Abstract: An electron source comprises one or more electron-emitting devices, especially of surface conduction type, and is provided with means for supplying an activating substance to the device(s). The means comprises preferably a substance source and a heater or electron beam generator for gasifying the substance source. The electron source can be combined with an image-forming member (e.g. fluorescent body) to constitute an image-forming apparatus. The means is used for in situ activation or re-activation of the electron-emitting device(s).

Abstract: The present invention includes a cathode for an electron gun having a base metal mainly composed of nickel and containing one kind of reducing element at least, a metal layer mainly composed of nickel or nickel-zirconium on the upper side of the base metal, and an electron emitting material layer containing alkaline earth metal oxide including barium at least on the upper side of the metal layer. The metal layer is formed by spreading nickel or nickel-zirconium on the base metal and heating it or by adhering nickel or nickel-zirconium powder thereon to have particle smaller than that of the base metal, to increase its life cycle under a high current density load by ensuring a diffusion route of reducing element steadily for good generation of free radical barium atom.

Abstract: A thermal field emission cathode comprising a tungsten single crystal having an axis direction of <100> and a coating layer of zirconium and oxygen formed thereon, wherein a source for supplying zirconium and oxygen contains an element capable of forming cubic or tetragonal zirconium oxide at an operation temperature of the thermal field emission cathode.

Abstract: A field emission cathode for use in flat panel displays is disclosed comprising a layer of conductive material and a layer of amorphic diamond film, functioning as a low effective work-function material, deposited over the conductive material to form emission sites. The emission sites each contain at least two sub-regions having differing electron affinities. Use of the cathode to form a computer screen is also disclosed along with the use of the cathode to form a fluorescent light source.

Abstract: A cathode-ray tube is provided with an electron gun having a cathode and a control electrode and some other electrodes. The cathode includes an electron emissive material layer for emission of electrons through a hole in the control electrode. The hole in the control electrode has a diameter substantially in a rage of from 0.3 mm to 0.4 mm. The electron emissive material layer has a first layer made of an oxide of an alkaline earth metal formed on a support and containing no oxide of a rare earth metal, and a second layer made of an oxide of an alkaline earth metal formed on the first layer and containing an oxide of a rare earth metal substantially in an amount of from 0.8 wt % to 5.0 wt %.

Abstract: An electron tube cathode comprises a base (1) formed mainly of nickel, an alloy layer (4) disposed on the base (1) and including nickel and tungsten having a grain size smaller than that of the base, and an electron emissive material layer (5) deposited on the alloy layer, and including an oxide (6) of an alkaline-earth metal containing at least barium, and a rare earth metal oxide (7) of 0.01 to 25 weight percent and containing at least one of scandium oxide and yttrium oxide. The cathode has a life characteristics improved compared with the prior art, even if operated with a current density of 3 A/cm.sup.2 or more.

Abstract: A field electron emission material comprises an electrically conductive substrate and, disposed thereon, electrically conductive particles embedded in, formed in, or coated by a layer of inorganic electrically insulating material. A first thickness material is defined between the particle and the environment in which the material is disposed. The dimension of each particle between the first and second thicknesses is significantly greater than each thickness. Upon application of a sufficient electric field, each thickness provides a conducting channel, to afford electron emission from the particles By use of an inorganic insulating material, surprisingly good stability and performance have been obtained. The particles can be relatively small, such that the electron emitting material can be applied to the substrate quite cheaply by a variety of methods, including printing. The material can be used in a variety of devices, including display and illuminating devices.

Abstract: A cathode has electropositive atoms directly bonded to a carbon-containing substrate. Preferably, the substrate comprises diamond or diamond-like (sp.sup.3) carbon, and the electropositive atoms are Cs. The cathode displays superior efficiency and durability. In one embodiment, the cathode has a negative electron affinity (NEA). The cathode can be used for field emission, thermionic emission, or photoemission. Upon exposure to air or oxygen, the cathode performance can be restored by annealing or other methods. Applications include detectors, electron multipliers, sensors, imaging systems, and displays, particularly flat panel displays.

Abstract: An electron emitter (121, 221, 321, 421) includes an electron emitter structure (118) having a passivation layer (120, 220, 320, 420) formed thereon. The passivation layer (120, 220, 320, 420) is made from an oxide selected from a group consisting of the oxides of Ba, Ca, Sr, In, Sc, Ti, Ir, Co, Sr, Y, Zr, Ru, Pd, Sn, Lu, Hf, Re, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Th, and combinations thereof. In the preferred embodiment, the electron emitter structure (118) is made from molybdenum, and the passivation layer (120, 220, 320, 420) is made from an emission-enhancing oxide having a work function that is less than the work function of the molybdenum.

Abstract: A cathode for an electron tube including a base body having nickel as a major component and including at least one kind of reducing agents, a metal member in a layer-like shape, which has as a major component a metal provided with a reducing power equivalent to or smaller than a reducing power of the at least one kind of reducing agents included in the base body and larger than a reducing power of nickel and which is formed on faces of the base body, an electron emitting substance layer formed by depositing alkaline earth metal oxides including barium on the metal member, wherein the metal member is formed on the faces of the base body such that the base body is restrained from deforming by thermal stresses of intermetallic compounds formed at portions of the base body bounded with the metal member.

Abstract: An electron-emissive film (170, 730) is made from graphite and has a surface defining a plurality of emissive clusters (100), which are uniformly distributed over the surface. Each of the emissive clusters (100) has dendrites (110) extending radially from a central point (120). Each of the dendrites (110) has a ridge (130), which has a radius of curvature of less than 10 nm. The graphene sheets (160) that form the dendrites (110) have a (002) lattice spacing within a range of 0.342-0.350 nanometers.

Abstract: Problems with a conventional cathode for electronic tubes arose because metals composing the substrate were subjected to heat deformation, resulting in a relatively lage drift of cutoff voltage. The present invention diminishes the heat deformation of the substrate to obtain a cathode with a small drift of cutoff voltage. Particularly, heat expansion coefficients can be made uniform while metals in the metal layer are prevented from diffusing into the substrate. This is done by incorporating the same metals present in the metal layer into the metals composing the substrate, thereby supressing deformation of the substrate.

Abstract: A field emission cathode is provided comprising an emissive member formed of a porous foam carbon material. The emissive member has an emissive surface defining a multiplicity of emissive edges.

Abstract: The present invention discloses a cathode for an electron gun comprising a base metal mainly composed of nickel and containing one kind of reducing element at least, a metal layer mainly composed of tungsten, tungsten-nickel, or zirconium-tungsten on the upper side of the base metal, and an electron emitting material layer containing alkaline earth metal oxide including barium at least on the upper side of the metal layer. The metal layer is formed by spreading tungsten, tungsten-nickel, or zirconium-tungsten on the base metal and heating it to have particle smaller than that of the base metal, to increase its life cycle under a high current density load by ensuring a diffusion route of reducing element steadily, used for good generation of free radical barium atom.

Abstract: The high-pressure metal halide discharge lamp comprises a quartz-glass lamp vessel (1) with an ionizable filling and two electrodes (2) which are connected to current conductors (3). The electrodes are provided with an emitter (6) which contains tungsten as a main component and at least three oxides, a first oxide which is chosen from hafnium oxide and zirconium oxide, a second oxide being lanthanum oxide, and a third oxide which is chosen from yttrium oxide.

Abstract: There is provided an impregnated-type cathode substrate comprising a large particle diameter low porosity region and a small particle diameter high porosity region which is provided in a side of an electron emission surface of the large particle diameter low porosity region and has an average particle diameter smaller than an average particle diameter of the large particle diameter low pore region and a porosity higher than a porosity of the large particle diameter low porosity region, the impregnated-type cathode being impregnated with an electron emission substance.

Abstract: A method for fabricating a field emission device (200) includes the steps of forming on the surface of a substrate (110) a cathode (112), forming on the cathode (112) a dielectric layer (114), forming an emitter well (115) in the dielectric layer (114), forming within the emitter well (115) an electron emitter structure (118) having a surface (123), forming on a portion of the dielectric layer (114) a gate electrode (116), depositing on the dielectric layer (114) a sacrificial layer (210), thereafter depositing on the surface (123) of the electron emitter structure (118) a coating material (220, 320, 420) that has an emission-enhancing material, and then removing the sacrificial layer (210).

Abstract: A rare earth hexaboride electron-emitting material of the formula ReB.sub.6+x, wherein Re is La, Ce or (La+Ce), and 0.05.ltoreq.x.ltoreq.0.20.

Abstract: A low power impregnated cathode consisting of a pallet, a cup, an inner sleeve, a cap, and an outer sleeve, is characterized in that the diameter of the pellet is less than at least one and half times of the thickness of the pellet, and is characterized in that an outer diameter of the bottom part of the outer sleeve is larger than an outer diameter of the top part thereof.

Abstract: An electron emission device can be driven with a low voltage and has an excellent mass production capability. A display device, such as a color flat panel or the like, which uses such electron emission devices has an excellent display quality. The electron emission device includes a first electrode, on which a plurality of fine particles of an electron emission body obtained by terminating carbon bodies formed on metal fine particles, serving as nuclei, with a low-work-function material via oxygen are partially arranged, on a first substrate, and a second electrode where a voltage for drawing electrons from the electron emission body into a vacuum is applied. A metal of the metal fine particles is a catalytic metal. The catalytic metal is an iron-family element, such as Ni, Co, Fe or the like, or a platinum-family element, such as Pd, Ir or Pt. The carbon bodies are made of graphite. The low-work-function material is an alkaline metal or an alkaline earth metal.

Abstract: An electron emission device exhibits a high electron emission efficiency. The device includes an electron supply layer of metal or semiconductor, an SiO.sub.2 insulator layer formed on the electron supply layer, and a thin-film metal electrode formed on the insulator layer. The peak intensity ratio of a Raman spectrum for 3-fold rings of SiO.sub.2 of the insulator layer to 4-fold rings or 5 or more-fold rings thereof is equal to or greater than 20%. When an electric field is applied between the electron supply layer and the thin-film metal electrode, the electron emission device emits electrons.

Abstract: A ceramic cathode fluorescent discharge lamp is provided including a pair of electrodes, a bulb plated with a fluorescent body on an inner surface of same, at least one of said pair of electrodes being a ceramic cathode having a bottomed cylindrical housing including an electron emission material of an aggregate type porous structure of conductive oxide having a first component consisting of at least one of Ba, Sr, and Ca, a second component consisting of at least one of Zr and Ti, and a third component consisting of at least one of Ta and Nb, said aggregate type porous structure having a surface plated with a conductive or semiconductive layer of at least one of carbide, nitride and oxide of Ta or Nb, rare gas being sealed in said bulb, and sealing pressure of said rare gas being in the range between 10 Torr and 170 Torr.

Abstract: Novel emitter materials, electrode assemblies amd lamps comprisinfg the same are provided in which, in accordance with the invention, novel electrodes are provided having a lamp electrode structure, preferably including a hollow ferrule for sealing in a lamp to permit evacuation; an emitter material of the invention on at least one surface thereof, preferably on a protrusion attached to the hollow ferrule; a thermal isolator, preferably in the form of a low thermal conductivity wire or an incised or cut-out portion of the hollow ferrule body, for thermally isolating the protrusion from the ferrule to maintain a sufficiently high temperature for thermionic emission, and further comprising an emitter material requiring no in-lamp processing. The emitter materials are a mixed oxide of Ba, Sr and mixtures thereof with one or more of the metals from the series comprising Ta, Ti, Zr, Sc, Y, and La, are preferably selected from the group consisting of Ba.sub.4 Ta.sub.2 O.sub.9, Ba.sub.5 Ta.sub.4 O.sub.15, BaY.sub.

Abstract: A cathode for an electron tube includes a layer of a electron emitting substance containing alkaline earth metal oxides containing 0.01--20.0 wt % of both a lanthanum compound and a magnesium compound or a lanthanum-magnesium compound disposed on a base metal including nickel as a major component and tungsten as a minor component. The tungsten prevents embrittlement and ensures a continuing supply of fill barium in the electron-emitting substance. The cathode enjoys full interchangeability with the conventional oxide cathode and a 15-30% longer life span.

Abstract: A cathode for an electron tube, includes a base metal having nickel as a main component, and an electron emitting material layer containing an alkaline earth metal oxide having barium oxide as a main component, wherein a metal layer having zirconium as a main component is located between the base metal and the electron emitting material layer. The cathode has an excellent initial electron emitting characteristic and can emit a large quantity of electrons for a long time. Therefore, the cathode is suitable for a larger and higher-definition CRT.

Abstract: The present invention provides for a field emission device including an anode assembly and a cathode assembly, wherein the cathode assembly further includes a substrate, a plurality of electrically conducting strips deposited on the substrate, and a continuous layer of diamond material deposited over the plurality of electrically conducting strips and portions of the substrate exposed between the plurality of electrically conducting strips. The field emission device may further include a grid assembly including a perforated silicon substrate, a first dielectric layer deposited on the silicon substrate, and a first conducting layer deposited on the first dielectric layer, wherein the first dielectric layer and the first conducting layer have perforations coinciding with perforations of the silicon substrate.

Abstract: There is disclosed a long-lived thermal field emission electron gun for use in a scanning electron microscope. The gun has a tungsten tip. The surface of this tip is coated with zirconium, zirconium oxide, titanium or titanium oxide. A wire member is mounted above the front end of the tungsten tip to prevent the coating of zirconium or other material from slipping off.

Abstract: A low pressure discharge lamp in which, even during uninterrupted operation, a low lamp voltage characteristic is maintained over a long time interval and in which high radiant efficiency can be obtained over a long time is achieved via a low pressure discharge lamp which has a tubular glass bulb in which a pair of electrodes are located opposite one another, by an electron emission material which contains lithium being included on or in the electrode substrate. Advantageously, the electron emission material contains at least one of the following materials: metallic lithium, an alloy of lithium and another metal, an oxide of lithium, a mixture of an oxide of lithium with another metal oxide, and an oxide which contains lithium and another metal element and which is a compound identified by the formula Li--M--O.sub.x where M designates at least one element selected from among the alkali earth metals, rare earth metals and transition metal, and x is the number of oxygen atoms required for valency equalization.

Abstract: A cathode ray tube is provided with an electron gun which comprises a cathode structure which contains an electron-emitting material at an end portion and in which a heating element of bifilarly wound wire is accommodated. Except in the vicinity of the ends of the wire, said wire is provided with an electrically insulating layer (46) whose radius decreases, near the transition between the covered wire and the uncovered ends, by at least 15%, preferably at least 30%. Preferably, the layer (46) having the reduced radius continues for at least 100 .mu.m in the direction of the transition (54). The distance between the transition (54) and the electric connection (61) is smaller than 250 .mu.m, preferably smaller than 150 .mu.m. As a result, the number of uncovered turns between the electric connection (61) and the transition (54) is reduced to below five.

Abstract: A cathode for an electron tube formed by coating the base of the cathode for the electron tube with an alkaline-earth metal carbonate containing at least barium as the alkaline-earth metal, and thermally decomposing in a vacuum to generate an emitter mainly comprising an alkaline-earth metal oxide, wherein a mixture of two or more kinds of alkaline-earth metal carbonate crystalline particles having different shapes is used as the above mentioned alkaline-earth metal carbonate. Since the present invention can provide a cathode for electron tube having improved both cut-off drift and emission characteristic at the same time, it is useful as a cathode for the electron gun of a CRT, or a cathode for the electron gun of an electron microscope.

Abstract: 0504221609 Nanometer-scale field emitter tips are fabricated on a single crystal silicon substrate and an optically active semiconductive material is deposited on the tip. A bias voltage is connected between the semiconductor and the substrate to cause the optically active material to emit light.

Abstract: An electron emitter formed with a layer of diamond-like carbon having a diamond bond structure with an electrically active defect at an emission site. The electrically active defect acts like a very thin electron emitter with a very low work function and improved current characteristics, including in improved saturation current.

Abstract: A PALC display panel has a cathode including a conductive core, a protective coating of a material that is electrically conductive and is non-reactive with hydrogen, and an outer coating of refractory material, and an anode having a surface of a material that is electrically conductive and is non-reactive with hydrogen.

Abstract: An electron emitting device includes a pair of device electrodes disposed at locations opposite to each other, a conductive thin film in contact with both the pair of device electrodes, and an electron emitting region formed in a part of the conductive thin film. The conductive thin film is composed of fine particles including a first metal element serving as a main constituent element and at least one second metal element. The second metal element is to precipitate at the surface of the conductive thin film and thus form a low work function material layer. When a voltage is applied between the pair of device electrodes, the second metal element moves from the inside of the conductive thin film to at least a part of the surface of the conductive thin film.

Abstract: The present invention relates to an electron gun having a grid and a cathode with the cathode having an emissive part (12) which defines a central hole (11) in order to reduce spurious electron emissions from the grid to enhance cooling.

Abstract: A cathode for an electron tube is described that has little deterioration of emission current after long operation, is used as a long-life oxide cathode even with high current density in a CRT, and is economical. An emissive material is adhered onto a substrate that is positioned at one opening of a cylindrical sleeve having a built-in heater coil and that includes nickel as a main component by thermally decomposing carbonate including an alkaline earth metal oxide and at least one element selected from the group consisting of titanium, nickel, zirconium, vanadium, niobium and tantalum.

Abstract: A cold cathode electron emission structure includes an amorphous carbon matrix having cesium dispersed therein, with the cesium present in substantially non-crystalline form. A cesium-carbon-oxide layer is positioned on the amorphous carbon matrix, constitutes an electron emission surface and causes the cold cathode electron emission structure to exhibit a lowered surface work function. A display structure including the aforedescribed cold cathode electron emission structure further includes a target electrode including a phosphor and exhibiting a target potential for attraction of electrons. A gate electrode is positioned between the electron emission structure and the target electrode and is biased at a gate potential which attracts electrons, but which is insufficient, in combination with the target potential, to cause emission of a beam of electrons from the electron emission structure.

Abstract: A cold-cathode discharge device for emitting light. The device has a fluorescent tube and electrodes containing R.sub.2 O.sub.3-z (where R is an atom or an atom group of rare earth elements, O is oxygen, and z is 0.0 to 1.0). The electrodes are made by oxidation of the rare earth elements under an atmosphere in which oxygen and/or oxygen-containing substance is 1% or less by volume, in order to control the stoichiometry of the oxide.

Abstract: An indirect cathode sleeve and manufacturing method thereof capable of substantially reducing electric power consumption of a heater disposed inside the cathode sleeve and simultaneously reducing a picture-producing time by oxidizing an inside surface of the cathode sleeve and reducing an outside surface thereof. The cathode sleeve includes a heater disposed inside the cathode sleeve; a base metal formed at the top of the cathode sleeve; an electron-emitting material layer formed at the outside surface of the base metal; and an indirect cathode sleeve including a black inside surface and a white outside surface.

Abstract: In an electron gun for a color cathode ray tube including a cathode structure having three electrodes, a control electrode and a screen electrode, and a plurality of focus electrodes and last accelerating electrodes for forming electron lenses, the cathode structure includes a rimmed electrode member, an insulating member inserted into the electrode member and having an indentation formed on the upper surface thereof, a field emission array cell having a base member which is inserted into the indentation, and a plurality of supporting members installed at the insulating member for pressing down on the upper surface of the edge of the field emission array cell which is inserted into the indentation toward the upper surface of the insulating member. Thus, the strength of attachment between the insulating member and a field emission device is improved.

Abstract: The present invention is directed to a conductor/electrode for a faceplate anode of a field emission display wherein said conductor/electrode is comprised of tin oxide. Alternatively, the present invention is directed to a transparent conductor/electrode for a faceplate anode of a field emission display wherein said conductor/electrode is comprised of from about 90% to about 99% tin oxide and from about 1% to about 10% antimony.

Abstract: A method of fabricating a cathode member or pellet is provided, which realizes the sufficiently large increase of the electron emission capability by the current activation process and that prevents the maximum cathode current from being lowered as long as an electron emissive agent exists in the cathode member. First, (a) a nickel powder and a rare-earth-metal oxide powder are provided. (b) The nickel powder and the rare-earth-metal oxide powder are uniformly mixed together, thereby producing a first powder mixture. (c) The first powder mixture is heated in a hydrogen atmosphere, an inert atmosphere, or a vacuum atmosphere, thereby producing an intermetallic compound of nickel and the rare-earth metal in the first powder mixture. (d) The first powder mixture containing the intermetallic compound is uniformly mixed with an electron-emissive agent powder, thereby producing a second powder mixture. (e) The second powder mixture is sintered by a HIP process, thereby forming a cathode member.

Abstract: An electrode structure for use in a sealed arc lamp is described. The electrode structure includes a tungsten containing rod surrounded by a block of sintered tungsten containing powder. The block may be impregnated with a thermally conductive material such as copper, silver or braze, and may have a high thermal emissivity surface.

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.

Abstract: A field emitter element comprising a bottom layer of material shaping the overall emitter element, and a top layer of low work function material or otherwise of high electron emissivity characteristic. The low work function top layer preferably is shaped to a sharp point. The bottom layer may be formed of a material such as tantalum, molybdenum, gold, or silicon (or alloys thereof), and the top layer may be formed of a material such as Cr.sub.3 Si, Cr.sub.3 Si.sub.2, CrSI.sub.2, Nb.sub.3 Si.sub.2, Nb, Cr.sub.2 O.sub.3 or SiC. In a specific aspect, at least one of the first and second emitter materials is chromium oxide (Cr.sub.2 O.sub.3). In another variant, the first emitter material is an insulator of leaky dielectric, e.g., SiO with a 10-60% Cr by weight based on the weight of SiO, and the second emitter material is SiO+50-90% Cr by weight, based on the weight of SiO.

Abstract: A cathode structure and an electron gun for a CRT adopting the same are provided. The cathode structure has an external case, an insulating member filled in the external case, a plurality of pins fixedly inserted into the insulating member and of which end portions extend from the upper surface of the insulating member, a field emission device (FED) unit attached on the insulating member, and a wire for electrically connecting the FED unit to the end portions of the pins. Electrons are emitted by a field effect rather than by thermal electron emission.

Abstract: An electric discharge tube or discharge lamp, in particular a flat-panel display screen, includes one or more low-temperature cathodes having a holder, which, optionally, is provided with a heating or cooling element, a conductive bottom layer which is applied to the holder, optionally a substrate with dispenser material, and a top coating of ultrafine particles having a nanostructure. The top coating has a surface layer consisting of an emitter complex formed from an emission material comprising several components. The cathodes have a high reliability and a long service life under a normal working load. The emission is stable, which contributes to a constant picture quality throughout the life of the discharge lamp or discharge tube. The discharge tubes or discharge lamps in accordance with the invention have short switching times and the advantage that their construction has been simplified and that their energy consumption is low.

Abstract: A directly heated cathode structure includes a porous pellet impregnated with a thermionic emission material, a supporter for applying electrical power, and a filament fixed to the porous pellet, having an end, and fixed to the supporter, wherein the filament includes a connecting portion wider than the filament and fixed to the supporter at the end of the filament. The cathode structure is suitable for a color CRT such as a color television or a CRT for industrial use and having a large screen.

Abstract: A low-pressure discharge lamp of the invention is provided with a gas-tight discharge vessel (10) which contains an ionizable filling. Electrodes are arranged inside At least one of the electrodes has a tungsten coil (20.sub.A) which is electrically connected to current supply conductors (30.sub.A, 30.sub.A ') which extend to outside the discharge vessel (10). The coil (20.sub.A) has a central zone (21.sub.A) covered with an electron-emitting material (22.sub.A) and, on either side, boundary zones (23.sub.A, 23.sub.A ') between the central zone (21.sub.A) and respective current supply conductors (30.sub.A, 30.sub.A '). The boundary zones (23.sub.A, 23.sub.A ') having a covering (24.sub.A, 24.sub.A ') of a protective material, comprising a ceramic material having a specific resistance less than 1000 .mu..OMEGA..cm.

Abstract: A cathode includes a hairpin type filament made of a refractory metal such as W, Mo or Re; a single crystal needle, made of a refractory metal such as W, Mo or Re joined to the filament; and a reservoir formed by applying a slurry of a powder of a metal or metal compound and an organic solvent containing nitrocellulose in the vicinity of a junction between the single crystal needle and the filament. The powder for a reservoir is made of a metal lower than the single crystal needle in a work function or electron affinity, such as Ti, Zr, Hf, Y, Th, Sc or Se, or a compound thereof.