A preparation method of Ag / Au nanoparticles and MIM structure

Abstract

The present invention provides a method for preparing Ag / Au nanoparticles and a MIM structure. Gold and silver are used as the first and second target materials, respectively, and ion sputtering technology is used. The first target material is first sputtered and then the second target material is sputtered on the surface of a substrate composed of a chemically inert insulating material, or the second target material is first sputtered and then the first target material is sputtered. Gold nanoparticles and silver nanoparticles are evenly dispersed on the surface of the substrate. The substrate is then irradiated with an electron beam, and the beam current density of the electron beam is controlled at an order of magnitude. The irradiation time is 1 to 30 minutes, and Ag / Au nanoparticles in which silver nanoparticles merge, fuse, or coat gold nanoparticles are obtained. The method is simple and easy to implement, and a MIM structure of Ag / Au nanoparticles-substrate-Ag / Au nanoparticles is obtained by using the method.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials, and in particular relates to a preparation method of Ag / Au nanoparticles and a MIM structure. Background Art

[0002] Noble metal nanoparticles have excellent biocompatibility, superior optical and electrical properties, a large specific surface area, and easy surface modification, making them promising applications in biotechnology. For example, the localized surface plasmon resonance (LSPR) excitation of noble metal nanoparticles such as gold and silver leads to an enhancement of the localized incident light field, which is the primary contributing mechanism to surface-enhanced Raman scattering (SERS) sensing. Compared to gold, silver has a larger adjustable range of surface plasmon resonance, higher plasmon intensity, and lower production cost. Therefore, coating gold nanoparticles with silver nanoparticles can enhance the local field of the gold nanoparticles while retaining the gold nanoparticle hotspots, offering broad application prospects in surface-enhanced Raman scattering detection technology.

[0003] Hexagonal boron nitride (h-BN) has excellent high-temperature stability, chemical stability, and mechanical properties. Furthermore, it possesses a wide band gap, resistance to chemical corrosion, high temperatures, and oxidation resistance, making it a promising material for high-tech applications in electronics, machinery, metallurgy, aerospace, and other fields. However, due to BN's chemical inertness, it is difficult to load nanometal ions onto its surface.

[0004] Metallic micro-nanostructures hold broad application prospects in optics due to the complex plasmon coupling between nanostructures. Metal-insulator-metal (MIM) is a typical metallic nanostructure, known as a "metal mirror-coupled structure." MIM exhibits unique optical properties due to the near-field coupling between the nanostructure and the metal mirror. Summary of the Invention

[0005] The present invention provides a method for preparing Ag / Au nanoparticles obtained by merging, fusing or coating silver nanoparticles with gold nanoparticles.

[0006] The technical solution provided by the present invention is: a method for preparing Ag / Au nanoparticles, selecting an insulating and chemically inert material (i.e., a chemically inert insulating material) as a matrix material, using ion sputtering technology and electron beam irradiation technology, comprising the following steps:

[0007] (1) Gold is used as a first target material and silver is used as a second target material. An ion sputtering technique is used to first sputter the first target material and then the second target material on the substrate surface, or first sputter the second target material and then the first target material on the substrate surface, and gold nanoparticles and silver nanoparticles are uniformly dispersed on the substrate surface;

[0008] Preferably, the sputtering current is 5 to 30 mA, for example, 5 mA, 10 mA, 15 mA, 20 mA, 25 mA, 30 mA, etc.

[0009] Preferably, the sputtering time is 5 to 30 s, for example, 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, etc.

[0010] Preferably, the size of the gold nanoparticles is between 2 and 15 nm.

[0011] Preferably, the size of the silver nanoparticles is between 2 and 15 nm.

[0012] In the step (1), the number and size of the gold nanoparticles and the silver nanoparticles are adjusted by adjusting the sputtering current, sputtering voltage and sputtering time.

[0013] (2) The substrate treated in step (1) is subjected to electron beam irradiation, and the electron beam current density is controlled to be The irradiation time is 30 seconds to 30 minutes, and Ag / Au nanoparticles in which silver nanoparticles merge, fuse or coat gold nanoparticles are obtained.

[0014] As an example, the electron beam current density is controlled to be For example wait.

[0015] Preferably, the irradiation time is 40 seconds to 20 minutes, more preferably 1 minute to 20 minutes.

[0016] Preferably, in step (2), a transmission electron microscope (TEM) with an electron beam as a light source is used for electron beam irradiation, which not only realizes electron beam irradiation, but also enables the structural changes of gold nanoparticles and silver nanoparticles to be observed by TEM real-time imaging. When imaging is performed during electron irradiation, in order to avoid the influence of electron beam irradiation during imaging, preferably, imaging is performed using The electron beam current density is lower than that of the order of magnitude, and is further preferably Preferably, the magnification of the TEM is adjusted to 300-1500 kX.

[0017] The present invention combines ion sputtering technology with electron beam irradiation technology, selects an insulating and chemically inert substrate, first uses ion sputtering to physically deposit gold nanoparticles and silver nanoparticles on the substrate surface, so that the gold nanoparticles and silver nanoparticles are evenly dispersed on the substrate surface, and then uses electron beam irradiation. Through the knock-on effect of the electron beam and the charging effect of the surface of the electron beam irradiated insulating material, the gold nanoparticles and silver nanoparticles loaded on the substrate surface are in an activated high-energy state, providing an energy source for the movement of the gold nanoparticles and silver nanoparticles. Moreover, because the substrate is chemically inert and does not have strong interactions with the gold nanoparticles and silver nanoparticles, the migration energy of the gold nanoparticles and silver nanoparticles on the substrate surface is low, and they are easy to migrate on the substrate surface. Therefore, when the electron beam is irradiated, the gold nanoparticles and silver nanoparticles merge and fuse, and even Ag nanoparticles cover Au nanoparticles to obtain Ag / Au nanostructures. This method has the following beneficial effects:

[0018] (1) This method is simple, easy, clean and efficient, and can achieve the merging and fusion of silver nanoparticles and gold nanoparticles, and even the formation of Ag / Au nanoparticles in which silver nanoparticles are coated with gold nanoparticles (forming a core-shell structure when completely coated); and by adjusting one or both of the electron beam current density and irradiation time, the morphology of the Ag / Au nanoparticles can be regulated, such as the structural state of the merging, fusion or coating of the silver nanoparticles and the gold nanoparticles, the size of the Ag / Au nanoparticles, the thickness of the gold core and the thickness of the silver shell when the silver nanoparticles coat the gold nanoparticles to form a core-shell structure, etc., thereby achieving precise control of the morphology of the Ag / Au nanoparticles and thus achieving regulation of the light absorption properties of the surface of the Ag / Au nanoparticles.

[0019] (2) In this method, the matrix material is not limited, including mica, B4C, hexagonal boron nitride (h-BN), etc. Hexagonal boron nitride is chemically inert and is an insulating material (normal temperature conductivity 10- 16 ~10- 18 Ω / cm), the method of the present invention can successfully obtain Ag / Au nanoparticles on the surface of hexagonal boron nitride, which solves the problem in the prior art that it is difficult to load nano metal ions on its surface due to the chemical inertness of BN.

[0020] (3) In this method, the structure of the matrix material is not limited, including two-dimensional layer structures, nanotube structures, etc., such as boron nitride nanotubes (BNNTs), boron nitride sheets, mica sheets, B4C sheets, etc.

[0021] When the substrate is a two-dimensional layer structure, the method is used to prepare Ag / Au nanoparticles on the upper and lower surfaces of the two-dimensional layer structure to obtain a MIM structure of Ag / Au nanoparticles-substrate-Ag / Au nanoparticles.

[0022] When the matrix is ​​a nanotube structure, the method is used to prepare Ag / Au nanoparticles on the outer wall of the nanotube structure to obtain a MIM structure of Ag / Au nanoparticles-matrix-Ag / Au nanoparticles.

[0023] As an implementation method, the preparation method of the Ag / Au nanoparticle-matrix-Ag / Au nanoparticle MIM structure includes the following steps:

[0024] (1) Using a substrate with a flat surface; preparing a base layer on the substrate surface; in the base layer, the surface connected to the substrate surface is recorded as the lower surface, and the surface opposite to the lower surface is recorded as the upper surface;

[0025] (2) First, using ion sputtering technology, first sputtering the first target material and then sputtering the second target material on the upper surface of the base layer, or first sputtering the second target material and then sputtering the first target material on the upper surface of the base layer, and gold nanoparticles and silver nanoparticles are uniformly deposited on the upper surface of the base layer; then, peeling the base layer from the substrate surface and turning it over so that the lower surface of the base layer faces upward, using ion sputtering technology, first sputtering the first target material and then sputtering the second target material on the lower surface of the base layer, or first sputtering the second target material and then sputtering the first target material on the lower surface of the base layer, and gold nanoparticles and silver nanoparticles are uniformly deposited on the lower surface of the base layer; then, peeling the base layer with gold nanoparticles and silver nanoparticles deposited on the upper and lower surfaces from the substrate surface;

[0026] (3) The substrate treated in step (2) is subjected to electron beam irradiation so that both the upper and lower surfaces are irradiated with electron beams, and the beam current density of the electron beam is controlled to be The irradiation time is 1 to 30 minutes, and Ag / Au nanoparticles with a core-shell structure of silver nanoparticles covering gold nanoparticles are obtained.

[0027] As an implementation method, in step (1), the method for preparing the matrix layer on the substrate surface is: uniformly dispersing matrix material powder in a first solvent to obtain a first dispersion liquid; spreading the first dispersion liquid on the substrate surface, and volatilizing the first solvent to obtain the matrix layer located on the substrate surface. The first solvent is not limited and includes dimethylformamide (DMF) and the like.

[0028] As an implementation method, in step (1), the solvent is volatilized by increasing the temperature.

[0029] As an implementation method, in step (2), a second solvent is added dropwise to the substrate surface to wet and soften the base layer, and then the base layer is scraped and peeled off. The second solvent is not limited and includes dimethylformamide (DMF) and the like.

[0030] As an implementation method, in step (3), the base layer is dissolved in a third solvent and uniformly dispersed to obtain a third dispersion liquid, which is then dropwise added to the micro-grating film and then dried and then electron beam irradiated. The third solvent is not limited and includes dimethylformamide (DMF) and the like.

[0031] The substrate is used to support the base layer, and its material is not limited, including glass, Si, etc.

[0032] Preferably, the micro-grid film is a 100-500 mesh micro-grid film.

[0033] In the MIM structure of Ag / Au nanoparticles-matrix-Ag / Au nanoparticles, the near-field coupling strength between the nanostructure and the metal film layer can be regulated by adjusting the thickness of the matrix, thereby achieving controllable adjustment of the light absorption performance of the MIM. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a physical picture and a structural schematic diagram of the glass slide in Example 1 of the present invention being transferred to an ion sputtering instrument for ion sputtering, wherein (a) is a physical picture and (b) is a structural schematic diagram.

[0035] Figure 2 TEM images of BN nanotubes before and after sputtering deposition of gold nanoparticles and silver nanoparticles in Example 1 of the present invention, wherein (a) is the TEM image before sputtering deposition, and (b) is the TEM image after sputtering deposition.

[0036] Figure 3 These are high-magnification TEM bright-field images and high-angle annular dark-field images (HAADF) of the outer wall of the BN nanotube after the deposition of gold nanoparticles and silver nanoparticles in Example 1 of the present invention, where (a) is a high-magnification TEM bright-field image and (b) is a high-angle annular dark-field image (HAADF) image.

[0037] Figure 4 These are structural diagrams of the same area of ​​the BN nanotubes after the deposition of gold nanoparticles and silver nanoparticles in Example 1 of the present invention under electron beam irradiation at 10s and 40s of irradiation, where (a) is the image after 10s of irradiation and (b) is the image after 40s of irradiation.

[0038] Figure 5 These are high-magnification scanning transmission (STEM) images and high-angle annular dark field (HAADF) images of the outer wall of the BN nanotube after the gold nanoparticles and silver nanoparticles are deposited in Example 1 of the present invention and irradiated under electron beam irradiation for 20 minutes, wherein (a) is a high-magnification TEM bright field image, and (b) is a high-angle annular dark field (HAADF) image. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below in conjunction with the embodiments and drawings. It should be pointed out that the embodiments described below are intended to facilitate understanding of the present invention. Some non-essential improvements and adjustments made to the present invention by technicians in this field based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0040] Example 1:

[0041] (1) First, 10 mg of white BN nanotube (BNNTs) powder was dispersed in 10 ml of dimethylformamide (DMF) solution and ultrasonicated for 20 min until the sample was completely dispersed.

[0042] (2) Take 2 ml of the dispersion liquid and drop it dropwise onto a clean glass slide. After the droplets are spread on the slide, they are baked with an infrared lamp to fully dry the liquid to obtain a BN nanotube layer.

[0043] (3) Figure 1 As shown, the glass slide was transferred to an ion sputtering instrument. A silver target was first installed, and silver nanoparticles were sputtered onto the upper surface of the BN nanotube layer at a sputtering current of 10 mA and a sputtering time of 5 seconds. Then, an Au target was replaced, and gold nanoparticles were sputtered onto the upper surface of the BN nanotube layer at a sputtering current of 10 mA and a sputtering time of 5 seconds.

[0044] (4) Remove the glass slide, add DMF solution to the BN nanotube layer area on the glass slide, gently scrape and peel off the BN nanotube layer and turn it over so that the lower surface of the BN nanotube layer faces upward.

[0045] (5) Using the method in step (3), gold nanoparticles and silver nanoparticles are sputter-deposited on the lower surface of the BN nanotube layer.

[0046] (6) The BN nanotube layer sample on the glass slide was collected with DMF solution, and after ultrasonic dispersion, a few drops were added to a 200-mesh microgrid membrane for TEM, and after drying, the solution was loaded into the TEM.

[0047] (7) The micro-grating film was irradiated with electron beam in TEM for 20 minutes, and the structural changes were observed by imaging. In order to avoid the influence of electron beam irradiation during imaging, the imaging conditions were adopted. Lower electron beam current density, while electron beam irradiation processing uses The electron beam current density is higher, that is, the electron beam current density under imaging conditions is reduced by 2 orders of magnitude compared with that under irradiation processing conditions.

[0048] In step (2), the TEM image of the BN nanotubes before sputtering and depositing gold nanoparticles and silver nanoparticles is as follows: Figure 2 As shown in Figure (a).

[0049] The TEM images of BN nanotubes after sputtering and depositing gold nanoparticles and silver nanoparticles in step (3) and step (4) are as follows: Figure 2 As shown in Figure (b), the high-magnification TEM bright field image and high-angle annular dark field image (HAADF) are as follows Figure 3 Figures (a) and (b) show that gold nanoparticles and silver nanoparticles are evenly dispersed on the outer wall of the BN nanotube. Figure 3 The dotted circles in Figure (b) indicate Ag nanoparticles.

[0050] In step (7), the same area of ​​the outer wall of the BN nanotube after the deposition of gold nanoparticles and silver nanoparticles is imaged by electron beam irradiation for 10 seconds and 40 seconds respectively. Figure 4 As shown in Figures (a) and (b), the Ag nanoparticles and Au nanoparticles on the outer wall of the BN nanotubes merge and fuse under the action of electron beam irradiation. Figure 4 The changes of the particles marked by the box in (a) and (b) are shown in Figure 2. After 20 minutes of electron beam irradiation, the high-magnification scanning transmission (STEM) image and high-angle annular dark field (HAADF) image of the outer wall of the BN nanotube are shown in Figure 2. Figure 5 As shown in Figures (a) and (b), a core-shell structure of Ag nanoparticles encapsulating Au nanoparticles is formed. Figure 5 The dotted lines in Figure (b) indicate that the core with higher contrast is Au, with a size of 5.0 nm, and the shell with lower contrast is Ag, with a thickness of 8.6 nm. Figure 4 and Figure 5 It can be seen that the electron beam irradiation process forms Ag / Au nanoparticles on the outer wall of the BN nanotubes, which are combined and fused with silver nanoparticles and coated with gold nanoparticles. With the BN nanotubes as the carrier, the overall structure of Ag / Au nanoparticle-BN-Ag / Au nanoparticle MIM is formed.

[0051] On the upper and lower surfaces of BN nanosheets

[0052] Example 2:

[0053] This embodiment is basically the same as embodiment 1, except that BN nanosheet powder is used instead of BN nanotube (BNNTs) powder in step (1), and the electron beam irradiation time in step (7) is 25 minutes.

[0054] After the ion sputtering deposition of Ag nanoparticles and Au nanoparticles in step (3) and step (4), the high magnification TEM bright field image and high angle annular dark field (HAADF) image of the BN nanosheet are similar. Figure 3 Figures (a) and (b) show that Ag nanoparticles and Au nanoparticles are evenly distributed on the upper and lower surfaces of the BN nanosheets.

[0055] In step (7), Ag nanoparticles and Au nanoparticles appear on the upper and lower surfaces of the BN nanosheets under the action of electron beam irradiation. Figure 4 The particle merging and fusion phenomenon shown in Figures (a) and (b) is similar to the high-magnification scanning transmission (STEM) image and high-angle annular dark field (HAADF) image of the BN nanosheet surface after 25 minutes of electron beam irradiation. Figure 5 Figures (a) and (b) in the figure show that electron beam irradiation forms Ag / Au nanoparticles on the upper and lower surfaces of the BN nanosheets, where silver nanoparticles merge, fuse, and coat the gold nanoparticles, forming a MIM structure of Ag / Au nanoparticles-BN-Ag / Au nanoparticles.

[0056] Example 3:

[0057] This embodiment is basically the same as embodiment 1, except that mica nanosheet powder is used instead of BN nanotube (BNNTs) powder in step (1), and the electron beam current density during electron beam irradiation in step (7) is

[0058] After the ion sputtering deposition of Ag nanoparticles and Au nanoparticles in step (3) and step (4), the high magnification TEM bright field image and high angle annular dark field (HAADF) image of the BN nanosheet are similar. Figure 3 Figures (a) and (b) show that Ag nanoparticles and Au nanoparticles are evenly distributed on the upper and lower surfaces of the mica nanosheets.

[0059] In step (7), Ag nanoparticles and Au nanoparticles appear on the upper and lower surfaces of the mica nanosheets under the action of electron beam irradiation. Figure 4 The particle merging and fusion phenomenon shown in Figures (a) and (b) is similar to the high-magnification scanning transmission (STEM) image and high-angle annular dark field (HAADF) image of the mica nanosheet surface after 20 minutes of electron beam irradiation. Figure 5 Figures (a) and (b) in the figure show that electron beam irradiation processes silver nanoparticles merge, fuse, and coat gold nanoparticles on the upper and lower surfaces of mica nanosheets, forming an MIM structure of Ag / Au nanoparticles-mica-Ag / Au nanoparticles.

[0060] Example 4:

[0061] This embodiment is basically the same as embodiment 1, except that B4C nanosheet powder is used instead of BN nanotube (BNNTs) powder in step (1), and the electron beam current density during electron beam irradiation in step (7) is The irradiation time was 15 minutes.

[0062] After the ion sputtering deposition of Ag nanoparticles and Au nanoparticles in step (3) and step (4), the high magnification TEM bright field image and high angle annular dark field (HAADF) image of the BN nanosheet are similar. Figure 3 Figures (a) and (b) show that Ag nanoparticles and Au nanoparticles are evenly distributed on the upper and lower surfaces of the B4C nanosheets.

[0063] In step (7), under the action of electron beam irradiation, Ag nanoparticles and Au nanoparticles appear on the upper and lower surfaces of the B4C nanosheets. Figure 4 The particle merging and fusion phenomenon shown in Figures (a) and (b) is similar to the high-magnification scanning transmission (STEM) image and high-angle annular dark field (HAADF) image of the B4C nanosheet surface after 20 minutes of electron beam irradiation. Figure 5 Figures (a) and (b) in the figure show that electron beam irradiation processes form Ag / Au nanoparticles on the upper and lower surfaces of the B4C nanosheets, where silver nanoparticles merge, fuse, and coat the gold nanoparticles, forming a MIM structure of Ag / Au nanoparticles-B4C-Ag / Au nanoparticles.

[0064] The above embodiments provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A MIM structure, characterized by: A chemically inert insulating material is used as the constituent material of the matrix; the preparation method of the MIM structure comprises the following steps: (1) Using a substrate with a flat surface; preparing a matrix layer on the substrate surface by uniformly dispersing matrix material powder in a first solvent to obtain a first dispersion; spreading the first dispersion on the substrate surface, and allowing the first solvent to evaporate to obtain a matrix layer on the substrate surface; In the base layer, the surface connected to the substrate surface is recorded as the lower surface, and the surface opposite to the lower surface is recorded as the upper surface; The constituent material of the matrix is ​​one or more of mica, B4C, and hexagonal boron nitride (h-BN); the structure of the constituent material of the matrix is ​​a nanotube structure; (2) First, gold is used as a first target material and silver is used as a second target material. An ion sputtering technique is used to first sputter the first target material and then the second target material on the upper surface of the substrate layer, or first sputter the second target material and then the first target material on the upper surface of the substrate layer, and gold nanoparticles and silver nanoparticles are uniformly deposited on the upper surface of the substrate layer; Then, the base layer is peeled off from the substrate surface and turned over so that the lower surface of the base layer faces upward. An ion sputtering technique is used to first sputter the first target material and then the second target material on the lower surface of the base layer, or first sputter the second target material and then the first target material on the lower surface of the base layer, so that the gold nanoparticles and the silver nanoparticles are uniformly deposited on the lower surface of the base layer. Next, the base layer with gold nanoparticles and silver nanoparticles deposited on the upper and lower surfaces is peeled off from the substrate surface; (3) The substrate layer treated in step (2) is dissolved in a third solvent and uniformly dispersed to obtain a third dispersion liquid. The third dispersion liquid is dropped onto the micro-grid film and irradiated with an electron beam after drying. The beam current density of the electron beam is controlled to be 1×10 4 e / Å 2 ·s~2×10 5 e / Å 2 ·s, the irradiation time is 30 seconds to 30 minutes, and Ag / Au nanoparticles in which silver nanoparticles merge, fuse, or coat gold nanoparticles are obtained on the upper and lower surfaces of the substrate, forming a MIM structure of Ag / Au nanoparticles-substrate-Ag / Au nanoparticles; the third solvent includes dimethylformamide.

2. The MIM structure according to claim 1, wherein: In the step (2), the sputtering current is 5-30 mA.

3. The MIM structure according to claim 1, wherein: In the step (2), the sputtering time is 5 to 30 s.

4. The MIM structure according to claim 1, wherein: The size of gold particles is 2~15 nm.

5. The MIM structure according to claim 1, wherein: The size of silver particles is 2~15 nm.

6. The MIM structure according to claim 1, wherein: In the step (2), the number and size of the gold particles and the silver particles are adjusted by adjusting one or more of the sputtering current, the sputtering voltage, and the sputtering time.

7. The MIM structure according to claim 1, wherein: In the step (3), electron beam irradiation is performed using a transmission electron microscope using an electron beam as a light source.

8. The MIM structure according to claim 1, wherein: Imaging is performed during electron irradiation, and 10 2 e / Å 2 · Electron beam current density of the order of s.

9. The MIM structure according to claim 1, wherein: In the step (3), the irradiation time is 40 seconds to 20 minutes.

10. The MIM structure according to claim 9, wherein: In the step (3), the irradiation time is 1 minute to 20 minutes.

11. The MIM structure according to claim 1, wherein: In the step (3), the structural state of the silver nanoparticles and the gold nanoparticles in the Ag / Au nanoparticles, the size of the Ag / Au nanoparticles, and the thickness of the gold core and the thickness of the silver shell when the silver nanoparticles cover the gold nanoparticles to form a core-shell structure are regulated by regulating one or both of the beam current density and the irradiation time of the electron beam.

12. The MIM structure according to claim 1, wherein: The first solvent includes dimethylformamide (DMF).

13. The MIM structure according to claim 1, wherein: In the step (1), the solvent is volatilized by heating.

14. The MIM structure according to claim 1, wherein: The substrate is made of glass, Si or both.

15. The MIM structure according to claim 1, wherein: In the step (2), a second solvent is added dropwise to the surface of the substrate to wet and soften the base layer, and then the base layer is scraped and peeled off.

16. The MIM structure according to claim 15, wherein: The second solvent includes dimethylformamide.

17. The MIM structure according to claim 1, wherein: The micro-grid film is a micro-grid film with a mesh size of 100-500.

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