JP2021150068A - Photocathode and manufacturing method of the same - Google Patents

Abstract

To provide a photocathode whose quantum efficiency is improved and which can be manufactured efficiently, and a manufacturing method of the same.SOLUTION: A photocathode 1 includes a substrate 100, a photoelectric conversion layer 400, which is provided on the substrate 100 and generates photoelectrons in response to incident light, and an intermediate layer 200, which is provided between the substrate 100 and the photoelectric conversion layer 400 in contact with the substrate 100. The intermediate layer 200 contains a hafnium nitride.SELECTED DRAWING: Figure 2

Description

The present invention relates to a photocathode and a method for manufacturing a photocathode.

Patent Document 1 describes a photoelectric surface. The photoelectric surface includes a substrate that transmits incident light, a photoelectron emitting layer containing an alkali metal, and an intermediate layer formed between the substrate and the photoelectron emitting layer. The intermediate layer consists of hafnium oxide.

Patent No. 4926504

On the above-mentioned photoelectric surface, an intermediate layer made of hafnium oxide functions as an antireflection film. As a result, the reflectance of a predetermined wavelength component of the light incident on the photoelectron emission layer is reduced, and it is possible to exhibit high effective quantum efficiency. On the other hand, in the above technical fields, it is desired to improve the efficiency of manufacturing.

Therefore, an object of the present invention is to provide a photocathode whose quantum efficiency is improved and which can be efficiently manufactured, and a method for manufacturing a photocathode.

The present inventor has made diligent research to solve the above problems, and found that the film formation rate of the intermediate layer containing hafnium nitride is higher than the film formation rate of the intermediate layer made of hafnium oxide, for example. I got the knowledge. The present inventor has completed the present invention by proceeding with further studies based on the findings.

That is, the photocathode according to the present invention comprises a translucent substrate, a photoelectric conversion layer provided on the translucent substrate and generating photoelectrons in response to light incident, and a translucent substrate and a photoelectric conversion layer. It comprises an intermediate layer provided in contact with the translucent substrate between them, the intermediate layer containing a hafnium nitride.

This photocathode includes an intermediate layer between the translucent substrate and the photoelectric conversion layer. Since this intermediate layer contains hafnium nitride, it functions as an antireflection film. Further, as described above, the film formation rate of the intermediate layer containing the hafnium nitride is relatively high. Therefore, this photocathode is efficiently manufactured while improving the quantum efficiency.

In the photocathode according to the present invention, the intermediate layer may contain an oxide of hafnium. In this case, the light transmittance of the intermediate layer is improved, and it can function as an antireflection film in a wider wavelength range.

In the photocathode according to the present invention, the amount of hafnium oxide may be larger than the amount of hafnium nitride in the intermediate layer. In this case, the light transmittance of the intermediate layer is further improved, and it can function as an antireflection film in a wider wavelength range.

In the photocathode according to the present invention, in the intermediate layer, the amount of at least one of the hafnium nitride and the hafnium oxide may be unevenly distributed in the thickness direction of the intermediate layer. At this time, in the intermediate layer, the amount of hafnium nitride is larger on the photoelectric conversion layer side than on the translucent substrate side, and the amount of hafnium oxide is larger on the translucent substrate side than on the photoelectric conversion layer side. There may be more on the side. Further, the intermediate layer has a first intermediate layer and a second intermediate layer laminated on each other, and the first intermediate layer is located on the translucent substrate side of the second intermediate layer and is an oxide of hafnium. May include.

Alternatively, in the photocathode according to the present invention, in the intermediate layer, the amount of hafnium nitride is distributed substantially uniformly in the thickness direction of the intermediate layer, and the amount of hafnium oxide is the thickness of the intermediate layer. It may be distributed substantially uniformly in the direction. In any of these cases, the light transmittance of the intermediate layer is further improved, and it can function as an antireflection film in a wider wavelength range.

The photocathode according to the present invention may be provided between the intermediate layer and the photoelectric conversion layer and may include a base layer containing beryllium. As described above, by using the base layer containing beryllium, the effective quantum efficiency is further improved and the sensitivity is improved.

Here, according to another finding of the present inventor, when forming a base layer containing beryllium, for example, compared with the film formation rate of the base layer made of an oxide of beryllium alloy or the base layer from beryllium oxide. , The formation rate of the underlying layer containing beryllium nitride is faster and can be produced efficiently.

Therefore, in the photocathode according to the present invention, the base layer may contain beryllium nitride. In this case, as described above, a photocathode having a base layer containing beryllium can be efficiently produced.

In the photocathode according to the present invention, the base layer may contain an oxide of beryllium. In this case, the quantum efficiency of the photocathode is improved, and it can function as an underlayer in a wider wavelength range.

In the photocathode according to the present invention, the amount of beryllium oxide may be larger than the amount of beryllium nitride in the base layer. In this case, the quantum efficiency of the photocathode is improved, and it can function as an underlayer in a wider wavelength range.

In the photocathode according to the present invention, in the base layer, at least one amount of beryllium nitride and beryllium oxide may be unevenly distributed in the thickness direction of the base layer. At this time, in the base layer, the amount of beryllium nitride is larger on the translucent substrate side than on the photoelectric conversion layer side, and the amount of beryllium oxide is larger on the photoelectric conversion layer side than on the translucent substrate side. May be as many as. Further, the base layer has a first base layer and a second base layer laminated on each other, and the second base layer is located closer to the photoelectric conversion layer than the first base layer and contains beryllium oxide. It may be included.

Alternatively, in the photocathode according to the present invention, in the base layer, the amount of beryllium nitride is distributed substantially uniformly in the thickness direction of the base layer, and the amount of beryllium oxide is the thickness of the base layer. It may be distributed substantially uniformly in the direction. In any of these cases, the quantum efficiency of the photocathode is further improved and it can function as an underlayer in a wider wavelength range.

The method for manufacturing a photoelectric cathode according to the present invention includes a first step of preparing a translucent substrate, a second step of forming an intermediate layer containing hafnium on the translucent substrate after the first step, and a second step. After the step, a third step of forming a photoelectric conversion layer that generates photoelectrons in response to light incident is provided on the intermediate layer, and in the second step, a translucent substrate is formed in an atmosphere containing nitrogen. It directly forms an intermediate layer containing hafnium nitride.

In this manufacturing method, in the second step, the second step of forming the intermediate layer containing hafnium is performed in an atmosphere containing nitrogen, so that the intermediate layer containing hafnium nitride is directly formed on the translucent substrate. Form. As shown in the above findings, the film formation rate of the intermediate layer containing the hafnium nitride is relatively high. Therefore, according to this manufacturing method, a photocathode with improved quantum efficiency can be efficiently manufactured.

In the method for producing a photocathode according to the present invention, in the second step, an intermediate layer containing a hafnium nitride and a hafnium oxide may be formed by using an atmosphere containing nitrogen and oxygen. In this case, the light transmittance of the intermediate layer is improved, and an intermediate layer capable of functioning as an antireflection film in a wider wavelength range can be formed.

In the method for producing a photocathode according to the present invention, an atmosphere containing an inert gas different from nitrogen may be used in the second step. According to the findings of the present inventor, the film formation rate of the intermediate layer is further improved by mixing an inert gas different from nitrogen such as argon with the atmosphere containing nitrogen when forming the intermediate layer. NS. Therefore, in this case, the photocathode with improved quantum efficiency can be manufactured more efficiently. According to a further finding of the present inventor, when the film formation rate of the intermediate layer is improved, the oxygen uptake of the intermediate layer is reduced, and as a result, the oxygen ratio of the intermediate layer is decreased. Therefore, the optical characteristics such as the light transmittance of the intermediate layer can be controlled by mixing the inert gas.

The method for producing a photocathode according to the present invention may include a fourth step of performing an oxidation treatment on the intermediate layer between the second step and the third step. In this case, the light transmittance is improved, and an intermediate layer capable of functioning as an antireflection film in a wider wavelength range can be formed.

The method for producing a photocathode according to the present invention includes a fifth step of forming a base layer containing beryllium on an intermediate layer between the second step and the third step, and in the third step, the photocathode is formed on the base layer. A photoelectric conversion layer may be formed. By forming the base layer containing beryllium on the intermediate layer in this way, it is possible to manufacture a photocathode having improved effective quantum efficiency and sensitivity.

In the method for producing a photocathode according to the present invention, in the fifth step, a base layer containing beryllium nitride may be formed in an atmosphere containing nitrogen. In this case, as described above, the photocathode including the base layer can be efficiently manufactured.

The method for producing a photocathode according to the present invention may include a sixth step of oxidizing the underlying layer after the fifth step. In this case, the quantum efficiency is improved and an underlayer that functions in a wider range can be formed.

In the method for producing a photocathode according to the present invention, in the sixth step, the intermediate layer and the underlying layer may be collectively oxidized. In this case, since the oxidation treatment of the intermediate layer and the base layer is performed collectively, the photocathode can be manufactured more efficiently.

According to the present invention, it is possible to provide a photocathode whose quantum efficiency is improved and which can be efficiently manufactured, and a method for manufacturing a photocathode.

It is a schematic cross-sectional view which shows the photomultiplier tube as an example of the electron tube which concerns on this embodiment. It is a partial cross-sectional view of the photocathode shown in FIG. It is a schematic cross-sectional view for demonstrating the manufacturing method of the photocathode shown in FIGS. It is a schematic cross-sectional view for demonstrating the manufacturing method of the photocathode shown in FIGS. It is a schematic cross-sectional view for demonstrating the manufacturing method of the photocathode shown in FIGS. It is a graph which shows the comparison result of the film formation rate. It is a graph which shows the comparison result of optical characteristics. It is a graph which shows the comparison result of quantum efficiency. It is a graph which shows the analysis result of the component of the intermediate layer according to a sputter gas (atmosphere in a sputtering method). It is a graph which shows the difference of the film formation rate by the type of a sputter gas.

Hereinafter, one embodiment will be described in detail with reference to the drawings. In each figure, the same or corresponding elements may be designated by the same reference numerals, and duplicate description may be omitted.

FIG. 1 is a schematic cross-sectional view showing a photomultiplier tube as an example of the electron tube according to the present embodiment. The photomultiplier tube (electron tube) 10 shown in FIG. 1 includes a photocathode 1, a container 32, a focusing electrode 36, an anode 38, a multiplying portion 40, a stem pin 44, and a stem plate 46. The container 32 has a cylindrical shape, and a vacuum is formed by sealing one end with an incident window 34 (here, the substrate 100 of the photocathode 1) and the other end with a stem plate 46. It is configured as a housing. The focusing electrode 36, the anode 38, and the multiplying portion 40 are arranged in the container 32.

The incident window 34 transmits the incident light hν. ^{The photocathode 1 emits photoelectrons e −} according to the incident light hν from the incident window 34. ^{The focusing electrode 36 guides the photoelectrons e −} emitted from the photocathode 1 to the multiplying portion 40. Multiplier section 40 includes a plurality of dynodes 42, photoelectrons e ^- are multiplying secondary electrons generated in response to incidence of. The anode 38 collects secondary electrons generated by the multiplying portion 40. The stem pin 44 is provided so as to penetrate the stem plate 46. A corresponding focusing electrode 36, an anode 38, and a dynode 42 are electrically connected to the stem pin 44.

FIG. 2 is a partial cross-sectional view of the photocathode shown in FIG. FIG. 2B is an enlarged view of the region A of FIG. 2A. As shown in FIG. 2, the photocathode 1 is configured as a transmissive type. The photocathode 1 has a substrate (translucent substrate) 100, an intermediate layer 200, a base layer 300, and a photoelectric conversion layer 400. The substrate 100 is made of a material that transmits light (incident light hν). The substrate 100 includes a surface 100a and a surface 100b opposite the surface 100a. The surface 100a is a surface facing the outside of the container 32, and here is an incident surface of the incident light hν. The intermediate layer 200 is provided on the surface 100b. The intermediate layer 200 is in contact with the surface 100b. That is, the intermediate layer 200 is directly formed on the substrate 100 (surface 100b).

The intermediate layer 200 has a surface 200a opposite to the surface 100b. The base layer 300 is provided on the surface 200a. In other words, the base layer 300 is provided on the substrate 100, and the intermediate layer 200 is provided between the substrate 100 and the base layer 300. The base layer 300 is in contact with the surface 200a of the intermediate layer 200. That is, the base layer 300 is directly provided on the intermediate layer 200 (surface 200a). The base layer 300 has a surface 300a opposite to the surface 200a.

The photoelectric conversion layer 400 is provided on the surface 300a. In other words, the photoelectric conversion layer 400 is provided on the substrate 100, and the intermediate layer 200 and the base layer 300 are provided between the substrate 100 and the photoelectric conversion layer 400. The photoelectric conversion layer 400 is in contact with the surface 300a of the base layer 300. That is, the photoelectric conversion layer 400 is directly provided on the base layer 300 (surface 300a).

As described above, in the photocathode 1, the intermediate layer 200, the base layer 300, and the photoelectric conversion layer 400 are laminated on the substrate 100 in this order. The photoelectric conversion layer 400 receives the incident light hν through the substrate 100, the intermediate layer 200, and the base layer 300, and generates ^{photoelectrons e − according to the incident light hν.} That is, here, the photocathode 1 is a transmissive photocathode. The photoelectric conversion layer 400 is on the opposite side of the substrate 100 and has a desired surface 400a inside the container 32. Photoelectrons e ⁻ are emitted from the surface 400a into the container 32.

Here, the intermediate layer 200 contains a hafnium nitride (for example, hafnium nitride). Further, the intermediate layer 200 may contain oxygen. Oxygen can be contained in the intermediate layer 200 as an oxide of hafnium (eg, hafnium oxide). The intermediate layer 200 is used as a layer including two regions, a first region 210 on the substrate 100 side and a second region 220 on the photoelectric conversion layer 400 side (for example, a layer composed of a first region 210 and a second region 220). When viewed, the distribution of hafnium nitrides and hafnium oxides in the first region 210 and the second region 220 can take various forms.

For example, in the intermediate layer 200, the amount of at least one of the hafnium nitride and the hafnium oxide is in the thickness direction of the intermediate layer 200 (the direction intersecting the surface 200a and goes from the substrate 100 to the photoelectric conversion layer 400). It may be unevenly distributed in the direction). More specifically, there may be a difference in the distribution of hafnium nitride and hafnium oxide between the first region 210 and the second region 220.

That is, as an example, the amount of hafnium nitride may be larger in the second region 220 than in the first region 210, and the amount of hafnium oxide may be larger in the first region 210 than in the second region 220. Further, hafnium is formed in the first region 210 and the second region 220 so that the first region 210 and the second region 220 can be discriminated as different layers (first intermediate layer and second intermediate layer) with the surface 210a in between. There may be a difference between the amount of nitride and the amount of hafnium oxide. In this case, the first region 210 can be regarded as the first intermediate layer which is the oxide layer of hafnium, and the second region 220 can be regarded as the second intermediate layer which is the nitride layer of hafnium. However, since the first intermediate layer and the second intermediate layer can be continuously formed, the surface 210a can be a virtual surface, not limited to a surface having a clear boundary as shown in the figure. The position of the intermediate layer 200 in the thickness direction can also vary.

On the other hand, in the intermediate layer 200, the amount of hafnium nitride is distributed substantially uniformly in the thickness direction of the intermediate layer 200, and the amount of hafnium oxide is also distributed substantially uniformly in the thickness direction of the intermediate layer 200. You may. In other words, the amount of hafnium nitride is distributed substantially uniformly in the thickness direction over at least two regions of the first region 210 and the second region 220, and the amount of hafnium oxide is also its thickness. It may be distributed substantially uniformly in the vertical direction. In any case, the amount of hafnium oxide is preferably larger than the amount of hafnium nitride.

Further, in any case, the above distribution is not limited to the case where the above distribution is accurately shown over the entire intermediate layer 200, and although the above distribution is basically the main body, there may be some regions showing different tendencies. It is judged that there are cases. The ratio of the amount of hafnium nitride to the amount of hafnium oxide is, for example, the atomic number ratio. That is, the ratio of the amount of hafnium nitride to the amount of hafnium oxide can be defined by the ratio of the number of oxygen atoms to the number of nitrogen atoms in the region of interest. Examples of the method for analyzing the number of atoms include an X-ray photoelectron spectroscopy and an Auger electron spectroscopy. The thickness of the intermediate layer 200 (dimensions in the direction intersecting the surface 200a) is, for example, about 5 Å to 1000 Å. The intermediate layer 200 functions as an antireflection film.

The base layer 300 contains a beryllium nitride (for example, beryllium nitride). Further, the base layer 300 may contain oxygen. Oxygen can be contained in the underlying layer 300 as an oxide of beryllium (eg, beryllium oxide). The base layer 300 is used as a layer including two regions, a first region 310 on the substrate 100 side and a second region 320 on the photoelectric conversion layer 400 side (as an example, a layer composed of a first region 310 and a second region 320). When viewed, the distribution of beryllium nitride and beryllium oxide in the first region 310 and the second region 320 can take various forms.

For example, in the base layer 300, the amount of at least one of the beryllium nitride and the beryllium oxide is in the thickness direction of the base layer 300 (the direction intersecting the surface 300a and goes from the substrate 100 to the photoelectric conversion layer 400. It may be unevenly distributed in the direction). More specifically, in the base layer 300, the distribution of beryllium nitride and beryllium oxide may be different between the first region 310 and the second region 320.

For example, in the base layer 300, the amount of beryllium nitride is larger in the first region 310 than in the second region 320, and the amount of beryllium oxide is larger in the second region 320 than in the first region 310. good. Further, the amount of beryllium nitride and beryllium oxide is so large that the first region 310 and the second region 320 can be discriminated as different layers (first base layer and second base layer) with the surface 310a interposed therebetween. There may be a difference. In this case, the first region 310 can be regarded as the first base layer which is the nitride layer of beryllium, and the second region 320 can be regarded as the second base layer which is the oxide layer of beryllium.

The total thickness of the base layer 300 is, for example, about 200 Å to 800 Å. In that case, the thickness of the first base layer is, for example, about 200 Å to 700 Å, and the thickness of the second base layer is, for example, about 0 to 100 Å. The ratio of the thickness of the second base layer to the thickness of the first base layer is, for example, about 0 to 0.5. The oxygen atom ratio in the second base layer is, for example, about 30 at% to 100 at%. However, since the first intermediate layer and the second intermediate layer can be continuously formed, the surface 310a can be a virtual surface, not limited to a surface having a clear boundary as shown in the figure. The position of the base layer 300 in the thickness direction can also fluctuate.

On the other hand, in the base layer 300, the amount of beryllium nitride is distributed substantially uniformly in the thickness direction of the base layer 300, and the amount of beryllium oxide is also distributed substantially uniformly in the thickness direction of the base layer 300. You may. In other words, the amount of beryllium nitride is distributed substantially uniformly in the thickness direction over at least two regions of the first region 310 and the second region 320, and the amount of beryllium oxide is also its thickness. It may be distributed substantially uniformly in the vertical direction.

In any case, the amount of beryllium oxide is preferably larger than the amount of beryllium nitride. Further, in any case, the above-mentioned distribution is not always shown accurately over the entire base layer 300, and basically, although the above-mentioned distribution is predominant, there are some regions showing different tendencies. It is judged that it may be possible. The ratio of the amount of beryllium nitride to the amount of beryllium oxide is, for example, the atomic number ratio. That is, it may be determined by the ratio of the number of atoms of oxygen and the ratio of the number of atoms of nitrogen. Examples of the method for analyzing the number of atoms include an X-ray photoelectron spectroscopy and an Auger electron spectroscopy.

The photoelectric conversion layer 400 is made of, for example, a compound of antimony (Sb) and an alkali metal. The alkali metal may contain, for example, at least one of cesium (Cs), potassium (K), and sodium (Na). The photocathode layer 400 functions as an active layer of the photocathode 1. The thickness of the photoelectric conversion layer 400 is, for example, about 100 Å to 2500 Å. The total thickness of the photocathode 1 excluding the substrate 100 is, for example, about 305 Å to 4300 Å.

Subsequently, a method for manufacturing the photocathode 1 will be described. 3 to 5 are schematic cross-sectional views for explaining the method for manufacturing the photocathode shown in FIGS. 1 and 2. FIG. 4 (c) is an enlarged view of the region G of FIG. 4 (b). In this manufacturing method, as shown in FIG. 3, first, a container 32 containing the substrate 100 is prepared (first step). The container 32 has been washed. Subsequently, the intermediate layer 200 is formed on the substrate 100 (second step).

In the second step, the container 32 is arranged in the chamber B1. Further, the target C1 for the intermediate layer is arranged in the chamber B1 so that the surface 100b, which is the inner surface of the container 32 of the substrate 100, faces the target C1. Then, while creating a nitrogen atmosphere in the chamber B1, the intermediate layer 200 is formed directly on the surface 100b of the substrate 100 by sputtering using the target C1 in the nitrogen atmosphere (see FIG. 4).

The atmosphere containing nitrogen in the chamber B1 is, for example, nitrogen, an atmosphere containing nitrogen and a mixed gas of an inert gas different from nitrogen (for example, argon, helium, neon, krypton, xenone, hydrogen, etc.), nitrogen and oxygen, or an atmosphere containing nitrogen. The atmosphere contains nitrogen, oxygen, and an inert gas different from nitrogen. Target C1 is made of hafnium.

In the second step, the intermediate layer 200 is formed directly on the surface 100b of the substrate 100 by performing sputtering under such a situation. That is, in the second step, the intermediate layer 200 containing the hafnium nitride is formed directly on the substrate 100 by performing sputtering using the hafnium target C1 in an atmosphere containing nitrogen. As described above, in the second step, sputtering is performed with the target C1 arranged in the container 32.

In the second step, vapor deposition may be performed instead of sputtering. That is, in the second step, vapor deposition or sputtering using the hafnium target C1 can be performed in an atmosphere containing nitrogen. As the vapor deposition method, a resistance heating vapor deposition method, a chemical vapor deposition method, or the like can be used. As the sputtering, DC magnetron reactive sputtering, RF magnetron sputtering (non-reactive), RF magnetron reactive sputtering, or the like can be used.

In the subsequent step, the intermediate layer 200 is subjected to an oxidation treatment (fourth step). As a result, the intermediate layer 200 containing the oxide of hafnium is obtained. In the second step, the oxidation treatment (fourth step) is omitted by forming the intermediate layer 200 containing the hafnium nitride and the hafnium oxide by using the atmosphere containing nitrogen and oxygen. Alternatively, the oxidation treatment (fourth step) may be further carried out to further increase the amount of hafnium oxide in the intermediate layer 200. As the oxidation treatment method, oxidation by discharge, oxidation by heat, oxidation by light, oxidation by an oxidizing atmosphere (ozone, steam atmosphere, etc.), oxidation by an oxidizing agent (oxidizing solution, etc.), and a combination thereof can be used. Then, by changing the conditions of the oxidation treatment method, the intermediate layer 200 having the above-mentioned distribution can be obtained.

In the subsequent step, the base layer 300 containing beryllium is formed on the intermediate layer 200 (fifth step). More specifically, first, the container 32 on which the intermediate layer 200 is formed is arranged in the chamber B2. Further, the target source (beryllium source) C3 for the base layer is arranged in the chamber B2 so as to face the intermediate layer 200. The chamber B2 may be shared with the chamber B1 used in the second step.

Then, while creating a nitrogen atmosphere in the chamber B2, the base layer 300 is directly formed on the intermediate layer 200 by vapor deposition or sputtering using a beryllium target in the nitrogen atmosphere (FIGS. 4B and 4c). )reference). The atmosphere in the chamber B2 at this time may be composed of only nitrogen or may be mixed with an inert gas different from nitrogen. Examples of the inert gas include argon, helium, neon, krypton, xenon, hydrogen and the like.

As the vapor deposition method, a resistance heating vapor deposition method, a chemical vapor deposition method, or the like can be used. As the sputtering, DC magnetron reactive sputtering, RF magnetron sputtering (non-reactive), RF magnetron reactive sputtering, or the like can be used. As for the sputtering here, the sputtering can be performed in a state where the target source C3 is arranged in the container 32.

In the subsequent step, the base layer 300 is subjected to an oxidation treatment (sixth step). As a result, the base layer 300 containing the oxide of beryllium is obtained. For example, the base layer 300 is oxidized from the side opposite to the intermediate layer 200 in the base layer 300. As a result, the film-like region of the base layer 300 including the surface 300a opposite to the intermediate layer 200 and containing the beryllium nitride is replaced with the region containing the beryllium oxide. As a result, the above-mentioned first base layer (first region 310) and the second base layer (second region 320) are formed. That is, in this step, as the base layer 300, the first base layer provided on the intermediate layer 200 and containing the nitride of beryllium and the surface 310a of the first base layer opposite to the intermediate layer 200 are provided on the beryllium. The base layer 300 is oxidized from the side opposite to the intermediate layer 200 so that the second base layer containing an oxide is formed.

In the fifth step, the oxidation treatment (sixth step) is omitted by forming the base layer 300 containing the nitride of beryllium and the oxide of beryllium by using the atmosphere containing nitrogen and oxygen. May be good. Alternatively, the oxidation treatment (sixth step) may be further carried out to further increase the amount of beryllium oxide in the base layer 300. As the oxidation treatment method, oxidation by discharge, oxidation by heat, oxidation by light, oxidation by an oxidizing atmosphere (ozone, steam atmosphere, etc.), oxidation by an oxidizing agent (oxidizing solution, etc.), and a combination thereof can be used. Then, by changing the conditions of the oxidation treatment method, the base layer 300 having the above-mentioned distribution can be obtained. Further, the intermediate layer 200 and the base layer 300 may be collectively oxidized. That is, the oxidation treatment of the base layer 300 (sixth step) may also serve as the oxidation treatment of the intermediate layer 200 (fourth step). In this case, the oxidation treatment of the intermediate layer 200 (fourth step) may be omitted. (The fourth step may be omitted and both the fourth step and the sixth step may be performed).

In the subsequent steps, as shown in FIG. 4B, the other end of the container 32 is held by the stem plate 46 to which the focusing electrode 36, the anode 38 (not shown), and the multiplying portion 40 are assembled. Seal. A thin-film deposition source D is arranged on the focusing electrode 36. Further, the alkali metal source E is arranged on the stem plate 46 via the stem pin 44.

The oxidation treatment of the base layer 300 (sixth step) and the batch oxidation treatment of the intermediate layer 200 and the base layer 300 are performed by the stem plate 46 at the other end of the container 32 as shown in FIG. 4 (b). It may be done after sealing the part. For example, when oxidation by electric discharge is used as the oxidation treatment (sixth step) for the underlying layer 300, DC discharge oxidation, AC discharge oxidation (for example, RF discharge oxidation) or the like can be used. For example, when glow discharge is used, After an appropriate amount of oxygen is sealed in the vacuum-conditioned container 32, a voltage is applied between the focusing electrode 36 and the container 32 (substrate 100), and the berylium nitride is discharged from the surface 300a side of the base layer 300. The region containing is replaced with a region containing an oxide of beryllium. The pressure (gas pressure) in the container 32 at this time is, for example, about 0.01 Pa to 1000 Pa.

In the subsequent steps, as shown in FIG. 5, the photoelectric conversion layer 400 is formed on the surface 300a of the base layer 300 opposite to the intermediate layer 200 (that is, on the intermediate layer 200 via the base layer 300) (that is, on the intermediate layer 200 via the base layer 300). Third step). More specifically, in the third step, first, as shown in FIG. 5A, the antimony layer 600 is formed on the surface 300a by vapor deposition of antimony using the vapor deposition source D. Subsequently, as shown in FIG. 5B, the antimony layer 600 is activated by supplying the alkali metal vapor from the alkali metal source E to the antimony layer 600. As a result, the antimony layer 600 forms a photoelectric conversion layer 400 made of a compound of antimony and an alkali metal.

Next, the action / effect will be described. FIG. 6 is a graph showing a comparison result of film formation speed. In FIG. 6, the broken line shows the film formation rate of the intermediate layer 200 (including the hafnium nitride) when the atmosphere in the second step is a nitrogen atmosphere, and the solid line shows the atmosphere in the second step as an oxygen atmosphere. The film formation rate of the intermediate layer (containing hafnium oxide and not containing nitride) is shown. As shown in FIG. 6, the film forming rate of the intermediate layer 200 containing the hafnium nitride is higher than the film forming rate of the intermediate layer made of hafnium oxide.

FIG. 7 is a graph showing a comparison result of optical characteristics. In FIG. 7, the broken line shows the intermediate layer 200 of hafnium nitride formed by the sputtering method (SP), and the solid line shows the intermediate layer of hafnium oxide formed by EB vapor deposition (EB). .. As shown in FIGS. 7A and 7B, the hafnium nitride intermediate layer 200 shows a tendency of a refractive index and a transmittance substantially similar to that of the hafnium oxide intermediate layer. It is understood that it functions as an antireflection film as well as.

FIG. 8 is a graph showing the comparison result of quantum efficiency. In FIG. 8A, the broken line shows the case where the intermediate layer 200 of hafnium nitride and the base layer 300 of beryllium are used in combination, and the solid line shows the case where only the base layer 300 of beryllium is used without using the intermediate layer 200. show. As shown in FIG. 8A, the use of the hafnium nitride intermediate layer 200 provides an antireflection effect on the incident light, thereby improving the quantum efficiency.

As described above, the intermediate layer 200 included in the photocathode 1 contains a hafnium nitride and functions as an antireflection film. Further, the film formation rate of the intermediate layer 200 containing the hafnium nitride is relatively high. Therefore, the photocathode 1 according to the present embodiment can be efficiently manufactured while improving the quantum efficiency.

Further, in the photocathode 1, the intermediate layer 200 contains an oxide of hafnium. In this case, the light transmittance of the intermediate layer 200 is improved, and it can function as an antireflection film in a wider wavelength range.

Further, in the photocathode 1, the amount of hafnium oxide in the intermediate layer 200 is larger than the amount of hafnium nitride. In this case, the light transmittance of the intermediate layer 200 is further improved, and it can function as an antireflection film in a wider wavelength range.

Further, in the photocathode 1, in the intermediate layer 200, the amount of at least one of the hafnium nitride and the hafnium oxide may be unevenly distributed in the thickness direction of the intermediate layer 200, or the hafnium nitride may be distributed unevenly. The amount of hafnium oxide may be distributed substantially uniformly in the thickness direction of the intermediate layer 200, and the amount of hafnium oxide may be distributed substantially uniformly in the thickness direction of the intermediate layer 200. In the case of uneven distribution, when the intermediate layer 200 is viewed as a layer composed of two regions, a first region 210 on the substrate 100 side and a second region 220 on the photoelectric conversion layer 400 side, the intermediate layer 200 contains hafnium. The amount of nitride is larger on the second region 220 side (photoelectric conversion layer 400 side) than on the first region 210 side (substrate 100 side), and the amount of hafnium oxide is on the second region 220 side (photoelectric conversion layer). It may be more on the first region 210 side (board 100 side) than on the 400 side). Further, the first region 210 and the second region 220 are a first intermediate layer and a second intermediate layer laminated on each other, and the first intermediate layer is located closer to the substrate 100 than the second intermediate layer, and It may contain an oxide of hafnium. In either case, the light transmittance of the intermediate layer 200 is further improved, and it can function as an antireflection film in a wider wavelength range.

The photocathode 1 is provided between the intermediate layer 200 and the photoelectric conversion layer 400, and includes a base layer 300 containing beryllium. As described above, by using the base layer 300 containing beryllium, the effective quantum efficiency is further improved and the sensitivity is improved.

Further, in the photocathode 1, the base layer 300 may contain beryllium nitride. Here, according to the findings of the present inventor, when forming the base layer 300 containing beryllium, the film formation rate of, for example, the base layer made of an oxide of beryllium alloy or the base layer made of beryllium oxide is higher. The film formation rate of the underlying layer containing beryllium nitride is faster and can be produced efficiently. Therefore, the photocathode 1 including the base layer 300 containing beryllium can be efficiently manufactured.

Further, in the photocathode 1, the base layer 300 may contain an oxide of beryllium. In this case, the quantum efficiency of the photocathode 1 is improved, and it can function as the base layer 300 in a wider wavelength range.

Further, in the photocathode 1, in the base layer 300, the amount of beryllium oxide may be larger than the amount of beryllium nitride. In this case, the quantum efficiency of the photocathode 1 is further improved, and it can function as an underlayer in a wider wavelength range.

Further, in the photoelectric cathode 1, in the base layer 300, at least one amount of beryllium nitride and beryllium oxide may be unevenly distributed in the thickness direction of the base layer 300, or beryllium nitride. The amount of beryllium oxide may be distributed substantially uniformly in the thickness direction of the base layer 300, and the amount of beryllium oxide may be distributed substantially uniformly in the thickness direction of the base layer 300. In the case of uneven distribution, when the base layer 300 is viewed as a layer composed of two regions, a first region 310 on the substrate 100 side and a second region 320 on the photoelectric conversion layer 400 side, the beryllium nitride in the base layer 300. The amount of the substance is larger on the first region 310 side (base 100 side) than on the second region 320 side (photoelectric conversion layer 400 side), and the amount of beryllium oxide is on the first region 310 side (base 100 side). It may be more on the second region 320 side (photoelectric conversion layer 400 side) than on the second region 320 side. Further, the first region 310 and the second region 320 are a first base layer and a second base layer laminated on each other, and the second base layer is located closer to the photoelectric conversion layer 400 than the first base layer. It may also contain an oxide of beryllium. In either case, the quantum efficiency of the photocathode 1 is further improved, and it can function as an underlayer in a wider wavelength range.

Further, in the method for manufacturing the photocathode 1, in the second step, as a step of forming an intermediate layer containing hafnium, vapor deposition or sputtering using the hafnium target C1 is performed in an atmosphere containing nitrogen, thereby performing the substrate 100. An intermediate layer 200 containing a hafnium nitride is formed directly on the surface. As shown in the above findings, the film formation rate of the intermediate layer 200 containing the hafnium nitride is relatively high. Therefore, according to this manufacturing method, the photocathode 1 having improved quantum efficiency can be efficiently manufactured.

Here, FIG. 9 is a graph showing the analysis results of the components of the intermediate layer according to the sputtering gas (atmosphere in the sputtering method) (analysis method: XPS). 9 (a) shows the case where the sputter gas is oxygen, FIG. 9 (b) shows the case where the sputter gas is nitrogen, and FIG. 9 (c) shows the case where the sputter gas is nitrogen and argon. The case where the gas is mixed with and is shown. When the sputter gas is nitrogen or the sputter gas is a mixed gas of nitrogen and argon, there is a high possibility that some residual gas is present in the atmosphere, especially due to the water content thereof. Oxygen is also supplied. Therefore, oxygen atoms are often detected in the formed intermediate layer. Further, oxygen may be intentionally added within a range that does not affect the film formation rate. Then, as shown in FIG. 9, the oxygen ratio is lower when the sputter gas is a mixed gas of nitrogen and argon as compared with the case where the sputter gas is nitrogen.

It is considered that this is a result of the fact that the film formation rate of the intermediate layer 200 was further improved by mixing argon with the sputtering gas, and thus the uptake of oxygen into the intermediate layer 200 at the time of film formation was reduced. Actually, as shown in FIG. 10, when the sputtering gas is a mixed gas of nitrogen and argon, the film forming rate is faster than in the case of using only oxygen and the case of using only nitrogen. Therefore, in the method for producing the photocathode 1, an atmosphere containing an inert gas different from nitrogen can be used in the second step. In this case, the photocathode 1 with improved quantum efficiency can be manufactured more efficiently.

As described above, in the method for producing the photocathode 1, in the second step, an intermediate layer 200 containing a hafnium nitride and a hafnium oxide is formed by using an atmosphere containing nitrogen and oxygen. In this case, the light transmittance of the intermediate layer 200 is improved, and the intermediate layer 200 capable of functioning as an antireflection film in a wider wavelength range can be formed.

Further, in the method for manufacturing the photocathode 1, a fourth step of oxidizing the intermediate layer 200 may be provided between the second step and the third step. In this case, the light transmittance of the intermediate layer 200 is improved, and it can function as an antireflection film in a wider wavelength range.

On the other hand, the method for manufacturing the photocathode 1 includes a fifth step of forming a base layer 300 containing beryllium on the intermediate layer 200 between the second step and the third step. Then, in the third step, the photoelectric conversion layer 400 is formed on the base layer 300. By forming the base layer 300 containing beryllium on the intermediate layer 200 in this way, the photocathode 1 having improved effective quantum efficiency and sensitivity can be manufactured.

Further, in the method for producing the photocathode 1, in the fifth step, the base layer 300 containing beryllium nitride is formed in an atmosphere containing nitrogen. As a result, the photocathode 1 including the base layer 300 can be efficiently manufactured.

Further, the method for manufacturing the photocathode 1 may include a sixth step of performing an oxidation treatment on the base layer 300 after the fifth step. In this case, the quantum efficiency of the photocathode 1 is improved, and it can function as the base layer 300 in a wider wavelength range. Further, in the sixth step, by oxidizing the region of the base layer 300 on the side opposite to the intermediate layer 200, the first region 310 (first base layer) containing beryllium nitride is intermediate between the first region 310 and the first region 310. A second region 320 (second base layer), which is located on the opposite side of the layer 200 and contains an oxide of beryllium, may be formed. In this case, it is possible to manufacture the photocathode 1 in which the effective quantum efficiency is further improved and the sensitivity is further improved.

Further, in the method for producing the photocathode 1, in the sixth step, the intermediate layer 200 and the base layer 300 may be collectively oxidized. In this case, since the oxidation treatment of the intermediate layer 200 and the base layer 300 is performed at once, the photocathode 1 can be efficiently manufactured.

The above-described embodiment describes one aspect of the present invention. Therefore, the present invention is not limited to the above embodiment, and various modifications can be made.

For example, the photocathode 1 does not have to include the base layer 300. In this case, the photoelectric conversion layer 400 is provided directly on the intermediate layer 200 (plane 200a). That is, in this case, the intermediate layer 200 and the photoelectric conversion layer 400 are laminated in this order on the substrate 100.

1 ... Photocathode, 100 ... Substrate (translucent substrate), 200 ... Intermediate layer, 300 ... Underlayer, 310 ... First region (first underlayer), 320 ... Second region (second underlayer), 400 … Photocathode conversion layer.

Claims (24)

With a translucent substrate,
A photoelectric conversion layer provided on the translucent substrate and generating photoelectrons in response to light incident,
An intermediate layer provided in contact with the translucent substrate between the translucent substrate and the photoelectric conversion layer is provided.
The intermediate layer contains a hafnium nitride.
Photocathode. The intermediate layer contains a hafnium oxide.
The photocathode according to claim 1. In the intermediate layer, the amount of hafnium oxide is greater than the amount of hafnium nitride.
The photocathode according to claim 2. In the intermediate layer, the amount of at least one of the hafnium nitride and the hafnium oxide is distributed unevenly in the thickness direction of the intermediate layer.
The photocathode according to claim 2 or 3. In the intermediate layer, the amount of hafnium nitride is larger on the photoelectric conversion layer side than on the translucent substrate side, and the amount of hafnium oxide is more translucent than on the photoelectric conversion layer side. Many on the board side,
The photocathode according to claim 4. The intermediate layer has a first intermediate layer and a second intermediate layer laminated on each other.
The first intermediate layer is located closer to the translucent substrate than the second intermediate layer and contains an oxide of hafnium.
The photocathode according to claim 5. In the intermediate layer, the amount of hafnium nitride is distributed substantially uniformly in the thickness direction of the intermediate layer, and the amount of hafnium oxide is distributed substantially uniformly in the thickness direction of the intermediate layer.
The photocathode according to claim 2 or 3. A base layer provided between the intermediate layer and the photoelectric conversion layer and containing beryllium is provided.
The photocathode according to any one of claims 1 to 7. The underlayer contains beryllium nitride.
The photocathode according to claim 8. The base layer contains an oxide of beryllium.
The photocathode according to claim 8. The base layer contains an oxide of beryllium.
The photocathode according to claim 9. In the underlayer, the amount of beryllium oxide is greater than the amount of beryllium nitride.
The photocathode according to claim 11. In the base layer, at least one amount of beryllium nitride and beryllium oxide is unevenly distributed in the thickness direction of the base layer.
The photocathode according to claim 11 or 12. In the base layer, the amount of beryllium nitride is larger on the translucent substrate side than on the photoelectric conversion layer side, and the amount of beryllium oxide is larger on the translucent substrate side than on the translucent substrate side. Many on the layer side,
The photocathode according to claim 13. The base layer has a first base layer and a second base layer that are laminated on each other.
The second base layer is located closer to the photoelectric conversion layer than the first base layer and contains an oxide of beryllium.
The photocathode according to claim 14. In the base layer, the amount of beryllium nitride is distributed substantially uniformly in the thickness direction of the base layer, and the amount of oxide of beryllium is distributed substantially uniformly in the thickness direction of the base layer.
The photocathode according to claim 15. The first step of preparing a translucent substrate and
After the first step, a second step of forming an intermediate layer containing hafnium on the translucent substrate, and
After the second step, a third step of forming a photoelectric conversion layer that generates photoelectrons in response to the incident of light is provided on the intermediate layer.
In the second step, the intermediate layer containing a hafnium nitride is formed directly on the translucent substrate in an atmosphere containing nitrogen.
A method for manufacturing a photocathode. In the second step, the atmosphere containing nitrogen and oxygen is used to form the intermediate layer containing hafnium nitride and hafnium oxide.
The method for manufacturing a photocathode according to claim 17. In the second step, the atmosphere containing an inert gas different from nitrogen is used.
The method for producing a photocathode according to claim 17 or 18. Between the second step and the third step, a fourth step of oxidizing the intermediate layer is provided.
The method for producing a photocathode according to any one of claims 17 to 19. Between the second step and the third step, a fifth step of forming a base layer containing beryllium on the intermediate layer is provided.
In the third step, the photoelectric conversion layer is formed on the base layer.
The method for producing a photocathode according to any one of claims 17 to 20. In the fifth step, the base layer containing beryllium nitride is formed in an atmosphere containing nitrogen.
The method for manufacturing a photocathode according to claim 21. After the fifth step, a sixth step of performing an oxidation treatment on the base layer is provided.
The method for manufacturing a photocathode according to claim 22. In the sixth step, the intermediate layer and the base layer are collectively oxidized.
The method for manufacturing a photocathode according to claim 23.

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