Preparation method of metal nanometer film electrode with high limit working temperature
By preparing an aluminum nanofilm on the surface of a metal nanofilm to form an aluminum oxide film, thus isolating it from air contact, the problem of easy oxidation of metal nanofilm electrodes at high temperatures is solved, and the high limit operating temperature is improved. This method is applicable to metal nanofilm electrodes such as copper, iron, and silver.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGNAN UNIV
- Filing Date
- 2023-08-02
- Publication Date
- 2026-04-24
AI Technical Summary
Metal nanofilm electrodes are prone to oxidation at high temperatures, which leads to a decrease in conductivity and mechanical properties, and a low limiting operating temperature, making them difficult to use in high-temperature environments.
Aluminum nanofilms with nanoscale thickness are prepared on the surface of metal nanofilms to form a dense aluminum oxide film that covers the gaps and isolates them from air contact. The aluminum nanofilms are prepared simultaneously in a vacuum coating chamber using a multi-target electron beam evaporation coating instrument. The thickness of the aluminum nanofilms is adjustable, ensuring high bonding strength with the metal nanofilms.
It improves the oxidation resistance of metal nanofilm electrodes, significantly increases the limiting operating temperature, and has a simple and environmentally friendly preparation method, making it suitable for easily oxidized metal nanofilms such as copper, iron, and silver.
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Figure CN116970907B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of nanofilm electrodes, and in particular to a method for preparing a metal nanofilm electrode with a high limiting operating temperature. Background Technology
[0002] Metal nanofilm electrodes made of metals such as copper, zinc, silver, and nickel have excellent resistance to electromigration, low resistivity, and good thermal conductivity, and are widely used in integrated circuits and printed electronics.
[0003] However, at the nanoscale, due to their high specific surface area and high chemical reactivity, metal nanofilm electrodes are prone to reacting with oxygen or water vapor in the air, leading to performance degradation. For example, metals such as copper and iron easily oxidize to form metal oxides, severely affecting the electrical performance of metal nanofilm electrodes. Especially at high temperatures, the oxidation reaction of metal nanofilm electrodes becomes more intense. The resulting high-temperature oxidation products not only reduce the conductivity and mechanical properties of the metal nanofilm electrodes, but also, because the oxide layer is not dense, it cannot further block the high-temperature oxidation process. As a result, the current operating temperature limit of metal nanofilm electrodes is not high, making them difficult to apply in high-temperature environments. Summary of the Invention
[0004] To address the aforementioned problems and technical requirements, the applicant has proposed a method for preparing a metal nanofilm electrode with a high limiting operating temperature. The technical solution of this application is as follows:
[0005] A method for fabricating a metal nanofilm electrode with a high limiting operating temperature, the method comprising:
[0006] In a vacuum coating chamber, a multi-target electron beam evaporation coating instrument is used to prepare a metal nanofilm with a thickness of nanometers on the surface of a silicon wafer substrate using a metal target.
[0007] In a vacuum coating chamber, the multi-target electron beam evaporation coating instrument is switched to use an aluminum target. The aluminum target is then used in the multi-target electron beam evaporation coating instrument to prepare an aluminum nanofilm with a predetermined nanoscale thickness on the surface of the metal nanofilm, thus obtaining a metal nanofilm electrode.
[0008] A further technical solution is that after the prepared metal nanofilm electrode is taken out of the vacuum coating chamber, the surface of the aluminum nanofilm is oxidized and forms an aluminum oxide film. The formed aluminum oxide film covers the atomic gaps and isolates the metal nanofilm from the air, thus preventing the metal nanofilm from oxidizing.
[0009] A further technical solution is that the limiting operating temperature of the metal nanofilm electrode is related to the predetermined nanoscale thickness of the aluminum nanofilm, and the predetermined nanoscale thickness of the aluminum nanofilm is adjustable and always greater than the thickness threshold.
[0010] A further technical solution is that, in the process of preparing metal nanofilm electrodes, the evaporation rate used in the multi-target electron beam evaporation coating instrument and the rotation speed of the sample stage used to place the silicon wafer substrate are the same when preparing metal nanofilms and aluminum nanofilms.
[0011] A further technical solution is that the evaporation rate is... The sample stage rotates at a speed of 5 rpm.
[0012] A further technical solution is that the vacuum degree of the vacuum coating chamber is 9.8 × 10⁻⁶. -4 Pa.
[0013] A further technical solution is that the preparation method also includes:
[0014] Multiple sample thin film electrodes were prepared in a vacuum coating chamber. Each sample thin film electrode consisted of a silicon wafer substrate, a metal nanofilm, and an aluminum nanofilm stacked sequentially. The aluminum nanofilm in each sample thin film electrode had different thicknesses but the same other specifications.
[0015] Each sample thin film electrode was taken out of the vacuum coating chamber and subjected to oxidation test under the same environment. The characteristic parameters of each sample thin film electrode were obtained. The characteristic parameters are used to characterize the degree of oxidation of the metal nanofilm in the sample thin film electrode. The better the obtained characteristic parameters, the smaller the degree of oxidation of the metal nanofilm and the higher the limiting operating temperature of the sample thin film electrode.
[0016] The thickness of the aluminum nanofilm in the sample thin-film electrode with the optimal characteristic parameters is determined as the predetermined nanoscale thickness.
[0017] A further technical solution involves obtaining the characteristic parameters of the thin-film electrodes for each sample, including:
[0018] The size of the metal thin film oxide in the optical microscope image of each sample thin film electrode is determined. The metal thin film oxide is the oxide formed by the contact of metal nanofilm with air. The smaller the size of the metal thin film oxide, the less oxidation degree of the metal nanofilm is characterized.
[0019] And / or, the resistance increase of each sample thin film electrode is measured over time using the four-probe method. The smaller the increase in resistance over time, the less oxidation of the metal nanofilm is characterized.
[0020] And / or, the conductivity of each sample thin film electrode is measured over time using the four-probe method. The smaller the decrease in conductivity over time, the less oxidation of the metal nanofilm is characterized.
[0021] And / or, obtain the XPS energy spectrum of the metal target in each sample thin film electrode, and match the XPS energy spectrum of the metal target in the sample thin film electrode with the energy spectrum of the metal target and the oxide energy spectrum of the metal target, respectively. The higher the matching degree between the XPS energy spectrum of the metal target in the sample thin film electrode and the energy spectrum of the metal target, the smaller the oxidation degree of the characterized metal nanofilm.
[0022] The further technical solution involves conducting oxidation tests on the thin-film electrodes of each sample, including:
[0023] Each sample thin film electrode was placed in a room temperature environment for room temperature oxidation test;
[0024] as well as,
[0025] Each sample thin film electrode was placed on a heating stage at the same time, and the heating stage was used to heat each sample thin film electrode at multiple different predetermined temperatures to conduct high-temperature oxidation tests on each sample thin film electrode at different predetermined temperatures.
[0026] A further technical solution involves obtaining the characteristic parameters of each sample thin-film electrode separately, including:
[0027] The thin film electrodes of each sample were placed on a heating stage at the same time, and the resistance of each thin film electrode was detected by the four-probe method.
[0028] The thin film electrodes of each sample are heated using a heating stage, and the temperature rise of the heating stage is controlled. The resistance curve of each sample thin film electrode as a function of a predetermined temperature is obtained.
[0029] Based on the resistance change curve of each sample thin film electrode with a predetermined temperature, the temperature at which the resistance of each sample thin film electrode undergoes a sudden change is determined. The higher the temperature at which the resistance of the sample thin film electrode undergoes a sudden change, the lower the degree of oxidation of the characterized metal nanofilm.
[0030] The beneficial technical effects of this application are:
[0031] This application discloses a method for preparing a metal nanofilm electrode with a high limiting operating temperature. In the process of fabricating the metal nanofilm electrode, a nanometer-thick aluminum nanofilm is further fabricated on the surface of the metal nanofilm. The aluminum nanofilm is stably adsorbed on the surface of the metal nanofilm at high temperatures, with controllable thickness, a smooth surface, and high bonding strength with the metal nanofilm surface. In the air, aluminum atoms spontaneously combine with oxygen atoms to form a dense and high-temperature-resistant alumina film, covering the gaps and isolating the air. This process requires no artificial control and effectively avoids high-temperature oxidation of the metal nanofilm, thereby improving the oxidation resistance of the metal nanofilm electrode and enabling it to achieve a high limiting operating temperature.
[0032] This method achieves high-temperature oxidation protection for nanoscale metal nanofilm electrodes. The method is simple, aluminum nanofilms can be prepared in the same chamber as metal nanofilms, no other waste liquid is generated, the preparation process is simple and environmentally friendly, and this preparation method can be used for metal nanofilms made of easily oxidized materials such as copper, iron, nickel and silver, making it highly versatile.
[0033] The thickness of the prepared aluminum nanofilm is related to the limiting operating temperature of the prepared metal nanofilm electrode. The required thickness of the aluminum nanofilm can be determined by quantitative experimental methods, thereby achieving the performance requirements of the metal nanofilm electrode and making it easy to control. Attached Figure Description
[0034] Figure 1 This is a flowchart of a method for preparing a metal nanofilm electrode according to an embodiment of this application.
[0035] Figure 2 This is a schematic diagram of the structure of a metal nanofilm electrode prepared according to an embodiment of this application after preparation is completed and it is removed from the vacuum coating chamber.
[0036] Figure 3 This is a comparison of optical microscope images of three different thin-film electrodes in a room-temperature oxidation test in one experimental example.
[0037] Figure 4 Is Figure 3 In the experimental examples, the graphs show the change in resistance over time for three different thin-film electrodes during room temperature oxidation tests.
[0038] Figure 5 This is an XPS spectrum of copper in a conventional metal nanofilm electrode during a high-temperature oxidation test at 150°C, as shown in an experimental example.
[0039] Figure 6 Is Figure 5In the experimental example, the XPS spectrum of copper in the sample thin film electrode containing aluminum nanofilm during the high-temperature oxidation test at 150℃ is shown.
[0040] Figure 7 Is Figure 5 The experimental examples show the conductivity of each thin-film electrode changing over time.
[0041] Figure 8 This is a graph showing the change in resistance of each thin-film electrode with temperature in an experimental example. Detailed Implementation
[0042] The specific embodiments of this application will be further described below with reference to the accompanying drawings.
[0043] This application discloses a method for preparing a metal nanofilm electrode with a high limiting operating temperature. Please refer to [link / reference]. Figure 1 The flowchart and Figure 2 The schematic diagram of the metal nanofilm electrode shown illustrates the fabrication method, which includes:
[0044] Step 1: In the vacuum coating chamber, a metal nanofilm 2 with a nanometer-thickness is prepared on the surface of a silicon substrate 1 using a metal target with a multi-target electron beam evaporation coating instrument.
[0045] The metal targets used in this step include, but are not limited to, copper targets, zinc targets, silver targets, and nickel targets.
[0046] In one embodiment, the vacuum degree of the vacuum coating chamber is 9.8 × 10⁻⁶. -4 Pa.
[0047] When preparing metal nanofilms using a multi-target electron beam evaporation deposition system, it is necessary to set the deposition parameters for the system. These parameters include beam current, deposition rate, and the rotation speed of the sample stage used to place the silicon wafer substrate. Excessively high beam current will increase the deposition rate, reduce the crystallinity of the film, and thus affect the optical and electrical properties of the prepared film. A suitable rotation speed will result in a film with uniform thickness.
[0048] In one embodiment, the beam current used is 48 mA and the evaporation rate is... The sample stage rotates at a speed of 5 rpm.
[0049] The prepared metal nanofilm 2 has a nanometer-scale thickness, and the specific thickness can be adjusted according to actual needs. For example, in one embodiment, the thickness of the silicon substrate 1 is 1 mm, and the thickness of the prepared metal nanofilm 2 is 20 nm.
[0050] Step 2: In the vacuum coating chamber, the multi-target electron beam evaporation coating instrument is switched to use aluminum target material, and aluminum nanofilm 3 with a predetermined nanoscale thickness is prepared on the surface of metal nanofilm using aluminum target material, thus preparing metal nanofilm electrode.
[0051] When preparing aluminum nanofilms using a multi-target electron beam evaporation coating instrument, the vacuum level of the vacuum coating chamber, the evaporation rate of the multi-target electron beam evaporation coating instrument, and the rotation speed of the sample stage should be kept constant. The beam current used may vary, but it is sufficient to ensure that the evaporation rate is the same.
[0052] Similarly, the prepared metal nanofilm 2 has a nanometer-scale thickness, and the specific thickness can be adjusted according to actual needs.
[0053] After the prepared metal nanofilm electrode is removed from the vacuum coating chamber, the surface of the aluminum nanofilm 3 is oxidized. In a very short time, aluminum atoms spontaneously combine with oxygen atoms in the air to form an ultrathin, dense and high-temperature resistant aluminum oxide film 4. The thickness of the aluminum oxide film 4 is about 2nm to 3nm. The aluminum oxide film 4 can cover the atomic gaps and isolate the metal nanofilm 2 from the air, preventing the metal nanofilm 2 from oxidizing. This can improve the oxidation resistance of the metal nanofilm 2 and thus improve the limiting operating temperature of the metal nanofilm 2.
[0054] The limiting operating temperature of the prepared metal nanofilm electrode is related to the predetermined nanoscale thickness of the aluminum nanofilm 3. The predetermined nanoscale thickness of the aluminum nanofilm 3 is adjustable and always exceeds a thickness threshold. The preparation method of this application also pre-investigates the influence of the thickness of the aluminum nanofilm 3 on the limiting operating temperature of the metal nanofilm electrode through experiments, thereby selecting a more optimal predetermined nanoscale thickness for the aluminum nanofilm 3. Therefore, the preparation method further includes the following steps before the formal preparation of the metal nanofilm 2:
[0055] 1. Multiple sample thin-film electrodes are fabricated in a vacuum deposition chamber. Each sample thin-film electrode comprises a silicon substrate, a metal nanofilm, and an aluminum nanofilm stacked sequentially, such as... Figure 2 As shown, the thickness of the aluminum nanofilm in the thin film electrodes of each sample is different, while other specifications are the same.
[0056] For example, in one instance, the silicon substrate in the four sample thin film electrodes was 1 mm thick, the metal nanofilms were all made of copper target material and were 20 nm thick, and the aluminum nanofilms in the four sample thin film electrodes were 1 nm, 3 nm, 5 nm and 10 nm thick, respectively, denoted as 20 nm Cu + 1 nm Al, 20 nm Cu + 3 nm Al, 20 nm Cu + 5 nm Al and 20 nm Cu + 10 nm Al.
[0057] 2. Remove each sample thin film electrode from the vacuum coating chamber and conduct oxidation tests under the same environment to obtain the characteristic parameters of each sample thin film electrode.
[0058] The obtained characteristic parameters are used to characterize the degree of oxidation of the metal nanofilm in the sample thin film electrode. The better the obtained characteristic parameters, the smaller the degree of oxidation of the metal nanofilm, and the higher the limiting operating temperature of the sample thin film electrode.
[0059] The acquisition of characteristic parameters for each sample thin film electrode includes acquiring one or more of the following characteristic parameters:
[0060] (1) Determine the size of the metal thin film oxide in the optical microscope image of each sample thin film electrode. The metal thin film oxide is the oxide formed by the contact between the metal nanofilm and the air. The smaller the size of the metal thin film oxide, the less oxidation of the metal nanofilm it represents.
[0061] (2) The resistance increase of each sample thin film electrode was measured over time using the four-probe method. The smaller the resistance increase over time, the smaller the degree of oxidation of the metal nanofilm.
[0062] (3) The conductivity of each sample thin film electrode was measured over time using the four-probe method. The smaller the decrease in conductivity over time, the smaller the degree of oxidation of the metal nanofilm.
[0063] (4) Obtain the XPS energy spectrum of the metal target in each sample thin film electrode, and match the XPS energy spectrum of the metal target in the sample thin film electrode with the energy spectrum of the metal target and the oxide energy spectrum of the metal target, respectively. The higher the matching degree between the XPS energy spectrum of the metal target in the sample thin film electrode and the energy spectrum of the metal target, the smaller the oxidation degree of the metal nanofilm is characterized.
[0064] In addition, when conducting oxidation tests on the thin film electrodes of each sample, multiple oxidation tests will be carried out under different environments. This includes placing the thin film electrodes of each sample at room temperature for room temperature oxidation tests, and placing the thin film electrodes of each sample on a heating stage at the same time, using the heating stage to heat the thin film electrodes of each sample at multiple different predetermined temperatures, so as to carry out high temperature oxidation tests on the thin film electrodes of each sample at different predetermined temperatures.
[0065] In one example, a conventional metal nanofilm electrode was fabricated and its performance was compared with that of four sample thin-film electrodes with the structure described in this application. The conventional metal nanofilm electrode consisted only of a silicon substrate and a metal nanofilm on its surface. The thickness of the silicon substrate was 1 mm, and the metal nanofilm used a copper target with a thickness of 20 nm. This conventional metal nanofilm electrode is designated as 20 nm Cu. The comparative experimental results are as follows:
[0066] The first oxidation experiment involved placing the 20nm Cu thin film electrode and other sample thin film electrodes at room temperature for 15 days for oxidation. Optical microscope images of each thin film electrode were obtained after fabrication, as well as after the 15-day room temperature oxidation experiment. The optical microscope images of the 20nm Cu, 20nm Cu+5nm Al, and 20nm Cu+10nm Al thin film electrodes are shown below. Figure 3 As shown. Comparison Figure 3 It can be seen that metal oxide films appeared on all three thin-film electrodes after 15 days of room-temperature oxidation. However, the size of the metal oxide film in the optical microscope image of the 20nm Cu thin-film electrode was significantly larger than that of the other two thin-film electrodes. The metal oxide film in the thin-film electrode containing aluminum nanofilms fabricated using the structure of this application was significantly smaller, indicating a weaker degree of oxidation of the metal nanofilm, which is more conducive to improving the limiting operating temperature of the thin-film electrode. Furthermore, the aluminum nanofilm in the 20nm Cu+10nm Al thin-film electrode was thicker, and the size of the metal oxide film in its optical microscope image was smaller.
[0067] In addition, the increase in resistance of each thin film electrode during the 15-day room temperature oxidation test was observed using the four-probe method. The curves showing the change in resistance over time for the three thin film electrodes—20nm Cu, 20nm Cu+5nm Al, and 20nm Cu+10nm Al—are shown below. Figure 4 As shown. Comparison Figure 4 It can be seen that the increase in resistance of the thin-film electrode containing aluminum nanofilms fabricated using the structure of this application is significantly less than that of the 20nm Cu thin-film electrode. This indicates that the aluminum nanofilm has a significant protective effect on the metal nanofilm in air and can effectively inhibit the oxidation behavior of the metal nanofilm. Furthermore, although the thicknesses of the aluminum nanofilms in the 20nm Cu+5nm Al and 20nm Cu+10nm Al thin-film electrodes are different, the increase in resistance is not significantly different. This is because the increase in resistance is mainly due to the oxidation of the aluminum nanofilm, and the resistance will remain essentially unchanged over time.
[0068] In the second oxidation experiment, the 20nm Cu thin film electrode and the thin film electrodes of each sample were simultaneously placed on a heating stage and heated at 150℃ for 30 minutes for high-temperature oxidation. XPS spectra of copper on each thin film electrode were then acquired. The XPS spectrum of copper on the 20nm Cu thin film electrode is shown below. Figure 5 As shown, the XPS spectrum of copper is basically consistent with the standard spectrum of copper oxide, indicating that the 20nm Cu thin film electrode underwent significant oxidation during the high-temperature oxidation experiment. The XPS spectrum of copper for the 20nm Cu + 5nm Al thin film electrode is shown below. Figure 6 As shown, the XPS spectrum of copper is basically consistent with the standard spectrum of copper, indicating that the metal nanofilm is basically not oxidized under the protection of the alumina film obtained by oxidizing the aluminum nanofilm.
[0069] In addition, the conductivity of each thin-film electrode under a high-temperature oxidation test at 150℃ was observed using the four-probe method as a function of time, as shown in the figure below. Figure 7 As shown, from Figure 7 It can be seen that the conductivity of the 20nm Cu thin film electrode decreases significantly, while the conductivity of other sample thin film electrodes decreases slightly and then stabilizes. This indicates that the alumina film obtained by oxidizing the aluminum nanofilm protects the metal nanofilm, preventing oxidation. Afterward, the resistance of the thin film electrode remains unchanged. Among the sample thin film electrodes containing aluminum nanofilms, the conductivity of the 20nm Cu + 1nm Al sample thin film electrode is close to that of the 20nm Cu thin film electrode. This suggests that the protective effect of the 1nm thick aluminum nanofilm is not ideal, possibly because the aluminum nanofilm is too thin to form a continuous alumina film. When the thickness of the aluminum nanofilm is greater than 3nm, the conductivity curve is more ideal, indicating a stronger protective effect of the aluminum nanofilm on the metal nanofilm. Furthermore, the conductivity curve becomes more favorable with increasing aluminum nanofilm thickness, further demonstrating the stronger the protective effect. Based on this, the minimum thickness threshold that the aluminum nanofilm needs to reach can be determined.
[0070] In addition to constant-temperature heating via a heating stage to complete the high-temperature oxidation test, obtaining the characteristic parameters of each sample thin-film electrode also includes: simultaneously placing each sample thin-film electrode on the heating stage and using the four-probe method to detect the resistance of each sample thin-film electrode; then heating each sample thin-film electrode using the heating stage while controlling the temperature rise, and obtaining the resistance change curve of each sample thin-film electrode as a function of a predetermined temperature. Based on the resistance change curve of each sample thin-film electrode as a function of a predetermined temperature, the temperature at which the resistance of each sample thin-film electrode undergoes a sudden change is determined. The higher the temperature at which the resistance of the sample thin-film electrode undergoes a sudden change, the lower the degree of oxidation of the metal nanofilm.
[0071] In the third oxidation experiment, the 20nm Cu thin film electrode and the thin film electrodes of each sample were simultaneously placed on a heating stage. The temperature was increased from 0℃ to 500℃ using the heating stage, and the resistance of the 20nm Cu thin film electrode and the thin film electrodes of each sample were measured using the four-probe method. The resulting curves showing the change in resistance of the 20nm Cu thin film electrode and the thin film electrodes of each sample as a function of the predetermined temperature are shown below. Figure 8 As shown. Figure 8 In the study, the resistance of the 20nm Cu thin film electrode abruptly changed at 190℃, indicating significant oxidation of the metal nanofilm at this temperature. The resistance of the 20nm Cu + 1nm Al sample electrode abruptly changed at approximately 245℃, the 20nm Cu + 3nm Al sample electrode at approximately 290℃, the 20nm Cu + 5nm Al sample electrode at approximately 350℃, and the 20nm Cu + 10nm Al sample electrode at approximately 490℃. The comparison shows that the resistance abrupt changes at temperatures significantly higher for the aluminum nanofilm-containing electrodes than for the 20nm Cu thin film electrode. This indicates a significant increase in the limiting operating temperature of the aluminum nanofilm-containing electrodes. Furthermore, in this example, the greater the thickness of the aluminum nanofilm, the higher the temperature at which the resistance abrupt changes, indicating a higher temperature at which significant oxidation of the metal nanofilm occurs. A lower degree of oxidation in the metal nanofilm is beneficial for improving the limiting operating temperature.
[0072] 3. Determine the thickness of the aluminum nanofilm in the sample thin-film electrode with optimal characteristic parameters as the predetermined nanoscale thickness. Based on the above experimental results, a suitable predetermined nanoscale thickness can be selected for the aluminum nanofilm, thereby ensuring that the ultimate operating temperature and characteristic parameters of the fabricated metal nanofilm electrode meet the required design standards.
[0073] The above descriptions are merely preferred embodiments of this application, and this application is not limited to the above embodiments. It is understood that other improvements and variations that can be directly derived or conceived by those skilled in the art without departing from the spirit and concept of this application should be considered to be included within the protection scope of this application.
Claims
1. A method for preparing a metal nanofilm electrode with a high limiting operating temperature, characterized in that, The preparation method includes: In a vacuum coating chamber, a multi-target electron beam evaporation coating instrument is used to prepare a metal nanofilm with a thickness of nanometers on the surface of a silicon wafer substrate using a metal target. In the vacuum coating chamber, the multi-target electron beam evaporation coating instrument is switched to use aluminum target material, and aluminum nanofilm with a predetermined nanoscale thickness is prepared on the surface of the metal nanofilm using the aluminum target material in the multi-target electron beam evaporation coating instrument, thereby preparing metal nanofilm electrode. The limiting operating temperature of the metal nanofilm electrode is related to the predetermined nanometer-scale thickness of the aluminum nanofilm. The preparation method further includes: preparing multiple sample thin film electrodes in the vacuum coating chamber, each sample thin film electrode comprising a silicon wafer substrate, a metal nanofilm, and an aluminum nanofilm stacked sequentially, wherein the thickness of the aluminum nanofilm in each sample thin film electrode is different, while other specifications are the same; removing each sample thin film electrode from the vacuum coating chamber and conducting oxidation tests under the same environment to obtain characteristic parameters for each sample thin film electrode, wherein the characteristic parameters are used to characterize the degree of oxidation of the metal nanofilm in the sample thin film electrode, and the better the obtained characteristic parameters, the smaller the degree of oxidation of the metal nanofilm, and the higher the limiting operating temperature of the sample thin film electrode; determining the thickness of the aluminum nanofilm in the sample thin film electrode with the optimal characteristic parameters as the predetermined nanometer-scale thickness. The acquisition of characteristic parameters of each sample thin film electrode includes: determining the size of the metal thin film oxide in the optical microscope image of each sample thin film electrode; the metal thin film oxide is an oxide formed by the contact of the metal nanofilm with air, and the smaller the size of the metal thin film oxide, the lower the degree of oxidation of the metal nanofilm; and / or, measuring the change curve of the resistance increase of each sample thin film electrode over time using the four-probe method, and the smaller the increase in resistance over time, the lower the degree of oxidation of the metal nanofilm; and / or, measuring the change curve of the conductivity of each sample thin film electrode over time using the four-probe method, and the smaller the decrease in conductivity over time, the lower the degree of oxidation of the metal nanofilm; and / or, acquiring the XPS energy spectrum of the metal target in each sample thin film electrode, and matching the XPS energy spectrum of the metal target in the sample thin film electrode with the energy spectrum of the metal target and the oxide energy spectrum of the metal target, respectively. The higher the degree of matching between the XPS energy spectrum of the metal target in the sample thin film electrode and the energy spectrum of the metal target, the lower the degree of oxidation of the metal nanofilm.
2. The preparation method according to claim 1, characterized in that, After the prepared metal nanofilm electrode is removed from the vacuum coating chamber, the surface of the aluminum nanofilm is oxidized and forms an aluminum oxide film. The formed aluminum oxide film covers the atomic gaps and isolates the metal nanofilm from the air, preventing the metal nanofilm from oxidizing.
3. The preparation method according to claim 2, characterized in that, The predetermined nanoscale thickness of the aluminum nanofilm is adjustable and always greater than the thickness threshold.
4. The preparation method according to claim 1, characterized in that, In the process of preparing the metal nanofilm electrode, the evaporation rate used in the multi-target electron beam evaporation coating instrument and the rotation speed of the sample stage used to place the silicon wafer substrate are the same when preparing the metal nanofilm and the aluminum nanofilm.
5. The preparation method according to claim 4, characterized in that, The evaporation rate is 0.12 Å / s, and the rotation speed of the sample stage is 5 rpm.
6. The preparation method according to claim 1, characterized in that, The vacuum degree of the vacuum coating chamber is 9.8 × 10⁻⁶. -4 Pa.
7. The preparation method according to claim 1, characterized in that, Oxidation tests were performed on the thin-film electrodes of each sample, including: Each sample thin film electrode was placed in a room temperature environment for room temperature oxidation test; as well as, Each sample thin film electrode was placed on a heating stage at the same time, and the heating stage was used to heat each sample thin film electrode at multiple different predetermined temperatures to conduct high-temperature oxidation tests on each sample thin film electrode at different predetermined temperatures.
8. The preparation method according to claim 1, characterized in that, The process of obtaining the characteristic parameters of each sample thin film electrode also includes: The thin film electrodes of each sample were placed on a heating stage at the same time, and the resistance of each thin film electrode was detected by the four-probe method. The heating stage is used to heat the thin film electrodes of each sample and the temperature of the heating stage is controlled to rise, and the resistance of each thin film electrode as a function of a predetermined temperature is obtained. Based on the resistance change curves of each sample thin film electrode with a predetermined temperature, the temperature at which the resistance of each sample thin film electrode undergoes a sudden change is determined. The higher the temperature at which the resistance of the sample thin film electrode undergoes a sudden change, the lower the degree of oxidation of the characterized metal nanofilm.