JP2945732B2 - Image pickup tube and operation method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup tube in which at least a part of a photoconductive layer is made of an amorphous semiconductor mainly composed of Se, and an operation method thereof.

[Conventional technology]

Amorphous Se has photoconductivity and generally has p-type conductivity and makes rectifying contact with n-type conductive material. In this case, a blocking type image pickup tube target can be manufactured.

Further, when a high electric field is applied to the above-mentioned blocking type image pickup tube target, avalanche multiplication of charges is induced inside the material,
It is known that the light sensitivity of an image pickup tube increases remarkably. This is described, for example, in JP-A-63-304551.

[Problems to be solved by the invention]

Now, since amorphous Se has a glass transition temperature near room temperature, if an imaging tube using amorphous Se is operated continuously for a long time, local crystallization resulting from temperature rise, light irradiation, and electric field application Occurs, and a white spot-like screen defect (hereinafter, simply referred to as a white defect) occurs in the reproduced image.

As a means for improving this, a method of adding As to Se to raise the glass transition point is known. However, since the addition of As involves the formation of electron trap levels in the amorphous Se, the addition of a large amount of As uniformly over the entire amorphous Se-based photoconductive layer requires dark current and afterimages. It's not a good idea because it will increase.

The above-mentioned prior art is effective in preventing the occurrence of white scratches due to crystallization, but has a problem that the dark current increases when the image pickup tube is operated for a long time under a high electric field.

It is an object of the present invention to provide an image pickup tube using a photoconductive layer mainly composed of amorphous Se without causing white spots even when operated continuously for a long time, and reducing dark current even under a high electric field. It is to provide a structure that can be used.

[Means for solving the problem]

In order to achieve the above object, an image pickup tube according to the present invention has a photoconductive layer composed of an amorphous semiconductor containing Se as a main component, at least at an interface with or near an interface with an electron injection blocking layer or a hole injection blocking layer. This is achieved by minimizing the amount of As added in a narrow region in the photoconductive layer and making the amount of As added in a central region excluding the narrow region smaller than that in the narrow region.

That is, in the present invention, from the interface of the electron injection blocking layer in the photoconductive layer composed of an amorphous semiconductor layer mainly composed of Se, or from the vicinity of the interface to a region having a layer thickness of 10 nm or more and 400 nm or less,
s is added in an amount of 22% by weight or more and 38% by weight or less. Further, As is added in an amount of 1 wt% or more and 5 wt% or less from the interface of the hole injection blocking layer in the photoconductive layer or from the vicinity of the interface to a region having a layer thickness of 10 nm or more and 100 nm or less. Furthermore, 1% by weight or less of As is added to a region other than the above-mentioned specific region, so that the entire amorphous semiconductor layer has a thickness of 2 to 10 μm.

In addition, the method of operating the image pickup tube according to the present invention is characterized in that the image pickup tube is operated in an electric field region where avalanche multiplication of charges is induced inside the photoconductive layer.

[Action]

FIG. 1 is a sectional view showing an example of the image pickup tube of the present invention. 1 is a light-transmitting substrate, 2 is a light-transmitting conductive film, 3 is a hole injection blocking layer, 4 is a photoconductive layer made of an amorphous semiconductor layer mainly composed of Se, and 5 is an electron injection blocking layer. The photoconductive layer 4 is made of
-As (I) layer 41, Se-As (II) layer 42, Se-As (III) layer 4
Consists of three. A is the incident light side, and B is the electron beam scanning side.

According to recent studies by the present inventors, nucleation of crystallization in an amorphous Se film occurs only in an interface region in contact with another layer, and hardly occurs inside. Although the physical mechanism of this nucleation has not been fully elucidated yet, it is considered that the transition energy required for nucleation is the lowest at the interface with another layer.

The above fact is that, in order to reduce the dark current during the operation of the image pickup tube and to prevent white scratches due to crystallization, the electron injection blocking layer or the hole injection blocking layer in the amorphous semiconductor layer is
This suggests that it is important to make the material composition difficult to crystallize only at the interface or in the vicinity of the interface.

In the present invention, the Se-As (I) layer 41 shown in FIG.
As layer (III) 43 prevents crystallization in the interface region with electron injection blocking layer 5.

The layer thickness and the amount of As added of the Se-As layer (I) 41 and the Se-As layer (III) 43 are experimentally determined for the above purpose.

In the example of FIG. 1, the high-concentration As region and the hole injection blocking layer 3 or the electron injection blocking layer 5 are adjacent to each other, but a very thin (100 nm or less, preferably 30 to 60 nm) A
It has been found that the effect on crystallization hardly changes even if an Se-As layer (not shown) containing 1% by weight or less of s is interposed. In the example of FIG. 1, the Se-As (I) layer
The semiconductor layers other than 41 and the Se-As (III) layer 43 are made of Se and As. However, even if an additive other than As, for example, an element such as Te is added to this layer, the above-described crystallization prevention is prevented. Obviously, the effect is unchanged.

That is, in the image pickup tube of the present invention, by adding As to Se of the photoconductive layer, the glass transition point can be raised, so that white scratches do not occur even when the device is continuously operated for a long time. As only in a specific area near the interface like
Is introduced at a high concentration, so that dark current can be suppressed even under a high electric field.

〔Example〕

Embodiment 1 A first embodiment of the imaging tube of the present invention will be described with reference to FIG.

A transparent conductive film 2 mainly composed of indium oxide is formed on a glass substrate 1, and CeO ₂ is deposited thereon to a thickness of 30 nm to form a hole injection blocking layer 3. An amorphous semiconductor layer 41 made of Se and As and having a thickness of 60 nm is formed thereon by a vacuum evaporation method. At the time of film formation, Se and As ₂ Se ₃ are simultaneously deposited from different boats and deposited so that the As concentration becomes 3% by weight. An amorphous semiconductor layer made of Se and As is formed thereon by a vacuum evaporation method. As at this time
The concentration is 0.5% by weight. On top of that, an amorphous semiconductor layer 43 made of Se and As is formed by a vacuum evaporation method.
At this time, the As concentration is 10 to 39% by weight, and the film thickness is 5 to 500 nm.
And the thickness of the entire photoconductive layer is set to 5 μm.
Sb ₂ S ₃ as an electron injection blocking layer 5 is formed thereon at 1 × 10 ⁻¹ Torr.
Is deposited in an inert gas atmosphere to a thickness of 0.1 μm to obtain a photoconductive target having a blocking structure. Further, the obtained target is incorporated into an imaging tube housing containing an electron gun to obtain a photoconductive imaging tube.

When blue light was applied to the obtained image pickup tube and the electric field intensity was gradually increased, avalanche multiplication was started at about 7 × 10 ⁷ V / m in all the image pickup tubes, and about 1.1 × 10 ⁸ V / m And a multiplication factor of 10 was obtained. Each imaging tube was placed in a life test apparatus and operated continuously for 2000 hours under an electric field giving a multiplication factor of 10. After the end of the life test, the dark current value in a high electric field and the presence or absence of white flaws by the life test were examined.

The above results are shown in FIG. The dashed line A is a characteristic line connecting points at which the dark current becomes approximately 1 nA when an electric field having a multiplication factor of 10 is applied. The dark current is larger than 1 nA above the dashed line A and below the dashed line A. Is smaller than 1nA. Similarly, the dashed line B is a characteristic line connecting the points where the dark current becomes approximately 1 nA when an electric field having a multiplication factor of 30 is applied. Is smaller than 1nA.

On the other hand, a solid line C is a characteristic line for distinguishing whether or not white flaws are observed after the life test is performed. No white flaws occur above the solid line C, and white flaws appear below the solid line C. Indicates that a scratch has occurred.

That is, the area surrounded by the dashed-dotted line A and the solid line C is the appropriate range, and the area surrounded by the broken line B and the solid line C is the optimum range.

Note that for the dashed line A, y = 38 (x ≦ 350), y
= −0.32x + 150 (x ≧ 350), and for the broken line B, y = 36
(X ≦ 150), y = −0.28x + 78 (x ≧ 150), and for the solid line C, y = −0.8x + 46 (x ≦ 30), y = 22 (x
≧ 30).

Example 2 A transparent conductive film 2 mainly composed of tin oxide was formed on a glass substrate 1 (see FIG. 1), and GeO ₂ was deposited thereon to a thickness of 40 nm, and CeO ₂ was deposited thereon to a thickness of 40 nm. The hole injection blocking layer 3 is formed. An amorphous semiconductor layer 41 of Se, As, and LiF with a thickness of 60 nm is formed thereon by a vacuum evaporation method. At the time of film formation, Se, As ₂ Se ₃ and LiF are simultaneously evaporated from different boats and vapor-deposited, so that the As concentration is 2% by weight and the LiF concentration is 2000 ppm by weight. Next, an amorphous semiconductor layer made of Se and As is formed by a vacuum evaporation method. At this time, the As concentration is 0.5% by weight. An amorphous semiconductor layer 43 made of Se and As is formed thereon by changing the thickness in a range of 20 to 500 nm by a vacuum evaporation method. At this time, the As concentration is 30% by weight. An amorphous semiconductor layer (not shown) made of only Se is formed thereon to a thickness of 50 nm by a vacuum evaporation method, and the thickness of the entire amorphous semiconductor layer becomes 5 nm.
μm. On top of that, Sb ₂ S ₃ is deposited as an electron injection blocking layer 5 in an inert gas atmosphere of 2 × 10 ⁻² Torr by 0.1%.
It is deposited to a thickness of μm to obtain a photoconductive target having a blocking structure. Further, this is incorporated into an imaging tube housing containing an electron gun to obtain a photoconductive imaging tube.

In the same manner as in Example 1, the obtained image pickup tube was placed in a life test apparatus under an electric field giving a multiplication factor of 10 when irradiating blue light.
It was operated continuously for hours.

After the continuous operation, the presence or absence of white flaws was examined. The result was almost the same as the result of Example 1. Further, the data value regarding the dark current was about 0.8 to 1.0 times that of the first embodiment, and the same or better results as in the first embodiment were obtained.

According to the present embodiment, even if pure Se is interposed about 50 nm between the electron injection blocking layer 5 of Sb ₂ S ₃ and the layer 43 containing high concentration of As, the dark current of the high concentration layer of As can be reduced and white spots can be reduced. It turns out that the effect of suppressing the occurrence is sufficiently effective.

Example 3 A transparent photoconductive layer 2 mainly composed of indium oxide was formed on a glass substrate 1 (see FIG. 1), and CeO ₂ was deposited thereon as a hole injection blocking layer 3 to a thickness of 50 nm. I do. On top of this, a 50 nm thick amorphous semiconductor layer 4 composed of Se, As and LiF
1 is formed by a vacuum evaporation method. When forming the film, S
e, As ₂ Se ₃ and LiF are evaporated from different boats and vapor-deposited so that the As concentration becomes 2.0% by weight and the LiF becomes 1000 ppm by weight. Then, on top of that, Se, As, and Te
An amorphous semiconductor layer (not shown) having a thickness of 50 nm made of (red sensitization) is formed. At this time, the As concentration was 2.0% by weight and T
e The concentration is 10% by weight. An amorphous semiconductor layer made of Se and As is formed thereon. The As concentration at this time is 1.0
% By weight. On top of that, 20 consisting of Se, As and GaF ₃
An amorphous semiconductor layer 43 having a thickness of 0 nm is formed. A at this time
The s concentration is 25% by weight, and the concentration of GaF ₃ is 2000 ppm by weight. A 50 nm amorphous semiconductor layer (not shown) made of Se and GaF ₃ is formed thereon. The GaF ₃ concentration at this time is 2000
ppm, and the thickness of the entire photoconductive layer is 5 μm. next,
As the electron injection blocking layer 5, Sb ₂ S ₃ is deposited to a thickness of 0.2 μm in an inert gas atmosphere of 1 × 10 ⁻¹ Torr to obtain a photoconductive target having a blocking type structure. Further, this is incorporated into an imaging tube housing containing an electron gun to obtain a photoconductive imaging tube.

The obtained image pickup tube was continuously operated for 2000 hours in an electric field having a multiplication factor of 10 when blue light was applied, as in Examples 1 and 2. The dark current after the continuous operation was measured in the same manner as in Examples 1 and 2, and as a result, the dark current was as good as 1 nA or less. In addition, no white scratches occurred.

This example shows that the present invention is also effective for an amorphous Se-based photoconductive layer containing Te.

Example 4 A transparent photoconductive layer 2 made of Al is formed on a glass substrate 1 (see FIG. 1), and CeO ₂ is deposited thereon to a thickness of 30 nm to form a hole injection blocking layer 3. . An amorphous semiconductor (not shown) made of Se and LiF and having a thickness of 100 nm is formed thereon by a vacuum evaporation method. At the time of film formation, Se and LiF were evaporated from different boats and evaporated, and LiF was
pm weight%. Next, an amorphous semiconductor layer made of Se and As is formed thereon. At this time, the As concentration is 1.0% by weight. On top of that, 250nm consisting of Se and As
An amorphous semiconductor layer 43 having a thickness is formed. At this time, the As concentration is 25% by weight, and the film thickness of the entire photoconductive layer is 6 μm. Next, Sb ₂ S ₃ was applied to the electron injection blocking layer 5 at 2 × 10 ⁻¹ T
Evaporate to a thickness of 0.1 μm in an inert gas atmosphere of orr to obtain a blocking target. This is incorporated into an imaging tube housing containing an electron gun to obtain an imaging tube.

The obtained imaging tube was operated continuously for 1000 hours in an electric field having a multiplication factor of 10 when irradiated with blue light, as in Examples 1 to 3. The dark current after the continuous operation was measured in the same manner as in Examples 1 and 2, and as a result, the dark current was as good as 1 nA or less. In addition, no white scratches occurred.

According to the present embodiment, it can be seen that the Se-As layer (I) 41 of FIG.

Although the present invention has been specifically described based on the above embodiments, the present invention is not limited to the above embodiments, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

〔The invention's effect〕

As described above, according to the present invention, in an image pickup tube using a photoconductive layer mainly composed of amorphous Se, a dark current when a high electric field is applied is low, and even when the device is continuously operated for a long time, white light is generated. This has the effect of not causing scratches.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a cross-sectional structure of an image pickup tube target using an amorphous Se-based photoconductive layer of the present invention, and FIG. 2 is an explanatory diagram showing a result of an example of the present invention. DESCRIPTION OF SYMBOLS 1 ... Translucent board 2 ... Translucent conductive film 3 ... Hole injection blocking layer 4 ... Photoconductive layer 5 ... Electron injection blocking layer 41 ... Se-As (I) layer 42 ... Se -As (II) layer 43 ... Se-As (III) layer

Continuing from the front page (72) Inventor Tadaaki Hirai 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Yukio Takasaki 3300 Hayano, Mobara-shi, Chiba Pref. (72) Inventor Keiichi Shitara 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute (72) Inventor Kenkichi Tanioka 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute (72) Inventor Junichi Yamazaki 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute (72) Inventor Kubota 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute (56) References JP-A-57-80639 (JP, A) JP-A-63-19738 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01J 29/45

Claims (5)

(57) [Claims] At least a light-transmitting conductive film, a hole injection blocking layer, a photoconductive layer at least partially composed of an amorphous semiconductor mainly composed of Se, and an electron injection blocking layer are formed on a light-transmitting substrate. In an image pickup tube having a target composed of the above and an electron beam control unit that scans the target with an electron beam, a layer thickness of 10 nm or more from the interface with or near the interface with the electron injection blocking layer in the photoconductive layer. An imaging tube, characterized in that As is added in an amount of 22% by weight or more and 38% by weight or less in a region of 400 nm or less. 2. A light-transmitting conductive film, a hole injection blocking layer, a photoconductive layer at least partially composed of an amorphous semiconductor mainly composed of Se, and an electron injection blocking layer formed on a light-transmitting substrate. A target having a thickness of 12.5 nm or more from the interface with or near the interface with the electron injection blocking layer in the photoconductive layer in an imaging tube having an electron beam control unit that scans the target with an electron beam. -An image pickup tube characterized by adding As to 22% by weight or more and 36% by weight or less in a region of 200nm or less. 3. The method according to claim 1, wherein 1% by weight or more and 5% by weight or less of As are added to a region having a layer thickness of 10 nm or more and 100 nm or less from or near the interface of the photoconductive layer with the hole injection blocking layer. The imaging tube according to claim 1, wherein: 4. The image pickup tube according to claim 1, wherein 1% by weight or less of As is added to a region other than said specific region of said photoconductive layer. 5. The imaging tube according to claim 1, wherein the imaging tube is operated in an electric field region in which avalanche multiplication of charges is induced inside the photoconductive layer. How it works.