Method for regulating and controlling oxygen content of oxide film based on in-situ monitoring

Abstract

The invention relates to a method for regulating and controlling the oxygen content of an oxide film based on in-situ monitoring, which comprises the following steps: S1, independently regulating the reaction temperature of the oxide film and the atmosphere concentration of an oxidizing / reducing atmosphere regulator so as to oxidize or reduce the oxide film; the resistance change of the oxide film is monitored in real time in the oxidation / reduction reaction process of the oxide film; and S2, according to the monitored resistance change of the oxide thin film, adjusting the atmosphere concentration of the oxidation / reduction atmosphere regulator, the reaction temperature, the reaction duration and the cooling rate for terminating the reaction of the oxide thin film in real time so as to regulate and control the oxidation or reduction degree of the oxide thin film. The method has the beneficial effects that the matter state of the oxide can be intuitively, accurately and widely regulated, so that the process of preparing the oxide film is more efficient.

Description

Technical Field

[0001] The present invention relates to the technical field of oxide thin films, and in particular to a method for regulating the oxygen content of an oxide thin film based on in-situ monitoring. Background Art

[0002] Nickel-based metal oxides, as unconventional superconducting materials, exhibit distinct superconducting properties compared to traditional superconducting materials. As the earliest discovered nickel-based superconducting system, nickel-based oxides possess a complex electronic structure, stemming from the varying oxidation states of nickel ions and the influence of factors such as oxygen vacancies. These factors work together to produce a rich array of physical properties. Furthermore, magnetism and superconductivity coexist and compete in nickel-based oxides, creating a subtle relationship between the two. Therefore, obtaining high-quality nickel-based superconducting thin films or single crystal samples is extremely challenging.

[0003] Currently, the preparation method for nickel oxide thin films primarily involves growing a matrix and then reducing or oxidizing it to produce a superconducting thin film. The current mainstream reduction method involves sealing a tube with calcium hydride and heating it in a tubular furnace. While this method is simple to operate, the entire reaction process is not intuitively displayed to the experimenter, and the experimenter cannot control the reaction process in a timely manner. As a result, accurately producing high-quality nickel-based superconducting thin films using the matrix requires numerous repetitive experiments, resulting in very low production efficiency. Summary of the Invention

[0004] (1) Technical issues to be resolved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for controlling the oxygen content of oxide films based on in-situ monitoring, which solves the technical problems of poor controllability and low preparation efficiency in the existing oxide film preparation process.

[0006] (2) Technical solution

[0007] In order to achieve the above objectives, the main technical solutions adopted by the present invention include:

[0008] An embodiment of the present invention provides a method for controlling the oxygen content of an oxide film based on in-situ monitoring, comprising the following steps:

[0009] S1. independently adjusting the oxide film reaction temperature and the atmospheric concentration of the oxidation / reduction atmosphere regulator to oxidize or reduce the oxide film;

[0010] Real-time monitoring of resistance changes in oxide films during oxidation / reduction reactions;

[0011] S2. Based on the monitored resistance change of the oxide film, adjusting in real time the concentration of the oxidation / reduction atmosphere modifier, as well as the reaction temperature, reaction time, and cooling rate for terminating the reaction of the oxide film, to control the degree of oxidation or reduction of the oxide film;

[0012] The atmosphere concentration of the oxidation / reduction atmosphere regulator is the concentration of the reaction atmosphere formed by the oxidation / reduction atmosphere regulator during the reaction process.

[0013] By regulating the degree of oxidation or reduction of the oxide film, oxide films with different reaction states can be obtained.

[0014] As a preferred embodiment of the present invention, in the control method, in S1, an insulating heating plate is used to heat or cool the oxide film;

[0015] If the oxidizing / reducing atmosphere conditioner includes solid matter, use another insulating heating plate to heat or cool the solid matter;

[0016] Among them, heating the solid matter can increase the concentration of the reaction atmosphere, and cooling the solid matter can reduce the concentration of the reaction atmosphere;

[0017] If the oxidation / reduction atmosphere modifier includes a gaseous substance, the concentration of the oxidation / reduction atmosphere modifier is adjusted by controlling the amount of the gaseous substance introduced.

[0018] Different insulating heating plates are independently controlled to heat or cool the reactants thereon as needed to facilitate regulation of the reaction process.

[0019] As a preferred embodiment of the present invention, in the control method, in S1, when the oxide film needs to be oxidized, the oxidizing atmosphere regulator is selected from at least one of potassium permanganate, oxygen and ozone; when the oxide film needs to be reduced, the reducing atmosphere regulator is selected from calcium hydride and / or hydrogen.

[0020] The selection of different oxidation / reduction atmosphere modifiers depends on the oxidation / reduction strength requirements of the oxide film.

[0021] As a preferred embodiment of the present invention, in the control method, in S2, the Van der Pauw method is used to monitor the resistance change of the oxide film, wherein the resistance change includes the resistance value and the resistance change rate.

[0022] Generally, during the oxidation / reduction process of an oxide film, as the reaction proceeds, the resistance of the oxide film will show three stages: rise-fall-slow rise. It is generally believed that the lowest point of the resistance of the oxide film before the slow rise is the optimal superconducting state of the oxide film under the current reaction conditions. How to adjust the reaction conditions based on the resistance change, for example, the time taken for the oxide film resistance value to reach the peak value (the first half of the oxidation / reduction reaction) reflects the resistance change rate; if the resistance value has not reached the peak value within 30 minutes, the resistance change rate is too small. At this time, it is necessary to increase the atmosphere concentration of the oxidation / reduction atmosphere regulator and the reaction temperature of the oxide film so that the oxide film resistance value reaches the peak value as soon as possible. If the resistance value reaches the peak value within 2 minutes, the resistance change rate is too large. In this case, the oxide film reacts too quickly, which may cause the oxide film to react unevenly. At this time, it is necessary to reduce the atmosphere concentration of the oxidation / reduction atmosphere regulator and the reaction temperature of the oxide film so that the oxide film reacts fully and the resistance value gradually reaches the peak value.

[0023] As a preferred embodiment of the present invention, in the control method, in S1, when the oxidation / reduction atmosphere modifier includes a solid object, the reaction temperature of the solid object is 260-350°C;

[0024] When the oxidation / reduction atmosphere modifier includes a gas, the gas is introduced at room temperature;

[0025] The reaction temperature for oxidation / reduction of the oxide film is 260-350°C, and the reaction environment pressure is 0.01-0.02 MPa; the environment pressure can indirectly indicate the concentration of the oxidation / reduction atmosphere.

[0026] The reaction time of the oxide film and the oxidation / reduction atmosphere modifier is 0.5-2 hours.

[0027] As a preferred embodiment of the present invention, in the control method, in S1, in the oxidation / reduction reaction of the oxide film, the adjustment range of the oxide film is 1-3 valence states, and the range for precise control of the oxygen content of the sample is wide.

[0028] As a preferred embodiment of the present invention, in the control method, in S1, the heating rates of the oxide film and the solid oxidation / reduction atmosphere regulator are both 500-600°C / min, and the cooling rates are both 90-100°C / min.

[0029] It should be noted that when the oxidizing / reducing atmosphere modifier is a gas, its heating and cooling rates are based on the gas surrounding the oxide film, and the gas temperature rises and falls synchronously with the oxide film. A faster cooling rate is beneficial for quickly maintaining the oxide film in the reactive state before cooling.

[0030] As a preferred embodiment of the present invention, in the control method, the oxide film is a nickel-based metal oxide film.

[0031] (3) Beneficial effects

[0032] The beneficial effects of the present invention are as follows: the present invention is a method for regulating the oxygen content of an oxide film based on in-situ monitoring, which independently regulates the reaction temperature of the oxide film and the concentration of the oxidation / reduction atmosphere regulator to regulate the oxidation or reduction process of the oxide film. At the same time, according to the resistance change of the monitored oxide film, the atmospheric concentration of the oxidation / reduction atmosphere regulator, as well as the reaction temperature, reaction time and cooling rate of the oxide film for terminating the reaction are adjusted in real time to regulate the degree of oxidation or reduction of the oxide film. Compared with the prior art, it can visualize the oxidation or reduction process of the oxide film so as to facilitate the regulation of the degree of oxidation or reduction reaction at any time; during the reaction process, the reaction can be terminated at any time according to the resistance change, the electrical properties of the oxide film can be detected, and the variation law of the electrical parameters of the oxide film can be accumulated; the physical state change of the oxide film oxidation or reduction process can be characterized and precisely regulated, and the physical state of the oxide can be regulated intuitively, accurately and widely, making the process of preparing the oxide film more efficient.

[0033] Rapidly heating and cooling the oxide film, solid oxidant or reducing agent by the ceramic heating plate is conducive to quickly adjusting the reaction conditions to accurately control the degree of oxidation or reduction reaction of the oxide film. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the reaction apparatus used in Example 1 of the present invention;

[0035] Figure 2 is Nd in Example 1 of the present invention 0.8 Sr 0.2 During the reduction of NiO3 infinite layer thin film, Nd 0.8 Sr 0.2 Schematic diagram of the resistance change of NiO3 infinite layer film;

[0036] Figure 3 is Nd in Example 1 of the present invention 0.8 Sr 0.2 XRD characterization diagrams of NiO3 infinite layer thin film samples at different reduction stages: 6 curves from bottom to top correspond to Nd 0.8 Sr 0.2 XRD characterization diagram of NiO3 infinite layer film when the resistance values ​​are 10kΩ, 5kΩ, 1kΩ, 700Ω, 500Ω, and 200Ω in the resistance drop region;

[0037] Figure 4 To correspond Figure 3 Low temperature RT test curves of samples in three stages: the three curves are respectively for Nd 0.8 Sr 0.2 The low temperature RT test curves corresponding to the resistance values ​​of NiO3 infinite layer films are 700Ω, 500Ω, and 200Ω;

[0038] Figure 5 This is the reduction process of the nickel-based 327 phase thin film in Example 2 of the present invention;

[0039] Figure 6 This is the low-temperature RT test curve of the reduced nickel-based 327 phase thin film sample in Example 2 of the present invention.

[0040] [Description of Reference Numerals]

[0041] 1: Pump group; 2: Vacuum gauge; 3: Reaction sample; 4: Ceramic heating plate; 5: Oxidation / reduction atmosphere regulator; 7: Terminal block; 8: Temperature controller; 9: Resistance meter; 10: Reaction chamber. DETAILED DESCRIPTION

[0042] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods in conjunction with the accompanying drawings.

[0043] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Instead, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0044] Example 1

[0045] This embodiment provides a Nd 0.8 Sr 0.2 The control method of NiO3 infinite layer thin film reduction process, refer to Figure 1 , the control method is based on Figure 1 Specifically, the pump assembly 1 is used to provide a vacuum environment, and the vacuum gauge 2 is used to measure the reaction gas pressure within the reaction chamber 10. The resistance meter 9 is used to detect the resistance of the thin film (reaction sample 3) in real time. The temperature controller 8 is used to control the temperature of the two ceramic heating plates 4 to adjust the temperature of the reaction sample 3 and the oxidation / reduction atmosphere conditioner 5 respectively.

[0046] In addition, the reaction device is also provided with a general controller to control the overall working state of the reaction device.

[0047] The control method specifically comprises the following steps:

[0048] (1) Select Nd with high mechanical strength, density, uniformity, electrical conductivity and thermal stability 0.8 Sr 0.2 The NiO3 infinite layer thin film sample is divided into 2.5*2.5cm square samples as required. Cut four pieces of platinum wire of appropriate length and lightly burn the platinum wire with a lighter to improve its plasticity. Use silver glue to make electrodes at the four corners of the sample. Connect the platinum wire to the silver glue electrode and lead it out to electrically connect to the terminal 7. Place the sample in the vacuum reaction chamber 10 and fix it to the sample ceramic heating plate with silver glue. Connect the four platinum wires to the four terminals of the resistance meter and monitor the sample resistance using the four-wire method.

[0049] (2) Take 0.5g of calcium hydride, wrap it in aluminum foil, and place it on another ceramic heating plate;

[0050] (3) Start the pump group, use the dry pump and molecular pump to pump the vacuum degree of the vacuum chamber to below 3E-5 mbar, and seal the vacuum chamber;

[0051] Start the control program, set the heating temperature of the ceramic heating plate, and control the temperature of calcium hydride and the sample respectively to observe the effect of different temperatures on the resistance and resistance change rate of the sample under different environments. When the resistance change rate of the sample is too fast (for example, the reaction time for the resistance value to rise to the highest is less than 2 minutes), reduce the temperature of calcium hydride and the sample. The specific reduction amount is a test value or empirical value. On the contrary, if the reaction time for the sample resistance value to rise to the highest is more than 30 minutes, increase the temperature of calcium hydride and the sample to accelerate the reaction. 0.8 Sr 0.2 For the NiO3 system, the sample temperature is 290℃ and the calcium hydride temperature is 330℃, which are more suitable reduction conditions. The heating rate of the ceramic heater is 500-600℃ / min. After the two ceramic heaters reach the corresponding temperature, the sample gradually undergoes reduction reaction.

[0052] (4)Reference Figure 2 , for Nd 0.8 Sr 0.2 As the reduction process progresses, the NiO3 infinite layer film will first quickly enter the insulating 112.5 phase, at which point the sample resistance can reach the order of 10GΩ. Subsequently, the resistance begins to decrease at a rate close to the resistance increase rate, gradually entering the 112 metallic phase from the 112.5 phase. The speed and duration of the decrease process will vary depending on the sample. When the reduction time is sufficient, there is an inflection point in the resistance decrease. After reaching the lowest point, the sample resistance begins to slowly rise, entering an over-reduction state. The lowest resistance point appears after 1 hour of reduction, and the sample will exhibit good superconducting properties.

[0053] Monitoring Nd 0.8 Sr0.2 The reduction process of NiO3 infinite layer thin film is to obtain samples at different stages: in the sample resistance drop area, some points such as 10kΩ, 5kΩ, 1kΩ, 700Ω, 500Ω, and 200Ω are selected according to the resistance value, where each resistance value represents a Nd 0.8 Sr 0.2 The reduction state of the NiO3 film. At these points, the temperature is set to room temperature using a control program (i.e., the reaction is temporarily terminated at the points selected above). The reaction device will begin to rapidly cool down at a rate of 100°C / min. During this process, the resistance of the sample below 200°C can be observed as a function of temperature.

[0054] Furthermore, after cooling to room temperature, the sample was taken out and subjected to XRD test and low-temperature RT test to clearly observe the insulating-metal-superconducting phase transition of the sample at low temperature. Figure 3 The XRD test curves in correspond to the 6 points selected above from bottom to top. Figure 3 The trend marked by the arrow in the middle shows that as the reduction degree of the sample increases, the nickel-based 113 phase gradually transforms to the 112 phase at the structural level. When the peak position no longer moves further to the right, the superconducting performance of the corresponding sample reaches its optimal state.

[0055] Figure 4 To correspond Figure 3 The RT curves of the three XRD test curves in the upper middle section show that as the reduction stage progresses, the sample exhibits significant superconducting properties when the resistance reaches 200Ω. Therefore, the separate control of the sample and the reduced product, as well as the real-time monitoring of the sample resistance and resistance change rate, make the sample reduction process more intuitive, allowing for the adjustment of reaction conditions and termination of the reduction reaction at any time.

[0056] Example 2

[0057] This embodiment provides a method for controlling the oxidation process of a nickel-based 327 phase thin film sample based on in-situ monitoring. Based on the reaction device in Example 1, a gas supply pipe with an adjustable flow rate is connected to the reaction chamber.

[0058] Nickel-based 327 phase thin film is a normal-pressure nickel-based high-temperature superconducting system. Experiments have shown that this oxide system is very sensitive to changes in oxygen content, and a small amount of oxygen change can bring about improvements in superconducting performance; on the other hand, this system requires a special oxidizing environment, that is, stronger than oxygen and weaker than pure ozone. The former cannot supplement enough oxygen, and the latter will transform the system into 113 phase.

[0059] By monitoring oxidation, the state of the sample can be characterized in real time, significantly improving the superconducting properties of the nickel-based 327 phase.

[0060] The control method includes the following steps: (1) fixing the sample on the heating plate with silver glue, and monitoring the resistance of the sample by leading out a measuring section with a platinum wire and silver glue electrode.

[0061] (2) At this time, the pump group stops working, refer to Figure 5 First, pure oxygen was introduced for purge. The sample was heated to 290°C. The resistance of the sample was observed to gradually increase as oxygen atoms were lost in the high-temperature oxygen environment. An oxygen-ozone mixture was then introduced through the gas pipe. As the reaction proceeded, the resistance of the sample was observed to drop sharply, and eventually the resistance approached saturation, terminating the oxidation reaction.

[0062] (3) The samples before and after oxidation were subjected to low temperature RT test. The results are shown in Figure 6 Compared with the samples before oxidation, the superconducting properties of the samples after oxidation have been significantly improved.

[0063] By observing the changes in sample resistance and changing the ozone concentration and oxidation time at any time, the final value of the sample resistance can be controlled, and then the superconducting properties of the sample can be controlled, thereby achieving the purpose of improving the superconducting properties of the sample.

[0064] It should be noted that if the resistance point is selected correctly, the insulating-to-metallic phase transition process of the sample can be clearly observed (the slope of the resistance changes from negative to positive with temperature), which avoids the heavy workload caused by blindly selecting a time point to terminate the reaction. It should be noted that due to the complexity of the redox reaction of each oxide film, the specific resistance value selected needs to be selected by the staff according to the specific situation and is not limited here.

[0065] The same sample can terminate the reaction at a certain reaction time point, and after sample testing (for example, XRD testing and low-temperature RT testing), it can continue to enter the next period of oxidation or reduction reaction, so as to continue to find the oxidation or reduction state of the sample that meets the electrical parameters of the application scenario.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the oxygen content of an oxide film based on in-situ monitoring, characterized in that: The following steps are involved: S1. independently adjusting the oxide film reaction temperature and the atmospheric concentration of the oxidation / reduction atmosphere regulator to oxidize or reduce the oxide film; Real-time monitoring of resistance changes in oxide films during oxidation / reduction reactions; S2. Based on the monitored resistance change of the oxide film, adjusting in real time the concentration of the oxidation / reduction atmosphere modifier, as well as the reaction temperature, reaction time, and cooling rate for terminating the reaction of the oxide film, to control the degree of oxidation or reduction of the oxide film; The atmosphere concentration of the oxidation / reduction atmosphere regulator is the concentration of the reaction atmosphere formed by the oxidation / reduction atmosphere regulator during the reaction process.

2. The control method according to claim 1, wherein In S1, an insulating heating plate is used to heat or cool the oxide film; If the oxidizing / reducing atmosphere conditioner includes solid matter, use another insulating heating plate to heat or cool the solid matter; Among them, heating the solid matter can increase the concentration of the reaction atmosphere, and cooling the solid matter can reduce the concentration of the reaction atmosphere; If the oxidation / reduction atmosphere modifier includes a gaseous substance, the concentration of the oxidation / reduction atmosphere modifier is adjusted by controlling the amount of the gaseous substance introduced.

3. The control method according to claim 2, wherein In S1, when the oxide film needs to be oxidized, the oxidizing atmosphere regulator is selected from at least one of potassium permanganate, oxygen and ozone; when the oxide film needs to be reduced, the reducing atmosphere regulator is selected from calcium hydride and / or hydrogen.

4. The control method according to claim 1, wherein In S2, the Van der Pauw method is used to monitor the resistance change of the oxide film, wherein the resistance change includes the resistance value and the resistance change rate.

5. The control method according to claim 2, wherein: In S1, when the oxidation / reduction atmosphere modifier includes a solid, the reaction temperature of the solid is 260-350°C; When the oxidation / reduction atmosphere modifier includes a gas, the gas is introduced at room temperature; The reaction temperature for oxide film oxidation / reduction is 260-350°C, and the reaction environment pressure is 0.01-0.02MPa; The reaction time of the oxide film and the oxidation / reduction atmosphere modifier is 0.5-2 hours.

6. The control method according to claim 1, wherein In S1, during the oxidation / reduction reaction of the oxide film, the adjustment range of the oxide film is 1-3 valence states.

7. The control method according to claim 2, wherein: In S1, the heating rates of the oxide film and the solid oxidation / reduction atmosphere regulator are both 500-600°C / min, and the cooling rates are both 90-100°C / min.

8. The control method according to claim 1, wherein The oxide film is a nickel-based metal oxide film.

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