JPH07122228A - Photoelectric transfer tube - Google Patents

Abstract

PURPOSE:To provide a cathode contact electrode structure of photoelectric transfer tube which can generate the photoelectric surface of good workmanship at a low cost. CONSTITUTION:A cathode contact electrode consisting of the first cathode contact electrode 17 and the second cathode contact electrodes 16a, 16b is pinched between an optical glass base board 11 and a side tubing 15. A semiconductor photoelectric surface 12 is provided on the surface of the base board 11, and the first electrode 17 is in contact with this photoelectric surface 12. A spring 17a is furnished at the first electrode 17, which is in contact with one of the second electrodes 16b through the spring 17a. This second electrode 16b encloses the circumferential end part 12a of the photoelectric surface 12 and is embodied with roundness. The other end of the second electrode 16a in a single piece structure with this second electrode 16b is exposed at the outside of an airtight vessel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion tube having a photoelectric surface such as a photomultiplier tube or an image tube, and more particularly to a photoelectric conversion tube characterized by a structure for applying a cathode voltage to the photoelectric surface.

[0002]

2. Description of the Related Art There are a transmission type photocathode and a reflection type photocathode as photocathodes which emit photoelectrons in response to incident light, and in the transmission type photocathode, optical glass or the like is used as a substrate of the photocathode. .

FIG. 7 and FIG. 8 show this transmission type photocathode, and these photocathodes have different end shapes depending on the size of the optical glass and the size of the photocathode. FIG. 7A shows a side cross-sectional view of the photocathode in which the end of the photocathode 1 protrudes from the peripheral edge of the optical glass substrate 2. This photocathode 1
Is formed of a single crystal semiconductor photocathode, for example, a GaAs transmission type photocathode, and as shown in the plan view of FIG. 2B, a very sharp protrusion 1a is always formed at the end of the photocathode 1 where the crystal fracture surface appears. Existing.

Further, in FIG. 8A, the end of the GaAs transmission type photocathode 3 does not protrude from the peripheral end of the optical glass substrate 4,
It shows a side sectional view of a photocathode having a diameter smaller than that of the optical glass substrate 4. The figure (b) has shown the sectional view which expanded the A section in the figure (a). In this photocathode structure, the sharp protrusions 3a existing on the peripheral edge of the photocathode 3 are formed.
Are covered by the raised portion formed on the peripheral edge portion 4 a of the optical glass substrate 4.

In order to apply a cathode voltage to each of these photocathodes 1, 3 each glass substrate 2, which is conventionally formed in a "T" shape,
Aluminum metal or the like was vapor-deposited on the shoulder portions 2b and 4b of No. 4 in electrical contact with the photocathodes 1 and 3 to form contact electrodes (not shown). The contact electrodes were guided to the outside of an airtight container in which the photocathodes 1 and 3 were placed in a vacuum atmosphere, and a cathode voltage was applied to the photocathodes 1 and 3 from outside the airtight container through the contact electrodes.

[0006]

However, in the transmission type semiconductor photocathode having the above-mentioned conventional structure, a high electric field is formed in the photocathode portion and its periphery due to the recent tendency of miniaturization of the photoelectric conversion tube. In many cases, the field emission phenomenon is likely to occur. Therefore, the optical glass substrates 2, 4
In order to eliminate all the protrusions and scratches where the electric field is likely to concentrate, the entire inner surface kept in a vacuum atmosphere was optically polished. In particular, the end portion of an optical glass substrate, which is a so-called stepped face plate, is polished more carefully, and the process is advanced while paying close attention to the handling and processing in the manufacturing process.

Further, it has been difficult to form the photocathode. That is, in the conventional photocathode 1 shown in FIG. 7, the single crystal thin film wafer for photocathode is formed on the optical glass substrate 2, and then the sharp protrusions present at the peripheral edge are removed by polishing. . After that, the process moves to the step of forming a contact electrode for applying a cathode voltage to the photocathode. Also in this electrode formation, the process proceeds while being careful so that dust adhesion, scratches, and protrusions do not occur. Further, FIG.
In the photocathode 3 shown in (1), the peripheral edge portion 4a of the optical glass substrate 4 must be raised so as to cover the peripheral edge portion of the single crystal thin film wafer for photocathode. Therefore, in the structure of the conventional photoelectric conversion tube, it is necessary to perform a difficult process of polishing the end surface of the optical glass substrate or the peripheral end portion of the photoelectric surface, or raising the peripheral edge portion of the optical glass substrate. It took time.

In addition, adhesion of an abrasive to the photocathode in the polishing step and adhesion of contaminants to the photocathode in the contact electrode formation step cause an undesirable state from the viewpoint of ensuring cleanliness of the photocathode surface. did. Therefore, conventionally, a step of removing such contaminants adhering to the surface of the photocathode has been required, resulting in an increase in manufacturing time and an increase in manufacturing cost. In addition, the contaminants on the surface of the photocathode could not be completely removed, and the attachment of the contaminants tended to deteriorate the light detection characteristics of the photocathode.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an airtight container whose inside is kept in a vacuum state and a translucent material forming a part of this airtight container. And a light-transmitting semiconductor photocathode disposed on the inner surface of the light-receiving face plate that photoelectrically converts incident light to emit electrons.
In a photoelectric conversion tube configured with an anode electrode formed in an airtight container for capturing electrons, a rounded one end covers a peripheral end portion of a semiconductor photoelectric surface while electrically contacting the photoelectric surface, The contact electrode is sandwiched between the airtight container and the light-receiving face plate, the other end of which is exposed to the outside of the airtight container.

The contact electrode includes a first contact electrode made of a metal plate which is in electrical contact with the peripheral edge of the photocathode, and a peripheral edge of the photocathode while contacting the first contact electrode. First
And a rounded second contact electrode which is made of a metal plate whose end is exposed to the outside of the airtight container, and the first contact electrode or the second contact electrode has a photocathode and a second contact electrode. A spring portion is formed to buffer between the contact electrodes.

[0011]

The peripheral edge of the semiconductor photocathode having the sharp projection is covered by the rounded contact electrode, and the electric field formed between the photocathode and the anode electrode is not concentrated.

Further, a cathode voltage is applied to the end of the contact electrode exposed to the outside of the airtight container, and the cathode voltage is transmitted through the contact electrode mechanically contacting the photocathode.

In addition, a spring portion is formed on the first contact electrode or the second contact electrode, and the space between the photocathode and the first contact electrode is buffered. The contact resistance is kept in a stable low resistance state.

[0014]

Next, a first embodiment in which the present invention is applied to a proximity type phototube having a GaAs transmission type photocathode will be described. The proximity photocell according to this example is manufactured as follows.

First, Ga which is a III-V compound semiconductor is used.
A GaAlAs etching stop layer, a GaAs single crystal layer, and a GaAlAs buffer layer are sequentially grown on the As semiconductor substrate. Next, silane (Si) is formed on the surface of the GaAlAs buffer layer which is the uppermost layer of this crystal laminated structure.
H ₄ ) is coated by the thermal CVD method to form a silicon oxide (SiO ₂ ) layer. Next, the optical glass substrate 11 is thermally bonded to this silicon oxide layer. At this time, the silicon oxide layer has a function of preventing impurities from invading the crystal laminated structure due to thermal adhesion with the optical glass substrate 11 and strengthening adhesion with the optical glass substrate 11. Next, the GaAs semiconductor substrate is removed by etching, and then the GaAlAs etching stop layer is removed to expose the GaAs single crystal layer. As a result, as shown in FIG. 2A, the surface of the optical glass substrate 11 has G
Transmission type photocathode (photocathode) consisting of aAs single crystal thin film 1
2 is formed. In FIG. 2, the left half of the center line is a side sectional view and the right half is a side view. This photocathode structure corresponds to the conventional structure shown in FIG. 7 (a) or FIG. 8 (a), and sharp projections are present at the peripheral edges of the optical glass substrate 11 and the photocathode 12.

The light-receiving surface plate 13 with the exposed photocathode 12 is set in the vacuum apparatus for producing a proximity type phototube shown in FIG. This vacuum device is called a transfer device. At this time, as in the conventional case, the optical glass substrate 11 and the photocathode 12 are used.
The light-receiving face plate 13 is set in the transfer device without polishing the end portion of the substrate and without forming the contact electrode by vapor-depositing aluminum metal. At the same time, the side tube assembly 14 that is integrated with the light-receiving surface plate 13 to form a vacuum-tight container is set at a position different from that of the light-receiving surface plate 13. This side tube assembly 14 is shown in FIGS. 2 (b) and 2 (c). On one opening surface of the side tube 15 made of an electrically insulating material, cathode contact electrodes 16a, 16b made of a metal plate and integrally formed by welding are provided. Further, a cathode contact electrode 17 (not shown), which will be described later, is provided in contact with the cathode contact electrode 16b.
7 is a first cathode contact electrode, the above-mentioned cathode contact electrode 16a,
b forms the second cathode contact electrode. Also, the side tube 1
A first anode contact electrode 18 made of a metal cylindrical plate is provided on the other opening surface of the electrode 5. Further, as shown in FIG. 2C, a second anode contact electrode 19 made of a metal plate is provided in contact with the first anode contact electrode 18, and contacts the second anode contact electrode 19. Then, the fiber plate 20 is arranged. This fiber plate 20
A fluorescent film and an anode electrode thin film (not shown) are formed on the surface of the anode electrode thin film.
9 is in electrical contact.

With the light-receiving face plate 13 and the side tube assembly 14 thus set in the transfer device,
The inside of the transfer device is evacuated by the vacuum pump. Subsequently, the photocathode 12 is subjected to a predetermined surface treatment, and the photocathode 12 is cleaned while floating in a vacuum.
By this cleaning step, the surface barrier of the photocathode 12 against the photoelectrons becomes extremely low, and a highly efficient photocathode can be obtained.
After that, the light-receiving surface plate 13 is moved within the transfer device by the manipulator 31, and is conveyed to a position where the photocathode 12 faces the fiber plate 20 in the upper space of the side tube assembly 14. In this state, the light-receiving face plate 13
The press machine 32 located above the
The light-receiving face plate 13 shown in FIG. 3 is pressed to the side tube assembly 14 shown in FIG. 3B to form the proximity photoelectric tube 41 shown in FIGS. 3C and 2C. In FIG. 3, the same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. By this pressing step, the first cathode contact electrode 16
A and b are sealed and integrated between the optical glass substrate 11 and the side tube 15. This sealing is performed by means of, for example, an indium (In) seal or cold weld. As a result, the cathode contact electrode composed of the first cathode contact electrode 17 and the second cathode contact electrodes 16a, 16b is sandwiched between the optical glass substrate 11 and the side tube 15.

Further, the light-receiving face plate 13 and the cathode contact electrode are in contact with each other as shown in the sectional view of FIG. 2C, and more specifically, it is shown in FIG. Be done. Figure 1
As shown in (a), the first cathode contact electrode 17 is in mechanical and electrical contact with the semiconductor photocathode 12 formed on the surface of the optical glass substrate 11. This first cathode contact electrode 17 is shown in the perspective view of FIG. The first cathode contact electrode 17 is made of an annular metal plate and has a leaf spring-shaped spring portion 17a formed thereon, and is placed on the second cathode contact electrode 16b as shown in FIG. 4 (b). To be done.
In FIG. 4B, the same parts as those in FIGS. 2 and 3 are designated by the same reference numerals, and the description thereof will be omitted. Therefore, the first cathode contact electrode 17 is connected to the second cathode contact electrode 16b via the spring portion 17a as shown in FIG.
Is in contact with.

Further, the second cathode contact electrode 16b is
While contacting the first cathode contact electrode 17, the peripheral end portion 12 a of the photocathode 12 and the first cathode contact electrode 17 are covered. Further, the other end of the second cathode contact electrode 16a integrated with the second cathode contact electrode 16b has a structure shown in FIG.
As shown in (c), it is exposed to the outside of the airtight container.
Further, the second cathode contact electrode 16b covering the peripheral end portion of the photocathode 12 is formed in a rounded shape as shown in the sectional view of FIG. 1 (b), and its end portion is mirror-finished to form a protrusion. And scratches have disappeared.

In the proximity type photoelectric tube according to the present embodiment, the peripheral end portion 12a of the semiconductor photocathode 12 having the sharp protrusion portion has the rounded second cathode contact electrode 16b.
Covered by the photocathode 12 and the fiber plate 20.
Concentration does not occur in the electric field formed between the anode electrode formed on the surface of the. That is, since there is no sharp portion such as a protrusion or a scratch that easily causes electric field concentration between the photocathode and the anode, unlike the conventional case, electric field concentration does not occur. Therefore, the photocathode 12 and its peripheral portion can withstand a higher electric field, and unnecessary field emission phenomenon does not occur unlike the conventional case. Further, since the peripheral end portion 12a of the semiconductor photocathode 12 is covered with the rounded second cathode contact electrode 16b, it is not necessary to provide a step of polishing the sharp protrusion existing on the peripheral end portion 12a. Therefore, unlike the conventional case, the polishing agent does not adhere to the photocathode in the polishing step and contaminate the photocathode. Further, the polishing of the end surface of the optical glass substrate 11 may be rough, so that no skilled technique is required for polishing, and the number of steps is reduced in combination with the fact that polishing of the peripheral end portion 12a of the semiconductor photocathode 12 is unnecessary. To do. For this reason,
The manufacturing cost of the photocell is reduced.

Further, a cathode voltage is applied to the end of the second cathode contact electrode 16a exposed to the outside of the airtight container, and the cathode voltage is transmitted to the cathode contact electrode 16b integrated with the cathode contact electrode 16a. Further, the cathode voltage is transmitted to the photocathode 12 via the first cathode contact electrode 17. That is,
In the photoelectric conversion tube according to the present embodiment, the structure for transmitting the cathode voltage from the outside of the airtight container to the photoelectric surface 12 is mechanically configured by the first cathode contact electrode 17 and the second cathode contact electrodes 16a and 16b. . Therefore, unlike the conventional structure in which a contact electrode is formed by depositing a metal material on the surface of an optical glass substrate, there is no phenomenon that gas is released from the deposited metal electrode during the cleaning process of the photocathode or that the deposited metal electrode is alloyed. I won't get up. Further, as described above, the polishing process is unnecessary and the electrode deposition process is not required, so that the active surface of the photocathode is prevented from being contaminated during each of these processes. Therefore, the photodetection characteristics of the photocathode are not deteriorated, and a good photocathode is obtained.

Further, since the spring portion 17a is formed on the first cathode contact electrode 17, the photocathode 12 and the first cathode contact electrode 17 that makes electrical and mechanical contact with the photocathode 12 are formed. The space is buffered by the spring portion 17a. Therefore, even if there is a temperature change in the environment in which the phototube is used or vibration is applied to the phototube, the electrical contact resistance between the photocathode 12 and the first cathode contact electrode 17 is always in a stable low resistance state. Kept in. That is, as in the present embodiment, the cathode contact electrode is not composed of a single electrode but is composed of a plurality of electrode parts, and by adopting a structure in which one of the parts has a spring function, the photocathode 12 The contact resistance with is stable and kept low for a long period of time. That is, in the electrode structure of the present embodiment, various mechanical requirements required for the electrical contact portion from the environment in which the device is used are satisfied.

Although the first cathode contact electrode 17 is provided with a spring function in this embodiment, the second cathode contact electrode 16b may be provided with a spring function. Also in the above, the same effect as this embodiment is exhibited.

The photocathode in this embodiment is Ga.
Although described as an As single crystal semiconductor photocathode, the present invention is not limited to this, and the same effect as that of the present embodiment can be obtained even with an InP-based semiconductor photocathode.

Further, although the case where the present invention is applied to the phototube is explained in the above-mentioned embodiment, it may be applied to the photomultiplier tube. FIG. 6 shows a photomultiplier tube according to a second embodiment of the present invention. In the figure, parts that are the same as or correspond to those in FIGS. 2 and 3 are given the same reference numerals, and descriptions thereof will be omitted. The photomultiplier tube is a phototube having an electron multiplying function, and a plurality of microchannel plates (MCP) 51 for multiplying photoelectrons emitted from the photocathode 12 are provided in the hermetic container. There is. A group of electrons emitted from these MCPs 51 as secondary electrons are converged on the anode plate 52. The anode plate 52 is electrically connected to a lead pin 54 via a wire 53, and the lead pin 54 is fixed to a base plate 55 made of an insulating material. The fixing of the lead pin 54 to the base plate 55 is performed by the tapered hermetic glass 5
It is done by 6.

Also in this embodiment, the cathode voltage is supplied from the outside of the airtight container to the photocathode 12 by the second cathode contact electrode 16.
a, b and the first cathode contact electrode 17 described above. Also, the anode voltage supply to the anode plate 52 is
This is performed via the lead pin 54 and the wire 53. Therefore, also in this embodiment, the cathode voltage is applied to the photocathode by the mechanical contact electrode without using the vapor-deposited metal electrode, and the same effect as that of the first embodiment can be obtained.

[0027]

As described above, according to the present invention, the peripheral edge portion of the semiconductor photocathode having the sharp protrusion is covered with the rounded contact electrode and formed between the photocathode and the anode electrode. There is no concentration in the electric field. Therefore, unlike the conventional case, the field emission phenomenon does not occur. In addition, there is no need for a process that requires skill to polish sharp protrusions, etc.
The photocathode is not contaminated by the abrasive. Therefore, the number of steps is reduced, and the manufacturing cost of the photoelectric conversion tube is reduced.

Further, a cathode voltage is applied to the end portion of the contact electrode exposed to the outside of the airtight container, and the cathode voltage is transmitted through the contact electrode mechanically contacting the photocathode. Therefore, the electrode vapor deposition process is not necessary and the polishing process is not required as described above, so that the photocathode is not contaminated during each of these processes. Therefore, the photodetection characteristics of the photocathode are not deteriorated, and a good photocathode is obtained.

In addition, a spring portion is formed on the first contact electrode or the second contact electrode, and the space between the photocathode and the first contact electrode is buffered, so that the electricity between the photocathode and the first contact electrode is reduced. The contact resistance is kept in a stable low resistance state. For this reason, stable electrical contact can always be obtained regardless of the usage environment of the photoelectric tube.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of a contact portion between a photocathode and a cathode contact electrode in a proximity type photocell according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a side cross-section and a side surface of each component forming the proximity photocell according to the first embodiment.

FIG. 3 is a partially cutaway perspective view showing each component that constitutes the proximity type photocell according to the first embodiment.

FIG. 4 is a partially cutaway perspective view showing the structure of a first cathode contact electrode used in the proximity photocell according to the first embodiment.

FIG. 5 is a diagram showing a configuration of a transfer device used for manufacturing the proximity type photocell according to the first embodiment.

FIG. 6 is a partially cutaway perspective view of a photomultiplier according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a photocathode structure used in a conventional first photoelectric conversion tube.

FIG. 8 is a diagram showing a photocathode structure used in a second conventional photoelectric conversion tube.

[Explanation of symbols]

11 ... Optical glass substrate, 12 ... Photocathode (photocathode), 1
5 ... Side tube, 16a, b ... 2nd cathode contact electrode, 17 ... 1st cathode contact electrode, 18 ... 1st anode contact electrode, 19 ...
Second anode contact electrode, 20 ... Fiber plate.

Claims (2)

[Claims] 1. An airtight container whose inside is kept in a vacuum state,
A light-transmissive light-receiving face plate that forms a part of the airtight container, a transmissive semiconductor photocathode disposed on the inner surface of the light-receiving face plate that photoelectrically converts incident light to emit electrons, and an anode electrode that traps electrons. In a photoelectric conversion tube configured with, a rounded one end covers a peripheral end of the semiconductor photocathode while electrically contacting the photocathode, and the other end is outside the airtight container. A photoelectric conversion tube comprising: an exposed contact electrode sandwiched between the airtight container and the light-receiving surface plate. 2. The contact electrode comprises a first contact electrode made of a metal plate that is in electrical contact with a peripheral edge of the photocathode, and a peripheral edge of the photocathode while contacting the first contact electrode. And a rounded second contact electrode made of a metal plate whose end portion covers the first contact electrode and is exposed to the outside of the airtight container, the first contact electrode or the second contact electrode. The photoelectric conversion tube according to claim 1, wherein a spring portion that buffers between the photocathode and the first contact electrode is formed on the contact electrode.