Showing papers on "Field electron emission published in 1992"

Method to form self-aligned gate structures around cold cathode emitter tips using chemical mechanical polishing technology

Abstract: A chemical mechanical polishing process for the formation of self-aligned gate structures surrounding an electron emission tip for use in field emission displays in which the emission tip is i) optionally sharpened through oxidation, ii) deposited with a conformal insulating material, iii) deposited with a flowable insulating material, which is reflowed below the level of the tip, iv) optionally deposited with another insulating material, v) deposited with a conductive material layer, and vi) optionally, deposited with a buffering material, vii) planarized with a chemical mechanical planarization (CMP) step, to expose the conformal insulating layer, viii) wet etched to remove the insulating material and thereby expose the emission tip, afterwhich ix) the emitter tip may be coated with a material having a lower work function than silicon.

Process and structure of an integrated vacuum microelectronic device

Abstract: The present invention relates generally to a new integrated Vacuum Microelectronic Device (VMD) and a method for making the same. Vacuum Microelectronic Devices require several unique three dimensional structures: a sharp field emission tip, accurate alignment of the tip inside a control grid structure in a vacuum environment, and an anode to collect electrons emitted by the tip. Also disclosed is a new structure and a process for forming diodes, triodes, tetrodes, pentodes and other similar structures. The final structure made can also be connected to other similar VMD devices or to other electronic devices.

Low‐temperature conductivity of ZnO films prepared by chemical vapor deposition

Abstract: c‐axis‐oriented ZnO films were prepared in O2 atmosphere by chemical vapor deposition using zinc acetylacetonate for source material. A minimum value of resistivity, 2.44 Ω cm, was obtained at a film formation temperature of 550 °C. The resistivity of the films was measured at low temperatures (87–297 K). For temperatures between 200 and 297 K band conduction included boundary scattering due to both thermionic emission and thermal‐field emission at the grain‐boundary barriers in the films, and the activation energy obtained ranged from 1.45 to 6.32×10−2 eV. For temperatures lower than about 200 K, the conductivity deviated from linear Arrhenius plots suggesting variable range‐hopping conduction. Discussions based on assumed electron mobility and concentration lead to variable range‐hopping conduction by localization of electrons in impurity levels in the intermediate concentration region. Mott’s parameters in the variable range‐hopping conduction were estimated for the films.

Field-emission electron spectroscopy of single-atom tips

Abstract: We show here that the experimental field-emission electron spectra from W nanoprotrusion tips ending in a single atom consist solely of well-separated peaks. Each spectrum shifts linearly with the applied field-emission voltage. The peaks in the spectra strongly suggest that the tunneling occurs only through a localized band structure at the topmost atom. A charge confinement and a field penetration over the top atom is introduced to explain the linear shifts.

Scanning electron microscope

Abstract: PURPOSE:To enable observation of atomic arrangement by providing an electrode for applying positive voltage on the reverse side of a detection means for sandwiching a sample when an electron beam is focused to scan the sample surface, and the secondary electron obtained at the time is put into the detection means, and the signal fro the detection means is displayed being synchronized with beam scanning to provide a scan image. CONSTITUTION:An electron beam 2 emitted from a field emission type electron gun 1 is focused by a condenser lens 3, deflected by a deflection coil 4, focused again by an objective lens 5, and is applied on the surface of a sample 7 put on a sample stage 6. A secondary element 8 is generated thereby from the surface of the sample 7, which is detected by a secondary electron detector 9, which is positioned in the side of the sample stage 6, and to which positive high voltage is applied, and the detection intensity is displayed on a CRT 1 while synchronizing with the scanning by the coil 4 of the beam 2, to provide a scan image. The same voltage as the drawing voltage of the detector 9 is supplied to an electrode 10 provided on the symmetric position of the detector 9 by which the sample 7 is sandwiched, to make the electric field around the sample 7 symmetric in terms of face.

Field emission electron device employing a modulatable diamond semiconductor emitter

Abstract: A field emission device having a diamond semiconductor electron emitter with an exposed surface exhibiting a low/negative electron affinity which is operably controlled by modulation of a junction depletion region. Application of a suitable operating voltage to a device gate electrode modulates the depletion width to control availability of electrons transiting the bulk of the electron emitter for emission at the exposed surface.

Regulatable field emitter device and method of production thereof

Abstract: A non-power generating current limiting device such as a field effect transistor is provided to output a regulated current in dependence upon a control voltage. An electron field emitter is connected to a drain or output of the non-power generating current limiting device to receive the regulated current. A tip of the electron field emitter emits electrons towards a collector anode. An extractor gate can be provided between the electron field emitter and the collector anode to control the rate of electron emission from the electron field emitter. Because the non-power generating current limiting device regulates the current to the electron field emitter, a maximum current output of the electron field emitter is limited to the regulated current from the voltage controlled current source. The electron field emitter is thus protected from destruction due to excess current. The non-power generating current limiting device can also be used to modulate electron emission from the field emitter.

Structures and processes for fabricating field emission cathodes

Abstract: The present invention relates generally to new structures for a field emission cathode and processes for fabricating the same. The field emission is made of any material that is capable of emitting electrons under the influence of an electrical potential. The field emission cathode has several unique three dimensional structures. The basic structure comprises of a layer of material with cathode tips. For a more complex structure the cathode tip is preferably accurately aligned inside an extraction/control electrode structure, in preferably a vacuum environment. The structures of this invention can be fabricated to be connected to other similar field emission cathodes or to other electronic devices.

Fowler-Nordheim tunneling in thin SiO2 films

Abstract: An analysis of the Fowler-Nordheim tunneling (FNT) theory and its application to temperature-dependent current-voltage characteristics of very thin SiO2 films on silicon, is presented. The final results are believed to provide the most complete examination in FN emission theory and predict the breakdown electric field in thin SiO2 films. The role of the roughness, at the Si-SiO2 interface, in determining the FNT current in these structures is also discussed.

Slow particle-induced electron emission from solid surfaces

Abstract: Theoretical Concepts and Methods for Electron Emission from Solid Surfaces.- Photon and Electron Induced Electron Emission from Solid Surfaces.- Potential Electron Emission from Metal and Insulator Surfaces.- Kinetic Electron Emission for Grazing Scattering of Atoms and Ions from Surfaces.- Spin Polarization of Electrons Emitted in the Neutralization of He+ Ions in Solids.- Electron Emission from Surfaces Mediated by Ion-Induced Plasmon Excitation.- Slow Ion-Induced Electron Emission from Thin Insulating Films.

Atomic‐scale manipulation in air with the scanning tunneling microscope

Abstract: From the practical point of view, the aim in nanofabrication is to build the smallest possible device operable in air and at room temperature. In this letter, we present a procedure in which a scanning tunneling microscope is used to remove a small number of atoms from a surface at room temperature and pressure. Its potential for high density storage of information is shown by two results: (i) two subnanometer marks, 1.2 nm apart were impressed and (ii) these marks remained unaltered after several observations.

Electron‐beam lithography with the scanning tunneling microscope

Abstract: The scanning tunneling microscope (STM), operated in vacuum in the field emission mode, has been used in lithographic studies of the resist SAL‐601 from Shipley. Patterns have been written by raising the tip–sample voltage above −12 V while operating the STM in the constant current mode. Resist films, 50 nm thick, have been patterned and the pattern transferred into the GaAs substrate by reactive ion etching. The variation of feature size with applied dose and tip–sample bias voltage has been studied. Comparisons have been made to lithography with a 10 nm, 50 kV electron e‐beam in a JEOL JBX‐5DII in the same resist thickness films. In all cases the resist films were processed in the standard fashion before and after exposure. The STM can write smaller minimum features sizes and has a greater process latitude. Proximity effects are absent due to the reduced scattering range of the low energy primary electrons. However, the writing speed is slower, being limited by the response of the piezoelectric scanner....

Monte Carlo simulations of secondary electron emission from CsI, induced by 1–10 keV x rays and electrons

Abstract: A model for electron transport and emission in CsI is proposed. It is based on theoretically calculated microscopic cross sections for electron interaction with the nuclear and the electronic components of the solid. A Monte Carlo program based on this model was developed to simulate secondary electron emission induced by x rays and electrons in the energy range of 1 to 10 keV. The calculated secondary emission yields agree with existing experimental data. The model provides all necessary characteristics for the design of radiation detectors based on secondary electron emission. It can be expanded to higher incident energies and other alkali halides.

Field emission from hafnium carbide

Abstract: We report on experiments to determine the feasibility of using refractory transition metal carbides as stable field emission cathodes. Applications of such cathodes could include radiation immune microcircuitry, radio frequency (rf) vacuum microelectronic amplifiers, flat panel displays, e‐beam lithography, and other uses where the need is for very high density, small spot size electron sources. Hafnium carbide (HfC) single crystal specimens were prepared by arc floating zone refinement from sintered stock. Field emission patterns from heated HfC emitters were observed, and emission stability measurements were made. Ordering of the work functions of low‐index crystal planes was determined through field emission microscopy and comparisons were made with thermionic projection microscopy. An effective thermionic work function of φ{100}=3.34 eV was obtained for a clean surface. The ability of heated HfC field emitters to operate at pressures above those commonly found for field emission cathodes is demonstrated. Current versus time plots are shown on heated emitters having stable dc currents of 0.5 mA and lifetimes ≳2400 h. Pulsed field emission measurements on room‐temperature HfC emitters are also reported.

Field-excited electron emission from ferroelectric ceramic in vacuum

Abstract: Electron emission into vacuum has been observed by applying pulse voltage to a thin plate of PZT ferroelectric ceramic. This electron emission has been obtained even in low vacuum of less than 10-1 Torr. The lowest pulse voltage for this emission is 75 V, and the largest emission current in a sample having a 7×0.3 mm2 electrode is 30 mA. The electrons are considered to be emitted from the surface of the ferroelectric plate near the electrode by very high field induced by polarization reversal. This electron emission can be applied as the electron emitter in vacuum electronic devices such as micro-triodes and flat panel displays.

Multiple electrode field electron emission device and method of manufacture

Abstract: A multiple electrode field electron emission device is formed on an insulating layer disposed on a surface of an insulated flat substrate and has a cathode with multiple of emission projections each having a projection tip that overhangs the insulating layer. The device further includes an anode for collecting electrons ejected from the cathode emission projections formed on the surface of the substrate. Control electrodes, having one of several alternate configurations, are formed between the cathode and the anode. The device is fabricated using over-etching and directional particulate deposition techniques.

Field electron emission device

Abstract: A field emission device and method for manufacturing which comprises using a diffusion mask to preserve an area of a silicon substrate for use as a cathode while all around the cathode the substrate is being diffused with oxygen to form an insulating layer. And further comprising depositing a molybdenum gate electrode layer on the insulating layer and etching the molybdenum gate electrode layer such that the diffusion mask falls off and the insulating layer is dissolved around the cathode through the hole formed in the gate electrode layer by the diffusion mask being removed. The gate electrode openings are therefore automatically and independently self-aligned with their respective cathodes.

Analysis of field emission from three‐dimensional structures

Abstract: An analysis of the field emission from emitter tips with the geometry of a prolate ellipsoid of revolution indicates that the field enhancement factor, β, and effective emission area, α, are not constant but instead depend on the applied field. The added complexity of a materials related limit on the minimum time for transition of an electron from the solid into the vacuum is also examined in the analysis. The calculated variations of α and β are as large as 35%, and in some instances could result in erroneous interpretation of measured current‐voltage (I‐V) characteristic data.

Fabrication of biologically based microstructure composites for vacuum field emission

Abstract: A multidisciplinary approach to the fabrication of biologically based microstructure composites for vacuum field emission is described. Diacetylenic lipid 1,2-bis(10,12-tricosadiynol)-sn-glycero-3-phosphocholine (DC 8.9 PC) was self-assembled to form hollow cylindrical tubules approximately 0.5 μm in average diameter and 50–80 μm long. Following the deposition of nickel on the inner and outer tubule surfaces by an electroless plating method, the nickel-plated tubules were magnetically aligned in an epoxy matrix to form a composite material. Subsequent selective removal of the matrix provided a composite base template of oriented exposed tubules. The tubule template was coated with a thin sputtered gold film to provide the surface electrical contact. The resultant microstructures demonstrated vacuum field emission of current I > 10 μ A at relatively low applied macroscopic electric fields (about 60–150 kV cm −1 ).

A theoretical study on field emission array for microsensors

Abstract: The authors present results on the analysis of two generic cone-shaped and wedge-shaped emitter-array diodes. The effects of the variations in device geometrical structure on the potential distribution, electric field, and emission current are discussed. The main geometric design parameters considered are the tip-to-collector distance, the emitter tip radius of curvature, and the intertip spacing. Pressure sensors based on these diode structures with one electrode fabricated on a pressure sensitive thin diaphragm were studied. The analysis shows that a cone-shaped emitter array has a larger emission current per emitter tip, but the wedge-shaped array has better pressure sensitivity. >

Intense electron emission due to picosecond laser-produced plasmas in high gradient electric fields

Abstract: Picosecond laser pulses at a wavelength of 266 nm have been focused onto a solid metal cathode in coincidence with high gradient electric fields to produce high brightness electron beams. At power densities exceeding 109 W/cm2, a solid density plasma is formed and intense bursts of electrons are emitted from the target accompanied by macroscopic surface damage. An inferred ∼1 μC of integrated charge with an average current of ∼20 A is emitted from a radio‐frequency cavity driven at electric field gradients of ∼80 MV/m. In another experiment, where a dc extraction field of ∼6 MV/m is used, we observed an electron charge of ∼0.17 μC. Both results are compared with the Schottky effect and the Fowler–Nordheim field emission. We found that this laser‐induced intense electron emission shares many features with the explosive electron emission processes. No selective wavelength dependence is observed in the production of the intense electron emission in the dc extraction field. The integrated electrons give an ap...

Field emission electron source employing a diamond coating

Abstract: A field emission electron emitter including a coating of diamond material disposed on a surface of a selectively formed conductive/semiconductive electrode wherein carbon ions are implanted at a surface of the electrode to function as nucleation sites for the diamond formation. A second field emission electron emitter is constructed by implanting carbon ions at a surface of a selectively shaped substrate to function as nucleation sites for the diamond formation. A conductive layer is deposited over the diamond and the substrate is removed to leave an electron emitter with a diamond coating.

Structures and processes for fabricating field emission cathode tips using secondary cusp

Abstract: The present invention relates generally to new structures for a field emission cathode and processes for fabricating the same. The field emission is made of any material that is capable of emitting electrons under the influence of an electrical potential. The field emission cathode has several unique three dimensional structures. The basic structure comprises of a layer of material with cathode tips. For a more complex structure the cathode tip is preferably accurately aligned inside an extraction/control electrode structure, in preferably a vacuum environment. The structures of this invention can be fabricated to be connected to other similar field emission cathodes or to other electronic devices.

Electron emitting structure and manufacturing method

Abstract: A field emitter includes an electron emitting structure (112) spaced from an anode structure (114), with the intervening gap (113) being substantially evacuated. The electron emitting structure (112) includes a first electrically conductive layer (128) spaced by an insulating layer (130) from a second conductive layer (132), and a generally circular aperture (134) disposed through the layers (128,132). The anode structure (114) includes an electrically conductive layer (142). Electrostatic forces, provided from a potential applied between the first conductive layer (128) and the anode structure (114), cause an electron beam to be drawn from a cathode provided by a peripheral edge portion (127a) of the first conductive layer (128) within the aperture (134) onto an adjacent surface portion of the anode structure (114). Such field emission occurs under the control of a potential applied between the first and second conductive layers (128,132) of the electron emitting structure with the second conductive layer (132) functioning as a control electrode of the emitting structure. The anode structure (114) has a phosphor layer (144) which converts the electrical energy from the electron bombardment into visible light energy. In one embodiment (Fig. 6), a potential applied to a third conductive layer (360) of the emitting structure (312) serves to focus the electron stream on the anode structure (314). Methods of manufacturing the electron emitting structures employ successive steps of layer deposition and subsequent selective etching.

Instrument and method for 3-dimensional atomic arrangement observation

Abstract: 3-dimensional observation is carried out on the atomic arrangement and atomic species in a thin-film specimen at an atomic level in order to clarify the existence states of defects and impure atoms in the crystals For that purposes, the present invention provides an instrument and a method for 3-dimensional observation of an atomic arrangement which are implemented by a system comprising a scanning transmission electron microscope equipped with a field emission electron gun operated at an acceleration voltage of greater than 200 kV, a specimen goniometer/tilting system having a control capability of the nanometer order, a multi-channel electron detector and a computer for executing software for controlling these components and 3-dimensional image-processing software Point defects and impure atoms, which exist in joint interfaces and contacts in a ULSI device, can thereby be observed As a result, the causes of bad devices such as current leak and poor voltage resistance can be analyzed at a high accuracy

Density-gradient analysis of field emission from metals.

Abstract: The conventional theory of field emission from metals consists of the Fowler-Nordheim tunneling analysis with space-charge effects accounted for using the «image-force» concept. This one-electron approach is highly questionable because the potential barrier through which the tunneling occurs is located very close (<3 A) to the cathode interface, a region in which the charge density is quite high due to «spillover» effects. In this paper, we give an improved analysis of the field-emission current based on an approximate many-body quantum transport theory known as density-gradient theory