Method for synchronously regulating and controlling optical frequency dielectric property and phase transition temperature of vanadium oxide film

Abstract

The invention discloses a method for synchronously regulating and controlling the optical frequency dielectric property and the phase transition temperature of a vanadium oxide film, and aims to solve the technical problems that in a process for preparing a VO2 film by using a magnetron sputtering technology, the composition of a VOx mixed phase is very sensitive to oxygen flow, and the stability of the VO2 film preparation process is poor. The regulation method comprises the following steps: 1, ultrasonically cleaning the substrate; 2, cleaning a metal target material; thirdly, the V metal target material is connected with a direct-current power source, and the W metal target material is connected with a radio-frequency power source; 4, vacuumizing; 5, heating the substrate; 6, performing luminance build-up; seventhly, the target material is subjected to pre-sputtering treatment; 8, controlling the oxygen flow to enable the coating state to be in a poisoning mode, and performing film deposition; 9, cooling; 10, vacuumizing in an annealing furnace; and 11, annealing treatment. By introducing W atoms, the crystal structure and the energy band structure of VO2 are regulated and controlled, and meanwhile, the electronegativity of W and V elements and the difference of atomic radiuses are fully utilized, so that synchronous regulation and control of microcosmic electron polarization response and optical frequency dielectric characteristics are realized.

Description

Technical Field

[0001] The invention relates to a method for preparing a vanadium dioxide film with adjustable optical frequency dielectric constant and phase transition temperature. Background Art

[0002] VO2 can undergo phase change under the driving force of external physical fields such as light, electricity, force, and heat, and its optical and electrical properties change dramatically before and after the phase change. It has a wide range of applications in storage, supersurfaces, microelectronic devices, thermal radiation regulation, smart windows, photonic chips, and other fields. VO2 film can undergo a structural phase change between two different crystal structures at around 68°C. VO2 is an insulating phase (or semiconductor phase) at low temperatures, has a monoclinic crystal structure, high infrared transmittance, a wide transmission band, but poor conductivity. When VO2 is heated to around 68°C, the crystal structure will gradually change from the monoclinic phase to the tetragonal rutile phase, and completely change to the tetragonal rutile phase after the temperature exceeds 68°C. The high-temperature tetragonal rutile phase can also be called a metallic phase, and its infrared transmittance decreases rapidly, but its conductivity is greatly improved.

[0003] Since the phase transition temperature of VO2 thin film is closest to room temperature, and it has high cycle stability and good cycle life, it has attracted widespread attention and has been widely used in the fields of optics and electromagnetics. However, when applying VO2 thin film to optical devices, it is necessary to take into account the phase transition temperature, optical properties and phase transition properties at the same time. On the one hand, while lowering the phase transition temperature of VO2, it is necessary to maintain a certain phase transition ability; on the other hand, while regulating the phase transition temperature, it is necessary to consider the impact on the dielectric constant of VO2. The optical frequency dielectric constant is a key parameter for the interaction between materials and photons. Therefore, while regulating the phase transition temperature of VO2, it is of great significance to consider the synchronous regulation of optical properties such as the optical frequency dielectric constant and the optical constant, which is of great significance for further promoting the application of VO2.

[0004] Due to the constraints of VO2 material properties, the preparation of high-purity VO2 thin films has become another issue that everyone focuses on. Using magnetron sputtering technology, VO2 thin films can be directly prepared, but the purity of VO2 is not ideal and the optical modulation performance needs to be improved. Through a two-step method, VO2 is first prepared by magnetron sputtering. x Mixed phase, followed by high temperature annealing, using VO x The thermal transition between different phases in VO2 can produce high-purity VO2 thin films. x The composition of the hybrid phase is very sensitive to the oxygen flow rate during magnetron sputtering, and VO x The transition conditions of different phases in the two-step preparation process are different, so the oxygen flow rate, VO x The composition and annealing conditions of the mixed phase are strictly required. If certain coating technology innovations can be achieved for VOx Precise control of the composition of the mixed phase can improve the stability of the VO2 thin film preparation process and reduce the time and economic cost required for VO2 thin film preparation. Although a large number of preliminary process controls can be performed by adjusting the oxygen flow rate, the appropriate oxygen flow rate can be found to achieve VO x The control of the mixed phase composition, but repeated experiments require a lot of time and economic costs, reducing the efficiency and having certain disadvantages.

[0005] Therefore, it is an important task to achieve controllable VO2 thin film preparation process, improve the stability of the preparation process, and achieve synchronous regulation of VO2 phase transition temperature and optical frequency dielectric constant through certain technical means. Summary of the invention

[0006] The present invention aims to solve the problem of VO2 thin film preparation process using magnetron sputtering technology. x The composition of the mixed phase is very sensitive to the oxygen flow rate, the stability of the VO2 thin film preparation process is poor, and there are technical problems such as how to achieve synchronous regulation of the VO2 phase transition temperature and the optical frequency dielectric constant. A method for synchronously regulating the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films is provided.

[0007] The method for synchronously regulating the optical frequency dielectric properties and phase transition temperature of the vanadium oxide film of the present invention is implemented according to the following steps:

[0008] 1. Performing ultrasonic cleaning on the substrate to obtain a cleaned substrate;

[0009] 2. Grinding and cleaning the V metal target and the W metal target respectively to obtain cleaned V metal target and W metal target;

[0010] 3. Install the cleaned V metal target and W metal target in the cabin of the magnetron sputtering device, place the substrate on the sample stage, connect the V metal target to a DC power supply, and connect the W metal target to a radio frequency power supply;

[0011] 4. Turn on the mechanical pump to vacuum the cavity of the magnetron sputtering device. When the vacuum degree reaches below 10Pa, turn on the molecular pump to continue vacuuming to complete the vacuuming process;

[0012] 5. Heat the substrate to 300-500°C and keep it warm;

[0013] 6. Turn on the RF power supply and DC power supply, set the power of both to 80-120W, the argon flow rate to 10-30sccm, adjust the cabin pressure to 3.0-5.0Pa, and start the ignition;

[0014] 7. After the ignition is successful, the air pressure in the chamber is adjusted to 1.0 Pa, and the V metal target and the W metal target are pre-sputtered;

[0015] 8. After the pre-sputtering is completed, the RF power is controlled to be 1-10W, the argon gas flow rate is 10-30sccm, the DC power is 80-120W, and the oxygen flow rate is controlled to make the coating state in the poisoning mode for thin film deposition;

[0016] 9. After the deposition is completed, the temperature is lowered in an argon atmosphere until the temperature drops to room temperature to obtain a W-doped vanadium oxide film;

[0017] 10. Place the W-doped vanadium oxide film in an annealing furnace, evacuate the furnace, and then introduce argon gas;

[0018] 11. The annealing temperature is controlled at 450-600°C, the holding time is 30-60 minutes, the argon flow rate is 40-80 sccm, and high-temperature post-treatment is carried out in a flowing argon atmosphere. After the heating is completed, the temperature is lowered to obtain a vanadium oxide film with synchronous regulation of the optical frequency dielectric properties and the phase transition temperature.

[0019] In the method for synchronously regulating the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films, W atoms with a low doping atomic ratio of 0.5% to 1% are used to achieve synchronous regulation of VO2 phase transition temperature and optical frequency dielectric constant. x V 1-x The phase transition temperature, relative dielectric constant and optical constant of the O2 film confirmed the effectiveness of the regulation method.

[0020] The method for determining the oxygen flow rate in the poisoning mode during the process of preparing vanadium dioxide thin film by magnetron sputtering process in the present invention is as follows:

[0021] 1. Performing ultrasonic cleaning on the substrate to obtain a cleaned substrate;

[0022] 2. Grind and clean the V metal target;

[0023] 3. Install the cleaned V metal target in the cabin of the magnetron sputtering device, place the substrate on the sample stage, and connect the V metal target to a DC power supply;

[0024] 4. Turn on the mechanical pump to vacuum the cavity of the magnetron sputtering device. When the vacuum degree reaches below 10Pa, turn on the molecular pump to continue vacuuming to complete the vacuuming process;

[0025] 5. Heat the substrate to 300-500°C and keep it warm;

[0026] 6. Turn on the DC power supply, set the power of the DC power supply to 80-120W, the argon flow rate to 10-30sccm, adjust the cabin pressure to 3.0-5.0Pa, and start the ignition;

[0027] 7. After the ignition is successful, the air pressure in the chamber is adjusted to 1.0 Pa, and the V metal target is pre-sputtered;

[0028] 8. After the pre-sputtering is completed, the DC power supply power is controlled to 80-120W, the argon gas flow rate is 10-30sccm, the oxygen flow rate is initially set to 0, and the test is started. The oxygen flow rate is continuously increased at fixed intervals, and then the oxygen flow rate is reduced at the same interval. The discharge voltage / discharge current parameters on the DC power supply during the entire test process are recorded, and the magnetron sputtering reaction hysteresis loop is obtained by drawing;

[0029] 9. In the high oxygen flow stage, the discharge voltage / discharge current overlap area in the oxygen flow increase stage and the oxygen flow decrease stage in the magnetron sputtering reaction hysteresis loop is determined as the poisoning mode, thereby determining the oxygen flow rate under the poisoning mode.

[0030] The preparation of the vanadium oxide film for synchronously regulating the optical frequency dielectric properties and the phase transition temperature of the present invention adopts a two-step method, that is, the first step is to prepare VO by reactive DC magnetron sputtering. x Mixed phase, the second step is VO x The mixed phase is annealed at high temperature to prepare a high-purity VO2 film. x In order to solve the problems of mixed phase being sensitive to oxygen flow, difficult to control composition and high process cost, reactive DC magnetron sputtering technology was used to establish the oxygen flow rate, discharge parameters (target discharge voltage, target discharge current), coating mode, VO x The relationship between the mixed phase components is realized by real-time feedback of the current coating state through oxygen flow and discharge parameters, and timely adjustment of coating parameters, so as to achieve VO x Precise control of the mixed phase (mainly generating V2O5 phase) greatly improves the coating stability and reduces the sensitivity of the subsequent annealing process to annealing conditions.

[0031] When DC magnetron sputtering is used for reactive sputtering coating, as the oxygen flow rate increases, the coating state will gradually go through the metal mode, transition mode and poisoning mode. As the oxygen flow rate changes, the coating state will show regular changes, and the discharge voltage and discharge current on the target surface will also change accordingly. The changes in the above parameters are very sensitive to changes in oxygen flow rate. In addition, VO x The composition of the mixed phase is also very sensitive to the oxygen flow rate.

[0032] Therefore, the present invention makes full use of reactive DC magnetron sputtering and VO xThe phenomenon that the components of the mixed phase are synchronously sensitive to oxygen is studied. By real-time monitoring the changes of discharge parameters such as discharge voltage and discharge current on the target surface with the oxygen flow rate, the corresponding magnetron sputtering coating state is obtained, and the relationship between oxygen flow rate, discharge parameters and coating mode is established, which realizes real-time monitoring and regulation of the coating state, and finally achieves the VO x The effect of controlled regulation of the mixed phase composition is beneficial to reducing the complexity and difficulty of the subsequent annealing process.

[0033] The present invention tests the primary reaction hysteresis loop to find the oxygen flow rate corresponding to the poisoning mode, directly controls the magnetron sputtering coating state in the poisoning mode, and directly controls the VO2O3 coating state in the poisoning mode by utilizing the highly oxidized state of the target surface. x The mixed phase composition is controlled to be a high-purity V2O5 film, which eliminates the tedious preliminary process exploration and further simplifies the annealing process to the transformation of V2O5 to VO2, greatly reducing the time cost and improving the controllability of the process and the film quality.

[0034] The method for synchronously regulating the dielectric properties and phase transition temperature of vanadium oxide thin films of the present invention includes the following beneficial effects:

[0035] 1. Taking advantage of the large radius of W atoms, W atoms are doped to occupy the lattice sites of V atoms and introduce larger lattice distortion into the VO2 lattice. At the same time, W+6 in the +6 valence state acts as a shallow donor doping, introducing free electrons, synchronously regulating the crystal structure and band structure of VO2 and reducing the phase transition temperature.

[0036] 2. By introducing W atoms, while regulating the crystal structure and band structure of VO2, the difference in electronegativity and atomic radius between W and V elements is fully utilized to affect the atomic bonding and electronic state in the lattice, thereby achieving synchronous regulation of the microscopic electronic polarization response of VO2.

[0037] 3. Dielectric properties refer to the ability of an object to be polarized under the action of an external electric field. The microscopic formation mechanism of the optical frequency dielectric properties of VO2 in the optical band is the electronic polarization response, and the macroscopic response is the change of the dielectric constant and the optical constant (n and k). Therefore, the present invention regulates the microscopic electronic polarization response of VO2 by doping with low-concentration W atoms, that is, it successfully realizes the regulation of the optical frequency dielectric properties of VO2. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a curve diagram showing the change of the discharge voltage and discharge current of the target surface along with the oxygen flow rate during the DC magnetron sputtering process in Example 1;

[0039] Figure 2 is the XRD diagram of the vanadium oxide film at different oxygen flow rates in Example 1;

[0040] Figure 3 is W in the second embodiment x V 1-x Test diagram of the phase transition temperature of O2 changing with W doping content;

[0041] Figure 4 is W in the second embodiment x V 1-x The real part (a) and imaginary part (b) of the dielectric constant of O2 are tested as the W doping content changes;

[0042] Figure 5 In the embodiment, x V 1-x Test graph of the optical constants n(a) and k(b) of O2 as a function of W doping content. DETAILED DESCRIPTION

[0043] Specific implementation method 1: The method for synchronously regulating the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films in this implementation method is implemented according to the following steps:

[0044] 1. Performing ultrasonic cleaning on the substrate to obtain a cleaned substrate;

[0045] 2. Grinding and cleaning the V metal target and the W metal target respectively to obtain cleaned V metal target and W metal target;

[0046] 3. Install the cleaned V metal target and W metal target in the cabin of the magnetron sputtering device, place the substrate on the sample stage, connect the V metal target to a DC power supply, and connect the W metal target to a radio frequency power supply;

[0047] 4. Turn on the mechanical pump to vacuum the cavity of the magnetron sputtering device. When the vacuum degree reaches below 10Pa, turn on the molecular pump to continue vacuuming to complete the vacuuming process;

[0048] 5. Heat the substrate to 300-500°C and keep it warm;

[0049] 6. Turn on the RF power supply and DC power supply, set the power of both to 80-120W, the argon flow rate to 10-30sccm, adjust the cabin pressure to 3.0-5.0Pa, and start the ignition;

[0050] 7. After the ignition is successful, the air pressure in the chamber is adjusted to 1.0 Pa, and the V metal target and the W metal target are pre-sputtered;

[0051] 8. After the pre-sputtering is completed, the RF power is controlled to be 1-10W, the argon gas flow rate is 10-30sccm, the DC power is 80-120W, and the oxygen flow rate is controlled to make the coating state in the poisoning mode for thin film deposition;

[0052] 9. After the deposition is completed, the temperature is lowered in an argon atmosphere until the temperature drops to room temperature to obtain a W-doped vanadium oxide film;

[0053] 10. Place the W-doped vanadium oxide film in an annealing furnace, evacuate the furnace, and then introduce argon gas;

[0054] 11. The annealing temperature is controlled at 450-600°C, the holding time is 30-60 minutes, the argon flow rate is 40-80 sccm, and high-temperature post-treatment is carried out in a flowing argon atmosphere. After the heating is completed, the temperature is lowered to obtain a vanadium oxide film with synchronous regulation of the optical frequency dielectric properties and the phase transition temperature.

[0055] Specific implementation method 2: The difference between this implementation method and specific implementation method 1 is that in step 1, the substrate is sequentially placed in acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning.

[0056] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that the material of the substrate in step one is sapphire, quartz glass or silicon wafer.

[0057] Specific embodiment 4: This embodiment differs from the specific embodiments 1 to 3 in that in step 4, the molecular pump is turned on to continue to evacuate the air until the vacuum degree reaches 1×10 -4 Pa.

[0058] Specific implementation method 5: This implementation method is different from specific implementation methods 1 to 4 in that in step 5, the substrate is heated to 300-500° C. and the heat preservation treatment time is 30-50 minutes.

[0059] Specific implementation method 6: The difference between this implementation method and any one of specific implementation methods 1 to 5 is that the pre-sputtering treatment time in step 6 is 10 to 20 minutes.

[0060] Specific embodiment 7: This embodiment is different from any one of specific embodiments 1 to 6 in that the thickness of the W-doped vanadium oxide film in step 9 is 80 nm to 200 nm.

[0061] Specific implementation example eight: This implementation example is different from any one of specific implementation examples one to seven in that the heating rate of the annealing in step ten is controlled to be 5° C. / min.

[0062] Specific implementation method 9: The difference between this implementation method and specific implementation methods 1 to 8 is that in step 11, the annealing temperature is controlled to be 500-550° C., and the holding time is 30-40 minutes.

[0063] Specific embodiment ten: This embodiment differs from specific embodiments one to nine in that the atomic doping amount of W in the vanadium oxide film for synchronously regulating the optical frequency dielectric properties and the phase transition temperature is 0.5%-1%.

[0064] Example 1: In this example, the method for determining the oxygen flow rate in the poisoning mode during the preparation of vanadium dioxide thin film by magnetron sputtering process is as follows:

[0065] 1. Performing ultrasonic cleaning on the substrate to obtain a cleaned substrate;

[0066] 2. Grind and clean the V metal target;

[0067] 3. Install the cleaned V metal target in the cabin of the magnetron sputtering device, place the substrate on the sample stage, and connect the V metal target to a DC power supply;

[0068] 4. Turn on the mechanical pump to vacuum the cavity of the magnetron sputtering device. When the vacuum degree reaches below 10Pa, turn on the molecular pump to continue vacuuming to complete the vacuuming process;

[0069] 5. Heat the substrate to 500°C and keep it warm for 30 minutes;

[0070] 6. Turn on the DC power supply, set the power of the DC power supply to 100W, the argon flow rate to 20sccm, adjust the chamber pressure to 4.0Pa, and start the ignition;

[0071] 7. After the ignition is successful, the air pressure in the chamber is adjusted to 1.0 Pa, and the V metal target is pre-sputtered;

[0072] 8. After the pre-sputtering is completed, the DC power supply power is controlled to 100W, the argon gas flow rate is 20sccm, the oxygen flow rate is initially set to 0, the test is started, the oxygen flow rate is increased at fixed intervals, and then the oxygen flow rate is reduced at the same intervals, and the discharge voltage / discharge current parameters on the DC power supply are recorded during the entire test process, and the magnetron sputtering reaction hysteresis loop is obtained by drawing;

[0073] 9. In the high oxygen flow stage, the discharge voltage / discharge current overlap area in the oxygen flow increase stage and the oxygen flow decrease stage in the magnetron sputtering reaction hysteresis loop is determined as the poisoning mode, thereby determining the oxygen flow rate under the poisoning mode.

[0074] The time interval and oxygen flow rate controlled in step eight of this embodiment are shown in Table 1.

[0075] Table 1 Oxygen flow parameter setting values ​​and setting time of the hysteresis loop corresponding to the oxygen flow increase process

[0076]

[0077] like Figure 1 As shown in the figure, during the reactive DC magnetron sputtering process, the discharge voltage and discharge current on the target surface change regularly with the change of oxygen flow rate, and show a certain hysteresis in the process of reducing the oxygen flow rate. Figure 1 The curve shown is also called a hysteresis loop. As the oxygen flow rate increases, the oxygen flow rate is in the transition mode in the range of 0-2.5 sccm, in the poisoning mode in the range of 2.5-4.0 sccm, and the metal mode is not significant.

[0078] like Figure 2 The XRD patterns of vanadium oxide films at different oxygen flow rates are shown. When the oxygen flow rate is 2.0, 2.5, and 3.0 sccm, all signal peaks belong to the characteristic peaks of V2O5. Figure 1 It can be seen that when the oxygen flow rate is ≥2.5sccm, the coating state is in the poisoning mode. Figure 1 and Figure 2 The results show that by using reactive DC magnetron sputtering, the coating state can be directly controlled in the poisoning mode by adjusting the oxygen flow rate ≥ 2.5sccm, and high-purity V2O5 thin films can be successfully prepared. Using the hysteresis loop of reactive DC magnetron sputtering, the VO2O5 film during magnetron sputtering can be quickly controlled. x The regulation of the mixed phase composition eliminates the process control stage, improves process stability and reduces production costs.

[0079] Embodiment 2: The method for synchronously regulating the optical frequency dielectric properties and phase transition temperature of the vanadium oxide thin film in this embodiment is implemented according to the following steps:

[0080] 1. placing the quartz glass substrate in acetone, anhydrous ethanol, and deionized water in turn for ultrasonic cleaning to remove pollutants on the substrate surface and obtain a cleaned substrate;

[0081] 2. Grinding and cleaning the V metal target and the W metal target respectively to obtain cleaned V metal target and W metal target;

[0082] 3. Install the cleaned V metal target and W metal target in the cabin of the magnetron sputtering device, place the substrate on the sample stage, connect the V metal target to a DC power supply, and connect the W metal target to a radio frequency power supply;

[0083] 4. Turn on the mechanical pump to evacuate the cavity of the magnetron sputtering device. When the vacuum degree reaches below 10Pa, turn on the molecular pump to continue evacuating to 1×10 -4 Pa, complete the vacuum treatment;

[0084] 5. Heat the substrate to 500°C and keep it warm for 30 minutes to ensure that the substrate is heated evenly;

[0085] 6. Turn on the RF power supply and DC power supply, set the power of both RF power supply and DC power supply to 100W, the argon flow rate to 20sccm, adjust the cabin pressure to 4.0Pa, start the DC and RF power supplies for ignition, and after ignition is successful, adjust the cabin pressure to 1.0Pa, and pre-sputter the target surface for 10 minutes;

[0086] 7. After the pre-sputtering is completed, the DC power is controlled to 100 W, the RF power is controlled to 5 W, the argon flow rate is controlled to 20 sccm, and the oxygen flow rate is controlled to 5 sccm, and the film deposition is performed for 60 min;

[0087] 8. After the deposition is completed, the temperature is lowered in an argon atmosphere until the temperature drops to room temperature, and a W-doped vanadium oxide film with a thickness of 100 nm is obtained;

[0088] 9. Place the W-doped vanadium oxide film in an annealing furnace, evacuate the chamber and introduce high-purity argon gas until the pressure in the chamber returns to the atmospheric pressure level, ensuring that the quartz tube is in an argon atmosphere;

[0089] 10. The annealing temperature is controlled to be 550°C, the heating rate is 5°C / min, the holding time is 30min, the argon flow rate is 60sccm, and high-temperature post-treatment is performed in a flowing argon atmosphere. After the heating is completed, the temperature is lowered to obtain a vanadium oxide film with synchronously regulated dielectric properties and phase transition temperature.

[0090] This embodiment utilizes a reactive multi-target DC co-sputtering process, using a metal V target and a metal W target as target materials, to deposit a thin film on a substrate.

[0091] Figure 3-Figure 5 The following are the curves showing the change of phase transition temperature, dielectric constant and optical constant of VO2 with W doping content. It can be seen that W doping can effectively achieve the synchronous regulation of phase transition temperature, dielectric constant and optical constant of VO2, and the regulation effect becomes more obvious with the increase of W doping content. In the figure, the W doping content of W1-VO2 and W2-VO2 samples is less than 1%, and W2>W1.

[0092] The corresponding relationship between the curve label and the preparation process is shown in Table 2 below. The M in the curve label represents the low-temperature monoclinic phase, and R represents the high-temperature metal phase. The sputtering power of the fixed V target remains unchanged. As the sputtering power of the W target increases, the W doping content gradually increases. It can be seen that as the W doping content increases, the phase transition temperature of the film gradually decreases, and the real part of the dielectric constant of the M and R phases ( Figure 4 a) shows a downward trend, and the imaginary part of the dielectric constant of the M and R phases ( Figure 4 b) shows a decreasing trend in the visible light band, while in the infrared band, the imaginary part of the dielectric constant of the M phase ( Figure 4 b) shows an upward trend, the imaginary part of the dielectric constant of the R phase ( Figure 4b) decreases first and then increases. For the optical constants n and k, as the W doping content increases, the refractive index n ( Figure 5 a) shows a downward trend, and the extinction coefficient k( Figure 5 b) shows a decreasing trend in the visible light band, while in the infrared band, the extinction coefficient k of the M phase ( Figure 5 b) shows an upward trend, and the extinction coefficient k of the R phase ( Figure 5 b) First decrease and then increase.

[0093] Table 2 Correspondence between curve labels and preparation processes

[0094] Curve Label V target sputtering power (W) W target sputtering power (W) <![CDATA[VO2]]> 100 0 <![CDATA[W1-VO2]]> 100 5 <![CDATA[W2-VO2]]> 100 10 .

Claims

1. A method for synchronously controlling the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films. Features The method for synchronously regulating the optical frequency dielectric properties and phase transition temperature of the vanadium oxide film is implemented according to the following steps:

1. Performing ultrasonic cleaning on the substrate to obtain a cleaned substrate; 2. Grinding and cleaning the V metal target and the W metal target respectively to obtain cleaned V metal target and W metal target; 3. Install the cleaned V metal target and W metal target in the cabin of the magnetron sputtering device, place the substrate on the sample stage, connect the V metal target to a DC power supply, and connect the W metal target to a radio frequency power supply; 4. Turn on the mechanical pump to vacuum the cavity of the magnetron sputtering device. When the vacuum degree reaches below 10Pa, turn on the molecular pump to continue vacuuming to complete the vacuuming process; 5. Heat the substrate to 300-500°C and keep it warm; 6. Turn on the RF power supply and DC power supply, set the power of both to 80-120W, the argon flow rate to 10-30sccm, adjust the cabin pressure to 3.0-5.0Pa, and start the ignition; 7. After the ignition is successful, the air pressure in the chamber is adjusted to 1.0 Pa, and the V metal target and the W metal target are pre-sputtered; 8. After the pre-sputtering is completed, the RF power is controlled to be 1-10W, the argon gas flow rate is 10-30sccm, the DC power is 80-120W, and the oxygen flow rate is controlled to make the coating state in the poisoning mode for thin film deposition; 9. After the deposition is completed, the temperature is lowered in an argon atmosphere until the temperature drops to room temperature to obtain a W-doped vanadium oxide film; 10. Place the W-doped vanadium oxide film in an annealing furnace, evacuate the furnace, and then introduce argon gas; 11. The annealing temperature is controlled at 450-600°C, the holding time is 30-60 minutes, the argon flow rate is 40-80 sccm, and high-temperature post-treatment is carried out in a flowing argon atmosphere. After the heating is completed, the temperature is lowered to obtain a vanadium oxide film with synchronous regulation of the optical frequency dielectric properties and the phase transition temperature.

2. The method for synchronously regulating the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films according to claim 1, Features The material of the substrate in step 1 is sapphire, quartz glass or silicon wafer.

3. The method for synchronously controlling the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films according to claim 1, Features In step 4, open the molecular pump and continue to evacuate until the vacuum reaches 1×10 -4 Pa.

4. The method for synchronously regulating the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films according to claim 1, Features In step 5, the substrate is heated to 300-500° C., and the heat preservation time is 30-50 minutes.

5. The method for synchronously regulating the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films according to claim 1, Features The pre-sputtering treatment time in step six is ​​10 to 20 minutes.

6. The method for synchronously controlling the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films according to claim 1, Features The method for determining the oxygen flow rate in poisoning mode in step 8 is as follows:

1. Performing ultrasonic cleaning on the substrate to obtain a cleaned substrate; 2. Grind and clean the V metal target; 3. Install the cleaned V metal target in the cabin of the magnetron sputtering device, place the substrate on the sample stage, and connect the V metal target to a DC power supply; 4. Turn on the mechanical pump to vacuum the cavity of the magnetron sputtering device. When the vacuum degree reaches below 10Pa, turn on the molecular pump to continue vacuuming to complete the vacuuming process; 5. Heat the substrate to 300-500°C and keep it warm; 6. Turn on the DC power supply, set the power of the DC power supply to 80-120W, the argon flow rate to 10-30sccm, adjust the cabin pressure to 3.0-5.0Pa, and start the ignition; 7. After the ignition is successful, the air pressure in the chamber is adjusted to 1.0 Pa, and the V metal target is pre-sputtered; 8. After the pre-sputtering is completed, the DC power supply power is controlled to 80-120W, the argon gas flow rate is 10-30sccm, the oxygen flow rate is initially set to 0, and the test is started. The oxygen flow rate is continuously increased at fixed intervals, and then the oxygen flow rate is reduced at the same interval. The discharge voltage / discharge current parameters on the DC power supply during the entire test process are recorded, and the magnetron sputtering reaction hysteresis loop is obtained by drawing; 9. In the high oxygen flow stage, the discharge voltage / discharge current overlap area in the oxygen flow increase stage and the oxygen flow decrease stage in the magnetron sputtering reaction hysteresis loop is determined as the poisoning mode, thereby determining the oxygen flow rate under the poisoning mode.

7. The method for synchronously controlling the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films according to claim 1, Features In step nine, the thickness of the W-doped vanadium oxide film is 80 nm to 200 nm.

8. The method for synchronously controlling the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films according to claim 1, Features In step 10, the heating rate of annealing is controlled to be 5°C / min.

9. The method for synchronously controlling the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films according to claim 1, Features In step 11, the annealing temperature is controlled to be 500-550° C., and the holding time is 30-40 minutes.

10. The method for synchronously controlling the optical frequency dielectric properties and phase transition temperature of vanadium oxide thin films according to claim 1, Features The atomic doping amount of W in the vanadium oxide film for synchronously regulating the optical frequency dielectric properties and the phase transition temperature is 0.5% to 1%.

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