. Our results suggest that preexisting and laser-generated defects play a critical role in particle desorption and Zn vacancy formation.

  3. Towards representation of a perceptual color manifold using associative memory for color constancy.

    Science.gov (United States)

    Seow, Ming-Jung; Asari, Vijayan K

    2009-01-01

    In this paper, we propose the concept of a manifold of color perception through empirical observation that the center-surround properties of images in a perceptually similar environment define a manifold in the high dimensional space. Such a manifold representation can be learned using a novel recurrent neural network based learning algorithm. Unlike the conventional recurrent neural network model in which the memory is stored in an attractive fixed point at discrete locations in the state space, the dynamics of the proposed learning algorithm represent memory as a nonlinear line of attraction. The region of convergence around the nonlinear line is defined by the statistical characteristics of the training data. This learned manifold can then be used as a basis for color correction of the images having different color perception to the learned color perception. Experimental results show that the proposed recurrent neural network learning algorithm is capable of color balance the lighting variations in images captured in different environments successfully.

  4. Hard-to-fill vacancies.

    Science.gov (United States)

    Williams, Ruth

    2010-09-29

    Skills for Health has launched a set of resources to help healthcare employers tackle hard-to-fill entry-level vacancies and provide sustainable employment for local unemployed people. The Sector Employability Toolkit aims to reduce recruitment and retention costs for entry-level posts and repare people for employment through pre-job training programmes, and support employers to develop local partnerships to gain access to wider pools of candidates and funding streams.

  5. Formation of vacancies in thermal equilibrium in α-range alloys

    International Nuclear Information System (INIS)

    Hehenkamp, Th.

    1982-01-01

    A model for aggregates (complexes) between vacancies and one or more impurity atoms is described for nearest neighbor interactions. Binding enthalpies in the different complexes have been unambigeously derived therefrom employing a variety of experimental techniques for the determination of vacancy concentrations as function of composition and temperature, (resistivity, positron annihilation, calorimetry, dl/l - da/a techniques), for some noble metals alloys. Solvent diffusion in these alloys has been found to be essentially governed by the increase of vacancy concentrations as function of these variables. Approximation for changes in the migration and correlation permits one to obtain the different binding enthalpies from measurements of solvent diffusion enhancement in an independent fashion and gives comparable results to the former techniques. (author)

  6. Phase control of electromagnetically induced acoustic wave transparency in a diamond nanomechanical resonator

    Energy Technology Data Exchange (ETDEWEB)

    Evangelou, Sofia, E-mail: Evangelousof@gmail.com

    2017-05-10

    Highlights: • A high-Q single-crystal diamond nanomechanical resonator embedded with nitrogen-vacancy (NV) centers is studied. • A Δ-type coupling configuration is formed. • The spin states of the ground state triplet of the NV centers interact with a strain field and two microwave fields. • The absorption and dispersion properties of the acoustic wave field are controlled by the use of the relative phase of the fields. • Phase-dependent acoustic wave absorption, transparency, and gain are obtained. • “Slow sound” and negative group velocities are also possible. - Abstract: We consider a high-Q single-crystal diamond nanomechanical resonator embedded with nitrogen-vacancy (NV) centers. We study the interaction of the transitions of the spin states of the ground state triplet of the NV centers with a strain field and two microwave fields in a Δ-type coupling configuration. We use the relative phase of the fields for the control of the absorption and dispersion properties of the acoustic wave field. Specifically, we show that by changing the relative phase of the fields, the acoustic field may exhibit absorption, transparency, gain and very interesting dispersive properties.

  7. Migration of O vacancies in α-quartz: The effect of excitons and electron holes

    International Nuclear Information System (INIS)

    Song, Jakyoung; Corrales, L. Rene; Kresse, Georg; Jonsson, Hannes

    2001-01-01

    We have used density-functional theory and the nudged elastic-band method to calculate migration pathways and estimated the activation energy for the diffusion of oxygen vacancies in α-quartz. While the energy barrier for the diffusion of a neutral vacancy is very high, 4.1 eV, the binding of a triplet-state exciton to the vacancy lowers the barrier to 1.7 eV and the attachment of a hole lowers the barrier to 1.9 eV, making the vacancy mobile at commonly used annealing temperatures

  8. Continuous determination of nitric oxide and nitrogen dioxide in the atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, S; Yamate, N; Mitsuzawa, S; Mori, M

    1966-10-01

    Continuous determinations of nitric oxide and nitrogen dioxide in that atmospheric air by the use of a modified Saltzman reagent is described. Measurement was made intermittently, once every 30 min., by an automatic continuous analyzer equipped with a single-path colorimeter. The response of the analyzer was obtained as an average of the concentration of nitrogen oxides over a period of 25 min. Two bubblers were used for absorbing nitrogen oxides into the modified Saltzman reagent, whose transmittance was measured for the determination. One bubbler was designed to absorb nitrogen dioxide, and the other, nitric oxide plus nitrogen dioxide after the oxidation of the nitric oxide by permanganate. The oxidizing efficiency of the permanganate was 96-100%. The acetic acid in the Saltzman reagent was replaced with n-propyl alcohol in the modified Saltzman reagent; the spontaneous coloration and corrosive quality of the reagent was decreased by this substitution. The concentration of nitric oxide was obtained from the difference between the two responses of the analyzer, while the concentration of nitrogen dioxide could be read directly from the indication of the recorder. The transmittance ratio method was applied to the measurements, accurate determinations were possible, even at high blank values. Therefore, the reagent was used repeatedly by cycling it on the basis of measuring the difference in the coloration of the reagent before and after the absorption of nitrogen oxides. The analyzer could be used for a long period without changing the reagent.

  9. Nitrogen diffusion in hafnia and the impact of nitridation on oxygen and hydrogen diffusion: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Sathiyanarayanan, Rajesh, E-mail: rajessat@in.ibm.com, E-mail: rajesh.sathiyanarayanan@gmail.com; Pandey, R. K.; Murali, K. V. R. M. [IBM Semiconductor Research and Development Center, Bangalore 560045 (India)

    2015-01-21

    Using first-principles simulations, we have computed incorporation energies and diffusion barriers of ammonia, the nitrogen molecule and atomic nitrogen in monoclinic hafnia (m-HfO{sub 2}). Our calculations show that ammonia is likely to dissociate into an NH{sub 2} molecular unit, whereas the nitrogen molecule remains as a molecule either in the interstitial space or at an oxygen lattice site. The lowest energy pathway for the diffusion of atomic nitrogen interstitials consists of the hopping of the nitrogen interstitial between neighboring three-coordinated lattice oxygen atoms that share a single Hf atom, and the barrier for such hops is determined by a switching mechanism. The substitutional nitrogen atom shows a preference for diffusion through the doubly positive oxygen vacancy-mediated mechanism. Furthermore, we have investigated the impact of nitrogen atoms on the diffusion barriers of oxygen and hydrogen interstitials in m-HfO{sub 2}. Our results show that nitrogen incorporation has a significant impact on the barriers for oxygen and hydrogen diffusion: nitrogen atoms attract oxygen and hydrogen interstitials diffusing in the vicinity, thereby slowing down (reducing) their diffusion (diffusion length)

  10. 2016 - Color & Infrared - Rutland and Windsor (0.15m)

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) This metadata record describes the acquisition and production of natural color and color infrared digital ground orthoimagery covering a portion...

  11. 2016 - Color & Infrared - Rutland and Windsor (0.3m)

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) This metadata record describes the acquisition and production of natural color and color infrared digital ground orthoimagery covering a portion...

  12. Two-step frequency conversion for connecting distant quantum memories by transmission through an optical fiber

    Science.gov (United States)

    Tamura, Shuhei; Ikeda, Kohei; Okamura, Kotaro; Yoshii, Kazumichi; Hong, Feng-Lei; Horikiri, Tomoyuki; Kosaka, Hideo

    2018-06-01

    Long-distance quantum communication requires entanglement between distant quantum memories. For this purpose, photon transmission is necessary to connect the distant memories. Here, for the first time, we develop a two-step frequency conversion process (from a visible wavelength to a telecommunication wavelength and back) involving the use of independent two-frequency conversion media where the target quantum memories are nitrogen-vacancy centers in diamonds (with an emission/absorption wavelength of 637.2 nm), and experimentally characterize the performance of this process acting on light from an attenuated CW laser. A total conversion efficiency of approximately 7% is achieved. The noise generated in the frequency conversion processes is measured, and the signal-to-noise ratio is estimated for a single photon signal emitted by a nitrogen-vacancy (NV) center. The developed frequency conversion system has future applications via transmission through a long optical fiber channel at a telecommunication wavelength for a quantum repeater network.

  13. The structure and properties of vacancies in Si nano-crystals calculated by real space pseudopotential methods

    International Nuclear Information System (INIS)

    Beckman, S.P.; Chelikowsky, James R.

    2007-01-01

    The structure and properties of vacancies in a 2 nm Si nano-crystal are studied using a real space density functional theory/pseudopotential method. It is observed that a vacancy's electronic properties and energy of formation are directly related to the local symmetry of the vacancy site. The formation energy for vacancies and Frenkel pair are calculated. It is found that both defects have lower energy in smaller crystals. In a 2 nm nano-crystal the energy to form a Frenkel pair is 1.7 eV and the energy to form a vacancy is no larger than 2.3 eV. The energy barrier for vacancy diffusion is examined via a nudged elastic band algorithm

  14. Oxygen vacancy defects in Ta{sub 2}O{sub 5} showing long-range atomic re-arrangements

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yuzheng; Robertson, John [Engineering Department, Cambridge University, Cambridge CB2 1PZ (United Kingdom)

    2014-03-17

    The structure, formation energy, and energy levels of the various oxygen vacancies in Ta{sub 2}O{sub 5} have been calculated using the λ phase model. The intra-layer vacancies give rise to unusual, long-range bonding rearrangements, which are different for each defect charge state. The 2-fold coordinated intra-layer vacancy is the lowest cost vacancy and forms a deep level 1.5 eV below the conduction band edge. The 3-fold intra-layer vacancy and the 2-fold inter-layer vacancy are higher cost defects, and form shallower levels. The unusual bonding rearrangements lead to low oxygen migration barriers, which are useful for resistive random access memory applications.

  15. FNTD radiation dosimetry system enhanced with dual-color wide-field imaging

    International Nuclear Information System (INIS)

    Akselrod, M.S.; Fomenko, V.V.; Bartz, J.A.; Ding, F.

    2014-01-01

    At high neutron and photon doses Fluorescent Nuclear Track Detectors (FNTDs) require operation in analog mode and the measurement results depend on individual crystal color center concentration (coloration). We describe a new method for radiation dosimetry using FNTDs, which includes non-destructive, automatic sensitivity calibration for each individual FNTD. In the method presented, confocal laser scanning fluorescent imaging of FNTDs is combined with dual-color wide field imaging of the FNTD. The calibration is achieved by measuring the color center concentration in the detector through fluorescence imaging and reducing the effect of diffuse reflection on the lapped surface of the FNTD by imaging with infra-red (IR) light. The dual-color imaging of FNTDs is shown to provide a good estimation of the detector sensitivity at high doses of photons and neutrons, where conventional track counting is impeded by track overlap. - Highlights: • New method and optical imaging head was developed for FNTD used at high doses. • Dual-color wide-field imaging used for color center concentration measurement. • Green fluorescence corrected by diffuse reflection used for sensitivity correction. • FNTD dose measurements performed in analog processing mode

  16. Nanoscale temperature sensing using single defects in diamond

    International Nuclear Information System (INIS)

    Philipp Neumann

    2014-01-01

    We experimentally demonstrate a novel nanoscale temperature sensing technique that is based on single atomic defects in diamonds, namely nitrogen vacancy color centers. Sample sizes range from millimeter down to a few tens of nanometers. In particular nanodiamonds were used as dispersed probes to acquire spatially resolved temperature profiles utilizing the sensitivity of the optically accessible electron spin level structure we achieve a temperature noise floor of 5mK/Mhz for bulk diamond and 130mK/Mhz for nanodiamonds and accuracies of 1mK. To this end we have developed a new decoupling technique in order to suppress to otherwise limiting effect of magnetic field fluctuations. In addition, high purity isotopically enriched 12C artificial diamonds is used. The high sensitivity to temperature changes adds to the well studied sensitivities to magnetic and electric fields and makes NV diamond a multipurpose nanoprobe. (author)

  17. Room temperature solid-state quantum bit with second-long memory

    Science.gov (United States)

    Kucsko, Georg; Maurer, Peter; Latta, Christian; Hunger, David; Jiang, Liang; Pastawski, Fernando; Yao, Norman; Bennet, Steven; Twitchen, Daniel; Cirac, Ignacio; Lukin, Mikhail

    2012-02-01

    Realization of stable quantum bits (qubits) that can be prepared and measured with high fidelity and that are capable of storing quantum information for long times exceeding seconds is an outstanding challenge in quantum science and engineering. Here we report on the realization of such a stable quantum bit using an individual ^13C nuclear spin within an isotopically purified diamond crystal at room temperature. Using an electronic spin associated with a nearby Nitrogen Vacancy color center, we demonstrate high fidelity initialization and readout of a single ^13C qubit. Quantum memory lifetime exceeding one second is obtained by using dissipative optical decoupling from the electronic degree of freedom and applying a sequence of radio-frequency pulses to suppress effects from the dipole-dipole interactions of the ^13C spin-bath. Techniques to further extend the quantum memory lifetime as well as the potential applications are also discussed.

  18. First-principles study of Ga-vacancy induced magnetism in β-Ga2O3.

    Science.gov (United States)

    Yang, Ya; Zhang, Jihua; Hu, Shunbo; Wu, Yabei; Zhang, Jincang; Ren, Wei; Cao, Shixun

    2017-11-01

    First principles calculations based on density functional theory were performed to study the electronic structure and magnetic properties of β-Ga 2 O 3 in the presence of cation vacancies. We investigated two kinds of Ga vacancies at different symmetry sites and the consequent structural distortion and defect states. We found that both the six-fold coordinated octahedral site and the four-fold coordinated tetrahedral site vacancies can lead to a spin polarized ground state. Furthermore, the calculation identified a relationship between the spin polarization and the charge states of the vacancies, which might be explained by a molecular orbital model consisting of uncompensated O 2- 2p dangling bonds. The calculations for the two vacancy systems also indicated a potential long-range ferromagnetic order which is beneficial for spintronics application.

  19. Color formation study of irradiated polymers by electron beam

    International Nuclear Information System (INIS)

    Nardi, Daniela Teves

    2004-01-01

    Color formation on national and commercial polymers (polymethyl methacrylate, polystyrene and polycarbonate) irradiated by electrons beam was investigated by colorimetry (CIELab), electron spectroscopy resonance (ESR), photoacoustic infrared spectroscopy (FTIR-PAS) and differential exploratory calorimetry (DSC). The heat effect on colorimetric properties was investigated after heating (110 deg C for 1 hour) of irradiated polymers at 150 kGy. The rule of oxygen in colorimetric properties of irradiated polycarbonate was investigated in the air presence and absence (p = 10 -3 mmHg). The visual aspect did not agree with colorimetric parameters only for polycarbonate. Yellow color and darkness were induced by radiation for all studied polymers varying only the intensity and behavior in function of post-irradiation time and heating. Polymethyl methacrylate and polystyrene ESR spectra showed that radicals could be responsible by yellow color centers. Wherever, in polycarbonate, color centers were not due radical species. The nature of color centers for any studied polymer was not study by FTIR-PAS because there were no changes in FTIR-PAS spectra neither in function of dose nor heating. Polycarbonate was the most radiosensible and polystyrene was the most radioresistant of all studied polymers in concern of colorimetric properties. (author)

  20. Energy Characteristics of Small Metal Clusters Containing Vacancies

    Science.gov (United States)

    Reva, V. I.; Pogosov, V. V.

    2018-02-01

    Self-consistent calculations of spatial distributions of electrons, potentials, and energies of dissociation, cohesion, vacancy formation, and electron attachment, as well as the ionization potential of solid Al N , Na N clusters ( N ≥ 254), and clusters containing a vacancy ( N ≥ 12) have been performed using a model of stable jellium. The contribution of a monovacancy to the energy of the cluster, the size dependences of the characteristics, and their asymptotic forms have been considered. The calculations have been performed on the SKIT-3 cluster at the Glushkov Institute of Cybernetics, National Academy of Sciences of Ukraine (Rpeak = 7.4 Tflops).

  1. Fabrication of all diamond scanning probes for nanoscale magnetometry

    OpenAIRE

    Appel Patrick; Neu Elke; Ganzhorn Marc; Barfuss Arne; Batzer Marietta; Gratz Micha; Tschoepe Andreas; Maletinsky Patrick

    2016-01-01

    The electronic spin of the nitrogen vacancy (NV) center in diamond forms an atomically sized, highly sensitive sensor for magnetic fields. To harness the full potential of individual NV centers for sensing with high sensitivity and nanoscale spatial resolution, NV centers have to be incorporated into scanning probe structures enabling controlled scanning in close proximity to the sample surface. Here, we present an optimized procedure to fabricate single-crystal, all-diamond scanning probes s...

  2. Effects of internal hydrogen on the vacancy loop formation probability in Al

    International Nuclear Information System (INIS)

    Bui, T.X.; Sirois, E.; Robertson, I.M.

    1990-04-01

    The effect of internal hydrogen on the formation of vacancy dislocation loops from heavy-ion generated displacement cascades in Al has been investigated. Samples of high-purity aluminum and aluminum containing 900 and 1300 appM of hydrogen were irradiated at room temperature with 50 keV Kr+ ions. The ion dose rate was typically 2 x 10 10 ions cm -2 sec -1 and the ion dose was between 10 11 and 10 13 ion cm -2 . Under these irradiation conditions, dislocation loops were observed in all compositions, although the formation probability was relatively low (less than 10 percent of the displacement cascades produced a vacancy loop). The loop formation probability was further reduced by the presence of hydrogen. No difference in the geometry or the size of the loops created in the hydrogen free and hydrogen charged samples was found. These results are difficult to interpret, and the explanation may lie in the distribution and form of the hydrogen. To account for the large hydrogen concentrations and from calculations of the energy associated with hydrogen entry into aluminum, it has been suggested that the hydrogen enters the aluminum lattice with an accompanying vacancy. This will create hydrogen-vacancy complexes in the material; two dimensional complexes have been detected in the hydrogen-charged, but unirradiated, samples by the small-angle x-ray scattering technique. The possibility of these complexes trapping the vacancies produced by the cascade process exists thus lowering the formation probability. However, such a mechanism must occur within the lifetime of the cascade. Alternatively, if a displacement cascade overlaps with the hydrogen-vacancy complexes, the lower atomic density of the region will result in an increase in the cascade volume (decrease in the local vacancy concentration) which will also reduce the loop formation probability

  3. High-temperature equilibrium vacancy formation in ceramic materials studied by positron annihilation

    International Nuclear Information System (INIS)

    Forster, M.; Claudy, W.; Hermes, H.; Major, J.; Schaefer, H.E.; Koch, M.; Maier, K.; Stoll, H.

    1992-01-01

    Positron lifetime measurements were used in order to study thermal vacancy formation in NiO, YBa 2 Cu 3 O 7-δ , α-Al 2 O 3 , MgO and 6H-SiC at high temperatures. In NiO two increases of the positron trapping rate at 450K and 1200K (po 2 =10 5 Pa) are attributed to the change of charge of neutral extrinsic Ni-vacancies (c ≅ 10 -4 ) into a negative charge state and to the nonstochiometric formation of charged Ni-vacancies at high temperatures. In YBa 2 Cu 3 O 7-δ the oxygen loss or uptake at T > 680K with an activation enthalpy of 1.03eV can be studied by the variation of the positron lifetime with temperature and oxygen partial pressure. In α-Al 2 O 3 the positrons are annihilated from the delocalized free state between 1000K and 2250K and no positron trapping of thermally formed vacancies was detected which may be understood in terms of the theoretically predicted low concentrations of thermal vacancies. In MgO and 6H-SiC positron lifetime measurements were performed up to temperatures of about 2000K

  4. Magnetic properties of ZnO nanowires with Li dopants and Zn vacancies

    Energy Technology Data Exchange (ETDEWEB)

    Guan, Xinhong; Cai, Ningning [Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), Ministry of Education, P.O. Box 72, Beijing 100876 (China); Yang, Chuanghua [School of Physics and Telecommunication Engineering, Shanxi University of Technology (SNUT), Hanzhong 723001, Shanxi (China); Chen, Jun [Beijing Applied Physics and Computational Mathematics, Beijing 100088 (China); Lu, Pengfei, E-mail: photon.bupt@gmail.com [Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), Ministry of Education, P.O. Box 72, Beijing 100876 (China)

    2016-04-30

    The electronic and magnetic properties of ZnO nanowire with Li dopants and vacancies have been investigated using first-principles density functional theory. It is found that the Zn vacancy can induce magnetism while increasing the formation energy of the system. However, the calculated results indicate that the introduction of Li-dopants will reduce the formation energy of system. We also have studied the magnetic couplings with vacancies as well as their corresponding configurations with Li-dopants for four configurations of ZnO nanowires. The results show that ferromagnetic properties can be improved/reversed after the introduction of Li-dopants. Ferromagnetic mechanism is originated from the fierce p–p hybridization of O near the Fermi level. We find that ferromagnetism of Li-doped ZnO nanowires with Zn vacancies can be realized at room temperature and they are promising spintronic materials. - Highlights: • Li-dopants will reduce the formation energy of ZnO nanowires with Zn vacancy. • The fierce p–p hybridization of O near Fermi level is responsible for FM properties. • Li-doped ZnO–V{sub Zn} nanowire is a promising FM semiconductor material.

  5. Understanding the presence of vacancy clusters in ZnO from a kinetic perspective

    Energy Technology Data Exchange (ETDEWEB)

    Bang, Junhyeok; Zhang, S. B., E-mail: zhangs9@rpi.edu, E-mail: kimyongsung@gmail.com [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Kim, Youg-Sung, E-mail: zhangs9@rpi.edu, E-mail: kimyongsung@gmail.com [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Department of Nano Science, University of Science and Technology, Daejeon 305-350 (Korea, Republic of); Park, C. H. [Research Center for Dielectric and Advanced Matter Physics, Pusan National University, Busan 609-735 (Korea, Republic of); Gao, F. [Pacific Northwest National Laboratory, MS K8-93, P.O. Box 999, Richland, Washington 99352 (United States)

    2014-06-23

    Vacancy clusters have been observed in ZnO by positron-annihilation spectroscopy (PAS), but detailed mechanisms are unclear. This is because the clustering happens in non-equilibrium conditions, for which theoretical method has not been well established. Combining first-principles calculation and kinetic Monte Carlo simulation, we determine the roles of non-equilibrium kinetics on the vacancies clustering. We find that clustering starts with the formation of Zn and O vacancy pairs (V{sub Zn} − Vo), which further grow by attracting additional mono-vacancies. At this stage, vacancy diffusivity becomes crucial: due to the larger diffusivity of V{sub Zn} compared to V{sub O}, more V{sub Zn}-abundant clusters are formed than V{sub O}-abundant clusters. The large dissociation energy barriers, e.g., over 2.5 eV for (V{sub Zn} − Vo), suggest that, once formed, it is difficult for the clusters to dissociate. By promoting mono-vacancy diffusion, thermal annealing will increase the size of the clusters. As the PAS is insensitive to V{sub O} donor defects, our results suggest an interpretation of the experimental data that could not have been made without the in-depth calculations.

  6. Luminescence of color centers in MgF{sub 2} crystals; Lyuminestsentsiya tsentrov okraski v kristallakh MgF{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Vakhidov, Sh A; Nuritdinov, I; Musaeva, M A [Inst. Yadernoj Fizili AN Uzbekistana, Tashkent (Uzbekistan)

    1999-08-01

    The photoluminescence characteristics of the proper radiation color centers of the MgF{sub 2} crystals are studied. The samples were irradiated by the {sup 60}Co source {gamma}-rays up to the dose 10{sup 7}Gy. The bands with the maxima in the area of 420, 460, 550 and 620 nm were identified, which are excited correspondingly in the bands with the maxima of 370, 320, 410 and 480 nm.

  7. Tricolore. A flexible color scale for ternary compositions

    DEFF Research Database (Denmark)

    2018-01-01

    tricolore is an R library providing a flexible color scale for the visualization of three-part/ternary compositions. Its main functionality is to color-code any ternary composition as a mixture of three primary colours and to draw a suitable color-key. tricolore flexibly adapts to different...... visualisation challenges via - discrete and continuous color support - support for unbalanced compositional data via centering - support for data with very narrow range via scaling - hue, chroma and lightness options...

  8. Primary and aggregate color centers in proton irradiated LiF crystals and thin films for luminescent solid state detectors

    Science.gov (United States)

    Piccinini, M.; Ambrosini, F.; Ampollini, A.; Bonfigli, F.; Libera, S.; Picardi, L.; Ronsivalle, C.; Vincenti, M. A.; Montereali, R. M.

    2015-04-01

    Proton beams of 3 MeV energy, produced by the injector of a linear accelerator for proton therapy, were used to irradiate at room temperature lithium fluoride crystals and polycrystalline thin films grown by thermal evaporation. The irradiation fluence range was 1011-1015 protons/cm2. The proton irradiation induced the stable formation of primary and aggregate color centers. Their formation was investigated by optical absorption and photoluminescence spectroscopy. The F2 and F3+ photoluminescence intensities, carefully measured in LiF crystals and thin films, show linear behaviours up to different maximum values of the irradiation fluence, after which a quenching is observed, depending on the nature of the samples (crystals and films). The Principal Component Analysis, applied to the absorption spectra of colored crystals, allowed to clearly identify the formation of more complex aggregate defects in samples irradiated at highest fluences.

  9. A comparative evaluation of nitrogen compounds in petroleum distillates

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Dheer; Chopra, Anju; Patel, Mitra Bhanu; Sarpal, Amarjit Singh [Indian Oil Corporation Limited, Faridabad (India). Research and Development Centre

    2011-07-15

    Although the concentration of nitrogen compounds in crude oil is relatively low, they can become more concentrated in petroleum distillates and poison the catalysts used in refining processes. They cause undesirable deposits, color formation and odor in products; they also contribute to air pollution and some are highly carcinogenic. The poisoned catalyst becomes deactivated for hydrodesulfurization and unable to remove sulfur from middle distillates. In order to understand the effect on catalytic processes, it is desirable to identify the nitrogen compounds in various petroleum distillates. This paper compares the nitrogen species profiles in different petroleum distillates using a nitrogen chemiluminescence detector. In addition, four different petroleum distillate samples from different refineries were analyzed to find the variation in their nitrogen profiles. The nitrogen compounds in petroleum distillate samples were identified as anilines, quinolines, indoles, and carbazoles and their alkyl derivatives. Quantitation was carried out against known reference standards. The quantitative data were compared to the total nitrogen content determined by elemental analysis. (orig.)

  10. Ionized zinc vacancy mediated ferromagnetism in copper doped ZnO thin films

    Directory of Open Access Journals (Sweden)

    Shi-Yi Zhuo

    2012-03-01

    Full Text Available This paper reports the origin of ferromagnetism in Cu-doped ZnO thin films. Room-temperature ferromagnetism is obtained in all the thin films when deposited at different oxygen partial pressure. An obviously enhanced peak corresponding to zinc vacancy is observed in the photoluminescence spectra, while the electrical spin resonance measurement implies the zinc vacancy is negative charged. After excluding the possibility of direct exchange mechanisms (via free carriers, we tentatively propose a quasi-indirect exchange model (via ionized zinc vacancy for Cu-doped ZnO system.

  11. Room temperature ferromagnetism and absorption red-shift in nitrogen-doped TiO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Gómez-Polo, C., E-mail: gpolo@unavarra.es [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Larumbe, S. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Monge, M. [Departamento de Química, Universidad de la Rioja, Centro de Investigación en Síntesis Química (CISQ), Complejo Científico Tecnológico, 26006 Logroño (Spain)

    2014-11-05

    Highlights: • N-doped TiO{sub 2} anatase nanoparticles were obtained by sol–gel. • The nanoparticle size, controlled by the N doping, determines lattice parameters. • Correlation between room temperature ferromagnetism and absorption red-shift. • Oxygen vacancies reinforce both phenomena. • Metal transition impurities contribute to the room temperature ferromagnetism. - Abstract: In this work, room-temperature ferromagnetism and the red-shift of the optical absorption is analyzed in nitrogen doped TiO{sub 2} semiconductor nanoparticles. The nanoparticles were synthesized by the sol–gel method using urea as the nitrogen source. Titanium Tetraisopropoxide (TTIP) was employed as the alkoxyde precursor and dissolved in ethanol. The as prepared gels were dried and calcined in air at 300 °C. Additionally, post-annealing treatments under vacuum atmosphere were performed to modify the oxygen stoichiometry of the samples. The anatase lattice parameters, analyzed by means of powder X-ray diffractometry, depend on the nanometer grain size of the nanoparticles (increase and decrease, respectively, of the tetragonal a and c lattice parameters with respect to the bulk values). The diffuse reflectance ultraviolet–visible (UV–Vis) absorbance spectra show a clear red-shift as consequence of the nitrogen and the occurrence of intragap energy levels. The samples display ferromagnetic features at room temperature that are reinforced with the nitrogen content and after the post annealings in vacuum. The results indicate a clear correlation between the room temperature ferromagnetism and the shift of the absorbance spectrum. In both phenomena, oxygen vacancies (either induced by the nitrogen doping or by the post vacuum annealings) play a dominant role. However, we conclude the existence of very low concentration of diluted transition metal impurities that determine the room ferromagnetic response (bound magnetic polaron BMP model). The contraction of the c soft axis

  12. Acceptor Type Vacancy Complexes In As-Grown ZnO

    International Nuclear Information System (INIS)

    Zubiaga, A.; Tuomisto, F.; Zuniga-Perez, J.

    2010-01-01

    One of the many technological areas that ZnO is interesting for is the construction of opto-electronic devices working in the blue-UV range as its large band gap (∼3.4 eV at 10 K) makes them suitable for that purpose. As-grown ZnO shows generally n-type conductivity partially due to the large concentration of unintentional shallow donors, like H, but impurities can also form complexes with acceptor type defects (Zn vacancy) leading to the creation of compensating defects. Recently, Li Zn and Na Zn acceptors have been measured and H could form similar type of defects. Doppler Broadening Positron Annihilation spectroscopy experimental results on the observation of Zn related vacancy complexes in ZnO thin films, as-grown, O implanted and Al doped will be presented. Results show that as-grown ZnO film show small Zn vacancy related complexed that could be related to presence of H as a unintentional doping element.

  13. Acceptor Type Vacancy Complexes In As-Grown ZnO

    Science.gov (United States)

    Zubiaga, A.; Tuomisto, F.; Zuñiga-Pérez, J.

    2010-11-01

    One of the many technological areas that ZnO is interesting for is the construction of opto-electronic devices working in the blue-UV range as its large band gap (˜3.4 eV at 10 K) makes them suitable for that purpose. As-grown ZnO shows generally n-type conductivity partially due to the large concentration of unintentional shallow donors, like H, but impurities can also form complexes with acceptor type defects (Zn vacancy) leading to the creation of compensating defects. Recently, LiZn and NaZn acceptors have been measured and H could form similar type of defects. Doppler Broadening Positron Annihilation spectroscopy experimental results on the observation of Zn related vacancy complexes in ZnO thin films, as-grown, O implanted and Al doped will be presented. Results show that as-grown ZnO film show small Zn vacancy related complexed that could be related to presence of H as a unintentional doping element.

  14. Electrolytic coloration of O22--doped NaCl crystals

    International Nuclear Information System (INIS)

    Qin Fang; Gu Hongen; Song Cuiying; Wang Na; Guo Meili; Wang Fen; Liu Jia

    2007-01-01

    O 2 2- -doped NaCl crystals are colored electrolytically by using a pointed cathode and a flat anode at various temperatures and voltages, which mainly benefit from appropriate coloration temperatures and voltages as well as anode structure of used electrolysis apparatus. Characteristic OH - , U, V 2 m , U A , V 2 , V 3 , O 2- -V a + complex, F, R 1 , R 2 and M absorption bands are observed in absorption spectra of the colored crystals. Production and conversion of color centers in electrolytic coloration is explained. Current-time curves for electrolytic colorations and their relationships with electrolytic colorations were given

  15. Optical patterning of trapped charge in nitrogen-doped diamond

    Science.gov (United States)

    Jayakumar, Harishankar; Henshaw, Jacob; Dhomkar, Siddharth; Pagliero, Daniela; Laraoui, Abdelghani; Manson, Neil B.; Albu, Remus; Doherty, Marcus W.; Meriles, Carlos A.

    2016-08-01

    The nitrogen-vacancy (NV) centre in diamond is emerging as a promising platform for solid-state quantum information processing and nanoscale metrology. Of interest in these applications is the manipulation of the NV charge, which can be attained by optical excitation. Here, we use two-colour optical microscopy to investigate the dynamics of NV photo-ionization, charge diffusion and trapping in type-1b diamond. We combine fixed-point laser excitation and scanning fluorescence imaging to locally alter the concentration of negatively charged NVs, and to subsequently probe the corresponding redistribution of charge. We uncover the formation of spatial patterns of trapped charge, which we qualitatively reproduce via a model of the interplay between photo-excited carriers and atomic defects. Further, by using the NV as a probe, we map the relative fraction of positively charged nitrogen on localized optical excitation. These observations may prove important to transporting quantum information between NVs or to developing three-dimensional, charge-based memories.

  16. A simple and rapid visual method for the determination of ammonia nitrogen in environmental waters using thymol

    Energy Technology Data Exchange (ETDEWEB)

    Okumura, M.; Fujinaga, K.; Seike, Y.; Honda, S. [Dept. of Material Science, Interdisciplinary Faculty of Science and Engineering, Shimane University, Matsue (Japan)

    1999-11-01

    Simple visual and spectrophotometric methods for the determination of ammonia nitrogen in water are proposed, based on the color development of indothymol blue formed between ammonia and thymol. The color development was accelerated by nitroprusside to complete in 3 min. This color development is remarkably rapid compared with that of the other conventional methods with indothymol blue and indophenol blue. The concentration range of ammonia nitrogen spectrophotometrically determined was 0.04-1.2 mg/L NH{sub 4}-N. The absorbance per 1 {mu}g NH{sub 4}-N was 0.0215 (molar absorptivity = 1.51 x 10{sup 4}) at 690 nm. The visual method not using any instrument as an in situ method in field works was developed based on the optimum conditions for the established spectrophotometric method. This visual method was successfully applied to the determination of ammonia nitrogen in environmental waters. (orig.)

  17. Vacancy-type defects in Al2O3/GaN structure probed by monoenergetic positron beams

    Science.gov (United States)

    Uedono, Akira; Nabatame, Toshihide; Egger, Werner; Koschine, Tönjes; Hugenschmidt, Christoph; Dickmann, Marcel; Sumiya, Masatomo; Ishibashi, Shoji

    2018-04-01

    Defects in the Al2O3(25 nm)/GaN structure were probed by using monoenergetic positron beams. Al2O3 films were deposited on GaN by atomic layer deposition at 300 °C. Temperature treatment above 800 °C leads to the introduction of vacancy-type defects in GaN due to outdiffusion of atoms from GaN into Al2O3. The width of the damaged region was determined to be 40-50 nm from the Al2O3/GaN interface, and some of the vacancies were identified to act as electron trapping centers. In the Al2O3 film before and after annealing treatment at 300-900 °C, open spaces with three different sizes were found to coexist. The density of medium-sized open spaces started to decrease above 800 °C, which was associated with the interaction between GaN and Al2O3. Effects of the electron trapping/detrapping processes of interface states on the flat band voltage and the defects in GaN were also discussed.

  18. Electron beam irradiation of gemstone for color enhancement

    Science.gov (United States)

    Idris, Sarada; Ghazali, Zulkafli; Hashim, Siti A'iasah; Ahmad, Shamshad; Jusoh, Mohd Suhaimi

    2012-09-01

    Numerous treatment of gemstones has been going on for hundreds of years for enhancing color and clarity of gems devoid of these attributes. Whereas previous practices included fraudulent or otherwise processes to achieve the color enhancement, the ionizing radiation has proven to be a reliable and reproducible technique. Three types of irradiation processes include exposure to gamma radiation, electron beam irradiation and the nuclear power plants. Electron Beam Irradiation of Gemstone is a technique in which a gemstone is exposed to highly ionizing radiation electron beam to knock off electrons to generate color centers culminating in introduction of deeper colors. The color centers may be stable or unstable. Below 9MeV, normally no radioactivity is introduced in the exposed gems. A study was conducted at Electron Beam Irradiation Centre (Alurtron) for gemstone color enhancement by using different kind of precious gemstones obtained from Pakistan. The study shows that EB irradiation not only enhances the color but can also improves the clarity of some type of gemstones. The treated stones included kunzite, tourmaline, topaz, quartz, aquamarine and cultured pearls. Doses ranging from 25 kGy to 200 KGy were employed to assess the influence of doses on color and clarity and to select the optimum doses. The samples used included both the natural and the faceted gemstones. It is concluded that significant revenue generation is associated with the enhancement of the color in clarity of gemstones which are available at very cheap price in the world market.

  19. Electron beam irradiation of gemstone for color enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Idris, Sarada; Ghazali, Zulkafli; Hashim, Siti A' iasah; Ahmad, Shamshad; Jusoh, Mohd Suhaimi [Malaysian Nuclear Agency, Bangi, Selangor (Malaysia); School of Chemicals and Material Engineering, NUST Islamabad (Pakistan); Malaysian Nuclear Agency, Bangi, Selangor (Malaysia)

    2012-09-26

    Numerous treatment of gemstones has been going on for hundreds of years for enhancing color and clarity of gems devoid of these attributes. Whereas previous practices included fraudulent or otherwise processes to achieve the color enhancement, the ionizing radiation has proven to be a reliable and reproducible technique. Three types of irradiation processes include exposure to gamma radiation, electron beam irradiation and the nuclear power plants. Electron Beam Irradiation of Gemstone is a technique in which a gemstone is exposed to highly ionizing radiation electron beam to knock off electrons to generate color centers culminating in introduction of deeper colors. The color centers may be stable or unstable. Below 9MeV, normally no radioactivity is introduced in the exposed gems. A study was conducted at Electron Beam Irradiation Centre (Alurtron) for gemstone color enhancement by using different kind of precious gemstones obtained from Pakistan. The study shows that EB irradiation not only enhances the color but can also improves the clarity of some type of gemstones. The treated stones included kunzite, tourmaline, topaz, quartz, aquamarine and cultured pearls. Doses ranging from 25 kGy to 200 KGy were employed to assess the influence of doses on color and clarity and to select the optimum doses. The samples used included both the natural and the faceted gemstones. It is concluded that significant revenue generation is associated with the enhancement of the color in clarity of gemstones which are available at very cheap price in the world market.

  20. Electron beam irradiation of gemstone for color enhancement

    International Nuclear Information System (INIS)

    Idris, Sarada; Ghazali, Zulkafli; Hashim, Siti A'iasah; Ahmad, Shamshad; Jusoh, Mohd Suhaimi

    2012-01-01

    Numerous treatment of gemstones has been going on for hundreds of years for enhancing color and clarity of gems devoid of these attributes. Whereas previous practices included fraudulent or otherwise processes to achieve the color enhancement, the ionizing radiation has proven to be a reliable and reproducible technique. Three types of irradiation processes include exposure to gamma radiation, electron beam irradiation and the nuclear power plants. Electron Beam Irradiation of Gemstone is a technique in which a gemstone is exposed to highly ionizing radiation electron beam to knock off electrons to generate color centers culminating in introduction of deeper colors. The color centers may be stable or unstable. Below 9MeV, normally no radioactivity is introduced in the exposed gems. A study was conducted at Electron Beam Irradiation Centre (Alurtron) for gemstone color enhancement by using different kind of precious gemstones obtained from Pakistan. The study shows that EB irradiation not only enhances the color but can also improves the clarity of some type of gemstones. The treated stones included kunzite, tourmaline, topaz, quartz, aquamarine and cultured pearls. Doses ranging from 25 kGy to 200 KGy were employed to assess the influence of doses on color and clarity and to select the optimum doses. The samples used included both the natural and the faceted gemstones. It is concluded that significant revenue generation is associated with the enhancement of the color in clarity of gemstones which are available at very cheap price in the world market.