JPS628433A - Image pickup tube target - Google Patents

Abstract

PURPOSE:To reduce the dark current considerably by applying impact of charged particles onto the scanning side surface of a-si:H photoconductive material layer. CONSTITUTION:Transparent conductive film 2 mainly composed of tin oxide is formed on a glass substrate 1 to form a layer 10 then polycrystal Si plate is employed as a target in high frequency spattering apparatus and to arrange the substrate 1 correspondingly. Upon highly evacuation in the apparatus, mixture gas of argon and hydrogen is led in. The substrate 1 formed with transparent conductive film and electron injection blocking layer through reactive spattering is deposited with a-si:H film 3 then arranged at the target side. Upon highly evacuation in the apparatus, hydrogen gas is led in the perform spattering to apply impact of hydrogen ions onto the surface of a-si:H film on the substrate arranged with a target to form a surface treating layer 11 then combined with an electron gun to produce an image pickup tube. Consequently, dark current reduction effect is achieved to reduce the residual image while to improve S/N ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a high-speed electron beam scanning type light guide image pickup tube that reads photoelectric conversion signals by high-speed electron beam scanning.

[Background of the invention]

Most conventional image pickup tubes use a scanning method using a low-speed electron beam (hereinafter referred to as the LP method), which causes problems such as large capacitive afterimages due to scanning electron beam resistance, poor peripheral resolution, and beam bending. It has drawbacks such as easy image distortion.

On the other hand, a method of scanning with a high-speed electron beam (hereinafter referred to as the HN method) has been proposed as a method for improving the above-mentioned problems. (For example, JP-A-54-44487). FIG. 1 is a diagram illustrating the operating principle of an HN type image pickup tube. HN
In this method, a secondary electron collector electrode 6 is provided on a transparent conductor layer 2.
Apply a lower voltage.

It is used so that the secondary electron emission ratio δ of the target surface is 1 or more. When the target surface is scanned with the accelerated electron beam 4 in this state, the target surface will be covered with 5 secondary electrons.
The potential of the collector electrode 6 is approximately equal to that of the collector electrode 6, and a positive potential is obtained with respect to the transparent electrode 2. The light passing through the transparent substrate 1 and the transparent ffi electrode 2 is absorbed by the photoconductor M3 and generates electron-hole pairs, but the light flows through 11 toward the scanning side, changing the scanning side potential in the negative direction. lower to. During the next scan of the electronic beam 11, this potential drop is read out as a video signal.

In Fig. 1, 7 is a cathode and 8 is a load resistor.

9 is a target voltage.

Compared to the conventional LP system, such an HN system image pickup tube has faster scanning electron speeds, so it has the following advantages: (1) less afterimage, (2) better peripheral resolution, and (3) less image distortion. There are advantages such as fewer

In addition, amorphous silicon containing hydrogen (hereinafter a-si
:H) has high photoelectric conversion efficiency and excellent thermal stability and homogeneity, and by using it as the photoconductor layer of the HN image pickup tube, high sensitivity and high resolution characteristics can be achieved. An excellent image pickup tube device has been proposed.

However, in an HN image pickup tube having an a-si:H photoconductor layer, when the a-si:H photoconductor layer is directly scanned with an electron beam, holes are injected from the electron beam scanning side. A large dark current is generated in the beam scanning side, causing problems such as deterioration of afterimage characteristics and reduction of S/N ratio due to secondary photocurrent. Therefore, in order to improve these problems, it is necessary to It is essential to suppress dark current due to hole injection.

As a method for reducing the above dark current in an HN type image pickup tube (hereinafter abbreviated as HN type a-si:H image pickup tube) using a-si:H in the photoconductor layer.

Up to now, there have been methods for providing a secondary electron emitting layer made of new oxides or purified materials on the scanning side surface of the photoconductor layer, and
A method of forming an N-type layer-si:H layer on the surface of the :H photoconductor layer has been proposed. However, although such a secondary electron emission layer also has the effect of reducing dark current due to hole injection from the electron beam scanning side, the dark current reduction effect cannot be said to be sufficient. Although the method of forming an N-type layer on the surface of the conductor layer certainly has the effect of lowering the dark current, this layer becomes a low-resistance layer and may cause secondary problems such as deterioration of resolution.

[Purpose of the invention]

An object of the present invention is to provide an image pickup tube target in which dark current is significantly reduced in an HN type a-si:H image pickup tube.

[Summary of the invention]

As a result of detailed experimental research regarding the dark current in HN B-si:H image pickup tubes, the inventor found that a-s
By applying MS using charged particles to the scanning side surface of the i:H photoconductor layer, it is possible to obtain a dark current suppression ability superior to that of the conventional method, regardless of whether or not a secondary electron emitting layer is provided separately. discovered. Hereinafter, the content of the present invention will be explained in detail.

FIG. 2 shows an example of the structure of an HN type a-si:H image pickup tube target used to demonstrate the effects of the present invention. , transparent electrode 2. Layer 10 for blocking electron injection from the transparent electrode 2. and a-si:H photoconductor layer 3
In the present invention, after creating the image pickup tube target as described above.

Before bonding to the electron gun section for generating the scanning electron beam shown in FIG. A back type particle aI bombardment treatment layer 11 is formed on the substrate. Charged particle bombardment can be achieved by irradiating the image pickup tube target with charged particles from an ion source in a vacuum, or by placing the image pickup tube target on the cathode side of a discharge device such as a sputtering device and exposing it to discharge plasma. This can be done by, for example. Charged particles include a type of inert gas such as helium, neon, argon, hydrogen, oxygen, nitrogen, etc.
Alternatively, two or more types of charged particles are used.

The polarity of charged particles can be either positive or negative, but
To avoid lifting during impact, a s x
a It is preferable to shine light on the photoconductor layer to lower the resistance of the photoconductor layer and allow the charge to escape from the transparent electrode.
The charged particles are not limited to those mentioned above, and high-energy electrons may be used, or a combination of the above-mentioned charged particles and electrons may be used. The processing time depends on the type of charged particles used, the equipment, etc., and should be determined for each case. However, the important thing to do is to select the charged particle density and energy so that the surface of the a-si:H photoconductor layer is not excessively dry etched by the impact of the charged particles. Further, it is desirable that the temperature of the image pickup tube target at the time of charged particle bombardment is 150° C. or lower, more preferably 120° C. or lower; if the temperature is increased, sufficient effects cannot be obtained.

When the image pickup tube target in which the a-si:H photoconductor layer is bombarded with charged particles and the charged particle bombardment treatment layer 11 is formed on one surface by the method described above is used in an HN type image pickup tube, from the electron beam scanning side The injection of holes is blocked, dark current can be significantly reduced, and images with low afterimages and high S/N ratio can be realized. The method of forming a surface treatment layer on the electron beam scanning side surface of the photoconductor layer by charged particle M bombardment is not limited to the method described above, but may include other methods,
For example, 150°C or less, preferably 1
1-reactive sputtering method or glow discharge C at a temperature below 20℃
An amorphous silicon film subjected to charged particle bombardment may be formed by the VD method.Furthermore, after the surface of the a-si:H photoconductor layer is subjected to charged particle bombardment treatment, a-si:
Material 1 with a higher secondary electron emission ratio than H, e.g. MgO,
MgF.

Even if a new thin film such as C or I is formed as a layer for emitting secondary electrons, the temperature at which the new thin film is formed is 1.
The above effects will not be lost at all if the temperature is below 50°C, preferably below 120°C.In such cases, MgO, MgF
If a new layer for emitting secondary electrons such as 2 etc. is formed by sputtering, the MgO
, MgF, etc., charged particle bombardment can also be applied to the surface of the a-si:H photoconductor layer through the deposited layer, with a similar effect. In this way, through the surface treatment layer formed by charged particle bombardment on the electron beam scanning side surface of the photoconductor layer.

Moreover, in the image pickup tube target, which has a new layer made of a material with a high secondary electron emission ratio of a-si:HJ: It is also advantageous in designing and realizing high-performance electron guns.

[Embodiments of the invention]

Specific examples will be described below.

Example 1 A transparent conductive film 2 mainly made of tin oxide is formed on a glass substrate 1 by a CVD method to form a layer 1 for blocking electron injection.
After forming 0, a polycrystalline Si plate is used as a target in a high-frequency sputtering apparatus, and the substrate is placed opposite to the target. After evacuating the inside of the apparatus to a high vacuum of less than I X 10-'Totr, a mixed gas of argon and hydrogen is thickened to evacuate the inside of the apparatus to 5 X 10-' to 5 X 10-
Set the pressure to 3 Torr. The concentration of hydrogen in the mixed gas is 3
0 to 65%. After setting the substrate temperature at 150 to 300°C, reactive sputtering is performed to form a film with a thickness of approximately 0.5 to 4μ on the substrate 1 on which the transparent conductive film and electron injection blocking layer have been formed.
In the 0th order in which the m a -si:H film 3 is deposited, the substrate is placed on the target side in a high frequency sputtering apparatus. After evacuating the inside of the apparatus to a high vacuum of less than I x 10-'' Torr, hydrogen gas was introduced and the temperature was 5 x 10-'' to 2 x
The pressure is 10-aTorr, the substrate temperature is 120°C or less,
A sputtering operation was performed for 10 seconds to 5 minutes at a power density of 0.5 to 5 W/cd, and the a-
After the surface of the si:H film is bombarded with hydrogen ions to form a surface treatment layer 11, it is combined with an electron gun to form an image pickup tube.

Example 2 In the same manner as in Example 1, a transparent conductive film, a layer for blocking electron injection, and an a-si:H film are formed on a glass substrate, and then combined with an electron gun to create an image pickup tube. . Next, in this image pickup tube, electron beam scanning was performed for 2 hours with the transparent conductive film at open potential, the cathode at ground potential, and the mesh electrode potential at 1500 V, and the electron beam was applied to the scanning side surface of the a-si:H photoconductive film. Form an impact treatment layer.

Example 3 In the same manner as in Example 1, a transparent conductive film, a layer for blocking electron injection, and an a-si:H film were formed on a glass substrate, and then an ion gun was used at a surface temperature of 120°C or less. After bombarding it with He ions for 2 minutes, it is combined with an electron gun to create an image pickup tube.

Example 4 In the same manner as in Example 1, a transparent electrode, a layer for blocking electron injection, and an a-si:H film were formed on a glass substrate, and then a film thickness of 50 to 50° C. was formed at a substrate temperature of 150° C. or lower. 200 people a
- After forming a si:H film by sputtering, it is combined with an electron gun to form an image pickup tube.

Example 5 As in Example 1, a transparent conductive film was placed on a glass substrate.

After forming a layer for blocking electron injection, an a-si:H film and forming a hydrogen ion bombardment layer on the a-si:H surface, MgO was used as a secondary electron emission layer at a surface temperature of 12
After being deposited by vapor deposition at temperatures below 0°C, it is combined with an electron gun to form an image pickup tube.

Example 6 In the same manner as in Example 1, a transparent conductive film, a layer for blocking electron injection, and an a-si:H film were formed on a glass substrate, and then the film thickness was 50 to 150°C at a substrate temperature of 120°C or less. person's M
gF2 was deposited on the a-si:H film by sputtering,
It is combined with an electron gun to create an image pickup tube.

When the image pickup tube obtained in the above example was subjected to HN operation using the method described in FIG. A remarkable effect was seen in that the

Figure 3 shows the dark current characteristics of the HN image pickup tubes of Examples 1 to 6 (hatched area 12 in the figure) and the surface of a-si:H, which has not been subjected to charged particle bombardment treatment, by direct electron beam. As an example of the dark current characteristic (curve 13) when scanning and the conventional method, a substrate temperature of 150
In this figure, which is a comparison of the dark current characteristics (curve 14) when Mg0Jl is formed by sputtering in the range of .degree. C. to 250.degree. C., the horizontal axis is the target voltage 9, and the vertical axis is the logarithmic representation of the dark current.

From a comparison of curves 12 and 13, it is clear that the dark current is significantly reduced by forming a 1 ft'l layer of charged particles according to the present invention. Further, from a comparison of curves 12 and 14, it is clear that the dark current reduction effect according to the present invention is even better than that of the conventional method.

Figure 4 shows the afterimage characteristics of the HN image pickup tube obtained in Examples 1 to 6 (tracks 4 and 15) and the electron beam scanning of the a-si:H surface directly without impact treatment with charged particles. Afterimage characteristics (16) and MgO at a substrate temperature of 150~2
This is a comparison of afterimage characteristics (17) when formed on a-si:H4l by sputtering at 50°C. Fourth
From the figure, the present invention not only suppresses dark current.

It can be seen that the afterimage, which is an important characteristic of an image pickup tube, can also be reduced with good reproducibility.

In the above embodiments, a-s formed by sputtering
i: Only the H photoconductor layer was mentioned.

A-SI created by glow discharge CVD method or other methods
The same effect can be obtained by applying charged particle bombardment to the :H photoconductor layer using the method described in the Examples.

〔Effect of the invention〕

As described above in detail, according to the present invention, a-s
In an HN image pickup tube using i:H as a photoconductive film, the scanning side surface of the a-si:H photoconductive film is subjected to impact treatment with charged particles, thereby forming a separate dark current suppression layer or Regardless of whether or not a layer for secondary electron emission is provided, the sail current reduction effect can be obtained, and advantages such as less afterimage and a good S/N ratio can be obtained. It goes without saying that the effects of the present invention are not limited to image pickup tube targets, but can also be applied to photoelectric conversion devices using a-si:H films, such as electrophotographic photoreceptors and optical sensors.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the operation of the HN type image pickup tube, FIG. 2 is a sectional view of the image pickup tube target according to the present invention, and FIG. 3 is for showing the effects of the present invention according to Examples 1 and 2.3 of the present invention. diagram,
FIG. 4 is a diagram showing the effect of the present invention according to Example 4. 1... Transparent substrate, 2... Transparent conductive film, 3...
Photoconductive film, 4... Scanning electron beam, 5... Secondary electrons, 6... Convergence and collector electrode, 7... Cathode, 8
...Load resistance, 9...Target voltage, 10...
Electron injection blocking layer, 11... Charged particle impact treatment layer.

Claims (1)

[Claims] 1. At least a light-transmitting conductive film and a photoconductor layer made of amorphous silicon containing hydrogen are provided on a predetermined light-transmitting insulating substrate, and the light-transmitting conductive film is In a high-speed electron beam scanning negatively charged image pickup tube disposed on the light incidence side, at least the beam scanning side surface of the photoconductor layer has a surface treatment layer formed by charged particle bombardment at a temperature of 150° C. or less. An image pickup tube target characterized by: 2. The charged particles described above are characterized by being composed of at least one selected from inert gas ions such as helium, neon, and argon, hydrogen ions, oxygen ions, nitrogen ions, and electrons. An image pickup tube target according to claim 1. 3. The beam scanning side surface layer of the photoconductor layer is an amorphous silicon containing at least hydrogen, which is formed by reactive sputtering or glow discharge CVD at a temperature of 150° C. or less while being bombarded with charged particles. An image pickup tube target according to claim 1, characterized in that the image pickup tube target comprises: 4. On the beam scanning side surface of the photoconductor layer, a layer made of a new material for emitting secondary electrons was deposited at a temperature of 150°C or less on the surface treatment layer formed by charged particle bombardment. An image pickup tube target according to claim 1, characterized in that: 5. A layer made of a new material for emitting secondary electrons is formed on the beam scanning side surface of the photoconductor layer by sputtering or glow discharge CVD at a temperature of 150° C. or less,
The image pickup tube target according to claim 1, wherein the image pickup tube target is formed while applying charged particle impact to the surface of the photoconductor layer. 6. The secondary electron emitting layer according to items 4 and 5 above is made of at least one selected from MgO, MgF_2, CaI, amorphous silicon nitride, and amorphous silicon carbon. image tube target.