Showing papers on "Field electron emission published in 1999"
TL;DR: The synthesis of massive arrays of monodispersed carbon nanotubes that are self-oriented on patterned porous silicon and plain silicon substrates is reported and the mechanisms of nanotube growth and self-orientation are elucidated.
Abstract: The synthesis of massive arrays of monodispersed carbon nanotubes that are self-oriented on patterned porous silicon and plain silicon substrates is reported. The approach involves chemical vapor deposition, catalytic particle size control by substrate design, nanotube positioning by patterning, and nanotube self-assembly for orientation. The mechanisms of nanotube growth and self-orientation are elucidated. 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 nanotube devices integrated into silicon technology.
3,093 citations
TL;DR: In this article, high-ordered arrays of parallel carbon nanotubes were grown by pyrolysis of acetylene on cobalt within a hexagonal close-packed nanochannel alumina template at 650°C.
Abstract: Highly-ordered arrays of parallel carbon nanotubes were grown by pyrolysis of acetylene on cobalt within a hexagonal close-packed nanochannel alumina template at 650 °C. The nanotubes are characterized by a narrow size distribution, large scale periodicity, and high densities. Using this method ordered nanotubes with diameters from 10 nm to several hundred nm and lengths up to 100 μm can be produced. The high level of ordering and uniformity in these arrays is useful for applications in data storage, field emission displays and sensors, and offers the prospect of deriving computational functions from the collective behavior of symmetrically coupled nanotubes. The fabrication method used is compatible with standard lithographic processes and thus enables future integration of such periodic carbon nanotube arrays with silicon microelectronics.
679 citations
TL;DR: In this paper, the authors observed that field emitters made from carbon nanotubes exhibit excellent macroscopic emission properties; they can operate at a very large current density, as high as 4 A/cm2.
Abstract: We observe that field emitters made from carbon nanotubes exhibit excellent macroscopic emission properties; they can operate at a very large current density, as high as 4 A/cm2. At electric fields as low as 4–7 V/μm, they emit technologically useful current densities of 10 mA/cm2. We show that the emission originates from nanotube ends with a characteristic structured ring pattern. The emission characteristics and durability of the carbon nanotube cold cathodes offer promising applications for vacuum microelectronic devices.
552 citations
TL;DR: In this article, the emission behavior of single-wall, closed and opened arc-discharge multi-wall and catalytically grown multilayer carbon nanotubes was investigated.
Abstract: We report on the extensive characterization of carbon nanotube electron field emitters. We studied the emission behavior of single-wall, closed and opened arc-discharge multi-wall, and catalytically grown multi-wall nanotubes, as single emitters and in film form. The nanotube field emitters show excellent field emission properties, but significant differences were observed between the different types of nanotubes. To obtain good performances as well as long emitter lifetimes, the nanotubes should be multi-walled and have closed, well-ordered tips. Complementary results such as energy distribution and luminescence induced by the field emission give further precious indications on the field emission mechanism. The large field amplification factor, arising from the small radius of curvature of the nanotube tips, is partly responsible for the good emission characteristics. Additional evidence however shows that the density of states at the tip is non-metallic, appearing in the form of localized states with well-defined energy levels.
467 citations
TL;DR: In this article, the authors demonstrate long-term field emission stability from single-walled carbon nanotubes and demonstrate 100 h of continuous bias field emission with no current degradation.
Abstract: We demonstrate long-term field emission stability from single-walled carbon nanotubes. Unballasted nanotubes operate without degradation for over 350 h at 10−9 Torr. Nanotubes are shown to be significantly less sensitive to operating environments than metallic emitters. In 10−7 Torr of H2O, we demonstrate 100 h of continuous bias field emission with no current degradation. Protrusion growth and current runaway, typical problems for unballasted metal emitters, are not observed with nanotubes. Single-walled nanotubes do show susceptibility to damage by oxidation. We suggest that the exceptional environmental stability of carbon nanotubes is due to a combination of geometry, strong carbon bonding, and the lack of protrusion growth.
304 citations
TL;DR: Aligned carbon nanotubes have been synthesized on transition metal-coated silicon substrates with C2H2 using thermal chemical vapor deposition as mentioned in this paper, and they can be mostly vertically aligned on a large area of plain Si substrates when the density of metal domains reaches a certain value.
250 citations
TL;DR: In this paper, the formation and alignment of the scanning transmission electron microscope (STEM) probe using electron Ronchigrams is described, and practical examples of probe formation, Z-contrast imaging and electron energy-loss spectroscopy (EELS) are demonstrated on a Schottky field emission, JEOL JEM-2010F microscope.
225 citations
TL;DR: In this article, a method for fabricating large-area patterned carbon nanotube field emitters was reported, in which the catalytically grown carbon-nanotube films were prepared by first depositing and patterning a transition metal catalyst film on a substrate and then by heating the substrate in a hydrocarbon atmosphere.
Abstract: A method for fabricating large-area patterned carbon nanotube field emitters is reported. Carbon nanotube films were prepared by first depositing and patterning a transition metal catalyst film on a substrate and then by heating the substrate in a hydrocarbon atmosphere. The catalytically grown carbon nanotube films had a high emission current density of about 100–1000 mA cm−2 at a low macroscopic electric field of 10–15 V μm−1. Electron emission from the carbon nanotube films was observed at a macroscopic electric field of 1–5 V μm−1. The I–V curve obeyed the Fowler–Nordheim (FN) relationship at low emission current density, but at high electric field, the I–V curve deviated from the FN relationship due to defects on the tip of the catalytically grown carbon nanotubes. The catalytic growth of carbon nanotubes offers an inexpensive and controllable process to produce a uniform, high density of emitters on large substrate surfaces.
208 citations
01 May 1999
TL;DR: In this article, the authors measured field emission energy distributions of electrons emitted from individual multi-walled carbon nanotubes mounted on tungsten tips, and extracted the distance between the highest filled energy level of the nanotube and the vacuum potential from the energy distribution and the Fowler-Nordheim plot.
Abstract: 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.
207 citations
TL;DR: In this article, a silicon carbide (SiC) nanowires on a silicon substrate were prepared using hot-filament-assisted chemical-vapor deposition with a solid silicon and carbon source.
Abstract: Silicon carbide (SiC) nanowires on a silicon substrate were prepared using hot-filament-assisted chemical-vapor deposition with a solid silicon and carbon source. The SiC nanowires show good field-emitting properties as revealed by the current–voltage characteristics. Together with its ease of preparation, these SiC nanowires are shown to have great potential in the area of electron field-emitting devices.
207 citations
TL;DR: In this paper, it was argued that the facile electron field emission from carbon systems occurs primarily because surface groups such as C-H can produce large changes in local electron affinity, so that electric fields from the anode can be focused toward unhydrogenated surface areas of high affinity, the fields ending on negative charges in an underlying depletion layer.
Abstract: It is argued that the facile electron field emission from carbon systems occurs primarily because surface groups such as C–H can produce large changes in local electron affinity, so that electric fields from the anode can be focused toward unhydrogenated surface areas of high affinity, the fields ending on negative charges in an underlying depletion layer. The resulting downward band bending creates large surface fields which allow Fowler–Nordheim emission, while not exceeding the material’s breakdown field.
TL;DR: In this article, a continuous SiNW film was prepared by grinding the pieces of sponge-like SiNWs to powder, then dispersing and sticking the powder onto a Si wafer.
Abstract: Silicon nanowires (SiNWs) were synthesized using laser ablation. A continuous SiNW film was prepared by grinding the pieces of sponge-like SiNWs to powder, then dispersing and sticking the powder onto a Si wafer. The field emission characteristics of the SiNW film were studied based on current–voltage measurements and the Fowler–Nordheim equation. The electron field emission increased with decreasing diameter of SiNWs. A hydrogen plasma treatment of the SiNW film aimed at reducing the oxide overlayer improved the emission uniformity of the film.
TL;DR: In this paper, an aligned nitrogen-containing carbon nanofibers consisting of polymerized "nanobells" have been grown on a large scale using microwave plasma-assisted chemical-vapor deposition with a mixture of methane and nitrogen.
Abstract: Aligned nitrogen-containing carbon nanofibers consisting of polymerized “nanobells” have been grown on a large scale using microwave plasma-assisted chemical-vapor deposition with a mixture of methane and nitrogen. A greater part of the fiber surface consists of open ends of the graphitic sheets. A side-emission mechanism is proposed. A low-threshold field of 1.0 V/μm and a high-emission current density of 200 mA/cm2 for an applied field of 5–6 V/μm were achieved, implying that the materials have a high potential for future application as electron field emitters, especially in flat-panel displays.
TL;DR: In this paper, the field-emission properties of cold cathodes produced using nano-porous anodic aluminum oxide (AAO) templates are reported, and significant field-emission currents are obtained at threshold voltages as low as 80 V (corresponding to fields of 3-4 V/μm) on samples of nanotube tangles.
Abstract: The field-emission properties of cold cathodes produced using nano-porous anodic aluminum oxide (AAO) templates are reported. Several types of field emitters were fabricated: aligned copper nanowires grown halfway up the parallel nano-pores of the AAO; aligned multiwalled carbon nanotubes grown to the top of the pores; surfaces overgrown with random tangles of carbon nanotubes; and empty AAO templates. Significant field-emission currents (field enhancement values ∼ 1800) were obtained at threshold voltages as low as 80 V (corresponding to fields of 3–4 V/μm) on samples of nanotube tangles. Perfectly aligned carbon nanotubes were less efficient field emitters and had lower field enhancement values. These observations are explained in terms of the mean separation of active tips in the two sets of samples. Empty templates and metal nanowire arrays show lower field enhancements and higher threshold electric fields (40–70 V/μm). In these samples significant field-emission currents are produced at relatively low applied voltages of 110–300 V due to the small inter-electrode separations achieved on depositing a metal grid directly on the surface of the porous template.
TL;DR: In this article, the authors observed three distinct behavioral states in field emission from single-walled carbon nanotubes between temperatures of 300 and 1800 K and found that the stable behavior of clean nanotube states breakdown at extremely high currents and temperatures.
Abstract: We observe three distinct behavioral states in field emission from single-walled carbon nanotubes between temperatures of 300 and 1800 K. At room temperature, nanotubes emit through adsorbate states correlated to the presence of water. These states are removed above 900 K. After adsorbate removal, the apparently clean nanotube state shows lower emission current and substantially reduced emission noise. Current-temperature measurements identify a deviation from metallic tunneling behavior. Nanotube field emission undergoes a second, field-stabilized transition at high temperatures which reduces the current by as much as five orders of magnitude relative to the room temperature current. This current decrease is 100% recoverable. In addition, the stable behavior of clean nanotube states breakdown at extremely high currents and temperatures. Rings form around the field emission images, similar to those observed in metals at extreme current densities. Under these extreme conditions, we also find evidence for t...
TL;DR: In this article, a spin-dependent screening electric field was proposed for electron screening at the surface of a ferromagnetic metal and a set of integrodifferential equations for screening potentials was derived and solved in some limiting cases.
Abstract: We have examined electron screening at the surface of a ferromagnetic metal. In an applied electric field, the surface develops an induced charge and magnetization. This can be described in terms of a novel spin-dependent screening electric field. A set of integrodifferential equations for screening potentials is derived and solved in some limiting cases. The significant implication relevant to spin-polarized transport in field emission and in magnetic tunnel junctions is discussed.
TL;DR: In this paper, the phase relaxation length and femtosecond lifetime of hot quasiparticles on metal surfaces were measured using a 4 K scanning tunneling microscope, which was used to study the spatial decay of interference patterns in the local density of states for surface state electrons on Ag and Cu.
Abstract: We report on a novel approach to measure the phase relaxation length and femtosecond lifetime of hot quasiparticles on metal surfaces A 4 K scanning tunneling microscope has been used to study the spatial decay of interference patterns in the local density of states for surface state electrons on Ag(111) and Cu(111) This decay is governed by inelastic; electron-electron scattering We find a (E - E-F)(-2) energy dependence of the lifetimes for both Ag and Cu, and our values are comparable to the corresponding bulk electron lifetimes This indicates that electron-electron interaction of hot surface state electrons with the Fermi sea is dominated by the underlying bulk electrons [S0031-9007(99)09260-1]
TL;DR: In this article, the photoassisted electron emission of single-crystal diamond (111) for photon energies from just above the diamond band gap of 5.5 eV well into the sub-band-gap regime was studied.
Abstract: We have studied the photoassisted electron emission of single-crystal diamond (111) for photon energies from just above the diamond band gap of 5.5 eV well into the sub-band-gap regime $(h\ensuremath{
u}\ensuremath{\approx}2.8\mathrm{eV}).$ As an independent parameter, the electron affinity was varied between -1.27 eV [negative electron affinity (NEA)] and +0.38 eV [positive electron affinity (PEA)] by changing the hydrogen coverage of the surface. A substantial sub-band-gap emission band with constant intensity is observed in all cases. Except for the NEA surfaces, it dominates the electron flux. We attribute this intense band to nanometer-size graphitic patches which cover less than 1% of the surface area. The low-energy threshold for this emission band is, however, not determined by intrinsic properties of graphite, but controlled by the work function of the surrounding diamond matrix. The details of this inhomogeneous emission model, which may have implications for the field emission from nanocrystalline diamond films, are discussed.
TL;DR: A blue emission powder phosphor Sr2CeO4 for field emission displays was prepared using a chemical coprecipitation technique, which was most suitable for large-scale production as mentioned in this paper.
Abstract: A blue emission powder phosphor Sr2CeO4 for field emission displays was prepared using a chemical coprecipitation technique, which is most suitable for large-scale production. The powders were fired at different temperatures to optimize the properties. Firing the powder at 1200 °C for 2 h gave the highest luminescence efficiency of 5.4 lm/W at 4 kV and 29.0 lm/W at 10 kV. The emission peak of this phosphor is at ∼470 nm and Commission International de l’Eclairage coordinates are x=0.19, y=0.26.
TL;DR: In this article, a thorough analytical model of a field emitter array is presented, beginning with a review of the nature of field emission and continuing with a single emitter and the operation of an array of emitters, and attention is directed towards those features of FEAs that render them attractive as cold cathode candidates for electron beam generation.
Abstract: Field emitter arrays (FEAs) stand to strongly impact device performance when physical size, weight, power consumption, beam current, and/or high pulse repetition frequencies are an issue. FEAs are capable of instant ON/OFF performance, high brightness, high current density, large transconductance to capacitance ratio, and low voltage operation characteristics. Advanced microwave power tubes, and in particular, inductive output amplifiers, are by far the most technically challenging use to date. Other important uses include, e.g., electron sources for micropropulsion systems–Hall thrusters–and tethers for satellites, and (the most widely pursued application) field emission displays. The characteristics of field emitters that make them attractive to such applications shall be surveyed. A thorough analytical model of a field emitter array, beginning with a review of the nature of field emission and continuing with an analytical model of a single emitter and the operation of an array of emitters, shall be presented. In particular, attention shall be directed towards those features of FEAs that render them attractive as cold cathode candidates for electron beam generation. Tip characteristics, such as emission distribution, and array operation, such as space charge effects, will be analyzed in the context of the model. Finally, restricting attention to microwave applications, the performance of a tapered-helix inductive output amplifier to highlight the advantages of high frequency emission gating of the electron beam in a power tube shall be investigated.
TL;DR: In this paper, tetrahedral amorphous carbon (ta-C) films were subjected to Ar, H2, and O2 plasma treatments to change their surface condition and were deposited on substrates of different work functions.
Abstract: To understand the mechanism of electron field emission from diamond-like carbon, tetrahedral amorphous carbon (ta-C) films were subjected to Ar, H2, and O2 plasma treatments to change their surface condition and were deposited on substrates of different work function. The threshold fields and current densities for undoped ta-C are found to be significantly improved by the plasma treatments, largely due to an increase in emission site density, while little dependence was found on work function of substrate. This suggests that the main barrier to emission from ta-C is at the front surface.
01 May 1999
TL;DR: In this article, an individual multi-wall nanotube and a bundle of single-wall nano-tubes were investigated using a field emission microscope with a probe hole and measured currentvoltage characteristics followed the Fowler-Nordheim equation at low current density, whereas at higher current the increase in current became dull and deviated from the F-N line.
Abstract: Field emission from an individual multiwall nanotube and a bundle of single-wall nanotubes was investigated using a field emission microscope with a probe hole. Measured current–voltage characteristics followed the Fowler–Nordheim equation at low current density, whereas at higher current the increase in current became dull and deviated from the F–N line. As an application of nanotube field emitters, we manufactured the lighting elements of a triode vacuum tube by replacing conventional thermionic cathodes with multiwall nanotube field emitters. Stable electron emission, adequate luminance, and long life of the emitters were demonstrated.
TL;DR: An aligned and well-distributed carbon nanotubes array was produced by pyrolysis of hydrocarbons catalyzed by nickel nanoparticles embedded in porous silicon (PS) substrates.
Abstract: An aligned and well-distributed carbon nanotubes array was produced by pyrolysis of hydrocarbons catalyzed by nickel nanoparticles embedded in porous silicon (PS) substrates. Scanning electron microscope images show that the nanotubes form an aligned array approximately perpendicular to the surface of the PS substrate and the diameters of most of the tubes within the array are 10–30 nm. High-magnification transmission electron microscopy images confirmed that the nanotubes are well graphitized and typically consist of about 15 concentric shells of carbon sheets. Furthermore, the strong field emission from the aligned carbon nanotubes emitter by pyrolysis of hydrocarbons was observed.
30 Sep 1999
TL;DR: In this paper, as-grown multi-wall nanotubes (MWNTs), purified MWNTs and single-wall NN were investigated by field emission microscopy (FEM).
Abstract: Field emission from (i) as-grown multiwall nanotubes (MWNTs), (ii) purified MWNTs and (iii) purified single-wall nanotubes (SWNTs) was investigated by field emission microscopy (FEM). As an application of nanotube field emitters, we manufactured cathode ray tube (CRT) lighting-elements by replacing conventional thermionic cathodes with nanotube field emitters. Stable electron emission, high emission current with low electric field (∼10 mA/cm2 at 1.5 V/μm), and long life of the emitters were demonstrated.
TL;DR: In this paper, the field emission properties of nitrogen-doped diamond grown by microwave plasma chemical vapor deposition were explored. But the results indicated relatively high threshold fields (>100 V/μm) for electron emission.
Abstract: This study explores the field emission properties of nitrogen-doped diamond grown by microwave plasma chemical vapor deposition. Over 70 nitrogen-doped diamond samples were grown on silicon and molybdenum under varying process conditions. Under certain conditions, films can be grown which exhibit photoluminescence bands at 1.945 and 2.154 eV that are attributed to single substitutional nitrogen. Photoelectron emission microscopy with UV free electron laser excitation indicated a 0 or negative electron affinity. Field emission characteristics were measured in an ultrahigh vacuum with a variable distance anode technique. For samples grown with gas phase [N]/[C] ratios less than 10, damage from microarcs occurred during the field emission measurements. Samples grown at higher [N]/[C] content could be measured prior to an arcing event. Contrary to other reports on nitrogen-doped diamond, these measurements indicate relatively high threshold fields (>100 V/μm) for electron emission. We suggest that the nitroge...
TL;DR: In this paper, a nanocrystalline diamond films were deposited on p-type Si(100) substrates using plasma enhanced chemical vapor deposition (CVD) and showed good field emission properties with threshold fields of around 5 V'μm−1 (for 1 nA emission current).
Abstract: We have deposited nanocrystalline diamond films on p-type Si(100) substrates using plasma enhanced chemical vapor deposition (CVD). The diamond films were deposited at substrate temperatures between 950 and 980 °C using a high methane concentration of 5% in H2. The films obtained showed good field emission properties with threshold fields of around 5 V μm−1 (for 1 nA emission current). X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy showed that the nanocrystalline films still exhibit the basic electronic features of diamond with a band gap of 5.5 eV and a negative electron affinity when the surface is hydrogen plasma treated. The Fermi level position in these films is found to be 1±0.2 eV above the valence band maximum. The energy resolved field emission measurements show the typical asymmetric peak shape of Fowler-Nordheim (FN) tunneling through a surface potential barrier. The electrons emitted originate from a continuum of electronic states at the Fermi energy of the emitter...
TL;DR: In this article, a high vacuum scanning tunneling-field emission microscope was applied for simultaneous mapping of FEE intensity, morphology, work function and local electroconductivity evaluation.
TL;DR: In this article, lowvoltage electron field emission was obtained for carbon films grown by the chemical vapor deposition (CVD) method in hydrogen-methane plasma activated by a d.c. discharge.
Patent•
13 May 1999
TL;DR: In this article, the authors describe the use of a high amplification factor film as a phosphor biasing electrode, and variability of the phosphor bias potential to achieve brightness or gray scale control.
Abstract: Cathodoluminescent field emission display devices feature phosphor biasing, amplification material layers for secondary electron emissions, oxide secondary emission enhancement layers, and ion barrier layers of silicon nitride, to provide high-efficiency, high-brightness field emission displays with improved operating characteristics and durability. The amplification materials include copper-barium, copper-beryllium, gold-barium, gold-calcium, silver-magnesium and tungsten-barium-gold, and other high amplification factor materials fashioned to produce high-level secondary electron emissions within a field emission display device. For enhanced secondary electron emissions, an amplification material layer can be coated with a near mono-molecular film consisting essentially of an oxide of barium, beryllium, calcium, magnesium or strontium. Use of a high amplification factor film as a phosphor biasing electrode, and variability of the phosphor biasing potential to achieve brightness or gray scale control are further described in the disclosure.
TL;DR: In this paper, a nanoscale electron tube with a field-emission cathode and a control gate (nanotriode) has been fabricated and characterized, and the turn-on voltage is less than 10 V and is independent of ambient temperature.
Abstract: A nanoscale electron tube with a field-emission cathode and a control gate (nanotriode) has been fabricated and characterized. Electrons are field emitted from metal nanopillars with radii of about 1 nm into a vacuum nanochamber, collected at the anode, and controlled by a gate electrode. The nanochamber is sealed by an integrated anode and has vertical and horizontal dimensions of 100 nm. The turn-on voltage is less than 10 V and is independent of ambient temperature. Currents of 10 nA and transconductances of up to 6 nS per device have been observed; this would yield a transconductance of 60 S cm−2 at the maximum packing density of 1010 nanotriodes cm−2 for these devices. The emission stability is better than 3% at room temperature and improves to 0.1% at 20 K.