Showing papers on "Field electron emission published in 1998"
TL;DR: In this article, the authors report on the field emission properties of single-wall carbon nanotube films, with emphasis on current-versus-voltage (I-V) characteristics and current stability.
Abstract: We report on the field emission properties of single-wall carbon nanotube films, with emphasis on current–versus–voltage (I–V) characteristics and current stability. The films are excellent field emitters, yielding current densities higher than 10 mA cm−2 with operating voltages that are far lower than for other film emitters, but show a significant degradation of their performances with time. The observed deviations from the Fowler-Nordheim behavior in the I–V characteristics point to the presence of a nonmetallic density of states at the tip of the nanotubes.
686 citations
TL;DR: Strong and sustained electron emission at low electric fields was observed in undoped, nanostructured diamond, which are the lowest fields ever reported for any field-emitting material at technologically useful current densities.
Abstract: Strong and sustained electron emission at low electric fields was observed in undoped, nanostructured diamond. Electron emission of 10 milliamperes per square centimeter was observed at applied fields of 3 to 5 volts per micrometer. These are the lowest fields ever reported for any field-emitting material at technologically useful current densities. The emitter consists of a layer of nanometer-size diamond particulates, which is heat-treated in a hydrogen plasma. These emission characteristics are attributed to the particles' high defect density and the low electron affinity of the diamond surface. Such emitters are technologically useful, because they can be easily and economically fabricated on large substrates.
398 citations
Patent•
12 Nov 1998
TL;DR: In this article, the cold cathode devices (cold cathodes) comprising electron emitting structures grown directly onto a substrate material were described. But the development of cold cathodes has not yet been considered in the field of field emission displays.
Abstract: Electron field emission devices (cold cathodes), vacuum microelectronic devices and field emission displays which incorporate cold cathodes and methods of making and using same. More specifically, cold cathode devices comprising electron emitting structures grown directly onto a substrate material. The invention also relates to patterned precursor substrates for use in fabricating field emission devices and methods of making same and also to catalytically growing other electronic structures, such as films, cones, cylinders, pyramids or the like, directly onto substrates.
272 citations
TL;DR: In this paper, the authors investigated the field emission properties of multiwalled carbon nanotubes, in the form of both single tips and films, and found that they show low operating voltages and produce high current densities.
253 citations
TL;DR: In this article, an electron-emission mechanism for cold cathodes is described based on the enhancement of electric fields at metal-diamond-vacuum triple junctions.
Abstract: An electron-emission mechanism for cold cathodes is described based on the enhancement of electric fields at metal–diamond–vacuum triple junctions. Unlike conventional mechanisms, in which electrons tunnel from a metal or semiconductor directly into vacuum, the electrons here tunnel from a metal into diamond surface states, where they are accelerated to energies sufficient to be ejected into vacuum. Diamond cathodes designed to optimize this mechanism exhibit some of the lowest operational voltages achieved so far.
219 citations
TL;DR: In this paper, the reverse leakage current is observed to depend on device area, Schottky barrier height, electric field at the metal-semiconductor interface, and temperature (a decreasing temperature dependence with increasing reverse bias).
Abstract: Practical design of high-voltage SiC Schottky rectifiers requires an understanding of the device physics that affect the key performance parameters. Forward characteristics of SiC Schottky rectifiers follow thermionic emission theory and are relatively well understood. However, the reverse characteristics are not well understood and have not been experimentally investigated in-depth. In this paper we report the analysis and experimental results of both the forward and reverse characteristics of high-voltage SiC Schottky rectifiers. Ti and Ni Schottky rectifiers with boron implant edge termination were fabricated on n-type 4H SiC samples. Ni Schottky rectifiers fabricated on a 13-/spl mu/m thick 3.5/spl times/10/sup 15/ cm/sup -3/ epilayer have a current density of 100 A/cm/sup 2/ at approximately 2 V forward bias and a reverse leakage current density of less than 0.1 A/cm/sup 2/ at a reverse bias of 1720 V. The reverse leakage current is observed to depend on device area, Schottky barrier height, electric field at the metal-semiconductor interface, and temperature (a decreasing temperature dependence with increasing reverse bias). In addition. the reverse leakage current magnitude is larger and the electric field dependence is stronger than predicted by thermionic emission and image-force barrier height lowering. This suggests the reverse leakage current is due to a combination of thermionic field emission and field emission.
219 citations
TL;DR: In this paper, phase pure nanotube films were grown on silicon substrates by a microwave plasma under conditions which normally are used for the growth of chemical vapor deposited diamond films, but instead of using any pretreatment leading to diamond nucleation, they deposited metal clusters on the silicon substrate.
Abstract: Phase pure nanotube films were grown on silicon substrates by a microwave plasma under conditions which normally are used for the growth of chemical vapor deposited diamond films. However, instead of using any pretreatment leading to diamond nucleation we deposited metal clusters on the silicon substrate. The resulting films contain only nanotubes and also onion-like structures. However, no other carbon allotropes like graphite or amorphous clustered material could be found. The nanotubes adhere very well to the substrates and do not need any further purification step. Electron field emission was observed at fields above 1.5 V/μm and we observed an emission site density up to 104/cm2 at 3 V/μm. Alternatively, we have grown nanotube films by the hot filament technique, which allows to uniformly cover a two inch wafer.
197 citations
TL;DR: In this paper, the field emission from closed and open-ended multi-walled nanotubes (MWNTs) was studied by field-emission microscopy, and a lighting element with the structure of a triode-type vacuum tube was manufactured by replacing the conventional thermionic cathodes with the MWNT field emitters.
Abstract: Field emission from closed and open-ended multi-walled nanotubes (MWNTs) was studied by field-emission microscopy. As an application of nanotube field emitters, we manufactured lighting elements with the structure of a triode-type vacuum tube by replacing the conventional thermionic cathodes with the MWNT field emitters. Stable electron emission, adequate luminance and long life of the tubes have been demonstrated.
147 citations
TL;DR: In this paper, the light emission is caused by electron transitions between different electronic levels participating in the field emission, which is not due to blackbody radiation or current-induced heating.
Abstract: We report on the observation of luminescence during electron field emission on singlewall and multiwall carbon nanotubes. Spectra acquired at different emitted currents, as well as the dependence of the luminescence intensity with the current, show that the light emission is not due to blackbody radiation or to current-induced heating. In fact, our results suggest that the light emission is caused by electron transitions between different electronic levels participating in the field emission.
142 citations
TL;DR: In this paper, field emission data from aligned graphitic nanofibers have been obtained and the Fowler-Nordheim model was used to analyze the data obtained, and the onset of emission current in microampere level was detected at about 1.8 V/μm with an emission area of 1 mm2.
Abstract: Field emission data from aligned graphitic nanofibers have been obtained. The aligned nanofibers are 50–100 nm in diameter and 6–10 μm in length, with a density of 109–1010/cm2. The fibers were grown on polycrystalline nickel substrate by plasma-assisted hot filament chemical vapor deposition using a gas mixture of nitrogen and acetylene. The onset of emission current in microampere level was detected at about 1.8 V/μm with an emission area of 1 mm2. The Fowler–Nordheim model was used to analyze the data obtained. The field emission current required for flat panel display can be easily achieved at 2.5 V/μm.
122 citations
TL;DR: In this paper, the electron field-emission properties of hydrogenated amorphous carbon and nitrogenated tetrahedral ammorphous carbon thin films were examined by measuring the field emission current as a function of the applied macroscopic electric field, which indicated the existence of an optimum film thickness for low-threshold electron field emission.
Abstract: The electron field-emission properties of hydrogenated amorphous carbon and nitrogenated tetrahedral amorphous carbon thin films are examined by measuring the field-emission current as a function of the applied macroscopic electric field The experimental results indicate the existence of an optimum film thickness for low-threshold electron field emission The predictions of various emission models are compared to the experimental results
TL;DR: In this paper, the authors reported field emission from thin films of regioregular poly(3-octylthiophene) deposited on n-doped silicon, with indium tin oxide as the anode.
Abstract: Field-emission displays contain materials that emit electrons when charged to a low (negative) potential; the electrons excite light emission from phosphor screens. These devices have the potential to provide flat-panel visual displays with good picture quality at low power consumption and low cost1. Field-emission devices at present use arrays of microfabricated tips as the emitting cathodes, but a potentially cheaper and simpler alternative is to use a thin-film cathode. This requires the identification of materials that will emit an appreciable electron current at low applied fields. Nitrogen-doped, chemical-vapour-deposited diamond films2 and amorphous carbon films3 have been explored for this purpose. The low electron affinity4, wide bandgap and excellent transport properties5 of some conducting organic polymers suggest that they might also provide good cathode materials. Here we demonstrate that this is so, reporting field emission from thin films of regioregular poly(3-octylthiophene) deposited on n-doped silicon, with indium tin oxide as the anode. The threshold fields that we measure for electron emission from these films are the lowest yet reported for any carbon-based material.
TL;DR: In this article, the electron emission properties of metal-diamond interfaces were characterized by means of UV photoemission spectroscopy (UPS) and field-emission measurements.
Abstract: The electron emission properties of metal–diamond (100), (111), and (110) interfaces were characterized by means of UV photoemission spectroscopy (UPS) and field-emission measurements. Different surface cleaning procedures including annealing in ultrahigh vacuum (UHV) and rf plasma treatments were used before metal deposition. This resulted in diamond surfaces terminated by oxygen, hydrogen, or free of adsorbates. The electron affinity and Schottky barrier height of Zr or Co thin films were correlated by means of UPS. A negative electron affinity (NEA) was observed for Zr on any diamond surface. Co on diamond resulted in NEA characteristics except for oxygen-terminated surfaces. The lowest Schottky barrier heights were obtained for the clean diamond surfaces. Higher values were measured for H termination, and the highest values were obtained for O on diamond. For Zr, the Schottky barrier height ranged from 0.70 eV for the clean to 0.90 eV for the O-terminated diamond (100) surface. Values for Co ranged fr...
TL;DR: InGaZnO4 is considered to be a better conductive transparent oxide than In2O3 for ZnGa2O4 blue phosphor applications in field emission displays as mentioned in this paper.
TL;DR: In this paper, spontaneous electrical polarization changes are induced at a submicrosecond time scale, strong uncompensated surface charge densities and related fields are generated, which may lead to the intense self-emission of electrons from the negatively charged free surface areas of the ferroelectric cathode.
Abstract: Spontaneous electrical polarization of ferroelectric materials can be changed either by reversal or by phase transition from a ferroelectric into a nonpolar state or vice versa If spontaneous polarization changes are induced at a submicrosecond time scale, strong uncompensated surface charge densities and related fields are generated, which may lead to the intense self-emission of electrons from the negatively charged free surface areas of the ferroelectric cathode The nature of this self-emission differs essentially from other methods of ferroelectric electron emission and from conventional electron emission in that the latter methods are only achieved by extracting electrons with externally applied electric fields When electron guns are constructed with ferroelectric cathodes, new design criteria have to be taken into account The intensity, the energy, the temporal and spatial distribution and the repetition rate of the emitted electron beams can be adjusted within wide limits The advantages of fer
TL;DR: In this article, field emission microscopy of single-walled nanotubes (SWNTs) and multi-walled nano-tubes (MWNTs), which were obtained after purification processes of carbon soot containing respective nanotsubes, was performed as an electron emitter.
TL;DR: In this article, the Fowler-Nordheim formula was used to calculate the electric field in the vicinity of a metallic edge attached to a dielectric half-space, and the resulting electric field is used to evaluate the current emitted from the edge.
Abstract: The electric field in the vicinity of a metallic edge attached to a dielectric half-space is calculated analytically. The resulting electric field is used to evaluate the current emitted from the edge using the Fowler-Nordheim formula. It is shown analytically that the emitted current is proportional to the dielectric coefficient of the material.
TL;DR: In this article, a series of tetrahedrally bonded amorphous carbon (ta-C) films produced by the filtered cathodic vacuum are measured and the threshold field and current densities achievable have been studied as a function of their sp 3 content and of nitrogen incorporation.
TL;DR: In this article, field emission properties of undoped chemical vapor deposited diamond and diamond-like carbon films have been measured for a variety of different deposition conditions, and the nature and appearance of the damage site after testing, together with the mathematical form of the observed current-voltage relations, are correlated with the conductivity of the film.
Abstract: Field emission properties of undoped chemical vapor deposited diamond and diamondlike carbon films have been measured for a variety of different deposition conditions. The nature and appearance of the damage site after testing, together with the mathematical form of the observed current–voltage relations, are correlated with the conductivity of the film. This is consistent with a model for the overall current which is a combination of conduction mechanisms through the bulk of the film with Fowler–Nordheim tunneling.
TL;DR: In this paper, a model to describe internal field emission through the interface between highly n-doped Si and nitrogen (N)-doped diamond is presented, where the roughness on the Si surface is described as a collection of sharp, spherically pointed Si asperities embedded in the diamond film.
Abstract: A model to describe internal field emission through the interface between highly n-doped Si and nitrogen (N)-doped diamond is presented. We describe the roughness on the Si surface as a collection of sharp, spherically pointed Si asperities embedded in the diamond film. These “tips” provide enhancement of the applied electric field, which, in conjunction with the high N doping of diamond, results in the formation of a Schottky barrier which allows for tunneling or internal field emission from the Si into the conduction band of diamond. This enhanced electric field is also sufficient to induce valence band tunneling from the Si into the diamond conduction band. In our model limitations on the field mediated transport of holes from the n-doped Si/diamond interface to the cathode base leads to charging of the Si asperities. This charge accumulation results in band bending in Si and a significant reduction in the valence band current. The calculated J–V characteristics for the internal field emission lead to nonlinear behavior when plotted in Fowler–Nordheim coordinates. This is a consequence of the limitation of the conduction band current due to density of states effects at high fields in addition to the suppression of the valence band current. The calculated results are in qualitative agreement with recent field emission studies of Okano et al. [K. Okano, S. Koizumi, S. Ravi, P. Silva, and G. A. J. Amaratunga, Nature 381, 140 (1996)] for a composite n-Si and N–diamond cold cathode source. A plausible geometric argument suggests that there is also reasonable quantitative agreement.
TL;DR: In this article, the authors measured the electron emission characteristics of arrays of silicon-doped GaN (Si:GaN) pyramids for field emitter applications using techniques such as field emission, field emission energy distribution analysis (FEED), photoemission electron microscopy (PEEM), and field emission electron microscope (FEEM).
Abstract: Selective growth of arrays of silicon-doped GaN (Si:GaN) pyramids for field emitter applications has been achieved. The electron emission characteristics of these arrays has been measured using techniques such as field emission, field emission energy distribution analysis (FEED), photoemission electron microscopy (PEEM), and field emission electron microscopy (FEEM). The field emission current–voltage (I–V) results indicate an average threshold field as low as 7 V/μm for an emission current of 10 nA. It is suggested that the low threshold field value is a consequence of both the low work function of Si:GaN and the field enhancement of the pyramids. The results of the FEEM and FEED measurements indicate agreement with the field emission I–V characteristics. The FEED results indicate that the Si:GaN pyramids are conducting, and that no significant ohmic losses are present between the top contact to the array and the field emitting pyramids. The PEEM and FEEM images show that the emission from the arrays is ...
TL;DR: In this article, an overview of fabrication and performance of a class of vacuum microelectronic devices, namely, silicon tip-on-post field emitter arrays (FEAs), is presented in the context of requirements for field emission flat panel display and microwave power amplifier applications.
Abstract: This article gives an overview of fabrication and performance of a class of vacuum microelectronic devices, namely, silicon tip-on-post field emitter arrays (FEAs). Experimental data illustrating the device performance are presented in the context of requirements for field emission flat panel display and microwave power amplifier applications. Critical geometrical parameters of the device are discussed, and a fabrication process flow designed to optimize these parameters is described. Equipment and methods for testing electrical performance of the FEAs and results thus generated are presented. Specifically, emission current versus gate voltage characteristics for arrays with tips formed using anisotropic (crystallographic–orientation–dependent) or isotropic etching techniques, uniformity of these characteristics across a 4 in. diameter substrate, stability of emission current in ultrahigh vacuum conditions, and changes in emission current upon exposure to active gases at varying pressure are discussed.
TL;DR: An aligned carbon nanotube film was fabricated on the surface of an α-SiC wafer by heating at 1700°C for 30 min. in a vacuum electric furnace due to the decomposition of SiC by selected desorption as discussed by the authors.
Abstract: An aligned carbon nanotube film was fabricated on the surface of an α-SiC wafer by heating at 1700°C for 30 min. in a vacuum electric furnace due to the decomposition of SiC by selected desorption. It was found to be easy to produce a large-area carbon nanotube film on the SiC substrate. The (0002) lattice distance of graphite constructing the CNTs was obtained to be 0.344 nm from the electron diffraction pattern.
TL;DR: In this article, the authors combined the spatially localized field and current of a scanning tunneling microscope tip with high-spatial-resolution characterization to simulate conditioning and assess its effect.
Abstract: The cold-cathode electron emission properties of amorphous tetrahedral diamondlike carbon are promising for flat-panel display and vacuum microelectronics technologies. The onset of electron emission is, typically, preceded by “conditioning” where the material is stressed by an applied electric field. To simulate conditioning and assess its effect, we combined the spatially localized field and current of a scanning tunneling microscope tip with high-spatial-resolution characterization. Scanning force microscopy shows that conditioning alters surface morphology and electronic structure. Spatially resolved electron-energy-loss spectroscopy indicates that the predominant bonding configuration changes from predominantly fourfold to threefold coordination.
TL;DR: In this article, the authors measured the field emission properties of undoped chemical vapor deposited diamond and diamond-like carbon films for a variety of different deposition conditions and investigated the damage site after testing with scanning electron microscopy and laser Raman mapping.
Abstract: Field emission properties of undoped chemical vapor deposited diamond and diamond-like carbon films have been measured for a variety of different deposition conditions. The nature and appearance of the damage site after testing has been investigated with scanning electron microscopy and laser Raman mapping. These observations, together with the mathematical form of the observed current–voltage relations, are correlated with the conductivity of the film. The results are consistent with a model for the overall emission current that combines conduction mechanisms through the bulk of the film with Fowler–Nordheim tunneling.
01 May 1998
TL;DR: In this paper, a carbon-nanotube array was mounted on a cathode substrate in several ways, and the fabrication process of carbon nanotube field emission displays (FEDs) were almost the same as those for vacuum fluorescent displays (VFDs).
Abstract: We succeeded for the first time in installing carbon nanotubes to vacuum tubes as field emitters. The fabrication processes of carbon nanotube field emission displays (FEDs) are almost the same as those for vacuum fluorescent displays (VFDs). A carbon-nanotube array was mounted on a cathode substrate in several ways. Surface treatment of fabricated carbon nanotube layers is important to emit electrons efficiently. Stable electron emission end adequate luminance of carbon nanotubes as field emitters were demonstrated using CRT-lighting-elements and VFD-like flat panel displays. A lighting-element is now undergoing a test of its lifetime under a dc12kV driving condition, suggesting a lifetime of over 10,000 hours.
TL;DR: In this article, the feasibility of using Ce-doped silicates as an alternative to the P22 blue phosphor (ZnS:Ag) was investigated for low voltage field emission displays (FEDs).
Abstract: The feasibility of using Ce-doped silicates as an alternative to the P22 blue phosphor (ZnS:Ag) was investigated for low voltage field emission displays (FEDs). Silicates of various composition were evaluated based on their chromaticity, intrinsic efficiency, and brightness saturation behavior. The influence of silicate composition and particle morphology on the cathodoluminescence properties was also assessed. Saturation measurements indicated that the high saturation resistance of the Ce-doped samples can yield better performance than ZnS:Ag when operating at low voltages. The silicates are also attractive for their stability in a FED environment.
Patent•
26 Aug 1998TL;DR: In this article, a field emission electron source consisting of an electrically conductive substrate, an oxidized or nitrided porous polysilicon layer formed on the surface of a substrate on one side of the source and having nano-structures and a thin metal film formed on said oxidized/nitrided porosity was presented.
Abstract: A field emission electron source comprising an electrically conductive substrate, an oxidized or nitrided porous polysilicon layer formed on the surface of said electrically conductive substrate on one side thereof and having nano-structures and a thin metal film formed on said oxidized or nitrided porous polysilicon layer. Voltage is applied to said thin metal film used as a positive electrode with respect to said electrically conductive substrate thereby to emit electron beam through said thin metal film.
TL;DR: In this paper, the effects of O2 exposure on the emission properties of several Spindt type molybdenum field emitter arrays were studied and the degradation effects are similar in both the dc and pulsed modes of operation of the device.
Abstract: Electron emission from molybdenum field emission microcathode arrays is sensitive to the contamination of the emitters by the residual gases. We studied the effects of O2 exposures on the emission properties of several Spindt type molybdenum field emitter arrays. The arrays were exposed to 0–10 000 L of O2 and the resulting changes in electron emission characteristics were measured. Exposure of the field emitters to O2 resulted in emission degradation ranging from 6.2±1.3% for 10 L to 99.2±0.4% for a 10 000 L exposure. The emission is recoverable for low exposures, but exposures beyond 1000 L result in permanent loss in emission current. We found that the degradation effects are similar in both the dc and pulsed modes of operation of the device. Therefore, dc mode testing can be used as an effective acceleration method in establishing the device lifetimes under various vacuum conditions.
TL;DR: In this article, a tunneling effective mass of 0.35m 0.60m 0 was derived for gate oxides by using multiple-scattering theory, in which the SiO2 layer is segmented into multiple rectangular potential barriers.
Abstract: Tunnel current through 1.27-8.12-nm-thick gate oxides has been calculated on the basis of multiple-scattering theory, in which the SiO2 layer is segmented into multiple rectangular potential barriers. By using the conduction band barrier height of 3.34 eV determined for the SiO2/Si(100) interfaces, a tunneling effective mass of 0.35m0 is obtained so as to reproduce the SiO2 thickness dependence on the direct tunnel current. The Fowler-Nordheim tunnel current oscillation due to interference between the propagating electron wave at the SiO2 conduction band and the wave reflected at the SiO2/Si interface has also been explained by employing an oxide conduction band effective mass of 0.60m0. It is found that the oxide thicknesses determined by ellipsometry are in good agreement with those extracted by fitting the measured tunnel current to theoretical one.