A preparation method of a multi-alkali photocathode based on micro-nano optical elements

Abstract

The present invention discloses a preparation method of a multi-alkali photocathode based on micro-nano optical elements, comprising: turning on the Na source current, introducing a certain amount of Na to raise the photocurrent to a certain level, continuously introducing Na vapor, and after a certain period of time, turning on the Sb source current and evaporating them simultaneously to form a Na3Sb layer on the inner surface of the AVG with a micro-nano optical structure; turning on the K source, Na source, and Sb source, and when the Sb source current increases at a certain rate - increases rapidly - and decreases, cutting off the Sb source current; turning on the Na source current, increasing the Na vapor at a certain rate to keep the photocurrent showing a downward trend, and when the photocurrent drops to a certain level, cutting off the K source, Na source, and Sb source currents, performing a cooling treatment, and activating the surface of the multi-alkali cathode to complete the preparation of the multi-alkali photocathode. The present invention can significantly improve the influence of micro-nano optical elements on the preparation process of multi-alkali cathodes.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocathodes, and particularly relates to a method for preparing a multi-alkali photocathode based on micro-nano optical elements. Background Art

[0002] A photocathode is a photo-electron sensor of various image tubes, and undertakes the key task of transforming an input photon image into a corresponding photo-electron image with a spatio-temporal distribution. Since the photocathode is located on the first input surface of the photo-electron imaging system, its quality and characteristics are directly related to the quality and applicability of the entire system. A highly sensitive photocathode must have strong absorption of incident light within the considered spectral region.

[0003] When people improve the photocathode process, they also attempt to increase the absorption of incident light by optical methods and reduce the loss of transmitted and reflected light to improve the sensitivity of the photocathode. Micro-nano optical elements are used to increase the absorption of incident light by optical methods. However, when fabricating a multi-alkali photocathode on an AVG glass substrate with micro-nano optical elements, the increase in the absorption rate of incident light will affect the normal execution of the photocathode process. Therefore, for an AVG glass substrate with micro-nano optical elements, a new preparation method is required when preparing a multi-alkali photocathode.

[0004] To solve this technical problem, it is necessary to solve the abnormal problem of the multi-alkali photocathode process caused by micro-nano optical elements from the perspective of the cathode fabrication process, so as to ensure the sensitivity of the multi-alkali photocathode based on micro-nano optical elements. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a multi-alkali photocathode based on micro-nano optical elements, which is used for preparing the multi-alkali photocathode film layer of a high-performance low-light-level image intensifier with micro-nano optical elements, and is applicable to the multi-alkali cathode preparation process of an AVG glass substrate with a micro-nano grating structure. During the process of preparing the multi-alkali photocathode film layer on an AVG glass substrate with a micro-nano grating structure, the micro-nano optical structure has a diffraction enhancement effect on incident light, and the photocurrent signal is significantly enhanced during the preparation process of the multi-alkali photocathode, which directly affects the multi-alkali photocathode preparation process.

[0006] The significant enhancement of the photocurrent signal mentioned above means that after the preparation of Na3Sb is completed, its photocurrent value is relatively high.

[0007] During the process that the micro-nano optical structure affects the preparation process of the multi-alkali photocathode, after introducing K and Na vapors, the change rate of the photocurrent is relatively fast.

[0008] The specific steps of the method of the present invention include:

[0009] Step 1: Turn on the Na source current, introduce Na for 1 - 5 minutes to increase the photocurrent to 10 - 15 nA, continue to introduce Na vapor, and after 1 - 3 minutes, turn off the Na source current.

[0010] Step 2: Turn on the Sb source current, introduce Sb, and form a Na3Sb layer on the inner surface of the AVG with micro - nano optical structure;

[0011] Step 3: Turn on the K source, Na source, and Sb source. During this process, the Sb source increases at a rate of 100 - 200 mA / min until the photocurrent increases rapidly. When the photocurrent reaches the maximum value and shows a downward trend, turn off the Sb source current;

[0012] Step 4: Turn on the Na source current again and gradually increase the Na vapor to keep the photocurrent showing a downward trend. When the photocurrent drops to 2 μA - 2.5 μA, turn off the K source, Na source, and Sb source currents, and perform a cooling process;

[0013] Step 5: When the temperature drops to 170 °C, perform a surface activation treatment on the multi - alkali cathode to complete the preparation of the multi - alkali photocathode.

[0014] Advantages of the present invention:

[0015] (1) During the execution of the multi - alkali photocathode process, the influence characteristics of the micro - nano optical elements on the multi - alkali cathode preparation process are obvious and easy to identify;

[0016] (2) The preparation process is simple, and it significantly improves the influence of the micro - nano optical elements on the multi - alkali cathode preparation process. Description of the Drawings

[0017] Figure 1 : Flow chart of the method for preparing a multi - alkali photocathode based on micro - nano optical elements of the present invention.

[0018] Figure 2 : Schematic diagram of the cathode preparation device.

[0019] In the figure: 1 - K source, 2 - Na source, 3 - Cs source, 4 - Sb source, 5 - AVG glass with micro - nano optical elements, 6 - photocathode. Detailed Embodiments

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention in detail with reference to specific embodiments and the accompanying drawings.

[0021] As Figure 1 and with reference to Figure 2 shown, a method for preparing a multi - alkali photocathode based on micro - nano optical elements includes:

[0022] Step 1: Turn on the current of the Na source 2 and heat the Na source 2 at a heating rate of 20 mA / min until the photocurrent increases. Introduce Na for 3 minutes until the photocurrent reaches the maximum value, generally 15 nA. Continue to introduce Na vapor for 1 minute, and then cut off the current of the Na source 2.

[0023] Step 2: Immediately after that, turn on the current of the Sb source 4 to form a base layer of Na3Sb on the inner surface of the AVG glass 5 with a micro-nano optical structure.

[0024] Step 3: Turn on the K source 1, the Na source 2, and the Sb source 4 to make the elements in 3 evaporate together to form a superposition reaction. The current of the Sb source 4 increases at a rate of 100 mA / min until the photocurrent increases rapidly. When the photocurrent reaches the maximum value, it is generally 28 μA. Cut off the current of the Sb source 4.

[0025] Step 4: Turn on the current of the Na source 2 again and evaporate the Na vapor for the second time at an increasing rate of 200 mA / min to keep the photocurrent decreasing. When the photocurrent drops to 15 - 20 μA, cut off the currents of the K source 1, the Na source 2, and the Sb source 4, and perform a cooling treatment.

[0026] Step 5: When the temperature drops to 170 °C, perform a surface activation treatment on the multi-alkali cathode 6 to complete the preparation of the multi-alkali photocathode 6.

[0027] Description of technical effects: As described in the implementation case, when using this multi-alkali photocathode preparation method to prepare the cathode on the surface of a micro-nano optical element, the current of the alkali source is easy to control during the preparation process, and the characteristics of the base layer are easy to identify; at the same time, the preparation process of this method is simple and does not involve complex and uncontrollable process. After a large number of repeated tests, it is confirmed that this process method has good repeatability. After testing, the performance of the multi-alkali cathode material formed by this preparation method is good, and the average value of the photocathode sensitivity is greater than 1000 μA / lm.

[0028] It should be noted that the evaporation device as Figure 2 shown adopts the evaporation device commonly used in the current field.

Claims

1. A method for preparing a multi-alkali photocathode based on micro-nano optical elements, characterized in that, The method includes the following steps: Step 1: Prepare the evaporation device, turn on the current of the Na source (2), introduce Na for 1 - 5 minutes to increase the photocurrent to 10 - 15 nA, continue to introduce Na vapor, and after 1 - 3 minutes, turn off the current of the Na source (2); Step 2: Turn on the current of the Sb source (4), introduce Sb, and form a Na3Sb layer on the inner surface of the AVG glass (5) with a micro - nano optical structure; Step 3: Turn on the K source (1), the Na source (2), and the Sb source (4). During this process, the Sb source (4) increases at a rate of 100 - 200 mA / min until the photocurrent increases rapidly. When the photocurrent reaches the maximum value and shows a downward trend, turn off the current of the Sb source (4); Step 4: Turn on the current of the Na source (2) again, and gradually increase the Na vapor to keep the photocurrent in a downward trend. When the photocurrent drops to 2 μA - 2.5 μA, turn off the currents of the K source (1), the Na source (2), and the Sb source (4), and perform a cooling treatment; Step 5: When the temperature drops to 170 °C, perform a surface activation treatment on the multi - alkali cathode to complete the preparation of the multi - alkali photocathode (6).

2. The method for preparing a multi-alkali photocathode based on micro-nano optical elements according to claim 1, characterized in that, In Step 4, the gradually increasing of the Na vapor means that the increasing rate of the Na vapor is 20 - 200 mA / min.

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