CN111627783A - Transmission type photoelectric cathode and preparation method and application thereof - Google Patents

Transmission type photoelectric cathode and preparation method and application thereof Download PDF

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CN111627783A
CN111627783A CN202010511186.2A CN202010511186A CN111627783A CN 111627783 A CN111627783 A CN 111627783A CN 202010511186 A CN202010511186 A CN 202010511186A CN 111627783 A CN111627783 A CN 111627783A
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film
layer
antireflection film
surface antireflection
glass window
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CN111627783B (en
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蔡志鹏
张景文
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Xian Jiaotong University
Shaanxi University of Technology
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Xian Jiaotong University
Shaanxi University of Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/34—Photo-emissive cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/50—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J40/00—Photoelectric discharge tubes not involving the ionisation of a gas
    • H01J40/02—Details
    • H01J40/04—Electrodes
    • H01J40/06—Photo-emissive cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
    • H01J43/04—Electron multipliers
    • H01J43/06—Electrode arrangements
    • H01J43/08—Cathode arrangements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/12—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes

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Abstract

The invention relates to the technical field of photocathodes, in particular to a transmission-type photocathode and a preparation method and application thereof. The photoelectric cathode can greatly improve the light absorption rate of the cathode through the arrangement of the outer surface antireflection film and the inner surface antireflection film, so that the quantum efficiency of the cathode is improved. Meanwhile, the bonding film and the inner surface antireflection film are distinguished, so that the cathode can be divided into a central antireflection area through which signal light passes and a peripheral adhesion area through which the signal light does not need to pass, the light antireflection area of a signal light response area does not need to bear the adhesion function, and the adhesion area does not need to bear the antireflection function of the signal light, so that the stress of the antireflection film can be greatly released on the basis of realizing adhesion, a series of adverse effects caused by adhesion are eliminated, and the cathode has higher spectral sensitivity in blue-green light and shorter wave bands; the invention also provides a preparation method of the photocathode, and the preparation method realizes the separation of the bonding function and the anti-reflection function, thereby reducing the adverse factors of bonding.

Description

Transmission type photoelectric cathode and preparation method and application thereof
Technical Field
The invention relates to the technical field of photocathodes, in particular to a transmission-type photocathode and a preparation method and application thereof.
Background
The GaAs-based transmission type photocathode represented by the negative electron affinity GaAs photocathode is a photoelectric conversion core element of vacuum detection and imaging devices such as a low-light-level image intensifier, a photomultiplier and the like, has the advantages of high quantum efficiency, wide response waveband, small dark current, small average electron energy, small angle distribution and the like, and is widely applied to the fields of photoelectric detection and imaging, high-energy physical electron sources and the like. Especially in military application, aerospace detection and environmental detection, the low-light-level image intensifier with the transmission GaAs photoelectric cathode as the core plays an important role. The quantum efficiency is one of the most important technical indexes of the photocathode, the wide-spectrum response band of the photocathode of the ITT company in the United states reaches more than 40%, and the difference between the domestic GaAs photocathode and foreign countries is obvious and is still at the laboratory level. How to improve the quantum efficiency of the domestic photocathode is one of the main bottlenecks restricting the development of the domestic GaAs photocathode at present.
The basic structure of the transmission type GaAs photoelectric cathode is glass window/Si3N4Antireflection film/GaAlAs window layer/GaAs emission layer/Cs: the O active layer is prepared by the following steps: first, the following epitaxial structure is grown on a high-quality GaAs substrate using a Metal Organic Chemical Vapor Deposition (MOCVD) or a Molecular Beam Epitaxy (MBE): GaAs substrate/GaAlAs barrier layer/GaAs emission layer/GaAlAs window layer/GaAs protective layer; next, etching off the GaAs protective layer and depositing a layer of Si of about 100nm on the epitaxial structure3N4Antireflection film and SiO with certain thickness2(SiO2To facilitate adhesion to the glazing) and then heating the glazing under vacuum to the above-mentioned deposited Si3N4Bonding the epitaxial structures of the antireflection film together; then, sequentially etching and removing the GaAs substrate and the GaAlAs barrier layer to expose the GaAs emission layer; and finally, depositing a layer of Cs with the size of about 1 nanometer on the surface of the GaAs emission layer under an ultrahigh vacuum activation system: o layer for forming negative electricity on the surface of the emitting layerAnd (5) completing the manufacture of the cathode in a sub-affinity state.
In the above technical scheme, Si3N4The antireflection film is only a thin film layer with the thickness of about 100nm, correspondingly, the antireflection film has a good antireflection effect only in a narrow band range (for a response band which is larger than or equal to 600 nm) of 100-200 nm, the antireflection effect of the short-wave response band is not obvious or even is weakened to a certain extent, so that the short-wave band has high reflectivity, the loss of light reflection in the short-wave band reaches 5-20% or even higher, and particularly, the light reflection loss in the band of 390-420 nm reaches more than 30% for a blue extension transmission type cathode with a super-wide band. In addition, photocathodes for some specific narrower spectral responses, such as GaAlAs photocathodes, despite the single Si3N4The antireflection film can achieve the light antireflection effect, but Si with enough thickness is required in the thermal bonding process3N4The antireflection film blocks the impurity contamination source in the glass and limits Si3N4The thickness of the antireflection film cannot meet the antireflection requirement of the photocathode with a specific spectral band. Therefore, the light reflection loss restricts the further improvement of the quantum effect of the current transmission-type photocathode, and how to further reduce the light reflectivity of the whole response waveband and improve the absorptivity of the cathode is one of the inevitable ways for improving the current quantum efficiency.
Disclosure of Invention
The invention aims to provide a transmission-type photocathode and a preparation method and application thereof. The transmission type photoelectric cathode has a high anti-reflection effect with a wider spectrum.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a transmission-type photocathode, which comprises an outer surface antireflection film, a glass window, an adhesive film/inner surface antireflection film, a buffer layer, an emitting layer and an activation layer which are sequentially stacked along a light incidence direction;
the adhesive film/inner surface antireflection film comprises an adhesive film and an inner surface antireflection film;
the inner surface antireflection film is positioned in the center of the surface of the glass window and does not reach the edge of the surface of the glass window; the bonding film is positioned at the edge of the surface of the glass window and is tightly connected with the inner surface antireflection film;
the thickness of the bonding film is larger than that of the inner surface antireflection film.
Preferably, the outer surface antireflection film or the inner surface antireflection film independently includes at least 1 layer of optical film;
the material of each layer of the optical film is TiO independently2、SiO2、Si3N4、SnO2、HfO2、Al2O3、Bi2O3、AlOxNy、AlF3、BiF3、CeF3、CeO2、CsBr、CsI、Cr2O3Diamond, Dy2O3、Eu2O3、Gd2O3、Ho2O3、In2O3、Nb2O5、Nd2O3、PbCl2、Pr6O11、Sc2O3、Sb2O3、Sm2O3、Y2O3、ZnO、ZnS、BeO、MgO、MgF2、ZrO2、La2O3、La2O5、LiF、CaF2、LaF3、BaF2、NaF、Na3AlF6、SrF2、NdF3、PbF2、YbF3、SmF3And ThF4One or more of them.
Preferably, the thickness of the outer surface antireflection film is 5 nm-10 μm;
the thickness of the inner surface antireflection film is 30 nm-10 mu m.
Preferably, when the internal antireflection film includes 1 optical film, the optical film is Si3N4A thin film having a thickness of 30 to 80 nm;
when the inner surface antireflection film comprises>1, the optical film in contact with the buffer layer and the antireflection film on the inner surface is Si3N4A film; and Si in the inner surface antireflection film3N4The total thickness of the film is more than or equal to 30 nm.
Preferably, the adhesive film includes, from the buffer layer, Si sequentially disposed3N4Film and SiO2A film; said Si3N4The thickness of the film is more than or equal to 30 nm.
Preferably, the material of the emission layer is GaAs or Ga1-xAlxAs or Ga1-x-yAlxAs1-yPy(ii) a Wherein, 0<x≤0.5，0<y≤0.2；
The thickness of the emitting layer is 0.4-2 μm;
the p-type doping concentration in the emitting layer is 1018～1019cm-3。
Preferably, the material of the buffer layer is Ga1-zAlzAs or Ga1-zAlzAs1-qPq(ii) a Wherein z is more than or equal to 0.5 and less than or equal to 1 and 0<q≤0.2；
The thickness of the buffer layer is 0.04-2 mu m;
the p-type doping concentration of the buffer layer is 1018～1019cm-3。
The invention also provides a preparation method of the transmission-type photocathode in the technical scheme, which comprises the following steps:
depositing an outer surface optical anti-reflection film on one surface of the glass window to obtain the glass window deposited with the outer surface optical anti-reflection film;
sequentially epitaxially growing a GaAs smooth layer, a barrier layer, an emission layer, a buffer layer and a protective layer on a GaAs substrate, and then corroding and removing the protective layer to expose the buffer layer;
respectively heating and degassing the glass window deposited with the external surface optical antireflection film, the internal surface antireflection film and the bonding film under a vacuum condition, pressing the glass window deposited with the external surface optical antireflection film into a concave part formed by the internal surface antireflection film and the bonding film, and bonding the glass window deposited with the external surface optical antireflection film and the bonding film together under a heating condition; one surface of the glass window which is evaporated with the external surface optical antireflection film and is not evaporated with the external surface optical antireflection film is contacted with the internal surface antireflection film;
after the bonding is finished, sequentially removing the GaAs substrate, the GaAs smooth layer and the barrier layer by corrosion to expose the emitting layer;
evaporating an active layer on the surface of the emitting layer under an ultrahigh vacuum activation system to obtain the transmission-type photocathode;
the vacuum degree of the ultrahigh vacuum activation system is less than or equal to 10-7Pa。
The invention also provides the application of the transmission-type photocathode in the technical scheme or the transmission-type photocathode prepared by the preparation method of the transmission-type photocathode in the technical scheme in the low-light-level night vision field, the underwater imaging detection field, the low-light-level remote sensing imaging field or the photomultiplier.
The invention provides a transmission-type photocathode, which comprises an outer surface antireflection film, a glass window, an adhesive film/inner surface antireflection film, a buffer layer, an emitting layer and an activation layer which are sequentially stacked along a light incidence direction; the adhesive film/inner surface antireflection film comprises an adhesive film and an inner surface antireflection film; the inner surface antireflection film is positioned in the center of the surface of the glass window and does not reach the edge of the surface of the glass window; the bonding film is positioned at the edge of the surface of the glass window and is tightly connected with the inner surface antireflection film; the thickness of the bonding film is larger than that of the inner surface antireflection film. The transmission-type photoelectric cathode can greatly improve the light absorption rate of the cathode through the arrangement of the outer surface antireflection film and the inner surface antireflection film, so that the quantum efficiency of the cathode is improved. Meanwhile, the bonding film and the inner surface antireflection film are distinguished, so that the cathode can be divided into a central antireflection area through which signal light passes and a peripheral adhesion area through which the signal light does not need to pass, the light antireflection area of a signal light response area does not need to bear the adhesion function, and the adhesion area does not need to bear the antireflection function of the signal light, so that the stress of the antireflection film can be greatly released on the basis of realizing adhesion, a series of adverse effects caused by adhesion are eliminated, and the selection of materials, the number of layers, the thickness and the like of the antireflection film is more free; in addition, after the adhesive film and the inner surface antireflection film are distinguishedCan ensure that the antireflection film does not need to be contacted with the glass window for a long time or even not contacted with the glass window in the bonding process, and the bonding process is carried out on Si3N4Even when the film is thin, contamination by impurities in the glass can be prevented. In a word, the bonding film and the inner surface antireflection film are distinguished, so that the light absorption rate and the quantum efficiency of the whole light response waveband are further improved, the adverse factor influence in the bonding process is eliminated, and the purpose of improving the response performance of the transmission type photocathode is achieved. Meanwhile, the response waveband of the transmission-type photocathode is 250-920 nm, and the effect of a blue-green light antireflection waveband is achieved through the antireflection of the inner antireflection film and the outer antireflection film on signal light, so that the light absorptivity of the cathode is improved; furthermore, due to the adoption of the anti-reflection films on the inner surface and the outer surface, the reflectivity of blue-green light and shorter wave bands is greatly reduced. Therefore, the transmission type photoelectric cathode has higher spectral sensitivity in blue-green light and shorter wave bands.
Drawings
FIG. 1 is a schematic structural diagram of the transmissive photocathode;
FIG. 2 is a graph comparing the absorption spectra of a transmissive photocathode prepared in example 1 and a photocathode prepared in comparative example 1 under the same conditions;
FIG. 3 is a graph comparing the absorption spectra of the transmissive photocathode prepared in example 2 and the photocathode prepared in comparative example 2 under the same conditions;
FIG. 4 is a graph comparing the absorption spectra of a transmissive photocathode prepared in example 3 with a photocathode prepared in comparative example 4 under the same conditions;
the transparent glass comprises, by weight, 1-an outer surface antireflection film, 2-a glass window, 3-an adhesive film, 4-an inner surface antireflection film, 5-a buffer layer, 6-an emitting layer and 7-an active layer.
Detailed Description
The invention provides a transmission-type photocathode, which comprises an outer surface antireflection film, a glass window, an adhesive film/inner surface antireflection film, a buffer layer, an emitting layer and an activation layer which are sequentially stacked along a light incidence direction;
the adhesive film/inner surface antireflection film comprises an adhesive film and an inner surface antireflection film;
the inner surface antireflection film is positioned in the center of the surface of the glass window and does not reach the edge of the surface of the glass window; the bonding film is positioned at the edge of the surface of the glass window and is tightly connected with the inner surface antireflection film;
the thickness of the bonding film is larger than that of the inner surface antireflection film.
In the invention, the transmission type photoelectric cathode comprises an outer surface antireflection film, and the outer surface antireflection film preferably comprises more than or equal to 1 layer of optical film. Each layer of the optical film is preferably TiO independently2、SiO2、Si3N4、SnO2、HfO2、Al2O3、Bi2O3、AlOxNy、AlF3、BiF3、CeF3、CeO2、CsBr、CsI、Cr2O3Diamond, Dy2O3、Eu2O3、Gd2O3、Ho2O3、In2O3、Nb2O5、Nd2O3、PbCl2、Pr6O11、Sc2O3、Sb2O3、Sm2O3、Y2O3、ZnO、ZnS、BeO、MgO、MgF2、ZrO2、La2O3、La2O5、LiF、CaF2、LaF3、BaF2、NaF、Na3AlF6、SrF2、NdF3、PbF2、YbF3、SmF3And ThF4One or more of them. When the material of each layer of the optical film is independently two or more of the above specific choices, the present invention does not have any particular limitation on the ratio of the above specific materials. In the present invention, the number of layers and the thickness of each layer of the optical film are not particularly limited, and the thickness of the outer surface antireflection film formed of the optical film can be ensured to be within a range of 5nm to 10 μm. In the present invention, the thickness of the outer surface antireflection film is preferably set to be thick5nm to 10 μm, more preferably 10nm to 100 nm. In a specific embodiment of the invention, the outer surface antireflection film specifically comprises TiO sequentially arranged on one side of the glass window2Layer (12.3nm), SiO2Layer (33.5nm), TiO2Layer (27nm), SiO2Layer (13.5nm), TiO2Layer (86.3nm), SiO2Layer (18.3nm), TiO2Layer (19nm) and MgF2A layer (95 nm); or the anti-reflection film on the outer surface specifically comprises TiO arranged on one side of the glass window in sequence2Layer (13.3nm), SiO2Layer (33.7nm), TiO2Layer (27nm), SiO2Layer (12nm), TiO2Layer (79.5nm), SiO2Layer (22nm), TiO2Layer (17.3nm) and MgF2A layer (99 nm); or the anti-reflection film on the outer surface specifically comprises TiO arranged on one side of the glass window in sequence2Layer (9.3nm), MgF2Layer (36nm), TiO2Layer (21nm), MgF2Layer (34nm), TiO2Layer (15.5nm) and MgF2Layer (90 nm).
In the present invention, the transmissive photocathode comprises a glass window; the glazing is preferably a double-side polished 9741 violet-transmitting glass or a double-side polished corning 7056 borosilicate glass. In the invention, the glass window is a signal light incidence window, and the glass window is polished on two sides to be favorable for being bonded with the bonding film/the inner surface antireflection film.
The thickness of the glass window is not particularly limited in the present invention, and the thickness of the glass window that can be used for a photocathode known to those skilled in the art may be used.
In the invention, the transmission type photoelectric cathode comprises an adhesive film/an inner surface antireflection film; the adhesive film/inner surface antireflection film comprises an adhesive film and an inner surface antireflection film; the inner surface antireflection film is positioned in the center of the surface of the glass window, and the bonding film is positioned around the inner surface antireflection film and is tightly connected with the inner surface antireflection film; the thickness of the bonding film is larger than that of the inner surface antireflection film. In the present invention, the tight connection is preferably achieved by partially overlapping the adhesive film and the inner surface antireflection film; the present invention does not have any particular limitation on the partial overlapping, and it suffices to prevent impurities precipitated from the glass during the bonding process from contaminating the buffer layer. In the present invention, the difference in thickness between the adhesive film and the inner surface antireflection film is preferably the thickness of the glass window.
In the invention, the bonding film is a non-signal light incidence area, and the inner surface antireflection film is a signal light incidence channel.
In the present invention, the adhesive film preferably includes Si sequentially disposed from the buffer layer3N4Film and SiO2And (3) a membrane. In the present invention, said Si3N4The thickness of the film is preferably more than or equal to 30 nm; in the present invention, the SiO2The film acts as an adhesive to the glazing. Because the main component of the glass window is SiO2Thus, when heat bonding, SiO2Easily adhere to the glass window to form a firm structure, therefore, the invention is applied to the SiO2The thickness of the film is not particularly limited, and may be a thickness known to those skilled in the art.
In the present invention, the internal antireflection film preferably includes 1 or more layers of optical films. Each layer of the optical film is preferably TiO independently2、SiO2、Si3N4、SnO2、HfO2、Al2O3、Bi2O3、AlOxNy、AlF3、BiF3、CeF3、CeO2、CsBr、CsI、Cr2O3Diamond, Dy2O3、Eu2O3、Gd2O3、Ho2O3、In2O3、Nb2O5、Nd2O3、PbCl2、Pr6O11、Sc2O3、Sb2O3、Sm2O3、Y2O3、ZnO、ZnS、BeO、MgO、MgF2、ZrO2、La2O3、La2O5、LiF、CaF2、LaF3、BaF2、NaF、Na3AlF6、SrF2、NdF3、PbF2、YbF3、SmF3And ThF4One or more of them. In the present invention, the material of the optical thin film layer in contact with the glass window is preferably not SiO2. In the present invention, when the number of the optical thin film layers is 1, the optical thin film is preferably Si3N4A film. When the number of the optical film layers is>In 1 layer, the optical film in contact with the buffer layer and the inner surface antireflection film is preferably Si3N4A film; and Si in the inner surface antireflection film3N4The total thickness of the film is preferably ≧ 30 nm. In the present invention, the thickness of the outer surface antireflection film is preferably 5nm to 10 μm, and more preferably 10nm to 100 nm. The total thickness of the antireflection film on the inner surface is not particularly limited. In a specific embodiment of the present invention, the inner surface antireflection film specifically includes: si in sequence from the buffer layer3N4Layer (60nm), MgF2(71nm)、Si3N4Layer (7.3nm) and MgF2(91 nm); or the internal surface antireflection film is specifically as follows: the buffer layer is sequentially as follows: si3N4Layer (62.5nm), MgF2(46.5nm)、Si3N4Layer (14.7nm) and MgF2(142.5 nm); or the internal surface antireflection film is specifically as follows: the buffer layer is sequentially as follows: si3N4Layer (12nm), MgF2(44nm)、Si3N4Layer (16.5nm), MgF2(79.2nm)、Si3N4Layer (9nm), MgF2(55.6nm) and Si3N4Layer (48 nm).
In the present invention, the transmissive photocathode includes a buffer layer; in the present invention, the material of the buffer layer is preferably Ga1-zAlzAs or Ga1-zAlzAs1-qPq(ii) a Wherein z is more than or equal to 0.5 and less than or equal to 1 and 0<q is less than or equal to 0.2; the thickness of the buffer layer is preferably 0.04-2 mu m; the p-type doping concentration of the buffer layer is preferably 1018～1019cm-3. In the invention, the number of the buffer layers is preferably not less than 2, and the direction from the interface of the emission layer and the buffer layer to the buffer layerWherein, the Al and P components independently show a gradient descending trend or independently keep unchanged; the p-type doping concentration is in a gradient descending trend or is unchanged; when the Al and P components or the P-type doping concentration independently have a gradient descending trend, the gradient descending degree is not limited in any way, and the gradient descending degree can be adjusted according to actual conditions. For example, when z is 1, that is, when the buffer layer is AlAs, a layer of Ga having a thickness of 5 to 20nm and z of 0.7 to 0.95 may be optionally added on the side close to the glass window1-zAlzA thin layer of As to prevent the AlAs from being oxidized during the bonding process.
In the present invention, the transmissive photocathode includes an emission layer; in the invention, the material of the emission layer is preferably GaAs or Ga1-xAlxAs or Ga1-x-yAlxAs1-yPy(ii) a Wherein, 0<x≤0.5，0<y is less than or equal to 0.2; the thickness of the emitting layer is preferably 0.4-2 μm; the p-type doping concentration in the emitting layer is preferably 1018～1019cm-3. In the present invention, the p-type doping concentration in the emission layer is preferably constant or has a gradient decreasing tendency from the interface of the emission layer and the buffer layer to the surface of the emission layer. In the present invention, the Al component or the P component in the emission layer is preferably independent of the Al component or the P component, and is preferably constant or has a tendency of descending in a gradient from the interface of the emission layer and the buffer layer to the surface of the emission layer.
In the present invention, the transmissive photocathode further includes an activation layer. The active layer is preferably Cs: an O active layer; the thickness of the activation layer is preferably 0.5-1.5 nm.
In the invention, the working principle of the transmission type photocathode is as follows: the signal light sequentially passes through the outer surface antireflection film, the glass window and the inner surface antireflection film, is sequentially subjected to antireflection by the inner surface antireflection film and the outer surface antireflection film, and then sequentially enters the buffer layer and the emitting layer; secondly, the signal light is absorbed by the emitting layer and converted into photoelectrons, which are transported toward and reach the cathode surface. Wherein the adhesive layer only bears the adhesive function and does not bear the signal light incidence function; finally, in Cs: the cathode surface under the O activation layer is in a negative electron affinity state, so that photoelectrons transported to the cathode surface can be emitted to vacuum with a certain probability.
The invention also provides a preparation method of the transmission-type photocathode in the technical scheme, which comprises the following steps:
depositing an outer surface optical anti-reflection film on one surface of the glass window to obtain the glass window deposited with the outer surface optical anti-reflection film;
sequentially epitaxially growing a GaAs smooth layer, a barrier layer, an emission layer, a buffer layer and a protective layer on a GaAs substrate, and then corroding and removing the protective layer to expose the buffer layer;
covering the part of the buffer layer to be deposited with the inner surface antireflection film by using a mask plate under a vacuum condition, after depositing an adhesive film on the surface of the buffer layer, covering the adhesive film by using the mask plate, depositing the inner surface antireflection film to obtain an adhesive film/inner surface antireflection film, and controlling the thickness of the adhesive film to be larger than that of the inner surface antireflection film;
respectively heating and degassing the glass window deposited with the external surface optical antireflection film, the internal surface antireflection film and the bonding film under a vacuum condition, pressing the glass window deposited with the external surface optical antireflection film into a concave part formed by the internal surface antireflection film and the bonding film, and bonding the glass window deposited with the external surface optical antireflection film and the bonding film together under a heating condition; and one surface of the glass window which is evaporated with the external surface optical antireflection film and is not evaporated with the external surface optical antireflection film is in contact with the internal surface antireflection film.
After the bonding is finished, removing the GaAs substrate, the GaAs smooth layer and the barrier layer in sequence by adopting wet etching to expose the emitting layer;
evaporating an active layer on the surface of the emitting layer under an ultrahigh vacuum activation system to obtain the transmission-type photocathode;
the vacuum degree of the ultrahigh vacuum activation system is less than or equal to 10-7Pa。
The preparation method of the transmission-type photoelectric cathode comprises the following steps: and depositing an outer surface optical anti-reflection film on one surface of the glass window to obtain the glass window deposited with the outer surface optical anti-reflection film. In the present invention, the deposition process is preferably performed by sequentially heating the outer surface optical anti-reflection film material under a vacuum condition of a vacuum coating machine to generate molecules of the outer surface optical anti-reflection film material in an evaporated state, and then bombarding the molecules of the outer surface optical anti-reflection film material in the evaporated state with an ion source to uniformly deposit the molecules on the surface of the glass window.
The preparation method of the transmission-type photocathode further comprises the steps of growing a GaAs smooth layer, a barrier layer, an emission layer, a buffer layer and a protective layer on the GaAs substrate in an epitaxial mode in sequence, and then corroding and removing the protective layer to expose the buffer layer; in the present invention, the substrate crystal orientation (100) of the GaAs substrate is preferably biased to (110)30Substrate dislocation density is preferred<103cm-3. In the invention, the thickness of the GaAs smooth layer is preferably 0.2-2 μm; the GaAs smooth layer is used as a transition layer between the GaAs substrate and other epitaxial structures so as to ensure that the other epitaxial structures are high-quality epitaxial structures without defects or low-density defects. In the invention, the blocking layer is preferably a GaAlAs blocking layer or a GaAlAsP blocking layer, and the thickness of the blocking layer is preferably 0.5-5 μm; the barrier layer is used for preventing the emitting layer and the buffer layer from being damaged by the corrosion process in the process of removing the GaAs substrate by corrosion after the bonding is finished. In the invention, the protective layer is preferably a GaAs protective layer, and the thickness of the protective layer is preferably 0.05-0.2 μm; the protective layer serves to protect the buffer layer and the emission layer after the growth is completed.
In the present invention, the epitaxial growth is preferably performed under vacuum conditions; the method of epitaxial growth preferably comprises Metal Organic Chemical Vapor Deposition (MOCVD) or Molecular Beam Epitaxy (MBE).
In the present invention, the process of epitaxially growing the GaAs smoothing layer is preferably: in a Metal Organic Chemical Vapor Deposition (MOCVD) apparatus or a Molecular Beam Epitaxy (MBE) apparatus, arsine (AsH)3) Introducing the mixed gas of trimethyl gallium (TMG) and the GaAs substrate surface into a reaction chamber, and carrying out thermal decomposition reaction on the mixed gas on the heated GaAs substrate surfaceThe GaAs smoothing layer should be epitaxially grown to a uniform thickness on the GaAs substrate. The ratio of the arsine to the trimethylgallium is not limited in any way, and can be adjusted according to the common general knowledge in the field according to the actual growth conditions.
In the present invention, the process of epitaxially growing the barrier layer is preferably: in a Metal Organic Chemical Vapor Deposition (MOCVD) apparatus or a Molecular Beam Epitaxy (MBE) apparatus, arsine (AsH)3) A mixed gas of trimethyl gallium (TMG) and trimethyl aluminum (TMA), or arsine (AsH)3) Phosphane (PH)3) Introducing a mixed gas of trimethyl gallium (TMG) and trimethyl aluminum (TMA) into the reaction chamber, wherein the mixed gas generates a thermal decomposition reaction on the surface of the heated GaAs substrate, and epitaxially growing a layer of GaAlAs barrier layer or GaAlAsP barrier layer with uniform thickness on the GaAs smooth layer. The proportion of the mixed gas is not limited in any way, and the proportion of the mixed gas is adjusted according to the difference of actual growth conditions according to the common knowledge in the field.
In the present invention, the process of epitaxially growing the emission layer is preferably: in a Metal Organic Chemical Vapor Deposition (MOCVD) apparatus or a Molecular Beam Epitaxy (MBE) apparatus, arsine (AsH)3) And trimethyl gallium (TMG), arsine (AsH)3) A mixed gas of trimethyl gallium (TMG) and trimethyl aluminum (TMA) or arsine (AsH)3) Phosphane (PH)3) And mixed gas of trimethyl gallium (TMG) and trimethyl aluminum (TMA) is mixed with p-type doping material dimethyl zinc (DMZ) and introduced into the reaction chamber, the mixed gas generates thermal decomposition reaction on the surface of the heated barrier layer, and a layer of p-type doping GaAs emission layer or GaAlAs emission layer or GaAlAsP emission layer with uniform thickness is epitaxially grown on the barrier layer. The proportion of the mixed gas is not limited in any way, and the proportion of the mixed gas is adjusted according to the difference of actual growth conditions according to the common knowledge in the field.
In the present invention, the process of epitaxially growing the buffer layer is preferably: in Metal Organic Chemical Vapor Deposition (MOCVD) apparatus or molecular beam epitaxyIn (MBE) apparatus, arsine (AsH)3) A mixed gas of trimethyl gallium (TMG) and trimethyl aluminum (TMA), or arsine (AsH)3) Phosphane (PH)3) And mixed gas of trimethyl gallium (TMG) and trimethyl aluminum (TMA) is mixed with a p-type doping material dimethyl zinc (DMZ) and introduced into the reaction chamber, the mixed gas is subjected to a thermal decomposition reaction on the surface of the heated emitting layer, and a layer of p-type doping GaAlAs buffer layer or GaAlAsP buffer layer with uniform thickness is epitaxially grown on the emitting layer. The proportion of the mixed gas is not limited in any way, and the proportion of the mixed gas is adjusted according to the difference of actual growth conditions according to the common knowledge in the field.
In the present invention, the process of epitaxially growing the protective layer is preferably: in a Metal Organic Chemical Vapor Deposition (MOCVD) apparatus or a Molecular Beam Epitaxy (MBE) apparatus, arsine (AsH)3) And introducing mixed gas of trimethyl gallium (TMG) into the reaction chamber, carrying out thermal decomposition reaction on the surface of the heated buffer layer, and epitaxially growing a GaAs protective layer with uniform thickness on the buffer layer.
In the present invention, the agent used for the corrosion protection layer is preferably hydrogen peroxide and NH in a volume ratio of 10:14A mixed solution of OH solution; in the invention, the mass concentration of the hydrogen peroxide is preferably 5-30%, and more preferably 10-20%; the NH4The mass concentration of the OH solution is preferably 5% to 40%, more preferably 10% to 30%.
After the buffer layer is exposed, the part of the buffer layer, to be deposited with the inner surface antireflection film, is covered by a mask plate under a vacuum condition, after an adhesive film is deposited on the surface of the buffer layer, the adhesive film is covered by the mask plate, the inner surface antireflection film is deposited, an adhesive film/inner surface antireflection film is obtained, and the thickness of the adhesive film is controlled to be larger than that of the inner surface antireflection film. In the present invention, the position of the inner surface antireflection film to be deposited is preferably the central position of the buffer layer. In the invention, the process of depositing the bonding film is preferably that in a vacuum coating machine, after the material of the bonding film is heated to obtain the molecules of the bonding film material in an evaporation state, the molecules of the bonding film material are bombarded by an ion source; the evaporation and ion source bombardment processes are not particularly limited in the present invention, and may be performed by processes well known to those skilled in the art. In the present invention, the process of depositing the inner surface antireflection film preferably refers to the process of depositing the adhesive film.
In the present invention, the processes of depositing the adhesive film and depositing the inner surface antireflection film are preferably performed under vacuum conditions.
The preparation method of the transmission-type photocathode further comprises the steps of respectively heating and degassing the glass window deposited with the external surface optical antireflection film, the internal surface antireflection film and the bonding film under a vacuum condition, pressing the glass window deposited with the external surface optical antireflection film into a concave part formed by the internal surface antireflection film and the bonding film, and bonding the glass window deposited with the external surface optical antireflection film and the bonding film together under a heating condition; and one surface of the glass window which is evaporated with the external surface optical antireflection film and is not evaporated with the external surface optical antireflection film is in contact with the internal surface antireflection film.
In the invention, the heating and degassing process preferably raises the temperature to 300-400 ℃ at a heating rate of 200 ℃/min, and keeps the temperature for 0.5-2 h. In the invention, the above process can prevent the damage of the temperature overshoot to the bonding assembly; in the present invention, the temperature for pressing is preferably 300 to 400 ℃. In the invention, the bonding process is preferably carried out by heating to the softening point temperature of the glass window at a heating rate of 200 ℃/min and carrying out heat preservation for 5-30 min. After the bonding is finished, the temperature is preferably reduced to room temperature at a cooling rate of less than or equal to 200 ℃/min. In the invention, the temperature reduction process can prevent the generation of larger bonding stress, which causes the reduction of the response performance of the cathode and even damages the bonding structure.
After the bonding is finished, the GaAs substrate, the GaAs smooth layer and the barrier layer are removed by corrosion in sequence, and the emitting layer is exposed; in the present invention, the agent used for etching the GaAs substrate and the GaAs smoothing layer is preferably a reagentHydrogen peroxide and NH with volume ratio of 10:14A mixed solution of OH solution; in the invention, the mass concentration of the hydrogen peroxide is preferably 5-30%, and more preferably 10-20%; the NH4The mass concentration of the OH solution is preferably 5-40%, and more preferably 10-30%; in the present invention, the reagent used for etching the barrier layer is preferably a hydrofluoric acid solution having a mass concentration of 20%.
After the emitting layer is exposed, the invention carries out vapor deposition on the surface of the emitting layer by an active layer under an ultrahigh vacuum activation system to obtain the transmission type photocathode. In the invention, the vacuum degree of the ultrahigh vacuum activation system is preferably less than or equal to 10-7Pa. In the present invention, the evaporation is preferably performed by heating a high purity Cs source and high purity O2The source evaporates Cs vapor with the purity of more than or equal to 99.99 percent and O with the purity of more than or equal to 99.99 percent2Depositing a layer of Cs with the thickness of about 0.5-1.5 nm on the surface of the emitting layer: and an O layer.
The invention also provides the application of the transmission-type photocathode in the technical scheme or the transmission-type photocathode prepared by the preparation method of the transmission-type photocathode in the technical scheme in the low-light-level night vision field, the underwater imaging detection field, the low-light-level remote sensing imaging field or the photomultiplier.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
A transmission-type photocathode comprises an outer surface antireflection film, a glass window, an adhesive film/inner surface antireflection film, a buffer layer, an emission layer and an activation layer (the structural relationship is shown in figure 1) which are sequentially stacked along the light incidence direction;
wherein, the outer surface antireflection film: TiO arranged in sequence from the glass window2Layer (12.3nm), SiO2Layer (33.5nm), TiO2Layer (27nm), SiO2Layer (13.5nm), TiO2Layer (86.3nm), SiO2Layer (18.3nm), TiO2Layer (19nm) and MgF2A layer (95 nm);
glass window: corning 7056 borosilicate glass with two polished sides;
adhesive film/inner surface antireflection film: adhesive film: si arranged in sequence from the buffer layer3N4Film (170nm) and SiO2A film;
inner surface antireflection film: si in sequence from the buffer layer3N4Layer (60nm), MgF2(71nm)、Si3N4Layer (7.3nm) and MgF2(91nm)；
Buffer layer: GaAlAs buffer layer, Al 0.7, p-type doping concentration 1019cm-3(0.4μm)；
An emission layer: GaAs emission layer with p-type doping concentration of 1019cm-3(1.5μm)；
An active layer: cs: an O active layer (1 nm);
the preparation method comprises the following steps:
respectively heating TiO under the vacuum condition of a vacuum coating machine2、SiO2、MgF2The material producing evaporated TiO2、SiO2、MgF2Molecular and bombarding evaporated TiO with an ion source2、SiO2、MgF2Molecules, depositing TiO in sequence on one side of the glazing2Layer (12.3nm), SiO2Layer (33.5nm), TiO2Layer (27nm), SiO2Layer (13.5nm), TiO2Layer (86.3nm), SiO2Layer (18.3nm), TiO2Layer (19nm) and MgF2A layer (95nm) for forming an external optical antireflection film to obtain a glass window deposited with the external optical antireflection film;
by Metal Organic Chemical Vapor Deposition (MOCVD), the GaAs substrate (substrate crystal orientation (100)) is deflected (110)30Substrate dislocation density<103cm-3) Epitaxially growing a GaAs smoothing layer on the substrate sequentially (in a Metal Organic Chemical Vapor Deposition (MOCVD) apparatus, arsine (AsH)3) Introducing mixed gas of trimethyl gallium (TMG) and oxygen into the reaction chamber, heating the mixed gasThe surface of the GaAs substrate is subjected to thermal decomposition reaction to obtain a GaAs smooth layer with the thickness of 0.5 mu m) and Ga0.5Al0.5As barrier layer (AsH)3) Introducing the mixed gas of trimethyl gallium (TMG) and trimethyl aluminum (TMA) into the reaction chamber, and carrying out thermal decomposition reaction on the surface of the heated GaAs substrate to obtain Ga with the thickness of 2 mu m0.5Al0.5As barrier layer), emitter layer (arsine (AsH)3) Mixing trimethyl gallium (TMG) mixed gas with p-type doping material dimethyl zinc (DMZ) and introducing the mixture into a reaction chamber, wherein the mixed gas is heated in the Ga0.5Al0.5The As barrier layer surface is thermally decomposed to obtain a layer with a thickness of 1.5 μm and a p-type doping concentration of 1019cm-3GaAs emission layer of (ii), buffer layer (arsine (AsH)3) Mixing the mixed gas of trimethyl gallium (TMG) and trimethyl aluminum (TMA) with p-type doping material dimethyl zinc (DMZ), introducing into a reaction chamber, and performing thermal decomposition reaction on the surface of the heated GaAs emission layer to obtain p-type doping material with a thickness of 0.4 μm and a doping concentration of 1019cm-3Of the Ga0.3Al0.7As buffer layer) and protective layer (AsH)3) Introducing mixed gas of trimethyl gallium (TMG) into the reaction chamber, carrying out thermal decomposition reaction on the surface of the heated buffer layer to obtain a GaAs protective layer with the thickness of 0.1 mu m), and corroding and removing the protective layer to expose the buffer layer;
under the vacuum condition, a mask plate is utilized to cover the part of the antireflection film on the inner surface to be deposited in the center of the buffer layer, and Si is sequentially and respectively heated3N4、SiO2Material generation of Si3N4、SiO2Molecular and bombarding Si with an ion source3N4、SiO2Molecules of Si deposited in sequence at the edge portion of the buffer layer3N4Film (170nm) and SiO2Depositing an adhesive film on the surface of the buffer layer, covering the adhesive film with a mask plate, and sequentially and respectively heating Si3N4、MgF2Material producing evaporated Si3N4、MgF2Molecular and bombarding evaporated Si with an ion source3N4、MgF2Molecules in said bufferThe central part of the layer being successively deposited with Si3N4Layer (60nm), MgF2(71nm)、Si3N4Layer (7.3nm) and MgF2(91nm), forming an inner surface antireflection film to obtain an adhesive film/inner surface antireflection film, and controlling the thickness of the adhesive film to be larger than that of the inner surface antireflection film;
gradually and slowly heating to 400 ℃ at the heating rate of 200 ℃/h under the vacuum condition, keeping for 2h, and heating and degassing the glass window deposited with the external surface optical antireflection film, the internal surface antireflection film and the bonding film; then pressing the glass window deposited with the external surface optical antireflection film into a concave part formed by the internal surface antireflection film and the bonding film; then, continuously and slowly heating to the vicinity of the softening point of the glass window at the heating rate of 200 ℃/h, keeping for 15min to soften the surface part of the glass corresponding to the bonding film, and then fully bonding the glass window and the bonding film to form a firm bonding structure and enabling the glass window with the inner surface antireflection film to be in good contact; and finally, slowly cooling to room temperature at the cooling rate of 200 ℃/h to complete the bonding of the glass window and the bonding film/inner surface antireflection film. Wherein one surface of the glass window evaporated with the external surface optical antireflection film, which is not evaporated with the external surface optical antireflection film, is in contact with the internal surface antireflection film;
after the bonding is finished, the GaAs substrate is removed by sequentially corroding with selective chemical reagents (the chemical reagents used for corroding are hydrogen peroxide and NH with the volume ratio of 10: 1)4Mixed solution of OH solution, hydrogen peroxide with mass concentration of 20 percent and NH4The mass concentration of OH solution is 40 percent), a GaAs smooth layer (chemical reagents used for corrosion are hydrogen peroxide and NH with the volume ratio of 10: 1)4Mixed solution of OH solution, hydrogen peroxide with mass concentration of 20 percent and NH4OH solution mass concentration of 40%) and Ga0.5Al0.5An As barrier layer (a chemical reagent used for corrosion is an HF solution with the mass concentration of 20 percent), and the emitting layer is exposed;
at most 10-7Pa ultra-high vacuum activating system, heating to 99.99% or more of high-purity Cs source and high-purity O2High-purity Cs vapor with the content of more than or equal to 99.99 percent and high-purity O with the content of more than or equal to 99.99 percent are obtained by source evaporation2And evaporating 1nm Cs: and O, activating the layer to obtain the transmission type photocathode.
Comparative example 1
The traditional cathode is as follows:
the structure is as follows: a light incident window and 100nmSi sequentially stacked in the light incident direction3N4Layer, 0.4 μmGa0.3Al0.7As buffer layer, 1.5 mu mGaAs emission layer. The photocathode of comparative example 1 had an internal surface antireflection film of 100nmSi, compared to the structure of example 13N4The layer is not provided with an external antireflection film, and the materials and parameters of the rest layers are completely the same.
FIG. 2 is a comparison graph of absorption spectra of the transmissive photocathode of example 1 and the transmissive conventional cathode of comparative example 1, wherein the response wavelength bands of the transmissive photocathode of example 1 and the conventional cathode of comparative example 1 are both 450-900 nm; as can be seen from fig. 2, compared with the conventional cathode described in comparative example 1, since the cathode of the present invention employs the arrangement of the antireflection films on the inner and outer surfaces, the light reflectance of the transmissive photocathode of example 1 of the present invention is reduced in a wide range, resulting in an increase in light absorption rate, wherein the light absorption rate in a short wavelength band is higher than that of the photocathode prepared in comparative example 1 by 5 to 15%. Therefore, the photoelectric cathode has higher quantum efficiency and spectral sensitivity, and the response performance of the cathode is obviously improved.
Example 2
A transmission-type photocathode comprises an outer surface antireflection film, a glass window, an adhesive film/inner surface antireflection film, a buffer layer, an emission layer and an activation layer (the structural relationship is shown in figure 1) which are sequentially stacked along the light incidence direction;
wherein, the outer surface antireflection film: TiO arranged in sequence from the glass window2Layer (13.3nm), SiO2Layer (33.7nm), TiO2Layer (27nm), SiO2Layer (12nm), TiO2Layer (79.5nm), SiO2Layer (22nm), TiO2Layer (17.3nm) and MgF2A layer (99 nm);
glass window: 9741 violet-transmitting glass with polished two sides;
adhesive film/inner surface antireflection film: adhesive film: si arranged in sequence from the buffer layer3N4Film (270nm) and SiO2A film;
inner surface antireflection film: the buffer layer is sequentially as follows: si3N4Layer (62.5nm), MgF2(46.5nm)、Si3N4Layer (14.7nm) and MgF2(142.5nm)；
Buffer layer: AlAs buffer layer with p-type doping concentration of 1019cm-3(0.1μm)；
An emission layer: GaAs emission layer with p-type doping concentration of 1019cm-3(1.5μm)；
An active layer: cs: an O active layer (1 nm);
the preparation process differs with reference to example 1 only in the choice of the materials and the thickness of the individual layers.
Comparative example 2
The traditional cathode is as follows:
the structure is as follows: a light incident window and 100nmSi sequentially stacked in the light incident direction3N4Layer, 0.1 mu m AlAs buffer layer, 1.5 mu m GaAs emission layer. The photocathode of comparative example 1 had an internal surface antireflection film of 100nmSi, compared to the structure of example 13N4Layer, no outer anti-reflection film, all the other materials and all the parameters are the same.
FIG. 3 shows absorption spectra of the transmissive photocathode of example 2 and the conventional cathode of comparative example 2, and it can be seen from FIG. 3 that the response wavelength bands of the transmissive photocathode of example 2 and the conventional cathode of comparative example 2 are both 300-900 nm (wide-spectrum blue-green light); the light absorptivity of the transmission type photoelectric cathode is greatly improved, wherein the light absorptivity of the transmission type photoelectric cathode is higher than that of a traditional cathode by more than 5-25% in a short wave band, and particularly higher than that of the traditional cathode by 20-26% in a 390-420 nm wave band. Therefore, the arrangement of the antireflection films on the inner surface and the outer surface ensures that the photocathode has higher spectral sensitivity and is expected to be greatly applied to the field of blue-extended wide-spectrum transmission-type photocathodes.
Example 3
A transmission type GaAlAs photocathode comprises an outer surface antireflection film, a glass window, an adhesive film/inner surface antireflection film, a buffer layer, an emission layer and an activation layer (the structural relationship is shown in figure 1) which are sequentially stacked along the light incidence direction;
wherein, the outer surface antireflection film: TiO arranged in sequence from the glass window2Layer (9.3nm), MgF2Layer (36nm), TiO2Layer (21nm), MgF2Layer (34nm), TiO2Layer (15.5nm) and MgF2A layer (90 nm);
glass window: 9741 violet-transmitting glass with polished two sides;
adhesive film/inner surface antireflection film: adhesive film: si arranged in sequence from the buffer layer3N4Film (260nm) and SiO2A film;
inner surface antireflection film: the buffer layer is sequentially as follows: si3N4Layer (48nm), MgF2(55.6nm)、Si3N4Layer (9nm), MgF2(79.2nm)、Si3N4Layer (16.5nm), MgF2(44nm), and Si3N4A layer (12 nm);
buffer layer: ga0.1Al0.9As buffer layer with p-type doping concentration of 1019cm-3(0.2μm)；
An emission layer: ga0.8Al0.2As emitting layer with p-type doping concentration of 1019cm-3(1μm)；
An active layer: cs: an O active layer (1 nm);
the preparation method comprises the following steps:
the preparation process differs with reference to example 1 only in the choice of the materials and the thickness of the individual layers.
Comparative example 3
The traditional cathode is as follows:
the structure is as follows: a light incident window and 100nmSi sequentially stacked in the light incident direction3N4Layer, 0.2 μmGa0.1Al0.9As buffer layer and 1Ga0.8Al0.2An As emitting layer. The photocathode of comparative example 1 had an internal surface antireflection film of 100nmSi, compared to the structure of example 13N4A layer of a material selected from the group consisting of,no external antireflection film is arranged, and other materials and parameters are completely the same.
FIG. 4 is a comparison graph of absorption spectra of the transmissive photocathode of example 3 and the conventional cathode of comparative example 3, and it can be seen from FIG. 4 that the response wavelength bands of the transmissive photocathode of example 3 and the conventional cathode of comparative example 3 are both 300-750 nm; compared with the comparative example 3, due to the arrangement of the antireflection films on the inner surface and the outer surface, the transmission type photocathode has higher light absorptivity, for example, the absorptivity of a wave band of 305-610 nm is 5-18% higher than that of the traditional cathode; has higher light sensitivity in blue green light and shorter wave bands, and is expected to be widely applied in the field of transmission type photocathodes of blue green light and shorter wave bands.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (9)

1. A transmission type photocathode is characterized by comprising an outer surface antireflection film, a glass window, an adhesive film/inner surface antireflection film, a buffer layer, an emitting layer and an activation layer which are sequentially stacked in the light incidence direction;
the adhesive film/inner surface antireflection film comprises an adhesive film and an inner surface antireflection film;
the inner surface antireflection film is positioned in the center of the surface of the glass window and does not reach the edge of the surface of the glass window; the bonding film is positioned at the edge of the surface of the glass window and is tightly connected with the inner surface antireflection film;
the thickness of the bonding film is larger than that of the inner surface antireflection film.
2. The transmissive photocathode of claim 1, wherein the outer surface antireflection film or the inner surface antireflection film independently comprises 1 or more layers of optical films;
the material of each layer of the optical film is TiO independently2、SiO2、Si3N4、SnO2、HfO2、Al2O3、Bi2O3、AlOxNy、AlF3、BiF3、CeF3、CeO2、CsBr、CsI、Cr2O3Diamond, Dy2O3、Eu2O3、Gd2O3、Ho2O3、In2O3、Nb2O5、Nd2O3、PbCl2、Pr6O11、Sc2O3、Sb2O3、Sm2O3、Y2O3、ZnO、ZnS、BeO、MgO、MgF2、ZrO2、La2O3、La2O5、LiF、CaF2、LaF3、BaF2、NaF、Na3AlF6、SrF2、NdF3、PbF2、YbF3、SmF3And ThF4One or more of them.
3. The transmissive photocathode of claim 2, wherein the outer surface antireflection film has a thickness of 5nm to 10 μ ι η;
the thickness of the inner surface antireflection film is 30 nm-10 mu m.
4. The transmissive photocathode of claim 3,
when the inner surface antireflection film includes 1 optical film, the optical film is Si3N4A thin film having a thickness of 30 to 80 nm;
when the inner surface antireflection film comprises>1, the optical film in contact with the buffer layer and the antireflection film on the inner surface is Si3N4A film; and Si in the inner surface antireflection film3N4The total thickness of the film is more than or equal to 30 nm.
5. The transmissive photocathode of claim 1, wherein the transmissive photocathode comprisesThen, the adhesive film includes Si sequentially arranged from the buffer layer3N4Film and SiO2A film; said Si3N4The thickness of the film is more than or equal to 30 nm.
6. The transmissive photocathode of claim 1, wherein the emissive layer is of a material selected from GaAs, Ga1- xAlxAs or Ga1-x-yAlxAs1-yPy(ii) a Wherein, 0<x≤0.5，0<y≤0.2；
The thickness of the emitting layer is 0.4-2 μm;
the p-type doping concentration in the emitting layer is 1018～1019cm-3。
7. The transmissive photocathode of claim 1, wherein the buffer layer comprises Ga1-zAlzAs or Ga1-zAlzAs1-qPq(ii) a Wherein z is more than or equal to 0.5 and less than or equal to 1 and 0<q≤0.2；
The thickness of the buffer layer is 0.04-2 mu m;
the p-type doping concentration of the buffer layer is 1018～1019cm-3。
8. The method of preparing a transmissive photocathode according to any one of claims 1 to 7, comprising the steps of:
depositing an outer surface optical anti-reflection film on one surface of the glass window to obtain the glass window deposited with the outer surface optical anti-reflection film;
sequentially epitaxially growing a GaAs smooth layer, a barrier layer, an emission layer, a buffer layer and a protective layer on a GaAs substrate, and then corroding and removing the protective layer to expose the buffer layer;
covering the part of the buffer layer to be deposited with the inner surface antireflection film by using a mask plate under a vacuum condition, after depositing an adhesive film on the surface of the buffer layer, covering the adhesive film by using the mask plate, depositing the inner surface antireflection film to obtain an adhesive film/inner surface antireflection film, and controlling the thickness of the adhesive film to be larger than that of the inner surface antireflection film;
respectively heating and degassing the glass window deposited with the external surface optical antireflection film, the internal surface antireflection film and the bonding film under a vacuum condition, pressing the glass window deposited with the external surface optical antireflection film into a concave part formed by the internal surface antireflection film and the bonding film, and bonding the glass window deposited with the external surface optical antireflection film and the bonding film together under a heating condition; one surface of the glass window which is evaporated with the external surface optical antireflection film and is not evaporated with the external surface optical antireflection film is contacted with the internal surface antireflection film;
after the bonding is finished, sequentially removing the GaAs substrate, the GaAs smooth layer and the barrier layer by corrosion to expose the emitting layer;
evaporating an active layer on the surface of the emitting layer under an ultrahigh vacuum activation system to obtain the transmission-type photocathode;
the vacuum degree of the ultrahigh vacuum activation system is less than or equal to 10-7Pa。
9. The use of the transmissive photocathode of any one of claims 1 to 7 or the transmissive photocathode prepared by the method of claim 8 in the field of low-light-level night vision, underwater imaging detection, low-light-level remote sensing imaging, or photomultiplier tubes.
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