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Sample records for nanotube field emitter

  1. Carbon Nanotube Field Emitters

    OpenAIRE

    Zhbanov, Alexander; Pogorelov, Evgeny; Chang, Yia-Chung

    2010-01-01

    In this chapter we theoretically investigate the field emission from carbon nanotube field emitters in diode configuration between a flat anode and cathode. Exact analytical formulas of the electrical field, field enhancement factor, ponderomotive force, and field emission current are found. Applied voltage, height of the needle, radius of curvature on its top, and the work function are the parameters at our disposal. The field enhancement factor, total force and emission current, as well as ...

  2. Scanning Anode Field Emission Characterisation of Carbon Nanotube emitter arrays

    NARCIS (Netherlands)

    Berhanu, S.; Gröning, O.; Chen, Z.; Merikhi, J.; Bachmann, P.K.

    2011-01-01

    Scanning anode field emission microscopy (SAFEM) was used to characterise carbon nanotube (CNT) emitter arrays produced within Philips CediX-Technotubes' activities. Four different samples were investigated and compared. The field enhancement distributions were determined and the local field

  3. Recent progress of carbon nanotube field emitters and their application.

    Science.gov (United States)

    Seelaboyina, Raghunandan; Choi, Wonbong

    2007-01-01

    The potential of utilizing carbon nanotube field emission properties is an attractive feature for future vacuum electronic devices including: high power microwave, miniature x-ray, backlight for liquid crystal displays and flat panel displays. Their high emission current, nano scale geometry, chemical inertness and low threshold voltage for emission are attractive features for the field emission applications. In this paper we review the recent developments of carbon nanotube field emitters and their device applications. We also discuss the latest results on field emission current amplification achieved with an electron multiplier microchannel plate, and emission performance of multistage field emitter based on oxide nanowire operated in poor vacuum.

  4. Theory of Carbon Nanotube (CNT-Based Electron Field Emitters

    Directory of Open Access Journals (Sweden)

    Alexander V. Eletskii

    2013-07-01

    Full Text Available Theoretical problems arising in connection with development and operation of electron field emitters on the basis of carbon nanotubes are reviewed. The physical aspects of electron field emission that underlie the unique emission properties of carbon nanotubes (CNTs are considered. Physical effects and phenomena affecting the emission characteristics of CNT cathodes are analyzed. Effects given particular attention include: the electric field amplification near a CNT tip with taking into account the shape of the tip, the deviation from the vertical orientation of nanotubes and electrical field-induced alignment of those; electric field screening by neighboring nanotubes; statistical spread of the parameters of the individual CNTs comprising the cathode; the thermal effects resulting in degradation of nanotubes during emission. Simultaneous consideration of the above-listed effects permitted the development of the optimization procedure for CNT array in terms of the maximum reachable emission current density. In accordance with this procedure, the optimum inter-tube distance in the array depends on the region of the external voltage applied. The phenomenon of self-misalignment of nanotubes in an array has been predicted and analyzed in terms of the recent experiments performed. A mechanism of degradation of CNT-based electron field emitters has been analyzed consisting of the bombardment of the emitters by ions formed as a result of electron impact ionization of the residual gas molecules.

  5. Theory of Carbon Nanotube (CNT)-Based Electron Field Emitters.

    Science.gov (United States)

    Bocharov, Grigory S; Eletskii, Alexander V

    2013-07-17

    Theoretical problems arising in connection with development and operation of electron field emitters on the basis of carbon nanotubes are reviewed. The physical aspects of electron field emission that underlie the unique emission properties of carbon nanotubes (CNTs) are considered. Physical effects and phenomena affecting the emission characteristics of CNT cathodes are analyzed. Effects given particular attention include: the electric field amplification near a CNT tip with taking into account the shape of the tip, the deviation from the vertical orientation of nanotubes and electrical field-induced alignment of those; electric field screening by neighboring nanotubes; statistical spread of the parameters of the individual CNTs comprising the cathode; the thermal effects resulting in degradation of nanotubes during emission. Simultaneous consideration of the above-listed effects permitted the development of the optimization procedure for CNT array in terms of the maximum reachable emission current density. In accordance with this procedure, the optimum inter-tube distance in the array depends on the region of the external voltage applied. The phenomenon of self-misalignment of nanotubes in an array has been predicted and analyzed in terms of the recent experiments performed. A mechanism of degradation of CNT-based electron field emitters has been analyzed consisting of the bombardment of the emitters by ions formed as a result of electron impact ionization of the residual gas molecules.

  6. Theory of Carbon Nanotube (CNT)-Based Electron Field Emitters

    Science.gov (United States)

    Bocharov, Grigory S.; Eletskii, Alexander V.

    2013-01-01

    Theoretical problems arising in connection with development and operation of electron field emitters on the basis of carbon nanotubes are reviewed. The physical aspects of electron field emission that underlie the unique emission properties of carbon nanotubes (CNTs) are considered. Physical effects and phenomena affecting the emission characteristics of CNT cathodes are analyzed. Effects given particular attention include: the electric field amplification near a CNT tip with taking into account the shape of the tip, the deviation from the vertical orientation of nanotubes and electrical field-induced alignment of those; electric field screening by neighboring nanotubes; statistical spread of the parameters of the individual CNTs comprising the cathode; the thermal effects resulting in degradation of nanotubes during emission. Simultaneous consideration of the above-listed effects permitted the development of the optimization procedure for CNT array in terms of the maximum reachable emission current density. In accordance with this procedure, the optimum inter-tube distance in the array depends on the region of the external voltage applied. The phenomenon of self-misalignment of nanotubes in an array has been predicted and analyzed in terms of the recent experiments performed. A mechanism of degradation of CNT-based electron field emitters has been analyzed consisting of the bombardment of the emitters by ions formed as a result of electron impact ionization of the residual gas molecules. PMID:28348342

  7. Evaluations of carbon nanotube field emitters for electron microscopy

    Science.gov (United States)

    Nakahara, Hitoshi; Kusano, Yoshikazu; Kono, Takumi; Saito, Yahachi

    2009-11-01

    Brightness of carbon nanotube (CNT) emitters was already reported elsewhere. However, brightness of electron emitter is affected by a virtual source size of the emitter, which strongly depends on electron optical configuration around the emitter. In this work, I- V characteristics and brightness of a CNT emitter are measured under a practical field emission electron gun (e-gun) configuration to investigate availability of CNT for electron microscopy. As a result, it is obtained that an emission area of MWNT is smaller than its tip surface area, and the emission area corresponds to a five-membered-ring with 2nd nearest six-membered-rings on the MWNT cap surface. Reduced brightness of MWNT is measured as at least 2.6×109 A/m 2 sr V. It is concluded that even a thick MWNT has enough brightness under a practical e-gun electrode configuration and suitable for electron microscopy.

  8. Evaluations of carbon nanotube field emitters for electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nakahara, Hitoshi, E-mail: nakahara@nagoya-u.jp [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kusano, Yoshikazu; Kono, Takumi; Saito, Yahachi [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2009-11-30

    Brightness of carbon nanotube (CNT) emitters was already reported elsewhere. However, brightness of electron emitter is affected by a virtual source size of the emitter, which strongly depends on electron optical configuration around the emitter. In this work, I-V characteristics and brightness of a CNT emitter are measured under a practical field emission electron gun (e-gun) configuration to investigate availability of CNT for electron microscopy. As a result, it is obtained that an emission area of MWNT is smaller than its tip surface area, and the emission area corresponds to a five-membered-ring with 2nd nearest six-membered-rings on the MWNT cap surface. Reduced brightness of MWNT is measured as at least 2.6x10{sup 9} A/m{sup 2} sr V. It is concluded that even a thick MWNT has enough brightness under a practical e-gun electrode configuration and suitable for electron microscopy.

  9. Field Emission from Lateral Multiwalled Carbon Nanotube Yarn Emitters

    Directory of Open Access Journals (Sweden)

    Guohai Chen

    2016-10-01

    Full Text Available A field emission from a lateral emitter made by a multiwalled carbon nanotube (MWCNT yarn was investigated. The lateral emitter showed an excellent field emission performance with a low turn-on electric field of 1.13 V/um at an emission current of 1 uA, high emission current of 0.2 mA at an applied voltage of 700 V, and long-time emission stability for over 20 h without any significant current decay under an initial emission current of about 0.10 mA. The lateral emitter also demonstrated a uniform line emission pattern. It is suggested that the field emission occurs from the outmost MWCNTs which are protruding out from the yarn surface.

  10. Field Emission from Lateral Multiwalled Carbon Nanotube Yarn Emitters

    Science.gov (United States)

    Chen, Guohai; Song, Yenan

    2016-10-01

    A field emission from a lateral emitter made by a multiwalled carbon nanotube (MWCNT) yarn was investigated. The lateral emitter showed an excellent field emission performance with a low turn-on electric field of 1.13 V/um at an emission current of 1 uA, high emission current of 0.2 mA at an applied voltage of 700 V, and long-time emission stability for over 20 h without any significant current decay under an initial emission current of about 0.10 mA. The lateral emitter also demonstrated a uniform line emission pattern. It is suggested that the field emission occurs from the outmost MWCNTs which are protruding out from the yarn surface.

  11. Fowler Nordheim theory of carbon nanotube based field emitters

    Science.gov (United States)

    Parveen, Shama; Kumar, Avshish; Husain, Samina; Husain, Mushahid

    2017-01-01

    Field emission (FE) phenomena are generally explained in the frame-work of Fowler Nordheim (FN) theory which was given for flat metal surfaces. In this work, an effort has been made to present the field emission mechanism in carbon nanotubes (CNTs) which have tip type geometry at nanoscale. High aspect ratio of CNTs leads to large field enhancement factor and lower operating voltages because the electric field strength in the vicinity of the nanotubes tip can be enhanced by thousand times. The work function of nanostructure by using FN plot has been calculated with reverse engineering. With the help of modified FN equation, an important formula for effective emitting area (active area for emission of electrons) has been derived and employed to calculate the active emitting area for CNT field emitters. Therefore, it is of great interest to present a state of art study on the complete solution of FN equation for CNTs based field emitter displays. This manuscript will also provide a better understanding of calculation of different FE parameters of CNTs field emitters using FN equation.

  12. Fowler Nordheim theory of carbon nanotube based field emitters

    Energy Technology Data Exchange (ETDEWEB)

    Parveen, Shama; Kumar, Avshish [Department of Physics, Jamia Millia Islamia (Central University), New Delhi (India); Husain, Samina [Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia (Central University), New Delhi (India); Husain, Mushahid, E-mail: mush_reslab@rediffmail.com [Department of Physics, Jamia Millia Islamia (Central University), New Delhi (India)

    2017-01-15

    Field emission (FE) phenomena are generally explained in the frame-work of Fowler Nordheim (FN) theory which was given for flat metal surfaces. In this work, an effort has been made to present the field emission mechanism in carbon nanotubes (CNTs) which have tip type geometry at nanoscale. High aspect ratio of CNTs leads to large field enhancement factor and lower operating voltages because the electric field strength in the vicinity of the nanotubes tip can be enhanced by thousand times. The work function of nanostructure by using FN plot has been calculated with reverse engineering. With the help of modified FN equation, an important formula for effective emitting area (active area for emission of electrons) has been derived and employed to calculate the active emitting area for CNT field emitters. Therefore, it is of great interest to present a state of art study on the complete solution of FN equation for CNTs based field emitter displays. This manuscript will also provide a better understanding of calculation of different FE parameters of CNTs field emitters using FN equation.

  13. A fabrication method for field emitter array of carbon nanotubes with improved carbon nanotube rooting

    Energy Technology Data Exchange (ETDEWEB)

    Chouhan, V., E-mail: vchouhan@post.kek.jp [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)

    2015-11-30

    We have developed a technique for fabrication of a field emitter array (FEA) of carbon nanotubes (CNTs) to obtain a high emission current along with a high current density. The FEA was prepared with many small equidistant circular emitters of randomly oriented multiwall carbon nanotubes. The fabrication of a FEA substrate followed with deposition of titanium nitride (TiN) film on a tantalum (Ta) substrate and circular titanium (Ti) islands on the TiN coated Ta substrate in a DC magnetron sputtering coater. CNTs were dispersed on the substrate and rooted into the circular Ti islands at a high temperature to prepare an array of circular emitters of CNTs. The TiN film was applied on a Ta substrate to make a reaction barrier between the Ta substrate and CNTs in order to root CNTs only into the Ti islands without a reaction with the Ta substrate at the high temperature. A high emission current of 31.7 mA with an effective current density of 34.5 A/cm{sup 2} was drawn at 6.5 V/μm from a FEA having 130 circular emitters in a diameter of 50 μm and with a pitch of 200 μm. The high emission current was ascribed to the good quality rooting of CNTs into the Ti islands and an edge effect, in which a high emission current was expected from the peripheries of the circular emitters. - Highlights: • We developed a method to fabricate a field emitter array of carbon nanotubes (CNTs). • CNT rooting into array of titanium islands was improved at a high temperature. • Titanium nitride film was used to stop reaction between CNT and tantalum substrate. • Strong edge effect was achieved from an array of small circular emitters of CNTs. • The good quality CNT rooting and the edge effect enhanced an emission current.

  14. Systems and Methods for Implementing Robust Carbon Nanotube-Based Field Emitters

    Science.gov (United States)

    Manohara, Harish (Inventor); Kristof, Valerie (Inventor); Toda, Risaku (Inventor)

    2015-01-01

    Systems and methods in accordance with embodiments of the invention implement carbon nanotube-based field emitters. In one embodiment, a method of fabricating a carbon nanotube field emitter includes: patterning a substrate with a catalyst, where the substrate has thereon disposed a diffusion barrier layer; growing a plurality of carbon nanotubes on at least a portion of the patterned catalyst; and heating the substrate to an extent where it begins to soften such that at least a portion of at least one carbon nanotube becomes enveloped by the softened substrate.

  15. New-type planar field emission display with superaligned carbon nanotube yarn emitter.

    Science.gov (United States)

    Liu, Peng; Wei, Yang; Liu, Kai; Liu, Liang; Jiang, Kaili; Fan, Shoushan

    2012-05-09

    With the superaligned carbon nanotube yarn as emitter, we have fabricated a 16 × 16 pixel field emission display prototype by adopting screen printing and laser cutting technologies. A planar diode field emission structure has been adopted. A very sharp carbon nanotube yarn tip emitter can be formed by laser cutting. Low voltage phosphor was coated on the anode electrodes also by screen printing. With a specially designed circuit, we have demonstrated the dynamic character display with the field emission display prototype. The emitter material and fabrication technologies in this paper are both easy to scale up to large areas.

  16. Field emission behavior of carbon nanotube field emitters after high temperature thermal annealing

    Directory of Open Access Journals (Sweden)

    Yuning Sun

    2014-07-01

    Full Text Available The carbon nanotube (CNT field emitters have been fabricated by attaching a CNT film on a graphite rod using graphite adhesive material. The CNT field emitters showed much improved field emission properties due to increasing crystallinity and decreasing defects in CNTs after the high temperature thermal annealing at 900 °C in vacuum ambient. The CNT field emitters showed the low turn-on electric field of 1.15 V/μm, the low threshold electric field of 1.62 V/μm, and the high emission current of 5.9 mA which corresponds to a current density of 8.5 A/cm2. In addition, the CNT field emitters indicated the enhanced field emission properties due to the multi-stage effect when the length of the graphite rod increases. The CNT field emitter showed good field emission stability after the high temperature thermal annealing. The CNT field emitter revealed a focused electron beam spot without any focusing electrodes and also showed good field emission repeatability.

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

    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); He, Hong; Yu, Hua; Cao, Yiqi [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Lei, Da, E-mail: leida126@126.com [Ordos College of Inner Mongolia University, Inner Mongolia University, Ordos 017000 (China); Menggen, QiQiGe [Ordos College of Inner Mongolia University, Inner Mongolia University, Ordos 017000 (China); Wu, Chaoxing; Hu, Liqin [College of Physics and Information Engineering, Fuzhou University, Fuzhou 350002 (China)

    2014-10-15

    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.

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

    Science.gov (United States)

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

    2016-04-01

    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/cm2 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.

  19. Energy distribution for undergate-type triode carbon nanotube field emitters

    Science.gov (United States)

    Yu, SeGi; Yi, Whikun; Lee, Jeonghee; Jeong, Taewon; Jin, Sunghwan; Heo, Jungna; Kang, J. H.; Choi, Y. S.; Lee, Chang Soo; Yoo, Ji-Beom; Kim, J. M.

    2002-05-01

    Field emission energy distribution (FEED) has been measured for undergate-type triode carbon nanotube (CNT) field emitters where the gate electrodes are located underneath the cathode electrodes. The diode-type emission for these CNT emitters was found to follow the Fowler-Nordheim relation, whereas the triode-type emission exhibited the deviation from this relation. The FEED peaks for the undergate CNT emitters under the triode-type emission shifted to lower energy as the gate voltage increased, indicating nonmetallic behavior for the CNT emitters. There exist two different characteristic FEED peaks, where their peak energy shifts as a function of the gate voltage belong to two different slopes. From the difference in the position and intensity of the peaks, it was found that one was field emission directly from CNTs and the other might be emitted from CNTs through glass powders which were added during the CNT field emitter fabrication process.

  20. 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.

  1. High-performance field emission of carbon nanotube paste emitters fabricated using graphite nanopowder filler

    Science.gov (United States)

    Sun, Yuning; Yun, Ki Nam; Leti, Guillaume; Lee, Sang Heon; Song, Yoon-Ho; Lee, Cheol Jin

    2017-02-01

    Carbon nanotube (CNT) paste emitters were fabricated using graphite nanopowder filler. The CNT paste emitters consist of CNTs as the emitting material, graphite nanopowder as the filler and a graphite rod as the cathode. Rather than metal or inorganic materials, graphite nanopowder was adapted as a filler material to make the CNT paste emitters. After fabricating the emitters, sandpaper treatment was applied to increase the density of emission sites. The CNT paste emitters showed a high field emission performance, for example a high emission current of 8.5 mA from a cylindrical emitter with a diameter of 0.7 mm (corresponding to a current density of 2.2 A cm-2) and an extremely stable emission current at 1 mA (260 mA cm-2 for 20 h). Interestingly, after a number of electrical arcing events, the emitters still showed a high emission current of 5-8 mA (higher than 1 A cm-2). In addition to the sound electrical and thermal properties of the graphite filler, effective mechanical adhesion of the CNTs onto the graphite cathode induced by the use of the graphite nanopowder filler contributed the excellent field emission properties of the CNT paste emitters.

  2. High Field Emission Current Density from Patterned Carbon Nanotube Field Emitter Arrays with Random Growth.

    Science.gov (United States)

    Khaneja, Mamta; Ghosh, Santanu; Gautam, Seema; Kumar, Prashant; Rawat, J S; Chaudhury, P K; Vankar, V D; Kumar, Vikram

    2015-05-01

    High field emission (FE) current density from carbon nanotube (CNT) arrays grown on lithographically patterned silicon substrates is reported. A typical patterned field emitter array consists of bundles of nanotubes separated by a fixed gap and spread over the entire emission area. Emission performance from such an array having randomly oriented nanotube growth within each bundle is reported for different bundle sizes and separations. One typical sample with aligned CNTs within the bundle is also examined for comparison. It is seen that the current density from an array having random nanotube growth within the bundles is appreciably higher as compared to its aligned counterpart. The influence of structure on FE current densities as revealed by Raman spectroscopy is also seen. It is also observed that current density depends on edge length and increases with the same for all samples under study. Highest current density of -100 mA cm(-2) at an applied field of 5 V/μm is achieved from the random growth patterned sample with a bundle size of 2 μm and spacing of 4 μm between the bundles.

  3. Stable Field Emitters for a Miniature X-ray Tube Using Carbon Nanotube Drop Drying on a Flat Metal Tip

    OpenAIRE

    Heo SungHwan; Ihsan Aamir; Yoo SeungHwa; Ali Ghafar; Cho SungOh

    2010-01-01

    Abstract Stable carbon nanotube (CNT) field emitters for a vacuum-sealed miniature X-ray tube have been fabricated. The field emitters with a uniform CNT coating are prepared by a simple drop drying of a CNT mixture solution that is composed of chemically modified multi-walled CNTs, silver nanoparticles, and isopropyl alcohol on flat tungsten tips. A highly thermal- and electrical-conductive silver layer strongly attaches CNTs to the tungsten tips. Consequently, the field emitters exhibit goo...

  4. Fabrication of Gate-Electrode Integrated Carbon-Nanotube Bundle Field Emitters

    Science.gov (United States)

    Toda, Risaku; Bronikowski, Michael; Luong, Edward; Manohara, Harish

    2008-01-01

    A continuing effort to develop carbon-nanotube-based field emitters (cold cathodes) as high-current-density electron sources has yielded an optimized device design and a fabrication scheme to implement the design. One major element of the device design is to use a planar array of bundles of carbon nanotubes as the field-emission tips and to optimize the critical dimensions of the array (principally, heights of bundles and distances between them) to obtain high area-averaged current density and high reliability over a long operational lifetime a concept that was discussed in more detail in Arrays of Bundles of Carbon Nanotubes as Field Emitters (NPO-40817), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 58. Another major element of the design is to configure the gate electrodes (anodes used to extract, accelerate, and/or focus electrons) as a ring that overhangs a recess wherein the bundles of nanotubes are located, such that by virtue of the proximity between the ring and the bundles, a relatively low applied potential suffices to generate the large electric field needed for emission of electrons.

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

    Science.gov (United States)

    Chen, YiWen; Miao, Hsin-Yuan; Lin, Ryan Jiyao; Zhang, Mei; Liang, Richard; Zhang, Chuck; Wang, Ben

    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(-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.

  6. Enhanced Field-Emission Performance from Carbon Nanotube Emitters on Nickel Foam Cathodes

    Science.gov (United States)

    Song, Meng; Xu, Peng; Han, Lijing; Yi, Lan; Wang, Xu; Li, Zhenhua; Shang, Xuefu; Wang, Xiumin; Wu, Huizhen; Zhao, Pei; Song, Yenan; Wang, Miao

    2016-04-01

    We present a three-dimensionally configured cathode with enhanced field-emission performance formed by combining carbon nanotube (CNT) emitters with a nickel foam (NiF) substrate via a conventional screen-printing technique. The CNT/NiF cathode has low turn-on electric field of 0.53 V μm-1 (with current density of 10 μA cm-2) and threshold electric field of 0.87 V μm-1 (with current density of 0.1 mA cm-2), and a very high field enhancement factor of 1.4 × 104. The porous structure of the NiF substrate can greatly improve the field-emission properties due to its large specific surface area that can accommodate more CNTs and increase the emitter density, as well as its high electrical and thermal conductivities that facilitate current transition and heat dissipation in the cathode. Most importantly, the local electric field was also enhanced by the multistage effect resulting from the rough metal surface, which furthermore leads to a high field enhancement factor. We believe that this improved field-emission performance makes such cathodes promising candidates for use in various field-emission applications.

  7. Highly reliable field electron emitters produced from reproducible damage-free carbon nanotube composite pastes with optimal inorganic fillers.

    Science.gov (United States)

    Kim, Jae-Woo; Jeong, Jin-Woo; Kang, Jun-Tae; Choi, Sungyoul; Ahn, Seungjoon; Song, Yoon-Ho

    2014-02-14

    Highly reliable field electron emitters were developed using a formulation for reproducible damage-free carbon nanotube (CNT) composite pastes with optimal inorganic fillers and a ball-milling method. We carefully controlled the ball-milling sequence and time to avoid any damage to the CNTs, which incorporated fillers that were fully dispersed as paste constituents. The field electron emitters fabricated by printing the CNT pastes were found to exhibit almost perfect adhesion of the CNT emitters to the cathode, along with good uniformity and reproducibility. A high field enhancement factor of around 10,000 was achieved from the CNT field emitters developed. By selecting nano-sized metal alloys and oxides and using the same formulation sequence, we also developed reliable field emitters that could survive high-temperature post processing. These field emitters had high durability to post vacuum annealing at 950 °C, guaranteeing survival of the brazing process used in the sealing of field emission x-ray tubes. We evaluated the field emitters in a triode configuration in the harsh environment of a tiny vacuum-sealed vessel and observed very reliable operation for 30 h at a high current density of 350 mA cm(-2). The CNT pastes and related field emitters that were developed could be usefully applied in reliable field emission devices.

  8. Highly reliable field electron emitters produced from reproducible damage-free carbon nanotube composite pastes with optimal inorganic fillers

    Science.gov (United States)

    Kim, Jae-Woo; Jeong, Jin-Woo; Kang, Jun-Tae; Choi, Sungyoul; Ahn, Seungjoon; Song, Yoon-Ho

    2014-02-01

    Highly reliable field electron emitters were developed using a formulation for reproducible damage-free carbon nanotube (CNT) composite pastes with optimal inorganic fillers and a ball-milling method. We carefully controlled the ball-milling sequence and time to avoid any damage to the CNTs, which incorporated fillers that were fully dispersed as paste constituents. The field electron emitters fabricated by printing the CNT pastes were found to exhibit almost perfect adhesion of the CNT emitters to the cathode, along with good uniformity and reproducibility. A high field enhancement factor of around 10 000 was achieved from the CNT field emitters developed. By selecting nano-sized metal alloys and oxides and using the same formulation sequence, we also developed reliable field emitters that could survive high-temperature post processing. These field emitters had high durability to post vacuum annealing at 950 °C, guaranteeing survival of the brazing process used in the sealing of field emission x-ray tubes. We evaluated the field emitters in a triode configuration in the harsh environment of a tiny vacuum-sealed vessel and observed very reliable operation for 30 h at a high current density of 350 mA cm-2. The CNT pastes and related field emitters that were developed could be usefully applied in reliable field emission devices.

  9. 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...

  10. A digital miniature x-ray tube with a high-density triode carbon nanotube field emitter

    Science.gov (United States)

    Jeong, Jin-Woo; Kang, Jun-Tae; Choi, Sungyoul; Kim, Jae-Woo; Ahn, Seungjoon; Song, Yoon-Ho

    2013-01-01

    We have fabricated a digital miniature x-ray tube (6 mm in diameter and 32 mm in length) with a high-density triode carbon nanotube (CNT) field emitter for special x-ray applications. The triode CNT emitter was densely formed within a diameter of below 4 mm with the focusing-functional gate. The brazing process enables us to obtain and maintain a desired vacuum level for the reliable electron emission from the CNT emitters after the vacuum packaging. The miniature x-ray tube exhibited a stable and reliable operation over 250 h in a pulse mode at an anode voltage of above 25 kV.

  11. A digital miniature x-ray tube with a high-density triode carbon nanotube field emitter

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Jin-Woo; Kang, Jun-Tae; Choi, Sungyoul [Nano Electron-source Creative Research Center, Electronics and Telecommunications Research Institute, 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700 (Korea, Republic of); Kim, Jae-Woo; Song, Yoon-Ho [Nano Electron-source Creative Research Center, Electronics and Telecommunications Research Institute, 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700 (Korea, Republic of); School of Advanced Device Engineering, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 305-350 (Korea, Republic of); Ahn, Seungjoon [Nano Electron-source Creative Research Center, Electronics and Telecommunications Research Institute, 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700 (Korea, Republic of); Department of Information Display, Sun Moon University, Kalsan-ri, Tangjeong-myoon, Asan-si, Chungnam 336-708 (Korea, Republic of)

    2013-01-14

    We have fabricated a digital miniature x-ray tube (6 mm in diameter and 32 mm in length) with a high-density triode carbon nanotube (CNT) field emitter for special x-ray applications. The triode CNT emitter was densely formed within a diameter of below 4 mm with the focusing-functional gate. The brazing process enables us to obtain and maintain a desired vacuum level for the reliable electron emission from the CNT emitters after the vacuum packaging. The miniature x-ray tube exhibited a stable and reliable operation over 250 h in a pulse mode at an anode voltage of above 25 kV.

  12. Carbon and metal nanotube hybrid structures on graphene as efficient electron field emitters

    Science.gov (United States)

    Heo, Kwang; Lee, Byung Yang; Lee, Hyungwoo; Cho, Dong-guk; Arif, Muhammad; Kim, Kyu Young; Choi, Young Jin; Hong, Seunghun

    2016-07-01

    We report a facile and efficient method for the fabrication of highly-flexible field emission devices by forming tubular hybrid structures based on carbon nanotubes (CNTs) and nickel nanotubes (Ni NTs) on graphene-based flexible substrates. By employing an infiltration process in anodic alumina oxide (AAO) templates followed by Ni electrodeposition, we could fabricate CNT-wrapped Ni NT/graphene hybrid structures. During the electrodeposition process, the CNTs served as Ni nucleation sites, resulting in a large-area array of high aspect-ratio field emitters composed of CNT-wrapped Ni NT hybrid structures. As a proof of concepts, we demonstrate that high-quality flexible field emission devices can be simply fabricated using our method. Remarkably, our proto-type field emission devices exhibited a current density higher by two orders of magnitude compared to other devices fabricated by previous methods, while maintaining its structural integrity in various bending deformations. This novel fabrication strategy can be utilized in various applications such as optoelectronic devices, sensors and energy storage devices.

  13. Cerium oxide dispersed multi walled carbon nanotubes as cathode material for flexible field emitters.

    Science.gov (United States)

    Baby, Tessy Theres; Rakhi, R B; Ravi, N; Ramaprabhu, S

    2012-08-01

    Nanomaterials based electron sources are omnipresent in modern flat panel displays. Multi walled carbon nanotubes (MWNT) are the well studied electron emitter among the carbon materials. Since the surface modification of MWNT with low work function materials would have a positive impact on the field emission property of MWNT, cerium oxide (CeO2) nanoparticles dispersed multi walled carbon nanotubes (CeO2/MWNT) were synthesized by catalytic chemical vapour deposition followed by chemical reduction and its field emission property was investigated. The high-purity MWNT as well as CeO2/MWNT showed crystalline structure conformed by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Further characterisation was done with Raman spectroscopy, UV-Visible absorption spectra and Fourier transform IR spectroscopy (FT-IR). The morphology and structural details of CeO2/MWNT composite was probed by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDX). The direct evidence of the formation of CeO2/MWNT composites was given by transmission electron microscopy (TEM). The synthesized sample was coated over a flexible carbon paper using spin coating technique. The experiment was performed under a vacuum of 1 x 10(-6) Torr and Fowler-Nordheim equation was used to analyse the data. The turn-on voltage for the cerium oxide dispersed MWNT was found for a current density of 10 microA/cm2. The emission current density from the CeO2 nanoparticles dispersed MWNT reached 0.2 mA/cm2 at a reasonable bias field of 2.58 V/microm. The results were compared with those of pure MWNT and pure CeO2 nanoparticles with literature values.

  14. Stable Field Emitters for a Miniature X-ray Tube Using Carbon Nanotube Drop Drying on a Flat Metal Tip

    Directory of Open Access Journals (Sweden)

    Heo SungHwan

    2010-01-01

    Full Text Available Abstract Stable carbon nanotube (CNT field emitters for a vacuum-sealed miniature X-ray tube have been fabricated. The field emitters with a uniform CNT coating are prepared by a simple drop drying of a CNT mixture solution that is composed of chemically modified multi-walled CNTs, silver nanoparticles, and isopropyl alcohol on flat tungsten tips. A highly thermal- and electrical-conductive silver layer strongly attaches CNTs to the tungsten tips. Consequently, the field emitters exhibit good electron emission stability: continuous electron emission of around 100 μA at 2.3 V/μm has stably lasted over 40 h even at non-high vacuum ambient (~10−3 Pa.

  15. Stable Field Emitters for a Miniature X-ray Tube Using Carbon Nanotube Drop Drying on a Flat Metal Tip

    Science.gov (United States)

    Heo, Sung Hwan; Ihsan, Aamir; Yoo, Seung Hwa; Ali, Ghafar; Cho, Sung Oh

    2010-04-01

    Stable carbon nanotube (CNT) field emitters for a vacuum-sealed miniature X-ray tube have been fabricated. The field emitters with a uniform CNT coating are prepared by a simple drop drying of a CNT mixture solution that is composed of chemically modified multi-walled CNTs, silver nanoparticles, and isopropyl alcohol on flat tungsten tips. A highly thermal- and electrical-conductive silver layer strongly attaches CNTs to the tungsten tips. Consequently, the field emitters exhibit good electron emission stability: continuous electron emission of around 100 μA at 2.3 V/μm has stably lasted over 40 h even at non-high vacuum ambient (~10-3 Pa).

  16. Asymmetrical field emitter

    Science.gov (United States)

    Fleming, J.G.; Smith, B.K.

    1995-10-10

    A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

  17. Enhanced field emission from compound emitters of carbon nanotubes and ZnO tetrapods by electron beam bombardment.

    Science.gov (United States)

    Wei, Lei; Zhang, Xiaobing; Lou, Chaogang; Zhao, Zhiwei; Jing, Chen; Wang, Baoping

    2011-06-01

    The enhancement of field emission from compound emitters of carbon nanotubes and ZnO tetrapods by the electron beam bombardment is reported. After 20 minutes electron bombardment with 6 keV energy, a few bird-nest micro structures are formed in the compound emitters array. As the simulation results shown, the electric field and field emission current density at the tip of ZnO tetrapod are increased due to the influences of these bird-nest micro structures. From the measurement of the field emission performance, it can be seen that the turn-on electric field and threshold electric field of the field emitter array decrease to 0.4 V/microm and 2.4 V/microm respectively. They have decreased 62% and 15% after the electron bombardment. After the electron bombardment, the emission sites density is increased. The field emission images show that the uniformity of field emission has been improved obviously after the proper electron bombardment. The methodology proposed in this paper has a promising application in the field emission devices.

  18. High Stability Electron Field Emitters Synthesized via the Combination of Carbon Nanotubes and N₂-Plasma Grown Ultrananocrystalline Diamond Films.

    Science.gov (United States)

    Chang, Ting-Hsun; Hsieh, Ping-Yen; Kunuku, Srinivasu; Lou, Shiu-Cheng; Manoharan, Divinah; Leou, Keh-Chyang; Lin, I-Nan; Tai, Nyan-Hwa

    2015-12-16

    An electron field emitter with superior electron field emission (EFE) properties and improved lifetime stability is being demonstrated via the combination of carbon nanotubes and the CH4/N2 plasma grown ultrananocrystalline diamond (N-UNCD) films. The resistance of the carbon nanotubes to plasma ion bombardment is improved by the formation of carbon nanocones on the side walls of the carbon nanotubes, thus forming strengthened carbon nanotubes (s-CNTs). The N-UNCD films can thus be grown on s-CNTs, forming N-UNCD/s-CNTs carbon nanocomposite materials. The N-UNCD/s-CNTs films possess good conductivity of σ = 237 S/cm and marvelous EFE properties, such as low turn-on field of (E0) = 3.58 V/μm with large EFE current density of (J(e)) = 1.86 mA/cm(2) at an applied field of 6.0 V/μm. Moreover, the EFE emitters can be operated under 0.19 mA/cm(2) for more than 350 min without showing any sign of degradation. Such a superior EFE property along with high robustness characteristic of these combination of materials are not attainable with neither N-UNCD films nor s-CNTs films alone. Transmission electron microscopic investigations indicated that the N-UNCD films contain needle-like diamond grains encased in a few layers of nanographitic phase, which enhanced markedly the transport of electrons in the N-UNCD films. Moreover, the needle-like diamond grains were nucleated from the s-CNTs without the necessity of forming the interlayer that facilitate the transport of electrons crossing the diamond-to-Si interface. Both these factors contributed to the enhanced EFE behavior of the N-UNCD/s-CNTs films.

  19. Carbon nanotube electron field emitters for X-ray imaging of human breast cancer

    OpenAIRE

    Gidcumb, Emily; Gao, Bo; Shan, Jing; Inscoe, Christy; Lu, Jianping; Zhou, Otto

    2014-01-01

    For imaging human breast cancer, digital breast tomosynthesis (DBT) has been shown to improve image quality and breast cancer detection in comparison to 2D mammography. Current DBT systems have limited spatial resolution and lengthy scan times. Stationary digital breast tomosynthesis (s-DBT), utilizing an array of carbon nanotube (CNT) field emission X-ray sources, provides increased spatial resolution and potentially faster imaging than current DBT systems. This study presents...

  20. Effect of increased crystallinity of single-walled carbon nanotubes used as field emitters on their electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Shimoi, Norihiro, E-mail: shimoi@mail.kankyo.tohoku.ac.jp [Graduate School of Environmental Studies, Tohoku University, 6-6-20 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

    2015-12-07

    Single-walled carbon nanotubes (SWCNTs) synthesized by arc discharge are expected to exhibit good field emission (FE) properties at a low driving voltage. We used a coating containing homogeneously dispersed highly crystalline SWCNTs produced by a high-temperature annealing process to fabricate an FE device by a wet-coating process at a low cost. Using the coating, we succeeded in reducing the power consumption of field emitters for planar lighting devices. SWCNTs synthesized by arc discharge have crystal defects in the carbon network, which are considered to induce inelastic electron tunneling that deteriorates the electrical conductivity of the SWCNTs. In this study, the blocking of the transport of electrons in SWCNTs with crystal defects is simulated using an inelastic electron tunneling model. We succeeded in clarifying the mechanism underlying the electrical conductivity of SWCNTs by controlling their crystallinity. In addition, it was confirmed that field emitters using highly crystalline SWCNTs can lead to new applications operating with low power consumption and new devices that may change our daily lives in the future.

  1. Carbon Nanotube Electron Emitter for X-ray Imaging

    Directory of Open Access Journals (Sweden)

    Jung Su Kang

    2012-11-01

    Full Text Available The carbon nanotube field emitter array was grown on silicon substrate through a resist-assisted patterning (RAP process. The shape of the carbon nanotube array is elliptical with 2.0 × 0.5 mm2 for an isotropic focal spot size at anode target. The field emission properties with triode electrodes show a gate turn-on field of 3 V/µm at an anode emission current of 0.1 mA. The author demonstrated the X-ray source with triode electrode structure utilizing the carbon nanotube emitter, and the transmitted X-ray image was of high resolution.

  2. A vacuum-sealed miniature X-ray tube based on carbon nanotube field emitters

    Science.gov (United States)

    Heo, Sung Hwan; Kim, Hyun Jin; Ha, Jun Mok; Cho, Sung Oh

    2012-05-01

    A vacuum-sealed miniature X-ray tube based on a carbon nanotube field-emission electron source has been demonstrated. The diameter of the X-ray tube is 10 mm; the total length of the tube is 50 mm, and no external vacuum pump is required for the operation. The maximum tube voltage reaches up to 70 kV, and the X-ray tube generates intense X-rays with the air kerma strength of 108 Gy·cm2 min-1. In addition, X-rays produced from the miniature X-ray tube have a comparatively uniform spatial dose distribution.

  3. A vacuum-sealed miniature X-ray tube based on carbon nanotube field emitters

    OpenAIRE

    Heo, Sung Hwan; Kim, Hyun Jin; Ha, Jun Mok; Cho, Sung Oh

    2012-01-01

    A vacuum-sealed miniature X-ray tube based on a carbon nanotube field-emission electron source has been demonstrated. The diameter of the X-ray tube is 10 mm; the total length of the tube is 50 mm, and no external vacuum pump is required for the operation. The maximum tube voltage reaches up to 70 kV, and the X-ray tube generates intense X-rays with the air kerma strength of 108 Gy·cm2 min−1. In addition, X-rays produced from the miniature X-ray tube have a comparatively uniform spatial dose ...

  4. Study of thermal-field emission properties and investigation of temperature dependent noise in the field emission current from vertical carbon nanotube emitters

    Science.gov (United States)

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

    2017-10-01

    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] 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 distribution of electron emission spots and ring like structures in Field Emission Microscope (FEM) image. The FEM images could be used to calculate the total number of emitters per cm2 for electron emission. The calculated number of emitters per cm2 from FEM image is typically, 4.5 × 107 and the actual number emitters per cm2 present as per Atomic Force Microscopy (AFM) data is 1.2 × 1012. The measured Current-Voltage (I-V) characteristics exhibit non linear Folwer-Nordheim (F-N) type behavior. The fluctuations in the emission current were recorded at different temperatures and Fast Fourier transformed into temperature dependent power spectral density. The latter was found to obey power law relation S(f) = A(Iδ/fξ), where δ and ξ are temperature dependent current and frequency exponents respectively.

  5. Carbon nanotube field emitters on KOVAR substrate modified by random pattern

    Energy Technology Data Exchange (ETDEWEB)

    Park, Seol Ah; Song, Eun-Ho; Kang, Byung Hyun; Ju, Byeong-Kwon, E-mail: bkju@korea.ac.kr [Korea University, Display and Nanosystem Laboratory, College of Engineering (Korea, Republic of)

    2015-07-15

    We investigated the field emission characteristics of patterned carbon nanotubes (CNTs) on KOVAR substrates with different surface morphologies. The substrate with a micro-sized random pattern was fabricated through chemical wet etching, whereas the substrate with a nano-sized random pattern was formed by surface roughening process of polymer and chemical wet etching. The field emission characteristics of these substrates were the compared with those of non-treated substrates. It was clearly revealed that the field emission characteristics of CNTs were influenced by the surface morphology of the cathode substrate. When the surface of cathode was modified by random pattern, the modified substrate provided a large surface area and a wider print area. Also, the modified surface morphology of the cathode provided strong adhesion between the CNT paste and the cathode. Particularly, the substrate with the nano-sized random pattern showed that the turn-on field value decreases and the field enhancement factor value improves as compared with non-treated substrate.

  6. Fabrication of barium/strontium carbonate coated amorphous carbon nanotubes as an improved field emitter

    Science.gov (United States)

    Maity, S.; Jha, A.; Das, N. S.; Chattopadhyay, K. K.

    2013-02-01

    Amorphous carbon nanotubes (aCNTs) were synthesized by a chemical reaction between ferrocene and ammonium chloride at a temperature ˜250 ∘C in an air furnace. As-synthesized aCNTs were coated with the barium/strontium carbonate through a simple chemical process. The coating of barium/strontium carbonate was confirmed by a high resolution transmission electron microscopy, X-ray diffraction, and Fourier transformed infrared spectroscopy. Morphology of the as-prepared samples was studied by field emission scanning electron microscopy. Thermal gravimetric analysis showed that barium/strontium carbonate coated aCNTs are more stable than the pristine aCNTs. As-prepared barium/strontium carbonate coated aCNTs showed significantly improved field emission properties with a turn-on field as low as 2.5 V/μm. The variation of field emission characteristics of the barium/strontium carbonate coated aCNTs with interelectrode distances was also studied.

  7. Controlled growth of carbon nanotube-graphene hybrid materials for flexible and transparent conductors and electron field emitters.

    Science.gov (United States)

    Nguyen, Duc Dung; Tai, Nyan-Hwa; Chen, Szu-Ying; Chueh, Yu-Lun

    2012-01-21

    We report a versatile synthetic process based on rapid heating and cooling chemical vapor deposition for the growth of carbon nanotube (CNT)-graphene hybrid materials where the thickness of graphene and density of CNTs are properly controlled. Graphene films are demonstrated as an efficient barrier layer for preventing poisoning of iron nanoparticles, which catalyze the growth of CNTs on copper substrates. Based on this method, the opto-electronic and field emission properties of graphene integrated with CNTs can be remarkably tailored. A graphene film exhibits a sheet resistance of 2.15 kΩ sq(-1) with a transmittance of 85.6% (at 550 nm), while a CNT-graphene hybrid film shows an improved sheet resistance of 420 Ω sq(-1) with an optical transmittance of 72.9%. Moreover, CNT-graphene films are demonstrated as effective electron field emitters with low turn-on and threshold electric fields of 2.9 and 3.3 V μm(-1), respectively. The development of CNT-graphene films with a wide range of tunable properties presented in this study shows promising applications in flexible opto-electronic, energy, and sensor devices.

  8. Decoration of cesium iodide nano particles on patterned carbon nanotube emitter arrays to improve their field emission

    Science.gov (United States)

    Shahi, Monika; Gautam, S.; Shah, P. V.; Rawat, J. S.; Chaudhury, P. K.; Harsh; Tandon, R. P.

    2013-03-01

    Arrays of aligned carbon nanotube (CNT) bundles were synthesized on the pre-patterned silicon substrate using thermal chemical vapor deposition. Silicon substrate was patterned with square arrays of 10 × 10 μm iron catalyst using photolithography, iron sputtering, and a lift-off process. After field emission (FE) measurement in diode configuration, CNT emitter arrays (CEAs) were decorated with cesium iodide (CsI) nano particles (NPs) using thermal evaporation with substrate heating at 300 °C. FE of pristine CEAs and CsI NPs decorated CEAs were carried out under same vacuum condition and constant inter-electrode separation. Pristine CEAs and CsI NPs decorated CEAs were characterized using scanning electron microscope, transmission electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman characterization. From FE comparison plots, it was observed that CsI NPs decoration on the CEAs had significantly lowered the turn-on electric field from 3.00 to 2.13 V/μm. A remarkable improvement of more than 50 % in the current density, from 11.02 to 17.33 mA/cm2, was also observed at a constant applied electric field of 5 V/μm.

  9. Decoration of cesium iodide nano particles on patterned carbon nanotube emitter arrays to improve their field emission

    Energy Technology Data Exchange (ETDEWEB)

    Shahi, Monika, E-mail: moni.binda@gmail.com; Gautam, S.; Shah, P. V.; Rawat, J. S.; Chaudhury, P. K. [Solid State Physics Laboratory (India); Harsh [Jamia Millia Islamia, Department of Physics (India); Tandon, R. P. [University of Delhi, Department of Physics and Astrophysics (India)

    2013-03-15

    Arrays of aligned carbon nanotube (CNT) bundles were synthesized on the pre-patterned silicon substrate using thermal chemical vapor deposition. Silicon substrate was patterned with square arrays of 10 Multiplication-Sign 10 {mu}m iron catalyst using photolithography, iron sputtering, and a lift-off process. After field emission (FE) measurement in diode configuration, CNT emitter arrays (CEAs) were decorated with cesium iodide (CsI) nano particles (NPs) using thermal evaporation with substrate heating at 300 Degree-Sign C. FE of pristine CEAs and CsI NPs decorated CEAs were carried out under same vacuum condition and constant inter-electrode separation. Pristine CEAs and CsI NPs decorated CEAs were characterized using scanning electron microscope, transmission electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman characterization. From FE comparison plots, it was observed that CsI NPs decoration on the CEAs had significantly lowered the turn-on electric field from 3.00 to 2.13 V/{mu}m. A remarkable improvement of more than 50 % in the current density, from 11.02 to 17.33 mA/cm{sup 2}, was also observed at a constant applied electric field of 5 V/{mu}m.

  10. Carbon nanotube electron field emitters for x-ray imaging of human breast cancer.

    Science.gov (United States)

    Gidcumb, Emily; Gao, Bo; Shan, Jing; Inscoe, Christy; Lu, Jianping; Zhou, Otto

    2014-06-20

    For imaging human breast cancer, digital breast tomosynthesis (DBT) has been shown to improve image quality and breast cancer detection in comparison to two-dimensional (2D) mammography. Current DBT systems have limited spatial resolution and lengthy scan times. Stationary DBT (s-DBT), utilizing an array of carbon nanotube (CNT) field emission x-ray sources, provides increased spatial resolution and potentially faster imaging than current DBT systems. This study presents the results of detailed evaluations of CNT cathodes for x-ray breast imaging tasks. The following were investigated: high current, long-term stability of CNT cathodes for DBT; feasibility of using CNT cathodes to perform a 2D radiograph function; and cathode performance through several years of imaging. Results show that a breast tomosynthesis system using CNT cathodes could run far beyond the experimentally tested lifetime of one to two years. CNT cathodes were found capable of producing higher currents than typical DBT would require, indicating that the s-DBT imaging time can be further reduced. The feasibility of using a single cathode of the s-DBT tube to perform 2D mammography in 4 s was demonstrated. Over the lifetime of the prototype s-DBT system, it was found that both cathode performance and transmission rate were stable and consistent.

  11. Carbon nanotube electron field emitters for x-ray imaging of human breast cancer

    Science.gov (United States)

    Gidcumb, Emily; Gao, Bo; Shan, Jing; Inscoe, Christy; Lu, Jianping; Zhou, Otto

    2014-06-01

    For imaging human breast cancer, digital breast tomosynthesis (DBT) has been shown to improve image quality and breast cancer detection in comparison to two-dimensional (2D) mammography. Current DBT systems have limited spatial resolution and lengthy scan times. Stationary DBT (s-DBT), utilizing an array of carbon nanotube (CNT) field emission x-ray sources, provides increased spatial resolution and potentially faster imaging than current DBT systems. This study presents the results of detailed evaluations of CNT cathodes for x-ray breast imaging tasks. The following were investigated: high current, long-term stability of CNT cathodes for DBT; feasibility of using CNT cathodes to perform a 2D radiograph function; and cathode performance through several years of imaging. Results show that a breast tomosynthesis system using CNT cathodes could run far beyond the experimentally tested lifetime of one to two years. CNT cathodes were found capable of producing higher currents than typical DBT would require, indicating that the s-DBT imaging time can be further reduced. The feasibility of using a single cathode of the s-DBT tube to perform 2D mammography in 4 s was demonstrated. Over the lifetime of the prototype s-DBT system, it was found that both cathode performance and transmission rate were stable and consistent.

  12. Direct Synthesis of Carbon Nanotube Field Emitters on Metal Substrate for Open-Type X-ray Source in Medical Imaging

    OpenAIRE

    Amar Prasad Gupta; Sangjun Park; Seung Jun Yeo; Jaeik Jung; Chonggil Cho; Sang Hyun Paik; Hunkuk Park; Young Chul Cho; Seung Hoon Kim; Ji Hoon Shin; Jeung Sun Ahn; Jehwang Ryu

    2017-01-01

    We report the design, fabrication and characterization of a carbon nanotube enabled open-type X-ray system for medical imaging. We directly grew the carbon nanotubes used as electron emitter for electron gun on a non-polished raw metallic rectangular-rounded substrate with an area of 0.1377 cm2 through a plasma enhanced chemical vapor deposition system. The stable field emission properties with triode electrodes after electrical aging treatment showed an anode emission current of 0.63 mA at a...

  13. Effect of purity, edge length, and growth area on field emission of multi-walled carbon nanotube emitter arrays

    Energy Technology Data Exchange (ETDEWEB)

    Shahi, Monika [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi 110054 (India); Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Gautam, S.; Shah, P. V.; Jha, P.; Kumar, P.; Rawat, J. S.; Chaudhury, P. K.; Harsh [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi 110054 (India); Tandon, R. P. [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

    2013-05-28

    Present report aims to study the effect of purity, edge length, and growth area on field emission of patterned carbon nanotube (CNT) emitter arrays. For development of four CNT emitter arrays (CEAs), low resistively silicon substrates were coated with thin film of iron catalyst using photolithography, sputtering, and lift off process. Four CEAs were synthesized on these substrates using thermal chemical vapor deposition with minor changes in pretreatment duration. Out of these, two CEAs have 10 {mu}m Multiplication-Sign 10 {mu}m and 40 {mu}m Multiplication-Sign 40 {mu}m solid square dots of CNTs with constant 20 {mu}m inter-dot separation. Other two CEAs have ring square bundles of CNTs and these CEAs are envisioned as 10 {mu}m Multiplication-Sign 10 {mu}m square dots with 4 {mu}m Multiplication-Sign 4 {mu}m scooped out area and 15 {mu}m Multiplication-Sign 15 {mu}m square dots with 5 {mu}m Multiplication-Sign 5 {mu}m lift out area with constant 20 {mu}m inter-dot spacing. Solid square dot structures have exactly constant edge length per unit area with more than four-fold difference in CNT growth area however ring square dot patterns have minor difference in edge length per unit area with approximately two times difference in CNT growth area. Quality and morphology of synthesized CEAs were assessed by scanning electron microscope and Raman characterization which confirm major differences. Field emission of all CEAs was carried out under same vacuum condition and constant inter-electrode separation. Field emission of solid square dot CEAs show approximately identical current density-electric field curves and Fowler-Nordheim plots with little difference in emission current density at same electric field. Similar results were observed for ring square structure CEAs when compared separately. Maximum emission current density observed from these four CEAs reduces from 14.53, 12.23, 11.01, to 8.66 mA/cm{sup 2} at a constant electric field of 5 V/{mu}m, according to edge

  14. 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.

  15. Carbon Nanotube Electron Emitter for X-ray Imaging

    OpenAIRE

    Jung Su Kang; Je Hwang Ryu; Kyu Chang Park

    2012-01-01

    The carbon nanotube field emitter array was grown on silicon substrate through a resist-assisted patterning (RAP) process. The shape of the carbon nanotube array is elliptical with 2.0 × 0.5 mm2 for an isotropic focal spot size at anode target. The field emission properties with triode electrodes show a gate turn-on field of 3 V/µm at an anode emission current of 0.1 mA. The author demonstrated the X-ray source with triode electrode structure utilizing the carbon nanotube em...

  16. Direct Synthesis of Carbon Nanotube Field Emitters on Metal Substrate for Open-Type X-ray Source in Medical Imaging.

    Science.gov (United States)

    Gupta, Amar Prasad; Park, Sangjun; Yeo, Seung Jun; Jung, Jaeik; Cho, Chonggil; Paik, Sang Hyun; Park, Hunkuk; Cho, Young Chul; Kim, Seung Hoon; Shin, Ji Hoon; Ahn, Jeung Sun; Ryu, Jehwang

    2017-07-29

    We report the design, fabrication and characterization of a carbon nanotube enabled open-type X-ray system for medical imaging. We directly grew the carbon nanotubes used as electron emitter for electron gun on a non-polished raw metallic rectangular-rounded substrate with an area of 0.1377 cm² through a plasma enhanced chemical vapor deposition system. The stable field emission properties with triode electrodes after electrical aging treatment showed an anode emission current of 0.63 mA at a gate field of 7.51 V/μm. The 4.5-inch cubic shape open type X-ray system was developed consisting of an X-ray aperture, a vacuum part, an anode high voltage part, and a field emission electron gun including three electrodes with focusing, gate and cathode electrodes. Using this system, we obtained high-resolution X-ray images accelerated at 42-70 kV voltage by digital switching control between emitter and ground electrode.

  17. Direct Synthesis of Carbon Nanotube Field Emitters on Metal Substrate for Open-Type X-ray Source in Medical Imaging

    Directory of Open Access Journals (Sweden)

    Amar Prasad Gupta

    2017-07-01

    Full Text Available We report the design, fabrication and characterization of a carbon nanotube enabled open-type X-ray system for medical imaging. We directly grew the carbon nanotubes used as electron emitter for electron gun on a non-polished raw metallic rectangular-rounded substrate with an area of 0.1377 cm2 through a plasma enhanced chemical vapor deposition system. The stable field emission properties with triode electrodes after electrical aging treatment showed an anode emission current of 0.63 mA at a gate field of 7.51 V/μm. The 4.5-inch cubic shape open type X-ray system was developed consisting of an X-ray aperture, a vacuum part, an anode high voltage part, and a field emission electron gun including three electrodes with focusing, gate and cathode electrodes. Using this system, we obtained high-resolution X-ray images accelerated at 42–70 kV voltage by digital switching control between emitter and ground electrode.

  18. A glass-sealed field emission x-ray tube based on carbon nanotube emitter for medical imaging

    Science.gov (United States)

    Yeo, Seung Jun; Jeong, Jaeik; Ahn, Jeung Sun; Park, Hunkuk; Kwak, Junghwan; Noh, Eunkyong; Paik, Sanghyun; Kim, Seung Hoon; Ryu, Jehwang

    2016-04-01

    We report the design and fabrication of a carbon nanotube based a glass-sealed field emission x-ray tube without vacuum pump. The x-ray tube consists of four electrodes with anode, focuser, gate, and cathode electrode. The shape of cathode is rectangular for isotropic focal spot size at anode target. The obtained x-ray images show clearly micrometer scale.

  19. Thionyl chloride assisted functionalization of amorphous carbon nanotubes: A better field emitter and stable nanofluid with better thermal conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, S.K.; Jha, A. [School of Materials Science and Nanotechnology, Jadavpur University, Kolkata 700 032 (India); Chattopadhyay, K.K., E-mail: kalyan_chattopadhyay@yahoo.com [Thin Film & Nanoscience Laboratory, Department of Physics, Jadavpur University, Kolkata 700 032 (India); School of Materials Science and Nanotechnology, Jadavpur University, Kolkata 700 032 (India)

    2015-06-15

    Highlights: • Thionyl chloride assisted functionalization of amorphous carbon nanotubes (a-CNTs). • Improved dispersion enhanced thermal conductivity of engine oil. • Again f-a-CNTs showed enhanced field emission property compared to pure a-CNTs. - Abstract: Amorphous carbon nanotubes (a-CNTs) were synthesized at low temperature in open atmosphere and further functionalized by treating them in thionyl chloride added stearic acid-dichloro methane solution. The as prepared functionalized a-CNTs (f-a-CNTs) were characterized by Raman spectroscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, transmission and scanning electron microscopy. The nanofluid was prepared by dispersing f-a-CNTs in engine oil using ultrasonic treatment. The effective thermal conductivity of as prepared nanofluid was investigated at different loading (volume fraction of f-a-CNTs). Obtained experimental data of thermal conductivity were compared with the predicted values, calculated using existing theoretical models. Stability of the nanofluid was tested by means of zeta potential measurement to optimize the loading. The as prepared f-a-CNTs sample also showed improved field emission result as compared to pristine a-CNTs. Dependence of field emission behavior on inter electrode distance was investigated too.

  20. Design of a carbon-nanotube yarn field emitter for micro-focus X-ray generation

    Science.gov (United States)

    Kim, Hyun Suk; Castro, Edward Joseph D.; Lee, Choong Hun

    2016-08-01

    The field-emission (F-E) characteristics of multi-walled carbon-nanotube (MWCNT) yarn and its contribution to X-ray generation have been investigated in the current work. A dry spinning method was used to fabricateMWCNT yarn from superMWCNTs that had been fabricated by using microwave plasma-enhanced chemical vapor deposition (MW-PECVD). The F-E behavior of the MWCNT yarn followed the Fowler-Nordheim model. Compared to a MWCNT, the MWCNT yarn displayed a significant F-E capability in both the diode and the triode X-ray generation structures. The low-voltage F-E of the MWCNT yarn can be attributed to the field-enhancing effect of the yarn due to its shape and to the contribution of the high-aspect-ratio nanotubes that protrude from the sides of the yarn. The effect of filters on the development of X-ray images has also been demonstrated. The amount of exposure of the samples to X-rays was also manipulated. Results of this study indicate that the MWCNT yarn may be a good candidate for use in low-voltage F-E applications for X-ray imaging.

  1. Carbon Nanotube-based Cold Cathode for High Power MicrowaveVacuum Electronic Devices: A Potential Field Emitter

    Directory of Open Access Journals (Sweden)

    P. Verma

    2008-09-01

    Full Text Available Carbon nanotubes (CNTs can be grown in the form of small, sharp spikes capable of carrying very highcurrent densities which suggest great potential application of CNTs as cold cathode in high power microwavevacuum device applications. These cold cathode vacuum microwave devices are expected to be ideally suitedfor air-borne and space applications. This paper  reports the initial efforts made in the development of coldcathode using PECVD grown vertically-aligned matrix of CNTs with uniform height and optimum tip densityon silicon substrate. The high aspect ratio (of the order of 10,000 and novel electrical, mechanical, and thermalproperties of the CNT are found to be very attractive characteristics for emission of large and stable currentdensities at reasonably low field. The field emission current voltage characteristics of a typical cathode gaveemission current density in excess of 35 mA/cm2 at reasonably low field. The emission current in most of thesamples is found to be stable over long period of time but is greatly effected by the vacuum condition duringmeasurement. The initial measured data suggests great promise for achieving high current densities at practicalelectric fields.Defence Science Journal, 2008, 58(5, pp.650-654, DOI:http://dx.doi.org/10.14429/dsj.58.1688

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

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong-Pil [Health and Medical Equipment R and D Team, Samsung Electronics, Suwon, Gyeonggi-do 443-742 (Korea, Republic of); Chang, Han-Beet; Kim, Bu-Jong [Dept. of Electronic Systems Engineering, Hanyang University, Ansan, Gyeonggi-do 426-791 (Korea, Republic of); Park, Jin-Seok, E-mail: jinsp@hanyang.ac.kr [Dept. of Electronic Systems Engineering, Hanyang University, Ansan, Gyeonggi-do 426-791 (Korea, Republic of)

    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.

  3. Vertically aligned carbon nanotube field emitter arrays with Ohmic base contact to silicon by Fe-catalyzed chemical vapor deposition

    NARCIS (Netherlands)

    Morassutto, M.; Tiggelaar, Roald M.; Smithers, M.A.; Smithers, M.A.; Gardeniers, Johannes G.E.

    2016-01-01

    Abstract In this study, dense arrays of aligned carbon nanotubes are obtained by thermal catalytic chemical vapor deposition, using Fe catalyst dispersed on a thin Ta layer. Alignment of the carbon nanotubes depends on the original Fe layer thickness from which the catalyst dispersion is obtained by

  4. Electric field distribution of electron emitter surfaces

    Science.gov (United States)

    Tagawa, M.; Takenobu, S.; Ohmae, N.; Umeno, M.

    1987-03-01

    The electric field distribution of a tungsten field emitter surface and a LaB6 thermionic emitter surface has been studied. The computer simulation of electric field distribution on the emitter surface was carried out with a charge simulation method. The electric field distribution of the LaB6 thermionic emitter was experimentally evaluated by the Schottky plot. Two independent equations are necessary for obtaining local electric field and work function; the Fowler-Nordheim equation and the equation of total energy distribution of emitted electron being used to evaluate the electric field distribution of the tungsten field emitter. The experimental results agreed with the computer simulation.

  5. Diamond/diamond-like carbon coated nanotube structures for efficient electron field emission

    Science.gov (United States)

    Dimitrijevic, Steven (Inventor); Withers, James C. (Inventor); Loutfy, Raouf O. (Inventor)

    2005-01-01

    The present invention is directed to a nanotube coated with diamond or diamond-like carbon, a field emitter cathode comprising same, and a field emitter comprising the cathode. It is also directed to a method of preventing the evaporation of carbon from a field emitter comprising a cathode comprised of nanotubes by coating the nanotube with diamond or diamond-like carbon. In another aspect, the present invention is directed to a method of preventing the evaporation of carbon from an electron field emitter comprising a cathode comprised of nanotubes, which method comprises coating the nanotubes with diamond or diamond-like carbon.

  6. Light emission from carbon nanofilaments/nanotubes at field electron emission

    Science.gov (United States)

    Ormont, A. B.; Izrael'yants, K. R.; Musatov, A. L.

    2016-01-01

    The spatial distribution of light emission has been studied in planar field electron emitters with long and sparse carbon nanofilaments/nanotubes. The photographic recording of light emission of the emitting nanofilaments/nanotubes is shown to be efficient to determine the position of individual nanofilaments/ nanotubes in different emitter surface areas, as well as to highlight the nanofilaments/nanotube agglomerate distribution over the emitter surface, which mainly contributes to its emission.

  7. Enhanced field emission of WS₂ nanotubes.

    Science.gov (United States)

    Viskadouros, G; Zak, A; Stylianakis, M; Kymakis, E; Tenne, R; Stratakis, E

    2014-06-25

    Results on electron field emission from free standing tungsten disulfide (WS2) nanotubes (NTs) are presented. Experiments show that the NTs protruding on top of microstructures are efficient cold emitters with turn-on fields as low as 1 V/μm and field enhancement of few thousands. Furthermore, the emission current shows remarkable stability over more than eighteen hours of continuous operation. Such performance and long-term stability of the WS2 cathodes is comparable to that reported for optimized carbon nanotube (CNTs) based emitters. Besides this, it is found that the WS2 cathodes prepared are less sensitive than CNTs in chemical reactive ambients. The high field enhancement and superior reliability achieved indicates a potential for vacuum nanoelectronics and flat panel display applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Surface-conduction electron-emitter characteristics and fabrication based on vertically aligned carbon nanotube arrays

    Science.gov (United States)

    Shih, Yi-Ting; Li, Kuan-Wei; Honda, Shin-ichi; Lin, Pao-Hung; Huang, Ying-Sheng; Lee, Kuei-Yi

    2017-06-01

    The carbon nanotube (CNT) has replaced palladium oxide (PdO) as the electrode material for surface-conduction electron-emitter (SCE) applications. Vertically aligned CNT arrays with a delta-star arrangement were patterned and synthesized onto a quartz substrate using photolithography and thermal chemical vapor deposition. Delta-star shaped VACNT arrays with 20° tips are used as cathodes that easily emit electrons because of their high electrical field gradient. In order to improve the field emission and secondary electrons (SEs) in SCE applications, magnesium oxide (MgO) nanostructures were coated onto the VACNT arrays to promote the surface-conduction electron-emitter display (SED) efficiency (η). According to the definition of η in SCE applications, in this study, the η was stably maintained in the 75-85% range. The proposed design provides a facile new method for developing SED applications.

  9. Memristive model of hysteretic field emission from carbon nanotube arrays

    Science.gov (United States)

    Gorodetskiy, Dmitriy V.; Gusel'nikov, Artem V.; Shevchenko, Sergey N.; Kanygin, Mikhail A.; Okotrub, Alexander V.; Pershin, Yuriy V.

    2016-01-01

    Some instances of electron field emitters are characterized by frequency-dependent hysteresis in their current-voltage characteristics. We argue that such emitters can be classified as memristive systems and introduce a general framework to describe their response. As a specific example of our approach, we consider field emission from a carbon nanotube array. Our experimental results demonstrate a low-field hysteresis, which is likely caused by an electrostatic alignment of some of the nanotubes in the applied field. We formulate a memristive model of such phenomena, whose results are in agreement with the experimental results.

  10. Source brightness and useful beam current of carbon nanotubes and other very small emitters

    NARCIS (Netherlands)

    Kruit, P.; Bezuijen, M.; Barth, J.E.

    2006-01-01

    The potential application of carbon nanotubes as electron sources in electron microscopes is analyzed. The resolution and probe current that can be obtained from a carbon nanotube emitter in a low-voltage scanning electron microscope are calculated and compared to the state of the art using Schottky

  11. Nanoelectrospray emitter arrays providing interemitter electric field uniformity.

    Science.gov (United States)

    Kelly, Ryan T; Page, Jason S; Marginean, Ioan; Tang, Keqi; Smith, Richard D

    2008-07-15

    Arrays of electrospray ionization (ESI) emitters have been reported previously as a means of enhancing ionization efficiency or signal intensity. A key challenge when working with multiple, closely spaced ESI emitters is overcoming the deleterious effects caused by electrical interference among neighboring emitters. Individual emitters can experience different electric fields depending on their relative position in the array, such that it becomes difficult to operate all of the emitters optimally for a given applied potential. In this work, we have developed multi-nanoESI emitters arranged with a circular pattern, which enable the constituent emitters to experience a uniform electric field. The performance of the circular emitter array was compared to a single emitter and to a previously developed linear emitter array, which verified that improved electric field uniformity was achieved with the circular arrangement. The circular arrays were also interfaced with a mass spectrometer via a matching multicapillary inlet, and the results were compared with those obtained using a single emitter. By minimizing interemitter electric field inhomogeneities, much larger arrays having closer emitter spacing should be feasible.

  12. Group-III Nitride Field Emitters

    Science.gov (United States)

    Bensaoula, Abdelhak; Berishev, Igor

    2008-01-01

    Field-emission devices (cold cathodes) having low electron affinities can be fabricated through lattice-mismatched epitaxial growth of nitrides of elements from group III of the periodic table. Field emission of electrons from solid surfaces is typically utilized in vacuum microelectronic devices, including some display devices. The present field-emission devices and the method of fabricating them were developed to satisfy needs to reduce the cost of fabricating field emitters, make them compatible with established techniques for deposition of and on silicon, and enable monolithic integration of field emitters with silicon-based driving circuitry. In fabricating a device of this type, one deposits a nitride of one or more group-III elements on a substrate of (111) silicon or other suitable material. One example of a suitable deposition process is chemical vapor deposition in a reactor that contains plasma generated by use of electron cyclotron resonance. Under properly chosen growth conditions, the large mismatch between the crystal lattices of the substrate and the nitride causes strains to accumulate in the growing nitride film, such that the associated stresses cause the film to crack. The cracks lie in planes parallel to the direction of growth, so that the growing nitride film becomes divided into microscopic growing single-crystal columns. The outer ends of the fully-grown columns can serve as field-emission tips. By virtue of their chemical compositions and crystalline structures, the columns have low work functions and high electrical conductivities, both of which are desirable for field emission of electrons. From examination of transmission electron micrographs of a prototype device, the average column width was determined to be about 100 nm and the sharpness of the tips was determined to be characterized by a dimension somewhat less than 100 nm. The areal density of the columns was found to about 5 x 10(exp 9)/sq cm . about 4 to 5 orders of magnitude

  13. Plasmons in doped finite carbon nanotubes and their interactions with fast electrons and quantum emitters

    Science.gov (United States)

    de Vega, Sandra; Cox, Joel D.; de Abajo, F. Javier García

    2016-08-01

    We study the potential of highly doped finite carbon nanotubes to serve as plasmonic elements that mediate the interaction between quantum emitters. Similar to graphene, nanotubes support intense plasmons that can be modulated by varying their level of electrical doping. These excitations exhibit large interaction with light and electron beams, as revealed upon examination of the corresponding light extinction cross-section and electron energy-loss spectra. We show that quantum emitters experience record-high Purcell factors, while they undergo strong mutual interaction mediated by their coupling to the tube plasmons. Our results show the potential of doped finite nanotubes as tunable plasmonic materials for quantum optics applications.

  14. Field emission energy distributions from individual multiwalled carbon nanotubes

    Science.gov (United States)

    Fransen, M. J.; van Rooy, Th. L.; Kruit, P.

    1999-05-01

    We measured field emission energy distributions of electrons emitted from individual multiwalled carbon nanotubes mounted on tungsten tips. The shape of the energy distribution is strongly sample dependent. Some nanotube emitters exhibit an almost metallic behaviour, while others show sharply peaked energy distributions. The smallest half-width we measured was only 0.11 eV, without correction for the broadening of the energy analyzer. A common feature of both types of carbon nanotube energy spectra is that the position of the peaks in the spectrum depends linearly on the extraction voltage, unlike metallic emitters, where the position stays in the vicinity of the Fermi level. With a small modification to the field emission theory for metals we extract the distance between the highest filled energy level of the nanotube and the vacuum potential, the field on the emitter surface, the emitter radius and the emitting area, from the energy distribution and the Fowler-Nordheim plot. The last two parameters are in good agreement with transmission electron micrographs of such samples. The sharply-peaked energy distributions from other samples indicate that resonant states can exist at the top of the nanotube.

  15. Measurement of transverse emittance and coherence of double-gate field emitter array cathodes

    Science.gov (United States)

    Tsujino, Soichiro; Das Kanungo, Prat; Monshipouri, Mahta; Lee, Chiwon; Miller, R. J. Dwayne

    2016-12-01

    Achieving small transverse beam emittance is important for high brightness cathodes for free electron lasers and electron diffraction and imaging experiments. Double-gate field emitter arrays with on-chip focussing electrode, operating with electrical switching or near infrared laser excitation, have been studied as cathodes that are competitive with photocathodes excited by ultraviolet lasers, but the experimental demonstration of the low emittance has been elusive. Here we demonstrate this for a field emitter array with an optimized double-gate structure by directly measuring the beam characteristics. Further we show the successful application of the double-gate field emitter array to observe the low-energy electron beam diffraction from suspended graphene in minimal setup. The observed low emittance and long coherence length are in good agreement with theory. These results demonstrate that our all-metal double-gate field emitters are highly promising for applications that demand extremely low-electron bunch-phase space volume and large transverse coherence.

  16. Beam characterization for the field-emitter-array cathode-based low-emittance gun

    Directory of Open Access Journals (Sweden)

    S. C. Leemann

    2007-07-01

    Full Text Available A 1   Å x-ray free electron laser can be operated at 6 GeV provided a very high brightness electron beam. Therefore, Paul Scherrer Institute has initiated development of the low-emittance gun based on field emission. A field-emitter array (FEA is expected to deliver high peak current while reducing the source emittance to levels close to the thermal limit. A 100 keV gun test stand has been designed in order to gain experience with electron bunches emitted by pulsed FEAs, investigate emittance compensation, and develop diagnostic procedures to characterize the beam. First FEA samples have been installed and pulsed in the gun; the emitted bunches have been accelerated and characterized. We present results acquired with the first FEA samples.

  17. Field Emission from Carbon Nanotube/Tin Composite

    Institute of Scientific and Technical Information of China (English)

    ZHAO Bo; ZHANG Ya-fei

    2009-01-01

    Powder metallurgy was used to fabricate carbon nanotube (CNT) field emission cathodes. CNTs and tin (Sn) powder were blended, compacted and sintered. After polishing and etching, CNTs were exposed and protruded from the metal surface. CNTs were embedded into the Sn matrix, which acted as stable field emitters. The J-E curves show excellent field emission properties, such as low turn-on field of 2.8 V/μm, high emission current density and good current stability.

  18. Nanotube field electron emission: principles, development, and applications.

    Science.gov (United States)

    Li, Yunhan; Sun, Yonghai; Yeow, J T W

    2015-06-19

    There is a growing trend to apply field emission (FE) electron sources in vacuum electronic devices due to their fast response, high efficiency and low energy consumption compared to thermionic emission ones. Carbon nanotubes (CNTs) have been regarded as a promising class of electron field emitters since the 1990s and have promoted the development of FE technology greatly because of their high electrical and thermal conductivity, chemical stability, high aspect ratio and small size. Recent studies have shown that FE from CNTs has the potential to replace conventional thermionic emission in many areas and that it exhibits advanced features in practical applications. Consequently, FE from nanotubes and applications thereof have attracted much attention. This paper provides a comprehensive review of both recent advances in CNT field emitters and issues related to applications of CNT based FE. FE theories and principles are introduced, and the early development of field emitters is related. CNT emitter types and their FE performance are discussed. The current situation for applications based on nanotube FE is reviewed. Although challenges remain, the tremendous progress made in CNT FE over the past ten years indicates the field's development potential.

  19. Modeling of external electric field effect on the carbon and silicon carbide nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Sorokina, Veronika, E-mail: ansonika@mail.ru [Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034 (Russian Federation); Nikiforov, Konstantin, E-mail: knikiforov@cc.spbu.ru [Saint Petersburg Electrotechnical University “LETI”, 5 Prof. Popova, St. Petersburg, 197376 (Russian Federation)

    2016-06-17

    Studying emission characteristics of nanotubes is extremely important for development of electronics. Compared to other electron sources nanotube-based field emitters allow obtaining significant emission currents at relatively low values of the applied field. It is possible due to their unique structure. This article is devoted to theoretical investigation how external electric field effects several samples of open single-wall nanotubes from carbon and silicon carbide. Total energies, dipole moments and band gaps for five types of nanotubes were calculated from the first principles. The numerical experiment results indicate the adequacy of modeling. It was concluded that considered configurations of achiral carbon nanotubes should be semiconductors.

  20. Nanotube field electron emission: principles, development, and applications

    Science.gov (United States)

    Li, Yunhan; Sun, Yonghai; Yeow, J. T. W.

    2015-06-01

    There is a growing trend to apply field emission (FE) electron sources in vacuum electronic devices due to their fast response, high efficiency and low energy consumption compared to thermionic emission ones. Carbon nanotubes (CNTs) have been regarded as a promising class of electron field emitters since the 1990s and have promoted the development of FE technology greatly because of their high electrical and thermal conductivity, chemical stability, high aspect ratio and small size. Recent studies have shown that FE from CNTs has the potential to replace conventional thermionic emission in many areas and that it exhibits advanced features in practical applications. Consequently, FE from nanotubes and applications thereof have attracted much attention. This paper provides a comprehensive review of both recent advances in CNT field emitters and issues related to applications of CNT based FE. FE theories and principles are introduced, and the early development of field emitters is related. CNT emitter types and their FE performance are discussed. The current situation for applications based on nanotube FE is reviewed. Although challenges remain, the tremendous progress made in CNT FE over the past ten years indicates the field’s development potential.

  1. Physical electrostatics of small field emitter arrays/clusters

    Science.gov (United States)

    Forbes, Richard G.

    2016-08-01

    This paper aims to improve qualitative understanding of electrostatic influences on apex field enhancement factors (AFEFs) for small field emitter arrays/clusters. Using the "floating sphere at emitter-plate potential" (FSEPP) model, it re-examines the electrostatics and mathematics of three simple systems of identical post-like emitters. For the isolated emitter, various approaches are noted. An adequate approximation is to consider only the effects of sphere charges and (for significantly separated emitters) image charges. For the 2-emitter system, formulas are found for charge-transfer ("charge-blunting") effects and neighbor-field effects, for widely spaced and for "sufficiently closely spaced" emitters. Mutual charge-blunting is always the dominant effect, with a related (negative) fractional AFEF-change δtwo. For sufficiently small emitter spacing c, |δtwo| varies approximately as 1/c; for large spacing, |δtwo| decreases as 1/c3. In a 3-emitter equispaced linear array, differential charge-blunting and differential neighbor-field effects occur, but differential charge-blunting effects are dominant, and cause the "exposed" outer emitters to have higher AFEF (γ0) than the central emitter (γ1). Formulas are found for the exposure ratio Ξ = γ0/γ1, for large and for sufficiently small separations. The FSEPP model for an isolated emitter has accuracy around 30%. Line-charge models (LCMs) are an alternative, but an apparent difficulty with recent LCM implementations is identified. Better descriptions of array electrostatics may involve developing good fitting equations for AFEFs derived from accurate numerical solution of Laplace's equation, perhaps with equation form(s) guided qualitatively by FSEPP-model results. In existing fitting formulas, the AFEF-reduction decreases exponentially as c increases, which is different from the FSEPP-model formulas. This discrepancy needs to be investigated, using systematic Laplace-based simulations and appropriate results

  2. Bulk molybdenum field emitters by inductively coupled plasma etching.

    Science.gov (United States)

    Zhu, Ningli; Cole, Matthew T; Milne, William I; Chen, Jing

    2016-12-07

    In this work we report on the fabrication of inductively coupled plasma (ICP) etched, diode-type, bulk molybdenum field emitter arrays. Emitter etching conditions as a function of etch mask geometry and process conditions were systematically investigated. For optimized uniformity, aspect ratios of >10 were achieved, with 25.5 nm-radius tips realised for masks consisting of aperture arrays some 4.45 μm in diameter and whose field electron emission performance has been herein assessed.

  3. Flexible Field Emitter for X-ray Generation by Implanting CNTs into Nickel Foil

    Science.gov (United States)

    Sun, Bin; Wang, Yan; Ding, Guifu

    2016-07-01

    This paper reports a novel implanting micromachining technology. By using this method, for the first time, we could implant nano-scale materials into milli-scale metal substrates at room temperature. Ni-based flexible carbon nanotube (CNT) field emitters were fabricated by the novel micromachining method. By embedding CNT roots into Ni foil using polymer matrix as transfer media, effective direct contact between Ni and CNTs was achieved. As a result, our novel emitter shows relatively good field emission properties such as low turn-on field and good stability. Moreover, the emitter was highly flexible with preservation of the field emission properties. The excellent field emission characteristics attributed to the direct contact and the strong interactions between CNTs and the substrate. To check the practical application of the novel emitter, a simple X-ray imaging system was set up by modifying a traditional tube. The gray shadow that appears on the sensitive film after being exposed to the radiation confirms the successful generation of X-ray.

  4. Diamond-Coated Carbon Nanotubes for Efficient Field Emission

    Science.gov (United States)

    Dimitrijevic, Stevan; Withers, James C.

    2005-01-01

    Field-emission cathodes containing arrays of carbon nanotubes coated with diamond or diamondlike carbon (DLC) are undergoing development. Multiwalled carbon nanotubes have been shown to perform well as electron field emitters. The idea underlying the present development is that by coating carbon nanotubes with wideband- gap materials like diamond or DLC, one could reduce effective work functions, thereby reducing threshold electric-field levels for field emission of electrons and, hence, improving cathode performance. To demonstrate feasibility, experimental cathodes were fabricated by (1) covering metal bases with carbon nanotubes bound to the bases by an electrically conductive binder and (2) coating the nanotubes, variously, with diamond or DLC by plasma-assisted chemical vapor deposition. In tests, the threshold electric-field levels for emission of electrons were reduced by as much as 40 percent, relative to those of uncoated- nanotube cathodes. Coating with diamond or DLC could also make field emission-cathodes operate more stably by helping to prevent evaporation of carbon from nanotubes in the event of overheating of the cathodes. Cathodes of this type are expected to be useful principally as electron sources for cathode-ray tubes and flat-panel displays.

  5. A novel field emission microscopy method to study field emission characteristics of freestanding carbon nanotube arrays

    Science.gov (United States)

    Li, Yunhan; Sun, Yonghai; Jaffray, David A.; Yeow, John T. W.

    2017-04-01

    Field emission (FE) uniformity and the mechanism of emitter failure of freestanding carbon nanotube (CNT) arrays have not been well studied due to the difficulty of observing and quantifying FE performance of each emitter in CNT arrays. Herein a field emission microscopy (FEM) method based on poly(methyl methacrylate) (PMMA) thin film is proposed to study the FE uniformity and CNT emitter failure of freestanding CNT arrays. FE uniformity of freestanding CNT arrays and different levels of FE current contributions from each emitter in the arrays are recorded and visualized. FEM patterns on the PMMA thin film contain the details of the CNT emitter tip shape and whether multiple CNT emitters occur at an emission site. Observation of real-time FE performance and the CNT emitter failure process in freestanding CNT arrays are successfully achieved using a microscopic camera. High emission currents through CNT emitters causes Joule heating and light emission followed by an explosion of the CNTs. The proposed approach is capable of resolving the major challenge of building the relationship between FE performance and CNT morphologies, which can significantly facilitate the study of FE non-uniformity, the emitter failure mechanism and the development of stable and reliable FE devices in practical applications.

  6. Field emission from open ended aluminum nitride nanotubes

    Science.gov (United States)

    Tondare, V. N.; Balasubramanian, C.; Shende, S. V.; Joag, D. S.; Godbole, V. P.; Bhoraskar, S. V.; Bhadbhade, M.

    2002-06-01

    This letter reports the field emission measurements from the nanotubes of aluminum nitride which were synthesized by gas phase condensation using the solid-vapor equilibria. A dc arc plasma reactor was used for producing the vapors of aluminum in a reactive nitrogen atmosphere. Nanoparticles and nanotubes of aluminum nitride were first characterized by transmission electron microscope and tube dimensions were found to be varying from 30 to 200 nm in diameter and 500 to 700 nm in length. These tubes were mixed with nanoparticles of size range between 5 and 200 nm in diameter. Tungsten tips coated with these nanoparticles and tubes were used as a field emitter. The field emission patterns display very interesting features consisting of sharp rings which were often found to change their shapes. The patterns are attributed to the open ended nanotubes of aluminum nitride. A few dot patterns corresponding to the nanoparticles were also seen to occur. The Fowler-Nordheim plots were seen to be nonlinear in nature, which reflects the semi-insulating behavior of the emitter. The field enhancement factor is estimated to be 34 500 indicating that the field enhancement due to the nanometric size of the emitter is an important cause for the observed emission.

  7. Field emitters made of the contacted ytterbium and carbon nanolayers

    Directory of Open Access Journals (Sweden)

    G.G. Sominski

    2015-10-01

    Full Text Available The operation of field emitters of a new type prepared from contacted nanolayers of ytterbium and carbon has been investigated. The performed calculations and experiments allowed to optimize the emission characteristics of the emitters. The calculations took into account the existence of a transition zone between the layers of Yb and C. Emission characteristics of the cathodes including up to 40 pairs of layers of carbon and ytterbium with optimum thicknesses of 5 and 2 nm respectively were measured. The created multilayered emitters provide the average emission current density over the surface of the emitter up to 10–20 A/cm2 and show promise for use in miniature electronic devices.

  8. Field emission characteristics of regular arrays of carbon nanotubes.

    Science.gov (United States)

    Al-Ghamdi, A A; Al-Heniti, S; Al-Hazmi, F S; Faidah, Adel S; Shalaan, E; Husain, M

    2014-06-01

    The developments of electronic devices based on micron-sized vacuum electron sources during the last decades have triggered intense research on highly efficient carbon based thin film electron emitters. The synthesis of massive arrays of carbon nanotubes that are oriented on patterned Fe catalyst deposited on quartz substrates is reported. The well-ordered nanotubes can be used as electron field emission arrays. Scaling up of the synthesis process should be entirely compatible with the existing semiconductor processes, and should allow the development of nanotubes devices integrated into future technology. The emission from carbon nanotubes array is explained by Fowler-Nordheim tunneling of electrons from tip-like structures in the nanometer range, which locally amplify the applied field by the field enhancement factor beta. We found that the low pressure chemical vapour deposition (LPCVD) system can produce nanotubes capable of excellent emission currents at lower voltages. The carbon nanotubes array shows good field emission with turn on field E(alpha) = 1.30 V/microm at the current density of 3.50 mA/cm2 with enhancement factor beta = 1.22 x 10(2).

  9. Wide-range Vacuum Measurements from MWNT Field Emitters Grown Directly on Stainless Steel Substrates

    Science.gov (United States)

    Zhang, Jian; Li, Detian; Zhao, Yangyang; Cheng, Yongjun; Dong, Changkun

    2016-01-01

    The field emission properties and the vacuum measurement application are investigated from the multi-walled carbon nanotubes (MWNTs) grown directly on catalytic stainless steel substrates. The MWNT emitters present excellent emission properties after the acid treatment of the substrate. The MWNT gauge is able to work down to the extreme-high vacuum (XHV) range with linear measurement performance in wide range from 10-11 to 10-6 Torr. A modulating grid is attempted with improved gauge sensitivity. The extension of the lower pressure limit is attributed largely to low outgassing effect due to direct growth of MWNTs and justified design of the electron source.

  10. Spectrum of classes of point emitters of electromagnetic wave fields.

    Science.gov (United States)

    Castañeda, Román

    2016-09-01

    The spectrum of classes of point emitters has been introduced as a numerical tool suitable for the design, analysis, and synthesis of non-paraxial optical fields in arbitrary states of spatial coherence. In this paper, the polarization state of planar electromagnetic wave fields is included in the spectrum of classes, thus increasing its modeling capabilities. In this context, optical processing is realized as a filtering on the spectrum of classes of point emitters, performed by the complex degree of spatial coherence and the two-point correlation of polarization, which could be implemented dynamically by using programmable optical devices.

  11. Ultra-Sensitivity Glucose Sensor Based on Field Emitters

    Directory of Open Access Journals (Sweden)

    Song Yinglin

    2009-01-01

    Full Text Available Abstract A new glucose sensor based on field emitter of ZnO nanorod arrays (ZNA was fabricated. This new type of ZNA field emitter-based sensor shows high sensitivity with experimental limit of detection of 1 nM glucose solution and a detection range from 1 nM to 50 μM in air at room temperature, which is lower than that of glucose sensors based on surface plasmon resonance spectroscopy, fluorescence signal transmission, and electrochemical signal transduction. The new glucose sensor provides a key technique for promising consuming application in biological system for detecting low levels of glucose on single cells or bacterial cultures.

  12. 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.

  13. Brightness limitations of cold field emitters caused by Coulomb interactions

    NARCIS (Netherlands)

    Cook, B.J.; Verduin, T.; Hagen, C.W.; Kruit, P.

    2010-01-01

    Emission theory predicts that high brightness cold field emitters can enhance imaging in the electron microscope. This (neglecting chromatic aberration) is because of the large (coherent) probe current available from a high brightness source and is based on theoretically determined values of reduced

  14. Synthesis, characterization and field emission properties of nanotubes and nanowires

    Science.gov (United States)

    Dong, Lifeng

    2005-11-01

    with different work functions and explore new emitter candidates, nanowires with various compositions (CdS, ZnO, SiOx, WOx, and WS 2), diameters, morphologies and crystal structures were synthesized on tungsten substrates. In comparison to carbon nanotubes, these nanowires exhibit higher turn-on fields and threshold fields, but demonstrate similar noise power spectral of a 1/f3/2 characteristic from 1 Hz to 6 KHz.

  15. Improvement of carbon nanotube field emission properties by ultrasonic nanowelding

    Science.gov (United States)

    Zhao, Bo; Yadian, Boluo; Chen, Da; Xu, Dong; Zhang, Yafei

    2008-12-01

    Ultrasonic nanowelding was used to improve the field emission properties of carbon nanotube (CNT) cathodes. The CNTs were deposited on the Ti-coated glass substrate by electrophoretic deposition. By pressing CNTs against metal (Ti) substrate under a vibrating force at ultrasonic frequency, a reliable and low resistance contact was obtained between CNTs and Ti. The scanning electron microscopy results show that CNTs are embedded into the metal substrate and act as stable field emitters. The welded cathode demonstrates an excellent field emission with high emission current density and good current stability.

  16. 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

  17. Emittance of a Field Emission Electron Source

    Science.gov (United States)

    2010-01-05

    approximately correct. The gate and switching time A thermionic source is run space-charge limited for which the current varies as a power 3 /2 of the grid...and millimeter-wave power amplifiers that use thermionic cathodes, requiring the sources to produce a current density characteristic of that in the...Rb radius, magnetic field strength B, accelerating voltage Vb, frequency f inversely related to Rb, harmonic number n, and emit- tance via 1− J

  18. Compliance with High-Intensity Radiated Fields Regulations - Emitter's Perspective

    Science.gov (United States)

    Statman, Joseph; Jamnejad, Vahraz; Nguyen, Lee

    2012-01-01

    NASA's Deep Space Network (DSN) uses high-power transmitters on its large antennas to communicate with spacecraft of NASA and its partner agencies. The prime reflectors of the DSN antennas are parabolic, at 34m and 70m in diameter. The DSN transmitters radiate Continuous Wave (CW) signals at 20 kW - 500 kW at X-band and S-band frequencies. The combination of antenna reflector size and high frequency results in a very narrow beam with extensive oscillating near-field pattern. Another unique feature of the DSN antennas is that they (and the radiated beam) move mostly at very slow sidereal rate, essentially identical in magnitude and at the opposite direction of Earth rotation.The DSN is in the process of revamping its documentation to provide analysis of the High Intensity Radiation Fields (HIRF) environment resulting from radio frequency radiation from DSN antennas for comparison to FAA regulations regarding certification of HIRF protection as outlined in the FAA regulations on HIRF protection for aircraft electrical and electronic systems (Title 14, Code of Federal Regulations (14 CFR) [section sign][section sign] 23.1308, 25.1317, 27.1317, and 29.1317).This paper presents work done at JPL, in consultation with the FAA. The work includes analysis of the radiated field structure created by the unique DSN emitters (combination of transmitters and antennas) and comparing it to the fields defined in the environments in the FAA regulations. The paper identifies areas that required special attention, including the implications of the very narrow beam of the DSN emitters and the sidereal rate motion. The paper derives the maximum emitter power allowed without mitigation and the mitigation zones, where required.Finally, the paper presents summary of the results of the analyses of the DSN emitters and the resulting DSN process documentation.

  19. The effects of emitter-tied field plates on lateral PNP ionizing radiation response

    Energy Technology Data Exchange (ETDEWEB)

    Barnaby, H.J.; Schrimpf, R.D.; Cirba, C.R. [Vanderbilt Univ., Nashville, TN (United States); Pease, R.L. [RLP Research, Inc., Albuquerque, NM (United States); Fleetwood, D.M. [Sandia National Labs., Albuquerque, NM (United States); Kosier, S.L. [VTC Inc., Bloomington, MN (United States)

    1998-03-01

    Radiation response comparisons of lateral PNP bipolar technologies reveal that device hardening may be achieved by extending the emitter contact over the active base. The emitter-tied field plate suppresses recombination of carriers with interface traps.

  20. 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...

  1. Mechanism of field electron emission from carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    LI Zhi-bing; DENG Shao-zhi; XU Ning-sheng

    2006-01-01

    Field electron emission (FE) is a quantum tunneling process in which electrons are injected from materials (usually metals) into a vacuum under the influence of an applied electric field.In order to obtain usable electron current,the conventional way is to increase the local field at the surface of an emitter.For a plane metal emitter with a typical work function of 5 eV,an applied field of over 1000V/μm is needed to obtain a significant current.The high working field (and/or the voltage between the electrodes)has been the bottleneck for many applications of the FE technique.Since the 1960s,enormous effort has been devoted to reduce the working macroscopic field (voltage).A widely adopted idea is to sharpen the emitters to get a large surface field enhancement.The materials of emitters should have good electronic conductivity,high melting points,good chemical inertness,and high mechanical stiffness.Carbon nanotubes (CNTs) are built with such needed properties.As a quasi-one-dimensional material,the CNT is expected to have a large surface field enhancement factor.The experiments have proved the excellent FE performance of CNTs.The turn-on field (the macroscopic field for obtaining a density of 10 μA/cm2 ) of CNT based emitters can be as low as 1 V/μm.However,this turn-on field is too good to be explained by conventional theory.There are other observations,such as the non-linear Fowler-Nordheim plot and multi-peaks field emission energy distribution spectra,indicating that the field enhancement is not the only story in the FE of CNTs.Since the discovery of CNTs,people have employed more serious quantum mechanical methods,including the electronic band theory,tight-binding theory,scattering theory and density function theory,to investigate FE of CNTs.A few theoretical models have been developed at the same time.The multi-walled carbon nanotubes (MWCNTs)should be assembled with a sharp metal needle of nano-scale radius,for which the FE mechanism is more or less clear

  2. A thin film triode type carbon nanotube field emission cathode

    Science.gov (United States)

    Sanborn, Graham; Turano, Stephan; Collins, Peter; Ready, W. Jud

    2013-01-01

    The field electron emission of carbon nanotubes has been heavily studied over the past two decades for various applications, such as in display technologies, microwave amplifiers, and spacecraft propulsion. However, a commercializable lightweight and internally gated electron source has yet to be realized. This work presents the fabrication and testing of a novel internally gated carbon nanotube field electron emitter. Several specific methods are used to prevent electrical shorting of the gate layer, a common failure for internally gated devices. A unique design is explored where the etch pits extend into the silicon substrate and isotropic etching is used to create a lateral buffer zone between the gate and carbon nanotubes. Carbon nanotubes are self-aligned to and within 10 microns from the gate, which creates large electric fields at low potential inputs. Initial tests confirm high field emission performance with an anode current density (based on total area of the device) of 293 μA cm-2 and a gate current density of 1.68 mA cm-2 at 250 V.

  3. 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.

  4. Field emission from laterally aligned carbon nanotube flower arrays for low turn-on field emission

    Directory of Open Access Journals (Sweden)

    Hiroe Kimura

    2013-09-01

    Full Text Available Laterally aligned carbon nanotube (CNT arrays “blossomed” homogeneously in honeycomb holes of a metal grid substrate were explored as rational architecture for field emission. A low turn-on field (TOF of 1.09 V/μm for 10 μA/cm2 emission was achieved, which approaches or exceeds the lowest reported TOF values for field emitter arrays. We interpret that these lateral CNT arrays act as source of CNT “loop” arrays enabling a structure suited toward low TOF field emission.

  5. Nanoseconds field emitted current pulses from ZrC needles and field emitter arrays

    CERN Document Server

    Ganter, R; Betemps, R; Dehler, M; Gerber, T; Gobrecht, J; Gough, C; Johnson, M; Kirk, E; Knopp, G; Le Pimpec, F; Li, K; Paraliev, M; Pedrozzi, M; Rivkin, L; Schulz, L; Sehr, H; Wrulich, A F

    2006-01-01

    The properties of the electron source define the ultimate limit of the beam quality in linear accelerators like Free Electron Lasers (FEL). The goal is to develop an electron gun delivering beam emittance lower than current state of the art. Such a gun should reduce the cost and size of an X-ray Free Electron Laser (XFEL). In this paper we present two concepts of field emitter cathodes which could potentially produce low emittance beam. The first challenging parameter for such cathode is to emit peak current as high as 5 A. This is the minimum current requirement for the XFEL concept from Paul Scherrer Institut.1 Maximum current of 0.12 A and 0.58 A have been reached respectively with field emitter arrays (FEA) and single needle cathodes. Laser assisted field emission gave encouraging results to reach even higher peak current and to pre-bunch the beam.

  6. Focusing performance and thermal property of carbon-nanotube emitter-based X-ray sources

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Ho; Kim, Wan Sun; Ryu, Je Hwang; Kim, Kyung Sook; Park, Hun Kuk [Kyung Hee University, Seoul (Korea, Republic of)

    2014-12-15

    Carbon-nanotube (CNT) emitter-based X-ray sources have been extensively investigated as new imaging devices. The electron-beam trajectory in the CNT emitter-based X-ray sources were simulated to determine the optimized conditions for high focusing performance and limited thermal damage to the anode. The beam trajectory from the cathode to the anode was simulated, and the focal spot size (FSS) of the beam was determined by varying the structure of the electrode in the X-ray system. The temperature change of the anode caused by the electron-beam was calculated. The effects of electrode voltage and of the distance between the electrode and the anode on the FSS were significant while the effect of electrode thickness was small in all structures. When the electron-beam was emitted with an FSS of 170 μm and a power of 130 W, the thermal damage to the anode was reduced by using a 2-ms pulsed-voltage operation for a duration of 8 ms.

  7. Single-walled carbon nanotubes of controlled diameter and bundle size and their field emission properties.

    Science.gov (United States)

    Zhang, Liang; Balzano, Leandro; Resasco, Daniel E

    2005-08-04

    Field emission studies were conducted on as-produced CoMoCAT single-walled carbon nanotube/silica composites with controlled nanotube diameter and bundle size. It has been observed that the as-produced nanotube material does not need to be separated from the high-surface area catalyst to be an effective electron emitter. By adjusting the catalytic synthesis conditions, single-walled carbon nanotubes (SWNT) of different diameters and bundle sizes were synthesized. A detailed characterization involving Raman spectroscopy, optical absorption (vis-NIR), SEM, and TEM was conducted to identify the nanotube species present in the different samples. The synthesis reaction temperature was found to affect the nanotube diameter and bundle size in opposite ways; that is, as the synthesis temperature increased the nanotube average diameter became larger, but the bundle size became smaller. A gradual and consistent reduction in the emission onset field was observed as the synthesis temperature increased. It is suggested that the bundle size, more than the nanotube diameter or chirality, determines the field emission characteristics of these composites. This is a clear demonstration that field emission characteristics of SWNT can be controlled by the nanotube synthesis conditions.

  8. Effect of Purity and Substrate on Field Emission Properties of Multi-walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Sethupathi K

    2007-01-01

    Full Text Available AbstractMulti-walled carbon nanotubes (MWNT have been synthesized by chemical vapour decomposition (CVD of acetylene over Rare Earth (RE based AB2(DyNi2 alloy hydride catalyst. The as-grown carbon nanotubes were purified by acid and heat treatments and characterized using powder X-ray diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, Thermo Gravimetric Analysis and Raman Spectroscopy. Fully carbon based field emitters have been fabricated by spin coating a solutions of both as-grown and purified MWNT and dichloro ethane (DCE over carbon paper with and without graphitized layer. The use of graphitized carbon paper as substrate opens several new possibilities for carbon nanotube (CNT field emitters, as the presence of the graphitic layer provides strong adhesion between the nanotubes and carbon paper and reduces contact resistance. The field emission characteristics have been studied using an indigenously fabricated set up and the results are discussed. CNT field emitter prepared by spin coating of the purified MWNT–DCE solution over graphitized carbon paper shows excellent emission properties with a fairly stable emission current over a period of 4 h. Analysis of the field emission characteristics based on the Fowler–Nordheim (FN theory reveals current saturation effects at high applied fields for all the samples.

  9. Effect of Purity and Substrate on Field Emission Properties of Multi-walled Carbon Nanotubes.

    Science.gov (United States)

    Rakhi, Rb; Sethupathi, K; Ramaprabhu, S

    2007-06-21

    Multi-walled carbon nanotubes (MWNT) have been synthesized by chemical vapour decomposition (CVD) of acetylene over Rare Earth (RE) based AB2(DyNi2) alloy hydride catalyst. The as-grown carbon nanotubes were purified by acid and heat treatments and characterized using powder X-ray diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, Thermo Gravimetric Analysis and Raman Spectroscopy. Fully carbon based field emitters have been fabricated by spin coating a solutions of both as-grown and purified MWNT and dichloro ethane (DCE) over carbon paper with and without graphitized layer. The use of graphitized carbon paper as substrate opens several new possibilities for carbon nanotube (CNT) field emitters, as the presence of the graphitic layer provides strong adhesion between the nanotubes and carbon paper and reduces contact resistance. The field emission characteristics have been studied using an indigenously fabricated set up and the results are discussed. CNT field emitter prepared by spin coating of the purified MWNT-DCE solution over graphitized carbon paper shows excellent emission properties with a fairly stable emission current over a period of 4 h. Analysis of the field emission characteristics based on the Fowler-Nordheim (FN) theory reveals current saturation effects at high applied fields for all the samples.

  10. Extension of the general thermal field equation for nanosized emitters

    Energy Technology Data Exchange (ETDEWEB)

    Kyritsakis, A., E-mail: akyritsos1@gmail.com; Xanthakis, J. P. [Department of Electrical and Computer Engineering, National Technical University of Athens, Zografou Campus, Athens 15700 (Greece)

    2016-01-28

    During the previous decade, Jensen et al. developed a general analytical model that successfully describes electron emission from metals both in the field and thermionic regimes, as well as in the transition region. In that development, the standard image corrected triangular potential barrier was used. This barrier model is valid only for planar surfaces and therefore cannot be used in general for modern nanometric emitters. In a recent publication, the authors showed that the standard Fowler-Nordheim theory can be generalized for highly curved emitters if a quadratic term is included to the potential model. In this paper, we extend this generalization for high temperatures and include both the thermal and intermediate regimes. This is achieved by applying the general method developed by Jensen to the quadratic barrier model of our previous publication. We obtain results that are in good agreement with fully numerical calculations for radii R > 4 nm, while our calculated current density differs by a factor up to 27 from the one predicted by the Jensen's standard General-Thermal-Field (GTF) equation. Our extended GTF equation has application to modern sharp electron sources, beam simulation models, and vacuum breakdown theory.

  11. 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.

  12. Quantum emitters dynamically coupled to a quantum field

    Energy Technology Data Exchange (ETDEWEB)

    Acevedo, O. L.; Quiroga, L.; Rodríguez, F. J. [Departamento de Física, Universidad de los Andes, A.A. 4976, Bogotá (Colombia); Johnson, N. F. [Department of Physics, University of Miami, Coral Gables, Miami, FL 33124 (United States)

    2013-12-04

    We study theoretically the dynamical response of a set of solid-state quantum emitters arbitrarily coupled to a single-mode microcavity system. Ramping the matter-field coupling strength in round trips, we quantify the hysteresis or irreversible quantum dynamics. The matter-field system is modeled as a finite-size Dicke model which has previously been used to describe equilibrium (including quantum phase transition) properties of systems such as quantum dots in a microcavity. Here we extend this model to address non-equilibrium situations. Analyzing the system’s quantum fidelity, we find that the near-adiabatic regime exhibits the richest phenomena, with a strong asymmetry in the internal collective dynamics depending on which phase is chosen as the starting point. We also explore signatures of the crossing of the critical points on the radiation subsystem by monitoring its Wigner function; then, the subsystem can exhibit the emergence of non-classicality and complexity.

  13. Quantum emitters dynamically coupled to a quantum field

    Science.gov (United States)

    Acevedo, O. L.; Quiroga, L.; Rodríguez, F. J.; Johnson, N. F.

    2013-12-01

    We study theoretically the dynamical response of a set of solid-state quantum emitters arbitrarily coupled to a single-mode microcavity system. Ramping the matter-field coupling strength in round trips, we quantify the hysteresis or irreversible quantum dynamics. The matter-field system is modeled as a finite-size Dicke model which has previously been used to describe equilibrium (including quantum phase transition) properties of systems such as quantum dots in a microcavity. Here we extend this model to address non-equilibrium situations. Analyzing the system's quantum fidelity, we find that the near-adiabatic regime exhibits the richest phenomena, with a strong asymmetry in the internal collective dynamics depending on which phase is chosen as the starting point. We also explore signatures of the crossing of the critical points on the radiation subsystem by monitoring its Wigner function; then, the subsystem can exhibit the emergence of non-classicality and complexity.

  14. Field Emitter Arrays for a Free Electron Laser Application

    CERN Document Server

    Shing-Bruce-Li, Kevin; Ganter, Romain; Gobrecht, Jens; Raguin, Jean Yves; Rivkin, Leonid; Wrulich, Albin F

    2004-01-01

    The development of a new electron gun with the lowest possible emittance would help reducing the total length and cost of a free electron laser. Field emitter arrays (FEAs) are an attractive technology for electron sources of ultra high brightness. Indeed, several thousands of microscopic tips can be deposited on a 1 mm diameter area. Electrons are then extracted by applying voltage to a first grid layer close to the tip apexes, the so called gate layer, and focused by a second grid layer one micrometer above the tips. The typical aperture diameter of the gate and the focusing layer is in the range of one micrometer. One challenge for such cathodes is to produce peak currents in the ampere range since the usual applications of FEAs require less than milliampere. Encouraging peak current performances have been obtained by applying voltage pulses at low frequency between gate and tips. In this paper we report on different tip materials available on the market: diamond FEAs from Extreme Devices Inc., ZrC single ...

  15. Field Emission Characteristics of the Structure of Vertically Aligned Carbon Nanotube Bundles

    Science.gov (United States)

    Lin, Pao-Hung; Sie, Cong-Lin; Chen, Ching-An; Chang, Hsuan-Chen; Shih, Yi-Ting; Chang, Hsin-Yueh; Su, Wei-Jhih; Lee, Kuei-Yi

    2015-07-01

    In this study, we performed thermal chemical vapor deposition for growing vertically aligned carbon nanotube (VACNT) bundles for a field emitter and applied photolithography for defining the arrangement pattern to simultaneously compare square and hexagonal arrangements by using two ratios of the interbundle distance to the bundle height ( R) of field emitters. The hexagon arrangement with R = 2 had the lowest turn-on electric field ( E to) and highest enhancement factor, whereas the square arrangement with R = 3 had the most stable field emission (FE) characteristic. The number density can reveal the correlation to the lowest E to and highest enhancement factor more effectively than can the R or L. The fluorescent images of the synthesized VACNT bundles manifested the uniformity of FE currents. The results of our study indicate the feasibility of applying the VACNT field emitter arrangement to achieve optimal FE performance.

  16. Field emission of GaN-filled carbon nanotubes: high and stable emission current.

    Science.gov (United States)

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

    2007-03-01

    Field electron emission of GaN-filled carbon nanotubes, grown by microwave plasma enhanced chemical vapor deposition, was investigated. The detailed structural characterization shows that the filled nanotube has a GaN-core/C-shell structure, in which the GaN wire corresponds to a wurtzite structure. The field emission properties of the GaN-filled carbon nanotubes have been achieved with high and stable emission current. It is attributed to the unique cable-like structure, which makes the GaN-core/C-shell composite mechanically solid and chemically stable. This study suggests the GaN-filled carbon nanotube as an ideal candidate for future high-current and high-power field emitter applications.

  17. Electric Field Screening by the Proximity of Two Knife-Edge Field Emitters of Finite Width

    Science.gov (United States)

    Wong, P.; Tang, W.; Lau, Y. Y.; Hoff, B.

    2015-11-01

    Field emitter arrays have the potential to provide high current density, low voltage operation, and high pulse repetition for radar and communication. It is well known that packing density of the field emitter arrays significantly affect the emission current. Previously we calculated analytically the electric field profile of two-dimensional knife-edge cathodes with arbitrary separation by using a Schwarz-Christoffel transformation. Here we extend this previous work to include the finite width of two identical emitters. From the electric field profile, the field enhancement factor, thereby the severity of the electric field screening, are determined. It is found that for two identical emitters with finite width, the magnitude of the electric field on the knife-edge cathodes depends strongly on the ratio h / a and h / r , where h is the height of the knife-edge cathode, 2a is the distance between the cathodes, and 2 r represents their width. Particle-in-cell simulations are performed to compare with the analytical results on the emission current distribution. P. Y. Wong was supported by a Directed Energy Summer Scholar internship at Air Force Research Laboratory, Kirtland AFB, and by AFRL Award No. FA9451-14-1-0374.

  18. A carbon nanotube field emission cathode with high current density and long-term stability

    Science.gov (United States)

    Calderón-Colón, Xiomara; Geng, Huaizhi; Gao, Bo; An, Lei; Cao, Guohua; Zhou, Otto

    2009-08-01

    Carbon nanotube (CNT) field emitters are now being evaluated for a wide range of vacuum electronic applications. However, problems including short lifetime at high current density, instability under high voltage, poor emission uniformity, and pixel-to-pixel inconsistency are still major obstacles for device applications. We developed an electrophoretic process to fabricate composite CNT films with controlled nanotube orientation and surface density, and enhanced adhesion. The cathodes have significantly enhanced macroscopic field emission current density and long-term stability under high operating voltages. The application of this CNT electron source for high-resolution x-ray imaging is demonstrated.

  19. Carbon Nanotubes as an Ultrafast Emitter with a Narrow Energy Spread at Optical Frequency.

    Science.gov (United States)

    Li, Chi; Zhou, Xu; Zhai, Feng; Li, Zhenjun; Yao, Fengrui; Qiao, Ruixi; Chen, Ke; Cole, Matthew Thomas; Yu, Dapeng; Sun, Zhipei; Liu, Kaihui; Dai, Qing

    2017-08-01

    Ultrafast electron pulses, combined with laser-pump and electron-probe technologies, allow ultrafast dynamics to be characterized in materials. However, the pursuit of simultaneous ultimate spatial and temporal resolution of microscopy and spectroscopy is largely subdued by the low monochromaticity of the electron pulses and their poor phase synchronization to the optical excitation pulses. Field-driven photoemission from metal tips provides high light-phase synchronization, but suffers large electron energy spreads (3-100 eV) as driven by a long wavelength laser (>800 nm). Here, ultrafast electron emission from carbon nanotubes (≈1 nm radius) excited by a 410 nm femtosecond laser is realized in the field-driven regime. In addition, the emitted electrons have great monochromaticity with energy spread as low as 0.25 eV. This great performance benefits from the extraordinarily high field enhancement and great stability of carbon nanotubes, superior to metal tips. The new nanotube-based ultrafast electron source opens exciting prospects for extending current characterization to sub-femtosecond temporal resolution as well as sub-nanometer spatial resolution. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Elementary framework for cold field emission from quantum-confined, non-planar emitters

    Energy Technology Data Exchange (ETDEWEB)

    Patterson, A. A., E-mail: apatters@mit.edu; Akinwande, A. I. [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2015-05-07

    For suitably small field emitters, the effects of quantum confinement at the emitter tip may have a significant impact on the emitter performance and total emitted current density (ECD). Since the geometry of a quantum system uniquely determines the magnitude and distribution of its energy levels, a framework for deriving ECD equations from cold field electron emitters of arbitrary geometry and dimensionality is developed. In the interest of obtaining semi-analytical ECD equations, the framework is recast in terms of plane wave solutions to the Schrödinger equation via the use of the Jeffreys-Wentzel-Kramers-Brillouin approximation. To demonstrate the framework's consistency with our previous work and its capabilities in treating emitters with non-planar geometries, ECD equations were derived for the normally unconfined cylindrical nanowire (CNW) and normally confined (NC) CNW emitter geometries. As a function of the emitter radius, the NC CNW emitter ECD profile displayed a strong dependence on the Fermi energy and had an average ECD that exceeded the Fowler-Nordheim equation for typical values of the Fermi energy due to closely spaced, singly degenerate energy levels (excluding electron spin), comparatively large electron supply values, and the lack of a transverse, zero-point energy. Such characteristics suggest that emitters with non-planar geometries may be ideal for emission from both an electron supply and electrostatics perspective.

  1. Hot electron field emission via individually transistor-ballasted carbon nanotube arrays.

    Science.gov (United States)

    Li, Chi; Zhang, Yan; Cole, Matthew T; Shivareddy, Sai G; Barnard, Jon S; Lei, Wei; Wang, Baoping; Pribat, Didier; Amaratunga, Gehan A J; Milne, William I

    2012-04-24

    We present electronically controlled field emission characteristics of arrays of individually ballasted carbon nanotubes synthesized by plasma-enhanced chemical vapor deposition on silicon-on-insulator substrates. By adjusting the source-drain potential we have demonstrated the ability to controllable limit the emission current density by more than 1 order of magnitude. Dynamic control over both the turn-on electric field and field enhancement factor have been noted. A hot electron model is presented. The ballasted nanotubes are populated with hot electrons due to the highly crystalline Si channel and the high local electric field at the nanotube base. This positively shifts the Fermi level and results in a broad energy distribution about this mean, compared to the narrow spread, lower energy thermalized electron population in standard metallic emitters. The proposed vertically aligned carbon nanotube field-emitting electron source offers a viable platform for X-ray emitters and displays applications that require accurate and highly stable control over the emission characteristics.

  2. Effects of base resistor on electron emission from a field emitter

    Energy Technology Data Exchange (ETDEWEB)

    Luginsland, J.W.; Valfells, A.; Lau, Y.Y. [Univ. of Michigan, Ann Arbor, MI (United States)

    1996-12-31

    Field emitters have remained an important, high brightness electron source for display and for generation of coherent radiation. The rapid rise in the emitter current with voltage in these emitters leads to serious implications on the emitter stability (thermal, mechanical, and electrical), and an obvious way to improve the emitter stability is to add a series resistor to the emitters. However, the addition of a series resistor would result in a higher operating voltage, loss in efficiency, and much higher cost. In this paper, the authors use a simple model to provide a quantitative analysis of the effects of a base resistor on the voltage-current (V-I) characteristics of a single field emitter. Two features of the present work are noteworthy. First, they present a set of universal curves, from which the effects of a series resistor can immediately be determined once the Fowler-Nordheim coefficients A, B, and the gap spacing D are specified. Thus, these curves are applicable to a large class of field emitters. Second, the calculations take into account the effects of space charge that is present in the gap. The relative importance of the space charge and of the series resistor will become apparent from these curves. Examples will be given.

  3. Electron transferring from titanium ion irradiated carbon nanotube arrays into vacuum under low applied fields

    Science.gov (United States)

    Deng, Jian-hua; Ping, Zhao-xia; Zheng, Rui-ting; Cheng, Guo-an

    2011-05-01

    Field emission characteristics of carbon nanotube arrays synthesized by thermal chemical vapor deposition on iron ion pre-bombarded silicon substrate are enhanced by titanium ion irradiation. A pronounced degradation of turn-on electric field of 0.305 V/μm and threshold field, of which the lowest value is only 1.054 V/μm, about 0.482 V/μm at the dose of 5 × 10 16 ions/cm 2 is as an expression of this enhancement. Scanning electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, Photoelectron spectrometer and transmission electron microscopy are measured for comparison before and after the Ti ion irradiation of the carbon nanotube arrays, and the results reveal that the formation of carbon nanorod/nanotube heterostructure during ion irradiation plays a dominative role in the promotion of the field emission properties. However, high-dose irradiating transaction on carbon nanotube arrays will exert repulsive effects on the field emission characteristics for the introduction of severe structural damage. Additionally, the longtime eminent stability behaviors under high applied fields have provided a possibility for the potential application of field emission flat panel display or electron emitters based on carbon nanotube arrays.

  4. On the Importance of Symmetrizing RF Coupler Fields for Low Emittance Beams

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zenghai; Zhou, Feng; Vlieks, Arnold; Adolphsen, Chris; /SLAC

    2011-06-23

    The input power of accelerator structure is normally fed through a coupling slot(s) on the outer wall of the accelerator structure via magnetic coupling. While providing perfect matching, the coupling slots may produce non-axial-symmetric fields in the coupler cell that can induce emittance growth as the beam is accelerated in such a field. This effect is especially important for low emittance beams at low energies such as in the injector accelerators for light sources. In this paper, we present studies of multipole fields of different rf coupler designs and their effect on beam emittance for an X-band photocathode gun being jointly designed with LLNL, and X-band accelerator structures. We will present symmetrized rf coupler designs for these components to preserve the beam emittance.

  5. The effect of built-in drift field and emitter recombinations on FCVD of a p- n junction diode

    Science.gov (United States)

    Jain, S. C.; Ray, U. C.

    1983-06-01

    This paper discusses the Forward Current induced open circuit Voltage Decay (FCVD) of a p- n junction diode including the effects of recombinations in the emitter as well as the built-in drift fields in the base and in the emitter. The analysis is based on the quasi-static approximation (QSA) of the carrier profiles in the emitter. It is shown that the emitter effects on FCVD is completely determined by JEO, the dark saturation current in the emitter. The value of JEO in general, depends on the heavy doping effects in the emitter, the drift field in the emitter, emitter thickness and surface recombination velocity at the emitter surface. It is shown that for a diode with retarding drift field in the base, emitter recombinations play a very significant role in FCVD. The decay time constant for large values of time in this case is given by τ eff = τ B/[1 + ƒ B2 - (a - ƒ B) 2], where a = J EO/J BO, ƒ B is the drift field parameter in the base. The higher value of a, the faster is the voltage decay. For accelerating fields in the base, the time constant for large values of time is independent of emitter recombinations and is given by τ eff = τ B/(1 + ƒ B2) . However, the decay rate for small values of time is strongly affected by emitter recombinations for both types of the field; the higher the emitter recombinations, the faster is the initial rate of the voltage decay. For extremely strong drift fields in the base, QSA in the emitter is not valid. The coupled continuity equations are solved with the conditions ƒ B2 ≫ τ B/τ E and an analytic expression for FCVD is derived. It is seen that FCVD for strong base fields is determined solely by emitter lifetime τE except for small values of time of the order of a few τE.

  6. 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.

  7. Flexible field emission of nitrogen-doped carbon nanotubes/reduced graphene hybrid films.

    Science.gov (United States)

    Lee, Duck Hyun; Lee, Jin Ah; Lee, Won Jong; Kim, Sang Ouk

    2011-01-03

    The outstanding flexible field emission properties of carbon hybrid films made of vertically aligned N-doped carbon nanotubes grown on mechanically compliant reduced graphene films are demonstrated. The bottom-reduced graphene film substrate enables the conformal coating of the hybrid film on flexible device geometry and ensures robust mechanical and electrical contact even in a highly deformed state. The field emission properties are precisely examined in terms of the control of the bending radius, the N-doping level, and the length or wall-number of the carbon nanotubes and analyzed with electric field simulations. This high-performance flexible carbon field emitter is potentially useful for diverse, flexible field emission devices.

  8. Highly flexible and robust N-doped SiC nanoneedle field emitters

    KAUST Repository

    Chen, Shanliang

    2015-01-23

    Flexible field emission (FE) emitters, whose unique advantages are lightweight and conformable, promise to enable a wide range of technologies, such as roll-up flexible FE displays, e-papers and flexible light-emitting diodes. In this work, we demonstrate for the first time highly flexible SiC field emitters with low turn-on fields and excellent emission stabilities. n-Type SiC nanoneedles with ultra-sharp tips and tailored N-doping levels were synthesized via a catalyst-assisted pyrolysis process on carbon fabrics by controlling the gas mixture and cooling rate. The turn-on field, threshold field and current emission fluctuation of SiC nanoneedle emitters with an N-doping level of 7.58 at.% are 1.11 V μm-1, 1.55 V μm-1 and 8.1%, respectively, suggesting the best overall performance for such flexible field emitters. Furthermore, characterization of the FE properties under repeated bending cycles and different bending states reveal that the SiC field emitters are mechanically and electrically robust with unprecedentedly high flexibility and stabilities. These findings underscore the importance of concurrent morphology and composition controls in nanomaterial synthesis and establish SiC nanoneedles as the most promising candidate for flexible FE applications. © 2015 Nature Publishing Group All rights reserved.

  9. Planar Field Emitters and High Efficiency Photocathodes Based on Ultrananocrystalline Diamond

    Science.gov (United States)

    Sumant, Anirudha V. (Inventor); Baryshev, Sergey V. (Inventor); Antipov, Sergey P. (Inventor)

    2016-01-01

    A method of forming a field emitter comprises disposing a first layer on a substrate. The first layer is seeded with nanodiamond particles. The substrate with the first layer disposed thereon is maintained at a first temperature and a first pressure in a mixture of gases which includes nitrogen. The first layer is exposed to a microwave plasma to form a nitrogen doped ultrananocrystalline diamond film on the first layer, which has a percentage of nitrogen in the range of about 0.05 atom % to about 0.5 atom %. The field emitter has about 10.sup.12 to about 10.sup.14 emitting sites per cm.sup.2. A photocathode can also be formed similarly by forming a nitrogen doped ultrananocrystalline diamond film on a substrate similar to the field emitter, and then hydrogen terminating the film. The photocathode is responsive to near ultraviolet light as well as to visible light.

  10. Planar field emitters and high efficiency photocathodes based on ultrananocrystalline diamond

    Energy Technology Data Exchange (ETDEWEB)

    Sumant, Anirudha V.; Baryshev, Sergey V.; Antipov, Sergey P.

    2016-08-16

    A method of forming a field emitter comprises disposing a first layer on a substrate. The first layer is seeded with nanodiamond particles. The substrate with the first layer disposed thereon is maintained at a first temperature and a first pressure in a mixture of gases which includes nitrogen. The first layer is exposed to a microwave plasma to form a nitrogen doped ultrananocrystalline diamond film on the first layer, which has a percentage of nitrogen in the range of about 0.05 atom % to about 0.5 atom %. The field emitter has about 10.sup.12 to about 10.sup.14 emitting sites per cm.sup.2. A photocathode can also be formed similarly by forming a nitrogen doped ultrananocrystalline diamond film on a substrate similar to the field emitter, and then hydrogen terminating the film. The photocathode is responsive to near ultraviolet light as well as to visible light.

  11. Field-effect transistors assembled from functionalized carbon nanotubes

    OpenAIRE

    Klinke, Christian; Hannon, James B.; Afzali, Ali; Avouris, Phaedon

    2006-01-01

    We have fabricated field effect transistors from carbon nanotubes using a novel selective placement scheme. We use carbon nanotubes that are covalently bound to molecules containing hydroxamic acid functionality. The functionalized nanotubes bind strongly to basic metal oxide surfaces, but not to silicon dioxide. Upon annealing, the functionalization is removed, restoring the electronic properties of the nanotubes. The devices we have fabricated show excellent electrical characteristics.

  12. Field-emission microscopy of the surface of an Ir-C-Cs point emitter

    Science.gov (United States)

    Bernatskii, D. P.; Pavlov, V. G.

    2013-12-01

    The emissive properties of an iridium-based point emitter with various forms of carbon (chemisorbed species, two-dimensional graphite structures) and cesium atoms adsorbed on the surface has been studied by the field-electron emission microscopy (FEM) and field-desorption microscopy (FDM) techniques. The FEE and FDM images of the emitter surface corresponding to various phase states of carbon have been obtained. It is established that two-dimensional graphite structures grow predominantly in the regions of (100) and (111) faces of iridium.

  13. Root Causes of Field Emitters in SRF Cavities Placed in CEBAF Tunnel

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Rongli

    2016-05-01

    It has been suspected that appearance of new field emitters can occur in SRF cavities after their placement in accelerator tunnel for long term beam operation. This apparently has been the case for CEBAF. However, no physical evidence has been shown in the past. In this contribution, we will report on the recent results concerning the root cause of field emitters in SRF cavities placed in CEBAF tunnel. We will discuss these results in the context of high-reliability and low-cryogenic-loss operation of CEBAF.

  14. Triode field emitter with a gated planar carbon-nanoparticle cathode

    Science.gov (United States)

    Park, Kyung Ho; Seo, Woo Jong; Lee, Soonil; Koh, Ken Ha

    2002-07-01

    We fabricated a triode field emitter with a normal gate structure and a planar cathode of carbon nanoparticles (CNPs), which consisted of good quality graphitic sheets encapsulating metal (carbide) cores. For the quantitative analysis of the emission from the CNP triode emitter, we carried out a two-dimensional numerical calculation of electrostatic potential using the finite element method. As it turned out, a radial variation of electric field was very important to account for the emission from a planar emitting layer. By assuming the work function of 5 eV for CNPs, a set of consistent Fowler-Nordheim parameters, together with the radial position of emitting sites, were determined.

  15. Analysis of electric field screening by the proximity of two knife-edge field emitters

    Science.gov (United States)

    Tang, Wilkin; Shiffler, Don; Cartwright, Keith L.

    2011-08-01

    The electric field of two semi-infinitely wide knife-edge cathodes with arbitrary separation is calculated by using a Schwarz-Christoffel transformation. This geometry could also represent a trench (or scratch) on a flat surface. It is found that the magnitude of the electric field on the knife-edge cathodes depends strongly on the ratio h/a, where h is the height of the knife-edge cathodes and 2a is the distance between the cathodes. When h/a increases, the magnitude of the electric field on the cathode's surface decreases. This shows the screening of one cathode by another cathode; for example, keeping the height fixed and decreasing the distance between the cathodes, the field enhancement on the corner decreases. Analytic approximations for the divergent electric field in the immediate vicinity of the sharp edge are derived for the cases where h /a>>1, and h /a≪1. These results lead to insight on the relationship of the density of field emitter in field emitting arrays and field emission from rough surfaces.

  16. Influence of surface roughness on field emission of electrons from carbon nanotube films.

    Science.gov (United States)

    Liu, Huarong; Saito, Yahachi

    2010-06-01

    Electron field emission properties of a nanotube film are influenced not only by a field enhancement factor of carbon nanotubes (CNTs) beta(CNT) but also by that of film morphology beta(P). A simple method to separate beta(P), and beta(CNT) is proposed by using their different dependences on the cathode-anode distance. Analyses conducted for CNT emitters with rough surface exhibit that beta(P) ranges from 1 to approximately 4.5. The separated beta(CNT) values are in good agreement with the CNT geometries observed by a scanning electron microscope. Variation in beta(P)-values is ascribed to the surface roughness of the CNT films.

  17. Novel planar field emission of ultra-thin individual carbon nanotubes.

    Science.gov (United States)

    Song, Xuefeng; Gao, Jingyun; Fu, Qiang; Xu, Jun; Zhao, Qing; Yu, Dapeng

    2009-10-07

    In this work, we proposed and realized a new prototype of planar field emission device based on as-grown individual carbon nanotubes (CNTs) on the surface of a Si-SiO2 substrate. The anode, cathode and the CNT tip all lie on the same surface, so the electron emission is reduced from three-dimensional to two-dimensional. The benefits of such a design include usage of thinner CNT emitters, integrity with planar technology, stable construction, better heat dissipation, etc. A tip-to-tip field emission device was presented besides the tip-to-electrode one. Real-time, in situ observation of the planar field emission was realized in a scanning electron microscope (SEM). Measurements showed that the minimum voltage for 10 nA field emission current was only 8.0 V and the maximum emission current density in an individual CNT emitter (1.0 nm in diameter) exceeded 5.7 x 10(8) A cm(-2). These results stand out in the comparison with recent works on individual CNT field emission, indicating that the planar devices based on ultra-thin individual CNTs are more competitive candidates for next-generation electron field emitters.

  18. Amp\\`ere-Class Pulsed Field Emission from Carbon-Nanotube Cathodes in a Radiofrequency Resonator

    CERN Document Server

    Mihalcea, D; Hartzell, J; Panuganti, H; Boucher, S M; Murokh, A; Piot, P; Thangaraj, J C T

    2015-01-01

    Pulsed field emission from cold carbon-nanotube cathodes placed in a radiofrequency resonant cavity was observed. The cathodes were located on the backplate of a conventional $1+\\frac{1}{2}$-cell resonant cavity operating at 1.3-GHz and resulted in the production of bunch train with maximum average current close to 0.7 Amp\\`ere. The measured Fowler-Nordheim characteristic, transverse emittance, and pulse duration are presented and, when possible, compared to numerical simulations. The implications of our results to high-average-current electron sources are briefly discussed.

  19. A device for the remote detection of alpha emitters under field conditions

    NARCIS (Netherlands)

    Simakov, AB

    2005-01-01

    The portable DOP device was designed for the ecological monitoring of the radiation of alpha radioactive nuclides, such as plutonium, uranium, radium, etc. Under field conditions, it can detect alpha emitters at distances of up to 0.5 m. The device's performance data are as follows: the lower thresh

  20. 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.

  1. Densification effects of the carbon nanotube pillar array on field-emission properties

    Science.gov (United States)

    Wang, Kuang-Yu; Chou, Chia-Hsin; Liao, Chan-Yu; Li, Yu-Ren; Cheng, Huang-Chung

    2016-06-01

    In this study, a simple densification method for carbon nanotube (CNT) pillars is proposed to achieve high-performance field emission characteristics and stable emission. Through capillary force during solution evaporation, the CNT density in each pillar can be increased by about six times without causing damage to the crystallinity of CNTs. The densified CNT pillars exhibit lower series resistance, sharper pillars, better contacts, higher thermal conductivity, and better mechanical stiffness than as-grown ones. Therefore, the threshold field of the field emitter with such CNT pillars of 50 µm height can be reduced to 1.98 V/µm, as compared with 2.2 V/µm for the undensified ones. Moreover, the fluctuation of field-emission current decreases from 15.5 to 9.4% after the stress tests at a field of 2 V/µm for 1800 s. These findings imply that the densified CNT pillars are promising for the field-emission applications.

  2. Field Emission Study of Carbon Nanotubes: High Current Density from Nanotube Bundle Arrays

    Science.gov (United States)

    Bronikowski, Micheal J.; Manohara, Harish M.; Siegel, Peter H.; Hunt, Brian D.

    2004-01-01

    We have investigated the field emission behavior of lithographically patterned bundles of multiwalled carbon nanotubes arranged in a variety of array geometries. Such arrays of nanotube bundles are found to perform significantly better in field emission than arrays of isolated nanotubes or dense, continuous mats of nanotubes, with the field emission performance depending on the bundle diameter and inter-bundle spacing. Arrays of 2-micrometers diameter nanotube bundles spaced 5 micrometers apart (edge-to-edge spacing) produced the largest emission densities, routinely giving 1.5 to 1.8 A/cm(sup 2) at approximately 4 V/micrometer electric field, and greater than 6 A/cm(sup 2) at 20 V/micrometers.

  3. Doped carbon nanostructure field emitter arrays for infrared imaging

    Science.gov (United States)

    Korsah, Kofi [Knoxville, TN; Baylor, Larry R [Farragut, TN; Caughman, John B [Oak Ridge, TN; Kisner, Roger A [Knoxville, TN; Rack, Philip D [Knoxville, TN; Ivanov, Ilia N [Knoxville, TN

    2009-10-27

    An infrared imaging device and method for making infrared detector(s) having at least one anode, at least one cathode with a substrate electrically connected to a plurality of doped carbon nanostructures; and bias circuitry for applying an electric field between the anode and the cathode such that when infrared photons are adsorbed by the nanostructures the emitted field current is modulated. The detectors can be doped with cesium to lower the work function.

  4. Use of coated silicon field emitters as neutralisers for fundamental physics missions in space

    CERN Document Server

    Aplin, K L; Collingwood, C M; Wang, L; Stevens, R; Huq, S E; Malik, A

    2005-01-01

    Spacecraft neutralisers are required as part of the ion propulsion system for accurate station keeping in fundamental physics missions. A silicon field emitter neutraliser is under development at the Rutherford Appleton Laboratory. Thin layers of insulating materials as coatings for the gated field emitter array structure are described, which are postulated to reduce power consumption and reduce overheating. The power consumption and lifetime of aluminium nitrude and amorphous hydrogen diamond-like carbon coatings were promising, performing better in endurance tests than uncoated samples, but further work is required to characterise the coating's physical properties and its effects on field emission. The thermal conductivity of the coating material appeared to have little effect on the sample lifetimes. Aluminium nitride had reduced power consumption compared to diamond-like carbon coated and uncoated samples. A thin (~5nm)layer was optimal, meeting European Space Agency specifications for the neutraliser eng...

  5. Re-grown aligned carbon nanotubes with improved field emission.

    Science.gov (United States)

    Lim, Xiaodai; Zhu, Yanwu; Varghese, Binni; Gao, Xingyu; Wee, Andrew Thye Shen; Sow, Chorng-Haur

    2012-01-01

    In this work, a simple technique to improve the field emission property of multi-walled carbon nanotubes is presented. Re-grown multi-walled carbon nanotubes are grown on the same substrates after the as-grown multi-walled carbon nanotubes are transferred to other substrates using polydimethylsiloxane as intermediation. For the duration of the synthesis of the re-grown multi-walled carbon nanotubes, similar synthesis parameters used in growing the as-grown multi-walled carbon nanotubes are utilized. As a form of possible application, field emission studies show -2.6 times improvement in field enhancement factor and more uniform emission for the re-grown multi-walled carbon nanotubes. In addition, the turn-on field is reduced from 2.85 V/microm to 1.40 V/microm. Such significant improvements are attributed to new emission sites comprising of sharp carbonaceous impurities encompassing both tip and upper portion of the multi-walled carbon nanotubes. As such, this technique presents a viable route for the production of multi-walled carbon nanotubes with better field emission quality.

  6. Self-organized growth of bamboo-like carbon nanotube arrays for field emission properties

    Science.gov (United States)

    Padya, Balaji; Kalita, Dipankar; Jain, P. K.; Padmanabham, G.; Ravi, M.; Bhat, K. S.

    2012-09-01

    Well-aligned nitrogen-doped carbon nanotube (N-CNTs) film was fabricated on silicon substrate by thermal chemical vapor deposition process with varying the growth temperature. The effect of growth temperature on morphology, microstructure and crystallinity for the growth of N-CNTs was studied. At all growth temperatures, the bamboo-like morphology of graphene layers with compartments in CNTs were observed in transmission electron microscope micrographs. The doping level and the type of nitrogen-related moieties were determined by X-ray photoelectron spectroscopy analysis. The compartment distance decreases with increase in nitrogen doping level in hexagonal graphite network. The increase in nitrogen doping level in N-CNTs will lead to decrease in crystallinity and in-plane crystallite size. Field emission study of nitrogen-doped carbon nanotubes grown at optimum parameters showed that they are good emitters with a turn-on and threshold field of 0.3 and 1.6 V/μm, respectively. The maximum current density was observed to be 18.8 mA/cm2 at the electric field of 2.1 V/μm. It is considered that the enhanced field emission performance of doped nanotube is due to the presence of lone pairs of electrons on nitrogen atom that supplies more electrons to the conduction band.

  7. Behavior of molecules and molecular ions near a field emitter

    CERN Document Server

    Gault, Baptiste; Ashton, Michael V; Sinnott, Susan B; Chiaramonti, Ann N; Moody, Michael P; Schreiber, Daniel K

    2015-01-01

    The cold emission of particles from surfaces under intense electric fields is a process which underpins a variety of applications including atom probe tomography (APT), an analytical microscopy technique with near-atomic spatial resolution. Increasingly relying on fast laser pulsing to trigger the emission, APT experiments often incorporate the detection of molecular ions emitted from the specimen, in particular from covalently or ionically bonded materials. Notably, it has been proposed that neutral molecules can also be emitted during this process. However, this remains a contentious issue. To investigate the validity of this hypothesis, a careful review of the literature is combined with the development of new methods to treat experimental APT data, the modelling of ion trajectories, and the application of density-functional theory (DFT) simulations to derive molecular ion energetics. It is demonstrated that the direct thermal emission of neutral molecules is extremely unlikely. However, neutrals can still...

  8. Diamond field emitter array cathodes and possibilities of employing additive manufacturing for dielectric laser accelerating structures

    Science.gov (United States)

    Simakov, Evgenya I.; Andrews, Heather L.; Herman, Matthew J.; Hubbard, Kevin M.; Weis, Eric

    2017-03-01

    Demonstration of a stand-alone practical dielectric laser accelerator (DLA) requires innovation in two major critical components: high-current ultra-low-emittance cathodes and efficient laser accelerator structures. LANL develops two technologies that in our opinion are applicable to the novel DLA architectures: diamond field emitter array (DFEA) cathodes and additive manufacturing of photonic band-gap (PBG) structures. This paper discusses the results of testing of DFEA cathodes in the field-emission regime and the possibilities for their operation in the photoemission regime, and compares their emission characteristics to the specific needs of DLAs. We also describe recent advances in additive manufacturing of dielectric woodpile structures using a Nanoscribe direct laser-writing device capable of maskless lithography and additive manufacturing, and the development of novel infrared dielectric materials compatible with additive manufacturing.

  9. Handheld deep ultraviolet emission device based on aluminum nitride quantum wells and graphene nanoneedle field emitters.

    Science.gov (United States)

    Matsumoto, Takahiro; Iwayama, Sho; Saito, Takao; Kawakami, Yasuyuki; Kubo, Fumio; Amano, Hiroshi

    2012-10-22

    We report the successful fabrication of a compact deep ultraviolet emission device via a marriage of AlGaN quantum wells and graphene nanoneedle field electron emitters. The device demonstrated a 20-mW deep ultraviolet output power and an approximately 4% power efficiency. The performance of this device may lead toward the realization of an environmentally friendly, convenient and practical deep ultraviolet light source.

  10. Near-field Electrodynamics of Atomically Doped Carbon Nanotubes

    OpenAIRE

    Bondarev, Igor V.; Lambin, Philippe

    2005-01-01

    We develop a quantum theory of near-field electrodynamical properties of carbon nanotubes and investigate spontaneous decay dynamics of excited states and van der Waals attraction of the ground state of an atomic system close to a single-wall nanotube surface. Atomic spontaneous decay exhibits vacuum-field Rabi oscillations -- a principal signature of strong atom-vacuum-field coupling. The strongly coupled atomic state is nothing but a 'quasi-1D cavity polariton'. Its stability is mainly dete...

  11. Field emission from a selected multiwall carbon nanotube.

    Science.gov (United States)

    Passacantando, M; Bussolotti, F; Santucci, S; Di Bartolomeo, A; Giubileo, F; Iemmo, L; Cucolo, A M

    2008-10-01

    The electron field emission characteristics of individual multiwalled carbon nanotubes were investigated by a piezoelectric nanomanipulation system operating inside a scanning electron microscopy chamber. The experimental set-up ensures a precise evaluation of the geometric parameters (multiwalled carbon nanotube length and diameter and anode-cathode separation) of the field emission system. For several multiwalled carbon nanotubes, reproducible and quite stable emission current behaviour was obtained, with a dependence on the applied voltage well described by a series resistance modified Fowler-Nordheim model. A turn-on field of ∼30 V µm(-1) and a field enhancement factor of around 100 at a cathode-anode distance of the order of 1 µm were evaluated. Finally, the effect of selective electron beam irradiation on the nanotube field emission capabilities was extensively investigated.

  12. SAPHIRE: A New Flat-Panel Digital Mammography Detector With Avalanche Photoconductor and High-Resolution Field Emitter Readout

    Science.gov (United States)

    2006-06-01

    AD_________________ Award Number: W81XWH-04-1-0554 TITLE: SAPHIRE : A New Flat-Panel Digital... SAPHIRE : A New Flat-Panel Digital Mammography Detector with Avalanche Photoconductor and High-Resolution Field Emitter Readout 5b. GRANT NUMBER w81xwh-04...CsI), and form a charge image that is read out by a high-resolution field emitter array (FEA). We call the proposed detector SAPHIRE (Scintillator

  13. Enhanced field-emission from a mixture of carbon nanotubes, ZnO tetrapods and conductive particles.

    Science.gov (United States)

    Wei, Lei; Xiaobing, Zhang; Zhiwei, Zhao; Jing, Chen; Yiping, Cui; Baoping, Wang

    2012-08-01

    We report the enhancement of field-emission current from a mixture of carbon nanotubes, ZnO tetrapod-like nano structures, and conductive particles. Carbon nanotubes are deposited on the electrode as the field emitters. A MgO layer is printed around the cathode electrode, and ZnO tetrapod-like nano structures are deposited on this layer for the generation of secondary emission electrons. A few conductive particles are also distributed on the MgO layer by spraying or screen-printing. These conductive particles enhance the transverse electric field around the cathode electrode. Consequently, more primary electrons emitted from the carbon nanotubes bombard on the ZnO tetrapods, and secondary emission electrons and scattered electrons are yielded. Finally, the field-emission current is enhanced obviously. As experimental results shown, a high field-emission current about 32 mA in a direct current emission mode has been obtained from a 0.5 cm2 emission site when an electric field of 9 V/microm is applied between cathode and anode. Compared with a conventional carbon nanotube cathode, the field-emission current has been improved about 80%.

  14. Field emission arrays fabricated utilizing conjugated ZnO quantum dot/carbon nanotube hybrid nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Wu Chaoxing [Institute of Optoelectronic Display, Fuzhou University, Fuzhou 350002 (China); Li Fushan, E-mail: fushanli@hotmail.com [Institute of Optoelectronic Display, Fuzhou University, Fuzhou 350002 (China); Zhang Yongai [Institute of Optoelectronic Display, Fuzhou University, Fuzhou 350002 (China); Guo Tailiang, E-mail: gtl@fzu.edu.cn [Institute of Optoelectronic Display, Fuzhou University, Fuzhou 350002 (China); Qu Bo; Chen Zhijian [State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871 (China)

    2011-02-15

    In situ growth of ZnO quantum dots (QDs) on the surface of multiwalled carbon nanotube (MWCNTs) was realized via a mild solution-process method, and their application in field emission device was demonstrated. High resolution transmission electron microscopy observation revealed the conjugation between ZnO QDs and MWCNTs. Field emission arrays based on ZnO QD/MWCNT hybrid nanocomposite exhibited significantly improved luminance intensity and emitting dot density when compared with the MWCNT-only arrays. It is proposed that the introduction of the ZnO QDs on the sidewall of MWCNTs can enhance the tunnelling probability, and result in the improved field emission property for the hybrid emitters.

  15. Determination of satellite valley position in GaN emitter from photoexcited field emission investigations

    Science.gov (United States)

    Semenenko, M.; Yilmazoglu, O.; Hartnagel, H. L.; Pavlidis, D.

    2011-01-01

    Argon plasma etched GaN field-emitter rods with nanometer-scale diameter were fabricated on GaN grown on an n+-GaN substrate. Their electron field emission properties were investigated both without and under illumination by using light sources with various wavelengths. The Fowler-Nordheim current-voltage characteristics of the cathodes show a change in slope for illuminated cathodes. The electron affinity difference ΔE between the different valleys in the conduction band has been ascertained and is in the range from 1.18 up to 1.21 eV.

  16. Field emission behavior of carbon nanotube yarn for micro-resolution X-ray tube cathode.

    Science.gov (United States)

    Hwang, Jae Won; Mo, Chan Bin; Jung, Hyun Kyu; Ryu, Seongwoo; Hong, Soon Hyung

    2013-11-01

    Carbon nanotube (CNT) has excellent electrical and thermal conductivity and high aspect ratio for X-ray tube cathode. However, CNT field emission cathode has been shown unstable field emission and short life time due to field evaporation by high current density and detachment by electrostatic force. An alternative approach in this direction is the introduction of CNT yarn, which is a one dimensional assembly of individual carbon nanotubes bonded by the Van der Waals force. Because CNT yarn is composed with many CNTs, CNT yarns are expected to increase current density and life time for X-ray tube applications. In this research, CNT yarn was fabricated by spinning of a super-aligned CNT forest and was characterized for application to an X-ray tube cathode. CNT yarn showed a high field emission current density and a long lifetime of over 450 hours. Applying the CNT yarn field emitter to the X-ray tube cathode, it was possible to obtain micro-scale resolution images. The relationship between the field emission properties and the microstructure evolution was investigated and the unraveling effect of the CNT yarn was discussed.

  17. Resonance fluorescence of a two-level quantum emitter near a plasmonic nanoparticle: role of the near-field polarization

    Science.gov (United States)

    Vladimirova, Yu V.; Chubchev, E. D.; Zadkov, V. N.

    2017-02-01

    It is demonstrated that the interaction of a two-level quantum emitter (atom, molecule, etc) with a plasmonic nanoparticle (prolate nanospheroid) in an external laser field features either an essential increase (up to a few orders of magnitude) or reduction (up to a few times) of the total decay rate of the emitter in specific areas around the nanoparticle in contrast to its decay rate in a vacuum. It is also shown that the resonance fluorescence spectrum of the emitter in close proximity to a plasmonic nanoparticle is very sensitive to both the location of the emitter around the nanoparticle and to polarization of the near-field, which depends in turn on the polarization of the incident laser field. This can be used in engineering potential quantum optics experiments with quantum emitters in the near-field, as well as for 3D nanoscopy of the near-field by registering the resonance fluorescence spectra of quantum emitters scattered in the vicinity of a plasmonic nanoparticle.

  18. An Investigation of Emitters Clogging Under Magnetic Field and Water Quality

    Directory of Open Access Journals (Sweden)

    A. Kiani

    2016-02-01

    Full Text Available Introduction: Water scarcity is one of the major problems for crop production. Using drip irrigation as an effective method in the efficient use of water is expanding in arid and semi-arid regions. One of the problems in under pressure irrigation during use of saline, unconventional and waste is emitters clogging. There are several ways to prevent particle deposits in pipes and clogging of emitters. Generally, conventional methods are divided into two categories: physical and chemical methods. In physical method, suspended solids and inorganic materials are removed using particles sediment sand and disc filters. In the chemical method the pH drops by adding acid to water resulting in the dissolution of carbonate sediments. With chlorine handling, organisms (i.e. algae, fungi and bacteria that are the main causes of biological clogging are destroyed. However, the application of these methods is not successful in all cases. It has been observed that the emitters have gradually become obstructed. Magnetic water is obtained by passing water through permanent magnets or through the electromagnets installed in or on a feed pipeline. When a fluid passes through the magnetized field, its structure and some physical characteristic such as density, salt solution capacity, and deposition ratio of solid particles will be changed. An experimental study showed that a relatively weak magnetic influence increases the viscosity of water and consequently causes stronger hydrogen bonds under the magnetic field.There exist very few documented research projects related to the magnetization of water technology and its application to agricultural issues in general and emitter clogging in drip irrigation method, in particular. This technology is already used in some countries, especially in the Persian Gulf states. This research was designed and implemented aimed at increasing knowledge about the application of magnetic technology and its effects on emitters clogging

  19. Carbon Nanotube Electron Sources: From Electron Beams to Energy Conversion and Optophononics

    OpenAIRE

    Alireza Nojeh

    2014-01-01

    Carbon nanotubes have a host of properties that make them excellent candidates for electron emitters. A significant amount of research has been conducted on nanotube-based field-emitters over the past two decades, and they have been investigated for devices ranging from flat-panel displays to vacuum tubes and electron microscopes. Other electron emission mechanisms from carbon nanotubes, such as photoemission, secondary emission, and thermionic emission, have also been studied, although to a ...

  20. Analysis of transverse RMS emittance growth of a beam induced by spherical and chromatic aberration in a solenoidal field

    Energy Technology Data Exchange (ETDEWEB)

    Dash, Radhakanta, E-mail: radhakanta.physics@gmail.com [Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094 (India); Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Nayak, Biswaranjan [Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094 (India); Sharma, Archana; Mittal, Kailash C. [Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094 (India); Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2016-01-21

    In a medium energy beam transport line transverse rms emittance growth associated with spherical aberration is analysed. An analytical expression is derived for beam optics in a solenoid field considering terms up to the third order in the radial displacement. Two important phenomena: effect of spherical aberrations in axial-symmetric focusing lens and influence of nonlinear space charge forces on beam emittance growth are discussed for different beam distributions. In the second part nonlinear effect associated with chromatic aberration that describes the growth of emittance and distortion of phase space area is discussed.

  1. Analysis of transverse RMS emittance growth of a beam induced by spherical and chromatic aberration in a solenoidal field

    Science.gov (United States)

    Dash, Radhakanta; Nayak, Biswaranjan; Sharma, Archana; Mittal, Kailash C.

    2016-01-01

    In a medium energy beam transport line transverse rms emittance growth associated with spherical aberration is analysed. An analytical expression is derived for beam optics in a solenoid field considering terms up to the third order in the radial displacement. Two important phenomena: effect of spherical aberrations in axial-symmetric focusing lens and influence of nonlinear space charge forces on beam emittance growth are discussed for different beam distributions. In the second part nonlinear effect associated with chromatic aberration that describes the growth of emittance and distortion of phase space area is discussed.

  2. Theoretical Study on Field Emission Patterns of the Nanotube

    Institute of Scientific and Technical Information of China (English)

    HU Chen-guo; WANG Wan-lu; LIAO Ke-jun; WANG Hao; XIAO Jin-long

    2003-01-01

    The distributions of the electrical potential and field have been given from Maxwell's field equations.The results show that there exists very strong electric field intensity on the tip of the nanotube,and the intensity decays rapidly as the distance increases away from the tip. The strong electric field intensity on the tip is consistent with the low threshold voltage under the electric field emission from a nanotube. The calculation also revealed that the higher the aspect ratio is,the stronger the electric field intensity on the tip of the nanotube will be,if the distance and voltage between the cathode and the anode do not change, which predicts the lower threshold voltage under the field emission.

  3. Modified NEGF method for atomistic modeling of field emission from carbon nanotube

    Science.gov (United States)

    Monshipouri, Mahta; Behrooz, Milad; Abdi, Yaser

    2017-09-01

    A model to simulate the atomistic properties of the field emission (FE) from a zigzag-single walled carbon nanotube (Z-SWCNT) is presented. By a modification of the self-energy in non-equilibrium Green's function (NEGF) method, we simulated the field emission current, considering the quantum transport of electrons within the CNT. The paper involves investigation on the effect of the n index of the (n , 0) Z-SWCNT and the number of carbon dimers in the length direction as well as the anode-cathode separation on the FE current. Effect of additional gate voltage and substitutional impurities on the FE current is also studied. A comparison between the experimental data and simulation results are also included in the paper. The model can be used to consider different quantum effects of the atomistic emitter structure on the FE current.

  4. 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.

  5. Well-aligned carbon nanotube array membrane and its field emission properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ensembles of aligned and monodispersed carbon nanotubes (CNTs)can be prepared by templating method which involves fabrication of porous anodic aluminum oxide (AAO) template, control of catalytic iron particle size and chemical vapor deposition of carbon in the cylindrical pores of AAO. Here we show that template-synthesized CNTs can be fabricated as well-aligned nanoporous CNTs membrane, which can be directly used as an electron field emitter. A low threshold electric field of 2-4 V/μm and maximum emission current density of ~12 mA/cm2 are observed. The results also show that the electron emission current is a function of the applied electrical field and the Fowler-Nordheim (F-N) plot almost follows a linear relationship which indicates a Fowler-Nordheim tunneling mechanism, and the field enhancement factor estimated is about 1100-7500. The simple and convenient approach should be significant for the development of nanotube devices integrated into field emission displays (FEDs) technology.

  6. Bow-tie optical antenna probes for single-emitter scanning near-field optical microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Farahani, Javad N [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Eisler, Hans-Juergen [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Pohl, Dieter W [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Pavius, Michael [Center of MicroNanoTechnology (CMI), Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Flueckiger, Philippe [Center of MicroNanoTechnology (CMI), Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Gasser, Philippe [EMPA, Swiss Federal Laboratories for Materials Testing and Research, Electronics/Metrology Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Hecht, Bert [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

    2007-03-28

    A method for the fabrication of bow-tie optical antennas at the apex of pyramidal Si{sub 3}N{sub 4} atomic force microscopy tips is described. We demonstrate that these novel optical probes are capable of sub-wavelength imaging of single quantum dots at room temperature. The enhanced and confined optical near-field at the antenna feed gap leads to locally enhanced photoluminescence (PL) of single quantum dots. Photoluminescence quenching due to the proximity of metal is found to be insignificant. The method holds promise for single quantum emitter imaging and spectroscopy at spatial resolution limited by the engineered antenna gap width exclusively.

  7. Cylindrical-shaped nanotube field effect transistor

    KAUST Repository

    Hussain, Muhammad Mustafa

    2015-12-29

    A cylindrical-shaped nanotube FET may be manufactured on silicon (Si) substrates as a ring etched into a gate stack and filled with semiconductor material. An inner gate electrode couples to a region of the gate stack inside the inner circumference of the ring. An outer gate electrode couples to a region of the gate stack outside the outer circumference of the ring. The multi-gate cylindrical-shaped nanotube FET operates in volume inversion for ring widths below 15 nanometers. The cylindrical-shaped nanotube FET demonstrates better short channel effect (SCE) mitigation and higher performance (I.sub.on/I.sub.off) than conventional transistor devices. The cylindrical-shaped nanotube FET may also be manufactured with higher yields and cheaper costs than conventional transistors.

  8. Carbon nanotubes field effect transistors biosensors

    OpenAIRE

    Martínez, M.T.; Tseng, Y. C.; Ormategui, N.; Loinaz, I.; Eritja Casadellà, Ramón; Salvador, Juan Pablo; Marco, María Pilar; Bokor, J.

    2012-01-01

    [EN] Carbon nanotube transistor arrays (CNTFETs) were used as biosensors to detect NA hybridization and to recognize two anabolic steroids, stanozolol (Stz) and methylboldenone (MB). Single strand DNA and antibodies specific for STz and MB were immobilized on the carbon nanotubes (CNTs) in situ in the device using two different approaches: direct noncovalent bonding of antibodies to the devices and covalently trough a polymer previously attached to the CNTFETs. A new approach to ensure specif...

  9. Carbon nanotubes field effect transistors biosensors

    OpenAIRE

    Martínez, M. T.; Y.C. Tseng; N. Ormategui; I. Loinaz; Eritja Casadellà, Ramón; Salvador, Juan Pablo; Marco, María Pilar; Bokor, J.

    2012-01-01

    [EN] Carbon nanotube transistor arrays (CNTFETs) were used as biosensors to detect NA hybridization and to recognize two anabolic steroids, stanozolol (Stz) and methylboldenone (MB). Single strand DNA and antibodies specific for STz and MB were immobilized on the carbon nanotubes (CNTs) in situ in the device using two different approaches: direct noncovalent bonding of antibodies to the devices and covalently trough a polymer previously attached to the CNTFETs. A new approach to ensure specif...

  10. Pulsed laser-deposited nanocrystalline GdB6 thin films on W and Re as field emitters

    Science.gov (United States)

    Suryawanshi, Sachin R.; Singh, Anil K.; Phase, Deodatta M.; Late, Dattatray J.; Sinha, Sucharita; More, Mahendra A.

    2016-10-01

    Gadolinium hexaboride (GdB6) nanocrystalline thin films were grown on tungsten (W), rhenium (Re) tips and foil substrates using optimized pulsed laser deposition (PLD) technique. The X-ray diffraction analysis reveals formation of pure, crystalline cubic phase of GdB6 on W and Re substrates, under the prevailing PLD conditions. The field emission (FE) studies of GdB6/W and GdB6/Re emitters were performed in a planar diode configuration at the base pressure ~10-8 mbar. The GdB6/W and GdB6/Re tip emitters deliver high emission current densities of ~1.4 and 0.811 mA/cm2 at an applied field of ~6.0 and 7.0 V/µm, respectively. The Fowler-Nordheim ( F- N) plots were found to be nearly linear showing metallic nature of the emitters. The noticeably high values of field enhancement factor ( β) estimated using the slopes of the F- N plots indicate that the PLD GdB6 coating on W and Re substrates comprises of high-aspect-ratio nanostructures. Interestingly, the GdB6/W and GdB6/Re planar emitters exhibit excellent current stability at the preset values over a long-term operation, as compared to the tip emitters. Furthermore, the values of workfunction of the GdB6/W and GdB6/Re emitters, experimentally measured using ultraviolet photoelectron spectroscopy, are found to be same, ~1.6 ± 0.1 eV. Despite possessing same workfunction value, the FE characteristics of the GdB6/W emitter are markedly different from that of GdB6/Re emitter, which can be attributed to the growth of GdB6 films on W and Re substrates.

  11. Extremely environment-hard and low work function transfer-mold field emitter arrays

    Energy Technology Data Exchange (ETDEWEB)

    Nakamoto, Masayuki, E-mail: m-nakamoto@rie.shizuoka.ac.jp [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8011 (Japan); Moon, Jonghyun [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8011 (Japan)

    2013-06-15

    Extremely environment-hard and low work function field-emitter arrays (FEAs) were fabricated by a transfer-mold emitter fabrication method to produce highly reliable vacuum nanoelectronic devices able to operate stably at low voltage in highly oxidizing atmospheres. Amorphous carbon (a-C) having a work function of 3.6 eV and sp{sup 3} fraction of 85.6% prepared by plasma-enhanced chemical vapor deposition was used as the emitter material. The field-emission characteristics of the obtained transfer-mold FEAs strongly depended on their work function and morphology. The environment-hard characteristics of the transfer-mold a-C FEAs were compared with those of the transfer-mold titanium nitride FEAs and nickel FEAs. X-ray photoelectron spectroscopy was used to confirm the stable chemical states of the FEAs after oxygen radical treatment. The small amount of material oxidized (6.3%) at the surface of the a-C FEAs compared with 11.8% for the TiN-FEAs and 39.0% for Ni FEAs after oxygen radical treatment explained their almost constant work function in oxidizing atmospheres. The emission fluctuation rates of transfer-mold a-C FEAs without resistive layers under in situ radical treatment were as low as ±5.0%, compared with 5–100% for conventional FEAs with resistive layers not under highly oxidizing atmospheres. Therefore, the present environment-hard and low work function transfer-mold a-C FEAs are expected to be useful for reliable vacuum nanoelectronic devices.

  12. Transfer-matrix simulations of field emission from bundles of open and closed (5,5) carbon nanotubes

    Science.gov (United States)

    Mayer, A.; Miskovsky, N. M.; Cutler, P. H.; Lambin, Ph.

    2003-12-01

    We present simulations of field emission from bundles of metallic (5,5) carbon nanotubes, which are either ideally open or closed. The scattering calculations are achieved using a transfer-matrix methodology for consideration of three-dimensional aspects of both the emitting structure and the surface barrier. Band-structure effects are reproduced by using pseudopotentials and enforcing the incident states to first travel through a periodic repetition of the tubes’ basic cell before entering the region containing the fields. The bundles consist of three and six identical structures, which are placed at the corners of equilateral triangles. In all cases, the closed emitters are found to emit less current than the open ones and to be more sensitive to the electric field in their response to neighboring tubes. Due to the enhanced screening of the electric field, the bundles’ emission rates are reduced compared to those of the isolated tubes. It turns out that the rates characterizing bundle and isolated emitters are related by a simple formula, whose dependence on the electric field suggests deviations from the Fowler-Nordheim equation at high fields. Finally, the position of peaks associated with quasilocalized states on top of the closed emitters appears to be a strong indicator of the tubes’ environment.

  13. Integration of field emitter array and thin-film transistor using polycrystalline silicon process technology

    CERN Document Server

    Song, Y H; Kang, S Y; Park Jeong Man; Cho, K I

    1998-01-01

    We present the monolithic integration of a gated polycrystalline silicon field emitter array (poly-Si FEA) and a thin-film transistor(TFT) on an insulating substrate for active-matrix field emission displays (AMFEDs). The TFT was designed to have low off-state currents even at a high drain voltage. Amorphous silicon has been used as a starting material of the poly-Si FEA for improving surface smoothness and uniformity of the tips, and the gate holes have been formed by using an etch-back process. The integrated poly-Si TFT controlled electron emissions of the poly-Si FEA actively, resulting in great improvement in the emission reliability along with a low-voltage control, below 15 V, of field emission, The developed technology has potential applications in AMFEDs on glass substrates.

  14. Ampère-Class Pulsed Field Emission from Carbon-Nanotube Cathodes in a Radiofrequency Resonator

    Energy Technology Data Exchange (ETDEWEB)

    Mihalcea, D. [Northern Illinois U.; Faillace, L. [RadiaBeam Tech.; Hartzell, J. [RadiaBeam Tech.; Panuganti, H. [Northern Illinois U.; Boucher, S. M. [RadiaBeam Tech.; Murokh, A. [RadiaBeam Tech.; Piot, P. [Fermilab; Thangaraj, J. C.T. [Fermilab

    2014-12-01

    Pulsed field emission from cold carbon-nanotube cathodes placed in a radiofrequency resonant cavity was observed. The cathodes were located on the backplate of a conventional $1+\\frac{1}{2}$-cell resonant cavity operating at 1.3-GHz and resulted in the production of bunch train with maximum average current close to 0.7 Amp\\`ere. The measured Fowler-Nordheim characteristic, transverse emittance, and pulse duration are presented and, when possible, compared to numerical simulations. The implications of our results to high-average-current electron sources are briefly discussed.

  15. Radiation tolerant compact image sensor using CdTe photodiode and field emitter array (Conference Presentation)

    Science.gov (United States)

    Masuzawa, Tomoaki; Neo, Yoichiro; Mimura, Hidenori; Okamoto, Tamotsu; Nagao, Masayoshi; Akiyoshi, Masafumi; Sato, Nobuhiro; Takagi, Ikuji; Tsuji, Hiroshi; Gotoh, Yasuhito

    2016-10-01

    A growing demand on incident detection is recognized since the Great East Japan Earthquake and successive accidents in Fukushima nuclear power plant in 2011. Radiation tolerant image sensors are powerful tools to collect crucial information at initial stages of such incidents. However, semiconductor based image sensors such as CMOS and CCD have limited tolerance to radiation exposure. Image sensors used in nuclear facilities are conventional vacuum tubes using thermal cathodes, which have large size and high power consumption. In this study, we propose a compact image sensor composed of a CdTe-based photodiode and a matrix-driven Spindt-type electron beam source called field emitter array (FEA). A basic principle of FEA-based image sensors is similar to conventional Vidicon type camera tubes, but its electron source is replaced from a thermal cathode to FEA. The use of a field emitter as an electron source should enable significant size reduction while maintaining high radiation tolerance. Current researches on radiation tolerant FEAs and development of CdTe based photoconductive films will be presented.

  16. Carbon-nanotube-polymer nanocomposites for field-emission cathodes.

    Science.gov (United States)

    Connolly, Thomas; Smith, Richard C; Hernandez, Yenny; Gun'ko, Yurii; Coleman, Jonathan N; Carey, J David

    2009-04-01

    The electron field-emission (FE) characteristics of functionalized single-walled carbon-nanotube (CNT)-polymer composites produced by solution processing are reported. It is shown that excellent electron emission can be obtained by using as little as 0.7% volume fraction of nanotubes in the composite. Furthermore by tailoring the nanotube concentration and type of polymer, improvements in the charge transfer through the composite can be obtained. The synthesis of well-dispersed randomly oriented nanotube-polymer composites by solution processing allows the development of CNT-based large area cathodes produced using a scalable technology. The relative insensitivity of the cathode's FE characteristics to the electrical conductivity of the composite is also discussed.

  17. Waferscale assembly of Field-Aligned nanotube Networks (FANs)

    DEFF Research Database (Denmark)

    Dimaki, Maria; Bøggild, Peter

    2006-01-01

    We demonstrate the integration of nanotube networks on 512 individual devices on a full 4-inch wafer in less than 60 seconds with a roughly 80% yield using dielectrophoresis. We present here investigations of the morphology and electrical resistance of such field aligned networks for different...... frequencies of the electrical field used to attract the nanotubes to the electrodes. Preliminary data of response to visible light irradiation as well as changes in the humidity indicate that the field aligned networks could be used as sensor components that may well integrate with CMOS due to mild assembly...

  18. Designing variable height carbon nanotube bundle for enhanced electron field emission

    Science.gov (United States)

    Khaneja, Mamta; Ghosh, Santanu; Chaudhury, P. K.; Vankar, V. D.; Kumar, Vikram

    2015-05-01

    A variable height model has been implemented in order to improve the emission performance from a nanotube bundle. A Gaussian distribution of nanotube heights has been considered. This resulted in a nearly uniform electric field distribution across all the nanotubes and consequently an enhanced emission current in comparison to a nanotube bundle with all the nanotubes having the same height. Simulation results from linear as well as area nanotube bundles are reported. The analysis helped in providing a better understanding of the previously reported experimental results on enhanced field emission from plasma treated nanotube bundles having CNTs of variable heights.

  19. Electron emission properties of gated silicon field emitter arrays driven by laser pulses

    Science.gov (United States)

    Shimawaki, Hidetaka; Nagao, Masayoshi; Neo, Yoichiro; Mimura, Hidenori; Wakaya, Fujio; Takai, Mikio

    2016-10-01

    We report optically modulated electron emission from gated p-type silicon field emitter arrays (Si-FEAs). The device's "volcano" structure is designed to control the photoexcitation of electrons by transmitting light through the small gate aperture, thereby minimizing the photogeneration of slow diffusion carriers outside the depletion region in the tip. Compared to that in the dark, the emission current was enhanced by more than three orders of magnitude in the high field region when irradiated with blue laser pulses. Results from the time-resolved measurements of photoassisted electron emission showed that these possess the same response as the laser pulse with no discernible delay. These results indicate that the volcano device structure is effective at eliminating the generation of diffusion carriers and that a fully optimized FEA is promising as a photocathode for producing high-speed modulated electron beams.

  20. Preparation of Powdery Carbon Nanotwist and Application to Printed Field Emitter

    Directory of Open Access Journals (Sweden)

    Yuji Hosokawa

    2007-01-01

    Full Text Available In the present study, an automatic production system with sequencer control for the synthesis of carbon nanofibriform based on catalytic CVD using a substrate was developed. The carbon nanotwist (CNTw, which is one of the helical carbon nanofibers, was then synthesized in powdery form with an Ni–SnO2-composed catalyst. The production rate was 5 400 times that of the conventional CVD system and Ni–Cu–In2O3 catalyst. The powdery CNTw was easily scraped off the substrate, then pasted with organic binder, and printed by a squeegee method on ITO glass substrate for an electron field emitter. The field emission performance was found to be better than that of the directly grown CNTw film in conventional CVD with Ni–Cu catalyst.

  1. Effect of nonlinear radiofrequency electromagnetic fields on the emittance of bunched beams

    Science.gov (United States)

    Phadte, D. S.; Patidar, C. B.

    2013-07-01

    Gap transformations are frequently used in ion Linac codes, to efficiently describe the particle dynamics. Using similar approach, we analyze the uniformly bunched beam passing through an axis-symmetric radiofrequency (RF) cavity. The method can be used for other distributions as well using a similar six dimensional analysis. The effect of non-linear RF field in radial and axial directions in an RF cavity and the finite phase width of the bunch, on the transverse and longitudinal emittance growth have been studied. The expressions obtained have been verified for the two types of cavity cells namely the zero mode DTL and pi mode CCL type used frequently in ion linacs. The results are seen to be valid for the entire maximum phase acceptance up to 360 degrees. Simulations with the equivalent beams of non-uniform distributions namely Waterbag and Gaussian show that at synchronous phases closer to the wave crest, the results give a good approximation of emittance growth in both planes for non-uniform beams.

  2. Transmission type flat-panel X-ray source using ZnO nanowire field emitters

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Daokun; Song, Xiaomeng; Zhang, Zhipeng; Chen, Jun, E-mail: stscjun@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, Sun Yat-sen University, Guangzhou 510275 (China); School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Li, Ziping [The First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510275 (China); She, Juncong; Deng, Shaozhi; Xu, Ningsheng [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, Sun Yat-sen University, Guangzhou 510275 (China); School of Microelectronics, Sun Yat-sen University, Guangzhou 510275 (China)

    2015-12-14

    A transmission type flat-panel X-ray source in diode structure was fabricated. Large-scale patterned ZnO nanowires grown on a glass substrate by thermal oxidation were utilized as field emitters, and tungsten thin film coated on silica glass was used as the transmission anode. Uniform distribution of X-ray generation was achieved, which benefited from the uniform electron emission from ZnO nanowires. Self-ballasting effect induced by the intrinsic resistance of ZnO nanowire and decreasing of screening effect caused by patterned emitters account for the uniform emission. Characteristic X-ray peaks of W-L lines and bremsstrahlung X-rays have been observed under anode voltages at a range of 18–20 kV, the latter of which were the dominant X-ray signals. High-resolution X-ray images with spatial resolution less than 25 μm were obtained by the flat-panel X-ray source. The high resolution was attributed to the small divergence angle of the emitted X-rays from the transmission X-ray source.

  3. Field emission properties of the graphenated carbon nanotube electrode

    Science.gov (United States)

    Zanin, H.; Ceragioli, H. J.; Peterlevitz, A. C.; Baranauskas, Vitor; Marciano, F. R.; Lobo, A. O.

    2015-01-01

    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.

  4. Transport properties of hydrogen passivated silicon nanotubes and silicon nanotube field effect transistors

    KAUST Repository

    Montes Muñoz, Enrique

    2017-01-24

    We investigate the electronic transport properties of silicon nanotubes attached to metallic electrodes from first principles, using density functional theory and the non-equilibrium Green\\'s function method. The influence of the surface termination is studied as well as the dependence of the transport characteristics on the chirality, diameter, and length. Strong electronic coupling between nanotubes and electrodes is found to be a general feature that results in low contact resistance. The conductance in the tunneling regime is discussed in terms of the complex band structure. Silicon nanotube field effect transistors are simulated by applying a uniform potential gate. Our results demonstrate very high values of transconductance, outperforming the best commercial silicon field effect transistors, combined with low values of sub-threshold swing.

  5. Mechanism of Carbon Nanotubes Aligning along Applied Electric Field

    Institute of Scientific and Technical Information of China (English)

    MA Shao-Jie; GUO Wan-Lin

    2008-01-01

    The mechanism of single-walled carbon nanotubes (SWCNTS)aligning in the direction of external electric field is studied by quantum mechanics calculations.The rotational torque on the carbon nanotubes is proportional to the difference between the longitudinal and transverse polarizabilities and varies with the angle of SWCNTs to the external electric field.The longitudinal polarizability increases with second power of length,while the transverse polarizability increases linearly with length.A zigzag SWCNT has larger longitudinal and transverse polarizabilities than an armchair SWCNT with the same diameter and the discrepancy becomes larger for longer tubes.

  6. 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.

  7. Diamond field emitter array cathodes and possibilities for employing additive manufacturing for dielectric laser accelerating structures

    Energy Technology Data Exchange (ETDEWEB)

    Simakov, Evgenya Ivanovna [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Andrews, Heather Lynn [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Herman, Matthew Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hubbard, Kevin Mark [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Weis, Eric [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-09-20

    These are slides for a presentation at Stanford University. The outline is as follows: Motivation: customers for compact accelerators, LANL's technologies for laser acceleration, DFEA cathodes, and additive manufacturing of micron-size structures. Among the stated conclusions are the following: preliminary study identified DFEA cathodes as promising sources for DLAs--high beam current and small emittance; additive manufacturing with Nanoscribe Professional GT can produce structures with the right scale features for a DLA operating at micron wavelengths (fabrication tolerances need to be studied, DLAs require new materials). Future plans include DLA experiment with a beam produced by the DFEA cathode with field emission, demonstration of photoemission from DFEAs, and new structures to print and test.

  8. Near-field relaxation of a quantum emitter to two-dimensional semiconductors: Surface dissipation and exciton polaritons

    Science.gov (United States)

    Karanikolas, Vasilios D.; Marocico, Cristian A.; Eastham, Paul R.; Bradley, A. Louise

    2016-11-01

    The total spontaneous emission rate of a quantum emitter in the presence of an infinite MoS2 monolayer is enhanced by several orders of magnitude, compared to its free-space value, due to the excitation of surface exciton polariton modes and lossy modes. The spectral and distance dependence of the spontaneous emission rate are analyzed and the lossy surface wave, surface exciton polariton mode and radiative contributions are identified. The transverse magnetic and transverse electric exciton polariton modes can be excited for different emission frequencies of the quantum emitter, and their contributions to the total spontaneous emission rate are different. To calculate these different decay rates we use the non-Hermitian description of light-matter interactions, employing a Green's tensor formalism. The distance dependence follows different trends depending on the emission energy of the quantum emitter. For the case of the lossy surface waves, the distance dependence follows a z-n,n =2 ,3 ,4 , trend. When transverse magnetic exciton polariton modes are excited, they dominate and characterize the distance dependence of the spontaneous emission rate of a quantum emitter in the presence of the MoS2 layers. The interaction between a quantum emitter and a MoS2 superlattice is investigated, and we observe a splitting of the modes supported by the superlattice. Moreover, a blueshift of the peak values of the spontaneous emission rate of a quantum emitter is observed as the number of layers is increased. The field distribution profiles, created by a quantum emitter, are used to explain this behavior.

  9. Improvements in emittance wake field optimization for the SLAC Linear Collider

    CERN Document Server

    Decker, Franz Josef

    2003-01-01

    The transverse emittances in the SLAC Linear Collider can be severely diluted by collective wakefield effects and dispersion. For the 1997/98 SLC/SLD run important changes were implemented in the way the emittance is optimized. Early in the linac, where the energy spread is large due to BNS damping, the emittance growth is dominated by dispersion. In this regime emittance tuning bumps may introduce additional wakefield tails and their use is now avoided. At the end of the linac the energy spread is minimal and the emittance measurement is most sensitive to wakefield emittance dilution. In previous years, the emittances were tuned on wire scanners located near but not at the end of the linac (after about 90% of its length). Simulations show that emittance growth of up to 100% can occur in the remaining 10%. In this run wire scanners at the entrance of the Final Focus, the last place where the emittances can be measured, were used for the optimization. Screens at the end of the linac allow additional real time ...

  10. Carbon nanotubes as electron source in an x-ray tube

    OpenAIRE

    H., Sugie; Masaki, Tanemura; V., Filip; K., Iwata; K., Takahashi; F., Okuyama

    2001-01-01

    Field emitters comprised of aligned carbon nanotubes are shown to be promising as a primary electron source in an x-ray tube working in a nonultrahigh vacuum ambience. At a pressure of 2×10-7Torr, the nanotube emitters continue to emit electrons for more than 1 h, and yield better resolved x-ray images than do thermionic emitters, independently of whether the sample is biological or nonbiological. The near-uniformity in energy distribution of electrons emitted from carbon nanotubes might be r...

  11. 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

  12. 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.

  13. Vertically aligned carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi

    2012-10-01

    Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been developed using pure semiconducting carbon nanotubes. The source and drain were vertically stacked, separated by a dielectric, and the carbon nanotubes were placed on the sidewall of the stack to bridge the source and drain. Both the effective gate dielectric and gate electrode were normal to the substrate surface. The channel length is determined by the dielectric thickness between source and drain electrodes, making it easier to fabricate sub-micrometer transistors without using time-consuming electron beam lithography. The transistor area is much smaller than the planar CNTFET due to the vertical arrangement of source and drain and the reduced channel area. © 2012 Elsevier Ltd. All rights reserved.

  14. Pulsed laser-deposited nanocrystalline GdB{sub 6} thin films on W and Re as field emitters

    Energy Technology Data Exchange (ETDEWEB)

    Suryawanshi, Sachin R.; More, Mahendra A. [Savitribai Phule Pune University, Department of Physics, Centre for Advanced Studies in Materials Science and Condensed Matter Physics, Pune (India); Singh, Anil K.; Sinha, Sucharita [Bhabha Atomic Research Centre, Laser and Plasma Technology Division, Trombay, Mumbai (India); Phase, Deodatta M. [UGC-DAE Consortium for Scientific Research Indore Centre, Indore (India); Late, Dattatray J. [CSIR-National Chemical Laboratory, Physical and Materials Chemistry Division, Pune (India)

    2016-10-15

    Gadolinium hexaboride (GdB{sub 6}) nanocrystalline thin films were grown on tungsten (W), rhenium (Re) tips and foil substrates using optimized pulsed laser deposition (PLD) technique. The X-ray diffraction analysis reveals formation of pure, crystalline cubic phase of GdB{sub 6} on W and Re substrates, under the prevailing PLD conditions. The field emission (FE) studies of GdB{sub 6}/W and GdB{sub 6}/Re emitters were performed in a planar diode configuration at the base pressure ∝10{sup -8} mbar. The GdB{sub 6}/W and GdB{sub 6}/Re tip emitters deliver high emission current densities of ∝1.4 and 0.811 mA/cm{sup 2} at an applied field of ∝6.0 and 7.0 V/μm, respectively. The Fowler-Nordheim (F-N) plots were found to be nearly linear showing metallic nature of the emitters. The noticeably high values of field enhancement factor (β) estimated using the slopes of the F-N plots indicate that the PLD GdB{sub 6} coating on W and Re substrates comprises of high-aspect-ratio nanostructures. Interestingly, the GdB{sub 6}/W and GdB{sub 6}/Re planar emitters exhibit excellent current stability at the preset values over a long-term operation, as compared to the tip emitters. Furthermore, the values of workfunction of the GdB{sub 6}/W and GdB6/Re emitters, experimentally measured using ultraviolet photoelectron spectroscopy, are found to be same, ∝1.6 ± 0.1 eV. Despite possessing same workfunction value, the FE characteristics of the GdB{sub 6}/W emitter are markedly different from that of GdB{sub 6}/Re emitter, which can be attributed to the growth of GdB{sub 6} films on W and Re substrates. (orig.)

  15. Carbon nanotubes field effect transistors biosensors

    Directory of Open Access Journals (Sweden)

    M.P. Marco

    2012-03-01

    Full Text Available Carbon nanotube transistor arrays (CNTFETs wereused as biosensors to detect DNA hybridization andto recognize two anabolic steroids, stanozolol (Stzand methylboldenone (MB. Single strand DNA andantibodies specific for STz and MB were immobilizedon the carbon nanotubes (CNTs in situ in the deviceusing two different approaches: direct noncovalentbonding of antibodies to the devices and covalentlytrough a polymer previously attached to theCNTFETs. A new approach to ensure specificadsorption of the biomolecules to the nanotubeswas developed. The polymer poly(methylmethacrylate0.8-co-poly (ethyleneglycolmethacrylate0.8-co-N-succinimidyl methacrylate0.1was synthesized and bonded noncovalently to thenanotube. Aminated single-strand DNA or antibodiesspecific for Stz and MB were then attached covalentlyto the polymer. Statistically significant changes wereobserved in key transistor parameters for both DNAhybridization and steroids recognition. Regardingthe detection mechanism, in addition to chargetransfer, Schottky barrier, SB, modification, andscattering potential reported by other authors, anelectron/hole trapping mechanism leading tohysteresis modification has been determined. Thepresence of polymer seems to hinder the modulationof the electrode-CNT contact.

  16. Characterisation of carbon nanotube pastes for field emission using their sheet resistances

    Science.gov (United States)

    Floweri, Octia; Kim, Jihan; Seo, Yongho; Park, Jun-Young; Lee, Naesung

    2015-10-01

    Carbon nanotube (CNT) pastes for field emitters were fabricated by varying the milling speed, CNT amount and glass frit (GF) powder size. The CNTs remained agglomerated at lower milling speeds while they were damaged and shortened at higher speeds. Increasing the amount of CNTs improved the field emission properties, but excessive CNTs led to increased removal of the CNT paste with surface activation because of lower cohesion strength. Small GF particles were incorporated to provide a flat surface to the CNT paste, which improved its field emission uniformity and lifespan. The dispersion, density and milling damage characteristics of CNTs in the pastes were assessed by their sheet resistances under the assumption of equal printed thicknesses. Tape activation reduced the thickness of the CNT pastes by different amounts that depended on the cohesion strength of the paste. This reduction caused the sheet resistance to increase. For all cases in this study, the field emission properties of the CNT pastes were closely related to their sheet resistances, suggesting that sheet resistance could be used as a figure-of-merit for the evaluation of CNT pastes for field emission applications.

  17. Self-modulated field electron emitter: Gated device of integrated Si tip-on-nano-channel

    Science.gov (United States)

    Huang, Zhijun; Huang, Yifeng; Pan, Zhangxu; She, Juncong; Deng, Shaozhi; Chen, Jun; Xu, Ningsheng

    2016-12-01

    We report the featured gated field electron emission devices of Si nano-tips with individually integrated Si nano-channels and the interpretation of the related physics. A rational procedure was developed to fabricate the uniform integrated devices. The electrical and thermal conduction tests demonstrated that the Si nano-channel can limit both the current and heat flows. The integrated devices showed the specialties of self-enhancement and self-regulation. The heat resistance results in the heat accumulation at the tip-apex, inducing the thermally enhanced field electron emission. The self-regulated effect of the electrical resistance is benefit for impeding the current overloading and prevents the emitters from a catastrophic breakdown. The nano-channel-integrated Si nano-tip array exhibited emission current density up to 24.9 mA/cm2 at a gate voltage of 94 V, much higher than that of the Si nano-tip array without an integrated nano-channel.

  18. Robust CNT field emitters: patterning, growth, transfer, and in situ anchoring

    Science.gov (United States)

    Scott, Valerie J.; Manohara, Harish; Toda, Risaku; Del Castillo, Linda; Murthy, Rakesh; Mulder, Jerry; Murty, Eshwari; Clark Thompson, M.

    2016-12-01

    Robust carbon nanotube (CNT)-based cold cathodes were fabricated on titanium (Ti) substrates. Methods to grow vertically aligned CNTs directly on Ti substrates were developed. These cathodes can be treated post-growth at elevated temperatures under inert atmosphere which causes the surface-grown CNTs to become anchored to the substrate surface. These samples offer improvements in field emission properties over previously studied silicon (Si) substrate-based cathodes with no anchoring, displaying low threshold voltages, high field enhancement factors, and long operating lifetimes. Current densities of 25 mA cm-2 were held for over 24 h with anchored samples at low electric fields (observed thresholds as low as 0.5 V μm-1) and more current stability. Higher current densities of up to 150 mA cm-2 could be reached with anchored samples, limited only by the experimental setup. In efforts to generate even more stable and reproducible field emission, a transfer process of CNTs from polished Si to Ti with copper (Cu) was developed (flipCNTs). These cathodes display extreme improvements over previous results, with observed thresholds as low as 0.2 V μm-1 and γ-factors as high as 30 000. To demonstrate the utility of these robust cathodes, a flipCNT-based cathode was assembled into a fully functioning vacuum triode.

  19. Enhancement of field emission characteristics of carbon nanotubes on oxidation.

    Science.gov (United States)

    Mathur, Ashish; Roy, Susanta Sinha; Ray, Sekhar Chandra; Hazra, Kiran Shankar; Hamilton, Jeremy; Dickinson, Calum; McLaughlin, James; Misra, Devi Shankar

    2011-08-01

    Vertically aligned multi-walled carbon nanotubes (CNTs) were grown on p-type silicon wafer using thermal chemical vapor deposition process and subsequently treated with oxygen plasma for oxidation. It was observed that the electron field emission (EFE) characteristics are enhanced. It showed that the turn-on electric field (E(TOE)) of CNTs decreased from 0.67 (untreated) to 0.26 V/microm (oxygen treated). Raman spectra showed that the numbers of defects are increased, which are generated by oxygen-treatment, and absorbed molecules on the CNTs are responsible for the enhancement of EFE. Scanning electron microscopy and Transmission electron microscopy images were used to identify the quality and physical changes of the nanotube morphology and surfaces; revealing the evidence of enhancement in the field emission properties after oxygen-plasma treatment.

  20. Morphology dependent field emission of acid-spun carbon nanotube fibers

    Science.gov (United States)

    Fairchild, S. B.; Boeckl, J.; Back, T. C.; Ferguson, J. B.; Koerner, H.; Murray, P. T.; Maruyama, B.; Lange, M. A.; Cahay, M. M.; Behabtu, N.; Young, C. C.; Pasquali, M.; Lockwood, N. P.; Averett, K. L.; Gruen, G.; Tsentalovich, D. E.

    2015-03-01

    Acid spun carbon nanotube (CNT) fibers were investigated for their field emission properties and performance was determined to be dependent on fiber morphology. The fibers were fabricated by wet-spinning of pre-made CNTs. Fiber morphology was controlled by a fabrication method and processing conditions, as well as purity, size, and type of the CNT starting material. The internal fiber structure consisted of CNT fibrils held together by van der Waals forces. Alignment and packing density of the CNTs affects the fiber’s electrical and thermal conductivity. Fibers with similar diameters and differing morphology were compared, and those composed of the most densely packed and well aligned CNTs were the best field emitters as exhibited by a lower turn-on voltage and a larger field enhancement factor. Fibers with higher electrical and thermal conductivity demonstrated higher maximum current before failure and longer lifetimes. A stable emission current at 3 mA was obtained for 10 h at a field strength of electron sources for vacuum electronic devices.

  1. Morphology dependent field emission of acid-spun carbon nanotube fibers.

    Science.gov (United States)

    Fairchild, S B; Boeckl, J; Back, T C; Ferguson, J B; Koerner, H; Murray, P T; Maruyama, B; Lange, M A; Cahay, M M; Behabtu, N; Young, C C; Pasquali, M; Lockwood, N P; Averett, K L; Gruen, G; Tsentalovich, D E

    2015-03-13

    Acid spun carbon nanotube (CNT) fibers were investigated for their field emission properties and performance was determined to be dependent on fiber morphology. The fibers were fabricated by wet-spinning of pre-made CNTs. Fiber morphology was controlled by a fabrication method and processing conditions, as well as purity, size, and type of the CNT starting material. The internal fiber structure consisted of CNT fibrils held together by van der Waals forces. Alignment and packing density of the CNTs affects the fiber's electrical and thermal conductivity. Fibers with similar diameters and differing morphology were compared, and those composed of the most densely packed and well aligned CNTs were the best field emitters as exhibited by a lower turn-on voltage and a larger field enhancement factor. Fibers with higher electrical and thermal conductivity demonstrated higher maximum current before failure and longer lifetimes. A stable emission current at 3 mA was obtained for 10 h at a field strength of <1 V μm(-1). This stable high current operation makes these CNT fibers excellent candidates for use as low voltage electron sources for vacuum electronic devices.

  2. 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

  3. Electric field enhancement at multiple densities in laser-irradiated nanotube plasma

    Indian Academy of Sciences (India)

    U Chakravarty; P A Naik; P D Gupta

    2012-09-01

    The electric field enhancement inside a nanotube irradiated by intense ultrashort laser pulse ($\\ll 1$ ps) is calculated. The hollowness of the nanotubes determines the field enhancement and the electron density at which such structures exhibit resonance. The electric field in a nanotube plasma is shown to be resonantly enhanced at multiple densities during the two phases of interaction: the ionization phase and the hydrodynamic expansion phase. It is further shown that by a proper choice of hollowness of the nanotubes, a continued occurrence of the resonance over a longer time can be achieved. These properties make nanotubes efficient absorbers of intense ultrashort laser pulses.

  4. Optimal dipole-field profiles for emittance reduction in storage rings

    Directory of Open Access Journals (Sweden)

    Chun-xi Wang

    2011-03-01

    Full Text Available In recent years nonuniform dipoles with bending-radius variation have been studied for reducing storage ring emittance. According to a new minimum-emittance theory, the effects of an arbitrary dipole can be characterized with two parameters determined by the dipole. To have a better idea of the potentials of nonuniform dipoles, here we numerically explore the possible values of these two parameters and associated bending profiles for optimal emittance reduction. Such optimization results provide a useful reference for lattice designs involving nonuniform bending. Simple bending-radius profiles (a short segment of constant radius with linear ramps on the sides were found to be close to the optimal. Basic beam and lattice properties such as emittance, energy spread, and phase advances are presented based on the optimal dipole solutions.

  5. Application of the general thermal field model to simulate the behaviour of nanoscale Cu field emitters

    Energy Technology Data Exchange (ETDEWEB)

    Eimre, Kristjan; Aabloo, Alvo [Intelligent Materials and Systems Lab, Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu (Estonia); Parviainen, Stefan, E-mail: stefan.parviainen@iki.fi; Djurabekova, Flyura [Helsinki Institute of Physics and Department of Physics, P.O. Box 43, 00014 University of Helsinki (Finland); Zadin, Vahur [Intelligent Materials and Systems Lab, Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu (Estonia); Helsinki Institute of Physics and Department of Physics, P.O. Box 43, 00014 University of Helsinki (Finland)

    2015-07-21

    Strong field electron emission from a nanoscale tip can cause a temperature rise at the tip apex due to Joule heating. This becomes particularly important when the current value grows rapidly, as in the pre-breakdown (the electrostatic discharge) condition, which may occur near metal surfaces operating under high electric fields. The high temperatures introduce uncertainties in calculations of the current values when using the Fowler–Nordheim equation, since the thermionic component in such conditions cannot be neglected. In this paper, we analyze the field electron emission currents as the function of the applied electric field, given by both the conventional Fowler–Nordheim field emission and the recently developed generalized thermal field emission formalisms. We also compare the results in two limits: discrete (atomistic simulations) and continuum (finite element calculations). The discrepancies of both implementations and their effect on final results are discussed. In both approaches, the electric field, electron emission currents, and Joule heating processes are simulated concurrently and self-consistently. We show that the conventional Fowler–Nordheim equation results in significant underestimation of electron emission currents. We also show that Fowler–Nordheim plots used to estimate the field enhancement factor may lead to significant overestimation of this parameter especially in the range of relatively low electric fields.

  6. Smith-Purcell experiment utilizing a field-emitter array cathode measurements of radiation

    CERN Document Server

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

    2001-01-01

    Smith-Purcell (SP) radiation at wavelengths of 350-750 nm was produced in a tabletop experiment using a field-emitter array (FEA) cathode. The electron gun was 5 cm long, and a 25 mmx25 mm holographic replica grating was placed behind the slit provided in the anode. A regulated DC power supply accelerated electron beams in excess of 10 mu A up to 45 keV, while a small Van de Graaff generator accelerated smaller currents to higher energies. The grating had a 0.556 mu m period, 30 deg. blaze and a 0.2 mu m thick aluminum coating. Spectral characteristics of the radiation were measured both manually and automatically; in the latter case, the spectrometer was driven by a stepping motor to scan the wavelength, and AD-converted signals from a photomultiplier tube were processed by a personal computer. The measurement, made at 80 deg. relative to the electron beam, showed good agreement with theoretical wavelengths of the SP radiation. Diffraction orders were -2 and -3 for beam energies higher than 45 keV, -3 to -5 ...

  7. Planar ultrananocrystalline diamond field emitter in accelerator radio frequency electron injector: Performance metrics

    Energy Technology Data Exchange (ETDEWEB)

    Baryshev, Sergey V., E-mail: sergey.v.baryshev@gmail.com; Antipov, Sergey; Jing, Chunguang; Qiu, Jiaqi [Euclid TechLabs, 365 Remington Blvd., Bolingbrook, Illinois 60440 (United States); High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439 (United States); Shao, Jiahang; Liu, Wanming; Gai, Wei [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439 (United States); Pérez Quintero, Kenneth J.; Sumant, Anirudha V., E-mail: sumant@anl.gov [Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439 (United States); Kanareykin, Alexei D. [Euclid TechLabs, 365 Remington Blvd., Bolingbrook, Illinois 60440 (United States)

    2014-11-17

    A case performance study of a planar field emission cathode (FEC) based on nitrogen-incorporated ultrananocrystalline diamond, (N)UNCD, was carried out in an RF 1.3 GHz electron gun. The FEC was a 100 nm (N)UNCD film grown on a 20 mm diameter stainless steel disk with a Mo buffer layer. At surface gradients 45–65 MV/m, peak currents of 1–80 mA (equivalent to 0.3–25 mA/cm{sup 2}) were achieved. Imaging with two YAG screens confirmed emission from the (N)UNCD surface with (1) the beam emittance of 1.5 mm × mrad/mm-rms and (2) longitudinal FWHM and rms widths of non-Gaussian energy spread of 0.7% and 11% at an electron energy of 2 MeV. Current stability was tested over the course of 36 × 10{sup 3} RF pulses (equivalent to 288 × 10{sup 6 }GHz oscillations)

  8. 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.

  9. Field emission from non-uniform carbon nanotube arrays.

    Science.gov (United States)

    Dall'agnol, Fernando F; den Engelsen, Daniel

    2013-07-10

    Regular arrays of carbon nanotubes (CNTs) are frequently used in studies on field emission. However, non-uniformities are always present like dispersions in height, radius, and position. In this report, we describe the effect of these non-uniformities in the overall emission current by simulation. We show that non-uniform arrays can be modeled as a perfect array multiplied by a factor that is a function of the CNTs spacing.

  10. Enhanced Field Emission from a Carbon Nanotube Array Coated with a Hexagonal Boron Nitride Thin Film.

    Science.gov (United States)

    Yang, Xiaoxia; Li, Zhenjun; He, Feng; Liu, Mingju; Bai, Bing; Liu, Wei; Qiu, Xiaohui; Zhou, Hang; Li, Chi; Dai, Qing

    2015-08-12

    A high-quality field emission electron source made of a highly ordered array of carbon nanotubes (CNTs) coated with a thin film of hexagonal boron nitride (h-BN) is fabricated using a simple and scalable method. This method offers the benefit of reproducibility, as well as the simplicity, safety, and low cost inherent in using B(2)O(3) as the boron precursor. Results measured using h-BN-coated CNT arrays are compared with uncoated control arrays. The optimal thickness of the h-BN film is found to be 3 nm. As a result of the incorporation of h-BN, the turn-on field is found to decrease from 4.11 to 1.36 V μm(-1), which can be explained by the significantly lower emission barrier that is achieved due to the negative electron affinity of h-BN. Meanwhile, the total emission current is observed to increase from 1.6 to 3.7 mA, due to a mechanism that limits the self-current of any individual emitting tip. This phenomenon also leads to improved emission stability and uniformity. In addition, the lifetime of the arrays is improved as well. The h-BN-coated CNT array-based field emitters proposed in this work may open new paths for the development of future high-performance vacuum electronic devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Integrating carbon nanotubes into silicon by means of vertical carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi

    2014-01-01

    Single-walled carbon nanotubes have been integrated into silicon for use in vertical carbon nanotube field-effect transistors (CNTFETs). A unique feature of these devices is that a silicon substrate and a metal contact are used as the source and drain for the vertical transistors, respectively. These CNTFETs show very different characteristics from those fabricated with two metal contacts. Surprisingly, the transfer characteristics of the vertical CNTFETs can be either ambipolar or unipolar (p-type or n-type) depending on the sign of the drain voltage. Furthermore, the p-type/n-type character of the devices is defined by the doping type of the silicon substrate used in the fabrication process. A semiclassical model is used to simulate the performance of these CNTFETs by taking the conductance change of the Si contact under the gate voltage into consideration. The calculation results are consistent with the experimental observations. This journal is © the Partner Organisations 2014.

  12. Ultrafast transmission electron microscopy using a laser-driven field emitter: femtosecond resolution with a high coherence electron beam

    CERN Document Server

    Feist, Armin; da Silva, Nara Rubiano; Danz, Thomas; Möller, Marcel; Priebe, Katharina E; Domröse, Till; Gatzmann, J Gregor; Rost, Stefan; Schauss, Jakob; Strauch, Stefanie; Bormann, Reiner; Sivis, Murat; Schäfer, Sascha; Ropers, Claus

    2016-01-01

    We present the development of the first ultrafast transmission electron microscope (UTEM) driven by localized photoemission from a field emitter cathode. We describe the implementation of the instrument, the photoemitter concept and the quantitative electron beam parameters achieved. Establishing a new source for ultrafast TEM, the G\\"ottingen UTEM employs nano-localized linear photoemission from a Schottky emitter, which enables operation with freely tunable temporal structure, from continuous wave to femtosecond pulsed mode. Using this emission mechanism, we achieve record pulse properties in ultrafast electron microscopy of 9 {\\AA} focused beam diameter, 200 fs pulse duration and 0.6 eV energy width. We illustrate the possibility to conduct ultrafast imaging, diffraction, holography and spectroscopy with this instrument and also discuss opportunities to harness quantum coherent interactions between intense laser fields and free electron beams.

  13. INFLUENCES OF DENSITY AND DIMENSION OF CARBON NANOTUBES ON THEIR FIELD EMISSION

    Institute of Scientific and Technical Information of China (English)

    Y.B. Zhu; W.L. Wang; C.G. Hu

    2003-01-01

    The influences of density and dimension of carbon nanotubes on their electron emission from arrays are studied. The tip electric field of nanotubes, electric field enhancement factor, and optimum nanotube density are expressed by analytic equations. The theoretical analyses show that the field enhancement factor is sensitive to nanotube density, and can be sharply improved at a specific and optimum density. Some experiments have demonstrated these. Owning to electrostatic screening effect, the length of carbon nanotubes has little effect on their emission. A uniformly-distributed carbon nanotube array model is set up, and applied to analysis of carbon nanotube arrays.The results obtained here are in good agreement with the experimental data.

  14. Fabrication of carbon nanotubes field emission cathode by composite plating.

    Science.gov (United States)

    Wang, Fang-Hsing; Lin, Tzu-Ching; Tzeng, Shien-Der

    2010-07-01

    Carbon nanotubes (CNTs) have high aspect ratio and have great potential to be applied as the field emission cathode because of its large field enhancement factor. In this work, a high performance carbon nanotube field emission cathode (CNTFC) was fabricated by using a composite plating method. The CNTs were purified by acid solutions and then dispersed in electrobath with nickel ions at temperatures of 60, 70, or 80 degrees C for the electroless plating process on glass substrate. The resulting CNT-Ni composite film has strong adhesion on the glass substrate. The degree of graphitization and the microstructure of the CNTFCs were studied by Raman spectroscopy and scanning electron microscopy. The field emission properties of the CNTFCs show a low turn-on electric field E(on) of about 1.2 V/microm, and a low threshold electric field E(th) of about 1.9 V/microm. Such a composite plating method could be applied to the fabrication of large area CNT field-emission displays.

  15. Chemically derived graphene sheets top assembled over multi-walled carbon nanotube thin film by Langmuir Blodgett method for improved dual field emission.

    Science.gov (United States)

    Roy, Rajarshi; Jha, Arunava; Chattopadhyay, Kalyan K

    2013-01-01

    Graphene and carbon nanotubes are very much known as effective field emitter materials. However field emission applications with hybrid carbon nanostructures have mostly remained elusive so far. Here we report, top assembly of very thin layer of reduced graphene oxide (RGO) by Langmuir Blodgett method over a multi-walled carbon nanotubes (MWCNTs) thin film/ITO substrate to investigate the dual field emission property of the hybrid structure. The non-functionalized type of attachment in between the hybrid carbon nanostructures mainly due to van der Waals force of attraction ensured easy fabrication procedure. Evidence of uniform distribution of web like networks of very thin transparent RGO sheets top assembled over densely packed MWCNTs thin film was found from the field emission scanning electron microscopy analysis. The base layer conductivity was enhanced due to the incorporation of MWCNTs bottom layer over ITO and the former also additionally facilitated as emitter site pockets in between RGO planes. Finally, the RGO top assembly resulted in achieving significant improvement in current density and turn-on field in tandem with MWCNTs bottom layer bed making this hybrid system a much feasible candidate for future field emission (FE) based device applications.

  16. Water-methanol separation with carbon nanotubes and electric fields

    Science.gov (United States)

    Winarto, Affa; Takaiwa, Daisuke; Yamamoto, Eiji; Yasuoka, Kenji

    2015-07-01

    Methanol is used in various applications, such as fuel for transportation vehicles, fuel cells, and in chemical industrial processes. Conventionally, separation of methanol from aqueous solution is by distillation. However, this method consumes a large amount of energy; hence development of a new method is needed. In this work, molecular dynamics simulations are performed to investigate the effect of an electric field on water-methanol separation by carbon nanotubes (CNTs) with diameters of 0.81 to 4.07 nm. Without an electric field, methanol molecules fill the CNTs in preference to water molecules. The preference of methanol to occupy the CNTs over water results in a separation effect. This separation effect is strong for small CNT diameters and significantly decreases with increasing diameter. In contrast, under an electric field, water molecules strongly prefer to occupy the CNTs over methanol molecules, resulting in a separation effect for water. More interestingly, the separation effect for water does not decrease with increasing CNT diameter. Formation of water structures in CNTs induced by an electric field has an important role in the separation of water from methanol.Methanol is used in various applications, such as fuel for transportation vehicles, fuel cells, and in chemical industrial processes. Conventionally, separation of methanol from aqueous solution is by distillation. However, this method consumes a large amount of energy; hence development of a new method is needed. In this work, molecular dynamics simulations are performed to investigate the effect of an electric field on water-methanol separation by carbon nanotubes (CNTs) with diameters of 0.81 to 4.07 nm. Without an electric field, methanol molecules fill the CNTs in preference to water molecules. The preference of methanol to occupy the CNTs over water results in a separation effect. This separation effect is strong for small CNT diameters and significantly decreases with increasing

  17. Field Emission Lamps Prepared with Dip-Coated and Nickel Electroless Plated Carbon Nanotube Cathodes.

    Science.gov (United States)

    Pu, N W; Youh, M J; Chung, K J; Liu, Y M; Ger, M D

    2015-07-01

    Fabrication and efficiency enhancement of tubal field emission lamps (FELs) using multi-walled carbon nanotubes (MWNTs) as the cathode field emitters were studied. The cathode filaments were prepared by eletrolessly plating a nickel (Ni) film on the cathode made of a 304 stainless steel wire dip-coated with MWNTs. The 304 wire was dip-coated with MWNTs and nano-sized Pd catalyst in a solution, and then eletrolessly plated with Ni to form an MWNT-embedded composite film. The MWNTs embedded in Ni not only had better adhesion but also exhibited a higher FE threshold voltage, which is beneficial to our FEL system and can increase the luminous efficiency of the anode phosphor. Our results show that the FE cathode prepared by dipping three times in a solution containing 400 ppm Pd nano-catalysts and 0.2 wt.% MWNTs and then eletrolessly plating a Ni film at a deposition temperature of 60 °C, pH value of 5, and deposition time of 7 min has the best FE uniformity and efficiency. Its emission current can stay as low as 2.5 mA at a high applied voltage of 7 kV, which conforms to the high-voltage-and-low-current requirement of the P22 phosphor and can therefore maximize the luminous efficiency of our FEL. We found that the MWNT cathodes prepared by this approach are suitable for making high-efficiency FELs.

  18. Effect of a concave grid mesh in a carbon nanotube-based field emission X-ray source

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyun Suk; Castro, Edward Joseph D. [Regional Innovation Center for Next Generation Industrial Radiation Technology, Division of Microelectronics and Display Technology, Iksan (Korea, Republic of); Lee, Choong Hun, E-mail: chlee12345@gmail.com [Regional Innovation Center for Next Generation Industrial Radiation Technology, Division of Microelectronics and Display Technology, Iksan (Korea, Republic of); Solar Cell Research Institute, Wonkwang University, Iksan (Korea, Republic of)

    2014-10-15

    Highlights: • Successful design using a concave grid mesh for the focusing electron. • Much better X-ray image due to the concave grid mesh. • Higher anode current efficiency using the concave grid mesh versus a flat grid mesh. - Abstract: This study introduces a simple approach to improve the X-ray image quality produced by the carbon nanotube (CNT) field emitter X-ray source by altering the geometrical shape of the grid mesh from the conventional flat shape to a concave one in a typical triode structure. The concave shape of the grid electrode increases the effective number of the grid cells in the mesh, which exerted an electric field in the direction of the emitted electrons, thereby increasing the emission current reaching the anode. Furthermore, the curved mesh (concave grid mesh), which was responsible for the extraction of electrons from the field emitter, exhibited a focusing effect on the electron beam trajectory thereby, reducing the focal spot size impinging on the anode and resulted in a better spatial resolution of the X-ray images produced.

  19. Field electron emission from LaB{sub 6} and TiN emitter arrays fabricated by transfer mold technique

    Energy Technology Data Exchange (ETDEWEB)

    Nakamoto, Masayuki; Fukuda, Katsuyoshi

    2002-12-30

    LaB{sub 6} and TiN field emitter arrays (FEAs) have been developed by the transfer mold technique to fabricate sharp, uniform, and low operation voltage FEAs using low work function materials. Because of the sharpening effect on the tips by thermally oxidized SiO{sub 2} layer of the molds, emitter tip radii are as small as less than 10 nm. The turn-on voltages of LaB{sub 6} and TiN FEA are 110-130 V lower than that of conventional Mo FEA by decreasing the surface barrier heights for field emission, having the same emitter shape. That of the gated LaB{sub 6} FEA is as low as 28 V even without high vacuum baking treatment. Transfer mold technique provides easiness of selecting low work function materials as well as superior uniform sharpness of FEAs. Transfer mold LaB{sub 6} and TiN FEAs are useful for low operation vacuum microelectronic devices.

  20. Measurement of Ampère-class pulsed electron beams via field emission from carbon-nanotube cathodes in a radiofrequency gun

    Science.gov (United States)

    Mihalcea, D.; Faillace, L.; Hartzell, J.; Panuganti, H.; Boucher, S.; Murokh, A.; Piot, P.; Thangaraj, J. C. T.

    2015-07-01

    Pulsed field emission from cold carbon-nanotube cathodes placed in a radiofrequency resonant cavity was directly measured. The cathodes were located on the backplate of a conventional 1 + /1 2 -cell resonant cavity operating at 1.3-GHz and resulted in the production of bunch train with maximum average current close to 0.7 Ampère. The measured Fowler-Nordheim characteristic, transverse emittance, and pulse duration are presented and, when possible, compared to numerical simulations. The implications of our results to the promise of high-average-current electron sources are briefly discussed.

  1. Growth of Aligned Multiwall Carbon Nanotubes and the Effect of Adsorbates on the Field Emission Properties

    Science.gov (United States)

    Milne, W. I.; Teo, K. B. K.; Lansley, S. B.; Chhowalla, M.; Amaratunga, G. A. J.; Semet, V.; Binh, Vu Thien; Pirio, G.; Legagneux, P.

    2003-10-01

    In attempt to decipher the field emission characteristics of multiwall carbon nanotubes (MWCNTs), we have developed a fabrication method based on plasma enhanced chemical vapour deposition (PECVD) to provide utmost control of the nanotube structure such as their alignment, individual position, diameter, length and morphology. We investigated the field emission properties of these nanotubes to elucidate the effect of adsorbates on the nanotubes. Our results show that although the adsorbates cause an apparent lowering of the required turn on voltage/field of the nanotubes, the adsorbates undesirably cause a saturation of the current, large temporal fluctuations in the current, and also a deviation of the emission characteristics from Fowler-Nordheim like emission. The adsorbates are easily removed by extracting an emission current of 1 uA per nanotube or using a high applied electric field (˜25V/um).

  2. Field evap oration b ehaviour for carb on nanotub e thin-film%碳纳米管薄膜场蒸发效应∗

    Institute of Scientific and Technical Information of China (English)

    马玉龙; 向伟; 金大志; 陈磊; 姚泽恩; 王琦龙

    2016-01-01

    In recent years, the carbon nanotube (CNT) emitters used for ion sources or gas sensors have been investigated, and the progress of several approaches such as field ionization and field desorption sources has been reported. However, a major concern for these applications is possible loss of CNTs caused by field evaporation, which can shorten the lifetimes of CNT-based emitters used for high electric field ion sources. So in CNT-based field emitter technology, emitter lifetime and degradation will be key parameters to be controlled. However, up to now only very few investigations in this direction have been conducted. The reason for this might lie in the fact that one often considers that the threshold value of field evaporation for a kind of material (>40 V/nm) is much higher than the field of ionization or desorption (> 10 V/nm) according to the metal material characteristics (such as the threshold values of field evaporation for tungsten and molybdenum are 54 V/nm and 45 V/nm, respectively). In this work, the carbon nanotube thin-film (the density of CNTs is about 2.5 × 108/cm2) is fabricated by screen-printing method, and the field evaporation behavior of CNT thin-film is studied experimentally in an ultrahigh vacuum system typically operating at a pressure of lower than 10−9 Torr after a 4-hour bake-out at∼200 ◦C. Unlike the vertically aligned CNT array having higher electric field around the edge of the array because of the shielding effect, the printed CNT thin-film has more uniform distribution of electric field and is very easy to relize the mass production. The results show that the prepared CNT thin-film has quite obvious field evaporation behavior (some contaminants have deposited on the surface of grid after field evaporation, and energy-dispersive X-ray spectroscopy elemental mapping result of the grid indicates that the contaminants consist mainly of carbon elements), with turn-on field in a range of 10.0–12.6 V/nm, ion current could reach up

  3. Charge transport effects in field emission from carbon nanotube-polymer composites

    OpenAIRE

    Smith, RC; Carey, JD; Murphy, RJ; Blau, WJ; Coleman, JN; Silva, SRP

    2006-01-01

    Electron field emission measurements have been made on multiwall arc discharge carbon nanotubes embedded in a conjugated polymer host. Electron emission at low nanotube content is observed and attributed to an enhancement of the applied electric field at the polymer/nanotube/vacuum interface where the electron supply through the film is attributed to fluctuation induced tunneling in a disordered percolation network. A high network resistance is attributed to a polymer coating surrounding each...

  4. Lipid nanotube formation using space-regulated electric field above interdigitated electrodes.

    Science.gov (United States)

    Bi, Hongmei; Fu, Dingguo; Wang, Lei; Han, Xiaojun

    2014-04-22

    Lipid nanotubes have great potential in biology and nanotechnology. Here we demonstrate a method to form lipid nanotubes using space-regulated AC electric fields above coplanar interdigitated electrodes. The AC electric field distribution can be regulated by solution height above the electrodes. The ratio of field component in x axis (Ex) to field component in z axis (Ez) increases dramatically at solution height below 50 μm; therefore, at lower solution height, the force from Ex predominantly drives lipids to form lipid nanotubes along with the electric field direction. The forces exerted on the lipid nanotube during its formation were analyzed in detail, and an equation was obtained to describe the relationship among nanotube length and field frequency, amplitude, and time. We believe that the presented approach opens a way to design and prepare nanoscale materials with unique structural and functional properties using space-regulated electric fields.

  5. Generation of two-lobe light fields with a rotating intensity distribution under propagation for single emitter spectroscopy

    Science.gov (United States)

    Volostnikov, V. G.; Vorontsov, E. N.; Kotova, S. P.; Losevsky, N. N.; Prokopova, D. V.; Razueva, E. V.; Samagin, S. A.

    2016-12-01

    The paper outlines the results of studies on the generation of two-lobe light fields with the intensity distribution rotating during the field propagation. Such fields are needed to determine the depth of bedding of single emitters in spectral studies of substance properties. On the base of the spiral beam optics, the phase distributions were obtained for the synthesis of two-lobe fields with different speeds of rotation of the intensity distribution. The light fields have been formed by using a liquid-crystal spatial phase modulator HOLOEYE HEO-1080P. The influence of the illuminating beam parameters and the aberrations of the system on the quality of the formed light field was also studied.

  6. Generation of two-lobe light fields with a rotating intensity distribution under propagation for single emitter spectroscopy

    Directory of Open Access Journals (Sweden)

    Volostnikov V.G.

    2017-01-01

    Full Text Available The paper outlines the results of studies on the generation of two-lobe light fields with the intensity distribution rotating during the field propagation. Such fields are needed to determine the depth of bedding of single emitters in spectral studies of substance properties. On the base of the spiral beam optics, the phase distributions were obtained for the synthesis of two-lobe fields with different speeds of rotation of the intensity distribution. The light fields have been formed by using a liquid-crystal spatial phase modulator HOLOEYE HEO-1080P. The influence of the illuminating beam parameters and the aberrations of the system on the quality of the formed light field was also studied.

  7. Photometric properties of Ly alpha emitters at z=4.86 in the COSMOS 2 square degree field

    CERN Document Server

    Shioya, Y; Sasaki, S S; Nagao, T; Murayama, T; Saitô, T; Ideue, Y; Nakajima, A; Matsuoka, K L; Trump, J; Scoville, N Z; Sanders, D B; Mobasher, B; Aussel, H; Capak, P; Kartaltepe, J; Koekemoer, A; Carilli, C; Ellis, Richard S; Garilli, B; Giavalisco, M; Kitzbichler, M G; Impey, C; LeFevre, O; Schinnerer, E; Smolcic, V

    2009-01-01

    We present results of a survey for Ly alpha emitters at z=4.86 based on optical narrowband (lambda_c=7126 angstrom, Delta lambda=73 angstrom) and broadband (B, V, r', i', and z') observations of the Cosmic Evolution Survey (COSMOS) field using Suprime-Cam on the Subaru Telescope. We find 79 LAE candidates at z=4.86 over a contiguous survey area of 1.83 deg^2, down to the Ly alpha line flux of 1.47 x 10^-17 ergs s^-1 cm^-2. We obtain the Ly alpha luminosity function with a best-fit Schechter parameters of log L^*=42.9^+0.5_-0.3 ergs s^-1 and phi^* = 1.2^+8.0_-1.1 x 10^-4 Mpc^-3 for alpha=-1.5 (fixed). The two-point correlation function for our LAE sample is xi(r) = (r/4.4^+5.7_-2.9 Mpc)^-1.90+/-0.22. In order to investigate the field-to-field variations of the properties of Ly alpha emitters, we divide the survey area into nine tiles of 0.5^circ x 0.5^circ each. We find that the number density varies with a factor of ~ 2 from field to field with high statistical significance. However, we find no significant fi...

  8. Enhanced Field Emission from Printed Carbon Nanotubes by Hard Hairbrush

    Institute of Scientific and Technical Information of China (English)

    ZOU Ru-jia; ZHAN Ya-ge; LIU Yang; XUE Shao-lin

    2008-01-01

    A method, the morphology of screen printed carbon nanotube pastes is modified using a hard hairbrush, is presented.In this way, the organic matrix material is preferentially removed.Compared to those untreated films, the turn-on electric field of the treated film decreases from 2.2 V/um to 1.6 V/um, while the total emission current of the treated increases from 0.6 mA/cm2 to 3 mA/cm2, and uniform emission site density image has also been observed.

  9. 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.

  10. Carbon Nanotube Field-Effect Transistor for DNA Sensing

    Science.gov (United States)

    Xuan, Chu T.; Thuy, Nguyen T.; Luyen, Tran T.; Huyen, Tran T. T.; Tuan, Mai A.

    2017-01-01

    A field-effect transistor (FET) using carbon nanotubes (CNTs) as the conducting channel (CNTFET) has been developed, designed such that the CNT conducting channel (15 μm long, 700 μm wide) is directly exposed to medium containing target deoxyribonucleic acid (DNA). The CNTFET operates at high ON-current of 1.91 μA, ON/OFF-current ratio of 1.2 × 105, conductance of 4.3 μS, and leakage current of 16.4 pA. We present initial trials showing the response of the CNTFET to injection of target DNA into aqueous medium.

  11. Electric field effect in the growth of carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Plaza, E., E-mail: ericvpp@gmail.com; Briceño-Fuenmayor, H. [Instituto Venezolano de Investigaciones Científicas (IVIC), Laboratorio de Física de Fluidos y Plasma (Venezuela, Bolivarian Republic of); Arévalo, J. [Instituto Zuliano de Investigaciones Tecnológicas (INZIT), Unidad de Caracterización y Estructura de Materiales (Venezuela, Bolivarian Republic of); Atencio, R. [Instituto Venezolano de Investigaciones Científicas (IVIC), Centro de Investigación y Tecnología de Materiales (Venezuela, Bolivarian Republic of); Corredor, L. [Instituto Zuliano de Investigaciones Tecnológicas (INZIT), Unidad de Caracterización y Estructura de Materiales (Venezuela, Bolivarian Republic of)

    2015-06-15

    The growth of carbon nanotubes (CNTs) under a controlled electric field in a chemical vapor deposition system is investigated. We evaluate the influence of this external field on the morphological and structural characteristics of CNTs. Scanning electron microscopy results display a large presence of carbonaceous material in the positive plate, which appear to be a consequence of the attraction of electric forces over the electronically unbalanced cracked carbon molecules in the heating zone. We also observe a growth behavior for CNTs, in which catalyst particles are localized either at the bottom or the upper part of the nanotube, depending on the intensity and direction of the electric field. A Raman analysis from all obtained carbon materials shows the presence of two peaks, corresponding to the D ∼ 1340 cm{sup −1} and G ∼ 1590 cm{sup −1} bands attributed to multiwall CNTs. The average diameter of the CNTs is in the range between 90 and 40 nm. These results provide experimental evidence for the dependence of the catalyst and subtract interaction on the growing mechanism, in which weak chemical or electronic interactions could stimulate a top-growing as the strongest base-growing process.

  12. Structures of water molecules in carbon nanotubes under electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Winarto,; Takaiwa, Daisuke; Yamamoto, Eiji; Yasuoka, Kenji, E-mail: yasuoka@mech.keio.ac.jp [Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)

    2015-03-28

    Carbon nanotubes (CNTs) are promising for water transport through membranes and for use as nano-pumps. The development of CNT-based nanofluidic devices, however, requires a better understanding of the properties of water molecules in CNTs because they can be very different from those in the bulk. Using all-atom molecular dynamics simulations, we investigate the effect of axial electric fields on the structure of water molecules in CNTs having diameters ranging from (7,7) to (10,10). The water dipole moments were aligned parallel to the electric field, which increases the density of water inside the CNTs and forms ordered ice-like structures. The electric field induces the transition from liquid to ice nanotubes in a wide range of CNT diameters. Moreover, we found an increase in the lifetime of hydrogen bonds for water structures in the CNTs. Fast librational motion breaks some hydrogen bonds, but the molecular pairs do not separate and the hydrogen bonds reform. Thus, hydrogen bonds maintain the water structure in the CNTs, and the water molecules move collectively, decreasing the axial diffusion coefficient and permeation rate.

  13. Integrated ZnO Nano-Electron-Emitter with Self-Modulated Parasitic Tunneling Field Effect Transistor at the Surface of the p-Si/ZnO Junction

    Science.gov (United States)

    Cao, Tao; Luo, Laitang; Huang, Yifeng; Ye, Bing; She, Juncong; Deng, Shaozhi; Chen, Jun; Xu, Ningsheng

    2016-09-01

    The development of high performance nano-electron-emitter arrays with well reliability still proves challenging. Here, we report a featured integrated nano-electron-emitter. The vertically aligned nano-emitter consists of two segments. The top segment is an intrinsically lightly n-type doped ZnO nano-tip, while the bottom segment is a heavily p-type doped Si nano-pillar (denoted as p-Si/ZnO nano-emitter). The anode voltage not only extracted the electron emission from the emitter apex but also induced the inter-band electron tunneling at the surface of the p-Si/ZnO nano-junction. The designed p-Si/ZnO emitter is equivalent to a ZnO nano-tip individually ballasted by a p-Si/ZnO diode and a parasitic tunneling field effect transistor (TFET) at the surface of the p-Si/ZnO junction. The parasitic TFET provides a channel for the supply of emitting electron, while the p-Si/ZnO diode is benefit for impeding the current overloading and prevent the emitters from a catastrophic breakdown. Well repeatable and stable field emission current were obtained from the p-Si/ZnO nano-emitters. High performance nano-emitters was developed using diamond-like-carbon coated p-Si/ZnO tip array (500 × 500), i.e., 178 μA (4.48 mA/cm2) at 75.7 MV/m.

  14. Integrated ZnO Nano-Electron-Emitter with Self-Modulated Parasitic Tunneling Field Effect Transistor at the Surface of the p-Si/ZnO Junction.

    Science.gov (United States)

    Cao, Tao; Luo, Laitang; Huang, Yifeng; Ye, Bing; She, Juncong; Deng, Shaozhi; Chen, Jun; Xu, Ningsheng

    2016-09-22

    The development of high performance nano-electron-emitter arrays with well reliability still proves challenging. Here, we report a featured integrated nano-electron-emitter. The vertically aligned nano-emitter consists of two segments. The top segment is an intrinsically lightly n-type doped ZnO nano-tip, while the bottom segment is a heavily p-type doped Si nano-pillar (denoted as p-Si/ZnO nano-emitter). The anode voltage not only extracted the electron emission from the emitter apex but also induced the inter-band electron tunneling at the surface of the p-Si/ZnO nano-junction. The designed p-Si/ZnO emitter is equivalent to a ZnO nano-tip individually ballasted by a p-Si/ZnO diode and a parasitic tunneling field effect transistor (TFET) at the surface of the p-Si/ZnO junction. The parasitic TFET provides a channel for the supply of emitting electron, while the p-Si/ZnO diode is benefit for impeding the current overloading and prevent the emitters from a catastrophic breakdown. Well repeatable and stable field emission current were obtained from the p-Si/ZnO nano-emitters. High performance nano-emitters was developed using diamond-like-carbon coated p-Si/ZnO tip array (500 × 500), i.e., 178 μA (4.48 mA/cm(2)) at 75.7 MV/m.

  15. Integrated ZnO Nano-Electron-Emitter with Self-Modulated Parasitic Tunneling Field Effect Transistor at the Surface of the p-Si/ZnO Junction

    Science.gov (United States)

    Cao, Tao; Luo, Laitang; Huang, Yifeng; Ye, Bing; She, Juncong; Deng, Shaozhi; Chen, Jun; Xu, Ningsheng

    2016-01-01

    The development of high performance nano-electron-emitter arrays with well reliability still proves challenging. Here, we report a featured integrated nano-electron-emitter. The vertically aligned nano-emitter consists of two segments. The top segment is an intrinsically lightly n-type doped ZnO nano-tip, while the bottom segment is a heavily p-type doped Si nano-pillar (denoted as p-Si/ZnO nano-emitter). The anode voltage not only extracted the electron emission from the emitter apex but also induced the inter-band electron tunneling at the surface of the p-Si/ZnO nano-junction. The designed p-Si/ZnO emitter is equivalent to a ZnO nano-tip individually ballasted by a p-Si/ZnO diode and a parasitic tunneling field effect transistor (TFET) at the surface of the p-Si/ZnO junction. The parasitic TFET provides a channel for the supply of emitting electron, while the p-Si/ZnO diode is benefit for impeding the current overloading and prevent the emitters from a catastrophic breakdown. Well repeatable and stable field emission current were obtained from the p-Si/ZnO nano-emitters. High performance nano-emitters was developed using diamond-like-carbon coated p-Si/ZnO tip array (500 × 500), i.e., 178 μA (4.48 mA/cm2) at 75.7 MV/m. PMID:27654068

  16. Carbon nanotube based separation columns for high electrical field strengths in microchip electrochromatography

    DEFF Research Database (Denmark)

    Mogensen, Klaus Bo; Chen, Miaoxiang Max; Mølhave, Kristian

    2011-01-01

    Patterning carbon nanotubes into an array of pillars makes it possible to increase the electrical field strength applied across a separation column by more than one order of magnitude.......Patterning carbon nanotubes into an array of pillars makes it possible to increase the electrical field strength applied across a separation column by more than one order of magnitude....

  17. Analytical optimization for field emission of carbon nanotube array

    Institute of Scientific and Technical Information of China (English)

    WANG XinQing; LI Liang; CHEN Min; JIN HongXiao; JIN DingFeng; PENG Min; GE HongLiang

    2009-01-01

    To optimize field emission (FE) property of carbon nanotube (CNT) array on a planar cathode surface,the Fowler-Nordheim formula has been used to discuss the maximum of the emission current density with the floating sphere model in this paper. The emission current density is dominating as the ane-lytical Fowler-Nordheim function of the intertube distance, and the maximum of the emission current density is deduced and discussed. The results indicate that the intertube distance in CNT array criti-cally affects the field enhancement factor and the emission current density, whose maximum occurs at the intertube distance approximating a tenth of the tube height. Considering the emission current den-sity and the field enhancement factor, the FE can be optimized analytically when the intertube distance is about a tenth of the tube height.

  18. A case for ZnO nanowire field emitter arrays in advanced x-ray source applications

    Science.gov (United States)

    Robinson, Vance S.; Bergkvist, Magnus; Chen, Daokun; Chen, Jun; Huang, Mengbing

    2016-09-01

    Reviewing current efforts in X-ray source miniaturization reveals a broad spectrum of applications: Portable and/or remote nondestructive evaluation, high throughput protein crystallography, invasive radiotherapy, monitoring fluid flow and particulate generation in situ, and portable radiography devices for battle-front or large scale disaster triage scenarios. For the most part, all of these applications are being addressed with a top-down approach aimed at improving portability, weight and size. That is, the existing system or a critical sub-component is shrunk in some manner in order to miniaturize the overall package. In parallel to top-down x-ray source miniaturization, more recent efforts leverage field emission and semiconductor device fabrication techniques to achieve small scale x-ray sources via a bottom-up approach where phenomena effective at a micro/nanoscale are coordinated for macro-scale effect. The bottom-up approach holds potential to address all the applications previously mentioned but its entitlement extends into new applications with much more ground-breaking potential. One such bottom-up application is the distributed x-ray source platform. In the medical space, using an array of microscale x-ray sources instead of a single source promises significant reductions in patient dose as well as smaller feature detectability and fewer image artifacts. Cold cathode field emitters are ideal for this application because they can be gated electrostatically or via photonic excitation, they do not generate excessive heat like other common electron emitters, they have higher brightness and they are relatively compact. This document describes how ZnO nanowire field emitter arrays are well suited for distributed x-ray source applications because they hold promise in each of the following critical areas: emission stability, simple scalable fabrication, performance, radiation resistance and photonic coupling.

  19. Fabrication of small diameter few-walled carbon nanotubes with enhanced field emission property.

    Science.gov (United States)

    Qian, Cheng; Qi, Hang; Gao, Bo; Cheng, Yuan; Qiu, Qi; Qin, Lu-Chang; Zhou, Otto; Liu, Jie

    2006-05-01

    A unique type of carbon nanotubes with 2 to 5 layers of sidewalls and diameters less than 10 nm was synthesized by the thermal chemical vapor deposition (CVD) method with MgO supported Fe/Mo catalyst. Unlike the typical CVD grown multi-walled carbon nanotubes, these few-walled carbon nanotubes (FWNTs) have a high degree of structural perfection. They have enhanced electron field emission characteristics compared to the current commercial nanotubes, with a low threshold field for emission and improved emission stability.

  20. Potential of carbon nanotube field effect transistors for analogue circuits

    KAUST Repository

    Hayat, Khizar

    2013-05-11

    This Letter presents a detailed comparison of carbon nanotube field effect transistors (CNFETs) and metal oxide semiconductor field effect transistors (MOSFETs) with special focus on carbon nanotube FET\\'s potential for implementing analogue circuits in the mm-wave and sub-terahertz range. The latest CNFET lithographic dimensions place it at-par with complementary metal oxide semiconductor in terms of current handling capability, whereas the forecasted improvement in the lithography enables the CNFETs to handle more than twice the current of MOSFETs. The comparison of RF parameters shows superior performance of CNFETs with a g m , f T and f max of 2.7, 2.6 and 4.5 times higher, respectively. MOSFET- and CNFET-based inverter, three-stage ring oscillator and LC oscillator have been designed and compared as well. The CNFET-based inverters are found to be ten times faster, the ring oscillator demonstrates three times higher oscillation frequency and CNFET-based LC oscillator also shows improved performance than its MOSFET counterpart.

  1. Microwave Spectroscopy of Carbon Nanotube Field Effect Transistor

    Directory of Open Access Journals (Sweden)

    Mina A. N.

    2010-10-01

    Full Text Available The quantum transport property of a carbon nanotube field effect transistor (CNTFET is investigated under the effect of microwave radiation and magnetic field. The photon-assisted tunneling probability is deduced by solving Dirac equation. Then the current is deduced according to Landauer-Buttiker formula. Oscillatory behavior of the current is observed which is due to the Coulomb blockade oscillations. It was found, also, that the peak heights of the dependence of the current on the parameters under study are strongly affected by the interplay between the tunneled electrons and the photon energy. This interplay affects on the sidebands resonance. The results obtained in the present paper are found to be in concordant with those in the literature, which confirms the correctness of the proposed model. This study is valuable for nanotechnology applications, e.g., photo-detector devices and solid state quantum computing systems and quantum information processes.

  2. Microwave Spectroscopy of Carbon Nanotube Field Effect Transistor

    Directory of Open Access Journals (Sweden)

    Mina A. N.

    2010-10-01

    Full Text Available The quantum transport property of a carbon nanotube field effect transistor (CNTFET is investigated under the effect of microwave radiation and magnetic field. The photon- assisted tunneling probability is deduced by solving Dirac equation. Then the current is deduced according to Landauer-Buttiker formula. Oscillatory behavior of the cur- rent is observed which is due to the Coulomb blockade oscillations. It was found, also, that the peak heights of the dependence of the current on the parameters under study are strongly affected by the interplay between the tunneled electrons and the photon energy. This interplay affects on the sidebands resonance. The results obtained in the present paper are found to be in concordant with those in the literature, which confirms the cor- rectness of the proposed model. This study is valuable for nanotechnology applications, e.g., photo-detector devices and solid state quantum computing systems and quantum information processes.

  3. Hydrogen sensing characteristics from carbon nanotube field emissions

    Science.gov (United States)

    Dong, Changkun; Luo, Haijun; Cai, Jianqiu; Wang, Fuquan; Zhao, Yangyang; Li, Detian

    2016-03-01

    An innovative hydrogen sensing concept is demonstrated based on the field emission from multi-walled carbon nanotubes, where the low emission currents rise in proportion to hydrogen partial pressures above 10-9 Torr. Experimental and first principles studies reveal that the sensing mechanism is attributed to the effective work function reduction from dissociative hydrogen chemisorption. The embedded Ni catalyst would assist both the hydrogen dissociation and work function reduction. This technique is promising to build miniature low cost hydrogen sensors for multiple applications. This work is valuable for studies of nanocarbon-gas reaction mechanisms and the work function properties in adsorption related applications, including field emission, hydrogen storage, energy cells, and gas sensing.

  4. Distribution of electric field for carbon nanotube assembly: Simulation (Ⅰ)

    Institute of Scientific and Technical Information of China (English)

    Soon-Geun KWON; Soo-Hyun KIM; Kwang-Ho KIM; Myung-Chang KANG; Hyung-Woo LEE

    2011-01-01

    The distribution of electric field for the alignment and attachment of carbon nanotubes (CNTs) was simulated. To be attached at the desired place. the aligned and attracted CNTs should be stayed in the desired area called the stable region or the quasi-stable region for an instant where the change of electric field is minimized. Since the conical electrode has the very narrow sized quasi-stable region, few CNTs can be attached. The rectangular electrodes have a wide stable region, so lots of CNTs can be attached. The results indicate that the round electrode which has a proper sized quasi-stable region is more effective for aligning and attaching a single CNT than the conical or rectangular shaped electrodes.

  5. Distribution of electric field for carbon nanotube assembly: Experiments (Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    Soongeun KWON; Soo-Hyun KIM; Kwang-ho KIM; Myung-chang KANG; Hyung-woo LEE

    2011-01-01

    The distribution effect of electric field on the alignment and attachment of carbon nanotubes (CNTs) were investigated.The experimental results were compared with the simulation results according to three different shaped electrodes. In previous simulation, the round shaped electrodes were expected to be more effective for aligning and attaching a single CNT between two electrodes than conical or rectangular shaped electrodes. To verify the simulation results, three different shaped electrodes were introduced and a single multi-walled carbon nanotube (MWNT) was attached. The optimal conditions for aligning and attaching MWNTs such as the frequency, applied voltage and concentration of MWNTs solution were investigated. Through repeated experiments, frequency of 100 kHz-10 MHz, applied voltage of 0.3-1.3 Vrms/μm, concentration of 5 μg/mL in MWNTs solution were obtained as a possible condition range to attach MWNTs. Under these conditions, the yield of MWNTs attachment between two electrodes was up to 70%. In previous simulation, furthermore, it was verified that the size of the stable or quasi-stable region made CNTs aligned and attached on different shaped electrodes from the comparison of the experimental and simulation results. Most single MWNT attachment was accomplished on the round shaped electrodes.

  6. Electron field emission characteristics of different surface morphologies of ZnO nanostructures coated on carbon nanotubes.

    Science.gov (United States)

    Li, Kuan-Wei; Lian, Huan-Bin; Cai, Jhen-Hong; Wang, Yao-Te; Lee, Kuei-Yi

    2011-12-01

    The optimal carbon nanotube (CNT) bundles with a hexagonal arrangement were synthesized using thermal chemical vapor deposition (TCVD). To enhance the electron field emission characteristics of the pristine CNTs, the zinc oxide (ZnO) nanostructures coated on CNT bundles using another TCVD technique. Transmission electron microscopy (TEM) images showed that the ZnO nanostructures were grown onto the CNT surface uniformly, and the surface morphology of ZnO nanostructures varied with the distance between the CNT bundle and the zinc acetate. The results of field emissions showed that the ZnO nanostructures grown onto the CNTs could improve the electron field emission characteristics. The enhancement of field emission characteristics was attributed to the increase of emission sites formed by the nanostructures of ZnO grown onto the CNT surface, and each ZnO nanostructure could be regarded as an individual field emission site. In addition, ZnO-coated CNT bundles exhibited a good emission uniformity and stable current density. These results demonstrated that ZnO-coated CNTs is a promising field emitter material.

  7. A comparative study of nitrogen plasma effect on field emission characteristics of single wall carbon nanotubes synthesized by plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad; Harsh; Husain, Mushahid

    2014-12-01

    Vertically aligned single wall carbon nanotubes (SWCNTs) with large scale control of diameter, length and alignment have successfully been grown by plasma enhanced chemical vapor deposition (PECVD) system. The nickel (Ni) as catalyst deposited on silicon (Si) substrate was used to grow the SWCNTs. Field emission (FE) characteristics of the as grown SWCNTs were measured using indigenously designed setup in which a diode is configured in such a way that by applying negative voltage on the copper plate (cathode) with respect to stainless steel anode plate, current density can be recorded. To measure the FE characteristics, SWCNTs film pasted on the copper plate with silver epoxy was used as electron emitter source. The effective area of anode was ∼78.5 mm2 for field emission measurements. The emission measurements were carried out under high vacuum pressure of the order of 10-6 Torr to minimize the electron scattering and degradation of the emitters. The distance between anode and cathode was kept 500 μm (constant) during entire field emission studies. The grown SWCNTs are excellent field emitters, having emission current density higher than 25 mA/cm2 at turn-on field 1.3 V/μm. In order to enhance the field emission characteristics, the as grown SWCNTs have been treated under nitrogen (N2) plasma for 5 min and again field emission characteristics have been measured. The N2 plasma treated SWCNTs show a good enhancement in the field emission properties with emission current density 81.5 mA/cm2 at turn on field 1.2 V/μm. The as-grown and N2 plasma treated SWCNTs were also characterized by field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), Raman spectrometer, Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS).

  8. Thermionic field emission transport in carbon nanotube transistors.

    Science.gov (United States)

    Perello, David J; Lim, Seong Chu; Chae, Seung Jin; Lee, Innam; Kim, Moon J; Lee, Young Hee; Yun, Minhee

    2011-03-22

    With experimental and analytical analysis, we demonstrate a relationship between the metal contact work function and the electrical transport properties saturation current (Isat) and differential conductance (σsd=∂Isd/∂Vsd) in ambient exposed carbon nanotubes (CNT). A single chemical vapor deposition (CVD) grown 6 mm long semiconducting single-walled CNT is electrically contacted with a statistically significant number of Hf, Cr, Ti, Pd, and Au electrodes, respectively. The observed exponentially increasing relationship of Isat and σsd with metal contact work function is explained by a theoretical model derived from thermionic field emission. Statistical analysis and spread of the data suggest that the conduction variability in same CNT devices results from differences in local surface potential of the metal contact. Based on the theoretical model and methodology, an improved CNT-based gas sensing device layout is suggested. A method to experimentally determine gas-induced work function changes in metals is also examined.

  9. Role of carbon nanotube interlayer in enhancing the electron field emission behavior of ultrananocrystalline diamond coated Si-tip arrays.

    Science.gov (United States)

    Chang, Ting-Hsun; Kunuku, Srinivasu; Kurian, Joji; Manekkathodi, Afsal; Chen, Lih-Juann; Leou, Keh-Chyang; Tai, Nyan-Hwa; Lin, I-Nan

    2015-04-15

    We improved the electron field emission properties of ultrananocrystalline diamond (UNCD) films grown on Si-tip arrays by using the carbon nanotubes (CNTs) as interlayer and post-treating the films in CH4/Ar/H2 plasma. The use of CNTs interlayer effectively suppresses the presence of amorphous carbon in the diamond-to-Si interface that enhances the transport of electrons from Si, across the interface, to diamond. The post-treatment process results in hybrid-granular-structured diamond (HiD) films via the induction of the coalescence of the ultrasmall grains in these films that enhanced the conductivity of the films. All these factors contribute toward the enhancement of the electron field emission (EFE) process for the HiDCNT/Si-tip emitters, with low turn-on field of E0 = 2.98 V/μm and a large current density of 1.68 mA/cm(2) at an applied field of 5.0 V/μm. The EFE lifetime stability under an operation current of 6.5 μA was improved substantially to τHiD/CNT/Si-tip = 365 min. Interestingly, these HiDCNT/Si-tip materials also show enhanced plasma illumination behavior, as well as improved robustness against plasma ion bombardment when they are used as the cathode for microplasma devices. The study concludes that the use of CNT interlayers not only increase the potential of these materials as good EFE emitters, but also prove themselves to be good microplasma devices with improved performance.

  10. Lyman Alpha Emitters at Redshift 5.7 in the COSMOS Field

    CERN Document Server

    Murayama, T; Scoville, N Z; Ajiki, M; Sanders, D B; Mobasher, B; Aussel, H; Capak, P; Koekemoer, A; Shioya, Y; Nagao, T; Carilli, C; Ellis, Richard S; Garilli, B; Giavalisco, M; Kitzbichler, M G; LeFevre, O; MacCagni, D; Schinnerer, E; Smolcic, V; Tribiano, S; Cimatti, A; Komiyama, Yu; Miyazaki, S; Sasaki, S S; Koda, J; Karoji, H

    2007-01-01

    We present results from a narrow-band optical survey of a contiguous area of 1.95 deg^2, covered by the Cosmic Evolution Survey (COSMOS). Both optical narrow-band (lambda_c = 8150 AA and Delta_lambda = 120 AA) and broad-band (B, V, g', r', i', and z') imaging observations were performed with the Subaru prime-focus camera, Suprime-Cam on the Subaru Telescope. We provide the largest contiguous narrow-band survey, targetting Ly alpha emitters (LAEs) at z~5.7. We find a total of 119 LAE candidates at z~5.7. Over the wide-area covered by this survey, we find no strong evidence for large scale clustering of LAEs. We estimate a star formation rate (SFR) density of ~7*10^-4 M_sun yr^-1 Mpc^-3 for LAEs at z~5.7, and compare it with previous measurements.

  11. Carboxylated Capped Carbon Nanotubes Interacting with Nimesulide Molecules: Applied Electric Fields Effects

    Directory of Open Access Journals (Sweden)

    Vivian Machado de Menezes

    2015-01-01

    Full Text Available Interactions of carboxylated capped carbon nanotubes with nimesulide molecules under electric fields were investigated by ab initio simulations. Repulsive forces between the nimesulide molecules and the carboxyl group of the carbon nanotubes, except for the nimesulide radical configuration, were observed. To keep the original molecule in the pristine form, electric fields with different intensities were applied, where changes in the behavior of the interactions between the molecules were noticed. It was shown that the intensity of the interaction between the nimesulide and the hydrophilic carboxylated capped carbon nanotube can be modulated by the action of the external electric fields making promising systems for drug delivery applications.

  12. Water–methanol separation with carbon nanotubes and electric fields.

    Science.gov (United States)

    Winarto; Takaiwa, Daisuke; Yamamoto, Eiji; Yasuoka, Kenji

    2015-08-07

    Methanol is used in various applications, such as fuel for transportation vehicles, fuel cells, and in chemical industrial processes. Conventionally, separation of methanol from aqueous solution is by distillation. However, this method consumes a large amount of energy; hence development of a new method is needed. In this work, molecular dynamics simulations are performed to investigate the effect of an electric field on water–methanol separation by carbon nanotubes (CNTs) with diameters of 0.81 to 4.07 nm. Without an electric field, methanol molecules fill the CNTs in preference to water molecules. The preference of methanol to occupy the CNTs over water results in a separation effect. This separation effect is strong for small CNT diameters and significantly decreases with increasing diameter. In contrast, under an electric field, water molecules strongly prefer to occupy the CNTs over methanol molecules, resulting in a separation effect for water. More interestingly, the separation effect for water does not decrease with increasing CNT diameter. Formation of water structures in CNTs induced by an electric field has an important role in the separation of water from methanol.

  13. Effect of vacancy defect on electrical properties of chiral single-walled carbon nanotube under external electrical field

    Institute of Scientific and Technical Information of China (English)

    Luo Yu-Pin; Tien Li-Gan; Tsai Chuen-Horng; Lee Ming-Hsien; Li Feng-Yin

    2011-01-01

    Ab initio calculations demonstrated that the energy gap modulation of a chiral carbon nanotube with monovacancy defect can be achieved by applying a transverse electric field. The bandstructure of this defective carbon nanotube varying due to the external electric field is distinctly different from those of the perfect nanotube and defective zigzag nanotube. This variation in bandstructure strongly depends on not only the chirality of the nanotube and also the applied direction of the transverse electric field. A mechanism is proposed to explain the response of the local energy gap between the valence band maximum state and the local gap state under external electric field. Several potential applications of these phenomena are discussed.

  14. 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.

  15. Effect of substrate material on the growth and field emission characteristics of large-area carbon nanotube forests

    Science.gov (United States)

    Ummethala, Raghunandan; Wenger, Daniela; Tedde, Sandro F.; Täschner, Christine; Leonhardt, Albrecht; Büchner, Bernd; Eckert, Jürgen

    2016-01-01

    Carbon nanotubes (CNTs) are a promising replacement for tungsten filaments as electron emitters in conventional x-ray sources, owing to their higher aspect ratio, superior mechanical stability, chemical inertness, and high electrical and thermal conductivities. Conditions for realizing the best emission behavior from CNTs have been formulated over the last few years. In this paper, we report the relatively less-investigated factor, namely, the influence of the nature of substrate material on the growth as well as field emission characteristics of large-area multiwalled CNTs for their practical application in medical x-ray sources. We compare the morphology of CNTs on a variety of substrates such as stainless steel, copper, molybdenum, graphite, few-layer graphene, and carbon nanowalls grown by thermal chemical vapor deposition following a simple drop-coating of catalyst. We find that CNTs grown on stainless steel and graphite show the best combination of emission characteristics under pulsed operation mode. These studies are helpful in selecting the optimum substrate material for field emission applications. Ex situ studies on field emission degradation of CNTs are presented towards the end.

  16. Effect of substrate material on the growth and field emission characteristics of large-area carbon nanotube forests

    Energy Technology Data Exchange (ETDEWEB)

    Ummethala, Raghunandan; Täschner, Christine; Leonhardt, Albrecht; Büchner, Bernd [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Wenger, Daniela; Tedde, Sandro F. [Siemens Healthcare GmbH, Technology Centre, Guenther-Scharowsky-Strasse 1, 91058 Erlangen (Germany); Eckert, Jürgen [Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstrasse 12, A-8700 Leoben (Austria); Department Materials Physics, Montanuniversität Leoben, Jahnstraße 12, A-8700 Leoben (Austria)

    2016-01-28

    Carbon nanotubes (CNTs) are a promising replacement for tungsten filaments as electron emitters in conventional x-ray sources, owing to their higher aspect ratio, superior mechanical stability, chemical inertness, and high electrical and thermal conductivities. Conditions for realizing the best emission behavior from CNTs have been formulated over the last few years. In this paper, we report the relatively less-investigated factor, namely, the influence of the nature of substrate material on the growth as well as field emission characteristics of large-area multiwalled CNTs for their practical application in medical x-ray sources. We compare the morphology of CNTs on a variety of substrates such as stainless steel, copper, molybdenum, graphite, few-layer graphene, and carbon nanowalls grown by thermal chemical vapor deposition following a simple drop-coating of catalyst. We find that CNTs grown on stainless steel and graphite show the best combination of emission characteristics under pulsed operation mode. These studies are helpful in selecting the optimum substrate material for field emission applications. Ex situ studies on field emission degradation of CNTs are presented towards the end.

  17. A vacuum-sealed compact x-ray tube based on focused carbon nanotube field-emission electrons.

    Science.gov (United States)

    Jeong, Jin-Woo; Kim, Jae-Woo; Kang, Jun-Tae; Choi, Sungyoul; Ahn, Seungjoon; Song, Yoon-Ho

    2013-03-01

    We report on a fully vacuum-sealed compact x-ray tube based on focused carbon nanotube (CNT) field-emission electrons for various radiography applications. The specially designed two-step brazing process enabled us to accomplish a good vacuum level for the stable and reliable operation of the x-ray tube without any active vacuum pump. Also, the integrated focusing electrodes in the field-emission electron gun focused electron beams from the CNT emitters onto the anode target effectively, giving a small focal spot of around 0.3 mm with a large current of above 50 mA. The active-current control through the cathode electrode of the x-ray tube led a fast digital modulation of x-ray dose with a low voltage of below 5 V. The fabricated compact x-ray tube showed a stable and reliable operation, indicating good maintenance of a vacuum level of below 5 × 10(-6) Torr and the possibility of field-emission x-ray tubes in a stand-alone device without an active pumping system.

  18. A vacuum-sealed compact x-ray tube based on focused carbon nanotube field-emission electrons

    Science.gov (United States)

    Jeong, Jin-Woo; Kim, Jae-Woo; Kang, Jun-Tae; Choi, Sungyoul; Ahn, Seungjoon; Song, Yoon-Ho

    2013-03-01

    We report on a fully vacuum-sealed compact x-ray tube based on focused carbon nanotube (CNT) field-emission electrons for various radiography applications. The specially designed two-step brazing process enabled us to accomplish a good vacuum level for the stable and reliable operation of the x-ray tube without any active vacuum pump. Also, the integrated focusing electrodes in the field-emission electron gun focused electron beams from the CNT emitters onto the anode target effectively, giving a small focal spot of around 0.3 mm with a large current of above 50 mA. The active-current control through the cathode electrode of the x-ray tube led a fast digital modulation of x-ray dose with a low voltage of below 5 V. The fabricated compact x-ray tube showed a stable and reliable operation, indicating good maintenance of a vacuum level of below 5 × 10-6 Torr and the possibility of field-emission x-ray tubes in a stand-alone device without an active pumping system.

  19. 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.

  20. Enhanced electron field emission from carbon nanotubes irradiated by energetic C ions.

    Science.gov (United States)

    Sun, Peng-Cheng; Deng, Jian-Hua; Cheng, Guo-An; Zheng, Rui-Ting; Ping, Zhao-Xia

    2012-08-01

    The field emission performance and structure of the vertically aligned multi-walled carbon nanotube arrays irradiated by energetic C ion with average energy of 40 keV have been investigated. During energetic C ion irradiation, the curves of emission current density versus the applied field of samples shift firstly to low applied fields when the irradiation doses are less than 9.6 x 10(16) cm(-2), and further increase of dose makes the curves reversing to a high applied field, which shows that high dose irradiation in carbon nanotube arrays makes their field emission performance worse. After energetic ion irradiation with a dose of 9.6 x 1016 cm(-2), the turn-on electric field and the threshold electric field of samples decreased from 0.80 and 1.13 V/microm to 0.67 and 0.98 V/microm respectively. Structural analysis of scanning electron microscopy, transmission electron microscopy and Raman spectroscopy indicates that the amorphous carbon nanowire/carbon nanotube hetero nano-structures have been fabricated in the C ion irradiated carbon nanotubes. The enhancement of electron field emission is due to the formation of amorphous carbon nanowires at the tip of carbon nanotube arrays, which is an electron emitting material with low work function.

  1. Electric field effect on (6,0) zigzag single-walled aluminum nitride nanotube.

    Science.gov (United States)

    Baei, Mohammad T; Peyghan, Ali Ahmadi; Moghimi, Masoumeh

    2012-09-01

    Structural, electronic, and electrical responses of the H-capped (6,0) zigzag single-walled aluminum nitride nanotube was studied under the parallel and transverse electric fields with strengths 0-140 × 10(-4) a.u. by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using a locally modified version of the GAMESS electronic structure program. The dipole moments, atomic charge variations, and total energy of the (6,0) zigzag AlNNT show increases with increase in the applied external electric field strengths. The length, tip diameters, electronic spatial extent, and molecular volume of the nanotube do not significantly change with increasing electric field strength. The energy gap of the nanotube decreases with increases of the electric field strength and its reactivity is increased. Increase of the ionization potential, electron affinity, chemical potential, electrophilicity, and HOMO and LUMO in the nanotube with increase of the applied parallel electric field strengths shows that the parallel field has a much stronger interaction with the nanotube with respect to the transverse electric field strengths. Analysis of the parameters indicates that the properties of AlNNTs can be controlled by the proper external electric field.

  2. DESIGN OF MODULO-6-COUNTER USING CARBON NANOTUBE FIELD EFFECT TRANSISTOR

    Directory of Open Access Journals (Sweden)

    V.Saravanan

    2012-11-01

    Full Text Available In many digital applications like digital clock, frequency divider circuit and nano applications etc., designing of low power modulo counters is highly desirable. Designing of such a counters using existing technology i.e., CMOS technology has the limitations in-terms of power consumption, device scaling limitations andfabrications difficulties in nanometre range. This paper proposes the new design technique for modulo counters using the carbon nanotube field effect transistor (CNTFET. Counter performance is analyzed interms of speed and power consumption. This paper also analyses carbon nanotube (CNT types, how the carbon nanotube is formed, and scaling limitations of the CMOS technology in nanometre range.

  3. Phase transition of nanotube-confined water driven by electric field.

    Science.gov (United States)

    Fu, Zhaoming; Luo, Yin; Ma, Jianpeng; Wei, Guanghong

    2011-04-21

    The effects of electric field on the phase behaviors of water encapsulated in a thick single-walled carbon nanotube (SWCNT) (diameter = 1.2 nm) have been studied by performing extensive molecular dynamics simulations at atmospheric pressure. We found that liquid water can freeze continuously into either pentagonal or helical solidlike ice nanotube in SWCNT, depending on the strengths of the external electric field applied along the tube axis. Remarkably, the helical one is new ice phase which was not observed previously in the same size of SWCNT in the absence of electric field. Furthermore, a discontinuous solid-solid phase transition is observed between pentagonal and helical ice nanotubes as the strengths of the external electric field changes. The mechanism of electric-field-induced phase transition is discussed. The dependence of ice structures on the chiralities of SWCNTs is also investigated. Finally, we present a phase diagram of confined water in the electric field-temperature plane.

  4. 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.

  5. Field emission from entangled carbon nanotubes coated on/in a hollow metallic tube

    CERN Document Server

    Tokura, Y; Ohigashi, N; Akita, S; Nakayama, Y; Imasaki, K; Mima, K; Nakai, S

    2001-01-01

    Field emission properties of entangled carbon nanotubes were studied for an electron beam source of Cherenkov or Smith-Purcell free electron laser. The cathode was made of carbon nanotubes which were mixed with a very small amount of resin and coated on/in a hollow metallic tube with outer diameter of 0.5 mm. The emission current was as high as 2.2 mA with a fluctuation of <4%. It seems that some entangled nanotubes were frayed under the high electric field and then electrons were emitted mainly from their tips. Reduction of the work function of the carbon nanotubes was observed with the degradation of vacuum pressure in the experimental apparatus.

  6. The fabrication of carbon-nanotube-coated electrodes and a field-emission-based luminescent device.

    Science.gov (United States)

    Agarwal, Sanjay; Yamini Sarada, B; Kar, Kamal K

    2010-02-10

    Tungsten substrates were coated with an Ni or Ni-Co catalyst by the electroless dip coating technique. Various carbon nanotubes were synthesized by the catalytic chemical vapor deposition (CVD) method under different growth conditions. It was observed that Ni-and Ni-Co-coated tungsten substrates give very good growth of carbon nanotubes (CNT) in terms of yield, uniformity and alignment at a growth temperature of 600 degrees C. We fabricated a field-emission-based luminescent light bulb where a tungsten wire coated with carbon nanotubes served as a cathode. Results show lower threshold voltage, better emission stability and higher luminescence for CNT cathodes in comparison with uncoated tungsten cathodes. We found that aligned-coiled carbon nanotubes are superior to straight CNTs in terms of field emission characteristics and luminescence properties.

  7. Field-Flow Fractionation of Carbon Nanotubes and Related Materials

    Energy Technology Data Exchange (ETDEWEB)

    John P. Selegue

    2011-11-17

    During the grant period, we carried out FFF studies of carbonaceous soot, single-walled and multi-walled carbon nanotubes, carbon nano-onions and polyoxometallates. FFF alone does not provide enough information to fully characterize samples, so our suite of characterization techniques grew to include light scattering (especially Photon Correlation Spectroscopy), scanning and transmission electron microscopy, thermogravimetric analysis and spectroscopic methods. We developed convenient techniques to deposit and examine minute FFF fractions by electron microscopy. In collaboration with Arthur Cammers (University of Kentucky), we used Flow Field-Flow Fractionation (Fl-FFF) to monitor the solution-phase growth of keplerates, a class of polyoxometallate (POM) nanoparticles. We monitored the evolution of Mo-POM nanostructures over the course of weeks by by using flow field-flow fractionation and corroborated the nanoparticle structures by using transmission electron microscopy (TEM). Total molybdenum in the solution and precipitate phases was monitored by using inductively coupled plasma analyses, and total Mo-POM concentration by following the UV-visible spectra of the solution phase. We observe crystallization-driven formation of (Mo132) keplerate and solution phase-driven evolution of structurally related nanoscopic species (3-60 nm). FFF analyses of other classes of materials were less successful. Attempts to analyze platelets of layered materials, including exfoliated graphite (graphene) and TaS2 and MoS2, were disappointing. We were not able to optimize flow conditions for the layered materials. The metal sulfides react with the aqueous carrier liquid and settle out of suspension quickly because of their high density.

  8. 不同电场下碳纳米管场致发射电流密度研究∗%Field-emission current densities of carb on nanotub e under the different electric fields

    Institute of Scientific and Technical Information of China (English)

    王益军; 严诚

    2015-01-01

    The field emission current variation law of carbon nanotube in a large electric field range (0–32 V·µm−1) is analyzed in depth by combining the density functional theory with metal electron theory. The results show that their emission current densities are determined by their densities of states, the pseudogap, the length and the local electric field, showing the different variation laws in the different electric field ranges. In the lower electric field (corresponding macroscopic field is less than 18 V·µm−1), when their density of states increases, their pseudogap decreases: the two trends are opposite, the former increases the number of electrons for emission, and the latter improves the ability to transfer electrons, they all turn to the increase of the emission current, so their field-emission current density increases linearly with increasing electric field in this range. But in the higher electric field (corresponding macroscopic field is less than 32 V·µm−1 and more than 18 V·µm−1 ), their densities of states and the pseudogaps take on the same decrease and increase, so do they in the opposite change case, therefore the emission current density behaves as a non-periodic oscillation in the increasing electric field, moreover the higher electric conductivity lead to the rising of current density, the combined effect of the emitter current density exhibits an oscillatory growth in this electric field range, and the carbon nanotubes behave as ionizing radiation. So the too high electric field may cause the emission current to be instable. The electric conductivity variation law of the metallic carbon nanotube is further studied in this paper. In the lower electric field (corresponding macroscopic field is less than 5 V·µm−1), the electric conductivity of CNT increases linearly with increasing electric field;when the macroscopic electric field increases up to a value in a range from 5 to 14 V·µm−1, the electric conductivity only changes

  9. van der Waals energy under strong atom-field coupling in doped carbon nanotubes

    OpenAIRE

    Bondarev, Igor; Lambin, Philippe

    2004-01-01

    Using a unified macroscopic QED formalism, we derive an integral equation for the van der Waals energy of a two-level atomic system near a carbon nanotube. The equation is valid for both strong and weak atom-vacuum-field coupling. By solving it numerically, we demonstrate the inapplicability of weak-coupling-based van der Waals interaction models in a close vicinity of the nanotube surface.

  10. Structural change at the carbon-nanotube tip by field emission

    OpenAIRE

    Kuzumaki, Toru; Takamura, Yuzuru; Ichinose, Hideki; Horiike, Yasuhiro

    2001-01-01

    Carbon-nanotube tips are plastically deformed during field emission. High-resolution transmission electron microscopy and structural simulations suggest that the deformed structure of the closed nanotube is explained by heterogeneous nucleation of the pentagonal and heptagonal carbon ring pairs, and that of the opened one is represented by sp^3-like line defects in the hexagonal carbon network. It is considered that the changing of the inclination of the Fowler-Nordheim plots corresponds to t...

  11. van der Waals energy under strong atom field coupling in doped carbon nanotubes

    Science.gov (United States)

    Bondarev, I. V.; Lambin, Ph.

    2004-10-01

    Using a unified macroscopic QED formalism, we derive an integral equation for the van der Waals energy of a two-level atomic system near a carbon nanotube. The equation is valid for both strong and weak atom-vacuum-field coupling. By solving it numerically, we demonstrate the inapplicability of weak-coupling-based van der Waals interaction models in a close vicinity of the nanotube surface.

  12. Field emission from hybrid diamond-like carbon and carbon nanotube composite structures.

    Science.gov (United States)

    Zanin, H; May, P W; Hamanaka, M H M O; Corat, E J

    2013-12-11

    A thin diamond-like carbon (DLC) film was deposited onto a densely packed "forest" of vertically aligned multiwalled carbon nanotubes (VACNT). DLC deposition caused the tips of the CNTs to clump together to form a microstructured surface. Field-emission tests of this new composite material show the typical low threshold voltages for carbon nanotube structures (2 V μm(-1)) but with greatly increased emission current, better stability, and longer lifetime.

  13. HST/ACS Morphology of Lyman Alpha Emitters at Redshift 5.7 in the COSMOS Field

    CERN Document Server

    Taniguchi, Y; Scoville, N Z; Sasaki, S S; Nagao, T; Shioya, Y; Saitô, T; Ideue, Y; Nakajima, A; Matsuoka, K; Sanders, D B; Mobasher, B; Aussel, H; Capak, P; Salvato, M; Koekemoer, A; Carilli, C; Cimatti, A; Ellis, Richard S; Garilli, B; Giavalisco, M; Ilbert, O; Impey, C D; Kitzbichler, M G; Le Fèvre, O; McCracken, H J; Scarlata, C; Schinnerer, E; Smolcic, V; Tribiano, S; Trump, J R

    2009-01-01

    We present detailed morphological properties of Lyman alpha emitters (LAEs) at z~ 5.7 in the COSMOS field, based on {\\it Hubble Space Telescope} Advanced Camera for Surveys (ACS) data. The ACS imaging in the F814W filter covered 85 LAEs of the 119 LAEs identified in the full two square degree field, and 47 LAEs of them are detected in the ACS images. Nearly half of them are spatially extended with a size larger than 0.15 arcsec (~0.88 kpc at z=5.7) up to 0.4 arcsec (~2.5 kpc at z=5.7). The others are nearly unresolved compact objects. Two LAEs show double-component structures, indicating interaction or merging of building components to form more massive galaxies. By stacking the ACS images of all the detected sources, we obtain a Sersic parameter of n~0.7 with a half-light radius of 0.13 arcsec (0.76 kpc), suggesting that the majority of ACS detected LAEs have not spheroidal-like but disk-like or irregular light profiles. Comparing ACS F814W magnitudes (I_814) with Subaru/Suprime-Cam magnitudes in the NB816, ...

  14. Electrokinetics of scalable, electric-field-assisted fabrication of vertically aligned carbon-nanotube/polymer composites

    Science.gov (United States)

    Castellano, Richard J.; Akin, Cevat; Giraldo, Gabriel; Kim, Sangil; Fornasiero, Francesco; Shan, Jerry W.

    2015-06-01

    Composite thin films incorporating vertically aligned carbon nanotubes (VACNTs) offer promise for a variety of applications where the vertical alignment of the CNTs is critical to meet performance requirements, e.g., highly permeable membranes, thermal interfaces, dry adhesives, and films with anisotropic electrical conductivity. However, current VACNT fabrication techniques are complex and difficult to scale up. Here, we describe a solution-based, electric-field-assisted approach as a cost-effective and scalable method to produce large-area VACNT composites. Multiwall-carbon nanotubes are dispersed in a polymeric matrix, aligned with an alternating-current (AC) electric field, and electrophoretically concentrated to one side of the thin film with a direct-current (DC) component to the electric field. This approach enables the fabrication of highly concentrated, individually aligned nanotube composites from suspensions of very dilute ( ϕ = 4 × 10 - 4 ) volume fraction. We experimentally investigate the basic electrokinetics of nanotube alignment under AC electric fields, and show that simple models can adequately predict the rate and degree of nanotube alignment using classical expressions for the induced dipole moment, hydrodynamic drag, and the effects of Brownian motion. The composite AC + DC field also introduces complex fluid motion associated with AC electro-osmosis and the electrochemistry of the fluid/electrode interface. We experimentally probe the electric-field parameters behind these electrokinetic phenomena, and demonstrate, with suitable choices of processing parameters, the ability to scalably produce large-area composites containing VACNTs at number densities up to 1010 nanotubes/cm2. This VACNT number density exceeds that of previous electric-field-fabricated composites by an order of magnitude, and the surface-area coverage of the 40 nm VACNTs is comparable to that of chemical-vapor-deposition-grown arrays of smaller-diameter nanotubes.

  15. Developing and using the field emitter as a high intensity electron source

    Science.gov (United States)

    Charbonnier, Francis

    1996-03-01

    In the 1940's, Erwin Müller dominated field emission research. The 50's and 60's saw considerable growth in the number of scientists interested in field emission. While many made important contributions, three persons stood out who had different talents and interests. First and foremost: Erwin Müller, a very innovative, creative and skilled inventor and experimentalist. Second: Robert Gomer, equally adept at theory and experiment, with a unique mastery of fundamental physics concepts. Third: Walter Dyke, who was intrigued by the unique properties of field emission and resolved to develop field emission cathodes as high performance electron sources for a variety of electron beam devices. This paper summarizes Dyke's work at Linfield College, Linfield Research Institute and Field Emission Corporation from 1948 to 1972. However, while Dyke established a solid foundation for useful field emission cathodes and investigated several devices, particularly in microwaves, electron optics and flash radiography, he was unable to complete his work and produce commercial devices, except for flash radiography. Many groups have pursued this work in recent years, sometimes with great success. This paper briefly summarizes current work on field emission cathodes and device applications, as this puts Dyke's work in better perspective and adds to its significance.

  16. 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.

  17. Anode distance effect on field electron emission from carbon nanotubes: a molecular/quantum mechanical simulation.

    Science.gov (United States)

    He, Chunshan; Wang, Weiliang; Deng, Shaozhi; Xu, Ningsheng; Li, Zhibing; Chen, Guihua; Peng, Jie

    2009-06-25

    Field electron emission from single-walled (5,5) carbon nanotubes was simulated with a quantum chemistry method, emphasizing the effect of distance between the anode and apex. The emission probability and the field enhancement factor were obtained for different anode-apex separations with two representative applied macroscopic fields. The quantum chemistry simulation was compared to the classical finite element calculation. It was found that the field enhancement factor was overestimated by about a factor 2 in the classical calculation (for the capped carbon nanotube). The effective work function lowering due to the field penetration into the apex has important contribution to the emission probability. A peculiar decrease of the effective work function with the anode-apex separation was found for the capped carbon nanotube, and its quantum mechanical origin is discussed.

  18. Hysteresis phenomenon of the field emission from carbon nanotube/polymer nanocomposite

    Science.gov (United States)

    Filippov, S. V.; Popov, E. O.; Kolosko, A. G.; Romanov, P. A.

    2015-11-01

    Using the high voltage scanning method and the technique of multichannel recording and processing of field emission (FE) characteristics in real time mode we found out some subtle effects on current voltage characteristics (IVC) of the multi-tip field emitters. We observed the direct and reverse hysteresis simultaneously in the same field emission experiment. Dependence of the form of IVC hysteresis on time of high voltage scanning was observed.

  19. Secondary nanotube growth on aligned carbon nanofibre arrays for superior field emission.

    Science.gov (United States)

    Watts, Paul C P; Lyth, Stephen M; Henley, Simon J; Silva, S Ravi P

    2008-04-01

    We report substantial improvement of the field emission properties from aligned carbon nanotubes grown on aligned carbon nanofibres by a two-stage plasma enhanced chemical vapour deposition (PECVD) process. The threshold field decreased from 15.0 to 3.6 V/microm after the secondary growth. The field enhancement factor increased from 240 to 1480. This technique allows for superior emission of electrons for carbon nanotube/nanofibre arrays grown directly on highly doped silicon for direct integration in large area displays.

  20. The screening effects of carbon nanotube arrays and its field emission optimum density

    Directory of Open Access Journals (Sweden)

    Dan Cai

    2013-12-01

    Full Text Available In order to investigate the field emission optimum density of carbon nanotube (CNT array, the screening effects of CNT array have been studied. It has been shown that the electric field in the vicinity of an individual nanotube of array can be notable distorted due to the screening action of the surrounding neighbors. The optimum normalized spacing s/l(as referred to the length for the maximum emission current is inversely proportional to aspect ratio l/r and electric field strength for CNT arrays with a fixed dimension.

  1. Tunable narrow-band near-field thermal emitters based on resonant metamaterials

    Science.gov (United States)

    Li, Jiayu; Liu, Baoan; Shen, Sheng

    2017-08-01

    In the near field, Planck's law of blackbody radiation breaks down, and radiative heat transfer can be enhanced by orders of magnitude when surface polaritons are supported by interacting materials. However, such thermal radiation enhancement is strongly material dependent, thus difficult to control. Here, we propose a metamaterial-based structure consisting of patterned doped silicon nanorods that exhibits tunable narrow-band thermal emission. Direct numerical simulation based on the Wiener chaos expansion (WCE) method is performed to accurately investigate the heat transfer mechanism of metamaterials in the near field. The fundamental principle of the WCE method is elucidated, and an algorithm for symmetric and periodic structures is discussed. Implementation of the WCE method with the finite-difference time-domain method using the discrete dipole approximation (DDA) is also addressed in this paper.

  2. The luminosity function of Ly-alpha emitters at 2.3 < z < 4.6 from integral-field spectroscopy

    CERN Document Server

    Van Breukelen, C; Venemans, B P; Breukelen, Caroline van; Jarvis, Matt J.; Venemans, Bram P.

    2005-01-01

    We have used VIsible MultiObject Spectrograph Integral-Field Unit (VIMOS-IFU) observations centred on a radio galaxy at z=2.9 to search for Ly-alpha emitters within a comoving volume of ~ 10^4 Mpc^3. We find 14 Ly-alpha emitters with flux > 1.4 x 10^-20 Wm^-2, yielding a comoving space density of 0.0018 +/- 0.0006 Mpc^-3. We fit a Schechter luminosity function which agrees well with previous studies both at similar redshift (z ~ 3.4) and higher redshift (z ~ 5.7). We therefore find no evidence for evolution in the properties of Ly-alpha emitters between 3 < z < 6, although our sample is small. By summing the star-formation rates of the individual Ly-alpha emitters we find a total cosmic star-formation rate density of rho_SFR = 6.7 +/- 0.5 x 10^-3 M_solar yr^-1 Mpc^-3. Integrating over the luminosity function for the combined Ly-alpha surveys at z ~ 3.4 and accounting for the difference in obscuration between the Ly-alpha line and the UV-continuum yields an estimate of rho_SFR ~ 2.2 x 10^-2 M_solar yr^-1...

  3. Photo-enhanced field emission study of TiO{sub 2} nanotubes array

    Energy Technology Data Exchange (ETDEWEB)

    Chavan, Padmakar G.; Shende, Sugat V.; Joag, Dilip S. [Center for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007 (India); 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)

    2011-05-15

    Aligned TiO{sub 2} nanotubes were synthesized by simple anodization of the Ti foil surface. The as-anodized product is further characterized by SEM, XRD, and PL. The tube inner diameter is found to be {approx}60-80 nm with the average wall thickness {approx}30 nm and areal density {approx}15x10{sup 6}/ cm{sup 2}. FE studies of the aligned TiO{sub 2} nanotubes are carried out at base pressure of {approx}1x10{sup -8} mbar. The turn-on field observed for an emission current density of {approx}10 {mu}A/cm{sup 2} is found to be {approx}1.7 V/{mu}m and current density of {approx}44 {mu}A/cm{sup 2} is obtained at an applied field of {approx}2.3 V/{mu}m. Photo-enhanced FE study is carried out by shining visible and UV light on the cathode. The aligned TiO{sub 2} nanotubes show sensitivity to both the light sources. The FE current shows fast switching response to the visible light. The increment in the preset current upon UV illumination can be attributed to the band edge excitation of the electrons. The free excitons associated with band gap of the TiO{sub 2} nanotubes array may be responsible for the visible light sensitivity. TiO{sub 2} nanotubes are also grown on the Ti wire and exhibit similar photo-enhanced behavior. The FE and photo-enhanced FE properties demonstrate the applicability of the aligned TiO{sub 2} nanotubes in the FE based micro/nanoelectronic devices. -- Research Highlights: {yields} TiO{sub 2} nanotubes array is easily synthesized by simple anodization method. {yields} Field emission results are found to be superior. {yields} Good correlation is found between photoluminescence, photo-enhanced field emission, and photoconductivity of the TiO{sub 2}.

  4. Nanoshaping field emitters from glassy carbon sheets: a new functionality induced by H-plasma etching.

    Science.gov (United States)

    Gay, S; Orlanducci, S; Passeri, D; Rossi, M; Terranova, M L

    2016-09-14

    This paper reports on the morphological and electrical characterization at the nanometer scale and the investigation of the field emission characteristics of glassy carbon (GC) plates which underwent H-induced physical/chemical processes occurring in a dual-mode MW-RF plasma reactor. Plasma treatment produced on the GC surface arrays of vertically aligned conically shaped nanostructures, with density and height depending on the plasma characteristics. Two kinds of samples obtained under two different bias regimes have been deeply analyzed using an AFM apparatus equipped with tools for electric forces and surface potential measurements. The features of electron emission via the Field Emission (FE) mechanism have been correlated with the morphology and the structure at the nanoscale of the treated glassy carbon samples. The measured current density and the characteristics of the emission, which follow the Fowler-Nordheim law, indicate that the plasma-based methodology utilized for the engineering of the GC surfaces is able to turn conventional GC plates into efficient emission devices. The outstanding properties of GC suggest the use of such nanostructured materials for the assembling of cold cathodes to be used in a harsh environment and under extreme P/T conditions.

  5. Induced electric fields and plasmonic interactions between a metallic nanotube and a thin metallic film

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We have numerically simulated the induced electric fields and the plasmonic interactions of a metallic nanotube near a thin metallic film. Our study shows that the energies and intensities of the plasmon resonances depend strongly on the aspect ratio (the ratio of the inner to outer radius) of the nanotube as well as the separation between the center of the nanotube and the upper surface of the metallic film and the thickness of the film. The enhancement of the induced electric field of this system reaches as high as 10 4 orders of magnitude and its field distribution is characterized by waveguide-mode resonance. The report proposes that these phenomena can be applied to designing surface enhanced spectroscopies such as surface enhanced Raman spectroscopy for efficient chemical and biological sensing.

  6. Residual gas properties in a field emission device with ZnO emitters

    Institute of Scientific and Technical Information of China (English)

    Wang Jin-Chan

    2013-01-01

    In this paper,a vacuum system is employed to compare the emission stabilities of the same ZnO cathode in a sealed field emission (FE) device and under ultrahigh vacuum (UHV) conditions.It is observed that the emission current is more stable under the UHV level than in the device.When all conditions except the ambient gases are kept unchanged,the emission current degradation is mainly caused by the residual gases in the sealed device.The quadrupole mass spectrometer (QMS) equipped on the vacuum system is used to investigate the residual gas components.Based on the obtained QMS data,the following conclusions can be drawn:the residual gases in ZnO-FE devices are H2,CH4,CO,Ar,and CO2.These residual gases can change the work function at the surface through adsorption or ion bombardment,thereby degrading the emission current of the cathode.

  7. Residual gas properties in a field emission device with ZnO emitters

    Science.gov (United States)

    Wang, Jin-Chan

    2013-06-01

    In this paper, a vacuum system is employed to compare the emission stabilities of the same ZnO cathode in a sealed field emission (FE) device and under ultrahigh vacuum (UHV) conditions. It is observed that the emission current is more stable under the UHV level than in the device. When all conditions except the ambient gases are kept unchanged, the emission current degradation is mainly caused by the residual gases in the sealed device. The quadrupole mass spectrometer (QMS) equipped on the vacuum system is used to investigate the residual gas components. Based on the obtained QMS data, the following conclusions can be drawn: the residual gases in ZnO-FE devices are H2, CH4, CO, Ar, and CO2. These residual gases can change the work function at the surface through adsorption or ion bombardment, thereby degrading the emission current of the cathode.

  8. Flexible Field Emitter for X-ray Generation by Implanting CNTs into Nickel Foil

    Science.gov (United States)

    Sun, Bin; Wang, Yan; Ding, Guifu

    2016-09-01

    This paper reports on a flexible Ni micro wire with CNTs embedded into its surface. By using micromachining technology, for the first time, we could implant nanoscale materials into micro-scale metal substrate at room temperature. Thanks to the effective direct contact and the strong interactions between CNTs and the substrate, field emission current of 1.11 mA (current density of 22.2 mA/cm2) could be achieved from the micro wire. Moreover, the wire shows excellent mechanical properties for large amplitude bending, which is beneficial for geometric designing. To check the practical application of the wire, a simplified X-ray imaging system was set up by modifying a conventional tube. The gray shade that appears on the sensitive film after being exposed to the radiation confirms the X-ray generation.

  9. Three-dimensional electromagnetic breathers in carbon nanotubes with the field inhomogeneity along their axes

    Science.gov (United States)

    Zhukov, Alexander V.; Bouffanais, Roland; Fedorov, Eduard G.; Belonenko, Mikhail B.

    2013-10-01

    We study the propagation of extremely short electromagnetic three-dimensional bipolar pulses in an array of semiconductor carbon nanotubes. The heterogeneity of the pulse field along the axis of the nanotubes is accounted for the first time. The evolution of the electromagnetic field and the charge density of the sample are described by Maxwell's equations supplemented by the continuity equation. Our analysis reveals for the first time the possibility of propagation of three-dimensional electromagnetic breathers in CNTs arrays. Specifically, we found that the propagation of short electromagnetic pulse induces a redistribution of the electron density in the sample.

  10. Field-effect ion-transport devices with carbon nanotube channels: schematics and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ju Yul; Kang, Jeong Won; Byun, Ki Ryang; Kang, Eu Seok; Hwang, Ho Jung [Chung-Ang University, Seoul (Korea, Republic of); Lee, Jun Ha; Lee, Hoong Joo [Sangmyung University, Chonan (Korea, Republic of); Kwon, Oh Keun [Semyung University, Jecheon (Korea, Republic of); Kim, Young Min [Chung-Cheong University, Cheongwon (Korea, Republic of)

    2004-08-15

    We investigated field-effect ion-transport devices based on carbon nanotubes by using classical molecular dynamics simulations under applied external force fields, and we present model schematics that can be applied to the nanoscale data storage devices and unipolar ionic field-effect transistors. As the applied external force field is increased, potassium ions rapidly flow through the nanochannel. Under low external force fields, thermal fluctuations of the nanochannels affect tunneling of the potassium ions whereas the effects of thermal fluctuations are negligible under high external force fields. Since the electric current conductivity increases when potassium ions are inserted into fullerenes or carbon nanotubes, the field effect due to the gate, which can modify the position of the potassium ions, changes the tunneling current between the drain and the source.

  11. 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.

  12. Near-field relaxation of a quantum emitter to 2D semiconductors: surface dissipation and exciton polaritons

    CERN Document Server

    Karanikolas, Vasilios D; Eastham, Paul R; Bradley, A Louise

    2016-01-01

    The total spontaneous emission rate of a quantum emitter in the presence of an infinite MoS\\textsubscript{2} monolayer is enhanced by several orders of magnitude, compared to its free-space value, due to the excitation of surface exciton polariton modes and lossy modes. The spectral and distance dependence of the spontaneous emission rate are analyzed and the lossy-surface-wave, surface exciton polariton mode and radiative contributions are identified. The transverse magnetic and transverse electric exciton polariton modes can be excited for different emission frequencies of the quantum emitter, and their contributions to the total spontaneous emission rate are different. To calculate these different decay rates, we use the non-Hermitian description of light-matter interactions, employing a Green's tensor formalism. The distance dependence follows different trends depending on the emission energy of quantum emitter. For the case of the lossy surface waves, the distance dependence follows a $z^{-n}$, $n=2,3,4$...

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

    Science.gov (United States)

    Xu, Jinzhuo; Xu, Peng; Ou-Yang, Wei; Chen, Xiaohong; Guo, Pingsheng; Li, Jun; Piao, Xianqing; Wang, Miao; Sun, Zhuo

    2015-02-01

    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-1 and threshold field of 0.657 V μm-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.

  14. MUSE integral-field spectroscopy towards the Frontier Fields cluster Abell S1063: II. Properties of low luminosity Lyman alpha emitters at z>3

    CERN Document Server

    Karman, W; Caminha, G B; Gronke, M; Grillo, C; Balestra, I; Rosati, P; Vanzella, E; Coe, D; Dijkstra, M; Koekemoer, A M; Mercurio, A; Nonino, M

    2016-01-01

    In spite of their conjectured importance for the Epoch of Reionization, the properties of low-mass galaxies are currently still under large debate. In this article, we study the stellar and gaseous properties of faint, low-mass galaxies at z>3. We observed the Frontier Fields cluster Abell S1063 with MUSE over a 2 arcmin^2 field, and combined integral-field spectroscopy with gravitational lensing to perform a blind search for intrinsically faint Lya emitters (LAEs). We found in total 14 lensed LAEs and increased the number of spectroscopically-confirmed multiple-image families from 6 to 17, and updated our gravitational-lensing model accordingly. The lensing-corrected Lya luminosities are with L(Lya) =3 are reported. We performed SED modelling to broadband photometry from the {\\em U}-band through the infrared to determine the stellar properties of these LAEs. The stellar masses are very low (10^{6-8} Msun), and are accompanied by very young ages of 1-100 Myr. The very high specific star formation rates (~100/...

  15. Field Emission Properties of the Dendritic Carbon Nanotubes Film Embedded with ZnO Quantum Dots

    Directory of Open Access Journals (Sweden)

    Shu Zuo

    2011-01-01

    Full Text Available Response on the effects of individual differences of common carbon nanotubes on the field emission current stability and the luminescence uniformity of cathode film, a new type of cathode film made of dendritic carbon nanotubes embedded with Zinc oxide quantum dots is proposed. The film of dendritic carbon nanotubes was synthesized through high-temperature pyrolysis of iron phthalocyanine on a silicon substrate coated with zinc oxide nanoparticles. The dendritic structure looks like many small branches protrude from the main branches in SEM and TEM images, and both the branch and the trunk are embedded with Zinc oxide quantum dots. The turn-on field of the dendritic structure film is ∼1.3 V/μm at a current of 2 μA, which is much lower than that of the common carbon nanotube film, and the emission current and the luminescence uniformity are better than that of the common one. The whole film emission uniformity has been improved because the multi-emission sites out from the dendritic structure carbon nanotubes cover up the failure and defects of the single emission site.

  16. Emittance growth due to the wake field driven by an electron beam accelerated in an RF-gun of free electron laser 'ELSA'

    CERN Document Server

    Salah, W

    2000-01-01

    It appears that the ease of the parameter chosen for 'ELSA' photo injector, the influence of the exit aperture, in terms of beam quality, is slight concerning the transverse emittance: (DELTA epsilon sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r /epsilon sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub = = r)(z)approx 3% at maximum, and negligible concerning the axial emittance. To complete this paper, we recall the results previously obtained concerning the wake field of a closed or open cavity for a beam approaching the anode . They had quantitatively specified the expected deep asymmetry between the conducting walls regarding their contribution to the total wake field, besides the space-charge contribution. (Given that the radial walls have no time to contribute, these conducting walls are the cathode and the anode.) Thus, concerning the effects on whole-beam emittances, the correction (DELTA epsilon sub p sub e sub r sub p sub e sub n sub d sub i ...

  17. Miniaturized reaction chamber for optimized laser-assisted carbon nanotube growth

    NARCIS (Netherlands)

    Burgt, Y. van de; Loon, W. van; Mandamparambil, R.; Bellouard, Y.

    2014-01-01

    The localized growth of carbon nanotube structures has potential in many applications such as interconnects, field emitters and sensors. Using a laser to locally heat the substrate offers a highly versatile process compatible with a broad range of substrates and devices. However, for laser-assisted

  18. Plasma excitations in a single-walled carbon nanotube with an external transverse magnetic field

    Indian Academy of Sciences (India)

    K A Vijayalakshmi; T P Nafeesa Baby

    2013-02-01

    The effect of different uniform transverse external magnetic fields in plasma frequency when propagated parallel to the surface of the single-walled metallic carbon nanotubes is studied. The classical electrodynamics as well as Maxwell’s equations are used in the calculations. Equations are developed for both short- and long-wavelength limits and the variations are studied graphically.

  19. Spin-orbit interaction in chiral carbon nanotubes probed in pulsed magnetic fields

    NARCIS (Netherlands)

    Jhang, S.H.; Marganska, M.; Skourski, Y.; Preusche, D.; Witkamp, B.; Grifoni, M.; Van der Zant, H.; Wosnitza, J.; Strunk, C.

    2010-01-01

    The magnetoconductance of an open carbon nanotube (CNT)-quantum wire was measured in pulsed magnetic fields. At low temperatures, we find a peculiar split magnetoconductance peak close to the chargeneutrality point. Our analysis of the data reveals that this splitting is intimately connected to the

  20. High Performance Ambipolar Field-Effect Transistor of Random Network Carbon Nanotubes

    NARCIS (Netherlands)

    Bisri, Satria Zulkarnaen; Gao, Jia; Derenskyi, Vladimir; Gomulya, Widianta; Iezhokin, Igor; Gordiichuk, Pavlo; Herrmann, Andreas; Loi, Maria Antonietta

    2012-01-01

    Ambipolar field-effect transistors of random network carbon nanotubes are fabricated from an enriched dispersion utilizing a conjugated polymer as the selective purifying medium. The devices exhibit high mobility values for both holes and electrons (3 cm(2)/V.s) with a high on/off ratio (10(6)). The

  1. Brownian Emitters

    Science.gov (United States)

    Tsekov, Roumen

    2016-06-01

    A Brownian harmonic oscillator, which dissipates energy either by friction or via emission of electromagnetic radiation, is considered. This Brownian emitter is driven by the surrounding thermo-quantum fluctuations, which are theoretically described by the fluctuation-dissipation theorem. It is shown how the Abraham-Lorentz force leads to dependence of the half-width on the peak frequency of the oscillator amplitude spectral density. It is found that for the case of a charged particle moving in vacuum at zero temperature, its root-mean-square velocity fluctuation is a universal constant, equal to roughly 1/18 of the speed of light. The relevant Fokker-Planck and Smoluchowski equations are also derived.

  2. Magnetic-Field Dependence of Tunnel Couplings in Carbon Nanotube Quantum Dots

    DEFF Research Database (Denmark)

    Grove-Rasmussen, Kasper; Grap, S.; Paaske, Jens;

    2012-01-01

    By means of sequential and cotunneling spectroscopy, we study the tunnel couplings between metallic leads and individual levels in a carbon nanotube quantum dot. The levels are ordered in shells consisting of two doublets with strong- and weak-tunnel couplings, leading to gate-dependent level...... renormalization. By comparison to a one- and two-shell model, this is shown to be a consequence of disorder-induced valley mixing in the nanotube. Moreover, a parallel magnetic field is shown to reduce this mixing and thus suppress the effects of tunnel renormalization....

  3. Biosensors based on carbon nanotube-network field-effect transistors.

    Science.gov (United States)

    Cid, Cristina C; Riu, Jordi; Maroto, Alicia; Rius, F Xavier

    2010-01-01

    We describe in detail the different steps involved in the construction of a carbon nanotube field-effect transistor (CNTFET) based on a network of single-walled carbon nanotubes (SWCNTs), which can selectively detect human immunoglobulin G (HIgG). HIgG antibodies, which are strongly adsorbed onto the walls of the SWCNTs, are the basic elements of the recognition layer. The nonspecific binding of proteins or other interferences are avoided by covering the nonadsorbed areas of the SWCNTs with Tween 20. The CNTFET is a reagentless device that does not need labels to detect HIgG.

  4. Anisotropic high-field terahertz response of free-standing carbon nanotubes

    Science.gov (United States)

    Lee, Byounghwak; Mousavian, Ali; Paul, Michael J.; Thompson, Zachary J.; Stickel, Andrew D.; McCuen, Dalton R.; Jang, Eui Yun; Kim, Yong Hyup; Kyoung, Jisoo; Kim, Dai-Sik; Lee, Yun-Shik

    2016-06-01

    We demonstrate that unidirectionally aligned, free-standing multi-walled carbon nanotubes (CNTs) exhibit highly anisotropic linear and nonlinear terahertz (THz) responses. For the polarization parallel to the CNT axis, strong THz pulses induce nonlinear absorption in the quasi-one-dimensional conducting media, while no nonlinear effect is observed in the perpendicular polarization configuration. Time-resolved measurements of transmitted THz pulses and a theoretical analysis of the data reveal that intense THz fields enhance permittivity in carbon nanotubes by generating charge carriers.

  5. CARBON NANOTUBES: A REVIEW ON PREPARATION TECHNIQUES AND APPLICATIONS IN VARIOUS FIELDS

    Directory of Open Access Journals (Sweden)

    SaiSowjanya Palla

    2013-02-01

    Full Text Available Carbon nanotubes (CNTs are allotropes of carbon with a nanostructure that can have a length-to-diameter ratio greater than 1,000,000. Different types of carbon nanotubes can be produced by different methods: Arc discharge, laser ablation, chemical vapour deposition and flame synthesis. Purification of the tubes can be divided into a couple of main techniques: oxidation, acid treatment, annealing, sonication, filtering and functionalisation techniques. Economically feasible large-scale production and purification techniques still have to be developed. Fundamental and practical nanotube researches have shown possible applications in the fields of energy storage, molecular electronics, nanomechanic devices, composite materials and immobilization of enzymes. Various immobilization methods have been developed, and in particular, specific attachment of enzymes on carbon nanotubes has been an important focus of attention. With the growing attention paid to cascade enzymatic reaction, it is possible that multi enzyme co-immobilization would be one of the next goals in the future. In this paper, we focus on preparation techniques, various applications of CNTs and enzyme immobilization on carbon nanotubes.

  6. Carbon nanotube mode lockers with enhanced nonlinearity via evanescent field interaction in D-shaped fibers

    Science.gov (United States)

    Song, Yong-Won; Yamashita, Shinji; Goh, Chee S.; Set, Sze Y.

    2007-01-01

    We demonstrate a novel passive mode-locking scheme for pulsed lasers enhanced by the interaction of carbon nanotubes (CNTs) with the evanescent field of propagating light in a D-shaped optical fiber. The scheme features all-fiber operation as well as a long lateral interaction length, which guarantees a strong nonlinear effect from the nanotubes. Mode locking is achieved with less than 30% of the CNTs compared with the amount of nanotubes used for conventional schemes. Our method also ensures the preservation of the original morphology of the individual CNTs. The demonstrated pulsed laser with our CNT mode locker has a repetition rate of 5.88 MHz and a temporal pulse width of 470 fs.

  7. Carbon nanotube mode lockers with enhanced nonlinearity via evanescent field interaction in D-shaped fibers.

    Science.gov (United States)

    Song, Yong-Won; Yamashita, Shinji; Goh, Chee S; Set, Sze Y

    2007-01-15

    We demonstrate a novel passive mode-locking scheme for pulsed lasers enhanced by the interaction of carbon nanotubes (CNTs) with the evanescent field of propagating light in a D-shaped optical fiber. The scheme features all-fiber operation as well as a long lateral interaction length, which guarantees a strong nonlinear effect from the nanotubes. Mode locking is achieved with less than 30% of the CNTs compared with the amount of nanotubes used for conventional schemes. Our method also ensures the preservation of the original morphology of the individual CNTs. The demonstrated pulsed laser with our CNT mode locker has a repetition rate of 5.88 MHz and a temporal pulse width of 470 fs.

  8. Si/Ge hetero-structure nanotube tunnel field effect transistor

    KAUST Repository

    Hanna, A. N.

    2015-01-07

    We discuss the physics of conventional channel material (silicon/germanium hetero-structure) based transistor topology mainly core/shell (inner/outer) gated nanotube vs. gate-all-around nanowire architecture for tunnel field effect transistor application. We show that nanotube topology can result in higher performance through higher normalized current when compared to nanowire architecture at Vdd-=-1-V due to the availability of larger tunneling cross section and lower Shockley-Reed-Hall recombination. Both architectures are able to achieve sub 60-mV/dec performance for more than five orders of magnitude of drain current. This enables the nanotube configuration achieving performance same as the nanowire architecture even when Vdd is scaled down to 0.5-V.

  9. Modelling of Chirality-Dependent Current-Voltage Characteristics of Carbon-Nanotube Field-Effect Transistors

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xu; WANG Yan; YU Zhi-Ping

    2006-01-01

    @@ Current-voltage characteristics of ballistic carbon-nanotube field-effect transistors are characterized with an it-erative simulation program. The influence of carbon-nanotube chirality and diameter on the output current is considered. An analytical current-voltage expression under the quantum capacitance limit and low-voltage application is derived. Our simulation results are compared with actual measurement data.

  10. A new method of emittance measurement for electron beams from the Micro-emitter

    Energy Technology Data Exchange (ETDEWEB)

    Ishizuka, Hiroshi [Fukuoka Inst. of Technology (Japan); Nakahara, Yuriko; Kawasaki, Sunao; Musyoki, Stephen; Shimizu, Hiroshi; Watanabe, Akihiko; Shiho, Makoto

    1994-03-01

    Recently a new type of cathode called Micro-emitter is in progress. This cathode is micro fabricated field emitter having the characteristics of very low emittance and high brightness. We can not measure the emittance of the cathode with conventional method like pepper-pot method. The reasons are ; 1. The angle between the electron orbit and the axis is very small. ; and 2. We can not focus the electron beam in the vacuum or on the surface of the material since the current density of the cathode is extremely high. For the emittance measurement for such low emittance and high brightness cathode, we need to expand the beam, and measure the beam cross section without any slits or apertures. We study and propose a new emittance measurement method for the Micro-emitter. (author).

  11. Field emission properties of capped carbon nanotubes doped by alkali metals:a theoretical investigation

    Institute of Scientific and Technical Information of China (English)

    Jin Lei; Fu Hong-Gang; Xie Ying; Yu Hai-Tao

    2012-01-01

    The electronic structures and field emission properties of capped CNT55 systems with or without alkali metal atom adsorption were systematically investigated by density functional theory calculation.The results indicate that the adsorption of alkali metal on the center site of a CNT tip is energetically favorable.In addition,the adsorption energies increase with the introduction of the electric field.The excessive negative charges on CNT tips make electron emittance much easier and result in a decrease in work function.Furthermore,the inducing effect by positively charged alkali metal atoms can be reasonably considered as the dominant reason for the improvement in field emission properties.

  12. Selective growth of carbon nanotube on silicon substrates

    Institute of Scientific and Technical Information of China (English)

    ZOU Xiao-ping; H. ABE; T. SHIMIZU; A. ANDO; H. TOKUMOT; ZHU Shen-ming; ZHOU Hao-shen

    2006-01-01

    The carbon nanotube (CNT) growth of iron oxide-deposited trench-patterns and the locally-ordered CNT arrays on silicon substrate were achieved by simple thermal chemical vapor deposition(STCVD) of ethanol vapor. The CNTs were uniformly synthesized with good selectivity on trench-patterned silicon substrates. This fabrication process is compatible with currently used semiconductor-processing technologies,and the carbon-nanotube fabrication process can be widely applied for the development of electronic devices using carbon-nanotube field emitters as cold cathodes and can revolutionize the area of field-emitting electronic devices. The site-selective growth of CNT from an iron oxide nanoparticle catalyst patterned were also achieved by drying-mediated self-assembly technique. The present method offers a simple and cost-effective method to grow carbon nanotubes with self-assembled patterns.

  13. Multiscale model of heat dissipation mechanisms during field emission from carbon nanotube fibers

    Science.gov (United States)

    Cahay, M.; Zhu, W.; Fairchild, S.; Murray, P. T.; Back, T. C.; Gruen, G. J.

    2016-01-01

    A multiscale model of field emission (FE) from carbon nanotube fibers (CNFs) is developed, which takes into account Joule heating within the fiber and radiative cooling and the Nottingham effect at the tip of the individual carbon nanotubes (CNTs) in the array located at the fiber tip. The model predicts the fraction of CNTs being destroyed as a function of the applied external electric field and reproduces many experimental features observed in some recently investigated CNFs, such as order of magnitude of the emission current (mA range), low turn on electric field (fraction of V/μm), deviation from pure Fowler-Nordheim behavior at large applied electric field, hysteresis of the FE characteristics, and a spatial variation of the temperature along the CNF axis with a maximum close to its tip of a few hundred °C.

  14. Multiscale model of heat dissipation mechanisms during field emission from carbon nanotube fibers

    Energy Technology Data Exchange (ETDEWEB)

    Cahay, M.; Zhu, W. [Spintronics and Vacuum Nanoelectronics Laboratory, University of Cincinnati, Cincinnati, Ohio 45221 (United States); Fairchild, S. [Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, Ohio 45433 (United States); Murray, P. T.; Back, T. C. [Research Institute, University of Dayton, Dayton, Ohio 45469-0170 (United States); Center of Excellence for Thin Film Research and Surface Engineering, University of Dayton, Dayton, Ohio 45469-0170 (United States); Gruen, G. J. [Research Institute, University of Dayton, Dayton, Ohio 45469-0170 (United States)

    2016-01-18

    A multiscale model of field emission (FE) from carbon nanotube fibers (CNFs) is developed, which takes into account Joule heating within the fiber and radiative cooling and the Nottingham effect at the tip of the individual carbon nanotubes (CNTs) in the array located at the fiber tip. The model predicts the fraction of CNTs being destroyed as a function of the applied external electric field and reproduces many experimental features observed in some recently investigated CNFs, such as order of magnitude of the emission current (mA range), low turn on electric field (fraction of V/μm), deviation from pure Fowler-Nordheim behavior at large applied electric field, hysteresis of the FE characteristics, and a spatial variation of the temperature along the CNF axis with a maximum close to its tip of a few hundred  °C.

  15. Carbon Nanotube Field Emission Devices With Integrated Gate for High Current Applications

    Science.gov (United States)

    2008-08-01

    exhibits an edge effect and in fact, shows a slight enhancement. A baseline structure, consisting of two parallel plates with the same applied field and...electrostatics the addition of the gate electrode will not reduce the edge effect for the CNT pillars. As a result of this it is expected that the voltage...field emission from an individual aligned carbon nanotube bundle enhanced by edge effect ", Appl. Phys. Lett., 90, 153108, 2007. [6] Killian, J. L

  16. A carbon nanotube field emission multipixel x-ray array source for microradiotherapy application

    OpenAIRE

    Wang, Sigen; Calderon, Xiomara; Peng, Rui; Schreiber, Eric C.; Zhou, Otto; Chang, Sha

    2011-01-01

    The authors report a carbon nanotube (CNT) field emission multipixel x-ray array source for microradiotherapy for cancer research. The developed multipixel x-ray array source has 50 individually controllable pixels and it has several distinct advantages over other irradiation source including high-temporal resolution (millisecond level), the ability to electronically shape the form, and intensity distribution of the radiation fields. The x-ray array was generated by a CNT cathode array (5×10)...

  17. Hexagonal Boron Nitride Coated Carbon Nanotubes: Interlayer Polarization Improved Field Emission.

    Science.gov (United States)

    Chang, Han-Chen; Tsai, Hsin-Jung; Lin, Wen-Yi; Chu, Yung-Chi; Hsu, Wen-Kuang

    2015-07-08

    Coating of h-BN onto carbon nanotubes induces polarization at interfaces, and charges become localized at N and C atoms. Field emission of coated tubes is found to be highly stable, and current density fluctuates within 4%. Study further reveals that the electric field established between coatings and tubes facilitates charge transfer across interfaces and electrons are emitted through occupied and unoccupied bands of N and B atoms.

  18. MUSE integral-field spectroscopy towards the Frontier Fields cluster Abell S1063. II. Properties of low luminosity Lyman α emitters at z > 3

    Science.gov (United States)

    Karman, W.; Caputi, K. I.; Caminha, G. B.; Gronke, M.; Grillo, C.; Balestra, I.; Rosati, P.; Vanzella, E.; Coe, D.; Dijkstra, M.; Koekemoer, A. M.; McLeod, D.; Mercurio, A.; Nonino, M.

    2017-02-01

    In spite of their conjectured importance for the Epoch of Reionization, the properties of low-mass galaxies are currently still very much under debate. In this article, we study the stellar and gaseous properties of faint, low-mass galaxies at z > 3. We observed the Frontier Fields cluster Abell S1063 with MUSE over a 2 arcmin2 field, and combined integral-field spectroscopy with gravitational lensing to perform a blind search for intrinsically faint Lyα emitters (LAEs). We determined in total the redshift of 172 galaxies of which 14 are lensed LAEs at z = 3-6.1. We increased the number of spectroscopically-confirmed multiple-image families from 6 to 17 and updated our gravitational-lensing model accordingly. The lensing-corrected Lyα luminosities are with LLyα ≲ 1041.5 erg/s among the lowest for spectroscopically confirmed LAEs at any redshift. We used expanding gaseous shell models to fit the Lyα line profile, and find low column densities and expansion velocities. This is, to our knowledge, the first time that gaseous properties of such faint galaxies at z ≳ 3 are reported. We performed SED modelling to broadband photometry from the U band through the infrared to determine the stellar properties of these LAEs. The stellar masses are very low (106-8M⊙ ), and are accompanied by very young ages of 1-100 Myr. The very high specific star-formation rates ( 100 Gyr-1) are characteristic of starburst galaxies, and we find that most galaxies will double their stellar mass in ≲20 Myr. The UV-continuum slopes β are low in our sample, with β expected for a scenario where low mass galaxies reionise the Universe.

  19. Dynamic characteristics of multi-walled carbon nanotubes under a transverse magnetic field

    Indian Academy of Sciences (India)

    S Li; H J Xie; X Wang

    2011-02-01

    This paper reports the results of an investigation into the effect of transverse magnetic fields on dynamic characteristics of multi-walled carbon nanotubes (MWNTs). Couple dynamic equations of MWNTs subjected to a transverse magnetic field are derived and solved by considering the Lorentz magnetic forces induced by a transverse magnetic field exerted on MWCNTs. Results show that the transverse magnetic field exerted on MWNTs makes the lowest frequency of the MWNTs nonlinearly decrease and the highest frequency, changeless. When the strength of applied transverse magnetic fields is larger than a given value the two walls of MWNTs appear in the radial and axial coaxial vibration phenomena.

  20. Simultaneous alignment and micropatterning of carbon nanotubes using modulated magnetic field

    Directory of Open Access Journals (Sweden)

    Kaoru Tsuda and Yoshio Sakka

    2009-01-01

    Full Text Available We report simultaneous alignment and micropatterning of carbon nanotubes (CNTs using a high magnetic field. It is important to prepare well-dispersed CNTs for alignment and patterning because CNT aggregation obstructs alignment. In magnetic field, highly anisotropic CNTs rotate in the direction stabilized in energy. Owing to their diamagnetic nature, CNTs suspended in a liquid medium are trapped in a weak magnetic field generated by a field modulator; meanwhile, they align to the applied strong magnetic field. The alignment has been achieved not only in polymers but also in ceramic and silicone composites.

  1. Effect of Electrochemical Treatment in a Lithium Chloride Solution on Field Emission from Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    WANG Qiang; LI Chun; YUAN Guang; GU Chang-Zhi

    2009-01-01

    Carbon nanotubes (CNTs) are electrochemically treated in a lithium chloride solution at a concentration 0.1 mol/L.The field emission properties of the CNTs are investigated at different temperatures before and after the electrochemical treatment.After treatment,the turn-on voltage to produce field emission current of 10 μA decreases from 4.2kV to 2.7kV and the field emission current increases distinctly,but the stability falls off.Based on the Fowler-Nordheim plot,the values of the work function for the CNTs are calculated,which reveals that work function decreases after the electrochemical treatment.These results are attributed to the decrease of the work function of the carbon nanotubes.

  2. High performance field emission and Nottingham effect observed from carbon nanotube yarn

    Science.gov (United States)

    Choi, Young Chul; Kang, Jun-Tae; Park, Sora; Go, Eunsol; Jeon, Hyojin; Kim, Jae-Woo; Jeong, Jin-Woo; Park, Kyung-Ho; Song, Yoon-Ho

    2017-02-01

    Vertically aligned CNTs were synthesized on a four inch wafer, followed by the preparation of a CNT yarn. The yarn emitter was found to have an extremely high field enhancement factor, which was confirmed to have originated from multi-stage effect. In addition to superb field emission characteristics, the energy exchange during field emission, called Nottingham effect, was observed from the CNT yarn emitter. A CNT yarn was attached to the thermistor whose resistance depends on temperature. Then, the change of resistance was monitored during the field emission, which enabled us to calculate the energy exchange. It was found that the observed heating originated from both Nottingham and Joule heating. Nottingham heating was dominant at low current region while Joule heating became larger contribution at high current region. Very large Nottingham region of up to 33.35 mA was obtained, which is due presumably to the high performance field emission characteristics of a CNT yarn. This is believed to be an important observation for developing reliable field emission devices with suppressed Joule heating effect.

  3. Enhancement of Emission Lifetime of CNT Emitters by Coating ZnO on the CNT Surface.

    Science.gov (United States)

    Yoon, Sang Hyun; Chung, Dae Joon; Lee, Jong; Park, Kyu Chang; Kang, Chi Jung; Yoon, Tae-Sik; Shim, Ee Le; Choi, Young Jin

    2015-11-01

    Carbon nanotubes (CNTs) have been investigated as field-emission sources owing to their high electrical conductivity and high aspect ratio. However, practical applications demand that the emission lifetime of CNTs be further improved. Since ZnO demonstrates impressive electrical and thermal conductivity, when coated on the surface of CNTs, it can allow the CNT field emitters to endure high electrical stress and high temperature. Moreover, ZnO nanostructures protect the CNT emitters from being bombarded by high-energy ions, which are accelerated by the high electric field. From the result of emission lifetime measurements at the emission current density of 100 mA/cm2, we found that the emission lifetime was increased by more than a factor of 2 when ZnO had been coated onto the CNT emitters. The observation registers as an important contribution to the practical application of CNT emitters with long-term emission stability, as well as with high emission currents. In this work, we elucidate the detailed mechanism of long-term stability that can be achieved by coating ZnO nanostructures on the surface of CNTs.

  4. Electroluminescent Polymers and Carbon Nanotubes for Flat Panel Displays

    Institute of Scientific and Technical Information of China (English)

    Liming Dai; Limin Dong; Mei Gao; Shaoming Huang; Oddvar Johansen; Albert W.H.Mau,Zoran Vasic; Berthold Winkler; Yongyuang Yang

    2000-01-01

    polymeric light-emitting diodes(LEDs) with sufficient brightness. efficiencies, low driving voltages, and various interesting features have been reported. The relatively short device lifetime, however, still remains as a major problem to be solved before any commercial applications will be realized. In this regard,carbon nanotubes have recently been proposed as more robust electron field emitters for flat panel displays. We have synthesised large arrays of vertically aligned carbon nanotubes, from which micropatterns of the aligned nanotubes suitable for flat panel displays were fabricated on various substrates. In this paper, we summarise our work on the synthesis and microfabrication of electroluminescent polymers and carbon nanotubes for flat panel displays with reference to other complementary work as appropriate.

  5. Emittance Theory for Thin Film Selective Emitter

    Science.gov (United States)

    Chubb, Donald L.; Lowe, Roland A.; Good, Brian S.

    1994-01-01

    Thin films of high temperature garnet materials such as yttrium aluminum garnet (YAG) doped with rare earths are currently being investigated as selective emitters. This paper presents a radiative transfer analysis of the thin film emitter. From this analysis the emitter efficiency and power density are calculated. Results based on measured extinction coefficients for erbium-YAG and holmium-YAG are presented. These results indicated that emitter efficiencies of 50 percent and power densities of several watts/sq cm are attainable at moderate temperatures (less than 1750 K).

  6. Ion-sensitive field effect transistors using carbon nanotubes as the transducing layer.

    Science.gov (United States)

    Cid, Cristina C; Riu, Jordi; Maroto, Alicia; Rius, F Xavier

    2008-08-01

    We report a new type of ion-sensitive field effect transistor (ISFET). This type of ISFET incorporates a new architecture, containing a network of single-walled carbon nanotubes (SWCNTs) as the transduction layer, making an external reference electrode unnecessary. To show an example of its application, the SWCNT-based ISFET is able to detect at least 10(-8) M of potassium in water using an ion-selective membrane containing valinomycin.

  7. Frequency kesponse of top-gated carbon nanotube field-effect transistors

    OpenAIRE

    Singh, Dinkar V.; Jenkins, Keith A.; Appenzeller, Joerg; Neumayer, D.; Grill, Alfred; Wong, H. S. Philip

    2004-01-01

    The ac performance of carbon nanotube field-effect transistors (CNFETs) has been characterized using two approaches involving: 1) time- and 2) frequency-domain measurements. A high input impedance measurement system was used to demonstrate time-domain switching of CNFETs at frequencies up to 100 kHz. The low level of signal crosstalk in CNFETs fabricated on quartz substrates enabled frequency-domain measurements of the ac response of CNFETs in the megahertz range, over five orders of magnitud...

  8. Enhanced field emission from Ti{sup 3+} self-doped TiO{sub 2} nanotube arrays synthesized by a facile cathodic reduction process

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Wei-Dong; Wang, Cheng-Wei, E-mail: cwwang@nwnu.edu.cn; Chen, Jian-Biao; Li, Yan; Wang, Jian

    2014-05-01

    Highlights: • A facile strategy of cathodic reduction is developed to prepare Ti{sup 3+} self-doped TNAs. • This strategy greatly reduces the requirements of instruments and resources. • Ti{sup 3+} self-doped TNAs show sharply improved conductivity and lowered work function. • The FE properties of Ti{sup 3+} self-doped TNAs are substantially improved. • The dependence of FE properties of the sample on Ti{sup 3+} concentration is investigated. - Abstract: A facile strategy of cathodic reduction has been developed to successfully prepare Ti{sup 3+} self-doped TiO{sub 2} nanotube field emitter arrays (TNAs). This strategy significantly reduces the requirements of instruments and resources compared to the conventional strategies and can controllable introduction of Ti{sup 3+} sites (oxygen vacancies) into TNAs with morphology retention. The introduced Ti{sup 3+} sites (oxygen vacancies) served as electron donors, can substantially improve the conductivity and decrease the work function of TNAs. Importantly, compared to pristine TNAs, the Ti{sup 3+} self-doped TNAs show enhanced field emission (FE) properties including sharply decreased turn-on field from 12.49 to 2.67 V/μm and large FE current density of 4.31 mA/cm{sup 2} at 4.45 V/μm.

  9. Improved field emission stability from single-walled carbon nanotubes chemically attached to silicon.

    Science.gov (United States)

    Shearer, Cameron J; Fahy, Adam; Barr, Matthew; Dastoor, Paul C; Shapter, Joseph G

    2012-08-01

    Here, we demonstrate the simple fabrication of a single-walled carbon nanotube (SWCNT) field emission electrode which shows excellent field emission characteristics and remarkable field emission stability without requiring posttreatment. Chemically functionalized SWCNTs were chemically attached to a silicon substrate. The chemical attachment led to vertical alignment of SWCNTs on the surface. Field emission sweeps and Fowler-Nordheim plots showed that the Si-SWCNT electrodes field emit with a low turn-on electric field of 1.5 V μm-1 and high electric field enhancement factor of 3,965. The Si-SWCNT electrodes were shown to maintain a current density of >740 μA cm-2 for 15 h with negligible change in applied voltage. The results indicate that adhesion strength between the SWCNTs and substrate is a much greater factor in field emission stability than previously reported.

  10. Optimization of Magnetic Field-Assisted Synthesis of Carbon Nanotubes for Sensing Applications

    Directory of Open Access Journals (Sweden)

    Grzegorz Raniszewski

    2014-10-01

    Full Text Available One of the most effective ways of synthesizing carbon nanotubes is the arc discharge method. This paper describes a system supported by a magnetic field which can be generated by an external coil. An electric arc between two electrodes is stabilized by the magnetic field following mass flux stabilization from the anode to the cathode. In this work four constructions are compared. Different configurations of cathode and coils are calculated and presented. Exemplary results are discussed. The paper describes attempts of magnetic field optimization for different configurations of electrodes.

  11. The dissipation of field emitting carbon nanotubes in an oxygen environment as revealed by in situ transmission electron microscopy.

    Science.gov (United States)

    Koh, Ai Leen; Gidcumb, Emily; Zhou, Otto; Sinclair, Robert

    2016-09-15

    In this work, we report the first direct experimental observations of carbon nanotubes (CNT) field emitting in an oxygen environment, using aberration-corrected environmental transmission electron microscopy in combination with an electrical biasing specimen holder under low-dose, field-free imaging conditions. Our studies show that while the CNTs remain stable during high vacuum field emission, they experience abrupt decreases in length, also termed "burn-back", when field-emitting in an oxygen environment at around 30 Pa pressure. Furthermore, we perform correlative field-free and aberration-corrected, high-resolution transmission electron microscopy imaging to understand how the structure of the CNTs - particularly the opening of the nanotube caps - is influenced by its gas environment during field emission. This work provides significant insight into the mechanism of carbon nanotube behavior under non-ideal field emission conditions.

  12. Electric field effect on the zigzag (6,0) single-wall BC2N nanotube for use in nano-electronic circuits.

    Science.gov (United States)

    Baei, Mohammad T; Peyghan, Ali Ahmadi; Moghimi, Masoumeh; Hashemian, Saeede

    2013-01-01

    We have analyzed the effect of external electric field on the zigzag (6,0) single-wall BC2N nanotube using density functional theory calculations. Analysis of the structural parameters indicates that the nanotube is resistant against the external electric field strengths. Analysis of the electronic structure of the nanotube indicates that the applied parallel electric field strengths have a much stronger interaction with the nanotube with respect to the transverse electric field strengths and the nanotube is easier to modulate by the applied parallel electric field. Our results show that the properties of the nanotube can be controlled by the proper external electric field for use in nano-electronic circuits.

  13. 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.

  14. Wide dynamic range enrichment method of semiconducting single-walled carbon nanotubes with weak field centrifugation.

    Science.gov (United States)

    Reis, Wieland G; Tomović, Željko; Weitz, R Thomas; Krupke, Ralph; Mikhael, Jules

    2017-03-20

    The potential of single-walled carbon nanotubes (SWCNTs) to outperform silicon in electronic application was finally enabled through selective separation of semiconducting nanotubes from the as-synthesized statistical mix with polymeric dispersants. Such separation methods provide typically high semiconducting purity samples with narrow diameter distribution, i.e. almost single chiralities. But for a wide range of applications high purity mixtures of small and large diameters are sufficient or even required. Here we proof that weak field centrifugation is a diameter independent method for enrichment of semiconducting nanotubes. We show that the non-selective and strong adsorption of polyarylether dispersants on nanostructured carbon surfaces enables simple separation of diverse raw materials with different SWCNT diameter. In addition and for the first time, we demonstrate that increased temperature enables higher purity separation. Furthermore we show that the mode of action behind this electronic enrichment is strongly connected to both colloidal stability and protonation. By giving simple access to electronically sorted SWCNTs of any diameter, the wide dynamic range of weak field centrifugation can provide economical relevance to SWCNTs.

  15. Emittance exchange results

    Energy Technology Data Exchange (ETDEWEB)

    Fliller, R.P., III; /Brookhaven; Koeth, T.; /Rutgers U., Piscataway

    2009-09-01

    The promise of next-generation light sources depends on the availability of ultra-low emittance electron sources. One method of producing low transverse emittance beams is to generate a low longitudinal emittance beam and exchange it with a large transverse emittance. Experiments are underway at Fermilab's A0 Photoinjector and ANL's Argonne Wakefield Accelerator using the exchange scheme of Kim and Sessler. The experiment at the A0 Photoinjector exchanges a large longitudinal emittance with a small transverse emittance. AWA expects to exchange a large transverse emittance with a small longitudinal emittance. In this paper we discuss recent results at A0 and AWA and future plans for these experiments.

  16. Emittance Exchange Results

    Energy Technology Data Exchange (ETDEWEB)

    Fliller III,R.; Koeth, T.

    2009-05-04

    The promise of next-generation light sources depends on the availability of ultra-low emittance electron sources. One method of producing low transverse emittance beams is to generate a low longitudinal emittance beam and exchange it with a large transverse emittance. Experiments are underway at Fermilab's A0 Photoinjector and ANL's Argonne Wakefield Accelerator using the exchange scheme of Kim and Sessler. The experiment at the A0 Photoinjector exchanges a large longitudinal emittance with a small transverse emittance. AWA expects to exchange a large transverse emittance with a small longitudinal emittance. In this paper we discuss recent results at A0 and AWA and future plans for these experiments.

  17. Aberration Corrected Emittance Exchange

    CERN Document Server

    Nanni, Emilio A

    2015-01-01

    Full exploitation of emittance exchange (EEX) requires aberration-free performance of a complex imaging system including active radio-frequency (RF) elements which can add temporal distortions. We investigate the performance of an EEX line where the exchange occurs between two dimensions with normalized emittances which differ by orders of magnitude. The transverse emittance is exchanged into the longitudinal dimension using a double dog-leg emittance exchange setup with a 5 cell RF deflector cavity. Aberration correction is performed on the four most dominant aberrations. These include temporal aberrations that are corrected with higher order magnetic optical elements located where longitudinal and transverse emittance are coupled. We demonstrate aberration-free performance of emittances differing by 4 orders of magnitude, i.e. an initial transverse emittance of $\\epsilon_x=1$ pm-rad is exchanged with a longitudinal emittance of $\\epsilon_z=10$ nm-rad.

  18. Selective functionalization and loading of biomolecules in crystalline silicon nanotube field-effect-transistors.

    Science.gov (United States)

    Kwon, Soonshin; Chen, Zack C Y; Noh, Hyunwoo; Lee, Ju Hun; Liu, Hang; Cha, Jennifer N; Xiang, Jie

    2014-07-21

    Crystalline silicon nanotubes (Si NTs) provide distinctive advantages as electrical and biochemical analysis scaffolds through their unique morphology and electrical tunability compared to solid nanowires or amorphous/non-conductive nanotubes. Such potential is investigated in this report. Gate-dependent four-probe current-voltage analysis reveals electrical properties such as resistivity to differ by nearly 3 orders of magnitude between crystalline and amorphous Si NTs. Analysis of transistor transfer characteristics yields a field effect mobility of 40.0 cm(2) V(-1) s(-1) in crystalline Si NTs. The hollow morphology also allows selective inner/outer surface functionalization and loading capability either as a carrier for molecular targets or as a nanofluidic channel for biomolecular assays. We present for the first time a demonstration of internalization of fluorescent dyes (rhodamine) and biomolecules (BSA) in Si NTs as long as 22 μm in length.

  19. Are Nanotube Architectures More Advantageous Than Nanowire Architectures For Field Effect Transistors?

    KAUST Repository

    Fahad, Hossain M.

    2012-06-27

    Decade long research in 1D nanowire field effect transistors (FET) shows although it has ultra-low off-state leakage current and a single device uses a very small area, its drive current generation per device is extremely low. Thus it requires arrays of nanowires to be integrated together to achieve appreciable amount of current necessary for high performance computation causing an area penalty and compromised functionality. Here we show that a FET with a nanotube architecture and core-shell gate stacks is capable of achieving the desirable leakage characteristics of the nanowire FET while generating a much larger drive current with area efficiency. The core-shell gate stacks of silicon nanotube FETs tighten the electrostatic control and enable volume inversion mode operation leading to improved short channel behavior and enhanced performance. Our comparative study is based on semi-classical transport models with quantum confinement effects which offers new opportunity for future generation high performance computation.

  20. A comparative study of field emission from NanoBuds, nanographite and pure or N-doped single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Kleshch, V.I. [Department of Physics, M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); A.M. Prokhorov General Physics Institute, RAS, 119991 Moscow (Russian Federation); Susi, T.; Nasibulin, A.G.; Kauppinen, E.I. [NanoMaterials Group, Department of Applied Physics, Aalto University, P.O. Box 15100, 00076 Aalto, Espoo (Finland); Obraztsova, E.D. [A.M. Prokhorov General Physics Institute, RAS, 119991 Moscow (Russian Federation); Obraztsov, A.N. [Department of Physics, M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Department of Physics and Mathematics, University of Eastern Finland, 80101 Joensuu (Finland)

    2010-12-15

    Field emission characteristics of multi-emitter flat cathodes prepared from NanoBuds, few-layer graphite flakes (nanographite, NG) and pure or N-doped single-wall carbon nanotubes (SWNTs) have been examined. The cathodes demonstrated a low-voltage electron emission with the threshold field values of few Volts per micron, which were ascribed to the high-aspect ratio of nanocarbons. The films of NanoBuds and NG possess excellent emission pattern homogeneity with an emission site density of more than 10{sup 5} cm{sup -2}. This is much higher than for cathodes made of conventional SWNT films. It was found that the achievable maximal current density depends on the type of carbon material and reaches 10 A/cm{sup 2} for NanoBuds film, while for the NG film cathodes, it is about one order of magnitude less. Possible mechanisms responsible for the experimentally observed differences are discussed. The materials examined are of great interest due to their high-emission characteristics and are promising for the development of new types of vacuum electronic devices. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Core-Shell Structure of a Silicon Nanorod/Carbon Nanotube Field Emission Cathode

    Directory of Open Access Journals (Sweden)

    Bohr-Ran Huang

    2012-01-01

    Full Text Available A novel core-shell structure of silicon nanorods/carbon nanotubes (SiNRs/CNTs is developed for use in field emission cathodes. The CNTs were synthesized on SiNRs, using the Ag-assisted electroless etching technique to form the SiNRs/CNT core-shell structure. This resulting SiNRs/CNT field emission cathode demonstrated improved field emission properties including a lower turn-on electric field on (1.3 V/μm, 1 μA/cm2, a lower threshold electric field th (1.8 V/μm, 1 mA/cm2, and a higher enhancement factor (2347. These superior properties indicate that this core-shell structure of SiNRs/CNTs has good potential in field emission cathode applications.

  2. Field-ion microscopy observation of single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    张兆祥; 张耿民; 杜民; 金新喜; 侯士敏; 孙建平; 顾镇南; 赵兴钰; 刘惟敏; 吴锦雷; 薛增泉

    2002-01-01

    Field-ion microscopy (FIM), a tool for surface analysis with atomic resolution, has been employed to observethe end structure of single-walled carbon nanotubes (SWCNTs). FIM images revealed the existence of open SWCNTends. Amorphous carbon atoms were also observed to occur around SWCNTs and traditional field evaporation failedto remove them. Heat treatment was found to be efficacious in altering the end structures of SWCNT bundles. Carbonand oxygen atoms released from heated tungsten filament are believed to be responsible for the decoration imposed onthe SWCNT ends.

  3. Competition between magnetic field dependent band structure and coherent backscattering in multiwall carbon nanotubes

    Science.gov (United States)

    Stojetz, B.; Roche, S.; Miko, C.; Triozon, F.; Forró, L.; Strunk, C.

    2007-03-01

    Magnetotransport measurements in large diameter multiwall carbon nanotubes (20 40 nm) demonstrate the competition of a magnetic-field dependent bandstructure and Altshuler Aronov Spivak oscillations. By means of an efficient capacitive coupling to a backgate electrode, the magnetoconductance oscillations are explored as a function of Fermi level shift. Changing the magnetic field orientation with respect to the tube axis and by ensemble averaging, allows the contributions of different Aharonov Bohm phases to be identified. The results are in qualitative agreement with numerical calculations of the band structure and the conductance.

  4. Noncollinear Spin-Orbit Magnetic Fields in a Carbon Nanotube Double Quantum Dot

    Science.gov (United States)

    Hels, M. C.; Braunecker, B.; Grove-Rasmussen, K.; Nygârd, J.

    2016-12-01

    We demonstrate experimentally that noncollinear intrinsic spin-orbit magnetic fields can be realized in a curved carbon nanotube two-segment device. Each segment, analyzed in the quantum dot regime, shows near fourfold degenerate shell structure allowing for identification of the spin-orbit coupling and the angle between the two segments. Furthermore, we determine the four unique spin directions of the quantum states for specific shells and magnetic fields. This class of quantum dot systems is particularly interesting when combined with induced superconducting correlations as it may facilitate unconventional superconductivity and detection of Cooper pair entanglement. Our device comprises the necessary elements.

  5. Solid-state single-photon emitters

    Science.gov (United States)

    Aharonovich, Igor; Englund, Dirk; Toth, Milos

    2016-10-01

    Single-photon emitters play an important role in many leading quantum technologies. There is still no 'ideal' on-demand single-photon emitter, but a plethora of promising material systems have been developed, and several have transitioned from proof-of-concept to engineering efforts with steadily improving performance. Here, we review recent progress in the race towards true single-photon emitters required for a range of quantum information processing applications. We focus on solid-state systems including quantum dots, defects in solids, two-dimensional hosts and carbon nanotubes, as these are well positioned to benefit from recent breakthroughs in nanofabrication and materials growth techniques. We consider the main challenges and key advantages of each platform, with a focus on scalable on-chip integration and fabrication of identical sources on photonic circuits.

  6. Emittance measurements of the CLIO electron beam

    Science.gov (United States)

    Chaput, R.; Devanz, G.; Joly, P.; Kergosien, B.; Lesrel, J.

    1997-02-01

    We have designed a setup to measure the transverse emittance at the CLIO accelerator exit, based on the "3 gradients" method. The beam transverse size is measured simply by scanning it with a steering coil across a fixed jaw and recording the transmitted current, at various quadrupole strengths. A code then performs a complete calculation of the emittance using the transfer matrix of the quadrupole instead of the usual classical lens approximation. We have studied the influence of various parameters on the emittance: Magnetic field on the e-gun and the peak current. We have also improved a little the emittance by replacing a mismatched pipe between the buncher and accelerating section to avoid wake-field effects; The resulting improvements of the emittance have led to an increase in the FEL emitted power.

  7. Influence of Zn ion implantation on structures and field emission properties of multi-walled carbon nanotube arrays

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The structures and field emission properties of multi-walled carbon nanotube arrays implanted with Zn+ by MEVVA ion implanter have been investigated.The results revealed that Zn+implantation induced structural damage and that the top of carbon nanotubes with multi-layered graphite structure were transformed into carbon nanowires with amorphous structure.Meanwhile,C:Zn solid solution was synthesized after Zn+ implantation.The turn-on field and threshold field were 0.80 and 1.31 V/μm,respectively for original multi-walled carbon nanotube arrays and were reduced to 0.66 and 1.04 V/μm due to the synthesis of C and Zn composite,in which the work function was reduced after low doses of Zn+implantation.It is indicated that low doses of Zn+implantation can improve field emission performance of multi-walled carbon nanotube arrays.Otherwise,high doses of Zn+implantation can reduce field emission properties of multi-walled carbon nanotube arrays,because radiation damage reduces the electric field enhancement factor.

  8. Single Nucleotide Polymorphism Detection Using Au-Decorated Single-Walled Carbon Nanotube Field Effect Transistors

    Directory of Open Access Journals (Sweden)

    Keum-Ju Lee

    2011-01-01

    Full Text Available We demonstrate that Au-cluster-decorated single-walled carbon nanotubes (SWNTs may be used to discriminate single nucleotide polymorphism (SNP. Nanoscale Au clusters were formed on the side walls of carbon nanotubes in a transistor geometry using electrochemical deposition. The effect of Au cluster decoration appeared as hole doping when electrical transport characteristics were examined. Thiolated single-stranded probe peptide nucleic acid (PNA was successfully immobilized on Au clusters decorating single-walled carbon nanotube field-effect transistors (SWNT-FETs, resulting in a conductance decrease that could be explained by a decrease in Au work function upon adsorption of thiolated PNA. Although a target single-stranded DNA (ssDNA with a single mismatch did not cause any change in electrical conductance, a clear decrease in conductance was observed with matched ssDNA, thereby showing the possibility of SNP (single nucleotide polymorphism detection using Au-cluster-decorated SWNT-FETs. However, a power to discriminate SNP target is lost in high ionic environment. We can conclude that observed SNP discrimination in low ionic environment is due to the hampered binding of SNP target on nanoscale surfaces in low ionic conditions.

  9. First-principles density-functional investigation of the effect of water on the field emission of carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, L; Zheng, W T; Wen, Q B; Jiang, Q [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials of MOE, Jilin University, QianWei Road 2699, Changchun 130012 (China)

    2007-04-18

    The geometrical structures and the field-emission properties of capped (5, 5) single-walled carbon nanotubes with water adsorbed on the tip with and without an applied electric field have been investigated using first-principles density-functional theory. It is found that the structures of carbon nanotubes with water molecules are stable under field-emission conditions. The dipole moments induced by the adsorption of water molecules point from the water molecules to the CNT tips. The Mulliken charges are redistributed and accumulated on the carbon nanotube tips. Under an applied electric field, the number of Mulliken charges that transfer from the carbon nanotube body to both its tip and water molecules increases with the increase of the number of water molecules. The local density of states at the Fermi level increases with the adsorption of water molecules. These results elucidate that the field-emission properties of carbon nanotubes can be enhanced by the adsorption of water molecules, and are consistent with the experimental results.

  10. Electrophoretic Carb on Nanotub e Field Emission Layer for Plasma Display Panels

    Institute of Scientific and Technical Information of China (English)

    Qifa Liu; Zhuoqing Yang; Yan Wang; Guifu Ding∗

    2012-01-01

    A carbon-nanotube (CNT) electrophoretic deposition (EPD) process has been developed to pre-pare a field emission layer in plasma display panels (PDP) for discharge voltage reduction. The CNT layer as a source of discharge priming electrons has been fabricated on the PDP front panel. The balling grinding, mix-acid treatment and EPD parameters have been investigated in order to obtain good uniformity and ex-cellent field emission capability of CNT layer, in order to meet the specifications of CNTs in PDP cell. The measured turn-on field was around 1.1 V/µm in the field emission testing while the minimum sustaining voltage was decreased by 30∼40 V with the use of CNT layer in the discharge testing.

  11. Radio and millimeter properties of $z \\sim 5.7$ Ly$\\alpha$ emitters in the COSMOS field: limits on radio AGN, submm galaxies, and dust obscuration

    CERN Document Server

    Carilli, C L; Wang, R; Schinnerer, E; Taniguchi, Y; Smolcic, V; Bertoldi, F; Ajiki, M; Nagao, T; Sasaki, S S; Shioya, Y; Aguirre, J E; Blain, A W; Scoville, N Z; Sanders, D B

    2006-01-01

    We present observations at 1.4 and 250 GHz of the $z\\sim 5.7$ Ly$\\alpha$ emitters (LAE) in the COSMOS field found by Murayama et al.. At 1.4 GHz there are 99 LAEs in the lower noise regions of the radio field. We do not detect any individual source down to 3$\\sigma$ limits of $\\sim 30\\mu$Jy beam$^{-1}$ at 1.4 GHz, nor do we detect a source in a stacking analysis, to a 2$\\sigma$ limit of $2.5\\mu$Jy beam$^{-1}$. At 250 GHz we do not detect any of the 10 LAEs that are located within the central regions of the COSMOS field covered by MAMBO ($20' \\times 20'$) to a typical 2$\\sigma$ limit of $S_{250} 6\\times 10^{24}$ W Hz$^{-1}$ in the LAE sample. The radio and millimeter observations also rule out any highly obscured, extreme starbursts in the sample, ie. any galaxies with massive star formation rates $> 1500$ M$_\\odot$ year$^{-1}$ in the full sample (based on the radio data), or 500 M$_\\odot$ year$^{-1}$ for the 10% of the LAE sample that fall in the central MAMBO field. The stacking analysis implies an upper li...

  12. Low Emittance X-FEL Development

    CERN Document Server

    Li, K S B; Anghel, A; Bakker, R J; Böge, M; Candel, A E; Dehler, M; Ganter, R; Gough, C; Ingold, G; Leemann, S C; Pedrozzi, M; Raguin, J Y; Rivkin, L; Schlott, V; Streun, A; Wrulich, A F

    2005-01-01

    The Paul Scherrer Institute (PSI) in Switzerland currently develops a Low-Emittance electron-Gun (LEG) based on field-emitter technology [1]. The target is a normalized transverse emittance of 5 10(-8) m rad or less. Such a source is particularly interesting for FELs that target wavelengths below 0.3 nm since it permits a reduction of the required beam-energy and hence, a reduction of the construction- and operational costs of X-ray FELs. That is, for the case that this initial low emittance can be maintained throughout the accelerator. Here we present a concept for a 0.1 nm X-FEL based on LEG, which can be located close to the Swiss Light Source (SLS). Special attention goes to the maintenance of the emittance during the process of acceleration and bunch-compression, in particular in the regimes where either space-charge forces or coherent-synchrotron radiation are of importance.

  13. Flow Field Induced Steady Alignment of Oxidized Multi-walled Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Ai Zhong XU; Ming Shu YANG; Qiang WU; Xiao Ming HU; Lei JIANG

    2005-01-01

    The steady ordered micro-ribbons of oxidized multi-walled carbon nanotubes (MWNTs)were obtained through micro-aperture PTFE membrane by vacuum filtration. After treatment by mixture of concentrated nitric acid and sulfuric acid, the surface functional groups modified MWNTs can be easily dispersed to form a homogeneous suspension. It is found that the steady micro-ribbons existed in the films obtained by vacuum filtration of the suspension. The filtration formed steady flow field and induced steady alignment of oxidized MWNTs. The chemical treatment of MWNTs forming strong interaction between MWNTs is necessity to keep steady of the micro-ribbons microstructure.

  14. Coherent field emission from a multi-walled carbon nanotube with two open-ended branches

    Institute of Scientific and Technical Information of China (English)

    Bai Xin; Zhang Geng-Min; Wang Ming-Sheng; Zhang Zhao-Xiang; Yu Jie; Zhao Xing-Yu; Guo Deng-Zhu; Xue Zeng-Quan

    2009-01-01

    Interference fringes are obtained in a field-emission microscopy (FEM) study of a multi-walled carbon nanotube (MWCNT) with two open-ended branches.The FEM pattern,which is composed of three parallel streaks,can be interpreted by using classical Young's double-slit interference with the ends of the two MWCNT branches treated as two secondary sources of the electron wave.The origin of the coherency of the electron beams from the two branches is discussed on the basis of the quantitative analysis of the FEM pattern.The result suggests a new approach to obtaining a coherent electron source.

  15. Origins of charge noise in carbon nanotube field-effect transistor biosensors.

    Science.gov (United States)

    Sharf, Tal; Kevek, Joshua W; Deborde, Tristan; Wardini, Jenna L; Minot, Ethan D

    2012-12-12

    Determining the major noise sources in nanoscale field-effect transistor (nanoFET) biosensors is critical for improving bioelectronic interfaces. We use the carbon nanotube (CNT) FET biosensor platform to examine the noise generated by substrate interactions and surface adsorbates, both of which are present in current nanoFET biosensors. The charge noise model is used as a quantitative framework to show that insulating substrates and surface adsorbates are both significant contributors to the noise floor of CNT FET biosensors. Removing substrate interactions and surface adsorbates reduces the power spectral density of background voltage fluctuations by 19-fold.

  16. High current, low voltage carbon nanotube enabled vertical organic field effect transistors.

    Science.gov (United States)

    McCarthy, Mitchell A; Liu, Bo; Rinzler, Andrew G

    2010-09-08

    State-of-the-art performance is demonstrated from a carbon nanotube enabled vertical field effect transistor using an organic channel material. The device exhibits an on/off current ratio >10(5) for a gate voltage range of 4 V with a current density output exceeding 50 mA/cm(2). The architecture enables submicrometer channel lengths while avoiding high-resolution patterning. The ability to drive high currents and inexpensive fabrication may provide the solution for the so-called OLED backplane problem.

  17. Performances of carbon nanotube field effect transistors with altered channel length

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The influence of channel length on the performances of carbon nanotube field effect transistors(CNT-FETs) has been studied.Buffered oxide etching was used to remove approximately a 60 nm layer from the original 100 nm silicon dioxide layer,to thin the dielectric layer of the back gate.Channel length of the CNT-FETs was changed along with the etching process.The dependence of drain-source current on gate voltage was measured to analyze the performance of the CNT-FETs,including the transconductance,carrier mobility,current ON/OFF ratio,etc.The results indicate that the devices still keep good quality.

  18. Dynamic response of carbon nanotube field-effect transistors analyzed by S-parameters measurement

    Energy Technology Data Exchange (ETDEWEB)

    Bethoux, J.-M. [Institut d' Electronique, de Microelectronique et de Nanotechnologie, C.N.R.S. U.M.R. 8520, BP 60069, F-59652, Villeneuve d' Ascq Cedex (France); Happy, H. [Institut d' Electronique, de Microelectronique et de Nanotechnologie, C.N.R.S. U.M.R. 8520, BP 60069, F-59652, Villeneuve d' Ascq Cedex (France)]. E-mail: henri.happy@iemn.univ-lille1.fr; Dambrine, G. [Institut d' Electronique, de Microelectronique et de Nanotechnologie, C.N.R.S. U.M.R. 8520, BP 60069, F-59652, Villeneuve d' Ascq Cedex (France); Derycke, V. [Laboratoire d' Electronique Moleculaire, SPEC, Commissariat a l' Energie Atomique, Saclay F-91191, Gif sur Yvette Cedex (France); Goffman, M. [Laboratoire d' Electronique Moleculaire, SPEC, Commissariat a l' Energie Atomique, Saclay F-91191, Gif sur Yvette Cedex (France); Bourgoin, J.-P. [Laboratoire d' Electronique Moleculaire, SPEC, Commissariat a l' Energie Atomique, Saclay F-91191, Gif sur Yvette Cedex (France)

    2006-12-15

    Carbon nanotube field-effect transistors (CN-FET) with a metallic back gate have been fabricated. By assembling a number of CNs in parallel, driving currents in the mA range have been obtained. The dynamic response of the CN-FETs has been investigated through S-parameters measurements. A current gain (|H {sub 21}|{sup 2}) cut-off frequency (f {sub t}) of 8 GHz, and a maximum stable gain (MSG) value of 10 dB at 1 GHz have been obtained. The extraction of an equivalent circuit is proposed.

  19. Comment on ``Numerical calculation of the temperature distribution and evolution of the field-ion emitter under pulsed and continuous-wave laser irradiation'' [J. Appl. Phys. 59, 1334 (1986)

    Science.gov (United States)

    Gipson, G. Steven

    1987-08-01

    A recent paper having to do with numerical calculations of the temperature distribution in field emitters is criticized for an error in the governing heat-conduction equation used to formulate the finite difference algorithm. The correct form of the equation is derived retaining a possibly significant nonlinear term in the final formula.

  20. Three-dimensional extremely-short optical pulses in carbon nanotube arrays in the presence of an external magnetic field

    Science.gov (United States)

    Zhukov, Alexander V.; Bouffanais, Roland; Belonenko, Mikhail B.; Galkina, Elena N.

    2016-12-01

    In this paper, we study the behavior of three-dimensional extremely-short optical pulses propagating in a system made of carbon nanotubes in the presence of an external magnetic field applied perpendicular both to the nanotube axis and to the direction of propagation of the pulse. The evolution of the electromagnetic field is classically derived on the basis of the Maxwell’s equations. The electronic system of carbon nanotubes is considered in the low-temperature approximation. Our analysis reveals the novel and unique ability of controlling the shape of propagating short optical pulses by tuning the intensity of the applied magnetic field. This effect paves the way for the possible development of innovative applications in optoelectronics.

  1. Field emission mechanism from nanotubes through gas ionization induced nanoscale surface charging

    CERN Document Server

    Zhan, Changhua

    2012-01-01

    Experimental evidences reported in this letter show that the gas ionization induced positive charge accumulation can lead to the electron field emission from carbon nanotubes (CNTs) in an electrode system with proper range of gap spacing, where the CNT film with ethocel was covered with ZnO nanorods. The hypothesis for illustration is suggested that: 1) the cosmic ray ionization frequency increases 108~1010 times due to the metastable population resulted from the interaction between the gases and the CNTs; 2) the flux of positive charges is enhanced in the converged field due to the ZnO nanostructures. The resulted positive charge local density is high enough to trigger the field emission of the CNTs. The methodology may be useful in particle detectors and ionization gas sensors.

  2. A carbon nanotube field emission multipixel x-ray array source for microradiotherapy application

    Science.gov (United States)

    Wang, Sigen; Calderon, Xiomara; Peng, Rui; Schreiber, Eric C.; Zhou, Otto; Chang, Sha

    2011-05-01

    The authors report a carbon nanotube (CNT) field emission multipixel x-ray array source for microradiotherapy for cancer research. The developed multipixel x-ray array source has 50 individually controllable pixels and it has several distinct advantages over other irradiation source including high-temporal resolution (millisecond level), the ability to electronically shape the form, and intensity distribution of the radiation fields. The x-ray array was generated by a CNT cathode array (5×10) chip with electron field emission. A dose rate on the order of >1.2 Gy/min per x-ray pixel beam is achieved at the center of the irradiated volume. The measured dose rate is in good agreement with the Monte Carlo simulation result.

  3. 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).

  4. High current density and longtime stable field electron transfer from large-area densely arrayed graphene nanosheet-carbon nanotube hybrids.

    Science.gov (United States)

    Deng, Jian-Hua; Cheng, Lin; Wang, Fan-Jie; Li, Guo-Zheng; Li, De-Jun; Cheng, Guo-An

    2014-12-10

    Achieving high current and longtime stable field emission from large area (larger than 1 mm(2)), densely arrayed emitters is of great importance in applications for vacuum electron sources. We report here the preparation of graphene nanosheet-carbon nanotube (GNS-CNT) hybrids by following a process of iron ion prebombardment on Si wafers, catalyst-free growth of GNSs on CNTs, and high-temperature annealing. Structural observations indicate that the iron ion prebombardment influences the growth of CNTs quite limitedly, and the self-assembled GNSs sparsely distributed on the tips of CNTs with their sharp edges unfolded outside. The field emission study indicates that the maximum emission current density (Jmax) is gradually promoted after these treatments, and the composition with GNSs is helpful for decreasing the operation fields of CNTs. An optimal Jmax up to 85.10 mA/cm(2) is achieved from a 4.65 mm(2) GNS-CNT sample, far larger than 7.41 mA/cm(2) for the as-grown CNTs. This great increase of Jmax is ascribed to the reinforced adhesion of GNS-CNT hybrids to substrates. We propose a rough calculation and find that this adhesion is promoted by 7.37 times after the three-step processing. We consider that both the ion prebombardment produced rough surface and the wrapping of CNT foot by catalyst residuals during thermal processing are responsible for this enhanced adhesion. Furthermore, the three-step prepared GNS-CNT hybrids present excellent field emission stability at high emission current densities (larger than 20 mA/cm(2)) after being perfectly aged.

  5. Characteristic Features of Stone-Wales Defects in Single-Walled Carbon Nanotube; Adsorption, Dispersion, and Field Emission

    Directory of Open Access Journals (Sweden)

    Seungkwang Roh

    2010-01-01

    Full Text Available Adsorption behaviors of dodecanethiol (C12H25SH molecules are investigated on the surface of single-walled carbon nanotubes (SWCNTs with vibrational and X-ray photoelectron spectrometers. The active adsorption sites are proved as Stone-Wales (SW defects (5–7 ring defects. The SW defect-removed SWCNTs formed by reacting nanotubes with allyl acrylate molecules are compared with pristine SWCNTs in dispersion and field emission. The former shows higher dispersion and field emission than the latter.

  6. 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.

  7. 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.

  8. Impact of Scaling Gate Insulator Thickness on the Performance of Carbon Nanotube Field Effect Transistors (CNTFETs

    Directory of Open Access Journals (Sweden)

    Devi Dass

    2013-05-01

    Full Text Available As scaling down Si MOSFET devices degrade device performance in terms of short channel effects. Carbon nanotube field effect transistor (CNTFET is one of the novel nanoelectronics devices that overcome those MOSFET limitations. The carbon nanotube field effect transistors (CNTFETs have been explored and proposed to be the promising candidate for the next generation of integrated circuit (IC devices. To explore the role of CNTFETs in future integrated circuits, it is important to evaluate their performance. However, to do that we need a model that can accurately describe the behavior of the CNTFETs so that the design and evaluation of circuits using these devices can be made. In this paper, we have investigated the effect of scaling gate insulator thickness on the device performance of cylindrical shaped ballistic CNTFET in terms of transfer characteristics, output characteristics, average velocity, gm/Id ratio, mobile charge, quantum capacitance/insulator capacitance, drive current (Ion, Ion / Ioff ratio, transconductance, and output conductance. We concluded that the device metrics such as Ion, Ion / Ioff ratio, transconductance, and output conductance increases with the decrease in gate insulator thickness. Also, we concluded that the gate insulator thickness reduction causes subthreshold slope close to the theoretical limit of 60 mV/decade and DIBL close to zero at room temperature.

  9. Magnetic field asymmetry and high temperature magnetoresistance in single-walled carbon nanotubes

    Science.gov (United States)

    Cobden, David

    2006-03-01

    The length scales and scattering processes in the one-dimensional electron system in single-walled carbon nanotubes remain only partially understood. Measuring the magnetoresistance, in both linear and nonlinear response, is a way to investigate these processes. In disordered nanotubes with ballistic paths much shorter than the length, we observe magnetoresistance in the metallic regime which at low temperatures resembles the universal fluctuations and weak localization seen in higher dimensional metals. A parabolic magnetoresistance persists at room temperature, indicating a significant role for phase coherence and/or interactions at high temperatures. While the linear resistance of a two-terminal sample must be an even function of magnetic field B by Onsager's principle, the nonlinear resistance need not be. Importantly, the B-asymmetric nonlinear terms can in principle be used to infer the strength of electron-electron interactions in the sample [1]. We have therefore also measured in detail the lowest order B-asymmetric current contributions, with a focus on the B-linear term. This has apparently not been done before in any system. Consistent with general theory, at high temperatures the term is small and has a constant sign independent of Fermi energy. At low temperatures it grows and develops mesoscopic fluctuations. Although these result imply that interactions are involved in the transport, calculations specific to nanotubes are needed in order to extract interaction parameters. This work was done by the authors of Ref [2]. References: [1] E.L. Ivchenko and B. Spivak, Phys. Rev. B 66, 155404 (2002); [2] Jiang Wei, Michael Shimogawa, Zenghui Wang, Iuliana Radu, Robert Dormaier, and David H. Cobden, Phys. Rev. Lett. (Dec. 2005) (cond-mat/0506275).

  10. Field-effect transistors with multiple channels constructed by carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    CHEN; Changxin; ZHANG; Yafei

    2005-01-01

    Single-wall carbon nanotubes (SWNTs) pre-decorated with functional molecules are directly aligned in the AC electric field, which makes SWNTs parallelly bridge the source and drain electrodes and act as the multiple conduction channels of the field-effect transistor (FET). The method avoids the mutual tanglement of SWNTs and makes them align between the source and drain electrodes abreast and dispersedly. It is indicated that aligning SWNTs in the high-volatility solvents can decrease the contaminant around the electrodes and has a function to purify the raw SWNTs. The obtained multi-channel FET not only takes on a high transconductance, but also holds the good reliability and stability.

  11. Intrinsic memory function of carbon nanotube-based ferroelectric field-effect transistor.

    Science.gov (United States)

    Fu, Wangyang; Xu, Zhi; Bai, Xuedong; Gu, Changzhi; Wang, Enge

    2009-03-01

    We demonstrate the intrinsic memory function of ferroelectric field-effect transistors (FeFETs) based on an integration of individual single-walled carbon nanotubes (SWCNTs) and epitaxial ferroelectric films. In contrast to the previously reported "charge-storage" CNT-FET memories, whose operations are haunted by a lack of control over the "charge traps", the present CNT-FeFETs exhibit a well-defined memory hysteresis loop induced by the reversible remnant polarization of the ferroelectric films. Large memory windows approximately 4 V, data retention time up to 1 week, and ultralow power consumption (energy per bit) of femto-joule, are highlighted in this report. Further simulations and experimental results show that the memory device is valid under operation voltage less than 1 V due to an electric-field enhancement effect induced by the ultrathin SWCNTs.

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

    Science.gov (United States)

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

    2016-10-01

    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.

  13. Purification of carbon nanotubes through an electric field near the arranged microelectrodes

    Science.gov (United States)

    Shim, Hyung Cheoul; Lee, Hyung Woo; Yeom, Sujin; Kwak, Yoon Keun; Lee, Seung S.; Kim, Soo Hyun

    2007-03-01

    In this work, we attempt to purify multi-walled carbon nanotubes (MWNTs) using electrophoresis induced by the application of an AC electric field to a set of microelectrodes in a microliquid channel. This purifying method is different from conventional methods based on chemical processes. It was observed that most of the MWNTs could pass along the microliquid channel without attaching to the electrode under specific conditions of 1 kHz, at 0.2 Vrms μm-1. On the other hand, the majority of the carbon impurities attached to the electrodes under identical conditions. Field emission scanning electron microscopy (FESEM) images and Raman spectra confirm that this condition is beneficial for removing carbon impurities. The proposed approach has potential applicability in the development of microdevices that can simultaneously perform the purification and fabrication of MWNTs.

  14. Purification of carbon nanotubes through an electric field near the arranged microelectrodes

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Hyung Cheoul [School of Mechanical, Aerospace and Systems Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, Hyung Woo [Massachusetts Institute of Technology (MIT), Micro and Nano Systems Laboratory, 77 Massachusetts Avenue, Room 5-008, Cambridge, MA 02139 (United States); Yeom, Sujin [School of Mechanical, Aerospace and Systems Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Kwak, Yoon Keun [School of Mechanical, Aerospace and Systems Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, Seung S [School of Mechanical, Aerospace and Systems Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Kim, Soo Hyun [School of Mechanical, Aerospace and Systems Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2007-03-21

    In this work, we attempt to purify multi-walled carbon nanotubes (MWNTs) using electrophoresis induced by the application of an AC electric field to a set of microelectrodes in a microliquid channel. This purifying method is different from conventional methods based on chemical processes. It was observed that most of the MWNTs could pass along the microliquid channel without attaching to the electrode under specific conditions of 1 kHz, at 0.2 V{sub rms} {mu}m{sup -1}. On the other hand, the majority of the carbon impurities attached to the electrodes under identical conditions. Field emission scanning electron microscopy (FESEM) images and Raman spectra confirm that this condition is beneficial for removing carbon impurities. The proposed approach has potential applicability in the development of microdevices that can simultaneously perform the purification and fabrication of MWNTs.

  15. Single-Walled Carbon Nanotube Network Field Effect Transistor as a Humidity Sensor

    Directory of Open Access Journals (Sweden)

    Prasantha R. Mudimela

    2012-01-01

    Full Text Available Single-walled carbon nanotube network field effect transistors were fabricated and studied as humidity sensors. Sensing responses were altered by changing the gate voltage. At the open channel state (negative gate voltage, humidity pulse resulted in the decrease of the source-drain current, and, vice versa, the increase in the source-drain current was observed at the positive gate voltage. This effect was explained by the electron-donating nature of water molecules. The operation speed and signal intensity was found to be dependent on the gate voltage polarity. The positive or negative change in current with humidity pulse at zero-gate voltage was found to depend on the previous state of the gate electrode (positive or negative voltage, respectively. Those characteristics were explained by the charge traps in the gate dielectric altering the effective gate voltage, which influenced the operation of field effect transistor.

  16. 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.

  17. 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.

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

    Directory of Open Access Journals (Sweden)

    Meng Song

    2015-09-01

    Full Text Available 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/cm2, and field enhancement factor of ∼1.3 × 104. 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.

  19. Improved field emission properties of carbon nanotube cathodes by nickel electroplating and corrosion

    Science.gov (United States)

    Xiaojing, Xiao; Yun, Ye; Longwu, Zheng; Tailiang, Guo

    2012-05-01

    Carbon nanotube (CNT) cathodes prepared by electrophoretic deposition were treated by a combination of nickel electroplating and cathode corrosion technologies. The characteristics of the samples were measured by scanning electron microscopy, energy dispersive X-ray spectroscopy, J-E and F—N plots. After the treatment, the CNT cathodes showed improved field emission properties such as turn-on field, threshold electric field, current density, stability and luminescence uniformity. Concretely, the turn-on field decreased from 0.95 to 0.45 V/μm at an emission current density of 1 mA/cm2, and the threshold electric field decreased from 0.99 to 0.46 V/μm at a current density of 3 mA/cm2. The maximum current density was up to 7 mA/cm2 at a field of 0.48 V/μm. In addition, the current density of the CNT cathodes fluctuated at around 0.7 mA/cm2 for 20 h, with an initial current density 0.75 mA/cm2. The improvement in field emission properties was found to be due to the exposure of more CNT tips, the wider gaps among the CNTs and the infiltration of nickel particles.

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

    Science.gov (United States)

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

    2015-09-01

    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/cm2, and field enhancement factor of ˜1.3 × 104. 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.

  1. Improved field emission performance of carbon nanotube by introducing copper metallic particles.

    Science.gov (United States)

    Chen, Yiren; Jiang, Hong; Li, Dabing; Song, Hang; Li, Zhiming; Sun, Xiaojuan; Miao, Guoqing; Zhao, Haifeng

    2011-10-03

    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.

  2. Unique Characteristics of Vertical Carbon Nanotube Field-effect Transistors on Silicon

    KAUST Repository

    Li, Jingqi

    2014-07-01

    A vertical carbon nanotube field-effect transistor (CNTFET) based on silicon (Si) substrate has been proposed and simulated using a semi-classical theory. A single-walled carbon nanotube (SWNT) and an n-type Si nanowire in series construct the channel of the transistor. The CNTFET presents ambipolar characteristics at positive drain voltage (Vd) and n-type characteristics at negative Vd. The current is significantly influenced by the doping level of n-Si and the SWNT band gap. The n-branch current of the ambipolar characteristics increases with increasing doping level of the n-Si while the p-branch current decreases. The SWNT band gap has the same influence on the p-branch current at a positive Vd and n-type characteristics at negative Vd. The lower the SWNT band gap, the higher the current. However, it has no impact on the n-branch current in the ambipolar characteristics. Thick oxide is found to significantly degrade the current and the subthreshold slope of the CNTFETs.

  3. Influence of contact height on the performance of vertically aligned carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi

    2013-01-01

    Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been experimentally demonstrated (J. Li et al., Carbon, 2012, 50, 4628-4632). The source and drain contact heights in vertical CNTFETs could be much higher than in flat CNTFETs if the fabrication process is not optimized. To understand the impact of contact height on transistor performance, we use a semi-classical method to calculate the characteristics of CNTFETs with different contact heights. The results show that the drain current decreases with increasing contact height and saturates at a value governed by the thickness of the oxide. The current reduction caused by the increased contact height becomes more significant when the gate oxide is thicker. The higher the drain voltage, the larger the current reduction. It becomes even worse when the band gap of the carbon nanotube is larger. The current can differ by a factor of more than five between the CNTEFTs with low and high contact heights when the oxide thickness is 50 nm. In addition, the influence of the contact height is limited by the channel length. The contact height plays a minor role when the channel length is less than 100 nm. © 2013 The Royal Society of Chemistry.

  4. Rapid detection of Aspergillus flavus in rice using biofunctionalized carbon nanotube field effect transistors.

    Science.gov (United States)

    Villamizar, Raquel A; Maroto, Alicia; Rius, F Xavier

    2011-01-01

    In the present study, we have used carbon nanotube field effect transistors (FET) that have been functionalized with protein G and IgG to detect Aspergillus flavus in contaminated milled rice. The adsorbed protein G on the carbon nanotubes walls enables the IgG anti-Aspergillus antibodies to be well oriented and therefore to display full antigen binding capacity for fungal antigens. A solution of Tween 20 and gelatine was used as an effective blocking agent to prevent the non-specific binding of the antibodies and other moulds and also to protect the transducer against the interferences present in the rice samples. Our FET devices were able to detect at least 10 μg/g of A. flavus in only 30 min. To evaluate the selectivity of our biosensors, Fusarium oxysporum and Penicillium chrysogenum were tested as potential competing moulds for A. flavus. We have proved that our devices are highly selective tools for detecting mycotoxigenic moulds at low concentrations in real samples.

  5. Frequency, delay and velocity analysis for intrinsic channel region of carbon nanotube field effect transistors

    Directory of Open Access Journals (Sweden)

    P. Geetha

    2014-03-01

    Full Text Available Gate wrap around field effect transistor is preferred for its good channel control. To study the high frequency behaviour of the device, parameters like cut-off frequency, transit or delay time, velocity are calculated and plotted. Double-walled and array of channels are considered in this work for enhanced output and impedance matching of the device with the measuring equipment terminal respectively. The perfomance of double-walledcarbon nanotube is compared with single-walled carbon nanotube and found that the device with double-wall shows appreciable improvement in its characteristics. Analysis of these parameters are done with various values of source/drain length, gate length, tube diameters and channel densities. The maximum cut-off frequency is found to be 72.3 THz with corresponding velocity as 5x106 m/s for channel density as 3 and gate length as 11nm. The number of channel is varied from 3 to 21 and found that the perfromance of the device containing double-walled carbon nano tube is better for channel number lesser than or equal to 12. The proposed modelling can be used for designing devices to handle high speed applications of future generation.

  6. Water structures inside and outside single-walled carbon nanotubes under perpendicular electric field

    Institute of Scientific and Technical Information of China (English)

    Zhen XU; Guo-hui HU; Zhi-liang WANG; Zhe-wei ZHOU

    2014-01-01

    The structures of water inside and outside (6,6), (8,8), and (10,10) single-walled carbon nanotubes (SWCNTs) under an electric field perpendicular to the tube axis are investigated by molecular dynamics simulations. The results show that dipole reorientation induced by electric field plays a significant role on the structures of confined water inside and outside SWCNTs. Inside SWCNTs, the average water occupancy and the average number of hydrogen bonds (H-bonds) per water molecule decrease as the electric intensity increases. Because the field intensity is sufficiently strong, the initial water structures inside the SWCNTs are destroyed, and the isolated water clusters are found. Outside SWCNTs, the azimuthal distributions of the density and the average number of H-bonds per water molecule around the solid walls become more and more asymmetric as the electric intensity increases. The percentages of water molecules involved in 0-5 H-bonds for all the three types of SWCNTs under different field intensities are displayed. The results show that those water molecules involved with most H-bonds are the most important to hold the original structures. When the electric field direction is parallel with the original preferred orientation, the density and the H-bond connections in water will be increased; when the electric field direction is perpendicular to the original preferred orientation, the density and the H-bond connections in water will be decreased.

  7. Separation of water-ethanol solutions with carbon nanotubes and electric fields.

    Science.gov (United States)

    Winarto; Takaiwa, Daisuke; Yamamoto, Eiji; Yasuoka, Kenji

    2016-12-07

    Bioethanol has been used as an alternative energy source for transportation vehicles to reduce the use of fossil fuels. The separation of water-ethanol solutions from fermentation processes is still an important issue in the production of anhydrous ethanol. Using molecular dynamics simulations, we investigate the effect of axial electric fields on the separation of water-ethanol solutions with carbon nanotubes (CNTs). In the absence of an electric field, CNT-ethanol van der Waals interactions allow ethanol to fill the CNTs in preference to water, i.e., a separation effect for ethanol. However, as the CNT diameter increases, this ethanol separation effect significantly decreases owing to a decrease in the strength of the van der Waals interactions. In contrast, under an electric field, the energy of the electrostatic interactions within the water molecule structure induces water molecules to fill the CNTs in preference to ethanol, i.e., a separation effect for water. More importantly, the electrostatic interactions are dependent on the water molecule structure in the CNT instead of the CNT diameter. As a result, the separation effect observed under an electric field does not diminish over a wide CNT diameter range. Moreover, CNTs and electric fields can be used to separate methanol-ethanol solutions too. Under an electric field, methanol preferentially fills CNTs over ethanol in a wide CNT diameter range.

  8. 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.

  9. Tumour Cell Membrane Poration and Ablation by Pulsed Low-Intensity Electric Field with Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Lijun Wang

    2015-03-01

    Full Text Available Electroporation is a physical method to increase permeabilization of cell membrane by electrical pulses. Carbon nanotubes (CNTs can potentially act like “lighting rods” or exhibit direct physical force on cell membrane under alternating electromagnetic fields thus reducing the required field strength. A cell poration/ablation system was built for exploring these effects of CNTs in which two-electrode sets were constructed and two perpendicular electric fields could be generated sequentially. By applying this system to breast cancer cells in the presence of multi-walled CNTs (MWCNTs, the effective pulse amplitude was reduced to 50 V/cm (main field/15 V/cm (alignment field at the optimized pulse frequency (5 Hz of 500 pulses. Under these conditions instant cell membrane permeabilization was increased to 38.62%, 2.77-fold higher than that without CNTs. Moreover, we also observed irreversible electroporation occurred under these conditions, such that only 39.23% of the cells were viable 24 h post treatment, in contrast to 87.01% cell viability without presence of CNTs. These results indicate that CNT-enhanced electroporation has the potential for tumour cell ablation by significantly lower electric fields than that in conventional electroporation therapy thus avoiding potential risks associated with the use of high intensity electric pulses.

  10. Edge effect enhanced photo-thermionic emission from a carbon nanotubes array

    Science.gov (United States)

    Li, Chi; Li, Zhenjun; Chen, Ke; Bai, Bing; Dai, Qing

    2017-02-01

    Employing optical field enhancement at the edges of the nanostructures, an enhanced photo-thermionic emission (PTE) was obtained from a well-defined carbon nanotube (CNT) cluster array. Compared with the un-patterned carbon nanotube film, the PTE from the CNT cluster array was enhanced 10 times at the same laser intensity. The concept was proved by the computer simulation as well. We believe that an edge effect enhanced CNT PTE emitter is of great potential for application in next-generation portable and inexpensive vacuum electronic devices.

  11. Silicon based light emitters utilizing radiation from dislocations; electric field induced shift of the dislocation-related luminescence

    NARCIS (Netherlands)

    Arguirov, T.; Mchedlidze, T.; Kittler, M.; Reiche, M.; Wilhelm, T.; Hoang, T.; Holleman, J.; Schmitz, J.

    2009-01-01

    Dislocation rich regions can be controllably formed at a certain location inside a silicon wafer. We studied the light emission properties of such regions located in an electric field of a p–n junction under different excitation conditions. It was found that the luminescence spectra of the dislocati

  12. Reorientation of the high mobility plane in pentacene-based carbon nanotube enabled vertical field effect transistors.

    Science.gov (United States)

    McCarthy, Mitchell A; Liu, Bo; Jayaraman, Ramesh; Gilbert, Stephen M; Kim, Do Young; So, Franky; Rinzler, Andrew G

    2011-01-25

    The large current densities attained by carbon nanotube enabled vertical field effect transistors using crystalline organic channel materials are somewhat unexpected given the known large anisotropy in the mobility of crystalline organics and their conventional ordering on dielectric surfaces which tends to orient their high mobility axes parallel to the surface. This seeming contradiction is resolved by the finding that the nanotubes induce a molecular ordering that reorients the high mobility axes to favor current flow in a direction perpendicular to the substrate surface.

  13. Carbon nanotube substrates and catalyzed hot stamp for polishing and patterning the substrates

    Science.gov (United States)

    Wang, Yuhuang [Evanston, IL; Hauge, Robert H [Houston, TX; Schmidt, Howard K [Houston, TX; Kim, Myung Jong [Houston, TX; Kittrell, W Carter [Houston, TX

    2009-09-08

    The present invention is generally directed to catalyzed hot stamp methods for polishing and/or patterning carbon nanotube-containing substrates. In some embodiments, the substrate, as a carbon nanotube fiber end, is brought into contact with a hot stamp (typically at 200-800.degree. C.), and is kept in contact with the hot stamp until the morphology/patterns on the hot stamp have been transferred to the substrate. In some embodiments, the hot stamp is made of material comprising one or more transition metals (Fe, Ni, Co, Pt, Ag, Au, etc.), which can catalyze the etching reaction of carbon with H.sub.2, CO.sub.2, H.sub.2O, and/or O.sub.2. Such methods can (1) polish the carbon nanotube-containing substrate with a microscopically smooth finish, and/or (2) transfer pre-defined patterns from the hot stamp to the substrate. Such polished or patterned carbon nanotube substrates can find application as carbon nanotube electrodes, field emitters, and field emitter arrays for displays and electron sources.

  14. The Luminosity Function and Star Formation Rate between Redshifts of 0.07 and 1.47 for Narrow-band Emitters in the Subaru Deep Field

    CERN Document Server

    Ly, C; Kashikawa, N; Shimasaku, K; Doi, M; Nagao, T; Iye, M; Kodama, T; Morokuma, T; Motohara, K; Ly, Chun; Malkan, Matt A.; Kashikawa, Nobunari; Shimasaku, Kazuhiro; Doi, Mamoru; Nagao, Tohru; Iye, Masanori; Kodama, Tadayuki; Morokuma, Tomoki; Motohara, Kentaro

    2006-01-01

    Abridged: Subaru Deep Field line-emitting galaxies in four narrow-band filters at low and intermediate redshifts are presented. Broad-band colors, follow-up optical spectroscopy, and multiple NB filters are used to distinguish Ha, [O II], and [O III] emitters between redshifts of 0.07 and 1.47 to construct their luminosity functions (LFs). These LFs are derived down to faint magnitudes, which allows for a more accurate determination of the faint end slope. With a large (N~200-900) sample for each redshift interval, a Schechter profile is fitted to each LF. Prior to dust extinction corrections, the [O III] and [O II] LFs reported in this paper agree reasonably well with those of Hippelein et al. The z=0.08 Ha LF, which reaches two orders of magnitude fainter than Gallego et al., is steeper by 25%. This indicates that there are more low luminosity star-forming galaxies for z1, the star-formation rate densities are more or less constant. The latter is consistent with previous UV and [O II] measurements. Below z&...

  15. Nanofabrication of Arrays of Silicon Field Emitters with Vertical Silicon Nanowire Current Limiters and Self-Aligned Gates

    Science.gov (United States)

    2016-08-19

    Akinwande Department of Electrical Engineering and Computer Science and Microsystems Technology Laboratories, Massachusetts Institute of Technology ...Cambridge, MA 02139, USA E-mail: guerrera@alum.mit.edu Received 16 September 2015, revised 2 December 2015 Accepted for publication 11 January 2016...series with the tip. Using the current voltage characteristics and with the aid of numerical device models , we estimated the tip radius of our field

  16. Enhanced field emission from lanthanum hexaboride coated multiwalled carbon nanotubes: Correlation with physical properties

    Energy Technology Data Exchange (ETDEWEB)

    Patra, Rajkumar; Ghosh, S., E-mail: santanu1@physics.iitd.ac.in [Nanostech Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India); Sheremet, E.; Rodriguez, R. D.; Lehmann, D.; Zahn, D. R. T. [Semiconductor Physics, Technische Universität Chemnitz, 09107 Chemnitz (Germany); Jha, Menaka; Ganguli, A. K. [Department of Chemistry, Indian Institute of Technology Delhi, New Delhi 110016 (India); Schmidt, H. [Department of Materials for Nanoelectronics, Technische Universität Chemnitz, 09107 Chemnitz (Germany); Schulze, S.; Hietschold, M. [Solid Surfaces Analysis, Technische Universität Chemnitz, 09107 Chemnitz (Germany); Schmidt, O. G. [Department of Materials for Nanoelectronics, Technische Universität Chemnitz, 09107 Chemnitz (Germany); Leibniz Institute for Solid State Materials Research, IFW Dresden, Helmholtz Straße 20, 01069 Dresden (Germany)

    2014-10-28

    Detailed results from field emission studies of lanthanum hexaboride (LaB{sub 6}) coated multiwalled carbon nanotube (MWCNT) films, pristine LaB{sub 6} films, and pristine MWCNT films are reported. The films have been synthesized by a combination of chemical and physical deposition processes. An impressive increase in field enhancement factor and temporal stability as well as a reduction in turn-on field and threshold field are observed in LaB{sub 6}-coated MWCNTs compared to pristine MWCNT and pristine LaB{sub 6} films. Surface morphology of the films has been examined by scanning electron microscopy. Introduction of LaB{sub 6} nanoparticles on the outer walls of CNTs LaB{sub 6}-coated MWCNTs films is confirmed by transmission electron microscopy. The presence of LaB{sub 6} was confirmed by X-ray photoelectron spectroscopy results and further validated by the Raman spectra. Raman spectroscopy also shows 67% increase in defect concentration in MWCNTs upon coating with LaB{sub 6} and an upshift in the 2D band that could be attributed to p-type doping. Ultraviolet photoelectron spectroscopy studies reveal a reduction in the work function of LaB{sub 6}-coated MWCNT with respect to its pristine counterpart. The enhanced field emission properties in LaB{sub 6}-coated MWCNT films are correlated with a change in microstructure and work function.

  17. Enhanced field emission from lanthanum hexaboride coated multiwalled carbon nanotubes: Correlation with physical properties

    Science.gov (United States)

    Patra, Rajkumar; Ghosh, S.; Sheremet, E.; Jha, Menaka; Rodriguez, R. D.; Lehmann, D.; Ganguli, A. K.; Schmidt, H.; Schulze, S.; Hietschold, M.; Zahn, D. R. T.; Schmidt, O. G.

    2014-10-01

    Detailed results from field emission studies of lanthanum hexaboride (LaB6) coated multiwalled carbon nanotube (MWCNT) films, pristine LaB6 films, and pristine MWCNT films are reported. The films have been synthesized by a combination of chemical and physical deposition processes. An impressive increase in field enhancement factor and temporal stability as well as a reduction in turn-on field and threshold field are observed in LaB6-coated MWCNTs compared to pristine MWCNT and pristine LaB6 films. Surface morphology of the films has been examined by scanning electron microscopy. Introduction of LaB6 nanoparticles on the outer walls of CNTs LaB6-coated MWCNTs films is confirmed by transmission electron microscopy. The presence of LaB6 was confirmed by X-ray photoelectron spectroscopy results and further validated by the Raman spectra. Raman spectroscopy also shows 67% increase in defect concentration in MWCNTs upon coating with LaB6 and an upshift in the 2D band that could be attributed to p-type doping. Ultraviolet photoelectron spectroscopy studies reveal a reduction in the work function of LaB6-coated MWCNT with respect to its pristine counterpart. The enhanced field emission properties in LaB6-coated MWCNT films are correlated with a change in microstructure and work function.

  18. Post-treatment method for improving field emission from carbon nanotubes/nanofibers

    Institute of Scientific and Technical Information of China (English)

    GUO Ping-sheng; SUN Zhuo; ZHENG Zhi-hao

    2006-01-01

    A novel post-treatment method is reported for improving the field emission characteristics of screen-printed carbon nanotubes/nanofibers (CNTs/CNFs) cathodes.After the treatment at the temperature of 500℃ in H2 and C2H2 gas for 20 minutes,the CNTs/CNFs cathodes exhibit much better field emission properties than those untreated.The emission current increases from 0.02 mA/cm2 to 0.5 mA/cm2 at 3.9 V/μm with a decrease in the turn-on field from 2.4 V to 1.8 V ,and the emission site density is increased by almost four orders in magnitude.The enhanced field emission of treated CNTs/CNFs cathodes is attributed to the appearance of a large number of exposed CNTs/CNFs caused by heat treatment.This surface morphology is very favorable for the electron field emission.

  19. Multinozzle Emitter Arrays for Nanoelectrospray Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Pan; Wang, Hung-Ta; Yang, Peidong; Wang, Daojing

    2011-06-16

    Mass spectrometry (MS) is the enabling technology for proteomics and metabolomics. However, dramatic improvements in both sensitivity and throughput are still required to achieve routine MS-based single cell proteomics and metabolomics. Here, we report the silicon-based monolithic multinozzle emitter array (MEA), and demonstrate its proof-of-principle applications in high-sensitivity and high-throughput nanoelectrospray mass spectrometry. Our MEA consists of 96 identical 10-nozzle emitters in a circular array on a 3-inch silicon chip. The geometry and configuration of the emitters, the dimension and number of the nozzles, and the micropillar arrays embedded in the main channel, can be systematically and precisely controlled during the microfabrication process. Combining electrostatic simulation and experimental testing, we demonstrated that sharpened-end geometry at the stem of the individual multinozzle emitter significantly enhanced the electric fields at its protruding nozzle tips, enabling sequential nanoelectrospray for the high-density emitter array. We showed that electrospray current of the multinozzle emitter at a given total flow rate was approximately proportional to the square root of the number of its spraying-nozzles, suggesting the capability of high MS sensitivity for multinozzle emitters. Using a conventional Z-spray mass spectrometer, we demonstrated reproducible MS detection of peptides and proteins for serial MEA emitters, achieving sensitivity and stability comparable to the commercial capillary emitters. Our robust silicon-based MEA chip opens up the possibility of a fully-integrated microfluidic system for ultrahigh-sensitivity and ultrahigh-throughput proteomics and metabolomics.

  20. Size dependency and potential field influence on deriving mechanical properties of carbon nanotubes using molecular dynamics

    Directory of Open Access Journals (Sweden)

    K.G.S. Dilrukshi

    2015-07-01

    Full Text Available A thorough understanding on the mechanical properties of carbon nanotube (CNT is essential in extending the advanced applications of CNT based systems. However, conducting experiments to estimate mechanical properties at this scale is extremely challenging. Therefore, development of mechanistic models to estimate the mechanical properties of CNTs along with the integration of existing continuum mechanics concepts is critically important. This paper presents a comprehensive molecular dynamics simulation study on the size dependency and potential function influence of mechanical properties of CNT. Commonly used reactive bond order (REBO and adaptive intermolecular reactive bond order (AIREBO potential functions were considered in this regard. Young’s modulus and shear modulus of CNTs are derived by integrating classical continuum mechanics concepts with molecular dynamics simulations. The results indicate that the potential function has a significant influence on the estimated mechanical properties of CNTs, and the influence of potential field is much higher when studying the torsional behaviour of CNTs than the tensile behaviour.

  1. Reorientation of single-wall carbon nanotubes in negative anisotropy liquid crystals by an electric field

    Directory of Open Access Journals (Sweden)

    Amanda García-García

    2016-06-01

    Full Text Available Single-wall carbon nanotubes (SWCNT are anisotropic nanoparticles that can cause modifications in the electrical and electro-optical properties of liquid crystals. The control of the SWCNT concentration, distribution and reorientation in such self-organized fluids allows for the possibility of tuning the liquid crystal properties. The alignment and reorientation of CNTs are studied in a system where the liquid crystal orientation effect has been isolated. Complementary studies including Raman spectroscopy, microscopic inspection and impedance studies were carried out. The results reveal an ordered reorientation of the CNTs induced by an electric field, which does not alter the orientation of the liquid crystal molecules. Moreover, impedance spectroscopy suggests a nonnegligible anchoring force between the CNTs and the liquid crystal molecules.

  2. Second harmonic generation in carbon nanotubes induced by transversal electrostatic field.

    Science.gov (United States)

    Trolle, Mads Lund; Pedersen, Thomas Garm

    2013-08-14

    Carbon nanotubes (CNTs) of armchair and zigzag type contain an inversion centre, and are thus intrinsically unable to generate dipole even-order nonlinearities, such as second harmonic generation (SHG). Breaking the inversion symmetry by application of an external voltage transversal to the CNT axis will, however, induce a second harmonic response. Similarly, additional non-vanishing second harmonic tensor elements will be induced in chiral tubes already displaying an intrinsic response. Many geometries realizing such a setup can be envisaged, e.g., an experimental gate setup or deposition of CNTs on, or integration in, strongly polarized host media, perhaps facilitating a tunable second harmonic response. In this work, we calculate the SHG signal from CNTs under transversally applied electric fields based on a tight-binding model.

  3. Detection of influenza A virus using carbon nanotubes field effect transistor based DNA sensor

    Science.gov (United States)

    Tran, Thi Luyen; Nguyen, Thi Thuy; Huyen Tran, Thi Thu; Chu, Van Tuan; Thinh Tran, Quang; Tuan Mai, Anh

    2017-09-01

    The carbon nanotubes field effect transistor (CNTFET) based DNA sensor was developed, in this paper, for detection of influenza A virus DNA. Number of factors that influence the output signal and analytical results were investigated. The initial probe DNA, decides the available DNA strands on CNTs, was 10 μM. The hybridization time for defined single helix was 120 min. The hybridization temperature was set at 30 °C to get a net change in drain current of the DNA sensor without altering properties of any biological compounds. The response time of the DNA sensor was less than one minute with a high reproducibility. In addition, the DNA sensor has a wide linear detection range from 1 pM to 10 nM, and a very low detection limit of 1 pM. Finally, after 7-month storage in 7.4 pH buffer, the output signal of DNA sensor recovered 97%.

  4. A mathematical space mapping model for ballistic carbon nanotube field-effect transistors

    Science.gov (United States)

    Emamifar, Farnousha; Yousefi, Reza

    2016-11-01

    In this study, a mathematical model is presented based on mathematical space mapping for ballistic carbon nanotube field-effect transistors. This model is generalized from another model that was based on the concept of neural space mapping to calculate the three parameters of a coarse model. These parameters were the threshold voltage, the Early voltage, and assumed constant k of a modified "level 1" MOSFET model in simulation program with integrated circuit emphasis (SPICE). In this work, three analytical relations are introduced to replace the neural networks of the main model. The comparisons between the proposed model and a well-known reference model, named FETToy, show that the proposed model had reasonable accuracy in terms of different biases and physical parameters.

  5. Modeling and simulation of carbon nanotube field effect transistor and its circuit application

    Science.gov (United States)

    Singh, Amandeep; Saini, Dinesh Kumar; Agarwal, Dinesh; Aggarwal, Sajal; Khosla, Mamta; Raj, Balwinder

    2016-07-01

    The carbon nanotube field effect transistor (CNTFET) is modelled for circuit application. The model is based on the transport mechanism and it directly relates the transport mechanism with the chirality. Also, it does not consider self consistent equations and thus is used to develop the HSPICE compatible circuit model. For validation of the model, it is applied to the top gate CNTFET structure and the MATLAB simulation results are compared with the simulations of a similar structure created in NanoTCAD ViDES. For demonstrating the circuit compatibility of the model, two circuits viz. inverter and SRAM are designed and simulated in HSPICE. Finally, SRAM performance metrics are compared with those of device simulations from Nano TCAD ViDES.

  6. Reorientation of single-wall carbon nanotubes in negative anisotropy liquid crystals by an electric field

    Science.gov (United States)

    García-García, Amanda; Vergaz, Ricardo; Algorri, José F; Zito, Gianluigi; Cacace, Teresa; Marino, Antigone; Otón, José M

    2016-01-01

    Summary Single-wall carbon nanotubes (SWCNT) are anisotropic nanoparticles that can cause modifications in the electrical and electro-optical properties of liquid crystals. The control of the SWCNT concentration, distribution and reorientation in such self-organized fluids allows for the possibility of tuning the liquid crystal properties. The alignment and reorientation of CNTs are studied in a system where the liquid crystal orientation effect has been isolated. Complementary studies including Raman spectroscopy, microscopic inspection and impedance studies were carried out. The results reveal an ordered reorientation of the CNTs induced by an electric field, which does not alter the orientation of the liquid crystal molecules. Moreover, impedance spectroscopy suggests a nonnegligible anchoring force between the CNTs and the liquid crystal molecules. PMID:27547599

  7. Predicting excitonic gaps of semiconducting single-walled carbon nanotubes from a field theoretic analysis

    Science.gov (United States)

    Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.

    2015-02-01

    We demonstrate that a nonperturbative framework for the treatment of the excitations of single-walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. We test this theory explicitly on the data reported by Dukovic et al. [Nano Lett. 5, 2314 (2005), 10.1021/nl0518122] and Sfeir et al. [Phys. Rev. B 82, 195424 (2010), 10.1103/PhysRevB.82.195424] and so demonstrate the method works over a wide range of reported excitonic spectra.

  8. Field emission with ultralow turn on voltage from metal decorated carbon nanotubes.

    Science.gov (United States)

    Sridhar, Srividya; Tiwary, Chandrasekhar; Vinod, Soumya; Taha-Tijerina, Jose Jaime; Sridhar, Srividvatha; Kalaga, Kaushik; Sirota, Benjamin; Hart, Amelia H C; Ozden, Sehmus; Sinha, Ravindra Kumar; Harsh; Vajtai, Robert; Choi, Wongbong; Kordás, Krisztián; Ajayan, Pulickel M

    2014-08-26

    A simple and scalable method of decorating 3D-carbon nanotube (CNT) forest with metal particles has been developed. The results observed in aluminum (Al) decorated CNTs and copper (Cu) decorated CNTs on silicon (Si) and Inconel are compared with undecorated samples. A significant improvement in the field emission characteristics of the cold cathode was observed with ultralow turn on voltage (Eto ∼ 0.1 V/μm) due to decoration of CNTs with metal nanoparticles. Contact resistance between the CNTs and the substrate has also been reduced to a large extent, allowing us to get stable emission for longer duration without any current degradation, thereby providing a possibility of their use in vacuum microelectronic devices.

  9. Aerosol assisted fabrication of carbon nanotube/zinc oxide arrays for a field emission device.

    Science.gov (United States)

    Byeon, Jeong Hoon; Kim, Jang-Woo

    2013-03-01

    Aerosol deposition of zinc oxide (ZnO) nanoparticles was used to catalyze a silicon substrate site-selectively for a carbon nanotube (CNT) growth. An ambient spark discharge was used to produce aerosol ZnO nanoparticles, and the particle deposition on the substrate through a shadow mask was enhanced by thermophoresis. The ZnO-deposited substrate was then loaded into a chemical vapor deposition chamber, resulting in the formation of CNT/ZnO arrays. The turn-on field of an emission device constructed with the CNT/ZnO arrays was 1.7 V μm(-1) at a current of 2 μA, which was lower than that of the common CNT arrays. Copyright © 2012 Elsevier Inc. All rights reserved.

  10. Au nanoparticles attached carbon nanotubes as a high performance active element in field effect transistor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Myeongsoon; Kim, Don, E-mail: donkim@pknu.ac.kr

    2016-08-15

    The Au nanoparticles attached carbon nanotubes (Au-CNTs), diameter ranged from 40 to 250 nm, were prepared and discussed their chemical and electrical properties. The shape and crystallinity of the carbon nanotubes (CNTs) phase depended main2ly on the diameter of CNTs (r{sub Au-CNT}). Highly crystalline, straight CNTs were observed when the r{sub Au-CNT} exceeded 80 nm, and less crystalline noodle-shaped CNTs were observed when the r{sub Au-CNT} was smaller than 80 nm. The crystallinity of the CNT phase was confirmed by analyzing the G and D bands in their Raman spectra and the electrical conductivities of the Au-CNTs. The electrical conductivity of the highly crystalline carbon phase of Au-CNTs (r{sub Au-CNT} = 250 nm) was ∼10{sup 4} S/cm. The back-gated field effect transistors (FETs) based on the Au-CNTs, which were assembled on a SiO{sub 2}/Si wafer using the dielectrophoresis technique, showed that the Au-CNTs would be a good functional electronic material for future electronic and sensing applications. The transconductance and hole mobility of the FETs, which were assembled with the highly crystalline Au-CNTs (r{sub Au-CNT} = 250 nm), reached to 3.6 × 10{sup −4} A/V and 3.1 × 10{sup 4} cm{sup 2}/V s, respectively. These values are in the middle of those of reported for single walled carbon nanotubes and graphene. However, we could not find any field effect in a CNTFET, which assembled without Au nanoparticles, through the same process. - Highlights: • The shape and crystallinity of the CNTs depended mainly on the diameter of CNTs. • The electrical conductivity of the highly crystalline Au-CNTs was ∼10{sup 4} S/cm. • The Au-CNT FET shows typical p-channel gate effect with the on/off ratio of ∼10{sup 4}. • The Au-CNT FET shows very high transconductance (g{sub m}) and carrier mobility (μ{sub h}).

  11. Beam emittance measurements on multicusp ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Sarstedt, M.; Lee, Y.; Leung, K.N.; Perkins, L.T.; Pickard, D.S.; Weber, M.; Williams, M.D.

    1995-08-01

    Multicusp ion sources are used for various applications. Presently, the implementation of this type of ion source is planned for the development of an ion beam lithography machine, which will be used for the projection of sub-0.2 micron patterns onto a wafer substrate. Since, for this application, a very good beam quality and a small ion energy spread are required, emittance measurements have been performed on a multicusp ion source for various source conditions. It is shown that the installation of proper capacitors between the extraction electrodes is necessary to avoid rf-pickup, which otherwise leads to a distortion of the beam emittance. The influence of the magnetic filter field on the beam emittance has been investigated, and the beam emittance of a dc filament-discharge plasma has also been compared to that of an rf-generated plasma.

  12. Beam emittance measurements on multicusp ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Sarstedt, M.; Lee, Y.; Leung, K.N. [and others

    1995-08-01

    Multicusp ion sources are used for various applications. Presently, the implementation of this type of ion source planned for the development of an ion beam lithography machine, which will be used for the projection of sub-0.2 {mu}m patterns onto a wafer substrate. Since, for this application, a very good beam quality and a small ion energy spread are required, emittance measurements have been performed on a multicusp ion source for various source conditions. It is shown that the installation of proper capacitors between the extraction electrodes is necessary to avoid rf-pickup, which otherwise leads to a distortion of the beam emittance. The influence of the magnetic filter field on the beam emittance has been investigated, and the beam emittance of a dc filament-discharge plasma has also been compared to that of an rf-generated plasma.

  13. Beam emittance measurements on multicusp ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Sarstedt, M.; Lee, Y.; Leung, K.N.; Perkins, L.T.; Pickard, D.S.; Weber, M.; Williams, M.D. [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)

    1996-03-01

    Multicusp ion sources are used for various applications. Presently, the implementation of this type of ion source is planned for the development of an ion beam lithography machine, which will be used for the projection of sub-0.2 {mu}m patterns onto a wafer substrate. Since, for this application, a very good beam quality and a small ion energy spread are required, emittance measurements have been performed on a multicusp ion source for various source conditions. It is shown that the installation of proper capacitors between the extraction electrodes is necessary to avoid rf pickup, which otherwise leads to a distortion of the beam emittance. The influence of the magnetic filter field on the beam emittance has been investigated, and the beam emittance of a dc filament-discharge plasma has also been compared to that of a rf-generated plasma. {copyright} {ital 1996 American Institute of Physics.}

  14. Beam emittance measurements on multicusp ion sources

    Science.gov (United States)

    Sarstedt, M.; Lee, Y.; Leung, K. N.; Perkins, L. T.; Pickard, D. S.; Weber, M.; Williams, M. D.

    1996-03-01

    Multicusp ion sources are used for various applications. Presently, the implementation of this type of ion source is planned for the development of an ion beam lithography machine, which will be used for the projection of sub-0.2 μm patterns onto a wafer substrate. Since, for this application, a very good beam quality and a small ion energy spread are required, emittance measurements have been performed on a multicusp ion source for various source conditions. It is shown that the installation of proper capacitors between the extraction electrodes is necessary to avoid rf pickup, which otherwise leads to a distortion of the beam emittance. The influence of the magnetic filter field on the beam emittance has been investigated, and the beam emittance of a dc filament-discharge plasma has also been compared to that of a rf-generated plasma.

  15. Field Emission Properties of the Graphene Double-Walled Carbon Nanotube Hybrid Films Prepared by Vacuum Filtration and Screen Printing

    OpenAIRE

    Jinzhuo Xu; Tao Feng; Yiwei Chen; Zhuo Sun

    2013-01-01

    The graphene double-walled carbon nanotube (DWCNT) hybrid films were prepared by vacuum filtration and screen printing. Their electron field emission properties have been studied systematically. The electron emission properties of the hybrid films are much better than those of pure DWCNT films and pure graphene films. Comparing with the screen printed films, the vacuum filtered films have many advantages, such as lower turn-on field, higher emission current density, better uniformity, better ...

  16. Hot electrons injection in carbon nanotubes under the influence of quasi-static ac-field

    Science.gov (United States)

    Amekpewu, M.; Mensah, S. Y.; Musah, R.; Mensah, N. G.; Abukari, S. S.; Dompreh, K. A.

    2016-07-01

    The theory of hot electrons injection in carbon nanotubes (CNTs) where both dc electric field (Ez), and a quasi-static ac field exist simultaneously (i.e. when the frequency ω of ac field is much less than the scattering frequency v (ω ≪ v or ωτ ≪ 1, v =τ-1) where τ is relaxation time) is studied. The investigation is done theoretically by solving semi-classical Boltzmann transport equation with and without the presence of the hot electrons source to derive the current densities. Plots of the normalized current density versus dc field (Ez) applied along the axis of the CNTs in the presence and absence of hot electrons reveal ohmic conductivity initially and finally negative differential conductivity (NDC) provided ωτ ≪ 1 (i.e. quasi- static case). With strong enough axial injection of the hot electrons, there is a switch from NDC to positive differential conductivity (PDC) about Ez ≥ 75 kV / cm and Ez ≥ 140 kV / cm for a zigzag CNT and an armchair CNT respectively. Thus, the most important tough problem for NDC region which is the space charge instabilities can be suppressed due to the switch from the NDC behaviour to the PDC behaviour predicting a potential generation of terahertz radiations whose applications are relevance in current-day technology, industry, and research.

  17. Field emission luminescence of nanodiamonds deposited on the aligned carbon nanotube array

    Science.gov (United States)

    Fedoseeva, Yu. V.; Bulusheva, L. G.; Okotrub, A. V.; Kanygin, M. A.; Gorodetskiy, D. V.; Asanov, I. P.; Vyalikh, D. V.; Puzyr, A. P.; Bondar, V. S.

    2015-03-01

    Detonation nanodiamonds (NDs) were deposited on the surface of aligned carbon nanotubes (CNTs) by immersing a CNT array in an aqueous suspension of NDs in dimethylsulfoxide (DMSO). The structure and electronic state of the obtained CNT-ND hybrid material were studied using optical and electron microscopy and Infrared, Raman, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy. A non-covalent interaction between NDs and CNT and preservation of vertical orientation of CNTs in the hybrid were revealed. We showed that current-voltage characteristics of the CNT-ND cathode are changed depending on the applied field; below ~3 V/µm they are similar to those of the initial CNT array and at the higher field they are close to the ND behavior. Involvement of the NDs in field emission process resulted in blue luminescence of the hybrid surface at an electric field higher than 3.5 V/µm. Photoluminescence measurements showed that the NDs emit blue-green light, while blue luminescence prevails in the CNT-ND hybrid. The quenching of green luminescence was attributed to a partial removal of oxygen-containing groups from the ND surface as the result of the hybrid synthesis.

  18. High-temperature annealing effects on multiwalled carbon nanotubes: electronic structure, field emission and magnetic behaviors.

    Science.gov (United States)

    Ray, Sekhar Chandra; Pao, Chih-Wen; Tsai, Huang-Ming; Chen, Huang-Chin; Chen, Yu-Shin; Wu, Shang-Lun; Ling, Dah-Chin; Lin, I-Nan; Pong, Way-Faung; Gupta, Sanju; Giorcelli, Mauro; Bianco, Stefano; Musso, Simone; Tagliaferro, Alberto

    2009-12-01

    This work elucidates the effects of high-temperature annealing on the microscopic and electronic structure of multiwalled carbon nanotubes (MWCNTs) using high-resolution transmission electron microscopy, micro-Raman spectroscopy, X-ray diffraction, X-ray absorption near-edge structure (XANES) and valence-band photoemission spectroscopy (VBPES), respectively. The field emission and magnetization behaviors are also presented. The results of annealing are as follows: (1) MWCNTs tend to align in the form of small fringes along their length, promote graphitization and be stable in air, (2) XANES indicates an enhancement in oxygen content on the sample, implying that it can be adopted for sensing and storing oxygen gas, (3) the electron field emission current density (J) is enhanced and the turn-on electric field (E(TOE)) reduced, suggesting potential use in field emission displays and as electron sources in microwave tube amplifiers and (4) as-grown MWCNTs with embedded iron nanoparticles exhibits significantly higher coercivity approximately 750 Oe than its bulk counterpart (Fe(bulk) approximately 0.9 Oe), suggesting its potential use as low-dimensional high-density magnetic recording media.

  19. Field emission luminescence of nanodiamonds deposited on the aligned carbon nanotube array.

    Science.gov (United States)

    Fedoseeva, Yu V; Bulusheva, L G; Okotrub, A V; Kanygin, M A; Gorodetskiy, D V; Asanov, I P; Vyalikh, D V; Puzyr, A P; Bondar, V S

    2015-03-23

    Detonation nanodiamonds (NDs) were deposited on the surface of aligned carbon nanotubes (CNTs) by immersing a CNT array in an aqueous suspension of NDs in dimethylsulfoxide (DMSO). The structure and electronic state of the obtained CNT-ND hybrid material were studied using optical and electron microscopy and Infrared, Raman, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy. A non-covalent interaction between NDs and CNT and preservation of vertical orientation of CNTs in the hybrid were revealed. We showed that current-voltage characteristics of the CNT-ND cathode are changed depending on the applied field; below ~3 V/µm they are similar to those of the initial CNT array and at the higher field they are close to the ND behavior. Involvement of the NDs in field emission process resulted in blue luminescence of the hybrid surface at an electric field higher than 3.5 V/µm. Photoluminescence measurements showed that the NDs emit blue-green light, while blue luminescence prevails in the CNT-ND hybrid. The quenching of green luminescence was attributed to a partial removal of oxygen-containing groups from the ND surface as the result of the hybrid synthesis.

  20. Single-WalledCarbon Nanotube Networked Field-Effect Transistors Functionalized with Thiolated Heme for NO2 Sensing

    Institute of Scientific and Technical Information of China (English)

    魏昂; 李维维; 汪静霞; 龙庆; 王钊; 熊莉; 董晓臣; 黄维

    2011-01-01

    The gas sensing properties of the single-walled carbon nanotube networked field-effect transistors for NO2 are investigated. After the modification of the gold contact electrodes of the carbon nanotube transistors with the thiolated heme, the NO2 sensing results indicate that the sensing sensitivity of the modified transistors is enhanced greatly and the sensing limit can reach below Woppb. It is also proposed that the mechanism of the sensitivity enhancement for NO2 detection mainly results from the modulation of the Schottky energy barrier at the Au/CNTs junction upon thiolated heme facilitated NO2 adsorption.%The gas sensing properties of the single-walled carbon nanotube networked field-effect transistors for NO2 are investigated.After the modification of the gold contact electrodes of the carbon nanotube transistors with the thiolated heme,the NO2 sensing results indicate that the sensing sensitivity of the modified transistors is enhanced greatly and the sensing limit can reach below 100ppb.It is also proposed that the mechanism of the sensitivity enhancement for NO2 detection mainly results from the modulation of the Schottky energy barrier at the Au/CNTs junction upon thiolated heme facilitated NO2 adsorption.

  1. The DIORAMA Neutron Emitter

    Energy Technology Data Exchange (ETDEWEB)

    Terry, James Russell [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-05

    Emission of neutrons in a given event is modeled by the DioramaEmitterNeutron object, a subclass of the abstract DioramaEmitterModule object. The GenerateEmission method of this object is the entry point for generation of a neutron population for a given event. Shown in table 1, this method requires a number of parameters to be defined in the event definition.

  2. Rectangular computed tomography using a stationary array of CNT emitters: initial experimental results

    Science.gov (United States)

    Gonzales, Brian; Spronk, Derrek; Cheng, Yuan; Zhang, Zheng; Pan, Xiaochuan; Beckmann, Moritz; Zhou, Otto; Lu, Jianping

    2013-03-01

    XinRay Systems Inc has a rectangular x-ray computed tomography (CT) imaging setup using multibeam x-ray tubes. These multibeam x-ray tubes are based on cold cathodes using carbon nanotube (CNT) field emitters. Due to their unique design, a CNT x-ray tube can contain a dense array of independently controlled electron emitters which generate a linear array of x-ray focal spots. XinRay uses a set of linear CNT x-ray tubes to design and construct a stationary CT setup which achieves sufficient CT coverage from a fixed set of views. The CT system has no moving gantry, enabling it to be enclosed in a compact rectangular tunnel. The fixed locations of the x-ray focal spots were optimized through simulations. The rectangular shape creates significant variation in path length from the focal spots to the detector for different x-ray views. The shape also results in unequal x-ray coverage in the imaged space. We discuss the impact of this variation on the reconstruction. XinRay uses an iterative reconstruction algorithm to account for this unique geometry, which is implemented on a graphics processing unit (GPU). The fixed focal spots prohibit the use of an antiscatter grid. Quantitative measure of the scatter and its impact on the reconstruction will be discussed. These results represent the first known implementation of a completely stationary CT setup using CNT x-ray emitter arrays.

  3. Fast Growth of Highly Ordered TiO2 Nanotube Arrays on Si Substrate under High-Field Anodization

    Science.gov (United States)

    Song, Jingnan; Zheng, Maojun; Zhang, Bin; Li, Qiang; Wang, Faze; Ma, Liguo; Li, Yanbo; Zhu, Changqing; Ma, Li; Shen, Wenzhong

    2017-04-01

    Highly ordered TiO2 nanotube arrays (NTAs) on Si substrate possess broad applications due to its high surface-to-volume ratio and novel functionalities, however, there are still some challenges on facile synthesis. Here, we report a simple and cost-effective high-field (90-180 V) anodization method to grow highly ordered TiO2 NTAs on Si substrate, and investigate the effect of anodization time, voltage, and fluoride content on the formation of TiO2 NTAs. The current density-time curves, recorded during anodization processes, can be used to determine the optimum anodization time. It is found that the growth rate of TiO2 NTAs is improved significantly under high field, which is nearly 8 times faster than that under low fields (40-60 V). The length and growth rate of the nanotubes are further increased with the increase of fluoride content in the electrolyte.

  4. Improved analog and AC performance with increased noise immunity using nanotube junctionless field effect transistor (NJLFET)

    Science.gov (United States)

    Rewari, Sonam; Nath, Vandana; Haldar, Subhasis; Deswal, S. S.; Gupta, R. S.

    2016-12-01

    In this paper for the first time, the noise immunity and analog performance of nanotube junctionless field effect transistor (NJLFET) has been investigated. Small signal AC performance metrics namely Scattering parameters (S-parameters) have been analyzed along with analog parameters to validate the suitability of NJLFET for RFIC design. NJLFET performance is examined by comparing its performance with junctionless gate-all-around (JLGAA) MOSFET. It has been inferred that NJLFET has improved I on/ I off ratio directing improved digital performance at higher channel lengths, reduced channel resistance ( R ch) which enables the MOSFET to provide a low resistance path to current and improved early voltage ( V EA) which shows the capability for high-gain amplification and higher g m/ g d directing high intrinsic dc gain. Higher f Tmax for NJLFET has been observed posing its potential for terahertz applications. Higher gain transconductance frequency product makes NJLFET an ultimate device for high-speed switching applications. Higher maximum transducer power gain in NJLFET implies higher power gain than JLGAA MOSFET. Also, NJLFET exhibits lower harmonic distortion and it has been explained by significant reduction in third-order derivative of transconductance, g m3. Reduction in g m3 shows that NJLFET provides better linearity over JLGAA and is more suitable for RFIC design. Also the S-parameters namely S11, S12, S21 and S22 have been analyzed to verify the small signal performance. A lower magnitude for reflection coefficients S11 and S22 depicts minimum reflection and higher matching between ports in NJLFET than JLGAA MOSFET. Higher voltage gains S12 and S21 are present in NJLFET than its counterpart which shows the higher gains that can be achieved using nanotube architecture. The noise metrics which are noise figure and noise conductance show significant reduction for NJLFET justifying its noise immunity.

  5. Disposable immunosensors for C-reactive protein based on carbon nanotubes field effect transistors.

    Science.gov (United States)

    Justino, Celine I L; Freitas, Ana C; Amaral, José P; Rocha-Santos, Teresa A P; Cardoso, Susana; Duarte, Armando C

    2013-04-15

    Label-free immunosensors based on single-walled carbon nanotubes field effect transistor (NTFET) devices were developed for the detection of C-reactive protein (CRP) which is currently the best validated inflammatory biomarker associated with cardiovascular diseases. The immunoreaction principle consists in the direct adsorption of CRP specific antibodies (anti-CRP) to single-walled carbon nanotubes (SWCNTs) networks. Such anti-CRP are the molecular receptors of CRP antigens which, in turn, can be detected by the developed NTFET devices in a linear dynamic range of 10(-4)-10(2) μg/mL. Thus, typical values of CRP (in blood serum) for healthy persons (5 μg/mL) corresponding to pathological states, can be both detected with the NTFET immunosensors, becoming an advantageous alternative as the basis for the development of analytical instrumentation for assessment of risk of occurrence of cardiovascular diseases. A log-log linear regression was applied to the experimental data with a correlation coefficient of r=0.9962 (pdevices (p=0.9582), demonstrating acceptable reproducibility. According to the experimental results, the estimate of detection limit (LOD, 10(-4)μg/mL) is 3-fold lower than that of some conventional immunoassay techniques for blood serum (e.g., LOD of 0.2 μg/mL for high-sensitivity enzyme-linked immunosorbent assay), and the dynamic range (10(-4)-10(2)μg/mL) is about 6-fold higher. Furthermore, this simple and low-cost methodology allows the use of sample volumes as low as 1 μL for the label-free detection of CRP.

  6. Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: circuitry and mechanical design.

    Science.gov (United States)

    Kia, Kaveh Kazemi; Bonabi, Fahimeh

    2012-12-01

    A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 μs. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.

  7. Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: Circuitry and mechanical design

    Science.gov (United States)

    Kia, Kaveh Kazemi; Bonabi, Fahimeh

    2012-12-01

    A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 μs. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.

  8. A multifinger microtriode with carbon nanotubes field emission cathode operating at GHz frequency

    Science.gov (United States)

    Ulisse, G.; Brunetti, F.; Ciceroni, C.; Gemma, F.; Dispenza, M.; Fiorello, A. M.; Ricci, F.; Di Carlo, A.

    2015-05-01

    Vacuum microelectronic devices play an important role in the field of micro- and nano-electronics and they have been strongly developed in recent decades. Vacuum microelectronics are mainly based on the field emission effect and the employment of electrons in vacuum in a device with dimensions from tenths to hundredths of a micrometer. In this work, we present the development of a carbon-nanotube-based multifinger microtriode operating from 0.5 to 2 GHz. In this frequency range, a minimum RF signal gain of 5 dB is achieved. Such a device represents an optimized alternative to the standard Spindt-type microtriode. The advantage of such multifinger architecture consists in the possibility to reduce the cathode-grid capacitance by reducing the overlap between the two electrodes using a parallel patterning. This approach allows increasing the cut-off frequency of the devices with respect to the Spindt-type triode. We realized a prototype of the multifinger triode and the field emission properties have been characterized. The frequency behavior has been measured, demonstrating the possibility to amplify RF signal.

  9. Chemical Ionization Mass Spectrometry Using Carbon Nanotube Field Emission Electron Sources

    Science.gov (United States)

    Radauscher, Erich J.; Keil, Adam D.; Wells, Mitch; Amsden, Jason J.; Piascik, Jeffrey R.; Parker, Charles B.; Stoner, Brian R.; Glass, Jeffrey T.

    2015-11-01

    A novel chemical ionization (CI) source has been developed based on a carbon nanotube (CNT) field emission electron source. The CNT-based electron source was evaluated and compared with a standard filament thermionic electron source in a commercial explosives trace detection desktop mass spectrometer. This work demonstrates the first reported use of a CNT-based ion source capable of collecting CI mass spectra. Both positive and negative modes were investigated. Spectra were collected for a standard mass spectrometer calibration compound, perfluorotributylamine (PFTBA), as well as trace explosives including trinitrotoluene (TNT), Research Department explosive (RDX), and pentaerythritol tetranitrate (PETN). The electrical characteristics, lifetime at operating pressure, and power requirements of the CNT-based electron source are reported. The CNT field emission electron sources demonstrated an average lifetime of 320 h when operated in constant emission mode under elevated CI pressures. The ability of the CNT field emission source to cycle on and off can provide enhanced lifetime and reduced power consumption without sacrificing performance and detection capabilities.

  10. Geometry dependence of the electrostatic and thermal response of a carbon nanotube during field emission.

    Science.gov (United States)

    Sanchez, Jaime A; Mengüç, M Pinar

    2008-02-20

    In this paper we present an analysis to simulate heating within an isolated carbon nanotube (CNT) attached to an etched tungsten tip during field emission of an electron beam. The length, radius, wall thickness and shape of the tip (closed with a hemispherical shape or open and flat) of the CNT and its separation distance from the flat surface are considered as variables. Using a finite element method, we predict the field enhancement, emission current and temperature of the CNT as a function of these parameters. The electrostatic and transient thermal analyses are integrated with the field-emission models based on the Fowler-Nordheim approximation and heating/cooling due to emitting energetic electrons (the Nottingham effect). These simulations suggest that the main mechanism responsible for heating of the CNT is Joule heating, which is significantly larger than the Nottingham effect. Results also indicate that the electrostatic characteristics of CNTs are very sensitive to the considered parameters whereas the transient thermal response is only a function of the CNT radius and wall thickness. Further, the thermal response of the CNT is independent of its geometry, meaning that, as long as a given set of geometrical conditions are present that result in a given emission current, the maximum temperature a CNT attains will be the same.

  11. Near-field radiation between graphene-covered carbon nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Richard Z.; Liu, Xianglei; Zhang, Zhuomin M., E-mail: zhuomin.zhang@me.gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2015-05-15

    It has been shown that at small separation distances, thermal radiation between hyperbolic metamaterials is enhanced over blackbodies. This theoretical study considers near-field radiation when graphene is covered on the surfaces of two semi-infinite vertically aligned carbon nanotube (VACNT) arrays separated by a sub-micron vacuum gap. Doped graphene is found to improve photon tunneling in a broad hyperbolic frequency range, due to the interaction with graphene-graphene surface plasmon polaritons (SPP). In order to elucidate the SPP resonance between graphene on hyperbolic substrates, vacuum-suspended graphene sheets separated by similar gap distances are compared. Increasing the Fermi energy through doping shifts the spectral heat flux peak toward higher frequencies. Although the presence of graphene on VACNT does not offer huge near-field heat flux enhancement over uncovered VACNT, this study identifies conditions (i.e., gap distance and doping level) that best utilize graphene to augment near-field radiation. Through the investigation of spatial Poynting vectors, heavily doped graphene is found to increase penetration depths in hyperbolic modes and the result is sensitive to the frequency regime. This study may have an impact on designing carbon-based vacuum thermophotovoltaics and thermal switches.

  12. Near-field radiation between graphene-covered carbon nanotube arrays

    Directory of Open Access Journals (Sweden)

    Richard Z. Zhang

    2015-05-01

    Full Text Available It has been shown that at small separation distances, thermal radiation between hyperbolic metamaterials is enhanced over blackbodies. This theoretical study considers near-field radiation when graphene is covered on the surfaces of two semi-infinite vertically aligned carbon nanotube (VACNT arrays separated by a sub-micron vacuum gap. Doped graphene is found to improve photon tunneling in a broad hyperbolic frequency range, due to the interaction with graphene-graphene surface plasmon polaritons (SPP. In order to elucidate the SPP resonance between graphene on hyperbolic substrates, vacuum-suspended graphene sheets separated by similar gap distances are compared. Increasing the Fermi energy through doping shifts the spectral heat flux peak toward higher frequencies. Although the presence of graphene on VACNT does not offer huge near-field heat flux enhancement over uncovered VACNT, this study identifies conditions (i.e., gap distance and doping level that best utilize graphene to augment near-field radiation. Through the investigation of spatial Poynting vectors, heavily doped graphene is found to increase penetration depths in hyperbolic modes and the result is sensitive to the frequency regime. This study may have an impact on designing carbon-based vacuum thermophotovoltaics and thermal switches.

  13. Near-field radiation between graphene-covered carbon nanotube arrays

    Science.gov (United States)

    Zhang, Richard Z.; Liu, Xianglei; Zhang, Zhuomin M.

    2015-05-01

    It has been shown that at small separation distances, thermal radiation between hyperbolic metamaterials is enhanced over blackbodies. This theoretical study considers near-field radiation when graphene is covered on the surfaces of two semi-infinite vertically aligned carbon nanotube (VACNT) arrays separated by a sub-micron vacuum gap. Doped graphene is found to improve photon tunneling in a broad hyperbolic frequency range, due to the interaction with graphene-graphene surface plasmon polaritons (SPP). In order to elucidate the SPP resonance between graphene on hyperbolic substrates, vacuum-suspended graphene sheets separated by similar gap distances are compared. Increasing the Fermi energy through doping shifts the spectral heat flux peak toward higher frequencies. Although the presence of graphene on VACNT does not offer huge near-field heat flux enhancement over uncovered VACNT, this study identifies conditions (i.e., gap distance and doping level) that best utilize graphene to augment near-field radiation. Through the investigation of spatial Poynting vectors, heavily doped graphene is found to increase penetration depths in hyperbolic modes and the result is sensitive to the frequency regime. This study may have an impact on designing carbon-based vacuum thermophotovoltaics and thermal switches.

  14. Synthesis,field emission and microwave absorption of carbon nanotubes filled with ferromagnetic nanowires

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Carbon nanotubes filled with ferromagnetic metal nanowires (M-CNTs) were synthesized by using chlorine-contained benzene (e.g.trichlorobenzene) as precursor.The wall thicknesses of M-CNTs synthesized by trichlorobenzene are much thinner than those by precursor without Cl (e.g.benzene).As-synthesized thin-walled M-CNTs exhibit remarkably enhanced field electron emission performance with a low turn-on field of 0.3 V/μm and better field-emission stability.Microwave-absorption coatings were made by dispersing as-synthesized M-CNTs into epoxy resin matrix.It is found that the reflection losses in S-band (2-4 GHz),C-band (4-8 GHz) and X-band (8-12 GHz) are enhanced in the order of FeCoNi-CNTs < FeNi-CNTs< FeCo-CNTs.The areal density of as-prepared coatings is only 2.35 kg/m2 when the coating thickness is 2.0 mm.This demonstrates that M-CNTs are promising to be used as lightweight and wide-band microwave absorbers.

  15. Highly Efficient and Scalable Separation of Semiconducting Carbon Nanotubes via Weak Field Centrifugation

    Science.gov (United States)

    Reis, Wieland G.; Weitz, R. Thomas; Kettner, Michel; Kraus, Alexander; Schwab, Matthias Georg; Tomović, Željko; Krupke, Ralph; Mikhael, Jules

    2016-05-01

    The identification of scalable processes that transfer random mixtures of single-walled carbon nanotubes (SWCNTs) into fractions featuring a high content of semiconducting species is crucial for future application of SWCNTs in high-performance electronics. Herein we demonstrate a highly efficient and simple separation method that relies on selective interactions between tailor-made amphiphilic polymers and semiconducting SWCNTs in the presence of low viscosity separation media. High purity individualized semiconducting SWCNTs or even self-organized semiconducting sheets are separated from an as-produced SWCNT dispersion via a single weak field centrifugation run. Absorption and Raman spectroscopy are applied to verify the high purity of the obtained SWCNTs. Furthermore SWCNT - network field-effect transistors were fabricated, which exhibit high ON/OFF ratios (105) and field-effect mobilities (17 cm2/Vs). In addition to demonstrating the feasibility of high purity separation by a novel low complexity process, our method can be readily transferred to large scale production.

  16. A multifinger microtriode with carbon nanotubes field emission cathode operating at GHz frequency.

    Science.gov (United States)

    Ulisse, G; Brunetti, F; Ciceroni, C; Gemma, F; Dispenza, M; Fiorello, A M; Ricci, F; Di Carlo, A

    2015-05-29

    Vacuum microelectronic devices play an important role in the field of micro- and nano-electronics and they have been strongly developed in recent decades. Vacuum microelectronics are mainly based on the field emission effect and the employment of electrons in vacuum in a device with dimensions from tenths to hundredths of a micrometer. In this work, we present the development of a carbon-nanotube-based multifinger microtriode operating from 0.5 to 2 GHz. In this frequency range, a minimum RF signal gain of 5 dB is achieved. Such a device represents an optimized alternative to the standard Spindt-type microtriode. The advantage of such multifinger architecture consists in the possibility to reduce the cathode-grid capacitance by reducing the overlap between the two electrodes using a parallel patterning. This approach allows increasing the cut-off frequency of the devices with respect to the Spindt-type triode. We realized a prototype of the multifinger triode and the field emission properties have been characterized. The frequency behavior has been measured, demonstrating the possibility to amplify RF signal.

  17. MORPHOLOGICAL PROPERTIES OF Lyα EMITTERS AT REDSHIFT 4.86 IN THE COSMOS FIELD: CLUMPY STAR FORMATION OR MERGER?

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Masakazu A. R.; Taniguchi, Yoshiaki; Kajisawa, Masaru; Shioya, Yasuhiro; Nagao, Tohru [Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577 (Japan); Murata, Katsuhiro L. [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Murayama, Takashi [Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai 980-8578 (Japan); Scoville, Nick Z.; Capak, Peter L., E-mail: kobayashi@cosmos.phys.sci.ehime-u.ac.jp [Department of Astronomy, MS 105-24, California Institute of Technology, Pasadena, CA 91125 (United States)

    2016-03-01

    We investigate morphological properties of 61 Lyα emitters (LAEs) at z = 4.86 identified in the COSMOS field, based on Hubble Space Telescope Advanced Camera for Surveys (ACS) imaging data in the F814W band. Out of the 61 LAEs, we find the ACS counterparts for 54 LAEs. Eight LAEs show double-component structures with a mean projected separation of 0.″63 (∼4.0 kpc at z = 4.86). Considering the faintness of these ACS sources, we carefully evaluate their morphological properties, that is, size and ellipticity. While some of them are compact and indistinguishable from the point-spread function (PSF) half-light radius of 0.″07 (∼0.45 kpc), the others are clearly larger than the PSF size and spatially extended up to 0.″3 (∼1.9 kpc). We find that the ACS sources show a positive correlation between ellipticity and size and that the ACS sources with large size and round shape are absent. Our Monte Carlo simulation suggests that the correlation can be explained by (1) the deformation effects via PSF broadening and shot noise or (2) the source blending in which two or more sources with small separation are blended in our ACS image and detected as a single elongated source. Therefore, the 46 single-component LAEs could contain the sources that consist of double (or multiple) components with small spatial separation (i.e., ≲0.″3 or 1.9 kpc). Further observation with high angular resolution at longer wavelengths (e.g., rest-frame wavelengths of ≳4000 Å) is inevitable to decipher which interpretation is adequate for our LAE sample.

  18. Coated nano-particle jamming of quantum emitters

    DEFF Research Database (Denmark)

    Arslanagic, Samel; Ziolkowski, Richard W.

    2012-01-01

    Spherical active coated nano-particles are examined analytically and numerically in the presence of one, two or four quantum emitters (electric Hertzian dipoles). The ability of the coated nano-particle to effectively cloak the emitters to a far-field observer is reported. This offers an interest...... an interesting route towards the jamming of quantum emitters/nano-antennas, for instance, in biological fluorescence assays....

  19. Electron optics simulation for designing carbon nanotube based field emission x-ray source

    Science.gov (United States)

    Sultana, Shabana

    In this dissertation, electron optics simulation for designing carbon nanotube (CNT) based field emission x-ray source for medical imaging applications will be presented. However, for design optimization of x-ray tubes accurate electron beam optics simulation is essential. To facilitate design of CNT x-ray sources a commercial 3D finite element software has been chosen for extensive simulation. The results show that a simplified model of uniform electron field emission from the cathode surface is not sufficient when compared to experimental measurements. This necessitated the development of a refined model to describe a macroscopic field emission CNT cathode for electron beam optics simulations. The model emulates the random distribution of CNTs and the associated variation of local field enhancement factor. The main parameter of the model has been derived empirically from the experimentally measured I-V characteristics of the CNT cathode. Simulation results based on this model agree well with experiments which include measurements of the transmission rate and focus spot size. The model provides a consistent simulation platform for optimization of electron beam optics in CNT x-ray source design. A systematic study of electron beam optics in CNT x-ray tubes led to the development of a new generation of compact x-ray source with multiple pixels. A micro focus field emission x-ray source with a variable focal spot size has been fully characterized and evaluated. It has been built and successfully integrated into micro-CT scanners which are capable of dynamic cardiac imaging of free-breathing small animals with high spatial and temporal resolutions. In addition a spatially distributed high power multi-beam x-ray source has also been designed and integrated into a stationary digital breast tomosynthesis (s-DBT) configuration. This system has the potential to reduce the total scan time to 4 seconds and yield superior image quality in breast imaging.

  20. Evaluation of Aromatic Boronic Acids as Ligands for Measuring Diabetes Markers on Carbon Nanotube Field-Effect Transistors

    Directory of Open Access Journals (Sweden)

    Steingrimur Stefansson

    2012-01-01

    Full Text Available Biomolecular detections performed on carbon nanotube field-effect transistors (CNT-FETs frequently use reactive pyrenes as an anchor to tether bioactive ligands to the hydrophobic nanotubes. In this paper, we explore the possibility of directly using bioactive aromatic compounds themselves as CNT-FET ligands. This would be an efficient way to functionalize CNT-FETs since many aromatic compounds bind avidly to nanotubes, and it would also ensure that ligand-binding molecules would be brought in close proximity to the nanotubes. Using a model system consisting of pyrene, phenanthrene, naphthalene, or phenyl boronic acids immobilized on CNT-FET wafers, we show that all are able to bind glycated human serum albumin (gHSA, which is an important diabetes marker. Pyrene boronic acid proved to bind CNTs with the greatest apparent affinity as measured by gHSA impedance. Interestingly, gHSA CNT-FET signal intensity, which is proportional to amount of protein bound, remained essentially unchanged for all the boronic acids tested.

  1. A Carbon Nanotube-based NEMS Parametric Amplifier for Enhanced Radio Wave Detection and Electronic Signal Amplification

    Energy Technology Data Exchange (ETDEWEB)

    Aleman, B J; Sussman, A; Zettl, A [Physics Department, University of California, Berkeley, CA 94720 (United States); Mickelson, W, E-mail: azettl@berkeley.edu [Center of Integrated Nanomechanical Systems, University of California, Berkeley, CA 94720 (United States)

    2011-07-20

    We propose a scheme for a parametric amplifier based on a single suspended carbon nanotube field-emitter. This novel electromechanical nanotube device acts as a phase-sensitive, variable-gain, band-pass-filtering amplifier for electronic signal processing and, at the same time, can operate as a variable-sensitivity, tuneable detector and transducer of radio frequency electromagnetic waves. The amplifier can exhibit infinite gain at pumping voltages much less than 10 Volts. Additionally, the amplifier's low overhead power consumption (10-1000 nW) make it exceptionally attractive for ultra-low-power applications.

  2. Point Defects in Carbon Nanotubes: ab initio and Force-Fields Based Simulations

    Science.gov (United States)

    Kroes, Jaap; Pietrucci, Fabio; Curioni, Alessandro; Andreoni, Wanda

    2014-03-01

    We present an extended investigation of point defects in carbon nanotubes (CNTs) and their effects on mechanical and electronic properties. This study is based on large-scale calculations using DFT with exchange and correlation functionals of the GGA - including empirical corrections for van-der-Waals interactions - and of the hybrid type. Additional simulations using classical interatomic potentials allow us to obtain a critical comparison between the outcome of DFT and force-fields. The CNT models adopted have a range of sizes and chiralities. In particular, (i) our simulations of oxygen chemisorption revealed a tendency to clustering and the existence of kinetic traps (epoxides), which explain STS data; (ii) the extension to oxygen isovalent species on CNTs and other graphitic surfaces has suggested a simple predictive model for the chemisorption pattern. Moreover, (iii) our analysis shows an intrinsic difficulty of available force fields to account for the energetics of vacancies and adsorption site preferences. Additional results aiming at characterizing the interaction of nitrogen oxides (NOx) with the CNT surface will also be presented. Work supported by SNSF Nano-Tera.ch and CSCS.

  3. 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.

  4. Purification of Carbon Nanotubes through an Electric Field near a Microelectrode

    Energy Technology Data Exchange (ETDEWEB)

    Shim, H C [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of); Lee, H W [Massachusetts Institute of Technology(MIT), Micro and Nano Systems Laboratory, 77 Massachusetts Ave. Room 5-008, Cambridge, MA 02139 (United States); Yeom, S J [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of); Kwak, Y K [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of); Lee, S S [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of); Kim, S H [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of)

    2007-04-15

    In this work, we attempt to purify multi-walled carbon nanotubes (MWNTs) using electrophoresis induced by application of an ac electric field to a set of microelectrodes in a microliquid channel. This purifying method is different from conventional methods based on chemical processes. We observed that the most of the MWNTs could pass along the microliquid channel without attaching to the electrode under specific conditions of 1 kHz, 0.2 V{sub rms}/{mu}m. On the other hand, the majority of the carbon impurities attached to the electrodes under same condition. Field emission scanning electron microscopy (FESEM) images confirm that this condition is beneficial for removing the carbon impurities. We aligned and attached this purified MWNTs and raw materials to extra electrodes with 5 MHz, 0.8 V{sub rms}/{mu}m. This experimental FESEM images show a clear difference between before and after purification. The proposed approach has potential applicability to the development of microdevices that can simultaneously perform purification and fabrication of MWNTs.

  5. Purification of Carbon Nanotubes through an Electric Field near a Microelectrode

    Science.gov (United States)

    Shim, H. C.; Lee, H. W.; Yeom, S. J.; Kwak, Y. K.; Lee, S. S.; Kim, S. H.

    2007-04-01

    In this work, we attempt to purify multi-walled carbon nanotubes (MWNTs) using electrophoresis induced by application of an ac electric field to a set of microelectrodes in a microliquid channel. This purifying method is different from conventional methods based on chemical processes. We observed that the most of the MWNTs could pass along the microliquid channel without attaching to the electrode under specific conditions of 1 kHz, 0.2 Vrms/μm. On the other hand, the majority of the carbon impurities attached to the electrodes under same condition. Field emission scanning electron microscopy (FESEM) images confirm that this condition is beneficial for removing the carbon impurities. We aligned and attached this purified MWNTs and raw materials to extra electrodes with 5 MHz, 0.8 Vrms/μm. This experimental FESEM images show a clear difference between before and after purification. The proposed approach has potential applicability to the development of microdevices that can simultaneously perform purification and fabrication of MWNTs.

  6. Enhanced field-dependent conductivity of magnetorheological gels with low-doped carbon nanotubes

    Science.gov (United States)

    Qu, Hang; Yu, Miao; Fu, Jie; Yang, Pingan; Liu, Yuxuan

    2017-10-01

    Magnetorheological gels (MRG) exhibit field-dependent conductivity and controllable mechanical properties. In order to extend their application field, filling a large number of traditional conductive materials is the most common means to enhance the poor conductivity of MRG. In this study, the conductivity of MRG is improved by low-doped carbon nanotubes (CNTs). The influence of CNTs on the magnetoresistance of MRG is discussed from two aspects—the improvement in electrical conductivity and the magnetic sensitivity of conductivity variation. The percolation threshold of CNTs in MRG should be between 1 wt% and 2 wt%. The conductivity of a 4 wt% CNT-doped sample increases more than 28 000 times compared with pure MRG. However, there is a cliff-like drop for the range and rate of conductivity variation when the doping amount of CNTs is between 3 wt% and 4 wt%. Therefore, it is concluded that the optimal mass fraction of CNTs is 3%, which can maintain a suitable variation range and a strong conductivity. Compared with pure MRG, its conductivity increases by at least two orders of magnitude. Finally, a sketch of particle motion simulation is developed to understand the improving mechanism and the effect of CNTs.

  7. Chiral-index resolved length mapping of carbon nanotubes in solution using electric-field induced differential absorption spectroscopy

    Science.gov (United States)

    Li, Wenshan; Hennrich, Frank; Flavel, Benjamin S.; Kappes, Manfred M.; Krupke, Ralph

    2016-09-01

    The length of single-walled carbon nanotubes (SWCNTs) is an important metric for the integration of SWCNTs into devices and for the performance of SWCNT-based electronic or optoelectronic applications. In this work we propose a rather simple method based on electric-field induced differential absorption spectroscopy to measure the chiral-index-resolved average length of SWCNTs in dispersions. The method takes advantage of the electric-field induced length-dependent dipole moment of nanotubes and has been verified and calibrated by atomic force microscopy. This method not only provides a low cost, in situ approach for length measurements of SWCNTs in dispersion, but due to the sensitivity of the method to the SWCNT chiral index, the chiral index dependent average length of fractions obtained by chromatographic sorting can also be derived. Also, the determination of the chiral-index resolved length distribution seems to be possible using this method.

  8. Pronounced Hysteresis and High Charge Storage Stability of Single-Walled Carbon Nanotube-Based Field-Effect Transistors

    OpenAIRE

    Wang, S.G.; Sellin, P.

    2005-01-01

    In this letter, pronounced hysteresis loops were observed in single-walled carbon nanotube-based field-effect transistors (CNTFETs). The shift in threshold voltage was found to increase with increasing gate voltage sweep ranges. A significant enhancement in the charge storage stability over 14 days was obtained at room temperature after a two-stage hydrogen and air annealing process was applied to the CNTFETs. The passivation of interface traps by annealing in hydrogen and the removal of phys...

  9. Monte Carlo simulation of a compact microbeam radiotherapy system based on carbon nanotube field emission technology.

    Science.gov (United States)

    Schreiber, Eric C; Chang, Sha X

    2012-08-01

    Microbeam radiation therapy (MRT) is an experimental radiotherapy technique that has shown potent antitumor effects with minimal damage to normal tissue in animal studies. This unique form of radiation is currently only produced in a few large synchrotron accelerator research facilities in the world. To promote widespread translational research on this promising treatment technology we have proposed and are in the initial development stages of a compact MRT system that is based on carbon nanotube field emission x-ray technology. We report on a Monte Carlo based feasibility study of the compact MRT system design. Monte Carlo calculations were performed using EGSnrc-based codes. The proposed small animal research MRT device design includes carbon nanotube cathodes shaped to match the corresponding MRT collimator apertures, a common reflection anode with filter, and a MRT collimator. Each collimator aperture is sized to deliver a beam width ranging from 30 to 200 μm at 18.6 cm source-to-axis distance. Design parameters studied with Monte Carlo include electron energy, cathode design, anode angle, filtration, and collimator design. Calculations were performed for single and multibeam configurations. Increasing the energy from 100 kVp to 160 kVp increased the photon fluence through the collimator by a factor of 1.7. Both energies produced a largely uniform fluence along the long dimension of the microbeam, with 5% decreases in intensity near the edges. The isocentric dose rate for 160 kVp was calculated to be 700 Gy∕min∕A in the center of a 3 cm diameter target. Scatter contributions resulting from collimator size were found to produce only small (<7%) changes in the dose rate for field widths greater than 50 μm. Dose vs depth was weakly dependent on filtration material. The peak-to-valley ratio varied from 10 to 100 as the separation between adjacent microbeams varies from 150 to 1000 μm. Monte Carlo simulations demonstrate that the proposed compact MRT system

  10. Correlated spontaneous emission of fluorescent emitters mediated by single plasmons

    CERN Document Server

    Bouchet, Dorian; Ithurria, Sandrine; Gulinatti, Angelo; Rech, Ivan; Carminati, Rémi; De Wilde, Yannick; Krachmalnicoff, Valentina

    2016-01-01

    Manipulating the spontaneous emission of a fluorescent emitter can be achieved by placing the emitter in a nanostructured environment. A privileged spot is occupied by plasmonic structures that provide a strong confinement of the electromagnetic field, which results in an enhancement of the emitter-environment interaction. While plasmonic nanostructures have been widely exploited to control the emission properties of single photon emitters, performing the coupling between quantum emitters with plasmons poses a huge challenge. In this Letter we report on a first crucial step towards this goal by the observation of correlated emission between a single CdSe/CdS/ZnS quantum dot exhibiting single photon statistics and a fluorescent nanobead located micrometers apart. This is accomplished by coupling both emitters to a silver nanowire. Single-plasmons are created on the latter from the quantum dot, and transfer energy to excite in turn the fluorescent nanobead.

  11. Nanotube cathodes.

    Energy Technology Data Exchange (ETDEWEB)

    Overmyer, Donald L.; Lockner, Thomas Ramsbeck; Siegal, Michael P.; Miller, Paul Albert

    2006-11-01

    Carbon nanotubes have shown promise for applications in many diverse areas of technology. In this report we describe our efforts to develop high-current cathodes from a variety of nanotubes deposited under a variety of conditions. Our goal was to develop a one-inch-diameter cathode capable of emitting 10 amperes of electron current for one second with an applied potential of 50 kV. This combination of current and pulse duration significantly exceeds previously reported nanotube-cathode performance. This project was planned for two years duration. In the first year, we tested the electron-emission characteristics of nanotube arrays fabricated under a variety of conditions. In the second year, we planned to select the best processing conditions, to fabricate larger cathode samples, and to test them on a high-power relativistic electron beam generator. In the first year, much effort was made to control nanotube arrays in terms of nanotube diameter and average spacing apart. When the project began, we believed that nanotubes approximately 10 nm in diameter would yield sufficient electron emission properties, based on the work of others in the field. Therefore, much of our focus was placed on measured field emission from such nanotubes grown on a variety of metallized surfaces and with varying average spacing between individual nanotubes. We easily reproduced the field emission properties typically measured by others from multi-wall carbon nanotube arrays. Interestingly, we did this without having the helpful vertical alignment to enhance emission; our nanotubes were randomly oriented. The good emission was most likely possible due to the improved crystallinity, and therefore, electrical conductivity, of our nanotubes compared to those in the literature. However, toward the end of the project, we learned that while these 10-nm-diameter CNTs had superior crystalline structure to the work of others studying field emission from multi-wall CNT arrays, these nanotubes still

  12. Field emission properties of N-doped capped single-walled carbon nanotubes: a first-principles density-functional study.

    Science.gov (United States)

    Qiao, L; Zheng, W T; Xu, H; Zhang, L; Jiang, Q

    2007-04-28

    The geometrical structures and field emission properties of pristine and N-doped capped (5,5) single-walled carbon nanotubes have been investigated using first-principles density-functional theory. The structures of N-doped carbon nanotubes are stable under field emission conditions. The calculated work function of N-doped carbon nanotube decreases drastically when compared with pristine carbon nanotube, which means the enhancement of field emission properties. The ionization potentials of N-doped carbon nanotubes are also reduced significantly. The authors analyze the field emission mechanism in terms of energy gap between the lowest unoccupied molecular orbital and the highest occupied molecular orbital, Mulliken charge population, and local density of states. Due to the doping of nitrogen atom, the local density of states at the Fermi level increases dramatically and donor states can be observed above the Fermi level. The authors' results suggest that the field emission properties of carbon nanotubes can be enhanced by the doping of nitrogen atom, which are consistent with the experimental results.

  13. Organic modification of carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The organic modification of carbon nanotubes is a novel research field being developed recently. In this article, the history and newest progress of organic modification of carbon nanotubes are reviewed from two aspects:organic covalent modification and organic noncovalent modification of carbon nanotubes. The preparation and properties of organic modified carbon nanotubes are discussed in detail. In addition, the prospective development of organic modification of carbon nanotubes is suggested.

  14. Superradiance of a subwavelength array of independent classical nonlinear emitters

    CERN Document Server

    Nefedkin, N E; Zyablovsky, A A; Pukhov, A A; Vinogradov, A P; Lisyansky, A A

    2015-01-01

    We suggest a mechanism for the emergence of a superradiance burst in a subwavelength array of nonlinear classical emitters. We assume that the emitters interact via their common field of radiative response and that they may have an arbitrary distribution of initially phases. We show that only if this distribution is not uniform, a non-zero field of radiative response arises leading to a superradiance burst. Although this field cannot synchronize the emitters, it forces fast oscillations of a classical nonlinear emitter to have long-period envelopes. Constructive interference in the envelopes creates a large dipole moment of the array which results in a superradiance pulse. The intensity of the superradiance is proportional to the squared number of the emitters, which envelopes participate in the fluctuation.

  15. Morphological Properties of Lyα Emitters at Redshift 4.86 in the Cosmos Field: Clumpy Star Formation or Merger?

    Science.gov (United States)

    Kobayashi, Masakazu A. R.; Murata, Katsuhiro L.; Koekemoer, Anton M.; Murayama, Takashi; Taniguchi, Yoshiaki; Kajisawa, Masaru; Shioya, Yasuhiro; Scoville, Nick Z.; Nagao, Tohru; Capak, Peter L.

    2016-03-01

    We investigate morphological properties of 61 Lyα emitters (LAEs) at z = 4.86 identified in the COSMOS field, based on Hubble Space Telescope Advanced Camera for Surveys (ACS) imaging data in the F814W band. Out of the 61 LAEs, we find the ACS counterparts for 54 LAEs. Eight LAEs show double-component structures with a mean projected separation of 0.″63 (˜4.0 kpc at z = 4.86). Considering the faintness of these ACS sources, we carefully evaluate their morphological properties, that is, size and ellipticity. While some of them are compact and indistinguishable from the point-spread function (PSF) half-light radius of 0.″07 (˜0.45 kpc), the others are clearly larger than the PSF size and spatially extended up to 0.″3 (˜1.9 kpc). We find that the ACS sources show a positive correlation between ellipticity and size and that the ACS sources with large size and round shape are absent. Our Monte Carlo simulation suggests that the correlation can be explained by (1) the deformation effects via PSF broadening and shot noise or (2) the source blending in which two or more sources with small separation are blended in our ACS image and detected as a single elongated source. Therefore, the 46 single-component LAEs could contain the sources that consist of double (or multiple) components with small spatial separation (i.e., ≲0.″3 or 1.9 kpc). Further observation with high angular resolution at longer wavelengths (e.g., rest-frame wavelengths of ≳4000 Å) is inevitable to decipher which interpretation is adequate for our LAE sample. Based on observations with NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555, and also based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  16. Diameter dependence of 1/f noise in carbon nanotube field effect transistors using noise spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kawahara, Toshio, E-mail: toshi@isc.chubu.ac.jp [Center of Applied Superconductivity and Sustainable Energy Research, Chubu University, 1200, Matsumoto-cho, Kasugai-shi, Aichi 487-8501 (Japan); Yamaguchi, Satarou [Center of Applied Superconductivity and Sustainable Energy Research, Chubu University, 1200, Matsumoto-cho, Kasugai-shi, Aichi 487-8501 (Japan); Ohno, Yasuhide; Maehashi, Kenzo; Matsumoto, Kazuhiko [The Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Mizutani, Shin [NTT Communication Science Laboratories, 2-4, Hikaridai Seika-cho, Soraku-gun, Kyoto 619-0237 (Japan); Itaka, Kenji [North Japan Research Institute for Sustainable Energy, Hirosaki University, 2-1-3 Matsubara, Aomori 030-0813 (Japan)

    2013-02-15

    Carbon nanotubes (CNTs) have many interesting properties for nano devices such as high sensitive sensors or noise enhanced nonlinear devices. A field effect transistor (FET) structure is one of the key features for these applications, and the control of noise in FETs is important for the actual operation of the application. Several origins of noise have been proposed, and defects and/or surface adsorption of molecules seem to be dominant for the 1/f type noise in CNTs. To study the origins of noise, the diameter dependence of noise properties was studied. We analyzed the noise properties in CNTs using noise spectroscopy with different fabrication parameters or ambient environments. We observed the crossover of noise properties in CNTs, which involved transition between different origins of noise depending on their diameter. Additionally, noise spectroscopy was used to observe such crossover between air and vacuum environments. We can control noise intensity using the gate voltage, and noise properties can be controlled by the fabrication parameters. These phenomena are useful for the stochastic operation of CNT-FETs.

  17. Very stable electron field emission from strontium titanate coated carbon nanotube matrices with low emission thresholds.

    Science.gov (United States)

    Pandey, Archana; Prasad, Abhishek; Moscatello, Jason P; Engelhard, Mark; Wang, Chongmin; Yap, Yoke Khin

    2013-01-22

    Novel PMMA-STO-CNT matrices were created by opened-tip vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) with conformal coatings of strontium titanate (STO) and poly(methyl methacrylate) (PMMA). Emission threshold of 0.8 V/μm was demonstrated, about 5-fold lower than that of the as-grown VA-MWCNTs. This was obtained after considering the related band structures under the perspective of work functions and tunneling width as a function of the STO thickness. We showed that there is an optimum thickness of STO coatings to effectively reduce the work function of CNTs and yet minimize the tunneling width for electron emissions. Furthermore, simulation and modeling suggest that PMMA-STO-CNT matrices have suppressed screening effects and Coulombs' repulsion forces between electrons in adjacent CNTs, leading to low emission threshold, high emission density, and prolonged emission stability. These findings are important for practical application of VA-MWCNTs in field emission devices, X-ray generation, and wave amplification.

  18. Fabrication and characterization of junctionless carbon nanotube field effect transistor for cholesterol detection

    Science.gov (United States)

    Barik, Md. Abdul; Dutta, Jiten Ch.

    2014-08-01

    We have reported fabrication and characterization of polyaniline (PANI)/zinc oxide (ZnO) membrane-based junctionless carbon nanotube field effect transistor deposited on indium tin oxide glass plate for the detection of cholesterol (0.5-22.2 mM). Cholesterol oxidase (ChOx) has been immobilized on the PANI/ZnO membrane by physical adsorption technique. Electrical response has been recorded using digital multimeter (Agilent 3458A) in the presence of phosphate buffer saline of 50 mM, pH 7.0, and 0.9% NaCl contained in a glass pot. The results of response studies for cholesterol reveal linearity as 0.5-16.6 mM and improved sensitivity of 60 mV/decade in good agreement with Nernstian limit ˜59.2 mV/decade. The life time of this sensor has been found up to 5 months and response time of 1 s. The limit of detection with regression coefficient (r) ˜ 0.998 and Michaelis-Menten constant (Km) were found to be ˜0.25 and 1.4 mM, respectively, indicating high affinity of ChOx to cholesterol. The results obtained in this work show negligible interference with glucose and urea.

  19. Fabrication and characterization of junctionless carbon nanotube field effect transistor for cholesterol detection

    Energy Technology Data Exchange (ETDEWEB)

    Barik, Md. Abdul, E-mail: abdulnpl@gmail.com; Dutta, Jiten Ch. [Department of Electronics and Communication Engineering, Tezpur University, Napaam, Tezpur, Assam 784028 (India)

    2014-08-04

    We have reported fabrication and characterization of polyaniline (PANI)/zinc oxide (ZnO) membrane-based junctionless carbon nanotube field effect transistor deposited on indium tin oxide glass plate for the detection of cholesterol (0.5–22.2 mM). Cholesterol oxidase (ChOx) has been immobilized on the PANI/ZnO membrane by physical adsorption technique. Electrical response has been recorded using digital multimeter (Agilent 3458A) in the presence of phosphate buffer saline of 50 mM, pH 7.0, and 0.9% NaCl contained in a glass pot. The results of response studies for cholesterol reveal linearity as 0.5–16.6 mM and improved sensitivity of 60 mV/decade in good agreement with Nernstian limit ∼59.2 mV/decade. The life time of this sensor has been found up to 5 months and response time of 1 s. The limit of detection with regression coefficient (r) ∼ 0.998 and Michaelis-Menten constant (K{sub m}) were found to be ∼0.25 and 1.4 mM, respectively, indicating high affinity of ChOx to cholesterol. The results obtained in this work show negligible interference with glucose and urea.

  20. Highly Uniform Carbon Nanotube Field-Effect Transistors and Medium Scale Integrated Circuits.

    Science.gov (United States)

    Chen, Bingyan; Zhang, Panpan; Ding, Li; Han, Jie; Qiu, Song; Li, Qingwen; Zhang, Zhiyong; Peng, Lian-Mao

    2016-08-10

    Top-gated p-type field-effect transistors (FETs) have been fabricated in batch based on carbon nanotube (CNT) network thin films prepared from CNT solution and present high yield and highly uniform performance with small threshold voltage distribution with standard deviation of 34 mV. According to the property of FETs, various logical and arithmetical gates, shifters, and d-latch circuits were designed and demonstrated with rail-to-rail output. In particular, a 4-bit adder consisting of 140 p-type CNT FETs was demonstrated with higher packing density and lower supply voltage than other published integrated circuits based on CNT films, which indicates that CNT based integrated circuits can reach to medium scale. In addition, a 2-bit multiplier has been realized for the first time. Benefitted from the high uniformity and suitable threshold voltage of CNT FETs, all of the fabricated circuits based on CNT FETs can be driven by a single voltage as small as 2 V.

  1. Temperature Dependence of Electrical Characteristics of Carbon Nanotube Field-Effect Transistors: A Quantum Simulation Study

    Directory of Open Access Journals (Sweden)

    Ali Naderi

    2012-01-01

    Full Text Available By developing a two-dimensional (2D full quantum simulation, the attributes of carbon nanotube field-effect transistors (CNTFETs in different temperatures have been comprehensively investigated. Simulations have been performed by employing the self-consistent solution of 2D Poisson-Schrödinger equations within the nonequilibrium Green's function (NEGF formalism. Principal characteristics of CNTFETs such as current capability, drain conductance, transconductance, and subthreshold swing (SS have been investigated. Simulation results present that as temperature raises from 250 to 500 K, the drain conductance and on-current of the CNTFET improved; meanwhile the on-/off-current ratio deteriorated due to faster growth in off-current. Also the effects of temperature on short channel effects (SCEs such as drain-induced barrier lowering (DIBL and threshold voltage roll-off have been studied. Results show that the subthreshold swing and DIBL parameters are almost linearly correlated, so the degradation of these parameters has the same origin and can be perfectly influenced by the temperature.

  2. Targeting Antibodies to Carbon Nanotube Field Effect Transistors by Pyrene Hydrazide Modification of Heavy Chain Carbohydrates

    Directory of Open Access Journals (Sweden)

    Steingrimur Stefansson

    2012-01-01

    Full Text Available Many carbon nanotube field-effect transistor (CNT-FET studies have used immobilized antibodies as the ligand binding moiety. However, antibodies are not optimal for CNT-FET detection due to their large size and charge. Their size can prevent ligands from reaching within the Debye length of the CNTs and a layer of charged antibodies on the circuits can drown out any ligand signal. In an attempt to minimize the antibody footprint on CNT-FETs, we examined whether pyrene hydrazide modification of antibody carbohydrates could reduce the concentration required to functionalize CNT circuits. The carbohydrates are almost exclusively on the antibody Fc region and this site-specific modification could mediate uniform antibody orientation on the CNTs. We compared the hydrazide modification of anti-E. coli O157:H7 polyclonal antibodies to pyrenebutanoic acid succinimidyl ester-coated CNTs and carbodiimide-mediated antibody CNT attachment. Our results show that the pyrene hydrazide modification was superior to those methods with respect to bacteria detection and less than 1 nM labeled antibody was required to functionalize the circuits.

  3. High-Throughput Peptide Epitope Mapping Using Carbon Nanotube Field-Effect Transistors

    Directory of Open Access Journals (Sweden)

    Steingrimur Stefansson

    2013-01-01

    Full Text Available Label-free and real-time detection technologies can dramatically reduce the time and cost of pharmaceutical testing and development. However, to reach their full promise, these technologies need to be adaptable to high-throughput automation. To demonstrate the potential of single-walled carbon nanotube field-effect transistors (SWCNT-FETs for high-throughput peptide-based assays, we have designed circuits arranged in an 8 × 12 (96-well format that are accessible to standard multichannel pipettors. We performed epitope mapping of two HIV-1 gp160 antibodies using an overlapping gp160 15-mer peptide library coated onto nonfunctionalized SWCNTs. The 15-mer peptides did not require a linker to adhere to the non-functionalized SWCNTs, and binding data was obtained in real time for all 96 circuits. Despite some sequence differences in the HIV strains used to generate these antibodies and the overlapping peptide library, respectively, our results using these antibodies are in good agreement with known data, indicating that peptides immobilized onto SWCNT are accessible and that linear epitope mapping can be performed in minutes using SWCNT-FET.

  4. Carbon nanotube field effect transistors for the fast and selective detection of human immunoglobulin G.

    Science.gov (United States)

    Cid, Cristina C; Riu, Jordi; Maroto, Alicia; Rius, F Xavier

    2008-08-01

    We report a field effect transistor (FET) based on a network of single-walled carbon nanotubes (SWCNTs) which can selectively detect human immunoglobulin G (HIgG). HIgG antibodies, which are strongly adsorbed onto the walls of the SWCNTs, are the basic elements of the recognition layer. The non-specific binding of proteins and the effects of other interferences are avoided by covering the non-adsorbed areas of the SWCNTs with Tween 20. The selectivity of the sensor has been tested against bovine serum albumin (BSA), the most abundant protein in plasma. HIgG in aqueous solution with concentrations from 1.25 mg L(-1) (8 nM) can be readily detected with response times of about 10 min. The SWCNT networks that form the basis of the sensor are easily grown by chemical vapour deposition. Silver screen-printed electrodes make the sensor quick to build. The sensitivity obtained with this sensor is similar to other FET devices based on SWCNTs built using much more complicated lithography processes. Moreover, the sensor is a reagentless device that does not need labels to detect HIgG.

  5. High performance dendrimer functionalized single-walled carbon nanotubes field effect transistor biosensor for protein detection

    Science.gov (United States)

    Rajesh, Sharma, Vikash; Puri, Nitin K.; Mulchandani, Ashok; Kotnala, Ravinder K.

    2016-12-01

    We report a single-walled carbon nanotube (SWNT) field-effect transistor (FET) functionalized with Polyamidoamine (PAMAM) dendrimer with 128 carboxyl groups as anchors for site specific biomolecular immobilization of protein antibody for C-reactive protein (CRP) detection. The FET device was characterized by scanning electron microscopy and current-gate voltage (I-Vg) characteristic studies. A concentration-dependent decrease in the source-drain current was observed in the regime of clinical significance, with a detection limit of ˜85 pM and a high sensitivity of 20% change in current (ΔI/I) per decade CRP concentration, showing SWNT being locally gated by the binding of CRP to antibody (anti-CRP) on the FET device. The low value of the dissociation constant (Kd = 0.31 ± 0.13 μg ml-1) indicated a high affinity of the device towards CRP analyte arising due to high anti-CRP loading with a better probe orientation on the 3-dimensional PAMAM structure.

  6. Demonstration of high current carbon nanotube enabled vertical organic field effect transistors at industrially relevant voltages

    Science.gov (United States)

    McCarthy, Mitchell

    The display market is presently dominated by the active matrix liquid crystal display (LCD). However, the active matrix organic light emitting diode (AMOLED) display is argued to become the successor to the LCD, and is already beginning its way into the market, mainly in small size displays. But, for AMOLED technology to become comparable in market share to LCD, larger size displays must become available at a competitive price with their LCD counterparts. A major issue preventing low-cost large AMOLED displays is the thin-film transistor (TFT) technology. Unlike the voltage driven LCD, the OLEDs in the AMOLED display are current driven. Because of this, the mature amorphous silicon TFT backplane technology used in the LCD must be upgraded to a material possessing a higher mobility. Polycrystalline silicon and transparent oxide TFT technologies are being considered to fill this need. But these technologies bring with them significant manufacturing complexity and cost concerns. Carbon nanotube enabled vertical organic field effect transistors (CN-VFETs) offer a unique solution to this problem (now known as the AMOLED backplane problem). The CN-VFET allows the use of organic semiconductors to be used for the semiconductor layer. Organics are known for their low-cost large area processing compatibility. Although the mobility of the best organics is only comparable to that of amorphous silicon, the CN-VFET makes up for this by orienting the channel vertically, as opposed to horizontally (like in conventional TFTs). This allows the CN-VFET to achieve sub-micron channel lengths without expensive high resolution patterning. Additionally, because the CN-VFET can be easily converted into a light emitting transistor (called the carbon nanotube enabled vertical organic light emitting transistor---CN-VOLET) by essentially stacking an OLED on top of the CN-VFET, more potential benefits can be realized. These potential benefits include, increased aperture ratio, increased OLED

  7. Detection of the Odor Signature of Ovarian Cancer using DNA-Decorated Carbon Nanotube Field Effect Transistor Arrays

    Science.gov (United States)

    Kehayias, Christopher; Kybert, Nicholas; Yodh, Jeremy; Johnson, A. T. Charlie

    Carbon nanotubes are low-dimensional materials that exhibit remarkable chemical and bio-sensing properties and have excellent compatibility with electronic systems. Here, we present a study that uses an electronic olfaction system based on a large array of DNA-carbon nanotube field effect transistors vapor sensors to analyze the VOCs of blood plasma samples collected from patients with malignant ovarian cancer, patients with benign ovarian lesions, and age-matched healthy subjects. Initial investigations involved coating each CNT sensor with single-stranded DNA of a particular base sequence. 10 distinct DNA oligomers were used to functionalize the carbon nanotube field effect transistors, providing a 10-dimensional sensor array output response. Upon performing a statistical analysis of the 10-dimensional sensor array responses, we showed that blood samples from patients with malignant cancer can be reliably differentiated from those of healthy control subjects with a p-value of 3 x 10-5. The results provide preliminary evidence that the blood of ovarian cancer patients contains a discernable volatile chemical signature that can be detected using DNA-CNT nanoelectronic vapor sensors, a first step towards a minimally invasive electronic diagnostic technology for ovarian cancer.

  8. Coupling of semiconductor carbon nanotubes emission with silicon photonic micro ring resonators

    Science.gov (United States)

    Sarti, Francesco; Caselli, Niccolò; La China, Federico; Biccari, Francesco; Torrini, Ughetta; Intonti, Francesca; Vinattieri, Anna; Durán-Valdeiglesias, Elena; Zhang, Weiwei; Noury, Adrien; Alonso-Ramos, Carlos; Hoang, ThiHong Cam; Serna, Samuel; Le Roux, Xavier; Cassan, Eric; Izard, Nicolas; Yang, Hongliu; Bezugly, Viktor; Cuniberti, Gianaurelio; Filoramo, Arianna; Vivien, Laurent; Gurioli, Massimo

    2016-05-01

    Hybrid structures are needed to fully exploit the great advantages of Si photonics and several approaches have been addressed where Si devices are bonded to different materials and nanostructures. Here we study the use of semiconductor carbon nanotubes for emission in the 1300 nm wavelength range to functionalize Si photonic structures in view of optoelectronic applications. The Si micro-rings are fully characterized by near field forward resonant scattering with 100 nm resolution. We show that both TE and TM modes can be addressed on the top of the micro-rings in a vectorial imaging of the in-plane polarization components. We coupled the Si micro-resonators with selected carbon nanotubes for high photoluminescence emission. Coupling nanotubes with the evanescent tails in air of the electric field localized in the photonic modes of the micro-resonators is demonstrated by sharp resonances over imposed to the nanotube emission bands. By mapping the Si and the nanotube emission we demonstrate that strong enhancement of the nanotube photoluminescence can be achieved both in the photonic modes of micro-disks and slot micro-rings, whenever the spatial overlap between nano-emitters and photonic modes is fulfilled.

  9. Photoluminescence microscopy on air-suspended carbon nanotubes coupled to photonic crystal nanobeam cavities

    Science.gov (United States)

    Miura, R.; Imamura, S.; Shimada, T.; Ohta, R.; Iwamoto, S.; Arakawa, Y.; Kato, Y. K.

    2014-03-01

    Because carbon nanotubes are room-temperature telecom-band emitters and can be grown on silicon substrates, they are ideal for coupling to silicon photonic cavities.[2,3 In particular, as-grown air-suspended carbon nanotubes show excellent optical properties, but cavity modes with large fields in the air are needed in order to achieve efficient coupling. Here we investigate individual air-suspended nanotubes coupled to photonic crystal nanobeam cavities. We utilize cavities that confine air-band modes which have large fields in the air. Dielectric mode cavities are also prepared for comparison. We fabricate the devices from silicon-on-insulator substrates by using electron beam lithography and dry etching to form the nanobeam structure. The buried oxide layer is removed by wet etching, and carbon nanotubes are grown onto the cavities by chemical vapor deposition. We perform photoluminescence imaging and excitation spectroscopy to find the positions of the nanotubes and identify their chiralities. For both types of devices, cavity modes with quality factors of ~3000 are observed within the nanotube emission peak. Work supported by SCOPE, KAKENHI, The Telecommunications Advancement Foundation, The Toyota Physical and Chemical Research Institute, Project for Developing Innovation Systems of MEXT, Japan and the Photon Frontier Network Program of MEXT, Japan.

  10. Electrical Transport and Channel Length Modulation in Semiconducting Carbon Nanotube Field-Effect Transistors

    Science.gov (United States)

    2013-11-25

    vulnerability assessment; contamination, thermal and structural control; lubrication and surface phenomena. Microelectromechanical systems (MEMS) for...vapor detection," Nano Letters, 3, pp. 929-933, Jul 2003. 3. V. Sazonova, et ai, "A tunable carbon nanotube electromechanical oscillator," Nature, 431...symmetric SWCNT-based CMOS devices and scaling," Acs Nano , 3, pp. 3781-3787, Nov 2009. 33. A. D. Franklin, et al, "Sub-10 nm carbon nanotube

  11. Ultrashort single-wall carbon nanotubes reveal field-emission coulomb blockade and highest electron-source brightness.

    Science.gov (United States)

    Pascale-Hamri, A; Perisanu, S; Derouet, A; Journet, C; Vincent, P; Ayari, A; Purcell, S T

    2014-03-28

    We present here well-defined Coulomb staircases using an original field-emission experiment on several individual in situ-grown single-wall carbon nanotubes. A unique in situ process was applied nine times to progressively shorten one single-wall carbon nanotube down to ≃10  nm, which increased the oscillations periods from 5.5 to 80 V, the temperature for observable Coulomb staircase to 1100 K and the currents to 1.8  μA. This process led to the brightest electron source ever reported [9×1011  A/(str m2 V)].

  12. The Nano-Memory Devices of a Single Wall and Peapod Structural Carbon Nanotube Field Effect Transistor

    Science.gov (United States)

    Lee, C. H.; Kang, K. T.; Park, K. S.; Kim, M. S.; Kim, H. S.; Kim, H. G.; Fischer, J. E.; Johnson, A. T.

    2003-08-01

    The rediscovery and the memory application of single walled carbon nanotubes (SWNTs) give a new method in nanoelectronics applications. At first we will report the memory effects of a SWNT, and attempt to use this property in a memory device. To use a SWNT field effect transistor (FET) as a charge-storage memory device, the device operates by injecting electrons from the nanotube channel of a TubeFET into charge traps on the surface of the SiO2 gate dielectric, thus shifting the threshold voltage. This memory can be written and erased many times, and has a hold time of hundreds of seconds at room temperature. At second we have attempted to make a Peapod tubeFET. It is the structure that a C60 was contained within the tube and separated from it by a graphitic Van der Waals gap. I-V property of the Peapod shows semiconducting property.

  13. Cathodoluminescence and electroluminescence from multi-layered organic structures induced by field electron emission from carbon nanotubes

    Science.gov (United States)

    Kuznetzov, Alexander A.; Zakhidov, Alexander A.; Ovalle, Raquel; Nanjundaswami, Rashmi; Williams, Christopher; Zhang, Mei; Lee, Sergey B.; Ferraris, John; Zakhidov, Anvar A.

    2005-10-01

    We report the observation of cathodoluminescence (CL) of organic multilayers of tris-(8-hydroxyquinoline) aluminium (Alq3) and 2- (4biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD) deposited on ITO-coated glass, with and without hole transport layer and compare it with electroluminescence (EL) from similar devices. Excitation of the CL of such multilayer organic anodes was accomplished by low energy electrons field emitted by single walled carbon nanotube cathodes. The dependence of CL spectrum and intensity on voltage (V), current (I), type of transport layer and the cathode-anode geometry has been studied. We propose carbon nanotubes as efficient cathodes for stable CL emission from multi-layer anodes at small cathode-anode separations. The role of hole-transport layer is also discussed.

  14. Ultralow field emission from thinned, open-ended, and defected carbon nanotubes by using microwave hydrogen plasma processing

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Jian-Hua, E-mail: jhdeng1983@163.com [College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387 (China); Cheng, Lin; Wang, Fan-Jie; Yu, Bin; Li, Guo-Zheng; Li, De-Jun [College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387 (China); Cheng, Guo-An [Key Laboratory of Beam Technology and Material Modification of Ministry of Education, Beijing Normal University, Beijing 100875 (China)

    2015-01-01

    Graphical abstract: Thinned, open-ended, and defected carbon nanotubes were prepared by using hydrogen plasma processing. The processed carbon nanotubes have far better field emission performance than that of the pristine ones. - Highlights: • CVD prepared CNT arrays were processed by microwave hydrogen plasma. • Thinned, open-ended, and defected CNTs were obtained. • Processed CNTs have far better field emission performance than the pristine ones. • Processed CNTs have applicable emission stability after being perfectly aged. - Abstract: Ultralow field emission is achieved from carbon nanotubes (CNTs) by using microwave hydrogen plasma processing. After the processing, typical capped CNT tips are removed, with thinned, open-ended, and defected CNTs left. Structural analyses indicate that the processed CNTs have more SP{sup 3}-hybridized defects as compared to the pristine ones. The morphology of CNTs can be readily controlled by adjusting microwave powers, which change the shape of CNTs by means of hydrogen plasma etching. Processed CNTs with optimal morphology are found to have an ultralow turn-on field of 0.566 V/μm and threshold field of 0.896 V/μm, much better than 0.948 and 1.559 V/μm of the as-grown CNTs, respectively. This improved FE performance is ascribed to the structural changes of CNTs after the processing. The thinned and open-ended shape of CNTs can facilitate electron tunneling through barriers and additionally, the increased defects at tube walls can serve as new active emission sites. Furthermore, our plasma processed CNTs exhibit excellent field emission stability at a large emission current density of 10.36 mA/cm{sup 2} after being perfectly aged, showing promising prospects in applications as high-performance vacuum electron sources.

  15. Synthesis of carbon nanotubes.

    Science.gov (United States)

    Awasthi, Kalpana; Srivastava, Anchal; Srivastava, O N

    2005-10-01

    Carbon nanotubes play a fundamental role in the rapidly developing field of nanoscience and nanotechnology because of their unique properties and high potential for applications. In this article, the different synthesis methods of carbon nanotubes (both multi-walled and single-walled) are reviewed. From the industrial point of view, the chemical vapor deposition method has shown advantages over laser vaporization and electric arc discharge methods. This article also presents recent work in the controlled synthesis of carbon nanotubes with ordered architectures. Special carbon nanotube configurations, such as nanocoils, nanohorns, bamboo-shaped and carbon cylinder made up from carbon nanotubes are also discussed.

  16. A power system design and analysis of carbon nano-tubes field emission displays

    Science.gov (United States)

    Wang, Jong C.; Yao, W. C.

    2006-01-01

    In new generation Flat Panel Displays(FPD), a lot of design methods are being deployed, including OLED, PDP, TFT-LCD, Back Projection and Field Emission Display(FED) etc. These new generation FPDs have their respective pluses and minuses. Each has its selling points and market attractions. But among them, FED principles are most close to that of CRT displays. Not only FEDs are advantageous in their good degree of saturation of color, but also they have excellent contrast, luminance and electricity consumption etc. It has been considered as the main products of future generation FPDs. Japan and countries all over the world are successively proposing and launching related FED products in the fields. This will not only drive the FEDs into a wave of new trends, but also it will be able to replace most of the current FPD products within a short time. In this paper, based on these solid trends, we are determined to put into our resources and efforts to perform research on these important FEDs technologies and products, particularly in Carbon Nano-Tubes FEDs(CNT-FED). Our research group has already performed research on CNT-FED subjects for almost three years. During the course of our research, we have run into a lot of issues and problems. We have made every effort to overcome some of them. This paper performs comparative analysis of three power option for small size (4-inch) CNT-FEDs to drive the FED effects such as the direct current power, pulsed power and sinusoidal power respectively. This paper performs comparative analysis of three power options for small sized CNT-FEDs. It was concluded that the pulsed power option will produce the best results overall among the three power options. It is felt that these data presented can then be referenced and used to design a power system circuit to get an optimum design for better luminance and least power consumption for small sized commercial CNT-FED products.

  17. Using copper substrate to enhance electron field emission properties of carbon nanotube/diamond double-layered structure

    Science.gov (United States)

    Yang, Lezhi; Sujith Kumar, C. S.; Li, Yuan-shi; Niakan, Hamid; Zhang, Chunzi; Hirose, Akira; Aravind, Suresh; Yang, Qiaoqin

    2015-01-01

    Vertically aligned carbon nanotube (CNT)/diamond double-layered structure was synthesized on copper (Cu) substrate by hot-filament chemical vapor deposition. The structure was characterized by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The results show that the diamond layer has good adhesion to the Cu substrate and the CNTs have direct contact with the diamond layer. Field electron emission measurement shows that the double-layered structure on copper has very good emission stability and a much lower turn-on field than that on silicon (Si).

  18. Polarized light transmission in ferrofluids loaded with carbon nanotubes in the presence of a uniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Vales-Pinzón, C., E-mail: cvales@mda.cinvestav.mx [Applied Physics Department, CINVESTAV-Unidad Mérida, Antigua carretera a Progreso km 6, A.P. 73, Cordemex, Mérida Yucatán 97310 (Mexico); Alvarado-Gil, J.J. [Applied Physics Department, CINVESTAV-Unidad Mérida, Antigua carretera a Progreso km 6, A.P. 73, Cordemex, Mérida Yucatán 97310 (Mexico); Medina-Esquivel, R. [Facultad de Ingeniería-UADY, Av. Industrias no Contaminantes por Periférico Norte, A.P. 150, Cordemex, Mérida, Yucatán (Mexico); Martínez-Torres, P. [Department of Mechanical Engineering, University of California, Riverside, 900 University Ave., Riverside, CA 92521 (United States)

    2014-11-15

    Magneto-optic phenomena in ferrofluids have been shown to be related to the formation of chain structures, due to the arrangement of the ferromagnetic particles, induced by an applied magnetic field. In this work, the effects on transmission of polarized light due to anisotropic effects induced by an external magnetic field in ferrofluids with carbon nanotubes are studied. The time response of the system presents two well defined stages, in the first one, which is very short, the fluid behaves as a polarizer. In contrast in the second stage, the effects of light transmission dominate. In this stage the transmitted light intensity grows with time and after a long time reaches a constant stable value. It is shown that these phenomena depend on the carbon nanotubes concentration as well as on the strength of the applied magnetic field. Using a simple model that considers a chain-like structure formation, it is possible to determine the rate of agglomeration of the formed structures and the attenuation coefficient of the transmitted light. The formation of nanostructures leads to variation in the transmitted light, depending on the polarization of the incident light. These magnetic nanostructures can find numerous applications in nanotechnology, optical devices and medicine. - Highlights: • Carbon nanotubes in ferrofluids favor the formation of chain-like structures. • In the presence of a magnetic field ferrofluids loaded with CNT behaves as a polarizer. • Transmitted light increases when samples are under a magnetic field then stabilizes. • Attenuation time for transmitted light and agglomeration parameters were studied.

  19. Power flow from a dipole emitter near an optical antenna.

    Science.gov (United States)

    Huang, Kevin C Y; Jun, Young Chul; Seo, Min-Kyo; Brongersma, Mark L

    2011-09-26

    Current methods to calculate the emission enhancement of a quantum emitter coupled to an optical antenna of arbitrary geometry rely on analyzing the total Poynting vector power flow out of the emitter or the dyadic Green functions from full-field numerical simulations. Unfortunately, these methods do not provide information regarding the nature of the dominant energy decay pathways. We present a new approach that allows for a rigorous separation, quantification, and visualization of the emitter output power flow captured by an antenna and the subsequent reradiation power flow to the far field. Such analysis reveals unprecedented details of the emitter/antenna coupling mechanisms and thus opens up new design strategies for strongly interacting emitter/antenna systems used in sensing, active plasmonics and metamaterials, and quantum optics.

  20. Emittance measurement of high-brightness microbeams

    Energy Technology Data Exchange (ETDEWEB)

    Ishizuka, Hiroshi; Nakahara, Yuriko (Fukuoka Inst. of Tech. (Japan)); Kawasaki, Sunao; Musyoki, S.; Shimizu, Hiroshi; Watanabe, Akihiko; Shiho, Makoto

    1994-09-01

    Arrays of microtriodes have recently become available due to the development of microfabricated field-emission electron sources. Computer simulation has shown that the brightness of beams emitted by them is significantly higher than that of the common microbeams, and possible application of the accelerated beam to free electron lasers has been discussed. Experimentation on beam generation has started, but methods for diagnosing the beam have not yet been established. Difficulty is predicted, because of the high brightness, in applying the conventional methods of emittance measurement. In this paper we propose a new method that determines the emittance without using apertures. The cross section of a converging beam is elongated by a quadrupole lens, and parameters of the emittance ellipse are obtained from the beam size on a screen when changing either the strength or the axial position of the quadrupole lens. (author).

  1. Effect of magnetic field on thermal conductivity and viscosity of a magnetic nanofluid loaded with carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Shahsavar, Amin [Kermanshah University of Technology, Kermanshah (Iran, Islamic Republic of); Salimpour, Mohammad Reza; Saghafian, Mohsen [Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Shafii, M. B. [Sharif University of Technology, Tehran(Iran, Islamic Republic of)

    2016-02-15

    The present work examines experimentally the effect of magnetic field on the viscosity and thermal conductivity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe{sub 3}O{sub 4} nanoparticles and Gum arabic (GA) coated carbon nanotubes (CNTs). The hybrid nanofluid was prepared by using ultrasonic dispersion method. Magnetic field was created by a pair of spaced apart magnet plates. The effect of temperature on the time variation of thermal conductivity under applied magnetic field was also investigated. According to the results of this study, viscosity of the hybrid nanofluid increases with the strength of magnetic field, while it decreases with the increase of temperature. Additionally, it is found that the hybrid nanofluid behaves as a shear thinning fluid at low shear rates while it exhibits Newtonian behavior at high shear rates. Furthermore, results show that when an external magnetic field is applied to the studied magnetic nanofluids, the thermal conductivity experiences a peak.

  2. Simulation of diode characteristics of carbon nanotube field-effect transistors with symmetric source and drain contacts

    KAUST Repository

    Li, Jingqi

    2011-09-01

    The diode characteristics of carbon nanotube field-effect transistors (CNTFETs) with symmetric source and drain contacts have been experimentally found at zero gate voltage (Li J. et al., Appl. Phys. Lett., 92 (2008) 133111). We calculate this characteristic using a semiclassical method based on Schottky barrier transistor mechanism. The influences of metal work function, the diameter of the carbon nanotubes and the dielectric thickness on the rectification behavior have been studied. The calculation results show that the metal with a higher work function results in a better diode characteristics for a p-type CNTFET. For single-walled carbon nanotubes (SWNTs) with different band gaps, both forward current and reverse current increase with decreasing band gap, but the ratio of forward current to reverse current decreases with decreasing band gap. This result is well consistent with the experimental observations reported previously. The simulation of the dielectric thickness effect indicates that the thinner the dielectric layer, the better the rectification behavior. The CNTFETs without a bottom gate could not show the diode characteristics, which is consistent with the reported experimental observation. © 2011 Europhysics Letters Association.

  3. Characteristic dynamic modes and domain-wall motion in magnetic nanotubes excited by resonant rotating magnetic fields

    Science.gov (United States)

    Yang, Jaehak; Kim, Junhoe; Kim, Bosung; Cho, Young-Jun; Lee, Jae-Hyeok; Kim, Sang-Koog

    2016-07-01

    We performed micromagnetic numerical calculations to explore a cylindrical nanotube's magnetization dynamics and domain-wall (DW) motions driven by eigen-circular-rotating magnetic fields of different frequencies. We discovered the presence of two different localized DW oscillations as well as asymmetric ferromagnetic resonance precession and azimuthal spin-wave modes at the corresponding resonant frequencies of the circular-rotating fields. Associated with these intrinsic modes, there exist very contrasting DW motions of different speed and propagation direction for a given DW chirality. The direction and speed of the DW propagation were found to be controllable according to the rotation sense and frequency of noncontact circular-rotating fields. Furthermore, spin-wave emissions from the moving DW were observed at a specific field frequency along with their Doppler effect. This work furthers the fundamental understanding of soft magnetic nanotubes' intrinsic dynamic modes and spin-wave emissions and offers an efficient means of manipulating the speed and direction of their DW propagations.

  4. Analysing one isolated single walled carbon nanotube in the near-field domain with selective nanovolume Raman spectroscopy.

    Science.gov (United States)

    Atalay, Han; Lefrant, Serge

    2004-09-01

    In this paper, we describe a new method to the selective nanovolume analysing of one isolated single walled carbon nanotube (SWNT). This concept is based on actually available imaging micro-spectrometry systems for working in near-field domain combined with a stigmatic solid immersion lens. This combination of different analytical methods, and modified and configured equipment entitles us to expand the functionality toward a three-dimensional (3D) nanovolume Raman mapping and photoluminescence intensity with a possible discrimination in polarization, as well as photoluminescence decaytime constant mapping with their unique combination. Subsequently, selective spectra can be acquired from the same location on the samples. By spectrally selecting a SWNT, we registered the spatial distribution of the emitted photons in x, y, z vectors to determine the position of a SWNT in the near-field domain. For the SWNTs that are localized with an accuracy better than 18 nm in the x, y and unity throughput. This near-field capability is applied to resolve local variations unambiguously in the Raman spectrum along one single SWNT. Finally, in this paper, we report what we believe to be the first evidence of Raman mapping and 3D real optical imaging of carbon nanotubes with near-field resolution.

  5. Integration and characterization of aligned carbon nanotubes on metal/silicon substrates and effects of water

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yong; Li Ruying; Liu Hao [Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON. N6A 5B9 (Canada); Sun Xueliang, E-mail: xsun@eng.uwo.ca [Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON. N6A 5B9 (Canada); Merel, Philippe; Desilets, Sylvain [Defence Research and Development Canada- Valcartier, 2459 Boulevard Pie-XI nord, Quebec, QC G3J 1X5 (Canada)

    2009-02-15

    We report here a facile way to grow aligned multi-walled carbon nanotubes (MWCNTs) on various metal (e.g. gold, tungsten, vanadium and copper)/silicon electrically conductive substrates by aerosol-assisted chemical vapor deposition (AACVD). Without using any buffer layers, integration of high quality MWCNTs to the conductive substrates has been achieved by introducing appropriate amount of water vapor into the growth system. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) determination indicate tidy morphology and narrow diameter distribution of the nanotubes as well as promising growth rate suitable for industrial applications. Raman spectra analysis illustrates that the structural order and purity of the nanotubes are significantly improved in the presence of water vapor. The growth mechanism of the nanotubes has been discussed. It is believed that water vapor plays a key role in the catalyst-substrate interaction and nucleation of the carbon nanotubes on the conductive substrates. This synthesis approach is expected to be extended to other catalyst-conductive substrate systems and provide some new insight in the direct integration of carbon nanotubes onto conductive substrates, which promises great potential for applications in electrical interconnects, contacts for field emitters, and other electronic nanodevices.

  6. Field Emission Properties of the Graphene Double-Walled Carbon Nanotube Hybrid Films Prepared by Vacuum Filtration and Screen Printing

    Directory of Open Access Journals (Sweden)

    Jinzhuo Xu

    2013-01-01

    Full Text Available The graphene double-walled carbon nanotube (DWCNT hybrid films were prepared by vacuum filtration and screen printing. Their electron field emission properties have been studied systematically. The electron emission properties of the hybrid films are much better than those of pure DWCNT films and pure graphene films. Comparing with the screen printed films, the vacuum filtered films have many advantages, such as lower turn-on field, higher emission current density, better uniformity, better long-term stability, and stronger adhesive strength with conductive substrates. The optimized hybrid films with 20% weight ratio of graphene, which were fabricated by vacuum filtration, show the best electron emission performances with a low turn-on field of 0.50 Vμm−1 (at 1 μAcm−2 and a high field enhancement factor β of 27000.

  7. Field Effect Transistor Using Carbon Nanotubes and DNA as Electrical Gate

    Science.gov (United States)

    Abdalla, S.; Al-Marzouki, F. M.; Al-Ghamdi, Ahmed A.

    2017-02-01

    We present an electronic sensor in the molecular scale, which is very sensitive for detection and sensing of DNA characteristics and DNA activities in particular activities between DNA duplex and any protein. Here, the device shows that DNA is electronically inserted to be on the same time as an electrical device transducer and as a biological target in a carbon nanotube-DNA-carbon nanotube electronic sensor. We have performed a DNA binding through an amide group by the electron transfer through amide group. The presented device has shown an efficient and rapid procedure to bind the electrical vulnerability of DNA with the detection of enzymatic effectiveness leading to high efficient biosensor.

  8. Magnetic field effect on Poiseuille flow and heat transfer of carbon nanotubes along a vertical channel filled with Casson fluid

    Directory of Open Access Journals (Sweden)

    Sidra Aman

    2017-01-01

    Full Text Available Applications of carbon nanotubes, single walls carbon nanotubes (SWCNTs and multiple walls carbon nanotubes (MWCNTs in thermal engineering have recently attracted significant attention. However, most of the studies on CNTs are either experimental or numerical and the lack of analytical studies limits further developments in CNTs research particularly in channel flows. In this work, an analytical investigation is performed on heat transfer analysis of SWCNTs and MWCNTs for mixed convection Poiseuille flow of a Casson fluid along a vertical channel. These CNTs are suspended in three different types of base fluids (Water, Kerosene and engine Oil. Xue [Phys. B Condens. Matter 368, 302–307 (2005] model has been used for effective thermal conductivity of CNTs. A uniform magnetic field is applied in a transverse direction to the flow as magnetic field induces enhancement in the thermal conductivity of nanofluid. The problem is modelled by using the constitutive equations of Casson fluid in order to characterize the non-Newtonian fluid behavior. Using appropriate non-dimensional variables, the governing equations are transformed into the non-dimensional form, and the perturbation method is utilized to solve the governing equations with some physical conditions. Velocity and temperature solutions are obtained and discussed graphically. Expressions for skin friction and Nusselt number are also evaluated in tabular form. Effects of different parameters such as Casson parameter, radiation parameter and volume fraction are observed on the velocity and temperature profiles. It is found that velocity is reduced under influence of the exterior magnetic field. The temperature of single wall CNTs is found greater than MWCNTs for all the three base fluids. Increase in volume fraction leads to a decrease in velocity of the fluid as the nanofluid become more viscous by adding CNTs.

  9. Magnetic field effect on Poiseuille flow and heat transfer of carbon nanotubes along a vertical channel filled with Casson fluid

    Science.gov (United States)

    Aman, Sidra; Khan, Ilyas; Ismail, Zulkhibri; Salleh, Mohd Zuki; Alshomrani, Ali Saleh; Alghamdi, Metib Said

    2017-01-01

    Applications of carbon nanotubes, single walls carbon nanotubes (SWCNTs) and multiple walls carbon nanotubes (MWCNTs) in thermal engineering have recently attracted significant attention. However, most of the studies on CNTs are either experimental or numerical and the lack of analytical studies limits further developments in CNTs research particularly in channel flows. In this work, an analytical investigation is performed on heat transfer analysis of SWCNTs and MWCNTs for mixed convection Poiseuille flow of a Casson fluid along a vertical channel. These CNTs are suspended in three different types of base fluids (Water, Kerosene and engine Oil). Xue [Phys. B Condens. Matter 368, 302-307 (2005)] model has been used for effective thermal conductivity of CNTs. A uniform magnetic field is applied in a transverse direction to the flow as magnetic field induces enhancement in the thermal conductivity of nanofluid. The problem is modelled by using the constitutive equations of Casson fluid in order to characterize the non-Newtonian fluid behavior. Using appropriate non-dimensional variables, the governing equations are transformed into the non-dimensional form, and the perturbation method is utilized to solve the governing equations with some physical conditions. Velocity and temperature solutions are obtained and discussed graphically. Expressions for skin friction and Nusselt number are also evaluated in tabular form. Effects of different parameters such as Casson parameter, radiation parameter and volume fraction are observed on the velocity and temperature profiles. It is found that velocity is reduced under influence of the exterior magnetic field. The temperature of single wall CNTs is found greater than MWCNTs for all the three base fluids. Increase in volume fraction leads to a decrease in velocity of the fluid as the nanofluid become more viscous by adding CNTs.

  10. Non-Planar Nanotube and Wavy Architecture Based Ultra-High Performance Field Effect Transistors

    KAUST Repository

    Hanna, Amir

    2016-11-01

    This dissertation presents a unique concept for a device architecture named the nanotube (NT) architecture, which is capable of higher drive current compared to the Gate-All-Around Nanowire architecture when applied to heterostructure Tunnel Field Effect Transistors. Through the use of inner/outer core-shell gates, heterostructure NT TFET leverages physically larger tunneling area thus achieving higher driver current (ION) and saving real estates by eliminating arraying requirement. We discuss the physics of p-type (Silicon/Indium Arsenide) and n-type (Silicon/Germanium hetero-structure) based TFETs. Numerical TCAD simulations have shown that NT TFETs have 5x and 1.6 x higher normalized ION when compared to GAA NW TFET for p and n-type TFETs, respectively. This is due to the availability of larger tunneling junction cross sectional area, and lower Shockley-Reed-Hall recombination, while achieving sub 60 mV/dec performance for more than 5 orders of magnitude of drain current, thus enabling scaling down of Vdd to 0.5 V. This dissertation also introduces a novel thin-film-transistors architecture that is named the Wavy Channel (WC) architecture, which allows for extending device width by integrating vertical fin-like substrate corrugations giving rise to up to 50% larger device width, without occupying extra chip area. The novel architecture shows 2x higher output drive current per unit chip area when compared to conventional planar architecture. The current increase is attributed to both the extra device width and 50% enhancement in field effect mobility due to electrostatic gating effects. Digital circuits are fabricated to demonstrate the potential of integrating WC TFT based circuits. WC inverters have shown 2× the peak-to-peak output voltage for the same input, and ~2× the operation frequency of the planar inverters for the same peak-to-peak output voltage. WC NAND circuits have shown 2× higher peak-to-peak output voltage, and 3× lower high-to-low propagation

  11. Observation of picometer vertical emittance with a vertical undulator.

    Science.gov (United States)

    Wootton, K P; Boland, M J; Dowd, R; Tan, Y-R E; Cowie, B C C; Papaphilippou, Y; Taylor, G N; Rassool, R P

    2012-11-09

    Using a vertical undulator, picometer vertical electron beam emittances have been observed at the Australian Synchrotron storage ring. An APPLE-II type undulator was phased to produce a horizontal magnetic field, which creates a synchrotron radiation field that is very sensitive to the vertical electron beam emittance. The measured ratios of undulator spectral peak heights are evaluated by fitting to simulations of the apparatus. With this apparatus immediately available at most existing electron and positron storage rings, we find this to be an appropriate and novel vertical emittance diagnostic.

  12. Isolated High-Purity Platinum Nanowire Growth via Field Emission from a Multi-Walled Carbon Nanotube

    Science.gov (United States)

    Yang, Zhan; Nakajima, Masahiro; Saito, Yahachi; Ode, Yasuhito; Fukuda, Toshio

    2011-03-01

    Isolated high-purity platinum nanowire growth was presented via field emission from the tip of a multi-walled carbon nanotube (MWCNT) with a precursor of cyclopentadienyl-trimethyl-platinum(IV) (CpPtMe3) inside a scanning electron microscope (SEM). A nanomanipulation system was used to adjust the gap between the anode (tungsten probe) and cathode (MWCNT) in order to control the nanowire growth length which achieved a platinum nanowire length of 1.18 µm. The chemical composition of the platinum nanowire analyzed by energy-dispersive X-ray spectroscopy (EDS) shows that the purity of the platinum in the nanowire reaches 94.9 wt %.

  13. Dependence of beam emittance on plasma electrode temperature and rf-power, and filter-field tuning with center-gapped rod-filter magnets in J-PARC rf-driven H{sup −} ion source

    Energy Technology Data Exchange (ETDEWEB)

    Ueno, A., E-mail: akira.ueno@j-parc.jp; Koizumi, I.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H. [J-PARC Center, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan)

    2014-02-15

    The prototype rf-driven H{sup −} ion-source with a nickel plated oxygen-free-copper (OFC) plasma chamber, which satisfies the Japan Proton Accelerator Research Complex (J-PARC) 2nd stage requirements of a H{sup −} ion beam current of 60 mA within normalized emittances of 1.5 π mm mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500 μs × 25 Hz) and a life-time of more than 50 days, was reported at the 3rd international symposium on negative ions, beams, and sources (NIBS2012). The experimental results of the J-PARC ion source with a plasma chamber made of stainless-steel, instead of nickel plated OFC used in the prototype source, are presented in this paper. By comparing these two sources, the following two important results were acquired. One was that the about 20% lower emittance was produced by the rather low plasma electrode (PE) temperature (T{sub PE}) of about 120 °C compared with the typically used T{sub PE} of about 200 °C to maximize the beam current for the plasma with the abundant cesium (Cs). The other was that by using the rod-filter magnets with a gap at each center and tuning the gap-lengths, the filter-field was optimized and the rf-power necessary to produce the J-PARC required H{sup −} ion beam current was reduced typically 18%. The lower rf-power also decreases the emittances.

  14. Effect of N/B doping on the electronic and field emission properties for carbon nanotubes, carbon nanocones, and graphene nanoribbons.

    Science.gov (United States)

    Yu, Shan-Sheng; Zheng, Wei-Tao

    2010-07-01

    Carbon nanotubes, carbon nanocones, and graphene nanoribbons are carbon-based nanomaterials, and their electronic and field emission properties can be altered by either electron donors or electron acceptors. Among both donors and accepters, nitrogen and boron atoms are typical substitutional dopants for carbon materials. The contribution of this paper mainly provides a comprehensive overview of the theoretical topics. The effect of nitrogen/boron doping on the electronic and field emission properties for carbon nanotubes, carbon nanocones, and graphene nanoribbons is reviewed. It is also suggested that nitrogen is more an n-type donor. The discussion about the mechanism of field emission for N-doped carbon nanotubes and electronic structures of N-doped graphene nanoribbons is interesting and timely.

  15. Monolithic multinozzle emitters for nanoelectrospray mass spectrometry

    Science.gov (United States)

    Wang, Daojing; Yang, Peidong; Kim, Woong; Fan, Rong

    2011-09-20

    Novel and significantly simplified procedures for fabrication of fully integrated nanoelectrospray emitters have been described. For nanofabricated monolithic multinozzle emitters (NM.sup.2 emitters), a bottom up approach using silicon nanowires on a silicon sliver is used. For microfabricated monolithic multinozzle emitters (M.sup.3 emitters), a top down approach using MEMS techniques on silicon wafers is used. The emitters have performance comparable to that of commercially-available silica capillary emitters for nanoelectrospray mass spectrometry.

  16. Magnetic-Field Dependence of Tunnel Couplings in Carbon Nanotube Quantum Dots

    DEFF Research Database (Denmark)

    Grove-Rasmussen, Kasper; Grap, S.; Paaske, Jens;

    2012-01-01

    By means of sequential and cotunneling spectroscopy, we study the tunnel couplings between metallic leads and individual levels in a carbon nanotube quantum dot. The levels are ordered in shells consisting of two doublets with strong- and weak-tunnel couplings, leading to gate-dependent level...

  17. Printed PEDOT layers as transparent emitter electrodes for application in flexible inorganic photovoltaic structures

    Science.gov (United States)

    Znajdek, Katarzyna; Sibiński, Maciej; Przymecki, Krzysztof; Wróblewski, Grzegorz; Lisik, Zbigniew

    2016-12-01

    The purpose of the work is to find an appropriate flexible material to replace commonly used transparent conductive oxides (TCO) in photovoltaic (PV) emitter electrode applications. Authors show the alternative, potential possibility of using PEDOT conductive polymer as transparent emitter contacts for thin-film, flexible photovoltaic structures. The vast majority of contacts made of TCO layers, dominantly indium tin oxide ITO, are electrically unstable under the influence of mechanical stresses [1,2,3]. This drawback inhibits their usage in flexible devices, such as solar cells. The need of the development in the field of flexible PV structures induces searching for new materials. Investigated transparent conductive layers (TCL) were made of organic compositions based on PEDOT polymer and their parameters were compared with equally measured parameters of carbon nanotube (CNT) layers, commercial ITO and AgHT ultra-thin silver layers. Transparent conductive layers based on PEDOT:PSS compound were deposited on flexible substrates by screen printing technique. The analysis of achieved results shows the broad spectrum of application possibilities for PEDOT layers.

  18. Length separation of single-walled carbon nanotubes and its impact on structural and electrical properties of wafer-level fabricated carbon nanotube-field-effect transistors

    Science.gov (United States)

    Böttger, Simon; Hermann, Sascha; Schulz, Stefan E.; Gessner, Thomas

    2016-10-01

    For an industrial realization of devices based on single-walled carbon nanotube (SWCNTs) such as field-effect transistors (FETs) it becomes increasingly important to consider technological aspects such as intrinsic device structure, integration process controllability as well as yield. From the perspective of a wafer-level integration technology, the influence of SWCNT length on the performance of short-channel CNT-FETs is demonstrated by means of a statistical and comparative study. Therefore, a methodological development of a length separation process based on size-exclusion chromatography was conducted in order to extract well-separated SWCNT dispersions with narrowed length distribution. It could be shown that short SWCNTs adversely affect integrability and reproducibility, underlined by a 25% decline of the integration yield with respect to long SWCNTs. Furthermore, it turns out that the significant changes in electrical performance are directly linked to a SWCNT chain formation in the transistor channel. In particular, CNT-FETs with long SWCNTs outperform reference and short SWCNTs with respect to hole mobility and subthreshold controllability by up to 300% and up to 140%, respectively. As a whole, this study provides a statistical and comparative analysis towards chain-less CNT-FETs fabricated with a wafer-level technology.

  19. Field emission luminescence of nanodiamonds deposited on the aligned carbon nanotube array

    OpenAIRE

    Fedoseeva, Yu. V.; Bulusheva, L. G.; Okotrub, A. V.; Kanygin, M. A.; Gorodetskiy, D. V.; Asanov, I. P.; Vyalikh, D. V.; A. P. Puzyr; Bondar, V. S.

    2015-01-01

    Detonation nanodiamonds (NDs) were deposited on the surface of aligned carbon nanotubes (CNTs) by immersing a CNT array in an aqueous suspension of NDs in dimethylsulfoxide (DMSO). The structure and electronic state of the obtained CNT?ND hybrid material were studied using optical and electron microscopy and Infrared, Raman, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy. A non-covalent interaction between NDs and CNT and preservation of vertical orientation of...

  20. Field-effect and frequency dependent transport in semiconductor-enriched single-wall carbon nanotube network device.

    Science.gov (United States)

    Jaiswal, Manu; Sangeeth, C S Suchand; Wang, Wei; Sun, Ya-Ping; Menon, Reghu

    2009-11-01

    The electrical and optical response of a field-effect device comprising a network of semiconductor-enriched single-wall carbon nanotubes, gated with sodium chloride solution is investigated. Field-effect is demonstrated in a device that uses facile fabrication techniques along with a small-ion as the gate electrolyte-and this is accomplished as a result of the semiconductor enhancement of the tubes. The optical transparency and electrical resistance of the device are modulated with gate voltage. A time-response study of the modulation of optical transparency and electrical resistance upon application of gate voltage suggests the percolative charge transport in the network. Also the ac response in the network is investigated as a function of frequency and temperature down to 5 K. An empirical relation between onset frequency and temperature is determined.