US3669735A - Method for activating a semiconductor electron emitter - Google Patents

Method for activating a semiconductor electron emitter Download PDF

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Publication number
US3669735A
US3669735A US69537A US3669735DA US3669735A US 3669735 A US3669735 A US 3669735A US 69537 A US69537 A US 69537A US 3669735D A US3669735D A US 3669735DA US 3669735 A US3669735 A US 3669735A
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Prior art keywords
semiconductor
cesium
sample
oxygen
strongly
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US69537A
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English (en)
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Dennis Glendon Fisher
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Burle Technologies Inc
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RCA Corp
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Assigned to NPD SUBSIDIARY INC., 38 reassignment NPD SUBSIDIARY INC., 38 ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: RCA CORPORATION
Assigned to BURLE INDUSTRIES, INC. reassignment BURLE INDUSTRIES, INC. MERGER (SEE DOCUMENT FOR DETAILS). PENNSYLVANIA, EFFECTIVE JULY 14, 1987 Assignors: NPD SUBSIDIARY, INC., 38
Assigned to BURLE TECHNOLOGIES, INC., A CORP. OF DE reassignment BURLE TECHNOLOGIES, INC., A CORP. OF DE ASSIGNMENT OF ASSIGNORS INTEREST. (SEE RECORD FOR DETAILS) Assignors: BURLE INDUSTRIES, INC., A CORP. OF PA
Assigned to BANCBOSTON FINANCIAL COMPANY reassignment BANCBOSTON FINANCIAL COMPANY SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BURLE INDUSTRIES, INC., A CORP. OF PA
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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
    • H01J9/20—Manufacture of screens on or from which an image or pattern is formed, picked up, converted or stored; Applying coatings to the vessel
    • H01J9/22—Applying luminescent coatings
    • H01J9/221—Applying luminescent coatings in continuous layers
    • 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
    • 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
    • H01J9/20—Manufacture of screens on or from which an image or pattern is formed, picked up, converted or stored; Applying coatings to the vessel
    • H01J9/22—Applying luminescent coatings
    • H01J9/227—Applying luminescent coatings with luminescent material discontinuously arranged, e.g. in dots or lines

Definitions

  • the invention relates generally to a method for increasing the electron emission into vacuum of semiconductor surfaces, and is particularly applicable where the semiconductor is a III-V compound.
  • Semiconductor compounds containing one or more elements from each of Groups III-A and V-A of the Periodic Table of the elements have been found to be particularly useful for emitting electrons intovacuum.
  • the electron emission efficiency of such emitters is especially high, since surfaces of these semiconductors can be activated with a strongly electronegative and a strongly electro-positive material such as oxygen and cesium, respectively, to produce a negative effective electron afiinity.
  • Semiconductor electron emitters and methods of activating them by sensitizing with low work function materials to increase photoemission are discussed, for example, in the following references:
  • a present method of activating a IIIV compound sample with cesium and oxygen includes first cleaning the sample of adsorbed gases and other contaminants by heating it in vacuum for about one minute to a temperature just below its decomposition temperature of about 650 C.700 C. The sample is then cooled to room temperature and sensitized by deposition of cesium and oxygen.
  • Sensitizing lowers the work function for electrons near the sample surface.
  • the photosensitivity of the sample is 3,669,735 Patented June 13, 1972 "ice monitored as an indication of the general electron emission performance. In some instances, optimum activation is achieved by resensitizing after each of one or more additional beatings at successively higher temperatures.
  • the word sensitizing as used here refers to any of a number of various known techniques for increasing electron emission from a surface by depositing other materials on the surface to lower the work function for electrons at the surface.
  • cesium and oxygen may be continually admitted to the chamber containing the sample, with the oxygen introduced intermittantly, as in the preferred embodiment.
  • oxygen may be continually admitted to the chamber, withthe cesium introduced intermittantly.
  • a single introduction of both cesium and oxygen may also be sufficient in some instances.
  • the novel method for activating a semiconductor electron emitter comprises sensitizing a surface of the semiconductor with at least a strongly electronegative material and a strongly electropositive material, then heating the semiconductor to between about 470 0:10 C. and 590 C.il0 C., and cooling, and then resensitizing the surface with at least a strongly electropositive material.
  • the novel method results in substantially increased electron emission, especially in III-V semiconductor compounds.
  • FIG. 1 is a partially sectional, partially schematic view of an apparatus for activating a semiconductor in accordance with a preferred embodiment of the novel method.
  • FIG. 2 is a flow chart of the preferred embodiment of the novel method as practiced with the apparatus of FIG. 1.
  • a layer sample 10 of indium gallium arsenide (In Ga As) about 1 cm. square and about 25 microns thick is epitaxially grown on one face of a 20 mils thick gallium arsenide crystal substrate 12.
  • the substrate 12 with the sample 10 is mounted in an ultra-high vacuum chamber 14 connected to a sputter-ion vacuum pump 16 with a pumping speed on the order of 500 liters per second at the chamber entrance.
  • the pump 16 is operated continuously during the entire activation to maintain the sample 10 in a relatively high vacuum as measured by an ionization gauge.
  • a loop of resistance heating wire 18 is mounted near the face of the substrate 12 which is opposite the sample 10.
  • a closed tube 20 containing at its extended end a small amount 21 of cesium metal.
  • the tube 20 is normally immersed in a flask 22 of liquid nitrogen to prevent unwanted cesium from vaporizing into the vacuum system.
  • an electrically insulating jacket 26 about which is coiled a resistance heating element 28.
  • pure oxygen passes from the atmosphere through the silver tube 24 and into the chamber 14.
  • the wall of the chamber 14 further contains a window 30.
  • a lumen light source 32 located outside the chamber directs light to the sample through the window 30. Photoemission from the sample is collected by an anode 36 near the sample 10 and measured by a current sensing device 34.
  • the sample is heated to a cleaning temperature of about 630 C. for a period of about 1 minute. Thereafter, it is cooled to room temperature of about 25 C. and sensitized with cesium and oxygen generally as follows: A small amount of cesium vapor is introduced into the chamber 14 by removal of the liquid nitrogen flask 24 and heating of the cesium-containing tube 20. When the photoemission of the sample 10 is observed to pass a peak, oxygen is introduced into the system in addition to the cesium by heating the silver tube 24. When the photoemission is observed to increase and to reach a.
  • the sample is heated to a temperature of about 535 C. for about one minute, then cooled back to room temperature and resensitized with cesium and oxygen as in the first sensitizing step above.
  • the novel method results in a completely unanticipated and substantial increase in photoemission from a semiconductor as compared to present methods.
  • the following chart shows a comparison of the photoemission of samples processed first by present methods and then by the novel method.
  • the column labeled A indicates the maximum photoemissions in microamperes per lumen from separate samples which have been sensitized with cesium and oxygen either after a single heating step or after each of one or more additional heatings at successively higher temperatures.
  • the column labeled "B indicates the maximum photoemission in microamperes per lumen from the same samples, but which have in accordance with the novel method undergone a lower temperature heating step followed by a resensitizing with cesium and oxygen.
  • the sensitizing of the semiconductor surface is with cesium and oxygen
  • a strongly electropositive and a strongly electronegative material respectively
  • other combinations of strongly electropositive and strongly electronegative materials are suitable for practicing the novel method.
  • the strongly electropositive elements are, for instance, alkali or alkaline earth metals such as cesium and barium.
  • the strongly electronegative materials are, for instance, calcogens and halogens such as oxygen and fluorine.
  • ultra-high vacuum of 10- torr or less pressure is desirable throughout activation, it is not necessarily critical.
  • a lower vacuum may require more extensive cleaning, such as a longer first heating step.
  • IHV semiconductors are generally cleaned by heating in a vacuum to at least 600 C.
  • the novel method does not appear to depend on a particular cleaning technique.
  • Other known cleaning techniques which may be used for obtaining a clean semiconductor sample are, for instance, bombardment with an inert gas such as argon and subsequent annealing. Such a. technique is often used with silicon, since silicon doesnot readily clean by baking at high temperatures. For best results, the sensitizing should be done with the temperature of the sample at below 200 C.
  • the temperature of the sample was measured with a calibrated infra-red sensitive optical device.
  • Other means such as a thermocouple, may also be used.
  • any of the varioun available temperature measurement means will give the absolute temperature of the sample.
  • the temperature as measured herein is believed to be within about 10 C. of the absolute temperature of the sample.
  • the temperature range of the heating step of the novel method was measured to be from 470 C. l0 C. to 590 C.il0 C. Heating temperatures in the central portion of the range, near 535 C., result in considerably better electron emission from the sample than temperatures near the ends of the range, but temperatures from any portion of the region result in some improvement.
  • the optimum temperature varies somewhat with the time for which the sample is held at that temperature. Lower temperatures generally require longer time.
  • a method for activating a semiconductor electron emitter comprising:
  • steps (a), (b), (c), and (d) are carried out while said semiconductor is a vacuum having a pressure on the order of 10- torr or less.
  • step ,(a) is with a strongly electropositive material and a strongly electronegative material until said semiconductor exhibits a substantially maximum electron emission as a result of such sensitizing.
  • step (d) is with a strongly electropositive material and to a strongly electronegative material until said semiconductor exhibits a substantially maximum electron emission as a result of such sensitizing.
  • sensitizing is with cesium and oxygen
  • heating after said sensitizing is to about 535 C.
  • cooling is to less than 200 C.
  • resensitizing is with cesium and oxygen.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Cleaning Or Drying Semiconductors (AREA)
  • Cold Cathode And The Manufacture (AREA)
US69537A 1970-09-04 1970-09-04 Method for activating a semiconductor electron emitter Expired - Lifetime US3669735A (en)

Applications Claiming Priority (1)

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US6953770A 1970-09-04 1970-09-04

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US3669735A true US3669735A (en) 1972-06-13

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US (1) US3669735A (de)
JP (1) JPS5120153B1 (de)
DE (1) DE2127658A1 (de)
FR (1) FR2105234B1 (de)
GB (1) GB1321005A (de)
NL (1) NL7106981A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3811002A (en) * 1971-08-17 1974-05-14 Philips Corp Method of manufacturing an electric discharge tube having an electron emitting electrode comprising a cesium-containing layer on a support
US3894258A (en) * 1973-06-13 1975-07-08 Rca Corp Proximity image tube with bellows focussing structure
US4019082A (en) * 1975-03-24 1977-04-19 Rca Corporation Electron emitting device and method of making the same
CN110706989A (zh) * 2019-10-30 2020-01-17 南京工程学院 提高GaAs光电阴极稳定性的Cs/NF3激活方法

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1555762A (en) * 1975-08-14 1979-11-14 Mullard Ltd Method of cleaning surfaces
JPS58114027U (ja) * 1982-01-28 1983-08-04 松下電工株式会社 安定器取付構造
JPS5998636U (ja) * 1982-12-21 1984-07-04 明治ナシヨナル工業株式会社 放電灯用安定器装置

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3811002A (en) * 1971-08-17 1974-05-14 Philips Corp Method of manufacturing an electric discharge tube having an electron emitting electrode comprising a cesium-containing layer on a support
US3894258A (en) * 1973-06-13 1975-07-08 Rca Corp Proximity image tube with bellows focussing structure
US4019082A (en) * 1975-03-24 1977-04-19 Rca Corporation Electron emitting device and method of making the same
CN110706989A (zh) * 2019-10-30 2020-01-17 南京工程学院 提高GaAs光电阴极稳定性的Cs/NF3激活方法

Also Published As

Publication number Publication date
DE2127658A1 (de) 1972-03-09
GB1321005A (en) 1973-06-20
FR2105234B1 (de) 1977-11-18
DE2127658B2 (de) 1979-03-29
FR2105234A1 (de) 1972-04-28
JPS5120153B1 (de) 1976-06-23
NL7106981A (de) 1972-03-07

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Free format text: SECURITY INTEREST;ASSIGNOR:BURLE INDUSTRIES, INC., A CORP. OF PA;REEL/FRAME:004940/0952

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