Gas Discharge Dielectric Containing a Source of Boron, Gallium, Indium, or Thallium

This invention relates to novel multiple gas discharge display/memory panels or units which have an electrical memory and which are capable of producing a visual display or representation of data such as numerals, letters, television display, radar displays, binary words, etc.

Multiple gas discharge and/or memory panels of one particular type with which the present invention is concerned are characterized by an ionizable gaseous medium, usually a mixture of at least two gases at an appropriate gas pressure, in a thin gas chamber or space between a pair of opposed dielectric charge storage members which are backed by conductor (electrode) members, the conductor members backing each dielectric member typically being transversely oriented to define a plurality of discrete gas discharge units or cells. In some prior art panels the discharge units are additionally defined by surrounding or confining physical structure such as by cells or apertures in perforated glass plates and the like so as to be physically isolated relative to other units. In either case, with or without the confining physical structure, charges (electrons, ions) produced upon ionization of the elemental gas volume of a selected discharge unit, when proper alternating operating potentials are applied to selected conductors thereof, are collected upon the surfaces of the dielectric at specifically defined locations and constitute an electrical field opposing the electrical field which created them so as to terminate the discharge for the remainder of the half cycle and aid in the initiation of a discharge on a succeeding opposite half cycle of applied voltage, such charges as are stored constituting an electrical memory.

Thus, the dielectric layers prevent the passage of substantial conductive current from the conductor members to the gaseous medium and also serve as collecting surfaces for ionized gaseous medium charges (electrons, ions) during the alternate half cycles of the A.C. operating potentials, such charges collecting first on one elemental or discrete dielectric surface area and then on an opposing elemental or discrete dielectric surface area on alternate half cycles to constitute an electrical memory.

An example of a panel structure containing non-physically isolated or open discharge units is disclosed in U.S. Pat. No. 3,499,167 issued to Theodore C. Baker, et al.

An example of a panel containing physically isolated units is disclosed in the article by D. L. Bitzer and H. G. Slottow entitled "The Plasma Display Panel - A Digitally Addressable Display With Inherent Memory," Proceeding of the Fall Joint Computer Conference, IEEE, San Francisco, California, Nov. 1966, pages 541-547. Also reference is made to U.S. Pat. No. 3,559,190.

In the construction of the panel, a continuous volume of ionizable gas is confined between a pair of dielectric surfaces backed by conductor arrays forming matrix elements. The cross conductor arrays may be orthogonally related (but any other configuration of conductor arrays may be used) to define a plurality of opposed pairs of charge storage areas on the surfaces of the dielectric bounding or confining the gas. Thus, for a conductor matrix having H rows and C columns the number of elemental discharge units will be the product H .times. C and the number of elemental or discrete areas will be twice the number of such elemental discharge units.

In addition, the panel may comprise a so-called monolithic structure in which the conductor arrays are created on a single substrate and wherein two or more arrays are separated from each other and from the gaseous medium by at least one insulating member. In such a device the gas discharge takes place not between two opposing electrodes, but between two contiguous or adjacent electrodes on the same substrate; the gas being confined between the substrate and an outer retaining wall.

It is also feasible to have a gas discharge device wherein some of the conductive or electrode members are in direct contact with the gaseous medium and the remaining electrode members are appropriately insulated from such gas.

In addition to the matrix configuration, the conductor arrays may be shaped otherwise. Accordingly, while the preferred conductor arrangement is of the crossed grid type as shown herein, it is likewise apparent that where a maximal variety of two dimensional display patterns is not necessary, as where specific standardized visual shapes (e.g., numerals, letters, words, etc.) are to be formed and image resolution is not critical, the conductors may be shaped accordingly, i.e. a segmented display.

The gas is one which produces visible light or invisible radiation which stimulates a phosphor (if visual display is an objective) and a copious supply of charges (ions and electrons) during discharge. In an open cell Baker, et al. type panel, the gas pressure and the electric field are sufficient to laterally confine charges generated on discharge within elemental or discrete dielectric areas within the perimeter of such areas, especially in a panel containing non-isolated units.

In prior art, a wide variety of gases and gas mixtures have been utilized as the gaseous medium in a gas discharge device. Typical of such gases include CO; CO.sub.2 ; halogens, nitrogen; NH.sub.3 ; oxygen; water vapor; hydrogen; hydrocarbons; P.sub.2 O.sub.5 ; boron fluoride; acid fumes; TiCl.sub.4 ; Group VIII gases; air; H.sub.2 O.sub.2 ; vapors of sodium, mercury, thallium, cadmium, rubidium, and cesium; carbon disulfide; laughing gas; H.sub.2 S; deoxygenated air; phosphorus vapors; C.sub.2 H.sub.2 ; CH.sub.4 ; naphthalene vapor; anthracene; freon; ethyl alcohol; methylene bromide; heavy hydrogen; electron attaching gases; sulfur hexafluoride; tritium; radioactive gases; and the rare or inert gases.

In one preferred embodiment there is used a gas mixture comprising at least one rare gas, more preferably at least two, selected from neon, argon, xenon, and krypton. Beneficial amounts of mercury and/or helium may be present.

As described in the Baker, et al. patent, the space between the dielectric surfaces occupied by the gas is such as to permit photons generated on discharge in a selected discrete or elemental volume of gas to pass freely through the gas space and strike surface areas of dielectric remote from the selected discrete volumes, such remote, photon struck dielectric surface areas thereby emitting electrons so as to condition at least one elemental volume other than the elemental volume in which the photons originated.

With respect to the memory function of a given discharge panel, the allowable distance or spacing between the dielectric surfaces depends, inter alia, on the frequency of the alternating current supply, the distance typically being greater for lower frequencies.

While the prior art does disclose gaseous discharge devices having externally positioned electrodes for initiating a gaseous discharge, sometimes called "electrodeless discharge," such prior art devices utilized frequencies and spacings or discharge volumes and operating pressures such that although discharges are initiated in the gaseous medium, such discharges are ineffective or not utilized for charge generation and storage at higher frequencies; although charge storage may be realized at lower frequencies, such charge storage has not been utilized in a display/memory device in the manner of the Bitzer-Slottow or Baker, et al. invention.

The term "memory margin" is defined as

where V.sub.f is the half amplitude of the smallest sustaining voltage signal which results in a discharge every half cycle, but at which the cell is not Bi-stable and V.sub.E is the half amplitude of the minimum applied voltage sufficient to sustain discharges once initiated.

It will be understood that basic electrical phenomenon utilized in this invention is the generation of charges (ions and electrons) alternately storable at pairs of opposed or facing discrete points or areas on a pair of dielectric surfaces backed by conductors connected to a source of operating potential. Such stored charges result in an electrical field opposing the field produced by the applied potential that created them and hence operate to terminate ionization in the elemental gas volume between opposed or facing discrete points or areas of dielectric surface. The term "sustain a discharge" means producing a sequence of momentary discharges, one discharge for each half cycle of applied alternating sustaining voltage, once the elemental gas volume has been fired, to maintain alternate storing of charges at pairs of opposed discrete areas on the dielectric surfaces.

The features and advantages of the invention will be better understood by reference to the following detailed description when considered in connection with the accompanying drawings. FIGS. 1-4 and the description of these figures are from the above mentioned Baker et al U.S. Pat. No. 3,499,167.

FIG. 1 is a partially cut-away plan view of a gaseous display/memory panel as connected to a diagrammatically illustrated source of operating potentials,

FIG. 2 is a cross-sectional view (enlarged, but not to proportional scale since the thickness of the gas volume, dielectric members and conductor arrays have been enlarged for purposes of illustration) taken on the lines 2--2 of FIG. 1,

FIG. 3 is an explanatory partial cross-sectional view simlar to FIG. 1 (enlarged, but not to proportional scale),

FIG. 4 is an isometric view of a larger gaseous discharge display/memory panel, and

FIGS. 5, 6, 7, 8, 9 and 10 are explanatory partial cross-sectional views similar to FIG. 3 showing different embodiments of the present invention.

The invention utilizes a pair of dielectric films or coatings 10 and 11 separated by a thin layer or volume of a gaseous discharge medium 12, said medium 12 producing a copious supply of charges (ions and electrons) which are alternately collectable on the surfaces of the dielectric members at opposed or facing elemental or discrete areas X and Y defined by the conductor matrix on nongas-contacting sides of the dielectric members, each dielectric member presenting large open surface areas and a plurality of pairs of elemental X and Y areas. While the electrically operative structural members such as the dielectric members 10 and 11 and conductor matrixes 13 and 14 are all relatively thin (being exaggerated in thickness in the drawings) they are formed on and supported by rigid nonconductive support members 16 and 17 respectively.

Preferably, one or both of nonconductive support members 16 and 17 pass light produced by discharge in the elemental gas volumes. Preferably, they are transparent glass members and these members essentially define the overall thickness and strength of the panel. For example, the thickness of gas layer 12 as determined by spacer 15 is under 10 mils and preferably about 5 to 6 mils, dielectric layers 10 and 11 (over the conductors at the elemental or discrete X and Y areas) is between 1 and 2 mils thick, and conductors 13 and 14 about 8,000 angstroms thick (tin oxide). However, support members 16 and 17 are much thicker (particularly larger panels) so as to provide as much ruggedness as may be desired to compensate for stresses in the panel. Support members 16 and 17 also serve as heat sinks for heat generated by discharges and thus minimize the effect of temperature on operation of the device. If it is desired that only the memory function be utilized, then none of the members need be transparent to light although for purposes described later herein it is preferred that one of the support members and members formed thereon be transparent to or pass ultraviolet radiation.

Except for being nonconductive or good insulators the electrical properties of support members 16 and 17 are not critical. The main function of support members 16' and 17 is to provide mechanical support and strength for the entire panel, particularly with respect to pressure differential acting on the panel and thermal shock. As noted earlier, they should have thermal expansion characteristics substantially matching the thermal expansion characteristics of dielectric layers 10 and 11. Ordinary 1/4 inch commercial grade soda lime plate glasses have been used for this purpose. Other glasses such as low expansion glasses or transparent devitrified glasses can be used provided they can withstand processing and have expansion characteristics substantially matching expansion characteristics of the dielectric coatings 10 and 11. For given pressure differentials and thickness of plates the stress and deflection of plates may be determined by following standard stress and strain formulas (see R. J. Roark, Formulas for Stress and Strain, McGraw-Hill, 1954).

Spacer 15 may be made of the same glass material as dielectric films 10 and 11 and may be an integral rib formed on one of the dielectric members and fused to the other members to form a bakeable hermetic seal enclosing and confining the ionizable gas volume 12. However, a separate final hermetic seal may be effected by a high-strength devitrified glass sealant 15S. Tubulation 18 is provided for exhausting the space between dielectric members 10 and 11 and filling that space with the volume of ionizable gas. For large panels small bead-like solder glass spacers such as shown at 15B may be located between conductors intersections and fused to dielectric members 10 and 11 to aid in withstanding stress on the panel and maintain uniformity of thickness of gas volume 12.

Conductor arrays 13 and 14 may be formed on support members 16 and 17 by a number of well known processes, such as photoetching, vacuum deposition, stencil screening, etc. In the panel shown in FIG. 4, the center spacing of conductors in the respective arrays is about 30 mils. Transparent or semitransparent conductive material such as tin oxide, gold or aluminum can be used to form the conductor arrays and should have a resistance less than 3000 ohms per line. It is important to select a conductor material that is not attacked during processing by the dielectric material.

It will be appreciated that conductor arrays 13 and 14 may be wires or filaments of copper, gold, silver or aluminum or any other conductive metal or material. For example, 1 mil wire filaments are commercially available and may be used in the invention. However, formed in situ conductor arrays are preferred since they may be more easily and uniformly placed on and adhered to the support plates 16 and 17.

Dielectric layer members 10 and 11 are formed of an inorganic material and are preferably formed in situ as an adherent film or coating which is not chemically or physically effected during bake-out of the panel. One such material is a solder glass such as Kimble SG-68 manufactured by and commercially available from the assignee of the present invention.

This glass has thermal expansion characteristics substantially matching the thermal expansion characteristics of certain soda-lime glasses, and can be used as the dielectric layer when the support members 16 and 17 are soda-lime glass plates. Dielectric layers 10 and 11 must be smooth and have a dielectric strength of about 1000 v. and be electrically homogeneous on a microscopic scale (e.g., no cracks, bubbles, crystals, dirt, surface films, etc). In addition, the surfaces of dielectric layers 10 and 11 should be good photoemitters of electrons in a baked out condition. However, a supply of free electrons for conditioning gas 12 for the ionization process may be provided by inclusion of a radioactive material within the glass or gas space. A preferred range of thickness of dielectric layers 10 and 11 overlying the conductor arrays 13 and 14 is between 1 and 2 mils. Of course, for an optical display at least one of dielectric layers 10 and 11 should pass light generated on discharge and be transparent or translucent and, preferably, both layers are optically transparent.

The preferred spacing between surfaces of the dielectric films is about 5 to 6 mils with conductor arrays 13 and 14 having center-to-center spacing of about 30 mils.

The ends of conductors 14-1 . . . 14-4 and support member 17 extend beyond the enclosed gas volume 12 and are exposed for the purpose of making electrical connection to interface and addressing circuitry 19. Likewise, the ends of conductors 13-1 . . . 13-4 on support member 16 extend beyond the enclosed gas volume 12 and are exposed for the purpose of making electrical connection to interface and addressing circuitry 19.

As in known display systems, the interface and addressing circuitry or system 19 may be relatively inexpensive line scan systems or the somewhat more expensive high speed random access systems. However, it is to be noted that a lower amplitude of operating potentials helps to reduce problems associated with the interface circuitry between the addressing system and the display/memory panel per se. Thus, by providing a panel having greater uniformity in the discharge characteristics throughout the panel, tolerances and operating characteristics of the panel with which the interfacing circuitry cooperate, are made less rigid.

One mode of initiating operation of the panel will be described with reference to FIG. 3, which illustrates the condition of one elemental gas volume 30 having an elemental cross-sectional area and volume which is quite small relative to the entire volume and cross-sectional area of gas 12. The cross-sectional area of volume 30 is defined by the overlapping common elemental areas of the conductor arrays and the volume is equal to the product of the distance between the dielectric surfaces and the elemental area. It is apparent that if the conductor arrays are uniform and linear and are orthogonally (at right angles to each other) related each of elemental areas X and Y will be squares and if conductors of one conductor array are wider than conductors of the other conductor array, said areas will be rectangles. If the conductor arrays are at transverse angles relative to each other, other than 90.degree., the areas will be diamond shaped so that the cross-sectional shape of each volume is determined solely in the first instance by the shape of the common area of overlap between conductors in the conductor arrays 13 and 14. The dotted lines 30 are imaginary lines to show a boundary of one elemental volume about the center of which each elemental discharge takes place. As described earlier herein, it is known that the cross-sectional area of the discharge in a gas is affected by, inter alia, the pressure of the gas, such that, if desired, the discharge may even be constricted to within an area smaller than the area of conductor overlap. By utilization of this phenomena, the light production may be confined or resolved substantially to the area of the elemental cross-sectional area defined by conductor overlap. Moreover, by operating at such pressure charges (ions and electrons) produced on discharge are laterally confined so as to not materially affect operation of adjacent elemental discharge volumes.

In the instant shown in FIG. 3, a conditioning discharge about the center of elemental volume 30 has been initiated by application to conductor 13-1 and conductor 14-1 firing potential V.sub.x ' as derived from a source 35 of variable phase, for example, and source 36 of sustaining potential V.sub.s (which may be a sine wave, for example). The potential V.sub.x ' is added to the sustaining potential V.sub.s as sustaining potential V.sub.s increases in magnitude to initiate the conditioning discharge about the center of elemental volume 30 shown in FIG. 3. There, the phase of the source 35 of potential V.sub.x ' has been adjusted into adding relation to the alternating voltage from the source 36 of sustaining voltage V.sub.s to provide a voltage V.sub.f ', when switch 33 has been closed, to conductors 13-1 and 14-1 defining elementary gas volume 30 sufficient (in time and/or magnitude) to produce a light generating discharge centered about discrete elemental gas volume 30. At the instant shown, since conductor 13-1 is positive, electrons 32 have collected on and are moving to an elemental area of dielectric member 10 substantially corresponding to the area of elemental gas volume 30 and the less mobile positive ions 31 are beginning to collect on the opposed elemental area of dielectric member 11 since it is negative. As these charges build up, they constitute a back voltage opposed to the voltage applied to conductors 13-1 and 14-1 and serve to terminate the discharge in elemental gas volume 30 for the remainder of a half cycle.

During the discharge about the center of elemental gas volume 30, photons are produced which are free to move or pass through gas medium 12, as indicated by arrows 37, to strike or impact remote surface areas of photoemissive dielectric members 10 and 11, causing such remote areas to release electrons 38. Electrons 38 are, in effect, free electrons in gas medium 12 and condition each other discrete elemental gas volume for operation at a lower firing potential V.sub.f which is lower in magnitude than the firing potential V.sub.f ' for the initial discharge about the center of elemental volume 30 and this voltage is substantially uniform for each other elemental gas volume.

Thus, elimination of physical obstructions or barriers between discrete elemental volumes, permits photons to travel via the space occupied by the gas medium 12 to impact remote surface areas of dielectric members 10 and 11 and provides a mechanism for supplying free electrons to all elemental gas volumes, thereby conditioning all discrete elemental gas volumes for subsequent discharges, respectively, at a uniform lower applied potential. While in FIG. 3, a single elemental volume 30 is shown, it will be appreciated that an entire row (or column) of elemental gas volumes may be maintained in a "fired" condition during normal operation of the device with the light produced thereby being masked or blocked off from the normal viewing area and not used for display purposes. It can be expected that in some applications there will always be at least one elemental volume in a "fired" condition and producing light in a panel, and in such application it is not necessary to provide separate discharge of generation of photons for purposes described earlier.

However, as described earlier, the entire gas volume can be conditioned for operation at uniform firing potentials by use of external or internal radiation so that there will be no need for a separate source of higher potential for initiating an initial discharge. Thus, by radiating the panel with ultraviolet radiation or by inclusion of a radioactive material within the glass materials or gas space, all discharge volumes can be operated at uniform potentials from addressing and interface circuit 19.

Since each discharge is terminated upon a build up or storage of charges at opposed pairs of elemental areas, the light produced is likewise terminated. In fact, light production lasts for only a small fraction of a half cycle of applied alternating potential and depending on design parameters, is in the nanosecond range.

After the initial firing or discharge of discrete elemental gas volume 30 by a firing potential V.sub.f ', switch 33 may be opened so that only the sustaining voltage V.sub.s from source 36 is applied to conductors 13-1 and 14-1. Due to the storage of charges (e.g., the memory) at the opposed elemental areas X and Y, the elemental gas volume 30 will discharge again at or near the peak of negative half cycles of sustaining voltage V.sub.s to again produce a momentary pulse of light. At this time, due to reversal of field direction, electrons 32 will collect on and be stored on elemental surface area Y of dielectric member 11 and positive ions 31 will collect and be stored on elemental surface area X of dielectric member 10. After a few cycles of sustaining voltage V.sub.s, the times of discharges become symmetrically located with respect to the wave form of sustaining voltage V.sub.s. At remote elemental volumes, as for example, the elemental volumes defined by conductor 14-1 with conductors 13-2 and 13-3, a uniform magnitude or potential V.sub.x from source 60 is selectively added by one or both of switches 34-2 or 34-3 to the sustaining voltage V.sub.s, shown as 36' to fire one or both of these elemental discharge volumes. Due to the presence of free electrons produced as a result of the discharge centered about elemental volume 30, each of these remote discrete elemental volumes have been conditioned for operation at uniform firing potential V.sub.f.

In order to turn "off" an elemental gas volume (i.e. terminate a sequence of discharge representing the "on" state), the sustaining voltage may be removed. However, since this would also turn "off" other elemental volumes along a row or column, it is preferred that the volumes be selectively turned "off" by application to selected "on" elemental volumes a voltage which can neutralize the charges stored at the pairs of opposed elemental areas.

This can be accomplished in a number of ways, as for example, varying the phase or time position of the potential from source 60 to where that voltage combined with the potential form source 36' falls substantially below the sustaining voltage.

It is apparent that the plates 16-17 need not be flat but may be curved, curvature of facing surfaces of each plate being complementary to each other. While the preferred conductor arrangement is of the crossed grid type as shown herein, it is likewise apparent that where an infinite variety of two dimensional display patterns are not necessary, as where specific standardized visual shapes (e.g. numerals, letters, words, etc.) are to be formed and image resolution is not critical, the conductors may be shaped accordingly.

The device shown in FIG. 4 is a panel having a large number of elemental volumes similar to elemental volume 30 (FIG. 3). In this case more room is provided to make electrical connection to the conductor arrays 13' and 14', respectively, by extending the surfaces of support members 16' and 17' beyond seal 15S', alternate conductors being extended on alternate sides. Conductor arrays 13' and 14' as well as support members 16' and 17' are transparent. The dielectric coatings are not shown in FIG. 4 but are likewise transparent so that the panel may be viewed from either side.

In accordance with the practice of this invention, there is incorporated into the dielectric of a gas discharge device a beneficial amount of a source of at least one element selected from boron, gallium, indium, or thallium.

As used herein, the phrase "incorporated into" is intended to comprise any suitable means whereby a source of the selected element is appropriately combined with the dielectric, such as by intimately adding or mixing the source into the dielectric pre-melt batch or to the melt; by ion exchange; by ion implantation; by diffusion techniques. FIG. 5 is a cross-sectional view of a panel wherein the members 110, 111 consist of a mixture of at least one selected element and the dielectric. "Incorporated into" is also intended to comprise the application of one or more layers 210a, 211a to the charge storage surface of the dielectric 210, 211 as shown in FIG. 6, or one or more layers 410, 411a to the electrode contact surface of the dielectric 410, 411 as shown in FIG. 8, or as an internal layer 510a, 511a within the dielectric layers 510, 510b and 511, 511b as shown in FIG. 9.

In one particular embodiment hereof, the source of the selected element is applied as one or more layers to the charge-storage surface of the dielectric.

As used herein, the term "layer" is intended to be all inclusive of other similar terms such as film, deposit, coating, finish, spread, covering, etc.

It is contemplated in such embodiment that the element source may be applied as a layer over previously applied dielectric layers. Likewise, layers 510c, 511c of other substances may be applied over the layer 510a, 511a of the element source as shown in FIG. 10. Such other dielectric layers may comprise phosphors and/or any other suitable compounds, especially inorganic oxides of Pb, Si, Al, Ti, Zr, Hf, Group IA, Group II, and the rare earths.

The source of B, Ga, In, or Tl, is applied to the dielectric surface (or over a previously applied layer) by any convenient means including not by way of limitation vapor deposition; vacuum deposition; chemical vapor deposition; wet spraying upon the surface a mixture or solution of the layer substance suspended or dissolved in a liquid followed by evaporation of the liquid; dry spraying of the layer upon the surface; thermal evaporation using direct heat, electron beam, or laser; plasma flame and/or arc spraying and/or deposition; and sputtering target techniques.

In a further embodiment hereof, a layer of an oxide of B, Ga, In, or Tl is applied to the dielectric surface, such as by one of the foregoing methods, especially electron beam evaporation.

In still a further embodiment of this invention, the oxide layer is formed in situ on the charge storage surface of the dielectric, such as by applying the element to the surface followed by oxidation.

Each layer of the source of B, Ga, In, or Tl is applied to the dielectric, as a surface or sub-layer, in an amount sufficient to obtain the desired beneficial result, usually to a thickness of at least about 100 angstrom units with a range of about 200 angstrom units per layer up to about 1 micron (10,000 angstrom units) per layer.

In the fabrication of a gaseous discharge panel, the dielectric material is typically applied to and cured on the surface of a supporting glass substrate or base to which the electrode or conductor elements have been previously applied. The glass substrate may be of any suitable composition such as a soda lime glass composition. Two glass substrates containing electrodes and cured dielectric are then appropriately sealed together, e.g., using thermal means, so as to form a panel.

In one preferred practice of this invention, each element containing layer is applied to the surface of the cured dielectric before the panel heat sealing cycle, with the substrate temperature during material application ranging from about 150.degree. F. to about 600.degree. F.

In the practice of this invention it is contemplated using any suitable source of boron, gallium, indium and/or thallium, especially inorganic compounds and more especially, inorganic oxides.

Although insulating or semi-conductor materials are typically used, conductor materials may be used if the material is appropriately isolated within or on the dielectric so as not to be in electrical contact with a source of potential and/or ground as shown in FIGS. 6, 7, 9 and 10. Likewise, if a conductive material is used in a multiple cell device, the geometric arrangement of the material may be such that no two cells are electrically connected by the conductive material. For example, the material could be deposited as a spot over each discharge site. Such an arrangement of spots 310a, 311a on the dielectric layer 310, 311 is shown in FIG. 7.

Typical inorganic compounds of boron include boron arsenate, boron tribromide, boron dibromide, boron monobromide, boron monopentahydride bromide, boron tetracarbide, boron trichloride, boron chloride, boron hydride (including: B.sub.5 H.sub.11, B.sub.5 H.sub.9, B.sub.6 H.sub.10, B.sub.10 H.sub.14), boron triiodide, boron diiodide, boron monoiodide, boron nitride, boron oxide, boron phosphide, boron triselenide, boron hexasilicide, boron trisilicide, boron trisulfide, boron pentasulfide, and boron trichloride.

Typical compounds of gallium include gallium arsenide, gallium tribromide, gallium tribromide hexamine, gallium tribromide monamine, gallium perchlorate, gallium dichloride, gallium trichloride, gallium trichloride hexamine, gallium trichloride monoamine, gallium dibromide, gallium trichloride, gallium ferrocyanide, gallium trifluoride, gallium trifluoride triamine, gallium hydride, gallium triiodide, gallium triiodide hexamine, gallium triiodide monoamine, gallium nitrate, gallium nitride, gallium oxide (sesqui-beta or alpha), gallium suboxide, gallium oxychloride, gallium selenate, gallium monoselenide, gallium sesquiselenide, gallium subselenide, gallium sulfate, gallium monosulfide, gallium sesquisulfide, gallium subsulfide, gallium monotelluride, and gallium sesquitelluride.

Typical compounds of indium include indium antimonide, indium arsenide, indium dibromide, indium monobromide, indium tribromide, indium perchlorate, indium dichloride, indium monochloride, indium trichloride, indium cyanide, indium fluoride, indium iodate, indium diiodide, indium triiodide, indium monoiodide, indium nitrate, indium monoxide, indium sesquioxide, indium suboxide, indium phosphide, indium selenate, indium sesquiselenide, indium sulfate, indium monosulfide, indium sesquisulfide, indium subsulfide, indium basic sulfite, indium sesquitelluride, and indium telluride.

Typical compounds of thallium include thallium azide, thallium bromate, thallium dibromide, thallium monobromide, thallium tribromide, thallium dichloride, thallium monochloride, thallium trichloride, thallium carbonate, thallium chlorate, thallium perchlorate, thallium chloroplatinate, thallium chromate, thallium dichromate, thallium chrominum sulfate, thallium cyanate, thallium cyanide, thallium ferrocyanide, thallium fluogallate, thallium monofluoride, thallium trifluoride, thallium fluosilicate, thallium iodate, thallium iodide (alpha and beta), thallium triiodide, thallium magnesium sulfate, thallium molybdate, thallium nitrate (alpha, beta, and gamma), thallium nitrate, thallium nitrite, thallium oxide (Tl.sub.2 O, Tl.sub.2 O.sub.3), thallium orthophosphate, thallium di-beta-orthophosphate, thallium pyrophosphate, thallium rhodanide, thallium selnate, thallium selenide, thallium silver nitrate, thallium sulfate, thallium sulfate hydrogen, thallium sulfide, thallium sulfite, thallium metatellurate, thallium thiocyanate, thallium dithionate, thallium thiosulfate, thallium metavanadate, and thallium pyrovanadate.

The use of a source of B, Ga, In, and/or Tl, in accordance with this invention, has many potential benefits. For example, sources of such elements may be utilized alone, or in combination with other elements (as noted hereinbefore), to achieve lower panel operating voltages, thermal stability, more uniform panel operating voltages, decreased aging cycle time, etc.

The source of B, Ga, In, and/or Tl used in this invention may be of any suitable state, preferably as a solid. However, a liquid or gaseous state may be utilized, e.g. combined with a suitable binder.