Multi-alkali cathode for improving quantum efficiency of specific wave band and preparation method thereof

Abstract

The application discloses a multi-alkali cathode for improving quantum efficiency of specific wave band and a preparation method thereof. The photoelectric cathode is composed of a glass substrate, a SiO2 substrate layer, a multi-alkali photoelectric cathode matching anti-reflection layer, an Al2O3 diffusion barrier layer and a multi-alkali photoelectric cathode layer from bottom to top. The multi-alkali photoelectric cathode anti-reflection layer is composed of 10-300 pairs of Ta2O5 / TiO2 / HfO2 / Si3N4 and SiO2. The multi-alkali photoelectric cathode layer is composed of a K3Sb substrate layer, a Na2KSb light absorption layer, a Cs / Sb activation layer and a Sb surface layer. The application introduces the multi-alkali photoelectric cathode matching anti-reflection layer, controls the thickness ratio of the multi-alkali photoelectric cathode layer and the multi-alkali photoelectric cathode matching anti-reflection layer, reduces the interface reflectivity of the multi-alkali photoelectric cathode in specific wave band, improves the light absorption utilization rate of the multi-alkali photoelectric cathode in specific wave band, and finally realizes the improvement of the quantum efficiency of the multi-alkali photoelectric cathode in specific wave band.

Description

Technical Field

[0001] This invention belongs to the field of detection materials for specific wavelengths in low-light night vision, and relates to a multi-alkali photocathode for improving the quantum efficiency of specific wavelengths in low-light image intensifiers and its preparation method. Background Technology

[0002] The low-light image intensifier (hereinafter referred to as the image intensifier), as the core component of low-light night vision, consists of a glass input window, a photocathode, an electron multiplier (MCP), a fluorescent screen, and an optical fiber output window. It converts extremely weak light signals, invisible to the human eye, into electrical signals, which are then amplified by the MCP to form a bright signal visible to the naked eye on the fluorescent screen. Traditionally, image intensifiers are mainly used in nighttime combat, but thanks to their strong weak signal detection capabilities, they can be used in various fields such as scientific research, medical treatment, and civilian applications where there is a need to detect signals in specific frequency bands.

[0003] Photocathodes are the core components of image intensifiers for detecting signals. Compared to other photocathode materials, multi-alkali photocathodes possess superior properties such as high photoelectric conversion efficiency, low background noise, fast response time, and controllable manufacturing processes. Traditional multi-alkali photocathodes primarily detect in the visible light band, without optimizing the response band for specific applications. This makes them unsuitable for applications such as underwater imaging in the blue-green light band, explosion and combustion analysis in the blue light band, and corona detection in the ultraviolet band. Furthermore, the relatively wide detection spectrum of traditional multi-alkali photocathodes results in low quantum efficiency across various bands and weak detection capabilities in specific bands, making it difficult to meet the needs of various scientific research, industrial monitoring, and biomedical analysis fields for detecting extremely weak signals and high-speed moving targets. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for preparing a multi-alkali photocathode with improved quantum efficiency in a specific wavelength band. Based on the actual application scenario, the quantum efficiency of the multi-alkali photocathode in a specific wavelength band is improved, so as to further enhance the detection and imaging capabilities of the image enhancement for specific application scenarios.

[0005] The technical solution for implementing the present invention is as follows:

[0006] A multi-alkali photocathode for improving quantum efficiency in a specific wavelength band is provided. The photocathode is composed of a glass substrate, a SiO2 substrate layer, an anti-reflection layer matched with the multi-alkali photocathode, an Al2O3 diffusion barrier layer, and a multi-alkali photocathode layer from bottom to top. The anti-reflection layer of the multi-alkali photocathode is composed of 10-300 pairs of Ta2O5 / TiO2 / HfO2 / Si3N4 and SiO2 overlapping.

[0007] Furthermore, the thickness of the multi-alkali photocathode antireflection layer is 10–300 nm.

[0008] Furthermore, the thickness of the Al2O3 diffusion barrier layer is 2–30 nm.

[0009] Furthermore, the multi-alkali photocathode layer is composed of a K3Sb substrate layer, a Na2KSb light absorption layer, a Cs / Sb activation layer, and an Sb surface layer.

[0010] Furthermore, the thickness of the multi-alkali photocathode layer is 20–180 nm.

[0011] Furthermore, the ratio of the antireflection layer of the multi-alkali photocathode to the thickness of the multi-alkali photocathode is 0.05 to 2.

[0012] Furthermore, the Cs / Sb activation layer and Sb surface layer are deposited on the surface of the Na2KSb light absorption layer using ultra-high vacuum thermal evaporation technology.

[0013] A method for preparing a multi-alkali cathode to improve quantum efficiency in a specific wavelength band, comprising the following steps:

[0014] The first step is to fabricate a SiO2 substrate layer on a borosilicate glass window substrate that has undergone surface chemical cleaning and physical cleaning using thermal evaporation.

[0015] The second step involves preparing an antireflection layer and an Al2O3 diffusion barrier layer for matching a multi-alkali photocathode on a SiO2 substrate using coating techniques such as electron beam evaporation or atomic layer deposition.

[0016] The third step involves growing a multi-alkali photocathode layer on the surface of the anti-reflection layer and the Al2O33 diffusion barrier layer matched with the multi-alkali photocathode using ultra-high vacuum thermal evaporation technology.

[0017] The fourth step involves encapsulating the borosilicate glass of the multi-alkali photocathode, which is fabricated on an antireflection layer and an Al2O3 diffusion barrier layer matched with the multi-alkali photocathode, and testing whether the quantum efficiency of the developed multi-alkali photocathode is improved in a specific wavelength band.

[0018] Furthermore, in the first step, the thickness of the SiO2 substrate layer is controlled to be 10–20 nm;

[0019] Furthermore, in the second and third steps, the thickness ratio of the antireflection layer to the multi-alkali photocathode layer is controlled to be 0.05 to 2.

[0020] The beneficial effects of this invention are:

[0021] This invention matches the antireflection layer with the multi-alkali cathode layer. Compared with traditional multi-alkali cathodes, by matching the thickness of the antireflection layer and the multi-alkali cathode, the detection response band of the multi-alkali photocathode can be shifted, reducing the reflectivity of a specific band and thus improving the quantum efficiency of the multi-alkali photocathode in a specific band. It can be applied to various scientific research, industrial monitoring and biomedical analysis fields for the detection of extremely weak signals and high-speed moving targets in a specific band. Attached Figure Description

[0022] Figure 1 : Schematic diagram of the multi-alkali photocathode structure for improving quantum efficiency in a specific wavelength band according to the present invention.

[0023] Figure 2 Example 1: Quantum efficiency curves at different wavelengths compared to a traditional multi-alkali photocathode.

[0024] Figure 3 Quantum efficiency curves at different wavelengths for Example 1 and Comparative Example 1.

[0025] Figure 4 : Schematic diagram of the antireflection layer and multi-alkali photocathode structure in Comparative Example 2.

[0026] Figure 5 Quantum efficiency curves at different wavelengths for Example 1 and Comparative Example 2.

[0027] Figure 6 Example 2: Quantum efficiency curves at different wavelengths compared to a traditional multi-alkali photocathode.

[0028] Figure 7 Example 3: Quantum efficiency curves at different wavelengths compared to a traditional multi-alkali photocathode. Detailed Implementation

[0029] As previously stated, the purpose of this invention is to provide a multi-alkali photocathode that improves quantum efficiency in a specific wavelength band. This photocathode, from bottom to top, comprises a glass substrate, a SiO2 substrate layer, an anti-reflection layer matched with the multi-alkali photocathode, an Al2O3 diffusion barrier layer, and a multi-alkali photocathode layer. The anti-reflection layer of the multi-alkali photocathode is composed of 10-300 pairs of overlapping Ta2O5 / TiO2 / HfO2 / Si3N4 and SiO2. The multi-alkali photocathode layer consists of a K3Sb substrate layer, a Na2KSb light-absorbing layer, a Cs / Sb activation layer, and an Sb surface layer. The thickness ratio of the anti-reflection layer matched with the multi-alkali photocathode to the multi-alkali photocathode layer is 0.05–2.

[0030] This invention also provides a method for preparing a multi-alkali cathode to improve quantum efficiency in a specific wavelength band, the method comprising:

[0031] (1) A SiO2 thin film substrate was fabricated on a clean borosilicate glass window substrate;

[0032] (2) A multi-alkali photocathode matching antireflection layer and an Al2O3 diffusion barrier layer were prepared on a SiO2 thin film substrate by electron beam evaporation or atomic layer deposition and other coating techniques.

[0033] (3) A multi-alkali photocathode layer was grown on the surface of the anti-reflection layer and the Al2O3 diffusion barrier layer matched with the multi-alkali photocathode using ultra-high vacuum thermal evaporation technology.

[0034] (4) The borosilicate glass of the multi-alkali photocathode prepared on the anti-reflection layer and Al2O3 diffusion barrier layer matched with the multi-alkali photocathode is encapsulated, and the quantum efficiency of the multi-alkali photocathode is tested in a specific band.

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0036] A schematic diagram of the multi-alkali photocathode with improved quantum efficiency in a specific wavelength band in this invention is shown below. Figure 1 As shown, the multi-alkali photocathode consists of a glass substrate 1, a SiO2 substrate layer 2, an anti-reflection layer 3 matching the multi-alkali photocathode, an Al2O3 diffusion barrier layer 4, and a multi-alkali photocathode layer 5 from bottom to top.

[0037] The antireflection layer 3 of the multi-alkali photocathode is composed of 10-300 pairs of overlapping Ta2O5 / TiO2 / HfO2 / Si3N4 and SiO2, with a thickness of 10-300 nm; the multi-alkali photocathode layer is composed of a K3Sb substrate layer, a Na2KSb light absorption layer, a Cs / Sb activation layer and an Sb surface layer, with a thickness of 20-180 nm; the thickness ratio of the antireflection layer matched to the multi-alkali photocathode to the multi-alkali photocathode layer is 0.05-2. For example, the following example parameters can be used to prepare a multi-alkali photocathode with improved quantum efficiency in a specific wavelength band.

[0038] Example 1

[0039] A 20nm SiO2 substrate layer 2 thin film was deposited on a clean borosilicate glass window substrate 1 that had undergone chemical and physical cleaning using thermal evaporation coating technology.

[0040] A multi-alkali photocathode antireflection layer 3 was deposited on a 20nm SiO2 substrate layer 2 using electron beam thermal evaporation technology. It was formed by alternating growth of 10 pairs of HfO2 and SiO2 structures. The thickness of the alternating HfO2 and SiO2 antireflection layer was 10nm. An Al2O3 diffusion barrier layer 4 with a thickness of 20nm was grown on the alternating HfO2 and SiO2 antireflection layer using the same growth method.

[0041] A multi-alkali photocathode 5 was deposited on the surface of the Al2O3 diffusion barrier layer 4 using ultra-high vacuum thermal evaporation technology. The deposition method was to sequentially deposit a K3Sb substrate layer 6, a Na2KSb light absorption layer 7, a Cs / Sb activation layer 8, and an Sb surface layer 9. The ratio of the thickness of the multi-alkali photocathode antireflection layer 3 to the thickness of the multi-alkali photocathode 5 was controlled to be 0.16, so the thickness of the multi-alkali photocathode 5 was 60 nm.

[0042] The multi-alkali photocathode, fabricated on an antireflection layer and an Al2O3 diffusion barrier layer matched with the multi-alkali photocathode, was encapsulated in borosilicate glass, and the quantum efficiency curve of the fabricated multi-alkali photocathode was tested.

[0043] See Figure 2 Compared with traditional multi-alkali photocathodes, the embodiments of the present invention effectively reduce the reflectivity of the multi-alkali photocathode in the ultraviolet band and improve the quantum efficiency of the multi-alkali photocathode in the ultraviolet band by introducing an anti-reflection layer of a specific thickness matched to the multi-alkali photocathode and adjusting the ratio of the thickness of the anti-reflection layer matched to the thickness of the multi-alkali photocathode.

[0044] Comparative Example 1

[0045] A 20nm SiO2 substrate layer 2 thin film was deposited on a clean borosilicate glass window substrate 1 that had undergone chemical and physical cleaning using thermal evaporation coating technology.

[0046] A multi-alkali photocathode antireflection layer 3 was deposited on a 20nm SiO2 substrate layer 2 using electron beam thermal evaporation technology. It was formed by alternating growth of 10 pairs of HfO2 and SiO2 structures. The thickness of the alternating HfO2 and SiO2 antireflection layer was 10nm. An Al2O3 diffusion barrier layer 4 with a thickness of 20nm was grown on the alternating HfO2 and SiO2 antireflection layer using the same growth method.

[0047] A multi-alkali photocathode 5 was deposited on the surface of the Al2O3 diffusion barrier layer 4 using ultra-high vacuum thermal evaporation technology. The deposition method was to sequentially deposit a K3Sb substrate layer 6, a Na2KSb light absorption layer 7, a Cs / Sb activation layer 8, and an Sb surface layer 9. The ratio of the thickness of the multi-alkali photocathode antireflection layer 3 to the thickness of the multi-alkali photocathode 5 was controlled to be 0.06, so the thickness of the multi-alkali photocathode 5 was 150 nm.

[0048] The multi-alkali photocathode, fabricated on an antireflection layer and an Al2O3 diffusion barrier layer matched with the multi-alkali photocathode, was encapsulated in borosilicate glass, and the quantum efficiency curve of the fabricated multi-alkali photocathode was tested.

[0049] See Figure 3Compared with Example 1, this comparative example uses the same material and thickness as Example 1 to match the antireflection layer of the multi-alkali photocathode. However, the ratio of the thickness of the antireflection layer to the thickness of the multi-alkali photocathode is adjusted to 0.05. This comparative example cannot achieve the improvement of quantum efficiency in the ultraviolet band of the multi-alkali photocathode.

[0050] Comparative Example 2

[0051] like Figure 4 As shown, a multi-alkali photocathode antireflection layer 2 is deposited on a clean borosilicate glass window substrate 1 that has undergone chemical and physical cleaning using ultra-high vacuum thermal evaporation technology. The multi-alkali photocathode antireflection layer is formed by alternating growth of 10 pairs of HfO2 and SiO2 structures. The thickness of the alternating HfO2 and SiO2 antireflection layer is 10 nm. An Al2O3 diffusion barrier layer 3 with a thickness of 20 nm is grown on the alternating HfO2 and SiO2 antireflection layer using the same growth method.

[0052] A 20 nm SiO2 layer 4 thin film was deposited on the Al2O3 diffusion barrier layer 3 using thermal evaporation coating technology;

[0053] A multi-alkali photocathode 5 was deposited on a 20nm SiO2 layer 4 using ultra-high vacuum thermal evaporation technology. The deposition method was to sequentially deposit a K3Sb substrate layer 6, a Na2KSb light absorption layer 7, a Cs / Sb activation layer 8, and an Sb surface layer 9. The ratio of the thickness of the antireflection layer 3 to the thickness of the multi-alkali photocathode 5 was controlled to be 0.16, so the thickness of the multi-alkali photocathode 5 was 60nm.

[0054] The borosilicate photocathode prepared on the SiO2 layer was encapsulated in borosilicate glass, and the quantum efficiency curve of the prepared multi-alkali photocathode was tested.

[0055] See Figure 5 Compared with Example 1, this comparative example has the same material, thickness and multi-alkali photocathode thickness ratio as Example 1, but the preparation order of SiO24 layer, multi-alkali photocathode antireflection layer 2 and Al2O3 diffusion barrier layer 3 is changed. This comparative example cannot achieve the improvement of quantum efficiency of multi-alkali photocathode in the ultraviolet band.

[0056] Example 2

[0057] A 10 nm SiO2 substrate layer 2 thin film was deposited on a clean borosilicate glass window substrate 1 that had undergone chemical and physical cleaning using thermal evaporation coating technology.

[0058] A multi-alkali photocathode antireflection layer 3 was deposited on a 10nm SiO2 substrate layer 2 using electron beam thermal evaporation technology. It was formed by alternating growth of 50 pairs of TiO2 and SiO2 structures. The thickness of the alternating TiO2 and SiO2 antireflection layer was 50nm. An Al2O3 diffusion barrier layer 4 with a thickness of 30nm was grown on the alternating TiO2 and SiO2 antireflection layer using the same growth method.

[0059] A multi-alkali photocathode 5 was deposited on the surface of the Al2O3 diffusion barrier layer 4 using ultra-high vacuum thermal evaporation technology. The deposition method was to sequentially deposit a K3Sb substrate layer 6, a Na2KSb light absorption layer 7, a Cs / Sb activation layer 8, and an Sb surface layer 9. The ratio of the thickness of the multi-alkali photocathode antireflection layer 3 to the thickness of the multi-alkali photocathode 5 was controlled to be 0.55, so the thickness of the multi-alkali photocathode 5 was 90 nm.

[0060] The multi-alkali photocathode, fabricated on an antireflection layer and an Al2O3 diffusion barrier layer matched with the multi-alkali photocathode, was encapsulated in borosilicate glass, and the quantum efficiency curve of the fabricated multi-alkali photocathode was tested.

[0061] See Figure 6 Compared with traditional multi-alkali photocathodes, the embodiments of the present invention effectively reduce the reflectivity of the multi-alkali photocathode in the blue light band and improve the quantum efficiency of the multi-alkali photocathode in the blue light band by introducing an anti-reflection layer of a specific thickness and adjusting the ratio of the thickness of the anti-reflection layer to the thickness of the multi-alkali photocathode.

[0062] Example 3

[0063] A 30nm SiO2 substrate layer 2 thin film was deposited on a clean borosilicate glass window substrate 1 that had undergone chemical and physical cleaning using thermal evaporation coating technology.

[0064] A multi-alkali photocathode antireflection layer 3 was deposited on a 10nm SiO2 substrate layer 2 using electron beam thermal evaporation technology. It was formed by alternating growth of 100 pairs of Ta2O5 and SiO2 structures. The thickness of the alternating Ta2O5 and SiO2 antireflection layer was 100nm. An Al2O3 diffusion barrier layer 4 with a thickness of 30nm was grown on the alternating Ta2O5 and SiO2 antireflection layer using the same growth method.

[0065] A multi-alkali photocathode 5 was deposited on the surface of the Al2O3 diffusion barrier layer 4 using ultra-high vacuum thermal evaporation technology. The deposition method was to sequentially deposit a K3Sb substrate layer 6, a Na2KSb light absorption layer 7, a Cs / Sb activation layer 8, and an Sb surface layer 9. The ratio of the thickness of the multi-alkali photocathode antireflection layer 3 to the thickness of the multi-alkali photocathode 5 was controlled to be 0.83, so the thickness of the multi-alkali photocathode 5 was 120 nm.

[0066] The multi-alkali photocathode, fabricated on an antireflection layer and an Al2O3 diffusion barrier layer matched with the multi-alkali photocathode, was encapsulated in borosilicate glass, and the quantum efficiency curve of the fabricated multi-alkali photocathode was tested.

[0067] See Figure 7 Compared with traditional multi-alkali photocathodes, the embodiments of the present invention effectively reduce the reflectivity of the multi-alkali photocathode in the green light band and improve the quantum efficiency of the multi-alkali photocathode in the green light band by introducing an anti-reflection layer of a specific thickness matched to the multi-alkali photocathode and adjusting the ratio of the thickness of the anti-reflection layer matched to the thickness of the multi-alkali photocathode.

Claims

1. A multi-alkali cathode for improving quantum efficiency in a specific wavelength band, characterized in that: The multi-alkali cathode is composed of a glass substrate (1), a SiO2 substrate layer (2), a multi-alkali photocathode antireflection layer (3), an Al2O3 diffusion barrier layer (4), and a multi-alkali photocathode layer (5) from bottom to top. The multi-alkali photocathode antireflection layer (3) is composed of 10 to 300 pairs of Ta2O5 / TiO2 / HfO2 / Si3N4 and SiO2 overlapping. The multi-alkali photocathode layer (5) is composed of a K3Sb substrate layer (6), a Na2KSb light absorption layer (7), a Cs / Sb activation layer (8), and an Sb surface layer (9). The thickness ratio of the multi-alkali photocathode antireflection layer (3) to the multi-alkali photocathode layer (5) is 0.05~2; The period logarithm of the multi-alkali photocathode antireflection layer (3), the material combination, and the thickness of the multi-alkali photocathode layer (5) are all set to selectively improve the quantum efficiency of the multi-alkali photocathode in a specific band of the ultraviolet band, blue band, or green band relative to other bands.

2. The multi-alkali cathode for improving quantum efficiency in a specific wavelength band according to claim 1, characterized in that: The thickness of the multi-alkali photocathode antireflection layer (3) is 10~300nm.

3. The multi-alkali cathode for improving quantum efficiency in a specific wavelength band according to claim 1, characterized in that: The Al2O3 diffusion barrier layer (4) has a thickness of 2~30nm.

4. A multi-alkali cathode for improving quantum efficiency in a specific wavelength band according to claim 1, characterized in that: The thickness of the multi-alkali photocathode layer (5) is 20~180nm.

5. A multi-alkali cathode for improving quantum efficiency in a specific wavelength band according to claim 1, characterized in that: The Cs / Sb activation layer (8) and Sb surface layer (9) were deposited on the surface of the Na2KSb light absorption layer (7) by ultra-high vacuum thermal evaporation.

6. A multi-alkali cathode for improving quantum efficiency in a specific wavelength band according to any one of claims 1 to 5, characterized in that: The multi-alkali photocathode antireflection layer (3) is composed of 10 pairs of overlapping HfO2 and SiO2.

7. A multi-alkali cathode for improving quantum efficiency in a specific wavelength band according to any one of claims 1 to 5, characterized in that: The multi-alkali photocathode antireflection layer (3) is composed of 50 pairs of TiO2 and SiO2 overlapping.

8. A multi-alkali cathode for improving quantum efficiency in a specific wavelength band according to any one of claims 1 to 5, characterized in that: The multi-alkali photocathode antireflection layer (3) is composed of 100 pairs of overlapping Ta2O5 and SiO2.

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