WorldWideScience

Sample records for field emission property

  1. Effect of annealing on field emission properties of nanodiamond coating

    International Nuclear Information System (INIS)

    Zhai, C.X.; Yun, J.N.; Zhao, L.L.; Zhang, Z.Y.; Wang, X.W.; Chen, Y.Y.

    2011-01-01

    Field electron emission of detonation nanodiamond (ND) coated on a titanium substrate by electrophoretic deposition is investigated. It is found that thermal annealing can significantly improve the field emission properties of the ND layer, which can be mainly attributed to the formation of the TiC phase between diamond and Ti. The first-principles calculated results show that the formation of transition layers can lower the interface barrier and enhance the field electron emission of ND coating. Besides, the transformation of diamond to graphite after annealing has been revealed by Raman spectra. This transformation also benefits the electron emission enhancement.

  2. Effect of annealing on field emission properties of nanodiamond coating

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, C.X., E-mail: zhaicatty@126.co [School of Information Science and Technology, Northwest University, Xi' an 710127, Shaanxi (China); Yun, J.N.; Zhao, L.L.; Zhang, Z.Y.; Wang, X.W.; Chen, Y.Y. [School of Information Science and Technology, Northwest University, Xi' an 710127, Shaanxi (China)

    2011-03-01

    Field electron emission of detonation nanodiamond (ND) coated on a titanium substrate by electrophoretic deposition is investigated. It is found that thermal annealing can significantly improve the field emission properties of the ND layer, which can be mainly attributed to the formation of the TiC phase between diamond and Ti. The first-principles calculated results show that the formation of transition layers can lower the interface barrier and enhance the field electron emission of ND coating. Besides, the transformation of diamond to graphite after annealing has been revealed by Raman spectra. This transformation also benefits the electron emission enhancement.

  3. Fundamental properties of field emission-driven direct current microdischarges

    International Nuclear Information System (INIS)

    Rumbach, Paul; Go, David B.

    2012-01-01

    For half a century, it has been known that the onset of field emission in direct current microdischarges with gap sizes less than 10 μm can lead to breakdown at applied voltages far less than predicted by Paschen's law. It is still unclear how field emission affects other fundamental plasma properties at this scale. In this work, a one-dimensional fluid model is used to predict basic scaling laws for fundamental properties including ion density, electric field due to space charge, and current-voltage relations in the pre-breakdown regime. Computational results are compared with approximate analytic solutions. It is shown that field emission provides an abundance of cathode electrons, which in turn create large ion concentrations through ionizing collisions well before Paschen's criterion for breakdown is met. Breakdown due to ion-enhanced field emission occurs when the electric field due to space charge becomes comparable to the applied electric field. Simple scaling analysis of the 1D Poisson equation demonstrates that an ion density of n + ≈ 0.1V A ε 0 /qd 2 is necessary to significantly distort the electric field. Defining breakdown in terms of this critical ion density leads analytically to a simple, effective secondary emission coefficient γ ′ of the same mathematical form initially suggested by Boyle and Kisliuk [Phys. Rev. 97, 255 (1955)].

  4. Electrophoretic deposition and field emission properties of patterned carbon nanotubes

    International Nuclear Information System (INIS)

    Zhao Haifeng; Song Hang; Li Zhiming; Yuan Guang; Jin Yixin

    2005-01-01

    Patterned carbon nanotubes on silicon substrates were obtained using electrophoretic method. The carbon nanotubes migrated towards the patterned silicon electrode in the electrophoresis suspension under the applied voltage. The carbon nanotubes arrays adhered well on the silicon substrates. The surface images of carbon nanotubes were observed by scanning electron microscopy. The field emission properties of the patterned carbon nanotubes were tested in a diode structure under a vacuum pressure below 5 x 10 -4 Pa. The measured emission area was about 1.0 mm 2 . The emission current density up to 30 mA/cm 2 at an electric field of 8 V/μm has been obtained. The deposition of patterned carbon nanotubes by electrophoresis is an alternative method to prepare field emission arrays

  5. Field emission properties of an array of pyramidal structures

    Energy Technology Data Exchange (ETDEWEB)

    De Assis, Thiago A [Departamento de QuImica, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Borondo, F [Departamento de QuImica, Instituto Mixto de Ciencias Matematicas CSIC-UAM-UC3M-UCM, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); De Castilho, C M C; Brito Mota, F [Grupo de Fisica de SuperfIcies e Materiais, Instituto de Fisica, Universidade Federal da Bahia, Campus Universitario da Federacao, 40210-340, Salvador, BA (Brazil); Benito, R M, E-mail: t.albuquerque@uam.e, E-mail: f.borondo@uam.e, E-mail: caio@ufba.b, E-mail: fbmota@ufba.b, E-mail: rosamaria.benito@upm.e [Grupo de Sistemas Complejos, Departamento de Fisica y Mecanica, Escuela Tecnica Superior de Ingenieros Agronomos, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain)

    2009-10-07

    The properties and efficiency of the emission current density produced by a metallic array of pyramidal structures are investigated. The theoretical results obtained by numerical integration of the corresponding Laplace equation using a finite differences scheme offer useful information for the optimization of field emission devices based on cathodes with this geometry. Our study shows that the inter-pyramidal distance strongly affects the current density, and even more important for this issue is the protrusion characteristics of these structures. Another relevant, although less important, parameter determining this density is the anode-cathode distance. The effect of the array characteristics on the maximum local electric field intensity is also discussed.

  6. Field emission properties of ZnO nanosheet arrays

    International Nuclear Information System (INIS)

    Naik, Kusha Kumar; Rout, Chandra Sekhar; Khare, Ruchita; More, Mahendra A.; Chakravarty, Disha; Late, Dattatray J.; Thapa, Ranjit

    2014-01-01

    Electron emission properties of electrodeposited ZnO nanosheet arrays grown on Indium tin oxide coated glass substrates have been studied. Influence of oxygen vacancies on electronic structures and field emission properties of ZnO nanosheets are investigated using density functional theory. The oxygen vacancies produce unshared d electrons which form an impurity energy state; this causes shifting of Fermi level towards the vacuum, and so the barrier energy for electron extraction reduces. The ZnO nanosheet arrays exhibit a low turn-on field of 2.4 V/μm at 0.1 μA/cm 2 and current density of 50.1 μA/cm 2 at an applied field of 6.4 V/μm with field enhancement factor, β = 5812 and good field emission current stability. The nanosheet arrays grown by a facile electrodeposition process have great potential as robust high performance vertical structure electron emitters for future flat panel displays and vacuum electronic device applications

  7. Investigation of field emission properties of laser irradiated tungsten

    International Nuclear Information System (INIS)

    Akram, Mahreen; Bashir, Shazia; Hayat, Asma; Mahmood, Khaliq; Jalil, Sohail Abdul; Rafique, Muhammad Shahid

    2018-01-01

    Nd:YAG laser irradiation of Tungsten (W) has been performed in air at atmospheric pressure for four laser fluences ranging from 130 to 500 J/cm 2 . Scanning electron microscope analysis revealed the formation of micro and nanoscale surface features including cones, grains, mounds and pores. Field emission (FE) studies have been performed in a planar diode configuration under ultra-high vacuum conditions by recording I-V characteristics and plotting corresponding electric field (E) versus emission current density (J). The Fowler-Nordheim (FN) plots are found to be linear confirming the quantum mechanical tunneling phenomena for the structured targets. The irradiated samples at different fluences exhibit a turn-on field, field enhancement factor β and a maximum current density ranging from 5 to 8.5 V/μm, 1300 to 3490 and 107 to 350 μA/cm 2 , respectively. The difference in the FE properties is attributed to the variation in the nature and density of the grown structures at different fluences. (orig.)

  8. Field emission properties of the graphenated carbon nanotube electrode

    Energy Technology Data Exchange (ETDEWEB)

    Zanin, H., E-mail: hudson.zanin@bristol.ac.uk [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Faculdade de Engenharia Elétrica e Computação, Departamento de Semicondutores, Instrumentos e Fotônica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N. 400, CEP 13 083-852 Campinas, São Paulo (Brazil); Ceragioli, H.J.; Peterlevitz, A.C.; Baranauskas, Vitor [Faculdade de Engenharia Elétrica e Computação, Departamento de Semicondutores, Instrumentos e Fotônica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N. 400, CEP 13 083-852 Campinas, São Paulo (Brazil); Marciano, F.R.; Lobo, A.O. [Laboratory of Biomedical Nanotechnology/Institute of Research and Development at UNIVAP, Av. Shishima Hifumi, 2911, CEP 12244-000 Sao Jose dos Campos, SP (Brazil)

    2015-01-01

    Graphical abstract: - Highlights: • Facile method to prepare graphenated carbon nanotubes (g-CNTs). • The electric field emission behaviour of g-CNTs was studied. • g-CNTs show better emission current stability than non-graphenated CNTs. - Abstract: Reduced graphene oxide-coated carbon nanotubes (RGO-CNT) electrodes have been prepared by hot filament chemical vapour deposition system in one-step growth process. We studied RGO-CNT electrodes behaviour as cold cathode in field emission test. Our results show that RGO-CNT retain the low threshold voltage typical of CNTs, but with greatly improved emission current stability. The field emission enhancement value is significantly higher than that expected being caused by geometric effect (height divided by the radius of nanotube). This suggested that the field emission of this hybrid structure is not only from a single tip, but eventually it is from several tips with contribution of graphene nanosheets at CNT's walls. This phenomenon explains why the graphenated carbon nanotubes do not burn out as quickly as CNT does until emission ceases completely. These preliminaries results make nanocarbon materials good candidates for applications as electron sources for several devices.

  9. Emission Spectrum Property of Modulated Atom-Field Coupling System

    International Nuclear Information System (INIS)

    Gao Yun-Feng; Feng Jian; Li Yue-Ke

    2013-01-01

    The emission spectrum of a two-level atom interacting with a single mode radiation field in the case of periodic oscillation coupling coefficient is investigated. A general expression for the emission spectrum is derived. The numerical results for the initial field in pure number stare are calculated. It is found that the effect of the coupling coefficient modulation on the spectral structure is very obvious in the case of a low modulation frequency and larger amplitude when the initial field is vacuum, which is potentially useful for exploring a modulated light source. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  10. Outstanding field emission properties of wet-processed titanium dioxide coated carbon nanotube based field emission devices

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jinzhuo; Ou-Yang, Wei, E-mail: ouyangwei@phy.ecnu.edu.cn; Chen, Xiaohong; Guo, Pingsheng; Piao, Xianqing; Sun, Zhuo [Engineering Research Center for Nanophotonics and Advanced Instrument, Ministry of Education, Department of Physics, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062 (China); Xu, Peng; Wang, Miao [Department of Physics, Zhejiang University, 38 ZheDa Road, Hangzhou 310027 (China); Li, Jun [Department of Electronic Science and Technology, Tongji University, 4800 Caoan Road, Shanghai 201804 (China)

    2015-02-16

    Field emission devices using a wet-processed composite cathode of carbon nanotube films coated with titanium dioxide exhibit outstanding field emission characteristics, including ultralow turn on field of 0.383 V μm{sup −1} and threshold field of 0.657 V μm{sup −1} corresponding with a very high field enhancement factor of 20 000, exceptional current stability, and excellent emission uniformity. The improved field emission properties are attributed to the enhanced edge effect simultaneously with the reduced screening effect, and the lowered work function of the composite cathode. In addition, the highly stable electron emission is found due to the presence of titanium dioxide nanoparticles on the carbon nanotubes, which prohibits the cathode from the influence of ions and free radical created in the emission process as well as residual oxygen gas in the device. The high-performance solution-processed composite cathode demonstrates great potential application in vacuum electronic devices.

  11. As-pyrolyzed sugarcane bagasse possessing exotic field emission properties

    Science.gov (United States)

    Krishnia, Lucky; Yadav, Brajesh S.; Palnitkar, Umesh; Satyam, P. V.; Gupta, Bipin Kumar; Koratkar, Nikhil A.; Tyagi, Pawan K.

    2018-06-01

    The present study aims to demonstrate the application of sugarcane bagasse as an excellent field emitter. Field emission property of as-pyrolyzed sugarcane bagasse (p-SBg) before and after the plasma treatment has been investigated. It has been observed that electronic nature of p-SBg transformed from semiconducting to metallic after plasma treatment. Maximum current and turn-on field defined at 10 μA/cm2 was found to be 800 μA/cm2 and 2.2 V/μm for as-pyrolyzed sugarcane bagasse (p-SBg) and 25 μA/cm2 and 8.4 V/μm for H2-plasma treated p-SBg. These values are found to be better than the reported values for graphene and activated carbon. In this report, pyrolysis of bagasse has been carried in a thermal chemical vapor deposition (Th-CVD) system in inert argon atmosphere. Scanning electron microscopy (SEM), X-ray Diffraction (XRD), High-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) have been used to study the structure of both pre and post plasma-treated p-SBg bagasse's sample. HRTEM study reveals that carbonaceous structures such as 3D-nanographene oxide (3D-NGO), graphite nanodots (GNDs), carbon nanotubes (CNTs), and carbon onions are present in both pre-treated and plasma-treated p-SBg. Hence, we envision that the performed study will be a forwarding step to facilitate the application of p-SBg in display devices.

  12. The field emission properties from the pristine/B-doped graphene–C{sub 70} composite

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiaoju; Wang, Yan; Yang, Ping, E-mail: yangpingdm@ujs.edu.cn

    2017-06-28

    The aim of this paper is to implement a theoretical prediction and evaluation on the quality of graphene–C{sub 70} composite as cathode material. The pristine graphene–C{sub 70} composite and the B-doped graphene–C{sub 70} composites were constructed to investigate their field emission properties. The results suggest that the work function (WF) and ionization potential (IP) of the composites decrease with the increasing electric field. It implies that the electron emission becomes more and more easy. Under the field, the molecular orbital energy levels close to the vacuum level and their energy gap also has a declining trend. It means a good trend for improving the field emission properties of the composites. The above mentioned results show that the composites have the advanced capacity for electron emission and the potential for cathode material. It makes us believe that the composites will be the good field emission electron sources in the electronic device fabrication and the investigation can give a theoretical guidance for the corresponding experiments and may develop the application of fullerene for field emission. - Highlights: • We implement a theoretical prediction on graphene–C{sub 70} composite as cathode materials. • We detect the work function of the composite decrease with increasing electric field. • The ionization potential of the composites decrease with increasing electric field. • We find the molecular orbital energy level close to the vacuum level under the field. • The composites have the advanced capacity for electron emission as cathode material.

  13. Synthesis, field emission properties and optical properties of ZnSe nanoflowers

    Energy Technology Data Exchange (ETDEWEB)

    Xue, S.L., E-mail: slxue@dhu.edu.cn [Department of Applied Physics, College of Science, Donghua University, Shanghai 201620 (China); Wu, S.X.; Zeng, Q.Z.; Xie, P.; Gan, K.X.; Wei, J.; Bu, S.Y.; Ye, X.N.; Xie, L. [Department of Applied Physics, College of Science, Donghua University, Shanghai 201620 (China); Zou, R.J. [State Key Laboratory for Modification and Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620 (China); Zhang, C.M.; Zhu, P.F. [Department of Physics, School of Fundamental Studies, Shanghai University of Engineering Science, Shanghai 201620 (China)

    2016-03-01

    Graphical abstract: Unique ZnSe nanoflowers have been successfully synthesized by reaction of Se powder with Zn substrates. They are characterized by XRD, SEM, TEM, XPS, EDS and Raman spectroscopy and were single crystals with cubic zinc blende (ZB) structure. They also have excellent field emission properties and optical properties. - Highlights: • Novel ZnSe nanoflowers are grown on Zn foils. • ZnSe nanoflowers are characterized by XRD, SEM, TEM, XPS and Raman spectra. • ZnSe nanoflowers on Zn foils as cathodes possess good FE properties. - Abstract: ZnSe nanoflowers have been synthesized by reaction of Se powder with Zn substrates at low temperature. The as-prepared ZnSe nanoflowers were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray energy dispersive spectroscope (EDS) and Raman spectroscopy measurements. It was found that the morphologies of the as-prepared samples highly depended on reaction time. ZnSe nanoclusters and nanoflowers formed at 573 K when the reaction time was 20 and 60 min, respectively. The as-prepared ZnSe nanoflowers were composed of radically aligned ZnSe nanorods with smooth surfaces. The results of XRD, XPS, EDS, TEM and Raman showed that the as-prepared ZnSe nanocrystals were single crystals with cubic zinc blende (ZB) structure. The formation mechanism of the as-prepared ZnSe nanoflowers was also discussed. In addition, the as-prepared ZnSe nanoflowers had excellent electron emission properties. The turn-on field of the as-prepared ZnSe nanoflowers was 3.5 V/μm and the enhancement factor was 3499. The optical properties of the as-prepared ZnSe nanoflowers were also investigated. The results demonstrated that the as-prepared ZnSe nanoflowers were potential candidates for optoelectronic devices.

  14. Enhancement of field emission and photoluminescence properties of graphene-SnO2 composite nanostructures.

    Science.gov (United States)

    Ding, Jijun; Yan, Xingbin; Li, Jun; Shen, Baoshou; Yang, Juan; Chen, Jiangtao; Xue, Qunji

    2011-11-01

    In this study, the SnO(2) nanostructures and graphene-SnO(2) (G-SnO(2)) composite nanostructures were prepared on n-Si (100) substrates by electrophoretic deposition and magnetron sputtering techniques. The field emission of SnO(2) nanostructures is improved largely by depositing graphene buffer layer, and the field emission of G-SnO(2) composite nanostructures can also further be improved by decreasing sputtering time of Sn nanoparticles to 5 min. The photoluminescence (PL) spectra of the SnO(2) nanostructures revealed multipeaks, which are consistent with previous reports except for a new peak at 422 nm. Intensity of six emission peaks increased after depositing graphene buffer layer. Our results indicated that graphene can also be used as buffer layer acting as interface modification to simultaneity improve the field emission and PL properties of SnO(2) nanostructures effectively.

  15. Field emission properties of ring-shaped Si ridges with DLC coating

    Science.gov (United States)

    Prommesberger, Christian; Ławrowski, Robert; Langer, Christoph; Mecani, Mirgen; Huang, Yifeng; She, Juncong; Schreiner, Rupert

    2017-05-01

    We report on the fabrication and the emission characterization of single ring-shaped Si ridges with a coating of diamond-like carbon (DLC). The reactive ion etching and the subsequent inductively coupled plasma step were adjusted to realize ring-shaped Si ridges with a height of 7.5 μm respectively 15 μm and an apex radius of 20 - 25 nm. The samples were coated with a DLC layer (thickness ≈ 2 - 5 nm) by a filtered cathodic vacuum arc deposition system in order to lower the work function of the emitter and to improve the field emission characteristics. The field emission characterizations were done in diode configuration with cathode and anode separated by a 50 μm thick mica spacer. A higher emission current was carried out for the ring-shaped Si ridge in comparison to the point-shaped Si tips due to the increased emission area. The highest emission current of 0.22 μA at 1000 V was measured on a DLC-coated sample with the highest aspect ratio. No degradation of the emission current was observed in the plateau regime during a measurement period of 6 h. Finally, no decreasing performance of the field emission properties was found due to changes in the geometry or destructions.

  16. Water-processed carbon nanotube/graphene hybrids with enhanced field emission properties

    International Nuclear Information System (INIS)

    Song, Meng; Xu, Peng; Wang, Xu; Wu, Huizhen; Wang, Miao; Song, Yenan; Li, Zhenhua; Zhao, Pei; Shang, Xuefu

    2015-01-01

    Integrating carbon nanotubes (CNTs) and graphene into hybrid structures provides a novel approach to three dimensional (3D) materials with advantageous properties. Here we present a water-processing method to create integrated CNT/graphene hybrids and test their field emission properties. With an optimized mass ratio of CNTs to graphene, the hybrid shows a significantly enhanced field emission performance, such as turn-on electric field of 0.79 V/μm, threshold electric field of 1.05 V/μm, maximum current density of 0.1 mA/cm 2 , and field enhancement factor of ∼1.3 × 10 4 . The optimized mass ratio for field emission emphasizes the importance of both CNTs and graphene in the hybrid. We also hypothesize a possible mechanism for this enhanced field emission performance from the CNT/graphene hybrid. During the solution treatment, graphene oxide behaves as surfactant sheets for CNTs to form a well dispersed solution, which leads to a better organized 3D structure with more conducting channels for electron transport

  17. Water-processed carbon nanotube/graphene hybrids with enhanced field emission properties

    Energy Technology Data Exchange (ETDEWEB)

    Song, Meng; Xu, Peng; Wang, Xu; Wu, Huizhen; Wang, Miao, E-mail: peizhao@zju.edu.cn, E-mail: miaowang@css.zju.edu.cn [Department of Physics, Zhejiang University, Hangzhou 310027 (China); Song, Yenan; Li, Zhenhua; Zhao, Pei, E-mail: peizhao@zju.edu.cn, E-mail: miaowang@css.zju.edu.cn [Institute of Applied Mechanics, Zhejiang University, Hangzhou 310027 (China); Shang, Xuefu [Department of Physics, Faculty of Science, Jiangsu University, Zhenjiang 212013 (China)

    2015-09-15

    Integrating carbon nanotubes (CNTs) and graphene into hybrid structures provides a novel approach to three dimensional (3D) materials with advantageous properties. Here we present a water-processing method to create integrated CNT/graphene hybrids and test their field emission properties. With an optimized mass ratio of CNTs to graphene, the hybrid shows a significantly enhanced field emission performance, such as turn-on electric field of 0.79 V/μm, threshold electric field of 1.05 V/μm, maximum current density of 0.1 mA/cm{sup 2}, and field enhancement factor of ∼1.3 × 10{sup 4}. The optimized mass ratio for field emission emphasizes the importance of both CNTs and graphene in the hybrid. We also hypothesize a possible mechanism for this enhanced field emission performance from the CNT/graphene hybrid. During the solution treatment, graphene oxide behaves as surfactant sheets for CNTs to form a well dispersed solution, which leads to a better organized 3D structure with more conducting channels for electron transport.

  18. Excellent field emission properties of vertically oriented CuO nanowire films

    Directory of Open Access Journals (Sweden)

    Long Feng

    2018-04-01

    Full Text Available Oriented CuO nanowire films were synthesized on a large scale using simple method of direct heating copper grids in air. The field emission properties of the sample can be enhanced by improving the aspect ratio of the nanowires just through a facile method of controlling the synthesis conditions. Although the density of the nanowires is large enough, the screen effect is not an important factor in this field emission process because few nanowires sticking out above the rest. Benefiting from the unique geometrical and structural features, the CuO nanowire samples show excellent field emission (FE properties. The FE measurements of CuO nanowire films illustrate that the sample synthesized at 500 °C for 8 h has a comparatively low turn-on field of 0.68 V/μm, a low threshold field of 1.1 V/μm, and a large field enhancement factor β of 16782 (a record high value for CuO nanostructures, to the best of our knowledge, indicating that the samples are promising candidates for field emission applications.

  19. Enhanced field emission properties of vertically aligned double-walled carbon nanotube arrays

    International Nuclear Information System (INIS)

    Chen, Guohai; Shin, Dong Hoon; Lee, Cheol Jin; Iwasaki, Takayuki; Kawarada, Hiroshi

    2008-01-01

    Vertically aligned double-walled carbon nanotube (VA-DWCNT) arrays were synthesized by point-arc microwave plasma chemical vapor deposition on Cr/n-Si and SiO 2 /n-Si substrates. The outer tube diameters of VA-DWCNTs are in the range of 2.5-3.8 nm, and the average interlayer spacing is approximately 0.42 nm. The field emission properties of these VA-DWCNTs were studied. It was found that a VA-DWCNT array grown on a Cr/n-Si substrate had better field emission properties as compared with a VA-DWCNT array grown on a SiO 2 /n-Si substrate and randomly oriented DWCNTs, showing a turn-on field of about 0.85 V μm -1 at the emission current density of 0.1 μA cm -2 and a threshold field of 1.67 V μm -1 at the emission current density of 1.0 mA cm -2 . The better field emission performance of the VA-DWCNT array was mainly attributed to the vertical alignment of DWCNTs on the Cr/n-Si substrate and the low contact resistance between CNTs and the Cr/n-Si substrate

  20. Field-emission properties of transparent tungsten oxide nano-urchins

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Do-Hyung [Kyungpook National University, Nano-applied Physics Laboratory, Department of Physics, Daegu (Korea, Republic of)

    2012-09-15

    The field-emission properties of transparent tungsten oxide nano-urchin (NU) films deposited on conducting glass substrates were examined. The novel crystalline tungsten oxide NUs consisted of nanowires added to a spherical shell. The WO{sub 2.72} NUs showed better field-emission properties than the WO{sub 3} NUs with a low turn-on field of approximately 5.8 V/{mu}m and a current density as high as 1.3 mA/cm{sup 2} at 7.2 V/mm. The WO{sub x} NUs films could be used in FE applications using a large-area glass substrate without the need for a catalyst and a mechanical rubbing or lift-up process. These results have implications for the enhancement of FE properties by further tuning the WO{sub x} phases. (orig.)

  1. Experimental and theoretical study on field emission properties of zinc oxide nanoparticles decorated carbon nanotubes

    Science.gov (United States)

    Li, Xin; Zhou, Wei-Man; Liu, Wei-Hua; Wang, Xiao-Li

    2015-05-01

    Field emission properties of zinc oxide (ZnO) nanoparticles (NPs) decorated carbon nanotubes (CNTs) are investigated experimentally and theoretically. CNTs are in situ decorated with ZnO NPs during the growth process by chemical vapor deposition using a carbon source from the iron phthalocyanine pyrolysis. The experimental field emission test shows that the ZnO NP decoration significantly improves the emission current from 50 μA to 275 μA at 550 V and the reduced threshold voltage from 450 V to 350 V. The field emission mechanism of ZnO NPs on CNTs is theoretically studied by the density functional theory (DFT) combined with the Penn-Plummer method. The ZnO NPs reconstruct the ZnO-CNT structure and pull down the surface barrier of the entire emitter system to 0.49 eV so as to reduce the threshold electric field. The simulation results suggest that the presence of ZnO NPs would increase the LDOS near the Fermi level and increase the emission current. The calculation results are consistent with the experiment results. Project supported by the National Natural Science Foundation of China (Grant Nos. 91123018, 61172040, and 61172041) and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7277).

  2. Experimental and theoretical study on field emission properties of zinc oxide nanoparticles decorated carbon nanotubes

    International Nuclear Information System (INIS)

    Li Xin; Zhou Wei-Man; Liu Wei-Hua; Wang Xiao-Li

    2015-01-01

    Field emission properties of zinc oxide (ZnO) nanoparticles (NPs) decorated carbon nanotubes (CNTs) are investigated experimentally and theoretically. CNTs are in situ decorated with ZnO NPs during the growth process by chemical vapor deposition using a carbon source from the iron phthalocyanine pyrolysis. The experimental field emission test shows that the ZnO NP decoration significantly improves the emission current from 50 μA to 275 μA at 550 V and the reduced threshold voltage from 450 V to 350 V. The field emission mechanism of ZnO NPs on CNTs is theoretically studied by the density functional theory (DFT) combined with the Penn–Plummer method. The ZnO NPs reconstruct the ZnO–CNT structure and pull down the surface barrier of the entire emitter system to 0.49 eV so as to reduce the threshold electric field. The simulation results suggest that the presence of ZnO NPs would increase the LDOS near the Fermi level and increase the emission current. The calculation results are consistent with the experiment results. (paper)

  3. Optical and field emission properties of layer-structure GaN nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Zhen [Science School, Xi’an University of Technology, Xi’an 710048 (China); School of automation and Information Engineering, Xi’an University of Technology, Xi’an 710048 (China); Li, Enling, E-mail: Lienling@xaut.edu.cn [Science School, Xi’an University of Technology, Xi’an 710048 (China); Shi, Wei; Ma, Deming [Science School, Xi’an University of Technology, Xi’an 710048 (China)

    2014-08-15

    Highlights: • The layer-structure GaN nanowires with hexagonal-shaped cross-sections are produced via a process based on the CVD method. • The diameter of the layer-structure GaN nanowire gradually decreases from ∼500 nm to ∼200 nm along the wire axis. • The layer-structure GaN nanowire film possesses good field emission property. - Abstract: A layer-structure gallium nitride (GaN) nanowires, grown on Pt-coated n-type Si (1 1 1) substrate, have been synthesized using chemical vapor deposition (CVD). The results show: (1) SEM indicates that the geometry structure is layer-structure. HRTEM indicates that GaN nanowire’s preferential growth direction is along [0 0 1] direction. (2) The room temperature PL emission spectrum of the layer-structure GaN nanowires has a peak at 375 nm, which proves that GaN nanowires have potential application in light-emitting nano-devices. (3) Field-emission measurements show that the layer-structure GaN nanowires film has a low turn-on field of 4.39 V/μm (at room temperature), which is sufficient for electron emission devices, field emission displays and vacuum nano-electronic devices. The growth mechanism for GaN nanowires has also been discussed briefly.

  4. The Field Emission Properties of Graphene Aggregates Films Deposited on Fe-Cr-Ni alloy Substrates

    Directory of Open Access Journals (Sweden)

    Zhanling Lu

    2010-01-01

    Full Text Available The graphene aggregates films were fabricated directly on Fe-Cr-Ni alloy substrates by microwave plasma chemical vapor deposition system (MPCVD. The source gas was a mixture of H2 and CH4 with flow rates of 100 sccm and 12 sccm, respectively. The micro- and nanostructures of the samples were characterized by Raman scattering spectroscopy, field emission scanning electron microscopy (SEM, and transparent electron microscopy (TEM. The field emission properties of the films were measured using a diode structure in a vacuum chamber. The turn-on field was about 1.0 V/m. The current density of 2.1 mA/cm2 at electric field of 2.4 V/m was obtained.

  5. Morphology-control of VO2 (B) nanostructures in hydrothermal synthesis and their field emission properties

    International Nuclear Information System (INIS)

    Yin Haihong; Yu Ke; Zhang Zhengli; Zhu Ziqiang

    2011-01-01

    VO 2 (B) nanostructures were synthesized via a facile hydrothermal process using V 2 O 5 as source material and oxalic acid as reductant. Three nanostructures of nanorods, nanocarambolas and nanobundles were found existing in the products, and a continuous changing of morphology was found in the synthesis process, during which the proportion of these three types of nanostructures can be adjusted by altering the concentrations of oxalic acid. The microstructures were evaluated using X-ray diffraction and scanning and transmission electron microscopies, respectively. FE properties measurement of these three types of nanostructures showed that the nanobundles have the best field emission performance with a turn-on field of ∼1.4 V/μm and a threshold field of ∼5.38 V/μm. These characteristics make VO 2 (B) nanostructures a competitive cathode material in field emission devices.

  6. Field penetration induced charge redistribution effects on the field emission properties of carbon nanotubes - a first-principle study

    International Nuclear Information System (INIS)

    Chen, C.-W.; Lee, M.-H.; Clark, S.J.

    2004-01-01

    The effect of field penetration induced charge redistribution on the field emission properties of carbon nanotubes (CNTs) have been studied by the first-principle calculations. It is found that the carbon nanotube becomes polarized under external electric field leading to a charge redistribution. The resulting band bending induced by field penetration into the nanotube tip surface can further reduce the effective workfunction of the carbon nanotubes. The magnitude of the redistributed charge ΔQ is found to be nearly linear to the applied external field strength. In addition, we found that the capped (9, 0) zigzag nanotube demonstrates better field emission properties than the capped (5, 5) armchair nanotube due to the fact that the charge redistribution of π electrons along the zigzag-like tube axis is easier than for the armchair-like tube. The density of states (DOS) of the capped region of the nanotube is found to be enhanced with a value 30% higher than that of the sidewall part for the capped (5, 5) nanotube and 40% for the capped (9, 0) nanotube under an electric field of 0.33 V/A. Such enhancements of the DOS at the carbon nanotube tip show that electrons near the Fermi level will emit more easily due to the change of the surface band structure resulting from the field penetration in a high field

  7. Optimization of field emission properties of carbon nanotubes by Taguchi method

    International Nuclear Information System (INIS)

    Ting, J.-H.; Chang, C.-C.; Chen, S.-L.; Lu, D.-S.; Kung, C.-Y.; Huang, F.-Y.

    2006-01-01

    It is the purpose of this study to evaluate the field emission property of carbon nanotubes (CNTs) prepared by microwave plasma-enhanced chemical vapor deposition (MPCVD) method. Nickel layer of 5 nm in thickness on 20-nm thickness titanium nitride film was transformed into discrete islands after hydrogen plasma pretreatment. CNTs were then grown up on Ni-coated areas by MPCVD. Through the practice of Taguchi method, superior CNT films with very low emission onset electric field, about 0.7 V/μm (at J = 10 μA/cm 2 ), are attained without post-deposition treatment. It is found that microwave power has the most important influence on the field emission characteristics of CNT films. The increase of methane flow ratio will downgrade the degree of graphitization of CNT and thus its field emission characteristics. Scanning electron microscope and transmission electron microscopy (TEM) observation and energy dispersive X-ray spectrometer analysis reveal that CNT growth by MPCVD is based on tip-growth mechanism. TEM micrographs validate the hollow, bamboo-like structure of the multi-walled CNTs

  8. Emitter spacing effects on field emission properties of laser-treated single-walled carbon nanotube buckypapers

    Energy Technology Data Exchange (ETDEWEB)

    Chen Yiwen; Miao, Hsin-Yuan; Zhang Mei; Liang, Richard; Zhang, Chuck; Wang, Ben [High-Performance Materials Institute, Florida State University, Tallahassee, FL 32310 (United States); Lin, Ryan Jiyao, E-mail: kenymiao@thu.edu.tw, E-mail: mzhang@eng.fsu.edu [Department of Electrical and Computer Engineering, Rose-Hulman Institute of Technology, Terre Haute, IN 47803 (United States)

    2010-12-10

    Carbon nanotube (CNT) emitters on buckypaper were activated by laser treatment and their field emission properties were investigated. The pristine buckypapers and CNT emitters' height, diameter, and spacing were characterized through optical analysis. The emitter spacing directly impacted the emission results when the laser power and treatment times were fixed. The increasing emitter density increased the enhanced field emission current and luminance. However, a continuous and excessive increase of emitter density with spacing reduction generated the screening effect. As a result, the extended screening effect from the smaller spacing eventually crippled the field emission effectiveness. Luminance intensity and uniformity of field emission suggest that the highly effective buckypaper will have a density of 2500 emission spots cm{sup -2}, which presents an effective field enhancement factor of 3721 and a moderated screening effect of 0.005. Proper laser treatment is an effective post-treatment process for optimizing field emission, luminance, and durability performance for buckypaper cold cathodes.

  9. Theoretical modeling of the plasma-assisted catalytic growth and field emission properties of graphene sheet

    International Nuclear Information System (INIS)

    Sharma, Suresh C.; Gupta, Neha

    2015-01-01

    A theoretical modeling for the catalyst-assisted growth of graphene sheet in the presence of plasma has been investigated. It is observed that the plasma parameters can strongly affect the growth and field emission properties of graphene sheet. The model developed accounts for the charging rate of the graphene sheet; number density of electrons, ions, and neutral atoms; various elementary processes on the surface of the catalyst nanoparticle; surface diffusion and accretion of ions; and formation of carbon-clusters and large graphene islands. In our investigation, it is found that the thickness of the graphene sheet decreases with the plasma parameters, number density of hydrogen ions and RF power, and consequently, the field emission of electrons from the graphene sheet surface increases. The time evolution of the height of graphene sheet with ion density and sticking coefficient of carbon species has also been examined. Some of our theoretical results are in compliance with the experimental observations

  10. Enhanced field emission properties of carbon nanotube bundles confined in SiO2 pits

    Science.gov (United States)

    Lim, Yu Dian; Grapov, Dmitry; Hu, Liangxing; Kong, Qinyu; Tay, Beng Kang; Labunov, Vladimir; Miao, Jianmin; Coquet, Philippe; Aditya, Sheel

    2018-02-01

    It has been widely reported that carbon nanotubes (CNTs) exhibit superior field emission (FE) properties due to their high aspect ratios and unique structural properties. Among the various types of CNTs, random growth CNTs exhibit promising FE properties due to their reduced inter-tube screening effect. However, growing random growth CNTs on individual catalyst islands often results in spread out CNT bundles, which reduces overall field enhancement. In this study, significant improvement in FE properties in CNT bundles is demonstrated by confining them in microfabricated SiO2 pits. Growing CNT bundles in narrow (0.5 μm diameter and 2 μm height) SiO2 pits achieves FE current density of 1-1.4 A cm-2, which is much higher than for freestanding CNT bundles (76.9 mA cm-2). From the Fowler Nordheim plots, confined CNT bundles show a higher field enhancement factor. This improvement can be attributed to the reduced bundle diameter by SiO2 pit confinement, which yields bundles with higher aspect ratios. Combining the obtained outcomes, it can be conclusively summarized that confining CNTs in SiO2 pits yields higher FE current density due to the higher field enhancement of confined CNTs.

  11. Effect of the local morphology in the field emission properties of conducting polymer surfaces

    International Nuclear Information System (INIS)

    De Assis, T A; Borondo, F; Benito, R M; Losada, J C; Andrade, R F S; Miranda, J G V; De Souza, Nara C; De Castilho, C M C; De B Mota, F

    2013-01-01

    In this work, we present systematic theoretical evidence of a relationship between the point local roughness exponent (PLRE) (which quantifies the heterogeneity of an irregular surface) and the cold field emission properties (indicated by the local current density and the macroscopic current density) of real polyaniline (PANI) surfaces, considered nowadays as very good candidates in the design of field emission devices. The latter are obtained from atomic force microscopy data. The electric field and potential are calculated in a region bounded by the rough PANI surface and a distant plane, both boundaries held at distinct potential values. We numerically solve Laplace’s equation subject to appropriate Dirichlet’s condition. Our results show that local roughness reveals the presence of specific sharp emitting spots with a smooth geometry, which are the main ones responsible (but not the only) for the emission efficiency of such surfaces for larger deposition times. Moreover, we have found, with a proper choice of a scale interval encompassing the experimentally measurable average grain length, a highly structured dependence of local current density on PLRE, considering different ticks of PANI surfaces. (paper)

  12. The enhanced nucleation factors and field electron emission property of diamond synthesized by RF-PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Yang Guangmin [College of Physics, Changchun Normal University, Jilin Province, Changchun 130032 (China); Xu Qiang [Changchun Institute of Technology, Changchun 130021 (China); Wang Xin [Department of Materials Science, Key Laboratory of Mobile Materials, MOE, and State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Zheng Weitao, E-mail: wtzheng@jlu.edu.cn [Department of Materials Science, Key Laboratory of Mobile Materials, MOE, and State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Submicron-diamond, microcrystalline diamond, and nanocrystalline diamond were synthesized using different substrates and pretreatment methods. Black-Right-Pointing-Pointer Three techniques have been developed to create some density of diamond on substrate surfaces by PECVD deposition procedure. Black-Right-Pointing-Pointer The field electron emission property was also investigated. - Abstract: In this work, submicron-diamond (SD), microcrystalline diamond (MD), and nanocrystalline diamond (ND) were synthesized using different substrates and pretreatment methods. In order to investigate influencing factors on nucleation, three techniques have been developed to create some density of diamond on substrate surfaces: (a) with chemical-etching technique (NaOH water solution at 80 Degree-Sign C for 3, 8, 15 min, respectively), (b) (Co(NO{sub 3}){sub 3}/Mg(NO{sub 3}){sub 2}{center_dot}6H{sub 2}O or Fe(NO{sub 3}){sub 3}{center_dot}9H{sub 2}O/Mg(NO{sub 3}){sub 2}{center_dot}6H{sub 2}O alcohol solution) dripping on silicon substrate, and (c) NaCl substrate directly by following a same PECVD deposition procedure. Furthermore, the field electron emission property was also investigated.

  13. Laser induced surface structuring of Cu for enhancement of field emission properties

    Science.gov (United States)

    Akram, Mahreen; Bashir, Shazia; Jalil, Sohail Abdul; Shahid Rafique, Muhammad; Hayat, Asma; Mahmood, Khaliq

    2018-02-01

    The effect of Nd:YAG (1064 nm, 10 ns, 10 Hz) laser induced surface structuring of copper (Cu) for enhancement of field emission (FE) properties has been investigated. X-ray diffraction analysis was employed to investigate the surface structural and compositional modifications. The surface structuring was explored by scanning electron microscope investigation. FE properties were studied under UHV conditions in a parallel plate configuration of planar un-irradiated Cu anode and laser irradiated Cu cathode. The Fowler-Nordheim plots were drawn to confirm the dominance of FE behavior of the measured I-V characteristics. The obtained values of turn-on field ‘E o’, field enhancement factor ‘β’ and maximum current density ‘J max’ come out to be to be in the range of 5.5-8.5 V μm-1, 1380-2730 and 147-375 μA cm-2 respectively for the Cu samples irradiated at laser irradiance ranging from 13 to 50 GW cm-2. The observed enhancement in the FE properties has been correlated with the growth of various surface structures such as ridged protrusions, cones and pores/tiny holes. The porous morphology is found to be responsible for a significant enhancement in the FE parameters.

  14. Field Emission Property of Double-walled Carbon Nanotubes Related to Purification and Transmittance

    International Nuclear Information System (INIS)

    Ahn, KiTae; Jang, HyunChul; Hong, Wanshick; Park, Kyoungwan; Sok, Junghyun; Lyu, SeungChul; Lee, Hansung; Lee, Naesung; Han, Moonsup; Park, Yunsun

    2011-01-01

    Double-walled carbon nanotubes (DWCNTs) with high purity were produced by the catalytic decomposition of tetrahydrofuran (THF) using a Fe-Mo/MgO catalyst at 800°C. The as-synthesized DWCNTs typically have catalytic impurities and amorphous carbon, which were removed by a two-step purification process consisting of acid treatment and oxidation. In the acid treatment, metallic catalysts were removed in HCl at room temperature for 5 hr with magnetic stirring. Subsequently, the oxidation, using air at 380°C for 5 hr in the a vertical-type furnace, was used to remove the amorphous carbon particles. The DWCNT suspension was prepared by dispersing the purified DWCNTs in the aqueous sodium dodecyl sulfate solution with horn-type sonication. This was then air-sprayed on ITO glass to fabricate DWCNT field emitters. The field emission properties of DWCNT films related to transmittance were studied. This study provides the possibility of the application of large-area transparent CNT field emission cathodes.

  15. Effectively Improved Field Emission Properties of Multiwalled Carbon Nanotubes/Graphenes Composite Field Emitter by Covering on the Si Pyramidal Structure

    DEFF Research Database (Denmark)

    Chen, Leifeng; Yu, Hua; Zhong, Jiasong

    2015-01-01

    The composite nanostructure emitter of multiwalled carbon nanotubes and graphenes was deposited on pyramidal silicon substrate by the simple larger scale electrophoretic deposition process. The field emission (FE) properties of the composite/pyramidal Si device were greatly improved compared...

  16. Method of synthesizing small-diameter carbon nanotubes with electron field emission properties

    Science.gov (United States)

    Liu, Jie (Inventor); Du, Chunsheng (Inventor); Qian, Cheng (Inventor); Gao, Bo (Inventor); Qiu, Qi (Inventor); Zhou, Otto Z. (Inventor)

    2009-01-01

    Carbon nanotube material having an outer diameter less than 10 nm and a number of walls less than ten are disclosed. Also disclosed are an electron field emission device including a substrate, an optionally layer of adhesion-promoting layer, and a layer of electron field emission material. The electron field emission material includes a carbon nanotube having a number of concentric graphene shells per tube of from two to ten, an outer diameter from 2 to 8 nm, and a nanotube length greater than 0.1 microns. One method to fabricate carbon nanotubes includes the steps of (a) producing a catalyst containing Fe and Mo supported on MgO powder, (b) using a mixture of hydrogen and carbon containing gas as precursors, and (c) heating the catalyst to a temperature above 950.degree. C. to produce a carbon nanotube. Another method of fabricating an electron field emission cathode includes the steps of (a) synthesizing electron field emission materials containing carbon nanotubes with a number of concentric graphene shells per tube from two to ten, an outer diameter of from 2 to 8 nm, and a length greater than 0.1 microns, (b) dispersing the electron field emission material in a suitable solvent, (c) depositing the electron field emission materials onto a substrate, and (d) annealing the substrate.

  17. Facile solution synthesis of hexagonal Alq3 nanorods and their field emission properties.

    Science.gov (United States)

    Hu, Jin-Song; Ji, Heng-Xing; Cao, An-Min; Huang, Zheng-Xi; Zhang, Yang; Wan, Li-Jun; Xia, An-Dong; Yu, Da-Peng; Meng, Xiang-Min; Lee, Shuit-Tong

    2007-08-07

    A facile self-assembly growth route assisted by surfactant has been developed to synthesize tris(8-hydroxyquinoline)aluminium (Alq(3)) nanorods with regular hexagonal shape and good crystallinity, which exhibit field-emission characteristics with a very low turn-on field of ca. 3.1 V microm(-1) and a high field-enhancement factor of ca. 1300.

  18. Modeling on the cathodoluminescence properties of the thin film phosphors for field emission flat panel displays

    Science.gov (United States)

    Cho, Kyu-Gong

    2000-12-01

    utilized to optimize the thin film phosphor properties for the application of field emission flat panel displays.

  19. Evaluation of field emission properties from multiple-stacked Si quantum dots

    International Nuclear Information System (INIS)

    Takeuchi, Daichi; Makihara, Katsunori; Ohta, Akio; Ikeda, Mitsuhisa; Miyazaki, Seiichi

    2016-01-01

    Multiple-stacked Si quantum dots (QDs) with ultrathin SiO 2 interlayers were formed on ultrathin SiO 2 layers by repeating a process sequence consisting of the formation of Si-QDs by low pressure chemical vapor deposition using a SiH 4 gas and the surface oxidation and subsequent surface modification by remote hydrogen and oxygen plasmas, respectively. To clarify the electron emission mechanism from multiple-stacked Si-QDs covered with an ultrathin Au top electrode, the energy distribution of the emitted electrons and its electric field dependence was measured using a hemispherical electron energy analyzer in an X-ray photoelectron spectroscopy system under DC bias application to the multiple-stacked Si-QD structure. At − 6 V and over, the energy distributions reached a peak at ~ 2.5 eV with a tail toward the higher energy side. While the electron emission intensity was increased exponentially with an increase in the applied DC bias, there was no significant increase in the emission peak energy. The observed emission characteristics can be interpreted in terms of field emissions from the second and/or third topmost Si-QDs resulting from the electric concentration there. - Highlights: • Electron field emission from 6-fold stack of Si-QDs has been evaluated. • AFM measurements show the local electron emission from individual Si-QDs. • Impact of applied bias on the electron emission energy distribution was investigated.

  20. Improved field emission properties of carbon nanotubes grown on stainless steel substrate and its application in ionization gauge

    Science.gov (United States)

    Li, Detian; Cheng, Yongjun; Wang, Yongjun; Zhang, Huzhong; Dong, Changkun; Li, Da

    2016-03-01

    Vertically aligned carbon nanotube (CNT) arrays were fabricated by chemical vapor deposition (CVD) technique on different substrates. Microstructures and field emission characteristics of the as-grown CNT arrays were investigated systematically, and its application in ionization gauge was also evaluated preliminarily. The results indicate that the as-grown CNT arrays are vertically well-aligned relating to the substrate surfaces, but the CNTs grown on stainless steel substrate are longer and more crystalline than the ones grown on silicon wafer substrate. The field emission behaviors of the as-grown CNT arrays are strongly dependent upon substrate properties. Namely, the CNT array grown on stainless steel substrate has better field emission properties, including lower turn on and threshold fields, better emission stability and repeatability, compared with the one grown on silicon wafer substrate. The superior field emission properties of the CNT array grown on stainless steel substrate are mainly attributed to low contact resistance, high thermal conductivity, good adhesion strength, etc. In addition, the metrological behaviors of ionization gauge with the CNT array grown on stainless steel substrate as an electron source were investigated, and this novel cathode ionization gauge extends the lower limit of linear pressure measurement to 10-8 Pa, which is one order of magnitude lower than the result reported for the same of gauge with CNT cathode.

  1. Improved field emission properties of carbon nanotubes grown on stainless steel substrate and its application in ionization gauge

    Energy Technology Data Exchange (ETDEWEB)

    Li, Detian; Cheng, Yongjun [Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Wang, Yongjun, E-mail: wyjlxlz@163.com [Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Zhang, Huzhong [Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Dong, Changkun [Institute of Micro-Nano Structures and Optoelectronics, Wenzhou University, Wenzhou 325035 (China); Li, Da [Division of Advanced Nanomaterials, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215125 (China)

    2016-03-01

    Graphical abstract: - Highlights: • The high quality CNT arrays were successfully grown on conductive stainless steel substrates. • The CNT array grown on stainless steel substrate exhibited superior field emission properties. • A high vacuum level about 10–8 Pa was measured by resultant CNT-based ionization gauge. • The ionization gauge with CNT cathode demonstrated a high stability. - Abstract: Vertically aligned carbon nanotube (CNT) arrays were fabricated by chemical vapor deposition (CVD) technique on different substrates. Microstructures and field emission characteristics of the as-grown CNT arrays were investigated systematically, and its application in ionization gauge was also evaluated preliminarily. The results indicate that the as-grown CNT arrays are vertically well-aligned relating to the substrate surfaces, but the CNTs grown on stainless steel substrate are longer and more crystalline than the ones grown on silicon wafer substrate. The field emission behaviors of the as-grown CNT arrays are strongly dependent upon substrate properties. Namely, the CNT array grown on stainless steel substrate has better field emission properties, including lower turn on and threshold fields, better emission stability and repeatability, compared with the one grown on silicon wafer substrate. The superior field emission properties of the CNT array grown on stainless steel substrate are mainly attributed to low contact resistance, high thermal conductivity, good adhesion strength, etc. In addition, the metrological behaviors of ionization gauge with the CNT array grown on stainless steel substrate as an electron source were investigated, and this novel cathode ionization gauge extends the lower limit of linear pressure measurement to 10{sup −8} Pa, which is one order of magnitude lower than the result reported for the same of gauge with CNT cathode.

  2. Synthesis, property and field-emission behaviour of amorphous polypyrrole nanowires

    International Nuclear Information System (INIS)

    Yan Hongliang; Zhang Lan; Shen Jiaoyan; Chen Zhaojia; Shi Gaoquan; Zhang Binglin

    2006-01-01

    Polypyrrole nanowires have been electrosynthesized by direct oxidation of 0.1 mol l -1 pyrrole in a medium of 75% isopropyl alcohol + 20% boron trifluoride diethyl etherate + 5% poly (ethylene glycol) (by volume) using porous alumina membranes as the templates. The as-prepared nanowires had a smooth surface and uniform diameter and were arranged in an orderly manner in a high density. The conductivity of a single nanowire was measured by the four-electrode technique to be 23.4 S cm -1 at room temperature. The field emission devices based on the nanowire array were fabricated and their operations were explored. The experimental results indicated that the field emission characteristics of the devices fitted well to the Fowler-Nordheim model of emission. The turn-on electric field was only 1.2 V μm -1 and the current density reached 200 μA cm -2 at 2.6 V μm -1

  3. Field emission properties of low-density carbon nanotubes prepared on anodic aluminum-oxide template

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Soo-Hwan [Samsung Advanced Institute of Technology, Suwon (Korea, Republic of); Lee, Kun-Hong [Pohang University of Science and Technology, Pohang (Korea, Republic of)

    2004-08-15

    Anodic aluminum-oxide (AAO) templates were fabricated by two-step anodizing an Al film. After the Co catalyst had been electrochemically deposited onto the bottom of the AAO template, carbon nanotubes (CNTs) were grown by using catalytic pyrolysis of C{sub 2}H{sub 2} and H{sub 2} at 650 .deg. C. Overgrowth of CNTs with low density on the AAO templates was observed. The field-emission measurements on the samples showed a turn-on field of 2.17 V/mum and a field enhancement factor of 5700. The emission pattern on a phosphor screen was quite homogeneous over the area at a relatively low electric field.

  4. A Platform to Optimize the Field Emission Properties of Carbon Nanotube Based Fibers (Postprint)

    Science.gov (United States)

    2016-08-25

    characterization of key metrics , such as effective field enhancement factor and emission area. It is imperative to address issues relating to whether...important are the effects of Coulomb repulsion between adjacent emitting CNTs on the FE characteristics? When do space-charge effects become important and

  5. Influence of high-energy electron irradiation on field emission properties of multi-walled carbon nanotubes (MWCNTs) films

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Sandip S. [Center for Advanced Studies in Material Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007 (India); Koinkar, Pankaj M. [Center for International Cooperation in Engineering Education (CICEE), University of Tokushima, 2-1 Minami-Josanjima-Cho, Tokushima 770-8506 (Japan); Dhole, Sanjay D. [Center for Advanced Studies in Material Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007 (India); More, Mahendra A., E-mail: mam@physics.unipune.ac.i [Center for Advanced Studies in Material Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007 (India); Murakami, Ri-ichi, E-mail: murakami@me.tokushima-u.ac.j [Department of Mechanical Engineering, University of Tokushima, 2-1 Minami-Josanjima-Cho, Tokushima 770-8506 (Japan)

    2011-04-15

    The effect of very high energy electron beam irradiation on the field emission characteristics of multi-walled carbon nanotubes (MWCNTs) has been investigated. The MWCNTs films deposited on silicon (Si) substrates were irradiated with 6 MeV electron beam at different fluence of 1x10{sup 15}, 2x10{sup 15} and 3x10{sup 15} electrons/cm{sup 2}. The irradiated films were characterized using scanning electron microscope (SEM) and micro-Raman spectrometer. The SEM analysis clearly revealed a change in surface morphology of the films upon irradiation. The Raman spectra of the irradiated films show structural damage caused by the interaction of high-energy electrons. The field emission studies were carried out in a planar diode configuration at the base pressure of {approx}1x10{sup -8} mbar. The values of the threshold field, required to draw an emission current density of {approx}1 {mu}A/cm{sup 2}, are found to be {approx}0.52, 1.9, 1.3 and 0.8 V/{mu}m for untreated, irradiated with fluence of 1x10{sup 15}, 2x10{sup 15} and 3x10{sup 15} electrons/cm{sup 2}. The irradiated films exhibit better emission current stability as compared to the untreated film. The improved field emission properties of the irradiated films have been attributed to the structural damage as revealed from the Raman studies.

  6. Surface properties and field emission characteristics of chemical vapor deposition diamond grown on Fe/Si substrates

    International Nuclear Information System (INIS)

    Hirakuri, Kenji; Yokoyama, Takahiro; Enomoto, Hirofumi; Mutsukura, Nobuki; Friedbacher, Gernot

    2001-01-01

    Electron field emission characteristics of diamond grains fabricated on iron dot-patterned silicon (Fe/Si) substrates at different methane concentrations have been investigated. The characteristics of the samples could be improved by control of the methane concentration during diamond fabrication. Etching treatment of the as-grown diamond has enhanced the emission properties both with respect to current and threshold voltage. In order to study the influence of etching effects on the field emission characteristics, the respective surfaces were studied by Raman spectroscopy, Auger electron spectroscopy, and electron spectroscopy for chemical analysis (ESCA). ESCA revealed intensive graphite and FeO x peaks on the sample surface grown at high methane concentration. For the etched samples, the peaks of diamond and silicon carbide were observed, and the peaks of nondiamond carbon disappeared. The experimental results show that the etching process removes graphitic and nondiamond carbon components. [copyright] 2001 American Institute of Physics

  7. Improved field emission properties of thiolated multi-wall carbon nanotubes on a flexible carbon cloth substrate

    International Nuclear Information System (INIS)

    Chuang, F T; Chen, P Y; Cheng, T C; Chien, C H; Li, B J

    2007-01-01

    In this paper we report the observation of enhanced field emission properties from thiolated multi-wall carbon nanotubes (MWCNTs) produced by a simple and effective two-step chemical surface modification technique. This technique implements carboxylation and thiolation on the MWCNTs synthesized by microwave plasma chemical vapor deposition (MPCVD) on the flexible carbon cloth substrate. The resulting thiolated MWCNTs were found to have a very low threshold field value of 1.25 V μm -1 and a rather high field enhancement factor of 1.93 x 10 4 , which are crucial for applications in versatile vacuum microelectronics

  8. Effects of potassium hydroxide post-treatments on the field-emission properties of thermal chemical vapor deposited carbon nanotubes.

    Science.gov (United States)

    Lee, Li-Ying; Lee, Shih-Fong; Chang, Yung-Ping; Hsiao, Wei-Shao

    2011-12-01

    In this study, a simple potassium hydroxide treatment was applied to functionalize the surface and to modify the structure of multi-walled carbon nanotubes grown on silicon substrates by thermal chemical vapor deposition. Scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive spectrometry were employed to investigate the mechanism causing the modified field-emission properties of carbon nanotubes. From our experimental data, the emitted currents of carbon nanotubes after potassium hydroxide treatment are enhanced by more than one order of magnitude compared with those of untreated carbon nanotubes. The emitted current density of carbon nanotubes increases from 0.44 mA/cm2 to 7.92 mA/cm2 after 30 minutes KOH treatment. This technique provides a simple, economical, and effective way to enhance the field-emission properties of carbon nanotubes.

  9. Effect of Substrate Morphology on Growth and Field Emission Properties of Carbon Nanotube Films

    Directory of Open Access Journals (Sweden)

    Kumar Vikram

    2008-01-01

    Full Text Available AbstractCarbon nanotube (CNT films were grown by microwave plasma-enhanced chemical vapor deposition process on four types of Si substrates: (i mirror polished, (ii catalyst patterned, (iii mechanically polished having pits of varying size and shape, and (iv electrochemically etched. Iron thin film was used as catalytic material and acetylene and ammonia as the precursors. Morphological and structural characteristics of the films were investigated by scanning and transmission electron microscopes, respectively. CNT films of different morphology such as vertically aligned, randomly oriented flowers, or honey-comb like, depending on the morphology of the Si substrates, were obtained. CNTs had sharp tip and bamboo-like internal structure irrespective of growth morphology of the films. Comparative field emission measurements showed that patterned CNT films and that with randomly oriented morphology had superior emission characteristics with threshold field as low as ~2.0 V/μm. The defective (bamboo-structure structures of CNTs have been suggested for the enhanced emission performance of randomly oriented nanotube samples.

  10. Field emission electronics

    CERN Document Server

    Egorov, Nikolay

    2017-01-01

    This book is dedicated to field emission electronics, a promising field at the interface between “classic” vacuum electronics and nanotechnology. In addition to theoretical models, it includes detailed descriptions of experimental and research techniques and production technologies for different types of field emitters based on various construction principles. It particularly focuses on research into and production of field cathodes and electron guns using recently developed nanomaterials and carbon nanotubes. Further, it discusses the applications of field emission cathodes in new technologies such as light sources, flat screens, microwave and X-ray devices.

  11. Enhanced field emission properties of tilted graphene nanoribbons on aggregated TiO{sub 2} nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Hung, Shang-Chao, E-mail: schung99@gmail.com [Department of Information Technology & Communication, Shih Chien University Kaohsiung Campus, Neimen, Kaohsiung 845, Taiwan (China); Chen, Yu-Jyun [Graduate Institute of Electro-Optical Engineering & Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China)

    2016-07-15

    Highlights: • Graphene nanoribbons (GNBs) slanted on aggregate TiO{sub 2} nanotube (A-TNTs) as field-emitters. • Turn-on electric field and field enhancement factor β are dependent on the substrate morphology. • Various quantities of GNRs are deposited on top of A-TNTs (GNRs/A-TNTs) with different morphologies. • With an increase of GNBs compositions, the specimens' turn-on electric field is reduced to 2.8 V/μm. • The field enhancement factor increased rapidly to about 1964 with the addition of GNRs. - Abstract: Graphene nanoribbons (GNRs) slanted on aggregate TiO{sub 2} nanotube arrays (A-TNTs) with various compositions as field-emitters are reported. The morphology, crystalline structure, and composition of the as-obtained specimens were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Raman spectrometry. The dependence of the turn-on electric field and the field enhancement factor β on substrate morphology was studied. An increase of GNRs reduces the specimens’ turn-on electric field to 2.8 V/μm and the field enhancement factor increased rapidly to about 1964 with the addition of GNRs. Results show a strong dependence of the field emission on GNR composition aligned with the gradient on the top of the A-TNT substrate. Enhanced FE properties of the modified TNTs can be mainly attributed to their improved electrical properties and rougher surface morphology.

  12. Large-scale aligned silicon carbonitride nanotube arrays: Synthesis, characterization, and field emission property

    International Nuclear Information System (INIS)

    Liao, L.; Xu, Z.; Liu, K. H.; Wang, W. L.; Liu, S.; Bai, X. D.; Wang, E. G.; Li, J. C.; Liu, C.

    2007-01-01

    Large-scale aligned silicon carbonitride (SiCN) nanotube arrays have been synthesized by microwave-plasma-assisted chemical vapor deposition using SiH 4 , CH 4 , and N 2 as precursors. The three elements of Si, C, and N are chemically bonded with each other and the nanotube composition can be adjusted by varying the SiH 4 concentration, as revealed by electron energy loss spectroscopy and x-ray photoelectron spectroscopy. The evolution of microstructure of the SiCN nanotubes with different Si concentrations was characterized by high-resolution transmission electron microscopy and Raman spectroscopy. The dependence of field emission characteristics of the SiCN nanotubes on the composition has been investigated. With the increasing Si concentration, the SiCN nanotube exhibits more favorable oxidation resistance, which suggests that SiCN nanotube is a promising candidate as stable field emitter

  13. Field Emission from Carbon Nanostructures

    Directory of Open Access Journals (Sweden)

    Filippo Giubileo

    2018-03-01

    Full Text Available Field emission electron sources in vacuum electronics are largely considered to achieve faster response, higher efficiency and lower energy consumption in comparison with conventional thermionic emitters. Carbon nanotubes had a leading role in renewing attention to field emission technologies in the early 1990s, due to their exceptional electron emitting properties enabled by their large aspect ratio, high electrical conductivity, and thermal and chemical stability. In the last decade, the search for improved emitters has been extended to several carbon nanostructures, comprising carbon nanotubes, either individual or films, diamond structures, graphitic materials, graphene, etc. Here, we review the main results in the development of carbon-based field emitters.

  14. Controlling the diameters and field emission properties of vertically aligned carbon nanotubes synthesized by thermal chemical vapor deposition

    International Nuclear Information System (INIS)

    Choi, Sung Yool; Kang, Young Il; Cho, Kyoung Ik; Choi, Kyu Seok; Kim, Do Jin

    2001-01-01

    We report here the synthesis of vertically well-aligned carbon nanotubes and the effect of catalytic metal layer on the diameter of grown carbon nanotubes and the field emission characteristics of them, The carbon nanotubes were grown by thermal chemical vapor deposition at temperatures below 900 .deg. C on Fe metal catalytic layer, deposited by sputtering process on a Si substrate and pretreated by heat and NH 3 gas. We found that the thickness of metal layers could be an important parameter in controlling the diameters of carbon nanotubes. With varying the thickness of the metal layers the grain sizes of them also vary so that the diameters of the nanotubes could be controlled. Field emission measurement has been made on the carbon nanotube field emitters at room temperature in a vacuum chamber below 10 -6 Torr. Our vertically aligned carbon nanotube field emitter of the smallest diameter emits a current density about 10 mA/cm 2 at 7.2 V/μm. The field emission property of the carbon nanotubes shows strong dependence on the nanotube diameters as expected

  15. High-aspect-ratio HfC nanobelts accompanied by HfC nanowires: Synthesis, characterization and field emission properties

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Song, E-mail: tiansong22@126.com [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); School of Materials Science and Engineering, Chongqing Jiaotong University, Chongqing 400074 (China); Zhang, Yulei; Ren, Jincui; Qiang, Xinfa; Zhang, Shouyang [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Hejun, E-mail: lihejun@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China)

    2017-04-30

    Highlights: • HfC naobelts accompanied by HfC nanowires were synthesized by a catalytic CVD method. • HfC nanobelts as a novel structure of HfC ceramic are reported for the first time. • HfC nanobelts have 100–200 μm in lengths and reach up to 10 μm in widths. • The synthesized product is promising field nanoemitters. - Abstract: As a key refractory carbide, hafnium carbide (HfC) is commonly used as structural materials while the field emission (FE) application of HfC in the field of vacuum microelectronics is almost the only one for functional material purposes. Based on its outstanding physical and chemical characteristics, HfC is identified as a potential candidate with satisfactory mechanical properties and long-term and/or high-temperature FE stability for future applications in high-performance field emitters. However, the development of HfC in various FE applications is hindered because it is not facile to fabricate large-scale low-dimensional HfC field nanoemitters. Herein, High-aspect-ratio HfC nanobelts accompanied by HfC nanowires were synthesized on a large scale by a traditional and simple catalytic chemical vapor deposition (CVD) method. Classical vapor–liquid–solid (VLS) theory was employed to explain the growth of the HfC nanowires and nanobelts along axial direction. The thin HfO{sub 2} shell and thin C layer surrounding the nanostructures might give rise to the diameter fluctuation of HfC nanowires and the width increase of HfC nanobelts in lateral direction. Field emission results show that the high-aspect-ratio HfC nanobelts accompanied by the nanowires are promising field nanoemitters, which exhibit excellent field emission properties with a fairly low turn-on field of ∼1.5 V μm{sup −1} and a low current fluctuation less than ∼10%. This suggests that HfC ceramics with high-aspect-ratio nanostructures are ideal cathode material for various field emission applications.

  16. Bias-enhanced post-treatment process for enhancing the electron field emission properties of ultrananocrystalline diamond films

    International Nuclear Information System (INIS)

    Saravanan, A.; Huang, B. R.; Sankaran, K. J.; Tai, N. H.; Dong, C. L.; Lin, I. N.

    2015-01-01

    The electron field emission (EFE) properties of ultrananocrystalline diamond films were markedly improved via the bias-enhanced plasma post-treatment (bep) process. The bep-process induced the formation of hybrid-granular structure of the diamond (bep-HiD) films with abundant nano-graphitic phase along the grain boundaries that increased the conductivity of the films. Moreover, the utilization of Au-interlayer can effectively suppress the formation of resistive amorphous-carbon (a-C) layer, thereby enhancing the transport of electrons crossing the diamond-to-Si interface. Therefore, bep-HiD/Au/Si films exhibit superior EFE properties with low turn-on field of E 0  = 2.6 V/μm and large EFE current density of J e  = 3.2 mA/cm 2 (at 5.3 V/μm)

  17. Engineering the interface characteristics on the enhancement of field electron emission properties of vertically aligned hexagonal boron nitride nanowalls

    Energy Technology Data Exchange (ETDEWEB)

    Sankaran, K.J.; Hoang, D.Q.; Drijkoningen, S.; Pobedinskas, P.; Haenen, K. [Institute for Materials Research (IMO), Hasselt University, Diepenbeek (Belgium); IMOMEC, IMEC vzw, Diepenbeek (Belgium); Srinivasu, K.; Leou, K.C. [Department of Engineering and System Science, National Tsing Hua University, Hsinchu (China); Korneychuk, S.; Turner, S.; Verbeeck, J. [Electron Microscopy for Materials Science (EMAT), University of Antwerp (Belgium); Lin, I.N. [Department of Physics, Tamkang University, Tamsui (China)

    2016-10-15

    Utilization of Au and nanocrystalline diamond (NCD) as interlayers noticeably modifies the microstructure and field electron emission (FEE) properties of hexagonal boron nitride nanowalls (hBNNWs) grown on Si substrates. The FEE properties of hBNNWs on Au could be turned on at a low turn-on field of 14.3 V μm{sup -1}, attaining FEE current density of 2.58 mA cm{sup -2} and life-time stability of 105 min. Transmission electron microscopy reveals that the Au-interlayer nucleates the hBN directly, preventing the formation of amorphous boron nitride (aBN) in the interface, resulting in enhanced FEE properties. But Au forms as droplets on the Si substrate forming again aBN at the interface. Conversely, hBNNWs on NCD shows superior in life-time stability of 287 min although it possesses inferior FEE properties in terms of larger turn-on field and lower FEE current density as compared to that of hBNNWs-Au. The uniform and continuous NCD film on Si also circumvents the formation of aBN phases and allows hBN to grow directly on NCD. Incorporation of carbon in hBNNWs from the NCD-interlayer improves the conductivity of hBNNWs, which assists in transporting the electrons efficiently from NCD to hBNNWs that results in better field emission of electrons with high life-time stability. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. 3 MeV proton irradiation effects on surface, structural, field emission and electrical properties of brass

    Science.gov (United States)

    Ali, Mian Ahsan; Bashir, Shazia; Akram, Mahreen; Mahmood, Khaliq; Faizan-ul-Haq; Hayat, Asma; Mutaza, G.; Chishti, Naveed Ahmed; Khan, M. Asad; Ahmad, Shahbaz

    2018-05-01

    Ion-induced modifications of brass in terms of surface morphology, elemental composition, phase changes, field emission properties and electrical conductivity have been investigated. Brass targets were irradiated by proton beam at constant energy of 3 MeV for various doses ranges from 1 × 1012 ions/cm2 to 1.5 × 1014 ions/cm2 using Pelletron Linear Accelerator. Field Emission Scanning Electron Microscope (FESEM) analysis reveals the formation of randomly distributed clusters, particulates, droplets and agglomers for lower ion doses which are explainable on the basis of cascade collisional process and thermal spike model. Whereas, at moderate ion doses, fiber like structures are formed due to incomplete melting. The formation of cellular like structure is observed at the maximum ion dose and is attributed to intense heating, melting and re-solidification. SRIM software analysis reveals that the penetration depth of 3 MeV protons in brass comes out to be 38 μm, whereas electronic and nuclear energy losses come out to be 5 × 10-1 and 3.1 × 10-4 eV/Å respectively. The evaluated values of energy deposited per atom vary from 0.01 to 1.5 eV with the variation of ion doses from 1 × 1012 ions/cm2 to 1.5 × 1014 ions/cm2. Both elemental analysis i.e. Energy Dispersive X-ray spectroscopy (EDX) and X-ray Diffraction (XRD) supports each other and no new element or phase is identified. However, slight change in peak intensity and angle shifting is observed. Field emission properties of ion-structured brass are explored by measuring I-V characteristics of targets under UHV condition in diode-configuration using self designed and fabricated setup. Improvement in field enhancement factor (β) is estimated from the slope of Fowler-Nordheim (F-N) plots and it shows significant increase from 5 to 1911, whereas a reduction in turn on field (Eo) from 65 V/μm to 30 V/μm and increment in maximum current density (Jmax) from 12 μA/cm2 to 3821 μA/cm2 is observed. These enhancements

  19. Sensing Properties of a Novel Temperature Sensor Based on Field Assisted Thermal Emission

    Directory of Open Access Journals (Sweden)

    Zhigang Pan

    2017-02-01

    Full Text Available The existing temperature sensors using carbon nanotubes (CNTs are limited by low sensitivity, complicated processes, or dependence on microscopy to observe the experimental results. Here we report the fabrication and successful testing of an ionization temperature sensor featuring non-self-sustaining discharge. The sharp tips of nanotubes generate high electric fields at relatively low voltages, lowering the work function of electrons emitted by CNTs, and thereby enabling the safe operation of such sensors. Due to the temperature effect on the electron emission of CNTs, the collecting current exhibited an exponential increase with temperature rising from 20 °C to 100 °C. Additionally, a higher temperature coefficient of 0.04 K−1 was obtained at 24 V voltage applied on the extracting electrode, higher than the values of other reported CNT-based temperature sensors. The triple-electrode ionization temperature sensor is easy to fabricate and converts the temperature change directly into an electrical signal. It shows a high temperature coefficient and good application potential.

  20. Tuning vertical alignment and field emission properties of multi-walled carbon nanotube bundles

    Science.gov (United States)

    Sreekanth, M.; Ghosh, S.; Srivastava, P.

    2018-01-01

    We report the growth of vertically aligned carbon nanotube bundles on Si substrate by thermal chemical vapor deposition technique. Vertical alignment was achieved without any carrier gas or lithography-assisted deposition. Growth has been carried out at 850 °C for different quantities of solution of xylene and ferrocene ranging from 2.25 to 3.00 ml in steps of 0.25 ml at a fixed concentration of 0.02 gm (ferrocene) per ml. To understand the growth mechanism, deposition was carried out for different concentrations of the solution by changing only the ferrocene quantity, ranging from 0.01 to 0.03 gm/ml. A tunable vertical alignment of multi-walled carbon nanotubes (CNTs) has been achieved by this process and examined by scanning and transmission electron microscopic techniques. Micro-crystalline structural analysis has been done using Raman spectroscopy. A systematic variation in field emission (FE) current density has been observed. The highest FE current density is seen for the film grown with 0.02 gm/ml concentration, which is attributed to the better alignment of CNTs, less structural disorder and less entanglement of CNTs on the surface. The alignment of CNTs has been qualitatively understood on the basis of self-assembled catalytic particles.

  1. Study of Thermal-Field Emission Properties and Investigation of Temperature dependent Noise in the Emission Current form vertical Carbon nanotube emitters

    KAUST Repository

    Kolekar, Sadhu; Patole, Shashikant P.; Patil, Sumati; Yoo, J.B.; Dharmadhikari, C.V.

    2017-01-01

    We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well defined cathode surface is given by Millikan and Lauritsen [1

  2. Comment on "Water-processed carbon nanotube/graphene hybrids with enhanced field emission properties" [AIP Advances 5, 097130 (2015)

    Science.gov (United States)

    Rani, Reena; Bhatia, Ravi

    2018-03-01

    In their research paper, M. Song et al. [AIP ADVANCES 5, 097130 (2015)] have claimed to have achieved enhanced field emission (FE) characteristics of carbon nanotubes (CNT)/graphene hybrids experimentally, exhibiting improved FE parameters e.g. turn-on electric field of 0.79 V/μm, threshold electric field of 1.05 V/μm, maximum emission current density (Jmax) of 5.76 mA/cm2, and field enhancement factor (β) of ˜1.3 × 104. The authors have emphasized on the surprisingly high value of β to be the basis of their claim of achieving superior FE performance which is further attributed to the optimized mass ratio CNT/ graphene, which is 5:1 in the present case. However, the claim based upon high value of β is misleading because it does not corroborate with the obtained Jmax parameter. Also, the obtained value of J is quite low in the mentioned study as compared to the reported values. For an instance, Sameera et al. [J. Appl. Phys. 111, 044307 (2012) & Appl. Phys. Lett. 102, 033102 (2013)] have reported FE properties of CNT composites and reduced graphene oxide with Jmax and β values of the order of ˜102 mA/cm2 and 6 × 103, respectively. Therefore, the conclusions drawn by M. Song et al. [AIP ADVANCES 5, 097130 (2015)] in their paper do no hold.

  3. A computational study on the electronic and field emission properties of Mg and Si doped AlN nanocones

    Science.gov (United States)

    Saedi, Leila; Soleymanabadi, Hamed; Panahyab, Ataollah

    2018-05-01

    Following an experimental work, we explored the effect of replacing an Al atom of an AlN nanocone by Si or Mg atom on its electronic and field emission properties using density functional theory calculations. We found that both Si-doping and Mg-doping increase the electrical conductivity of AlN nanocone, but their influences on the filed emission properties are significantly different. The Si-doping increases the electron concentration of AlN nanocone and results in a large electron mobility and a low work function, whereas Mg-doping leads to a high hole concentration below the conduction level and increases the work function in agreement with the experimental results. It is predicted that Si-doped AlN nanocones show excellent filed emission performance with higher emitted electron current density compared to the pristine AlN nanocone. But the Mg-doping meaningfully decreases the emitted electron current density from the surface of AlN nanocone. The Mg-doping can increase the work function about 41.9% and the Si-doping can decrease it about 6.3%. The Mg-doping and Si-doping convert the AlN nanocone to a p-type and n-type semiconductors, respectively. Our results explain in a molecular level what observed in the experiment.

  4. Black carbon aerosol properties measured by a single particle soot photometer in emissions from biomass burning in the laboratory and field

    Science.gov (United States)

    G. R. McMeeking; J. W. Taylor; A. P. Sullivan; M. J. Flynn; S. K. Akagi; C. M. Carrico; J. L. Collett; E. Fortner; T. B. Onasch; S. M. Kreidenweis; R. J. Yokelson; C. Hennigan; A. L. Robinson; H. Coe

    2010-01-01

    We present SP2 observations of BC mass, size distributions and mixing state in emissions from laboratory and field biomass fires in California, USA. Biomass burning is the primary global black carbon (BC) source, but understanding of the amount emitted and its physical properties at and following emission are limited. The single particle soot photometer (SP2) uses a...

  5. Study of Thermal-Field Emission Properties and Investigation of Temperature dependent Noise in the Emission Current form vertical Carbon nanotube emitters

    KAUST Repository

    Kolekar, Sadhu

    2017-05-05

    We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well defined cathode surface is given by Millikan and Lauritsen [1] for the combination of temperature and electric field effect. The same expression has been used to explain the electron emission characteristics from vertical CNT emitters. Furthermore, this has been applied to explain the electron emission for different temperatures ranging from room temperature to 1500 K. The real-time field electron emission images at room temperature and 1500 K are recorded by using Charge Coupled Device (CCD), in order to understand the effect of temperature on electron emission spots in image morphology (as indicated by ring like structures) and electron emission spot intensity of the emitters. Moreover, the field electron emission images can be used to calculate the total number of emitters per cm2 for electron emission. The calculated number of emitters per cm2 is 4.5x107 and, the actual number emitters per cm2 present for electron emission calculated from Atomic Force Microscopy (AFM) data is 1.2x1012. The measured Current-Voltage (I-V) characteristics obey the Folwer-Nordheim (F-N) type behavior. The fluctuations in the emission current are recorded at different temperatures and, temperature dependence of power spectral density obeys power law relation s(f)=I2/f2 with that of emission current and frequency.

  6. Field emission properties of nano-structured cobalt ferrite (CoFe2O4) synthesized by low-temperature chemical method

    Science.gov (United States)

    Ansari, S. M.; Suryawanshi, S. R.; More, M. A.; Sen, Debasis; Kolekar, Y. D.; Ramana, C. V.

    2018-06-01

    We report on the field-emission properties of structure-morphology controlled nano-CoFe2O4 (CFO) synthesized via a simple and low-temperature chemical method. Structural analyses indicate that the spongy-CFO (approximately, 2.96 nm) is nano-structured, spherical, uniformly-distributed, cubic-structured and porous. Field emission studies reveal that CFO exhibit low turn-on field (4.27 V/μm) and high emission current-density (775 μA/cm2) at a lower applied electric field of 6.80 V/μm. In addition, extremely good emission current stability is obtained at a pre-set value of 1 μA and high emission spot-density over large area (2 × 2 cm2) suggesting the applicability of these materials for practical applications in vacuum micro-/nano-electronics.

  7. Field emission in RF cavities

    International Nuclear Information System (INIS)

    Bonin, B.

    1996-01-01

    Electron field emission limits the accelerating gradient in superconducting cavities. It is shown how and why it is an important problem. The phenomenology of field emission is then described, both in DC and RF regimes. Merits of a few plausible 'remedies' to field emission are discussed. (author)

  8. Morphology-controlled synthesis of grass-like GO-CdSe nanocomposites with excellent optical properties and field emission properties

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Pei, E-mail: peipeixie@163.com [College of Science, Donghua University, Shanghai 201620 (China); Xue, Shaolin, E-mail: slxue@dhu.edu.cn [College of Science, Donghua University, Shanghai 201620 (China); Wei, Jia, E-mail: Jojo.1125@hotmail.com [College of Science, Donghua University, Shanghai 201620 (China); Han, Junwei, E-mail: hjw0323@sina.com [College of Science, Donghua University, Shanghai 201620 (China); Zhou, Weikang, E-mail: dhuzwk@sina.com [College of Science, Donghua University, Shanghai 201620 (China); Zou, Rujia, E-mail: rujiazou@dhu.edu.cn [College of Science, Donghua University, Shanghai 201620 (China); State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China)

    2016-02-15

    Four different morphologies of the CdSe semiconductor nanograss have been successfully grown on graphene oxide (GO) sheets via hydrothermal method at 220 °C for 12 h. The morphologies, structures, chemical compositions and optical properties of the as-obtained GO-CdSe nanocomposites were characterized by XRD, SEM, TEM, EDS, XPS and Raman spectra. It was found that the EDTA/Cd{sup 2+} molar ratio is important for the formation of morphology of GO-CdSe nanocomposites. The results of XRD revealed that all the as-obtained GO-CdSe nanocomposites have zinc blend structure. Room temperature photoluminescence (PL) showed that the sample emits red light under different excitation wavelengths. The results of Raman spectra, EDS and XPS showed that the CdSe nanograss is grown on GO sheets. The results showed that GO-CdSe nanocomposites composed of nanorods have best field emission (FE) properties with a low turn-on electric field of 4.14 V μm{sup −1} and a high field enhancement factor of 3315 among all the samples. - Graphical abstract: SEM images of as-synthesized CdSe nanograss grown on GO sheets. Room temperature PL emission spectra of the as-synthesized CdSe nanograss grown on GO sheets. Field emission J–E curve of the as-synthesized CdSe nanograss grown on GO sheets. - Highlights: • Novel CdSe nanograsses are grown on graphene oxide sheets by hydrothermal method. • The morphology of CdSe nanograsses is controlled by adjusting EDTA/Cd{sup 2+} molar ratio. • The FE performance of sample is investigated. • Optimum morphology for FE performance is CdSe nanograsses composed of nanorods on GO.

  9. Effect of magnetic and electric coupling fields on micro- and nano- structure of carbon films in the CVD diamond process and their electron field emission property

    Science.gov (United States)

    Wang, Yijia; Li, Jiaxin; Hu, Naixiu; Jiang, Yunlu; Wei, Qiuping; Yu, Zhiming; Long, Hangyu; Zhu, Hekang; Xie, Youneng; Ma, Li; Lin, Cheng-Te; Su, Weitao

    2018-03-01

    In this paper, both electric field and magnetic field were used to assist the hot filament chemical vapor deposition (HFCVD) and we systematically investigated the effects of which on the (1) phase composition, (2) grain size, (3) thickness and (4) preferred orientation of diamond films through SEM, Raman and XRD. The application of magnetic field in electric field, so called ‘the magnetic and electric coupling fields’, enhanced the graphitization and refinement of diamond crystals, slowed down the decrease of film thickness along with the increase of bias current, and suppressed diamond (100) orientation. During the deposition process, the electric field provided additional energy to HFCVD system and generated large number of energetic particles which might annihilate at the substrate and lose kinetic energy, while the Lorentz force, provided by magnetic field, could constrict charged particles (including electrons) to do spiral movement, which prolonged their moving path and life, thus the system energy increased. With the graphitization of diamond films intensified, the preferred orientation of diamond films completely evolved from (110) to (100), until the orientation and diamond phase disappeared, which can be attributed to (I) the distribution and concentration ratio of carbon precursors (C2H2 and CH3) and (II) graphitization sequence of diamond crystal facets. Since the electron field emission property of carbon film is sensitive to the phase composition, thickness and preferred orientation, nano- carbon cones, prepared by the negative bias current of 20 mA and magnetic field strength of 80 Gauss, exhibited the lowest turn-on field of 6.1 V -1 μm-1.

  10. Observations Of Polarized Dust Emission In Protostars: How To Reconstruct Magnetic Field Properties?

    Science.gov (United States)

    Maury, Anaëlle; Galametz, M.; Girart; Guillet; Hennebelle, P.; Houde; Rao; Valdivia, V.; Zhang, Q.

    2017-10-01

    I will present our ALMA Cycle 2 polarized dust continuum data towards the Class 0 protostar B335 where the absence of detected rotational motions in the inner envelope might suggest an efficient magnetic braking at work to inhibit the formation of a large disk. The Band 6 data we obtained shows an intriguing polarized vectors topology, which could either suggest (i) at least two different grain alignment mechanisms at work in B335 to produce the observed polarization pattern, or (ii) an interferometric bias leading to filtering of the polarized signal that is different from the filtering of Stokes I. I will discuss both options, proposing multi-wavelength and multi observatory (ALMA Band3 data in Cycle 5, NIKA2Pol camera on the IRAM-30m) strategies to lift the degeneracy when using polarization observations as a proxy of magnetic fields in dense astrophysical environments. This observational effort in the framework of the MagneticYSOs project, is also supported by our development of an end-to-end chain of ALMA synthetic observations of the polarization from non-ideal MHD simulations of protostellar collapse (see complementary contributions by V. Valdivia and M. Galametz).

  11. Field emission properties and strong localization effect in conduction mechanism of nanostructured perovskite LaNiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kamble, Ramesh B., E-mail: rbk.physics@coep.ac.in [Department of Physics, Indian Institute of Science, Bangalore 560012, Karnataka (India); Department of Physics, College of Engineering, Pune 411005, Maharashtra (India); Tanty, Narendra; Patra, Ananya; Prasad, V. [Department of Physics, Indian Institute of Science, Bangalore 560012, Karnataka (India)

    2016-08-22

    We report the potential field emission of highly conducting metallic perovskite lanthanum nickelate (LaNiO{sub 3}) from the nanostructured pyramidal and whisker shaped tips as electron emitters. Nano particles of lanthanum nickelate (LNO) were prepared by sol-gel route. Structural and morphological studies have been carried out. Field emission of LNO exhibited high emission current density, J = 3.37 mA/cm{sup 2} at a low threshold electric field, E{sub th} = 16.91 V/μm, obeying Fowler–Nordheim tunneling. The DC electrical resistivity exhibited upturn at 11.6 K indicating localization of electron at low temperature. Magnetoresistance measurement at different temperatures confirmed strong localization in nanostructured LNO obeying Anderson localization effect at low temperature.

  12. Growth and field emission properties of one-dimensional carbon composite structure consisting of vertically aligned carbon nanotubes and nanocones

    International Nuclear Information System (INIS)

    Zhang Hongxin; Feng, Peter X; Fonseca, Luis; Morell, Gerardo; Makarov, Vladimir I; Weiner, Brad R

    2009-01-01

    A simple approach is demonstrated for quickly growing a large-area aligned carbon composite nanostructure consisting of vertically aligned nanotubes and nanocones by the catalyst-assisted pulsed laser deposition techniques. The pyrolytic graphite was used as carbon source. The carbon nanocones were first grown on the molybdenum substrate with Ni catalysts. The carbon nanotubes have a uniform shape and length, aligned vertically on carbon nanocones, and the average diameter is about 7 nm. The special carbon composite arrays exhibit excellent field emission behaviours. The long-term field emission current stability of the one-dimensioned carbon nanostructure has also been investigated. No obvious current density decay was observed after a 10-day continuous experiment, indicating the super stability of the sample as cathode material.

  13. Synthesis and field emission properties of carbon nanotubes grown in ethanol flame based on a photoresist-assisted catalyst annealing process

    International Nuclear Information System (INIS)

    Yang Xiaoxia; Fang Guojia; Liu Nishuang; Wang Chong; Zheng Qiao; Zhou Hai; Zhao Dongshan; Long Hao; Liu Yuping; Zhao Xingzhong

    2009-01-01

    Carbon nanotubes (CNTs) have been grown directly on a Si substrate without a diffusion barrier in ethanol diffusion flame using Ni as the catalyst after a photoresist-assisted catalyst annealing process. The growth mechanism of as-synthesized CNTs is confirmed by scanning electron microscopy, high resolution transmission-electron microscopy and energy-dispersive spectroscopy. The photoresist is the key for the formation of active catalyst particles during annealing process, which then result in the growth of CNTs. The catalyst annealing temperature has been found to affect the morphologies and field electron emission properties of CNTs significantly. The field emission properties of as-grown CNTs are investigated with a diode structure and the obtained CNTs exhibit enhanced characteristics. This technique will be applicable to a low-cost fabrication process of electron-emitter arrays.

  14. Field emission for cantilever sensors

    NARCIS (Netherlands)

    Yang, C.K.; le Fèbre, A.J.; Pandraud, G.; van der Drift, E.; French, P.J.

    2008-01-01

    Field emission provides an alternative sensing solution in scaled electromechanical systems and devices, when typical displacement detection techniques fail in submicron and nanodimenions. Apart from its independency from device dimension, it has also a high response, integration and high

  15. A computational study on tuning the field emission and electronic properties of BN nanocones by impurity atom doping

    Science.gov (United States)

    Ahmadi, S.; Delir Kheirollahi Nezhad, P.; Hosseinian, A.; Vessally, E.

    2018-06-01

    We have inspected the effect of substituting a boron or nitrogen atom of a BN nanocone (BNNC) by two impurity atoms with lower and higher atomic numbers based on the density functional theory calculations. Our results explain the experimental observations in a molecular level. Orbital and partial density of states analyses show that the doping processes increase the electrical conductivity by creating new states within the gap of BNNC as follows: BeB > ON > CB > CN. The electron emission current from the surface of BNNC is improved after the CB and BeB dopings, and it is decreased by CN and ON dopings. The BeB and CN dopings make the BNNC a p-type semiconductor and the CB and ON dopings make it an n-type one in good agreement with the experimental results. The ON and BeB doping processes are suggested for the field emission current, and electrical conductivity enhancement, respectively.

  16. Dynamical Evolution of Properties for Atom and Field in the Process of Two-Photon Absorption and Emission Between Atomic Levels

    Science.gov (United States)

    Wang, Jian-ming; Xu, Xue-xiang

    2018-04-01

    Using dressed state method, we cleverly solve the dynamics of atom-field interaction in the process of two-photon absorption and emission between atomic levels. Here we suppose that the atom is initially in the ground state and the optical field is initially in Fock state, coherent state or thermal state, respectively. The properties of the atom, including the population in excited state and ground state, the atom inversion, and the properties for optical field, including the photon number distribution, the mean photon number, the second-order correlation function and the Wigner function, are discussed in detail. We derive their analytical expressions and then make numerical analysis for them. In contrast with Jaynes-Cummings model, some similar results, such as quantum Rabi oscillation, revival and collapse, are also exhibit in our considered model. Besides, some novel nonclassical states are generated.

  17. Modeling the effect of doping on the catalyst-assisted growth and field emission properties of plasma-grown graphene sheet

    International Nuclear Information System (INIS)

    Gupta, Neha; Sharma, Suresh C.; Sharma, Rinku

    2016-01-01

    A theoretical model describing the effect of doping on the plasma-assisted catalytic growth of graphene sheet has been developed. The model accounts the charging rate of the graphene sheet, kinetics of all the plasma species, including the doping species, and the growth rate of graphene nuclei and graphene sheet due to surface diffusion, and accretion of ions on the catalyst nanoparticle. Using the model, it is observed that nitrogen and boron doping can strongly influence the growth and field emission properties of the graphene sheet. The results of the present investigation indicate that nitrogen doping results in reduced thickness and shortened height of the graphene sheet; however, boron doping increases the thickness and height of the graphene sheet. The time evolutions of the charge on the graphene sheet and hydrocarbon number density for nitrogen and boron doped graphene sheet have also been examined. The field emission properties of the graphene sheet have been proposed on the basis of the results obtained. It is concluded that nitrogen doped graphene sheet exhibits better field emission characteristics as compared to undoped and boron doped graphene sheet. The results of the present investigation are consistent with the existing experimental observations.

  18. Modeling the effect of doping on the catalyst-assisted growth and field emission properties of plasma-grown graphene sheet

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Neha; Sharma, Suresh C.; Sharma, Rinku [Department of Applied Physics, Delhi Technological University (DTU), Shahbad Daulatpur, Bawana Road, Delhi-110042 (India)

    2016-08-15

    A theoretical model describing the effect of doping on the plasma-assisted catalytic growth of graphene sheet has been developed. The model accounts the charging rate of the graphene sheet, kinetics of all the plasma species, including the doping species, and the growth rate of graphene nuclei and graphene sheet due to surface diffusion, and accretion of ions on the catalyst nanoparticle. Using the model, it is observed that nitrogen and boron doping can strongly influence the growth and field emission properties of the graphene sheet. The results of the present investigation indicate that nitrogen doping results in reduced thickness and shortened height of the graphene sheet; however, boron doping increases the thickness and height of the graphene sheet. The time evolutions of the charge on the graphene sheet and hydrocarbon number density for nitrogen and boron doped graphene sheet have also been examined. The field emission properties of the graphene sheet have been proposed on the basis of the results obtained. It is concluded that nitrogen doped graphene sheet exhibits better field emission characteristics as compared to undoped and boron doped graphene sheet. The results of the present investigation are consistent with the existing experimental observations.

  19. Study of field emission phenomena

    International Nuclear Information System (INIS)

    Ramanathan, Devaki; Vijendran, P.

    1976-01-01

    The theory of field emission has been explained, using Fowler-Nordheim equation and the Fowler-Nordheim plot. The imaging theory is also described in brief. The fabrication details of a field emission microscope (FEM) are mentioned. The design of the tube and the emitter assemblies are explained in detail. Simple experiments that can be demonstrated on the FEM such as indexing, detetermination of work function and surface diffusion constants, etc. are also mentioned. The use of FEM as a simple teaching aid has been brought out. (K.B.)

  20. Electron field emission for ultrananocrystalline diamond films

    Energy Technology Data Exchange (ETDEWEB)

    Krauss, A. R.; Auciello, O.; Ding, M. Q.; Gruen, D. M.; Huang, Y.; Zhirnov, V. V.; Givargizov, E. I.; Breskin, A.; Chechen, R.; Shefer, E. (and others)

    2001-03-01

    Ultrananocrystalline diamond (UNCD) films 0.1--2.4 {mu}m thick were conformally deposited on sharp single Si microtip emitters, using microwave CH{sub 4}--Ar plasma-enhanced chemical vapor deposition in combination with a dielectrophoretic seeding process. Field-emission studies exhibited stable, extremely high (60--100 {mu}A/tip) emission current, with little variation in threshold fields as a function of film thickness or Si tip radius. The electron emission properties of high aspect ratio Si microtips, coated with diamond using the hot filament chemical vapor deposition (HFCVD) process were found to be very different from those of the UNCD-coated tips. For the HFCVD process, there is a strong dependence of the emission threshold on both the diamond coating thickness and Si tip radius. Quantum photoyield measurements of the UNCD films revealed that these films have an enhanced density of states within the bulk diamond band gap that is correlated with a reduction in the threshold field for electron emission. In addition, scanning tunneling microscopy studies indicate that the emission sites from UNCD films are related to minima or inflection points in the surface topography, and not to surface asperities. These data, in conjunction with tight binding pseudopotential calculations, indicate that grain boundaries play a critical role in the electron emission properties of UNCD films, such that these boundaries: (a) provide a conducting path from the substrate to the diamond--vacuum interface, (b) produce a geometric enhancement in the local electric field via internal structures, rather than surface topography, and (c) produce an enhancement in the local density of states within the bulk diamond band gap.

  1. Correlation of CVD Diamond Electron Emission with Film Properties

    Science.gov (United States)

    Bozeman, S. P.; Baumann, P. K.; Ward, B. L.; Nemanich, R. J.; Dreifus, D. L.

    1996-03-01

    Electron field emission from metals is affected by surface morphology and the properties of any dielectric coating. Recent results have demonstrated low field electron emission from p-type diamond, and photoemission measurements have identified surface treatments that result in a negative electron affinity (NEA). In this study, the field emission from diamond is correlated with surface treatment, surface roughness, and film properties (doping and defects). Electron emission measurements are reported on diamond films synthesized by plasma CVD. Ultraviolet photoemission spectroscopy indicates that the CVD films exhibit a NEA after exposure to hydrogen plasma. Field emission current-voltage measurements indicate "threshold voltages" ranging from approximately 20 to 100 V/micron.

  2. (Zn, Mg)2GeO4:Mn2+ submicrorods as promising green phosphors for field emission displays: hydrothermal synthesis and luminescence properties.

    Science.gov (United States)

    Shang, Mengmeng; Li, Guogang; Yang, Dongmei; Kang, Xiaojiao; Peng, Chong; Cheng, Ziyong; Lin, Jun

    2011-10-07

    (Zn(1-x-y)Mg(y))(2)GeO(4): xMn(2+) (y = 0-0.30; x = 0-0.035) phosphors with uniform submicrorod morphology were synthesized through a facile hydrothermal process. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL), and cathodoluminescence (CL) spectroscopy were utilized to characterize the samples. SEM and TEM images indicate that Zn(2)GeO(4):Mn(2+) samples consist of submicrorods with lengths around 1-2 μm and diameters around 200-250 nm, respectively. The possible formation mechanism for Zn(2)GeO(4) submicrorods has been presented. PL and CL spectroscopic characterizations show that pure Zn(2)GeO(4) sample shows a blue emission due to defects, while Zn(2)GeO(4):Mn(2+) phosphors exhibit a green emission corresponding to the characteristic transition of Mn(2+) ((4)T(1)→(6)A(1)) under the excitation of UV and low-voltage electron beam. Compared with Zn(2)GeO(4):Mn(2+) sample prepared by solid-state reaction, Zn(2)GeO(4):Mn(2+) phosphors obtained by hydrothermal process followed by high temperature annealing show better luminescence properties. In addition, codoping Mg(2+) ions into the lattice to substitute for Zn(2+) ions can enhance both the PL and CL intensity of Zn(2)GeO(4):Mn(2+) phosphors. Furthermore, Zn(2)GeO(4):Mn(2+) phosphors exhibit more saturated green emission than the commercial FEDs phosphor ZnO:Zn, and it is expected that these phosphors are promising for application in field-emission displays.

  3. Electronic structure and field emission properties of nitrogen doped graphene nano-flakes (GNFs:N) and carbon nanotubes (CNTs:N)

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Sekhar C., E-mail: Raysc@unisa.ac.za [Department of Physics, College of Science, Engineering and Technology, University of South Africa, Private Bag X6, Florida, 1710, Science Campus, Christiaan de Wet and Pioneer Avenue, Florida Park, Johannesburg (South Africa); Pong, W.F. [Department of Physics, Tamkang University, Tamsui 251, New Taipei City, Taiwan (China); Papakonstantinou, P. [Nanotechnology and Integrated Bio-Engineering Centre, University of Ulster, Shore Road, Newtownabbey BT37 0QB (United Kingdom)

    2016-09-01

    Highlights: • Nitrogen doped graphene nano-flakes (GNFs:N) and carbon nano-tubes (CNTs:N) are used to study the electronic/bonding structure along with their defects state. • The I{sub D}/I{sub G} ratio obtained from Raman spectroscopy used for the study of the defects states of CNTs:N than GNFs:N. • The electron field emission result shows that the turn on electric field is lower in case of CNTs:N than GNFs:N. • All results are good agreement with XANES and the results obtained from Raman spectra. - Abstract: Substitution of hetero-atom doping is a promising route to modulate the outstanding material properties of carbon nanotubes and graphene for customized applications. Nitrogen-doping has been introduced to ensure tunable work-function, enhanced n-type carrier concentration, diminished surface energy, and manageable polarization. Along with the promising assessment of N-doping effects, research on the N-doped carbon based composite structures is emerging for the synergistic integration with various functional materials. Nitrogen undoped/doped graphene nano-flakes (GNFs/GNFs:N) and multiwall carbon nano-tubes (MWCNTs/MWCNTs:N) are used for comparative study of their electronic/bonding structure along with their defects state. X-ray absorption near edge structure (XANES) spectroscopy shows that the GNFs:N produce mainly pyridine like structure; whereas MWCNTs:N shows graphitic nitrogen atoms are attached with the carbon lattice. The I{sub D}/I{sub G} ratio obtained from Raman spectroscopy shows that the defects is higher in MWCNTs:N than GNFs:N. The electron field emission result shows that the turn on electric field is lower (higher electron emission current) in case of MWCNTs:N than GNFs:N and are good agreement with XANES and the results obtained from Raman spectra.

  4. Field-emission property of self-purification SiC/SiOx coaxial nanowires synthesized via direct microwave irradiation using iron-containing catalyst

    Science.gov (United States)

    Zhou, Qing; Yu, Yongzhi; Huang, Shan; Meng, Jiang; Wang, Jigang

    2017-07-01

    SiC/SiOx coaxial nanowires were rapidly synthesized via direct microwave irradiation in low vacuum atmosphere. During the preparation process, only graphite, silicon, silicon dioxide powders were used as raw materials and iron-containing substance was employed as catalyst. Comprehensive characterizations were employed to investigate the microstructure of the products. The results showed that a great quantity of coaxial nanowires with uniform sizes and high aspect ratio had been successfully achieved. The coaxial nanowires consist of a silicon oxide (SiOx) shell and a β-phase silicon carbide (β-SiC) core that exhibited in special tube brush like. In additional, nearly all the products were achieved in the statement of pure SiC/SiOx coaxial nanowires without the existence of metallic catalyst, indicating that the self-removal of iron (Fe) catalyst should be occurred during the synthesis process. Photoluminescence (PL) spectral analysis result indicated that such novel SiC/SiOx coaxial nanowires exhibited significant blue-shift. Besides, the measurement results of field-emission (FE) demonstrated that the SiC/SiOx coaxial nanowires had ultralow turn-on field and threshold field with values of 0.2 and 2.1 V/μm, respectively. The hetero-junction structure formed between SiOx shell and SiC core, lots of emission sites, as well as clear tips of the nanowires were applied to explain the excellent FE properties.[Figure not available: see fulltext.

  5. Electron field emission from boron doped microcrystalline diamond

    International Nuclear Information System (INIS)

    Roos, M.; Baranauskas, V.; Fontana, M.; Ceragioli, H.J.; Peterlevitz, A.C.; Mallik, K.; Degasperi, F.T.

    2007-01-01

    Field emission properties of hot filament chemical vapor deposited boron doped polycrystalline diamond have been studied. Doping level (N B ) of different samples has been varied by the B/C concentration in the gas feed during the growth process and doping saturation has been observed for high B/C ratios. Threshold field (E th ) for electron emission as function of B/C concentration has been measured, and the influences of grain boundaries, doping level and surface morphology on field emission properties have been investigated. Carrier transport through conductive grains and local emission properties of surface sites have been figured out to be two independent limiting effects in respect of field emission. Emitter current densities of 500 nA cm -2 were obtained using electric fields less than 8 V/μm

  6. Field emission studies at Saclay and Orsay

    International Nuclear Information System (INIS)

    Tan, J.

    1996-01-01

    During the last five years, DC and RF equipment for field emission studies have been developed at Saclay and Orsay laboratories. Combining these devices, straight comparison has been carried out between DC and RF field emission from artificial emission sites on the same sample. Other topics are also reviewed: high field cleaning, plausible origins of thermal effects that occurred on emission sites in RF, behaviour of alumina particles under RF field, and optical observations and measurements. (author)

  7. Field emission of carbon nanotubes grown on nickel substrate

    International Nuclear Information System (INIS)

    Hu Yemin; Huo Kaifu; Chen Hong; Lu Yinong; Xu Li; Hu Zheng; Chen Yi

    2006-01-01

    Carbon nanotubes (CNTs) have been synthesized directly on the electrically conducting nickel substrate without additional catalyst. Field emission properties of the as-prepared sample were characterized using parallel plate diode configurations. It was observed that the field emission qualitatively follows the conventional Fowler-Nordheim (F-N) theory from the straight line of ln(I/V 2 ) versus 1/V plot at the high applied field region. The uniformity and stability of the electron emission have also been examined. The low electron turn-on field (E to ) and high emission current density indicates the potential applications of this new CNT-based emitter

  8. Fluxon induced resistance and field emission

    CERN Document Server

    Calatroni, Sergio; Darriulat, Pierre; Peck, M A; Valente, A M; Van't Hof, C A

    2000-01-01

    The surface resistance of superconducting niobium films induced by the presence of trapped magnetic flux, presumably in the form of a pinned fluxon lattice, is shown to be modified by the presence of a field emitting impurity or defect. The modification takes the form of an additional surface resistance proportional to the density of the fluxon lattice and increasing linearly with the amplitude of the microwave above a threshold significantly lower than the field emission threshold. Such an effect, precursor of electron emission, is observed here for the first time in a study using radiofrequency cavities operated at their fundamental 1.5 GHz frequency. The measured properties of the additional surface resistance severely constrain possible explanations of the observed effect.

  9. Sensing Properties of Multiwalled Carbon Nanotubes Grown in MW Plasma Torch: Electronic and Electrochemical Behavior, Gas Sensing, Field Emission, IR Absorption

    Directory of Open Access Journals (Sweden)

    Petra Majzlíková

    2015-01-01

    Full Text Available Vertically aligned multi-walled carbon nanotubes (VA-MWCNTs with an average diameter below 80 nm and a thickness of the uniform VA-MWCNT layer of about 16 µm were grown in microwave plasma torch and tested for selected functional properties. IR absorption important for a construction of bolometers was studied by Fourier transform infrared spectroscopy. Basic electrochemical characterization was performed by cyclic voltammetry. Comparing the obtained results with the standard or MWCNT‑modified screen-printed electrodes, the prepared VA-MWCNT electrodes indicated their high potential for the construction of electrochemical sensors. Resistive CNT gas sensor revealed a good sensitivity to ammonia taking into account room temperature operation. Field emission detected from CNTs was suitable for the pressure sensing application based on the measurement of emission current in the diode structure with bending diaphragm. The advantages of microwave plasma torch growth of CNTs, i.e., fast processing and versatility of the process, can be therefore fully exploited for the integration of surface-bound grown CNTs into various sensing structures.

  10. High performance field emission of silicon carbide nanowires and their applications in flexible field emission displays

    Science.gov (United States)

    Cui, Yunkang; Chen, Jing; Di, Yunsong; Zhang, Xiaobing; Lei, Wei

    2017-12-01

    In this paper, a facile method to fabricate the flexible field emission devices (FEDs) based on SiC nanostructure emitters by a thermal evaporation method has been demonstrated. The composition characteristics of SiC nanowires was characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED) and energy dispersive X-ray spectrometer (EDX), while the morphology was revealed by field emission scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The results showed that the SiC nanowires grew along the [111] direction with the diameter of ˜110 nm and length of˜30 μm. The flexible FEDs have been fabricated by transferring and screen-printing the SiC nanowires onto the flexible substrates exhibited excellent field emission properties, such as the low turn-on field (˜0.95 V/μm) and threshold field (˜3.26 V/μm), and the high field enhancement factor (β=4670). It is worth noting the current density degradation can be controlled lower than 2% per hour during the stability tests. In addition, the flexible FEDs based on SiC nanowire emitters exhibit uniform bright emission modes under bending test conditions. As a result, this strategy is very useful for its potential application in the commercial flexible FEDs.

  11. High performance field emission of silicon carbide nanowires and their applications in flexible field emission displays

    Directory of Open Access Journals (Sweden)

    Yunkang Cui

    2017-12-01

    Full Text Available In this paper, a facile method to fabricate the flexible field emission devices (FEDs based on SiC nanostructure emitters by a thermal evaporation method has been demonstrated. The composition characteristics of SiC nanowires was characterized by X-ray diffraction (XRD, selected area electron diffraction (SAED and energy dispersive X-ray spectrometer (EDX, while the morphology was revealed by field emission scanning electron microscopy (SEM and high resolution transmission electron microscopy (HRTEM. The results showed that the SiC nanowires grew along the [111] direction with the diameter of ∼110 nm and length of∼30 μm. The flexible FEDs have been fabricated by transferring and screen-printing the SiC nanowires onto the flexible substrates exhibited excellent field emission properties, such as the low turn-on field (∼0.95 V/μm and threshold field (∼3.26 V/μm, and the high field enhancement factor (β=4670. It is worth noting the current density degradation can be controlled lower than 2% per hour during the stability tests. In addition, the flexible FEDs based on SiC nanowire emitters exhibit uniform bright emission modes under bending test conditions. As a result, this strategy is very useful for its potential application in the commercial flexible FEDs.

  12. Field electron emission spectrometer combined with field ion/electron microscope as a field emission laboratory

    International Nuclear Information System (INIS)

    Shkuratov, S.I.; Ivanov, S.N.; Shilimanov, S.N.

    1996-01-01

    The facility, combining the field ion microscope, field electron emission microscope and field electron emission spectrometer, is described. Combination of three methodologies makes it possible to carry out the complete cycle of emission studies. Atom-plane and clean surface of the studied samples is prepared by means of field evaporation of the material atom layers without any thermal and radiation impact. This enables the study of atom and electron structure of clean surface of the wide range materials, the study whereof through the field emission methods was previously rather difficult. The temperature of the samples under study changes from 75 up to 2500 K. The energy resolution of the electron analyzer equals 30 MeV. 19 refs., 10 figs

  13. Marshmallowing of nanopillar arrays by field emission

    International Nuclear Information System (INIS)

    Qin Hua; Kim, Hyun-Seok; Blick, Robert H.

    2010-01-01

    We fabricated nanoscale field electron emitters formed by highly-doped silicon nanopillars on a silicon membrane. Electron-beam induced deposition of carbon-based contaminants is employed as a probe of the spatial activity of electron emission from the nanopillars. In stark contrast to the general assumption that field emission only occurs at the tips of nanoscale emitters, we found strong emission from the sidewalls of the nanopillars. This is revealed by the deposition of carbon contaminants on these sidewalls, so that the nanopillars finally resemble marshmallows. We conclude that field emission from nanostructured surfaces is more intricate than previously expected.

  14. Marshmallowing of nanopillar arrays by field emission

    International Nuclear Information System (INIS)

    Park, J; Qin, H; Kim, H-S; Blick, R H

    2009-01-01

    We have fabricated mechanically flexible field electron emitters formed by highly-doped silicon nanopillars on a silicon membrane. Electron beam induced deposition of carbon-based contaminants is employed to probe the spatial activity of electron emission from the nanopillars. The experimental configuration provides a powerful tool to investigate the physics of the field electron emission (FEE). In contrast to the general assumption that field emission only occurs at the tips of nanoscale emitters, we found that the emission from the nanopillars' sidewalls is as strong as from their tips.

  15. Field emission from a single nanomechanical pillar

    International Nuclear Information System (INIS)

    Kim, Hyun S; Qin Hua; Westphall, Michael S; Smith, Lloyd M; Blick, Robert H

    2007-01-01

    We measured field emission from a silicon nanopillar mechanically oscillating between two electrodes. The pillar has a height of about 200 nm and a diameter of 50 nm, allowing resonant mechanical excitations at radio frequencies. The tunnelling barriers for field emission are mechanically modulated via displacement of the gold island on top of the pillar. We present a rich frequency-dependent response of the emission current in the frequency range of 300-400 MHz at room temperature. Modified Fowler-Nordheim field emission is observed and attributed to the mechanical oscillations of the nanopillar

  16. Growth, microstructure, and field-emission properties of synthesized diamond film on adamantane-coated silicon substrate by microwave plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Tiwari, Rajanish N.; Chang Li

    2010-01-01

    Diamond nucleation on unscratched Si surface is great importance for its growth, and detailed understanding of this process is therefore desired for many applications. The pretreatment of the substrate surface may influence the initial growth period. In this study, diamond films have been synthesized on adamantane-coated crystalline silicon {100} substrate by microwave plasma chemical vapor deposition from a gaseous mixture of methane and hydrogen gases without the application of a bias voltage to the substrates. Prior to adamantane coating, the Si substrates were not pretreated such as abraded/scratched. The substrate temperature was ∼530 deg. C during diamond deposition. The deposited films are characterized by scanning electron microscopy, Raman spectrometry, x-ray diffraction, and x-ray photoelectron spectroscopy. These measurements provide definitive evidence for high-crystalline quality diamond film, which is synthesized on a SiC rather than clean Si substrate. Characterization through atomic force microscope allows establishing fine quality criteria of the film according to the grain size of nanodiamond along with SiC. The diamond films exhibit a low-threshold (55 V/μm) and high current-density (1.6 mA/cm 2 ) field-emission (FE) display. The possible mechanism of formation of diamond films and their FE properties have been demonstrated.

  17. Coulomb scattering in field and photofield emission

    International Nuclear Information System (INIS)

    Donders, P.J.; Lee, M.J.G.

    1987-01-01

    An anomalous high-energy tail has been observed in the measured total energy distribution (TED) in photofield emission from tungsten. The strength of this tail is proportional to the product of the photofield emission current and the total emission current. Similar high- and low-energy tails in the TED's in field emission, which have previously been reported by several workers, are also observed. In any given measurement, the fraction of the total photofield-emission current in the anomalous photofield-emission tail is approximately equal to the fraction of the total field-emission current in the anomalous field-emission tail. Measurements of both the absolute strengths and energy dependences of the anomalous tails are reported. The experimental observations are consistent with the predictions of a classical calculation of the energy transfer that results from the Coulomb interaction between electrons in the vacuum near the field emitter. The various internal mechanisms that have previously been invoked to account for the tails in field-emission TED's do not appear to contribute significantly to the anomalous distributions observed in the present work

  18. Carbon nanowalls in field emission cathodes

    Directory of Open Access Journals (Sweden)

    Belyanin A. F.

    2017-12-01

    Full Text Available The carbon nanowall (CNW layers were grown from a gas mixture of hydrogen and methane, activated by a DC glow discharge, on Si substrates (Si/CNW layered structure. The second layer of CNW was grown either on the first layer (Si/CNW/CNW structure or on Ni or NiO films deposited on the first CNW layer (Si/CNW/Ni/CNW and Si/CNW/NiO/CNW structures. The composition and structure of the resulting layered structures were studied using scanning electron microscopy, Raman spectroscopy, and X-ray diffractometry. It was found that annealing of Si/CNW structure in vacuum, growing of the second CNW layer on Si/CNW, as well as deposition of Ni or NiO films prior to the growing of the second CNW layer improve functional properties of field emission cathodes based on the electron-emitting CNW layers.

  19. Field emission from finite barrier quantum structures

    Energy Technology Data Exchange (ETDEWEB)

    Biswas Sett, Shubhasree, E-mail: shubhasree24@gmail.com [The Institution of Engineers - India, 8, Gokhale Road, Kolkata 700 020 (India); Bose, Chayanika, E-mail: chayanikab@ieee.org [Electronics and Telecommunication Engg. Dept., Jadavpur University, Kolkata 700 032 (India)

    2014-10-01

    We study field emission from various finite barrier quasi-low dimensional structures, taking image force into account. To proceed, we first formulate an expression for field emission current density from a quantum dot. Transverse dimensions of the dot are then increased in turn, to obtain current densities respectively from quantum wire and quantum well with infinite potential energy barriers. To find out field emission from finite barrier structures, the above analysis is followed with a correction in the energy eigen values. In course, variations of field emission current density with strength of the applied electric field and structure dimensions are computed considering n-GaAs and n-GaAs/Al{sub x}Ga{sub 1−x}As as the semiconductor materials. In each case, the current density is found to increase exponentially with the applied field, while it oscillates with structure dimensions. The magnitude of the emission current is less when the image force is not considered, but retains the similar field dependence. In all cases, the field emission from infinite barrier structures exceeds those from respective finite barrier ones.

  20. 3D periodic structures grown on silicon by radiation of a pulsed Nd:YAG laser and their field emission properties

    Energy Technology Data Exchange (ETDEWEB)

    Karabutov, A.V. [A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov Street, 119991 Moscow (Russian Federation); Shafeev, G.A. [A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov Street, 119991 Moscow (Russian Federation)]. E-mail: shafeev@kapella.gpi.ru; Badi, N. [Physics Department, The University of Houston, Houston, TX 77204-5005 (United States); Nair, A.M. [TcSAM, The University of Houston, Houston, TX 77204-5004 (United States); Bensaoula, A. [Physics Department, The University of Houston, Houston, TX 77204-5005 (United States)

    2006-04-30

    Periodic three-dimensional structures were successfully grown on single crystal Si wafers either bare or Au-covered under their exposure to a pulsed radiation of a Nd:YAG laser in vacuum. The structures protrude above the initial wafer surface for 10 {mu}m while their spatial period is about 70 {mu}m. The coupling of the laser radiation to Si surface is related to the thermal non-linear absorption of the near band gap radiation. The structures exhibit an efficient field emission with an average emission current of 5 mA/cm{sup 2} and is sensitive to the post-treatment of samples. The drawbacks of the emission current densities are discussed.

  1. Pulsar Emission Geometry and Accelerating Field Strength

    Science.gov (United States)

    DeCesar, Megan E.; Harding, Alice K.; Miller, M. Coleman; Kalapotharakos, Constantinos; Parent, Damien

    2012-01-01

    The high-quality Fermi LAT observations of gamma-ray pulsars have opened a new window to understanding the generation mechanisms of high-energy emission from these systems, The high statistics allow for careful modeling of the light curve features as well as for phase resolved spectral modeling. We modeled the LAT light curves of the Vela and CTA I pulsars with simulated high-energy light curves generated from geometrical representations of the outer gap and slot gap emission models. within the vacuum retarded dipole and force-free fields. A Markov Chain Monte Carlo maximum likelihood method was used to explore the phase space of the magnetic inclination angle, viewing angle. maximum emission radius, and gap width. We also used the measured spectral cutoff energies to estimate the accelerating parallel electric field dependence on radius. under the assumptions that the high-energy emission is dominated by curvature radiation and the geometry (radius of emission and minimum radius of curvature of the magnetic field lines) is determined by the best fitting light curves for each model. We find that light curves from the vacuum field more closely match the observed light curves and multiwavelength constraints, and that the calculated parallel electric field can place additional constraints on the emission geometry

  2. Edge field emission of large-area single layer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Kleshch, Victor I., E-mail: klesch@polly.phys.msu.ru [Department of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Bandurin, Denis A. [Department of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Orekhov, Anton S. [Department of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); A.V. Shubnikov Institute of Crystallography, RAS, Moscow 119333 (Russian Federation); Purcell, Stephen T. [ILM, Université Claude Bernard Lyon 1 et CNRS, UMR 5586, 69622 Villeurbanne (France); Obraztsov, Alexander N. [Department of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Department of Physics and Mathematics, University of Eastern Finland, Joensuu 80101 (Finland)

    2015-12-01

    Graphical abstract: - Highlights: • Stable field emission was observed from the edge of large-area graphene on quartz. • A strong hysteresis in current–voltage characteristics was observed. • The hysteresis was explained by mechanical peeling of graphene edge from substrate. • Reversible peeling of graphene edge may be used in microelectromechanical systems. - Abstract: Field electron emission from the edges of large-area (∼1 cm × 1 cm) graphene films deposited onto quartz wafers was studied. The graphene was previously grown by chemical vapour deposition on copper. An extreme enhancement of electrostatic field at the edge of the films with macroscopically large lateral dimensions and with single atom thickness was achieved. This resulted in the creation of a blade type electron emitter, providing stable field emission at low-voltage with linear current density up to 0.5 mA/cm. A strong hysteresis in current–voltage characteristics and a step-like increase of the emission current during voltage ramp up were observed. These effects were explained by the local mechanical peeling of the graphene edge from the quartz substrate by the ponderomotive force during the field emission process. Specific field emission phenomena exhibited in the experimental study are explained by a unique combination of structural, electronic and mechanical properties of graphene. Various potential applications ranging from linear electron beam sources to microelectromechanical systems are discussed.

  3. Electron beam brightness with field immersed emission

    International Nuclear Information System (INIS)

    Boyd, J.K.; Neil, V.K.

    1985-01-01

    The beam quality or brightness of an electron beam produced with field immersed emission is studied with two models. First, an envelope formulation is used to determine the scaling of brightness with current, magnetic field and cathode radius, and examine the equilibrium beam radius. Second, the DPC computer code is used to calculate the brightness of two electron beam sources

  4. Resonant tunnelling from nanometre-scale silicon field emission cathodes

    International Nuclear Information System (INIS)

    Johnson, S.; Markwitz, A.

    2005-01-01

    In this paper we report the field emission properties of self-assembled silicon nanostructures formed on an n-type silicon (100) substrate by electron beam annealing. The nanostructures are square based, with an average height of 8 nm and are distributed randomly over the entire substrate surface. Following conditioning, the silicon nanostructure field emission characteristics become stable and reproducible with electron emission occurring for fields as low as 3 Vμm-1. At higher fields, a superimposed on a background current well described by conventional Fowler-Nordheim theory. These current peaks are understood to result from enhanced tunnelling through resonant states formed at the substrate-nanostructure and nanostructure-vacuum interface. (author). 13 refs., 3 figs

  5. The oxidized porous silicon field emission array

    International Nuclear Information System (INIS)

    Smith, D.D.; Demroff, H.P.; Elliott, T.S.; Kasprowicz, T.B.; Lee, B.; Mazumdar, T.K.; McIntyre, P.M.; Pang, Y.; Trost, H.J.

    1993-01-01

    The goal of developing a highly efficient microwave power source has led the authors to investigate new methods of electron field emission. One method presently under consideration involves the use of oxidized porous silicon thin films. The authors have used this technology to fabricate the first working field emission arrays from this substance. This approach reduces the diameter of an individual emitter to the nanometer scale. Tests of the first samples are encouraging, with extracted electron currents to nearly 1 mA resulting from less than 20 V of pulsed DC gate voltage. Modulated emission at 5 MHz was also observed. Developments of a full-scale emission array capable of delivering an electron beam at 18 GHz of minimum density 100 A/cm 2 is in progress

  6. Emission properties of aluminium-lithium alloy

    International Nuclear Information System (INIS)

    Bondarenko, G.G.; Shishkov, A.V.

    1995-01-01

    High secondary emission properties at comparatively low operation temperatures were obtained when investigating aluminum-lithium alloy Al - 2.2 mass % Li. The maximal value of the coefficient of secondary electron emission for alloy, activated under optimal conditions, is achieved at comparatively low energy of primary electrons, equal to 600 eV. Low value of the first critical potential (15 ± 2 eV) was obtained. It is important for operation of secondary emission cathodes. 12 refs.; 4 figs

  7. Enhanced field emission from carbon nanotubes by hydrogen plasma treatment

    International Nuclear Information System (INIS)

    Zhi, C.Y.; Bai, X.D.; Wang, E.G.

    2002-01-01

    The field emission capability of the carbon nanotubes (CNTs) has been improved by hydrogen plasma treatment, and the enhanced emission mechanism has been studied systematically using Fourier-transform infrared spectroscopy, Raman, and transmission electron microscopy. The hydrogen concentration in the samples increases with increasing plasma treatment duration. A C δ- -H δ+ dipole layer may form on CNTs' surface and a high density of defects results from the plasma treatment, which is likely to make the external surface of CNTs more active to emit electrons after treatment. In addition, the sharp edge of CNTs' top, after removal of the catalyst particles, may increase the local electronic field more effectively. The present study suggests that hydrogen plasma treatment is a useful method for improving the field electron emission property of CNTs

  8. Synthesis, structure, and luminescence properties of SrSiAl2O3N2:Eu(2+) phosphors for light-emitting devices and field emission displays.

    Science.gov (United States)

    Wang, Xicheng; Zhao, Zhengyan; Wu, Quansheng; Li, Yanyan; Wang, Chuang; Mao, Aijun; Wang, Yuhua

    2015-06-28

    A series of SrSiAl2O3N2:Eu(2+) (0.005 ≤x≤ 0.05) phosphors were successfully synthesized through a pressureless, facile, and efficient solid state route. The crystal structure, band structure, and their photoluminescence and cathodoluminescence properties were investigated in detail. The phosphors exhibit rod shape morphology with a uniform Eu(2+) distribution. Under n-UV excitation the emission spectra shift from 477 to 497 nm with an increase of Eu(2+) concentration. The concentration quenching mechanism of Eu(2+) emission was dominated by the dipole-dipole interaction. The thermal stability is comparable to that of the commercial Ba2SiO4:Eu(2+) phosphor. The phosphor also exhibits high current saturation and high resistance under low voltage electron bombardment. All the results indicate that the SrSiAl2O3N2:Eu(2+) phosphors can be considered as candidates for application in both white LEDs and FEDs.

  9. Field electron emission from branched nanotubes film

    International Nuclear Information System (INIS)

    Zeng Baoqing; Tian Shikai; Yang Zhonghai

    2005-01-01

    We describe the preparation and analyses of films composed of branched carbon nanotubes (CNTs). The CNTs were grown on a Ni catalyst film using chemical vapor deposition from a gas containing acetylene. From scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses, the branched structure of the CNTs was determined; the field emission characteristics in a vacuum chamber indicated a lower turn on field for branched CNTs than normal CNTs

  10. Field emission current from a junction field-effect transistor

    International Nuclear Information System (INIS)

    Monshipouri, Mahta; Abdi, Yaser

    2015-01-01

    Fabrication of a titanium dioxide/carbon nanotube (TiO 2 /CNT)-based transistor is reported. The transistor can be considered as a combination of a field emission transistor and a junction field-effect transistor. Using direct current plasma-enhanced chemical vapor deposition (DC-PECVD) technique, CNTs were grown on a p-typed (100)-oriented silicon substrate. The CNTs were then covered by TiO 2 nanoparticles 2–5 nm in size, using an atmospheric pressure CVD technique. In this device, TiO 2 /CNT junction is responsible for controlling the emission current. High on/off-current ratio and proper gate control are the most important advantages of device. A model based on Fowler–Nordheim equation is utilized for calculation of the emission current and the results are compared with experimental data. The effect of TiO 2 /CNT hetero-structure is also investigated, and well modeled

  11. Field-emission from quantum-dot-in-perovskite solids.

    Science.gov (United States)

    García de Arquer, F Pelayo; Gong, Xiwen; Sabatini, Randy P; Liu, Min; Kim, Gi-Hwan; Sutherland, Brandon R; Voznyy, Oleksandr; Xu, Jixian; Pang, Yuangjie; Hoogland, Sjoerd; Sinton, David; Sargent, Edward

    2017-03-24

    Quantum dot and well architectures are attractive for infrared optoelectronics, and have led to the realization of compelling light sensors. However, they require well-defined passivated interfaces and rapid charge transport, and this has restricted their efficient implementation to costly vacuum-epitaxially grown semiconductors. Here we report solution-processed, sensitive infrared field-emission photodetectors. Using quantum-dots-in-perovskite, we demonstrate the extraction of photocarriers via field emission, followed by the recirculation of photogenerated carriers. We use in operando ultrafast transient spectroscopy to sense bias-dependent photoemission and recapture in field-emission devices. The resultant photodiodes exploit the superior electronic transport properties of organometal halide perovskites, the quantum-size-tuned absorption of the colloidal quantum dots and their matched interface. These field-emission quantum-dot-in-perovskite photodiodes extend the perovskite response into the short-wavelength infrared and achieve measured specific detectivities that exceed 10 12 Jones. The results pave the way towards novel functional photonic devices with applications in photovoltaics and light emission.

  12. Electron injection in diodes with field emission

    International Nuclear Information System (INIS)

    Denavit, J.; Strobel, G.L.

    1986-01-01

    This paper presents self-consistent steady-state solutions of the space charge, transmitted current, and return currents in diodes with electron injection from the cathode and unlimited field emission of electrons and ions from both electrodes. Time-dependent particle simulations of the diode operation confirm the analytical results and show how these steady states are reached. The results are applicable to thermionic diodes and to photodiodes

  13. The influence of ion bombardment on emission properties of carbon materials

    International Nuclear Information System (INIS)

    Chepusov, Alexander; Komarskiy, Alexander; Kuznetsov, Vadim

    2014-01-01

    When electric-vacuum device works its cathode surface experiences bombardment with ions of residual gases. Effects of ion bombardment impact on surface of field emission cathodes made of carbon materials may essentially change emission properties of such cathodes. It changes emission start electric field strength, voltage vs. current characteristic of material, its relief and electron structure of the surface layer. Field emission cathode operating mode, variation of radiation doses allow to obtain both good effects: maximal electric current, surface recovery – and negative ones: the worst emission properties and surface destruction, amorphization.

  14. The influence of ion bombardment on emission properties of carbon materials

    Energy Technology Data Exchange (ETDEWEB)

    Chepusov, Alexander, E-mail: chepusov@iep.uran.ru [The Institute of Electrophysics of the Ural Division of the Russian Academy of Sciences (IEP UD RAS), 620016, 106 Amundsen Street, Ekaterinburg (Russian Federation); Ural Federal University, 620002, 19 Mira Street, Ekaterinburg (Russian Federation); Komarskiy, Alexander, E-mail: aakomarskiy@gmail.com [The Institute of Electrophysics of the Ural Division of the Russian Academy of Sciences (IEP UD RAS), 620016, 106 Amundsen Street, Ekaterinburg (Russian Federation); Ural Federal University, 620002, 19 Mira Street, Ekaterinburg (Russian Federation); Kuznetsov, Vadim, E-mail: kuznetsov@iep.uran.ru [The Institute of Electrophysics of the Ural Division of the Russian Academy of Sciences (IEP UD RAS), 620016, 106 Amundsen Street, Ekaterinburg (Russian Federation)

    2014-07-01

    When electric-vacuum device works its cathode surface experiences bombardment with ions of residual gases. Effects of ion bombardment impact on surface of field emission cathodes made of carbon materials may essentially change emission properties of such cathodes. It changes emission start electric field strength, voltage vs. current characteristic of material, its relief and electron structure of the surface layer. Field emission cathode operating mode, variation of radiation doses allow to obtain both good effects: maximal electric current, surface recovery – and negative ones: the worst emission properties and surface destruction, amorphization.

  15. Emission properties of biomimetic composites for dentistry

    Directory of Open Access Journals (Sweden)

    P.V. Seredin

    Full Text Available Biocomposites based on carbonate-substituted hydroxyapatite synthesized from the biological source of calcium (Goloshchapov et al., 2013 and organic primer on the basis of amino acids found in the enamel tubules of teeth, namely, arginine, histidine, lysine and hyaluronic acid were obtained and studied in this work. Incorporation of organic primer into biocomposite formulation allowed us to obtain the emission characteristics (luminescence that were identical to those inherent to the native tissues of the human tooth (enamel and dentine. Keywords: Biocomposites, IR-spectroscopy, Optical and emission properties, Hydroxyapatite, Human tooth tissues

  16. Field emission from a new type of electron source

    International Nuclear Information System (INIS)

    Mousa, M.S.

    1987-01-01

    A new type of field emission electron source has been developed. In this paper, the construction, characteristics and behaviour of tungsten micropoint emitters coated with a sub-micron layer of hydrocarbon using a TEM with poor ( ∼ 1 0 -3 torr) vacuum conditions are described. The hydrocarbon coating has been verified using the X-Ray energy dispersive analysis technique of a SEM. The technical capabilities and potential of the new type of electron source are compared with those of other comparable composite micropoint field emitters and other types of electron sources currently in use. The emission properties presented here include I-V characteristics, emission images and electron energy spectra of this type of composite micropoint emitters. The effect on the behaviour and characteristics of baking the coated emitters at temperatures ranging between 140 0 C and 350 0 C is also studied. The behaviour of the emitter has been interpreted in terms of a field-induced hot-electron emission mechanism associated with metal-insulator-vacuum (M-I-V) regime

  17. Field emission current from a junction field-effect transistor

    Energy Technology Data Exchange (ETDEWEB)

    Monshipouri, Mahta; Abdi, Yaser, E-mail: y.abdi@ut.ac.ir [University of Tehran, Nano-Physics Research Laboratory, Department of Physics (Iran, Islamic Republic of)

    2015-04-15

    Fabrication of a titanium dioxide/carbon nanotube (TiO{sub 2}/CNT)-based transistor is reported. The transistor can be considered as a combination of a field emission transistor and a junction field-effect transistor. Using direct current plasma-enhanced chemical vapor deposition (DC-PECVD) technique, CNTs were grown on a p-typed (100)-oriented silicon substrate. The CNTs were then covered by TiO{sub 2} nanoparticles 2–5 nm in size, using an atmospheric pressure CVD technique. In this device, TiO{sub 2}/CNT junction is responsible for controlling the emission current. High on/off-current ratio and proper gate control are the most important advantages of device. A model based on Fowler–Nordheim equation is utilized for calculation of the emission current and the results are compared with experimental data. The effect of TiO{sub 2}/CNT hetero-structure is also investigated, and well modeled.

  18. Structure, composition, morphology, photoluminescence and cathodoluminescence properties of ZnGeN{sub 2} and ZnGeN{sub 2}:Mn{sup 2+} for field emission displays

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Q.-H. [MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou, Guangdong 510275 (China); Guangzhou Research Institute of Non-ferrous Metals, Guangzhou, Guangdong 510651 (China); Wang, J., E-mail: ceswj@mail.sysu.edu.cn [MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou, Guangdong 510275 (China); Yeh, C.-W.; Ke, W.-C.; Liu, R.-S. [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Tang, J.-K. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Xie, M.-B.; Liang, H.-B.; Su, Q. [MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou, Guangdong 510275 (China)

    2010-12-15

    Yellowish-orange-emitting ZnGeN{sub 2} and orange-red-emitting ZnGeN{sub 2}:Mn were synthesized by a facile and mild gas-reduction-nitridation reaction at 1153 K under NH{sub 3} flow with air-stable raw materials ZnO, GeO{sub 2} and MnCO{sub 3}. The structure, composition, morphology, photoluminescence and cathodoluminescence properties of ZnGeN{sub 2} doped with or without Mn{sup 2+} were systematically investigated. Rietveld refinements show that the as-synthesized samples are obtained as single-phase compounds and crystallize as an orthorhombic structure with a space group of Pna2{sub 1}. The actual chemical composition of the as-prepared ZnGeN{sub 2} determined by energy dispersive X-ray spectroscopy suggests that the Ge vacancy defects probably exist in the host. The SEM image reveals that the Zn{sub 0.99}Mn{sub 0.01}GeN{sub 2} particles form aggregates {approx}500-600 nm in size. The diffuse reflection spectrum and photoluminescence excitation spectrum confirm that the band edge absorption of ZnGeN{sub 2} at low energy is 3.3 eV ({approx}376 nm). Upon UV light excitation and electron beam excitation, ZnGeN{sub 2} gives an intense yellowish-orange emission around 580-600 nm, associated with a deep defect level due to the Ge vacancy defects, and ZnGeN{sub 2}:Mn shows an intense red emission at 610 nm due to the {sup 4}T{sub 1g}({sup 4}G) {yields} 6A{sub 1g}({sup 6}S) of Mn{sup 2+}. The unusual red emission of Mn{sup 2+} in tetrahedral Zn{sup 2+} sites is attributed to the strong nephelauxetic effect between Mn{sup 2+} and the surrounding tetrahedrally coordinated nitrogen. The photoluminescence and cathodoluminescence emission colors of ZnGeN{sub 2}:Mn have a high color purity of {approx}93-98%. These results demonstrate that ZnGeN{sub 2}:Mn is a novel, promising red-emitting nitride, potentially applicable to field emission displays with brilliant color-rendering properties and a large color gamut.

  19. Electron field emission characteristics of graphene/carbon nanotubes hybrid field emitter

    International Nuclear Information System (INIS)

    Chen, Leifeng; He, Hong; Yu, Hua; Cao, Yiqi; Lei, Da; Menggen, QiQiGe; Wu, Chaoxing; Hu, Liqin

    2014-01-01

    The graphene (GP) and multi-walled carbon nanotubes (MCNTs) hybrid nanostructure emitter was constructed by a larger scale electrophoretic deposition (EPD) method. The field emission (FE) performance of the hybrid emitter is greatly improved compared with that of only GP or MCNTs emitter. The low turn-on electric field (EF), the low threshold EF and the reliability FE properties are obtained from the hybrid emitter. The better FE properties result from the improved electrical properties. For further enhancement FE of hybrids, Ag Nanoparticles (NPs) were decorated on the hybrids and FE characteristics were also studied. These studies indicate that we can use the hybrid nanostructure to improve conductivity and contact resistance, which results in enhancement of the FE properties

  20. On vector fields having properties of Reeb fields

    OpenAIRE

    Hajduk, Boguslaw; Walczak, Rafal

    2011-01-01

    We study constructions of vector fields with properties which are characteristic to Reeb vector fields of contact forms. In particular, we prove that all closed oriented odd-dimensional manifold have geodesible vector fields.

  1. Graphene field emitters: A review of fabrication, characterization and properties

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Leifeng, E-mail: chlf@hdu.edu.cn [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Yu, Hu; Zhong, Jiasong; Song, Lihui [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Wu, Jun, E-mail: wujun@hdu.edu.cn [Institute of Electron Device & Application, Hangzhou Dianzi University, Hangzhou, Zhejiang 310018 (China); Su, Weitao [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China)

    2017-06-15

    Highlights: • The preparation, characterization and field emission properties for Gs are reviewed. • The review provides an updated progress on design and construction of Gs field emitters. • The review offers fundamental insights into understanding and design of Gs emitters. • The review can broach the subject and inspire readers in field of Gs based emitters. - Abstract: Graphenes are beneficial to electrons field emission due to its high aspect ratio, high carrier density, the larger carrier mobility, excellent electrical and thermal conductivity, excellent mechanical strength and chemical stability. In recent years, graphene or reduced oxide graphene field emitters have been successfully constructed by various methods such as chemical vapor deposition, chemical exfoliation, electrophoretic deposition, screen-printing and chemical synthesis methods. Graphene emitters are tried to construct in distribution with some angles or vertical orientation with respect to the substrate surface. The vertical alignment of graphene sheets or edges arrays can facilitate efficient electron emission from the atomically thick sheets. Therefore they have even more a low turn-on and threshold-field electronic field, high field enhancement factor, high current stability and high luminance. In this review, we shortly survey and discuss recent research progress in graphene field emission properties with particular an emphasis on their preparing method, characterization and applications in devices especially for vertical graphene and single layer graphene, also including their challenges and future prospects.

  2. Role of adsorbates on current fluctuations in DC field emission

    International Nuclear Information System (INIS)

    Luong, M.; Bonin, B.; Long, H.; Safa, H.

    1996-01-01

    Field emission experiments in DC regime usually show important current fluctuations for a fixed electric field. These fluctuations are attributed to adsorbed layers (molecules or atoms), liable to affect the work function, height and shape of the potential barrier binding the electron in the metal. The role of these adsorbed species is investigated by showing that the field emission from a well desorbed sample is stable and reproducible and by comparing the emission from the same sample before and after desorption. (author)

  3. N2O Emission from energy crop fields

    International Nuclear Information System (INIS)

    Joergensen, B.J.; Nyholm Joergensen, R.

    1996-03-01

    The interest in N 2 O emissions from soils with energy crops is a results of its properties as a greenhouse gas, since the global warming potential of N 2 O per unit mass is about 320 times greater than CO 2 . The contribution of N 2 O from the soil to the atmosphere may increase due to agricultural management. Consequently, large N 2 O emissions can lower the reduction of the greenhouse effect achieved by the substitution of fossil fuels by energy crops. For this reason it is crucial to find the crops for combustion with the lowest potential for emission of N 2 O from the soil per produced energy unit. The aims of this study were to assess the annual N 2 O flux from a Miscanthus 'Giganteus' (M. 'Giganteus') and winter rye (Secale cereale) field, and to investigate the factors affecting the N 2 O emission. To obtain these aims a method was developed for measurements in tall crops. The thesis contains a literature review on the N 2 O emission from the soils, a section with development of the technique for N 2 O flux measurements, and an experimental section. Finally, the thesis contains a section where the results are discussed in relation to the use of energy crops. In all the filed studies, the N 2 O emission was measured by using a new developed closed-chamber technique. The main advantages of the chamber method were the ability to contain growing plants up to a height of 3 m, and the relatively large area (2X2m) covered by each other. Soils with annual and perennial crops can be expected to emit less then 3 kg N 2 O ha -1 yr -1 . This amount corresponds to 960 kg CO 2 ha -1 yr -1 compared to a total CO 2 reduction of 10 to 19 tons CO 2 ha -1 yr -1 using the energy crops as substitution for fossil fuels. An efficient way to reduce the N 2 O emission is to exclude use of fertiliser but this also reduces the dry matter yield and consequently also the CO 2 reduction per unit dry matter. Following the guidelines for good agricultural practice concerning the

  4. Penetration length-dependent hot electrons in the field emission from ZnO nanowires

    Science.gov (United States)

    Chen, Yicong; Song, Xiaomeng; Li, Zhibing; She, Juncong; Deng, Shaozhi; Xu, Ningsheng; Chen, Jun

    2018-01-01

    In the framework of field emission, whether or not hot electrons can form in the semiconductor emitters under a surface penetration field is of great concern, which will provide not only a comprehensive physical picture of field emission from semiconductor but also guidance on how to improve device performance. However, apart from some theoretical work, its experimental evidence has not been reported yet. In this article, the field penetration length-dependent hot electrons were observed in the field emission of ZnO nanowires through the in-situ study of its electrical and field emission characteristic before and after NH3 plasma treatment in an ultrahigh vacuum system. After the treatment, most of the nanowires have an increased carrier density but reduced field emission current. The raised carrier density was caused by the increased content of oxygen vacancies, while the degraded field emission current was attributed to the lower kinetic energy of hot electrons caused by the shorter penetration length. All of these results suggest that the field emission properties of ZnO nanowires can be optimized by modifying their carrier density to balance both the kinetic energy of field induced hot electrons and the limitation of saturated current under a given field.

  5. High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

    International Nuclear Information System (INIS)

    Hojati-Talemi, Pejman; Gibson, Mark A.; East, Daniel; Simon, George P.

    2011-01-01

    We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

  6. High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

    Energy Technology Data Exchange (ETDEWEB)

    Hojati-Talemi, Pejman [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia); Mawson Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Gibson, Mark A. [Process Science and Engineering, Commonwealth Scientific and Industrial Research Organisation, Clayton, Vic 3168 (Australia); East, Daniel; Simon, George P. [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia)

    2011-11-07

    We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

  7. X-Ray Emission Properties of Supernova Remnants

    NARCIS (Netherlands)

    Vink, J.; Alsabti, A.W.; Murdin, P.

    2016-01-01

    X-ray emission from supernova remnants can be broadly divided into thermal X-ray emission from the shock-heated plasmas and in nonthermal (synchrotron) emission caused by very high-energy (10–100 TeV) electrons moving in the magnetic fields of the hot plasmas. The thermal X-ray emission of young

  8. Fabrication of graphene and ZnO nanocones hybrid structure for transparent field emission device

    Energy Technology Data Exchange (ETDEWEB)

    Zulkifli, Zurita [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology (Japan); Faculty of Electrical Engineering, Universiti Teknologi Mara (Malaysia); Shinde, Sachin M.; Suguira, Takatoshi [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology (Japan); Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology (Japan); Center for Fostering Young and Innovative Researchers, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Tanemura, Masaki [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology (Japan)

    2015-11-30

    Graphical abstract: Fabrication of a transparent field emission device with chemical vapor deposited graphene and zinc oxide nanocones showing low turn-on field due to locally enhance electric field. - Highlights: • Demonstrated transparent field emission device with CVD graphene and ZnO nanocones. • Graphene film was coated on carbon doped ZnO nanocone prepared by ion irradiation. • Low turn-on field for the graphene/C:ZnO nanocones hybrid structure is achieved. • Graphene/C:ZnO heterostructure is promising for transparent field emission devices. - Abstract: Fabrication of a transparent and high performance electron emission device is the key challenge for suitable display applications. Here, we demonstrate fabrication of a transparent and efficient field emission device integrating large-area chemical vapor deposited graphene and carbon doped zinc oxide (C:ZnO) nanocones. The ZnO nanocones were obtained with ion irradiation process at room temperature, over which the graphene film was transferred without destroying nanocone tips. Significant enhancement in field emission properties were observed with the transferred graphene film on C:ZnO nanocones. The threshold field for hybrid and pristine C:ZnO nanocones film at current density of 1 μA/cm{sup 2} was obtained as 4.3 V/μm and 6.5 V/μm, respectively. The enhanced field emission properties with low turn-on field for the graphene/C:ZnO nanocones can be attributed to locally enhance electric field. Our finding shows that a graphene/C:ZnO hybridized structure is very promising to fabricate field emission devices without compromising with high transparency.

  9. Knife-edge thin film field emission cathodes

    International Nuclear Information System (INIS)

    Lee, B.; Demroff, H.P.; Drew, M.M.; Elliott, T.S.; Mazumdar, T.K.; McIntyre, P.M.; Pang, Y.; Smith, D.D.; Trost, H.J.

    1993-01-01

    Cathodes made of thin-film field emission arrays (FEA) have the advantages of high current density, pulsed emission, and low bias voltage operation. The authors have developed a technology to fabricate knife-edge field emission cathodes on (110) silicon wafers. The emitter geometry is optimized for efficient modulation at high frequency. Cathode fabrication progress and preliminary analysis of their applications in RF power sources are presented

  10. Making of an electronic interferometer to study emissive properties of field-effect microtips. Diffraction and interferences of slow electrons; Construction d`un interferometre electronique pour l`etude des proprietes emissives de micropointes a effet de champ. Diffraction et interferences d`electrons lents

    Energy Technology Data Exchange (ETDEWEB)

    Py, C

    1993-10-01

    The substitution of hot filaments by field-effect microtips has several advantages in many electronic applications. LETI has already proved the interest of this principle for flat panel displays; many people believe it could also provide novel microwave sources. Moreover, the properties of the emission enable to seek new electron optics applications that were not possible with hot filaments. An interferometry experiment was designed, developed and characterized in order to evaluate the potential of the microtips fabricated in the LETI for such applications. This experiment is composed of a Mollenstedt biprism, of electrostatic lenses and an imaging system composed of deflection plates, a small aperture diaphragm (1 {mu}m) and a channel electron multiplier. Quantum wave effects have been observed, which confirms the good coherence properties of the source. Moreover, this experimental setup enables to better understand the physical phenomenon of the emission of the tips fabricated in the LETI, and to propose some technological improvements for the applications we seek. It is also designed for electron holography applications, and should allow the study of new compact electron optics apparatus taking account of the wave properties of the electrons emitted by microtips. (author). 68 figs. 2 annexes. 41 refs.

  11. Predicting nitrous oxide emissions from manure properties and soil moisture: An incubation experiment

    DEFF Research Database (Denmark)

    Baral, Khagendra Raj; Arthur, Emmanuel; Olesen, Jørgen Eivind

    2016-01-01

    Field-applied manure is a source of essential plant nutrients, but benefits may be partly offset by high rates of nitrous oxide (N2O) emissions, as modified by manure characteristics and soil properties. In a 28-d incubation experiment we quantified short-term emissions of N2O from a sandy loam...

  12. Thermionic field emission in gold nitride Schottky nanodiodes

    Science.gov (United States)

    Spyropoulos-Antonakakis, N.; Sarantopoulou, E.; Kollia, Z.; Samardžija, Z.; Kobe, S.; Cefalas, A. C.

    2012-11-01

    We report on the thermionic field emission and charge transport properties of gold nitride nanodomains grown by pulsed laser deposition with a molecular fluorine laser at 157 nm. The nanodomains are sandwiched between the metallic tip of a conductive atomic force microscope and a thin gold layer forming thus a metal-semiconductor-metal junction. Although the limited existing data in the literature indicate that gold nitride was synthesized previously with low efficiency, poor stability, and metallic character; in this work, it is shown that gold nitride nanodomains exhibit semiconducting behavior and the metal-semiconductor-metal contact can be modeled with the back-to-back Schottky barrier model. From the experimental I-V curves, the main charge carrier transport process is found to be thermionic field emission via electron tunneling. The rectifying, near symmetric and asymmetric current response of nanocontacts is related to the effective contact area of the gold nitride nanodomains with the metals. A lower limit for the majority charge carriers concentration at the boundaries of nanodomains is also established using the full depletion approximation, as nanodomains with thickness as low as 6 nm were found to be conductive. Current rectification and charge memory effects are also observed in "quite small" conductive nanodomains (6-10 nm) due to stored charges. Indeed, charges near the surface are identified as inversion domains in the phase shift mapping performed with electrostatic force microscopy and are attributed to charge trapping at the boundaries of the nanodomains.

  13. Improved field emission from indium decorated multi-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Sreekanth, M.; Ghosh, S., E-mail: santanu1@physics.iitd.ernet.in; Biswas, P.; Kumar, S.; Srivastava, P.

    2016-10-15

    Graphical abstract: Improved field emission properties have been achieved for Indium (In) decorated MWCNTs and are shown using the schematic of field emission set up with In/CNT cathode, and a plot of J-E characteristics for pristine and In decorated CNTs. - Highlights: • Field emission (FE) properties have been studied for the first time from Indium (In) decorated MWCNT films. • Observed increased density of states near the Fermi level for In decorated films. • Superior field emission properties have been achieved for In decorated CNT films. - Abstract: Multi-walled carbon nanotube (MWCNT) films were grown using thermal chemical vapor deposition (T-CVD) process and were decorated with indium metal particles by thermal evaporation technique. The In metal particles are found to get oxidized. The In decorated films show 250% enhancement in the FE current density, lower turn-on and threshold fields, and better temporal stability as compared to their undecorated counterpart. This improvement in field emission properties is primarily attributed to increased density of states near the Fermi level. The presence of O 2p states along with a small contribution from In 5s states results in the enhancement of density of states in the vicinity of the Fermi level.

  14. Field emission from the surface of highly ordered pyrolytic graphite

    Energy Technology Data Exchange (ETDEWEB)

    Knápek, Alexandr, E-mail: knapek@isibrno.cz [Institute of Scientific Instruments of the ASCR, v.v.i., Královopolská 147, Brno (Czech Republic); Sobola, Dinara; Tománek, Pavel [Department of Physics, FEEC, Brno University of Technology, Technická 8, Brno (Czech Republic); Pokorná, Zuzana; Urbánek, Michal [Institute of Scientific Instruments of the ASCR, v.v.i., Královopolská 147, Brno (Czech Republic)

    2017-02-15

    Highlights: • HOPG shreds were created and analyzed in the UHV conditions. • Current-voltage measurements have been done to confirm electron tunneling, based on the Fowler-Nordheim theory. • Surface was characterized by other surface evaluation methods, in particular by: SNOM, SEM and AFM. - Abstract: This paper deals with the electrical characterization of highly ordered pyrolytic graphite (HOPG) surface based on field emission of electrons. The effect of field emission occurs only at disrupted surface, i.e. surface containing ripped and warped shreds of the uppermost layers of graphite. These deformations provide the necessary field gradients which are required for measuring tunneling current caused by field electron emission. Results of the field emission measurements are correlated with other surface characterization methods such as scanning near-field optical microscopy (SNOM) or atomic force microscopy.

  15. Field emission from the surface of highly ordered pyrolytic graphite

    International Nuclear Information System (INIS)

    Knápek, Alexandr; Sobola, Dinara; Tománek, Pavel; Pokorná, Zuzana; Urbánek, Michal

    2017-01-01

    Highlights: • HOPG shreds were created and analyzed in the UHV conditions. • Current-voltage measurements have been done to confirm electron tunneling, based on the Fowler-Nordheim theory. • Surface was characterized by other surface evaluation methods, in particular by: SNOM, SEM and AFM. - Abstract: This paper deals with the electrical characterization of highly ordered pyrolytic graphite (HOPG) surface based on field emission of electrons. The effect of field emission occurs only at disrupted surface, i.e. surface containing ripped and warped shreds of the uppermost layers of graphite. These deformations provide the necessary field gradients which are required for measuring tunneling current caused by field electron emission. Results of the field emission measurements are correlated with other surface characterization methods such as scanning near-field optical microscopy (SNOM) or atomic force microscopy.

  16. Electron field emission from screen-printed graphene/DWCNT composite films

    International Nuclear Information System (INIS)

    Xu, Jinzhuo; Pan, Rong; Chen, Yiwei; Piao, Xianqin; Qian, Min; Feng, Tao; Sun, Zhuo

    2013-01-01

    Highlights: ► The field emission performance improved significantly when adding graphene into DWCNTs as the emission material. ► We set up a model of pure DWCNT films and graphene/DWCNT composite films. ► We discussed the contact barrier between emission films and electric substrates by considering the Fermi energies of silver, DWCNT and graphene. - Abstract: The electron field emission properties of graphene/double-walled carbon nanotube (DWCNT) composite films prepared by screen printing have been systematically studied. Comparing with the pure DWCNT films and pure graphene films, a significant enhancement of electron emission performance of the composite films are observed, such as lower turn-on field, higher emission current density, higher field enhancement factor, and long-term stability. The optimized composite films with 20% weight ratio of graphene show the best electron emission performance with a low turn-on field of 0.62 V μm −1 (at 1 μA cm −2 ) and a high field enhancement factor β of 13,000. A model of the graphene/DWCNT composite films is proposed, which indicate that a certain amount of graphene will contribute the electron transmission in the silver substrate/composite films interface and in the interior of composite films, and finally improve the electron emission performance of the graphene/DWCNT composite films.

  17. Laser terahertz emission microscopy with near-field probes

    DEFF Research Database (Denmark)

    Pedersen, Pernille Klarskov; Mittleman, Daniel M.

    2016-01-01

    Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm.......Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm....

  18. Increased field-emission site density from regrown carbon nanotube films

    International Nuclear Information System (INIS)

    Wang, Y.Y.; Gupta, S.; Liang, M.; Nemanich, R.J.

    2005-01-01

    Electron field-emission properties of as-grown, etched, and regrown carbon nanotube thin films were investigated. The aligned carbon nanotube films were deposited by the microwave plasma-assisted chemical vapor deposition technique. The surface of the as-grown film contained a carbon nanotube mat of amorphous carbon and entangled nanotubes with some tubes protruding from the surface. Hydrogen plasma etching resulted in the removal of the surface layer, and regrowth on the etched surface displayed the formation of a new carbon nanotube mat. The emission site density and the current-voltage dependence of the field emission from all of the samples were analyzed. The results showed that the as-grown sample had a few strong emission spots and a relatively high emission current density (∼20 μA/cm 2 at 1 V/μm), while the regrown sample exhibited a significantly increased emission site density

  19. Absorption and emission properties of photonic crystals and metamaterials

    International Nuclear Information System (INIS)

    Peng, Lili

    2007-01-01

    We study the emission and absorption properties of photonic crystals and metamaterials using Comsol Multiphysics and Ansoft HFSS as simulation tools. We calculate the emission properties of metallic designs using drude model and the results illustrate that an appropriate termination of the surface of the metallic structure can significantly increase the absorption and therefore the thermal emissivity. We investigate the spontaneous emission rate modifications that occur for emitters inside two-dimensional photonic crystals and find the isotropic and directional emissions with respect to different frequencies as we have expected.

  20. Reducing field emission in the superconducting rf cavities for the next generation of particle accelerators

    International Nuclear Information System (INIS)

    Shu, Q.S.; Hartung, W.; Leibovich, A.; Kirchgessner, J.; Moffat, D.; Padamsee, H.; Rubin, D.; Sears, J.

    1991-01-01

    This paper reports on field emission, which is an obstacle to reaching the higher fields called for in future applications of superconducting radio frequency cavities to particle accelerators. The authors used heat treatment up to 1500 degrees C in an ultra-high vacuum furnace, along with processing of cavities and temperature mapping, to suppress field emission and analyze emitter properties. In 27 tests of 1-cell 1500 MHz fired accelerating cavities, on the average the accelerating field E acc increased to 24 MV/m (H pk = 1250 Oe) from 13 MV/m with chemical treatment alone; the highest E acc reached was 30.5 MV/m

  1. Electron field emission characteristics of carbon nanotube on tungsten tip

    International Nuclear Information System (INIS)

    Phan Ngoc Hong; Bui Hung Thang; Nguyen Tuan Hong; Phan Ngoc Minh; Lee, Soonil

    2009-01-01

    Electron field emission characteristic of carbon nanotubes on tungsten tip was investigated in 2x10 -6 Torr vacuum. The measurement results showed that the CNTs/W tip could emit electron at 0.7 V/μm (nearly 10 times lower than that of the W tip itself) and reach up to 26 μA at the electric field of 1 V/μm. The emission characteristic follows the Fowler-Nordheim mechanism. Analysis of the emission characteristic showed that the CNTs/W tip has a very high value of field enhancement factor (β = 4.1 x 10 4 cm -1 ) that is much higher than that of the tungsten tip itself. The results confirmed the excellent field emission behavior of the CNTs materials and the CNTs/W tip is a prospective candidate for advanced electron field emitter.

  2. Recent progress in nanostructured next-generation field emission devices

    International Nuclear Information System (INIS)

    Mittal, Gaurav; Lahiri, Indranil

    2014-01-01

    Field emission has been known to mankind for more than a century, and extensive research in this field for the last 40–50 years has led to development of exciting applications such as electron sources, miniature x-ray devices, display materials, etc. In the last decade, large-area field emitters were projected as an important material to revolutionize healthcare and medical devices, and space research. With the advent of nanotechnology and advancements related to carbon nanotubes, field emitters are demonstrating highly enhanced performance and novel applications. Next-generation emitters need ultra-high emission current density, high brightness, excellent stability and reproducible performance. Novel design considerations and application of new materials can lead to achievement of these capabilities. This article presents an overview of recent developments in this field and their effects on improved performance of field emitters. These advancements are demonstrated to hold great potential for application in next-generation field emission devices. (topical review)

  3. Recent progress in nanostructured next-generation field emission devices

    Science.gov (United States)

    Mittal, Gaurav; Lahiri, Indranil

    2014-08-01

    Field emission has been known to mankind for more than a century, and extensive research in this field for the last 40-50 years has led to development of exciting applications such as electron sources, miniature x-ray devices, display materials, etc. In the last decade, large-area field emitters were projected as an important material to revolutionize healthcare and medical devices, and space research. With the advent of nanotechnology and advancements related to carbon nanotubes, field emitters are demonstrating highly enhanced performance and novel applications. Next-generation emitters need ultra-high emission current density, high brightness, excellent stability and reproducible performance. Novel design considerations and application of new materials can lead to achievement of these capabilities. This article presents an overview of recent developments in this field and their effects on improved performance of field emitters. These advancements are demonstrated to hold great potential for application in next-generation field emission devices.

  4. Enhanced performance of thermal-assisted electron field emission based on barium oxide nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Yunkang [Department of Mathematics and Physics, Nanjing Institute of technology, Nanjing, 211167 (China); Chen, Jing, E-mail: chenjingmoon@gmail.com [School of Electronic Science & Engineering, Southeast University, Nanjing, 210096 (China); Zhang, Yuning; Zhang, Xiaobing; Lei, Wei; Di, Yunsong [School of Electronic Science & Engineering, Southeast University, Nanjing, 210096 (China); Zhang, Zichen, E-mail: zz241@ime.ac.cn [Integrated system for Laser applications Group, Institute of Microelectronics of Chinese Academy of Sciences, 100029, Beijing (China)

    2017-02-28

    Highlights: • A possible mechanism for thermal-assisted electric field was demonstrated. • A new path for the architecture of the novel nanomaterial and methodology for its potential application in the field emission device area was provided. • The turn-on field, the threshold field and the field emission current density were largely related to the temperature of the cathode. • The relationship between the work function of emitter material and the temperature of emitter was found. - Abstract: In this paper, thermal-assisted field emission properties of barium oxide (BaO) nanowire synthesized by a chemical bath deposition method were investigated. The morphology and composition of BaO nanowire were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SED), X-ray diffraction (XRD), and energy dispersive X-ray spectrometer (EDX) respectively. The turn-on field, threshold field and the emission current density could be affected relatively due to the thermal-assisted effect when the electric field was applied, in the meanwhile, the turn-on field for BaO nanowire was measured to be decreased from 1.12 V/μm to 0.66 V/μm when the temperature was raised from 293 K to 593 K, whereas for the threshold field was found to decrease from 3.64 V/μm to 2.12 V/μm. The improved performance was demonstrated due to the reduced work function of the BaO nanowire as the agitation temperature increasing, leading to the higher probability of electrons tunneling through the energy barrier and enhancement of the field emission properties of BaO emitters.

  5. Enhanced performance of thermal-assisted electron field emission based on barium oxide nanowire

    International Nuclear Information System (INIS)

    Cui, Yunkang; Chen, Jing; Zhang, Yuning; Zhang, Xiaobing; Lei, Wei; Di, Yunsong; Zhang, Zichen

    2017-01-01

    Highlights: • A possible mechanism for thermal-assisted electric field was demonstrated. • A new path for the architecture of the novel nanomaterial and methodology for its potential application in the field emission device area was provided. • The turn-on field, the threshold field and the field emission current density were largely related to the temperature of the cathode. • The relationship between the work function of emitter material and the temperature of emitter was found. - Abstract: In this paper, thermal-assisted field emission properties of barium oxide (BaO) nanowire synthesized by a chemical bath deposition method were investigated. The morphology and composition of BaO nanowire were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SED), X-ray diffraction (XRD), and energy dispersive X-ray spectrometer (EDX) respectively. The turn-on field, threshold field and the emission current density could be affected relatively due to the thermal-assisted effect when the electric field was applied, in the meanwhile, the turn-on field for BaO nanowire was measured to be decreased from 1.12 V/μm to 0.66 V/μm when the temperature was raised from 293 K to 593 K, whereas for the threshold field was found to decrease from 3.64 V/μm to 2.12 V/μm. The improved performance was demonstrated due to the reduced work function of the BaO nanowire as the agitation temperature increasing, leading to the higher probability of electrons tunneling through the energy barrier and enhancement of the field emission properties of BaO emitters.

  6. Rf Gun with High-Current Density Field Emission Cathode

    International Nuclear Information System (INIS)

    Jay L. Hirshfield

    2005-01-01

    High current-density field emission from an array of carbon nanotubes, with field-emission-transistor control, and with secondary electron channel multiplication in a ceramic facing structure, have been combined in a cold cathode for rf guns and diode guns. Electrodynamic and space-charge flow simulations were conducted to specify the cathode configuration and range of emission current density from the field emission cold cathode. Design of this cathode has been made for installation and testing in an existing S-band 2-1/2 cell rf gun. With emission control and modulation, and with current density in the range of 0.1-1 kA/cm2, this cathode could provide performance and long-life not enjoyed by other currently-available cathodes

  7. Application of field blanks in odour emission research

    NARCIS (Netherlands)

    Ogink, Nico W.M.; Klarenbeek, Johannes V.

    2016-01-01

    In the Netherlands field blanks are mandatory when sampling odour emission. Field blanks are matrices that have negligible or unmeasurable amounts of the substance of interest. They are used to document possible contamination during sampling, transport and storage of samples. Although field

  8. New results on RF and DC field emission

    International Nuclear Information System (INIS)

    Padamsee, H.; Kirchgessner, J.; Moffat, D.; Noer, R.; Rubin, D.; Sears, J.; Shu, Q.S.

    1990-01-01

    This paper reviews progress in RF and DC field emission since the last workshop held two years ago at Argonne National Laboratory. Through better characterization, progress has been made towards improved understanding of FE in cavities. Through development of new cures, gains have made towards higher fields. Through better rinsing procedures low-frequency (500 and 350 MHz) cavities regularly reach surface electric fields of 20 MV/m. Processing times are substantially reduced. Through heat treatment at 1350degC high frequency (1500 MHz) cavities have reached 53 MV/m, and 3000 MHz cavities have reached 70 MV/m. The state of the art in Epk is described first. Then, benefits of high temperature treatment are discussed, focusing on highest temperature (1300-1350degC) treatment, intermediate heat treatments, and heat treatment without final methanol rinsing. He processing, heat treatment of 3-GHz cavitie, general inferences concerning emitter properties, influence of condensed gases, and sources of emitters are also addressed. Finally, lessons to be learned from copper cavities and high power processing is pointed out and discussed. (N.K.)

  9. Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets

    Science.gov (United States)

    Nishikawa, K.-I.; Hardee, P.; Hededal, C.; Mizuno, Yosuke; Fishman, G. Jerry; Hartmann, D. H.

    2006-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), supernova remnants, and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that particle acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration' is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different spectral properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations of relativistic jets and try to make a connection with observations.

  10. N{sub 2}O Emission from energy crop fields

    Energy Technology Data Exchange (ETDEWEB)

    Joergensen, B.J. [The Royal Veterinary and Agricultural Univ., Dept. of Agricultural Sciences, Section of Soil, Water and Plant Nutrition (Denmark); Nyholm Joergensen, R. [Research Centre Foulum, The Danish Inst. of Plant and Soil Science, Dept. of Soil Science (Denmark)

    1996-03-01

    The interest in N{sub 2}O emissions from soils with energy crops is a results of its properties as a greenhouse gas, since the global warming potential of N{sub 2}O per unit mass is about 320 times greater than CO{sub 2}. The contribution of N{sub 2}O from the soil to the atmosphere may increase due to agricultural management. Consequently, large N{sub 2}O emissions can lower the reduction of the greenhouse effect achieved by the substitution of fossil fuels by energy crops. For this reason it is crucial to find the crops for combustion with the lowest potential for emission of N{sub 2}O from the soil per produced energy unit. The aims of this study were to assess the annual N{sub 2}O flux from a Miscanthus `Giganteus` (M. `Giganteus`) and winter rye (Secale cereale) field, and to investigate the factors affecting the N{sub 2}O emission. To obtain these aims a method was developed for measurements in tall crops. The thesis contains a literature review on the N{sub 2}O emission from the soils, a section with development of the technique for N{sub 2}O flux measurements, and an experimental section. Finally, the thesis contains a section where the results are discussed in relation to the use of energy crops. In all the filed studies, the N{sub 2}O emission was measured by using a new developed closed-chamber technique. The main advantages of the chamber method were the ability to contain growing plants up to a height of 3 m, and the relatively large area (2X2m) covered by each other. Soils with annual and perennial crops can be expected to emit less then 3 kg N{sub 2}O ha{sup -1} yr{sup -1}. This amount corresponds to 960 kg CO{sub 2} ha{sup -1} yr{sup -1} compared to a total CO{sub 2} reduction of 10 to 19 tons CO{sub 2} ha{sup -1} yr{sup -1} using the energy crops as substituion for fossil fuels. An efficient way to reduce the N{sub 2}O emission is to exclude use of fertiliser but this also reduces the dry matter yield and consequently also the CO{sub 2} reduction

  11. N{sub 2}O Emission from energy crop fields

    Energy Technology Data Exchange (ETDEWEB)

    Joergensen, B.J. [The Royal Veterinary and Agricultural Univ., Dept. of Agricultural Sciences, Section of Soil, Water and Plant Nutrition (Denmark); Nyholm Joergensen, R. [Research Centre Foulum, The Danish Inst. of Plant and Soil Science, Dept. of Soil Science (Denmark)

    1996-03-01

    The interest in N{sub 2}O emissions from soils with energy crops is a results of its properties as a greenhouse gas, since the global warming potential of N{sub 2}O per unit mass is about 320 times greater than CO{sub 2}. The contribution of N{sub 2}O from the soil to the atmosphere may increase due to agricultural management. Consequently, large N{sub 2}O emissions can lower the reduction of the greenhouse effect achieved by the substitution of fossil fuels by energy crops. For this reason it is crucial to find the crops for combustion with the lowest potential for emission of N{sub 2}O from the soil per produced energy unit. The aims of this study were to assess the annual N{sub 2}O flux from a Miscanthus 'Giganteus' (M. 'Giganteus') and winter rye (Secale cereale) field, and to investigate the factors affecting the N{sub 2}O emission. To obtain these aims a method was developed for measurements in tall crops. The thesis contains a literature review on the N{sub 2}O emission from the soils, a section with development of the technique for N{sub 2}O flux measurements, and an experimental section. Finally, the thesis contains a section where the results are discussed in relation to the use of energy crops. In all the filed studies, the N{sub 2}O emission was measured by using a new developed closed-chamber technique. The main advantages of the chamber method were the ability to contain growing plants up to a height of 3 m, and the relatively large area (2X2m) covered by each other. Soils with annual and perennial crops can be expected to emit less then 3 kg N{sub 2}O ha{sup -1} yr{sup -1}. This amount corresponds to 960 kg CO{sub 2} ha{sup -1} yr{sup -1} compared to a total CO{sub 2} reduction of 10 to 19 tons CO{sub 2} ha{sup -1} yr{sup -1} using the energy crops as substitution for fossil fuels. An efficient way to reduce the N{sub 2}O emission is to exclude use of fertiliser but this also reduces the dry matter yield and consequently also the

  12. Negative ion emission at field electron emission from amorphous (alpha-C:H) carbon

    CERN Document Server

    Bernatskij, D P; Ivanov-Omskij, V I; Pavlov, V G; Zvonareva, T K

    2001-01-01

    The study on the electrons field emission from the plane cathode surface on the basis of the amorphous carbon film (alpha-C:H) is carried out. The methodology, making it possible to accomplish simultaneously the registration of the emission currents and visually observe the distribution of the emission centers on the plane emitter surface is developed. The analysis of the oscillograms indicated that apart from the proper electron constituent the negative ions of hydrogen (H sup - and H sub 2 sup -), carbon (C sup -) and hydrocarbon (CH sub n sup -) are observed. The ions emission is connected with the processes of formation and degradation of the local emission centers

  13. Field electron emission from pencil-drawn cold cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jiangtao; Yang, Bingjun; Liu, Xiahui; Yang, Juan; Yan, Xingbin, E-mail: xbyan@licp.cas.cn [Laboratory of Clean Energy Chemistry and Materials, State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2016-05-09

    Field electron emitters with flat, curved, and linear profiles are fabricated on flexible copy papers by direct pencil-drawing method. This one-step method is free of many restricted conditions such as high-temperature, high vacuum, organic solvents, and multistep. The cold cathodes display good field emission performance and achieve high emission current density of 78 mA/cm{sup 2} at an electric field of 3.73 V/μm. The approach proposed here would bring a rapid, low-cost, and eco-friendly route to fabricate but not limited to flexible field emitter devices.

  14. Vector fields satisfying the barycenter property

    Directory of Open Access Journals (Sweden)

    Lee Manseob

    2018-04-01

    Full Text Available We show that if a vector field X has the C1 robustly barycenter property then it does not have singularities and it is Axiom A without cycles. Moreover, if a generic C1-vector field has the barycenter property then it does not have singularities and it is Axiom A without cycles. Moreover, we apply the results to the divergence free vector fields. It is an extension of the results of the barycenter property for generic diffeomorphisms and volume preserving diffeomorphisms [1].

  15. Field electron emission characteristics of chemical vapour deposition diamond films with controlled sp2 phase concentration

    International Nuclear Information System (INIS)

    Lu, X.; Yang, Q.; Xiao, C.; Hirose, A.

    2008-01-01

    Diamond films were synthesized in a microwave plasma-enhanced chemical vapour deposition reactor. The microstructure and surface morphology of deposited films were characterized by Raman spectroscope and scanning electron microscope. The sp 2 phase concentration in diamond films was varied and its effect on the field electron emission (FEE) properties was investigated. Diamond films deposited under higher methane concentration exhibit better FEE property including lower turn-on electric field and larger emission current. The predominating factor modifying the FEE property is presumed to be the increase of sp 2 phase concentration. The influence of bias voltage on the FEE property of diamond films is not monotonic. Postgrowth acid treatment reduces the sp 2 phase content in diamond films without changing diamond grain sizes. The corresponding FEE property was degraded

  16. Field emission from optimized structure of carbon nanotube field emitter array

    International Nuclear Information System (INIS)

    Chouhan, V.; Noguchi, T.; Kato, S.

    2016-01-01

    The authors report a detail study on the emission properties of field emitter array (FEA) of micro-circular emitters of multiwall carbon nanotubes (CNTs). The FEAs were fabricated on patterned substrates prepared with an array of circular titanium (Ti) islands on titanium nitride coated tantalum substrates. CNTs were rooted into these Ti islands to prepare an array of circular emitters. The circular emitters were prepared in different diameters and pitches in order to optimize their structure for acquiring a high emission current. The pitch was varied from 0 to 600 μm, while a diameter of circular emitters was kept constant to be 50 μm in order to optimize a pitch. For diameter optimization, a diameter was changed from 50 to 200 μm while keeping a constant edge-to-edge distance of 150 μm between the circular emitters. The FEA with a diameter of 50 μm and a pitch of 120 μm was found to be the best to achieve an emission current of 47 mA corresponding to an effective current density of 30.5 A/cm"2 at 7 V/μm. The excellent emission current was attributed to good quality of CNT rooting into the substrate and optimized FEA structure, which provided a high electric field on a whole circular emitter of 50 μm and the best combination of the strong edge effect and CNT coverage. The experimental results were confirmed with computer simulation.

  17. Field emission from optimized structure of carbon nanotube field emitter array

    Energy Technology Data Exchange (ETDEWEB)

    Chouhan, V., E-mail: vchouhan@post.kek.jp, E-mail: vijaychouhan84@gmail.com [School of High Energy Accelerator, The Graduate University for Advanced Studies, Tsukuba 305-0801 (Japan); Noguchi, T. [High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 (Japan); Kato, S. [School of High Energy Accelerator, The Graduate University for Advanced Studies, Tsukuba 305-0801 (Japan); High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 (Japan)

    2016-04-07

    The authors report a detail study on the emission properties of field emitter array (FEA) of micro-circular emitters of multiwall carbon nanotubes (CNTs). The FEAs were fabricated on patterned substrates prepared with an array of circular titanium (Ti) islands on titanium nitride coated tantalum substrates. CNTs were rooted into these Ti islands to prepare an array of circular emitters. The circular emitters were prepared in different diameters and pitches in order to optimize their structure for acquiring a high emission current. The pitch was varied from 0 to 600 μm, while a diameter of circular emitters was kept constant to be 50 μm in order to optimize a pitch. For diameter optimization, a diameter was changed from 50 to 200 μm while keeping a constant edge-to-edge distance of 150 μm between the circular emitters. The FEA with a diameter of 50 μm and a pitch of 120 μm was found to be the best to achieve an emission current of 47 mA corresponding to an effective current density of 30.5 A/cm{sup 2} at 7 V/μm. The excellent emission current was attributed to good quality of CNT rooting into the substrate and optimized FEA structure, which provided a high electric field on a whole circular emitter of 50 μm and the best combination of the strong edge effect and CNT coverage. The experimental results were confirmed with computer simulation.

  18. Field emission from ZnS nanorods synthesized by radio frequency magnetron sputtering technique

    Science.gov (United States)

    Ghosh, P. K.; Maiti, U. N.; Jana, S.; Chattopadhyay, K. K.

    2006-11-01

    The field emission property of zinc sulphides nanorods synthesized in the thin film form on Si substrates has been studied. It is seen that ZnS nanorod thin films showed good field emission properties with a low-macroscopic turn-on field (2.9-6.3 V/μm). ZnS nanorods were synthesized by using radio frequency magnetron sputtering of a polycrystalline prefabricated ZnS target at a relatively higher pressure (10 -1 mbar) and at a lower substrate temperature (233-273 K) without using any catalyst. Transmission electron microscopic image showed the formation of ZnS nanorods with high aspect ratio (>60). The field emission data were analysed using Fowler-Nordhiem theory and the nearly straight-line nature of the F-N plots confirmed cold field emission of electrons. It was also found that the turn-on field decreased with the decrease of nanorod's diameters. The optical properties of the ZnS nanorods were also studied. From the measurements of transmittance of the films deposited on glass substrates, the direct allowed bandgap values have been calculated and they were in the range 3.83-4.03 eV. The thickness of the films was ˜600 nm.

  19. Methane emission from wetland rice fields

    NARCIS (Netherlands)

    Denier van der Gon, H.A.C.

    1996-01-01


    Methane (CH 4 ) is an important greenhouse gas and plays a key role in tropospheric and stratospheric chemistry. Wetland rice fields are an important source of methane, accounting for approximately 20% of the global anthropogenic

  20. Field Emission of ITO-Coated Vertically Aligned Nanowire Array.

    KAUST Repository

    Lee, Changhwa

    2010-04-29

    An indium tin oxide (ITO)-coated vertically aligned nanowire array is fabricated, and the field emission characteristics of the nanowire array are investigated. An array of vertically aligned nanowires is considered an ideal structure for a field emitter because of its parallel orientation to the applied electric field. In this letter, a vertically aligned nanowire array is fabricated by modified conventional UV lithography and coated with 0.1-μm-thick ITO. The turn-on electric field intensity is about 2.0 V/μm, and the field enhancement factor, β, is approximately 3,078 when the gap for field emission is 0.6 μm, as measured with a nanomanipulator in a scanning electron microscope.

  1. Field Emission of ITO-Coated Vertically Aligned Nanowire Array.

    KAUST Repository

    Lee, Changhwa; Lee, Seokwoo; Lee, Seung S

    2010-01-01

    An indium tin oxide (ITO)-coated vertically aligned nanowire array is fabricated, and the field emission characteristics of the nanowire array are investigated. An array of vertically aligned nanowires is considered an ideal structure for a field emitter because of its parallel orientation to the applied electric field. In this letter, a vertically aligned nanowire array is fabricated by modified conventional UV lithography and coated with 0.1-μm-thick ITO. The turn-on electric field intensity is about 2.0 V/μm, and the field enhancement factor, β, is approximately 3,078 when the gap for field emission is 0.6 μm, as measured with a nanomanipulator in a scanning electron microscope.

  2. Influence of local field on spontaneous light emission by nanoparticles

    DEFF Research Database (Denmark)

    Keller, Ole; Lozovski, V.; Iezhokin, I.

    2009-01-01

    moment of transition that takes local-field effects into account. The effective dipole moment depends on the particle shape and size. Therefore, dipole radiation depends on those parameters too. The direction patterns of light emission by cubic particles have been calculated. The particles have been......A self-consistent approach based on the local-field concept has been proposed to calculate the direction patterns of light emission by nanoparticles with various shapes. The main idea of the method consists in constructing self-consistent equations for the electromagnetic field at any point...... of the system. The solution of the equations brings about relationships between the local field at an arbitrary point in the system and the external long-wave field via the local-field factor. The latter connects the initial moment of optical dipole transition per system volume unit and the effective dipole...

  3. Enhancement of electron field emission of vertically aligned carbon nanotubes by nitrogen plasma treatment

    Energy Technology Data Exchange (ETDEWEB)

    Wang, B.B. [College of Chemistry and Chemical Engineering, Chongqing University of Technology, 69 Hongguang Rd, Lijiatuo, Banan District, Chongqing 400054 (China); Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Cheng, Q.J. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Chen, X. [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Ostrikov, K., E-mail: kostya.ostrikov@csiro.au [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

    2011-09-22

    Highlights: > A new and custom-designed bias-enhanced hot-filament chemical vapor deposition system is developed to synthesize vertically aligned carbon nanotubes. > The carbon nanotubes are later treated with nitrogen plasmas. > The electron field emission characteristics of the carbon nanotubes are significantly improved after the nitrogen plasma treatment. > A new physical mechanism is proposed to interpret the improvement of the field emission characteristics. - Abstract: The electron field emission (EFE) characteristics from vertically aligned carbon nanotubes (VACNTs) without and with treatment by the nitrogen plasma are investigated. The VACNTs with the plasma treatment showed a significant improvement in the EFE property compared to the untreated VACNTs. The morphological, structural, and compositional properties of the VACNTs are extensively examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy. It is shown that the significant EFE improvement of the VACNTs after the nitrogen plasma treatment is closely related to the variation of the morphological and structural properties of the VACNTs. The high current density (299.6 {mu}A/cm{sup 2}) achieved at a low applied field (3.50 V/{mu}m) suggests that the VACNTs after nitrogen plasma treatment can serve as effective electron field emission sources for numerous applications.

  4. Enhancement of electron field emission of vertically aligned carbon nanotubes by nitrogen plasma treatment

    International Nuclear Information System (INIS)

    Wang, B.B.; Cheng, Q.J.; Chen, X.; Ostrikov, K.

    2011-01-01

    Highlights: → A new and custom-designed bias-enhanced hot-filament chemical vapor deposition system is developed to synthesize vertically aligned carbon nanotubes. → The carbon nanotubes are later treated with nitrogen plasmas. → The electron field emission characteristics of the carbon nanotubes are significantly improved after the nitrogen plasma treatment. → A new physical mechanism is proposed to interpret the improvement of the field emission characteristics. - Abstract: The electron field emission (EFE) characteristics from vertically aligned carbon nanotubes (VACNTs) without and with treatment by the nitrogen plasma are investigated. The VACNTs with the plasma treatment showed a significant improvement in the EFE property compared to the untreated VACNTs. The morphological, structural, and compositional properties of the VACNTs are extensively examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy. It is shown that the significant EFE improvement of the VACNTs after the nitrogen plasma treatment is closely related to the variation of the morphological and structural properties of the VACNTs. The high current density (299.6 μA/cm 2 ) achieved at a low applied field (3.50 V/μm) suggests that the VACNTs after nitrogen plasma treatment can serve as effective electron field emission sources for numerous applications.

  5. Effect of synthesis parameters on morphology of polyaniline (PANI) and field emission investigation of PANI nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Bankar, Prashant K.; More, Mahendra A., E-mail: mam@physics.unipune.ac.in [Center for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune-411007 (India); Patil, Sandip S. [Department of Physics, Modern College of Arts, Science and Commerce, Shivajinagar, Pune-411005. India (India)

    2015-06-24

    Polyaniline (PANI) nanostructures have been synthesized by simple chemical oxidation route at different monomer concentration along with variation in synthesis temperature. The effect of variation of synthesis parameters has been revealed using different characterization techniques. The structural and morphological characterization of the synthesized PANI nanostructures was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), whereas Fourier Transform Infrared spectroscopy (FTIR) has been used to reveal the chemical properties. With the variation in the synthesis temperature and monomer concentration, various morphologies characterized by formation of PANI nanoparticles, nanofibres, nanotubes and nanospheres, are revealed from the SEM analysis. The FTIR analysis reveals the formation of conducting state of PANI under prevailing experimental conditions. The field emission investigation of the conducting PANI nanotubes was performed in all metal UHV system at base pressure of 1x10{sup −8} mbar. The turn on field required to draw emission of 1 nA current was observed to be ∼ 2.2 V/μm and threshold field (corresponding to emission current density of 1 µA/cm2) was found to be 3.2 V/μm. The emission current was observed to be stable for more than three hours at a preset value 1 µA. The simple synthesis route and good field emission characteristics indicate potential of PANI nanofibres as a promising emitter for field emission based micro/nano devices.

  6. Process system and method for fabricating submicron field emission cathodes

    Science.gov (United States)

    Jankowski, Alan F.; Hayes, Jeffrey P.

    1998-01-01

    A process method and system for making field emission cathodes exists. The deposition source divergence is controlled to produce field emission cathodes with height-to-base aspect ratios that are uniform over large substrate surface areas while using very short source-to-substrate distances. The rate of hole closure is controlled from the cone source. The substrate surface is coated in well defined increments. The deposition source is apertured to coat pixel areas on the substrate. The entire substrate is coated using a manipulator to incrementally move the whole substrate surface past the deposition source. Either collimated sputtering or evaporative deposition sources can be used. The position of the aperture and its size and shape are used to control the field emission cathode size and shape.

  7. Field emission study of MWCNT/conducting polymer nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Alvi, M.A., E-mail: maalvee@yahoo.co.in [Department of Physics, King Abdulaziz University, Jeddah-21589 (Saudi Arabia); Al-Ghamdi, A.A. [Department of Physics, King Abdulaziz University, Jeddah-21589 (Saudi Arabia); Husain, M. [Department of Physics, Jamia Millia Islamia, New Delhi-110025 (India)

    2014-12-01

    MWCNTs/Polypyrrole nanocomposites were synthesized by solution mixing method. These synthesized nanocomposites were studied carefully by Raman Spectroscopy and Scanning Electron Microscopy measurements. The field emission study of MWCNTs/Polypyrrole nanocomposites were performed in diode arrangement under vacuum of the order of 10{sup −5} Torr. The emission current under exploration depends on applied voltage. The prepared nanocomposites depict low turn-on field at 1.4 V/μm that reaches to a maximum emission current density 0.020 mA/cm{sup 2} at 2.4 V/µm, which is calculated from the graph of current density (J) against the applied electric field (E) and from Fowler–Nordheim (F–N) plot.

  8. High-Performance Field Emission from a Carbonized Cork.

    Science.gov (United States)

    Lee, Jeong Seok; Lee, Hak Jun; Yoo, Jae Man; Kim, Taewoo; Kim, Yong Hyup

    2017-12-20

    To broaden the range of application of electron beams, low-power field emitters are needed that are miniature and light. Here, we introduce carbonized cork as a material for field emitters. The light natural cork becomes a graphitic honeycomb upon carbonization, with the honeycomb cell walls 100-200 nm thick and the aspect ratio larger than 100, providing an ideal structure for the field electron emission. Compared to nanocarbon field emitters, the cork emitter produces a high current density and long-term stability with a low turn-on field. The nature of the cork material makes it quite simple to fabricate the emitter. Furthermore, any desired shape of the emitter tailored for the final application can easily be prepared for point, line, or planar emission.

  9. Field emission studies of silver nanoparticles synthesized by electron cyclotron resonance plasma

    International Nuclear Information System (INIS)

    Purohit, Vishwas; Mazumder, Baishakhi; Bhise, A.B.; Poddar, Pankaj; Joag, D.S.; Bhoraskar, S.V.

    2011-01-01

    Field emission has been studied for silver nanoparticles (25-200 nm), deposited within a cylindrical silver target in an electron cyclotron resonance (ECR) plasma. Particle size distribution was controlled by optimum biasing voltages between the chamber and the target. Presence of non-oxidized silver was confirmed from the X-Ray diffraction analysis; however, thin protective layer of oxide was identified from the selective area electron diffraction pattern obtained with transmission electron microscopy. The silver nanoparticles were seen to exhibit hilly pointed like structures when viewed under the atomic force microscopy (AFM). The emissive properties of these particles were investigated by field emission microscopy. It is found that this technique of deposition is ideal for formation of nanoparticles films on different substrate geometries with size controllability as well as its application to emission devices.

  10. Plasma-induced field emission study of carbon nanotube cathode

    Directory of Open Access Journals (Sweden)

    Yi Shen

    2011-10-01

    Full Text Available An investigation on the plasma-induced field emission (PFE properties of a large area carbon nanotube (CNT cathode on a 2 MeV linear induction accelerator injector is presented. Experimental results show that the cathode is able to emit intense electron beams. Intense electron beams of 14.9–127.8  A/cm^{2} are obtained from the cathode. The CNT cathode desorbs gases from the CNTs during the PFE process. The fast cathode plasma expansion affects the diode perveance. The amount of outgassing is estimated to be 0.06–0.49  Pa·L, and the ratio of outgassing and electron are roughly calculated to be within the range of 170–350 atoms per electron. The effect of the outgassing is analyzed, and the outgassing mass spectrum of the CNT cathode has been studied during the PFE. There is a significant desorption of CO_{2}, N_{2}(CO, and H_{2} gases, which plays an important role during the PFE process. All the experiments demonstrate that the outgassing plays an important role in the formation of the cathode plasma. Moreover, the characteristic turn-on time of the CNT cathode was measured to be 39 ns.

  11. CYANOBACTERIA FOR MITIGATING METHANE EMISSION FROM SUBMERGED PADDY FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Upasana Mishra; Shalini Anand [Department of Environmental Studies, Inderprastha Engineering College, Sahibabad, Ghaziabad (India)

    2008-09-30

    Atmospheric methane, a potent greenhouse gas with high absorption potential for infrared radiation, is responsible for one forth of the total anticipated warming. It is forming a major part of green house gases, next after carbon dioxide. Its concentration has been increasing alarmingly on an average at the rate of one percent per year. Atmospheric methane, originating mainly from biogenic sources such as paddy fields, natural wetlands and landfills, accounts for 15-20% of the world's total anthropogenic methane emission. With intensification of rice cultivation in coming future, methane emissions from paddy fields are anticipated to increase. India's share in world's rice production is next after to China and likewise total methane emission from paddy fields also. Methane oxidation through planktophytes, particularly microalgae which are autotrophic and abundant in rice rhizospheres, hold promise in controlling methane emission from submerged paddy fields. The present study is focused on the role of nitrogen fixing, heterocystous cyanobacteria and Azolla (a water fern harboring a cyanobacterium Anabaena azollae) as biological sink for headspace concentration of methane in flooded soils. In this laboratory study, soil samples containing five potent nitrogen fixer cyanobacterial strains from paddy fields, were examined for their methane reducing potential. Soil sample without cyanobacterial strain was tested and taken as control. Anabaena sp. was found most effective in inhibiting methane concentration by 5-6 folds over the control. Moist soil cores treated with chemical nitrogen, urea, in combination with cyanobacteria mixture, Azolla microphylla or cyanobacteria mixture plus Azolla microphylla exhibited significance reduction in the headspace concentration of methane than the soil cores treated with urea alone. Contrary to other reports, this study also demonstrates that methane oxidation in soil core samples from paddy fields was stimulated by

  12. Field emission from vertically aligned few-layer graphene

    International Nuclear Information System (INIS)

    Malesevic, Alexander; Kemps, Raymond; Vanhulsel, Annick; Chowdhury, Manish Pal; Volodin, Alexander; Van Haesendonck, Chris

    2008-01-01

    The electric field emission behavior of vertically aligned few-layer graphene was studied in a parallel plate-type setup. Few-layer graphene was synthesized in the absence of any metallic catalyst by microwave plasma enhanced chemical vapor deposition with gas mixtures of methane and hydrogen. The deposit consists of nanostructures that are several micrometers wide, highly crystalline stacks of four to six atomic layers of graphene, aligned vertically to the substrate surface in a high density network. The few-layer graphene is found to be a good field emitter, characterized by turn-on fields as low as 1 V/μm and field amplification factors up to several thousands. We observe a clear dependence of the few-layer graphene field emission behavior on the synthesis parameters: Hydrogen is identified as an efficient etchant to improve field emission, and samples grown on titanium show lower turn-on field values and higher amplification factors when compared to samples grown on silicon

  13. Field emission and high voltage cleaning of particulate contaminants on extended metallic surfaces

    International Nuclear Information System (INIS)

    Tan, J.; Bonin, B.; Safa, H.

    1996-01-01

    The vacuum insulation properties of extended metallic surfaces depends strongly on their cleanliness. The usual technique to reduce electronic field emission from such surfaces consists in exposing them to very high electric fields during limited periods of time. This kind of processing also reduces the occurrence of vacuum breakdown. The processing of the surface is generally believed to be due to a thermomechanical destruction of the emitting sites, initiated by the emission itself. Comparison of the electric forces vs adherence forces which act on dust particles lying on the surface shows that the processing could also be due simply to the mechanical removal of the dust particles, with a subsequent reduction of field emission from the contaminated surface. (author)

  14. Structural origination of charge transfer complex nanostructures: Excellent candidate for field emission

    International Nuclear Information System (INIS)

    Pal, Shreyasi; Chattopadhyay, Kalyan Kumar

    2016-01-01

    Worldwide strategies for amalgamating rationally controlled one-dimensional organic nanowires are of fundamental importance for their applications in flexible, cheaper and lighter electronics. In this work we have fabricated large-area, ordered CuTCNQ (copper-7,7,8,8-tetracyanoquinodimethane) nano architecture arrays over flexible conducting substrate and discussed the rational growth and integration of nanostructures. Here we adopted the organic solid phase reaction (VLS) technique for the growth of organic hierarchies and investigated how field emission properties changes by tuning the nanostructures morphology i.e., by varying length, diameter, alignment and orientation over flexible substrate. The CuTCNQ nanowires with optimized geometry exhibit excellent high field emission performance with low turn-on and threshold field values. The result strongly indicate that CuTCNQ nanowires on flexible carbon cloth substrate are promising candidates for constructing cold cathode based emission display devices, vacuum nanoelectronics, and etc.

  15. Structural origination of charge transfer complex nanostructures: Excellent candidate for field emission

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Shreyasi; Chattopadhyay, Kalyan Kumar [Thin Films and Nanoscience Laboratory, Department of Physics, Jadavpur University, Kolkata 700032 (India)

    2016-05-23

    Worldwide strategies for amalgamating rationally controlled one-dimensional organic nanowires are of fundamental importance for their applications in flexible, cheaper and lighter electronics. In this work we have fabricated large-area, ordered CuTCNQ (copper-7,7,8,8-tetracyanoquinodimethane) nano architecture arrays over flexible conducting substrate and discussed the rational growth and integration of nanostructures. Here we adopted the organic solid phase reaction (VLS) technique for the growth of organic hierarchies and investigated how field emission properties changes by tuning the nanostructures morphology i.e., by varying length, diameter, alignment and orientation over flexible substrate. The CuTCNQ nanowires with optimized geometry exhibit excellent high field emission performance with low turn-on and threshold field values. The result strongly indicate that CuTCNQ nanowires on flexible carbon cloth substrate are promising candidates for constructing cold cathode based emission display devices, vacuum nanoelectronics, and etc.

  16. Initiation of vacuum breakdown and failure mechanism of the carbon nanotube during thermal field emission

    Science.gov (United States)

    Dan, Cai; Lie, Liu; Jin-Chuan, Ju; Xue-Long, Zhao; Hong-Yu, Zhou; Xiao, Wang

    2016-04-01

    The carbon nanotube (CNT)-based materials can be used as vacuum device cathodes. Owing to the excellent field emission properties of CNT, it has great potentials in the applications of an explosive field emission cathode. The falling off of CNT from the substrate, which frequently appears in experiments, restricts its application. In addition, the onset time of vacuum breakdown limits the performance of the high-power explosive-emission-cathode-based diode. In this paper, the characteristics of the CNT, electric field strength, contact resistance and the kind of substrate material are varied to study the parameter effects on the onset time of vacuum breakdown and failure mechanism of the CNT by using the finite element method. Project supported by the National Natural Science Foundation of China (Grant Nos. 11305263 and 61401484).

  17. Field electron emission from dense array of microneedles of tungsten

    International Nuclear Information System (INIS)

    Okuyama, F.; Aoyagi, M.; Kitai, T.; Ishikawa, K.

    1978-01-01

    Characteristics of field electron emission from the dense array of microneedles of tungsten prepared on a 10-μm tungsten filament were measured at an environmental pressure of approx.1 x 10 -8 Torr (1.33 x 10 -6 Pa). Electron emission was not uniform over the filament surface, but the variation of emission current with applied voltage explicitly obeyed the Fowler-Nordheim relationship. At an emission current of approx.10 -4 A, a vacuum arc was induced that led to a permanent change in current-voltage characteristic. Current fluctuation was dependent on emitter temperature and applied voltage, and the lowest fluctuation of about 4% was routinely obtained at approx.550 K and at applied voltages several percent lower than the arc-inducing voltage. Macroscopic current density amounted to approx.20-80 mA/cm 2 at the best stability

  18. Field emission from the surface of highly ordered pyrolytic graphite

    Czech Academy of Sciences Publication Activity Database

    Knápek, Alexandr; Sobola, D.; Tománek, P.; Pokorná, Zuzana; Urbánek, Michal

    2017-01-01

    Roč. 395, FEB 15 (2017), s. 157-161 ISSN 0169-4332 R&D Projects: GA TA ČR(CZ) TE01020118 Institutional support: RVO:68081731 Keywords : field emission * HOPG * scanning electron microscopy * scanning near-field optical microscopy Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Nano-processes (applications on nano-scale) Impact factor: 3.387, year: 2016

  19. A comparative study of field-emission from different one dimensional carbon nanostructures synthesized via thermal CVD system

    International Nuclear Information System (INIS)

    Jha, A.; Banerjee, D.; Chattopadhyay, K.K.

    2011-01-01

    Different one dimensional (1D) carbon nanostructures, such as carbon nanonoodles (CNNs), carbon nanospikes (CNSs) and carbon nanotubes (CNTs) have been synthesized via thermal chemical vapour deposition (TCVD) technique. The different 1D morphologies were synthesized by varying the substrate material and the deposition conditions. The as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). FESEM and TEM images showed that the diameters of the CNNs and CNTs were ∼40 nm while the diameters of the CNSs were around 100 nm. Field emission studies of the as-prepared samples showed that CNSs to be a better field emitter than CNNs, whereas CNTs are the best among the three producing large emission current. The variation of field emission properties with inter-electrode distance has been studied in detail. Also the time dependent field emission studies of all the nanostructures have been carried out.

  20. Probe-Hole Field Emission Microscope System Controlled by Computer

    Science.gov (United States)

    Gong, Yunming; Zeng, Haishan

    1991-09-01

    A probe-hole field emission microscope system, controlled by an Apple II computer, has been developed and operated successfully for measuring the work function of a single crystal plane. The work functions on the clean W(100) and W(111) planes are measured to be 4.67 eV and 4.45 eV, respectively.

  1. Development of Field-Emission Electron Gun from Carbon Nanotubes

    CERN Document Server

    Hozumi, Y

    2004-01-01

    Aiming to use a narrow energy-spread electron beam easily and low costly on injector electron guns, we have been tested field emission cathodes of carbon nanotubes (CNTs). Experiments for these three years brought us important suggestions and a few rules of thumb. Now at last, anode current of 3.0 [A/cm2

  2. Focus-variation image reconstruction in field-emission TEM

    NARCIS (Netherlands)

    Coene, W.M.J.; Janssen, A.J.E.M.; Op de Beeck, M.; Van Dyck, D.; Van Zwet, E.J.; Zandbergen, H.W.; Bailey, G.W.; Rieder, C.L.

    1993-01-01

    The use of a field emission gun (FEG) in high resolution TEM (HRTEM) improves the information limit much below the point resolution. In the area between point and information resolution of the FEG-TEM, image interpretation is complicated by the lens aberrations and focus effects. Different

  3. A Comprehensive Review of Effect of Biodiesel Additives on Properties, Performance, and Emission

    Science.gov (United States)

    Madiwale, S.; Karthikeyan, A.; Bhojwani, V.

    2017-05-01

    Objectives:- To presents the literature review on effect of biodiesel additives on properties, performance and on emission. Method:-In the current paper reviews are taken from previous years paper which necessitates the need of addition of additives in the blends of biodiesel and studied the its effect on properties, performance and emissions. Emissions from the diesel powered vehicles mostly damaged the earth’s environment and also increased the overall earth’s temperature. This attracts the need of alternative fuels in the field of transportation sector. Past inventions and research showed that Biodiesel can be used as an alternative fuel for the diesel engine. Biodiesel have good combustion characteristics because of their long chain hydrocarbon structure. However biodiesel possesses few disadvantages such as lower heating value, higher flow ability, much high density and not able to flow at low temperature. Higher rate of fuel consumption is identified and higher level of NOx emissions when biodiesel used in an engine as an alternative fuels. Findings:-Different additives such as antioxidants, improvers for cetane number, cold flow properties improver, etc were investigated by the many researcher and scientists and added in the different feedstock of biodiesel or blends of biodiesel with diesel in different proportions. Directly or indirectly fuel additives can improve the reduction in the emissions, improve the fuel economy, and reduce the dependency of the one’s nation on other. Performances of biodiesel vehicles were drastically improved because of additioninthe blends of biodiesel with diesel fuel in specific percentages to meet the international emission standards. Addition of additives in the biodiesel or in the blends of biodiesel basically changes the high temperature and low temperature flow properties of blends of biodiesel. Current paper finds and compares properties of different additives and its effect on blends of biodiesel properties

  4. Control of spontaneous emission from a microwave-field-driven four-level atom in an anisotropic photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Duo, E-mail: zhangduo10@gmail.com [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Li, Jiahua, E-mail: huajia_li@163.com [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Ding, Chunling; Yang, Xiaoxue [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2012-05-21

    The spontaneous emission properties of a microwave-field-driven four-level atom embedded in anisotropic double-band photonic crystals (PCs) are investigated. We discuss the influences of the band-edge positions, Rabi frequency and detuning of the microwave field on the emission spectrum. It is found that several interesting features such as spectral-line enhancement, spectral-line suppression, spectral-line overlap, and multi-peak structures can be observed in the spectra. The proposed scheme can be achieved by use of a microwave-coupled field into hyperfine levels in rubidium atom confined in a photonic crystal. These theoretical investigations may provide more degrees of freedom to manipulate the atomic spontaneous emission. -- Highlights: ► Spontaneous emission properties of an atom embedded in PCs are investigated. ► Spectral-line enhancement, suppression and overlapping are observed. ► The results provide more degrees of freedom to control atomic spontaneous emission.

  5. Control of spontaneous emission from a microwave-field-driven four-level atom in an anisotropic photonic crystal

    International Nuclear Information System (INIS)

    Zhang, Duo; Li, Jiahua; Ding, Chunling; Yang, Xiaoxue

    2012-01-01

    The spontaneous emission properties of a microwave-field-driven four-level atom embedded in anisotropic double-band photonic crystals (PCs) are investigated. We discuss the influences of the band-edge positions, Rabi frequency and detuning of the microwave field on the emission spectrum. It is found that several interesting features such as spectral-line enhancement, spectral-line suppression, spectral-line overlap, and multi-peak structures can be observed in the spectra. The proposed scheme can be achieved by use of a microwave-coupled field into hyperfine levels in rubidium atom confined in a photonic crystal. These theoretical investigations may provide more degrees of freedom to manipulate the atomic spontaneous emission. -- Highlights: ► Spontaneous emission properties of an atom embedded in PCs are investigated. ► Spectral-line enhancement, suppression and overlapping are observed. ► The results provide more degrees of freedom to control atomic spontaneous emission.

  6. Field-emission from parabolic tips: Current distributions, the net current, and effective emission area

    Science.gov (United States)

    Biswas, Debabrata

    2018-04-01

    Field emission from nano-structured emitters primarily takes place from the tips. Using recent results on the variation of the enhancement factor around the apex [Biswas et al., Ultramicroscopy 185, 1-4 (2018)], analytical expressions for the surface distribution of net emitted electrons, as well as the total and normal energy distributions are derived in terms of the apex radius Ra and the local electric field at the apex Ea. Formulae for the net emitted current and effective emission area in terms of these quantities are also obtained.

  7. Laser annealed HWCVD and PECVD thin silicon films. Electron field emission

    International Nuclear Information System (INIS)

    O'Neill, K.A.; Shaikh, M.Z.; Lyttle, G.; Anthony, S.; Fan, Y.C.; Persheyev, S.K.; Rose, M.J.

    2006-01-01

    Electron Field Emission (FE) properties of various laser annealed thin silicon films on different substrates were investigated. HWCVD microcrystalline and PECVD amorphous silicon films were irradiated with Nd : YAG and XeCl Excimer lasers at varying energy densities. Encouraging FE results were mainly from XeCl Excimer laser processed PECVD and HWCVD films on metal backplanes. FE measurements were complemented by the study of film surface morphology. Geometric field enhancement factors from surface measurements and Fowler-Nordheim Theory (FNT) were compared. FE properties of the films were also found to be particularly influenced by the backplane material

  8. Novel field emission SEM column with beam deceleration technology

    Energy Technology Data Exchange (ETDEWEB)

    Jiruše, Jaroslav; Havelka, Miloslav; Lopour, Filip

    2014-11-15

    A novel field-emission SEM column has been developed that features Beam Deceleration Mode, high-probe current and ultra-fast scanning. New detection system in the column is introduced to detect true secondary electron signal. The resolution power at low energy was doubled for conventional SEM optics and moderately improved for immersion optics. Application examples at low landing energies include change of contrast, imaging of non-conductive samples and thin layers. - Highlights: • A novel field-emission SEM column has been developed. • Implemented beam deceleration improves the SEM resolution at 1 keV two times. • New column maintains high analytical potential and wide field of view. • Detectors integrated in the column allow gaining true SE and BE signal separately. • Performance of the column is demonstrated on low energy applications.

  9. Novel field emission SEM column with beam deceleration technology

    International Nuclear Information System (INIS)

    Jiruše, Jaroslav; Havelka, Miloslav; Lopour, Filip

    2014-01-01

    A novel field-emission SEM column has been developed that features Beam Deceleration Mode, high-probe current and ultra-fast scanning. New detection system in the column is introduced to detect true secondary electron signal. The resolution power at low energy was doubled for conventional SEM optics and moderately improved for immersion optics. Application examples at low landing energies include change of contrast, imaging of non-conductive samples and thin layers. - Highlights: • A novel field-emission SEM column has been developed. • Implemented beam deceleration improves the SEM resolution at 1 keV two times. • New column maintains high analytical potential and wide field of view. • Detectors integrated in the column allow gaining true SE and BE signal separately. • Performance of the column is demonstrated on low energy applications

  10. Laser-assisted electron emission from gated field-emitters

    CERN Document Server

    Ishizuka, H; Yokoo, K; Mimura, H; Shimawaki, H; Hosono, A

    2002-01-01

    Enhancement of electron emission by illumination of gated field-emitters was studied using a 100 mW cw YAG laser at a wavelength of 532 nm, intensities up to 10 sup 7 W/m sup 2 and mechanically chopped with a rise time of 4 mu s. When shining an array of 640 silicon emitters, the emission current responded quickly to on-off of the laser. The increase of the emission current was proportional to the basic emission current at low gate voltages, but it was saturated at approx 3 mu A as the basic current approached 100 mu A with the increase of gate voltage. The emission increase was proportional to the square root of laser power at low gate voltages and to the laser power at elevated gate voltages. For 1- and 3-tip silicon emitters, the rise and fall of the current due to on-off of the laser showed a significant time lag. The magnitude of emission increase was independent of the position of laser spot on the emitter base and reached 2 mu A at a basic current of 5 mu A without showing signs of saturation. The mech...

  11. Electron field emission from undoped and doped DLC films

    International Nuclear Information System (INIS)

    Chakhovskoi, A G; Evtukh, A A; Felter, T E; Klyui, N I; Kudzinovsky, S Y; Litovchenko, V G; Litvin, Y M

    1999-01-01

    Electron field emission and electrical conductivity of undoped and nitrogen doped DLC films have been investigated. The films were grown by the PE CVD method from CH(sub 4):H(sub 2) and CH(sub 4):H(sub 2):N(sub 2) gas mixtures, respectively. By varying nitrogen content in the gas mixture over the range 0 to 45%, corresponding concentrations of 0 to 8% (atomic) could be achieved in the films. Three different gas pressures were used in the deposition chamber: 0.2, 0.6 and 0.8 Torr. Emission current measurements were performed at approximately 10(sup -6) Torr using the diode method with emitter-anode spacing set at 20(micro)m. The current - voltage characteristics of the Si field electron emission arrays covered with DLC films show that threshold voltage (V(sub th)) varies in a complex manner with nitrogen content. As a function of nitrogen content, V(sub th) initially increases rapidly, then decreases and finally increases again for the highest concentration. Corresponding Fowler-Nordheim (F-N) plots follow F-N tunneling over a wide range. The F-N plots were used for determination of the work function, threshold voltage, field enhancement factor and effective emission area. For a qualitative explanation of experimental results, we treat the DLC film as a diamond-like (sp(sup 3) bonded) matrix with graphite-like inclusions

  12. Enhancement on field emission characteristics of pulsed laser deposited diamondlike carbon films using Au precoatings

    International Nuclear Information System (INIS)

    Chuang, F.Y.; Sun, C.Y.; Cheng, H.F.; Lin, I.N.

    1997-01-01

    Using Au precoatings has been observed to significantly enhance the field emission properties of diamondlike carbon (DLC) films deposited on Si substrates. The electron emission can be turned on at a low field as 7 V/μm and a large emission current density as 2000 μA/cm 2 can be obtained at 20 V/μm applied field. However, preannealing the Au-coated Si substrates at 500 degree C for 30 min is necessary to achieve such a performance. Microscopic examination on surface and cross-sectional morphologies of the DLC/Au/Si films using atomic force microscopy and scanning electron microscopy, respectively, in conjunction with the elemental depth profile examination of these films using secondary ion mass spectroscopy, indicated that substantial interdiffusion between DLC, Au, and Si layers has occurred. Such kind of reaction is proposed to lower the resistance for electrons to transport across the interfaces and, thereafter, enhances the field emission properties of the DLC/Au/Si films. copyright 1997 American Institute of Physics

  13. Combined effect of nitrogen doping and nanosteps on microcrystalline diamond films for improvement of field emission

    International Nuclear Information System (INIS)

    Mengui, U.A.; Campos, R.A.; Alves, K.A.; Antunes, E.F.; Hamanaka, M.H.M.O.; Corat, E.J.; Baldan, M.R.

    2015-01-01

    Highlights: • Hot filament chemical vapor deposition using methane, hydrogen and a solution of urea in methanol produced nitrogen-doped diamond films. • Diamonds had the grain morphology changed for long growth time (28 h), and the nitrogen doping were evaluated by Raman spectroscopy. • Field emission characterization shows a decrease up to 70% in threshold field, related to reference diamond layer. - Abstract: Nitrogen-doped microcrystalline diamond (N-MCD) films were grown on Si substrates using a hot filament reactor with methanol solution of urea as N source. Electrostatic self-assembly seeding of nanocrystalline diamond were used to obtain continuous and uniform films. Simultaneous changes in grains morphology and work function of diamond by nitrogen doping decreased the threshold field and the angular coefficient of Fowler–Nordhein plots. The field emission properties of our N-MCD films are comparable to carbon nanotube films

  14. Field emission response from multi-walled carbon nanotubes grown on electrochemically engineered copper foil

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, Amit Kumar; Jain, Vaibhav [Nanomaterials and Applications Lab., Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Saini, Krishna [Nanomaterials and Applications Lab., Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Centre of Excellence: Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Lahiri, Indranil, E-mail: indrafmt@iitr.ac.in [Nanomaterials and Applications Lab., Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Centre of Excellence: Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India)

    2017-02-01

    Exciting properties of carbon nanotube has proven it to be a promising candidate for field emission applications, if its processing cost can be reduced effectively. In this research, a new electrochemical technique is proposed for growing carbon nanotubes in selective areas by thermal chemical vapour deposition. In this process, electrochemical processing is used to create localized pits and deposition of catalysts, which act as roots to support growth and alignment of the CNTs on copper substrate. CNTs grown thus were characterized and studied using scanning electron microscope, transmission electron microscope and Raman spectroscopy, elucidating presence of multiwall carbon nanotubes (MWCNT). These CNT emitters have comparatively lower turn-on field and higher field enhancement factor. - Highlights: • Electrochemical pitting for localized carbon nanotube growth is proposed. • Electrochemical pitting method shows patterning effect on the substrate. • Size and density of pits depend on voltage, pH and temperature. • CNTs thus grown shows good field emission response.

  15. Combined effect of nitrogen doping and nanosteps on microcrystalline diamond films for improvement of field emission

    Energy Technology Data Exchange (ETDEWEB)

    Mengui, U.A., E-mail: ursulamengui@gmail.com [INPE – Instituto Nacional de Pesquisas Espaciais Laboratório Associado de Sensores e Materiais – LAS, Av. dos Astronautas 1758, CP 515, CEP 12.245-970, São José dos Campos, SP (Brazil); Campos, R.A.; Alves, K.A.; Antunes, E.F. [INPE – Instituto Nacional de Pesquisas Espaciais Laboratório Associado de Sensores e Materiais – LAS, Av. dos Astronautas 1758, CP 515, CEP 12.245-970, São José dos Campos, SP (Brazil); Hamanaka, M.H.M.O. [Centro de Tecnologia da Informação Renato Archer, Divisão de Superfícies de Interação e Displays, Rodovia D. Pedro I (SP 65) km 143.6, CP 6162, CEP 13089-500, Campinas, SP (Brazil); Corat, E.J.; Baldan, M.R. [INPE – Instituto Nacional de Pesquisas Espaciais Laboratório Associado de Sensores e Materiais – LAS, Av. dos Astronautas 1758, CP 515, CEP 12.245-970, São José dos Campos, SP (Brazil)

    2015-04-15

    Highlights: • Hot filament chemical vapor deposition using methane, hydrogen and a solution of urea in methanol produced nitrogen-doped diamond films. • Diamonds had the grain morphology changed for long growth time (28 h), and the nitrogen doping were evaluated by Raman spectroscopy. • Field emission characterization shows a decrease up to 70% in threshold field, related to reference diamond layer. - Abstract: Nitrogen-doped microcrystalline diamond (N-MCD) films were grown on Si substrates using a hot filament reactor with methanol solution of urea as N source. Electrostatic self-assembly seeding of nanocrystalline diamond were used to obtain continuous and uniform films. Simultaneous changes in grains morphology and work function of diamond by nitrogen doping decreased the threshold field and the angular coefficient of Fowler–Nordhein plots. The field emission properties of our N-MCD films are comparable to carbon nanotube films.

  16. Mathematical Properties Relevant to Geomagnetic Field Modeling

    DEFF Research Database (Denmark)

    Sabaka, Terence J.; Hulot, Gauthier; Olsen, Nils

    2010-01-01

    be directly measured. In this chapter, the mathematical foundation of global (as opposed to regional) geomagnetic field modeling is reviewed, and the spatial modeling of the field in spherical coordinates is focussed. Time can be dealt with as an independent variable and is not explicitly considered......Geomagnetic field modeling consists in converting large numbers of magnetic observations into a linear combination of elementary mathematical functions that best describes those observations.The set of numerical coefficients defining this linear combination is then what one refers.......The relevant elementary mathematical functions are introduced, their properties are reviewed, and how they can be used to describe the magnetic field in a source-free (such as the Earth’s neutral atmosphere) or source-dense (such as the ionosphere) environment is explained. Completeness and uniqueness...

  17. Mathematical Properties Relevant to Geomagnetic Field Modeling

    DEFF Research Database (Denmark)

    Sabaka, Terence J.; Hulot, Gauthier; Olsen, Nils

    2014-01-01

    be directly measured. In this chapter, the mathematical foundation of global (as opposed to regional) geomagnetic field modeling is reviewed, and the spatial modeling of the field in spherical coordinates is focused. Time can be dealt with as an independent variable and is not explicitly considered......Geomagnetic field modeling consists in converting large numbers of magnetic observations into a linear combination of elementary mathematical functions that best describes those observations. The set of numerical coefficients defining this linear combination is then what one refers....... The relevant elementary mathematical functions are introduced, their properties are reviewed, and how they can be used to describe the magnetic field in a source-free (such as the Earth’s neutral atmosphere) or source-dense (such as the ionosphere) environment is explained. Completeness and uniqueness...

  18. Discrete space charge affected field emission: Flat and hemisphere emitters

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, Kevin L., E-mail: kevin.jensen@nrl.navy.mil [Code 6854, Naval Research Laboratory, Washington, DC 20375 (United States); Shiffler, Donald A.; Tang, Wilkin [Air Force Research Laboratory, Kirtland AFB, New Mexico 87117 (United States); Rittersdorf, Ian M. [Code 6770, Naval Research Laboratory, Washington, DC 20375 (United States); Lebowitz, Joel L. [Department of Mathematics and Department of Physics, Rutgers University, Piscataway, New Jersey 08854-8019 (United States); Harris, John R. [U.S. Navy Reserve, New Orleans, Louisiana 70143 (United States); Lau, Y. Y. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States); Petillo, John J. [Leidos, Billerica, Massachusetts 01821 (United States); Luginsland, John W. [Physics and Electronics Directorate, AFOSR, Arlington, Virginia 22203 (United States)

    2015-05-21

    Models of space-charge affected thermal-field emission from protrusions, able to incorporate the effects of both surface roughness and elongated field emitter structures in beam optics codes, are desirable but difficult. The models proposed here treat the meso-scale diode region separate from the micro-scale regions characteristic of the emission sites. The consequences of discrete emission events are given for both one-dimensional (sheets of charge) and three dimensional (rings of charge) models: in the former, results converge to steady state conditions found by theory (e.g., Rokhlenko et al. [J. Appl. Phys. 107, 014904 (2010)]) but show oscillatory structure as they do. Surface roughness or geometric features are handled using a ring of charge model, from which the image charges are found and used to modify the apex field and emitted current. The roughness model is shown to have additional constraints related to the discrete nature of electron charge. The ability of a unit cell model to treat field emitter structures and incorporate surface roughness effects inside a beam optics code is assessed.

  19. Thermal field emission observation of single-crystal LaB6

    International Nuclear Information System (INIS)

    Nagata, H.; Harada, K.; Shimizu, R.

    1990-01-01

    TFE (thermal field emission) properties of LaB 6 left-angle 100 right-angle and left-angle 310 right-angle single crystals were investigated by emission pattern observation. It was found that field evaporation with the tip temperature held at ∼1500 degree C is very useful to get a clean pattern of fourfold symmetry. Each of four bright spots in the clean pattern was presumed to correspond to left-angle 310 right-angle emission. It is proposed, as the most appropriate operating condition, to use the left-angle 310 right-angle LaB 6 tip at a temperature ∼1000 degree C in vacuum of 10 -9 Torr region, promising a new TF emitter of high brightness and stability for practical use

  20. FIELD EVALUATION OF LOW-EMISSION COAL BURNER TECHNOLOGY ON UTILITY BOILERS VOLUME III. FIELD EVALUATIONS

    Science.gov (United States)

    The report gives results of field tests conducted to determine the emission characteristics of a Babcock and Wilcox Circular burner and Dual Register burner (DRB). The field tests were performed at two utility boilers, generally comparable in design and size except for the burner...

  1. A statistical model for field emission in superconducting cavities

    International Nuclear Information System (INIS)

    Padamsee, H.; Green, K.; Jost, W.; Wright, B.

    1993-01-01

    A statistical model is used to account for several features of performance of an ensemble of superconducting cavities. The input parameters are: the number of emitters/area, a distribution function for emitter β values, a distribution function for emissive areas, and a processing threshold. The power deposited by emitters is calculated from the field emission current and electron impact energy. The model can successfully account for the fraction of tests that reach the maximum field Epk in an ensemble of cavities, for eg, 1-cells at sign 3 GHz or 5-cells at sign 1.5 GHz. The model is used to predict the level of power needed to successfully process cavities of various surface areas with high pulsed power processing (HPP)

  2. Dust from southern Africa: rates of emission and biogeochemical properties

    Science.gov (United States)

    Bhattachan, A.; D'Odorico, P.; Zobeck, T. M.; Okin, G. S.; Dintwe, K.

    2012-12-01

    The stabilized linear dunefields in the southern Kalahari show signs of reactivation due to reduced vegetation cover owing to drought and/or overgrazing. It has been demonstrated with a laboratory dust generator that the southern Kalahari soils are good emitters of dust and that large-scale dune reactivation can potentially make the region an important dust source in the relatively low-dust Southern Hemisphere. We show that emergence of the southern Kalahari as a new dust source may affect ocean biogeochemistry as the soils are rich in soluble iron and the dust from the southern Kalahari commonly reaches the Southern Ocean. We investigate the biogeochemical properties of the fine fraction of soil from the Kalahari dunes and compare them to those of currently active dust sources such as the Makgadikgadi and the Etosha pans as well as other smaller pans in the region. Using field measurements of sediment fluxes and satellite images, we calculate the rates of dust emission from the southern Kalahari under different land cover scenarios. To assess the reversibility of dune reactivation in the southern Kalahari, we investigate the resilience of dunefield vegetation by looking at changes in soil nutrients, fine soil fractions, and seed bank in areas affected by intense denudation.

  3. Continuous measurements of N2O emissions from arable fields

    Science.gov (United States)

    Wallman, Magdalena; Lammirato, Carlo; Rütting, Tobias; Delin, Sofia; Weslien, Per; Klemedtsson, Leif

    2017-04-01

    Agriculture represents 59 % of the anthropogenic nitrous oxide (N2O) emissions, according to the IPCC (Ciais et al. 2013). N2O emissions are typically irregular and vary widely in time and space, which makes it difficult to get a good representation of the emissions (Henault et al. 2012), particularly if measurements have low frequency and/or cover only a short time period. Manual measurements are, for practical reasons, often short-term and low-frequent, or restricted to periods where emissions are expected to be high, e.g. after fertilizing. However, the nature of N2O emissions, being largely unpredictable, calls for continuous or near-continuous measurements over long time periods. So far, rather few long-term, high resolution measurements of N2O emissions from arable fields are reported; among them are Flessa et al. (2002) and Senapati et al. (2016). In this study, we have a two-year data set (2015-2017) with hourly measurements from ten automatic chambers, covering unfertilized controls as well as different nitrogen fertilizer treatments. Grain was produced on the field, and effects of tillage, harvest and other cropping measures were covered. What we can see from the experiment is that (a) the unfertilized control plots seem to follow the same emission pattern as the fertilized plots, at a level similar to the standard mineral fertilized plots (120 kg N ha-1 yr-1) and (b) freeze/thaw emissions are comparable in size to emissions after fertilizing. These two findings imply that the importance of fertilizing to the overall N2O emissions from arable soils may be smaller than previously expected. References: Ciais, P., C. Sabine, G. Bala, L. Bopp, V. Brovkin, J. Canadell et al. 2013: Carbon and Other Biogeochemical Cycles. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung et

  4. Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets and Supernova Remnants

    Science.gov (United States)

    Nishikawa, K.-I.; Hartmann, D. H.; Hardee, P.; Hededal, C.; Mizunno, Y.; Fishman, G. J.

    2006-01-01

    We performed numerical simulations of particle acceleration, magnetic field generation, and emission from shocks in order to understand the observed emission from relativistic jets and supernova remnants. The investigation involves the study of collisionless shocks, where the Weibel instability is responsible for particle acceleration as well as magnetic field generation. A 3-D relativistic particle-in-cell (RPIC) code has been used to investigate the shock processes in electron-positron plasmas. The evolution of theWeibe1 instability and its associated magnetic field generation and particle acceleration are studied with two different jet velocities (0 = 2,5 - slow, fast) corresponding to either outflows in supernova remnants or relativistic jets, such as those found in AGNs and microquasars. Slow jets have intrinsically different structures in both the generated magnetic fields and the accelerated particle spectrum. In particular, the jet head has a very weak magnetic field and the ambient electrons are strongly accelerated and dragged by the jet particles. The simulation results exhibit jitter radiation from inhomogeneous magnetic fields, generated by the Weibel instability, which has different spectral properties than standard synchrotron emission in a homogeneous magnetic field.

  5. Field Emission of Wet Transferred Suspended Graphene Fabricated on Interdigitated Electrodes.

    Science.gov (United States)

    Xu, Ji; Wang, Qilong; Tao, Zhi; Qi, Zhiyang; Zhai, Yusheng; Wu, Shengqi; Zhang, Xiaobing; Lei, Wei

    2016-02-10

    Suspended graphene (SG) membranes could enable strain-engineering of ballistic Dirac fermion transport and eliminate the extrinsic bulk disorder by annealing. When freely suspended without contact to any substrates, graphene could be considered as the ultimate two-dimensional (2D) morphology, leading to special field characteristics with the 2D geometrical effect and effectively utilized as an outstanding structure to explore the fundamental electronic or optoelectronic mechanism. In this paper, we report field emission characterization on an individual suspended few-layer graphene. A controllable wet transfer method is used to obtain the continuous and suspended graphene membrane on interdigitated gold electrodes. This suspended structure displays an overall field emission from the entirely surface, except for the variation in the emitting positions, acquiring a better enhancement than the exfoliated graphene on the conventional flat substrate. We also observe the transition process from space charge flow at low bias to the Fowler-Nordheim theory at high current emission regime. It could enable theoretical and experimental investigation of the typical electron emission properties of the 2D regime. Numerical simulations are also carried out to study the electrical properties of the suspended structure. Further improvement on the fabrication would realize low disorder, high quality, and large-scale suspended graphene devices.

  6. UV emission properties of thulium-doped fluorozirconate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Piramidowicz, R., E-mail: r.piramidowicz@elka.pw.edu.p [Institute of Microelectronics and Optoelectronics, Koszykowa 75, 00-662 Warsaw (Poland); Telekomunikacja Polska Research and Development Centre, Obrzezna 7, 02-691 Warsaw (Poland); Bok, A.; Klimczak, M.; Malinowski, M. [Institute of Microelectronics and Optoelectronics, Koszykowa 75, 00-662 Warsaw (Poland)

    2009-12-15

    In this work, we present our latest results on UV emission in bulk ZBLAN glasses doped with thulium ions, broadening knowledge of the short-wavelength optical properties of this system. We examined a set of samples with different activator concentrations (2500, 10,000, 25,000 and 50,000 ppm) in respect of absorption and short-wavelength emission properties. The concentration-dependant spectra of UV emission from the {sup 1}I{sub 6}+{sup 3}P{sub 0} and {sup 1}D{sub 2} levels and fluorescence dynamics profiles have been recorded and carefully examined under direct (one-photon) excitation, enabling discussion of fluorescence quenching mechanisms and determination of appropriate cross-relaxation rates. According to authors' best knowledge, the three-photon red-to-UV up-conversion has been reported for the first time under excitation of a laser diode.

  7. Emission and null coordinates: geometrical properties and physical construction

    International Nuclear Information System (INIS)

    Coll, Bartolome; Ferrando, Joan J; Morales-Lladosa, Juan A

    2011-01-01

    A Relativistic Positioning System is defined by four clocks (emitters) broadcasting their proper time. Then, every event reached by the signals is naturally labeled by these four times which are the emission coordinates of this event. The coordinate hypersurfaces of the emission coordinates are the future light cones based on the emitter trajectories. For this reason the emission coordinates have been also named null coordinates or light coordinates. Nevertheless, other coordinate systems used in different relativistic contexts have the own right to be named null or light coordinates. Here we analyze when one can say that a coordinate is a null coordinate and when one can say that a coordinate system is null. Moreover, we examine the physical construction and the geometrical properties of several n ull coordinate systems : the emission and the reception coordinates, the radar coordinates, and the Bondi-Sachs coordinates, among others.

  8. Simulation and fabrication of carbon nanotubes field emission pressure sensors

    International Nuclear Information System (INIS)

    Qian Kaiyou; Chen Ting; Yan Bingyong; Lin Yangkui; Xu Dong; Sun Zhuo; Cai Bingchu

    2006-01-01

    A novel field emission pressure sensor has been achieved utilizing carbon nanotubes (CNTs) as the electron source. The sensor consists of the anode sensing film fabricated by wet etching process and multi-wall carbon nanotubes (MWNTs) cathode in the micro-vacuum chamber. MWNTs on the silicon substrate were grown by thermal CVD. The prototype pressure sensor has a measured sensitivity of about 0.17-0.77 nA/Pa (101-550 KPa). The work shows the potential use of CNTs-based field-emitter in microsensors, such as accelerometers and tactile sensors

  9. Synthesis, characterization and emission properties of quinolin-8 ...

    Indian Academy of Sciences (India)

    Unknown

    chelated ruthenium organometallics. BIKASH KUMAR PANDA. Department of Inorganic ... Ruthenium organometallics; quinolin-8-olato chelation; emission properties; trivalent ruthenium. 1. Introduction. There is continuing ... chem.istry of orthometallated ruthenium compounds is of current interest in the context of synthesis ...

  10. Characterization of radiofrequency field emissions from smart meters.

    Science.gov (United States)

    Tell, Richard A; Kavet, Robert; Mezei, Gabor

    2013-01-01

    This study presents measurement data that describe radiofrequency emission levels and patterns from smart meters (rated nominally at 1 W) currently deployed in Pacific Gas and Electric Company's service territory in northern California. The smart meters in our investigation could not be set to operate continuously and required a Field Service Unit to induce short periods of emitted fields. To obtain peak field data under both laboratory and ambient conditions, a spectrum analyzer scanned across the 83 transmitting channels between 902 and 928 MHz used by the smart meter on a random frequency-hopping basis. To obtain data describing temporal emission patterns, the analyzer operated in scope mode. Duty cycle was estimated using transmit data acquired by the system operator from over 88,000 m. Instantaneous peak fields at 0.3 m in front of the meters were no more than 15% of the US Federal Communications Commission (FCC) exposure limit for the general public, and 99.9% of the meters operated with a duty cycle of 1.12% or less during the sampling period. In a sample of measurements in six single-detached residences equipped with individual smart meters, no interior measurement of peak field exceeded 1% of the FCC's general public exposure limit.

  11. Study of field induced hot-electron emission using the composite microemitters with varying dielectric layer thickness

    International Nuclear Information System (INIS)

    Mousa, M.S.

    1987-07-01

    The analysis of the measurements obtained from the of field emission of electrons from composite metal-insulator (M-I) micropoint cathodes, using the combination of a high resolution electron spectrometer and a field emission microscope, has been presented. Results obtained describe the reversible current-voltage characteristic, emission images and electron energy distribution measurements of both thin and the optimum thick coatings. The observed effects, e.g. the threshold switch-on phenomena and the field-dependence of the F.W.H.M. and energy shift of the electron spectra have been identified in terms of a field-induced hot-electron emission (FIHEE) mechanism resulting from field penetration in the insulating film where conducting channels are formed. The theoretical implications accounts for the channels field intensification mechanism and the conduction properties with applied field, and the F.W.H.M. dependence on electron temperature. The control of the emission process at low fields by the M-I contact junction and at high fields by the bulk properties of the insulator have also been accounted for. These experimental and theoretical findings have been shown to be consistent with recently published data on M-I microstructures on broad-area (BA) high-voltage electrodes. (author). 18 refs, 6 figs

  12. Interface control: A modified rooting technique for enhancing field emission from multiwall carbon nanotube based bulk emitters

    Energy Technology Data Exchange (ETDEWEB)

    Lahiri, Indranil [Nanomaterials and Device Lab, Department of Mechanical and Materials Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174 (United States); Choi, Wonbong, E-mail: choiw@fiu.edu [Nanomaterials and Device Lab, Department of Mechanical and Materials Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174 (United States)

    2011-08-15

    The unique properties of carbon nanotubes (CNTs) have raised hopes that these materials might find wide application as cold cathodes in various electron sources. The excellent field emission properties shown by CNT-based field emitters has further stimulated this expectation. However, efficient performance of a practical field emitter, which comprises a large number of randomly or regularly oriented CNTs, is restricted primarily due to poor junctions formed between CNTs and substrates. This study is aimed at enhancing the junction performance by way of a modified 'rooting' technique-interface control. In this process, the interface between CNTs and substrate has been tailored with different metals in an attempt to improve the CNT-substrate junction performance. Multiwall carbon nanotubes (MWCNTs) were synthesized on different interface-controlled substrates, i.e. Cu, Al, W, Si and low-temperature co-fired ceramic. All the samples produced mat-type, randomly oriented MWCNT structures. Among the four different substrates studied, MWCNT-based field emitters on Cu substrate demonstrated the best field emission response, in terms of low turn-on field, high emission current, good field enhancement factor and excellent stability in long-term operation. Emitter structures and their field emission behavior were correlated and it was shown that interface control, as an advanced 'rooting' process, plays an important role in determining the emission response from a bulk field emitter.

  13. Interface control: A modified rooting technique for enhancing field emission from multiwall carbon nanotube based bulk emitters

    International Nuclear Information System (INIS)

    Lahiri, Indranil; Choi, Wonbong

    2011-01-01

    The unique properties of carbon nanotubes (CNTs) have raised hopes that these materials might find wide application as cold cathodes in various electron sources. The excellent field emission properties shown by CNT-based field emitters has further stimulated this expectation. However, efficient performance of a practical field emitter, which comprises a large number of randomly or regularly oriented CNTs, is restricted primarily due to poor junctions formed between CNTs and substrates. This study is aimed at enhancing the junction performance by way of a modified 'rooting' technique-interface control. In this process, the interface between CNTs and substrate has been tailored with different metals in an attempt to improve the CNT-substrate junction performance. Multiwall carbon nanotubes (MWCNTs) were synthesized on different interface-controlled substrates, i.e. Cu, Al, W, Si and low-temperature co-fired ceramic. All the samples produced mat-type, randomly oriented MWCNT structures. Among the four different substrates studied, MWCNT-based field emitters on Cu substrate demonstrated the best field emission response, in terms of low turn-on field, high emission current, good field enhancement factor and excellent stability in long-term operation. Emitter structures and their field emission behavior were correlated and it was shown that interface control, as an advanced 'rooting' process, plays an important role in determining the emission response from a bulk field emitter.

  14. Enhanced field emission behavior of layered MoSe2

    International Nuclear Information System (INIS)

    Suryawanshi, Sachin R; Pawbake, Amit S; Jadkar, Sandesh R; More, Mahendra A; Pawar, Mahendra S; Late, Dattatray J

    2016-01-01

    Herein, we report one step facile chemical vapor deposition method for synthesis of single-layer MoSe 2 nanosheets with average lateral dimension ∼60 μm on 300 nm SiO 2 /Si and n-type silicon substrates and field emission investigation of MoSe 2 /Si at the base pressure of ∼1 × 10 −8 mbar. The morphological and structural analyses of the as-deposited single-layer MoSe 2 nanosheets were carried out using an optical microscopy, Raman spectroscopy and atomic force microscopy. Furthermore, the values of turn-on and threshold fields required to extract an emission current densities of 1 and 10 μA cm −2 , are found to be ∼1.9 and ∼2.3 V μm −1 , respectively. Interestingly, the MoSe 2 nanosheet emitter delivers maximum field emission current density of ∼1.5 mA cm −2 at a relatively lower applied electric field of ∼3.9 V μm −1 . The long term operational current stability recorded at the preset values of 35 μA over 3 hr duration and is found to be very good. The observed results demonstrates that the layered MoSe 2 nanosheet based field emitter can open up many opportunities for their potential application as an electron source in flat panel display, transmission electron microscope, and x-ray generation. Thus, the facile one step synthesis approach and robust nature of single-layer MoSe 2 nanosheets emitter can provide prospects for the future development of practical electron sources. (paper)

  15. Field emission from carbon nanotube bundle arrays grown on self-aligned ZnO nanorods

    International Nuclear Information System (INIS)

    Li Chun; Fang Guojia; Yuan Longyan; Liu Nishuang; Ai Lei; Xiang Qi; Zhao Dongshan; Pan Chunxu; Zhao Xingzhong

    2007-01-01

    The field emission (FE) properties of carbon nanotube (CNT) bundle arrays grown on vertically self-aligned ZnO nanorods (ZNRs) are reported. The ZNRs were first synthesized on ZnO-seed-coated Si substrate by the vapour phase transport method, and then the radically grown CNTs were grown directly on the surface of the ZNRs from ethanol flames. The CNT/ZNR composite showed a turn-on field of 1.5 V μm -1 (at 0.1 μA cm -2 ), a threshold field of 4.5 V μm -1 (at 1 mA cm -2 ) and a stable emission current with fluctuations of 5%, demonstrating significantly enhanced FE of ZNRs due to the low work function and high aspect ratio of the CNTs, and large surface-to-volume ratio of the underlying ZNRs

  16. Research of the Electron Cyclotron Emission with Vortex Property excited by high power high frequency Gyrotron

    Science.gov (United States)

    Goto, Yuki; Kubo, Shin; Tsujimura, Tohru; Takubo, Hidenori

    2017-10-01

    Recently, it has been shown that the radiation from a single electron in cyclotron motion has vortex property. Although the cyclotron emission exists universally in nature, the vortex property has not been featured because this property is normally cancelled out due to the randomness in gyro-phase of electrons and the development of detection of the vortex property has not been well motivated. In this research, we are developing a method to generate the vortex radiation from electrons in cyclotron motion with controlled gyro-phase. Electron that rotates around the uniform static magnetic field is accelerated by right-hand circular polarized (RHCP) radiation resonantly when the cyclotron frequency coincides with the applied RHCP radiation frequency. A large number of electrons can be coherently accelerated in gyro-phase by a RHCP high power radiation so that these electrons can radiate coherent emission with vortex feature. We will show that vortex radiation created by purely rotating electrons for the first time.

  17. Oxygen plasma assisted end-opening and field emission enhancement in vertically aligned multiwall carbon nanotubes

    International Nuclear Information System (INIS)

    Mathur, A.; Roy, S.S.; Hazra, K.S.; Wadhwa, S.; Ray, S.C.; Mitra, S.K.; Misra, D.S.; McLaughlin, J.A.

    2012-01-01

    Highlights: ► We showed Ar/O 2 plasma can be effective for the end opening of aligned CNTs. ► The field emission property was dramatically enhanced after plasma modification. ► Microstructures were clearly understood by Raman and SEM analysis. ► Surface wet-ability at various functionalised conditions was studied. - Abstract: This paper highlights the changes in micro-structural and field emission properties of vertically aligned carbon nanotubes (VACNTs) via oxygen plasma treatment. We find that exposure of very low power oxygen plasma (6 W) at 13.56 MHz for 15–20 min, opens the tip of vertically aligned CNTs. Scanning electron microscopy and transmission electron microscopy images were used to identify the quality and micro-structural changes of the nanotube morphology and surfaces. Raman spectra showed that the numbers of defects were increased throughout the oxygen plasma treatment process. In addition, the hydrophobic nature of the VACNTs is altered significantly and the contact angle decreases drastically from 110° to 40°. It was observed that the electron field emission (EFE) characteristics are significantly enhanced. The turn-on electric field (ETOE) of CNTs decreased from ∼0.80 V μm −1 (untreated) to ∼0.60 V μm −1 (oxygen treated). We believe that the open ended VACNTs would be immensely valuable for applications such as micro/nanofluidic based filtering elements and display devices.

  18. Optical Emissions of Sprite Streamers in Weak Electric Fields

    Science.gov (United States)

    Liu, N.; Pasko, V. P.

    2004-12-01

    Sprites commonly consist of large numbers of needle-shaped filaments of ionization [e.g., Gerken and Inan, JASTP, 65, 567, 2003] and typically initiate at altitudes 70-75 km in a form of upward and downward propagating streamers [Stanley et al., GRL, 26, 3201, 1999; Stenbaek-Nielsen et al., GRL, 27, 3829, 2000; McHarg et al., JGR, 107, 1364, 2002; Moudry et al., JASTP, 65, 509, 2003]. The strong electric fields E exceeding the conventional breakdown threshold field Ek are needed for initiation of sprite streamers from single electron avalanches and recent modeling studies indicate that streamers propagating in fields E>Ek experience strong acceleration and expansion in good agreement with the above cited observations [Liu and Pasko, JGR, 109, A04301, 2004]. The initiated streamers are capable of propagating in fields substantially lower than Ek [Allen and Ghaffar, J. Phys. D: Appl. Phys., 28, 331, 1995] and it is expected that a significant part of sprite optical output comes from regions with EEk). Additionally, the values of electric fields inside of the streamer channel are always well below Ek and since the excitation coefficients for optical emissions are very sensitive to the driving electric field magnitude most of the optical luminosity of streamers in this case arises from streamer tips, indicating that observed streamer filaments in many cases may be produced by time averaging of optical luminosity coming from localized regions around streamer tips as streamers move through an instrument's field of view. We will discuss pressure dependent differences of optical emissions at different sprite altitudes, and important similarities between observed sprite streamers and recent time resolved (van Veldhuizen et al., IEEE Trans. Plasma Sci., 30, 162, 2002; Yi and Williams, J. Phys. D. Appl. Phys., 35, 205, 2002].

  19. Statistical properties of antisymmetrized molecular dynamics for non-nucleon-emission and nucleon-emission processes

    International Nuclear Information System (INIS)

    Ono, A.; Horiuchi, H.

    1996-01-01

    Statistical properties of antisymmetrized molecular dynamics (AMD) are classical in the case of nucleon-emission processes, while they are quantum mechanical for the processes without nucleon emission. In order to understand this situation, we first clarify that there coexist mutually opposite two statistics in the AMD framework: One is the classical statistics of the motion of wave packet centroids and the other is the quantum statistics of the motion of wave packets which is described by the AMD wave function. We prove the classical statistics of wave packet centroids by using the framework of the microcanonical ensemble of the nuclear system with a realistic effective two-nucleon interaction. We show that the relation between the classical statistics of wave packet centroids and the quantum statistics of wave packets can be obtained by taking into account the effects of the wave packet spread. This relation clarifies how the quantum statistics of wave packets emerges from the classical statistics of wave packet centroids. It is emphasized that the temperature of the classical statistics of wave packet centroids is different from the temperature of the quantum statistics of wave packets. We then explain that the statistical properties of AMD for nucleon-emission processes are classical because nucleon-emission processes in AMD are described by the motion of wave packet centroids. We further show that when we improve the description of the nucleon-emission process so as to take into account the momentum fluctuation due to the wave packet spread, the AMD statistical properties for nucleon-emission processes change drastically into quantum statistics. Our study of nucleon-emission processes can be conversely regarded as giving another kind of proof of the fact that the statistics of wave packets is quantum mechanical while that of wave packet centroids is classical. copyright 1996 The American Physical Society

  20. Field emission study from an array of hierarchical micro protrusions on stainless steel surface generated by femtosecond pulsed laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Singh, A.K., E-mail: anilks@barc.gov.in [Laser & Plasma Technology Division, BARC, Mumbai, 400085 (India); Suryawanshi, Sachin R.; More, M.A. [Department of Physics, Savitribai Phule Pune University, Pune, 411007 (India); Basu, S. [Solid State Physics Division, BARC, Mumbai, 40085 (India); Sinha, Sucharita [Laser & Plasma Technology Division, BARC, Mumbai, 400085 (India)

    2017-02-28

    Highlights: • Array of self assembled micro-protrusions have been generated on stainless steel surfaces by femtosecond pulsed laser irradiation. • Density of the formed micro-protrusions is ∼5.6 × 105 protrusions/cm{sup 2}. • Laser treated surface is mainly composed of iron oxide and cementite phases. • Micro-structured sample has shown good field emission properties – low turn on field, high field enhancement factor and stable emission current. - Abstract: This paper reports our results on femtosecond (fs) pulsed laser induced surface micro/nano structuring of stainless steel 304 (SS 304) samples and their characterization in terms of surface morphology, formed material phases on laser irradiation and field emission studies. Our investigations reveal that nearly uniform and dense array of hierarchical micro-protrusions (density: ∼5.6 × 10{sup 5} protrusions/cm{sup 2}) is formed upon laser treatment. Typical tip diameters of the generated protrusions are in the range of 2–5 μm and these protrusions are covered with submicron sized features. Grazing incidence X-ray diffraction (GIXRD) analysis of the laser irradiated sample surface has shown formation mainly of iron oxides and cementite (Fe{sub 3}C) phases in the treated region. These laser micro-structured samples have shown good field emission properties such as low turn on field (∼4.1 V/μm), high macroscopic field enhancement factor (1830) and stable field emission current under ultra high vacuum conditions.

  1. Enhanced Field Emission from Argon Plasma-Treated Ultra-sharp α-Fe2O3Nanoflakes

    Directory of Open Access Journals (Sweden)

    Zhang JX

    2009-01-01

    Full Text Available Abstract Hematite nanoflakes have been synthesized by a simple heat oxide method and further treated by Argon plasmas. The effects of Argon plasma on the morphology and crystal structures of nanoflakes were investigated. Significant enhancement of field-induced electron emission from the plasma-treated nanoflakes was observed. The transmission electron microscopy investigation shows that the plasma treatment effectively removes amorphous coating and creates plenty of sub-tips at the surface of the nanoflakes, which are believed to contribute the enhancement of emission. This work suggests that plasma treatment technique could be a direct means to improve field-emission properties of nanostructures.

  2. Vertically aligned zinc selenide nanoribbon arrays: microstructure and field emission

    International Nuclear Information System (INIS)

    Zhao Lijuan; Pang Qi; Cai Yuan; Wang Ning; Ge Weikun; Wang Jiannong; Yang Shihe

    2007-01-01

    Uniform ZnSe precursor (ZnSe : 0.38en, en = ethylenediamine) nanoribbon arrays are grown vertically on Zn foils in ethylenediamine (en) using a solvothermal method. After the annealing treatment in N 2 , the ZnSe nanoribbon arrays can be obtained without an obvious morphology change and the crystallinity of ribbons is greatly improved. The microstructures of both individual ZnSe precursor and ZnSe nanoribbons are investigated. Field emission characteristics show that the onset field required drawing a current density of ∼0.1 μ A cm -2 from the ZnSe nanoribbons is 5.0 V μm -1 and the field enhancement factors are determined to be ∼1382

  3. Electronic field emission models beyond the Fowler-Nordheim one

    Science.gov (United States)

    Lepetit, Bruno

    2017-12-01

    We propose several quantum mechanical models to describe electronic field emission from first principles. These models allow us to correlate quantitatively the electronic emission current with the electrode surface details at the atomic scale. They all rely on electronic potential energy surfaces obtained from three dimensional density functional theory calculations. They differ by the various quantum mechanical methods (exact or perturbative, time dependent or time independent), which are used to describe tunneling through the electronic potential energy barrier. Comparison of these models between them and with the standard Fowler-Nordheim one in the context of one dimensional tunneling allows us to assess the impact on the accuracy of the computed current of the approximations made in each model. Among these methods, the time dependent perturbative one provides a well-balanced trade-off between accuracy and computational cost.

  4. Molecular dynamics simulations of field emission from a planar nanodiode

    Energy Technology Data Exchange (ETDEWEB)

    Torfason, Kristinn; Valfells, Agust; Manolescu, Andrei [School of Science and Engineering, Reykjavik University, Menntavegur 1, IS-101 Reykjavik (Iceland)

    2015-03-15

    High resolution molecular dynamics simulations with full Coulomb interactions of electrons are used to investigate field emission in planar nanodiodes. The effects of space-charge and emitter radius are examined and compared to previous results concerning transition from Fowler-Nordheim to Child-Langmuir current [Y. Y. Lau, Y. Liu, and R. K. Parker, Phys. Plasmas 1, 2082 (1994) and Y. Feng and J. P. Verboncoeur, Phys. Plasmas 13, 073105 (2006)]. The Fowler-Nordheim law is used to determine the current density injected into the system and the Metropolis-Hastings algorithm to find a favourable point of emission on the emitter surface. A simple fluid like model is also developed and its results are in qualitative agreement with the simulations.

  5. Chiral properties of baryon interpolating fields

    International Nuclear Information System (INIS)

    Nagata, Keitaro; Hosaka, Atsushi; Dmitrasinovic, V.

    2008-01-01

    We study the chiral transformation properties of all possible local (non-derivative) interpolating field operators for baryons consisting of three quarks with two flavors, assuming good isospin symmetry. We derive and use the relations/identities among the baryon operators with identical quantum numbers that follow from the combined color, Dirac and isospin Fierz transformations. These relations reduce the number of independent baryon operators with any given spin and isospin. The Fierz identities also effectively restrict the allowed baryon chiral multiplets. It turns out that the non-derivative baryons' chiral multiplets have the same dimensionality as their Lorentz representations. For the two independent nucleon operators the only permissible chiral multiplet is the fundamental one, ((1)/(2),0)+(0,(1)/(2)). For the Δ, admissible Lorentz representations are (1,(1)/(2))+((1)/(2),1) and ((3)/(2),0)+(0,(3)/(2)). In the case of the (1,(1)/(2))+((1)/(2),1) chiral multiplet, the I(J)=(3)/(2)((3)/(2)) Δ field has one I(J)=(1)/(2)((3)/(2)) chiral partner; otherwise it has none. We also consider the Abelian (U A (1)) chiral transformation properties of the fields and show that each baryon comes in two varieties: (1) with Abelian axial charge +3; and (2) with Abelian axial charge -1. In case of the nucleon these are the two Ioffe fields; in case of the Δ, the (1,(1)/(2))+((1)/(2),1) multiplet has an Abelian axial charge -1 and the ((3)/(2),0)+(0,(3)/(2)) multiplet has an Abelian axial charge +3. (orig.)

  6. Graphene coated subwavelength wires: a theoretical investigation of emission and radiation properties

    International Nuclear Information System (INIS)

    Cuevas, Mauro

    2017-01-01

    Highlights: • Decay rate in a dielectric graphene coated wire. • Localized surface plasmons. • Excitation of multipolar resonances. - Abstract: This work analyzes the emission and radiation properties of a single optical emitter embedded in a graphene–coated subwavelength wire. We discuss the modifications of the spontaneous emission rate and the radiation efficiency as a function of the position and orientation of the dipole inside the wire. Our results show that these quantities can be enhanced by several orders of magnitude when the emission frequency coincides with one of the resonance frequencies of the graphene–coated wire. In particular, high–order plasmon resonances are excited when the emitter is moved from the wire center. Modifications resulting from varying the orientation of the dipole in the near field distribution and in the far field intensities are shown.

  7. Effect of very high magnetic field on the optical properties of firefly light emitter oxyluciferin

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Weihang; Nakamura, Daisuke [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Wang, Yu [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (China); Mochizuki, Toshimitsu [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Fukushima Renewable Energy Institute, National Institute of Advanced Industrial Science and Technology, 2-2-9 Machiike-dai, Koriyama, Fukushima 963-0215 (Japan); Akiyama, Hidefumi [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Takeyama, Shojiro, E-mail: takeyama@issp.u-tokyo.ac.jp [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)

    2015-09-15

    Magnetic field effect on enzymatic reactions is under intensive study in the past decades. Recently, it was reported that firefly bioluminescence was suppressed and red-shifted significantly when exposed to external magnetic field. However in this work, by means of selective excitation, we confirmed that emission properties of firefly light emitter “oxyluciferin” are completely immune to external magnetic field of up to 53 T. These findings pose strong contrast to existing relevant results. Potential reasons for the discrepancies found and the underlying physics towards the understanding of firefly bioluminescence were discussed. - Highlights: • Effect of ultra-high magnetic field on the optical properties of firefly light emitter oxyluciferin was reported. • Emission properties of oxyluciferin were confirmed to be immune to external high magnetic fields up to 53 T. • .Potential reasons for the discrepancies between our results and previous reports and the underlying physics were discussed.

  8. Plasma-induced field emission and plasma expansion of carbon nanotube cathodes

    International Nuclear Information System (INIS)

    Liao Qingliang; Zhang Yue; Qi Junjie; Huang Yunhua; Xia Liansheng; Gao Zhanjun; Gu Yousong

    2007-01-01

    High intensity electron emission cathodes based on carbon nanotube films have been successfully fabricated. An investigation of the explosive field emission properties of the carbon nanotube cathode in a double-pulse mode was presented and a high emission current density of 245 A cm -2 was obtained. The formation of the cathode plasma layer was proved and the production process of the electron beams from the cathode was explained. The time and space resolution of the electron beams flow from the cathode was investigated. The plasma expanded at a velocity of ∼8.17 cm μs -1 towards the anode and influenced on the intensity and distribution of electron beams obviously. The formation of cathode plasma had no preferential position and the local enhancement of electron beams was random. This carbon nanotube cathode appears to be suitable for high-power microwave device applications

  9. Soliton emission stimulated by sound wave or external field

    International Nuclear Information System (INIS)

    Malomed, B.A.

    1987-01-01

    Langmuir soliton interaction with ion-acoustic wave results in soliton radiative decay at the expence of emission by the soliton of linear langmuir waves. Intensity of this radiation in the ''subsonic'' regime as well as the rate of energy transfer from acoustic waves to langmuir ones and soliton decay rate are calculated. Three cases are considered: monochromatic acoustic wave, nonmonochromatic wave packet with a wide spectrum, random acoustic field, for which results appear to be qualitatively different. A related problem, concerning the radiation generation by soliton under external electromagnetic wave effect is also considered. Dissipation effect on radiation is investigated

  10. Performance of a carbon nanotube field emission electron gun

    Science.gov (United States)

    Getty, Stephanie A.; King, Todd T.; Bis, Rachael A.; Jones, Hollis H.; Herrero, Federico; Lynch, Bernard A.; Roman, Patrick; Mahaffy, Paul

    2007-04-01

    A cold cathode field emission electron gun (e-gun) based on a patterned carbon nanotube (CNT) film has been fabricated for use in a miniaturized reflectron time-of-flight mass spectrometer (RTOF MS), with future applications in other charged particle spectrometers, and performance of the CNT e-gun has been evaluated. A thermionic electron gun has also been fabricated and evaluated in parallel and its performance is used as a benchmark in the evaluation of our CNT e-gun. Implications for future improvements and integration into the RTOF MS are discussed.

  11. Active vacuum brazing of CNT films to metal substrates for superior electron field emission performance

    Science.gov (United States)

    Longtin, Rémi; Sanchez-Valencia, Juan Ramon; Shorubalko, Ivan; Furrer, Roman; Hack, Erwin; Elsener, Hansrudolf; Gröning, Oliver; Greenwood, Paul; Rupesinghe, Nalin; Teo, Kenneth; Leinenbach, Christian; Gröning, Pierangelo

    2015-02-01

    The joining of macroscopic films of vertically aligned multiwalled carbon nanotubes (CNTs) to titanium substrates is demonstrated by active vacuum brazing at 820 °C with a Ag-Cu-Ti alloy and at 880 °C with a Cu-Sn-Ti-Zr alloy. The brazing methodology was elaborated in order to enable the production of highly electrically and thermally conductive CNT/metal substrate contacts. The interfacial electrical resistances of the joints were measured to be as low as 0.35 Ω. The improved interfacial transport properties in the brazed films lead to superior electron field-emission properties when compared to the as-grown films. An emission current of 150 μA was drawn from the brazed nanotubes at an applied electric field of 0.6 V μm-1. The improvement in electron field-emission is mainly attributed to the reduction of the contact resistance between the nanotubes and the substrate. The joints have high re-melting temperatures up to the solidus temperatures of the alloys; far greater than what is achievable with standard solders, thus expanding the application potential of CNT films to high-current and high-power applications where substantial frictional or resistive heating is expected.

  12. Charged Hadron Properties in Background Electric Fields

    International Nuclear Information System (INIS)

    Detmold, William; Tiburzi, Brian C.; Walker-Loud, Andre

    2010-01-01

    We report on a lattice calculation demonstrating a novel new method to extract the electric polarizability of charged pseudo-scalar mesons by analyzing two point correlation functions computed in classical background electric fields. A staple component of any electrodynamics or quantum mechanics course is the electric polarizability. Neutral material immersed in a weak external field polarizes, internally setting up an electric dipole moment, aligned so as to minimize the energy. At the atomic level, the electron clouds are distorted creating these microscopic dipole moments. The same process occurs at the hadronic level but the polarization effects are now constrained by the strong force. Polarizabilities of these bound QCD states can be viewed as a distortion of the charged pion cloud of a given hadron. One can use lattice QCD to non-perturbatively compute the quark and gluon interactions in the presence of background electric (or magnetic) fields. For sufficiently weak background fields, the low energy properties of the hadrons can be rigorously computed using effective field theory. With this treatment, a picture of hadrons emerges from chiral dynamics: that of a hadronic core surrounded by a pseudoscalar meson cloud. As some pseudoscalar mesons are charged, polarizabilities of hadrons encode the stiffness of the charged meson cloud (as well as that of the core). The form of pseudoscalar meson polarizabilities is consequently strongly constrained by chiral dynamics. However, beyond the leading order, the results depend upon essentially unknown low-energy constants, which must currently be estimated in a model-dependent fashion. In the case of the charged pion, the experimental measurement of the polarizability has proven difficult, both in the original measurement as well as the most recent published result. Currently, there is a 2-3 sigma discrepancy between the two-loop cPT prediction and the measured charged pion polarizability. New results with higher

  13. Plasmon mediated enhancement and tuning of optical emission properties of two dimensional graphitic carbon nitride nanosheets.

    Science.gov (United States)

    Bayan, Sayan; Gogurla, Narendar; Midya, Anupam; Singha, Achintya; Ray, Samit K

    2017-12-01

    We demonstrate surface plasmon induced enhancement and tunablilty in optical emission properties of two dimensional graphitic carbon nitride (g-C 3 N 4 ) nanosheets through the attachment of gold (Au) nanoparticles. Raman spectroscopy has revealed surface enhanced Raman scattering that arises due to the combined effect of the charge transfer process and localized surface plasmon induced enhancement in electromagnetic field, both occurring at the nanoparticle-nanosheet interface. Photoluminescence studies suggest that at an optimal concentration of nanoparticles, the emission intensity can be enhanced, which is maximum within the 500-525 nm region. Further, the fabricated electroluminescent devices reveal that the emission feature can be tuned from bluish-green to red (∼160 nm shift) upon attaching Au nanoparticles. We propose that the π*→π transition in g-C 3 N 4 can trigger surface plasmon oscillation in Au, which subsequently increases the excitation process in the nanosheets and results in enhanced emission in the green region of the photoluminescence spectrum. On the other hand, electroluminescence of g-C 3 N 4 can induce plasmon oscillation more efficiently and thus can lead to red emission from Au nanoparticles through the radiative damping of particle plasmons. The influence of nanoparticle size and coverage on the emission properties of two dimensional g-C 3 N 4 , nanosheets has also been studied in detail.

  14. Enhanced field emission from PbTiO{sub 3} nanodots prepared by phase separation approach

    Energy Technology Data Exchange (ETDEWEB)

    Li Jinna; Luo Ming [Department of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Weng Wenjian, E-mail: wengwj@zju.edu.cn [Department of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Cheng Kui; Du Piyi; Shen Ge; Han Gaorong [Department of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China)

    2009-10-15

    Uniformly distributed PbTiO{sub 3} nanodots were successfully prepared by phase separation approach. A precursor sol film was first spin-coated on Si wafer and then spontaneously separated into two distinct phases owing to the Marangoni instability. PT nanodots with tailorable size and density were obtained after further heat treatment. X-ray diffraction analysis indicated that these nanodots showed a perovskite structure. An excellent room temperature field emission property of PbTiO{sub 3} nanodots was observed: the minimum turn-on voltage was about 5.3 V/{mu}m; while the emission current density reached about 270 {mu}A cm{sup -2} at an applied field of about 9.25 V/{mu}m.

  15. Fluxon induced surface resistance and field emission in niobium films at 1.5 GHz

    CERN Document Server

    Benvenuti, Cristoforo; Darriulat, Pierre; Peck, M A; Valente, A M; Van't Hof, C A

    2001-01-01

    The surface resistance of superconducting niobium films induced by the presence of trapped magnetic flux, presumably in the form of a pinned fluxon lattice, is shown to be modified by the presence of a field emitting impurity or defect. The modification takes the form of an additional surface resistance proportional to the density of the fluxon lattice and increasing linearly with the amplitude of the microwave above a threshold significantly lower than the field emission threshold. Such an effect, a precursor of electron emission, is observed for the first time in a study using radiofrequency cavities operating at their fundamental 1.5 GHz frequency. The measured properties of the additional surface resistance severely constrain possible explanations of the observed effect. (23 refs).

  16. Silicon-based metallic micro grid for electron field emission

    International Nuclear Information System (INIS)

    Kim, Jaehong; Jeon, Seok-Gy; Kim, Jung-Il; Kim, Geun-Ju; Heo, Duchang; Shin, Dong Hoon; Sun, Yuning; Lee, Cheol Jin

    2012-01-01

    A micro-scale metal grid based on a silicon frame for application to electron field emission devices is introduced and experimentally demonstrated. A silicon lattice containing aperture holes with an area of 80 × 80 µm 2 and a thickness of 10 µm is precisely manufactured by dry etching the silicon on one side of a double-polished silicon wafer and by wet etching the opposite side. Because a silicon lattice is more rigid than a pure metal lattice, a thin layer of Au/Ti deposited on the silicon lattice for voltage application can be more resistant to the geometric stress caused by the applied electric field. The micro-fabrication process, the images of the fabricated grid with 88% geometric transparency and the surface profile measurement after thermal feasibility testing up to 700 °C are presented. (paper)

  17. Photo field emission spectroscopy of the tantalum band structure

    International Nuclear Information System (INIS)

    Kleint, Ch.; Radon, T.

    1978-01-01

    Photo field emission (PFE) currents of clean and barium covered tantalum tips have been measured with single lines of the mercury arc spectrum and phase-sensitive detection. Field strength and work function were determined from Fowler-Nordheim plots of the FE currents. Shoulders in the PFE current-voltage characteristics could be correlated to transitions in the band structure of tantalum according to a recently proposed two-step PFE model. A comparison with the relativistic calculations of Mattheiss and the nonrelativistic bands of Petroff and Viswanathan shows that Mattheiss' bands are more appropriate. Beside direct transitions several nondirect transitions from the different features composing the upper two density of states maxima below the Fermi edge of tantalum have been found. (Auth.)

  18. Graphene enhanced field emission from InP nanocrystals.

    Science.gov (United States)

    Iemmo, L; Di Bartolomeo, A; Giubileo, F; Luongo, G; Passacantando, M; Niu, G; Hatami, F; Skibitzki, O; Schroeder, T

    2017-12-08

    We report the observation of field emission (FE) from InP nanocrystals (NCs) epitaxially grown on an array of p-Si nanotips. We prove that FE can be enhanced by covering the InP NCs with graphene. The measurements are performed inside a scanning electron microscope chamber with a nano-controlled W-thread used as an anode. We analyze the FE by Fowler-Nordheim theory and find that the field enhancement factor increases monotonically with the spacing between the anode and the cathode. We also show that InP/p-Si junction has a rectifying behavior, while graphene on InP creates an ohmic contact. Understanding the fundamentals of such nanojunctions is key for applications in nanoelectronics.

  19. KILOPARSEC-SCALE PROPERTIES OF EMISSION-LINE GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Hemmati, Shoubaneh; Miller, Sarah H.; Mobasher, Bahram; Nayyeri, Hooshang [University of California, Riverside, CA 92512 (United States); Ferguson, Henry C.; Koekemoer, Anton M. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Guo, Yicheng; Koo, David C. [UCO/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Papovich, Casey, E-mail: shoubaneh.hemmati@ucr.edu [Texas A and M University, College Station, TX 77843 (United States)

    2014-12-20

    We perform a detailed study of the resolved properties of emission-line galaxies at kiloparsec scales to investigate how small-scale and global properties of galaxies are related. We use a sample of 119 galaxies in the GOODS fields. The galaxies are selected to cover a wide range in morphologies over the redshift range 0.2 < z < 1.3. High resolution spectroscopic data from Keck/DEIMOS observations are used to fix the redshift of all the galaxies in our sample. Using the HST/ACS and HST/WFC3 imaging data taken as a part of the CANDELS project, for each galaxy, we perform spectral energy distribution fitting per resolution element, producing resolved rest-frame U – V color, stellar mass, star formation rate (SFR), age, and extinction maps. We develop a technique to identify ''regions'' of statistical significance within individual galaxies, using their rest-frame color maps to select red and blue regions, a broader definition for what are called ''clumps'' in other works. As expected, for any given galaxy, the red regions are found to have higher stellar mass surface densities and older ages compared to the blue regions. Furthermore, we quantify the spatial distribution of red and blue regions with respect to both redshift and stellar mass, finding that the stronger concentration of red regions toward the centers of galaxies is not a significant function of either redshift or stellar mass. We find that the ''main sequence'' of star-forming galaxies exists among both red and blue regions inside galaxies, with the median of blue regions forming a tighter relation with a slope of 1.1 ± 0.1 and a scatter of ∼0.2 dex compared to red regions with a slope of 1.3 ± 0.1 and a scatter of ∼0.6 dex. The blue regions show higher specific SFRs (sSFRs) than their red counterparts with the sSFR decreasing since z ∼ 1, driven primarily by the stellar mass surface densities rather than the SFRs at a given

  20. The Properties of Faint Field Galaxies

    Science.gov (United States)

    Driver, Simon. P.

    1994-12-01

    One of the current drawbacks of Charge Coupled Devices (CCDs) is their restrictive fields of view. The Hitchhiker CCD camera overcomes this limitation by operating in parallel with existing instrumentation and is able to cover a large area as well as large volumes. Hitchhiker is mounted on the 4.2m William Herschel Telescope and has been operating for two years. The first use of the Hitchhiker data set has been to study the general properties of faint galaxies. The observed trend of how the differential numbers of galaxies vary with magnitude agrees extremely well with those of other groups and covers, for the first time, all four major optical bandpasses. This multi-band capability has also allowed the study of how the colors of galaxies change with magnitude and how the correlation of galaxies on the sky varies between the optical bandpasses. A dwarf dominated model has been developed to explain these observations and challenges our knowledge of the space-density of dwarf galaxies. The model demonstrates that a simple upward turn in the luminosity distribution of galaxies, similar to that observed in clusters, would remain undetected by the field surveys yet can explain many of the observations without recourse to non-passive galaxy evolution. The conclusion is that the field luminosity distribution is not constrained at faint absolute magnitudes. A combination of a high density of dwarf galaxies and mild evolution could explain all the observations. Continuing work with HST and the Medium Deep Survey Team now reveals the morphological mix of galaxies down to mI ~ 24.0. The results confirm that ellipticals and early-type spirals are well fitted by standard no-evolution models whilst the late-type spirals can only be fitted by strong evolution and/or a significant turn-up in the local field LF.

  1. Simultaneous fabrication of nanogap electrodes using field-emission-induced electromigration

    International Nuclear Information System (INIS)

    Ito, Mitsuki; Yagi, Mamiko; Morihara, Kohei; Shirakashi, Jun-ichi

    2015-01-01

    We present a simple technique for simultaneous control of the electrical properties of multiple Ni nanogaps. This technique is based on electromigration induced by a field emission current and is called “activation.” Simultaneous tuning of the tunnel resistance of multiple nanogaps was achieved by passing a Fowler–Nordheim (F-N) field emission current through an initial group of three Ni nanogaps connected in series. The Ni nanogaps, which had asymmetrical shapes with initial gap separations in the 80–110-nm range, were fabricated by electron-beam lithography and a lift-off process. By performing the activation procedure, the current–voltage properties of the series-connected nanogaps were varied simultaneously from “insulating” to “metallic” via “tunneling” properties by increasing the preset current of the activation procedure. We can also simultaneously control the tunnel resistances of the series-connected nanogaps, which range from a resistance of the order of 100 TΩ–100 kΩ, by increasing the preset current from 1 nA to 30 μA. This tendency is quite similar to that of individually activated nanogaps, and the tunnel resistance values of the simultaneously activated nanogaps were almost the same at each preset current. These results clearly imply that the electrical properties of the series-connected nanogaps can be controlled simultaneously via the activation procedure

  2. Silicon microelectronic field-emissive devices for advanced display technology

    Science.gov (United States)

    Morse, J. D.

    1993-03-01

    Field-emission displays (FED's) offer the potential advantages of high luminous efficiency, low power consumption, and low cost compared to AMLCD or CRT technologies. An LLNL team has developed silicon-point field emitters for vacuum triode structures and has also used thin-film processing techniques to demonstrate planar edge-emitter configurations. LLNL is interested in contributing its experience in this and other FED-related technologies to collaborations for commercial FED development. At LLNL, FED development is supported by computational capabilities in charge transport and surface/interface modeling in order to develop smaller, low-work-function field emitters using a variety of materials and coatings. Thin-film processing, microfabrication, and diagnostic/test labs permit experimental exploration of emitter and resistor structures. High field standoff technology is an area of long-standing expertise that guides development of low-cost spacers for FEDS. Vacuum sealing facilities are available to complete the FED production engineering process. Drivers constitute a significant fraction of the cost of any flat-panel display. LLNL has an advanced packaging group that can provide chip-on-glass technologies and three-dimensional interconnect generation permitting driver placement on either the front or the back of the display substrate.

  3. All-optical signatures of strong-field QED in the vacuum emission picture

    Science.gov (United States)

    Gies, Holger; Karbstein, Felix; Kohlfürst, Christian

    2018-02-01

    We study all-optical signatures of the effective nonlinear couplings among electromagnetic fields in the quantum vacuum, using the collision of two focused high-intensity laser pulses as an example. The experimental signatures of quantum vacuum nonlinearities are encoded in signal photons, whose kinematic and polarization properties differ from the photons constituting the macroscopic laser fields. We implement an efficient numerical algorithm allowing for the theoretical investigation of such signatures in realistic field configurations accessible in experiment. This algorithm is based on a vacuum emission scheme and can readily be adapted to the collision of more laser beams or further involved field configurations. We solve the case of two colliding pulses in full 3 +1 -dimensional spacetime and identify experimental geometries and parameter regimes with improved signal-to-noise ratios.

  4. Aerodynamic properties of turbulent combustion fields

    Science.gov (United States)

    Hsiao, C. C.; Oppenheim, A. K.

    1985-01-01

    Flow fields involving turbulent flames in premixed gases under a variety of conditions are modeled by the use of a numerical technique based on the random vortex method to solve the Navier-Stokes equations and a flame propagation algorithm to trace the motion of the front and implement the Huygens principle, both due to Chorin. A successive over-relaxation hybrid method is applied to solve the Euler equation for flows in an arbitrarily shaped domain. The method of images, conformal transformation, and the integral-equation technique are also used to treat flows in special cases, according to their particular requirements. Salient features of turbulent flame propagation in premixed gases are interpreted by relating them to the aerodynamic properties of the flow field. Included among them is the well-known cellular structure of flames stabilized by bluff bodies, as well as the formation of the characteristic tulip shape of flames propagating in ducts. In its rudimentary form, the mechanism of propagation of a turbulent flame is shown to consist of: (1) rotary motion of eddies at the flame front, (2) self-advancement of the front at an appropriate normal burning speed, and (3) dynamic effects of expansion due to exothermicity of the combustion reaction. An idealized model is used to illustrate these fundamental mechanisms and to investigate basic aerodynamic features of flames in premixed gases. The case of a confined flame stabilized behind a rearward-facing step is given particular care and attention. Solutions are shown to be in satisfactory agreement with experimental results, especially with respect to global properties such as the average velocity profiles and reattachment length.

  5. Two-photon cooperative emission in the presence of athermal electromagnetic field

    International Nuclear Information System (INIS)

    Enaki, N.A.; Mihalache, D.

    1997-01-01

    The possibility of cooperative spontaneous two-photon emission of an extended radiators system and the influence of the external thermal electromagnetic field on the spontaneous emission rate, in such a system, are investigated. It is concluded that, in an external electromagnetic field, the two-photon cooperative emission rate increases significantly. The importance of this effect on the emission of gamma rays from inverted long-lived isomers triggered by X-ray thermal fields, is emphasized

  6. Vertically aligned carbon nanotubes/diamond double-layered structure for improved field electron emission stability

    Energy Technology Data Exchange (ETDEWEB)

    Yang, L., E-mail: qiaoqin.yang@mail.usask.ca; Yang, Q.; Zhang, C.; Li, Y.S.

    2013-12-31

    A double-layered nanostructure consisting of a layer of vertically aligned Carbon Nanotubes (CNTs) and a layer of diamond beneath has been synthesized on silicon substrate by Hot Filament Chemical Vapor Deposition. The synthesis was achieved by first depositing a layer of diamond on silicon and then depositing a top layer of vertically aligned CNTs by applying a negative bias on the substrate holder. The growth of CNTs was catalyzed by a thin layer of spin-coated iron nitride. The surface morphology and structure of the CNTs/diamond double-layered structure were characterized by Scanning Electron Microscope, Energy Dispersive X-ray spectrum, and Raman Spectroscopy. Their field electron emission (FEE) properties were measured by KEITHLEY 237 high voltage measurement unit, showing much higher FEE current stability than single layered CNTs. - Highlights: • A new double-layered nanostructure consisting of a layer of vertically aligned CNTs and a layer of diamond beneath has been synthesized by hot filament chemical vapor deposition. • This double-layered structure exhibits superior field electron emission stability. • The improvement of emission stability is due to the combination of the unique properties of diamond and CNTs.

  7. Relaxing the electrostatic screening effect by patterning vertically-aligned silicon nanowire arrays into bundles for field emission application

    Energy Technology Data Exchange (ETDEWEB)

    Hung, Yung-Jr, E-mail: yungjrhung@gmail.com [Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Department of Photonics, National Sun Yat-sen University, No. 70, Lienhai Rd., Kaohsiung 80424, Taiwan, ROC (China); Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Lee, San-Liang [Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Beng, Looi Choon [Faculty of Engineering, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor (Malaysia); Chang, Hsuan-Chen [Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Huang, Yung-Jui [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Lee, Kuei-Yi; Huang, Ying-Sheng [Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China)

    2014-04-01

    Top-down fabrication strategies are proposed and demonstrated to realize arrays of vertically-aligned silicon nanowire bundles and bundle arrays of carbon nanotube–silicon nanowire (CNT–SiNW) heterojunctions, aiming for releasing the electrostatic screening effect and improving the field emission characteristics. The trade-off between the reduction in the electrostatic screening effect and the decrease of emission sites leads to an optimal SiNW bundle arrangement which enables the lowest turn-on electric field of 1.4 V/μm and highest emission current density of 191 μA/cm{sup 2} among all testing SiNW samples. Benefiting from the superior thermal and electrical properties of CNTs and the flexible patterning technologies available for SiNWs, bundle arrays of CNT–SiNW heterojunctions show improved and highly-uniform field emission with a lower turn-on electric field of 0.9 V/μm and higher emission current density of 5.86 mA/cm{sup 2}. The application of these materials and their corresponding fabrication approaches is not limited to the field emission but can be used for a variety of emerging fields like nanoelectronics, lithium-ion batteries, and solar cells. - Highlights: • Aligned silicon nanowire (SiNW) bundle arrays are realized with top-down methods. • Growing carbon nanotubes atop SiNW bundle arrays enable uniform field emission. • A turn-on field of 0.9 V/μm and an emission current of > 5 mA/cm{sup 2} are achieved.

  8. The influence of magnetic fields on absorption and emission spectroscopy

    International Nuclear Information System (INIS)

    Zhang, Heshou; Yan, Huirong

    2016-10-01

    Spectroscopic observations play essential roles in astrophysics. They are crucial for determining important physical parameters, providing information about the composition of various objects in the universe, as well as depicting motions in the universe. However, spectroscopic studies often do not consider the influence of magnetic fields. In this paper, we explore the influence of magnetic fields on the spectroscopic observations arising from Ground State Alignment (GSA). Synthetic spectra are generated to show the measurable changes of the spectra due to GSA. The influences of atomic alignment on absorption from DLAs, emission from H II Regions, submillimeter fine-structure lines from star forming regions are presented as examples to illustrate the effect in diffuse gas. Furthermore, we demonstrate the influence of atomic alignment on physical parameters derived from spectral line ratios, such as the alpha-to-iron ratio([X/Fe]), interstellar temperature, and ionization rate. Results in our paper show that due to GSA, magnetic fields will affect the spectra of diffuse gas with high signal-to-noise(S/N) ratio under the condition that photon-excitation is much more efficient than thermal collision.

  9. Vacuum field energy and spontaneous emission in anomalously dispersive cavities

    International Nuclear Information System (INIS)

    Bradshaw, Douglas H.; Di Rosa, Michael D.

    2011-01-01

    Anomalously dispersive cavities, particularly white-light cavities, may have larger bandwidth to finesse ratios than their normally dispersive counterparts. Partly for this reason, they have been proposed for use in laser interferometer gravitational-wave observatory (LIGO)-like gravity-wave detectors and in ring-laser gyroscopes. In this paper we analyze the quantum noise associated with anomalously dispersive cavity modes. The vacuum field energy associated with a particular cavity mode is proportional to the cavity-averaged group velocity of that mode. For anomalously dispersive cavities with group index values between 1 and 0, this means that the total vacuum field energy associated with a particular cavity mode must exceed (ℎ/2π)ω/2. For white-light cavities in particular, the group index approaches zero and the vacuum field energy of a particular spatial mode may be significantly enhanced. We predict enhanced spontaneous emission rates into anomalously dispersive cavity modes and broadened laser linewidths when the linewidth of intracavity emitters is broader than the cavity linewidth.

  10. Performance of a field emission gun TEM/STEM

    International Nuclear Information System (INIS)

    Carpenter, R.W.; Bentley, J.

    1979-01-01

    First experimental results on a Phillips EM 400 TEM/STEM fitted with a field-emission electron gun and objective twin lens are given here. Operation of the FEG is reliable up to maximum design voltage (120 kV). Highest resolution achieved in TEM was 1.9 A fringe. A wide variety of diffraction modes were demonstrated, ranging from CBDP from a small area (approx. 10 A dia) in STEM mode to SAD with angular resolution of 8 μrad in TEM mode. The EDS sensitivity is very high. STEM imaging performance to the highest magnifications examined (200 kx) is good. Work is in progress to evaluate the limits of STEM performance

  11. Bremsstrahlung emission coefficient of a plasma in a uniform magnetic field

    International Nuclear Information System (INIS)

    Pangborn, R.J.

    1976-01-01

    The leading (electron-ion, dipole) contribution to the bremsstrahlung spectrum of a Maxwellian plasma in a constant, uniform magnetic field is calculated. The plasma is assumed infinite and fully ionized. A simpler, more direct derivation of Kirchoff's Law for anisotropic media is presented. The plasma dispersion relation is then found using previously obtained expressions for the conductivity tensor (accurate to first order in collisional effects). From the dispersion the collisional damping, assumed small, is obtained and by means of Kirchoff's Law an expression for the bremsstrahlung emission coefficient is written. No terms of order (kappa 2 lambda 2 0 ) or higher are included. For wave frequencies large compared with the plasma and electron cyclotron frequencies (ω 2 much greater than ω 2 rho, ω 2 much greater than Ω 3 ) an expansion of the exact result is given accurate to fourth order in Ω/ω and ω rho/ω. The result is found to disagree with previous high frequency expressions. Analysis of the exact expression reveals that for certain frequencies and directions of propagation the emission spectrum exhibits a resonance quality. The results are presented in such fashion that for various magnetic field strengths the frequency of the resonant emission at arbitrary angle relative to the field is easily obtained. These phenomena arise due to the influence of the magnetic fieldon the dielectric properties of the plasma and not because of its effect on the binary collision process. A physical explanation of the results is presented

  12. Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

    International Nuclear Information System (INIS)

    Tong Wang

    2002-01-01

    Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radio frequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ∼140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ∼140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ∼140 MV

  13. Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tong [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2002-09-18

    Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m. To

  14. Realisation of a ultra-high vacuum system and technique development of microscopical emitters preparation in silicium. First measurements of field emission current and field photoemission

    International Nuclear Information System (INIS)

    El Manouni, A.

    1990-12-01

    The development of research in the domain of photocathode (electron sources) illuminated by laser light to produce intense multiple bunches of electrons in short time is needed by many applications as linear collider e + e - , free electron laser, lasertron, etc... In this way, after a study of field emission, of photoemission and of photofield emission, we prepared microscopical emitters in silicium heavy and weakly doped a boron using a technique of microlithography. Then, we realized a system of ultra-high vacuum of studying property of emission from photocathodes realized. The experiment results obtained in field emission and photofield emission have shown that a behaviour unexpected for P-silicium tips array compared to P + -silicon tips array. With P-type silicon, a quantum yield of 21 percent has been measured for laser power of 140 mW and for applied field of 1.125 x 10 7 V/m and an instantaneous response to laser light beam has been observed. It has been noted that presence of oxyde at the surface of photocathode limits extensively the emission current. The fluctuations of emission current are due to quality of vacuum [fr

  15. Image reconstruction using three-dimensional compound Gauss-Markov random field in emission computed tomography

    International Nuclear Information System (INIS)

    Watanabe, Shuichi; Kudo, Hiroyuki; Saito, Tsuneo

    1993-01-01

    In this paper, we propose a new reconstruction algorithm based on MAP (maximum a posteriori probability) estimation principle for emission tomography. To improve noise suppression properties of the conventional ML-EM (maximum likelihood expectation maximization) algorithm, direct three-dimensional reconstruction that utilizes intensity correlations between adjacent transaxial slices is introduced. Moreover, to avoid oversmoothing of edges, a priori knowledge of RI (radioisotope) distribution is represented by using a doubly-stochastic image model called the compound Gauss-Markov random field. The a posteriori probability is maximized by using the iterative GEM (generalized EM) algorithm. Computer simulation results are shown to demonstrate validity of the proposed algorithm. (author)

  16. Oxygen plasma assisted end-opening and field emission enhancement in vertically aligned multiwall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Mathur, A. [NIBEC, School of Engineering, University of Ulster, Jordanstown, BT37 0QB (United Kingdom); Roy, S.S., E-mail: sinharoy@ualberta.ca [Department of Mechanical Engineering, University of Alberta, Edmonton, T6T 2G8 (Canada); Hazra, K.S. [Department of Physics, IIT Bombay, Powai, Mumbai-400076 (India); Wadhwa, S. [NIBEC, School of Engineering, University of Ulster, Jordanstown, BT37 0QB (United Kingdom); Ray, S.C. [School of Physics, University of the Witwatersrand, WITS 2050, Johannesburg (South Africa); Mitra, S.K. [Department of Mechanical Engineering, University of Alberta, Edmonton, T6T 2G8 (Canada); Misra, D.S. [Department of Physics, IIT Bombay, Powai, Mumbai-400076 (India); McLaughlin, J.A. [NIBEC, School of Engineering, University of Ulster, Jordanstown, BT37 0QB (United Kingdom)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer We showed Ar/O{sub 2} plasma can be effective for the end opening of aligned CNTs. Black-Right-Pointing-Pointer The field emission property was dramatically enhanced after plasma modification. Black-Right-Pointing-Pointer Microstructures were clearly understood by Raman and SEM analysis. Black-Right-Pointing-Pointer Surface wet-ability at various functionalised conditions was studied. - Abstract: This paper highlights the changes in micro-structural and field emission properties of vertically aligned carbon nanotubes (VACNTs) via oxygen plasma treatment. We find that exposure of very low power oxygen plasma (6 W) at 13.56 MHz for 15-20 min, opens the tip of vertically aligned CNTs. Scanning electron microscopy and transmission electron microscopy images were used to identify the quality and micro-structural changes of the nanotube morphology and surfaces. Raman spectra showed that the numbers of defects were increased throughout the oxygen plasma treatment process. In addition, the hydrophobic nature of the VACNTs is altered significantly and the contact angle decreases drastically from 110 Degree-Sign to 40 Degree-Sign . It was observed that the electron field emission (EFE) characteristics are significantly enhanced. The turn-on electric field (ETOE) of CNTs decreased from {approx}0.80 V {mu}m{sup -1} (untreated) to {approx}0.60 V {mu}m{sup -1} (oxygen treated). We believe that the open ended VACNTs would be immensely valuable for applications such as micro/nanofluidic based filtering elements and display devices.

  17. Fabrication and field emission study of novel rod-shaped diamond-like carbon nanostructures

    International Nuclear Information System (INIS)

    Varshney, Deepak; Makarov, Vladimir I; Saxena, Puja; Weiner, Brad R; Morell, Gerardo; Gonzalez-BerrIos, Adolfo; Scott, James F

    2010-01-01

    Novel sp 3 rich diamond-like carbon nanorod films were fabricated by a hot filament chemical vapour deposition technique. The results are indicative of a bottom-up synthesis process, which results in a hierarchical structure that consists of microscale papillae comprising numerous nanorods. The papillae have diameters ranging from 2 to 4 μm and the nanorods have diameters in the 35-45 nm range. A growth mechanism based on the vapour-liquid-solid mechanism is proposed that accounts for the morphological aspects at the microscale and nanoscale. Investigation of field emission properties of fabricated nanorods reveals a low turn-on field of about 4.9 V μm -1 at 1 nA and a high field-enhancement factor.

  18. Mechanical Properties and Acoustic Emission Properties of Rocks with Different Transverse Scales

    Directory of Open Access Journals (Sweden)

    Xi Yan

    2017-01-01

    Full Text Available Since the stability of engineering rock masses has important practical significance to projects like mining, tunneling, and petroleum engineering, it is necessary to study mechanical properties and stability prediction methods for rocks, cementing materials that are composed of minerals in all shapes and sizes. Rocks will generate acoustic emission during damage failure processes, which is deemed as an effective means of monitoring the stability of coal rocks. In the meantime, actual mining and roadway surrounding rocks tend to have transverse effects; namely, the transverse scale is larger than the length scale. Therefore, it is important to explore mechanical properties and acoustic emission properties of rocks under transverse size effects. Considering the transverse scale effects of rocks, this paper employs the microparticle flow software PFC2D to explore the influence of different aspect ratios on damage mechanics and acoustic emission properties of rocks. The results show that (1 the transverse scale affects uniaxial compression strength of rocks. As the aspect ratio increases, uniaxial compression strength of rocks decreases initially and later increases, showing a V-shape structure and (2 although it affects the maximum hit rate and the strain range of acoustic emission, it has little influence on the period of occurrence. As the transverse scale increases, both damage degree and damage rate of rocks decrease initially and later increase.

  19. Field investigation to assess nutrient emission from paddy field to surface water in river catchment

    Science.gov (United States)

    Kogure, Kanami; Aichi, Masaatsu; Zessner, Matthias

    2015-04-01

    In order to maintain good river environment, it is remarkably important to understand and to control nutrient behavior such as Nitrogen and Phosphorus. Our former research dealing with nutrient emission analysis in the Tone River basin area in Japan, in addition to urban and industrial waste water, nutrient emission from agricultural activity is dominant pollution source into the river system. Japanese style agriculture produces large amount of rice and paddy field occupies large areas in Japanese river basin areas. While paddy field can deteriorate river water quality by outflow of fertilizer, it is also suggested that paddy field has water purification function. As we carried out investigation in the Tone River Basin area, data were obtained which dissolved nitrogen concentration is lower in discharging water from paddy field than inflowing water into the field. Regarding to nutrient emission impact from paddy field, sufficient data are required to discuss quantitatively seasonal change of material behavior including flooding season and dry season, difference of climate condition, soil type, and rice species, to evaluate year round comprehensive impact from paddy field to the river system. In this research, field survey in paddy field and data collection relating rice production were carried out as a preliminary investigation to assess how Japanese style paddy field contributes year round on surface water quality. Study sites are three paddy fields located in upper reach of the Tone River basin area. The fields are flooded from June to September. In 2014, field investigations were carried out three times in flooding period and twice in dry period. To understand characteristics of each paddy field and seasonal tendency accompanying weather of agricultural event, short term investigations were conducted and we prepare for further long term investigation. Each study site has irrigation water inflow and outflow. Two sites have tile drainage system under the field and

  20. Enhanced field emission characteristics of boron doped diamond films grown by microwave plasma assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Koinkar, Pankaj M. [Center for International Cooperation in Engineering Education (CICEE), University of Tokushima, 2-1 Minami-josanjima-cho, Tokushima 770-8506 (Japan); Patil, Sandip S. [Center for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007 (India); Kim, Tae-Gyu [Department of Nano System and Process Engineering, Pusan National University, 50 Cheonghak-ri, Samrangjin-eup, Miryang, Gyeongnam, Pusan 627-706 (Korea, Republic of); Yonekura, Daisuke [Department of Mechanical Engineering, University of Tokushima, 2-1 Minami-josanjima-cho, Tokushima 770-8506 (Japan); More, Mahendra A., E-mail: mam@physics.unipune.ac.in [Center for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007 (India); Joag, Dilip S. [Center for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007 (India); Murakami, Ri-ichi, E-mail: murakami@me.tokushima-u.ac.jp [Department of Mechanical Engineering, University of Tokushima, 2-1 Minami-josanjima-cho, Tokushima 770-8506 (Japan)

    2011-01-01

    Boron doped diamond films were synthesized on silicon substrates by microwave plasma chemical vapor deposition (MPCVD) technique. The effect of B{sub 2}O{sub 3} concentration varied from 1000 to 5000 ppm on the field emission characteristics was examined. The surface morphology and quality of films were characterized by scanning electron microscope (SEM) and Raman spectroscopy. The surface morphology obtained by SEM showed variation from facetted microcrystal covered with nanometric grains to cauliflower of nanocrystalline diamond (NCD) particles with increasing B{sub 2}O{sub 3} concentration. The Raman spectra confirm the formation of NCD films. The field emission properties of NCD films were observed to improve upon increasing boron concentration. The values of the onset field and threshold field are observed to be as low as 0.36 and 0.08 V/{mu}m, respectively. The field emission current stability investigated at the preset value of {approx}1 {mu}A is observed to be good, in each case. The enhanced field emission properties are attributed to the better electrical conductivity coupled with the nanometric features of the diamond films.

  1. Field emission from patterned SnO2 nanostructures

    International Nuclear Information System (INIS)

    Zhang Yongsheng; Yu Ke; Li Guodong; Peng Deyan; Zhang Qiuxiang; Hu Hongmei; Xu Feng; Bai Wei; Ouyang Shixi; Zhu Ziqiang

    2006-01-01

    A simple and reliable method has been developed for synthesizing finely patterned tin dioxide (SnO 2 ) nanostructure arrays on silicon substrates. A patterned Au catalyst film was prepared on the silicon wafer by radio frequency (RF) magnetron sputtering and photolithographic patterning processes. The patterned SnO 2 nanostructures arrays, a unit area is of ∼500 μm x 200 μm, were synthesized via vapor phase transport method. The surface morphology and composition of the as-synthesized SnO 2 nanostructures were characterized by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanism of formation of SnO 2 nanostructures was also discussed. The measurement of field emission (FE) revealed that the as-synthesized SnO 2 nanorods, nanowires and nanoparticles arrays have a lower turn-on field of 2.6, 3.2 and 3.9 V/μm, respectively, at the current density of 0.1 μA/cm 2 . This approach must have a wide variety of applications such as fabrications of micro-optical components and micropatterned oxide thin films used in FE-based flat panel displays, sensor arrays and so on

  2. Velocity field measurement in micro-bubble emission boiling

    International Nuclear Information System (INIS)

    Ito, Daisuke; Saito, Yasushi; Natazuka, Jun

    2017-01-01

    Liquid inlet behavior to a heat surface in micro-bubble emission boiling (MEB) was investigated by flow measurement using particle image velocimetry (PIV). Subcooled pool boiling experiments under atmospheric pressure were carried out using a heat surface with a diameter of 10 mm. An upper end of a heater block made of copper was used as the heat surface. Working fluid was the deionized water and the subcooling was varied from 40 K to 70 K. Three K-type thermocouples were installed in the copper block to measure the temperature gradient, and the heat flux and wall superheat were estimated from these temperature data to make a boiling curve. The flow visualization around the heat surface was carried out using a high-speed video camera and a light sheet. The microbubbles generated in the MEB were used as tracer particles and the velocity field was obtained by PIV analysis of the acquired image sequence. As a result, the higher heat fluxes than the critical heat flux could be obtained in the MEB region. In addition, the distribution characteristics of the velocity in MEB region were studied using the PIV results and the location of the stagnation point in the velocity fields was discussed. (author)

  3. Field line diversion properties of finite β Helias equilibria

    International Nuclear Information System (INIS)

    Hayashi, T.; Schwenn, U.; Strumberger, E.

    1992-03-01

    The diversion properties of the magnetic field outside the last closed magnetic surface of a Helias stellarator configuration are investigated for finite β-equilibria. The results support a divertor concept which has been developed from the diversion properties of the corresponding vacuum field. Cross-field transport is simulated by a simplified scrape-off layer (SOL) model. (author)

  4. Optimizing the e-beam profile of a single carbon nanotube field emission device for electric propulsion systems

    Directory of Open Access Journals (Sweden)

    Juliano Fujioka Mologni

    2010-04-01

    Full Text Available Preliminary studies on field emission (FE arrays comprised of carbon nanotubes (CNT as an electron source for electric propulsion system show remarkably promising results. Design parameters for a carbon nanotube (CNT field-emission device operating on triode configuration were numerically simulated and optimized in order to enhance the e-beam focusing quality. An additional focus gate (FG was integrated to the device to control the profile of the emitted e-beam. An axisymmetric finite element model was developed to calculate the electric field distribution on the vacuum region and a modified Fowler-Nordheim (FN equation was used to evaluate the current density emission and the effective emitter area. Afterward, a FE simulation was employed in order to calculate the trajectory of the emitted electrons and define the electron-optical properties of the e-beam. The integration of the FG was fully investigated via computational intelligence techniques. The best performance device according to our simulations presents a collimated e-beam profile that suits well for field emission displays, magnetic field detection and electron microscopy. The automated computational design tool presented in this study strongly benefits the robust design of integrated electron-optical systems for vacuum field emission applications, including electrodynamic tethering and electric propulsion systems.

  5. Density functional theory for field emission from carbon nano-structures

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhibing, E-mail: stslzb@mail.sysu.edu.cn

    2015-12-15

    Electron field emission is understood as a quantum mechanical many-body problem in which an electronic quasi-particle of the emitter is converted into an electron in vacuum. Fundamental concepts of field emission, such as the field enhancement factor, work-function, edge barrier and emission current density, will be investigated, using carbon nanotubes and graphene as examples. A multi-scale algorithm basing on density functional theory is introduced. We will argue that such a first principle approach is necessary and appropriate for field emission of nano-structures, not only for a more accurate quantitative description, but, more importantly, for deeper insight into field emission. - Highlights: • Applications of DFT to electron field emission of nano-structures are reviewed. • Fundamental concepts of field emission are re-visited with emphasis on the many-body effects. • New insights to field emission of nano-structures are obtained by multi-scale DFT calculations. • It is shown that the exchange–correlation effect on the emission barrier is significant. • Spontaneous symmetry breaking in field emission of CNT has been predicted.

  6. Dark matter properties implied by gamma ray interstellar emission models

    Energy Technology Data Exchange (ETDEWEB)

    Balázs, Csaba; Li, Tong, E-mail: csaba.balazs@monash.edu, E-mail: tong.li@monash.edu [ARC Centre of Excellence for Particle Physics at the Tera-scale, School of Physics and Astronomy, Monash University, Melbourne, Victoria 3800 (Australia)

    2017-02-01

    We infer dark matter properties from gamma ray residuals extracted using eight different interstellar emission scenarios proposed by the Fermi-LAT Collaboration to explain the Galactic Center gamma ray excess. Adopting the most plausible simplified ansatz, we assume that the dark matter particle is a Majorana fermion interacting with standard fermions via a scalar mediator. To trivially respect flavor constraints, we only couple the mediator to third generation fermions. Using this theoretical hypothesis, and the Fermi residuals, we calculate Bayesian evidences, including Fermi-LAT exclusion limits from 15 dwarf spheroidal galaxies as well. Our evidence ratios single out one of the Fermi scenarios as most compatible with the simplified dark matter model. In this scenario the dark matter (mediator) mass is in the 25-200 (1-1000) GeV range and its annihilation is dominated by bottom quark final state. Our conclusion is that the properties of dark matter extracted from gamma ray data are highly sensitive to the modeling of the interstellar emission.

  7. Role of work function in field emission enhancement of Au island decorated vertically aligned ZnO nanotapers

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Avanendra [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India); Senapati, Kartik, E-mail: kartik@niser.ac.in [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India); Kumar, Mohit; Som, Tapobrata [SUNAG Laboratory, Institute of Physics, Bhubaneswar 751005, Odisha (India); Sinha, Anil K. [Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India); Sahoo, Pratap K., E-mail: pratap.sahoo@niser.ac.in [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India)

    2017-07-31

    Highlights: • Hydrothermally synthesized nanotapers were decorated by gold corrugation using simple evaporation techniques for large area applications. • A significantly enhanced field emission properties of nanotapers were achieved. • The metal induced midgap states formed at the ZnO-Au interface and the reduced effective work function are responsible for low turn-on field. • TUNA measurements revealed a very uniform spatial emission profile in the Au decorated nanotapers. - Abstract: In this report, we demonstrate significantly enhanced field emission properties of ZnO nanotapers achieved via a corrugated decoration of Au. Field emission experiments on these Au-decorated ZnO nanotapers showed emission current densities comparable to the best results in the literature. Au decoration of 5 nm also reduced the effective turn-on field to ∼0.54 V/μm, compared to the as grown ZnO nanotapers, which showed a turn-on field of ∼1.1 V/μm. Tunneling atomic force microscopy measurements revealed a very uniform spatial emission profile in the 5 nm Au decorated nanotapers, which is a basic requirement for any large scale application. We believe that metal induced mid-gap states formed at the ZnO–Au interface are responsible for the observed low turn-on field because such interface states are known to reduce the effective work function. A direct measurement of effective work function using Kelvin probe force microscopy indeed showed more than 1.1 eV drop in the case of 5 nm Au decorated ZnO nanotapers compared to the pristine nanotapers, supporting the above argument.

  8. Control of spontaneous emission from a microwave-field-driven four-level atom in an anisotropic photonic crystal

    Science.gov (United States)

    Zhang, Duo; Li, Jiahua; Ding, Chunling; Yang, Xiaoxue

    2012-05-01

    The spontaneous emission properties of a microwave-field-driven four-level atom embedded in anisotropic double-band photonic crystals (PCs) are investigated. We discuss the influences of the band-edge positions, Rabi frequency and detuning of the microwave field on the emission spectrum. It is found that several interesting features such as spectral-line enhancement, spectral-line suppression, spectral-line overlap, and multi-peak structures can be observed in the spectra. The proposed scheme can be achieved by use of a microwave-coupled field into hyperfine levels in rubidium atom confined in a photonic crystal. These theoretical investigations may provide more degrees of freedom to manipulate the atomic spontaneous emission.

  9. Experimental Development of Low-emittance Field-emission Electron Sources

    Energy Technology Data Exchange (ETDEWEB)

    Lueangaranwong, A. [Northern Illinois Univ., DeKalb, IL (United States). Northern Illinois Center for Accelerator & Detector Development; Buzzard, C. [Northern Illinois Univ., DeKalb, IL (United States); Divan, R. [Argonne National Lab. (ANL), Argonne, IL (United States). Center for Nanoscale Materials; Korampally, V. [Northern Illinois Univ., DeKalb, IL (United States); Piot, P. [Northern Illinois Univ., DeKalb, IL (United States). Northern Illinois Center for Accelerator & Detector Development; Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2016-10-10

    Field emission electron sources are capable of extreme brightness when excited by static or time-dependent electro- magnetic fields. We are currently developing a cathode test stand operating in DC mode with possibility to trigger the emission using ultra-short (~ 100-fs) laser pulses. This contribution describes the status of an experiment to investigate field-emission using cathodes under development at NIU in collaboration with the Argonne’s Center for Nanoscale Materials.

  10. Optics and design of the fringe field monochromator for a Schottky field emission gun

    International Nuclear Information System (INIS)

    Mook, H.W.; Kruit, P.

    1999-01-01

    For the improvement of high-resolution electron energy loss spectroscopy a new electron source monochromator, based on the Wien filter principle, is presented. In the fringe field monochromator the electric and magnetic filter fields are tightly enclosed by field clamps to satisfy the Wien condition, E=vB. The whole monochromator including the 150 nm energy selection slits (Nanoslits) is positioned in the gun area. Its total length is only 42 mm. Using electron trajectory simulation through the filter fields the dispersion and aberrations are determined. The parasitic astigmatism of the gun lens needs to be corrected using an electrostatic quadrupole field incorporated in the filter. Estimations of the influence of filter electrode misalignment show that at least six filter electrodes must be used to loosen the alignment demands sufficiently. Using theoretical estimations of the Coulomb interaction the final energy resolution, beam brightness and current are predicted. For a Schottky field emission electron gun with typical brightness of 10 8 A/sr m 2 V the monochromator is expected to produce a 50 meV 1 nA beam with a brightness of 10 7

  11. Properties of electronic emissions of semiconductors III-IV in a status of negative electron affinity

    International Nuclear Information System (INIS)

    Piaget, Claude

    1977-01-01

    This research thesis reports the use of various properties (electron emission, photo emission, secondary electron emission) to highlight the relationships between various solid properties (optical, electronic, structural properties), surfaces (clean or covered with adsorbates such as caesium and oxygen) and emission properties (quantum efficiency, energy distribution, and so on). The first part addresses applications, performance, physical properties and technological processes, and also problems related to the physics and chemistry of surfaces and adsorption layers. The second part reports a study of the main electron transport properties in emitters displaying a negative electron affinity, for example GaP. Some aspects of electron excitation by ultra-violet radiations and high energy electrons are studied from UV photo-emission properties and secondary electron emission. Then GaAs and similar pseudo-binary compounds are studied

  12. Near-field emission profiling of tropical forest and Cerrado fires in Brazil during SAMBBA 2012

    Science.gov (United States)

    Hodgson, Amy K.; Morgan, William T.; O'Shea, Sebastian; Bauguitte, Stéphane; Allan, James D.; Darbyshire, Eoghan; Flynn, Michael J.; Liu, Dantong; Lee, James; Johnson, Ben; Haywood, Jim M.; Longo, Karla M.; Artaxo, Paulo E.; Coe, Hugh

    2018-04-01

    We profile trace gas and particulate emissions from near-field airborne measurements of discrete smoke plumes in Brazil during the 2012 biomass burning season. The South American Biomass Burning Analysis (SAMBBA) Project conducted during September and October 2012 sampled across two distinct fire regimes prevalent in the Amazon Basin. Combined measurements from a Compact Time-of-Flight Aerosol Mass Spectrometer (C-ToF-AMS) and a Single Particle Soot Photometer (SP2) are reported for the first time in a tropical biomass burning environment. Emissions from a mostly smouldering tropical forest wildfire in Rondônia state and numerous smaller flaming Cerrado fires in Tocantins state are presented. While the Cerrado fires appear to be representative of typical fire conditions in the existing literature, the tropical forest wildfire likely represents a more extreme example of biomass burning with a bias towards mostly smouldering emissions. We determined fire-integrated modified combustion efficiencies, emission ratios and emission factors for trace gas and particulate components for these two fire types, alongside aerosol microphysical properties. Seven times more black carbon was emitted from the Cerrado fires per unit of fuel combustion (EFBC of 0.13 ± 0.04 g kg-1) compared to the tropical forest fire (EFBC of 0.019 ± 0.006 g kg-1), and more than 6 times the amount of organic aerosol was emitted from the tropical forest fire per unit of fuel combustion (EFOM of 8.00 ± 2.53 g kg-1, EFOC of 5.00 ± 1.58 g kg-1) compared to the Cerrado fires (EFOM of 1.31 ± 0.42 g kg-1, EFOC of 0.82 ± 0.26 g kg-1). Particulate-phase species emitted from the fires sampled are generally lower than those reported in previous studies and in emission inventories, which is likely a combination of differences in fire combustion efficiency and fuel mixture, along with different measurement techniques. Previous modelling studies focussed on the biomass burning season in tropical South

  13. In situ manipulation and characterizations using nanomanipulators inside a field emission-scanning electron microscope

    International Nuclear Information System (INIS)

    Kim, Keun Soo; Lim, Seong Chu; Lee, Im Bok; An, Key Heyok; Bae, Dong Jae; Choi, Shinje; Yoo, Jae-Eun; Lee, Young Hee

    2003-01-01

    We have used two piezoelectric nanomanipulators to manage the multiwalled carbon nanotubes (MWCNTs) within the field emission-scanning electron microscope (FE-SEM). For an easy access of a tungsten tip to MWCNTs, we prepared the tungsten tip in sharp and long tip geometry using different electrochemical etching parameters. In addition, the sample stage was tilted by 45 deg. from the normal direction of the surface to allow a better incident angle to the approaching tungsten tip. For manipulations, a nanotube or the bundles were attached at the tungsten tip using an electron beam-induced deposition (EBID). Using two manipulators, we have then fabricated a CNT-based transistor, a cross-junction of MWCNTs, and a CNT-attached atomic force microscopy tip. After these fabrications, the field emission properties of the MWCNT and junction properties of the MWCNT and the tungsten tip have been investigated. We found that the EBID approach was very useful to weld the nanostructured materials on the tungsten tip by simply irradiating the electron beam, although this sometimes increased the contact resistance by depositing hydrocarbon materials

  14. Field Emission Scanning Electron Microscope (FESEM) Facility in BTI

    International Nuclear Information System (INIS)

    Cik Rohaida Che Hak; Foo, C.T.; Nor Azillah Fatimah Othman

    2015-01-01

    Field Emission Scanning Electron Microscope (FE-SEM) provides ultra-high resolution imaging at low accelerating voltages and small working distances. The GeminisSEM 500, a new FESEM imaging facility will be installed soon in MTEC, BTI. It provides resolution of the images is as low as 0.6 nm at 15 kV and 1.2 nm at 1 kV, allowing examination of the top surface of nano powders, nano film and nano fiber in the wide range of applications such as mineralogy, ceramics, polymer, metallurgy, electronic devices, chemistry, physics and life sciences. This system is equipped with several detectors to detect various signals such as secondary electrons (SE) detector for topographic information and back-scattered electrons (BSE) detector for materials composition contrast. Energy dispersive x-ray spectroscopy (EDS) with detector energy resolution of < 129 eV and detection limit in the range of 1000-3000 ppm coupled with FE-SEM is used to determine the chemical composition of micro-features including boron (B) to uranium (U). Wavelength dispersive x-ray spectroscopy (WDS) which has detector resolution of 2-20 eV and detection limit of 30-300 ppm coupled with FE-SEM is used to detect elements that cannot be resolved with EDS. The ultra-high resolution imaging combined with the high sensitivity WDS helps to resolve the thorium and rare earth elemental analysis. (author)

  15. Self-assembled InAs quantum dots. Properties, modification and emission processes

    International Nuclear Information System (INIS)

    Schramm, A.

    2007-01-01

    In this thesis, structural, optical as well as electronic properties of self-assembled InAs quantum dots (QD) were studied by means of atomic force microscopy (AFM), photoluminescence (PL), capacitance spectroscopy (CV) and capacitance transient spectroscopy (DLTS). The quantum dots were grown with molecular beam epitaxy (MBE) and embedded in Schottky diodes for electrical characterization. In this work growth aspects as well as the electronic structures of QD were discussed. By varying the QD growth parameters it is possible to control the structural, and thus the optical and electronic properties of QD. Two methods are presented. Adjusting the QD growth temperature leads either to small QD with a high areal density or to high QDs with a low density. The structural changes of the QD are reflected in the changes of the optical and electronic properties. The second method is to introduce a growth interruption after capping the QD with thin cap layers. It was shown that capping with AlAs leads to a well-developed alternative to control the QD height and thus the ground-state energies of the QD. A post-growth method modifying the QD properties ist rapid thermal annealing (RTA). Raising the RTA temperature causes a lifting of the QD energy states with respect to the GaAs band edge energy due to In/Ga intermixing processes. A further main part of this work covers the emission processes of charge carriers in QD. Thermal emission, thermally assisted tunneling, and pure tunneling emission are studied by capacitance transient spectroscopy techniques. In DLTS experiments a strong impact of the electric field on the activation energies of electrons was found interfering the correct determination of the QD level energies. This behaviour can be explained by a thermally assisted tunneling model. A modified model taking the Coulomb interaction of occupied QD into account describes the emission rates of the electrons. In order to avoid several emission pathes in the experiments

  16. Field emission mechanism from a single-layer ultra-thin semiconductor film cathode

    International Nuclear Information System (INIS)

    Duan Zhiqiang; Wang Ruzhi; Yuan Ruiyang; Yang Wei; Wang Bo; Yan Hui

    2007-01-01

    Field emission (FE) from a single-layer ultra-thin semiconductor film cathode (SUSC) on a metal substrate has been investigated theoretically. The self-consistent quantum FE model is developed by synthetically considering the energy band bending and electron scattering. As a typical example, we calculate the FE properties of ultra-thin AlN film with an adjustable film thickness from 1 to 10 nm. The calculated results show that the FE characteristic is evidently modulated by varying the film thickness, and there is an optimum thickness of about 3 nm. Furthermore, a four-step FE mechanism is suggested such that the distinct FE current of a SUSC is rooted in the thickness sensitivity of its quantum structure, and the optimum FE properties of the SUSC should be attributed to the change in the effective potential combined with the attenuation of electron scattering

  17. BATMAN beam properties characterization by the beam emission spectroscopy diagnostic

    Science.gov (United States)

    Bonomo, F.; Ruf, B.; Barbisan, M.; Cristofaro, S.; Schiesko, L.; Fantz, U.; Franzen, P.; Pasqualotto, R.; Riedl, R.; Serianni, G.; Wünderlich, D.

    2015-04-01

    The ITER neutral beam heating systems are based on the production and acceleration of negative ions (H/D) up to 1 MV. The requirements for the beam properties are strict: a low core beam divergence (BATMAN (BAvarian Test MAchine for Negative ions) allows for deepening the knowledge of the determination of the beam properties. One of the diagnostics routinely used to this purpose is the Beam Emission Spectroscopy (BES): the Hα light emitted in the beam is detected and the corresponding spectra are evaluated to estimate the beam divergence and the stripping losses. The BES number of lines of sight in BATMAN has been recently increased: five horizontal lines of sight providing a vertical profile of the beam permit to characterize the negative ion beam properties in relation to the source parameters. Different methods of Hα spectra analysis are here taken into account and compared for the estimation of the beam divergence and the amount of stripping. In particular, to thoroughly study the effect of the space charge compensation on the beam divergence, an additional hydrogen injection line has been added in the tank, which allows for setting different background pressure values (one order of magnitude, from about 0.04 Pa up to the source pressure) in the beam drift region.

  18. Morphology dependent field emission characteristics of ZnS/silicon nanoporous pillar array

    Science.gov (United States)

    Wang, Ling Li; Zhao, Cheng Zhou; Kang, Li Ping; Liu, De Wei; Zhao, Hui Chun; Hao, Shan Peng; Zhang, Yuan Kai; Chen, Zhen Ping; Li, Xin Jian

    2016-10-01

    Through depositing zinc sulphide (ZnS) nanoparticals on silicon nanoporous pillar array (Si-NPA) and crater-shaped silicon nanoporous pillar array (c-Si-NPA) by chemical bath deposition (CBD) method, ZnS/Si-NPA and c-ZnS/Si-NPA were prepared and the field emission (FE) properties of them were investigated. The turn-on electric fields of were 3.8 V/mm for ZnS/Si-NPA and 5.0 V/mm for c-ZnS/Si-NPA, respectively. The lower turn-on electric fields of ZnS/Si-NPA than that of c-ZnS/Si-NPA were attributed to the different electric distribution of the field emitters causing by the different surface morphology of the two samples, which was further demonstrated via the simulated results by finite element modeling. The FN curves for the ZnS/Si-NPA showed two-slope behavior. All the results indicate that the morphology play an important role in the FE properties and designing an appropriate top morphology for the emitter is a very efficient way to improve the FE performance.

  19. The ALFAM2 database on ammonia emission from field-applied manure

    NARCIS (Netherlands)

    Hafner, Sasha D.; Pacholski, Andreas; Bittman, Shabtai; Burchill, William; Bussink, Wim; Chantigny, Martin; Carozzi, Marco; Génermont, Sophie; Häni, Christoph; Hansen, Martin N.; Huijsmans, Jan; Hunt, Derek; Kupper, Thomas; Lanigan, Gary; Loubet, Benjamin; Misselbrook, Tom; Meisinger, John J.; Neftel, Albrecht; Nyord, Tavs; Pedersen, Simon V.; Sintermann, Jörg; Thompson, Rodney B.; Vermeulen, Bert; Voylokov, Polina; Williams, John R.; Sommer, Sven G.

    2018-01-01

    Ammonia (NH3) emission from animal manure contributes to air pollution and ecosystem degradation, and the loss of reactive nitrogen (N) from agricultural systems. Estimates of NH3 emission are necessary for national inventories and nutrient management, and NH3 emission from field-applied manure has

  20. Earthworms can increase nitrous oxide emissions from managed grassland: a field study

    NARCIS (Netherlands)

    Lubbers, I.M.; López González, E.; Hummelink, E.W.J.; Groenigen, van J.W.

    2013-01-01

    Earthworms are important in determining the greenhouse gas (GHG) balance of soils. In laboratory studies they have been shown to increase emissions of the potent GHG nitrous oxide (N2O). Here we test whether these earthworm-induced N2O emissions also occur in the field. We quantified N2O emissions

  1. The magnetoionic modes and propagation properties of auroral radio emissions

    International Nuclear Information System (INIS)

    Calvert, W.; Hashimoto, Kozo

    1990-01-01

    The different magnetoionic wave modes which accompany the aurora are identified using DE 1 not only by their appearance on satellite radio spectrograms, but also by concurrent measurements of their wave polarization and arrival directions, and by ray-tracing models of their expected propagation behavior. Of the four possible propagation modes, designated O, X, W, and Z for the ordinary, extraordinary, whistler, and Z modes, respectively, all four are found to occur in the auroral zone, as follows: The most intense, of course, is the well-known auroral kilometric radiation (AKR), which originates primarily in the X mode near the electron cyclotron frequency, but which is frequently also accompanied by a weaker O-mode component from the same location. The next most prominent auroral emission is the W-mode auroral hiss originating from altitudes always well below the DE 1 satellite at frequencies below the local cyclotron frequency. The previously reported Z-mode auroral radiation was also detected, but from sources also below the satellite and at the poleward edge of the cavity, and not from the expected AKR source at the cyclotron frequency. A weaker O-mode component seems to accompany these emissions also, both within the polar cap poleward of the source and inside the cavity, the latter seemingly being guided upward by the cavity's lower plasma densities. Finally, exactly on the source field lines at the poleward edge of the cavity, there also occasionally seems to be localized Z-mode emissions extending from the Z-mode cutoff at quite low frequencies up to and above the plasma frequency

  2. Mechanical Properties and Acoustic Emission Properties of Rocks with Different Transverse Scales

    OpenAIRE

    Yan, Xi; Jun, Li; Gonghui, Liu; Xueli, Guo

    2017-01-01

    Since the stability of engineering rock masses has important practical significance to projects like mining, tunneling, and petroleum engineering, it is necessary to study mechanical properties and stability prediction methods for rocks, cementing materials that are composed of minerals in all shapes and sizes. Rocks will generate acoustic emission during damage failure processes, which is deemed as an effective means of monitoring the stability of coal rocks. In the meantime, actual mining a...

  3. BATMAN beam properties characterization by the beam emission spectroscopy diagnostic

    International Nuclear Information System (INIS)

    Bonomo, F.; Ruf, B.; Schiesko, L.; Fantz, U.; Franzen, P.; Riedl, R.; Wünderlich, D.; Barbisan, M.; Pasqualotto, R.; Serianni, G.; Cristofaro, S.

    2015-01-01

    The ITER neutral beam heating systems are based on the production and acceleration of negative ions (H/D) up to 1 MV. The requirements for the beam properties are strict: a low core beam divergence (< 0.4 °) together with a low source pressure (≤ 0.3 Pa) would permit to reduce the ion losses along the beamline, keeping the stripping particle losses below 30%. However, the attainment of such beam properties is not straightforward. At IPP, the negative ion source testbed BATMAN (BAvarian Test MAchine for Negative ions) allows for deepening the knowledge of the determination of the beam properties. One of the diagnostics routinely used to this purpose is the Beam Emission Spectroscopy (BES): the H α light emitted in the beam is detected and the corresponding spectra are evaluated to estimate the beam divergence and the stripping losses. The BES number of lines of sight in BATMAN has been recently increased: five horizontal lines of sight providing a vertical profile of the beam permit to characterize the negative ion beam properties in relation to the source parameters. Different methods of H α spectra analysis are here taken into account and compared for the estimation of the beam divergence and the amount of stripping. In particular, to thoroughly study the effect of the space charge compensation on the beam divergence, an additional hydrogen injection line has been added in the tank, which allows for setting different background pressure values (one order of magnitude, from about 0.04 Pa up to the source pressure) in the beam drift region

  4. New perspectives in vacuum high voltage insulation. I. The transition to field emission

    CERN Document Server

    Diamond, W T

    1998-01-01

    Vacuum high-voltage insulation has been investigated for many years. Typically, electrical breakdown occurs between two broad-area electrodes at electric fields 100-1000 times lower than the breakdown field (about 5000 MV/m) between a well-prepared point cathode and a broad-area anode. Explanations of the large differences remain unsatisfactory, usually evoking field emission from small projections on the cathode that are subject to higher peak fields. The field emission then produces secondary effects that lead to breakdown. This article provides a significant resolution to this long standing problem. Field emission is not present at all fields, but typically starts after some process occurs at the cathode surface. Three effects have been identified that produce the transition to field emission: work function changes; mechanical changes produced by the strong electrical forces on the electrode surfaces; and gas desorption from the anode with sufficient density to support an avalanche discharge. Material adso...

  5. PLD synthesis of GaN nanowires and nanodots on patterned catalyst surface for field emission study

    Energy Technology Data Exchange (ETDEWEB)

    Ng, D.K.T.; Hong, M.H. [National University of Singapore (Singapore). Department of Electrical and Computer Engineering; Data Storage Institute, Singapore (Singapore); Tan, L.S. [National University of Singapore (Singapore). Department of Electrical and Computer Engineering; Zhu, Y.W.; Sow, C.H. [National University of Singapore (Singapore). Nanoscience and Nanotechnology Initiative; National University of Singapore (Singapore). Department of Physics

    2008-11-15

    Patterned gallium nitride nanowires and nanodots have been grown on n-Si(100) substrates by pulsed laser deposition. The nanostructures are patterned using a physical mask, resulting in regions of nanowire growth of different densities. The field emission (FE) characteristics of the patterned gallium nitride nanowires show a turn-on field of 9.06 V/{mu}m to achieve a current density of 0.01 mA/cm{sup 2} and an enhanced field emission current density as high as 0.156 mA/cm{sup 2} at an applied field of 11 V/{mu}m. Comparing the peak FE current densities of both the nanowires and nanodots, the peak FE current density of nanowires is around 700 times higher than that of the peak FE current density of nanodots since nanodots have a lower aspect ratio compared to nanowires. The field emission results indicate that, besides density difference, crystalline quality as well as the low electron affinity of gallium nitride, high aspect ratio of gallium nitride nanostructures will greatly enhance their field emission properties. (orig.)

  6. Field Measurements of PCB emissions from Building Surfaces Using a New Portable Emission Test Cell

    DEFF Research Database (Denmark)

    Lyng, Nadja; Haven, Rune; Gunnarsen, Lars Bo

    2016-01-01

    The purpose of the study was to measure PCB-emission rates from indoor surfaces on-site in contaminated buildings using a newly developed portable emission test cell. Emission rates were measured from six different surfaces; three untreated surfaces and three remediated surfaces in a contaminated...

  7. Inferring physical properties of galaxies from their emission-line spectra

    Science.gov (United States)

    Ucci, G.; Ferrara, A.; Gallerani, S.; Pallottini, A.

    2017-02-01

    We present a new approach based on Supervised Machine Learning algorithms to infer key physical properties of galaxies (density, metallicity, column density and ionization parameter) from their emission-line spectra. We introduce a numerical code (called GAME, GAlaxy Machine learning for Emission lines) implementing this method and test it extensively. GAME delivers excellent predictive performances, especially for estimates of metallicity and column densities. We compare GAME with the most widely used diagnostics (e.g. R23, [N II] λ6584/Hα indicators) showing that it provides much better accuracy and wider applicability range. GAME is particularly suitable for use in combination with Integral Field Unit spectroscopy, both for rest-frame optical/UV nebular lines and far-infrared/sub-millimeter lines arising from photodissociation regions. Finally, GAME can also be applied to the analysis of synthetic galaxy maps built from numerical simulations.

  8. Field emission electric propulsion thruster modeling and simulation

    Science.gov (United States)

    Vanderwyst, Anton Sivaram

    Electric propulsion allows space rockets a much greater range of capabilities with mass efficiencies that are 1.3 to 30 times greater than chemical propulsion. Field emission electric propulsion (FEEP) thrusters provide a specific design that possesses extremely high efficiency and small impulse bits. Depending on mass flow rate, these thrusters can emit both ions and droplets. To date, fundamental experimental work has been limited in FEEP. In particular, detailed individual droplet mechanics have yet to be understood. In this thesis, theoretical and computational investigations are conducted to examine the physical characteristics associated with droplet dynamics relevant to FEEP applications. Both asymptotic analysis and numerical simulations, based on a new approach combining level set and boundary element methods, were used to simulate 2D-planar and 2D-axisymmetric probability density functions of the droplets produced for a given geometry and electrode potential. The combined algorithm allows the simulation of electrostatically-driven liquids up to and after detachment. Second order accuracy in space is achieved using a volume of fluid correction. The simulations indicate that in general, (i) lowering surface tension, viscosity, and potential, or (ii) enlarging electrode rings, and needle tips reduce operational mass efficiency. Among these factors, surface tension and electrostatic potential have the largest impact. A probability density function for the mass to charge ratio (MTCR) of detached droplets is computed, with a peak around 4,000 atoms per electron. High impedance surfaces, strong electric fields, and large liquid surface tension result in a lower MTCR ratio, which governs FEEP droplet evolution via the charge on detached droplets and their corresponding acceleration. Due to the slow mass flow along a FEEP needle, viscosity is of less importance in altering the droplet velocities. The width of the needle, the composition of the propellant, the

  9. Duality property for a hermitian scalar field

    International Nuclear Information System (INIS)

    Bisognano, J.J.

    1975-01-01

    A general hermitian scalar Wightman field is considered. On the Hilbert space of physical states ''natural'' domains for certain complex Lorentz transformations are constructed, and a theorem relating these transformations to the TCP symmetry is stated and proved. Under the additional assumption that the field is ''locally'' essentially self-adjoint, duality is considered for the algebras generated by spectral projections of smeared fields. For a class of unbounded regions duality is proved, and for certain bounded regions ''local'' extensions of the algebras are constructed which satisfy duality. The relationship of the arguments presented to the Tomita--Takesaki theory of modular Hilbert algebras is discussed. A separate analysis for the free field is also given. (auth)

  10. The impact of capacitor bank inrush current on field emission current in vacuum

    NARCIS (Netherlands)

    Koochack-Zadeh, M.; Hinrichsen, V.; Smeets, R.P.P.; Lawall, A.

    2010-01-01

    Field emission current measurements during the recovery voltage are investigated to understand the origin of restrikes in vacuum interrupters in case of the interruption of capacitive loads. Measurement and analysis of very small field emission currents (0.01 - 1 mA) from the current zero crossing

  11. Development of a high brightness ultrafast Transmission Electron Microscope based on a laser-driven cold field emission source.

    Science.gov (United States)

    Houdellier, F; Caruso, G M; Weber, S; Kociak, M; Arbouet, A

    2018-03-01

    We report on the development of an ultrafast Transmission Electron Microscope based on a cold field emission source which can operate in either DC or ultrafast mode. Electron emission from a tungsten nanotip is triggered by femtosecond laser pulses which are tightly focused by optical components integrated inside a cold field emission source close to the cathode. The properties of the electron probe (brightness, angular current density, stability) are quantitatively determined. The measured brightness is the largest reported so far for UTEMs. Examples of imaging, diffraction and spectroscopy using ultrashort electron pulses are given. Finally, the potential of this instrument is illustrated by performing electron holography in the off-axis configuration using ultrashort electron pulses. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Ion-optical properties of Wien's filters with inhomogeneous fields

    International Nuclear Information System (INIS)

    Golikov, Yu.K.; Matyshev, A.A.; Solov'ev, K.V.

    1991-01-01

    Common conditions of beam stigmatic focusing in the Wien filters with direct axial trajectory in arbitrary two-dimensional inhomogeneous crossed electrical magnetic fields are obtained. Coefficients for geometrical aberrations of the second order of the crossed field system, characterized by stigmatic focusing properties, are found. Possibility of synthesis on the basis of the developed field system theory with required ion-optical properties is shown

  13. Field line diversion properties of finite β-helias equilibria

    International Nuclear Information System (INIS)

    Hayashi, Takaya; Schwenn, Ulrich; Strumberger, Erika.

    1992-01-01

    The diversion properties of the magnetic field outside the last closed magnetic surface of a Helias stellarator configuration are investigated for finite pressure equilibria. The results indicate that a divertor concept which has been developed from the diversion properties of the corresponding vacuum field can be maintained for finite pressure equilibria. Cross-field particle transport is simulated by a simplified scrape-off layer (SOL) model. (author)

  14. A new beam emission polarimetry diagnostic for measuring the magnetic field line angle at the plasma edge of ASDEX Upgrade.

    Science.gov (United States)

    Viezzer, E; Dux, R; Dunne, M G

    2016-11-01

    A new edge beam emission polarimetry diagnostic dedicated to the measurement of the magnetic field line angle has been installed on the ASDEX Upgrade tokamak. The new diagnostic relies on the motional Stark effect and is based on the simultaneous measurement of the polarization direction of the linearly polarized π (parallel to the electric field) and σ (perpendicular to the electric field) lines of the Balmer line D α . The technical properties of the system are described. The calibration procedures are discussed and first measurements are presented.

  15. Analysis of the Extremely Low Frequency Magnetic Field Emission from Laptop Computers

    Directory of Open Access Journals (Sweden)

    Brodić Darko

    2016-03-01

    Full Text Available This study addresses the problem of magnetic field emission produced by the laptop computers. Although, the magnetic field is spread over the entire frequency spectrum, the most dangerous part of it to the laptop users is the frequency range from 50 to 500 Hz, commonly called the extremely low frequency magnetic field. In this frequency region the magnetic field is characterized by high peak values. To examine the influence of laptop’s magnetic field emission in the office, a specific experiment is proposed. It includes the measurement of the magnetic field at six laptop’s positions, which are in close contact to its user. The results obtained from ten different laptop computers show the extremely high emission at some positions, which are dependent on the power dissipation or bad ergonomics. Eventually, the experiment extracts these dangerous positions of magnetic field emission and suggests possible solutions.

  16. Density functional theory for field emission from carbon nano-structures.

    Science.gov (United States)

    Li, Zhibing

    2015-12-01

    Electron field emission is understood as a quantum mechanical many-body problem in which an electronic quasi-particle of the emitter is converted into an electron in vacuum. Fundamental concepts of field emission, such as the field enhancement factor, work-function, edge barrier and emission current density, will be investigated, using carbon nanotubes and graphene as examples. A multi-scale algorithm basing on density functional theory is introduced. We will argue that such a first principle approach is necessary and appropriate for field emission of nano-structures, not only for a more accurate quantitative description, but, more importantly, for deeper insight into field emission. Copyright © 2015 The Author. Published by Elsevier B.V. All rights reserved.

  17. Study of electronic field emission from large surfaces under static operating conditions and hyper-frequency

    International Nuclear Information System (INIS)

    Luong, M.

    1997-09-01

    The enhanced electronic field emission from large area metallic surfaces lowers performances of industrial devices that have to sustain high electric field under vacuum. Despite of numerous investigations in the past, the mechanisms of such an emission have never been well clarified. Recently, research in our laboratory has pointed out the importance played by conducting sites (particles and protrusions). A refined geometrical model, called superposed protrusions model has been proposed to explain the enhanced emission by local field enhancement. As a logical continuation, the present work aims at testing this model and, in the same time, investigating the means to suppress the emission where it is undesirable. Thus, we have showed: the cause of current fluctuations in a continuous field regime (DC), the identity of emission characteristics (β, A e ) in both radiofrequency (RF) and DC regimes, the effectiveness of a thermal treatment by extern high density electronic bombardment, the effectiveness of a mechanical treatment by high pressure rinsing with ultra pure water, the mechanisms and limits of an in situ RF processing. Furthermore, the electronic emission from insulating particles has also been studied concurrently with a spectral analysis of the associated luminous emission. Finally, the refined geometrical model for conducting sites is reinforced while another model is proposed for some insulating sites. Several emission suppressing treatments has been explored and validated. At last, the characteristic of a RF pulsed field emitted electron beam has been checked for the first time as a possible application of such a field emission. (author)

  18. Pyrene-Phosphonate Conjugate: Aggregation-Induced Enhanced Emission, and Selective Fe3+ Ions Sensing Properties

    Directory of Open Access Journals (Sweden)

    Sachin D. Padghan

    2017-08-01

    Full Text Available A new pyrene-phosphonate colorimetric receptor 1 has been designed and synthesized in a one-step process via amide bond formation between pyrene butyric acid chloride and phosphonate-appended aniline. The pyrene-phosphonate receptor 1 showed aggregation-induced enhanced emission (AIEE properties in water/acetonitrile (ACN solutions. Dynamic light scattering (DLS characterization revealed that the aggregates of receptor 1 at 80% water fraction have an average size of ≈142 nm. Field emission scanning electron microscopy (FE-SEM analysis confirmed the formation of spherical aggregates upon solvent evaporation. The sensing properties of receptor 1 were investigated by UV-vis, fluorescence emission spectroscopy, and other optical methods. Among the tested metal ions, receptor 1 is capable of recognizing the Fe3+ ion selectively. The changes in spectral measurements were explained on the basis of complex formation. The composition of receptor 1 and Fe3+ ions was determined by using Job’s plot and found to be 1:1. The receptor 1–Fe3+ complex showed a reversible UV-vis response in the presence of EDTA.

  19. Enhancement of electron emission and long-term stability of tip-type carbon nanotube field emitters via lithium coating

    International Nuclear Information System (INIS)

    Kim, Jong-Pil; Chang, Han-Beet; Kim, Bu-Jong; Park, Jin-Seok

    2013-01-01

    Carbon nanotubes (CNTs) were deposited on conical tip-type substrates via electrophoresis and coated with lithium (Li) thin films with diverse thicknesses via electroplating. For the as-deposited (i.e., without Li coating) CNT, the turn-on (or triggering) electric field was 0.92 V/μm, and the emission current, which was generated at an applied field of 1.2 V/μm was 56 μA. In the case of the 4.7 nm-thick Li-coated CNT, the turn-on field decreased to 0.65 V/μm and the emission current at the same applied field increased more than ten times to 618 μA. The analysis based on the Kelvin probe measurement and Fowler–Nordheim theory indicated that the coating of Li caused a loss in the structural-aspect-ratio of the CNTs and it reduced their effective work functions from 5.36 eV to 4.90 eV, which led to a great improvement of their electron emission characteristics. The results obtained in this study also showed that the long-term emission stability could be enhanced by the coating of thin Li films on CNTs. - Highlights: ► CNTs are deposited via electrophoretic deposition (EPD). ► Thin films of Li are coated on CNTs via electroplating, without plasma damage. ► Li coating enhanced field emission properties and emission stability of CNTs. ► The effective work functions and field enhancement factors of CNTs are evaluated

  20. THERMIONIC EMISSION ENHANCEMENT FROM CESIUM COATED RHENIUM IN ELECTRIC FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    de Steese, J. G.; Zollweg, R. J.

    1963-04-15

    The plasma-anode technique was used to observe anomalously high thermionic emission from a rhenium surface with small cesium coverage, where the work function of the composite surface is greater than the ionization potential of cesium. Data suggest that emission enhancement is caused by increased cesium coverage because of cesiumion trapping near the emitter surface under the influence of an ion-rich sheath. (auth)

  1. The Adaptation Law for emissions trading. Part 2. A level playing field for emissions trading?

    International Nuclear Information System (INIS)

    Simonetti, S.

    2010-01-01

    To supplement, clarify and simplify the regulations for emission trading, the Amendment Act emission trading II was submitted to the Dutch Lower Chamber end of 2009. This article discusses the pending bill and comments on a number of remarkable stipulations that may be important to the market parties. First a brief overview is provided of the basic principles of emission trading and the players in the CO2 market. [nl

  2. Enhanced field emission from Si doped nanocrystalline AlN thin films

    International Nuclear Information System (INIS)

    Thapa, R.; Saha, B.; Chattopadhyay, K.K.

    2009-01-01

    Si doped and undoped nanocrystalline aluminum nitride thin films were deposited on various substrates by direct current sputtering technique. X-ray diffraction analysis confirmed the formation of phase pure hexagonal aluminum nitride with a single peak corresponding to (1 0 0) reflection of AlN with lattice constants, a = 0.3114 nm and c = 0.4986 nm. Energy dispersive analysis of X-rays confirmed the presence of Si in the doped AlN films. Atomic force microscopic studies showed that the average particle size of the film prepared at substrate temperature 200 deg. C was 9.5 nm, but when 5 at.% Si was incorporated the average particle size increased to ∼21 nm. Field emission study indicated that, with increasing Si doping concentration, the emission characteristics have been improved. The turn-on field (E to ) was 15.0 (±0.7) V/μm, 8.0 (±0.4) V/μm and 7.8 (±0.5) V/μm for undoped, 3 at.% and 5 at.% Si doped AlN films respectively and the maximum current density of 0.27 μA/cm 2 has been observed for 5 at.% Si doped nanocrystalline AlN film. It was also found that the dielectric properties were highly dependent on Si doping.

  3. Study of electrons photoemitted from field emission tips. Progress report, July 1, 1979-March 1, 1980

    International Nuclear Information System (INIS)

    Reifenberger, R.

    1980-02-01

    Photo-induced field emission is a technique which studies electrons that have been photoemitted from a field emission tip. This new experimental method promises to combine the proven utility of both field emission and photoemission for investigating the electronic states near a metal surface. The primary objective of the research being performed is to investigate photo-induced field emitted electrons using a tuneable cw dye laser. To fully exploit this continuously tuneable photon source, a differential energy analyzer is being constructed to allow energy resolved measurements of the photo-field emitted electrons. This report describes the progress made in implementing experiments on photo-induced field emission from July 1979 to March 1980

  4. Greenhouse gas emissions from dairy manure management: a review of field-based studies.

    Science.gov (United States)

    Owen, Justine J; Silver, Whendee L

    2015-02-01

    Livestock manure management accounts for almost 10% of greenhouse gas emissions from agriculture globally, and contributes an equal proportion to the US methane emission inventory. Current emissions inventories use emissions factors determined from small-scale laboratory experiments that have not been compared to field-scale measurements. We compiled published data on field-scale measurements of greenhouse gas emissions from working and research dairies and compared these to rates predicted by the IPCC Tier 2 modeling approach. Anaerobic lagoons were the largest source of methane (368 ± 193 kg CH4 hd(-1) yr(-1)), more than three times that from enteric fermentation (~120 kg CH4 hd(-1) yr(-1)). Corrals and solid manure piles were large sources of nitrous oxide (1.5 ± 0.8 and 1.1 ± 0.7 kg N2O hd(-1) yr(-1), respectively). Nitrous oxide emissions from anaerobic lagoons (0.9 ± 0.5 kg N2O hd(-1) yr(-1)) and barns (10 ± 6 kg N2O hd(-1) yr(-1)) were unexpectedly large. Modeled methane emissions underestimated field measurement means for most manure management practices. Modeled nitrous oxide emissions underestimated field measurement means for anaerobic lagoons and manure piles, but overestimated emissions from slurry storage. Revised emissions factors nearly doubled slurry CH4 emissions for Europe and increased N2O emissions from solid piles and lagoons in the United States by an order of magnitude. Our results suggest that current greenhouse gas emission factors generally underestimate emissions from dairy manure and highlight liquid manure systems as promising target areas for greenhouse gas mitigation. © 2014 John Wiley & Sons Ltd.

  5. Field emission of carbon quantum dots synthesized from a single organic solvent.

    Science.gov (United States)

    Liu, Xiahui; Yang, Bingjun; Yang, Juan; Yu, Shengxue; Chen, Jiangtao

    2016-11-04

    In this paper, a facile synthesis of carbon quantum dots (CQDs) and its field emission performance are reported. The CQDs are prepared from a single N, N-dimethylformamide acting as carbon and nitrogen-doping sources simultaneously. The CQDs are investigated by photoluminescence, transmission electron microscopy and x-ray photoelectron spectroscopy. The CQDs have an average size of 3 nm and are doped with N atoms. CQD dispersion shows strong fluorescence under UV illumination. For the first time, the field emission behavior of CQDs coated on Si substrate is studied. As a candidate of cold cathode, the CQDs display good field emission performance. The CQD emitter reaches the current density of 1.1 mA cm(-2) at 7.0 V μm(-1) and exhibits good long-term emission stability, suggesting promising application in field emission devices.

  6. Construction and characterization of the fringe field monochromator for a field emission gun

    Science.gov (United States)

    Mook; Kruit

    2000-04-01

    Although some microscopes have shown stabilities sufficient to attain below 0.1 eV spectral resolution in high-resolution electron energy loss spectroscopy, the intrinsic energy width of the high brightness source (0.3-0.6 eV) has been limiting the resolution. To lower the energy width of the source to 50 meV without unnecessary loss of brightness, a monochromator has been designed consisting of a short (4 mm) fringe field Wien filter and a 150 nm energy selection slit (nanoslit) both to be incorporated in the gun area of the microscope. A prototype has been built and tested in an ultra-high-vacuum setup (10(-9) mbar). The monochromator, operating on a Schottky field emission gun, showed stable and reproducible operation. The nanoslits did not contaminate and the structure remained stable. By measuring the current through the slit structure a direct image of the beam in the monochromator could be attained and the monochromator could be aligned without the use of a microscope. Good dispersed imaging conditions were found indicating an ultimate resolution of 55 meV. A Mark II fringe field monochromator (FFM) was designed and constructed compatible with the cold tungsten field emitter of the VG scanning transmission microscope. The monochromator was incorporated in the gun area of the microscope at IBM T.J. Watson research center, New York. The monochromator was aligned on 100 kV and the energy distribution measured using the monochromator displayed a below 50 meV filtering capability. The retarding Wien filter spectrometer was used to show a 61 meV EELS system resolution. The FFM is shown to be a monochromator which can be aligned without the use of the electron microscope. This makes it directly applicable for scanning transmission microscopy and low-voltage scanning electron microscopy, where it can lower the resolution loss which is caused by chromatic blur of the spot.

  7. Structural effects of field emission from GaN nanofilms on SiC substrates

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Cheng-Cheng; Wang, Ru-Zhi, E-mail: wrz@bjut.edu.cn; Zhu, Man-Kang; Yan, Hui [College of Materials Science and Engineering, Beijing University of Technology, 100 Pingleyuan, Chaoyang District, Beijing 100124 (China); Liu, Peng [Department of Physics Tsinghua University, Tsinghua-Foxconn Nanotechnology Research Center, Beijing 100084 (China); Wang, Bi-Ben [College of Chemistry and Chemical Engineering, Chongqing University of Technology, Chongqing 400054 (China)

    2014-04-21

    GaN nanofilms (NFs) with different structures are grown on SiC substrates by pulsed laser deposition under different conditions. The synthesized GaN NFs are studied by X-ray diffraction, field-emission (FE) scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The GaN NFs are composed of diversified GaN nanoparticles with a diameter of 9–38 nm, thickness of 10–50 nm, and roughness of 0.22–13.03 nm. FE from the GaN NFs is structure dependent, which is explained by stress changing the band gap of the NFs. By structure modulation, the turn-on field of GaN NFs can be as low as 0.66 V/μm at a current density of 1 μA/cm{sup 2}, with a current density of up to 1.1 mA/cm{sup 2} at a field of 4.18 V/μm. Fowler-Nordheim curves of some samples contain multiple straight lines, which originate from the structural change and diversification of GaN nanoparticles under an applied field. Overall, our results suggest that GaN NFs with excellent FE properties can be prepared on SiC substrates, which provides a new route to fabricate high-efficiency FE nanodevices.

  8. Direct observation and mechanism for enhanced field emission sites in platinum ion implanted/post-annealed ultrananocrystalline diamond films

    Energy Technology Data Exchange (ETDEWEB)

    Panda, Kalpataru, E-mail: panda@afm.eei.eng.osaka-u.ac.jp, E-mail: phy.kalpa@gmail.com; Inami, Eiichi; Sugimoto, Yoshiaki [Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka 565-0871 (Japan); Sankaran, Kamatchi J.; Tai, Nyan Hwa [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Lin, I-Nan, E-mail: inanlin@mail.tku.edu.tw [Department of Physics, Tamkang University, Tamsui 251, Taiwan (China)

    2014-10-20

    Enhanced electron field emission (EFE) properties for ultrananocrystalline diamond (UNCD) films upon platinum (Pt) ion implantation and subsequent post-annealing processes is reported, viz., low turn-on field of 4.17 V/μm with high EFE current density of 5.08 mA/cm{sup 2} at an applied field of 7.0 V/μm. Current imaging tunneling spectroscopy (CITS) mode in scanning tunneling spectroscopy directly revealed the increased electron emission sites density for Pt ion implanted/post-annealed UNCD films than the pristine one. The high resolution CITS mapping and local current–voltage characteristic curves demonstrated that the electrons are dominantly emitted from the diamond grain boundaries and Pt nanoparticles.

  9. Direct observation and mechanism for enhanced field emission sites in platinum ion implanted/post-annealed ultrananocrystalline diamond films

    International Nuclear Information System (INIS)

    Panda, Kalpataru; Inami, Eiichi; Sugimoto, Yoshiaki; Sankaran, Kamatchi J.; Tai, Nyan Hwa; Lin, I-Nan

    2014-01-01

    Enhanced electron field emission (EFE) properties for ultrananocrystalline diamond (UNCD) films upon platinum (Pt) ion implantation and subsequent post-annealing processes is reported, viz., low turn-on field of 4.17 V/μm with high EFE current density of 5.08 mA/cm 2 at an applied field of 7.0 V/μm. Current imaging tunneling spectroscopy (CITS) mode in scanning tunneling spectroscopy directly revealed the increased electron emission sites density for Pt ion implanted/post-annealed UNCD films than the pristine one. The high resolution CITS mapping and local current–voltage characteristic curves demonstrated that the electrons are dominantly emitted from the diamond grain boundaries and Pt nanoparticles.

  10. Statistical properties of single-mode emission in free-electron lasers

    International Nuclear Information System (INIS)

    Bertolotti, M.; Luks, A.; Perina, J.; Perinova, V.; Sibilia, C.

    1984-01-01

    The authors of this paper discuss the statistical properties of radiation produced in the free electron laser, in the case of singlemode emission when the system is used as an amplifier, with very small gain. The coherent states technique and the q-c number correspondence is employed, starting from the master-equation and obtaining the generalized Fokker-Planck equation for the anti-normal quasidistribution function. Solutions of Fokker-Planck equation provide the photocounting distribution and its factorial moments. No losses are included. It is shown that, in the short-time approximation, the radiation field exhibits antibunching, and that the photocounting distributions, when some suitable conditions on the field intensities are fulfilled, in the stationary regime shows a two-peak behavior, evidencing the existence of bistable states

  11. Creating a level playing field? The concentration and centralisation of emissions in the European Union Emissions Trading System

    International Nuclear Information System (INIS)

    Bryant, Gareth

    2016-01-01

    This article questions the assumption that carbon markets create a level playing field by exploring the relationship between the organisation of capital and the organisation of emissions in the European Union Emissions Trading System (EU ETS). It constructs a database by matching installations and owners to reveal that a relatively small number of large-scale coal-fired power stations, owned by a very small group of states and corporations, are responsible for a significant proportion of greenhouse gas emissions. The findings are analysed by considering how technological dependence on coal together with the corporate institutional form combine to support the socio-spatial concentration and centralisation of capital and emissions. Case studies of the consolidation of the seven largest polluting owners from Europe's coal-dependent electricity sector and the carbon trading strategies of the two largest polluters, RWE and E.ON, then assess the impacts of energy liberalisation and emissions trading policies. The article concludes that EU energy and climate policies are pulling in different directions by clustering responsibility for greenhouse gas emissions and diffusing responsibility to address climate change. The uneven distribution of emissions within the EU ETS makes an alternative policy approach that directly targets the biggest corporate and state polluters both feasible and necessary. - Highlights: • 20 ultimate owners are responsible for one-half of 2005–12 EU ETS emissions. • 83 installations are responsible for one-third of 2005–12 EU ETS emissions. • Focus on technological dependence on coal and the corporate institutional form. • Energy liberalisation policy has consolidated responsibility for emissions. • Carbon markets have diffused responsibility for addressing climate change.

  12. Low-macroscopic field emission from silicon-incorporated diamond-like carbon film synthesized by dc PECVD

    International Nuclear Information System (INIS)

    Ahmed, Sk.F.; Mitra, M.K.; Chattopadhyay, K.K.

    2007-01-01

    Silicon-incorporated diamond-like carbon (Si-DLC) films were deposited via dc plasma-enhanced chemical vapor deposition (PECVD), on glass and alumina substrates at a substrate temperature 300 deg. C. The precursor gas used was acetylene and for Si incorporation, tetraethyl orthosilicate dissolved in methanol was used. Si atomic percentage in the films was varied from 0% to 19.3% as measured from energy-dispersive X-ray analysis (EDX). The binding energies of C 1s, Si 2s and Si 2p were determined from X-ray photoelectron spectroscopic studies. We have observed low-macroscopic field electron emission from Si-DLC thin films deposited on glass substrates. The emission properties have been studied for a fixed anode-sample separation of 80 μm for different Si atomic percentages in the films. The turn-on field was also found to vary from 16.19 to 3.61 V/μm for a fixed anode-sample separation of 80 μm with a variation of silicon atomic percentage in the films 0% to 19.3%. The turn-on field and approximate work function are calculated and we have tried to explain the emission mechanism there from. It was found that the turn-on field and effective emission barrier were reduced by Si incorporation than undoped DLC

  13. Leakage and field emission in side-gate graphene field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Di Bartolomeo, A., E-mail: dibant@sa.infn.it; Iemmo, L.; Romeo, F.; Cucolo, A. M. [Physics Department “E.R. Caianiello,” University of Salerno, via G. Paolo II, 84084 Fisciano (Italy); CNR-SPIN Salerno, via G. Paolo II, 84084 Fisciano (Italy); Giubileo, F. [CNR-SPIN Salerno, via G. Paolo II, 84084 Fisciano (Italy); Russo, S.; Unal, S. [Physics Department, University of Exeter, Stocker Road 6, Exeter, Devon EX4 4QL (United Kingdom); Passacantando, M.; Grossi, V. [Department of Physical and Chemical Sciences, University of L' Aquila, Via Vetoio, 67100 Coppito, L' Aquila (Italy)

    2016-07-11

    We fabricate planar graphene field-effect transistors with self-aligned side-gate at 100 nm from the 500 nm wide graphene conductive channel, using a single lithographic step. We demonstrate side-gating below 1 V with conductance modulation of 35% and transconductance up to 0.5 mS/mm at 10 mV drain bias. We measure the planar leakage along the SiO{sub 2}/vacuum gate dielectric over a wide voltage range, reporting rapidly growing current above 15 V. We unveil the microscopic mechanisms driving the leakage, as Frenkel-Poole transport through SiO{sub 2} up to the activation of Fowler-Nordheim tunneling in vacuum, which becomes dominant at higher voltages. We report a field-emission current density as high as 1 μA/μm between graphene flakes. These findings are important for the miniaturization of atomically thin devices.

  14. First image from a combined positron emission tomography and field-cycled MRI system.

    Science.gov (United States)

    Bindseil, Geron A; Gilbert, Kyle M; Scholl, Timothy J; Handler, William B; Chronik, Blaine A

    2011-07-01

    Combining positron emission tomography and MRI modalities typically requires using either conventional MRI with a MR-compatible positron emission tomography system or a modified MR system with conventional positron emission tomography. A feature of field-cycled MRI is that all magnetic fields can be turned off rapidly, enabling the use of conventional positron emission tomography detectors based on photomultiplier tubes. In this demonstration, two photomultiplier tube-based positron emission tomography detectors were integrated with a field-cycled MRI system (0.3 T/4 MHz) by placing them into a 9-cm axial gap. A positron emission tomography-MRI phantom consisting of a triangular arrangement of positron-emitting point sources embedded in an onion was imaged in a repeating interleaved sequence of ∼1 sec MRI then 1 sec positron emission tomography. The first multimodality images from the combined positron emission tomography and field-cycled MRI system show no additional artifacts due to interaction between the systems and demonstrate the potential of this approach to combining positron emission tomography and MRI. Copyright © 2010 Wiley-Liss, Inc.

  15. FDTD simulations of near-field mediated semiconductor molecular optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Dai; Sakrow, Marcus; Mihaljevic, Josip; Meixner, Alfred J. [Institute of Physical and Theoretical Chemistry, University Tuebingen, Auf der Morgenstelle 8, Tuebingen (Germany)

    2010-07-01

    The optical properties of molecules can be dramatically altered when they are in a close proximity of an excited metal antenna. In order to get insight into how the antenna generated near-field influences the optical properties of low quantum yield molecules, we carried out FDTD simulations of a sharp laser-illuminated Au tip approaching to a semiconductor thin film. The time-averaged field distribution between the semiconductor thin film and the tip antenna is calculated regarding to different distances. Our calculation demonstrates that the coupling between the localized plasmon at the tip apex and semiconductor polariton can be achieved building up a distance-dependent high field enhancement. Our experimental results show that such a high field strength enhances not only the excitation process by a factor of 104, but alters the radiative: non-radiative decay rate giving approx. 15 times stronger photoluminescence emission.

  16. Optical properties of semiconductor nanostructures in magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Grochol, M.

    2007-04-03

    In this work, the near bandgap linear optical properties of semiconductor quantum structures under applied magnetic field are investigated. First, the exciton theory is developed starting with the one-electron Hamiltonian in a crystal, continuing with the Luttinger and Bir-Pikus Hamiltonian, and ending with the exciton Hamiltonian in the envelope function approximation. Further, concentrating on the quantum well and thus assuming strong confinement in the growth direction, the motion parallel and perpendicular to the xy-plane is factorized leading to the well-known single sublevel approximation. A magnetic field perpendicular to the xy-plane is applied, and a general theorem describing the behavior of the energy eigenvalues is derived. The strain calculation within the isotropic elasticity approach is described in detail. The Schroedinger equation is solved numerically for both the full model and the factorization with artificially generated disorder potentials. Furthermore the statistical properties of the disorder in a real quantum well have been analyzed. In particular, temperature dependent photoluminescence spectra and diamagnetic shift statistics, have been compared with the experimental ones and very good agreement has been found. The second part of this thesis deals predominantly with highly symmetrical structures embedded in the quantum well: namely quantum rings and dots. First, adopting an ansatz for the wave function, the Hamiltonian matrix is derived discussing which matrix elements are non-zero according to the symmetry of the potential. Additionally, the expectation values of the current and magnetization operators are evaluated. Then, concentrating on the case of the highest (circular) symmetry, the model of zero width ring is introduced. Within this model the close relation between the oscillatory component of the exciton energy (exciton Aharonov-Bohm effect) and the persistent current is revealed. Examples for different material systems follow

  17. Testing the near field/far field model performance for prediction of particulate matter emissions in a paint factory

    DEFF Research Database (Denmark)

    Koivisto, A.J.; Jensen, A.C.Ø.; Levin, Marcus

    2015-01-01

    A Near Field/Far Field (NF/FF) model is a well-accepted tool for precautionary exposure assessment but its capability to estimate particulate matter (PM) concentrations is not well studied. The main concern is related to emission source characterization which is not as well defined for PM emitters...

  18. Electron field emission from sp -induced insulating to metallic ...

    Indian Academy of Sciences (India)

    Administrator

    Materials Research Centre, Indian Institute of Science, Bangalore 560 012, India. MS received 20 ... emissions of amorphous carbon films have been investigated. The observed ... water followed by acetone was positioned at the centre of first zone ..... clusters islands, surface geometry, and internal structures of the films.

  19. Retrieval of Tropospheric Profiles from IR Emission Spectra: Field Experiment and Sensitivity Study

    National Research Council Canada - National Science Library

    Theriault, J

    1993-01-01

    .... The goal of this project was the retrieval of atmospheric temperature and water vapor profiles and possibly over relevant information on clouds and aerosol properties from high resolution IR emission...

  20. Experimental study on the luminous radiation associated to the field emission of samples submitted to high RF fields

    International Nuclear Information System (INIS)

    Maissa, S.; Junquera, T.; Fouaidy, M.; Le Goff, A.; Luong, M.; Tan, J.; Bonin, B.; Safa, H.

    1996-01-01

    Nowadays the accelerating gradient of the RF cavities is limited by the strong field emission (FE) of electrons stemming from the metallic walls. Previous experiments evidenced luminous radiations associated with electron emission on cathodes subjected to intense DC electric field. These observations led these authors to propose new theoretical models of the field emission phenomenon. The presented experimental study extends these previous DC works to the RF case. A special copper RF cavity has been developed equipped with an optical window and a removable sample. It has been designed for measuring both electron current and luminous radiation emitted by the sample, subjected to maximum RF electric field. The optical apparatus attached to the cavity permits to characterize the radiation in terms of intensity, glowing duration and spectral distribution. The results concerning different niobium or copper samples, whom top was either scratched or intentionally contaminated with metallic or dielectric particles are summarized. (author)

  1. Experimental study on the luminous radiation associated to the field emission of samples submitted to high RF fields

    International Nuclear Information System (INIS)

    Maissa, S.; Junquera, T.; Fouaidy, M.; Le Goff, A.; Luong, M.; Tan, J.; Bonin, B.; Safa, H.

    1996-01-01

    The accelerating gradient of the RF cavities is limited by the strong field emission (FE) of electrons stemming from the metallic walls. Previous experiments evidenced luminous radiations associated with electron emission of cathodes subjected to intense DC electric field. These observations invoked the proposal of new theoretical models of the field emission phenomenon. This experimental study extends the previous DC works to the RF case. A special copper RF cavity has been developed equipped with an optical window and a removable sample. It has been designed for measuring both electron current and luminous radiation emitted by the sample, subjected to maximum RF electric field. The optical apparatus attached to the cavity permits to characterize the radiation in terms of intensity, glowing duration and spectral distribution. The results concerning different niobium or copper samples, whom top was either scratched or intentionally contaminated with metallic or dielectric particles are summarized. (author)

  2. Effects of ZnO Quantum Dots Decoration on the Field Emission Behavior of Graphene.

    Science.gov (United States)

    Sun, Lei; Zhou, Xiongtu; Lin, Zhixian; Guo, Tailiang; Zhang, Yongai; Zeng, Yongzhi

    2016-11-23

    ZnO quantum dots (QDs) have been decorated on graphene deposited on patterned Ag electrodes as a field emission cathode by a solution process. Effects of ZnO QDs on the field emission behavior of graphene are studied by experiment and first-principles calculations. The results indicate that the attachment of ZnO QDs with a C atom leads to the enhancement of electron emission from graphene, which is mainly attributed to the reduction of the work function and ionization potential, and the increase of the Fermi level of graphene after the decoration. A change in the local density distribution and the density of states near the Fermi level may also account for this behavior. Our study may help to develop new field emission composites and expand ZnO QDs in applications for electron emission devices as well.

  3. Magnetic Field Emissions for Ferrite and Non-Ferrite Geometries for Wireless Power Transfer to Vehicles

    DEFF Research Database (Denmark)

    Batra, Tushar; Schaltz, Erik

    2014-01-01

    Minimizing magnetic field emissions to surroundings is one of the most challenging design criteria for wireless power transfer to vehicles. In this paper, concept of division of the emissions into three zones (primary, secondary, and combined zone) in the vertical direction is introduced. For geo......Minimizing magnetic field emissions to surroundings is one of the most challenging design criteria for wireless power transfer to vehicles. In this paper, concept of division of the emissions into three zones (primary, secondary, and combined zone) in the vertical direction is introduced...... for vertical separation between the coils in range of 100-180 mm. It is observed that lower vertical separation results in higher overlapping of the zones and the coils behave as they are effectively placed close to center of air gap. The analysis in this work provides a better understanding of the space...... profile of magnetic field emissions (with and without ferrite) for wireless power transfer to vehicles....

  4. Tunneling emission of electrons from semiconductors' valence bands in high electric fields

    International Nuclear Information System (INIS)

    Kalganov, V. D.; Mileshkina, N. V.; Ostroumova, E. V.

    2006-01-01

    Tunneling emission currents of electrons from semiconductors to vacuum (needle-shaped GaAs photodetectors) and to a metal (silicon metal-insulator-semiconductor diodes with a tunneling-transparent insulator layer) are studied in high and ultrahigh electric fields. It is shown that, in semiconductors with the n-type conductivity, the major contribution to the emission current is made by the tunneling emission of electrons from the valence band of the semiconductor, rather than from the conduction band

  5. Particle Acceleration, Magnetic Field Generation and Associated Emission in Collisionless Relativistic Jets

    Science.gov (United States)

    Nishikawa, K. I.; Ramirez-Ruiz, E.; Hardee, P.; Mizuno, Y.; Fishman. G. J.

    2007-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

  6. Odour emissions from poultry litter - A review litter properties, odour formation and odorant emissions from porous materials.

    Science.gov (United States)

    Dunlop, Mark W; Blackall, Patrick J; Stuetz, Richard M

    2016-07-15

    Odour emissions from meat chicken sheds can at times cause odour impacts on surrounding communities. Litter is seen as the primary source of this odour. Formation and emission of odour from meat chicken litter during the grow-out period are influenced by various factors such as litter conditions, the environment, microbial activity, properties of the odorous gases and management practices. Odour emissions vary spatially and temporally. This variability has made it challenging to understand how specific litter conditions contribute to odour emissions from the litter and production sheds. Existing knowledge on odorants, odour formation mechanisms and emission processes that contribute to odour emissions from litter are reviewed. Litter moisture content and water thermodynamics (i.e. water activity, Aw) are also examined as factors that contribute to microbial odour formation, physical litter conditions and the exchange of individual odorant gases at the air-water interface. Substantial opportunities exist for future research on litter conditions and litter formation mechanisms and how these contribute to odour emissions. Closing this knowledge gap will improve management strategies that intercept and interfere with odour formation and emission processes leading to an overall reduction in the potential to cause community impacts. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

  7. Multi-field electron emission pattern of 2D emitter: Illustrated with graphene

    Science.gov (United States)

    Luo, Ma; Li, Zhibing

    2016-11-01

    The mechanism of laser-assisted multi-field electron emission of two-dimensional emitters is investigated theoretically. The process is basically a cold field electron emission but having more controllable components: a uniform electric field controls the emission potential barrier, a magnetic field controls the quantum states of the emitter, while an optical field controls electron populations of specified quantum states. It provides a highly orientational vacuum electron line source whose divergence angle over the beam plane is inversely proportional to square root of the emitter height. Calculations are carried out for graphene with the armchair emission edge, as a concrete example. The rate equation incorporating the optical excitation, phonon scattering, and thermal relaxation is solved in the quasi-equilibrium approximation for electron population in the bands. The far-field emission patterns, that inherit the features of the Landau bands, are obtained. It is found that the optical field generates a characteristic structure at one wing of the emission pattern.

  8. Improved field emission performance of carbon nanotube by introducing copper metallic particles

    Directory of Open Access Journals (Sweden)

    Chen Yiren

    2011-01-01

    Full Text Available Abstract To improve the field emission performance of carbon nanotubes (CNTs, a simple and low-cost method was adopted in this article. We introduced copper particles for decorating the CNTs so as to form copper particle-CNT composites. The composites were fabricated by electrophoretic deposition technique which produced copper metallic particles localized on the outer wall of CNTs and deposited them onto indium tin oxide (ITO electrode. The results showed that the conductivity increased from 10-5 to 4 × 10-5 S while the turn-on field was reduced from 3.4 to 2.2 V/μm. Moreover, the field emission current tended to be undiminished after continuous emission for 24 h. The reasons were summarized that introducing copper metallic particles to decorate CNTs could increase the surface roughness of the CNTs which was beneficial to field emission, restrain field emission current from saturating when the applied electric field was above the critical field. In addition, it could also improve the electrical contact by increasing the contact area between CNT and ITO electrode that was beneficial to the electron transport and avoided instable electron emission caused by thermal injury of CNTs.

  9. Analytic properties of Feynman diagrams in quantum field theory

    CERN Document Server

    Todorov, I T

    1971-01-01

    Analytic Properties of Feynman Diagrams in Quantum Field Theory deals with quantum field theory, particularly in the study of the analytic properties of Feynman graphs. This book is an elementary presentation of a self-contained exposition of the majorization method used in the study of these graphs. The author has taken the intermediate position between Eden et al. who assumes the physics of the analytic properties of the S-matrix, containing physical ideas and test results without using the proper mathematical methods, and Hwa and Teplitz, whose works are more mathematically inclined with a

  10. Ultrafast electron field emission from gold resonant antennas studied by two terahertz pulse experiments

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew C.

    2015-01-01

    Summary form only given. Ultrafast electron field emission from gold resonant antennas induced by strong terahertz (THz) transient is investigated using two THz pulse experiments. It is shown that UV emission from nitrogen plasma generated by liberated electrons is a good indication of the local...

  11. Simulating emissions of 1,3-dichloropropene after soil fumigation under field conditions.

    Science.gov (United States)

    Yates, S R; Ashworth, D J

    2018-04-15

    Soil fumigation is an important agricultural practice used to produce many vegetable and fruit crops. However, fumigating soil can lead to atmospheric emissions which can increase risks to human and environmental health. A complete understanding of the transport, fate, and emissions of fumigants as impacted by soil and environmental processes is needed to mitigate atmospheric emissions. Five large-scale field experiments were conducted to measure emission rates for 1,3-dichloropropene (1,3-D), a soil fumigant commonly used in California. Numerical simulations of these experiments were conducted in predictive mode (i.e., no calibration) to determine if simulation could be used as a substitute for field experimentation to obtain information needed by regulators. The results show that the magnitude of the volatilization rate and the total emissions could be adequately predicted for these experiments, with the exception of a scenario where the field was periodically irrigated after fumigation. In addition, the timing of the daily peak 1,3-D emissions was not accurately predicted for these experiments due to the peak emission rates occurring during the night or early-morning hours. This study revealed that more comprehensive mathematical models (or adjustments to existing models) are needed to fully describe emissions of soil fumigants from field soils under typical agronomic conditions. Published by Elsevier B.V.

  12. Systematic Field Study of NO(x) Emission Control Methods for Utility Boilers.

    Science.gov (United States)

    Bartok, William; And Others

    A utility boiler field test program was conducted. The objectives were to determine new or improved NO (x) emission factors by fossil fuel type and boiler design, and to assess the scope of applicability of combustion modification techniques for controlling NO (x) emissions from such installations. A statistically designed test program was…

  13. “Comprehensive emission measurements from prescribed burning in Florida: field and laboratory, aerial and ground”

    Science.gov (United States)

    Simultaneous aerial- and ground-based emission sampling was conducted during prescribed burns at Eglin Air Force Base in November 2012 on a short grass/shrub field and a pine forest. Cumulative emission samples for volatile organic comounds, elemental carbon, organic carbon, ch...

  14. Comprehensive emission measurements from prescribed burning in Florida: field and laboratory, aerial and ground

    Science.gov (United States)

    Simultaneous aerial- and ground-based emission sampling was conducted during prescribed burns at Eglin Air Force Base in November 2012 on a short grass/shrub field and a pine forest. Cumulative emission samples for volatile organic compounds, elemental carbon, organic carbon, c...

  15. Effect of a microwave field on the cascade arc light emission

    NARCIS (Netherlands)

    Gerasimov, N.T.; Rosado, R.J.; Schram, D.C.

    1977-01-01

    The effect of a pulsed microwave field on the integral light emission from the argon plasma of a DC atmospheric-pressure cascade arc is investigated experimentally. An intensive light pulse and oscillations of light emission at frequencies of the order of 10 kHz are observed. The shape and amplitude

  16. Near-field emission profiling of tropical forest and Cerrado fires in Brazil during SAMBBA 2012

    Directory of Open Access Journals (Sweden)

    A. K. Hodgson

    2018-04-01

    Full Text Available We profile trace gas and particulate emissions from near-field airborne measurements of discrete smoke plumes in Brazil during the 2012 biomass burning season. The South American Biomass Burning Analysis (SAMBBA Project conducted during September and October 2012 sampled across two distinct fire regimes prevalent in the Amazon Basin. Combined measurements from a Compact Time-of-Flight Aerosol Mass Spectrometer (C-ToF-AMS and a Single Particle Soot Photometer (SP2 are reported for the first time in a tropical biomass burning environment. Emissions from a mostly smouldering tropical forest wildfire in Rondônia state and numerous smaller flaming Cerrado fires in Tocantins state are presented. While the Cerrado fires appear to be representative of typical fire conditions in the existing literature, the tropical forest wildfire likely represents a more extreme example of biomass burning with a bias towards mostly smouldering emissions. We determined fire-integrated modified combustion efficiencies, emission ratios and emission factors for trace gas and particulate components for these two fire types, alongside aerosol microphysical properties. Seven times more black carbon was emitted from the Cerrado fires per unit of fuel combustion (EFBC of 0.13 ± 0.04 g kg−1 compared to the tropical forest fire (EFBC of 0.019 ± 0.006 g kg−1, and more than 6 times the amount of organic aerosol was emitted from the tropical forest fire per unit of fuel combustion (EFOM of 8.00 ± 2.53 g kg−1, EFOC of 5.00 ± 1.58 g kg−1 compared to the Cerrado fires (EFOM of 1.31 ± 0.42 g kg−1, EFOC of 0.82 ± 0.26 g kg−1. Particulate-phase species emitted from the fires sampled are generally lower than those reported in previous studies and in emission inventories, which is likely a combination of differences in fire combustion efficiency and fuel mixture, along with different measurement techniques. Previous

  17. TAURUS observations of the emission-line velocity field of Centaurus A (NGC 5128)

    International Nuclear Information System (INIS)

    Taylor, K.; Atherton, P.D.

    1983-01-01

    Using TAURUS - an Imaging Fabry Perot system in conjunction with the IPCS on the AAT, the authors have studied the velocity field of the Hα emission line at a spatial resolution of 1.7'' over the dark lane structure of Centaurus A. The derived velocity field is quite symmetrical and strongly suggests that the emission line material is orbiting the elliptical component, as a warped disc. (orig.)

  18. Room temperature Coulomb blockade mediated field emission via self-assembled gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Fei [College of Physics and Electronics, Central South University, Changsha, Hunan 410073 (China); College of Science, National University of Defense Technology, Changsha, Hunan 410073 (China); Fang, Jingyue, E-mail: fjynudt@aliyun.com [College of Science, National University of Defense Technology, Changsha, Hunan 410073 (China); Chang, Shengli; Qin, Shiqiao; Zhang, Xueao [College of Science, National University of Defense Technology, Changsha, Hunan 410073 (China); Xu, Hui, E-mail: cmpxhg@csu.edu.cn [College of Physics and Electronics, Central South University, Changsha, Hunan 410073 (China)

    2017-02-05

    Coulomb blockade mediated field-emission current was observed in single-electron tunneling devices based on self-assembled gold nanoparticles at 300 K. According to Raichev's theoretical model, by fixing a proper geometric distribution of source, island and drain, the transfer characteristics can be well explained through a combination of Coulomb blockade and field emission. Coulomb blockade and field emission alternately happen in our self-assembled devices. The Coulomb island size derived from the experimental data is in good agreement with the average size of the gold nanoparticles used in the device. The integrated tunneling can be adjusted via a gate electrode. - Highlights: • The phenomenon of single-electron field emission in a transistor setting using self-assembled gold nanoparticles was investigated. • The transfer characteristics can be well explained by the model that is a combination of Coulomb blockage and field emission. • This transport mechanism is novel and may be used in many applications in field emission devices.

  19. Stability of field emission current from porous n-GaAs(110)

    Science.gov (United States)

    Tondare, V. N.; Naddaf, M.; Bhise, A. B.; Bhoraskar, S. V.; Joag, D. S.; Mandale, A. B.; Sainkar, S. R.

    2002-02-01

    Field electron emission from porous GaAs has been investigated. The emitter was prepared by anodic etching of n-GaAs (110) in 0.1 M HCl solution. The as-etched porous GaAs shows nonlinear Fowler-Nordheim (FN) characteristics, with a low onset voltage. The emitter, after operating for 6 h at the residual gas pressure of 1×10-8 mbar, shows a linear FN characteristics with a relatively high onset voltage and poor field emission current stability as compared to the as-etched emitter. The change in the behavior was attributed to the residual gas ion bombardment during field electron emission. X-ray photoelectron spectroscopic investigations were carried out on as-etched sample and the one which was studied for field emission. The studies indicate that the as-etched surface contains As2O3 and the surface after field electron emission for about 6 h becomes gallium rich. The presence of As2O3 seems to be a desirable feature for the stable field emission current.

  20. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    Energy Technology Data Exchange (ETDEWEB)

    Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal, E-mail: zainabh@petronas.com.my [Centre of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

    2014-03-24

    Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

  1. Interstellar Magnetic Fields and Polarimetry of Dust Emission

    Science.gov (United States)

    Dowell, Darren

    2010-01-01

    Magnetic fields are an important ingredient in the stormy cosmos. Magnetic fields: (1) are intimately involved with winds from Active Galactic Nuclei (AGN) and stars (2) create at least some of the structures observed in the ISM (3) modulate the formation of clouds, cores, and stars within a turbulent medium (4) may be dynamically important in protostellar accretion disks (5) smooth weak shocks (C-shocks).

  2. Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Shocks

    Science.gov (United States)

    Nishikawa, Ken-IchiI.; Hededal, C.; Hardee, P.; Richardson, G.; Preece, R.; Sol, H.; Fishman, G.

    2004-01-01

    Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (m) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient parallel magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. New simulations with an ambient perpendicular magnetic field show the strong interaction between the relativistic jet and the magnetic fields. The magnetic fields are piled up by the jet and the jet electrons are bent, which creates currents and displacement currents. At the nonlinear stage, the magnetic fields are reversed by the current and the reconnection may take place. Due to these dynamics the jet and ambient electron are strongly accelerated in both parallel and perpendicular directions.

  3. Coherence properties of the harmonic generation in intense laser field

    International Nuclear Information System (INIS)

    Salieres, P.

    1995-01-01

    In this thesis is presented an experimental and theoretical study of the harmonic generation in intense field and coherence properties of this radiation. The first part reminds the main harmonic specter characteristics. Follow then experimental studies of the tray extension with the laser lighting, the harmonic generation by ions, and the influence of the laser field on the efficiency of generation. The second part presents the quantum model of the harmonic generation in tunnel regime that we have used for the calculation of the dipoles. We compare dependence in lighting of some harmonic, by insisting on the characteristic behavior of the atomic phase. The theory of the propagation is presented in third part. After the reminder of the case of a perturbative polarization, we develop the case of the polarization in tunnel regime. With the help of numerical simulations, we show the influence of the atomic phase on the agreement of phase, and therefore on the efficiency of conversion and profiles of generation in the medium. The importance of the geometry of the interaction is underlined. The part IV presents the study of the spatial coherence of the harmonic radiation. We develop first consequences of the theory of the agreement of phase for profiles of emission. Then the comparison with experimental profiles is detailed in function of the different parameters( order of non linearity, laser lighting, position of the focus by report in the gaseous medium). The study of the spectral and temporal coherence of the part V begins with the experimental effect investigation of the ionization on specters of the harmonic of weak order. We present then theoretical predictions of the preceding model for spectral and temporal profiles of the harmonic of highest order, generated in tunnel regime. The part VI is devoted to the UVX source aspect of the harmonic radiation. General characteristics (number of photons, agreement) are first detailed, then we present the first experiences

  4. Estimation of methane and nitrous oxide emissions from paddy fields in Taiwan

    International Nuclear Information System (INIS)

    Yang, Shang-Shyng; Lai, Chao-Ming; Chang, Hsiu-Lan; Chang, Ed-Huan; Wei, Chia-Bei

    2009-01-01

    To investigate the greenhouse gases emissions from paddy fields, methane and nitrous oxide emissions were estimated with the local measurement and the IPCC method during 1990-2006 in Taiwan. Annual methane emission ranged from 9001 to 14,980 ton in the first crop season for 135,314-242,298 ha of paddy fields, and it was between 16,412 and 35,208 ton for 101,710-211,968 ha in the second crop season with the local measurement for intermittent irrigation. The value ranged from 31,122 to 55,729 ton of methane emission in the first crop season, and it was between 29,493 and 61,471 ton in the second crop season with the IPCC guideline for continuous flooding. Annual nitrous oxide emission from paddy fields was between 371 and 728 ton in the first crop season, and the value ranged from 163 to 365 ton in the second crop season with the local measurement. Methane emission from paddy fields in Taiwan for intermittent irrigation was only 26.72-28.92%, 55.65-57.32% and 41.19-43.10% with the IPCC guidelines for continuous flooding and mean temperature of transplanting stage in the first crop, the second crop and total paddy fields, respectively. The values were 53.44-57.84%, 111.29-114.55% and 82.38-86.20% with the IPCC guidelines for single aeration and mean temperature of transplanting stage, respectively; and the values were 133.60-144.61%, 282.56-286.62% and 205.96-215.49% with the IPCC guidelines for multiple aeration and mean temperature of transplanting stage, respectively. Intermittent irrigation in paddy fields reduces methane emission significantly; appropriate application of nitrogen fertilizer and irrigation in paddy fields also decreases nitrous oxide emission. (author)

  5. Beam Dynamics Simulations of Optically-Enhanced Field Emission from Structured Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Seymour, A. [Northern Illinois U.; Grote, D. [LLNL, Livermore; Mihalcea, D. [Northern Illinois U.; Piot, P. [Fermilab; Vay, J.-L. [LBNL, Berkeley

    2014-01-01

    Structured cathodes - cathodes with a segmented emission surface - are finding an increasing number of applications and can be combined with a variety of emission mechanisms, including photoemission and field emission. These cathodes have been used to enhance the quantum efficiency of metallic cathodes when operated as plasmonic cathodes, have produced high-current electron bunches though field emission from multiple tips, and can be used to form beams with transverse segmentations necessary for improving the performance of accelerator-based light sources. In this report we present recent progress towards the development of finite-difference time-domain particle-in-cell simulations using the emission process in structured cathodes based on the WARP framework. The simulations give further insight on the localized source of the emitted electrons which could be used for additional high-fidelity start-to-end simulations of electron accelerators that employ this type of electron source.

  6. HARD X-RAY EMISSION DURING FLARES AND PHOTOSPHERIC FIELD CHANGES

    International Nuclear Information System (INIS)

    Burtseva, O.; Petrie, G. J. D.; Pevtsov, A. A.; Martínez-Oliveros, J. C.

    2015-01-01

    We study the correlation between abrupt permanent changes of magnetic field during X-class flares observed by the Global Oscillation Network Group and Helioseismic and Magnetic Imager instruments, and the hard X-ray (HXR) emission observed by RHESSI, to relate the photospheric field changes to the coronal restructuring and investigate the origin of the field changes. We find that spatially the early RHESSI emission corresponds well to locations of the strong field changes. The field changes occur predominantly in the regions of strong magnetic field near the polarity inversion line (PIL). The later RHESSI emission does not correspond to significant field changes as the flare footpoints are moving away from the PIL. Most of the field changes start before or around the start time of the detectable HXR signal, and they end at about the same time or later than the detectable HXR flare emission. Some of the field changes propagate with speed close to that of the HXR footpoint at a later phase of the flare. The propagation of the field changes often takes place after the strongest peak in the HXR signal when the footpoints start moving away from the PIL, i.e., the field changes follow the same trajectory as the HXR footpoint, but at an earlier time. Thus, the field changes and HXR emission are spatio-temporally related but not co-spatial nor simultaneous. We also find that in the strongest X-class flares the amplitudes of the field changes peak a few minutes earlier than the peak of the HXR signal. We briefly discuss this observed time delay in terms of the formation of current sheets during eruptions

  7. Optical field emission from resonant gold nanorods driven by femtosecond mid-infrared pulses

    Energy Technology Data Exchange (ETDEWEB)

    Kusa, F. [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei Tokyo 184-8588 (Japan); Institute of Industrial Science, the University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Echternkamp, K. E.; Herink, G.; Ropers, C. [4th Physical Institute – Solids and Nanostructures, University of Göttingen, 37077 Göttingen (Germany); Ashihara, S., E-mail: ashihara@iis.u-tokyo.ac.jp [Institute of Industrial Science, the University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2015-07-15

    We demonstrate strong-field photoelectron emission from gold nanorods driven by femtosecond mid-infrared optical pulses. The maximum photoelectron yield is reached at the localized surface plasmon resonance, indicating that the photoemission is governed by the resonantly-enhanced optical near-field. The wavelength- and field-dependent photoemission yield allows for a noninvasive determination of local field enhancements, and we obtain intensity enhancement factors close to 1300, in good agreement with finite-difference time domain computations.

  8. Nitrogen plasma formation through terahertz-induced ultrafast electron field emission

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew

    2015-01-01

    Electron microscopy and electron diffraction techniques rely on electron sources. Those sources require strong electric fields to extract electrons from metals, either by the photoelectric effect, driven by multiphoton absorption of strong laser fields, or in the static field emission regime....... Terahertz (THz) radiation, commonly understood to be nonionizing due to its low photon energy, is here shown to produce electron field emission. We demonstrate that a carrier-envelope phase-stable single-cycle optical field at THz frequencies interacting with a metallic microantenna can generate...... and accelerate ultrashort and ultrabright electron bunches into free space, and we use these electrons to excite and ionize ambient nitrogen molecules near the antenna. The associated UV emission from the gas forms a novel THz wave detector, which, in contrast with conventional photon-counting or heat...

  9. Space density and clustering properties of a new sample of emission-line galaxies

    International Nuclear Information System (INIS)

    Wasilewski, A.J.

    1982-01-01

    A moderate-dispersion objective-prism survey for low-redshift emission-line galaxies has been carried out in an 825 sq. deg. region of sky with the Burrell Schmidt telescope of Case Western Reserve University. A 4 0 prism (300 A/mm at H#betta#) was used with the Illa-J emulsion to show that a new sample of emission-line galaxies is available even in areas already searched with the excess uv-continuum technique. The new emission-line galaxies occur quite commonly in systems with peculiar morphology indicating gravitational interaction with a close companion or other disturbance. About 10 to 15% of the sample are Seyfert galaxies. It is suggested that tidal interaction involving matter infall play a significant role in the generation of an emission-line spectrum. The space density of the new galaxies is found to be similar to the space density of the Makarian galaxies. Like the Markarian sample, the galaxies in the present survey represent about 10% of all galaxies in the absolute magnitude range M/sub p/ = -16 to -22. The observations also indicate that current estimates of dwarf galaxy space densities may be too low. The clustering properties of the new galaxies have been investigated using two approaches: cluster contour maps and the spatial correlation function. These tests suggest that there is weak clustering and possibly superclustering within the sample itself and that the galaxies considered here are about as common in clusters of ordinary galaxies as in the field

  10. Emission characteristics in solution-processed asymmetric white alternating current field-induced polymer electroluminescent devices

    Science.gov (United States)

    Chen, Yonghua; Xia, Yingdong; Smith, Gregory M.; Gu, Yu; Yang, Chuluo; Carroll, David L.

    2013-01-01

    In this work, the emission characteristics of a blue fluorophor poly(9, 9-dioctylfluorene) (PFO) combined with a red emitting dye: Bis(2-methyl-dibenzo[f,h]quinoxaline)(acetylacetonate)iridium (III) [Ir(MDQ)2(acac)], are examined in two different asymmetric white alternating current field-induced polymer electroluminescent (FIPEL) device structures. The first is a top-contact device in which the triplet transfer is observed resulting in the concentration-dependence of the emission similar to the standard organic light-emitting diode (OLED) structure. The second is a bottom-contact device which, however, exhibits concentration-independence of emission. Specifically, both dye emission and polymer emission are found for the concentrations as high as 10% by weight of the dye in the emitter. We attribute this to the significant different carrier injection characteristics of the two FIPEL devices. Our results suggest a simple and easy way to realize high-quality white emission.

  11. Aerosol Optical Properties and Trace Gas Emissions From Laboratory-Simulated Western US Wildfires

    Science.gov (United States)

    Selimovic, V.; Yokelson, R. J.; Warneke, C.; Roberts, J. M.; De Gouw, J. A.; Reardon, J.; Griffith, D. W. T.

    2017-12-01

    Western wildfires have a major impact on air quality in the US. In the fall of 2016, 107 fires were burned in the large-scale combustion facility at the US Forest Service Missoula Fire Sciences Laboratory as part of the Fire Influence on Regional and Global Environments Experiment (FIREX). Canopy, litter, duff, dead wood, and other fuels from various widespread coniferous and chaparral ecosystems were burned in combinations to represent relevant configurations in the field and as pure components to investigate the effects of individual fuels. The smoke emissions were characterized by a large suite of state-of-the-art instruments. In this study we report emission factor (EF, g compound emitted per kg fuel burned) measurements in fresh smoke of a diverse suite of critically-important trace gases measured by open-path Fourier transform infrared spectroscopy (OP-FTIR). We also report aerosol optical properties (absorption EF, single scattering albedo (SSA) and Ångström absorption exponent (AAE)) as well as black carbon (BC) EF measured by photoacoustic extinctiometers (PAX) at 870 and 401 nm. A careful comparison with available field measurements of wildfires confirms that representative data can be extracted from the lab fire data. The OP-FTIR data show that ammonia (1.65 g kg-1), acetic acid (2.44 g kg-1), and other trace gases are significant emissions not previously measured for US wildfires. The PAX measurements show that brown carbon (BrC) absorption is most dominant for combustion of duff (AAE 7.13) and rotten wood (AAE 4.60): fuels that are consumed in greater amounts during wildfires than prescribed fires. We confirm that about 86% of the aerosol absorption at 401 nm in typical fresh wildfire smoke is due to BrC.

  12. Testing climate-smart irrigation strategies to reduce methane emissions from rice fields

    Science.gov (United States)

    Runkle, B.; Suvocarev, K.; Reba, M. L.

    2017-12-01

    Approximately 11% of the global 308 Tg CH4 anthropogenic emissions are currently attributed to rice cultivation. In this study, the impact of water conservation practices on rice field CH4 emissions was evaluated in Arkansas, the leading state in US rice cultivation. While conserving water, the Alternate Wetting and Drying (AWD) irrigation practice can also reduce CH4 emissions through the deliberate, periodic introduction of aerobic conditions. Seasonal CH4emissions from a pair of adjacent, production-sized rice fields were estimated and compared during the 2015 to 2017 growing seasons using the eddy covariance method on each field. The fields were alternately treated with continuous flood (CF) and AWD irrigation. In 2015, the seasonal cumulative carbon losses by CH4 emission were 30.3 ± 6.3 and 141.9 ± 8.6 kg CH4-C ha-1 for the AWD and CF treatments, respectively. Data from 2016 and 2017 will be analyzed and shown within this presentation; an initial view demonstrates consistent findings to 2015. When accounting for differences in field conditions and soils, the AWD practice is attributable to a 36-51% reduction in seasonal emissions. The substantial decrease in CH4 emissions by AWD supports previous chamber-based research and offers strong evidence for the efficacy of AWD in reducing CH4 emissions in Arkansas rice production. The AWD practice has enabled the sale of credits for carbon offsets trading and this new market could encourage CH4 emissions reductions on a national scale. These eddy covariance towers are being placed into a regional perspective including crop and forest land in the three states comprising the Mississippi Delta: Arkansas, Mississippi, and Louisiana.

  13. Effect of Electric Field in the Stabilized Premixed Flame on Combustion Process Emissions

    Science.gov (United States)

    Otto, Krickis

    2017-10-01

    The effect of the AC and DC electrical field on combustion processes has been investigated by various researchers. The results of these experiments do not always correlate, due to different experiment conditions and experiment equipment variations. The observed effects of the electrical field impact on the combustion process depends on the applied voltage polarity, flame speed and combustion physics. During the experiment was defined that starting from 1000 V the ionic wind takes the effect on emissions in flue gases, flame shape and combustion instabilities. Simulation combustion process in hermetically sealed chamber with excess oxygen amount 3 % in flue gases showed that the positive effect of electrical field on emissions lies in region from 30 to 400 V. In aforementioned voltage range carbon monoxide emissions were reduced by 6 % and at the same time the nitrogen oxide emissions were increased by 3.5 %.

  14. Water-molecular emission from cavitation bubbles affected by electric fields.

    Science.gov (United States)

    Lee, Hyang-Bok; Choi, Pak-Kon

    2018-04-01

    Orange emission was observed during multibubble sonoluminescence at 1 MHz in water saturated with noble gas. The emission arose in the vicinity of the peeled ground electrode of a piezoceramic transducer exposed to water, suggesting that cavitation bubbles were affected by the electric fields that leaked from the transducer. The spectrum of the emission exhibited a broad component whose intensity increased towards the near-infrared region with peaks at 713 and 813 nm. The spectral shape was independent of the saturation gas of He, Ne, or Kr. The broad component was attributed to the superposition of lines due to vibration-rotation transitions of water molecules, each of which was broadened by the high pressure and electric fields at bubble collapse. An emission mechanism based on charge induction by electric fields and the charged droplet model is proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Harsh [Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi 110025 (India); Husain, Mushahid, E-mail: mush-reslab@rediffmail.com [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi 110025 (India)

    2014-02-28

    Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm{sup 2} at a turn-on field of 1.3 V/μm. The as grown SWCNTs were further treated with Oxygen (O{sub 2}) plasma for 5 min and again field emission characteristics were measured. The O{sub 2} plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm{sup 2} at a much lower turn on field of 0.8 V/μm. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O{sub 2} plasma treatment and the findings are being reported in this paper.

  16. Impact of surface morphology on the properties of light emission in InGaN epilayers

    Science.gov (United States)

    Kristijonas Uždavinys, Tomas; Marcinkevičius, Saulius; Mensi, Mounir; Lahourcade, Lise; Carlin, Jean-François; Martin, Denis; Butté, Raphaël; Grandjean, Nicolas

    2018-05-01

    Scanning near-field optical microscopy was used to study the influence of the surface morphology on the properties of light emission and alloy composition in InGaN epitaxial layers grown on GaN substrates. A strong correlation between the maps of the photoluminescence (PL) peak energy and the gradient of the surface morphology was observed. This correlation demonstrates that the In incorporation strongly depends on the geometry of the monolayer step edges that form during growth in the step-flow mode. The spatial distribution of nonradiative recombination centers — evaluated from PL intensity maps — was found to strongly anticorrelate with the local content of In atoms in the InGaN alloy.

  17. Electric field distribution and current emission in a miniaturized geometrical diode

    Science.gov (United States)

    Lin, Jinpu; Wong, Patrick Y.; Yang, Penglu; Lau, Y. Y.; Tang, W.; Zhang, Peng

    2017-06-01

    We study the electric field distribution and current emission in a miniaturized geometrical diode. Using Schwarz-Christoffel transformation, we calculate exactly the electric field inside a finite vacuum cathode-anode (A-K) gap with a single trapezoid protrusion on one of the electrode surfaces. It is found that there is a strong field enhancement on both electrodes near the protrusion, when the ratio of the A-K gap distance to the protrusion height d /h spot checked against COMSOL simulations. We calculate the effective field enhancement factor for the field emission current, by integrating the local Fowler-Nordheim current density along the electrode surfaces. We systematically examine the electric field enhancement and the current rectification of the miniaturized geometrical diode for various geometric dimensions and applied electric fields.

  18. Fundamental properties of secondary negative ion emission by sputtering

    International Nuclear Information System (INIS)

    Shimizu, Toshiki; Tsuji, Hiroshi; Ishikawa, Junzo

    1989-01-01

    The report describes some results obtained from preliminary experiments on secondary negative ion emission from a cesiated surface by Xe-ion beam sputtering, which give the production probability. A measuring system is constructed for secondary negative ion emission. The system consists of a microwave ion source with a lens, a sputtering target holder with a heater, a cesium oven, a limiting aperture with a substrate for deposition, a negative-ion extractor and lens, and a ExB type mass separator. Observations are made on the dependence of negative ion current on cesium supply, dependence of negative ion current on target temperature, and negative ion production probability. The cesium supply and the target temperature are found to strongly influence the negative ion emission. By controlling these factors, the optimum condition for secondary negative ion emission is achieved with a minimum surface work function. The production probability of the negative ion is found to be very high, about 20% for carbon. Therefore, the secondary negative ion emission is considered a useful and highly efficient method to obtain high current ion beams. The constant in the Rasser's theoretical equation is experimentally determined to be 4.1 x 10 -4 eV sec/m. (N.K.)

  19. Enhanced field emission of ZnO nanoneedle arrays via solution etching at room temperature

    DEFF Research Database (Denmark)

    Ma, Huanming; Qin, Zhiwei; Wang, Zaide

    2017-01-01

    ZnO nanoneedle arrays (ZnO nns) were synthesized by a facile two-step solution-phase method based on the etching of pre-synthesized ZnO nanowire arrays (ZnO nws) with flat ends at room temperature. Field emission measurement results showed that the turn-on electronic fields of ZnO nns and nws wer...

  20. Field emission from individual multiwalled carbon nanotubes prepared in an electron microscope

    NARCIS (Netherlands)

    de Jonge, N.; van Druten, N.J.

    2003-01-01

    Individual multiwalled carbon nanotube field emitters were prepared in a scanning electron microscope. The angular current density, energy spectra, and the emission stability of the field-emitted electrons were measured. An estimate of the electron source brightness was extracted from the

  1. Relative work function of clean molybdenum single-crystal planes determined by field emission microscopy

    International Nuclear Information System (INIS)

    Bergeret, G.; Abon, M.; Tardy, B.; Teichner, S.J.

    1974-01-01

    A probe-hole field emission microscope was used to determine the work function of clean molybdenum single crystal planes relative to the average work function of the field emitter, assumed to be 4.20 eV. Results are compared with other available data

  2. Surface and electron emission properties of hydrogen-free diamond-like carbon films investigated by atomic force microscopy

    International Nuclear Information System (INIS)

    Liu Dongping; Zhang, Sam; Ong, S.-E.; Benstetter, Guenther; Du Hejun

    2006-01-01

    In this study, we have deposited hydrogen-free diamond-like carbon (DLC) films by using DC magnetron sputtering of graphite target at various r.f. bias voltages. Surface and nanoscale emission properties of these DLC films have been investigated using a combination of atomic force microscopy (AFM)-based nanowear tests and conducting-AFM, by simultaneously measuring the topography and the conductivity of the samples. Nanowear tests show that these DLC films are covered with the thin (1.5-2.0 nm) graphite-like layers at surfaces. Compared to the film bulk structure, the graphite-like surface layers are more conductive. The graphite-like surface layers significantly influence the electron emission properties of these films. Low-energy carbon species can be responsible for the formation of graphite-like surface layers. Nanoscale electron emission measurements have revealed the inhomogeneous emission nature of these films. The low-field emission from these films can be attributed to the existence of sp 2 -configured nanoclusters inside the films

  3. A novel field measurement method for determining fine particle and gas emissions from residential wood combustion

    Science.gov (United States)

    Tissari, Jarkko; Hytönen, Kati; Lyyränen, Jussi; Jokiniemi, Jorma

    Emission data from residential wood combustion are usually obtained on test stands in the laboratory but these measurements do not correspond to the operational conditions in the field because of the technological boundary conditions (e.g. testing protocol, environmental and draught conditions). The field measurements take into account the habitual practice of the operators and provide the more reliable results needed for emission inventories. In this study, a workable and compact method for measuring emissions from residential wood combustion in winter conditions was developed. The emissions for fine particle, gaseous and PAH compounds as well as particle composition in real operational conditions were measured from seven different appliances. The measurement technique worked well and was evidently suitable for winter conditions. It was easy and fast to use, and no construction scaffold was needed. The dilution of the sample with the combination of a porous tube diluter and an ejector diluter was well suited to field measurement. The results indicate that the emissions of total volatile organic carbon (TVOC) (17 g kg -1 (of dry wood burned)), carbon monoxide (CO) (120 g kg -1) and fine particle mass (PM 1) (2.7 g kg -1) from the sauna stove were higher than in the other measured appliances. In the masonry heaters, baking oven and stove, the emissions were 2.9-9 g kg -1 TVOC, 28-68 g kg -1 CO and 0.6-1.6 g kg -1 PM 1. The emission of 12 PAHs (PAH 12) from the sauna stove was 164 mg kg -1 and consisted mainly of PAHs with four benzene rings in their structure. PAH 12 emission from other appliances was, on average, 21 mg kg -1 and was dominated by 2-ring PAHs. These results indicate that despite the non-optimal operational practices in the field, the emissions did not differ markedly from the laboratory measurements.

  4. Dielectric and Radiative Properties of Sea Foam at Microwave Frequencies: Conceptual Understanding of Foam Emissivity

    OpenAIRE

    Peter W. Gaiser; Magdalena D. Anguelova

    2012-01-01

    Foam fraction can be retrieved from space-based microwave radiometric data at frequencies from 1 to 37 GHz. The retrievals require modeling of ocean surface emissivity fully covered with sea foam. To model foam emissivity well, knowledge of foam properties, both mechanical and dielectric, is necessary because these control the radiative processes in foam. We present a physical description of foam dielectric properties obtained from the foam dielectric constant including foam skin depth; foam ...

  5. Developing Automatic Water Table Control System for Reducing Greenhouse Gas Emissions from Paddy Fields

    Science.gov (United States)

    Arif, C.; Fauzan, M. I.; Satyanto, K. S.; Budi, I. S.; Masaru, M.

    2018-05-01

    Water table in rice fields play important role to mitigate greenhouse gas (GHG) emissions from paddy fields. Continuous flooding by maintenance water table 2-5 cm above soil surface is not effective and release more GHG emissions. System of Rice Intensification (SRI) as alternative rice farming apply intermittent irrigation by maintaining lower water table is proven can reduce GHG emissions reducing productivity significantly. The objectives of this study were to develop automatic water table control system for SRI application and then evaluate the performances. The control system was developed based on fuzzy logic algorithms using the mini PC of Raspberry Pi. Based on laboratory and field tests, the developed system was working well as indicated by lower MAPE (mean absolute percentage error) values. MAPE values for simulation and field tests were 16.88% and 15.80%, respectively. This system can save irrigation water up to 42.54% without reducing productivity significantly when compared to manual irrigation systems.

  6. Thermal and superthermal properties of supersymmetric field theories

    International Nuclear Information System (INIS)

    Fuchs, J.

    1984-01-01

    We discuss the finite-temperature behaviour of supersymmetric field theories. We show that their 'superthermal' properties which concern the question of susy breaking at finite temperature and their thermal properties must be considered separately. Susy breaking is determined by the so-called superthermal ensemble, whereas thermodynamical properties follow from the conventional thermal ensemble, leading to the usual statistics for the bosonic and fermionic components of a superfield. We show that superspace techniques can be used in a straightforward way only for superthermal Green functions but not for thermal ones. We also discuss the possibility of finite-temperature susy restoration and the implications of Goldstone's theorem at finite temperature. (orig.)

  7. A look at some systemic properties of self-bioluminescent emission

    Science.gov (United States)

    Creath, Katherine

    2008-08-01

    Self-bioluminescent emission (SBE) is a type of biological chemiluminescence where photons are emitted as part of chemical reactions occurring during metabolic processes. This emission is also known as biophoton emission, ultraweak photon emission and ultraweak bioluminescence. This paper outlines research over the past century on some systemic properties of SBE as measured with biological detectors, photomultiplier detectors and ultra-sensitive imaging arrays. There is an apparent consensus in the literature that emission in the deep blue and ultraviolet (150-450nm) is related to DNA / RNA processes while emission in the red and near infrared (600-1000nm) is related to mitochondria and oxidative metabolisms involving reactive oxygen species, singlet oxygen and free radicals in plant, animal and human cells along with chlorophyll fluorescent decay in plants. Additionally, there are trends showing that healthy, unstressed and uninjured samples have less emission than samples that are unhealthy, stressed or injured. Mechanisms producing this emission can be narrowed down by isolating the wavelength region of interest and waiting for short-term fluorescence to decay leaving the ultraweak long-term metabolic emission. Examples of imaging this emission in healthy versus unhealthy, stressed versus unstressed, and injured versus uninjured plant parts are shown. Further discussion poses questions still to be answered related to properties such as coherence, photon statistics, and methodological means of isolating mechanisms.

  8. Development of new functional properties in traditional ceramics field

    International Nuclear Information System (INIS)

    Carda, J.B.; Pedra, J.M.; Nunez, I.; Peiro, N.C.; Gil, C.; Navarro, E.; Gomez, J.J.; Chiva, L.

    2004-01-01

    In the present communication, several ways to obtain functional properties in ceramic tiles will be exposed, developed by the research group in Solid State Chemistry of Jaume I University from Castellon, in close collaboration with the ceramic industry set in Castellon (Spain). Then, searching for a new properties, those that involve advanced fields in ceramics, such as mechanical, electrical or optical properties have been chosen, transferring their application to traditional products, selecting for it the development of this properties in surface (as the obtaining if glass-ceramic glazes) or in the ceramic body (increasing its mechanical resistance, more dense and with less thickness of layer). Related to the surface properties interesting in traditional ceramics field, glass-ceramic glazes have been designed, presenting high resistance to abrasion and chemical agents attack, formulating systems of devitrification of α-SiO 2 crystallization (cristobalite), anoritite and zircon. Systems that reduce resistivity of glazes have been developed too, causing the discharge to the ground of the static charge, designing a semiconductor system SnO 2 -Sb 2 O 3 . o finish with surface properties, bactericidal properties glazes have been originated, working with CeO 2 -ZrO 2 and TiO 2 (anatase) systems. According to ceramic bodies, highly gressificated systems have been developed, with an open porosity lower than 0.5% of water absorption and with high mechanical resistance, aspects that open ways to develop multilayer systems allowing the reduction of body thickness without a decrease of its technical features. (author)

  9. Emission Characteristics of Gas-Fired Boilers based on Category-Specific Emission Factor from Field Measurements in Beijing, China

    Science.gov (United States)

    Itahashi, S.; Yan, X.; Song, G.; Yan, J.; Xue, Y.

    2017-12-01

    Gas-fired boilers will become the main stationary sources of NOx in Beijing. However, the knowledge of gas-fired boilers in Beijing is limited. In the present study, the emission characteristics of NOx, SO2, and CO from gas-fired boilers in Beijing were established using category-specific emission factors (EFs) from field measurements. In order to obtain category-specific EFs, boilers were classified through influence analysis. Factors such as combustion mode, boiler type, and installed capacity were considered critical for establishing EFs because they play significant roles in pollutant formation. The EFs for NOx, CO, and SO2 ranged from 1.42-6.86 g m-3, 0.05-0.67 g m-3 and 0.03-0.48 g m-3. The emissions of NOx, SO2, and CO for gas-fired boilers in Beijing were 11121 t, 468 t, and 222 t in 2014, respectively. The emissions were spatially allocated into grid cells with a resolution of 1 km × 1 km, and the results indicated that top emitters were in central Beijing. The uncertainties were quantified using a Monte Carlo simulation. The results indicated high uncertainties in CO (-157% to 154%) and SO2 (-127% to 182%) emissions, and relatively low uncertainties (-34% to 34%) in NOx emission. Furthermore, approximately 61.2% and 96.8% of the monitored chamber combustion boilers (CCBs) met the standard limits for NOx and SO2, respectively. Concerning NOx, low-NOx burners and NOx emission control measures are urgently needed for implementing of stricter standards. Adopting terminal control measures is unnecessary for SO2, although its concentration occasionally exceeds standard limits, because reduction of its concentration can be achieved thorough control of the sulfur content of natural gas at a stable low level. Furthermore, the atmospheric combustion boilers (ACBs) should be substituted with CCBs, because ACBs have a higher emission despite lower gross installed capacity. The results of this study will enable in understanding and controlling emissions from gas

  10. The influence of oxidation properties on the electron emission characteristics of porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    He, Li [Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi’an Jiaotong University, Xi’an 710049 (China); Zhang, Xiaoning, E-mail: znn@mail.xjtu.edu.cn [Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Wenjiang [Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi’an Jiaotong University, Xi’an 710049 (China); Wei, Haicheng [School of Electrical and Information Engineering, Beifang University of Nationalities, Yinchuan750021 (China)

    2016-09-30

    Highlights: • Evaluated the oxidation properties of porous silicon from semi-quantitative methods. • Discovered the relationship between oxidation properties and emission characteristics. • Revealed the micro-essence of the electron emission of the porous silicon. - Abstract: In order to investigate the influence of oxidation properties such as oxygen content and its distribution gradient on the electron emission characteristics of porous silicon (PS) emitters, emitters with PS thickness of 8 μm, 5 μm, and 3 μm were prepared and then oxidized by electrochemical oxidation (ECO) and ECO-RTO (rapid thermal oxidation) to get different oxidation properties. The experimental results indicated that the emission current density, efficiency, and stability of the PS emitters are mainly determined by oxidation properties. The higher oxygen content and the smaller oxygen distribution gradient in the PS layer, the larger emission current density and efficiency we noted. The most favorable results occurred for the PS emitter with the smallest oxygen distribution gradient and the highest level of oxygen content, with an emission current density of 212.25 μA/cm{sup 2} and efficiency of 59.21‰. Additionally, it also demonstrates that thick PS layer benefits to the emission stability due to its longer electron acceleration tunnel. The FN fitting plots indicated that the effective emission areas of PS emitters can be enlarged and electron emission thresholds is decreased because of the higher oxygen content and smaller distribution gradient, which were approved by the optical micrographs of top electrode of PS emitters before and after electron emission.

  11. The influence of oxidation properties on the electron emission characteristics of porous silicon

    International Nuclear Information System (INIS)

    He, Li; Zhang, Xiaoning; Wang, Wenjiang; Wei, Haicheng

    2016-01-01

    Highlights: • Evaluated the oxidation properties of porous silicon from semi-quantitative methods. • Discovered the relationship between oxidation properties and emission characteristics. • Revealed the micro-essence of the electron emission of the porous silicon. - Abstract: In order to investigate the influence of oxidation properties such as oxygen content and its distribution gradient on the electron emission characteristics of porous silicon (PS) emitters, emitters with PS thickness of 8 μm, 5 μm, and 3 μm were prepared and then oxidized by electrochemical oxidation (ECO) and ECO-RTO (rapid thermal oxidation) to get different oxidation properties. The experimental results indicated that the emission current density, efficiency, and stability of the PS emitters are mainly determined by oxidation properties. The higher oxygen content and the smaller oxygen distribution gradient in the PS layer, the larger emission current density and efficiency we noted. The most favorable results occurred for the PS emitter with the smallest oxygen distribution gradient and the highest level of oxygen content, with an emission current density of 212.25 μA/cm"2 and efficiency of 59.21‰. Additionally, it also demonstrates that thick PS layer benefits to the emission stability due to its longer electron acceleration tunnel. The FN fitting plots indicated that the effective emission areas of PS emitters can be enlarged and electron emission thresholds is decreased because of the higher oxygen content and smaller distribution gradient, which were approved by the optical micrographs of top electrode of PS emitters before and after electron emission.

  12. Properties, performance and emissions of biofuels in blends with gasoline

    Science.gov (United States)

    Eslami, Farshad

    The emission performance of fuels and their blends in modern combustion systems have been studied with the purpose of reducing regulated and unregulated emissions, understanding of exhaust products of fuels such as gasoline, ethanol and 2,5-dimethylfuran and comparison of results. A quantitative analysis of individual hydrocarbon species from exhaust emissions of these three fuels were carried out with direct injects spark ignition (DISI) single cylinder engine. The analysis of hydrocarbon species were obtained using gas chromatography-mass spectrometry (GCMS) connected on-line to SI engine. During this project, novel works have been done including the set up of on-line exhaust emission measurement device for detection and quantification of individual volatile hydrocarbons. Setting of a reliable gas chromatography mass spectrometry measurement system required definition and development of a precise method. Lubricity characteristics of biofuels and gasoline were investigated using High Frequency Reciprocating Rig (HFRR). Results showed great enhancing lubricity characteristics of biofuels when added to conventional gasoline. 2,5-dimenthylfuran was found to be the best among the fuels used, addition of this fuel to gasoline also showed better result compared with ethanol addition.

  13. An experimental and theoretical study of new phosphors for full color field emission displays

    Science.gov (United States)

    Zhang, Fu-Li

    An in depth study is reported of the cathodoluminescent (CL) properties of three new highly efficiency blue phosphors for field emission display (FED) applications doped with fast activators. The superior performance of a new Eu-doped green SrGa2S4 will also be reported. This work addresses four main topics: (1) a detailed study of the dependence of the luminescent intensity on activator concentration, as a function of electron beam voltage and current density; (2) the optical properties of thew phosphors and the development of a CL efficiency characterization technique using a critical screen weight method, which can obtain maximum light output and improve measurement accuracy; (3) understanding the low voltage CL mechanism associated with nanocrystal size by developing a thin film and disk model based on transportation theory and experimental results; (4) Development of a comprehensive evaluation method of red, green, and blue (RGB) phosphors for full color displays by calculation of luminance ratios, required luminance, and measurements of spectra, efficiency and saturation behavior. For FEDs which combine the best properties of CRT and flat panel displays, the development of efficient phosphors at low voltages and high current densities is shown to be critical to meet the luminance and power requirement demands for portable displays. Of particular importance is the need for a good blue phosphor, and to understand the dependence of the CL efficiency on nanocrystal size, penetration depth, diffusion length and surface recombination rate. This has been obtained from the thin film and disk models and fits to experiment. Comparisons between full color phosphor sets show that the performance of a display can vary by over a factor of three depending on the choice of the RGB set. Other factors that are important for optimizing the performance of FED phosphors are reviewed.

  14. Effect of a DC external electric field on the properties of a nonuniform microwave discharge in hydrogen at reduced pressures

    Energy Technology Data Exchange (ETDEWEB)

    Lebedev, Yu. A., E-mail: lebedev@ips.ac.ru; Krashevskaya, G. V.; Tatarinov, A. V.; Titov, A. Yu.; Epshtein, I. L. [Russian Academy of Sciences, Topchiev Institute of Petrochemical Synthesis (Russian Federation)

    2017-01-15

    The effect of a dc external electrical field on the properties of a highly nonuniform electrode microwave discharge in hydrogen at a pressure of 1 Torr was studied using optical emission spectroscopy and selfconsistent two-dimensional simulations. It is shown that the negative voltage applied to the antenna electrode with respect to the grounded chamber increases the discharge radiation intensity, while the positive voltage does not affect the discharge properties. The simulation results agree well with the experimental data.

  15. Effect of a DC external electric field on the properties of a nonuniform microwave discharge in hydrogen at reduced pressures

    International Nuclear Information System (INIS)

    Lebedev, Yu. A.; Krashevskaya, G. V.; Tatarinov, A. V.; Titov, A. Yu.; Epshtein, I. L.

    2017-01-01

    The effect of a dc external electrical field on the properties of a highly nonuniform electrode microwave discharge in hydrogen at a pressure of 1 Torr was studied using optical emission spectroscopy and selfconsistent two-dimensional simulations. It is shown that the negative voltage applied to the antenna electrode with respect to the grounded chamber increases the discharge radiation intensity, while the positive voltage does not affect the discharge properties. The simulation results agree well with the experimental data.

  16. Low Emittance Gun Project based on Field Emission

    CERN Document Server

    Ganter, Romain; Dehler, M; Gobrecht, Jens; Gough, Chris; Ingold, Gerhard; Leemann, Simon C; Shing-Bruce-Li, Kevin; Paraliev, Martin; Pedrozzi, Marco; Raguin, Jean Yves; Rivkin, Leonid; Schlott, Volker; Sehr, Harald; Streun, Andreas; Wrulich, Albin F; Zelenika, Sasa

    2004-01-01

    The design of an electron gun capable of producing beam emittance one order of magnitude lower than current technology would reduce considerably the cost and size of a free electron laser emitting at 0.1nm. Field emitter arrays (FEAs) including a gate and a focusing layer are an attractive technology for such high brightness sources. Electrons are extracted from micrometric tips thanks to voltage pulses between gate and tips. The focusing layer should then reduce the initial divergence of each emitted beamlets. This FEA will be inserted in a high gradient diode configuration coupled with a radiofrequency structure. In the diode part very high electric field pulses (several hundreds of MV/m) will limit the degradation of emittance due to space charge effect. This first acceleration will be obtained with high voltage pulses (typically a megavolt in a few hundred of nanoseconds) synchronized with the low voltage pulses applied to the FEA (typically one hundred of volts in one nanosecond at frequency below kilohe...

  17. Surface modification by vacuum annealing for field emission from heavily phosphorus-doped homoepitaxial (1 1 1) diamond

    International Nuclear Information System (INIS)

    Yamada, Takatoshi; Nebel, Christoph E.; Somu, Kumaragurubaran; Shikata, Shin-ichi

    2008-01-01

    The relationship between field emission properties and C 1s core level shifts of heavily phosphorus-doped homoepitaxial (1 1 1) diamond is investigated as a function of annealing temperature in order to optimize surface carbon bonding configurations for device applications. A low field emission threshold voltage is observed from surfaces annealed at 800 deg. C for hydrogen-plasma treated surface, while a low field emission threshold voltage of wet-chemical oxidized surface is observed after annealing at 900 deg. C. The C 1s core level by X-ray photoelectron spectroscopy (XPS) showed a shoulder peak at 1 eV below the main peak over 800 and 900 deg. C annealing temperature for hydrogen-plasma treated and wet-chemical oxidized surfaces, respectively. When the shoulder peak intensity is less than 10% of the main peak intensity, lower threshold voltages are observed. This is due to the carbon-reconstruction which gives rise to a small positive electron affinity. By increasing annealing temperature, the shoulder peak ratios also increase, which indicates that a surface graphitization takes place. This leads to higher threshold voltages

  18. Synthesis and Properties of Gelators Derived from Tetraphenylethylene and Gallic Acid with Aggregation-Induced Emission

    Science.gov (United States)

    Luo, Miao; Zhou, Xie; Chi, Zhenguo; Ma, Chunping; Zhang, Yi; Liu, Siwei; Xu, Jiarui

    2013-09-01

    Two novel organogelators (TEG and TAG) based on tetraphenylethylene and 3,4,5-tris(dodecyloxy) benzoic acid were synthesized through ester bond and amido bond linkages, respectively. Compounds TEG and TAG were able to induce gelation in ethanol. Aggregation-induced enhanced emission was observed in these organogelator molecules, with increased fluorescence intensity from the solutions to the gels. The completely thermoreversible gelation occurred due to the aggregation of the organogelators. In the process, a fibrous network was formed by a combination of intermolecular hydrogen bonding, π-π stacking and van der Waals interactions. These phenomena were observed in the xerogels by field-emission scanning electron microscopy and Fourier-transform infrared spectroscopy. The results of differential scanning calorimetry and polarized optical microscopy indicated that compound TAG exhibited stable liquid crystalline phases over a wide temperature range. The linking groups have severe influence on the properties of the organogelators, which was mainly attributed to the hydrogen bonding interaction in compound TAG.

  19. Field emission characteristics of vertically aligned carbon nanotubes with honeycomb configuration grown onto glass substrate with titanium coating

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yung-Jui [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Chang, Hsin-Yueh; Chang, Hsuan-Chen [Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Shih, Yi-Ting; Su, Wei-Jhih [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Ciou, Chen-Hong [Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Chen, Yi-Ling [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Honda, Shin-ichi [Graduate School of Engineering, University of Hyogo, Himeji, Hyogo 671-2280 (Japan); Huang, Ying-Sheng [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Lee, Kuei-Yi, E-mail: kylee@mail.ntust.edu.tw [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China)

    2014-03-15

    Highlights: • We have successfully designed the honeycomb patterns on glass substrate by photolithography technique. • Honeycomb-VACNTs were synthesized successfully onto glass substrate by using thermal CVD and covered different Ti films on VACNTs by e-beam evaporation. • After coating the Ti films, the current density reached 7 mA/cm{sup 2} when the electric field was 2.5 V/μm. • The fluorescence of VACNTs with Ti 15 nm films exhibits the high brightness screen and emission uniformity. -- Abstract: Carbon nanotubes (CNTs) were grown successfully onto a glass substrate using thermal chemical vapor deposition (TCVD) with C{sub 2}H{sub 2} gas at 700 °C. The synthesized CNTs exhibited good crystallinity and a vertically aligned morphology. The vertically aligned CNTs (VACNTs) were patterned with a honeycomb configuration using photolithography and characterized using field emission (FE) applications. Owing to the electric field concentration, the FE current density of VACNTs with honeycomb configuration was higher than that of the un-patterned VACNTs. Ti was coated onto the VACNT surface utilizing the relatively lower work function property to enhance the FE current density. The FE current density reached up to 7.0 mA/cm{sup 2} at an applied electric field of 2.5 V/μm. A fluorescent screen was monitored to demonstrate uniform FE VACNTs with a honeycomb configuration. The designed field emitter provided an admirable example for FE applications.

  20. Linking Aerosol Optical Properties Between Laboratory, Field, and Model Studies

    Science.gov (United States)

    Murphy, S. M.; Pokhrel, R. P.; Foster, K. A.; Brown, H.; Liu, X.

    2017-12-01

    The optical properties of aerosol emissions from biomass burning have a significant impact on the Earth's radiative balance. Based on measurements made during the Fourth Fire Lab in Missoula Experiment, our group published a series of parameterizations that related optical properties (single scattering albedo and absorption due to brown carbon at multiple wavelengths) to the elemental to total carbon ratio of aerosols emitted from biomass burning. In this presentation, the ability of these parameterizations to simulate the optical properties of ambient aerosol is assessed using observations collected in 2017 from our mobile laboratory chasing wildfires in the Western United States. The ambient data includes measurements of multi-wavelength absorption, scattering, and extinction, size distribution, chemical composition, and volatility. In addition to testing the laboratory parameterizations, this combination of measurements allows us to assess the ability of core-shell Mie Theory to replicate observations and to assess the impact of brown carbon and mixing state on optical properties. Finally, both laboratory and ambient data are compared to the optical properties generated by a prominent climate model (Community Earth System Model (CESM) coupled with the Community Atmosphere Model (CAM 5)). The discrepancies between lab observations, ambient observations and model output will be discussed.

  1. ZnO nanorod arrays prepared by chemical bath deposition combined with rapid thermal annealing: structural, photoluminescence and field emission characteristics

    International Nuclear Information System (INIS)

    Chen, Hung-Wei; He, Hsin-Min; Lee, Yi-Mu; Yang, Hsi-Wen

    2016-01-01

    ZnO nanorod arrays were prepared by low temperature chemical bath deposition (CBD) combined with rapid thermal annealing (RTA) under different ambient conditions. The structure and morphology of the synthesized ZnO have been characterized by field-emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). The obtained ZnO samples are highly crystalline with a hexagonal wurtzite phase and also display well-aligned array structure. A pronounced effect on increased nanorod length was found for the RTA-treated ZnO as compared to the as-grown ZnO. Analysis of XRD indicates that the (0 0 2) feature peak of the as-grown ZnO was shifted towards a lower angle as compared to the peaks of RTA-treated ZnO samples due to the reduction of tensile strain along the c-axis by RTA. Photoluminescence (PL) studies reveal that the ZnO nanorod arrays receiving RTA in an O 2 environment have the sharpest UV emission band and greatest intensity ratio of near band-edge emission (NBE) to deep level emission (DLE). Additionally, the effects of RTA on the field emission properties were evaluated. The results demonstrate that RTA an O 2 environment can lower the turn-on field and improve the field enhancement factor. The stability of the field emission current was also tested for 4 h. (paper)

  2. Optical properties of a multibarrier structure under intense laser fields

    Science.gov (United States)

    Ospina, D. A.; Akimov, V.; Mora-Ramos, M. E.; Morales, A. L.; Tulupenko, V.; Duque, C. A.

    2015-11-01

    Using the diagonalization method and within the effective mass and parabolic band approximations, the energy spectrum and the wave functions are investigated in biased multibarrier structure taking into account the effects of nonresonant intense laser fields. We calculated the optical properties from the susceptibility using a nonperturbative formalism recently reported. We study the changes in the intersubband optical absorption coefficients and refraction index for several values of the dressing laser parameter and for some specific values of the electric field applied along the growth direction of the heterostructure. It is concluded from our study that the peaks in the optical absorption spectrum have redshifts or blueshifts as a function of the laser parameter and the electric field. These parameters could be suitable tools for tuning the electronic and optical properties of the multibarrier structure.

  3. High field dielectric properties of anisotropic polymer-ceramic composites

    International Nuclear Information System (INIS)

    Tomer, V.; Randall, C. A.

    2008-01-01

    Using dielectrophoretic assembly, we create anisotropic composites of BaTiO 3 particles in a silicone elastomer thermoset polymer. We study a variety of electrical properties in these composites, i.e., permittivity, dielectric breakdown, and energy density as function of ceramic volume fraction and connectivity. The recoverable energy density of these electric-field-structured composites is found to be highly dependent on the anisotropy present in the system. Our results indicate that x-y-aligned composites exhibit higher breakdown strengths along with large recoverable energy densities when compared to 0-3 composites. This demonstrates that engineered anisotropy can be employed to control dielectric breakdown strengths and nonlinear conduction at high fields in heterogeneous systems. Consequently, manipulation of anisotropy in high-field dielectric properties can be exploited for the development of high energy density polymer-ceramic systems

  4. Modification of C60/C70+Pd film structure under electric field influence during electron emission

    International Nuclear Information System (INIS)

    Czerwosz, E.; Dluzewski, P.; Kozlowski, M.

    2001-01-01

    We investigated the modification of structure of C 60 /C 70 +Pd films during cold electron emission from these films. Films were obtained by vacuum thermal deposition from two sources and were characterised before and after electron emission measurements by transmission electron microscopy and electron diffraction. Films were composed of nanocrystalline Pd objects dispersed in carbon/fullerenes matrix. I-V characteristics for electron emission were obtained in diode geometry with additionally applied voltage along the film surface. The modification of film structure occurred under applied electric field and the grouping of Pd nano crystals into bigger objects was observed

  5. Nanometer-scale discernment of field emission from tungsten surface with single carbon monoxide molecule

    Science.gov (United States)

    Matsunaga, Soichiro; Suwa, Yuji; Katagiri, Souichi

    2017-12-01

    Unusual quantized beam fluctuations were found in the emission current from a cold-field emitter (CFE) operating in an extremely high vacuum of 10-10 Pa. To clarify the microscopic mechanism behind these fluctuations, we developed a new calculation method to evaluate the field emission from a heterogeneous surface under a strong electric field of 4 × 109 V/m by using the local potential distribution obtained by a first-principles calculation, instead of by using the work function. As a result of the first-principles calculations of a single molecule adsorbed on a tungsten surface, we found that dissociative adsorption of a carbon monoxide (CO) molecule enhances the emission current by changing the potential barrier in the area surrounding the C and O adatoms when these two atoms are placed at their most stable positions. It is also found that the migration of the O atom from the most stable position reduces the emission current. These types of enhancement and reduction of the emission current quantitatively explain the observed quantized fluctuations of the CFE emission current.

  6. Design, Fabrication, and Characterization of Carbon Nanotube Field Emission Devices for Advanced Applications

    Science.gov (United States)

    Radauscher, Erich Justin

    Carbon nanotubes (CNTs) have recently emerged as promising candidates for electron field emission (FE) cathodes in integrated FE devices. These nanostructured carbon materials possess exceptional properties and their synthesis can be thoroughly controlled. Their integration into advanced electronic devices, including not only FE cathodes, but sensors, energy storage devices, and circuit components, has seen rapid growth in recent years. The results of the studies presented here demonstrate that the CNT field emitter is an excellent candidate for next generation vacuum microelectronics and related electron emission devices in several advanced applications. The work presented in this study addresses determining factors that currently confine the performance and application of CNT-FE devices. Characterization studies and improvements to the FE properties of CNTs, along with Micro-Electro-Mechanical Systems (MEMS) design and fabrication, were utilized in achieving these goals. Important performance limiting parameters, including emitter lifetime and failure from poor substrate adhesion, are examined. The compatibility and integration of CNT emitters with the governing MEMS substrate (i.e., polycrystalline silicon), and its impact on these performance limiting parameters, are reported. CNT growth mechanisms and kinetics were investigated and compared to silicon (100) to improve the design of CNT emitter integrated MEMS based electronic devices, specifically in vacuum microelectronic device (VMD) applications. Improved growth allowed for design and development of novel cold-cathode FE devices utilizing CNT field emitters. A chemical ionization (CI) source based on a CNT-FE electron source was developed and evaluated in a commercial desktop mass spectrometer for explosives trace detection. This work demonstrated the first reported use of a CNT-based ion source capable of collecting CI mass spectra. The CNT-FE source demonstrated low power requirements, pulsing

  7. Nanocrystalline silicon as the light emitting material of a field emission display device

    International Nuclear Information System (INIS)

    Biaggi-Labiosa, A; Sola, F; Resto, O; Fonseca, L F; Gonzalez-BerrIos, A; Jesus, J De; Morell, G

    2008-01-01

    A nanocrystalline Si-based paste was successfully tested as the light emitting material in a field emission display test device that employed a film of carbon nanofibers as the electron source. Stable emission in the 550-850 nm range was obtained at 16 V μm -1 . This relatively low field required for intense cathodoluminescence (CL) from the PSi paste may lead to longer term reliability of both the electron emitting and the light emitting materials, and to lower power consumption. Here we describe the synthesis, characterization, and analyses of the light emitting nanostructured Si paste and the electron emitting C nanofibers used for building the device, including x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The corresponding spectra and field emission curves are also shown and discussed

  8. Comparative field evaluation of vehicle cruise speed and acceleration level impacts on hot stabilized emissions

    International Nuclear Information System (INIS)

    El-Shawarby, Ihab; Ahn, Kyoungho; Rakha, Hesham

    2005-01-01

    The main objectives of this paper are two fold. First, the paper evaluates the impact of vehicle cruise speed and acceleration levels on vehicle fuel-consumption and emission rates using field data gathered under real-world driving conditions. Second, it validates the VT-Micro model for the modeling of real-world conditions. Specifically, an on-board emission-measurement device was used to collect emissions of oxides of nitrogen, hydrocarbons, carbon monoxide, and carbon dioxide using a light-duty test vehicle. The analysis demonstrates that vehicle fuel-consumption and emission rates per-unit distance are optimum in the range of 60-90 km/h, with considerable increase outside this optimum range. The study demonstrates that as the level of aggressiveness for acceleration maneuvers increases, the fuel-consumption and emission rates per maneuver decrease because the vehicle spends less time accelerating. However, when emissions are gathered over a sufficiently long fixed distance, fuel-consumption and mobile-source emission rates per-unit distance increase as the level of acceleration increases because of the history effects that accompany rich-mode engine operations. In addition, the paper demonstrates the validity of the VT-Micro framework for modeling steady-state vehicle fuel-consumption and emission behavior. Finally, the research demonstrates that the VT-Micro framework requires further refinement to capture non-steady-state history behavior when the engine operates in rich mode. (Author)

  9. Self-calibrating magnetic field diagnostics in beam emission spectroscopy

    International Nuclear Information System (INIS)

    Voslamber, D.

    1995-01-01

    Magnetic field diagnostics in tokamaks using the motional Stark effect in fast neutral beams have been based on two kinds of polarimetry which we call ''static'' and ''dynamic.'' A detailed analysis shows that static polarimetry presents a number of advantages over dynamic polarimetry, provided it is made complete in the sense that a sufficient number of polarization analyzers are installed and different parts of the spectrum are explored to yield full information on the set of unknowns inherent in the problem. A detailed scheme of complete static polarimetry is proposed, including the case where an in-vessel mirror with changing characteristics (coating by impurities) is placed in front of the optical detection system. The main merit of this scheme relies on the fact that it is self-calibrating with respect to both the characteristics of the mirror and the transmission of the different polarization channels, the latter item implying that it is uniquely based on relative measurements of spectra. Further advantages are a greater flexibility with regard to different kinds of diagnostics and the circumstance that the technical equipment is less involved. The above scheme is based on a detection system of moderate etendue exploiting a large spectral domain, which is the regime where static polarimetry usually operates. It is also possible, however, to work with large etendue and a small spectral domain, such as commonly adopted in dynamic polarimetry. Using such a regime, static polarimetry loses the advantages mentioned above but gains, as a new advantage, the benefit of a comparatively lower level of photon noise. copyright 1995 American Institute of Physics

  10. Electron Bernstein wave emission from an overdense reversed field pinch plasma

    International Nuclear Information System (INIS)

    Chattopadhyay, P.K.; Anderson, J.K.; Biewer, T.M.; Craig, D.; Forest, C.B.; Harvey, R.W.; Smirnov, A.P.

    2002-01-01

    Blackbody levels of emission in the electron cyclotron range of frequencies have been observed from an overdense (ω pe ∼3ω ce ) Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed field pinch plasma, a result of electrostatic electron Bernstein waves emitted from the core and mode converted into electromagnetic waves at the extreme plasma edge. Comparison of the measured radiation temperature with profiles measured by Thomson scattering indicates that the mode conversion efficiency can be as high as ∼75%. Emission is preferentially in the X-mode polarization, and is strongly dependent upon the density and magnetic field profiles at the mode conversion point

  11. Development of remote controlled type field-emission type scanning electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Yasuda, Ryo; Nishino, Yasuharu; Mita, Naoaki; Nakata, Masahito; Harada, Katsuya; Nozawa, Yukio; Amano, Hidetoshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2002-10-01

    The extending burn-up of Light Water Reactor Fuels has been promoted to reduce costs of the power generation and amount of waste mass. Information about the fuel behavior under high burn-up operation is needed to assess safety of the high burn-up fuels. Microstructures formed in high burn-up fuel pellets and Zircaloy tubes influence on their integrity. The fundamental information about morphology, sizes, and element compositions in those microstructures is necessary to estimate the formation mechanism and change in the properties of the fuels. The Field Emission type Scanning Electron Microscope (FE-SEM), which is effective for observation of very small area, i.e., nano-size structures, has been hence installed at the Reactor Fuel Examination Facility (RFEF) in JAERI. FE-SEM is designed for the remote handling type to use high radioactive materials and has equipments to keep the safety for operators. The Energy Dispersive Spectrometer (EDS) with a radiation-shielding collimator has been also equipped on FE-SEM to determine element compositions in the structures. Characterization tests were carried out using Zircaloy cladding tubes with oxide films and hydrides of confirm machine performance. In the results of the tests, high-resolution images with a magnification of 30,000 were obtained. Those results show that the apparatus maintains the original high performance with standard type. (author)

  12. A model to relate wind tunnel measurements to open field odorant emissions from liquid area sources

    Science.gov (United States)

    Lucernoni, F.; Capelli, L.; Busini, V.; Sironi, S.

    2017-05-01

    Waste Water Treatment Plants are known to have significant emissions of several pollutants and odorants causing nuisance to the near-living population. One of the purposes of the present work is to study a suitable model to evaluate odour emissions from liquid passive area sources. First, the models describing volatilization under a forced convection regime inside a wind tunnel device, which is the sampling device that typically used for sampling on liquid area sources, were investigated. In order to relate the fluid dynamic conditions inside the hood to the open field and inside the hood a thorough study of the models capable of describing the volatilization phenomena of the odorous compounds from liquid pools was performed and several different models were evaluated for the open field emission. By means of experimental tests involving pure liquid acetone and pure liquid butanone, it was verified that the model more suitable to describe precisely the volatilization inside the sampling hood is the model for the emission from a single flat plate in forced convection and laminar regime, with a fluid dynamic boundary layer fully developed and a mass transfer boundary layer not fully developed. The proportionality coefficient for the model was re-evaluated in order to account for the specific characteristics of the adopted wind tunnel device, and then the model was related with the selected model for the open field thereby computing the wind speed at 10 m that would cause the same emission that is estimated from the wind tunnel measurement furthermore, the field of application of the proposed model was clearly defined for the considered models during the project, discussing the two different kinds of compounds commonly found in emissive liquid pools or liquid spills, i.e. gas phase controlled and liquid phase controlled compounds. Lastly, a discussion is presented comparing the presented approach for emission rates recalculation in the field, with other approaches

  13. Scattering and short-distance properties in field theory models

    International Nuclear Information System (INIS)

    Iagolnitzer, D.

    1987-01-01

    The aim of constructive field theory is not only to define models but also to establish their general properties of physical interest. We here review recent works on scattering and on short-distance properties for weakly coupled theories with mass gap such as typically P(φ) in dimension 2, φ 4 in dimension 3 and the (renormalizable, asymptotically free) massive Gross-Neveu (GN) model in dimension 2. Many of the ideas would apply similarly to other (possibly non renormalizable) theories that might be defined in a similar way via phase-space analysis

  14. Mitigating nitrous oxide emissions from tea field soil using bioaugmentation with a Trichoderma viride biofertilizer.

    Science.gov (United States)

    Xu, Shengjun; Fu, Xiaoqing; Ma, Shuanglong; Bai, Zhihui; Xiao, Runlin; Li, Yong; Zhuang, Guoqiang

    2014-01-01

    Land-use conversion from woodlands to tea fields in subtropical areas of central China leads to increased nitrous oxide (N2O) emissions, partly due to increased nitrogen fertilizer use. A field investigation of N2O using a static closed chamber-gas chromatography revealed that the average N2O fluxes in tea fields with 225 kg N ha(-1) yr(-1) fertilizer application were 9.4 ± 6.2 times higher than those of woodlands. Accordingly, it is urgent to develop practices for mitigating N2O emissions from tea fields. By liquid-state fermentation of sweet potato starch wastewater and solid-state fermentation of paddy straw with application of Trichoderma viride, we provided the tea plantation with biofertilizer containing 2.4 t C ha(-1) and 58.7 kg N ha(-1). Compared to use of synthetic N fertilizer, use of biofertilizer at 225 kg N ha(-1) yr(-1) significantly reduced N2O emissions by 33.3%-71.8% and increased the tea yield by 16.2%-62.2%. Therefore, the process of bioconversion/bioaugmentation tested in this study was found to be a cost-effective and feasible approach to reducing N2O emissions and can be considered the best management practice for tea fields.

  15. The Field Emission Characteristics of Titanium-Doped Nano-Diamonds

    Institute of Scientific and Technical Information of China (English)

    YANG Yan-Ning; ZHANG Zhi-Yong; ZHANG Fu-Chun; DONG Jun-Tang; ZHAO Wu; ZHAI Chun-Xue; ZHANG Wei-Hu

    2012-01-01

    An electrophoresis solution,prepared in a specific ratio of titanium (Ti)-doped nano-diamond,is dispersed by ultrasound and the nano-diamond coating is then deposited on a polished Ti substrate by electrophoresis.After high-temperature vacuum annealing,the appearance of the surface and the microstructures of the coating are observed by a metallomicroscope,scanning electron microscopy and Raman spectroscopy.The field emission characteristics and luminescence features are also tested,and the mechanism of the field emission characteristics of the Ti-doped nano-diamond is analyzed.The experimental results show that under the same conditions,the diamond-coated surface (by deposition) is more uniform after doping with 5 mg of Ti powder.Compared with the undoped nano-diamond cathode,the turn-on fields decline from 6.95 to 5.95 V/μm.When the electric field strength is 13.80 V/μm,the field emission current density increases to 130.00 μA/cm2.Under the applied fields,the emission current is stable and the luminescence is at its best,while the field emission characteristics of the 10 mg Ti-doped coating become worse,as does the luminescence.The reason for this could be that an excessive amount of TiC is generated on the surface of the coating.%An electrophoresis solution, prepared in a speciGc ratio of titanium (Ti)-doped nano-diamond, is dispersed by ultrasound and the nano-diamond coating is then deposited on a polished Ti substrate by electrophoresis. After high-temperature vacuum annealing, the appearance of the surface and the microstructures of the coating are observed by a metallomicroscope, scanning electron microscopy and Raman spectroscopy. The field emission characteristics and luminescence features are also tested, and the mechanism of the field emission characteristics of the Ti-doped nano-diamond is analyzed. The experimental results show that under the same conditions, the diamond-coated surface (by deposition) is more uniform after doping with 5 mg of Ti

  16. Correlation of Coronal Plasma Properties and Solar Magnetic Field in a Decaying Active Region

    Science.gov (United States)

    Ko, Yuan-Kuen; Young, Peter R.; Muglach, Karin; Warren, Harry P.; Ugarte-Urra, Ignacio

    2016-01-01

    We present the analysis of a decaying active region observed by the EUV Imaging Spectrometer on Hinode during 2009 December 7-11. We investigated the temporal evolution of its structure exhibited by plasma at temperatures from 300,000 to 2.8 million degrees, and derived the electron density, differential emission measure, effective electron temperature, and elemental abundance ratios of Si/S and Fe/S (as a measure of the First Ionization Potential (FIP) Effect). We compared these coronal properties to the temporal evolution of the photospheric magnetic field strength obtained from the Solar and Heliospheric Observatory Michelson Doppler Imager magnetograms. We find that, while these coronal properties all decreased with time during this decay phase, the largest change was at plasma above 1.5 million degrees. The photospheric magnetic field strength also decreased with time but mainly for field strengths lower than about 70 Gauss. The effective electron temperature and the FIP bias seem to reach a basal state (at 1.5 x 10(exp 6) K and 1.5, respectively) into the quiet Sun when the mean photospheric magnetic field (excluding all areas correlated with each other and the correlation is the strongest in the high-temperature plasma. Such correlation properties should be considered in the quest for our understanding of how the corona is heated. The variations in the elemental abundance should especially be considered together with the electron temperature and density.

  17. Effects of organic matter application on methane emission from paddy fields adopting organic farming system

    Directory of Open Access Journals (Sweden)

    P Nungkat

    2015-01-01

    Full Text Available A study that was aimed to determine the effect of the use of organic manure and azolla on methane emission on paddy field of organic systems was conducted on paddy fields in the Gempol Village, Sambirejo District of Sragen Regency, Indonesia. The experimental design performed for this study was a completely randomized block design consisting of three factors; the factor I was rice cultivars (Mira-1; Mentik Wangi; Merah Putih; factor II was dose of organic manure (0 t/ha and 10 t/ha and factor III was Azolla inoculums dose (0 t/ha and 2 t/ha. Gas sampling was conducted 3 times in one growing season when the rice plants reached ages of 38, 66 and 90 days after planting. The results showed that there was no correlation between the uses of organic fertilizers for rice production on methane emission. The increase of methane emission was very much influenced by the redox potential. Methane emission from Mira-1 field was higher than that from Mentik Wangi and Merah Putih fields. Emission of methane gas from Mira-1 field ranged from -509.82 to 791.34 kg CH4/ha; that from Wangi ranged from -756.77 to d 547.50 kg CH4/ha and that from Merah Putih ranged from -399.63 to 459.94 kg CH4/ha. Application of 10 t organic manure /ha and 2 t azolla/ha in Mentik Wangi reduced methane emissions with a high rice production compared to Merah Putih and Mira-1.

  18. Relation between coal rank, char reactivity, textural properties and NO emissions

    Energy Technology Data Exchange (ETDEWEB)

    Arenillas, A.; Rubiera, F.; Parra, J.B.; Pis, J.J. [Instituto Nacional del Carbon, Oviedo (Spain)

    1999-07-01

    A low volatile bituminous coal was pyrolysed at different heating rates to produce chars with different textural properties. There was a linear relationship between char reactivity and active surface area. The effect of coal rank on coal char textural properties was studied using a range of bituminous coals. The influence of textural properties and reactivity on NO emissions, and on the heterogeneous reduction of NO is discussed. 6 refs., 2 figs., 2 tabs.

  19. [Effects of diurnal warming on soil N2O emission in soybean field].

    Science.gov (United States)

    Hu, Zheng-Hua; Zhou, Ying-Ping; Cui, Hai-Ling; Chen, Shu-Tao; Xiao, Qi-Tao; Liu, Yan

    2013-08-01

    To investigate the impact of experimental warming on N2O emission from soil of soybean field, outdoor experiments with simulating diurnal warming were conducted, and static dark chamber-gas chromatograph method was used to measure N2O emission fluxes. Results indicated that: the diurnal warming did not change the seasonal pattern of N2O emissions from soil. In the whole growing season, comparing to the control treatment (CK), the warming treatment (T) significantly enhanced the N2O flux and the cumulative amount of N2O by 17.31% (P = 0.019), and 20.27% (P = 0.005), respectively. The significant correlations were found between soil N2O emission and soil temperature, moisture. The temperature sensitivity values of soil N2O emission under CK and T treatments were 3.75 and 4.10, respectively. In whole growing stage, T treatment significantly increased the crop aboveground and total biomass, the nitrate reductase activity, and total nitrogen in leaves, while significantly decreased NO3(-) -N content in leaves. T treatment significantly increased soil NO3(-) -N content, but had no significant effect on soil organic carbon and total nitrogen contents. The results of this study suggested that diurnal warming enhanced N2O emission from soil in soybean field.

  20. Closed string emission from unstable D-brane with background electric field

    International Nuclear Information System (INIS)

    Nagami, Kenji

    2004-01-01

    We study the closed string emission from an unstable Dp-brane with constant background electric field in bosonic string theory. The average total number density and the average total energy density of emitted closed strings are explicitly calculated in the presence of electric field. It is explicitly shown that the energy density in the UV region becomes finite whenever the background electric field is switched on. The energy density converted into closed strings in the presence of electric field is negligibly small compared with the D-brane tension in the weak string coupling limit. (author)

  1. Room chamber assessment of the pollutant emission properties of (nominally) low-emission unflued gas heaters

    Energy Technology Data Exchange (ETDEWEB)

    Brown, S.K.; Mahoney, K.J., Min Cheng [CSIRO Manufacturing and Infrastructure Technology, Victoria (Australia)

    2004-07-01

    Pollutant emissions from unflued gas heaters were assessed in CSIRO'a Room Dynamic Environmental Chamber. This paper describes the chamber assessment procedure and presents findings for major commercial heaters that are nominally 'low-emission'. The chamber was operated at controlled conditions of temperature, humidity, ventilation and air mixing, representative of those encountered in typical indoor environments. A fixed rate of heat removal from the chamber air ensured that the heaters operated at constant heating rates, typically {approx}6 MJ/h which simulated operation of a heater after warm-up in an insulated dwelling in south-east Australia. The pollutants assessed were nitrogen dioxide, carbon monoxide, formaldehyde, VOCs and respirable suspended particulates. One type of heater was lower emitting for nigroen dioxide, but emitted greater amounts of carbon monoxide and formaldehyde (the latter becoming significant to indoor air quality). When operated with low line pressure of slight misalignment of the gas burner, this heater became a hazardous source of these pollutants. Emissions from the heates changed little after continous operation for up to 2 months. (au)

  2. Analysis of Field Emission of Fabricated Nanogap in Pd Strips for Surface Conduction Electron-Emitter Displays

    Science.gov (United States)

    Lo, Hsiang-Yu; Li, Yiming; Tsai, Chih-Hao; Pan, Fu-Ming

    2008-04-01

    We study the field emission (FE) property of a nanometer-scale gap structure in a palladium strip, which was fabricated by hydrogen absorption under high-pressure treatment. A vigorous cracking process could be accompanied by extensive atomic migration during the hydrogen treatment. A three-dimensional finite-difference time-domain particle-in-cell method is adopted to simulate the electron emission in a surface-conduction electron-emitter display (SED) device. Examinations of conducting characteristics, FE efficiency, the local field around the emitter, and the current density on the anode plate with one FE emitter are conducted. The image of a light spot is successfully produced on a phosphor plate, which implies that the explored electrode with nanometer separation possesses a potential SED application. Experimental observation and numerical simulation show that the proposed structure can be used as a surface conduction electron emitter and has a high FE efficiency with low turn-on voltage and a different electron emission mechanism. This study benefits the advanced SED design for a new type of electron source.

  3. Physical and morphological properties of z ~ 3 Lyman break galaxies: dependence on Lyα line emission

    Science.gov (United States)

    Pentericci, L.; Grazian, A.; Scarlata, C.; Fontana, A.; Castellano, M.; Giallongo, E.; Vanzella, E.

    2010-05-01

    Aims: We investigate the physical and morphological properties of Lyman break galaxies (LBGs) at redshift ~2.5 to ~3.5, to determine if and how they depend on the nature and strength of the Lyα emission. Methods: We selected U-dropout galaxies from the z-detected GOODS-MUSIC catalog by adapting the classical Lyman break criteria on the GOODS filter set. We kept only those galaxies with spectroscopic confirmation, mainly from VIMOS and FORS public observations. Using the full multi-wavelength 14-bands information (U to IRAC), we determined the physical properties of the galaxies through a standard spectral energy distribution fitting procedure with the updated Charlot & Bruzual (2009) templates. We also added other relevant observations of the GOODS field, i.e. the 24 μm observations from Spitzer/MIPS and the 2 MSec Chandra X-ray observations. Finally, using non parametric diagnostics (Gini, Concentration, Asymmetry, M20 and ellipticity), we characterized the rest-frame UV morphologies of the galaxies. We then analyzed how these physical and morphological properties correlate with the presence of the Lyα emission line in the optical spectra. Results: We find that unlike at higher redshift, the dependence of physical properties on the Lyα line is milder: galaxies without Lyα in emission tend to be more massive and dustier than the rest of the sample, but all other parameters, ages, star formation rates (SFR), X-ray emission and UV morphology do not depend strongly on the presence of the Lyα emission. A simple scenario where all LBGs have intrinsically high Lyα emission, but where the dust and neutral hydrogen content (which shapes the final appearance of the Lyα) depend on the mass of the galaxies, is able to reproduce the majority of the observed properties at z˜3. Some modification might be needed to account for the observed evolution of these properties with cosmic epoch, which is also discussed.

  4. An example of a vector field with the oriented shadowing property

    OpenAIRE

    Tikhomirov, Sergey

    2014-01-01

    We consider shadowing properties for vector fields corresponding to different type of reparametrisations. We give an example of a vector field which has the oriented shadowing properties, but does not have the standard shadowing property.

  5. Emissions of carbon dioxide and methane from fields fertilized with digestate from an agricultural biogas plant

    Science.gov (United States)

    Czubaszek, Robert; Wysocka-Czubaszek, Agnieszka

    2018-01-01

    Digestate from biogas plants can play important role in agriculture by providing nutrients, improving soil structure and reducing the use of mineral fertilizers. Still, less is known about greenhouse gas emissions from soil during and after digestate application. The aim of the study was to estimate the emissions of carbon dioxide (CO2) and methane (CH4) from a field which was fertilized with digestate. The gas fluxes were measured with the eddy covariance system. Each day, the eddy covariance system was installed in various places of the field, depending on the dominant wind direction, so that each time the results were obtained from an area where the digestate was distributed. The results showed the relatively low impact of the studied gases emissions on total greenhouse gas emissions from agriculture. Maximum values of the CO2 and CH4 fluxes, 79.62 and 3.049 µmol s-1 m-2, respectively, were observed during digestate spreading on the surface of the field. On the same day, the digestate was mixed with the topsoil layer using a disc harrow. This resulted in increased CO2 emissions the following day. Intense mineralization of digestate, observed after fertilization may not give the expected effects in terms of protection and enrichment of soil organic matter.

  6. Characterization of field-measured soil-water properties

    International Nuclear Information System (INIS)

    Nielsen, D.R.; Reichardt, K.; Wierenga, P.J.

    1983-01-01

    As part of a five-year co-ordinated research programme of the International Atomic Energy Agency, the Use of Radiation and Isotope Techniques in Studies of Soil-Water Regimes, soil physicists examined soil-water properties of one or two field sites in 11 different countries (Brazil, Belgium, Cyprus, Chile, Israel, Japan, Madagascar, Nigeria, Senegal, Syria and Thailand). The results indicate that the redistribution method yields values of soil-water properties that have a large degree of uncertainty, and that this uncertainty is not necessarily related to the kind of soil being analysed. Regardless of the fundamental cause of this uncertainty (experimental and computational errors versus natural soil variability), the conclusion is that further developments of field technology depend upon stochastic rather than deterministic concepts

  7. Effect of magnetic field on the physical properties of water

    Science.gov (United States)

    Wang, Youkai; Wei, Huinan; Li, Zhuangwen

    2018-03-01

    In this study, the effect of magnetic field (MF) on the partial physical properties of water are reported, tap water (TW) and 4 types of magnetized water (MW) were measured in the same condition. It was found that the properties of TW were changed following the MF treatment, shown as the increase of evaporation amount, the decrease of specific heat and boiling point after magnetization, the changes depend on the magnetization effect. In addition, magnetic field strength (MFS) has a marked influence on the magnetization effect, the optimal magnetizing condition was determined as the MFS of 300 mT. The findings of this study offered a facile approach to improve cooling and power generation efficiency in industrial.

  8. SURFACE FILMS TO SUPPRESS FIELD EMISSION IN HIGH-POWER MICROWAVE COMPONENTS

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay l

    2014-02-07

    Results are reported on attempts to reduce the RF breakdown probability on copper accelerator structures by applying thin surface films that could suppress field emission of electrons. Techniques for application and testing of copper samples with films of metals with work functions higher than copper are described, principally for application of platinum films, since platinum has the second highest work function of any metal. Techniques for application of insulating films are also described, since these can suppress field emission and damage on account of dielectric shielding of fields at the copper surface, and on account of the greater hardness of insulating films, as compared with copper. In particular, application of zirconium oxide films on high-field portions of a 11.424 GHz SLAC cavity structure for breakdown tests are described.

  9. Patterned growth of carbon nanotubes over vertically aligned silicon nanowire bundles for achieving uniform field emission.

    Science.gov (United States)

    Hung, Yung-Jr; Huang, Yung-Jui; Chang, Hsuan-Chen; Lee, Kuei-Yi; Lee, San-Liang

    2014-01-01

    A fabrication strategy is proposed to enable precise coverage of as-grown carbon nanotube (CNT) mats atop vertically aligned silicon nanowire (VA-SiNW) bundles in order to realize a uniform bundle array of CNT-SiNW heterojunctions over a large sample area. No obvious electrical degradation of as-fabricated SiNWs is observed according to the measured current-voltage characteristic of a two-terminal single-nanowire device. Bundle arrangement of CNT-SiNW heterojunctions is optimized to relax the electrostatic screening effect and to maximize the field enhancement factor. As a result, superior field emission performance and relatively stable emission current over 12 h is obtained. A bright and uniform fluorescent radiation is observed from CNT-SiNW-based field emitters regardless of its bundle periodicity, verifying the existence of high-density and efficient field emitters on the proposed CNT-SiNW bundle arrays.

  10. Manipulation of local optical properties and structures in molybdenum-disulfide monolayers using electric field-assisted near-field techniques.

    Science.gov (United States)

    Nozaki, Junji; Fukumura, Musashi; Aoki, Takaaki; Maniwa, Yutaka; Yomogida, Yohei; Yanagi, Kazuhiro

    2017-04-05

    Remarkable optical properties, such as quantum light emission and large optical nonlinearity, have been observed in peculiar local sites of transition metal dichalcogenide monolayers, and the ability to tune such properties is of great importance for their optoelectronic applications. For that purpose, it is crucial to elucidate and tune their local optical properties simultaneously. Here, we develop an electric field-assisted near-field technique. Using this technique we can clarify and tune the local optical properties simultaneously with a spatial resolution of approximately 100 nm due to the electric field from the cantilever. The photoluminescence at local sites in molybdenum-disulfide (MoS 2 ) monolayers is reversibly modulated, and the inhomogeneity of the charge neutral points and quantum yields is suggested. We successfully etch MoS 2 crystals and fabricate nanoribbons using near-field techniques in combination with an electric field. This study creates a way to tune the local optical properties and to freely design the structural shapes of atomic monolayers using near-field optics.

  11. Quantum field theoretic properties of nonabelian phase factors

    International Nuclear Information System (INIS)

    Wieczorek, E.

    1984-01-01

    The paper is concerned with quantum field theoretical properies of nonabelian phase factors. The phase factors defining parallel transport in fiber bundle space are the necessary tool for the construction of gauge invariant nonlocal operators describing bound states in QCD. General structures of such operators are discussed and renormalization properties as well as relations between meson and baryon operators are obtained from a study of the underlying phase factors

  12. FAR-UV EMISSION PROPERTIES OF FR1 RADIO GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Danforth, Charles W.; Stocke, John T.; France, Kevin; Begelman, Mitchell C. [Department of Astrophysical and Planetary Sciences, University of Colorado, 391-UCB, Boulder, CO 80309 (United States); Perlman, Eric, E-mail: danforth@colorado.edu [Department of Physics and Space Sciences, Florida Institute of Technology, 150 W. University Boulevard, Melbourne, FL 32901 (United States)

    2016-11-20

    The power mechanism and accretion geometry for low-power FR 1 radio galaxies are poorly understood in comparison to those for Seyfert galaxies and QSOs. In this paper, we use the diagnostic power of the Ly α recombination line observed using the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope ( HST ) to investigate the accretion flows in three well-known, nearby FR 1s: M87, NGC 4696, and Hydra A. The Ly α emission line’s luminosity, velocity structure, and the limited knowledge of its spatial extent provided by COS are used to assess conditions within a few parsecs of the supermassive black hole in these radio-mode active galactic nuclei. We observe strong Ly α emission in all three objects with total luminosity similar to that seen in BL Lacertae objects. M87 shows a complicated emission-line profile in Ly α , which varies spatially across the COS aperture and possibly temporally over several epochs of observation. In both NGC 4696 and M87, the Ly α luminosities ∼10{sup 40} erg s{sup -1} are closely consistent with the observed strength of the ionizing continuum in Case B recombination theory and with the assumption of a near-unity covering factor. It is possible that the Ly α -emitting clouds are ionized largely by beamed radiation associated with the jets. Long-slit UV spectroscopy can be used to test this hypothesis. Hydra A and the several BL Lac objects studied in this and previous papers have Ly α luminosities larger than M87 but their extrapolated, nonthermal continua are so luminous that they overpredict the observed strength of Ly α , a clear indicator of relativistic beaming in our direction. Given their substantial space density (∼4 × 10{sup -3} Mpc{sup -3}), the unbeamed Lyman continuum radiation of FR 1s may make a substantial minority contribution (∼10%) to the local UV background if all FR 1s are similar to M87 in ionizing flux level.

  13. Considerable Enhancement of Field Emission of SnO2Nanowires by Post-Annealing Process in Oxygen at High Temperature

    Directory of Open Access Journals (Sweden)

    Fang XS

    2009-01-01

    Full Text Available Abstract The field emission properties of SnO2nanowires fabricated by chemical vapor deposition with metallic catalyst-assistance were investigated. For the as-fabricated SnO2nanowires, the turn-on and threshold field were 4.03 and 5.4 V/μm, respectively. Considerable enhancement of field emission of SnO2nanowires was obtained by a post-annealing process in oxygen at high temperature. When the SnO2nanowires were post-annealed at 1,000 °C in oxygen, the turn-on and threshold field were decreased to 3.77 and 4.4 V/μm, respectively, and the current density was increased to 6.58 from 0.3 mA/cm2at the same applied electric field of 5.0 V/μm.

  14. Design and fabrication of carbon nanotube field-emission cathode with coaxial gate and ballast resistor.

    Science.gov (United States)

    Sun, Yonghai; Yeow, John T W; Jaffray, David A

    2013-10-25

    A low density vertically aligned carbon nanotube-based field-emission cathode with a ballast resistor and coaxial gate is designed and fabricated. The ballast resistor can overcome the non-uniformity of the local field-enhancement factor at the emitter apex. The self-aligned fabrication process of the coaxial gate can avoid the effects of emitter tip misalignment and height non-uniformity. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Emission properties of Mn doped ZnO nanoparticles prepared by mechanochemical processing

    Energy Technology Data Exchange (ETDEWEB)

    Sabri, Nurul Syahidah; Yahya, Ahmad Kamal [Faculty of Applied Sciences, Universiti Teknologi MARA, Shah Alam, Selangor 40450 (Malaysia); Talari, Mahesh Kumar, E-mail: talari@gmail.com [Faculty of Applied Sciences, Universiti Teknologi MARA, Shah Alam, Selangor 40450 (Malaysia)

    2012-07-15

    Mechanochemical processing was reported to introduce lot of crystal defects which can significantly influence emission properties. Nevertheless, to the best of our knowledge, there are no reports on effect of mechanochemical processing on emission properties of transition metal ion doped ZnO. In this study, Zn{sub 1-x}Mn{sub x}O nanoparticles with different Mn content (x=0, 0.02, 0.04, 0.06, 0.08, and 0.1) were prepared by mechanochemical processing to study the effect of Mn doping and processing on emission properties. Confirmation of nanoparticles size and nanocrystalline nature of hexagonal wurtzite ZnO structure is carried out using transmission electron microscopy (TEM) and selected area electron diffraction (SAED), respectively. The samples were also characterized using Fluorescence Spectroscope before and after heat-treatment. The emission studies revealed that blue emission intensity is stronger compared to UV and green emission in contrast to the earlier reports, where other synthesis routes were employed for the ZnO nanoparticles' preparation. The blue emission originates from the zinc interstitial (Zn{sub i}) and oxygen interstitial (O{sub i}) defects, which indicate that the mechanochemical route resulted in more interstitial defects compared to oxygen substitution (O{sub Zn}) and oxygen vacancy (V{sub o}) defects which otherwise would give green emission. Mn doping resulted in shifting of near-band-edge (NBE) emission and the reduction in the intensities of NBE, blue and green emissions. The initial red shift at lower Mn content could be due to s-d and p-d exchange interactions as well as band tailing effect where as the blue shift at higher Mn content can be attributed to the Burstein-Moss shift. The reduction in emission intensity could be due to non-radiative recombination processes promoted by Mn ions with increasing Mn content. - Highlights: Black-Right-Pointing-Pointer Zn{sub 1-x}Mn{sub x}O nanoparticles were prepared by mechanochemical

  16. Global volcanic aerosol properties derived from emissions, 1990-2014, using CESM1(WACCM): VOLCANIC AEROSOLS DERIVED FROM EMISSIONS

    Energy Technology Data Exchange (ETDEWEB)

    Mills, Michael J. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Schmidt, Anja [School of Earth and Environment, University of Leeds, Leeds UK; Easter, Richard [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Solomon, Susan [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge Massachusetts USA; Kinnison, Douglas E. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Ghan, Steven J. [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Neely, Ryan R. [School of Earth and Environment, University of Leeds, Leeds UK; National Centre for Atmospheric Science, University of Leeds, Leeds UK; Marsh, Daniel R. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Conley, Andrew [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Bardeen, Charles G. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Gettelman, Andrew [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA

    2016-03-06

    Accurate representation of global stratospheric aerosol properties from volcanic and non-volcanic sulfur emissions is key to understanding the cooling effects and ozone-loss enhancements of recent volcanic activity. Attribution of climate and ozone variability to volcanic activity is of particular interest in relation to the post-2000 slowing in the apparent rate of global average temperature increases, and variable recovery of the Antarctic ozone hole. We have developed a climatology of global aerosol properties from 1990 to 2014 calculated based on volcanic and non-volcanic emissions of sulfur sources. We have complied a database of volcanic SO2 emissions and plume altitudes for eruptions between 1990 and 2014, and a new prognostic capability for simulating stratospheric sulfate aerosols in version 5 of the Whole Atmosphere Community Climate Model, a component of the Community Earth System Model. Our climatology shows remarkable agreement with ground-based lidar observations of stratospheric aerosol optical depth (SAOD), and with in situ measurements of aerosol surface area density (SAD). These properties are key parameters in calculating the radiative and chemical effects of stratospheric aerosols. Our SAOD climatology represents a significant improvement over satellite-based analyses, which ignore aerosol extinction below 15 km, a region that can contain the vast majority of stratospheric aerosol extinction at mid- and high-latitudes. Our SAD climatology significantly improves on that provided for the Chemistry-Climate Model Initiative, which misses 60% of the SAD measured in situ. Our climatology of aerosol properties is publicly available on the Earth System Grid.

  17. Synthesis and atmospheric pressure field emission operation of W18O49 nanowires

    NARCIS (Netherlands)

    Agiral, A.; Gardeniers, Johannes G.E.

    2008-01-01

    Tungsten oxide W18O49 nanorods with diameters of 15−20 nm were grown on tungsten thin films exposed to ethene and nitrogen at 700 °C at atmospheric pressure. It was found that tungsten carbide formation enhances nucleation and growth of nanorods. Atmospheric pressure field emission measurements in

  18. Field emission characteristics of ZnO nanoneedle array cell under ultraviolet irradiation

    International Nuclear Information System (INIS)

    Lee, Woong; Jeong, Min-Chang; Kim, Min Jun; Myoung, Jae-Min

    2007-01-01

    Field emission (FE) behaviours of ZnO nanoneedle array under ultraviolet (UV) irradiation have been investigated. UV irradiation noticeably stabilized the FE behaviours. Modifications in the tunnelling barrier height and effective aspect ratio due to the oxygen-related surface species, which can be desorbed by UV irradiation, are supposed to be responsible for these observations

  19. Field determination of multipollutant, open area combustion source emission factors with a hexacopter unmanned aerial vehicle

    Science.gov (United States)

    An emission sensor/sampler system was coupled to a NASA hexacopter unmanned aerial system (UAS) to characterize gases and particles in the plume emitted from open burning of military ordnance. The UAS/sampler was tested at two field sites resulting in 33 flights at Radford, VA a...

  20. A vertex including emission of spin fields for an arbitrary bc system

    International Nuclear Information System (INIS)

    Di Vecchia, P.; Madsen, R.A.; Roland, K.

    1990-01-01

    We construct the (N+2M) Point Vertex involving the emission of N Neveu-Schwarz and 2M Ramond states for a bosonic and fermionic bc system with a bockground charge Q. From it one can compute correlation functions on the sphere involving any number of spin fields. We show in detail that the vertex satisfies overlap conditions. (orig.)

  1. Emissions from Prescribed Burning of Agricultural Fields in the Pacific Northwest

    Science.gov (United States)

    Prescribed burns of winter wheat stubble and Kentucky bluegrass fields in northern Idaho and eastern Washington states (U.S.A.) were sampled using ground-, aerostat-, airplane-, and laboratory-based measurement platforms to determine emission factors, compare methods, and provide...

  2. Field emission scanning electron microscopy (FE-SEM) as an approach for nanoparticle detection inside cells

    Czech Academy of Sciences Publication Activity Database

    Havrdová, M.; Poláková, K.; Skopalík, J.; Vůjtek, M.; Mokdad, A.; Homolková, M.; Tuček, J.; Nebesářová, Jana; Zbořil, R.

    2014-01-01

    Roč. 67, DEC 2014 (2014), s. 149-154 ISSN 0968-4328 Institutional support: RVO:60077344 Keywords : Field emission scanning electronmicroscopy (FE-SEM) * Stem cells * Iron oxide nanoparticles * Cellular morphology * Endosomes * Cell uptake Subject RIV: FD - Oncology ; Hematology Impact factor: 1.988, year: 2014

  3. Characteristics of a single photon emission tomography system with a wide field gamma camera

    International Nuclear Information System (INIS)

    Mathonnat, F.; Soussaline, F.; Todd-Pokropek, A.E.; Kellershohn, C.

    1979-01-01

    This text summarizes a work study describing the imagery possibilities of a single photon emission tomography system composed of a conventional wide field gamma camera, connected to a computer. The encouraging results achieved on the various phantoms studied suggest a significant development of this technique in clinical work in Nuclear Medicine Departments [fr

  4. Field emission characteristics of a small number of carbon fiber emitters

    Directory of Open Access Journals (Sweden)

    Wilkin W. Tang

    2016-09-01

    Full Text Available This paper reports an experiment that studies the emission characteristics of small number of field emitters. The experiment consists of nine carbon fibers in a square configuration. Experimental results show that the emission characteristics depend strongly on the separation between each emitter, providing evidence of the electric field screening effects. Our results indicate that as the separation between the emitters decreases, the emission current for a given voltage also decreases. The authors compare the experimental results to four carbon fiber emitters in a linear and square configurations as well as to two carbon fiber emitters in a paired array. Voltage-current traces show that the turn-on voltage is always larger for the nine carbon fiber emitters as compared to the two and four emitters in linear configurations, and approximately identical to the four emitters in a square configuration. The observations and analysis reported here, based on Fowler-Nordheim field emission theory, suggest the electric field screening effect depends critically on the number of emitters, the separation between them, and their overall geometric configuration.

  5. Architectured Bi{sub 2}S{sub 3} nanoflowers: photoenhanced field emission study

    Energy Technology Data Exchange (ETDEWEB)

    Warule, Sambhaji S.; Kashid, Ranjit V.; Shinde, Deodatta R. [University of Pune, Center for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics (India); Chaudhari, Nilima S.; Kale, Bharat B., E-mail: kbbb1@yahoo.com [Centre for Materials for Electronics Technology (C-MET), Department of Information Technology, Government of India (India); More, Mahendra A., E-mail: mam@physics.unipune.ac.in [University of Pune, Center for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics (India)

    2012-06-15

    In the present investigation, we demonstrate a facile hydrothermal/solvothermal route to fabricate elegant Bi{sub 2}S{sub 3} nanoflowers in large scale with highly oriented (001) surfaces. The synthesis route was observed to radically determine the overall morphology of the resultant product. Under hydrothermal conditions (12 h), formation of Bi{sub 2}S{sub 3} flowers on nickel foil composed with the self-assembled tapered nanorods were obtained. Whereas after prolonged reaction time (24 h), formation of ultra long micro belts were observed. Interestingly, the architectured Bi{sub 2}S{sub 3} flowers obtained by solvothermal route are seen to be composed with self assembled nanorods and it was also observed that the synthesis duration influences their shape, size, and areal density. Finding of such unique nanostructures on nickel foil arose by hydrothermal route exemplify a prominent photoenhanced field emission upon visible light illumination, which is attributed to the photoconductivity of Bi{sub 2}S{sub 3}. It is noteworthy that the field emission studies reveal low turn-on field of {approx}1.04 V/{mu}m, required to draw an emission current density of {approx}0.1 {mu}A/cm{sup 2}, which is found to be lower than the earlier reports. The average emission current is observed to be stable over the duration of 3 h. In addition, field emission behavior of a single Bi{sub 2}S{sub 3} flower (pasted on a tungsten microtip) has also been investigated. The high sensitivity and fast response of photoenhanced emission current switching indicate the Bi{sub 2}S{sub 3} nanoflowers as a promising candidate for micro/nano-optoelectronic devices.Graphical abstract.

  6. Seyfert Galaxies: Radio Continuum Emission Properties and the ...

    Indian Academy of Sciences (India)

    sample of Seyfert galaxies in the framework of the unification scheme. Key words. Galaxies: ... 25/49 sub-fields. Self-calibration is used iteratively to improve the image quality. 4. ... Antonucci, R. R. J., Miller, J. S. 1985, Astrophys. J., 297, 621.

  7. Influence of complex particle emission on properties of giant dipole resonance of hot nuclei

    International Nuclear Information System (INIS)

    Wen Wanxin; Jin Genming

    2003-01-01

    The possible reasons for the discrepancy between calculation results based on the statistical evaporation model and experimental data of giant dipole resonance of very hot nuclei are discussed. Both of simulations with the standard CASCADE code and the code coupling complex particle emission are carried out. It is shown that the complex particle emission affects the properties of giant dipole resonance of very hot nuclei

  8. Topological and statistical properties of nonlinear force-free fields

    Science.gov (United States)

    Mangalam, A.; Prasad, A.

    2018-01-01

    We use our semi-analytic solution of the nonlinear force-free field equation to construct three-dimensional magnetic fields that are applicable to the solar corona and study their statistical properties for estimating the degree of braiding exhibited by these fields. We present a new formula for calculating the winding number and compare it with the formula for the crossing number. The comparison is shown for a toy model of two helices and for realistic cases of nonlinear force-free fields; conceptually the formulae are nearly the same but the resulting distributions calculated for a given topology can be different. We also calculate linkages, which are useful topological quantities that are independent measures of the contribution of magnetic braiding to the total free energy and relative helicity of the field. Finally, we derive new analytical bounds for the free energy and relative helicity for the field configurations in terms of the linking number. These bounds will be of utility in estimating the braided energy available for nano-flares or for eruptions.

  9. Breakdown coefficients and scaling properties of rain fields

    Directory of Open Access Journals (Sweden)

    D. Harris

    1998-01-01

    Full Text Available The theory of scale similarity and breakdown coefficients is applied here to intermittent rainfall data consisting of time series and spatial rain fields. The probability distributions (pdf of the logarithm of the breakdown coefficients are the principal descriptor used. Rain fields are distinguished as being either multiscaling or multiaffine depending on whether the pdfs of breakdown coefficients are scale similar or scale dependent, respectively. Parameter  estimation techniques are developed which are applicable to both multiscaling and multiaffine fields. The scale parameter (width, σ, of the pdfs of the log-breakdown coefficients is a measure of the intermittency of a field. For multiaffine fields, this scale parameter is found to increase with scale in a power-law fashion consistent with a bounded-cascade picture of rainfall modelling. The resulting power-law exponent, H, is indicative of the smoothness of the field. Some details of breakdown coefficient analysis are addressed and a theoretical link between this analysis and moment scaling analysis is also presented. Breakdown coefficient properties of cascades are also investigated in the context of parameter estimation for modelling purposes.

  10. Properties and simulation of α-permanental random fields

    DEFF Research Database (Denmark)

    Møller, Jesper; Rubak, Ege Holger

    An α-permanental random field is briefly speaking a model for a collection of random variables with positive associations, where α is a positive number and the probability generating function is given in terms of a covariance or more general function so that density and moment expressions are given...... by certain α-permanents. Though such models possess many appealing probabilistic properties, many statisticians seem unaware of  α-permanental random fields and their potential applications. The purpose of this paper is first to summarize useful probabilistic results using the simplest possible setting......, and second to study stochastic constructions and simulation techniques, which should provide a useful basis for discussing the statistical aspects in future work. The paper also discusses some examples of  α-permanental random fields....

  11. String field theory. Algebraic structure, deformation properties and superstrings

    International Nuclear Information System (INIS)

    Muenster, Korbinian

    2013-01-01

    This thesis discusses several aspects of string field theory. The first issue is bosonic open-closed string field theory and its associated algebraic structure - the quantum open-closed homotopy algebra. We describe the quantum open-closed homotopy algebra in the framework of homotopy involutive Lie bialgebras, as a morphism from the loop homotopy Lie algebra of closed string to the involutive Lie bialgebra on the Hochschild complex of open strings. The formulation of the classical/quantum open-closed homotopy algebra in terms of a morphism from the closed string algebra to the open string Hochschild complex reveals deformation properties of closed strings on open string field theory. In particular, we show that inequivalent classical open string field theories are parametrized by closed string backgrounds up to gauge transformations. At the quantum level the correspondence is obstructed, but for other realizations such as the topological string, a non-trivial correspondence persists. Furthermore, we proof the decomposition theorem for the loop homotopy Lie algebra of closed string field theory, which implies uniqueness of closed string field theory on a fixed conformal background. Second, the construction of string field theory can be rephrased in terms of operads. In particular, we show that the formulation of string field theory splits into two parts: The first part is based solely on the moduli space of world sheets and ensures that the perturbative string amplitudes are recovered via Feynman rules. The second part requires a choice of background and determines the real string field theory vertices. Each of these parts can be described equivalently as a morphism between appropriate cyclic and modular operads, at the classical and quantum level respectively. The algebraic structure of string field theory is then encoded in the composition of these two morphisms. Finally, we outline the construction of type II superstring field theory. Specific features of the

  12. Investigation of Influence of Surface Nanoparticle on Emission Properties of Scandia-Doped Dispenser Cathodes

    Science.gov (United States)

    Zhang, Xizhu; Wang, Jinshu; Wang, Yiman; Liu, Wei; Zhou, Meiling; Gao, Zhiyuan

    2013-06-01

    The microstructure of a fully activated scandia doped dispenser (SDD) cathode has been studied by scanning electron microscope (SEM). The observation results display that nanoparticles appear at the growth steps and the surface of tungsten grains of the fully activated SDD cathode. To study the influence of the nanoparticles on the emission, the local electric field strengths around the nanoparticles have been calculated by Maxwell 2D code and Comsol. The calculation results show that the local electric field strengths are enhanced by 1.1 to 3.8 times to average value based on different model conditions. The highest field strength is about 1.54 × 105 V/cm at an average field strength of 40 KV/cm, which is related to a space-charge limited (SCL) current density of 100 A/cm2 in the experimental configuration. This implies the field strength is not high enough to cause field emission.

  13. Possible Correlations between the Emission Properties of SGRBs and Their Offsets from the Host Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shuai; Jin, Zhi-Ping; Li, Xiang; Fan, Yi-Zhong; Wei, Da-Ming [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210008 (China); Zhang, Fu-Wen, E-mail: jin@pmo.ac.cn, E-mail: yzfan@pmo.ac.cn, E-mail: dmwei@pmo.ac.cn [College of Science, Guilin University of Technology, Guilin 541004 (China)

    2017-07-20

    Short gamma-ray bursts (SGRBs) are widely believed to be from mergers of binary compact objects involving at least one neutron star and hence have a broad range of spatial offsets from their host galaxies. In this work, we search for possible correlations between the emission properties of 18 SGRBs and their offsets from the host galaxies. The SGRBs with and without extended emission do not show significant differences between their offset distributions, in agreement with some previous works. There are, however, possible correlations between the optical and X-ray afterglow emission and the offsets. The underlying physical origins are examined.

  14. Effect of solvent-controlled aggregation on the intrinsic emission properties of PAMAM dendrimers

    International Nuclear Information System (INIS)

    Jasmine, Maria J.; Kavitha, Manniledam; Prasad, Edamana

    2009-01-01

    Solvent-induced aggregation and its effect on the intrinsic emission properties of amine, hydroxy and carboxylate terminated, poly(amidoamine) (PAMAM) dendrimers have been investigated in glycerol, ethylene glycol, methanol, ethylene diamine and water. Altering the solvent medium induces remarkable changes in the intrinsic emission properties of the PAMAM dendrimers at identical concentration. Upon excitation at 370 nm, amine terminated PAMAM dendrimer exhibits an intense emission at 470 nm in glycerol, ethylene glycol as well as glycerol-water mixtures. Conversely, weak luminescence is observed for hydroxy and carboxylate terminated PAMAM dendrimers in the same solvent systems. When the solvent is changed to ethylene diamine, hydroxy terminated PAMAM exhibits intense blue emission at 425 nm. While the emission intensity is varied when the solvent milieu is changed, excited state lifetime values of PAMAM dendrimers remain independent of the solvent used. UV-visible absorption and dynamic light scattering (DLS) experiments confirm the formation of solvent-controlled dendrimer aggregates in the systems. Comparison of the fluorescence and DLS data reveals that the size distribution of the dendrimer aggregates in each solvent system is distinct, which control the intrinsic emission intensity from PAMAM dendrimers. The experimental results suggest that intrinsic emission intensity from PAMAM dendrimers can be regulated by proper selection of solvents at neutral conditions and room temperature

  15. PestLCI - a model for estimating field emissions of pesticides in agricultural LCA

    DEFF Research Database (Denmark)

    Birkved, Morten; Hauschild, Michael Zwicky

    2006-01-01

    of a product or service is a specific element of LCA termed life cycle inventory (LCI). Estimation of chemical emissions in agricultural LCA is typically based on standard emission factors which at best are determined by a few physical-chemical substance properties and the use scenario of the chemical compound...... to the different environmental compartments. It estimates the fractions of the applied quantity which is emitted to the air, surface water, and groundwater compartment based on information which will normally be available to the model user about: type and time of application, crop species and development stage...... for other regions of the world. (c) 2006 Elsevier B.V. All rights reserved....

  16. Correlation of Coronal Plasma Properties and Solar Magnetic Field in a Decaying Active Region

    Science.gov (United States)

    Ko, Yuan-Kuen; Young, Peter R.; Muglach, Karin; Warren, Harry P.; Ugarte-Urra, Ignacio

    2016-01-01

    We present the analysis of a decaying active region observed by the EUV Imaging Spectrometer on Hinode during 2009 December 7-11. We investigated the temporal evolution of its structure exhibited by plasma at temperatures from 300,000 to 2.8 million degrees, and derived the electron density, differential emission measure, effective electron temperature, and elemental abundance ratios of Si/S and Fe/S (as a measure of the First Ionization Potential (FIP) Effect). We compared these coronal properties to the temporal evolution of the photospheric magnetic field strength obtained from the Solar and Heliospheric Observatory Michelson Doppler Imager magnetograms. We find that, while these coronal properties all decreased with time during this decay phase, the largest change was at plasma above 1.5 million degrees. The photospheric magnetic field strength also decreased with time but mainly for field strengths lower than about 70 Gauss. The effective electron temperature and the FIP bias seem to reach a basal state (at 1.5 x 10(exp 6) K and 1.5, respectively) into the quiet Sun when the mean photospheric magnetic field (excluding all areas <10 G) weakened to below 35 G, while the electron density continued to decrease with the weakening field. These physical properties are all positively correlated with each other and the correlation is the strongest in the high-temperature plasma. Such correlation properties should be considered in the quest for our understanding of how the corona is heated. The variations in the elemental abundance should especially be considered together with the electron temperature and density.

  17. Solid state cathodoluminescence and the properties of its two emission peaks

    International Nuclear Information System (INIS)

    Xu Xurong

    2007-01-01

    We discovered solid state cathodoluminescence (SSCL). For its identification we excluded all artifacts, carried out its cross proof and studied its generality. Its spectrum is characterized by the appearance of short wavelength peak when the applied voltage is increased. Three voltage ranges are distinguished, in the lower voltage range we have the long wavelength emission, in the middle range we have both long and short wavelength emissions, and in the higher voltage range we have only the short wavelength emission. The mechanism of this spectral shift lies in the electrical field ionization of excitons. This effect initiates the applicability of band model besides molecular excitons theory. The temporal behaviors of both peaks in SSCL are studied with a method of estimating lifetime by means of frequency dependence on intensity. The lifetime of short wavelength emission is found to be 5 ms and that of long wavelength emission is less than 0.05 ms

  18. Nonlinear mean field theory for nuclear matter and surface properties

    International Nuclear Information System (INIS)

    Boguta, J.; Moszkowski, S.A.

    1983-01-01

    Nuclear matter properties are studied in a nonlinear relativistic mean field theory. We determine the parameters of the model from bulk properties of symmetric nuclear matter and a reasonable value of the effective mass. In this work, we stress the nonrelativistic limit of the theory which is essentially equivalent to a Skyrme hamiltonian, and we show that most of the results can be obtained, to a good approximation, analytically. The strength of the required parameters is determined from the binding energy and density of nuclear matter and the effective nucleon mass. For realistic values of the parameters, the nonrelativistic approximation turns out to be quite satisfactory. Using reasonable values of the parameters, we can account for other key properties of nuclei, such as the spin-orbit coupling, surface energy, and diffuseness of the nuclear surface. Also the energy dependence of the nucleon-nucleus optical model is accounted for reasonably well except near the Fermi surface. It is found, in agreement with empirical results, that the Landau parameter F 0 is quite small in normal nuclear matter. Both density dependence and momentum dependence of the NN interaction, but especially the former, are important for nuclear saturation. The required scalar and vector coupling constants agree fairly well with those obtained from analyses of NN scattering phase shifts with one-boson-exchange models. The mean field theory provides a semiquantitative justification for the weak Skyrme interaction in odd states. The strength of the required nonlinear term is roughly consistent with that derived using a new version of the chiral mean field theory in which the vector mass as well as the nucleon mass is generated by the sigma-field. (orig.)

  19. Spectral properties of X-ray selected narrow emission line galaxies

    Science.gov (United States)

    Romero-Colmenero, E.

    1998-03-01

    This thesis reports a study of the X-ray and optical properties of two samples of X-ray selected Narrow Emission Line Galaxies (NELGs), and their comparison with the properties of broad line Active Galactic Nuclei (AGN). One sample (18 NELGs) is drawn from the ROSAT International X-ray Optical Survey (RIXOS), the other (19 NELGs and 33 AGN) from the ROSAT UK Deep Survey. ROSAT multi-channel X-ray spectra have been extracted and fitted with power-law, bremsstrahlung and black body models for the brighter RIXOS sources. In most cases, power-law and bremsstrahlung models provide the best results. The average spectral energy index, alpha, of the RIXOS NELGs is 0.96 +/- 0.07, similar to that of AGN (alpha~1). For the fainter RIXOS NELGs, as well as for all the UK Deep Survey sources, counts in three spectral bands have been extracted and fitted with a power-law model, assuming the Galactic value for N_H. The brighter RIXOS sources demonstrated that the results obtained by these two different extraction and fitting procedures provide consistent results. Two average X-ray spectra, one for the NELGs and another for the AGN, were created from the UK Deep Survey sources. The power-law slope of the average NELG is alpha = 0.45 +/- 0.09, whilst that of the AGN is alpha = 0.96 +/- 0.03. ROSAT X-ray surveys have shown that the fractional surface density of NELGs increases with respect to AGN at faint fluxes (case for NELGs to be major contributors to the XRB at the fainter fluxes. The analysis of optical spectroscopy, obtained on La Palma and Hawaii, shows that NELGs form a very heterogeneous group, made up of a mixture of Seyfert 2, LINER and HII-region like galaxies. Seyfert 2 galaxies are found to possess in general the steepest X-ray slopes. Ways to explain this in the context of the unified model of AGN are discussed. The FWHM of some emission lines (Halpha, Hbeta, [NII]) in the NELGs appears to increase with steepening X-ray spectral slope. In the case of the Balmer lines

  20. Structure reactivity relationships during N2O hydrogenation over Au-Ag alloys: A study by field emission techniques

    Science.gov (United States)

    Jacobs, Luc; Barroo, Cédric; Gilis, Natalia; Lambeets, Sten V.; Genty, Eric; Visart de Bocarmé, Thierry

    2018-03-01

    To make available atomic oxygen at the surface of a catalyst is the key step for oxidation reactions on Au-based catalysts. In this context, Au-Ag alloys catalysts exhibit promising properties for selective oxidation reactions of alcohols: low temperature activity and high selectivity. The presence of O(ads) and its effects on the catalytic reactivity is studied via the N2O dissociative adsorption and subsequent hydrogenation. Field emission techniques are particularly suited to study this reaction: Field Ion Microscopy (FIM) and Field Emission Microscopy (FEM) enable to image the extremity of sharp metallic tips, the size and morphology of which are close to those of one single catalytic particle. The reaction dynamics is studied in the 300-320 K temperature range and at a pressure of 3.5 × 10-3 Pa. The main results are a strong structure/reactivity relationship during N2O + H2 reaction over Au-8.8 at.%Ag model catalysts. Comparison of high-resolution FIM images of the clean sample and FEM images during reaction shows a sensitivity of the reaction to the local structure of the facets, independently of the used partial pressures of both N2O and H2. This suggests a localised dissociative adsorption step for N2O and H2 with the formation of a reactive interface around the {210} facets.

  1. Low temperature synthesis and field emission characteristics of single to few layered graphene grown using PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Avshish; Khan, Sunny; Zulfequar, M.; Harsh; Husain, Mushahid, E-mail: mush_reslab@rediffmail.com

    2017-04-30

    Highlights: • Graphene was synthesized by PECVD system at a low temperature of 600 °C. • From different characterization techniques, the presence of single and few layered graphene was confirmed. • X-ray diffraction pattern of the graphene showed single crystalline nature of the film. • The as-grown graphene films were observed extremely good field emitters with long term emission current stability. - Abstract: In this work, high-quality graphene has successfully been synthesized on copper (Cu) coated Silicon (Si) substrate at very large-area by plasma enhanced chemical vapor deposition system. This method is low cost and highly effective for synthesizing graphene relatively at low temperature of 600 °C. Electron microscopy images have shown that surface morphology of the grown samples is quite uniform consisting of single layered graphene (SLG) to few layered graphene (FLG). Raman spectra reveal that graphene has been grown with high-quality having negligible defects and the observation of G and G' peaks is also an indicative of stokes phonon energy shift caused due to laser excitation. Scanning probe microscopy image also depicts the synthesis of single to few layered graphene. The field emission characteristics of as-grown graphene samples were studied in a planar diode configuration at room temperature. The graphene samples were observed to be a good field emitter having low turn-on field, higher field amplification factor and long term emission current stability.

  2. High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures

    Science.gov (United States)

    Gupta, Bipin Kumar; Kedawat, Garima; Gangwar, Amit Kumar; Nagpal, Kanika; Kashyap, Pradeep Kumar; Srivastava, Shubhda; Singh, Satbir; Kumar, Pawan; Suryawanshi, Sachin R.; Seo, Deok Min; Tripathi, Prashant; More, Mahendra A.; Srivastava, O. N.; Hahm, Myung Gwan; Late, Dattatray J.

    2018-01-01

    The vertical aligned carbon nanotubes (CNTs)-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si) wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness) as a barrier layer and iron (Fe, 1.5 nm thickness) as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2-30 walls with an inner diameter of 3-8 nm. Raman spectrum analysis shows G-band at 1580 cm-1 and D-band at 1340 cm-1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm), low turn-on field (0.6 V/μm) and field enhancement factor (6917) with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources.

  3. High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures

    Directory of Open Access Journals (Sweden)

    Bipin Kumar Gupta

    2018-01-01

    Full Text Available The vertical aligned carbon nanotubes (CNTs-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness as a barrier layer and iron (Fe, 1.5 nm thickness as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2–30 walls with an inner diameter of 3–8 nm. Raman spectrum analysis shows G-band at 1580 cm−1 and D-band at 1340 cm−1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm, low turn-on field (0.6 V/μm and field enhancement factor (6917 with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources.

  4. Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

    Energy Technology Data Exchange (ETDEWEB)

    Venkattraman, Ayyaswamy [Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036 (India)

    2013-11-15

    The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential and the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 μm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission.

  5. MAGNETIC FIELD STRUCTURE OF THE LARGE MAGELLANIC CLOUD FROM FARADAY ROTATION MEASURES OF DIFFUSE POLARIZED EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Mao, S. A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); McClure-Griffiths, N. M.; McConnell, D. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Epping, NSW 1710 (Australia); Gaensler, B. M. [Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Haverkorn, M. [Department of Astrophysics, Radboud University, P.O. Box 9010, 6500-GL Nijmegen (Netherlands); Beck, R. [Max-Planck-Institut fuer Radioastronomie, D-53121 Bonn (Germany); Wolleben, M. [Square Kilometre Array South Africa, The Park, Pinelands 7405 (South Africa); Stanimirovic, S. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Dickey, J. M. [Physics Department, University of Tasmania, Hobart, TAS 7001 (Australia); Staveley-Smith, L., E-mail: mao@astro.wisc.edu [International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, Crawley, WA 6009 (Australia)

    2012-11-01

    We present a study of the magnetic field of the Large Magellanic Cloud (LMC), carried out using diffuse polarized synchrotron emission data at 1.4 GHz acquired at the Parkes Radio Telescope and the Australia Telescope Compact Array. The observed diffuse polarized emission is likely to originate above the LMC disk on the near side of the galaxy. Consistent negative rotation measures (RMs) derived from the diffuse emission indicate that the line-of-sight magnetic field in the LMC's near-side halo is directed coherently away from us. In combination with RMs of extragalactic sources that lie behind the galaxy, we show that the LMC's large-scale magnetic field is likely to be of quadrupolar geometry, consistent with the prediction of dynamo theory. On smaller scales, we identify two brightly polarized filaments southeast of the LMC, associated with neutral hydrogen arms. The filaments' magnetic field potentially aligns with the direction toward the Small Magellanic Cloud (SMC). We suggest that tidal interactions between the SMC and the LMC in the past 10{sup 9} years are likely to have shaped the magnetic field in these filaments.

  6. Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

    International Nuclear Information System (INIS)

    Venkattraman, Ayyaswamy

    2013-01-01

    The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential and the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 μm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission

  7. Particle-in-cell modeling of the nanosecond field emission driven discharge in pressurized hydrogen

    Science.gov (United States)

    Levko, Dmitry; Yatom, Shurik; Krasik, Yakov E.

    2018-02-01

    The high-voltage field-emission driven nanosecond discharge in pressurized hydrogen is studied using the one-dimensional Particle-in-Cell Monte Carlo collision model. It is obtained that the main part of the field-emitted electrons becomes runaway in the thin cathode sheath. These runaway electrons propagate the entire cathode-anode gap, creating rather dense (˜1012 cm-3) seeding plasma electrons. In addition, these electrons initiate a streamer propagating through this background plasma with a speed ˜30% of the speed of light. Such a high streamer speed allows the self-acceleration mechanism of runaway electrons present between the streamer head and the anode to be realized. As a consequence, the energy of runaway electrons exceeds the cathode-anode gap voltage. In addition, the influence of the field emission switching-off time is analyzed. It is obtained that this time significantly influences the discharge dynamics.

  8. Field-emission liquid-metal ion source and triode ion gun

    International Nuclear Information System (INIS)

    Komuro, M.; Kawakatsu, H.

    1981-01-01

    A pointed-filament-type field-emission liquid-metal ion source is designed and employed as a gold ion source. By adding a crossbar across a hairpin bend, the amount of the gold adhering on the filament is increased. The lifetime is estimated to be over 200 h at 10-mA emission current. The emission current increases with increasing extraction voltage up to a saturation value which is ascribed to a limitation of the supply of liquid gold to the needle apex. The value of current density per unit solid angle is 30 mA/sr at a total current of 30 mA, which is of the same order as that obtained from a gallium ion source previously reported. Emission current fluctuations of a few tens of percent of the dc component are observed. In order to regulate the emission current and suppress current fluctuations, a bias electrode in addition to a counterelectrode is placed close to the needle apex. With such a triode structure, the emission current is regulated by a bias voltage of several hundred volts and stabilized to within 1% by means of feedback to the bias voltage of a current monitor output

  9. Diurnal variation of methane emission from a paddy field in Brazilian Southeast

    Directory of Open Access Journals (Sweden)

    Magda Aparecida de Lima

    2018-04-01

    Full Text Available ABSTRACT: This study aimed to investigate the diurnal variation of methane (CH4 emission in a flooded-irrigated rice field at different stages of the plant development under tropical climate in three growing seasons, in order to determine the most appropriate time for gas sampling in the Brazilian Southeast region. It aimed also to verify correlations between CH4 flux and air, water and soil temperatures, and solar radiation. The CH4 emissions were measured every 3-hour interval on specific days in different development stages of the flooded rice in the Experiment Station of the Agência Paulista de Tecnologia dos Agronegócios (APTA, Pólo Regional Vale do Paraíba, at Pindamonhangaba, State of São Paulo (22°55’ S, 45°30’ W, Brazil. Different CH4 emission rates were observed among the plant growth stages and also among the growing seasons. The CH4 emission showed high correlation with the soil temperature at 2cm depth. At this depth, the CH4 emission activation energy in response to soil temperature was higher in the stage R2. Emission peaks were observed at afternoon, while lower fluxes were recorded at the early morning. The most appropriate local time for gas sampling was estimated at 12:11:15a.m.±01:14:16 and 09:05:49p.m.±01:29:04.

  10. Scalar boson emission by electrons in the Weinberg-Salam theory under a constant electromagnetic field

    International Nuclear Information System (INIS)

    Rodionov, V.N.; Studenikin, A.I.

    1985-01-01

    Consideration of processes with the assistance of virtual and real Higgs scalar neutral σ-bosons in the presence of a constant external crossed electromagnetic field is conducted. In the second order of the perturbation theory in the Weinberg-Jalam model corresponding contribution into mass lepton operator in this base probability dependence of σ-boson emission and radiation field σ-bosn effects on the crossed field parameter is investigated: x=√(eFsub(μν)psup(ν)sup(2)/msup(3)

  11. Properties of bare strange stars associated with surface electric fields

    International Nuclear Information System (INIS)

    Picanco Negreiros, Rodrigo; Mishustin, Igor N.; Schramm, Stefan; Weber, Fridolin

    2010-01-01

    In this paper we investigate the electrodynamic surface properties of bare strange quark stars. The surfaces of such objects are characterized by the formation of ultrahigh electric surface fields which might be as high as ∼10 19 V/cm. These fields result from the formation of electric dipole layers at the stellar surfaces. We calculate the increase in gravitational mass associated with the energy stored in the electric dipole field, which turns out to be only significant if the star possesses a sufficiently strong net electric charge distribution. In the second part of the paper, we explore the intriguing possibility of what happens when the electron layer (sphere) rotates with respect to the stellar strange matter body. We find that in this event magnetic fields can be generated which, for moderate effective rotational frequencies between the electron layer and the stellar body, agree with the magnetic fields inferred for several central compact objects. These objects could thus be comfortably interpreted as strange stars whose electron atmospheres rotate at frequencies that are moderately different (∼10 Hz) from the rotational frequencies of the strange star itself.

  12. Field emission device driven by self-powered contact-electrification: Simulation and experimental analysis

    Science.gov (United States)

    Chen, Xiangyu; Jiang, Tao; Sun, Zhuo; Ou-Yang, Wei

    2015-09-01

    A self-powered field emission device (FED) driven by a single-electrode tribo-electric nanogenerator (TENG) is demonstrated. The mechanical motion works as both a power supply to drive the FED and a control unit to regulate the amount of emitted electrons. By using the Fowler-Nordheim equation and Kirchhoff laws, a theoretical model of this self-powered FED is proposed, and accordingly the real-time output characteristics of the device are systematically investigated. It is found that the motion distance of the TENG controls switch-on of the FED and determines the charge amount for emission, while the motion velocity regulates the amplitude of emission current. The minimum contact area for the TENG to generate field emission is about 9 cm2, which can be improved by optimizing FED structure and the tribo-materials of TENG. The demonstrated concept of this self-powered FED as well as the proposed physical analysis can serve as guidance for further applications of FED in such fields of self-powered electronics and soft electronics.

  13. Field emission device driven by self-powered contact-electrification: Simulation and experimental analysis

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiangyu, E-mail: chenxiangyu@binn.cas.cn, E-mail: ouyangwei@phy.ecnu.edu.cn; Jiang, Tao [Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083 (China); Sun, Zhuo; Ou-Yang, Wei, E-mail: chenxiangyu@binn.cas.cn, E-mail: ouyangwei@phy.ecnu.edu.cn [Engineering Research Center for Nanophotonics and Advanced Instrument, Ministry of Education, Department of Physics, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062 (China)

    2015-09-14

    A self-powered field emission device (FED) driven by a single-electrode tribo-electric nanogenerator (TENG) is demonstrated. The mechanical motion works as both a power supply to drive the FED and a control unit to regulate the amount of emitted electrons. By using the Fowler-Nordheim equation and Kirchhoff laws, a theoretical model of this self-powered FED is proposed, and accordingly the real-time output characteristics of the device are systematically investigated. It is found that the motion distance of the TENG controls switch-on of the FED and determines the charge amount for emission, while the motion velocity regulates the amplitude of emission current. The minimum contact area for the TENG to generate field emission is about 9 cm{sup 2}, which can be improved by optimizing FED structure and the tribo-materials of TENG. The demonstrated concept of this self-powered FED as well as the proposed physical analysis can serve as guidance for further applications of FED in such fields of self-powered electronics and soft electronics.

  14. Field electron emission improvement of ZnO nanorod arrays after Ar plasma treatment

    International Nuclear Information System (INIS)

    Li Chun; Fang Guojia; Yuan Longyan; Liu Nishuang; Li Jun; Li Dejie; Zhao Xingzhong

    2007-01-01

    Vertically well-aligned single crystal ZnO nanorod arrays were synthesized and enhanced field electron emission was achieved after radio-frequency (rf) Ar plasma treatment. With Ar plasma treatment for 30 min, flat tops of the as-grown ZnO nanorods have been etched into sharp tips without damaging ZnO nanorod geometrical morphologies and crystallinity. After the Ar ion bombardment, the emission current density increases from 2 to 20 μA cm -2 at 9.0 V μm -1 with a decrease in turn-on voltage from 7.1 to 4.8 V μm -1 at a current density of 1 μA cm -2 , which demonstrates that the field emission of the as-grown ZnO nanorods has been efficiently enhanced. The scanning electron microscopy (SEM) results, in conjunction with the results of transmission electron microscopy (TEM), Raman spectroscopy and photoluminescence observation, are used to investigate the mechanisms of the field emission enhancement. It is believed that the enhancements can be mainly attributed to the sharpening of rod tops, and the decrease of electrostatic screening effect

  15. Field emission device driven by self-powered contact-electrification: Simulation and experimental analysis

    International Nuclear Information System (INIS)

    Chen, Xiangyu; Jiang, Tao; Sun, Zhuo; Ou-Yang, Wei

    2015-01-01

    A self-powered field emission device (FED) driven by a single-electrode tribo-electric nanogenerator (TENG) is demonstrated. The mechanical motion works as both a power supply to drive the FED and a control unit to regulate the amount of emitted electrons. By using the Fowler-Nordheim equation and Kirchhoff laws, a theoretical model of this self-powered FED is proposed, and accordingly the real-time output characteristics of the device are systematically investigated. It is found that the motion distance of the TENG controls switch-on of the FED and determines the charge amount for emission, while the motion velocity regulates the amplitude of emission current. The minimum contact area for the TENG to generate field emission is about 9 cm 2 , which can be improved by optimizing FED structure and the tribo-materials of TENG. The demonstrated concept of this self-powered FED as well as the proposed physical analysis can serve as guidance for further applications of FED in such fields of self-powered electronics and soft electronics

  16. Long term continuous field survey to assess nutrient emission impact from irrigated paddy field into river catchment

    Science.gov (United States)

    Kogure, Kanami; Aichi, Masaatsu; Zessner, Matthias

    2017-04-01

    In order to achieve good river environment, it is very important to understand and to control nutrient behavior such as Nitrogen and Phosphorus. As we could reduce impact from urban and industrial activities by wastewater treatment, pollution from point sources are likely to be controlled. Besides them, nutrient emission from agricultural activity is dominant pollution source into the river system. In many countries in Asia and Africa, rice is widely cultivated and paddy field covers large areas. In Japan 54% of its arable land is occupied with irrigated paddy field. While paddy field can deteriorate river water quality due to fertilization, it is also suggested that paddy field can purify water. We carried out field survey in middle reach of the Tone River Basin with focus on a paddy field IM. The objectives of the research are 1) understanding of water and nutrient balance in paddy field, 2) data collection for assessing nutrient emission. Field survey was conducted from June 2015 to October 2016 covering two flooding seasons in summer. In our measurement, all input and output were measured regarding water, N and P to quantify water and nutrient balance in the paddy field. By measuring water quality and flow rate of inflow, outflow, infiltrating water, ground water and flooding water, we tried to quantitatively understand water, N and P cycle in a paddy field including seasonal trends, and changes accompanied with rainy events and agricultural activities like fertilization. Concerning water balance, infiltration rate was estimated by following equation. Infiltration=Irrigation water + Precipitation - Evapotranspiration -Outflow We estimated mean daily water balance during flooding season. Infiltration is 11.9mm/day in our estimation for summer in 2015. Daily water reduction depth (WRD) is sum of Evapotranspiration and Infiltration. WRD is 21.5mm/day in IM and agrees with average value in previous research. Regarding nutrient balance, we estimated an annual N and

  17. Oil palm and the emission of greenhouse gasses- from field measurements in Indonesia

    Science.gov (United States)

    Rahman, Niharika; Bruun, Thilde Bech; Giller, Ken E.; Magid, Jakob; van de Ven, Gerrie; de Neergaard, Andreas

    2017-04-01

    Palm oil from the oil palm (Elaeis guianensis) has in recent years become the world's most important vegetable oil. The increasing demand for palm oil has led to expansion of oil palm plantations, which has caused environmental controversies associated with carbon losses and the use of large amounts of mineral fertilizers. Efforts to increase sustainability of oil palm cultivation, include recycling of oil-mill residues and pruning's, but with this comes increased potential for methane emission from the plantations. Until now no field-based data on greenhouse gas emissions from oil palm plantations have been reported. Here for the first time we present data from a long term (360 days) field trial in Bah Lias Research Station, North Sumatra, Indonesia on greenhouse gas emissions from an oil palm plantation with various treatments of recycled oil palm waste products, fertilizers and simulated rainfall. The first experiment was conducted over a full year (dry + wet season) with mineral fertilizer treatments including urea and ammonium sulphate, and organic fertilizer treatments constituting: empty fruit bunches (EFB), enriched mulch (EFB + palm oil mill effluent (POME) ) and pruned oil palm fronds (OPF). Treatment doses represent the current management in Indonesian plantations and the higher doses that are expected in the imminent future. For the organic treatments several methods of application (applied in inter-rows, piles, patches or bands) were evaluated. The second experiment investigated effects of soil water saturation on GHG emissions through adding 25 mm simulated rainfall per day for 21 days. Each palm tree received 1 kg of N fertilizer as urea or ammonium sulphate and enriched mulch. The gas fluxes in the fields was measured by a large static-chamber (1.8 m x 1.2 m) method and CH4 and N2O concentrations were determined using gas chromatographs. We found that emissions were significantly affected by the type and dose of mineral fertilizers. Application of

  18. Properties and Applications of High Emissivity Composite Films Based on Far-Infrared Ceramic Powder.

    Science.gov (United States)

    Xiong, Yabo; Huang, Shaoyun; Wang, Wenqi; Liu, Xinghai; Li, Houbin

    2017-11-29

    Polymer matrix composite materials that can emit radiation in the far-infrared region of the spectrum are receiving increasing attention due to their ability to significantly influence biological processes. This study reports on the far-infrared emissivity property of composite films based on far-infrared ceramic powder. X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray powder diffractometry were used to evaluate the physical properties of the ceramic powder. The ceramic powder was found to be rich in aluminum oxide, titanium oxide, and silicon oxide, which demonstrate high far-infrared emissivity. In addition, the micromorphology, mechanical performance, dynamic mechanical properties, and far-infrared emissivity of the composite were analyzed to evaluate their suitability for strawberry storage. The mechanical properties of the far-infrared radiation ceramic (cFIR) composite films were not significantly influenced ( p ≥ 0.05) by the addition of the ceramic powder. However, the dynamic mechanical analysis (DMA) properties of the cFIR composite films, including a reduction in damping and shock absorption performance, were significant influenced by the addition of the ceramic powder. Moreover, the cFIR composite films showed high far-infrared emissivity, which has the capability of prolonging the storage life of strawberries. This research demonstrates that cFIR composite films are promising for future applications.

  19. Emission-Line Galaxies from the PEARS Hubble Ultra Deep Field: A 2-D Detection Method and First Results

    Science.gov (United States)

    Gardner, J. P.; Straughn, Amber N.; Meurer, Gerhardt R.; Pirzkal, Norbert; Cohen, Seth H.; Malhotra, Sangeeta; Rhoads, james; Windhorst, Rogier A.; Gardner, Jonathan P.; Hathi, Nimish P.; hide

    2007-01-01

    The Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) grism PEARS (Probing Evolution And Reionization Spectroscopically) survey provides a large dataset of low-resolution spectra from thousands of galaxies in the GOODS North and South fields. One important subset of objects in these data are emission-line galaxies (ELGs), and we have investigated several different methods aimed at systematically selecting these galaxies. Here we present a new methodology and results of a search for these ELGs in the PEARS observations of the Hubble Ultra Deep Field (HUDF) using a 2D detection method that utilizes the observation that many emission lines originate from clumpy knots within galaxies. This 2D line-finding method proves to be useful in detecting emission lines from compact knots within galaxies that might not otherwise be detected using more traditional 1D line-finding techniques. We find in total 96 emission lines in the HUDF, originating from 81 distinct "knots" within 63 individual galaxies. We find in general that [0 1111 emitters are the most common, comprising 44% of the sample, and on average have high equivalent widths (70% of [0 1111 emitters having rest-frame EW> 100A). There are 12 galaxies with multiple emitting knots; several show evidence of variations in H-alpha flux in the knots, suggesting that the differing star formation properties across a single galaxy can in general be probed at redshifts approximately greater than 0.2 - 0.4. The most prevalent morphologies are large face-on spirals and clumpy interacting systems, many being unique detections owing to the 2D method described here, thus highlighting the strength of this technique.

  20. Properties of field functionals and characterization of local functionals

    Science.gov (United States)

    Brouder, Christian; Dang, Nguyen Viet; Laurent-Gengoux, Camille; Rejzner, Kasia

    2018-02-01

    Functionals (i.e., functions of functions) are widely used in quantum field theory and solid-state physics. In this paper, functionals are given a rigorous mathematical framework and their main properties are described. The choice of the proper space of test functions (smooth functions) and of the relevant concept of differential (Bastiani differential) are discussed. The relation between the multiple derivatives of a functional and the corresponding distributions is described in detail. It is proved that, in a neighborhood of every test function, the support of a smooth functional is uniformly compactly supported and the order of the corresponding distribution is uniformly bounded. Relying on a recent work by Dabrowski, several spaces of functionals are furnished with a complete and nuclear topology. In view of physical applications, it is shown that most formal manipulations can be given a rigorous meaning. A new concept of local functionals is proposed and two characterizations of them are given: the first one uses the additivity (or Hammerstein) property, the second one is a variant of Peetre's theorem. Finally, the first step of a cohomological approach to quantum field theory is carried out by proving a global Poincaré lemma and defining multi-vector fields and graded functionals within our framework.

  1. METHANE EMISSION FROM PADDY FIELDS AS INFLUENCED BY DIFFERENT WATER REGIMES IN CENTRAL JAVA

    Directory of Open Access Journals (Sweden)

    Prihasto Setyanto

    2013-07-01

    Full Text Available The concentration of methane (CH4 in the atmosphere is increasing at 1% per annum and rice fields are one of the sources that contribute to about 10-15% of the atmospheric CH4. One of the options to reduce greenhouse gas emission from rice fields is probably through water management. A field study was conducted to investigate the effects of water management practices on CH4 emission from rice field plots on a silty sand Aeric Tropaquept soil at Research Station for Agricultural Environment Preservation, Jakenan, Central Java, Indonesia, during the dry season of March to June 2002. Four water regimes tested were: (1 5 cm continuous flooding (CF, (2 0-1 cm continuous flooding (ST, (3 intermittent irrigation (IR where plots received continuously 5 cm of flooding with two times of draining at 15-20 and 25-30 days after transplanting (DAT, and (4 pulse irrigation (PI where plots were watered until 5 cm level and left to dry by itself until the water table reached 30 cm beneath soil surface then watered again. The total CH4 emissions of the four water treatments were 254, 185, 136 and 96 kg CH4 ha-1 for CF, ST, IR and PI, respectively. Methane emission increased during the early growing season, which coincided with the low redox potential of -100 to -150 mV in all treatments. Dry matter weight of straw and filled grain among the water treatments did not show significant differences. Likewise, total grain yield at 14% moisture content was not significantly different among treatments. However, this result should be carefully interpreted because the rice plants in all water treatments were infested by stem borer, which reduced the total grain yield of IR64 between 11% and 16%. This study suggests that intermittent and pulse irrigation practices will be important not only for water use efficiency, but also for CH4 emission reduction.

  2. Transition from Fowler-Nordheim field emission to space charge limited current density

    International Nuclear Information System (INIS)

    Feng, Y.; Verboncoeur, J. P.

    2006-01-01

    The Fowler-Nordheim law gives the current density extracted from a surface under strong fields, by treating the emission of electrons from a metal-vacuum interface in the presence of an electric field normal to the surface as a quantum mechanical tunneling process. Child's law predicts the maximum transmitted current density by considering the space charge effect. When the electric field becomes high enough, the emitted current density will be limited by Child's law. This work analyzes the transition of the transmitted current density from the Fowler-Nordheim law to Child's law space charge limit using a one-dimensional particle-in-cell code. Also studied is the response of the emission model to strong electric fields near the transition point. We find the transition without geometrical effort is smooth and much slower than reported previously [J. P. Barbour, W. W. Dolan, J. K. Trolan, E. E. Martin, and W. P. Dyke, Phys. Rev. 92, 45 (1953)]. We analyze the effects of geometric field enhancement and work function on the transition. Using our previous model for effective field enhancement [Y. Feng and J. P. Verboncoeur, Phys. Plasmas 12, 103301 (2005)], we find the geometric effect dominates, and enhancement β>10 can accelerate the approach to the space charge limit at practical electric field. A damped oscillation near the local plasma frequency is observed in the transient system response

  3. Discrete field theories and spatial properties of strings

    International Nuclear Information System (INIS)

    Klebanov, I.; Susskind, L.

    1988-10-01

    We use the ground-state wave function in the light-cone gauge to study the spatial properties of fundamental strings. We find that, as the cut-off in the parameter space is removed, the strings are smooth and have a divergent size. Guided by these properties, we consider a large-N lattice gauge theory which has an unstable phase where the size of strings diverges. We show that this phase exactly describes free fundamental strings. The lattice spacing does not have to be taken to zero for this equivalence to hold. Thus, exact rotation and translation invariance is restored in a discrete space. This suggests that the number of fundamental short-distance degrees of freedom in string theory is much smaller than in a conventional field theory. 11 refs., 4 figs

  4. Electric Field Structures in Thin Films: Formation and Properties

    DEFF Research Database (Denmark)

    Cassidy, Andrew; Plekan, Oksana; Balog, Richard

    2014-01-01

    A newly discovered class of molecular materials, so-called “spontelectrics”, display spontaneous electric fields. Here we show that the novel properties of spontelectrics can be used to create composite spontelectrics, illustrating how electric fields in solid films may be structured on the nanoscale...... by combining layers of different spontelectric materials. This is demonstrated using the spontelectric materials nitrous oxide, toluene, isoprene, isopentane, and CF2Cl2. These yield a variety of tailored electric field structures, with individual layers harboring fields between 107 and 108 V/m. Fields may...

  5. Electronic properties of field aligned CrO2 powders

    International Nuclear Information System (INIS)

    Tripathy, D.; Adeyeye, A.O.

    2005-01-01

    We have investigated in detail the electronic transport properties of half metallic CrO 2 powder-based devices, fabricated using optical lithography and field alignment technique. A transition in the conduction mechanism from spin-dependent intergranular tunneling to inelastic hopping was observed at 215 K. This transition temperature shifts to 230 K in the presence of 10 kOe field cooling due to reduction of the spin-independent hopping conductance channel. I-V characteristics exhibit strong temperature dependence and are non-linear even at room temperature. Our experimental results are in good agreement with a simple theoretical model. A novel 'double switching' phenomenon was observed in the I-V curves below the transition temperature

  6. Investigating of the Field Emission Performance on Nano-Apex Carbon Fiber and Tungsten Tips

    Science.gov (United States)

    Mousa, Marwan S.; Alnawasreh, Shadi; Madanat, Mazen A.; Al-Rabadi, Anas N.

    2015-10-01

    Field electron emission measurements have been performed on carbon-based and tungsten microemitters. Several samples of both types of emitters with different apex radii have been obtained employing electrolytic etching techniques using sodium hydroxide (NaOH) solution with different molarities depending on the material used. A suitable, home-built, field electron microscope (FEM) with 10 mm tip to screen separation distance was used to electrically characterize the electron emitters. Measurements were carried out under ultra high vacuum (UHV) conditions with base pressure of 10-9 mbar. The current-voltage characteristics (I-V) presented as Fowler-Nordheim (FN) type plots, and field electron emission images have been recorded. In this work, initial comparison of the field electron emission performance of these micro and nanoemitters has been carried out, with the aim of obtaining a reliable, stable and long life powerful electron source. We compare the apex radii measured from the micrographs obtained from the SEM images to those extracted from the FN-type _I-V_plots for carbon fibers and tungsten tips.

  7. Investigating of the Field Emission Performance on Nano-Apex Carbon Fiber and Tungsten Tips

    International Nuclear Information System (INIS)

    Mousa, Marwan S; Alnawasreh, Shadi; Al-Rabadi, Anas N; Madanat, Mazen A

    2015-01-01

    Field electron emission measurements have been performed on carbon-based and tungsten microemitters. Several samples of both types of emitters with different apex radii have been obtained employing electrolytic etching techniques using sodium hydroxide (NaOH) solution with different molarities depending on the material used. A suitable, home-built, field electron microscope (FEM) with 10 mm tip to screen separation distance was used to electrically characterize the electron emitters. Measurements were carried out under ultra high vacuum (UHV) conditions with base pressure of 10 -9 mbar. The current-voltage characteristics (I-V) presented as Fowler-Nordheim (FN) type plots, and field electron emission images have been recorded. In this work, initial comparison of the field electron emission performance of these micro and nanoemitters has been carried out, with the aim of obtaining a reliable, stable and long life powerful electron source. We compare the apex radii measured from the micrographs obtained from the SEM images to those extracted from the FN-type -I-V-plots for carbon fibers and tungsten tips. (paper)

  8. Emission of massive scalar fields by a higher-dimensional rotating black hole

    International Nuclear Information System (INIS)

    Kanti, P.; Pappas, N.

    2010-01-01

    We perform a comprehensive study of the emission of massive scalar fields by a higher-dimensional, simply rotating black hole both in the bulk and on the brane. We derive approximate, analytic results as well as exact numerical ones for the absorption probability, and demonstrate that the two sets agree very well in the low and intermediate-energy regime for scalar fields with mass m Φ ≤1 TeV in the bulk and m Φ ≤0.5 TeV on the brane. The numerical values of the absorption probability are then used to derive the Hawking radiation power emission spectra in terms of the number of extra dimensions, angular-momentum of the black hole and mass of the emitted field. We compute the total emissivities in the bulk and on the brane, and demonstrate that, although the brane channel remains the dominant one, the bulk-over-brane energy ratio is considerably increased (up to 34%) when the mass of the emitted field is taken into account.

  9. Effect of sequential surface irrigations on field-scale emissions of 1,3-dichloropropene.

    Science.gov (United States)

    Yates, S R; Knuteson, J; Ernst, F F; Zheng, W; Wang, Q

    2008-12-01

    A field experiment was conducted to measure subsurface movement and volatilization of 1,3-dichloropropene (1,3-D) after shank injection to an agricultural soil. The goal of this study was to evaluate the effect of sprinkler irrigation on the emissions of 1,3-D to the atmosphere and is based on recent research that has shown that saturating the soil pore space reduces gas-phase diffusion and leads to reduced volatilization rates. Aerodynamic, integrated horizontal flux, and theoretical profile shape methods were used to estimate fumigant volatilization rates and total emission losses. These methods provide estimates of the volatilization rate based on measurements of wind speed, temperature, and 1,3-D concentration in the atmosphere. The volatilization rate was measured continuously for 16 days, and the daily peak volatilization rates for the three methods ranged from 18 to 60 microg m(-2) s(-1). The total 13-D mass entering the atmosphere was approximately 44-68 kg ha(-1), or 10-15% of the applied active ingredient This represents approximately 30-50% reduction in the total emission losses compared to conventional fumigant applications in field and field-plot studies. Significant reduction in volatilization of 1,3-D was observed when five surface irrigations were applied to the field, one immediately after fumigation followed by daily irrigations.

  10. Effect of an alternating electric field on the polluting emission from propane flame.

    Science.gov (United States)

    Ukradiga, I.; Turlajs, D.; Purmals, M.; Barmina, I.; Zake, M.

    2001-12-01

    The experimental investigations of the AC field effect on the propane combustion and processes that cause the formation of polluting emissions (NO_x, CO, CO_2) are performed. The AC-enhanced variations of the temperature and composition of polluting emissions are studied for the fuel-rich and fuel-lean conditions of the flame core. The results show that the AC field-enhanced mixing of the fuel-rich core with the surrounding air coflow enhances the propane combustion with increase in the mass fraction of NO_x and CO_2 in the products. The reverse field effect on the composition of polluting emissions is observed under the fuel-lean conditions in the flame core. The field-enhanced CO_2 destruction is registered when the applied voltage increase. The destruction of CO_2 leads to a correlating increase in the mass fraction of CO in the products and enhances the process of NO_x formation within the limit of the fuel lean and low temperature combustion. Figs 11, Refs 18.

  11. Realization and field emission of CdSe nano-tetrapods with different arm lengths

    International Nuclear Information System (INIS)

    Zhao Lijuan; Pang Qi; Yang Shihe; Ge Weikun; Wang Jiannong

    2009-01-01

    The arms of CdSe nano-tetrapods can be greatly elongated with the core diameters and arm width unchanged by multiple injections. Room-temperature absorption and photoluminescence (PL) spectra of tetrapods with different arm lengths show that these tetrapods have almost the same core size, which is consistent with the high resolution TEM results. Field emission characteristics show that the onset field required drawing a current density of ∼0.1 μAcm -2 from CdSe nano-tetrapods with different arm lengths are 22 Vμm -1 , 9 Vμm -1 , and 4 Vμm -1 , respectively, and the field enhancement factors are determined to be about 218, 554, and 946, respectively. Results show that the longer is the arm of the tetrapods, the lower the turn-on field and the higher the field enhancement factor.

  12. Realization and field emission of CdSe nano-tetrapods with different arm lengths

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Lijuan, E-mail: ljzhao@dhu.edu.c [Applied Physics Department, Donghua University, Shanghai 201620 (China); Physics Department and the Institute of Nano-Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay (Hong Kong); Pang Qi [Physics Department and the Institute of Nano-Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay (Hong Kong); Yang Shihe [Chemistry Department and the Institute of Nano-Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay (Hong Kong); Ge Weikun; Wang Jiannong [Physics Department and the Institute of Nano-Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay (Hong Kong)

    2009-08-10

    The arms of CdSe nano-tetrapods can be greatly elongated with the core diameters and arm width unchanged by multiple injections. Room-temperature absorption and photoluminescence (PL) spectra of tetrapods with different arm lengths show that these tetrapods have almost the same core size, which is consistent with the high resolution TEM results. Field emission characteristics show that the onset field required drawing a current density of approx0.1 muAcm{sup -2} from CdSe nano-tetrapods with different arm lengths are 22 Vmum{sup -1}, 9 Vmum{sup -1}, and 4 Vmum{sup -1}, respectively, and the field enhancement factors are determined to be about 218, 554, and 946, respectively. Results show that the longer is the arm of the tetrapods, the lower the turn-on field and the higher the field enhancement factor.

  13. Simultaneous field measurements of biogenic emissions of nitric oxide and nitrous oxide

    Science.gov (United States)

    Anderson, Iris Cofman; Levine, Joel S.

    1987-01-01

    Seasonal and diurnal emissions of NO and N2O from agricultural sites in Jamestown, Virginia and Boulder, Colorado are estimated in terms of soil temperature; percent moisture; and exchangeable nitrate, nitrite, and ammonium concentrations. The techniques and procedures used to analyze the soil parameters are described. The spatial and temporal variability of the NO and N2O emissions is studied. A correlation between NO fluxes in the Virginia sample and nitrate concentration, temperature, and percent moisture is detected, and NO fluxes for the Colorado site correspond with temperature and moisture. It is observed that the N2O emissions are only present when percent moisture approaches or exceeds the field capacity of the soil. The data suggest that NO is produced primarily by nitrification in aerobic soils, and N2O is formed by denitrification in anaerobic soils.

  14. Properties of Radio Sources in the FRB 121102 Field

    Science.gov (United States)

    Bower, Geoffrey C.; Chatterjee, Shami; Wharton, Robert; Law, Casey J.; Hessels, Jason; Spolaor, Sarah; Abruzzo, Matthew W.; Bassa, Cees; Butler, Bryan J.; Cordes, James M.; Demorest, Paul; Kaspi, Victoria M.; McLaughlin, Maura; Ransom, Scott M.; Scholz, Paul; Seymour, Andrew; Spitler, Laura; Tendulkar, Shriharsh P.; PALFA Survey; VLA+AO FRB121102 Simultaneous Campaign Team; EVN FRB121102 Campaign Team; Realfast Team

    2017-01-01

    Fast radio bursts are millisecond duration radio pulses of unknown origin. With dispersion measures substantially in excess of expected Galactic contributions, FRBs are inferred to originate extragalactically, implying very high luminosities. Models include a wide range of high energy systems such as magnetars, merging neutron star binaries, black holes, and strong stellar magnetic fields driving coherent radio emission. Central to the mystery of FRB origins are the absence of confirmed host objects at any wavelength. This is primarily the result of the poor localization from single dish detection of FRBs. Of the approximately 20 known examples, only one, FRB 121102, has been observed to repeat. This repetition presents an opportunity for detailed follow-up if interferometric localization to arcsecond accuracy can be obtained. The Very Large Array has previously been used to localize individual pulses from pulsars and rotating radio transients to arcsecond localizaiton. We present here the results of radio observations of the field of FRB 121102 that permit us to constrain models of possible progenitors of this bursting source. These observations can characterize active galactic nuclei, stars, and other progenitor objects.

  15. Coherent changes of multifractal properties of continuous acoustic emission at failure of heterogeneous materials

    Science.gov (United States)

    Panteleev, Ivan; Bayandin, Yuriy; Naimark, Oleg

    2017-12-01

    This work performs a correlation analysis of the statistical properties of continuous acoustic emission recorded in different parts of marble and fiberglass laminate samples under quasi-static deformation. A spectral coherent measure of time series, which is a generalization of the squared coherence spectrum on a multidimensional series, was chosen. The spectral coherent measure was estimated in a sliding time window for two parameters of the acoustic emission multifractal singularity spectrum: the spectrum width and the generalized Hurst exponent realizing the maximum of the singularity spectrum. It is shown that the preparation of the macrofracture focus is accompanied by the synchronization (coherent behavior) of the statistical properties of acoustic emission in allocated frequency intervals.

  16. HIGH-CURRENT COLD CATHODE FIELD EMISSION ARRAY FOR ELECTRON LENS APPLICATION

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L

    2012-12-28

    During Phase I, the following goals were achieved: (1) design and fabrication of a novel, nano-dimensional CNT field emitter assembly for high current density application, with high durability; (2) fabrication of a ceramic based micro channel plate (MCP) and characterization of its secondary electron emission; and (3) characterizing the CNT/MCP cathode for high field emission and durability. As a result of these achievements, a relatively high current density of ~ 1.2 A/cm2 from a CNT cathode and single channel MCP were measured. The emission current was also extremely stable with a peak-to-peak variation of only 1.8%. The emission current could be further enhanced to meet requirements for electron lens applications by increasing the number of MCP channels. A calculation for maximum possible current density with a 1200 channel/cm2 MCP, placed over a cathode with 1200 uniformly functioning CNTs, would be ~1.46 kA/cm2, neglecting space charge limitations. Clearly this level of emission is far greater than what is needed for the electron lens application, but it does offer a highly comforting margin to account for sub-standard emitters and/or to allow the lesser challenge of building a cathode with fewer channels/cm2. A satisfactory goal for the electron lens application would be a controllable emission of 2-4 mA per channel in an ensemble of 800-1200 uniformly-functioning channels/cm2, and a cathode with overall area of about 1 cm2.

  17. Comparison of anti-corrosion properties of polyurethane based composite coatings with low infrared emissivity

    International Nuclear Information System (INIS)

    Wang Yajun; Xu Guoyue; Yu Huijuan; Hu Chen; Yan Xiaoxing; Guo Tengchao; Li Jiufen

    2011-01-01

    Four polyurethane resins, pure polyurethane (PU), epoxy modified polyurethane (EPU), fluorinated polyurethane (FPU) and epoxy modified fluorinated polyurethane (EFPU), with similar polyurethane backbone structure but different grafting group were used as organic adhesive for preparing low infrared emissivity coatings with an extremely low emissivity near 0.10 at 8-14 μm, respectively. By using these four resins, the effect of different resin matrics on the corrosion protection of the low infrared emissivity coatings was investigated in detail by using neutral salt spray test, SEM and FTIR. It was found that the emissivity of the coatings with different resin matrics changes significantly in corrosion media. And the results indicated that the coating using EFPU as organic adhesive exhibited excellent corrosion resistance property which was mainly attributed to the presence of epoxy group and atomic fluorine in binder simultaneously.

  18. Statistical properties of compartmental model parameters extracted from dynamic positron emission tomography experiments

    International Nuclear Information System (INIS)

    Mazoyer, B.M.; Huesman, R.H.; Budinger, T.F.; Knittel, B.L.

    1986-01-01

    Over the past years a major focus of research in physiologic studies employing tracers has been the computer implementation of mathematical methods of kinetic modeling for extracting the desired physiological parameters from tomographically derived data. A study is reported of factors that affect the statistical properties of compartmental model parameters extracted from dynamic positron emission tomography (PET) experiments

  19. Effects of ethylene glycol ethers on diesel fuel properties and emissions in a diesel engine

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Cuenca, F.; Gomez-Marin, M. [Compania Logistica de Hidrocarburos (CLH), Central Laboratory, Mendez Alvaro 44, 28045 Madrid (Spain); Folgueras-Diaz, M.B., E-mail: belenfd@uniovi.es [Department of Energy, University of Oviedo, Independencia 13, 33004 Oviedo (Spain)

    2011-08-15

    Highlights: {yields} Effect of ethylene glycol ethers on diesel fuel properties. {yields} Effect of ethylene glycol ethers on diesel engine specific consumption and emissions. {yields} Blends with {<=}4 wt.% of oxygen do not change substantially diesel fuel quality. {yields} Blends with 1 and 2.5 wt.% of oxygen reduce CO and HC emissions, but not smoke. - Abstract: The effect of ethylene glycol ethers on both the diesel fuel characteristics and the exhaust emissions (CO, NO{sub x}, smoke and hydrocarbons) from a diesel engine was studied. The ethers used were monoethylene glycol ethyl ether (EGEE), monoethylene glycol butyl ether (EGBE), diethylene glycol ethyl ether (DEGEE). The above effect was studied in two forms: first by determining the modification of base diesel fuel properties by using blends with oxygen concentration around 4 wt.%, and second by determining the emission reductions for blends with low oxygen content (1 wt.%) and with 2.5 wt.% of oxygen content. The addition of DEGEE enhances base diesel fuel cetane number, but EGEE and EGBE decrease it. For concentrations of {>=}4 wt.% of oxygen, EGEE and diesel fuel can show immiscibility problems at low temperatures ({<=}0 {sup o}C). Also, every oxygenated compound, according to its boiling point, modifies the distillation curve at low temperatures and the distillate percentage increases. These compounds have a positive effect on diesel fuel lubricity, and slightly decrease its viscosity. Blends with 1 and 2.5 wt.% oxygen concentrations were used in order to determine their influence on emissions at both full and medium loads and different engine speeds. Generally, all compounds help to reduce CO, and hydrocarbon emissions, but not smoke. The best results were obtained for blends with 2.5 wt.% of oxygen. At this concentration, the additive efficiency in decreasing order was EGEE > DEGEE > EGBE for CO emissions and DGEE > EGEE > EGBE for hydrocarbon emissions. For NO{sub x}, both its behaviour and the

  20. Air pollutant emissions from rice straw open field burning in India, Thailand and the Philippines

    International Nuclear Information System (INIS)

    Gadde, Butchaiah; Bonnet, Sebastien; Menke, Christoph; Garivait, Savitri

    2009-01-01

    Rice is a widely grown crop in Asia. China (30%) and India (21%) contribute to about half of the world's total rice production. In this study, three major rice-producing countries in Asia are considered, India, Thailand and the Philippines (the later two contributing 4% and 2% of the world's rice production). Rice straw is one of the main field based residues produced along with this commodity and its applications vary widely in the region. Although rice production practises vary from one country to another, open burning of straw is a common practice in these countries. In this study, an approach was followed aiming at (a) determining the quantity of rice straw being subject to open field burning in those countries, (b) congregating pollutant specific emissions factors for rice straw burning, and (c) quantifying the resulting air pollutant emissions. Uncertainties in the results obtained as compared to a global approach are also discussed. - This research work contributes to enhance scientific knowledge for estimating air pollutant emissions from open burning of crop residues and improve emission results accuracy.

  1. Solar wind charge exchange emission in the Chandra deep field north

    Energy Technology Data Exchange (ETDEWEB)

    Slavin, Jonathan D.; Wargelin, Bradford J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Koutroumpa, Dimitra [LATMOS/IPSL, CNRS, Université Versailles Saint Quentin, 11 Boulevard d' Alembert, F-78280, Guyancourt (France)

    2013-12-10

    The diffuse soft X-ray background comes from distant galaxies, from hot Galactic gas, and from within the solar system. The latter emission arises from charge exchange between highly charged solar wind ions and neutral gas. This so-called solar wind charge exchange (SWCX) emission is spatially and temporally variable and interferes with our measurements of more distant cosmic emission while also providing important information on the nature of the solar wind-interstellar medium interaction. We present the results of our analysis of eight Chandra observations of the Chandra Deep Field North (CDFN) with the goal of measuring the cosmic and SWCX contributions to the X-ray background. Our modeling of both geocoronal and heliospheric SWCX emission is the most detailed for any observation to date. After allowing for ∼30% uncertainty in the SWCX emission and subtracting it from the observational data, we estimate that the flux of cosmic background for the CDFN in the O VII Kα, Kβ, and O VIII Lyα lines totals 5.8 ± 1.1 photons s{sup –1} cm{sup –2} sr{sup –1} (or LU). Heliospheric SWCX emission varied for each observation due to differences in solar wind conditions and the line of sight through the solar system, but was typically about half as strong as the cosmic background (i.e., one-third of the total) in those lines. The modeled geocoronal emission was 0.82 LU in one observation but averaged only 0.15 LU in the others. Our measurement of the cosmic background is lower than but marginally consistent with previous estimates based on XMM-Newton data.

  2. Field test of available methods to measure remotely SOx and NOx emissions from ships

    Science.gov (United States)

    Balzani Lööv, J. M.; Alfoldy, B.; Gast, L. F. L.; Hjorth, J.; Lagler, F.; Mellqvist, J.; Beecken, J.; Berg, N.; Duyzer, J.; Westrate, H.; Swart, D. P. J.; Berkhout, A. J. C.; Jalkanen, J.-P.; Prata, A. J.; van der Hoff, G. R.; Borowiak, A.

    2014-08-01

    Methods for the determination of ship fuel sulphur content and NOx emission factors based on remote measurements have been compared in the harbour of Rotterdam and compared to direct stack emission measurements on the ferry Stena Hollandica. The methods were selected based on a review of the available literature on ship emission measurements. They were either optical (LIDAR, Differential Optical Absorption Spectroscopy (DOAS), UV camera), combined with model-based estimates of fuel consumption, or based on the so called "sniffer" principle, where SO2 or NOx emission factors are determined from simultaneous measurement of the increase of CO2 and SO2 or NOx concentrations in the plume of the ship compared to the background. The measurements were performed from stations at land, from a boat and from a helicopter. Mobile measurement platforms were found to have important advantages compared to the land-based ones because they allow optimizing the sampling conditions and sampling from ships on the open sea. Although optical methods can provide reliable results it was found that at the state of the art level, the "sniffer" approach is the most convenient technique for determining both SO2 and NOx emission factors remotely. The average random error on the determination of SO2 emission factors comparing two identical instrumental set-ups was 6%. However, it was found that apparently minor differences in the instrumental characteristics, such as response time, could cause significant differences between the emission factors determined. Direct stack measurements showed that about 14% of the fuel sulphur content was not emitted as SO2. This was supported by the remote measurements and is in agreement with the results of other field studies.

  3. Field test of available methods to measure remotely SO2 and NOx emissions from ships

    Science.gov (United States)

    Balzani Lööv, J. M.; Alfoldy, B.; Beecken, J.; Berg, N.; Berkhout, A. J. C.; Duyzer, J.; Gast, L. F. L.; Hjorth, J.; Jalkanen, J.-P.; Lagler, F.; Mellqvist, J.; Prata, F.; van der Hoff, G. R.; Westrate, H.; Swart, D. P. J.; Borowiak, A.

    2013-11-01

    Methods for the determination of ship fuel sulphur content and NOx emission factors from remote measurements have been compared in the harbour of Rotterdam and compared to direct stack emission measurements on the ferry Stena Hollandica. The methods were selected based on a review of the available literature on ship emission measurements. They were either optical (LIDAR, DOAS, UV camera), combined with model based estimates of fuel consumption, or based on the so called "sniffer" principle, where SO2 or NOx emission factors are determined from simultaneous measurement of the increase of CO2 and SO2 or NOx concentrations in the plume of the ship compared to the background. The measurements were performed from stations at land, from a boat, and from a helicopter. Mobile measurement platforms were found to have important advantages compared to the landbased ones because they allow to optimize the sampling conditions and to sample from ships on the open sea. Although optical methods can provide reliable results, it was found that at the state of the art, the "sniffer" approach is the most convenient technique for determining both SO2 and NOx emission factors remotely. The average random error on the determination of SO2 emission factors comparing two identical instrumental set-ups was 6%. However, it was found that apparently minor differences in the instrumental characteristics, such as response time, could cause significant differences between the emission factors determined. Direct stack measurements showed that about 14% of the fuel sulphur content was not emitted as SO2. This was supported by the remote measurements and is in agreement with the results of other field studies.

  4. Solar wind charge exchange emission in the Chandra deep field north

    International Nuclear Information System (INIS)

    Slavin, Jonathan D.; Wargelin, Bradford J.; Koutroumpa, Dimitra

    2013-01-01

    The diffuse soft X-ray background comes from distant galaxies, from hot Galactic gas, and from within the solar system. The latter emission arises from charge exchange between highly charged solar wind ions and neutral gas. This so-called solar wind charge exchange (SWCX) emission is spatially and temporally variable and interferes with our measurements of more distant cosmic emission while also providing important information on the nature of the solar wind-interstellar medium interaction. We present the results of our analysis of eight Chandra observations of the Chandra Deep Field North (CDFN) with the goal of measuring the cosmic and SWCX contributions to the X-ray background. Our modeling of both geocoronal and heliospheric SWCX emission is the most detailed for any observation to date. After allowing for ∼30% uncertainty in the SWCX emission and subtracting it from the observational data, we estimate that the flux of cosmic background for the CDFN in the O VII Kα, Kβ, and O VIII Lyα lines totals 5.8 ± 1.1 photons s –1 cm –2 sr –1 (or LU). Heliospheric SWCX emission varied for each observation due to differences in solar wind conditions and the line of sight through the solar system, but was typically about half as strong as the cosmic background (i.e., one-third of the total) in those lines. The modeled geocoronal emission was 0.82 LU in one observation but averaged only 0.15 LU in the others. Our measurement of the cosmic background is lower than but marginally consistent with previous estimates based on XMM-Newton data.

  5. Study of material properties important for an optical property modulation-based radiation detection method for positron emission tomography

    OpenAIRE

    Tao, Li; Daghighian, Henry M.; Levin, Craig S.

    2017-01-01

    We compare the performance of two detector materials, cadmium telluride (CdTe) and bismuth silicon oxide (BSO), for optical property modulation-based radiation detection method for positron emission tomography (PET), which is a potential new direction to dramatically improve the annihilation photon pair coincidence time resolution. We have shown that the induced current flow in the detector crystal resulting from ionizing radiation determines the strength of optical modulation signal. A large...

  6. Photoluminescence and cathodoluminescence of Mn doped zinc silicate nanophosphors for green and yellow field emissions displays

    Science.gov (United States)

    Omri, K.; Alyamani, A.; Mir, L. El

    2018-02-01

    Mn2+-doped Zn2SiO4 (ZSM2+) was synthesized by a facile sol-gel technique. The obtained samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, photoluminescence (PL) and cathodoluminescence (CL) techniques. Under UV excitation, spectra showed that the α-ZSM2+ phosphor exhibited a strong green emission around 525 nm and reached the highest luminescence intensity with the Mn doping concentration of 5 at.%. However, for the β-ZSM2+ phase, an interesting yellow emission band centered at 575 nm of Mn2+ at the Zn2+ tetrahedral sites was observed. In addition, an unusual red shift with increasing Mn2+ content was also found and attributed to an exchange interaction between Mn2+. Both PL and CL spectra exhibit an intense green and yellow emission centered at 525 and 573 nm, respectively, due to the 4T1 (4G)-6A1 (6S) transition of Mn2+. Furthermore, these results indicated that the Mn2+-doped zinc silicate phosphors may have potential applications in green and yellow emissions displays like field emission displays (FEDs).

  7. Anomalous Transport Properties of Dense QCD in a Magnetic Field

    Science.gov (United States)

    de la Incera, Vivian

    2017-06-01

    Despite recent advancements in the study and understanding of the phase diagram of strongly interacting matter, the region of high baryonic densities and low temperatures has remained difficult to reach in the lab. Things are expected to change with the planned HIC experiments at FAIR in Germany and NICA in Russia, which will open a window to the high-density-low-temperature segment of the QCD phase map, providing a unique opportunity to test the validity of model calculations that have predicted the formation of spatially inhomogeneous phases with broken chiral symmetry at intermediate-to-high densities. Such a density region is also especially relevant for the physics of neutron stars, as they have cores that can have several times the nuclear saturation density. On the other hand, strong magnetic fields, whose presence is fairly common in HIC and in neutron stars, can affect the properties of these exotic phases and lead to signatures potentially observable in these two settings. In this paper, I examine the anomalous transport properties produced by the spectral asymmetry of the lowest Landau level (LLL) in a QCD-inspired NJL model with a background magnetic field that exhibits chiral symmetry breaking at high density via the formation of a Dual Chiral Density Wave (DCDW) condensate. It turns out that in this model the electromagnetic interactions are described by the axion electrodynamics equations and there is a dissipationless Hall current.

  8. Black carbon cookstove emissions: A field assessment of 19 stove/fuel combinations

    Science.gov (United States)

    Garland, Charity; Delapena, Samantha; Prasad, Rajendra; L'Orange, Christian; Alexander, Donee; Johnson, Michael

    2017-11-01

    Black carbon (BC) emissions from household cookstoves consuming solid fuel produce approximately 25 percent of total anthropogenic BC emissions. The short atmospheric lifetime of BC means that reducing BC emissions would result in a faster climate response than mitigating CO2 and other long-lived greenhouse gases. This study presents the results of optical BC measurements of two new cookstove emissions field assessments and 17 archived cookstove datasets. BC was determined from attenuation of 880 nm light, which is strongly absorbed by BC, and linearly related between 1 and 125 attenuation units. A relationship was experimentally determined correlating BC mass deposition on quartz filters determined via thermal optical analysis (TOA) and on PTFE and quartz filters using transmissometry, yielding an attenuation cross-section (σATN) for both filter media types. σATN relates TOA measurements to optical measurements on PTFE and quartz (σATN(PTFE) = 13.7 cm-2 μg, R2 = 0.87, σATN(Quartz) = 15.6 cm-2 μg, R2 = 0.87). These filter-specific σATN, optical measurements of archived filters were used to determine BC emission factors and the fraction of particulate matter (PM) in the form of black carbon (BC/PM). The 19 stoves measured fell into five stove classes; simple wood, rocket, advanced biomass, simple charcoal, and advanced charcoal. Advanced biomass stoves include forced- and natural-draft gasifiers which use wood or biomass pellets as fuel. Of these classes, the simple wood and rocket stoves demonstrated the highest median BC emission factors, ranging from 0.051 to 0.14 g MJ-1. The lowest BC emission factors were seen in charcoal stoves, which corresponds to the generally low PM emission factors observed during charcoal combustion, ranging from 0.0084 to 0.014 g MJ-1. The advanced biomass stoves generally showed an improvement in BC emissions factors compared to simple wood and rocket stoves, ranging from 0.0031 to 0.071 g MJ-1. BC/PM ratios were highest for the

  9. Effect of aircraft exhaust sulfur emissions on near field plume aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Brown, R.C.; Miake-Lye, R.C.; Anderson, M.R.; Kolb, C.E. [Aerodyne Research, Inc., Billerica, MA (United States). Center for Chemical and Environmental Physics

    1997-12-31

    Based on estimated exit plane sulfur speciation, a two dimensional, axisymmetric flow field model with coupled gas phase oxidation kinetics and aerosol nucleation and growth dynamics is used to