US3916227A

US3916227A - Piezoelectric igniter with a magnetic striking mechanism

Info

Publication number: US3916227A
Application number: US469762A
Authority: US
Inventors: Walter Mohr; Hans-Dieter Klauer
Original assignee: Braun GmbH
Current assignee: Braun GmbH
Priority date: 1972-01-24
Filing date: 1974-05-14
Publication date: 1975-10-28
Anticipated expiration: 1992-10-28

Abstract

A piezoelectric igniter with a manually operable striking mechanism which comprises a hammer, a piezoelectric transducer, and a energy storing or compression spring acting on said hammer and operated by an actuating member. The hammer is held in its rest position by a release device adapted to release the hammer when a definite compressive force is exerted on the same. A bounce plate is mounted at the end of the transducer facing the hammer and a return spring is provided between said bounce plate and the hammer. The transducer has a lateral clearance to a housing which receives all component parts.

Description

5 United States Patent n91 Mize [ DISPLAY SYSTEM COMPRISING SOLID STATE CHARGE CARRIER EMITTING DEVICE [75] inventor: John L. Mize, Dayton, Ohio [73] Assignee: Beta Industries, Inc.,

Dayton, Ohio [22] Filed: June 24, 1974 [ll] Appl. No.:482,466

Related U.S. Application Data 63] Continuation-impart of application Ser. No. 220.064, tiled Jan. 24, i972, and now issued as U.S. Pat.

UNITED STATES PATENTS 3,363,240 lll968 Cola et al ..3l3/495x 3,447,043 5/ l 969 Wallace ..3 l3/495x 3,390,295 6/1968 Simmons et al.. 3l3/509 Primary Examiner-Robert Segal Attorney, Agent, or F irm-Jacox & Meckstroth [H1 3,916,227 I 1 Oct. 28, 1975 [5 7 1 ABSTRACT Charge carriers are emitted from the surface of a heterojunction region which is formed within the film-like body of a semiconductor material. The emitting region is defined by an interface which is generally semicircular in cross-section or has at least a substantial portion neither parallel nor perpendicular to the surface of the film-like body. The thickness of the film-like body is somewhat greater than the depth of the emitting region so that continuous uninterrupted and generally semicylindrical inner and outer depletion regions exist adjacent the interface. When a voltage is applied across the film-like body and hence across the emitting region, the depletion regions distort in a particular fashion and produce an electric field within the emitting region. Electrons crossing the interface are heated" by this field to a degree permitting electron emission from the surface of the emitting region. in addition, electrons crossing the interface, due to the generally semicylindrical shape of the emitting region, are nonuniformly distributed within the emitting region. This space charge effect not only enhances the heating of the electrons as they approach the emission surface, but, in addition. tends to lower the surface work function. The electron emission may be varied by altering the voltage applied across the junction.

10 Claims, 3 Drawing Figures 'U.S. Patent Oct. 28, 1975 Sheet 1 5n 3,916,227

FIG-7 US. Patent 0.28, 1975 shwsorj 3,916,227

FIG-l6 /195 FIG-2O I50 FIG-2 I 1; :22

DISPLAY SYSTEM COMPRISING SOLID STATE CHARGE CARRIER EMITTING DEVICE RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 220,064, filed Jan. 24, 1972, and now issued as U.S. Pat. No. 3,821,773.

BACKGROUND OF THE INVENTION it is desirable for a low temperature solid state electron emitter to provide a long service life, to be of low cost construction, to be operable within a wide range of temperatures and to operate with relatively low applied voltages. It is further desirable for such an emitter to provide high beam'currents, high current densities, high current and power efficiencies and also to beoperable without requiring a high or good vacuum. in addition. the emitter should not require the use of any dangerous or poisonous materials.

Existing cold solid state electron emitters are generally of three basic types. These are the field emitter, the tunnel-type emitter, and the negative affinity emitter. Each of these emitters is lacking in providing one or more of the above desirable advantages. For example, the field emitters require a high voltage power source and a high vacuum. These emitters also have a short service life and provide low electron currents. The tunnel emitters and the negative affinity emitters have low efficiencies compared to the emitter, of this invention and negativeaffinity emitters employ the element caesium which is a dangerous and difficult material to handle. Furthermore, all of these emitters are expensive to construct.

in recent years, experimental work on another form of cold solid state electron emitter has been conducted by M1. Elinsonet al. in U.S.S.R. The results of this work are reported in a 1965, issue of a U.S.S.R. publication entitled Radiotekhn and Elektron (pages l290-l296) and indicate that hot electrons,. i.e.,'

electrons having an energy level above the bottom of the conduction f band, are emitted]. from, specially prepared high resistance regions in-a film of tin oxide semiconductor." material ..(Sn) when i a? voltage ,is

' applied across the high resistance "region. This work further shows that 'electroniemission"from the; high resistance region is distinguished by ahigh" emission efficiency at lowlvo ltages when compar tin oxide films have been conducted by A. Misoellner et al. at the University of Arkansas under a research program supported by..the Avco Corporation. Some types'of cold cathode solid stateemitters.' Subsequent experiments on electron emission from 1. Technical Report November 1969, Rome Air Development Center, Air Force Systems Command. Griffiss Air Force Base, New York (RADC-TR- 69342) The Formation and Characteristics of a BroadArea Semiconductor Field Emission Cathode Cornell University.

2. Laser Focus, January 1970, E. D. Savoya. J. J. Tietjen, et al.

3. F. L. Schoormeyer, C. R. Young and J. M. Blasingame.

a. Technical Report AFAL-TR-68-l 13. April 1968.

b. Technical Report AFAL-TR-68-l00, June i968.

c. Journal of Applied Physics Vol. 34. (3) pp. 179!- 1996 Feb. 15. i968.

4. Solid-State Electronics, Pergamon Press (Glill Britain) 1969, Vol. 12, pages 945-954, The Shottky Barrier Cold Cathode."

5. Solid State Electronics, Vol. 12. 1969, pages 945-954, C. A. Stolte, J. Vilms and R. J. Archer.

6. Journal of Applied Physics, Vol. 36. No. 9. September 1965, pages 2939-2943. M. K. Testerman et al. Cold Election Sources for Mass Spectrometric Applications."

7. Solid-State Electronics, Pergamon Press (Great Britain) Vol. 7, 1964, pages 445-453, "The Transport of Hot Electrons in Al- Al; 0 Al tunnel Cathodes.

8. Institute of Radio Engineering and Electronics. April 1964, pages 1107-1113, M. I. Elinson et al. The Theory of the No Contact Type of Hot Electron from Semiconductors."

Ithas'aiso been found desirable for display devices to have along service life, to be of low cost construction, to be operable over wide temperature ranges. to operate with relatively low applied voltages, to use a minimum of electrical power, to have high brightness, and to have small overall volume. The existing display'devices are generally of four basic types. These are thecathode ray tube, light emitting diodes. gas tubes, and liquid crystals. Each of these display types is lacking in one or more of the desired advantages.

SUMMARY OF THE INVENTION of charge carriers into a vacuum, gas, liquid or solid material." Specifically, the emitter of the invention provides for the emission of electrons, as one form of of the results of these latter experiments are reported in'the February01968lissue of the'Joumalof Applied 1 Physics and confirrnthat when a-voltage is applied across a tin oxide-film located within a vacuum. a narrow high resistance-region forms. sometimes adjaccnt the negative metal contact. and electrons are emitted from this region.

Other studies relating generally to cold solidstat electron emitters are reported in the following publications:

charge'cam'ers, from a particular form of junction in response to a voltage applied across the junction. The

electron; emitter of the present invention is adapted for emitting electrons both across a solid-vacuum barrieras is required in cold cathode displays, photo "cathodes, RF amplifiers and oscillators and across a solid-solid'barrier'as is required in injection lasers.

configuration of an electron-emitter constructed in accordance with the invention are illustrated with this structure taking the form of a non-stoichiometric tin i 3 v dioxide-tin monoxide heterojunction. However. it is to be understood that the invention relates to a charge carrier emitter and may-be formed of other semiconductor materials according to the performance characteristics desired for the particular application.

I In general,;the embodiment herein disclosed in I eludes a thin film-like body of tin dioxide whichis applied to a substratesuch as quartz. glass. or alumina. An electron emitting region in the form of an elongated the invention, with the'portion ofthe filmfremaining below the interface defining a narrow throatregi'on in a conduction path existing between two electrodes or contacts attached to' the film materitslonoppdsite sides of the junction region-Semicylihdrical inner and outer depletion regions exist withinthe tin dioxide and tin monoxide materials adjacent their interface.

The electrodes'or contacts on the film are positioned so that their respective depletionregions do not intersect with the outer depletion ,region in the tin dioxide material.

When a voltage is applied acrossthe electrodes or contacts attached to the film-like body. theenergy;

barriers associated with the depletion regions and the junction of the tin dioxide and tin monoxide'mate n'als shift to an asymmetric condition resulting in chargev carrier flow across the junction'and into'and out of the tin monoxide emitting regionrThe application of voltage to the electrodes or contacts al'so'modifies the shape of the depletion regions in the tin dioxide and tin monoxide materials adjacent the junction and creates an electric field internalto the tin monoxide emitting'region. This internalelectric filed acts-upon the electrons crossing the'junction into the'tin monox-f-E ide regionand excitesftheseelectrons intoajhi'gherf. -m I energy state.

As a result of the generally semicircular configura tion of the junction, thesev energetic or hot electrons, have component of ,momentum that equals orexceeds the surface .or interface barrier so that electronsare" emitted from the tinmonoxide'material.'InjQaddition this internal electric ,neie-rwn increase near the I emitting surface, more specifically th'e f-field'ywill" 1 increase near the originof the.semicylindricaliregion. .1; This increasing field not only enhances if the? excitation of electronsintohigher'energystates. but tends to lower the vacuum barrier dueto the increased I concentration of charge near the, surface and-particularly near the center'of theemission region. I

The present invention is also directed to display or... indicator devices incorporating an emitter as described above. For example. therinvention provides for a cathode ray tube having a cold election source which eliminates the need for a thermionic cathode; The

. e'mittin'g;devices of the invention; FIG. 12 illustrates another method of fabricating a cathode surface using the emitting devices;

invention further provides a cold cathode surface for a spatially addressable or controllabledisplay-device -displays. both vacuum and solid state as well as alpha-numeric displays or'indicator devices. both vacuum and solid state. In addition, the invention provides for producing small indicator lights. both vacuum and solid state.

Other features and advantages of the invention will become readily apparent to those skilled in the art from the following descriptions and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of a low temperature solid state electron emitting device or cathode constructed in accordancewith the invention and showing portions of the device greatly enlarged forpurposes of illustration;

FIG. 2 is an enlarged cross-section'of the electron emitting deviceshown in FIG. I as taken generally along the line 2-2 in FIG. 1 and illustrating its zero bias voltage condition;

' FIG. 3 is a cross-sectional view 'of the electron emitting region of the electron emitting device shown in FIG. 2 and showing a representation of the electrons flowing into the emitting region and the electric fields existing in the emitting region during operation of the device;

and illustrating the application of the device for emitting electrons directly into'a solid semiconductor n'ga'ccordance with another embodiment of the FIG."8 is an enlarged section similar to FIG. 7 and showing 'a solid state'display. modification in accordance with the invention;

;-1- FIG. 9 is a diagrammatic illustration of the emitting deviceof the invention and arranged as a cathode :within a. cathode ray tube;.- I

FIG.' 10 is'adiagrammatic illustration of a plurality offemitting'devices arranged to form a cathodic sur- "face'ffor a spatially addressable or controllable "display; I A

I FIG;1I is a diagrammaticillustration of one method of fabricating a cathode surface using a plurality of FIG. l3 -is a perspective view similar to FIG. 1 and showing a-low temperature solid state emitting device constructedin accordance with another embodiment of the invention;

FIG. 14 illustrates another method of using emitting devices as acathodic surface for a spatially addressable or controllable display;

FIG. 15 is a sectional view illustrating another method of fabricating a cathode surface using a plurality. of emitting devicesof the invention; 7

FIG. 16 is a plan view of cathode surface shown in section in FIG. I5; i I a FIG. 17 is a sectional viewillustrating another method of fabricating aplural; cathodesurfacein 5 FIG. 21 illustrates a methodof fabricating aphosphor conductor screen for'use in a spatially addressable display; f

FIG. 22 illustrates a solid state spatially addressable or controllable display using a plurality emitting devices as a cathodic surface in accordance .with the invention; and .i

FIG. 23 is a conduction band energy diagram similar to FIG. 6 but illustrating the injected space charge effects. I

DESCRIPTION OF THE ILLUSTRATED- EMBODIMENTS The solid state electron emitting device shown in FIG. I includes a supporting substrate which may 30 be a sheet of quartz' glass-.or-alumina- Afilm like body 16 of a 'wideband gap:semiconductorrnaterialis deposited; on the substrate' vliin an hour'glas's or bow tie configuration'as shown generally in.EIG 1 to form'a narrowconstrictedportio'nll7;:thissernicom 35 are substanttallyas shown. The energy band diagram :(SnOQwhich is an n-type'semiconductor. As will be explained later, the body' 16 maybe constructed of ductor material isfa .non-stoichiom'etric tin? dioxide other semiconducting.materials'and may also' be reference plane P (FIG. 2) of the emitting region is shown in FIG. 1 to be precisely half-cylindrical and precisely defined as to horizontal dimensions.

-, the region will usually be graded and only approximately half-cylindrical.

The semicylindrical configuration of the interface 22 assures a substantial portion of the interface extendslneither, parallel nor perpendicular to a center 9 reference plane P (FIG. 2) of the emitting region 20. lo Thus a plane tangent to the interface 22 at any point other than the points X. Y and Z. extends ungularly or forms an obtuse angle with the reference plane P. This assures that the electric field generated internally in the emitting region 20 has components perpendicular to the emitting surface 25 which is illustrated in FIG. 2. as being flush and coplanar with the upper o the emitting region 20 side of the interface 22, and a continuous positive outer depletion region exists on the film-like body side of the interface 22. These

depletion regions

28 and 30 are of generally uniform width'when the device is in a zero bias condition as shown in FIG. 2 and must contain equal and opposite amounts of electric charge. In FIG. 2 the depletion regions are shown as generally semicircular in crosssection; however,'depending upon the emitter dimensions such as the radius .R and the film thickness T. these depletion, regions maybe deformed. In panicular;,.the inner depletion region 28 tends to be of width R while the outer;depletio'nregion 30'tends to flatten in the throat regiomiiowever. in the following descriptions of the embodiments. the depletion regions of F l G.'4 is take'n'across the emitting region 20 along paths extended from A to 0 and from 0 to B vwhere A and B are located on the interface 22 and formed inconfigurations other than that shown in 0 at surface The abrupt changes in FIG. 1. Apair of parallel-spaced contacts'il8 and 19 the sy' c at h points A and B in this diagram extend along oppositeedges of the body.,1'6 and may: lP ffif l bottom of the demon Conducbe f d by b' m 3 m th i' g' p-i 1 tion band 38.'result from the different band gaps of conductor "ma erial iiorthe bodyjlsijwhiieg the-two hema cr a s fqr in'ay 16 ri the emitting contact-configuration oftheidevice-is illustrated in. S n ,20. The effectsof surface a in e f c states. F]G purposgspf. im ]ifi afi n 'ddditib al; which willsomewhat modify the FIG. 4 idealized contacts may be 'used on'the device. 3; I l 978) ba 8 considered- As' is apparent fromFIG. 4, the energy level of An elongated electronemittingregion} 20 projects} into the thickness of the body lti 'fro'm the'uppersur face 21 -of the'body andis formedof'a narrow band.

gap semiconductorj' material. consisting jof generally tin monoxide (SnO).' The junction"between-theemitting region 20 and the'body' lfi define aheterojunction interface 22 which is generally semicircular in crosssectional' configuration and extendsJ aIongZ-the restricted portion17 of the body 16 parallel'to the'contacts 18 and 19.In2 FIG. 2;- the emitting region 20 .is

18 or 19 in other embodiments of the invention. While the emitting regio'n 20 is shown in FIG. Ito be pre-. cisely half-cylindrical andpreci'sely' defined yasto horizontal dimensions. 'the' region will usually-be graded and only approximatelyhalf-cylindricaLi The 'semicylindrical=.configuration of theinterface 22 assures that a substantial portion of the interface extends neither parallel nor perpendicular to a center the conduction bandthrough the emitting region 20 inwardly of the inner depletion region 28 is substantially constant. The energy barrier at the surface 25 ofthe emitting region 20 is represented by a line 40.-Theyshortinclined line 42 at the top of the line 40.-'rep resents the vacuum energy level due to a voltage V-,' whichmay be applied to the collector 32 whenfthe deviceof FIG..2 is energized. In this 7 idealized case-jsuchefiects as Schottky Effect have positioned midway between the contacts=l8 and 119,? v but it may be located closer to oneof the contacts 60 not be considered.

.-When a voltage. is applied across the contacts I8 and-I9 in FIG. 2 and hence across the emitting region 20 inthe polarity shown in FIG. 2. a flow of current is produced in the conduction path between the contacts I8 and I9. The voltage drop resulting from this current flow causes each point on the body side of the interface 22 to be at a different electric potential.Most of the voltage drop along the conduction path 50 occurs in the body region immotliuicly necessary for any given point ,on the sutface 25 ofv v the emitting region to have anjelectrical potential whichis single valued orhas the same-value regard: lessof .the path used in reachingthe point. For" example, the potential at point in FlG. 3 must be the same regardless of whether the point Cl is reached by starting at the point A or the" point C. in FlG'.3 .1 1 The potential along the path A -O in FIG. 3 isdelined by the left hand portion of the FIG. 4 energydiagram. 1

Le. theportion up to the base of the line 40 while'the potential along the pathiO-B in. FlG.'3' is'definedby discontinuous bias conditions. That is. the positive "charge outer depletion region 30 in FIG. 5 is conthe right hand portion of the FIGA. energy diagram. i.e.. the portion to the right of the basejof the line40. The difference in the bottomof the conduction band energy level in the FlGA andFlGIf6 drawingsil is the result of differentfpotentials at the'points A and B in FlG. 4 and results fromthe'voltage drop along the path 50 shown in,FlG."2. In FIG. 6 the-space charge effects have not been included.

For the potential variation illustrated by the energy diagram of FIG. 6 to exist in theFlG'. 3 structure. it I is necessary that. an :electric field "internal to] the T- emitting region exist'; 'thislelectric field being? associated with afcharg'e field. Analysislof 'the semi-i shows that with alvoltage applied across the contacts 18 and liha'charge field exists'inithe forrnofjthe' altered depletion regions shown at 28jand30'infFlG. 5 111 and that electric fields'alsoexistin the emitting region 20 as illustrated bythe vectors F -FeintFlGfljlt 351 v V p ,4 j

'Tand' direction'o'f. force; exerted on a unit negative charge by the; asymmetrical charge distributions in E

the'two depletion regions

28 and 20. As illustrated in FIG. 6, the'jinternal electric field'is assumed sufficiently-small that band bending or a significant "variation-in the Fermi .level in the tin monoxide -"-material;"doe s1notoccun. Furthermore in FIG. 6 --the space'charge effects have beenassumed to be is notable that the configuration ofjthedepletion;

regions shown in FIG. 5 differs sharplytromfthe depletion region's associated with a conventional n-p-n transistor-like structure. ln the transistor-like structure, charge neutralityacross both the rip ju nc- '40 tion and thep-n' junction is strictly maintained if the bias voltage is notto'o largegThe magnitudes lofth'e negative and positive charges "associated f'withi'ith'e forward biased junction (n-p) are reduced by e'qual amounts, and the magnitudes of the'charges associated with the back or reversed biased -junction (p-n)' are increased by equal amounts. Thus charge -neutral it'y' is maintained across'eachiindiyidual junction as well as across both of the junctions}? "As shown in- FI G."." 5, -""t h charge'concentrationlfof the junction'inthe present invention are made asymmetrical 'by'a redistribution of charge 'throughout the depletion-jregions"so*that the positive charge associated with] point X-ha'sde creased while the negative charge has. increased by the application of a bias voltage tojthe device. Thus, charge neutrality acrossthe'forward biasedportion of the junction is violated. in like fashiomjin-theback biased portions of they junction (p'-n) of; the present device, as shown'in'FlG. 5, the depletion' regions (or charge concentration) are-made asyn'tmetricalby charge concentration asymmetries are such f'that although neutrality acrossthe .individual-..junction- (l'orward or reversed biased) is violatedfcharge circular emittingregion20-shown in FIGS- 2-and5 I d 1 The electric field *li' emitting" region 20 resulting from the asymmetrical .chafge-. ;distributions"illustrated in FIG. 5. is represented bysthe'familyofvectors FrFa shown in FIG.

I neutrality along any path such as A-O-B of F l0. 5.

is maintained. 'At some point C located approximately halfway between the region of "maximum charge asymmetry at X and Z the charge concentrations are equal. Point Cis thus the point dividing the forward .;and reversed biased regions of the junction.

The differencein the depletion region or charge due to the adjacent conduction path of the device as compared with'the interrupted nature of the depletion regionsof the normaln-p-n junction device and the tinuous all around the'interface 22 from the point X to thep'oint 2' without being interrupted by omission of the bottom part'of the interface (the portioning the-point Y for instance). .The

depletion regions

28 and 30 in the FIG. 5 device are also made continuous and free-of intersection by the depletion regions 34 formed

around'the contact electrodes

18 and 19 when voltage is applied to the device. That is. the electrodes l8 and l9 and separated from the emitting region 20 by af relatively large distance so that the depletion internal to the-tin monoxide 3. This family of. vectors represents themagnitude negligible.

The electric field represented bythe vectors Ft-F,t,

[has its maximum amplitude along the horizontal "-vectors -F and ;F. ,which=,are coincident with the urface' 25 in1FIG. 3, 13nd .has its minimumvalue at .null vector (not shownllwhich is1of zero length and ocatedyparallel'tojthe' reference plane P- at the point O.'- i'n"FlG.3. The magnitude of the individual vectors in the family Ft-Fe' is determined by the relation:

where .Q representselectriccharge, and r represents the-'distancefalong thei path starting atsome point of zero charge outside the region 20 and ending at the poin'tO'. Since-*thefhorizontal electric fieldvector F. in FIG. -.3- ha's.the maximum magnitude but a zero vertical component. andsince the zero length or null electric fleldvector has the maximum vertical componentqbut-has zero magnitude. there is a vector locatedbetween'the vectors.,-F,;and the null vector whichv will have a; maximum vertical component and I 'will hence be the most effective to accelerate electrons the surface 25 i's',- define d by-a combination of the 5 electric field vector having a -'maximum' vertical' component andlalso. by" the magnitude "of electron fiow across the interface 22. The magnitudeof electron fiowover the interface barrier 22 is represented in no.3. by thearrowsiEi. E,fand.E,. This flow being a maximum at E, due to the maximumreduction in charge density in depletion region 30 at point X reducing to zero at point C (E The electron flow is zero at poin C-since as noted before, this is a 5 point ofzero bias. v t The interaction of the field vectors and the variation of the-number of electrons crossing the interface barrier gives apreferential direction'to the electron emittedinto the vacuum. This preferential direction is indicatedin FIG. 3 by line '51. 'The'arrows E -E, represent the'electron'flow fromall mechanisms such, as thermionic. tunneling,, .;etc., by which 'charge carriers can cross a barrier. i

The netfl'differen'ce inelectrons flowing' into thefi emitting region 20, represented by' the family- Ei -E=.'

and the electrons fiowingout of the emitting'region 20. representedbyj the fami ly Ei'-E representsith yf electrons emitted from'the surface '25; assuming fre combination currents ','etc.,jare zero. I

The "curve 53 in FIG..3 represents the {angular distribution of "electrons emitted from; the. surface V 25, the greatest number of electrons being at thepeak of this curve along th'e'- arrow:- 51 'with decreasin'g application of the voltageV. across the

contacts

18 and 19.

Electron emission from the surface occurs when the electrons in the emitting region 20 have acquired sufficient energy from the internal electric field to overcome, the surface barrier 40. The curvature of the 1 generally cylindrical interface 22 effectively concentrates the electron fiow towards the center 0' of theregion20 so that the electrons are primarily emitted from a centralized portion of the region.

This concentration of electrons as they approach the surface at O or 0' will result in other effects which will enhance electron emission. These space charge effects are of two types. To maintain current continuity. it is necessary for the electric field to be a maximum near the surface 25 and specifically at the point 0' of FIG. 3. This will modify the energy band diagram of FIG. 6 as illustrated in FIG. 23. Furthermore the vacuum barrier 40 of H6. 6 results from the surface traps or imperfections, and the formation of a dipole layerat the surface. The increased charge' flconcentration near the point 0' of FIG. 3 will .,modify 'boththe number of trapped surface charges and the dipole layer in the vicinity of O. thus the vacuum barrier 40 will be reduced.

. As illustrated' in FIG. 5, the thickness T of the film-like body I6 is made somewhat greater than radius'R- of the semicylindrical region 20 so that the outer depletion region 30 is continuous and uninter- -rupted'ar'oundthe interface 22. Preferably. the radius R should be between .i and 1 micron and should not begreater than of the body thickness T at the reference. plane P. However, if the radius R exceeds numbers being'directed 'at angles slightly removed 35,% .T,' the'device will operate but at reduced emission 'fromthisJpeakQAs illustrated; by'jthe curve $3',-,the'f--*E number of electrons emitted at a smaller angle-than the arrow" .5l withrespect to the reference planePf decreases more ra'pidly-- than those *directed" at an angle 'gre'ater'than the arrow 51. Thepoint'O'on the 40 surface 25 represents the'point ofmaximum emission-3 of electrons and is displaced byja' very small distance] from the 'georne'tricjcenter O of the emitting region 20. This separationis shown greatly.exaggerated inii FIG. 3, and ,is the"resultoftheasymmetrical charge; distributions. hepoint; O shown. in 1 l !G.' 3 is the. pointcommon 1:10 .{all .electric field vectors F r-Fir, 1

increase inthe voltage applied acrossthe'device. 9.5- I'- electrons are:shown' as -fhot l. relative. tolthe lmaterialj of region 20.-; However, this is notim'portant', since etc..'" and the actual distribution isri quitef complex Regardless 'of the initial distribution;46;.thezelectro energy distribution :will be essentiallyijdriftedjMax-y; wellian at. the surfacel barrier,40 ,and ;at; tli e;right go micron. After depositiomthe film is placed in a re- '(FlG. 6) interface barrier52.-Thisflf-Maxwellian; j

the internalelectric 'field dueto the voltage-lappliedos across the device. In particular. the electrons average energy. line 49. is controlled relatlve to both the. surface burrler 40 and the interface barrier 52 by the and they separation between 'OQ' j increasesflwith The: electrons crossing thegjinterface barrierI22 are'illustrat'ed in FI G.6 by the'distribution46.;.These-,

' currents and .will require a higher film voltage V. ,(FlG.2). .y-

If the bodythickness T is increased at the reference plane QP. to a valuesubstantially greater than the radius-R. the resulting-greater cross-section area in thethroat region of the conduction path 50 effectively reduces the electric field inthe emitting region 20, Wand r'esults 'in'anelectron emitting device having a 5 'higher threshold voltage and lower efficiency as an ;-'emitter. It is also found that the threshold voltage increases as the radius R. increases. As a maximum practical limit. the'qradius Rwshould .not exceed 25 microns." It is 'als'ofimportanrfor thef'contacts 18 and l9 ,g,to be spaced at a. sufficient distance from the junction} 20. so that their corresponding depletion regions 34 do no'tj'intersect'with the outer depletion region atijsurroun'ding the interface 22.

.z; ln' .fabricatingftheelectron emitting device shown in, FlG, S.L l", and 2', i t is'preferatzle to deposit a tin dioxid e film on asubstrate such as quartz or alumina funtll t hejyfilnftl has 1 a thickness approximately twice 3 thefdesiredjv'alue of theradius R. For optimum performance. thefilm-thickness should be less than one ducing {atmosphere and is electrically heated by applying a voltage across the

contacts

18 and 19. The purpose of the electrical heating is to cause the formation of emission region 20.

"The voltage applied to the

contacts

18 and 19 may be either D. C.. A. C. or cylic D. C.. that is. the polarity being reversed during the forming process. There. are two forming techniques which result in flowing through the film, the current is' monitored and the voltage-g'is; slowlyl'increased until, without a further increasein voitage,the current'continues to rise and then-suddenlydropsusually to about one tenth of the valuebeforejthe current continuedto rise withoutavoltageincrease;-

The sharp drop in the current flow indicates a cor- .responding sharp increase. in the resistance of the film. This rapid increase, in resistance"results-from the formation of the region within the narrow 'co'nstricted portion 17 of. thebody, 16. At'thistimefoub gassing occurs, and if V2 of 510.2 were energized, electron emission. would be observed. Also, atthis time, the voltage V1 ismaintained constant and the emitter is allowed to seasonor age for'two t'o four hours. The film -current will slowly increase and the emission current will jalso increase." During this aging cycle, the emission current is' noisy. As the emitter ages; the film current will reach a maximum and then decrease. whcnlthe film current decreases, WW m?" i a f l to could housed and these could includesemiconductor two orders of magnitude. After operating for approx- 1 imately tenhours,'the emission current nois'ede I creases materially. M Another method of forming the emissionlregion 20 stood that in the FIG. 7 embodiment of the invention,

the emitter maybe constructed so that holes form the majority current carriers instead of electrons.

The embodiment of the charge carrier emitting device in FIG. 2 may be modified so that the collector 32 and the voltage V2 is eliminated. Upon the applicationof the voltage V] to

contacts

18 and 19, electrons will be emitted into the vacuum. These emitted electrons willbe' collected by the'surface 21 adjacent the positive contact 19.

is to preset the voltage Vl ata levelcorresponding to /4 watt dissipation. This voltage isthenappliedin a square wave to contacts 1 8 and: l9. Thedurationof the pulse is not critical. lf formationof the "emitting.

region 20 does not'o'ccur. then V1 is reset to' fz watt dissipation and the process is repeated. This continues until the emission region 20 forms. The aging'cycle previously described isthen initiated. e As mentioned above, the electron emitting device i illustrated in the form of a tin dioxide -tin monoxide heterojunction.Howeventhe emitting device may be,

formed of other semiconductor" materials-{and by other fabrication techniques. providing the general geometry and configuration of,the;-reg on -,20 aremaintained in relation to theibody 16; .fllt islalsolf-" possible to form the'electron emitting'region 20from,

' 1'68101120. Uusahy the semtconductor body 16 of a metal alloy or'jan insulator injplaceof band type semiconducting materiat.-@-:;

' While the "emitting. device disclosedum':EIQS.1 6' relates to theemission:of electron sfrom'the'surface e. row

25. the described 'deviee'rnayaiso be used fotemitting or ejecting electrons directly into" anotherf solid.

Thus referring to"FIG.'7. 'the emitting surface 25 metallic electron c'ollector-32*is located adjacent the other side of the semiconductor elementSS form ing by way of illustration a Schottky barrier between the element and the collector 32. Thus theemission of electrons from the region 20 cannot only be controlled or varied by changing thevoltageacross the.

contacts

18 and 19 and/or on the collector-32mm may also be controlled by changingjthevoltageVs'orithe element 55. At the present time. all of the specific Another embodiment of the charge carrier emitting devicesimilar to that shown in FIG. 7 is illustrated in FlG."8. In this embodiment. the surface 25 of the emitting region 20 is covered by a thin film or layer ofdielectric material 58, and over this dielectric materialother layers are deposited. such as. for example, a phosphor layer '59 acollector and a ceramic cover 61 .are shown. However, other layers this illustration. the collector 60 is tin oxide. a transparent semiconductor. t

relateto a device having a body 16 fabricated with a wide band gapn-type semiconductor. an emitting device m'ayalso be fabricated, in accordance with the invention by using narrow band gap. either retype or p-type, semiconductor materials. Emitting devices using p-type material for the body 16 are particularly important in the embodiment disclosed in FIG. 7 for photo-sensitive electron emitting devices.

As" mentioned above, the-emitting device of the "presentfiinvention maybe chemically formed by form the eie'ctron emitting region in a reducing atmosphereasspecified. A solid state-emitter device may alsobe'fabricated by other techniques depending on the; materials selected for both the body 16 and the the solid state emitter is fabricated-by using standard teehniques' such'.as chemical" vapor deposition or epitaxial formation.- Preferably, 'the'--'body is then annealed, especially" if the semiconductor material is onethat existsin more thanone-chemical combina- 'oitidesand chlorides. Byannealing in the presence of a 'suitable 'o;tidation or;.reducing}agent, the semiconductor. propertiescan be controlled.

"i -In "j'additio'n' to {chemical formation of the region 20 Ifby- .electrically-heating'the'body 16, this region may alsojjib'e formed by etching-as'mall region of ;-the semiconductor body 16 to* form a generally V- shaped-trough or groove in the upper surface 21 of the semiconductor body 16 The region 20 material. which may be either a semiconductor or a metal. is then-:fdeposited in the etched groove by a method such "as vapor depositionor sputtering. The region .20 'may' also be formed by ion implantation of the techniques.

extending to the cathode 72 region 20 material. using conventional implantation One application of an emitting device or cold cathode of the invention is in place of the conventional thermionic cathodenormally employed in a cathode ray tube. In this embodiment, which is illustrated in FIG. 9, only one emitting device or cathode is shown, however, multiple cathodes would normally be included,' for example, such as in a color cathode ray tube .'T h e reference numbers 68, 66, 67, 68 and 69 represent electrical connections or conductors to the cathode ray'tube. The conductor 63 connects to the first accelerating grid 70. and the electrical conductors 68 and 69 connect to the charge canier emitting device of the invention-or cold cathode 72. The; electrical conductor 66 connects-with the -"second phosphorous collector screen 75 which forms awall or is adjacent awall of an enclosure tube orsurrou'nd ing envelope76QAlthough not shown, other' standard cathode ray tube c'o'mponents, such as gette'r s',-*would be included in the embodiment. Furthermore, 'in-the'- cathode array 80, and electrical connections 84 extend to a spatial or scanning control unit 85. Conductor 86 extends to a control grid 88, and a conductor 89 extends to a phosphorous coated collector screen 90. All of the

components

80, 8S and 88 are sealed within a'tube'envelope 92 with'the screen 90 forming one wall, of the envelope. In the embodiment illustrated in FIG. 10,-the Digiscan method is'used for spatial controhhowever, other means of spatial control of theemitted electrons may be employed.

' In'operation of the apparatus shown in FIG. 10,

electrons are emitted from the surface of the cathode only' 'electronsfor one resolution element, as deterembodiment'of FIG-electrostatic deflection is 1 i contact;

extensions

94 and 96. The number of emitting regions 20 is established by thev CRT requirements such as electromagnetic'deflection.,

illustrated, but'other forms-of deflection may' befused.

When a voltage is applied to conductors and69, electrons are-emitted from the-cathode 72generally in the direction of the phosphorous collector screen 75. Theaccelerating grids 70 accelerate a-fraction of the emitted electrons" toward the focusing-fand'dei-y ass deflected to excite'the phosphor collector screen' 75 flection Sy tem 73. These electrons are focused and in accordance with the voltageapplied to conductors 68. Brightness or Z axis modulation in this embodiment is produced by either modulating the voltage applied toithe-accelerating grids 70 or by modulating the "voltage"appliedbetween conductors 68 and 69 In addition to theabove mentioneddirect cathode I modulation, theembodiment shown inFIG. 9has additional advantages} over a. thermionicc athode. One of theseadvantages is essentiallylinstantaneous warm up. That is, the coldcathodicemission inherentfl in this embodiment eliminates the need; for. heater;

cathodic devices. Another advantage in'theembodiment of F IG.-. 9 is-"the improved life ofthe ,CRT. It is known that the'life of thermionicgcathode' devices is:

- warm up power requiredin conventionalthermionic 1 mined b'y the voltages applied to connections 84. t passxthrough the spatialfllter and impinge on the Driving voltages for the emitting regions 20 are supplied by. the application of a voltage to contacts 18 and-.-19 throu'gh conductors ,81 and 82 connected to 80illustrated in FIG.- 11, may be modified to accomplish brightness of axis modulation by the modulation of the voltage applied-to contact

extensions

94 and 96, thereby eliminating the need for a control element such as the grid 88 shown in FIG. 10.

Another embodimentof an emitter array suitable for the CRT. shown in FIG. I0. is illustrated in FIG.

'12. In this-embodiment,.each emitting region 95 is addressable CRT described above in connection with Another embodiment of a charge carrier emitting when; the powerv is turned-off, other; associated. electronics. The cold cathode embodiment described herein does I not require. [this .icontinued-power con-J sumption to provide for a long service lifel-jy s I An embodiment of the charge'f'arrie'rfle'mitting vices for a spatiallyQaddressable CRT isfillustrated a planarssurface of the array 80. The

numbers

81 and 82 represent the electrical connections to the- CRT,is. !gene rally illustrated in FIG. 14. In this embodimenuelectrons are emitted from the surface of aicold 'icathodelemitter array 105 in response to a voltagefapplied -to '

conductors

106 and 108. The emitted electrons are accelerated across a drift I space" due-to the accelerating potential applied in FIG. 10. In this embodiment, a planan'cathode' to the high voltage conductor 67 connected to the phosphorcollector screen 75. While the electrical conductors 106'and 108 to the emitter array 105 are shown ,as two single connections. each conductor actually represents multiple conductors. Furthermore.

other accelerating. control, or focusing elements may be located in the drift space 110.as required. Focusing of the electrons emitted from the emitter array 105 in FIG. 14. is accomplished by proximity focusing which requires that the drift space 110 be very small. for example. on the order of .01 inch. However, specific dimensions of the space 110 are determined on the basis of the CRT requirements such as resolution. applied voltages. etc.

The emitter array 105 has an emission surface which is suitable for the spatially addressable CRT illustrated in FIG. 14. Thus referring to FIGS. 15 and 16. an array 105 of emitting devices or cathodes 20. similar to those previously described and illustrated in FIG. 11. is fabricated on the surface of an insulator or dielectric layer 122. Buried within this insulator layer 122 are conductors 124 which extend laterally or transversely to the parallel

elongated contacts

106 and 108. in operation, a voltage is applied through suitable external electronics to-anypair of

adjacent contacts

106 and 108 which will tend to cause electrons to be emitted from a lineor row of emitting regions located between the contacts. If a negative voltage is applied to all but one of theembedded contacts 124, the emission is inhibited at every resolution element except the one that is located between

energized contacts

106 and 108 and above the nonenergized contact 124.

A more detailed construction of each embedded conductor 124 is shown in FIG. 19 in relation to a single emitting region 20. When aburiedconductor 124 is energized by the application of a negative voltage to the conductor, a charge depletion region is formed in the film 16. As a result the impedance above in connection with FIGS. Hand 13, is fabricated on the surface of an insulator or dielectric layer 122. Buried within this dielectric layer l22'are conductors 124 which extend transversely ,to the

contacts

106 and 108. The operation of the array 130 is identical to that described above in connection with FiGS.15,16 and19.

A further embodiment of a cathode array 140 for a spatially addressable CRT, is illustrated in FIGS.

20 and 21. The emitter array 140 is constructed similar to either of the

arrays

105 or 130 described above in connection with FIGS. 15-19 with the exception that the buried conductors 124 are eliminated. Spatial control in one axis or direction is accomplished in the same manner as previously described. that is, by

energizing any two adjacent pair of

contacts

106 and 108. Control in the other axis is accomplished by inhibiting phosphorescence of a display screen 150 rather than by emission of electrons from the array 140. To accomplish this, the phosphor conductor display screen 150 (FIGS. 20 and 21) is fabricated with conducting strips 152 deposited on the tube envelope 154 by a suitable process. The conducting strips 152 extend transversely to the parallel

linear contacts

106 and 108 of the emitter array 140. and a phosphor layer 156 is deposited over the strips 152. When a positive voltage is applied to one of the conducting strips 152 through its contact lead 157. the area of that conducting strip directly opposite the crossing linear emission region between the energized

contacts

106 and 108 will phosphor and emit light. I

in accordance with another embodiment of the invention illustrated in FIG. 22. a cathode array or 130 forms the emitter oia solid state display. The essential difference between this display and those previously described and illustrated. is that the vacuum drift space (FIGS. 14 and 20) is replaced by a solid dielectric layer 160 which is sandwiched between the electron emitting array 105 or and j the phosphorous coated screen 75. The basic description of a charge carrier emitting device for injecting electrons into a solid state substance other than a partial vacuum. is described above in connection with FIG. 7.

From the drawing and the above description. it is apparent that a solid state electronic emitting device or cold cathode constructed or assembled in accordance with the invention. provides desirable features and advantages. For example, the emitting region 20 is constructed so that the interface 22.is generally semicircular in cross-section or at least a substantial portion of the interface is neither parallel nor perpendicular to the reference plane P of the emitting region. in addition, the emitting region does not extend through the body 16 so that continuous inner and

outer depletion regions

28 and 30 border the interface 22. As a result of this junction geometry and configuration, and electric field is created within the region 20 when a voltage is applied across the body 16 in a lateral direction normal to the reference plane P. This intemai electric field within the region 20 pro duees hot electrons within the region so that the emission of electrons from the surface 25 is directly proportional to the voltage drop across the throat region of the conductor path 50 and inversely proportional to the radius R of the junction 20. Thus. the size of the junction should be minimized so that electric field strengths near the 10 volts per centimeter believed desirable for electron emission from the tin oxide semiconductor materials, will be attained with reasonably low voltages applied across the

contact electrodes

18 and 19 Furthermore, the electron emitting device of the present invention does not require a good vacuum and it'aiso provides for a long service life since it has no life limiting'mechanisms other than heat. Aii prior'art cold cathode emitters have at least one life limiting mechanism in addition to heat; The emitter of the present invention also provides a high emission efficiency, at least up to 50 percent, and will operate in a wide'ran'ge of temperatures such as between 20 K and 700 K. As mentioned above, the body 16 may be formed of other semiconductor materials such as p-type semiconductor material. The heterojunction interface 22 described above in this specified provide sfor minimizing the voltage drop required across the region 20 to produce the electric fields within thejunction necessary for emission.

As also mentioned above. the described configuration of the heterojunction interface 22 insuresthat the fields within the junction 20 have components parallel to the reference plane P of the junction. these components are essential to assure emission of electrons from the surface 25. The depth of the region 20 relative to the thickness of the film or body T at the reference plan P is also important. As mentioned above. the thickness T of the body 16 should be at least equal to the depth or radius R of the interface 22 plus the width of the outer depletion region to assure that the

depletion regions

28 and 30 are continuous along the interface 22. However. it is desirable to minimize the film thickness so that the current by-passing thejunction is minimized.

As also described above in connection with FIGS. 9-22. electron emitting devices or cold cathodes constructed in accordance with the invention are embodied in various forms of display devices. An additional application is in the construction of photo cathodes for use in infrared or near infrared imaging devices. The emitting device is also adaptable for producing electron beam injection transistors and RF amplifiers and self oscillating RF oscillators as commonly used in radar and radio applications. The device may also be used in the production of transferred electron devices and various instruments such as electron emitters used in electronic equip ment adapted for outer space exploration. The emitting device of the invention may also be adapted for other instruments such as electron beam computer memories where low vacuum operation is desirable. and for beam readout devices such as for scanning a screen which is sensitive to infrared radiation.

While the forms and embodiments of solid state electron emitter devices and the methods of making the same herein described. constitute preferred embodiments of the invention. it is to be understood that the invention is not limited to these precise forms and embodiments and methods. and that changes may be made therein without departing from the scope and spirit of the invention.

What i claim is:

1. An improved solid state emitting and display device comprising a substrate, a cathode including a continuous film body of wide band gap semiconducting material on said substrate and having an outer surface. an emitting region projecting into said film body from said outer surface and comprising a narrow band gap semiconducting material having a resistivity higher than that of said film body material. said emitting region having an emitting surface interrupting said outer surface of said film body, a set of contacts on said film body and spaced with said emitting region therebetween for applying a voltage across said emitting region in a direction substantially perpendicular to a reference plane extending through the center of said emitting region generally normal to said outer surface. said emitting region being effective to produce a continuous emission of electrons from said emitting surface without an applied external collecting field in response to the application of a voltage to said contacts. a display screen having means for emitting light in response to engagement of electrons emitted from said emitting region. and means for controlling the emission of light from said display screen.

2. An-emitting and display device as defined in claim 1 including a plurality of said emitting regions arranged in a generallyplanar array. and means for selectively controlling the emission of light from a portion of said screen corresponding to each said emitting region.

3. An emitting and display device as defined in claim 1 including a plurality of said emitting regions arranged in a generally planar array. and means for selectively controlling the emission of electrons from said emitting regions.

4. An emitting and display device as defined in claim 3 wherein said means for selectively controlling the emission of electrons from said emitting regions comprise a plurality of control conductors arranged in generally parallel relation adjacent said emitting regions, and a layer of electrical insulating material extending between said control conductors and said emitting regions.

5. An emitting and display device as defined in claim 2 wherein each said emitting region is elongated. and said emitting regions are arranged in generally parallel spaced relation.

6. An emitting and display device as defined in claim 2 wherein said display screen is disposed in adjacent relation to said emitting regions.

7. An emitting device as defined in claim I wherein said display screen includes a phosphorous layer disposed generally adjacent said emitting surface of said emitting region. a conductor layer adjacent said phosphorous layer and having at least partial transparency. and a generally transparent insulator for supporting said phosphorous and conductor layers.

8. An improved solid state emitting and display device comprising a substrate. a cathode including a film body of side band gap semiconducting material on said substrate and having an outer surface. a plurality of emitting regions arranged in a generally planar array and projecting into said film body from said outer surface, each said emitting region comprises a narrow band gap semiconducting material having a resistivity higher than that of said film body material and having an emitting surface interrupting said outer surface of said body. a plurality of contacts on said film body and spaced with said emitting regions therebetween for applying a voltage across each said emitting region in a direction substantially perpendicular to a reference plane extending generally through the center of said emitting region generally normal to said outer surface of said film body. each said emitting region being effective to produce a continuous emission of electrons from said emitting surface without an applied external collection field in response to the application of a voltage to the corresponding said contacts. a display screen positioned adjacent said array of emitting regions and having a portion effective to emit light in response to the emission of electrons from a corresponding said emitting region. and means for selectively controlling the emission of light from each portion of said screen corresponding to each said emitting region.

9. An emitting device as defined in claim 8 wherein plurality of control conductors arranged in generally parallel relation adjacent said emitting regions, and a layer of electrical insulating material extending between said control conductors and said emitting regions.

# i i t i

Claims

1. A piezoelectric igniter with a striking mechanism, more especially for lighters, having a piezoelectric transformer, a hammer which is movable in the direction of the latter and which co-operates with a compression spring which can be compressed by an actuating member, having a movement release device for the hammer, and having a housing which receives these parts and at the one front end of which the piezoelectric transformer is situated, and having a bounce plate which is mounted at the exposed end of the latter, characterized in that a return spring is arranged between said hammer and said bounce plate and that the piezoelectric transformer has a lateral clearance with respect to the housing, said bounce plate being magnetized at the region of impact, and said hammer being magnetically attractive at the region contacting said plate.

2. A piezoelectric igniter as claimed in claim 1, characterized in that said bounce plate is provided with a projecting bounce mandrel, and a permanent magnet surrounding said mandrel.

3. A piezoelectric igniter as claimed in claim 2, characterized in that the permanent magnet is annular and is axially magnetized.

4. A piezoelectric igniter as claimed in claim 2, characterized in that the permanent magnet is movably mounted in relation to the magnetic bounce plate.

5. A piezoelectric igniter as claimed in claim 2, characterized in that a return spring is inserted between the hammer on the one hand, and the permanent magnet, on the other hand.