Magnesium titanate film and preparation method and application thereof

Abstract

The invention provides a magnesium titanate film as well as a preparation method and application thereof, and relates to the technical field of ilmenite type oxide materials. According to the preparation method of the magnesium titanate thin film, the magnetron sputtering technology is combined with the heat treatment technology, the TiN thin film is deposited on the magnesium oxide substrate, and then Mg in the magnesium oxide substrate is diffused to the TiN thin film layer in the heat treatment process by optimizing heat treatment technology parameters and reacts with TiN to generate the MgTiO3 thin film with the rhombohedral crystal structure. The MgTiO3 thin film has high visible light transmittance; the magnetron sputtering technology and the heat treatment technology adopted in the preparation method of the magnesium titanate thin film are stable and controllable in process conditions, and are very suitable for large-scale industrial production; the problems that various impure phases such as MgTiO2 easily exist in the magnesium titanate film prepared by a sol-gel method and the quality and the performance are inconsistent in large-scale industrial production are solved.

Description

Technical Field

[0001] The invention relates to the technical field of ilmenite-type oxide materials, and in particular to a magnesium titanate film and a preparation method and application thereof. Background Art

[0002] Ilmenite-type oxide materials have received extensive attention and research in the field of photodetectors in recent years due to their unique crystal structure and excellent physical and chemical properties. The crystal structure of ilmenite-type oxide materials is usually trigonal with a highly symmetrical lattice, which provides a basis for optimizing their performance in optoelectronic applications. The electronic structure and band gap characteristics of ilmenite-type oxide materials give them significant advantages in photoelectric conversion and detection. For example, they have high light absorption coefficients in the visible and ultraviolet regions, which helps to improve the sensitivity and response speed of photodetectors. In addition, these materials also have good thermal stability and chemical tolerance, and can maintain stable performance under harsh environmental conditions.

[0003] MgTiO3 (magnesium titanate) thin film materials have a wide range of application potential in microwave communications, integrated optics and electronic devices, especially under the requirements of high frequency, low loss and high thermal stability. Its unique rhombohedral crystal structure and high dielectric constant (about 17) make it an ideal microwave dielectric material, which is widely used in microwave ceramic capacitors, resonators, bandpass filters and other devices. In addition, MgTiO3 thin films not only maintain their excellent dielectric properties in bulk ceramic form, but also show excellent optical properties, such as optical waveguides and high dielectric constant insulating coatings, which make them also have important application value in optical communications and electronic devices. With the rapid development of microwave communication technology, the demand for miniaturized, integrated and high-efficiency thin film materials continues to increase. MgTiO3 thin films have become key materials in the manufacture of integrated circuits and optical devices due to their low processing temperature and excellent electrical and optical properties. Especially in thin film form, MgTiO3 can effectively reduce device size while maintaining low dielectric loss and high quality factor, which is crucial to improving integration and meeting the requirements of low loss and stability in microwave communication systems.

[0004] The prior art often uses the sol-gel method to prepare magnesium titanate films. In Chinese patent application CN103489766A, ethylene glycol monomethyl ether is used as a solvent and concentrated hydrochloric acid is used as a stabilizer to dissolve Mg(OC2H5)2 and Ti(C4H9O)4 to form a clear and stable precursor solution; the precursor solution is spin-coated on a glass substrate, and a magnesium titanium oxide film is obtained after preheating and subsequent high-temperature heat treatment. However, the magnesium titanate film prepared by the sol-gel method is prone to the presence of various impurities such as MgTiO2, which reduces the performance of the magnesium titanate film. In addition, the organic solvents and precursors used in the sol-gel method may cause pollution to the environment, and appropriate environmental protection measures need to be taken. The sol-gel method may perform well on a laboratory scale, but it is a challenge to maintain consistent quality and performance in large-scale industrial production. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a magnesium titanate film and a preparation method and application thereof. The magnesium titanate film contains only a MgTiO3 phase with a rhombohedral crystal structure and has a high visible light transmittance. The preparation method of the magnesium titanate film has a stable process, strong controllability, and is convenient for large-scale industrial production.

[0006] The specific technical scheme of the present invention is: In a first aspect, the present invention provides a method for preparing a magnesium titanate film, comprising the following steps: S1, depositing a TiN film on a magnesium oxide substrate by magnetron sputtering to obtain a prefabricated sample; S2. The prefabricated sample described in step S1 is subjected to heat treatment at a temperature of more than 750° C. and a time of more than 1 h to obtain a rhombohedral MgTiO 3 thin film.

[0007] The preparation method of the magnesium titanate film provided by the present invention adopts magnetron sputtering technology combined with a heat treatment process, first deposits a TiN film on a magnesium oxide substrate, and then optimizes the heat treatment process so that Mg in the magnesium oxide substrate diffuses into the TiN film layer during the heat treatment process and reacts with TiN to form a MgTiO3 film with a rhombohedral crystal structure, and the MgTiO3 film has a high visible light transmittance. In addition, the process conditions of the magnetron sputtering technology and the heat treatment technology used in the preparation method of the magnesium titanate film are stable and controllable, and are very suitable for large-scale industrial production.

[0008] In a possible implementation, the magnesium oxide substrate in step S1 is a magnesium oxide single crystal substrate or a magnesium oxide polycrystalline substrate. The magnesium titanate thin film can be prepared by using both magnesium oxide single crystal substrate and magnesium oxide polycrystalline substrate.

[0009] Furthermore, the crystal orientation of the magnesium oxide single crystal substrate is (100). Mg in the magnesium oxide single crystal substrate with a crystal orientation of (100) is more easily diffused into the TiN film, so using a magnesium oxide single crystal substrate with a crystal orientation of (100) is beneficial to improving the reaction speed.

[0010] In a possible implementation, the heat treatment temperature in step S2 is 800-1000° C. Within the heat treatment temperature range of 800-1000° C., the magnesium titanate film can be prepared in a short time, which is beneficial to improving the preparation efficiency of the magnesium titanate film.

[0011] In a possible implementation manner, the heating rate of the heat treatment in step S2 is 3-8° C. / min. By controlling the heating rate of the heat treatment, it is beneficial to obtain a more uniform magnesium titanate film.

[0012] In a possible implementation, the cooling rate of the heat treatment in step S2 is 4-6°C / min. By controlling the cooling rate within the range of 4-6°C / min, it is possible to avoid excessively rapid temperature changes that may cause stress in the film.

[0013] In a possible implementation manner, the deposition of the TiN film in step S1 includes sample loading, vacuuming, substrate heating, gas washing, sputtering deposition and cooling treatment in sequence.

[0014] Furthermore, the sample loading process is to load the Ti metal target into the target gun of the magnetron sputtering system, ultrasonically clean the magnesium oxide substrate in acetone and ethanol in sequence, blow dry the magnesium oxide substrate after the ultrasonic cleaning, and then load it into the sputtering chamber of the magnetron sputtering system. Ultrasonic cleaning can remove potential contaminants on the surface of the magnesium oxide substrate, which is more conducive to obtaining high-quality MgTiO3 film.

[0015] Furthermore, the vacuuming process is to use a mechanical pump and a molecular pump to vacuumize the sputtering chamber in sequence, so that the vacuum degree in the sputtering chamber is ≤9×10 -8 Pa. The air in the sputtering chamber is removed by vacuuming to prevent the oxygen in the air in the sputtering chamber from affecting the subsequent generation of TiN.

[0016] Furthermore, the heating rate used for heating the substrate is 40-60°C / min. By controlling the heating rate, the temperature of the magnesium oxide substrate can be quickly raised to the required temperature, while avoiding uneven heating of the magnesium oxide substrate caused by too fast a heating rate.

[0017] Furthermore, the heating temperature used for heating the substrate is 800-1000° C. Controlling the temperature of the magnesium oxide substrate is beneficial to the subsequent direct growth of a TiN film on a single crystal substrate.

[0018] Furthermore, the gas washing process is to introduce sputtering gas into the sputtering chamber until the pressure reaches 200 Pa, and then evacuate the sputtering chamber to a vacuum degree of ≤1×10 -7 Pa. The residual air in the sputtering chamber can be further removed by gas washing.

[0019] Furthermore, the sputtering deposition process is to introduce the sputtering gas into the sputtering chamber, use a radio frequency power supply to ignite the Ti metal target to generate plasma, pre-sputter the Ti metal target, and then purge the sputtering chamber after the pre-sputtering, and then sputter grow the TiN film after the purge.

[0020] Furthermore, the cooling process is to turn off the RF power supply, keep the gas pressure in the sputtering chamber unchanged, perform cooling treatment, cool to 200-400°C at a rate of 10-30°C / min, then turn off the temperature control power supply and cool to room temperature.

[0021] Furthermore, the sputtering gas is nitrogen. Nitrogen can be used as both a sputtering gas and a reaction gas for the subsequent preparation of TiN.

[0022] Furthermore, the sputtering growth time of the TiN film is more than 5 hours. By controlling the sputtering growth time of the TiN film, a TiN film of suitable thickness can be obtained.

[0023] Furthermore, the gas pressure of the sputtering deposition is 2-3 Pa, preferably 2.6 Pa.

[0024] Furthermore, the power of the radio frequency power supply is 95-110W, preferably 100W.

[0025] Single-phase TiN can be prepared by controlling the gas pressure of sputtering deposition and the power of the radio frequency power supply.

[0026] In a second aspect, the present invention also provides a magnesium titanate film prepared by the above method, wherein the constituent phase of the magnesium titanate film is rhombohedral MgTiO3.

[0027] In a third aspect, the present invention also provides applications of the magnesium titanate film in the field of photoelectric detectors and ultraviolet detectors.

[0028] Based on the common knowledge in this field, the above-mentioned implementation modes can be combined arbitrarily.

[0029] The reagents and raw materials used in the present invention are commercially available.

[0030] The positive and progressive effects of the present invention are: The method for preparing a magnesium titanate film provided by the present invention combines magnetron sputtering technology with heat treatment technology to prepare a magnesium titanate film with excellent optical properties. The method for preparing a magnesium titanate film can grow a MgTiO3 film with a rhombohedral crystal structure on a magnesium oxide substrate, and the MgTiO3 film has a high visible light transmittance and strong light stability. During the annealing process, Mg in the magnesium oxide substrate diffuses into TiN to react to form a MgTiO3 film. Compared with magnesium titanate films with other impurities, the visible light transmittance of the MgTiO3 film provided by the present invention is significantly improved. The magnesium titanate film provided by the present invention has broad application prospects in photodetectors, ultraviolet detectors and other high-efficiency photoelectric devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the crystal structure of the magnesium titanate film MgTiO3 prepared in Example 1.

[0032] Figure 2 The Raman spectra of the TiN film and the magnesium titanate film prepared in Example 1 of the present invention are shown.

[0033] Figure 3 The X-ray photoelectron spectra of the TiN film and the magnesium titanate film prepared in Example 1 of the present invention are shown.

[0034] Figure 4 Graphs showing the transmission spectra of the TiN film and the magnesium titanate film prepared in Example 1 of the present invention.

[0035] Figure 5 The Raman spectra of the films prepared in Example 2, Example 3, Example 4 and Comparative Example 1 are shown.

[0036] Figure 6 The Raman spectra of the films prepared in Example 2, Example 5 and Comparative Example 2 are shown. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation method and typical parameters of the present invention, and are not used to limit the parameter range described in the present invention. Reasonable changes derived therefrom are still within the scope of protection of the claims of the present invention.

[0038] It should be noted that the endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0039] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. In some cases, terms with conventionally understood meanings are defined herein for the purpose of clarification or ease of reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents and instruments is carried out in accordance with the protocols and parameters given by the manufacturer.

[0040] Example 1

[0041] This embodiment provides a magnesium titanate film, which is prepared by the following preparation method: The Ti metal target was loaded onto the target gun of the magnetron sputtering system, and the MgO (100) single crystal substrate was ultrasonically cleaned in acetone and ethanol for 10 min respectively. After the ultrasonic cleaning, the MgO (100) single crystal substrate was blown dry with a nitrogen gun, and then the MgO (100) single crystal substrate was loaded into the sputtering chamber of the magnetron sputtering system. Use mechanical pump and molecular pump to evacuate the sputtering chamber in turn, so that the vacuum degree in the sputtering chamber is ≤9×10 -8 Pa; Turn on the heating power to heat the MgO (100) single crystal substrate, set the temperature to 1000 °C, the heating rate to 50 °C / min, and bake the single crystal substrate at 1000 °C for 15 min; 99.999% high-purity N2 was introduced into the sputtering chamber for gas washing. When the pressure in the sputtering chamber reached 200 Pa, the vacuum degree in the sputtering chamber was evacuated to less than 1×10 -7 Pa, repeat the above operation to purge the sputtering chamber twice; 99.999% high-purity N2 was introduced into the sputtering chamber, and the N2 flow rate was adjusted to 2.5 sccm to maintain the pressure in the sputtering chamber at 2.6 Pa. The pre-sputtering power was set to 40 W, and the RF power was turned on to pre-sputter the Ti metal target for 30 min. After the pre-sputtering, the molecular pump and the vacuum chamber were turned on to purge the gas again, and the vacuum degree in the sputtering chamber was pumped to less than 1×10 -7Pa, after the purge, the sputtering power was set to 100 W, and the TiN film sputtering growth was started for 5 h; After the sputtering growth of the TiN film is completed, the RF power supply is turned off, the original N2 gas pressure is kept at 2.6 Pa, and the temperature is cooled at a rate of 10°C / min. When the temperature drops to 300°C, the temperature control power supply is turned off. After about 1 hour, the temperature is naturally cooled to room temperature, and the sample is taken out of the cavity to obtain a prefabricated sample with a TiN film deposited thereon; The prefabricated sample prepared in step (6) is placed in a muffle furnace for heat treatment at a heating rate of 5 °C / min until the temperature in the muffle furnace rises to 1000 °C and is kept at this temperature for 2 h; then the temperature is cooled to room temperature at a cooling rate of 4 °C / min to obtain a rhombohedral MgTiO3 film.

[0042] Example 2

[0043] This embodiment provides a magnesium titanate film, which is prepared by the following preparation method: (1) The Ti metal target was loaded onto the target gun of the magnetron sputtering system, and the MgO (100) single crystal substrate was ultrasonically cleaned in acetone and ethanol for 10 min respectively. After the ultrasonic cleaning, the MgO (100) single crystal substrate was blown dry with a nitrogen gun, and then the MgO (100) single crystal substrate was loaded into the sputtering chamber of the magnetron sputtering system; (2) Use mechanical pump and molecular pump to evacuate the sputtering chamber in turn, so that the vacuum degree in the sputtering chamber is ≤9×10 -8 Pa; (3) Turn on the heating power supply to heat the MgO (100) single crystal substrate, set the temperature to 1000 °C, the heating rate to 60 °C / min, and bake the single crystal substrate at 1000 °C for 20 min; (4) 99.999% high-purity N2 is introduced into the sputtering chamber to purge the chamber. When the pressure in the sputtering chamber reaches 200 Pa, the vacuum degree in the sputtering chamber is reduced to less than 1×10 -7 Pa, repeat the above operation to purge the sputtering chamber twice; (5) Introduce 99.999% high-purity N2 into the sputtering chamber, adjust the N2 flow rate to 2.5 sccm, and maintain the pressure in the sputtering chamber at 2.6 Pa; set the pre-sputtering power to 40 W, turn on the RF power supply to pre-sputter the Ti metal target for 30 min, and after the pre-sputtering, turn on the molecular pump and the vacuum chamber to purge the gas again, and draw the vacuum degree in the sputtering chamber to less than 1×10 -7 Pa Pa, after the gas purge, the sputtering power was set to 100 W, and the TiN film sputtering growth was started for 5 h; (6) After the sputtering growth of the TiN film is completed, the RF power supply is turned off, the original N2 gas pressure of 2.6 Pa is maintained unchanged, and the temperature is cooled at a rate of 10 °C / min. When the temperature drops to 400 °C, the temperature control power supply is turned off, and the temperature is allowed to naturally cool to room temperature. The sample is taken out of the cavity to obtain a prefabricated sample with a TiN film deposited thereon; (7) The prefabricated sample prepared in step (6) is placed in a muffle furnace for heat treatment at a heating rate of 3 °C / min until the temperature in the muffle furnace reaches 1000 °C and kept at that temperature for 1 h; then the temperature is cooled to room temperature at a cooling rate of 4 °C / min to obtain a rhombohedral MgTiO3 film.

[0044] Example 3

[0045] This embodiment provides a magnesium titanate film, which is prepared by the following preparation method: (1) The Ti metal target was loaded onto the target gun of the magnetron sputtering system, and the MgO (100) single crystal substrate was ultrasonically cleaned in acetone and ethanol for 10 min respectively. After the ultrasonic cleaning, the MgO (100) single crystal substrate was blown dry with a nitrogen gun, and then the MgO (100) single crystal substrate was loaded into the sputtering chamber of the magnetron sputtering system; (2) Use mechanical pump and molecular pump to evacuate the sputtering chamber in turn, so that the vacuum degree in the sputtering chamber is ≤9×10 -8 Pa; (3) Turn on the heating power supply to heat the MgO (100) single crystal substrate, set the temperature to 1000 °C, and the heating rate to 40 °C / min. The single crystal substrate is baked at 1000 °C for 15 min. (4) 99.999% high-purity N2 is introduced into the sputtering chamber to purge the chamber. When the pressure in the sputtering chamber reaches 200 Pa, the vacuum degree in the sputtering chamber is reduced to less than 1×10 -7 Pa, repeat the above operation to purge the sputtering chamber twice; (5) Introduce 99.999% high-purity N2 into the sputtering chamber, adjust the N2 flow rate to 2.5 sccm, and maintain the pressure in the sputtering chamber at 2 Pa; set the pre-sputtering power to 40 W, turn on the RF power supply to pre-sputter the Ti metal target for 30 min, and after the pre-sputtering, turn on the molecular pump and the vacuum chamber to purge the gas again, and draw the vacuum degree in the sputtering chamber to less than 1×10 -7 Pa Pa, after the gas purge, the sputtering power was set to 110 W, and the TiN film sputtering growth was started for 5 h; (6) After the sputtering growth of the TiN film is completed, the RF power supply is turned off, the original N2 gas pressure of 2 Pa is maintained unchanged, and the temperature is cooled at a rate of 30 °C / min. When the temperature drops to 200 °C, the temperature control power supply is turned off, and the temperature is naturally cooled to room temperature. The sample is taken out of the cavity to obtain a prefabricated sample with a TiN film deposited thereon; (7) The prefabricated sample prepared in step (6) is placed in a muffle furnace for heat treatment at a heating rate of 8 °C / min until the temperature in the muffle furnace rises to 900 °C and is kept at that temperature for 1 h; then the temperature is cooled to room temperature at a cooling rate of 6 °C / min to obtain a rhombohedral MgTiO3 film.

[0046] Example 4

[0047] This embodiment provides a magnesium titanate film, which is prepared by the following preparation method: (1) The Ti metal target was loaded onto the target gun of the magnetron sputtering system, and the MgO (100) single crystal substrate was ultrasonically cleaned in acetone and ethanol for 10 min respectively. After the ultrasonic cleaning, the MgO (100) single crystal substrate was blown dry with a nitrogen gun, and then the MgO (100) single crystal substrate was loaded into the sputtering chamber of the magnetron sputtering system; (2) Use mechanical pump and molecular pump to evacuate the sputtering chamber in turn, so that the vacuum degree in the sputtering chamber is ≤9×10 -8 Pa; (3) Turn on the heating power supply to heat the MgO (100) single crystal substrate, set the temperature to 1000 °C, the heating rate to 50 °C / min, and bake the single crystal substrate at 900 °C for 15 min; (4) 99.999% high-purity N2 is introduced into the sputtering chamber to purge the chamber. When the pressure in the sputtering chamber reaches 200 Pa, the vacuum degree in the sputtering chamber is reduced to less than 1×10 -7 Pa, repeat the above operation to purge the sputtering chamber twice; (5) Introduce 99.999% high-purity N2 into the sputtering chamber, adjust the N2 flow rate to 2.5 sccm, and maintain the pressure in the sputtering chamber at 2.6 Pa; set the pre-sputtering power to 40 W, turn on the RF power supply to pre-sputter the Ti metal target for 30 min, and after the pre-sputtering, turn on the molecular pump and the vacuum chamber to purge the gas again, and draw the vacuum degree in the sputtering chamber to less than 1×10 -7 Pa, after the purge, the sputtering power was set to 100 W, and the TiN film sputtering growth was started for 5 h; (6) After the sputtering growth of the TiN film is completed, the RF power supply is turned off, the original N2 gas pressure is kept unchanged at 2.6 Pa, and the temperature is cooled at a rate of 20 °C / min. When the temperature drops to 300 °C, the temperature control power supply is turned off, and the temperature is naturally cooled to room temperature. The sample is taken out of the cavity to obtain a prefabricated sample with a TiN film deposited thereon; (7) The prefabricated sample prepared in step (6) is placed in a muffle furnace for heat treatment at a heating rate of 5 °C / min until the temperature in the muffle furnace rises to 800 °C and is kept at that temperature for 1 h; then the temperature is cooled to room temperature at a cooling rate of 5 °C / min to obtain a rhombohedral MgTiO3 film.

[0048] Example 5

[0049] This embodiment provides a magnesium titanate film, which is prepared by the following preparation method: (1) The Ti metal target was loaded onto the target gun of the magnetron sputtering system, and the MgO (100) single crystal substrate was ultrasonically cleaned in acetone and ethanol for 10 min respectively. After the ultrasonic cleaning, the MgO (100) single crystal substrate was blown dry with a nitrogen gun, and then the MgO (100) single crystal substrate was loaded into the sputtering chamber of the magnetron sputtering system; (2) Use mechanical pump and molecular pump to evacuate the sputtering chamber in turn, so that the vacuum degree in the sputtering chamber is ≤9×10 -8 Pa; (3) Turn on the heating power supply to heat the MgO (100) single crystal substrate, set the temperature to 1000 °C, the heating rate to 45 °C / min, and bake the single crystal substrate at 950 °C for 15 min; (4) 99.999% high-purity N2 is introduced into the sputtering chamber to purge the chamber. When the pressure in the sputtering chamber reaches 200 Pa, the vacuum degree in the sputtering chamber is reduced to less than 1×10 -7 Pa Pa, repeat the above operation to purge the sputtering chamber twice; (5) Introduce 99.999% high-purity N2 into the sputtering chamber, adjust the N2 flow rate to 2.5 sccm, and maintain the pressure in the sputtering chamber at 2.6 Pa; set the pre-sputtering power to 40 W, turn on the RF power supply to pre-sputter the Ti metal target for 30 min, and after the pre-sputtering, turn on the molecular pump and the vacuum chamber to purge the gas again, and draw the vacuum degree in the sputtering chamber to less than 1×10 -7 Pa Pa, after the gas purge, the sputtering power was set to 100 W, and the TiN film sputtering growth was started for 5 h; (6) After the sputtering growth of the TiN film is completed, the RF power supply is turned off, the original N2 gas pressure of 2.6 Pa is maintained unchanged, and the temperature is cooled at a rate of 10 °C / min. When the temperature drops to 300 °C, the temperature control power supply is turned off, and the temperature is naturally cooled to room temperature. The sample is taken out of the cavity to obtain a prefabricated sample with a TiN film deposited thereon; (7) The prefabricated sample prepared in step (6) was placed in a muffle furnace for heat treatment at a heating rate of 6 °C / min until the temperature in the muffle furnace reached 750 °C and kept at that temperature for 24 h; then the temperature was cooled to room temperature at a cooling rate of 4 °C / min to obtain a rhombohedral MgTiO3 film.

[0050] Comparative Example 1 This comparative example provides a transparent film, which is prepared by the following preparation method: (1) The Ti metal target was loaded onto the target gun of the magnetron sputtering system, and the MgO (100) single crystal substrate was ultrasonically cleaned in acetone and ethanol for 10 min respectively. After the ultrasonic cleaning, the MgO (100) single crystal substrate was blown dry with a nitrogen gun, and then the MgO (100) single crystal substrate was loaded into the sputtering chamber of the magnetron sputtering system; (2) Use mechanical pump and molecular pump to evacuate the sputtering chamber in turn, so that the vacuum degree in the sputtering chamber is ≤9×10 -8 Pa; (3) Turn on the heating power supply to heat the MgO (100) single crystal substrate, set the temperature to 1000 °C, the heating rate to 60 °C / min, and bake the single crystal substrate at 1000 °C for 20 min; (4) 99.999% high-purity N2 is introduced into the sputtering chamber to purge the chamber. When the pressure in the sputtering chamber reaches 200 Pa, the vacuum degree in the sputtering chamber is reduced to less than 1×10 -7 Pa, repeat the above operation to purge the sputtering chamber twice; (5) Introduce 99.999% high-purity N2 into the sputtering chamber, adjust the N2 flow rate to 2.5 sccm, and maintain the gas pressure in the sputtering chamber at 2.6 Pa; set the pre-sputtering power to 40 W, turn on the RF power supply to pre-sputter the Ti metal target for 30 min, and after the pre-sputtering, turn on the molecular pump and the vacuum chamber to purge the gas again, and draw the vacuum degree in the sputtering chamber to less than 1×10 -7 Pa Pa, after the gas purge, the sputtering power was set to 100 W, and the TiN film sputtering growth was started for 5 h; (6) After the sputtering growth of the TiN film is completed, the RF power supply is turned off, the original N2 gas pressure of 2.6 Pa is maintained unchanged, and the temperature is cooled at a rate of 10 °C / min. When the temperature drops to 400 °C, the temperature control power supply is turned off, and the temperature is allowed to naturally cool to room temperature. The sample is taken out of the cavity to obtain a prefabricated sample with a TiN film deposited thereon; (7) The prefabricated sample prepared in step (6) was placed in a muffle furnace for heat treatment at a heating rate of 3 °C / min until the temperature in the muffle furnace reached 700 °C and kept at that temperature for 1 h; then the temperature was cooled to room temperature at a cooling rate of 4 °C / min to obtain a transparent film.

[0051] Comparative Example 2 This comparative example provides a transparent film, which is prepared by the following preparation method: (1) The Ti metal target was loaded onto the target gun of the magnetron sputtering system, and the MgO (100) single crystal substrate was ultrasonically cleaned in acetone and ethanol for 10 min respectively. After the ultrasonic cleaning, the MgO (100) single crystal substrate was blown dry with a nitrogen gun, and then the MgO (100) single crystal substrate was loaded into the sputtering chamber of the magnetron sputtering system; (2) Use mechanical pump and molecular pump to evacuate the sputtering chamber in turn, so that the vacuum degree in the sputtering chamber is ≤9×10 -8 Pa; (3) Turn on the heating power supply to heat the MgO (100) single crystal substrate, set the temperature to 1000 °C, the heating rate to 45 °C / min, and bake the single crystal substrate at 950 °C for 15 min; (4) 99.999% high-purity N2 is introduced into the sputtering chamber to purge the chamber. When the pressure in the sputtering chamber reaches 200 Pa, the vacuum degree in the sputtering chamber is reduced to less than 1×10 -7 Pa, repeat the above operation to purge the sputtering chamber twice; (5) Introduce 99.999% high-purity N2 into the sputtering chamber, adjust the N2 flow rate to 2.5 sccm, and maintain the pressure in the sputtering chamber at 2.6 Pa; set the pre-sputtering power to 40 W, turn on the RF power supply to pre-sputter the Ti metal target for 30 min, and after the pre-sputtering, turn on the molecular pump and the vacuum chamber to purge the gas again, and draw the vacuum degree in the sputtering chamber to less than 1×10 -7 Pa Pa, after the gas purge, the sputtering power was set to 100 W, and the TiN film sputtering growth was started for 5 h; (6) After the sputtering growth of the TiN film is completed, the RF power supply is turned off, the original N2 gas pressure of 2.6 Pa is maintained unchanged, and the temperature is cooled at a rate of 10 °C / min. When the temperature drops to 300 °C, the temperature control power supply is turned off, and the temperature is naturally cooled to room temperature. The sample is taken out of the cavity to obtain a prefabricated sample with a TiN film deposited thereon; (7) The prefabricated sample prepared in step (6) was placed in a muffle furnace for heat treatment at a heating rate of 6 °C / min until the temperature in the muffle furnace reached 600 °C and kept at that temperature for 24 h; then the temperature was cooled to room temperature at a cooling rate of 4 °C / min to obtain a transparent film.

[0052] Effect description: Figure 1 Schematic diagram of the crystal structure of the magnesium titanate thin film MgTiO3 prepared in Example 1. As can be seen from the figure, the MgTiO3 phase has a rhombohedral crystal structure.

[0053] Figure 2 The Raman spectra of the TiN film and the magnesium titanate film prepared in Example 1 are shown in FIG. As can be seen from the figure, the Raman spectra of the film change significantly before and after the heat treatment, and the Raman characteristic peak corresponding to TiN (100) is transformed into 10 Raman first-order active peaks of MgTiO3 with ilmenite structure.

[0054] Figure 3 The X-ray photoelectron spectra of the TiN film and the magnesium titanate film prepared in Example 1 are shown in FIG. Figure 3 The spectrum at the bottom is the X-ray photoelectron spectrum of the TiN film before heat treatment, located at Figure 3 The upper spectrum is the X-ray photoelectron spectrum of the magnesium titanate film prepared by heat treatment. It can be seen from the figure that except for the disappearance of the absorption peak of N before and after heat treatment, the absorption peak of Mg and the absorption peak intensity of O appear in the sample after heat treatment. In addition, the absorption peak intensity of Ti remains almost unchanged, indicating that TiN in the film is converted into magnesium titanate.

[0055] Figure 4 The transmission spectra of the TiN film and the magnesium titanate film prepared in Example 1 are shown in FIG. Figure 4 The spectrum at the bottom is the transmission spectrum of the TiN film before heat treatment. Figure 4 The upper spectrum is the transmission spectrum of the magnesium titanate film prepared by heat treatment. It can be seen that the transmittance of the magnesium titanate film after heat treatment increases significantly, changing from the low transmittance characteristics of TiN to a transparent magnesium titanate film.

[0056] Figure 5 The Raman spectra of the films prepared in Example 2 (1000°C, 1 h), Example 3 (900°C, 1 h), Example 4 (800°C, 1 h) and Comparative Example 1 (700°C, 1 h) are shown in FIG. As can be seen from the figure, after heat treatment for 1 h, rhombohedral MgTiO3 films were prepared in Examples 2, 3 and 4, while rhombohedral MgTiO3 films were not prepared in Comparative Example 1.

[0057] Figure 6The Raman spectra of the films prepared in Example 2 (1000°C, 1 h), Example 5 (750°C, 24 h) and Comparative Example 2 (600°C, 24 h) are shown in FIG. As can be seen from the figure, in Example 5, a rhombohedral MgTiO3 film can still be prepared after heat treatment at 750°C for 24 h; while in Comparative Example 2, a rhombohedral MgTiO3 film cannot be prepared after heat treatment at 600°C for 24 h.

[0058] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a magnesium titanate film, characterized in that: The following steps are involved: S1, depositing a TiN film on a magnesium oxide substrate by magnetron sputtering to obtain a prefabricated sample; S2. The prefabricated sample described in step S1 is subjected to heat treatment at a temperature of more than 750° C. and a time of more than 1 h to obtain a magnesium titanate film having a rhombohedral MgTiO 3 composition phase.

2. The method for preparing a magnesium titanate thin film according to claim 1, characterized in that: The magnesium oxide substrate described in step S1 is a magnesium oxide single crystal substrate or a magnesium oxide polycrystalline substrate; And / or, the temperature of the heat treatment in step S2 is 800-1000°C; And / or, the heating rate of the heat treatment in step S2 is 3-8°C / min; And / or, the cooling rate of the heat treatment in step S2 is 4-6°C / min.

3. The method for preparing a magnesium titanate thin film according to claim 2, characterized in that: The crystal orientation of the magnesium oxide single crystal substrate is (100).

4. The method for preparing a magnesium titanate thin film according to claim 1, characterized in that: The deposition of TiN film in step S1 includes sample loading, vacuuming, substrate heating, gas washing, sputtering deposition and cooling treatment in sequence.

5. The method for preparing a magnesium titanate thin film according to claim 4, characterized in that: The sample loading process is to load the Ti metal target into the target gun in the magnetron sputtering system, ultrasonically clean the magnesium oxide substrate in acetone and ethanol in sequence, blow dry the magnesium oxide substrate after the ultrasonic cleaning, and then load it into the sputtering chamber of the magnetron sputtering system.

6. The method for preparing a magnesium titanate thin film according to claim 5, characterized in that: The vacuuming process is to use a mechanical pump and a molecular pump to evacuate the sputtering chamber in sequence, so that the vacuum degree in the sputtering chamber is ≤9×10 -8 Pa; And / or, the heating rate adopted for heating the substrate is 40-60°C / min; And / or, the heating temperature used for heating the substrate is 800-1000° C.; And / or, the gas washing process is to introduce sputtering gas into the sputtering chamber until the pressure reaches 200 Pa, and then evacuate the sputtering chamber to a vacuum degree of ≤1×10 -7 Pa; And / or, the sputtering deposition process is to introduce sputtering gas into the sputtering chamber, use a radio frequency power supply to ignite the Ti metal target to generate plasma, pre-sputter the Ti metal target, purge the sputtering chamber after the pre-sputtering, and perform sputtering growth of the TiN film after the purge; And / or, the cooling process is to turn off the RF power supply, keep the gas pressure in the sputtering chamber unchanged, perform cooling treatment, cool to 200-400°C at a rate of 10-30°C / min, then turn off the temperature control power supply and cool to room temperature.

7. The method for preparing a magnesium titanate thin film according to claim 6, characterized in that: The sputtering gas is nitrogen; And / or, the sputtering growth time of the TiN film is more than 5 h; And / or, the gas pressure of the sputtering deposition is 2-3 Pa; And / or, the power of the radio frequency power supply is 95-110W.

8. The method for preparing a magnesium titanate thin film according to claim 6 or 7, characterized in that: The gas pressure of the sputtering deposition is 2.6 Pa; And / or, the power of the RF power supply is 100 W.

9. A magnesium titanate film, characterized in that: The magnesium titanate film is prepared by the method for preparing a magnesium titanate film according to any one of claims 1 to 8, and the constituent phase of the magnesium titanate film is rhombohedral MgTiO3.

10. Application of the magnesium titanate film according to claim 9 in the field of photoelectric detectors and ultraviolet detectors.

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