A preparation method of a dual-wavelength laser-induced periodic cerium oxide surface nanostructure

Abstract

The present invention relates to a method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure, which includes the process of pulsed laser depositing a cerium oxide thin film on a niobium-doped strontium titanate substrate; the process of introducing an ultraviolet-wavelength laser to irradiate and anneal the cerium oxide thin film to obtain a dense cerium oxide thin film; and the process of introducing an infrared-wavelength laser to induce the formation of periodic nanostructures on the surface of the dense cerium oxide thin film. The present invention has the advantage of improving the uniformity of the periodic nanostructures on the cerium oxide surface.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and particularly to a method for preparing a double-wavelength laser-induced periodic cerium oxide surface nanostructure. Background Art

[0002] Femtosecond lasers have a short pulse duration and high peak power. Compared with long-pulse lasers or continuous lasers, the pulse width of femtosecond lasers is much smaller than the electron-lattice relaxation time of the processed material. Electrons complete the absorption of photon energy before the lattice temperature rises. Therefore, during the processing, electrons and the lattice are in a non-equilibrium state, suppressing heat diffusion, thereby greatly reducing the heat-affected zone, decreasing the recast layer thickness, and reducing surface microcracks, ultimately achieving high-precision and high-quality processing of materials. Compared with nanosecond and other long-pulse lasers, femtosecond lasers can induce more regular and deeper periodic structures on different types of materials such as metals, semiconductors, dielectrics, and polymers without being affected by huge thermal effects. Laser-Induced Periodic Surface Structures (LIPSS) are the most characteristic micro-nano structures in laser micro-nano processing and have always been a research hotspot in the field of laser processing. However, the periodic structure of LIPSS changes significantly with the laser energy density and the number of overlapping pulses, making it more complex to determine the formation mechanism of LIPSS.

[0003] Cerium oxide (CeO2), as a special semiconductor material, has a special state due to the weak participation of Ce's 4+ 3d electrons in lattice formation. It has characteristics such as a simple structure, high dielectric constant, good thermal stability, and strong ability to capture / release electrons, enabling cerium oxide to occupy a place in semiconductor fields such as photocatalysis, sensors, energy storage, and conversion. Compared with semiconductors such as zinc sulfide, the valence band energy of cerium oxide is relatively high, and electrons are prone to transition under the action of an external electric field, forming Frenkel defects. At the same time, the surface morphology and micro-nano structure of the cerium oxide thin film have a crucial impact on its performance. The method for forming periodic nanostructures on the surface of the cerium oxide thin film usually includes the following steps: first, depositing the cerium oxide thin film by pulsed laser deposition, and then using femtosecond lasers to induce the formation of periodic nanostructures. However, this method is prone to interface structure defects such as lattice distortion and dislocations during the film deposition process, and the step-by-step process and the atmospheric environment are also likely to affect the cerium oxide thin film, resulting in poor consistency of the periodic nanostructures.

[0004] Chinese Patent No. CN118455713A discloses a dual-pulse laser processing method based on infrared femtosecond and ultraviolet femtosecond lasers. The specific steps of this method are as follows: (1): Configure a dual-pulse laser processing system. The center wavelength of the infrared femtosecond laser is 1030 nm, and the center wavelength of the ultraviolet femtosecond laser is 342 nm. (2): Start the femtosecond laser processing system and adjust the laser optical path. Fix a silicon wafer on a three-dimensional moving platform for positioning and adjusting the optical path. Set the parameters of the infrared femtosecond laser and the ultraviolet femtosecond laser respectively. Use a CCD camera to observe the silicon wafer to ensure the coincidence of the infrared-wavelength laser and the ultraviolet-wavelength laser. (3): Adjust the propagation path of the ultraviolet femtosecond laser with a one-dimensional moving platform to ensure an appropriate pulse delay for the femtosecond laser dual pulses. (4): Prepare a zinc sulfide workpiece to be processed and fix the zinc sulfide sample to be processed in the working area of the three-dimensional motion platform. (5): Set the processing parameters of the infrared femtosecond laser and the ultraviolet femtosecond laser, and turn on the dual-pulse laser processing system to perform laser processing. (6): Drive the workpiece to move at a certain speed by controlling the three-dimensional moving platform, and the dual-pulse laser periodically ablates the workpiece surface. (7): Clean and dry the prepared zinc sulfide workpiece to obtain a zinc sulfide surface antireflection microstructure.

[0005] In the above method, the infrared femtosecond laser and the ultraviolet femtosecond laser are carried out on one processing platform. The infrared femtosecond laser has high energy and can effectively ablate zinc sulfide materials, improving the overall processing efficiency and facilitating large-scale processing. The ultraviolet femtosecond laser performs secondary ablation on the surface of the workpiece to obtain a smooth and flat processing surface. The existing technical solutions have the following defects: For forming periodic nanostructures on the surface of cerium oxide thin films, it is difficult to precisely control the size and shape of the nanostructures by the above method, and it is difficult to balance the energy distribution of the infrared femtosecond laser and the ultraviolet femtosecond laser during the processing, which may lead to unstable processing quality. In addition, although zinc sulfide materials are suitable for this processing method, the physical and chemical properties of cerium oxide thin films are different from those of zinc sulfide, making it more challenging to fabricate periodic nanostructures on cerium oxide thin films. Therefore, a more precise and efficient method for fabricating periodic nanostructures by dual-wavelength lasers is needed to meet the requirement of forming high-quality periodic nanostructures on the surface of cerium oxide thin films. Summary of the Invention

[0006] The problem to be solved by the present invention is to provide a method for fabricating periodic nanostructures on the surface of cerium oxide by dual-wavelength laser induction, which has the advantages of improving the uniformity of periodic nanostructures on the surface of cerium oxide and reducing surface defects in view of the above deficiencies in the prior art.

[0007] The above object of the present invention is achieved by the following technical solutions:

[0008] A method for preparing a dual-wavelength laser-induced periodic nanostructure on the surface of cerium oxide, comprising:

[0009] The process of pulsed laser depositing a cerium oxide thin film on a niobium-doped strontium titanate substrate;

[0010] The process of introducing an ultraviolet-wavelength laser to irradiate and anneal the cerium oxide thin film to obtain a dense cerium oxide thin film;

[0011] And the process of introducing an infrared-wavelength laser to induce the formation of periodic nanostructures on the surface of the dense cerium oxide thin film.

[0012] Further, in the process of pulsed laser depositing a cerium oxide thin film on a niobium-doped strontium titanate substrate, the pulsed laser is an ultraviolet excimer laser with a wavelength of 248 nm.

[0013] Further, in the process of pulsed laser depositing a cerium oxide thin film on a niobium-doped strontium titanate substrate, the laser energy density is controlled to be 1.4 - 1.8 J / cm 2 , the laser pulse frequency is 5 - 15 Hz, the oxygen pressure in the cavity is 10 - 100 mTorr, the target heating temperature of the niobium-doped strontium titanate substrate is 300 - 700 °C, the number of laser pulses is 5000 - 10000, and the distance between the target in the cavity and the niobium-doped strontium titanate substrate is 6.5 cm.

[0014] Further, in the process of pulsed laser depositing a cerium oxide thin film on a niobium-doped strontium titanate substrate, the laser beam irradiates the cerium oxide target to generate high-energy-density laser pulses, forcing the surface of the cerium oxide target to evaporate rapidly to form a plasma plume, and the cerium atoms, ions, and molecules in the plasma plume migrate to the surface of the niobium-doped strontium titanate substrate under the action of an electric field and a magnetic field and deposit on the surface of the niobium-doped strontium titanate substrate to form a cerium oxide thin film.

[0015] Further, in the process of introducing an ultraviolet-wavelength laser to irradiate and anneal the cerium oxide thin film, the ultraviolet-wavelength laser is an ultraviolet excimer laser with a wavelength of 248 nm.

[0016] Further, in the process of introducing an ultraviolet-wavelength laser to irradiate and anneal the cerium oxide thin film, the laser energy density is controlled to be 0.8 - 1.2 J / cm 2 , the laser pulse frequency is 5 - 15 Hz, and the annealing time is 10 - 60 min.

[0017] Further, in the process of introducing an ultraviolet-wavelength laser to irradiate and anneal the cerium oxide thin film, the scanning path of the ultraviolet-wavelength laser is Z-shaped, and the filling pitch is 1 μm, so that the ultraviolet laser beam can uniformly irradiate the surface of the cerium oxide thin film, quickly absorb energy and heat up, and after the irradiation and annealing are completed, it is naturally cooled to room temperature.

[0018] Further, during the process of introducing an infrared wavelength laser to induce the formation of periodic nanostructures on the surface of the dense cerium oxide thin film, the infrared wavelength laser is a femtosecond laser with a wavelength of 1064 nm.

[0019] Further, during the process of introducing an infrared wavelength laser to induce the formation of periodic nanostructures on the surface of the dense cerium oxide thin film, the single pulse energy is controlled to be 1.4 - 1.8 J / cm 2 , the pulse frequency is 50 - 150 kHz, and the scanning speed is 10 - 30 mm / s.

[0020] Further, during the process of introducing an infrared wavelength laser to induce the formation of periodic nanostructures on the surface of the dense cerium oxide thin film, the scanning path of the infrared wavelength laser is Z-shaped, and the filling pitch is 1 μm.

[0021] In summary, the beneficial technical effects of the present invention are as follows:

[0022] 1. Through the synergistic effect of pulsed laser deposition technology and ultraviolet laser in-situ annealing technology, the present invention realizes the cross-scale regulation of the defect states of epitaxial thin films; during the growth process of the cerium oxide thin film, the repair of lattice defects and the reconstruction of the stress field are carried out synchronously; through selective photon excitation of the deposited thin film by ultraviolet wavelength laser, an epitaxial dense cerium oxide thin film is successfully prepared, providing a highly consistent substrate for the subsequent growth of laser-induced surface periodic nanostructures;

[0023] 2. The present invention innovatively constructs a full-process integrated process in a vacuum environment, adopts an in-situ cooperative processing mode of dual-wavelength cooperative lasers in the vacuum chamber of a pulsed laser deposition device, and realizes the continuous protection of the vacuum environment from thin film deposition to periodic nanostructure induction through the closed-loop design of the process chain of ultraviolet annealing - infrared forming; compared with the traditional step-by-step processing in the atmospheric environment, this technology significantly shortens the process cycle, avoids surface contamination caused by sample exposure, and makes the periodic uniformity of the induced nanostructures higher, significantly improving the reliability of the surface function of the device;

[0024] 3. During pulsed laser deposition, the present invention introduces an in-situ ultraviolet laser annealing technology to regulate the lattice defects and stress distribution of the cerium oxide thin film, thereby improving the interfacial structural defects of the thin film; at the same time, the present invention uses an infrared laser to synchronously induce surface periodic nanostructures, avoiding the interfacial defect problems easily generated in traditional step-by-step processes to improve the uniformity of the surface periodic nanostructures of cerium oxide. Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of the pulsed laser deposition device in Example 2 of the present invention during pulsed laser deposition.

[0026] Figure 2 It is a schematic structural diagram of the pulsed laser deposition equipment in Example 2 of the present invention during the ultraviolet wavelength laser annealing and infrared wavelength laser induction processes.

[0027] Figure 3 It is a schematic diagram of the scanning path of the laser beam in Example 2 of the present invention.

[0028] Figure 4 It is a scanning electron microscope schematic diagram of the periodic cerium oxide surface nanostructure prepared in Example 2 of the present invention.

[0029] Figure 5 It is a scanning electron microscope schematic diagram of the periodic cerium oxide surface nanostructure prepared in Comparative Example 1 of the present invention.

[0030] Figure 6 It is a scanning electron microscope schematic diagram of the periodic cerium oxide surface nanostructure prepared in Comparative Example 2 of the present invention. Detailed implementation manners

[0031] In order to make the technical means, creative features, achieved purposes and functions of the present invention clearer and easier to understand, the present invention will be further described below in conjunction with the drawings and specific implementation manners.

[0032] Example 1: A method for preparing a periodic cerium oxide surface nanostructure induced by dual-wavelength lasers disclosed in the present invention includes

[0033] The process of pulsed laser depositing a cerium oxide thin film on a niobium-doped strontium titanate substrate;

[0034] The process of irradiating and annealing the cerium oxide thin film with ultraviolet wavelength laser to obtain a dense cerium oxide thin film;

[0035] And the process of introducing an infrared wavelength laser to induce the formation of periodic nanostructures on the surface of the dense cerium oxide thin film.

[0036] Example 2: A method for preparing a periodic cerium oxide surface nanostructure induced by dual-wavelength lasers disclosed in the present invention, which is different from Example 1 in that it includes the following steps

[0037] S1 Refer to Figure 1 , first place the niobium-doped strontium titanate substrate in ethanol solution and deionized water in sequence, ultrasonically clean for 10 min to remove the residues and impurities on its surface, then install the cleaned niobium-doped strontium titanate substrate on the sample stage of the vacuum chamber of the pulsed laser deposition equipment, and install the cerium oxide target in the target holder; then adjust the equipment parameters: the laser energy density is 1.6 J / cm 2, the laser pulse frequency is 5 Hz, the oxygen pressure inside the cavity is 10 mTorr, the target heating temperature of the strontium titanate niobate substrate is 500 °C, the number of laser pulses is 7500, and the distance between the target material and the strontium titanate niobate substrate inside the cavity is 6.5 cm; then, an ultraviolet excimer laser with a wavelength of 248 nm is used as the pulsed laser, and the pulsed laser beam irradiates the cerium oxide target material to generate a laser pulse with a high energy density, forcing the surface of the cerium oxide target material to evaporate rapidly to form a plasma plume. Moreover, the cerium oxide atoms, ions, and molecules in the plasma plume migrate towards the surface of the strontium titanate niobate substrate under the action of an electric field and a magnetic field, and are deposited on the surface of the strontium titanate niobate substrate to form a thin film. With the continuous action of the laser pulse, the thin film gradually grows until it reaches the target thickness, and a cerium oxide thin film is obtained;

[0038] S2 reference Figure 2 and Figure 3 , after the deposition of the cerium oxide thin film is completed, ultraviolet wavelength laser with a wavelength of 248 nm is introduced into the vacuum chamber for irradiation annealing to regulate the lattice defects and stress distribution of the cerium oxide thin film, and the equipment parameters are adjusted: the laser energy density is 1.0 J / cm 2 , the laser pulse frequency is 5 Hz, and the annealing time is 10 min; at the same time, the sample stage is rotated to adjust the relative position between the cerium oxide thin film and the ultraviolet laser beam, and the scanning path of the ultraviolet wavelength laser is set as a Z shape with a filling pitch of 1 μm, so that the ultraviolet laser beam can evenly irradiate the surface of the cerium oxide thin film, quickly absorb energy and heat up. After the irradiation annealing is completed, it is naturally cooled to room temperature to obtain a dense cerium oxide thin film;

[0039] S3 reference Figure 2 and Figure 3 , after the irradiation annealing is completed, femtosecond laser with a wavelength of 1064 nm is introduced into the vacuum chamber to induce periodic nanostructures, and the equipment parameters are adjusted: the single pulse energy is 1.6 J / cm 2 , the pulse frequency is 100 kHz, and the scanning speed is 20 mm / s; at the same time, the sample stage is rotated to adjust the relative position between the cerium oxide thin film and the infrared laser beam, and the scanning path of the infrared wavelength laser is set as a Z shape with a filling pitch of 1 μm. The femtosecond laser single pulse is focused on the surface of the dense cerium oxide thin film that has completed annealing through an optical objective lens; the infrared laser beam is focused on the surface of the dense cerium oxide thin film, exciting the surface plasmon polaritons on the surface of the dense cerium oxide thin film. The surface plasmon polaritons on the surface of the dense cerium oxide thin film interact with the incident infrared laser beam, resulting in the concentration of laser energy in the local area on the surface of the dense cerium oxide thin film, thereby increasing the temperature and pressure in these areas, and finally forming periodic surface nanostructures.

[0040] Figure 4The scanning electron microscope image of the dual-wavelength laser-induced periodic cerium oxide surface nanostructure prepared in Example 2 of the present invention is shown. Annealing and preparation of periodic nanoscale stripe structures are carried out in a vacuum chamber, and the cerium oxide surface shows uniform periodic nanostructures and is pollution-free on the surface.

[0041] Example 3: A method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure disclosed in the present invention, which is different from Example 1 in that it includes the following steps:

[0042] S1 First, the niobium-doped strontium titanate substrate is successively placed in an ethanol solution and deionized water, and ultrasonically cleaned for 10 min to remove the residues and impurities on its surface. Then, the cleaned niobium-doped strontium titanate substrate is installed on the sample stage in the vacuum chamber of the pulsed laser deposition equipment, and the cerium oxide target is installed in the target holder. Then, the equipment parameters are adjusted: the laser energy density is 1.4 J / cm 2 , the laser pulse frequency is 10 Hz, the oxygen pressure in the chamber is 50 mTorr, the target heating temperature of the niobium-doped strontium titanate substrate is 300 °C, the number of laser pulses is 5000, and the distance between the target and the niobium-doped strontium titanate substrate in the chamber is 6.5 cm. Then, a pulsed laser with a wavelength of 248 nm ultraviolet excimer laser is used, and the pulsed laser beam irradiates the cerium oxide target to generate high-energy-density laser pulses to force the rapid evaporation of the surface of the cerium oxide target, forming a plasma plume. And the cerium oxide atoms, ions and molecules in the plasma plume migrate to the surface of the niobium-doped strontium titanate substrate under the action of the electric field and magnetic field, and are deposited on the surface of the niobium-doped strontium titanate substrate to form a thin film. With the continuous action of the laser pulses, the thin film gradually grows until the target thickness is reached, and a cerium oxide thin film is obtained;

[0043] S2 After the deposition of the cerium oxide thin film is completed, ultraviolet wavelength laser with a wavelength of 248 nm ultraviolet excimer laser is introduced in the vacuum chamber for irradiation annealing to regulate the lattice defects and stress distribution of the cerium oxide thin film. The equipment parameters are adjusted: the laser energy density is 1.0 J / cm 2 , the laser pulse frequency is 5 Hz, and the annealing time is 10 min. At the same time, the sample stage is rotated to adjust the relative position between the cerium oxide thin film and the ultraviolet laser beam, and the scanning path of the ultraviolet wavelength laser is set as a Z shape, and the filling pitch is 1 μm, so that the ultraviolet laser beam can evenly irradiate the surface of the cerium oxide thin film, quickly absorb energy and heat up. After the irradiation annealing is completed, it is naturally cooled to room temperature to obtain a dense cerium oxide thin film;

[0044] S3 After the irradiation annealing is completed, a femtosecond laser with a wavelength of 1064 nm is introduced in the vacuum chamber to induce periodic nanostructures. The equipment parameters are adjusted: the single-pulse energy is 1.6 J / cm 2, the pulse frequency is 100 kHz and the scanning speed is 20 mm / s; at the same time, rotate the sample stage, adjust the relative position between the cerium oxide film and the infrared laser beam, set the scanning path of the infrared wavelength laser to be Z-shaped, the filling pitch is 1 μm, and focus the single pulse of femtosecond laser on the surface of the annealed dense cerium oxide film through an optical objective lens; the infrared laser beam is focused on the surface of the dense cerium oxide film, exciting the surface plasmon polaritons on the surface of the dense cerium oxide film. The surface plasmon polaritons on the surface of the dense cerium oxide film interact with the incident infrared laser beam, resulting in the concentration of laser energy in the local area on the surface of the dense cerium oxide film, thereby increasing the temperature and pressure in these areas, and finally forming periodic surface nanostructures.

[0045] Example 4: A method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure disclosed in the present invention, which is different from Example 1 in that it includes the following steps.

[0046] S1 First, put the niobium-doped strontium titanate substrate into ethanol solution and deionized water in sequence, ultrasonically clean it for 10 min to remove the residues and impurities on its surface, then install the cleaned niobium-doped strontium titanate substrate on the sample stage in the vacuum chamber of the pulsed laser deposition equipment, and install the cerium oxide target in the target holder; then adjust the equipment parameters: the laser energy density is 1.8 J / cm 2 , the laser pulse frequency is 15 Hz, the oxygen pressure in the chamber is 100 mTorr, the target heating temperature of the niobium-doped strontium titanate substrate is 700 °C, the number of laser pulses is 10,000, and the distance between the target and the niobium-doped strontium titanate substrate in the chamber is 6.5 cm; then use a pulsed laser with a wavelength of 248 nm ultraviolet excimer laser, and the pulsed laser beam irradiates the cerium oxide target to generate a laser pulse with a high energy density, forcing the surface of the cerium oxide target to evaporate rapidly to form a plasma plume, and the cerium oxide atoms, ions and molecules in the plasma plume migrate to the surface of the niobium-doped strontium titanate substrate under the action of the electric field and magnetic field, and deposit on the surface of the niobium-doped strontium titanate substrate to form a film. With the continuous action of the laser pulse, the film gradually grows until it reaches the target thickness to obtain a cerium oxide film.

[0047] S2 After the deposition of the cerium oxide film is completed, introduce a ultraviolet wavelength laser in the vacuum chamber for irradiation annealing with a wavelength of 248 nm ultraviolet excimer laser to regulate the lattice defects and stress distribution of the cerium oxide film, and adjust the equipment parameters: the laser energy density is 1.0 J / cm 2, the laser pulse frequency is 5 Hz, and the annealing time is 10 min; at the same time, rotate the sample stage, adjust the relative position of the cerium oxide thin film and the ultraviolet laser beam, set the scanning path of the ultraviolet wavelength laser to be Z-shaped, and the filling pitch is 1 μm, so that the ultraviolet laser beam can uniformly irradiate the surface of the cerium oxide thin film, quickly absorb energy and heat up. After the irradiation is completed and annealed, it is naturally cooled to room temperature to obtain a dense cerium oxide thin film;

[0048] S3 After the irradiation annealing is completed, introduce femtosecond laser-induced periodic nanostructures with a wavelength of 1064 nm in the vacuum chamber, and adjust the equipment parameters: the single-pulse energy is 1.6 J / cm 2 , the pulse frequency is 100 kHz, and the scanning speed is 20 mm / s; at the same time, rotate the sample stage, adjust the relative position of the cerium oxide thin film and the infrared laser beam, set the scanning path of the infrared wavelength laser to be Z-shaped, and the filling pitch is 1 μm. Focus the femtosecond laser single pulse on the surface of the annealed dense cerium oxide thin film through an optical objective lens; the infrared laser beam is focused on the surface of the dense cerium oxide thin film to excite the surface plasmon polaritons of the dense cerium oxide thin film. The surface plasmon polaritons of the dense cerium oxide thin film interact with the incident infrared laser beam, resulting in the concentration of laser energy in the local area on the surface of the dense cerium oxide thin film, thereby increasing the temperature and pressure in these areas, and finally forming periodic surface nanostructures.

[0049] Example 5: A method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure disclosed in the present invention is different from Example 1 in that it includes the following steps

[0050] S1 First, put the niobium-doped strontium titanate substrate into ethanol solution and deionized water in sequence, ultrasonically clean for 10 min to remove the residues and impurities on its surface, and then install the cleaned niobium-doped strontium titanate substrate on the sample stage in the vacuum chamber of the pulsed laser deposition equipment, and install the cerium oxide target in the target holder; then adjust the equipment parameters: the laser energy density is 1.6 J / cm 2 , the laser pulse frequency is 5 Hz, the oxygen pressure in the chamber is 10 mTorr, the target heating temperature of the niobium-doped strontium titanate substrate is 500 °C, the number of laser pulses is 7500, and the distance between the target and the niobium-doped strontium titanate substrate in the chamber is 6.5 cm; then use a 248-nm ultraviolet excimer laser as the pulsed laser, and the pulsed laser beam irradiates the cerium oxide target to generate high-energy-density laser pulses to force the rapid evaporation of the surface of the cerium oxide target to form a plasma plume. And the cerium atoms, ions and molecules in the plasma plume migrate to the surface of the niobium-doped strontium titanate substrate under the action of the electric field and magnetic field, and are deposited on the surface of the niobium-doped strontium titanate substrate to form a thin film. With the continuous action of the laser pulses, the thin film gradually grows until it reaches the target thickness to obtain a cerium oxide thin film;

[0051] After the deposition of the cerium oxide thin film is completed, an ultraviolet wavelength laser with a wavelength of 248 nm, i.e., an ultraviolet excimer laser, is introduced into the vacuum chamber for irradiation annealing to regulate the lattice defects and stress distribution of the cerium oxide thin film. Adjust the equipment parameters: the laser energy density is 0.8 J / cm 2 , the laser pulse frequency is 10 Hz, and the annealing time is 10 min; at the same time, rotate the sample stage, adjust the relative position of the cerium oxide thin film and the ultraviolet laser beam, set the scanning path of the ultraviolet wavelength laser to be Z-shaped, and the filling pitch is 1 μm, so that the ultraviolet laser beam can evenly irradiate the surface of the cerium oxide thin film, quickly absorb energy and heat up. After the irradiation annealing is completed, it is naturally cooled to room temperature to obtain a dense cerium oxide thin film;

[0052] After the irradiation annealing is completed, a femtosecond laser with a wavelength of 1064 nm is introduced into the vacuum chamber to induce periodic nanostructures. Adjust the equipment parameters: the single-pulse energy is 1.6 J / cm 2 , the pulse frequency is 100 kHz, and the scanning speed is 20 mm / s; at the same time, rotate the sample stage, adjust the relative position of the cerium oxide thin film and the infrared laser beam, set the scanning path of the infrared wavelength laser to be Z-shaped, and the filling pitch is 1 μm. Focus the femtosecond laser single pulse on the surface of the dense cerium oxide thin film that has completed annealing through an optical objective lens; the infrared laser beam is focused on the surface of the dense cerium oxide thin film, exciting the surface plasmon polaritons on the surface of the dense cerium oxide thin film. The surface plasmon polaritons on the surface of the dense cerium oxide thin film interact with the incident infrared laser beam, resulting in the concentration of laser energy in the local area on the surface of the dense cerium oxide thin film, thereby increasing the temperature and pressure in these areas, and finally forming periodic surface nanostructures.

[0053] Example 6: A method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure disclosed in the present invention is different from Example 1 in that it includes the following steps,

[0054] First, the niobium-doped strontium titanate substrate is successively placed in an ethanol solution and deionized water, and ultrasonically cleaned for 10 min to remove the residues and impurities on its surface. Then, the cleaned niobium-doped strontium titanate substrate is installed on the sample stage in the vacuum chamber of the pulsed laser deposition equipment, and the cerium oxide target is installed in the target holder; then adjust the equipment parameters: the laser energy density is 1.6 J / cm 2, the laser pulse frequency is 5 Hz, the oxygen pressure in the cavity is 10 mTorr, the target heating temperature of the strontium titanate niobate substrate is 500 °C, the number of laser pulses is 7500, and the distance between the target material and the strontium titanate niobate substrate in the cavity is 6.5 cm; then, an ultraviolet excimer laser with a wavelength of 248 nm is used as the pulsed laser, and the pulsed laser beam is irradiated on the cerium oxide target material to generate laser pulses with a high energy density, forcing the surface of the cerium oxide target material to evaporate rapidly to form a plasma plume, and the cerium oxide atoms, ions and molecules in the plasma plume migrate to the surface of the strontium titanate niobate substrate under the action of the electric field and magnetic field, and are deposited on the surface of the strontium titanate niobate substrate to form a thin film. With the continuous action of the laser pulses, the thin film gradually grows until it reaches the target thickness, and a cerium oxide thin film is obtained;

[0055] After the deposition of the cerium oxide thin film is completed, an ultraviolet wavelength laser with a wavelength of 248 nm is introduced into the vacuum cavity for irradiation annealing to regulate the lattice defects and stress distribution of the cerium oxide thin film, and the equipment parameters are adjusted: the laser energy density is 1.2 J / cm 2 , the laser pulse frequency is 15 Hz, and the annealing time is 60 min; at the same time, the sample stage is rotated to adjust the relative position between the cerium oxide thin film and the ultraviolet laser beam, and the scanning path of the ultraviolet wavelength laser is set as a zigzag shape, and the filling spacing is 1 μm, so that the ultraviolet laser beam can uniformly irradiate the surface of the cerium oxide thin film, quickly absorb energy and heat up. After the irradiation annealing is completed, it is naturally cooled to room temperature to obtain a dense cerium oxide thin film;

[0056] After the irradiation annealing is completed, a femtosecond laser with a wavelength of 1064 nm is introduced into the vacuum cavity to induce periodic nanostructures, and the equipment parameters are adjusted: the single pulse energy is 1.6 J / cm 2 , the pulse frequency is 100 kHz, and the scanning speed is 20 mm / s; at the same time, the sample stage is rotated to adjust the relative position between the cerium oxide thin film and the infrared laser beam, and the scanning path of the infrared wavelength laser is set as a zigzag shape, and the filling spacing is 1 μm. The femtosecond laser single pulse is focused on the surface of the annealed dense cerium oxide thin film through an optical objective lens; the infrared laser beam is focused on the surface of the dense cerium oxide thin film to excite the surface plasmon polaritons of the dense cerium oxide thin film. The surface plasmon polaritons of the dense cerium oxide thin film interact with the incident infrared laser beam, resulting in the concentration of laser energy in the local area of the surface of the dense cerium oxide thin film, thereby increasing the temperature and pressure in these areas and finally forming periodic surface nanostructures.

[0057] Example 7: A method for preparing periodic cerium oxide surface nanostructures induced by dual-wavelength lasers disclosed in the present invention is different from Example 1 in that it includes the following steps,

[0058] S1 First, put the strontium niobate titanate substrate into ethanol solution and deionized water in sequence, and ultrasonically clean it for 10 min to remove the residues and impurities on its surface. Then, install the cleaned strontium niobate titanate substrate on the sample stage in the vacuum chamber of the pulsed laser deposition equipment, and install the cerium oxide target in the target holder. Then, adjust the equipment parameters: the laser energy density is 1.6 J / cm 2 , the laser pulse frequency is 5 Hz, the oxygen pressure in the chamber is 10 mTorr, the target heating temperature of the strontium niobate titanate substrate is 500 °C, the number of laser pulses is 7500, and the distance between the target and the strontium niobate titanate substrate in the chamber is 6.5 cm. Then, use the ultraviolet excimer laser with a wavelength of 248 nm as the pulsed laser. The pulsed laser beam irradiates on the cerium oxide target to generate laser pulses with high energy density, forcing the surface of the cerium oxide target to evaporate rapidly to form a plasma plume. And the cerium atoms, ions and molecules in the plasma plume migrate towards the surface of the strontium niobate titanate substrate under the action of the electric field and magnetic field, and deposit on the surface of the strontium niobate titanate substrate to form a thin film. With the continuous action of the laser pulses, the thin film gradually grows until it reaches the target thickness, and a cerium oxide thin film is obtained;

[0059] S2 After the deposition of the cerium oxide thin film is completed, introduce ultraviolet wavelength laser in the vacuum chamber for irradiation annealing with a wavelength of 248 nm ultraviolet excimer laser to regulate the lattice defects and stress distribution of the cerium oxide thin film. Adjust the equipment parameters: the laser energy density is 1.0 J / cm 2 , the laser pulse frequency is 5 Hz, and the annealing time is 10 min. At the same time, rotate the sample stage to adjust the relative position between the cerium oxide thin film and the ultraviolet laser beam, and set the scanning path of the ultraviolet wavelength laser as Z-shaped with a filling pitch of 1 μm, so that the ultraviolet laser beam can uniformly irradiate the surface of the cerium oxide thin film, quickly absorb energy and heat up. After the irradiation annealing is completed, it is naturally cooled to room temperature to obtain a dense cerium oxide thin film;

[0060] S3 After the irradiation annealing is completed, introduce femtosecond laser with a wavelength of 1064 nm in the vacuum chamber to induce periodic nanostructures. Adjust the equipment parameters: the single pulse energy is 1.4 J / cm 2 , the pulse frequency is 50 kHz, and the scanning speed is 10 mm / s. At the same time, rotate the sample stage to adjust the relative position between the cerium oxide thin film and the infrared laser beam, and set the scanning path of the infrared wavelength laser as Z-shaped with a filling pitch of 1 μm. Focus the femtosecond laser single pulse on the surface of the annealed dense cerium oxide thin film through the optical objective lens. The infrared laser beam is focused on the surface of the dense cerium oxide thin film to excite the surface plasmon polaritons on the surface of the dense cerium oxide thin film. The surface plasmon polaritons on the surface of the dense cerium oxide thin film interact with the incident infrared laser beam, resulting in the concentration of laser energy in the local area on the surface of the dense cerium oxide thin film, so that the temperature and pressure in these areas increase, and finally periodic surface nanostructures are formed.

[0061] Example 8: A method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure disclosed in the present invention, which is different from Example 1 in that it includes the following steps:

[0062] S1 First, the niobium-doped strontium titanate substrate is successively placed in an ethanol solution and deionized water, ultrasonically cleaned for 10 min to remove residues and impurities on its surface. Then, the cleaned niobium-doped strontium titanate substrate is installed on the sample stage in the vacuum chamber of the pulsed laser deposition equipment, and the cerium oxide target is installed in the target holder. Then, the equipment parameters are adjusted: the laser energy density is 1.6 J / cm 2 , the laser pulse frequency is 5 Hz, the oxygen pressure in the chamber is 10 mTorr, the target heating temperature of the niobium-doped strontium titanate substrate is 500 °C, the number of laser pulses is 7500, and the distance between the target and the niobium-doped strontium titanate substrate in the chamber is 6.5 cm. Then, an ultraviolet excimer laser with a wavelength of 248 nm is used as the pulsed laser. The pulsed laser beam irradiates the cerium oxide target to generate a high-energy-density laser pulse, forcing the surface of the cerium oxide target to evaporate rapidly to form a plasma plume. And the cerium oxide atoms, ions, and molecules in the plasma plume migrate towards the surface of the niobium-doped strontium titanate substrate under the action of the electric and magnetic fields, and are deposited on the surface of the niobium-doped strontium titanate substrate to form a thin film. With the continuous action of the laser pulse, the thin film gradually grows until it reaches the target thickness, and a cerium oxide thin film is obtained;

[0063] S2 After the deposition of the cerium oxide thin film is completed, ultraviolet wavelength laser with a wavelength of 248 nm is introduced into the vacuum chamber for irradiation annealing to regulate the lattice defects and stress distribution of the cerium oxide thin film. The equipment parameters are adjusted: the laser energy density is 1.0 J / cm 2 , the laser pulse frequency is 5 Hz, and the annealing time is 10 min. At the same time, the sample stage is rotated to adjust the relative position between the cerium oxide thin film and the ultraviolet laser beam. The scanning path of the ultraviolet wavelength laser is set as a Z-shape, and the filling pitch is 1 μm, so that the ultraviolet laser beam can uniformly irradiate the surface of the cerium oxide thin film, quickly absorb energy and heat up. After the irradiation annealing is completed, it is naturally cooled to room temperature to obtain a dense cerium oxide thin film;

[0064] S3 After the irradiation annealing is completed, a femtosecond laser with a wavelength of 1064 nm is introduced into the vacuum chamber to induce periodic nanostructures. The equipment parameters are adjusted: the single-pulse energy is 1.8 J / cm 2, the pulse frequency is 150 kHz and the scanning speed is 30 mm / s; at the same time, rotate the sample stage, adjust the relative position between the cerium oxide thin film and the infrared laser beam, set the scanning path of the infrared wavelength laser to be Z-shaped, the filling pitch is 1 μm, and focus the femtosecond laser single pulse on the surface of the annealed dense cerium oxide thin film through an optical objective lens; the infrared laser beam is focused on the surface of the dense cerium oxide thin film to excite the surface plasmon polaritons on the surface of the dense cerium oxide thin film. The surface plasmon polaritons on the surface of the dense cerium oxide thin film interact with the incident infrared laser beam, resulting in the concentration of laser energy in the local area on the surface of the dense cerium oxide thin film, thereby increasing the temperature and pressure in these areas, and finally forming periodic surface nanostructures.

[0065] Comparative Example 1: A method for preparing a dual-wavelength laser-induced periodic nanostructure on the surface of cerium oxide disclosed in the present invention. The difference from Example 1 is that without going through S3, after S2 ends, the cerium oxide thin film sample is taken out, and periodic surface nanostructures are prepared using a femtosecond laser with an infrared wavelength in an atmospheric environment.

[0066] Figure 5 It is a scanning electron microscope image of the dual-wavelength laser-induced periodic nanostructure on the surface of cerium oxide prepared in Comparative Example 1 of the present invention. After in-situ annealing in the pulsed laser deposition vacuum chamber, the cerium oxide thin film is dense and the surface periodic nanostructures are uniform. However, due to the preparation of periodic nanostructures by femtosecond in an atmospheric environment, a large amount of particulate pollutants are deposited on the film surface.

[0067] Comparative Example 2: A method for preparing a dual-wavelength laser-induced periodic nanostructure on the surface of cerium oxide disclosed in the present invention. The difference from Example 1 is that without going through S2 and S3, after S1 ends, the cerium oxide thin film sample is taken out, and periodic surface nanostructures are prepared using a femtosecond laser with an infrared wavelength in an atmospheric environment.

[0068] Figure 6 It is a scanning electron microscope image of the dual-wavelength laser-induced periodic nanostructure on the surface of cerium oxide prepared in Comparative Example 2 of the present invention. Since there is no annealing, defects are generated on the surface of the cerium oxide thin film, and there are serious ablation and uneven ablation phenomena in some areas during the preparation of periodic nanostructures by femtosecond laser (on the right side of the picture).

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for preparing a cerium oxide surface nanostructure with dual-wavelength laser-induced periodicity, characterized in that: Including, The process of pulsed laser depositing a cerium oxide thin film on a niobium-doped strontium titanate substrate; The process of irradiating and annealing the cerium oxide thin film by introducing an ultraviolet wavelength laser to obtain a dense cerium oxide thin film; And, the process of introducing an infrared wavelength laser in a vacuum chamber to induce the formation of periodic nanostructures on the surface of the dense cerium oxide thin film.

2. The preparation method of a dual-wavelength laser-induced periodic cerium oxide surface nanostructure according to claim 1, characterized in that: In the process of pulsed laser depositing a cerium oxide thin film on a niobium-doped strontium titanate substrate, the pulsed laser is an ultraviolet excimer laser with a wavelength of 248 nm.

3. A method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure according to claim 1, characterized in that: During the process of pulsed laser depositing cerium oxide thin film on a niobium-doped strontium titanate substrate, the laser energy density is controlled to be 1.4~1.8 J / cm 2 , the laser pulse frequency is 5~15 Hz, the oxygen pressure in the cavity is 10~100 mTorr, the target heating temperature of the niobium-doped strontium titanate substrate is 300~700 °C, the number of laser pulses is 5000~10000, and the distance between the target in the cavity and the niobium-doped strontium titanate substrate is 6.5 cm.

4. The preparation method of a dual-wavelength laser-induced periodic cerium oxide surface nanostructure according to claim 1, characterized in that: In the process of pulsed laser depositing a cerium oxide thin film on a niobium-doped strontium titanate substrate, the laser beam irradiates the cerium oxide target, generating a high-energy density laser pulse to force the rapid evaporation of the surface of the cerium oxide target to form a plasma plume, and the cerium atoms, ions and molecules in the plasma plume migrate towards the surface of the niobium-doped strontium titanate substrate under the action of an electric field and a magnetic field, and deposit on the surface of the niobium-doped strontium titanate substrate to form a cerium oxide thin film.

5. A method for preparing a double-wavelength laser-induced periodic cerium oxide surface nanostructure according to claim 1, characterized in that: In the process of irradiating and annealing the cerium oxide thin film by introducing an ultraviolet wavelength laser, the ultraviolet wavelength laser is an ultraviolet excimer laser with a wavelength of 248 nm.

6. A method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure according to claim 1, characterized in that: During the process of irradiating and annealing the cerium oxide thin film with the introduced ultraviolet wavelength laser, control the laser energy density to be 0.8~1.2 J / cm 2 , the laser pulse frequency is 5~15 Hz, and the annealing time is 10~60 min.

7. A method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure according to claim 1, characterized in that: In the process of irradiating and annealing the cerium oxide thin film by introducing an ultraviolet wavelength laser, the scanning path of the ultraviolet wavelength laser is Z-shaped, and the filling pitch is 1 μm, so that the ultraviolet laser beam can uniformly irradiate the surface of the cerium oxide thin film, quickly absorb energy and heat up, and after the irradiation and annealing are completed, it is naturally cooled to room temperature.

8. The preparation method of a double-wavelength laser-induced periodic cerium oxide surface nanostructure according to claim 1, characterized in that: In the process of introducing an infrared wavelength laser to induce the formation of periodic nanostructures on the surface of the dense cerium oxide thin film, the infrared wavelength laser is a femtosecond laser with a wavelength of 1064 nm.

9. A method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure according to claim 1, characterized in that: During the process of forming periodic nanostructures on the surface of the dense cerium oxide film by introducing infrared wavelength laser, control the single pulse energy to be 1.4~1.8 J / cm 2 , the pulse frequency is 50~150 kHz, and the scanning speed is 10~30 mm / s.

10. A method for preparing a dual-wavelength laser-induced periodic cerium oxide surface nanostructure according to claim 1, characterized in that: In the process of introducing an infrared wavelength laser to induce the formation of periodic nanostructures on the surface of the dense cerium oxide thin film, the scanning path of the infrared wavelength laser is Z-shaped, and the filling pitch is 1 μm.

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