US2914690A - Electron-emitting surfaces and methods of making them - Google Patents

Electron-emitting surfaces and methods of making them Download PDF

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Publication number
US2914690A
US2914690A US551028A US55102855A US2914690A US 2914690 A US2914690 A US 2914690A US 551028 A US551028 A US 551028A US 55102855 A US55102855 A US 55102855A US 2914690 A US2914690 A US 2914690A
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US
United States
Prior art keywords
potassium
antimony
electron
film
photocathode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US551028A
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English (en)
Inventor
Sommer Alfred Hermann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RCA Corp
Original Assignee
RCA Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to BE553132D priority Critical patent/BE553132A/xx
Priority to NL212695D priority patent/NL212695A/xx
Priority to NL96983D priority patent/NL96983C/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US551028A priority patent/US2914690A/en
Priority to GB34562/56A priority patent/GB842894A/en
Priority to FR1168953D priority patent/FR1168953A/fr
Priority to DEP1269A priority patent/DE1269253B/de
Application granted granted Critical
Publication of US2914690A publication Critical patent/US2914690A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/12—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/34—Photo-emissive cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/38—Photoelectric screens; Charge-storage screens not using charge storage, e.g. photo-emissive screen, extended cathode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/34—Photoemissive electrodes
    • H01J2201/342—Cathodes
    • H01J2201/3421—Composition of the emitting surface
    • H01J2201/3426—Alkaline metal compounds, e.g. Na-K-Sb

Definitions

  • This invention relates to electron discharge devices having -iilms and to the art of making them, and, particularly, to electron-emitting iilms for use Yin phototubes, photomultiplier tubes, camera tubes for television and the like.
  • Electron-emitting films emit electrons when bombarded by visible or invisible radiation, charged particles, electrons or the like. Such films may be made by properly depositing and reacting aplurality of chemical substances on a support member of glass or metal or the like.
  • One type of electron-emissive film emits electrons when bombarded by visible or invisible radiation and is known as a photocathode.
  • a good photocathode film has high .and uniy form sensitivity, that is, the iilm emits the same large posite lsurface.
  • the requirement y is imposed that the lm1be thin enough to be penetrated and excited by the incident light.
  • the cathode iilm is electrically connected to a t tsource of electrons and another requirement is that the cathode iilm be sufficiently thick to have the requisite conductivity to achieve electron replacement.
  • a suitable support plate of glass, or the like isiirst provided with ⁇ a thin film of potassium and then an electron-ernitting surface, such as a photo- Vcathode surface, is formed thereon.
  • the electron-emitting surface may be an alkali-activated antimony system or the like.
  • the thin potassium film promotes the formation of a uniform and sensitive-photocathode which vis comparatively easily reproduced.
  • Fig, 3 is a sectional view along therline 3-3 in Fig. 2;
  • Fig. 4 is an enlarged' sectional view of a portion of the face plate and photocathode in the tube shown in Fig. l.
  • a television camera Itube 1,0 for example, ofthe image orthicon type, includes an ⁇ envelope having a face plate y14 on the inner surface of which 'a photoemissive surface or photocathode 16 is provided 2,914,690 Patented Nov.. ⁇ 24, 195,9
  • 'I'he photoelectrons are also accelerated toward the glass target by ring electrodes 22 and 23 so that they strike the glass target 18 with sufficient energy to produce secondary emission therefrom.
  • a ne mesh screen 24 is positioned closely adjacent to the surface of the target 20 and collects the secondary electrons. The-loss of electrons from the surface of the glass target leaves a positive charge pattern on the glass target surface corresponding in distribution in intensity to the optical scene focused on the photocathode 16. Since the glass target is very thin, a corresponding pattern of potentials is. present on the surface away from the photocathode.
  • the last-mentioned surface of the glass target is scanned by an electron beam formed'by an electron gun 26 located at the oppositeL end of the tube from the photocathode.
  • the electron beam is aligned by oppositely disposed coils 25 and 25', and is focused on the target 18 by the coil 20.
  • the beam is scanned over the surface of the Vtarget by deflection fields produced by coils formed into a yoke 27, and is well known in the art.
  • Some ofthe electrons from the cathode ray beam are deposited on the positive areasl of the target surface in an amount to neutralize the positive charges on the opposite surface of the target.
  • a strip of silver 32 (Fig. 2) painted on the inner wall of the envelope ⁇ 12 in contact with the photo- Y cathode 16.
  • a spring contact lead 34 contacts the silver stripand is connected, as by welding, to a pin 36 which extends ⁇ through the wall of the envelope. and to which electrical contact may ,be made.
  • the accelerating electrodes 22 and 23 are welded to wire leads 37 and 38, respectively, which extend through the wall of the envelope.
  • One end of the filament is secured to a lead 42 which passes insulatingly' extends through the wall'of the envelope.
  • the ⁇ other end of the filament 40 is secured to the electrode 23 by a lead 44.
  • electrical connection to the filament is provided through the external pins 38 .and 43.
  • Three' other chemical carriers 45, 46 and 47 (Fig. 3), each vin the form of different elongated metal channels, as shown, or in any other convenient form, are also provided within the envelope 12.
  • one end of each carrier 45,46 and 47 is secured to the ,outer surface of accelerating electrode 23 and the other end-of each carrier is secured to wire leads 48, 49 and'50, re-
  • the materials to be evaporated are prepared as pellets, powders or the like and are secured to or deposited in their variousV carriers or supportv members.
  • a plurality of pellets or beads 52 comprising high grade commercial antimony with only traces ⁇ of iron, sulfur, arsenic and lead permitted are secured, lat spaced intervals, on the filament 40.
  • a mixture of one'part by weight of potassium chromate, one part by weight of ⁇ aluminum, Aand 8 parts by weight oftungsten is placed in the carrier 45.
  • a mixture ofone part -by Weight lof sodium chromate, one part by Weight of aluminum and 8 parts by weight of tungsten isfplaced the carrier 46.
  • a mixture of one part by 'weight of cesium chromate ⁇ and 3 parts by weight of siliconY is placed in the carrier 47.
  • the percentages of the Various components ⁇ of the latter three mixtures disposed in the carriers 45, 46 yand 47 are not critical and may be varied within Wide ranges, as desired.
  • the tube is mounted on an exhaust pump by means of an exhaust tubulation (not shown) and then baked yat a temperature in the range of 375 to 400 C. for about one hour to remove occluded gases from the envelope and from the metal parts.
  • the photocathode iilm 16 is prepared in the following manner: First, the tube is heated, for example in an oven, to a temperature in the range of 140 C. to 170 C. With the tube thus heated, a thin lm 54 (Fig. 4) of potassium is evaporated onto the inner surface of the face plate 14 of the envelope 12. This evaporation is effected by passing current from a suitable power source (not' shown) through the leads 38 and 43 and heating the carrier 45 and thereby evaporating potassium metal released by the reaction of the potassium chromate, aluminum and tungsten. As the potassium is deposited on the face plate the photoelectron emission therefrom is measured and when the emission reaches a peak value, the evaporation of potassium is discontinued.
  • a suitable power source not' shown
  • This electron emission from the potassium ilm may be measured by connecting the photocathode by its lead 36 andthe electrode 23 by its lead 38 in series with an ammeterk56 and then directing light from a source 58 ontothe face plate.
  • the tube is kept at an elevated temperature as described above to render the glass of the face plate conductive so that the foregoing measurement of the potassium film may be made during the evaporation of the potassium.
  • the potassium lm thus formed'is invisible and is believed toI -be in the form of a monatomic layer.
  • a film 60 of antimony is deposited over the potassium lm 54 on the face plate 14. This operation may be performed with the tube at room temperature.
  • a Vheating current is passed through the leads 38 and 43 to heat the filament 40 to the vaporization temperature for the antimony metal.
  • the deposition of the antimony may be continued until the light transmission from the source 58 through the face plate is in the range of 50 percent to 95 percent of the light passed prior to the formation of the film.
  • the light transmission through the face plate may be measured by means of a photocell in the manner disclosed in U.S. Patent No. 2,676,282 of I. I. Polkosky.
  • the light transmission prior to the deposition of the tilm may be arbitrarily assumed to be 100.
  • the antimony iilm '60 is then activated with three alkali metals, potassium,
  • the tube is again heated to a temperature in the range 'of 140 C. to 170 C. in order to control the amount of potassium deposited on the lm 60.
  • Potassium is then evaporated onto the antimony tilm from the material remaining in the carrier 45 by passing heating cun'ent therethrough by Way of the pins 38 and 48.
  • the evaporation of the potassium is continued until the photo-emission reaches a peak value as indicated by ammeter 56. Evaporation of potassium is then discontinued and the temperature of the tube is raised to about 220 C. and the excess potassium metal is pumped out.
  • the tube is then held at a temperature in the range of 180 C. to 220 C. Yand the antimony film is treated ⁇ with a second alkali metal, sodium, which is evaporated onto the coated face plate by heating land reacting the material in the carrier 46. The requisite heating may be achieved by passing current through the leads 38 and 49. The evaporation of sodium Vis also continued until peak photoemission is achieved and the excess is then pumped out of the tube.
  • the tube temperature is brought into the range of 130 C. to 160 C. and cesium is evaporated onto the coated face plate from the carrier 47 until electron emission from the photocathode reaches a peak value and the excess cesium is pumped out.
  • the photocathode 16 is essentially complete and the tube is cooledand processed further as required.
  • the order in which the sodium and potassium are evaporated onto the antimony coated face plate may be reversed.
  • the principles of the invention may also be employed with secondary electron-emissive coatings and with other photocathode systems, for example, antimony-potassiumrubidium, antimony-rubidium-potassium, antimony-potassium-sodium, antimony-sodium-potassium, antimony-potassium lithium or the like.
  • the selected photocathode system is formed on a face plate coated with a iilm of potassium.
  • the method of the invention provides electron emitting surfaces which exhibit sensitivities over their areas which do not vary by more than about 3 percent to 7 percent.
  • ⁇ one photocathode showed sensitivities varying Vover the whole surface in the range of l70 to 175 microamperes per lumen of incident light.
  • photocathodes made according to prior art practices have sensitivities over their areas which may vary up to percent.
  • one such photocathode had sensitivities in the range of 20 to 110 microamperes per lumen.
  • the method of the invention provides electronemitting surfaces which are reproducible and which have high and uniform sensitivity.
  • An electron-emissive electrode comprising a supporting base, a ilm of potassium on said base, a film of antimony on said potassium film, said antimony lm including reaction products of antimony with a plurality of alkali metals.
  • An electron-emissive electrode comprising a supporting base, a iilm of potassium on said base, a film of antimony on said potassium film, saidantimony film including reaction products of antimony with sodium and potassium.
  • An electron-emissive electrode comprising a supporting base, a film of potassium on said base, a lm of antimony on said potassium film, said antimony tilm including reaction products of antimony with sodium, potassium and cesium.
  • An electron-emissive electrode comprising a supporting base, a film of potassium on said base, a film of antimony on said potassium film, said lm including small amounts of a plurality of alkali metals.
  • An electron-emissive electrode comprising a supporting base, a ilm of potassium on said base, a lm of antimony on said potassium lm,rsaid lm including small amounts of sodium, potassium and cesium.
  • An electron-emissive electrode comprising a supporting glass base, a ilm of potassium on said base, a lm of antimony on said potassium film, said film including small amounts of potassium and lithium.
  • An electron-emissive electrode comprising a supporting glass base, a iilm of potassium on said base, a lm of antimony on said potassium film, said lilm including small amounts of at least two alkali metals.
  • An electron discharge device including an electronemitting portion, said portion comprising a supporting base, a film of potassium on said base, a lm of antimony on said potassium lm, said antimony lm including reaction products of antimony with a plurality of alkali metals.
  • a camera tube comprising an envelope, a face plate at one portion of said envelope, an electron-emissive surface on said face plate and including a film of potassium on said face plate, and a lm of antimony on said film of potassium, said lm of antimony including reaction products of antimony with a plurality of alkali metals.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
  • Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
US551028A 1955-12-05 1955-12-05 Electron-emitting surfaces and methods of making them Expired - Lifetime US2914690A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
BE553132D BE553132A (is") 1955-12-05
NL212695D NL212695A (is") 1955-12-05
NL96983D NL96983C (is") 1955-12-05
US551028A US2914690A (en) 1955-12-05 1955-12-05 Electron-emitting surfaces and methods of making them
GB34562/56A GB842894A (en) 1955-12-05 1956-11-12 Electron-emitting surfaces and methods of making them
FR1168953D FR1168953A (fr) 1955-12-05 1956-12-03 Procédé pour former des surfaces émettant des électrons et surfaces obtenues parce procédé
DEP1269A DE1269253B (de) 1955-12-05 1956-12-05 Durchsichtsphotokathode

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US551028A US2914690A (en) 1955-12-05 1955-12-05 Electron-emitting surfaces and methods of making them

Publications (1)

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US2914690A true US2914690A (en) 1959-11-24

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US551028A Expired - Lifetime US2914690A (en) 1955-12-05 1955-12-05 Electron-emitting surfaces and methods of making them

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US (1) US2914690A (is")
BE (1) BE553132A (is")
DE (1) DE1269253B (is")
FR (1) FR1168953A (is")
GB (1) GB842894A (is")
NL (2) NL212695A (is")

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3020432A (en) * 1959-11-24 1962-02-06 Westinghouse Electric Corp Photoconductive device
US3179835A (en) * 1960-11-22 1965-04-20 Rca Corp Pickup tube having a cesiated photocathode and a substantially leakagefree target, and method of making the same
US3303373A (en) * 1964-01-27 1967-02-07 Westinghouse Electric Corp Target assembly comprising insulating target, field and collector meshes
US3372967A (en) * 1966-07-06 1968-03-12 Rca Corp Method of making a multi-alkali cathode
US3434876A (en) * 1965-11-23 1969-03-25 Rca Corp Photosensitive cathodes
US3498834A (en) * 1967-02-03 1970-03-03 Weston Instruments Inc Photoelectric surfaces and methods for their production
US3535011A (en) * 1968-02-27 1970-10-20 Rca Corp Method of making photoemissive electron tubes
DE2109903A1 (de) * 1970-03-02 1971-09-30 Rca Corp Verfahren zum Herstellen einer Multi alkali Photokathode
US3753023A (en) * 1971-12-03 1973-08-14 Rca Corp Electron emissive device incorporating a secondary electron emitting material of antimony activated with potassium and cesium
US4002735A (en) * 1975-06-04 1977-01-11 Rca Corporation Method of sensitizing electron emissive surfaces of antimony base layers with alkali metal vapors
US4568567A (en) * 1984-10-09 1986-02-04 Rca Corporation Method of removing trace quantities of alkali metal impurities from a bialkali-antimonide photoemissive cathode

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2206372A (en) * 1939-03-15 1940-07-02 Baird Television Ltd Method of manufacturing secondary emitting electrodes
US2391280A (en) * 1942-11-26 1945-12-18 Bell Telephone Labor Inc Method of forming layers for electronic cathodes
US2603757A (en) * 1948-11-05 1952-07-15 Sheldon Edward Emanuel Photocathode
US2654048A (en) * 1949-06-03 1953-09-29 Emi Ltd Circuits embodying cathode potential stabilized electron discharge devices
US2747133A (en) * 1950-07-05 1956-05-22 Rca Corp Television pickup tube
US2770561A (en) * 1954-03-08 1956-11-13 Rca Corp Photoelectric cathode and method of producing same

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2206372A (en) * 1939-03-15 1940-07-02 Baird Television Ltd Method of manufacturing secondary emitting electrodes
US2391280A (en) * 1942-11-26 1945-12-18 Bell Telephone Labor Inc Method of forming layers for electronic cathodes
US2603757A (en) * 1948-11-05 1952-07-15 Sheldon Edward Emanuel Photocathode
US2654048A (en) * 1949-06-03 1953-09-29 Emi Ltd Circuits embodying cathode potential stabilized electron discharge devices
US2747133A (en) * 1950-07-05 1956-05-22 Rca Corp Television pickup tube
US2770561A (en) * 1954-03-08 1956-11-13 Rca Corp Photoelectric cathode and method of producing same

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3020432A (en) * 1959-11-24 1962-02-06 Westinghouse Electric Corp Photoconductive device
US3179835A (en) * 1960-11-22 1965-04-20 Rca Corp Pickup tube having a cesiated photocathode and a substantially leakagefree target, and method of making the same
US3303373A (en) * 1964-01-27 1967-02-07 Westinghouse Electric Corp Target assembly comprising insulating target, field and collector meshes
US3434876A (en) * 1965-11-23 1969-03-25 Rca Corp Photosensitive cathodes
US3372967A (en) * 1966-07-06 1968-03-12 Rca Corp Method of making a multi-alkali cathode
US3498834A (en) * 1967-02-03 1970-03-03 Weston Instruments Inc Photoelectric surfaces and methods for their production
US3535011A (en) * 1968-02-27 1970-10-20 Rca Corp Method of making photoemissive electron tubes
DE2109903A1 (de) * 1970-03-02 1971-09-30 Rca Corp Verfahren zum Herstellen einer Multi alkali Photokathode
US3658400A (en) * 1970-03-02 1972-04-25 Rca Corp Method of making a multialkali photocathode with improved sensitivity to infrared light and a photocathode made thereby
US3753023A (en) * 1971-12-03 1973-08-14 Rca Corp Electron emissive device incorporating a secondary electron emitting material of antimony activated with potassium and cesium
US4002735A (en) * 1975-06-04 1977-01-11 Rca Corporation Method of sensitizing electron emissive surfaces of antimony base layers with alkali metal vapors
US4568567A (en) * 1984-10-09 1986-02-04 Rca Corporation Method of removing trace quantities of alkali metal impurities from a bialkali-antimonide photoemissive cathode

Also Published As

Publication number Publication date
BE553132A (is")
FR1168953A (fr) 1958-12-19
GB842894A (en) 1960-07-27
DE1269253B (de) 1968-05-30
NL212695A (is")
NL96983C (is")

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