Showing papers on "Field electron emission published in 1996"
TL;DR: By combining electron paramagnetic resonance (EPR), optical absorption, and photoluminescence (PL) spectroscopy, a strong correlation is observed between the green 510 nm emission, the free-carrier concentration, and the density of singly ionized oxygen vacancies in commercial ZnO phosphor powders as mentioned in this paper.
Abstract: By combining electron paramagnetic resonance (EPR), optical absorption, and photoluminescence (PL) spectroscopy, a strong correlation is observed between the green 510 nm emission, the free‐carrier concentration, and the density of singly ionized oxygen vacancies in commercial ZnO phosphor powders. From these results, we demonstrate that free‐carrier depletion at the particle surface, and its effect on the ionization state of the oxygen vacancy, can strongly impact the green emission intensity. The relevance of these observations with respect to low‐voltage field emission displays is discussed.
1,888 citations
TL;DR: Large-scale synthesis of aligned carbon nanotubes was achieved by using a method based on chemical vapor deposition catalyzed by iron nanoparticles embedded in mesoporous silica to form an aligned array of isolated tubes with spacings between the tubes.
Abstract: Large-scale synthesis of aligned carbon nanotubes was achieved by using a method based on chemical vapor deposition catalyzed by iron nanoparticles embedded in mesoporous silica. Scanning electron microscope images show that the nanotubes are approximately perpendicular to the surface of the silica and form an aligned array of isolated tubes with spacings between the tubes of about 100 nanometers. The tubes are up to about 50 micrometers long and well graphitized. The growth direction of the nanotubes may be controlled by the pores from which the nanotubes grow.
1,772 citations
TL;DR: In this paper, a model based on the a−C:H:N acting as a space charge interlayer on the n++−Si cathodes was proposed to explain the emission at low electric fields.
Abstract: Field emission measurements using 0.3 μm thick nitrogen containing hydrogenated amorphous carbon films (a‐C:H:N) on n++‐Si cathodes are reported. Onset emission fields as low as 4 V μm−1 have been obtained using a flat plate anode configuration. Uniform emission is observed over the entire cathode area at current densities below 7×10−2 mA cm−2. At higher current density preferential emission from spots is observed. The spot emission is imaged using the ITO coated plate anode. A model based on the a‐C:H:N acting as a space charge interlayer on the n++‐Si is proposed to explain the emission at low electric fields.
471 citations
TL;DR: In this paper, a simple fabrication method is described to produce reliable and robust (self-repairing) field emission sources from randomly aligned carbon nanotubes, which display stable and reproducible currentvoltage characteristics with sharp turn on near 100 V and emission currents up to 400 mA/cm2 at 200 V.
Abstract: A simple fabrication method is described to produce reliable and robust (self‐repairing) field emission sources from randomly aligned carbon nanotubes. The sources display stable and reproducible current–voltage characteristics with sharp turn on near 100 V and emission currents up to 400 mA/cm2 at 200 V. Two successful methods are described for patterning the emission source area into emitting and nonemitting regions.
334 citations
TL;DR: In this paper, three derivatives of poly(paraphenylene) (PPP) have been synthesized, all with excellent solubility in common organic solvents.
Abstract: Three derivatives of poly(paraphenylene) (PPP) have been synthesized, all with excellent solubility in common organic solvents. Efficient blue polymer light‐emitting diodes (LEDs) are demonstrated using these PPPs as the semiconducting and luminescent polymers. Double‐layer polymer LEDs (consisting of a hole transport layer in addition to the electroluminescent layer) emit blue light with external quantum efficiencies between 1% and 3% photons per electron, when using indium tin oxide as the anode and calcium as the cathode. Using internal field emission (Fowler–Nordheim tunneling) of single carrier devices for both electrons and holes, the energies of the top of the π band and the bottom of the π* band have been determined as, respectively, 5.7 and 2.3 eV below the vacuum. The operating voltages of these LEDs have been lowered by using a porous polyaniline anode, or by blending PPP with a hole transport material. LEDs using air stable cathodes, silver, indium, aluminum, and copper, were also demonstrated...
330 citations
TL;DR: In this paper, the fabrication of gated diamond field-emission cathodes is described and a theory of their operation is discussed, and the cathodes are made using commercial diamond grit with the addition of Ni and Cs salts to enhance emission.
Abstract: The fabrication of gated diamond field‐emission cathodes is described and a theory of their operation is discussed. These cathodes are made using commercial diamond grit with the addition of Ni and Cs salts to enhance emission. The resulting structure resembles a field‐emission Spindt cathode with the internal metal cone replaced by a ∼100 nm layer of diamond grit. Emission from these cathodes occurs at the lowest reported gate voltage of any field emission device and is unaffected by operation at pressures of over 100 Pa of N2. Operation in oxygen and H2S at pressures of 6×10−4 Pa degrades emission, but the cathodes recover once the ambient pressure is reduced to below 1×10−4 Pa. The emission current noise is 2.5% rms over an 8 h period and 1% rms over 3 ms. These cathodes suffer from high gate current that varies from 0.2 to 1000 times the emitted current. The high gate current is known to be process dependent and not inherent to the cathodes. The emission performance is explained by the stable negative electron affinity of diamond, which allows for injection of electrons from diamond into vacuum with little to no electric field, 0–1 V μm−1. Cathode operation is limited by the injection of electrons into the diamond at the back metal–diamond interface, which depends upon the doping of the diamond and the roughness of that interface.
294 citations
TL;DR: In this paper, the authors compared the field emission of boron and nitrogen-doped diamond and showed that the latter is more conductive than the former, and that a roughened interface substantially reduces the potential in the diamond and increases emission.
Abstract: Field emission of electrons from boron‐ and nitrogen‐doped diamond is compared. Emission from boron‐doped diamond requires vacuum electric fields of 20–50 V μm−1, while nitrogen‐doped, type Ib diamond requires fields of 0–1 V μm−1. Since boron‐doped diamond is very conductive, very little voltage drop occurs in the diamond during emission. Nitrogen‐doped diamond is insulating, so during emission a potential of 1–10 kV appears in the diamond. This potential is a function of the back contact metal‐diamond interface. A roughened interface substantially reduces the potential in the diamond and increases emission. The electrons are often emitted from the nitrogen‐doped diamond as beamlets. These beamlets leave the surface of the diamond at angles up to 45° from the substrate normal. Although the vacuum field is small, these electrons have energies of several kV. It is unknown whether the electrons are accelerated to these energies in the bulk of the diamond, or at high electric fields near the emitting surface.
167 citations
TL;DR: In this article, spatially resolved electron field emission measurements from a nanocrystalline diamond film grown by plasmaenhanced chemical transport deposition have been obtained using a scanning probe apparatus with micrometer resolution.
Abstract: Spatially resolved electron field emission measurements from a nanocrystalline diamond film grown by plasma‐enhanced chemical transport deposition have been obtained using a scanning probe apparatus with micrometer resolution. Macroscopic regions with a high emission site density, and turn‐on fields below 3 V/μm, comprised approximately 1/2 of the total sample area. The emitting and the nonemitting regions of the specimen are differentiated distinctly by Raman spectra and subtly by morphologies. Both areas are largely sp3‐bonded, but only the nonemitting regions exhibit a sharp line at 1332 cm−1, a well‐known signature of diamond in larger crystallites.
141 citations
TL;DR: In this article, the procedure for three-dimensional additive lithography with electron-beam induced deposition is applied in a scanning electron microscope equipped with an image processor beam control system for lithography.
Abstract: The procedure for three‐dimensional additive lithography with electron‐beam induced deposition is applied in a scanning electron microscope equipped with an image processor beam control system for lithography. Employing organometallic materials, which contain gold or platinum, quantum dots, resistors, and field emitter tips are deposited. Changing the current, the properties of the deposited nanocrystalline compound materials can be selected to be insulating or conducting. High resolution and high aspect ratio structures are grown with this technique. To find the mechanism responsible for conductivity in the deposited material, resistors are characterized at temperatures ranging from −150 °C to +180 °C. Measurements are performed in a high‐vacuum chamber equipped with a gas cooling system cooled with liquid nitrogen and a resistive heater. Poole–Frenkel plots show that field electron emission and hopping of electrons is the dominant mechanism of conduction. The metal content of the deposits is increased w...
139 citations
TL;DR: In this paper, the electron field emission properties of the (111)1×1:H surface of natural semiconducting diamond have been examined with simultaneous field emission and photoemission measurements.
Abstract: The electron field emission properties of the (111)1×1:H surface of natural semiconducting (p‐type) diamond have been examined with simultaneous field emission and photoemission measurements. We find that the origin of the field emission is due to the electron tunneling from the valence band and show that the shape of the field emission energy distributions can be described by the theory of semiconductor field emission. Analysis of our results demonstrate that the combination of field emission and photoemission is a powerful technique for the study of the electron emission properties of materials.
139 citations
TL;DR: In this article, the authors show that the electric field required to induce electron emission from diamond can be significantly reduced when the samples are properly grown or postgrowth processed so that they contain a substantial amount of structural defects.
Abstract: Diamond films and islands have been synthesized with varying defect densities and dopant levels by chemical vapor deposition for field emission display applications. Vacuum field emission measurements show that the electric field required to induce electron emission from diamond can be significantly reduced when the samples are properly grown or postgrowth processed so that they contain a substantial amount of structural defects. The defective diamond is characterized by a broadened peak at 1332 cm−1 in Raman spectroscopy with a full width at half‐maximum in the range of 7–11 cm−1. These materials require a turn‐on field (for a current density of 0.01 mA/cm2) as low as 15 V/μm, and a threshold field (for a current density of 10 mA/cm2) as low as 30 V/μm for electron emission. These field values are almost an order of magnitude lower than those required for high quality, p‐type semiconducting diamond. Detailed numerical analysis of the emission current‐voltage data from multiple diamond tips with varying g...
TL;DR: In this article, field emission measurements on chemical vapor deposition diamond and laser ablated a‐C films show an activation step after reaching a certain critical electric field, where a vacuum arc of some hundred ns duration initiates.
Abstract: Field emission measurements on chemical vapor deposition diamond and laser ablated a‐C films show an activation step after reaching a certain critical electric field. At this field a vacuum arc of some hundred ns duration initiates. While high current arcing leads to the evaporation of the spot surface melting, amorphization or cracking of the film is encountered for lower currents. In any case, much higher electron emission can be observed after this activation procedure due possibly to tip formation resulting in an electric field enhancement. By using a 1 GΩ resistance the discharge current can be limited nevertheless, an activation is observed.
TL;DR: In this paper, a diamond layer was formed on molybdenum and single-crystal silicon field emitters using a dielectrophoresis coating method from a suspension of diamond powder in a nonconducting fluid.
Abstract: Thin diamond layers have been formed on molybdenum and single‐crystal silicon field emitters using a dielectrophoresis coating method from a suspension of diamond powder in a nonconducting fluid. Transmission and scanning electron microscopy observation revealed a significant amount of diamond on the tips. The average thickness of the deposited diamond layer depended on the applied bias and the immersion time. Field emission from these diamond‐coated emitters exhibited significant enhancement compared to the pure emitters.
TL;DR: In this article, the effect of diamond-like carbon (DLC) films coated by pulsed laser deposition technique on the electron emission characteristics of Mo tips was examined and the degradation of electron emission behavior can be attributed to the conversion of sp3-bonds, characteristic for diamond, to sp2-bond, characteristics for graphite.
Abstract: The effect of diamondlike carbon (DLC) films coated by pulsed laser deposition technique on the electron emission characteristics of Mo tips is examined. Turn‐on voltage (V0) was lowered from 40 V for Mo tips to 22 V for DLC coated Mo tips and maximum anode current (IA) was increased from ∼44 μA for Mo tips to ∼2.0 mA for DLC coated Mo tips. Maximum anode current (IA) for the DLC coated Mo tips, however, decreased during operation. Raman spectroscopy and selected area diffraction (SAD) in transmission electron microscopy (TEM) revealed that the degradation of electron emission behavior can be ascribed to the conversion of sp3‐bonds, characteristic for diamond, to sp2‐bonds, characteristics for graphite. The transformation of the structure is assumed to be induced by the local heat from the DLC coatings.
TL;DR: In this paper, two amorphous, tetrahedrally bonded diamond-like carbon films, one with (a−tC:N), and a second without nitrogen doping (a•tC), prepared by pulsed laser deposition has been investigated using a scanning probe apparatus with micrometer spatial resolution.
Abstract: Electron field emission from two amorphous, tetrahedrally bonded diamondlike carbon films, one with (a‐tC:N), and a second without nitrogen doping (a‐tC), prepared by pulsed laser deposition has been investigated using a scanning probe apparatus with micrometer spatial resolution Electric fields of 100 V/μm (180 V/μm) were required to initiate emission from our a‐tC:N (a‐tC) films; however, once emission was established at a particular location, electrons could be drawn at average fields as low as 10 V/μm (60 V/μm) from the same region The initiation of emission was concomitant with electrical discharges which were observed by video techniques These discharges left craters with micrometer dimensions on the surfaces of otherwise smooth films
TL;DR: In this paper, the first observation of electron emission from carbon-doped boron nitride (BN) was made using reactive laser ablation and the electron emission current density measured at room temperature showed a power law dependence.
Abstract: These results reflect what is believed to be the first observation of electron emission from carbon‐doped boron nitride (BN). The n‐type BN films were synthesized on n‐type polycrystalline diamond on (100)Si using reactive laser ablation. The electron emission current density measured at room temperature shows a power law dependence. Emission currents as high as 60 mA cm−2 have been measured from 150 nm thick n‐type BN films on a 24 μm n‐type polycrystalline diamond film on a (100)Si substrate. These films show a current density/applied field behavior indicative of negative electron affinity.
TL;DR: In this paper, a method to calculate the electrostatic field between a metallic tip of arbitrary shape and a sample surface is presented. But the method does not take into account the tip geometry.
Abstract: We present a method to calculate the electrostatic field between a metallic tip of arbitrary shape and a sample surface. The basic idea is to replace the electrodes by a set of ‘‘image’’ charges. These charges are adjusted in order to fit the boundary conditions on the surfaces. As an application of the method, we describe the field characteristics of a field‐emission diode as a function of the gap between electrodes for different tip shapes. A comparison between numerical and analytical results is presented. The results do not depend on the overall tip geometry only for gap distances smaller than ≊1/2 the tip radius. The field enhancement factor due to the presence of small protrusions on the tip apex is calculated and their influence in near‐field‐emission scanning tunneling microscopy is also discussed. We show that the electron‐field emission from the sample is stable against tip‐shape changes due to adsorbate diffusion or atomic rearrangements.
TL;DR: In this article, the electron detachment dynamics subsequent to multiphoton absorption were studied by measuring the electron emission time profiles and electron kinetic energy distributions, which indicated that these species undergo the cluster equivalent of thermionic emission.
Abstract: Resonant multiphoton detachment spectroscopy has been used to obtain vibrationally resolved spectra of the C 2Π←X 2Π electronic transitions in C−4, C−6, and C−8. Transitions due to vibrational excitations in the totally symmetric stretching modes as well as the bending modes are observed. The electron detachment dynamics subsequent to multiphoton absorption are studied by measuring the electron emission time profiles and electron kinetic energy distributions. The observation of delayed electron emission combined with the form of the electron kinetic energy distributions indicates that these species undergo the cluster equivalent of thermionic emission. This interpretation is supported by comparing the experimental results to a microcanonical model for cluster thermionic emission.
TL;DR: In this paper, the top and bottom of the π-π energy gap for poly (2-decyloxy-1,4-phenylene), DO-PPP and MEH-PPV diodes were determined using Fowler-Nordheim tunneling.
TL;DR: In this article, an improved method for characterizing thin oxide films using Fowler-Nordheim field emission is reported. But the method uses a conducting-tip atomic force microscope with dual feedback systems, one for the topography and the second for the field emission bias voltage.
Abstract: An improved method for characterizing thin oxide films using Fowler‐Nordheim field emission is reported. The method uses a conducting‐tip atomic force microscope with dual feedback systems, one for the topography and a second for the field emission bias voltage. Images of the voltage required to maintain a 10 pA emission current through a 3 nm oxide film thermally grown on p‐type Si(100) demonstrate a spatial resolution of 8 nm.
TL;DR: In this paper, an array of patterned pyramids of polycrystalline diamond for vacuum diode applications has been investigated and high current emission from the patterned diamond microtip arrays was obtained at low electric fields.
Abstract: Electron field emission from an array of patterned pyramids of polycrystalline diamond for vacuum diode applications has been investigated. High current emission from the patterned diamond microtip arrays was obtained at low electric fields. An emission current from the diamond microtips of 0.1 mA was observed for a field of <10 V/μm. Field emission for these diamond microtips exhibits significant enhancement in total emission current compared to silicon emitters. Moreover, field emission from patterned polycrystalline diamond pyramidal tip arrays is unique in that the applied field is found to be lower compared to that required for emission from Si, Ge, GaAs, and metal surfaces. The fabrication process utilizes selective deposition of diamond film in a silicon cavity mold and subsequent creation of free standing polycrystalline diamond diaphragm with diamond pyramidal microtip array. The processing techniques are compatible with integrated circuit fabrication technology.
TL;DR: In this paper, the authors describe nanometer-scale feature definition in adsorbed hydrogen layers on Si(001) surfaces by exposure to low energy electrons from a scanning tunneling microscope tip.
Abstract: We describe nanometer‐scale feature definition in adsorbed hydrogen layers on Si(001) surfaces by exposure to low energy electrons from a scanning tunneling microscope tip. Feature sizes range from <5 to ≳40 nm as a function of bias voltage (5–30 V) and exposure dose (1–104 μC/cm). We show that the cross section for electron stimulated desorption of hydrogen has a threshold at 6–8 eV and is nearly constant from 10 to 30 eV, so that above threshold the feature profiles are a direct reflection of the electron flux profile at the surface. Radial flux distributions are best fit by a simple exponential function, where the decay length is dependent primarily on the tip–sample separation. Low intensity tails at large radius are also observed for high bias emission. Comparison to field emission simulations shows that our tip has an ‘‘effective radius’’ of approximately 30 nm. Simulations demonstrate that tip geometry and tip–sample separation play the dominant role in defining the electron flux distribution, and ...
TL;DR: In this article, a model of emission through the diamond layer is proposed that depends primarily upon tunneling through the Schottky barrier into diamond, while assuming a negligible barrier to emission from the diamond surface into vacuum.
TL;DR: In this article, a silicon field emitter tip with a dual-gate metaloxide-semiconductor field effect transistor (MOSFET) structure was fabricated and demonstrated, and two coplanar gates of 0.3μm-thick Nb are made on a 0.6μm−thick thermally oxidized SiO2 insulator between the source and the tip and make inversion layers in a p-type Si substrate under each gate.
Abstract: A silicon field emitter tip with a dual‐gate metal–oxide–semiconductor field‐effect transistor (MOSFET) structure was fabricated and demonstrated. The present tip structure is just the same as an n‐channel MOSFET whose drain was replaced by a cone‐shaped Si tip. Two coplanar gates of 0.3‐μm‐thick Nb are made on a 0.6‐μm‐thick thermally oxidized SiO2 insulator between the source and the tip and make inversion layers in a p‐type Si substrate under each gate. One of the gates has a 1.8‐μm‐diam aperture surrounding the tip for extraction of electrons from the tip. The other is 3 μm wide and 300 μm long and is separated by 2 μm from this gate. Ultrastable emission of about 0.3 μA was demonstrated with a single tip for one day.
TL;DR: In this article, a measurement of the field emission current dependence of doped polycrystalline diamond (PCD) films on temperature was carried out to assess the thermal stability of PCD field emitters and gain some insight into a possible emission mechanism.
Abstract: This letter reports on the measurement of the field emission current dependence of doped polycrystalline diamond (PCD) films on temperature. The motivation for this type of measurement was to assess the thermal stability of PCD field emitters and gain some insight into a possible emission mechanism. Between room temperature and 300 °C, for a fixed electric field, the emission current from B doped films was found to remain constant. Heavily doped nitrogen films were also examined and the emission current was found to increase exponentially with an activation energy of 0.16 eV.
TL;DR: In this article, diamond deposition on single Mo field emitters was performed by two methods: microwave plasma chemical vapor deposition and a dielectrophoresis of diamond powder, which revealed a significant amount of deposition at the tips.
Abstract: Diamond deposition onto single Mo field emitters was accomplished by two methods: microwave plasma chemical vapor deposition and a dielectrophoresis of diamond powder. Observation by transmission electron microscopy and scanning electron microscopy revealed a significant amount of deposition at the tips. The field emission characteristics were measured before and after diamond deposition on the same emitters. Field emission from diamond coated emitters yielded significant increases in emission current and lower Fowler–Nordheim slopes. We discuss a possible mechanism to explain current enhancement that depends primarily upon the Mo‐diamond interface.
Patent•
19 Nov 1996TL;DR: In this article, the authors showed that defect-rich diamonds can emit electron current densities of 0.1 mA/mm or more at a low applied field of 25 V/µm or less.
Abstract: Applicants have discovered methods for making, treating and using diamonds which substantially enhance their capability for low voltage emission. Specifically, applicants have discovered that defect-rich diamonds -- diamonds grown or treated to increase the concentration of defects -- have enhanced properties of low voltage emission. Defect-rich diamonds are characterized in Raman spectroscopy by a diamond peak at 1332 cm⁻¹ broadened by a full width at half maximum ΔK in the range 5-15cm⁻¹ (and preferably 7 - 11 cm⁻¹). Such defect-rich diamonds can emit electron current densities of 0.1 mA/mm or more at a low applied field of 25 V/µm or less. Particularly advantageous structures use such diamonds in an array of islands or particles each less than 10µm in diameter at fields of 15 V/µm or less.
TL;DR: In this article, the authors presented the consolidated results obtained with controlled field emission from nanotips and in particular discussed the specific effects related to the fact that the source is atomic size.
Abstract: Publisher Summary This chapter presents the consolidated results obtained with controlled field emission from nanotips and in particular discusses the specific effects related to the fact that the source is atomic size The chapter summarizes the basic results of field emission theory, including discussions of thermionic emission, to place the field emission from nanotips in the global context of electron sources Characteristics of field emission from nanotips are also presented and discussed in the chapter The usefulness of the very specific properties of nanotips is convincing only if they permit new advances to be developed; the chapter presents the demonstration of their utility Among other examples, nanometric-resolved images of synthetic polymers and RNA-based biological molecules are presented and discussed They were obtained with the Fresnel projection microscope (FPM), using the nanotip as an atom size electron source The main features of the temperature and field dependence of the emission currents and the energy distributions of emitted electrons can be understood by considering the electrons inside the metal to be a free electron gas
Patent•
12 Jul 1996
TL;DR: In this paper, a method for forming resistors for regulating current in a field emission display (10) comprises integrating a high resistance resistor (32) into circuitry for the FEM display, which is in electrical communication with emitter sites and with other circuit components such as ground.
Abstract: A method for forming resistors for regulating current in a field emission display (10) comprises integrating a high resistance resistor (32) into circuitry for the field emission display The resistor (32) is in electrical communication with emitter sites (14) for the field emission display (10) and with other circuit components such as ground The high resistance resistor (32) can be formed as a layer of a high resistivity material, such as intrinsic polycrystalline silicon, polycrystalline silicon doped with a conductivity-degrading dopant, lightly doped polysilicon, titanium oxynitride, tantalum oxynitride or a glass type material deposited on a baseplate (12) of the field emission display (10) Contacts (38, 39) are formed in the high resistivity material to establish electrical communication between the resistor (32) and the emitter sites (14) and between the resistor (32) and the other circuit components The contacts (38, 39) can be formed as low resistance contacts (eg, ohmic contacts) or as high resistance contacts (eg, Schottky contacts)
TL;DR: In this article, a new electron source using electric field and low electron affinity semiconductor materials to bring charge to potential energy levels near the vacuum level while still in the solid was described.
Abstract: We describe a new electron source using electric field and low electron affinity semiconductor materials to bring charge to potential energy levels near the vacuum level while still in the solid. The basic idea involves moving some of the potential barrier from the surface to the bulk, and distributing the barrier over a thin layer below the surface. In so doing, the emission physics is changed fundamentally from a quantum mechanical tunneling process largely controlled by surface properties to a classical transport process largely controlled by the band structure of a wide bandgap semiconductor. The composition of the thin layer below the surface would be graded such that the conduction band minimum changes from an energy close to the substrate Fermi level to an energy significantly closer to the vacuum level. Electrons from the substrate would be drawn into the graded composition layer with an electric field produced by a pointed emitter structure and extraction gate similar to that used in field emitte...