Method for preparing vanadium dioxide film based on radio frequency magnetron sputtering and prepared vanadium dioxide film

Abstract

The invention discloses a method for preparing a vanadium dioxide film based on radio frequency magnetron sputtering and the prepared vanadium dioxide film, and belongs to the technical field of vanadium dioxide films. The method for preparing the vanadium dioxide film based on radio frequency magnetron sputtering comprises the following steps: taking a vanadium pentoxide target as a target material, taking argon gas with the flow rate of 4-8sccm as sputtering gas, coating a film by adopting a vacuum radio frequency magnetron sputtering method at the sputtering power of 80-150W and the temperature of 600-700 DEG C, and carrying out in-situ reaction, the proportion of V atoms and O atoms in the sputtering process is adjusted through argon flow, the sputtering speed of the V atoms and the O atoms in the sputtering process is adjusted through sputtering power, and then the vanadium dioxide film is prepared through crystallization. The preparation method does not need a high-oxygen environment and an annealing step, and is simple and convenient to operate.

Description

Technical Field

[0001] The invention relates to the technical field of vanadium dioxide thin films, and more specifically to a method for preparing a vanadium dioxide thin film based on radio frequency magnetron sputtering and the prepared vanadium dioxide thin film. Background Art

[0002] In 1959, researchers first discovered and studied the metal-insulator transition (MIT) characteristics of the phase change material vanadium dioxide. In the following decades, vanadium dioxide, as a typical phase change material, has been deeply studied by a large number of scholars.

[0003] Vanadium oxide, VO 2 ) As a phase change material, it has attracted widespread attention due to its significant changes in optical and electrical properties during the reversible metal-insulator transition. The metal-insulator transition of vanadium dioxide materials can be driven by light, electricity and thermal energy. The critical temperature of the metal-insulator transition of vanadium dioxide is 68°C. Below the critical temperature, the crystal structure of vanadium dioxide is the monoclinic M1 phase (space group P21 / C), and above the critical temperature it transforms to the rutile R phase (space group P42 / mnm). This special metal-insulator transition characteristic makes vanadium dioxide films widely used in different fields. The most representative fields are smart windows, infrared sensors, electrochromic devices, switching elements, Mott field effect transistors, memristors, etc.

[0004] Common preparation methods for vanadium dioxide thin films include chemical vapor deposition (CVD), magnetron sputtering, molecular beam epitaxy (MBE), pulsed laser deposition (PLD) and sol-gel. Thin films prepared by magnetron sputtering have the characteristics of uniformity, density, good adhesion to the substrate, low cost and high repeatability. The existing technical solutions mainly use DC magnetron sputtering, by controlling Ar and O 2 The vanadium dioxide film was prepared by adjusting the flow rate, film growth pressure and substrate temperature and undergoing high temperature and high oxygen annealing. However, due to the high temperature and high oxygen annealing step, VO 2 The valence state of the film is variable and impure, which means that the obtained VO 2 The phase transition amplitude and other properties of the film will be partially weakened, further hindering the VO 2 Thin film applications, and strict control of Ar and O 2 The traffic volume is large and the operation is difficult. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing a vanadium dioxide thin film based on radio frequency magnetron sputtering and the prepared vanadium dioxide thin film. The preparation method of the present invention does not require a high oxygen environment and an annealing step and is easy to operate.

[0006] The first object of the present invention is to provide a method for preparing a vanadium dioxide thin film based on radio frequency magnetron sputtering, comprising the following steps:

[0007] A vanadium pentoxide target is used as the target material, and argon gas with a flow rate of 4sccm to 8sccm is used as the sputtering gas. A vacuum radio frequency magnetron sputtering method is used to coat the film and perform an in-situ reaction at a sputtering power of 80W to 150W and a temperature of 600°C to 700°C. The ratio of V atoms to O atoms in the sputtering process is adjusted by the argon flow rate, and the sputtering rate of V atoms and O atoms in the sputtering process is adjusted by the sputtering power. Then, a vanadium dioxide film is prepared by crystallization.

[0008] Sputtering power mainly affects the film growth rate. Generally, the higher the sputtering power, the faster the film growth rate. For example, the sputtering power is 80W, 90W, 100W, 110W, 120W, 130W, 140W, 150W, etc.

[0009] For example, the argon gas flow rate is 4 sccm, 5 sccm, 6 sccm, 7 sccm, 8 sccm, 9 sccm, 10 sccm, etc.;

[0010] The temperature is 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0011] In a preferred embodiment of the present invention, the sputtering power is 100W.

[0012] In a preferred embodiment of the present invention, the temperature is 650°C.

[0013] In a preferred embodiment of the present invention, the target head angle is 39.24° to 41.24°. When the target head angle deviates from the optimal angle, the uniformity of the thin film will be reduced. For example, the target head angle is 39.24°, 39.44°, 39.64°, 39.84°, 40.04°, 40.24°, 40.44°, 40.64°, 40.84°, 41.04°, 41.24°, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0014] In a preferred embodiment of the present invention, the target head angle is 39.24°.

[0015] In a preferred embodiment of the present invention, the sputtering time is 1h to 2.5h. The longer the sputtering time, the thicker the film thickness. The sputtering time can be controlled according to the preparation requirements. For example, the sputtering time is 1h, 1.2h, 1.5h, 2h, 2.2h, 2.5h, etc., but is not limited to the listed values. Other values ​​not listed in the above numerical range are also applicable.

[0016] In a preferred embodiment of the present invention, the substrate is a sapphire substrate or a silicon substrate, and other epitaxial or non-epitaxial substrates may also be used.

[0017] In a preferred embodiment of the present invention, before sputtering, when the temperature is 600°C to 700°C, pre-sputtering is performed first, and the pre-sputtering time is 20min to 25min. The purpose of pre-sputtering is to stabilize the chamber temperature at 600°C to 700°C, stabilize the state of the target surface, and improve the uniformity of the film in the thickness direction. For example, the pre-sputtering time is 20min, 21min, 22min, 23min, 24min, 25min, etc., but it is not limited to the listed values, and other values ​​not listed in the above numerical range are also applicable.

[0018] In a preferred embodiment of the present invention, the sputtering pressure is 0.5 Pa to 0.7 Pa, and the sputtering pressure mainly affects the film growth rate and film density. For example, the sputtering pressure is 0.5 Pa, 0.6 Pa, 0.7 Pa, etc., but is not limited to the listed values, and other values ​​not listed in the above range are also applicable.

[0019] The second object of the present invention is to provide a vanadium dioxide film prepared by the above method, wherein the vanadium dioxide film is an M1 phase.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention performs in-situ growth in a high vacuum magnetron sputtering coating system. During the reaction process, argon ions are accelerated to bombard V under the action of an electric field. 2 O 5 The target material sputters a large number of V atoms and O atoms. Under the condition of an argon flow rate of 4sccm to 8sccm, the ratio of V atoms to O atoms is adjusted. Under a sputtering power of 80W to 150W, the sputtering power changes the sputtering rate of V atoms and O atoms during the sputtering process. As the power increases, the percentage of sputtered atoms increases. The ratio of V to O is adjusted to 1:2 by the argon flow rate and the sputtering power. Then, at a temperature of 600°C to 700°C, a vanadium dioxide film with high crystallinity and high resistivity is crystallized to obtain a uniform vanadium dioxide film within a radius of about 4cm on the substrate.

[0022] In the prior art, high temperature and high oxygen annealing is used to adjust the ratio of V atoms to oxygen atoms and promote VO 2 Crystallization, and the present invention has obtained VO by adjusting the argon flow rate and sputtering power during the in-situ growth process 2 The film has been crystallized into M1 phase, so it does not need to be annealed at high temperature and high oxygen;

[0023] Since the V used in the present invention 2 O 5 The target material itself contains oxygen. By adjusting the flow rate of Ar gas, the oxygen content in the deposited film can be adjusted to obtain VO 2 Therefore, during the film growth process, only the flow rate of Ar gas needs to be regulated, and no oxygen needs to be added, which simplifies the experiment and improves VO 2 Purity of the film;

[0024] (2) The entire film preparation process is simple to operate, and highly crystalline vanadium dioxide films can be prepared using only a single experimental instrument. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 These are actual pictures of vanadium dioxide films prepared using silicon substrates at different target head angles in Examples 1 to 3, where (a) the target head angle is 39.24°, (b) the target head angle is 40.24°, and (c) the target head angle is 41.24°.

[0026] Figure 2 The graphs are the EDS test results of vanadium dioxide films prepared using silicon substrates at different target head angles in Examples 1 to 3.

[0027] Figure 3 These are actual pictures of vanadium dioxide films prepared using silicon substrates at different temperatures in Examples 1, 4 and 5, where (a) the temperature is 600°C, (b) the temperature is 650°C, and (c) the temperature is 700°C.

[0028] Figure 4 The graph is a graph of EDS test results of vanadium dioxide films prepared at different temperatures using silicon substrates in Examples 1, 4 and 5.

[0029] Figure 5 These are Raman images of vanadium dioxide films prepared on different substrates in Example 1, Example 4-Example 8 and Comparative Examples 1-3, where (a) is Si, (b) is quartz, and (c) is sapphire substrate. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] During vacuum magnetron sputtering, electrons collide with argon atoms as they accelerate toward the substrate under the action of an electric field, ionizing a large number of argon ions and electrons. Electrons fly toward the substrate, the inner wall of the vacuum chamber, and the target source anode. Argon ions are accelerated to bombard the target under the action of the electric field, sputtering a large number of target atoms, and neutral target atoms or molecules are deposited on the substrate to form a film. Secondary electrons are affected by the Lorentz force of the magnetic field as they accelerate toward the substrate, and are bound in a plasma region close to the target surface. The plasma density in this region is very high, and secondary electrons move in a circle around the target surface under the action of the magnetic field. Magnetron sputtering film formation has the characteristics of high film formation rate, good uniformity, good density, good film adhesion, and high repeatability. Magnetron sputtering can be divided into DC magnetron sputtering and radio frequency magnetron sputtering.

[0032] The present invention adopts a radio frequency magnetron sputtering method to prepare a vanadium dioxide film. Specifically, the present invention adopts a vacuum radio frequency magnetron sputtering method to generate VO in situ in pure Ar gas. 2 Thin films, prepared VO 2 The film has good crystallinity and obvious Raman characteristic peaks. Since no high temperature and high oxygen annealing step is required, the VO prepared by the present invention 2 The film purity is higher, which means that the obtained VO 2 The physical and chemical properties of the film may be partially improved. 2 The film's unique metal-insulator transition properties allow it to be used in infrared sensors, electrochromic devices, switching elements, memristors and other fields.

[0033] The magnetron sputtering system used in the present invention is an AFS800F magnetron sputtering system.

[0034] The specific preparation method is as follows:

[0035] Example 1

[0036] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a 1cm×1cm silicon substrate is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%, and then in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0037] Turn on the RF power supply, adjust the angle of the vanadium pentoxide target to 39.24°, fix the silicon substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and rotate the sample stage at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 650°C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 5×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 650 ° C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0038] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0039] Example 2

[0040] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a 1cm×1cm silicon substrate is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%, and then in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0041] Turn on the RF power supply, adjust the angle of the vanadium pentoxide target to 40.24°, fix the silicon substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the temperature in the chamber to 650°C, adjust the Ar flow rate to 4 sccm, and adjust the pressure of the magnetron sputtering chamber to 5×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 650 ° C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0042] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0043] Example 3

[0044] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a 1cm×1cm silicon substrate is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0045] Turn on the RF power supply, adjust the vanadium pentoxide target head angle to 41.24°, fix the silicon substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 650°C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 5×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 650 ° C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0046] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0047] Example 4

[0048] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a 1cm×1cm silicon substrate is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0049] Turn on the RF power supply, adjust the angle of the vanadium pentoxide target to 39.24°, fix the silicon substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 600°C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 5×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 600 °C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0050] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0051] Example 5

[0052] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a 1cm×1cm silicon substrate is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0053] Turn on the RF power supply, adjust the angle of the vanadium pentoxide target to 39.24°, fix the silicon substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the temperature in the chamber to 700°C, adjust the Ar flow rate to 4 sccm, and adjust the pressure of the magnetron sputtering chamber to 5×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 700 °C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0054] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0055] Example 6

[0056] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a 1cm×1cm sapphire substrate is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0057] Turn on the RF power supply, adjust the vanadium pentoxide target head angle to 39.24°, fix the sapphire substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 600 °C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 5×10 -3hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 600 °C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0058] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0059] Example 7

[0060] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a 1cm×1cm sapphire substrate is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0061] Turn on the RF power supply, adjust the vanadium pentoxide target head angle to 39.24°, fix the sapphire substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 650°C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 5×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 650 ° C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0062] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0063] Example 8

[0064] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a 1cm×1cm sapphire substrate is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0065] Turn on the RF power supply, adjust the vanadium pentoxide target head angle to 39.24°, fix the sapphire substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 700 °C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 5×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 700 °C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0066] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0067] Example 9

[0068] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a 1cm×1cm sapphire substrate is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0069] Turn on the RF power supply, adjust the angle of the vanadium pentoxide target to 39.24°, fix the sapphire substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 650°C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 6×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 80 W, and carry out the pre-sputtering process. The pre-sputtering time is 25 min. During the pre-sputtering process, the chamber temperature is stabilized at 650 ° C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0070] The vanadium pentoxide target baffle was opened and coating began for 1 hour. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0071] Example 10

[0072] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a 1cm×1cm sapphire substrate is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0073] Turn on the RF power supply, adjust the angle of the vanadium pentoxide target to 39.24°, fix the sapphire substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 700°C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 7×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 150W, and carry out the pre-sputtering process. The pre-sputtering time is 23min. During the pre-sputtering process, the chamber temperature is stabilized at 700℃. After the pre-sputtering, the Ar flow rate is increased to 8sccm.

[0074] The vanadium pentoxide target baffle was opened and coating began for 2.5 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was naturally cooled to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0075] Comparative Example 1

[0076] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a quartz substrate of 1cm×1cm is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0077] Turn on the RF power supply, adjust the angle of the vanadium pentoxide target to 39.24°, fix the quartz substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 600°C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 5×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 600 °C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0078] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0079] Comparative Example 2

[0080] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a quartz substrate of 1cm×1cm is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0081] Turn on the RF power supply, adjust the angle of the vanadium pentoxide target to 39.24°, fix the quartz substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and rotate the sample stage at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 650°C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 5×10 -3 hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 650 ° C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0082] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0083] Comparative Example 3

[0084] In the magnetron sputtering system, a vanadium pentoxide target with a purity of 99.99% is used, a quartz substrate of 1cm×1cm is selected as the substrate, and the sputtering gas is argon with a purity of 99.99%. Then, in-situ vacuum magnetron sputtering coating is performed. The specific steps are as follows:

[0085] Turn on the RF power supply, adjust the vanadium pentoxide target head angle to 39.24°, fix the quartz substrate on the sample stage, adjust the target-substrate distance to 12.4 cm, and make the sample stage rotate at a constant speed of 20 rad / min. It should be noted that the sample stage needs to rotate at a constant speed of 20 rad / min during the entire film growth process. Adjust the chamber temperature to 700 °C, adjust the Ar flow rate to 4 sccm, and adjust the magnetron sputtering chamber pressure to 5×10 -3hPa, to ignite the vanadium pentoxide target, and adjust the sputtering power of the target to 100 W, and carry out the pre-sputtering process. The pre-sputtering time is 20 min. During the pre-sputtering process, the chamber temperature is stabilized at 700 °C. After the pre-sputtering, the Ar flow rate is increased to 8 sccm.

[0086] The vanadium pentoxide target baffle was opened and coating began for 2 hours. After coating, the RF power was turned off and the heating of the sample stage was stopped. After the sample stage was cooled naturally to room temperature, the sample was taken out to obtain an in-situ grown vanadium dioxide film.

[0087] Figure 1 The following are the actual pictures of vanadium dioxide films prepared using silicon substrates at different target head angles in Examples 1 to 3. From the color, it can be judged that when the target head angle during the sputtering process is 39.24°, the obtained vanadium dioxide film is the most uniform. Figure 2 The EDS test results also further proved that the vanadium dioxide film obtained was the most uniform when the target head angle was 39.24° during the sputtering process.

[0088] Figure 3 The following are the actual pictures of vanadium dioxide films prepared at different temperatures using silicon substrates in Examples 1, 4 and 5. From the color, it can be judged that when the target head angle during the sputtering process is 39.24° and the growth temperature is 600°C, 650°C, and 700°C, the vanadium dioxide films obtained are relatively uniform. Figure 4 The EDS test results also further prove that when the target head angle during sputtering is 39.24° and the growth temperature is 600, 650, and 700°C, the vanadium dioxide films obtained are relatively uniform.

[0089] The vanadium dioxide films prepared in Example 1, Example 4-Example 8 and Comparative Examples 1-3 were tested for their resistive switching performance. It can be seen from Table 1 that when the growth temperature is 650°C, the vanadium dioxide films grown on the sapphire substrate can undergo three orders of magnitude of resistive switching. Different growth temperatures make the VO 2 The crystallization state of the film is different. The crystallization state at 650°C is the best, and the resistance switching degree is the highest. The difference in resistance switching characteristics will have different effects on the electrical, optical and magnetic properties of the film.

[0090] Table 1 Resistive switching properties of vanadium dioxide films grown on different substrates and at different growth temperatures

[0091]

[0092] Figure 5The Raman images of the vanadium dioxide films prepared on different substrates in Example 1, Example 4-Example 8 and Comparative Examples 1-3 show that high-crystallinity vanadium dioxide films are grown on Si and sapphire substrates, while no obvious characteristic peaks of the vanadium dioxide films are observed on the quartz substrate, indicating that the film preparation conditions of the present invention can prepare vanadium dioxide films with excellent properties on sapphire and silicon substrates.

[0093] VO 2 The M1 phase of the film has 18 Raman modes (9A g and 9B g ), 12 of which are at 140cm -1 、193cm -1 、223cm -1 、261cm -1 、308cm -1 、338cm -1 、387cm -1 、395cm -1 、440cm -1 、497cm -1 、614cm -1 and 820cm -1 Isotope substitution and density functional theory calculations identify low-frequency A g Phononω v1 (193cm -1 ) and ω v2 (223cm -1 ) belongs to the VV lattice motion, where ω v1 It is related to the torsional vibration of the VV dimer. All other distinguishable peaks are related to the VO vibration. -1 Left and right VO vibration (ω 0 ) is to distinguish VO 2 Characteristic Raman peaks of M1, T, and M2 phases of the film.

[0094] Figure 5 615cm -1 The characteristic Raman peaks at 615 cm indicate that the vanadium dioxide film prepared by the present invention is M1 phase. The silicon dioxide film prepared on silicon and sapphire substrates has a Raman peak at 615 cm -1 There are obvious characteristic Raman peaks. The stronger the characteristic peaks are, the better the degree of crystallization is. This proves the optimum temperature for in-situ growth of vanadium dioxide thin films on silicon and sapphire substrates. There are no obvious characteristic Raman peaks for vanadium dioxide thin films grown on quartz substrates at the three growth temperatures, indicating that the prepared vanadium dioxide thin films are amorphous.

[0095] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0096] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a vanadium dioxide thin film based on radio frequency magnetron sputtering, characterized in that: The following steps are involved: A vanadium pentoxide target is used as the target material, and argon gas with a flow rate of 4sccm to 8sccm is used as the sputtering gas. A vacuum radio frequency magnetron sputtering method is used to coat the film and perform an in-situ reaction at a sputtering power of 80W to 150W and a temperature of 600°C to 700°C. The ratio of V atoms to O atoms in the sputtering process is adjusted by the argon flow rate, and the sputtering rate of V atoms and O atoms in the sputtering process is adjusted by the sputtering power. Then, a vanadium dioxide film is prepared by crystallization.

2. The method for preparing a vanadium dioxide thin film based on radio frequency magnetron sputtering according to claim 1, characterized in that: The sputtering power is 100W.

3. The method for preparing a vanadium dioxide thin film based on radio frequency magnetron sputtering according to claim 1, characterized in that: The temperature is 650°C.

4. The method for preparing a vanadium dioxide thin film based on radio frequency magnetron sputtering according to claim 1, characterized in that: The target head angle is 39.24°~41.24°.

5. The method for preparing a vanadium dioxide thin film based on radio frequency magnetron sputtering according to claim 2, characterized in that: The target head angle is 39.24°.

6. The method for preparing a vanadium dioxide thin film based on radio frequency magnetron sputtering according to claim 1, characterized in that: The sputtering time is 1h to 2.5h.

7. The method for preparing vanadium dioxide thin film based on radio frequency magnetron sputtering according to claim 1, characterized in that: The substrate is a sapphire substrate or a silicon substrate.

8. The method for preparing vanadium dioxide thin film based on radio frequency magnetron sputtering according to claim 1, characterized in that: Before sputtering, when the temperature is 600°C to 700°C, pre-sputtering is performed first, and the pre-sputtering time is 20min to 25min.

9. The method for preparing vanadium dioxide thin film based on radio frequency magnetron sputtering according to claim 1, characterized in that: The sputtering pressure is 0.5Pa~0.7Pa.

10. A vanadium dioxide film prepared by the method according to any one of claims 1 to 9, characterized in that: The vanadium dioxide film is M1 phase.

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