US3890525A - Photoconductive target of an image pickup tube comprising graded selenium-tellurium layer - Google Patents
Photoconductive target of an image pickup tube comprising graded selenium-tellurium layer Download PDFInfo
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- US3890525A US3890525A US370446A US37044673A US3890525A US 3890525 A US3890525 A US 3890525A US 370446 A US370446 A US 370446A US 37044673 A US37044673 A US 37044673A US 3890525 A US3890525 A US 3890525A
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- conductive layer
- type conductive
- image pickup
- tellurium
- pickup tube
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- 229910052714 tellurium Inorganic materials 0.000 title claims abstract description 47
- 239000011669 selenium Substances 0.000 claims abstract description 47
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 claims abstract description 43
- 229910052711 selenium Inorganic materials 0.000 claims abstract description 32
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 claims abstract description 28
- 239000000758 substrate Substances 0.000 claims abstract description 24
- 239000000203 mixture Substances 0.000 claims abstract description 16
- UHYPYGJEEGLRJD-UHFFFAOYSA-N cadmium(2+);selenium(2-) Chemical compound [Se-2].[Cd+2] UHYPYGJEEGLRJD-UHFFFAOYSA-N 0.000 claims description 11
- 239000000126 substance Substances 0.000 claims description 9
- 229910052785 arsenic Inorganic materials 0.000 claims description 7
- 229910052751 metal Inorganic materials 0.000 claims description 6
- 239000002184 metal Substances 0.000 claims description 6
- 229910052738 indium Inorganic materials 0.000 claims description 5
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 4
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- 229910052787 antimony Inorganic materials 0.000 claims description 4
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims description 4
- SBIBMFFZSBJNJF-UHFFFAOYSA-N selenium;zinc Chemical compound [Se]=[Zn] SBIBMFFZSBJNJF-UHFFFAOYSA-N 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- 229910052718 tin Inorganic materials 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 239000010936 titanium Substances 0.000 claims description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 239000010410 layer Substances 0.000 description 119
- 239000010408 film Substances 0.000 description 32
- 230000035945 sensitivity Effects 0.000 description 19
- 239000000463 material Substances 0.000 description 14
- 238000000034 method Methods 0.000 description 14
- 230000008020 evaporation Effects 0.000 description 9
- 238000001704 evaporation Methods 0.000 description 9
- 239000000306 component Substances 0.000 description 7
- 239000004065 semiconductor Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 239000011521 glass Substances 0.000 description 5
- 230000004044 response Effects 0.000 description 5
- 238000002425 crystallisation Methods 0.000 description 4
- 230000008025 crystallization Effects 0.000 description 4
- 238000010894 electron beam technology Methods 0.000 description 4
- 239000010409 thin film Substances 0.000 description 4
- 230000002411 adverse Effects 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000003595 spectral effect Effects 0.000 description 3
- 229910004613 CdTe Inorganic materials 0.000 description 2
- 206010070834 Sensitisation Diseases 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052732 germanium Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000008313 sensitization Effects 0.000 description 2
- 229910052715 tantalum Inorganic materials 0.000 description 2
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 2
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 2
- 229910001887 tin oxide Inorganic materials 0.000 description 2
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- YYDHEZLTMPKETQ-UHFFFAOYSA-N [Te].[Se] Chemical compound [Te].[Se] YYDHEZLTMPKETQ-UHFFFAOYSA-N 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 239000003708 ampul Substances 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910003437 indium oxide Inorganic materials 0.000 description 1
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 229910052740 iodine Inorganic materials 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
Images
Classifications
-
- 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
- H01J29/39—Charge-storage screens
- H01J29/45—Charge-storage screens exhibiting internal electric effects caused by electromagnetic radiation, e.g. photoconductive screen, photodielectric screen, photovoltaic screen
- H01J29/451—Charge-storage screens exhibiting internal electric effects caused by electromagnetic radiation, e.g. photoconductive screen, photodielectric screen, photovoltaic screen with photosensitive junctions
- H01J29/456—Charge-storage screens exhibiting internal electric effects caused by electromagnetic radiation, e.g. photoconductive screen, photodielectric screen, photovoltaic screen with photosensitive junctions exhibiting no discontinuities, e.g. consisting of uniform 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
- H01J9/20—Manufacture of screens on or from which an image or pattern is formed, picked up, converted or stored; Applying coatings to the vessel
- H01J9/233—Manufacture of photoelectric screens or charge-storage screens
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
Definitions
- FIG. 1 A first figure.
- FIG. 3 220:: ZOEmOmZOU THICKNESS 0F FILM (F PATEN'IEIIJIIII I 7 I975 COMPOSITION (ATOMIC 95)
- FIG. 3
- the present invention relates generally to the construction of a photoconductive layer used for the target of an image pickup tube of the vidicon type, or more particularly to a photoconductive layer with a rectifying contact which has an increased sensitivity and an improved spectral sensitivity to red light.
- Sb S PbO and Si are widely used as materials of photoconductive layers for the target of the vidicon type image pickup tube.
- Sb S constitutes a photoconductive layer of injecting contact type
- PhD and Si are used for the photoconductive layers of rectifying contact or junction type.
- the advantages of the photoconductive layer of rectifying contact or junction type over that of injection type are a higher response speed, small dark current and higher sensitivity.
- the photoconductive materials capable of forming a rectifying contact successfully used as a target of the image pickup tube are limited, and it is difficult to obtain a photoconductive material with properties suitable in all respects.
- the peak of spectral sensitivity for example, is located in the proximity of infrared range for Si and on the side of visible short wavelength for PhD, with the result that if they are used for a color image pickup tube, Si and PbO have insufficient sensitivity to blue and red respectively.
- the inventors have found that amorphous selenium is also capable of forming a rectifying contact suitable for the target of the image pickup tube, but this material also has the disadvantage of insufficient sensitivity to red light.
- U.S. Pat, No. 3,350,595 A method to improve the sensitivity to red light is disclosed in U.S. Pat, No. 3,350,595.
- a conductive thin film is deposited on an insulating substrate which is in turn covered with a photoconductive layer comprising mainly a mixture of tellurium and selenium.
- the surface portion of the photoconductive layer adjacent to the conductive thin film contains selenium of 70 to 80 by weight while the opposite surface portion thereof includes selenium of 90 to I by weight, the selenium content gently changing between both the surface portions.
- the tellurium content in the photoconductive layer near the interface thereof with the conductive thin film is high is accompanied by the disadvantage of increased dark current.
- U.S. Pat. No. 3,350,595 discloses a method in which a blocking layer of such metal as cesium with small work function is interposed between the conductive film and the photoconductive layer. This method, however, is disadvantageous in that the manufacturing processes are complicated.
- the object of the present invention is to obviate the above-mentioned disadvantages and to provide a photoconductive target of an image pickup tube which is high in sensitivity to red light, small in dark current and is easily manufactured.
- the photoconductive target of the image pickup tube comprises a light-transmitting substrate, a first N-type conductive layer deposited on said substrate and a P-type conductive layer making a rectifying contact with said first N-type conductive layer, said P-type conductive layer including at least selenium and tellurium, the composition of said P-type conductive layer being different along the direction of the thickness thereof, the average content of selenium in said P-type conductive layer being not less than 50 atomic percent, the content of tellurium at both surfaces of said P-type conductive layer being not more than l0 atomic percent, the maximum tellurium content of 10 to 40 atomic percent being located on a plane in said P-type conductive layer nearer to said first N-type conductive layer than the middle plane of said P-type conductive layer.
- the N-type conductive layer is a light-transmitting conductive film preferably including as its main component an oxide of tin, indium or titanium. Further, to prevent the crystallization of the P-type conductive layer, an N-type conductive layer formed of one substance selected from the group consisting of CdS, CdSe, ZnS, ZnSe and a mixture thereof may be interposed between the P-type conductive layer and the light-transmitting conductive film or a translucent metal making up the surface portion of the light-transmitting substrate nearer to the side of the N-type conductive film.
- the P-type conductive layer may include As, Sb, P, Bi, Ge and/or Si in addition to selenium and tellurium.
- Amorphous selenium is generally of P conduction type and forms a rectifying contact with a variety of N- type materials including films of single crystals or crystallites of such lV group semiconductors as Ge and Si, [I] V group semiconductors such as GaAs and GaP and II VI group semiconductors.
- the most suitable material of N-type conduction to form a photoconductive layer for the target of an image pickup tube in combination with selenium are an oxide of tin used for a transparent conductive film, an oxide of indium, an oxide of titanium, and II Vl group semiconductors such as ZnS, ZnSe, CdS and CdSe.
- the II Vl group semiconductors cannot be used as such an electrode at the same time without additional provision of the transparent electrode of any of the above-mentioned oxides or a translucent metal laid thereon.
- FIG. I is a sectional view showing the fundamental construction of the target of the image pickup tube according to the present invention.
- FIGS. 2 to 5 are graphs illustrating the distribution of component elements along the direction of the thickness of the P-type photoconductive layer.
- the target of an image pickup tube according to the invention generally comprises a glass substrate 1, a transparent electrode 2 extended on the glass substrate 1, an N-type conductive layer 3 and a P-type conductive layer 4.
- Reference numeral 5 shows incident light, and numeral 6 a scanning electron beam.
- a rectifying contact is formed between the N-type conductive layer 3 and the P-type conductive layer 4.
- the transparent electrode 2 is formed of an oxide of N-type conductivity
- the transparent electrode 2 and the N-type conductive electrode 3 are actually integrated into a single layer.
- sensitization is necessary to improve the sensitivity to red light since the abovementioned materials other than CdSe do not have sen sitivity to red light.
- a well-known method to improve sensitivity of ll Vl group to red light consists in doping into it Cl, Br, I, In, Ga or other elements acting as a donor together with Cu, Ag or the like element forming an acceptor.
- the sensitivity to red light is successfully improved in combination with the above-mentioned method concerning the sensitization of the N-type conductive layer of ll Vl group semiconductor.
- the sensitivity to red light can be improved by adding Te to amorphous selenium.
- the electrical resistance of Se to which Te has been added is sharply reduced. thereby degrading the char-- acteristics ofthe target of the image pickup tube. If, for example, the concentration of Te in the neighborhood ofthe interface between N-type conductive layer 3 and P-type conductive layer 4 is increased, the reverse breakdown voltage of the rectifying contact is decreased thereby to increase the dark current in the image pickup tube.
- the Te concentration of the P- type conductive layer 4 as a whole is increased, the resistance of the P-type layer is decreased or the carrier mobility in the layer is reduced, with the result that the dark current is increased or the time response characteristics are degraded.
- the intensity of electric field in such a portion is decreased for the degradation of the response characteristic thereof, and therefore it is necessary to maintain the Te concentration in that portion in the range from O to 10 atomic percent.
- the Te concentration of as little as l0 atomic percent in the P-type conductive layer cannot achieve sufficient improvement in sensitivity to red light.
- the most effective method to improve the sensitivity to red light is to provide a portion between the surfaces of the P-type conductive layer with the main component of Se where the Te concentration is maximum. If the excitation of carriers is to be effected satisfactorily at the point of high Te concentration, it is desirable that such a portion be located at a position the nearest possible to the plane of incidence ofa light signal into the P-type conductive layer, that is, the interface thereof with the N-type conductive layer. In other words, the
- portion of maximum Te concentration should be located on a plane in the P-type conductive layer nearer to the N-type conductive layer than the middle plane of the P-type conductive layer.
- Te concentration should preferably be between [0 to 40 atomic percent.
- Te is not necessarily required to be smoothly distributed in the P-type conductive layer, but it may consist of a laminated structure of a multiplicity of films each about 10 A thick comprising films of high Te concentration and films of low Te concentration laid one on another. For this reason, it should be noted that the abovementioned range of Te concentration from 10 to 40 atomic percent represents an average value in the region several hundred A thick including the portion of maximum Te concentration.
- the progressive change in Te concentration in the transverse direction of the P-type conductive layer may be abrupt in the microscopic order of, say, several tens of A. Somewhat macroscopically, however, the curve of the change should preferably be gentle in the order of several hundreds of A. If macroscopically there is a portion where the Te concentration is discontinued, the burning effect of the image pickup tube may be promoted.
- the disadvantage of the photoconductive layer with Se as a main component resides in that the layer is easily crystallized by heat, with the result that the picture produced is accompanied by defects in the form of white dots.
- an element such as As, Sb, P, Bi, Ge or Si is added to the material for the layer thereby to increase the viscosity thereof and delay the speed of crystallization.
- This principle also applies to the present invention, wherein the life of the target may be lengthened by adding such an element to the P-type conductive layer thereby to reduce the speed of crystallization.
- the addition of excessive amount of the element adversely affects the response characteristic of the target, the desirable amount of the element to be added being less than 20 atomic percent.
- An effective method to prevent the above-mentioned phenomena is to deposit by vacuum or gaseous evaporation on the P-type conductive layer a film of Sb S As Se or A5 8 approximately 1000 A thick.
- evaporation boats of tantalum are deposited simultaneously by evaporation in the vacuum of 3 X It) Torr on a transparent N-type conductive layer with tin oxide as a main component which is formed on a glass substrate.
- a P-type photoconductive layer as thick as 3 pm is produced.
- compositional profile of the P-type photoconductive layer is adjusted by controlling the current in each boat so as to be in consistence with the graph as shown in FIG. 2. Further, an Sb S film approximately 1000 A thick is deposited by evaporation on the sur face of the P-type photoconductive layer in the lowpressure argon of 5 X 10 Torr thereby to improve the landing characteristic of the scanning beam for the target of an image pickup tube.
- Embodiment 2 A transparent N-type layer consisting mainly of indium oxide is deposited on a glass substrate.
- a CdSe film 2000 A thick is further deposited in the vacuum of 2 X 10 Torr at the substrate temperature of 200C, on the surface ofa transparent N-type conductive layer by evaporation.
- a first photoconductive material of Se containing Te of 40 atomic percent and a second photoconductive material of Se containing As of IO atomic percent are prepared in a quartz ampule. These two types of photoconductive materials are crushed and put into different evaporation boats of tantalum and then they are simultaneously deposited on the CdSe layer in the vacuum of 3 X lo Torr.
- the speed of evaporation of the first and second photoconductive materials is continuously changed to form a film 4 pm thick with the composition distribution of Se, Te and As as shown in the graph of FIG. 3.
- a film of A5 Se approximately 500 A thick in the vacuum of 3 X 10 Torr.
- This As Se film is further covered by a similar method with an As Se film about 500 A thick in the low-pressure argon of 5 X l Torr.
- This double layer of As Se is formed for the purpose of improving the landing characteristic of the scanning electron beam.
- Embodiment 3 A translucent A] film is formed on a glsss substrate in the vacuum of l X l0 Torr at the substrate temperature of 150C, and then on this translucent Al film is deposited a CdS film 3000 A thick in the vacuum of X 10 Torr at the substrate temperature of l50C.
- the current in the Te boat or the opening of a slit interposed between the Te evaporation boat and the substrate is controlled continuously thereby to produce a macroscopic profile of transverse distribution of composition as shown in H0. 4.
- On this multiple layer is further deposited an A5 5 film about 500 A thick in the vacuum of 2 X l0 Torr thereby to improve the landing characteristic of the scanning electron beam.
- Embodiment 4 Films of CdSe, CdTe and Se are deposited one after another in the vacuum of 5 X 10 Torr on a transparent N-type conductive electrode with tin oxide as a main component which is in turn deposited on a glass substrate.
- a multiple layer 2 pm thick comprising 2000 to 4000 films of CdSe, CdTe and Se each having the average thickness of 10 A or less is obtained.
- the macroscopic composition of the elements in the transverse direction of the layer is controlled by similar means to those employed in the preceding embodiment thereby to obtain the profile of composition as shown in FIG. 5.
- the sensitivity especially to red light is improved without adverse effect on the rectifying contact with the N-type photoconductive layer by distributing Te in a P-type photoconductive layer containing Sc or 50 or more atomic percent in such a manner that the maximum Te content is located on a plane in the P-type conductive layer nearer to the N-type conductive layer than the middle plane of the Ptype conductive layer.
- the spectral sensitivity of the P-type conductive layer is thus changed greatly, making it possible to produce a photoconductive layer suitable for a specific purpose.
- a photoconductive target of an image pickup tube comprising a light-transmitting substrate, a first N-type conductive layer deposited on said substrate and a P- type conductive layer making a rectifying contact at a first surface thereof with said first N-type conductive layer and having a second outer surface to be scanned by electrons, said P-type conductive layer including at least selenium and tellurium, the composition of said P-type conductive layer being different along the direction of the thickness thereof, the average content of selenium in said P-type conductive layer being not less than 50 atomic percent, the content of tellurium at said first and second surfaces of said P-type conductive layer being not more than 10 atomic percent, the maximum tellurium content of 10 to 40 atomic percent being located on a plane in said P-type conductive layer between said first N-type conductive layer and the middle plane of said P-type conductive layer.
- said first N-type conduc tive layer is a transparent conductive film including one substance selected from the group consisting of an oxide of tin. indium, and titanium as a main compo nent.
- a photoconductive target of an image pickup tube according to claim I wherein a second N-type conductive layer formed of one substance selected from the group consisting of CdS, CdSe. ZnS, ZnSe and the mixture thereof is interposed between said P-type conductive layer and said first N-type conductive layer or a translucent metal electrode constituting the surface portion of said lighttransmitting substrate on the side of said first N-type conductive layer.
- a photoconductive target of an image pickup tube according to claim I wherein said P-type conductive layer contains one substance selected from the group consisting of As, Sb. P. Bi, Ge, Si and the mixture thereof in addition to selenium and tellurium.
- a photoconductive target of an image pickup tube wherein the concentration of said one substance in said P-type conductive layer is substantially uniform therethrough.
- a photoconductive target of an image pickup tube wherein the minimum concentra tion of said selenium in said P-type conductive layer is located at the location of said maximum tellurium content in said P-type conductive layer.
- a photoconductive target of an image pickup tube wherein the maximum concentration of said Cd in said P-type conductive layer is located at the location of said maximum tellurium content in said P-type conductive layer.
- a photoconductive target of an image pickup tube wherein the absolute rate of increase of the tellurium content in said P-type conductive layer as the location of said maximum tellurium content is approached is equal to the absolute rate of decrease of the tellurium content as the location of said maximum tellurium content is passed.
- a photoconductive target of an image pickup tube wherein the absolute rate of increase of the tellurium content in said P-type conductive layer as the location of said maximum tellurium content is approached is greater than the absolute rate of decrease of the tellurium content as the location of said maximum tellurium content is passed.
Abstract
A photoconductive target of an image pickup tube comprising a light-transmitting substrate, an N-type conductive layer deposited on the substrate and a P-type conductive layer making a rectifying contact with the N-type conductive layer, in which the P-type conductive layer includes at least selenium and tellurium, the composition of the P-type layer changes along the direction of the thickness of the layer, the average content of selenium in the P-type conductive layer is not less than 50 atomic percent, the content of tellurium at both surfaces of the P-type conductive layer is not more than 10 atomic percent, and the maximum tellurium content of 10 to 40 atomic percent is located on a plane in the P-type conductive layer nearer to the N-type conductive layer than the middle plane of the P-type conductive layer.
Description
United States Patent Hirai et al.
[ PHOTOCONDUCTIVE TARGET OF AN IMAGE PICKUP TUBE COMPRISING GRADED SELENIUM-TELLURIUM LAYER [75] Inventors: Tadaaki Hirai, Koganei; Eiichi Maruyama, Kodaira; Kiyohisa lnao, Hachioji; Hideaki Yamamoto, Kokubunji; Naohiro Goto; Yukinao lsozaki, both of Machida; Keiichi Shidara; Teruo Uchida, both of Tokyo. all of Japan [73] Assignees: Hitachi, Ltd.; Nippon Hoso Kyol-tai,
both of Japan [22] Filed: June 15, 1973 [21] Appl. No.: 370,446
[52] U.S. Cl 313/386; 313/94 [51] Int. Cl l-lOij 29/45; H0lj 31/38 [58] Field of Search 3l3/386, 385, 384, 65 A [56] References Cited UNITED STATES PATENTS 3,346,755 l0/l967 Dresner 3l3/65 A June 17, 1975 3,350,595 lO/l967 Kramer 313/65 A X Primary Examiner--Robert Segal Attorney, Agent, or Firm-Craig & Antonelli [57] ABSTRACT A photoconductive target of an image pickup tube comprising a light-transmitting substrate, an N-type conductive layer deposited on the substrate and a P- type conductive layer making a rectifying contact with the N-type conductive layer, in which the P-type conductive layer includes at least selenium and tellurium, the composition of the P-type layer changes along the direction of the thickness of the layer, the average content of selenium in the P-type conductive layer is not less than 50 atomic percent, the content of tellurium at both surfaces of the P-type conductive layer is not more than l0 atomic percent, and the maximum tellurium content of 10 to 40 atomic percent is located on a plane in the P-type conductive layer nearer to the N-type conductive layer than the middle plane of the P-type conductive layer.
10 Claims, 5 Drawing Figures PATENTEDJUII I 7 I975 SlIEEI FIG. 5
FIG.
3 220.53 ZOEmOnSOO I/ 1/ |\l L /1 FIG. 2
3 220:: ZOEmOmZOU THICKNESS 0F FILM (F PATEN'IEIIJIIII I 7 I975 COMPOSITION (ATOMIC 95) FIG. 3
1 PHOTOCONDUCTIVE TARGET OF AN IMAGE PICKUP TUBE COMPRISING GRADED SELENIUM-TELLURIUM LAYER The present invention relates generally to the construction of a photoconductive layer used for the target of an image pickup tube of the vidicon type, or more particularly to a photoconductive layer with a rectifying contact which has an increased sensitivity and an improved spectral sensitivity to red light.
Sb S PbO and Si are widely used as materials of photoconductive layers for the target of the vidicon type image pickup tube. Among these materials, Sb S constitutes a photoconductive layer of injecting contact type, while PhD and Si are used for the photoconductive layers of rectifying contact or junction type. The advantages of the photoconductive layer of rectifying contact or junction type over that of injection type are a higher response speed, small dark current and higher sensitivity. However, the photoconductive materials capable of forming a rectifying contact successfully used as a target of the image pickup tube are limited, and it is difficult to obtain a photoconductive material with properties suitable in all respects.
The peak of spectral sensitivity, for example, is located in the proximity of infrared range for Si and on the side of visible short wavelength for PhD, with the result that if they are used for a color image pickup tube, Si and PbO have insufficient sensitivity to blue and red respectively. The inventors have found that amorphous selenium is also capable of forming a rectifying contact suitable for the target of the image pickup tube, but this material also has the disadvantage of insufficient sensitivity to red light.
A method to improve the sensitivity to red light is disclosed in U.S. Pat, No. 3,350,595. According to this method, a conductive thin film is deposited on an insulating substrate which is in turn covered with a photoconductive layer comprising mainly a mixture of tellurium and selenium. The surface portion of the photoconductive layer adjacent to the conductive thin film contains selenium of 70 to 80 by weight while the opposite surface portion thereof includes selenium of 90 to I by weight, the selenium content gently changing between both the surface portions. However, the fact that the tellurium content in the photoconductive layer near the interface thereof with the conductive thin film is high is accompanied by the disadvantage of increased dark current. In order to overcome this disadvantage, U.S. Pat. No. 3,350,595 discloses a method in which a blocking layer of such metal as cesium with small work function is interposed between the conductive film and the photoconductive layer. This method, however, is disadvantageous in that the manufacturing processes are complicated.
The object of the present invention is to obviate the above-mentioned disadvantages and to provide a photoconductive target of an image pickup tube which is high in sensitivity to red light, small in dark current and is easily manufactured.
In order to achieve the above-mentioned object, the photoconductive target of the image pickup tube according to the invention comprises a light-transmitting substrate, a first N-type conductive layer deposited on said substrate and a P-type conductive layer making a rectifying contact with said first N-type conductive layer, said P-type conductive layer including at least selenium and tellurium, the composition of said P-type conductive layer being different along the direction of the thickness thereof, the average content of selenium in said P-type conductive layer being not less than 50 atomic percent, the content of tellurium at both surfaces of said P-type conductive layer being not more than l0 atomic percent, the maximum tellurium content of 10 to 40 atomic percent being located on a plane in said P-type conductive layer nearer to said first N-type conductive layer than the middle plane of said P-type conductive layer. The N-type conductive layer is a light-transmitting conductive film preferably including as its main component an oxide of tin, indium or titanium. Further, to prevent the crystallization of the P-type conductive layer, an N-type conductive layer formed of one substance selected from the group consisting of CdS, CdSe, ZnS, ZnSe and a mixture thereof may be interposed between the P-type conductive layer and the light-transmitting conductive film or a translucent metal making up the surface portion of the light-transmitting substrate nearer to the side of the N-type conductive film. The P-type conductive layer may include As, Sb, P, Bi, Ge and/or Si in addition to selenium and tellurium.
Amorphous selenium is generally of P conduction type and forms a rectifying contact with a variety of N- type materials including films of single crystals or crystallites of such lV group semiconductors as Ge and Si, [I] V group semiconductors such as GaAs and GaP and II VI group semiconductors. Among them, the most suitable material of N-type conduction to form a photoconductive layer for the target of an image pickup tube in combination with selenium are an oxide of tin used for a transparent conductive film, an oxide of indium, an oxide of titanium, and II Vl group semiconductors such as ZnS, ZnSe, CdS and CdSe. Although the low intrinsic resistance of conductive films of the above-mentioned oxides makes it possible to use them also as an electrode for taking out a signal from the image pickup tube, the II Vl group semiconductors cannot be used as such an electrode at the same time without additional provision of the transparent electrode of any of the above-mentioned oxides or a translucent metal laid thereon.
The better understanding of the present invention will be gained from the following description taken in conjunction with the accompanying drawings in which:
FIG. I is a sectional view showing the fundamental construction of the target of the image pickup tube according to the present invention; and
FIGS. 2 to 5 are graphs illustrating the distribution of component elements along the direction of the thickness of the P-type photoconductive layer.
An embodiment of the invention is shown in FlG. I. The target of an image pickup tube according to the invention generally comprises a glass substrate 1, a transparent electrode 2 extended on the glass substrate 1, an N-type conductive layer 3 and a P-type conductive layer 4. Reference numeral 5 shows incident light, and numeral 6 a scanning electron beam. A rectifying contact is formed between the N-type conductive layer 3 and the P-type conductive layer 4.
[n the case where the transparent electrode 2 is formed of an oxide of N-type conductivity, the transparent electrode 2 and the N-type conductive electrode 3 are actually integrated into a single layer. In the event that amorphous selenium and the above-mentioned oxide or a ll VI group semiconductor are used as the materials of the P-type conductive layer and the N-type conductive layer respectively, sensitization is necessary to improve the sensitivity to red light since the abovementioned materials other than CdSe do not have sen sitivity to red light.
A well-known method to improve sensitivity of ll Vl group to red light consists in doping into it Cl, Br, I, In, Ga or other elements acting as a donor together with Cu, Ag or the like element forming an acceptor. In the case where a P-type conductive layer including selenium is involved as in the present invention, the sensitivity to red light is successfully improved in combination with the above-mentioned method concerning the sensitization of the N-type conductive layer of ll Vl group semiconductor.
It is also well known that the sensitivity to red light can be improved by adding Te to amorphous selenium. The electrical resistance of Se to which Te has been added is sharply reduced. thereby degrading the char-- acteristics ofthe target of the image pickup tube. If, for example, the concentration of Te in the neighborhood ofthe interface between N-type conductive layer 3 and P-type conductive layer 4 is increased, the reverse breakdown voltage of the rectifying contact is decreased thereby to increase the dark current in the image pickup tube.
On the other hand, if the Te concentration of the P- type conductive layer 4 as a whole is increased, the resistance of the P-type layer is decreased or the carrier mobility in the layer is reduced, with the result that the dark current is increased or the time response characteristics are degraded.
The results of research by the inventors show that in improving the sensitivity of the Se conductive layer to red light by the use of Te, it is recommended that Te concentration in the Sc conductive layer be made pro gressively higher toward the side of the N-type conductive layer rather than uniformly distributing it, and the Te concentration at and in the vicinity of the interface between N-type conductive layer and P-type conductive layer is maintained at a low level, thus making it possible to prevent dark current from being increased without adversely affecting the characteristics of the target of the image pickup tube. For this purpose, it is necessary to limit the Te concentration at and in the vi cinity of the interface to a level ranging from to atomic percent. Also, if there is Te included in a considerable portion of the P-type conductive layer toward the opposite surface thereof, the intensity of electric field in such a portion is decreased for the degradation of the response characteristic thereof, and therefore it is necessary to maintain the Te concentration in that portion in the range from O to 10 atomic percent.
The Te concentration of as little as l0 atomic percent in the P-type conductive layer cannot achieve sufficient improvement in sensitivity to red light. In view of this, the most effective method to improve the sensitivity to red light is to provide a portion between the surfaces of the P-type conductive layer with the main component of Se where the Te concentration is maximum. If the excitation of carriers is to be effected satisfactorily at the point of high Te concentration, it is desirable that such a portion be located at a position the nearest possible to the plane of incidence ofa light signal into the P-type conductive layer, that is, the interface thereof with the N-type conductive layer. In other words, the
portion of maximum Te concentration should be located on a plane in the P-type conductive layer nearer to the N-type conductive layer than the middle plane of the P-type conductive layer.
Since an excessively high Te concentration in that portion results in an increased dark current, the maximum value of Te concentration should preferably be between [0 to 40 atomic percent. As will be explained later with reference to an embodiment, Te is not necessarily required to be smoothly distributed in the P-type conductive layer, but it may consist of a laminated structure of a multiplicity of films each about 10 A thick comprising films of high Te concentration and films of low Te concentration laid one on another. For this reason, it should be noted that the abovementioned range of Te concentration from 10 to 40 atomic percent represents an average value in the region several hundred A thick including the portion of maximum Te concentration.
The progressive change in Te concentration in the transverse direction of the P-type conductive layer may be abrupt in the microscopic order of, say, several tens of A. Somewhat macroscopically, however, the curve of the change should preferably be gentle in the order of several hundreds of A. If macroscopically there is a portion where the Te concentration is discontinued, the burning effect of the image pickup tube may be promoted.
The disadvantage of the photoconductive layer with Se as a main component resides in that the layer is easily crystallized by heat, with the result that the picture produced is accompanied by defects in the form of white dots. By a well-known method to prevent the defects, an element such as As, Sb, P, Bi, Ge or Si is added to the material for the layer thereby to increase the viscosity thereof and delay the speed of crystallization. This principle also applies to the present invention, wherein the life of the target may be lengthened by adding such an element to the P-type conductive layer thereby to reduce the speed of crystallization. The addition of excessive amount of the element adversely affects the response characteristic of the target, the desirable amount of the element to be added being less than 20 atomic percent.
When the element for prevention of the crystallization coexists with tellurium for improving the sensitivity, the maintaining of superior dark current and response characteristics require that selenium accounts for at least 50 atomic percent.
The fact that the emission of secondary electrons from the photoconductive layer containing much Se used as a target is comparatively great disturbs the landing of the scanning beam and often causes abnormal phenomena including the distortion of an image and the reversal ofa polarity ofa video signal at a high target voltage.
An effective method to prevent the above-mentioned phenomena is to deposit by vacuum or gaseous evaporation on the P-type conductive layer a film of Sb S As Se or A5 8 approximately 1000 A thick.
Embodiments of the invention will be explained below.
The compositional profile of the P-type photoconductive layer is adjusted by controlling the current in each boat so as to be in consistence with the graph as shown in FIG. 2. Further, an Sb S film approximately 1000 A thick is deposited by evaporation on the sur face of the P-type photoconductive layer in the lowpressure argon of 5 X 10 Torr thereby to improve the landing characteristic of the scanning beam for the target of an image pickup tube.
Embodiment 2 A transparent N-type layer consisting mainly of indium oxide is deposited on a glass substrate. A CdSe film 2000 A thick is further deposited in the vacuum of 2 X 10 Torr at the substrate temperature of 200C, on the surface ofa transparent N-type conductive layer by evaporation. On the other hand, a first photoconductive material of Se containing Te of 40 atomic percent and a second photoconductive material of Se containing As of IO atomic percent are prepared in a quartz ampule. These two types of photoconductive materials are crushed and put into different evaporation boats of tantalum and then they are simultaneously deposited on the CdSe layer in the vacuum of 3 X lo Torr. In the process, the speed of evaporation of the first and second photoconductive materials is continuously changed to form a film 4 pm thick with the composition distribution of Se, Te and As as shown in the graph of FIG. 3. On the surface of the resulting P-type conductive layer is deposited by evaporation a film of A5 Se approximately 500 A thick in the vacuum of 3 X 10 Torr. This As Se film is further covered by a similar method with an As Se film about 500 A thick in the low-pressure argon of 5 X l Torr. This double layer of As Se is formed for the purpose of improving the landing characteristic of the scanning electron beam.
Embodiment 3 A translucent A] film is formed on a glsss substrate in the vacuum of l X l0 Torr at the substrate temperature of 150C, and then on this translucent Al film is deposited a CdS film 3000 A thick in the vacuum of X 10 Torr at the substrate temperature of l50C.
Subsequently, thin films of Se, As Se and Te are deposited one after another on the CdS film in a rotary vacuum evaporator of 5 X 10" Torr. As a result, a film 5 pm thick comprising 3000 to 6000 layers of Se, As S63 and Te each having the average thickness of 10 A or less is obtained.
During the process of forming the multiple layer, the current in the Te boat or the opening of a slit interposed between the Te evaporation boat and the substrate is controlled continuously thereby to produce a macroscopic profile of transverse distribution of composition as shown in H0. 4. On this multiple layer is further deposited an A5 5 film about 500 A thick in the vacuum of 2 X l0 Torr thereby to improve the landing characteristic of the scanning electron beam.
An excessive amount of Cd tends to be included in the CdSe film by the ordinary method of production thereof, often resulting in the CdSe film having an N- type of conduction. This problem is overcome by adding Se as in the embodiment under consideration thereby to obtain an intrinsic or nearly P-type layer. On this layer is further deposited an Sb- S film approximately 1000 A thick in the low-pressure argon of 5 X 10 Torr for improving the landing characteristic of the scanning beam.
it will be understood from the above explanation of the embodiments that according to the invention the sensitivity especially to red light is improved without adverse effect on the rectifying contact with the N-type photoconductive layer by distributing Te in a P-type photoconductive layer containing Sc or 50 or more atomic percent in such a manner that the maximum Te content is located on a plane in the P-type conductive layer nearer to the N-type conductive layer than the middle plane of the Ptype conductive layer. The spectral sensitivity of the P-type conductive layer is thus changed greatly, making it possible to produce a photoconductive layer suitable for a specific purpose. Al though the above explanation of the embodiments in volves a light-receiving film of the target for the image pickup tube, it is possible to use the above-mentioned photoconductive layer for a solid-state light-receiving element, solid-state image pickup element or the like by employing an appropriate metal electrode in place of an electron beam.
What we claim is:
l. A photoconductive target of an image pickup tube comprising a light-transmitting substrate, a first N-type conductive layer deposited on said substrate and a P- type conductive layer making a rectifying contact at a first surface thereof with said first N-type conductive layer and having a second outer surface to be scanned by electrons, said P-type conductive layer including at least selenium and tellurium, the composition of said P-type conductive layer being different along the direction of the thickness thereof, the average content of selenium in said P-type conductive layer being not less than 50 atomic percent, the content of tellurium at said first and second surfaces of said P-type conductive layer being not more than 10 atomic percent, the maximum tellurium content of 10 to 40 atomic percent being located on a plane in said P-type conductive layer between said first N-type conductive layer and the middle plane of said P-type conductive layer.
2. A photoconductive target of an image pickup tube according to claim 1, wherein said first N-type conduc tive layer is a transparent conductive film including one substance selected from the group consisting of an oxide of tin. indium, and titanium as a main compo nent.
3. A photoconductive target of an image pickup tube according to claim I, wherein a second N-type conductive layer formed of one substance selected from the group consisting of CdS, CdSe. ZnS, ZnSe and the mixture thereof is interposed between said P-type conductive layer and said first N-type conductive layer or a translucent metal electrode constituting the surface portion of said lighttransmitting substrate on the side of said first N-type conductive layer.
4. A photoconductive target of an image pickup tube according to claim I, wherein said P-type conductive layer contains one substance selected from the group consisting of As, Sb. P. Bi, Ge, Si and the mixture thereof in addition to selenium and tellurium.
5. A photoconductive target of an image pickup tube according to claim 4, wherein the concentration of said one substance in said P-type conductive layer is substantially uniform therethrough.
6. A photoconductive target of an image pickup tube according to claim 1, wherein the minimum concentra tion of said selenium in said P-type conductive layer is located at the location of said maximum tellurium content in said P-type conductive layer.
7. A photoconductive target of an image pickup tube according to claim I, wherein said P-type conductive layer contains Cd in addition to selenium and tellurium.
8. A photoconductive target of an image pickup tube according to claim 7, wherein the maximum concentration of said Cd in said P-type conductive layer is located at the location of said maximum tellurium content in said P-type conductive layer.
9. A photoconductive target of an image pickup tube according to claim 1, wherein the absolute rate of increase of the tellurium content in said P-type conductive layer as the location of said maximum tellurium content is approached is equal to the absolute rate of decrease of the tellurium content as the location of said maximum tellurium content is passed.
10. A photoconductive target of an image pickup tube according to claim 1, wherein the absolute rate of increase of the tellurium content in said P-type conductive layer as the location of said maximum tellurium content is approached is greater than the absolute rate of decrease of the tellurium content as the location of said maximum tellurium content is passed.
Claims (10)
1. A PHOTOCONDUCTIVE TARGET OF AN IMAGE PICKUP TUBE COMPRISING A LIGHT-TRANSMITTING SUBSTRATE, A FIRST N-TYPE CONDUCTIVE LAYER DEPOSITED ON SAID SUBSTRATE AND A P-TYPE CONDUCTIVE LAYER MAKING A REACTIFYING CONTACT AT A FIRST SURFACE THEREOF WITH SAID FIRST N-TYPE CONDUCTIVE LAYER AND HAVING A SECOND OUTER SURFACE TO BE SCANNED BY ELECTRONS, SAID P-TYPE CONDUCTIVE LAYER INCLUDING AT LEAST SELENIUM AND TELLURIUM, THE COMPOSITION OF SAID P-TYPE CONDUCTIVE LAYER BEING DIFFERENT ALONG THE DIRECTION OF THE THICKNESS THEREOF, THE AVERAGE CONTENT OF SELENIUM IN SAID P-TYPE CONDUCTIVE LAYER BEING NOT LESS THAN 50 ATOMIC PERCENT, THE CONTENT OF TELLURIUM AT SAID FIRST AND SECOND SURFACES OF SAID P-TYPE CONDUCTIVE LAYER BEING NOT MORE THAN 10 ATOMIC PERCENT, THE MAXIMUM TELLURIUM CONTENT OF 10 TO 40 ATOMIC PERCENT BEING LOCATED ON A PLANE IN SAID P-TYPE
2. A photoconductive target of an image pickup tube according to claim 1, wherein said first N-type conductive layer is a transparent conductive film including one substance selected from the group consisting of an oxide of tin, indium, and titanium as a main component.
3. A photoconductive target of an image pickup tube according to claim 1, wherein a second N-type conductive layer formed of one substance selected from the group consisting of CdS, CdSe, ZnS, ZnSe and the mixture thereof is interposed between said P-type conductive layer and said first N-type conductive layer or a translucent metal electrode constituting the surface portion of said lighttransmitting substrate on the side of said first N-type conductive layer.
4. A photoconductive target of an image pickup tube according to claim 1, wherein said P-type conductive layer contains one substance selected from the group consisting of As, Sb, P, Bi, Ge, Si and the mixture thereof in addition to selenium and tellurium.
5. A photoconductive target of an image pickup tube according to claim 4, wherein the concentration of said one substance in said P-type conductive layer is substantially uniform therethrough.
6. A photoconductive target of an image pickup tube accordIng to claim 1, wherein the minimum concentration of said selenium in said P-type conductive layer is located at the location of said maximum tellurium content in said P-type conductive layer.
7. A photoconductive target of an image pickup tube according to claim 1, wherein said P-type conductive layer contains Cd in addition to selenium and tellurium.
8. A photoconductive target of an image pickup tube according to claim 7, wherein the maximum concentration of said Cd in said P-type conductive layer is located at the location of said maximum tellurium content in said P-type conductive layer.
9. A photoconductive target of an image pickup tube according to claim 1, wherein the absolute rate of increase of the tellurium content in said P-type conductive layer as the location of said maximum tellurium content is approached is equal to the absolute rate of decrease of the tellurium content as the location of said maximum tellurium content is passed.
10. A photoconductive target of an image pickup tube according to claim 1, wherein the absolute rate of increase of the tellurium content in said P-type conductive layer as the location of said maximum tellurium content is approached is greater than the absolute rate of decrease of the tellurium content as the location of said maximum tellurium content is passed.
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US370446A US3890525A (en) | 1972-07-03 | 1973-06-15 | Photoconductive target of an image pickup tube comprising graded selenium-tellurium layer |
GB2932373A GB1422381A (en) | 1972-07-03 | 1973-06-20 | Photoconductive target for an image pickup tube |
DE19732333283 DE2333283C3 (en) | 1972-07-03 | 1973-06-29 | Photocathode for image pickup tubes |
NL7309190.A NL158019B (en) | 1972-07-03 | 1973-07-02 | IMAGE TAKING TUBE FITTED WITH A PHOTO-CONDUCTING TARGET PLATE. |
FR7324257A FR2237307B1 (en) | 1972-07-03 | 1973-07-02 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP47059514A JPS5230091B2 (en) | 1972-07-03 | 1972-07-03 | |
US370446A US3890525A (en) | 1972-07-03 | 1973-06-15 | Photoconductive target of an image pickup tube comprising graded selenium-tellurium layer |
Publications (1)
Publication Number | Publication Date |
---|---|
US3890525A true US3890525A (en) | 1975-06-17 |
Family
ID=26400561
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US370446A Expired - Lifetime US3890525A (en) | 1972-07-03 | 1973-06-15 | Photoconductive target of an image pickup tube comprising graded selenium-tellurium layer |
Country Status (4)
Country | Link |
---|---|
US (1) | US3890525A (en) |
FR (1) | FR2237307B1 (en) |
GB (1) | GB1422381A (en) |
NL (1) | NL158019B (en) |
Cited By (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3984722A (en) * | 1973-05-21 | 1976-10-05 | Hitachi, Ltd. | Photoconductive target of an image pickup tube and method for manufacturing the same |
US4007395A (en) * | 1974-06-21 | 1977-02-08 | Hitachi, Ltd. | Target structure for use in photoconductive image pickup tubes |
US4025815A (en) * | 1974-06-14 | 1977-05-24 | Sony Corporation | Pick-up tube having photoconductor on zinc oxide layer |
US4040985A (en) * | 1975-04-16 | 1977-08-09 | Hitachi, Ltd. | Photoconductive films |
DE3021027A1 (en) * | 1979-06-07 | 1980-12-11 | Hitachi Ltd | PHOTOCONDUCTIVE TARGET |
US4249106A (en) * | 1978-11-08 | 1981-02-03 | Hitachi, Ltd. | Radiation sensitive screen |
US4254359A (en) * | 1978-05-19 | 1981-03-03 | U.S. Philips Corporation | Camera tube with graduated concentration of tellurium in target |
EP0036779A2 (en) * | 1980-03-24 | 1981-09-30 | Hitachi, Ltd. | Photoelectric conversion device and method of producing the same |
US4319159A (en) * | 1978-05-19 | 1982-03-09 | U.S. Philips Corporation | Camera tube selenium target including arsenic increasing in concentration from radiation side |
US4348610A (en) * | 1979-04-11 | 1982-09-07 | U.S. Philips Corporation | Camera tube with graded tellurium or arsenic target |
EP0067015A2 (en) * | 1981-05-29 | 1982-12-15 | Hitachi, Ltd. | Photoconductive film |
FR2577713A1 (en) * | 1985-02-20 | 1986-08-22 | Hitachi Ltd | TARGET TUBE TARGET |
US4617248A (en) * | 1984-05-21 | 1986-10-14 | Nippon Hoso Kyokai | Doped photoconductive film including selenium and tellurium |
EP0326178A2 (en) * | 1988-01-28 | 1989-08-02 | Hitachi, Ltd. | Method of making a photosensor |
US4866332A (en) * | 1986-03-26 | 1989-09-12 | Hitachi, Ltd. | Target of image pickup tube |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3346755A (en) * | 1966-03-31 | 1967-10-10 | Rca Corp | Dark current reduction in photoconductive target by barrier junction between opposite conductivity type materials |
US3350595A (en) * | 1965-11-15 | 1967-10-31 | Rca Corp | Low dark current photoconductive device |
-
1973
- 1973-06-15 US US370446A patent/US3890525A/en not_active Expired - Lifetime
- 1973-06-20 GB GB2932373A patent/GB1422381A/en not_active Expired
- 1973-07-02 NL NL7309190.A patent/NL158019B/en not_active Application Discontinuation
- 1973-07-02 FR FR7324257A patent/FR2237307B1/fr not_active Expired
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3350595A (en) * | 1965-11-15 | 1967-10-31 | Rca Corp | Low dark current photoconductive device |
US3346755A (en) * | 1966-03-31 | 1967-10-10 | Rca Corp | Dark current reduction in photoconductive target by barrier junction between opposite conductivity type materials |
Cited By (21)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3984722A (en) * | 1973-05-21 | 1976-10-05 | Hitachi, Ltd. | Photoconductive target of an image pickup tube and method for manufacturing the same |
US4025815A (en) * | 1974-06-14 | 1977-05-24 | Sony Corporation | Pick-up tube having photoconductor on zinc oxide layer |
US4007395A (en) * | 1974-06-21 | 1977-02-08 | Hitachi, Ltd. | Target structure for use in photoconductive image pickup tubes |
US4040985A (en) * | 1975-04-16 | 1977-08-09 | Hitachi, Ltd. | Photoconductive films |
US4319159A (en) * | 1978-05-19 | 1982-03-09 | U.S. Philips Corporation | Camera tube selenium target including arsenic increasing in concentration from radiation side |
US4254359A (en) * | 1978-05-19 | 1981-03-03 | U.S. Philips Corporation | Camera tube with graduated concentration of tellurium in target |
US4249106A (en) * | 1978-11-08 | 1981-02-03 | Hitachi, Ltd. | Radiation sensitive screen |
US4348610A (en) * | 1979-04-11 | 1982-09-07 | U.S. Philips Corporation | Camera tube with graded tellurium or arsenic target |
US4330733A (en) * | 1979-06-07 | 1982-05-18 | Nippon Hoso Kyokai | Photoconductive target |
DE3021027A1 (en) * | 1979-06-07 | 1980-12-11 | Hitachi Ltd | PHOTOCONDUCTIVE TARGET |
EP0036779A3 (en) * | 1980-03-24 | 1982-05-12 | Hitachi, Ltd. | Photoelectric conversion device and method of producing the same |
EP0036779A2 (en) * | 1980-03-24 | 1981-09-30 | Hitachi, Ltd. | Photoelectric conversion device and method of producing the same |
US4405879A (en) * | 1980-03-24 | 1983-09-20 | Hitachi, Ltd. | Photoelectric conversion device and method of producing the same |
EP0067015A2 (en) * | 1981-05-29 | 1982-12-15 | Hitachi, Ltd. | Photoconductive film |
EP0067015A3 (en) * | 1981-05-29 | 1983-02-09 | Hitachi, Ltd. | Photoconductive film |
US4463279A (en) * | 1981-05-29 | 1984-07-31 | Hitachi, Ltd. | Doped photoconductive film comprising selenium and tellurium |
US4617248A (en) * | 1984-05-21 | 1986-10-14 | Nippon Hoso Kyokai | Doped photoconductive film including selenium and tellurium |
FR2577713A1 (en) * | 1985-02-20 | 1986-08-22 | Hitachi Ltd | TARGET TUBE TARGET |
US4866332A (en) * | 1986-03-26 | 1989-09-12 | Hitachi, Ltd. | Target of image pickup tube |
EP0326178A2 (en) * | 1988-01-28 | 1989-08-02 | Hitachi, Ltd. | Method of making a photosensor |
EP0326178A3 (en) * | 1988-01-28 | 1990-06-27 | Hitachi, Ltd. | Method of making a photosensor |
Also Published As
Publication number | Publication date |
---|---|
FR2237307B1 (en) | 1977-05-13 |
FR2237307A1 (en) | 1975-02-07 |
GB1422381A (en) | 1976-01-28 |
DE2333283B2 (en) | 1976-05-06 |
NL7309190A (en) | 1974-01-07 |
DE2333283A1 (en) | 1974-01-31 |
NL158019B (en) | 1978-09-15 |
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