US3806372A - Method for making a negative effective-electron-affinity silicon electron emitter - Google Patents

Method for making a negative effective-electron-affinity silicon electron emitter Download PDF

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Publication number
US3806372A
US3806372A US00259037A US25903772A US3806372A US 3806372 A US3806372 A US 3806372A US 00259037 A US00259037 A US 00259037A US 25903772 A US25903772 A US 25903772A US 3806372 A US3806372 A US 3806372A
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Prior art keywords
silicon
electron
heating
temperature
cathode
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Expired - Lifetime
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US00259037A
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English (en)
Inventor
A Sommer
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RCA Corp
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RCA Corp
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Filing date
Publication date
Application filed by RCA Corp filed Critical RCA Corp
Priority to US00259037A priority Critical patent/US3806372A/en
Priority to MX006525U priority patent/MX2985E/es
Priority to IT22634/73A priority patent/IT982719B/it
Priority to DE2325869A priority patent/DE2325869A1/de
Priority to GB2453373A priority patent/GB1414400A/en
Priority to ES415185A priority patent/ES415185A1/es
Priority to FR7319093A priority patent/FR2186724B1/fr
Priority to CA172,267A priority patent/CA974296A/en
Priority to SE7307590*A priority patent/SE378939B/xx
Priority to JP6071773A priority patent/JPS551663B2/ja
Priority to AU56371/73A priority patent/AU468010B2/en
Priority to SU1925709A priority patent/SU520060A3/ru
Priority to BE131827A priority patent/BE800393A/fr
Priority to NL7307684A priority patent/NL7307684A/xx
Application granted granted Critical
Publication of US3806372A publication Critical patent/US3806372A/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
    • H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
    • 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
    • H01J9/125—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes of secondary emission electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/32—Secondary emission electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S438/00—Semiconductor device manufacturing: process
    • Y10S438/914—Doping
    • Y10S438/918—Special or nonstandard dopant

Definitions

  • a method for making a negative effective-electronatfinity silicon electron emitter includes the steps of preparing the silicon by first heating for a short time to near the melting point of the silicon, sensitizing by applying a layer of work-function-reducing material, heating again for a short time to a lower temperature than the first, and again sensitizing by applying a layer of work-function-reducing material.
  • the invention relates to silicon negative effective-electron-affinity electron emitters.
  • a P type silicon crystal which is sensitized by application of work-function-reducing material, such as cesium and oxygen, to its surface can function as an efficient electron emitter.
  • Sensitized silicon cathodes may be used, for instance, as long wavelength-sensitive photocathodes, secondary emitters, and electron gun cold cathodes.
  • silicon cathodes One problem with silicon cathodes is the difliculty of removing contaminants from, and otherwise preparing, the surface region of the crystal before the cesium and oxygen are applied. Such preparation is essential to obtaining a negative etfective-electron-afiinity characteristic in the cathode. If the negative effective-electron-aflinity is not attained, the cathode is not acceptable for commercial use.
  • Sputtering is a rather lengthy process which requires relatively complex internal tube structures, such as a special gun. Also, the annealing required after sputtering is likely to degrade the junction characteristic of junction devices, such as PN junction cold cathodes by impurity diffusion. For these reasons, silicon has as yet no significant use commercially for cathodes in electron tubes. Practical considerations require that cathodes for electron tubes be cleaned after they have been mounted in the tube envelope. Sputtering and annealing would require appropriate tube structures therefor to be located inside the tube envelope, which is not presently commercially feasible for electron tubes which might include silicon cathodes.
  • the novel method of making a silicon cathode comprises heating the silicon in vacuum to near its melting point for a brief time, sensitizing the emitting surface by applying a layer of work function reducing material, heating again for a brief time to a temperature lower than the first heating temperature, and again sensitizing.
  • the novel method makes it feasible to use a negative effective-electron-afiinity cathode in existing electron tube types.
  • FIG. 1 is a flow chart of the preferred embodiment of the novel method.
  • FIG. 2 is a partially sectional, partially schematic view of a phototube including a silicon cathode processed in accordance with the preferred embodiment of the novel method.
  • FIG. 1 shows a flow chart of a preferred embodiment of the novel method for processing a silicon reflecting photocathode for a phototube 10 shown in FIG. 2.
  • the phototube 10 has a transparent envelope 12, inside of which is mounted a silicon photocathode 14 and an anode ring electrode 16 spaced from the photocathode 12.
  • the cathode 12 is a round P type monocrystalline silicon disc about 2 cm. (centimeters) in diameter and about 200 m. (micrometers) thick, having an emitting surface 18 oriented in the Miller index plane of the crystal.
  • the emitting surface 18 is provided with a work function reducing layer 20 of cesium and oxygen.
  • the envelope is continuously evacuated through exhaust tabulation 22 by a vacuum pump 24.
  • Two appendages 26, 28 on the exhaust tabulation 22 contain compounds which release cesium and oxygen, respectively, when heated.
  • the pump 24 is operated continuously during the entire process to maintain a vacuum of on the order of 10- to 10- torr in the envelope, except during sensitizing, as measured by an ionization gauge.
  • the cathode 12 is first heated to a temperature of about 1300 C. (Celsius) for about 3 seconds by ohmic heating resulting from passing electric current through the leads 21. During the heating, the temperature is monitored by measuring the light radiation output of the silicon with a pyrometer. The cathode 12 is then allowed to cool. After the silicon reaches approximately 100 C., cesium is released from the cesium appendage 26 by heating thereof until the photoemission of the cathode 12 has passed a maximum. Thereafter, at near room temperature, oxygen is released from the oxygen appendage 28 by heating thereof until the photoemission is maximized.
  • the first heating and sensitizing is repeated once. This generally raises the photosensitivity to above that value.
  • the cesium and oxygen together form a portion of the final thickness of the work-function-reducing layer 20.
  • the cathode 12 is now again heated, this time to a temperature of 1000 C. for about 3 seconds, and allowed to cool to about 100 C.
  • the emitting surface 18 is again sensitized by release of cesium and oxygen from the appendages 26, 28. This last, lower temperature, heating followed by sensitizing, is repeated to the extent necessary to obtain peak photosensitivity from the emitting surface 18.
  • the novel method of preparing and sensitizing the silicon results in negative eiIective-electron-afiinity without the necessity of additional structures inside the envelope for sputtering and without a lengthy annealing step.
  • the novel method is readily adapted for processing a silicon cathode in existing commercially-available electron emissive tube types, with only minor modifications in presently used processing.
  • Such a silicon cathode may be used, for example as a photocathode, a secondary emissive dynode, or as a cold cathode in an electron gun.
  • the first, higher temperature heating should be within about 100 degrees of the melting point of silicon, generally given as 1420 C. However, the temperature may be lower where a longer time at that temperature can be tolerated by the associated cathode structure. For instance, the first heating temperature may be anywhere from about 1100 C. to as near the melting temperature as is practical without resulting in damage to the silicon crystal due to non-uniform heating.
  • a silicon cathode structure having a PN junction such as for a forward biased PN junction cold cathode, it is desirable to keep the time to a minimum in order to prevent undesired diffusion of the P type impurities at the thin junction region of the cathode.
  • the second heating should be on the order of 300 C. lower than the first heating, or in the range of between about 800 and about 1000 C. Again, the heating should be brief, as for the first heating, and should be minimized for a junction device. However, the time is not as critical for the second heating with regard to the diffusion problem in a junction device since the temperature is lower.
  • the sensitizing may be by application of cesium and oxygen or rubidium and oxygen to obtain negative efiectiveelectron-afiinity.
  • Other work-function-reducing layer materials do not appear to reduce the work function sufliciently to result in negative eifective-electron-afiinity.
  • the photosensitivity of the cathode is below about 2 microamperes per lumen, it is advisable to repeat the first heating, as such a low sensitivity is a sign that the heating was not entirely adequate to prepare the crystal. Also, if the final sensitivity is below about 150 microamperes per lumen, it may be advantageous to repeat the entire heating and sensitizing procedure, since it may be expected that the final sensitivity can be made higher. While these repeating steps are generally necessary, they are not considered at present to be essential.
  • the temperature of the silicon was measured with a pyrometer. Other means, such as a thermocouple, may also be used. While there is no assurance that any of the various temperature measurement means will give the absolute temperature of the silicon, the temperature as measured herein is believed to be within about 10 C. of the absolute temperature of the silicon. The optimum temperature varies somewhat with the time which the silicon was held at that temperature. Lower temperatures generally require a longer time.
  • a method for making a silicon negative effectiveelectron-aifinity electron emitter comprising the steps of:
  • said workfunction-reducing material is chosen from the group consisting of cesium plus oxygen and rubidium plus oxygen.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Cold Cathode And The Manufacture (AREA)
  • Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
  • Silicon Compounds (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
US00259037A 1972-06-02 1972-06-02 Method for making a negative effective-electron-affinity silicon electron emitter Expired - Lifetime US3806372A (en)

Priority Applications (14)

Application Number Priority Date Filing Date Title
US00259037A US3806372A (en) 1972-06-02 1972-06-02 Method for making a negative effective-electron-affinity silicon electron emitter
MX006525U MX2985E (es) 1972-06-02 1973-03-29 Mejoras en metodo para fabricar un emisor de electrones de silicio de afinidad efectiva negativa a electrones
IT22634/73A IT982719B (it) 1972-06-02 1973-04-05 Metodo per la fabbricazione di un emettitore di elettroni al silicio presentante una efficace affinita elettronica negativa
DE2325869A DE2325869A1 (de) 1972-06-02 1973-05-22 Verfahren zum herstellen eines silizium-elektronenemitters mit negativer effektiver elektronenaffinitaet
GB2453373A GB1414400A (en) 1972-06-02 1973-05-23 Method for making a silicon electron emitter
FR7319093A FR2186724B1 (fr) 1972-06-02 1973-05-25
ES415185A ES415185A1 (es) 1972-06-02 1973-05-25 Un metodo para fabricar un emisor de electrones.
CA172,267A CA974296A (en) 1972-06-02 1973-05-25 Method for making a negative effective-electron-affinity silicon electron emitter
SE7307590*A SE378939B (fr) 1972-06-02 1973-05-29
JP6071773A JPS551663B2 (fr) 1972-06-02 1973-05-30
AU56371/73A AU468010B2 (en) 1972-06-02 1973-05-31 Method for making a negative effective-electron-affinity silicon electron emitter
SU1925709A SU520060A3 (ru) 1972-06-02 1973-06-01 Способ изготовлени кремниевого электронного эмиттера
BE131827A BE800393A (fr) 1972-06-02 1973-06-01 Procede de fabrication d'emetteurs d'electrons en silicium a affinite electronique effective negative
NL7307684A NL7307684A (fr) 1972-06-02 1973-06-01

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00259037A US3806372A (en) 1972-06-02 1972-06-02 Method for making a negative effective-electron-affinity silicon electron emitter

Publications (1)

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US3806372A true US3806372A (en) 1974-04-23

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US00259037A Expired - Lifetime US3806372A (en) 1972-06-02 1972-06-02 Method for making a negative effective-electron-affinity silicon electron emitter

Country Status (14)

Country Link
US (1) US3806372A (fr)
JP (1) JPS551663B2 (fr)
AU (1) AU468010B2 (fr)
BE (1) BE800393A (fr)
CA (1) CA974296A (fr)
DE (1) DE2325869A1 (fr)
ES (1) ES415185A1 (fr)
FR (1) FR2186724B1 (fr)
GB (1) GB1414400A (fr)
IT (1) IT982719B (fr)
MX (1) MX2985E (fr)
NL (1) NL7307684A (fr)
SE (1) SE378939B (fr)
SU (1) SU520060A3 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4107564A (en) * 1974-05-21 1978-08-15 Alexandr Ivanovich Klimin Photoemitter
EP0206422A1 (fr) * 1985-06-24 1986-12-30 Koninklijke Philips Electronics N.V. Dispositif d'émission d'électrons muni d'un réservoir comprenant un matériau réducteur du potentiel de sortie
US5559342A (en) * 1986-07-04 1996-09-24 Canon Kabushiki Kaisha Electron emitting device having a polycrystalline silicon resistor coated with a silicide and an oxide of a work function reducing material
US5647998A (en) * 1995-06-13 1997-07-15 Advanced Vision Technologies, Inc. Fabrication process for laminar composite lateral field-emission cathode
US5703380A (en) * 1995-06-13 1997-12-30 Advanced Vision Technologies Inc. Laminar composite lateral field-emission cathode
USRE39633E1 (en) 1987-07-15 2007-05-15 Canon Kabushiki Kaisha Display device with electron-emitting device with electron-emitting region insulated from electrodes
USRE40062E1 (en) 1987-07-15 2008-02-12 Canon Kabushiki Kaisha Display device with electron-emitting device with electron-emitting region insulated from electrodes
USRE40566E1 (en) 1987-07-15 2008-11-11 Canon Kabushiki Kaisha Flat panel display including electron emitting device

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4107564A (en) * 1974-05-21 1978-08-15 Alexandr Ivanovich Klimin Photoemitter
EP0206422A1 (fr) * 1985-06-24 1986-12-30 Koninklijke Philips Electronics N.V. Dispositif d'émission d'électrons muni d'un réservoir comprenant un matériau réducteur du potentiel de sortie
US5559342A (en) * 1986-07-04 1996-09-24 Canon Kabushiki Kaisha Electron emitting device having a polycrystalline silicon resistor coated with a silicide and an oxide of a work function reducing material
USRE39633E1 (en) 1987-07-15 2007-05-15 Canon Kabushiki Kaisha Display device with electron-emitting device with electron-emitting region insulated from electrodes
USRE40062E1 (en) 1987-07-15 2008-02-12 Canon Kabushiki Kaisha Display device with electron-emitting device with electron-emitting region insulated from electrodes
USRE40566E1 (en) 1987-07-15 2008-11-11 Canon Kabushiki Kaisha Flat panel display including electron emitting device
US5647998A (en) * 1995-06-13 1997-07-15 Advanced Vision Technologies, Inc. Fabrication process for laminar composite lateral field-emission cathode
US5703380A (en) * 1995-06-13 1997-12-30 Advanced Vision Technologies Inc. Laminar composite lateral field-emission cathode

Also Published As

Publication number Publication date
FR2186724B1 (fr) 1977-02-11
NL7307684A (fr) 1973-12-04
GB1414400A (en) 1975-11-19
JPS4951869A (fr) 1974-05-20
IT982719B (it) 1974-10-21
ES415185A1 (es) 1976-02-16
CA974296A (en) 1975-09-09
BE800393A (fr) 1973-10-01
FR2186724A1 (fr) 1974-01-11
AU5637173A (en) 1974-12-05
DE2325869A1 (de) 1973-12-20
SU520060A3 (ru) 1976-06-30
JPS551663B2 (fr) 1980-01-16
AU468010B2 (en) 1975-12-18
MX2985E (es) 1980-01-23
SE378939B (fr) 1975-09-15

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