Showing papers on "Field electron emission published in 2004"
TL;DR: The carbon nanosheets were synthesized on a variety of substrates by radio-frequency plasma-enhanced chemical vapor deposition without any catalyst or special substrate treatment.
Abstract: Free-standing graphite sheets with thickness less than 1nm, “carbon nanosheets,” were synthesized on a variety of substrates by radio-frequency plasma-enhanced chemical vapor deposition without any catalyst or special substrate treatment. The nanosheets consist of one to three graphene layers with a large smooth surface topography, standing roughly vertical to the substrate. Due to the atomic thickness and corrugated nature of nanosheets, low-energy vibrational modes are present in the Raman spectra. The low turn-on field of 4.7 V/μm for electron field emission suggests that the carbon nanosheets could be used as a potential edge emitter.
445 citations
TL;DR: In this article, the PECVD growth process, and the microfabrication techniques needed to produce well defined carbon nanotube based micro-electron sources for use in novel parallel e-beam lithography and high frequency microwave amplifier systems are reviewed.
Abstract: Micro and nano-structurally rich carbon materials are alternatives to conventional metal/silicon tips for field emission sources. In particular, carbon nanotubes exhibit extraordinary field emission properties because of their high electrical conductivity, their high aspect ratio “whisker-like” shape for optimum geometrical field enhancement, and remarkable thermal stability. This paper will review the PECVD growth process, and the microfabrication techniques needed to produce well defined carbon nanotube based micro-electron sources for use in novel parallel e-beam lithography and high frequency microwave amplifier systems.
392 citations
TL;DR: An overview of the present status of research on carbon nanotube (CNT) field emitters and their applications is given and a detailed overview is given of the measured emission properties and related topics of CNT electron sources.
Abstract: In this review we give an overview of the present status of research on carbon nanotube (CNT) field emitters and their applications. Several different construction principles of field-emission devices with CNTs are summarized. The emission mechanism is introduced and a detailed overview is given of the measured emission properties and related topics of CNT electron sources. We give also several examples of field-emission devices with CNT electron emitters that are presently being investigated in the academic world as well as in industry. Carbon nanotube electron sources clearly have interesting properties, such as low voltage operation, good stability, long lifetime and high brightness. The most promising applications are the field-emission display and high-resolution electron-beam instruments. But several hurdles remain, such as the manufacture of an electron source or an array of electron sources with exactly the desired properties in a reproducible manner.
277 citations
TL;DR: In this article, the authors review the latest advances in the production and state-of-the-art characterization of B and N-doped carbon nanotubes and nanofibers and briefly discuss different approaches to producing these novel doped nano-systems.
255 citations
254 citations
TL;DR: In this article, a vertically aligned ZnO fiber array was fabricated by vapor phase transport method of heating the mixture of zinc oxide, gallium oxide, and graphite powders in air.
Abstract: Gallium-doped nanostructural zinc oxide fibers have been fabricated by vapor-phase transport method of heating the mixture of zinc oxide, gallium oxide, and graphite powders in air. The zinc oxide fibers grew along [002] direction, forming a vertically aligned array that is predominantly perpendicular to the substrate surface. With a gallium doping concentration of 0.73 at. %, the corresponding carrier concentration and resistivity were 3.77×1020 cm−3 and 8.9×10−4 Ω cm, respectively. The field emission of these vertically aligned ZnO fiber arrays showed a low field emission threshold (2.4 V/μm at a current density of 0.1 μA/cm2), high current density, and high field enhancement factor (2317). The dependence of emission current density on the electric field followed Fowler–Nordheim relationship. The enhanced field emission is attributed to the aligned structure, good crystal quality, and especially, the improved electrical properties (increased conductivity and reduced work function) of the nanofibers due ...
247 citations
TL;DR: In this article, a detailed study of the effects of electric field and temperature on the rate of electron emission from barrier traps in AlGaN/GaN high-electron-mobility transistors is presented.
Abstract: Defect-related localized electronic states in AlGaN/GaN transistors give rise to commonly observed charge trapping phenomena. Electron dynamics through the trapping centers is strongly affected by electric fields, which can exceed values of 10(6) V/cm during device operation. The field-assisted emission characteristics provide a unique way to determine the physical properties of the trapping centers. We present a detailed study of the effects of electric field and temperature on the rate of electron emission from the barrier traps in AlGaN/GaN high-electron-mobility transistors. We demonstrate that for temperatures above 250 K, the Poole-Frenkel (PF) emission is the dominant mechanism for electrons to escape from the trapping centers. The emission rate increases exponentially with the square root of the applied field consistent with the decrease of the apparent activation energy predicted by the PF model. We find that the observed trapping center is described by the attractive long-range Coulomb potential with the zero-field binding energy of similar to0.5 eV. (C) 2004 American Institute of Physics.
191 citations
TL;DR: In this article, an extremely low operating electric field has been achieved on zinc oxide (ZnO) nanowire field emitters grown on carbon cloth using thermal vaporization and condensation.
Abstract: An extremely low operating electric field has been achieved on zinc oxide (ZnO) nanowire field emitters grown on carbon cloth. Thermal vaporization and condensation was used to grow the nanowires from a mixture source of ZnO and graphite powders in a tube furnace. An emission current density of 1mA∕cm2 was obtained at an operating electric field of 0.7V∕μm. Such low field results from an extremely high field enhancement factor of 4.11×104 due to a combined effect of the high intrinsic aspect ratio of ZnO nanowires and the woven geometry of carbon cloth.
191 citations
TL;DR: In this article, the ZnO nanowires synthesized by vapor-liquid solid growth mechanism with Cu and Au as the catalyst were investigated and significant differences in their field emission and photofluorescent characteristics were observed.
Abstract: The ZnO nanowires synthesized by vapor-liquid-solid growth mechanism with Cu and Au as the catalyst were investigated. The principal differences in morphology between Cu and Au catalyzed ZnO nanowires are observed and lead to significant differences in their field emission and photofluorescent characteristics. The Cu catalyzed ZnO nanowires with a high-quality wurtzite structure were grown vertically on p-type Si(100) substrate along [0002] direction. A strong ultraviolet emission at 381 nm is observed. These ZnO nanowires show excellent field emission properties with turn-on field of 0.83 V/μm and corresponding current density of 25 μA/cm2. The emitted current density of the ZnO nanowires is 1.52 mA/cm2 at a bias field of 8.5 V/μm. The large field emission area factor, β arising from the morphology of the nanowire field emitter, is partly responsible for the good emission characteristics. The ZnO nanowires with high emission current density and low turn-on field are expected to be used in field emission ...
189 citations
172 citations
TL;DR: In this paper, the Fowler-Nordheim behavior of individual carbon nanotubes was investigated and it was shown conclusively that individual carbon-nanotube electron emitters exhibit Fowler-nordheim behaviour and have a work function of 5.1±0.1eV for the nanots under investigation, which had diameters of 1.4 and 4.9nm.
Abstract: Electron emission measurements were conducted on individual carbon nanotubes. The nanotubes had a closed end and their surfaces were thoroughly cleaned. It is shown conclusively that individual carbon nanotube electron emitters indeed exhibit Fowler–Nordheim behavior and have a work function of 5.1±0.1eV for the nanotubes under investigation, which had diameters of 1.4 and 4.9nm.
Patent•
22 Apr 2004TL;DR: In this paper, a computed tomography (CT) device consisting of an x-ray source and an X-ray detecting unit is described. But the authors do not provide a detailed description of the system.
Abstract: Computed tomography device comprising an x-ray source and an x-ray detecting unit. The x-ray source comprises a cathode with a plurality of individually programmable electron emitting units that each emit an electron upon an application of an electric field, an anode target that emits an x-ray upon impact by the emitted electron, and a collimator. Each electron emitting unit includes an electron field emitting material. The electron field emitting material includes a nanostructured material or a plurality of nanotubes or a plurality of nanowires. Computed tomography methods are also provided.
TL;DR: A quantum-mechanical simulation is carried out to investigate the charge distribution and electrostatic potential along a single-walled carbon nanotube under realistic field-emission experimental conditions and finds a single layer of carbon atoms is found sufficient to shield most of the electric field except at the tip where strong field penetration occurs.
Abstract: A quantum-mechanical simulation is carried out to investigate the charge distribution and electrostatic potential along a 1 microm long (5,5) single-walled carbon nanotube under realistic field-emission experimental conditions. A single layer of carbon atoms is found sufficient to shield most of the electric field except at the tip where strong field penetration occurs. The penetration leads to a nonlinear decrease of potential barrier for emission, which is equally responsible for the low threshold voltage besides the well-known geometrical field enhancement factor.
TL;DR: In this paper, the fabrication of vertically aligned cobalt nanowire arrays on planar surfaces as well as preliminary field-emission (FE) experiments using them as cold electron cathodes are presented.
Abstract: We present the fabrication of vertically aligned cobalt nanowire arrays on planar surfaces as well as preliminary field-emission (FE) experiments using them as cold electron cathodes. These arrays are obtained by electrodeposition into nanoporous templates on Au/Ti/Si substrates at very low temperature (<100 degreesC). After the removal of the template, the arrays consist of statistically positioned vertical free-standing nanowires with high aspect ratios, uniform dimensions, and predetermined densities. The electron field-emission measurements show metallic and reproducible characteristics. Emission is found to be reasonably homogeneous over the whole sample area, and a current density of 1 mA/cm(2) has been obtained. We show that the growth process permits us to predetermine the field amplification factor precisely, which is of primary importance for FE sources, A large variety of FE applications can be envisaged, including FE displays and microwave amplifiers.
TL;DR: In this paper, the authors demonstrate the production of integrated-gate nanocathodes which have a single carbon nanotube or silicon nanowire/whisker per gate aperture.
Abstract: We demonstrate the production of integrated-gate nanocathodes which have a single carbon nanotube or silicon nanowire/whisker per gate aperture. The fabrication is based on a technologically scalable, self-alignment process in which a single lithographic step is used to define the gate, insulator, and emitter. The nanotube-based gated nanocathode array has a low turn-on voltage of 25 V and a peak current of 5 μA at 46 V, with a gate current of 10 nA (i.e., 99% transparency). These low operating voltage cathodes are potentially useful as electron sources for field emission displays or miniaturizing electron-based instrumentation.
TL;DR: In this paper, tetrapod-like ZnO nanostructures with high purity were applied to a highly doped silicon substrate covered by a Au layer with a thickness of 300nm.
Abstract: Stable field emission is realized from well-separated tetrapod-like ZnO nanostructures with high purity. The ZnO nanostructures are painted on a highly doped silicon substrate covered by a Au layer with a thickness of 300nm. An emission current density of 18mA∕cm2 is obtained and degradation was not observed over a three day period. The fluctuations of the emission current are less than 2%. These experimental results indicate that tetrapod-like ZnO nanostructures are promising materials as cold cathodes for mass production.
TL;DR: In this paper, a simple and easily reproducible method of preparing single-atom tips by electroplating Pd or Pt on single-crystal W(111) tips followed by thermal annealing in a vacuum is reported.
Abstract: A new, simple, and easily reproducible method of preparing single-atom tips by electroplating Pd or Pt on single-crystal W(111) tips followed by thermal annealing in a vacuum is reported. These tips are both thermally and chemically stable and can also be regenerated when accidentally damaged. The atomic structures of the tips are identical to those prepared by vacuum evaporation, as observed by field ion microscopy. The corresponding field emission characteristics are investigated with field emission microscopy.
TL;DR: A quasidynamic method has been developed to simulate the breakdown process and calculate the critical field, critical emission current density and critical temperature beyond which thermal runaway occurs before the CNT temperature reaches its melting point.
Abstract: We report a physical mechanism responsible for initiating a vacuum breakdown process of a single carbon nanotube (CNT) during field emission. A quasidynamic method has been developed to simulate the breakdown process and calculate the critical field, critical emission current density and critical temperature beyond which thermal runaway occurs before the CNT temperature reaches its melting point. This model is in good agreement with experiments carried out with a single CNT on a silicon microtip.
TL;DR: AlN nanoneedles with an average tip dimension of ∼15nm were synthesized via a simple vapor deposition method as mentioned in this paper, and they exhibit excellent field-emission properties with a low turn-on field of 31V∕μm and a high current density of 47mA∕cm2 at the field of 99V√μm.
Abstract: AlN nanoneedles with an average tip dimension of ∼15nm were synthesized via a simple vapor deposition method The AlN nanoneedles exhibit excellent field-emission properties with a low turn-on field of 31V∕μm and a high current density of 47mA∕cm2 at the field of 99V∕μm The field enhancement factor for a single nanoneedle is estimated to be as high as 30 000 due to its small tip radius These features make the AlN nanoneedles a competitive candidate for field-emission-based displays
TL;DR: In this article, the authors synthesize well-ordered crystalline copper oxide (CuO) nanofibril arrays using a procedure involving electrodeposition followed by a gas-solid reaction.
Abstract: Films of well-ordered crystalline copper oxide (CuO) nanofibril arrays were synthesized using a procedure involving electrodeposition followed by a gas-solid reaction. Analyses showed that the nanocrystalline CuO nanofibrils with a mean length of 8 μm have an average density of 107–108/cm2. Photoluminescence measurements showed a main peak in the visible light band at 410 nm, and the band gap energy was estimated to be 1.67 eV. It was found that the film of aligned CuO nanofibrils has typical Fowler–Nordheim plots in the follow-up electron field emission test. Typical turn-on voltage was detected at ∼6 V/μm with an emission area of 1 mm2. The Fowler–Nordheim model was employed to analyze the I–V data obtained. The work function of the nanofibrils was estimated to be in the range of 4.1–4.3 eV.
TL;DR: In this article, the authors report on field emission from SnO2 nanobelt arrays with the length of about 90 μm grown on silicon substrates, and the current density rapidly reaches 2.1mA∕cm2 at the electrical field of 4.4V∕μm at d=0.35mm.
Abstract: We report on field emission from SnO2 nanobelt arrays with the length of about 90 μm grown on silicon substrates. The turn-on field of the nanobelt arrays at the current density of 1μA∕cm2, is 4.5, 3.0, 2.4, and 2.3V∕μm as the distance between anode and cathode (d) is 0.1, 0.2, 0.35, and 0.5 mm, respectively. The current density rapidly reaches 2.1mA∕cm2 at the electrical field of 4.4V∕μm at d=0.35mm. The current density is higher than or comparable to those of the carbon nanotubes and other one-dimensional nanostructured materials. We also discuss the mechanism of high current densities and estimate the enhancement factor according to both the Fowler–Nordheim law and the reported model on micrometer-long of carbon nanotubes.
TL;DR: In this article, high-resolution electron field emission cathodes were fabricated at room temperature by a high throughput electrophoresis process using functionalized carbon nanotubes (CNTs).
Abstract: High-resolution electron field emission cathodes were fabricated at room temperature by a high throughput electrophoresis process using functionalized carbon nanotubes (CNTs). Well-defined and adherent CNT patterns with 20 μm feature size were achieved on a variety of substrates with fine control of the CNT morphology. The cathodes show uniform emission pattern across the entire surfaces and emission current with long-term stability. This room-temperature liquid-phase process is efficient and has no intrinsic limit on the deposition area. The emission characteristics of these cathodes compare favorably to those from other fabrication methods for CNT based field emission display applications.
TL;DR: In this article, electrical transport properties of boron nitride nanotubes using an in situ manipulation stage inside a transmission electron microscope were measured in a field emission geometry, but in contact the Nanotubes are insulating at low bias.
TL;DR: In this article, the zinc oxide nanofibers were fabricated by a simple vapor transport method of heating the mixture of zinc oxide, gallium oxide, and carbon powders in air.
Abstract: Nanostructural zinc oxide fibers have been fabricated by a simple vapor transport method of heating the mixture of zinc oxide, gallium oxide, and carbon powders in air. The zinc oxide nanofibers showed cauliflower-like, disordered, vertically and horizontally aligned morphologies in different temperature regions. The aligned nanofibers were composed of hexagonal zinc oxide with good crystallinity. Gallium was doped into zinc oxide with a concentration of 0.73 at. %. The growth process and the characteristics can be interpreted by a vapor-liquid-solid mechanism. The field emission of the vertically aligned zinc oxide fiber array showed a low field emission threshold, high current density, rapid surge, and high field enhancement factor. The threshold electric field is about 2.4 V/μm at a current density of 0.1 μA/cm−2. The field enhancement factor was 2991. The emission current density and the electric field followed the Fowler–Nordheim relationship.
TL;DR: In this article, the effect of field emission cycles on printed carbon nanotubes was investigated using scanning electron microscopy and currentvoltage measurement, and it was shown that after multiple emission cycles, the printed carbon tubes irreversibly deformed to orient themselves parallel to the field direction and remarkably enhanced emission image with good uniformity was demonstrated.
Abstract: The effect of field emission cycles on printed carbon nanotubes was investigated using scanning electron microscopy and current–voltage measurement. After multiple emission cycles, the printed nanotubes irreversibly deformed to orient themselves parallel to the field direction and, from them, remarkably enhanced emission image with good uniformity was demonstrated. Corresponding gradual decrease in the field emission threshold and increase of field enhancement factor (β) were also observed during field emission cycles.
TL;DR: In this article, a triode-type field emission display was demonstrated using heavily Si-doped AlN, and the field emission current reached 9.5 μA at an electric field strength of 23 V/μm.
Abstract: Using heavily Si-doped AlN, a triode-type field emission display is demonstrated. The device consists of the heavily Si-doped AlN field emitter, mesh grid, and phosphor-coated anode screen. The device exhibits a low turn-on electric field of 11 V/μm, and the field emission current exponentially increases as the grid voltage increases. The field emission current reaches 9.5 μA at an electric field strength of 23 V/μm. Luminescence from the phosphor excited by the field-emitted electrons is uniform over the anode screen and is intense enough for the display application. The field emission current is stable over time.
TL;DR: In this article, a disordered sp2 phase embedded in an electrically insulating sp3 matrix is described, and the influence of structural disorder, associated with sp2 clusters of similar size, and topological disorder, due to undistorted clusters of different sizes, on both spin density and Raman measurements is discussed.
Abstract: The nanostructure of amorphous carbon thin films is described in terms of a disordered nanometer-sized conductive sp2 phase embedded in an electrically insulating sp3 matrix. It is shown that the degree of clustering and disorder within the sp2 phase plays a determining role in the electronic properties of these films. Clustering of the sp2 phase is shown to be important in explaining several experimental results including the reduction of the electron spin resonance linewidth with increasing spin density and the dispersion associated with the width of the Raman active G band. The influence of structural disorder, associated with sp2 clusters of similar size, and topological disorder, due to undistorted clusters of different sizes, on both spin density and Raman measurements, is discussed. An extension of this description to intercluster interactions to explain some of the electrical transport and electron field emission behavior is also presented.
TL;DR: By using multiwalled carbon nanotubes as an element of a nanobiprism, the coherence of electrons emitted from tungsten tips at room temperature and 78 K is evaluated quantitatively and the increase of the transverse coherence length of the electron beam agreed well with that of the inelastic mean free path of electrons in solids.
Abstract: By using multiwalled carbon nanotubes as an element of a nanobiprism, we evaluated quantitatively the coherence of electrons emitted from tungsten tips at room temperature and 78 K, and found an enhancement of coherence at 78 K. The increase of the transverse coherence length of the electron beam agreed well with that of the inelastic mean free path of electrons in solids, demonstrating the direct relationship between the coherences of the electron beam and the original electronic states. On the basis of this experimental fact, we comment on the interpretation of recent Hanbury Brown-Twiss type experiments for electrons reported by Kiesel et al. [Nature (London) 418, 392 (2002)]].
TL;DR: In this paper, a simple and efficient plasma-enhanced chemical vapor deposition (PECVD) technique for the fabrication of vertically aligned carbon nanotip arrays for electron field emitters is presented.
TL;DR: In this paper, the effect of argon ion irradiation on the field emission and luminescent properties of screen-printed carbon nanotubes with square pixels was examined, to further improve field emission displays (FEDs) applications.