Showing papers on "Field electron emission published in 1986"
TL;DR: McCord and Pease as mentioned in this paper used a modified scanning tunneling microscope (STM) operating in the field emission mode to generate an electron beam with an extraordinary combination of high current (>1 mA), low voltage (<100 V) and small diameter (<0.1 μm).
Abstract: In a recent paper [McCord and Pease, J. Vac. Sci. Technol. B 3, 198 (1985)] we described how it should be possible to generate, for lithography and other materials processing, an electron beam with an extraordinary combination of high current (>1 mA), low voltage (<100 V) and small diameter (<0.1 μm) using a modified scanning tunneling microscope (STM) operating in the field emission mode. To test this prediction we have built a modified STM onto the stage of a scanning electron microscope (SEM) so that we can monitor system geometry. The tip, an etched tungsten wire, can be manually moved in the z direction (normal to the target) for coarse motion and three PZT piezoelectric transducers allow 10 μm travel in the x, y, and z directions. A feedback system stabilizes the field emission current (and hence the tip‐to‐target spacing). We have obtained beams with currents from 1 nA to several microamps at voltages from 1 to 1000 V. We have used the beam to produce lines of contamination on a gold film; the cont...
139 citations
TL;DR: In this article, an ultrahigh vacuum scanning tunneling microscope (STM) equipped with a field ion microscope (FIM) was built for high STM resolution in a scan of the Au(001) surface, and the measured corrugation depth of the (1×5) rows was found to be a function of the size of the atomic cluster on the first plane of the tungsten tip.
Abstract: An ultrahigh vacuum scanning tunneling microscope (STM) equipped with a field ion microscope (FIM) has been built. By using the FIM image, a tungsten tip was tailored for high STM resolution in a scan of the Au(001) surface. The measured corrugation depth of the (1×5) rows was found to be a function of the size of the atomic cluster on the first plane of the tungsten tip.
105 citations
TL;DR: In this article, field electron emission measurements have been made on composite emitters consisting of electrolytically etched tungsten micropoint cathodes overlayed by a 40-200 nm thick layer of epoxy resin.
Abstract: Field electron emission measurements have been made on composite emitters consisting of electrolytically etched tungsten micropoint cathodes overlayed by a 40-200 nm thick layer of epoxy resin. Their emission properties include (a) an initial switch-on effect at threshold fields of approximately 109 V m-1, (b) a subsequent reversible I-V characteristic that gives a linear FN plot at low fields ( or approximately=4*108 V m-1, (c) electron spectra whose FWHM and energy shift is strongly field dependent, (d) single-spot emission images. This unusual pattern of behaviour has been interpreted in terms of a hot electron emission mechanism resulting from field penetration in the dielectric overlayer. Consideration is also given to the technological significance of such composite microemitters.
70 citations
TL;DR: In this article, it is shown that it is possible to focus electrons to a cross-over of width 3A or less and, with a suitable detection system, to obtain diffraction patterns from specimen regions of this size or greater.
Abstract: Because of the high brightness of the cold field emission source used in a dedicated scanning transmission electron microscopy (STEM) instrument, it is possible to focus electrons to a cross-over of width 3A or less and, with a suitable detection system, to obtain diffraction patterns from specimen regions of this size or greater. Coherent interference effects are visible in shadow images (in-line holograms) and in convergent beam diffraction patterns. Special techniques have been developed for gathering information from the diffraction patterns for application to the study of the structures of crystal defects, crystal surfaces and small particles. Possibilities have been explored for holographic reconstruction from shadow images.
69 citations
TL;DR: In this article, the authors present results made with a new apparatus for the study of localized field emission (FE) sites on broad-area cathodes, centered around a UHV field emission scanning microscope, consisting of a micromanipulator allowing precision cathode motion, a rotatable holder for broad and microtip anodes, and a fast highvoltage regulator allowing constant current measurement of a distribution of both weakly and strongly emitting sites.
Abstract: We present results made with a new apparatus for the study of localized field emission (FE) sites on broad‐area cathodes. The apparatus is centered around a UHV field emission scanning microscope, consisting of a micromanipulator allowing precision cathode motion, a rotatable holder for broad and microtip anodes, and a fast high‐voltage regulator allowing constant‐current measurement of a distribution of both weakly and strongly emitting sites. Also included are an in situ scanning electron microscope, and a facility for in situ microfocus Auger analysis as well as scanning Auger microscopy. Samples can be high‐temperature annealed without removal from UHV. These tools have been used to study the effects of heat treatment (HT) up to 2000 °C on the FE from nonanodized and anodized Nb cathodes. We find that HT at 800–900 °C increases the density of field emitters at a given electric field. HT at T>1000 °C reduces the density, while at T≥1400 °C a drastic decrease of the emission occurs. We have repeatedly o...
67 citations
TL;DR: In this article, an optical imaging technique is described that compares the spatial distribution of vacuum field emission sites on a planar cathode at fields of 10-20 Mv m-1 in high-pressure (10 bar) sulphur hexafluoride.
Abstract: An optical imaging technique is described that compares the spatial distribution of vacuum field emission sites on a planar cathode at fields of 10-20 Mv m-1 in high-pressure (10 bar) sulphur hexafluoride. It has been established that a direct correlation exists between the two processes provided a delay of at least 18 h is introduced between the two experiments. This observation indicates that a high-pressure breakdown event is associated with the switch-on of an electron emission site when a large burst of charge is suddenly injected into the electrically stressed gas.
65 citations
TL;DR: In this paper, it was shown that graphite flakes deposited on an extended electrode surface form MIM microstructures which promote a field-induced hot-electron emission mechanism in which electrons are coherently scattered from the edge of a flake.
Abstract: Emission image and electron spectral data is presented which qualitatively confirms that graphite flakes deposited on an extended electrode surface form MIM microstructures which promote a field-induced hot-electron emission mechanism in which electrons are coherently scattered from the edge of a flake. The model is further supported by evidence of how the emission characteristics are influenced by temperature.
61 citations
TL;DR: It is shown that electron acceleration in the cross-shock electron field can produce downstream electron temperature significantly higher than those expected for adiabatic compression.
Abstract: Fully kinetic simulations of high-Mach-number (HMN) perpendicular collisionless shocks are described. It is shown that electron acceleration in the cross-shock electron field can produce downstream electron temperature significantly higher than those expected for adiabatic compression. The momentum space for test electrons at Mach 6 is illustrated.
58 citations
TL;DR: In this paper, the emission properties of silicon cold cathodes are described and the factors which ultimately limit the performance of such cathodes were discussed, and it was tentatively concluded that the maximum available current density and brightness are limited by cesium migration and desorption, these maximum values (for emitters with 1 μm diam and with an efficiency of 1.5%) being jvac,max≂1500 A/cm2 and Bmax ≥ 9×106 A/ cm2 sr (at V=10 kV).
Abstract: The emission properties of cesiated silicon cold cathodes are described and the factors which ultimately limit the performance of such cathodes are discussed. It is tentatively concluded that the maximum available current density and brightness are limited by cesium migration and desorption, these maximum values (for emitters with 1 μm diam and with an efficiency of 1.5%) being jvac,max≂1500 A/cm2 and Bmax≂9×106 A/cm2 sr (at V=10 kV). The long term stability of the emission is surprisingly good, in spite of adsorption of oxidizing gases from the vacuum. This indicates that there is a desorption of such gases too, probably due to the outgoing electrons at high current densities.
54 citations
TL;DR: In this paper, the authors used the vacuum emission technique to study electron transport and heating in silicon nitride and silicon oxynitride and found that the number of hot electrons which can be heated to energies greater than 2 eV is greatly reduced because of increased trapping in these films.
Abstract: The vacuum emission technique has been used to study electron transport and heating in silicon nitride and silicon oxynitride. The experimental results are compared to data for silicon dioxide in which all the conduction‐band electrons can gain several eV of energy at electric fields greater than 2 MV/cm. Although average electron energy as a function of electric field curves are very similar to silicon dioxide, the total number of electrons which can be heated to energies greater than 2 eV is greatly reduced because of the increased trapping in these films. Reduction in hot electrons due to increased trapping is correlated to increasing nitrogen content through the oxynitride phases to silicon nitride. Trapping/detrapping on energetically shallow sites in the forbidden gap controls the bulk limited conduction in these films, and very few electrons are allowed to move freely in the conduction band.
45 citations
TL;DR: The enhanced field emission (EFE) occurs only for contaminated surfaces as discussed by the authors, which is caused by dust and contaminants initiating the following effects: the pulsating, self-sustained EFE has the same root as:
Abstract: Broad-area electrodes show electron emission already at electric field strengthsF≈107 V/m. This enhanced field emission (EFE) occurs only for contaminated surfaces. EFE is accompanied by photon emission and gas desorption yielding finally discharges. EFE is caused by dust and contaminants initiating the following effects:
The pulsating, self-sustained EFE has the same root as:
TL;DR: In this paper, an ion source that utilizes a pair of thin-film field emission cathodes to provide current for electric impact ionization is studied, which ionizes atoms and molecules that enter the mass spectrometer with a ram velocity of about 80 km/sec.
Abstract: An ion source that utilizes a pair of thin-film field emission cathodes to provide current for electric impact ionization is studied. The field emission cathodes are composed of microscopically small needle tips and an extraction electrode; the cathodes generate a 200-eV, 0.1-mA electron beam. The multistep process for the manufacturing of the field emission cathodes is examined. The operation of the ion source, which ionizes atoms and molecules that enter the mass spectrometer with a ram velocity of about 80 km/sec, is described.
IBM1
TL;DR: In this paper, the threshold for the onset of electron heating in silicon dioxide was found to be independent of oxide thickness and composition, and a minimum average electronic energy of ≊ 1.0 eV was shown to be necessary to observe emission of the electrons into vacuum.
Abstract: Novel metal‐oxide‐semiconductor structures with very large areas have been used together with the vacuum emission and carrier separation techniques to study electron heating down to low fields (≊1 MV/cm) and out to large oxide thicknesses (5200 A). At electric field magnitudes between 1.5 and 2.0 MV/cm, the threshold field for the onset of electron heating in silicon dioxide is observed. This onset is independent of oxide thickness and composition. Its value is consistent with all of the current theoretical calculations. At fields near threshold, a minimum average electronic energy of ≊1.0 eV is shown to be necessary to observe emission of the electrons into vacuum. Although the general trends in most of the data are approximately independent of oxide thickness out to 5200 A, certain thick oxide samples with higher water content and lower physical density do show deviations from stabilization at higher fields, particularly in the vacuum emission experiments. Also, the data tend to appear ‘‘noiser’’ as the...
TL;DR: In this article, the use of scanning tunneling microscopy and related techniques for the determination of surface diffusion coefficients of adsorbates is discussed and three schemes, all extensions of the field-emission current fluctuation method are presented and analyzed.
Abstract: The use of scanning tunneling microscopy and related techniques for the determination of surface diffusion coefficients of adsorbates is discussed. Three schemes, all extensions of the field-emission current fluctuation method are presented and analyzed. The first consists of determining single site correlation functions with a STM in its more or less normal operating mode. The second consists of retracting the tip approximately one tip radius so that a circular region of high field is created on the flat surface from which field emission and diffusion-induced current fluctuations can be obtained. The third considers creation of a long narrow region of high field by placing a very fine cylindrical wire parallel to and above the plane substrate. This last scheme allows determination of diffusion anisotropy. Detailed expressions for the current correlation functions for the three schemes and criteria for allowed vibrational amplitudes and drift are derived. It is concluded that all three schemes should be feasible but probably would differ in the range of diffusion coefficient values they would be able to handle.
TL;DR: In this paper, the authors performed a systematic investigation of thermally stimulated electron emission from virgin TGS crystals in vacuum of about 10−6 Torr and established that the electron emission phenomena observed are determined by the intensive change (breakage) of the domain structure of TGS crystal.
Abstract: Systematic investigations of thermally stimulated electron emission from virgin TGS crystals in vacuum of about 10−6 Torr are performed. It is established that the electron emission phenomena observed are determined by the intensive change (breakage) of the domain structure of TGS crystals. The apparent exoelectron emission and field emission participate in the observed emission phenomena.
Es werden systematische Untersuchungen der thermisch stimulierten Elektronenemission von TGS Kristallen im Vacuum von ca. 10−6 Torr durchgefuhrt. Die Emission wird von intensiven Anderungen der Domanen-Struktur der TGS Kristallen beeinflust. Die gemessene Emissionsintensitat enthalt einen Anteil der „scheinbaren” Exoelektronenemission wie auch der Feldemission.
TL;DR: In this paper, the voltage drop across the oxide (pad-oxide) in the oxide:nitride dual dielectric is determined for both positive and negative gate polarities.
Abstract: Using a simple but novel method of analysis, the voltage drop across the oxide (pad-oxide) in the oxide:nitride dual dielectric is determined for both positive and negative gate polarities. From the Fowler-Nordheim plot of the oxide voltage drop, the electron barrier from nitride to oxide is 3.2 ± 0.2 eV. However, the current injection from the nitride electrode is about 7 orders of magnitude lower than the current injection from the silicon electrode under the same oxide field values. This large field-current difference between the two directions of electron injection is consistent with the large difference observed in the J ★ t (charge fluence to breakdown) data.
TL;DR: In this paper, the atom superposition and electron delocalization molecular orbital method (ASED-MO) was used to calculate binding and activation energies, bond lengths, and charge transfers of rare gases adsorbed on metal surfaces in strong electric fields.
TL;DR: In this article, the field emission properties of microscopic particles of graphite, sulfur, and MoS2 deposited on nonemitting Nb surfaces under ultrahigh vacuum conditions are described.
Abstract: Field emission properties of microscopic particles of graphite, sulfur, and MoS2 deposited on nonemitting Nb surfaces under ultrahigh vacuum conditions are described. Both graphite and MoS2 particles are shown to emit strongly, with field enhancement factors of the order of 100, in contrast to sulfur particles, which emit only weakly. The emission characteristics are measured locally on the individual sites, and emitting particles are further characterized by microfocus Auger spectroscopy and scanning electron microscopy. Their behavior upon heat treatment was studied, with the main result that both for graphite and MoS2 particles the emission disappears after heating to 1200 °C. The properties of the artificially created emitters are compared with those of naturally occurring field emitters.
Patent•
11 Aug 1986
TL;DR: An axially compact field emission cathode assembly for use in an electron beam device comprises a field emission tip, an electriclly conductive filament for mechanically supporting said tip and for receiving and conducting to said tip a predetermined electrical potential for exciting said filament to cause electron emission from said tip as discussed by the authors.
Abstract: An axially compact field emission cathode assembly for use in an electron beam device comprises a field emission tip, an electriclly conductive filament for mechanically supporting said tip and for receiving and conducting to said tip a predetermined electrical potential for exciting said filament to cause electron emission from said tip. Filament support means supports the filament with the tip positioned on an electron beam axis within said device. The cathode assembly is characterized by the filament being supported by said filament support means to extend transversely to the electron beam axis, whereby to reduce the axial length of the device.
TL;DR: The wavelength of the illuminating radiation used in studies of photofield emission is comparable to the diameter of the shank of the field emitter under these conditions, diffraction is expected as discussed by the authors.
Abstract: The wavelength of the illuminating radiation used in studies of photofield emission is comparable to the diameter of the shank of the field emitter Under these conditions, diffraction is expected
TL;DR: In this paper, a photofield emission spectrometer was used to observe departures from free electron behaviour in the total energy distributions of photof-ield emission from the (100, (110), (111), (211), and (510) facets of a tungsten field emitter.
TL;DR: In this article, it is shown that electron cyclotron emission can be used for detailed diagnosis of mildly relativistic electron distribution functions, provided the plasma can be viewed along a line of constant magnetic field.
Abstract: It is shown that electron cyclotron emission can be used for detailed diagnosis of mildly relativistic electron distribution functions, provided the plasma can be viewed along a line of constant magnetic field. Calculations of the emissivity are performed, both for tenuous and finite-background-density plasmas whose results allow observations of emission to be deconvolved in terms of the density and anisotropy of the distribution as a function of total electron energy. For prolate distributions different harmonics have to be measured, while for oblate distributions different polarizations have to be measured. Absorption can also be treated using these results. Some of the issues concerning experimental application are discussed.
TL;DR: In this paper, a survey of the modern theory of the static electron response of a metal surface is reviewed, based on the analysis of the contradictions between the widely accepted sharp boundary models and experiment, is presented.
TL;DR: In this paper, the authors describe the ODE methods used to fabricate pyramidal electron emitter points 1.5 μm high, with radius of curvature of 20 to 100 nm from silicon.
Abstract: Vacuum integrated circuits and field emission (FE) devices with geometries on the micron and submicron scale have been discussed as alternatives to solid state devices for high speed and hostile environment application as well as for miniature electron sources for CRTs. These miniaturized vacuum devices have been developed on the basis of the advances in micromachining technology, i.e. orientation-dependent etching (ODE) of lithographically patterned silicon. This paper describes the ODE methods used to fabricate pyramidal electron emitter points 1.5 μm high, with radius of curvature of 20 to 100 nm from silicon. In order to reduce operating voltages, an integral extraction electrode (grid) was fabricated by a self-aligned technique. With a single gate mask level the extraction and planar collector structures were fabricated on chip, to form a planar vacuum triode. The final mask step provided the flexibility for fabricating a variety of planar vacuum integrated circuit elements.
TL;DR: In this paper, Schottky diodes prepared by Au/Pt/Ti evaporation and by Ti sputtering on GaAs substrates were measured as a function of temperature between 77 and 300 K. The ideality factor was found to follow the theory of thermionic field emission.
Abstract: I‐V and C‐V characteristics of Schottky diodes prepared by Au/Pt/Ti evaporation and by Ti sputtering on GaAs substrates with electron concentrations of 1.5×1017, 4.5×1017, and 3.5×1018 cm−3 were measured as a function of temperature between 77 and 300 K. The ideality factor was found to follow the theory of thermionic field emission. Closer agreement with that theory was observed for evaporated and annealed diodes and for sputtered diodes than for evaporated, as‐deposited devices. The sputtered diodes exhibited the best I‐V characteristics with an ideality factor n=1.04 and a reverse current lower by more than two orders of magnitude than that of the evaporated devices at 300 K. This behavior was attributed to the presence of an interfacial oxide layer in the evaporated devices. Departure from the thermionic field emission theory was observed in devices with Nd≥4.5×1017 cm−3 at low forward bias and was attributed to current transport due to a mechanism of multistep recombination tunneling through defects.
01 Mar 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the theoretical predictions of three electron transport models are compared for H+ induced secondary electron emission from Al. In particular, the secondary electron energy distribution and the ion energy dependence of secondary electron yield have been obtained.
Abstract: Theoretical predictions of three electron transport models are compared for H+ induced secondary electron emission from Al. In particular, the secondary electron energy distribution and the ion energy dependence of the secondary electron yield have been obtained. For thin targets, we have calculated the forward and backward electron yields as well as their dependence upon the angle of incidence of the ions. Our results are in agreement with the presently available experimental data. However, further work is needed to describe adequately the thin foil results.
TL;DR: In this paper, the authors reviewed the development of field electron emission as it is applied to electron sources and showed that the current fluctuations occur mainly due to the interaction with the residual gas in the vacuum.
Abstract: Field emission occurs at the sharp apex of a metal needle, so that it can be considered as providing a point electron source, which is a desirable feature for a fine focused electron beam. The disadvantage is its low stability. It is shown that the current fluctuations occur mainly due to the interaction with the residual gas in the vacuum; thus reduction of the interaction with the residual gas is essential for a stable field electron source. The stringency of the vacuum requirement has prevented wide application of the field emission electron source. New materials which have low work functions and high melting points are examined in the view of a stable field electron emitter, and it is shown that carbides of transition metals have potential as a stable field emitter. Very stable field emission has been reported for TiC single crystals. Operation in the thermal-field emission mode is examined and it is shown that ZrO/W(lOO) emitter gives stable emission, whose fluctuation is less than 0.23 % in the frequency interval 1 to 5000 Hz. The only disadvantage of the ZrO/W thermal field emitter is its rather high level of instability at very low frequencies. This paper reviews the development of field electron emission as it is applied to electron sources.
02 Jan 1986
TL;DR: In this paper, the Model S-6000 is developed for critical dimension measurement of circuit patterns on VLSI wafers utilizing a filed emission electron source, which has been designed to handle up to a 6" wafer.
Abstract: We have developed the Model S-6000 for critical dimension measurement of circuit patterns on VLSI wafers utilizing a filed emission electron source. This instrument has been designed to handle up to a 6" wafer. Measurements are made under low voltage operation, at a high resolving power and at a flicker-free TV-scan rate. Minimum dose feature protects the wafer under measurement from electron beam damage. The S-6000 is a state-of-the-art CD measurement, SEM for quality control of in-process wafers.
TL;DR: In this paper, the authors describe a novel method to achieve enhanced electron injection into silicon dioxide by tunnel emission from texturised silicon surfaces, achieving field enhancement factors from 4 to 8.
Abstract: We describe a novel method to achieve enhanced electron injection into silicon dioxide by tunnel emission from texturised silicon surfaces. Field enhancement factors from ~4 to ~8 have been realised for 60 nm-thick oxides thermally grown on anisotropically plasma-etched Si surfaces. Implementation of these textured interface structures should allow significant improvements in the write/erase processes of EEPROM memory devices.