A nanocrystal floating gate memory based on a thin film of silica-coated metal core-shell nanoparticles and a printing preparation method

Abstract

The present application belongs to the field of nano-electronic devices and nano-processing technology, and particularly relates to a kind of nanocrystal floating gate memory based on metal core-shell nanoparticle film coated with silicon dioxide and a printing preparation method. First, print the core-shell nanoparticle film, then deposit a silane coupling agent modification layer on the single layer film by chemical vapor deposition, print a polymer intermediate layer and an oriented active layer. The printing preparation technology used in the present application has the advantages of high raw material utilization rate, good controllability and strong repeatability. The core-shell nanoparticle film prepared has low roughness and high particle number density, and can be used as a nanocrystal floating gate / tunneling dielectric composite layer. The organic semiconductor crystal prepared has high crystallinity, obvious orientation and low grain boundary density, and can be used as an active layer. The nanocrystal floating gate memory composed of the above functional layers exhibits excellent electrical performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nano-electronic devices and nano-processing technology, and particularly relates to a nanocrystal floating gate memory based on a metal (such as Au@SiO2) core-shell nanoparticle film coated with silicon dioxide and a printing preparation method. BACKGROUND

[0002] Flash memory based on a floating gate structure is a typical non-volatile memory, which is widely used in various electronic products such as mobile phones, computers, cameras, etc. However, due to the bottleneck of ultraviolet lithography technology, it is very difficult to further reduce the device size of flash memory, which leads to the difficulty in improving the device number density. Moreover, with the continuous reduction of the thickness of the tunneling dielectric layer, the storage stability of the device gradually decreases. Therefore, it is urgent to develop a new type of memory device with large capacity, low power consumption and high stability.

[0003] Nanocrystal floating gate memory is one of the new types of memory with nanocrystals dispersed in the tunneling dielectric layer as storage sites. It has attracted much attention due to its large storage capacity and good storage stability. The nanocrystal floating gate / tunneling dielectric layer is the core functional layer of this type of memory, and its composition and structure directly affect the storage capacity and stability of the device. In addition, the surface structure and properties of the composite layer also affect the crystallinity and orientation of the active layer on it, and further affect the threshold voltage, mobility, on-off ratio and other performances of the device. AuNPs have become one of the most commonly used nanocrystal floating gate materials due to their high work function and good chemical stability. AuNPs with surface-modified tunneling dielectric layer form a monolayer film by self-assembly, which is an effective method for integrated preparation of nanocrystal floating gate / tunneling dielectric monolayer, especially the AuNPs monolayer film grafted with polymers. However, the polymer ligand has the problems of easy aging and poor thermal stability, which leads to a sharp decline in the performance of the nanocrystal floating gate memory during long-term use, and even failure. SUMMARY

[0004] In view of the above shortcomings of the prior art, the purpose of the present application is to provide a nanocrystal floating gate memory based on a metal (such as Au@SiO2) core-shell nanoparticle film coated with silicon dioxide and a printing preparation technology. By optimizing the structure of the nanocrystal floating gate / tunneling dielectric composite layer and the active layer, as well as the interface between the two functional layers, a high-performance nanocrystal floating gate memory is obtained. Thus, the technical problem of high interface trap density between the nanocrystal floating gate / tunneling dielectric monolayer and the active layer in the prior art and poor electrical performance of the nanocrystal floating gate memory is solved.

[0005] According to the first aspect of the present application, a printing preparation method of a nanocrystal floating gate memory based on a metal core-shell nanoparticle film coated with silicon dioxide is provided, which comprises the following steps:

[0006] (1) dispersing the silica-coated metal core-shell nanoparticles into an organic solvent to obtain a silica-coated metal core-shell nanoparticle ink;

[0007] (2) printing the nanoparticle ink obtained in step (1) on a substrate, after the solvent is dried, the silica-coated metal core-shell nanoparticles form a thin film on the substrate, which serves as a nanocrystal floating gate and a tunneling dielectric composite layer;

[0008] (3) depositing a silane coupling agent modification layer on the thin film obtained in step (2);

[0009] (4) dissolving a polymer and an organic semiconductor in an organic solvent, the polymer is at least one of polyethylene, polystyrene, polymethyl methacrylate, to obtain a mixed ink of polymer and organic semiconductor; printing the mixed ink on the thin film modified by the silane coupling agent, after the solvent is dried, due to the vertical phase separation behavior between the polymer and the organic semiconductor, a polymer interlayer and an organic semiconductor active layer are prepared from bottom to top;

[0010] (5) evaporating a source-drain electrode on the organic semiconductor active layer, to obtain a nanocrystal floating gate memory based on a silica-coated metal core-shell nanoparticle thin film.

[0011] Preferably, in the silica-coated metal core-shell nanoparticle ink, the mass fraction of silica-coated metal core-shell nanoparticles is 5-50wt%; the printing speed in step (2) is 1000-4000μm / s; the temperature of the substrate in step (2) is 30-45℃.

[0012] Preferably, the concentration of silica-coated metal core-shell nanoparticles in the silica-coated metal core-shell nanoparticle ink, the printing speed of the silica-coated metal core-shell nanoparticle ink, and the temperature of the printing substrate of the silica-coated metal core-shell nanoparticle ink are controlled so that the thin film is a monolayer film in which the silica-coated metal core-shell nanoparticles are arranged in a monolayer; the specific control parameters are as follows: in the silica-coated metal core-shell nanoparticle ink, the mass fraction of silica-coated metal core-shell nanoparticles is 10-20wt%; the printing speed in step (2) is 2000-2200μm / s; the temperature of the substrate in step (2) is 33-38℃.

[0013] Preferably, the core of the silica-coated metal core-shell nanoparticle is gold, platinum, silver or copper, and the shape of the core is one of spherical, rod-shaped, cubic and polyhedral; the shell layer of the silica-coated metal core-shell nanoparticle is silica, and the thickness of the shell layer is 2-100nm.

[0014] Preferably, the silane coupling agent is one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylphenylsilane.

[0015] Preferably, the organic semiconductor is at least one of polythiophene, copper phthalocyanine, 6,13-bis(triisopropylsilylethynyl) pentacene, and pentacene.

[0016] Preferably, the organic solvent in step (1) and step (4) is independently selected from at least one of methanol, ethanol, ethylene glycol, diethylene glycol, glycerol, formamide, acetoamide, chloroform, toluene, o-xylene, mesitylene, chlorobenzene, and o-dichlorobenzene.

[0017] Preferably, the printing in step (2) and step (4) is independently selected from inkjet printing or ink direct writing printing.

[0018] According to another aspect of the present application, there is provided a nanocrystal floating gate memory based on the thin film of silica-coated metal core-shell nanoparticles prepared by any of the above methods.

[0019] Preferably, the thickness of the silica-coated metal core-shell nanoparticles as the nanocrystal floating gate and the tunneling dielectric composite layer is 10-100 nm, and the area is 0.01-10 cm 2 .

[0020] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0021] (1) Compared with polymer ligands, SiO2 has excellent thermal stability, good solvent erosion resistance and suitable dielectric constant, and can be obtained by thermal oxidation of silicon substrate, so SiO2 is often used as gate insulating layer and tunneling dielectric layer of silicon-based memory. However, due to uncontrollable deposition mode and difficulty in transferring thin film to substrate, existing methods such as spin coating, electrostatic adsorption and interface assembly still have challenges in preparing uniform, high number density of silica-coated metal core-shell nanoparticle thin film. On the other hand, printing can simply and efficiently prepare large size, oriented active layer, reduce the interface trap and grain boundary density in semiconductor layer, and improve the electrical performance of the device. At the same time, through interface treatment, the interface trap density between nanocrystal floating gate / tunneling dielectric monolayer and active layer can be reduced, thereby improving the electrical performance of nanocrystal floating gate memory, the excellent solvent erosion resistance of SiO2 shell and the rich hydroxyl groups on the surface lay the foundation for orthogonal printing of oriented active layer and interface treatment. Therefore, constructing uniform, high nanoparticle number density of silica-coated metal (such as Au@SiO2) core-shell nanoparticle thin film is the premise of preparing high-performance nanocrystal floating gate memory. The present application uses silica-coated metal core-shell nanoparticles, based on steady-state limited convection assembly of printing technology (such as ink direct writing), to assemble in situ on the substrate to form uniform, high particle number density of silica-coated metal core-shell nanoparticle thin film.

[0022] (2) The preparation method of the present application first prints the silica-coated metal core-shell nanoparticle thin film, chemically vapor deposits a silane coupling agent modification layer on the monolayer film, prints a polymer intermediate layer and orients the active layer. Compared with traditional spin coating, evaporation, electron beam deposition and other methods, the printing preparation technology used in the present application has the advantages of high raw material utilization rate, good controllability and strong repeatability. The prepared silica-coated metal core-shell nanoparticle thin film has low roughness and high particle number density, and can be used as a nanocrystal floating gate / tunneling dielectric composite layer; the prepared organic semiconductor crystal has high crystallinity, obvious orientation and low grain boundary density, and can be used as an active layer. The nanocrystal floating gate memory composed of the above functional layers shows excellent electrical performance.

[0023] (3) Preferably, the concentration of the silica-coated metal core-shell nanoparticles in the silica-coated metal core-shell nanoparticle ink is 10-20 wt%, the printing speed of the silica-coated metal core-shell nanoparticle ink is 2000-2200 μm / s, and the temperature of the printing substrate of the silica-coated metal core-shell nanoparticle ink is 33-38°C, so that the thin film is a monolayer film in which the silica-coated metal core-shell nanoparticles are arranged in a monolayer. The monolayer film composed of core-shell structure nanoparticles not only simplifies the device structure, but also can serve as an integrated nanocrystal floating gate / tunneling dielectric layer, which is conducive to reducing the interface trap density between the nanocrystal floating gate layer and the tunneling dielectric layer, and thus improving the device performance. In addition, the uniform monolayer film has a low surface roughness, which is conducive to the crystallization and orientation of the upper semiconductor, thereby obtaining a high-quality semiconductor layer. The silica-coated metal core-shell nanoparticle monolayer film provided by the present application has a low roughness, with a root mean square roughness of only 0.8 nm within a range of 400 μm 2 , and a particle number density as high as 2.3×10 10 cm 2 , which can significantly widen the storage window of the nanocrystal floating gate memory.

[0024] (4) Based on the vertical phase separation behavior between the polymer and the organic semiconductor, the polymer interlayer and the organic semiconductor active layer can be prepared by one-step printing, and under the fluid shear effect of printing, an active layer composed of oriented large-size crystals is obtained, which can significantly reduce the grain boundary density in the active layer, thereby improving the carrier mobility of the device.

[0025] (5) Based on the synergistic effect between the structure-controllable functional layers, the prepared nanocrystal memory has the advantages of low threshold voltage (<1 V), large on-off ratio (8.3×10 4 ) and wide storage window (70 V), and can be used for multi-level nanocrystal floating gate memory.

[0026] (6) The printing preparation technology used in the present application has the advantages of high raw material utilization rate, strong controllability and good repeatability, and can be combined with various solution processing methods to realize the all-solution processing preparation of memory devices, sensor devices and optoelectronic devices. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The printing preparation flowchart of the nanocrystal floating gate memory based on the Au@SiO2 core-shell nanoparticle monolayer film.

[0028] Figure 2 The printing preparation schematic diagram of the nanocrystal floating gate memory based on the Au@SiO2 core-shell nanoparticle monolayer film.

[0029] Figure 3 (a) Transmission electron micrograph and (b) Gold core size histogram of Au@Si02core-shell nanoparticles in a specific embodiment of the present invention.

[0030] Figure 4 (a) Atomic force micrograph, (b) Scanning electron micrograph, (c) Atomic force micrograph and corresponding (d) Height map of a monolayer film of Au@Si02core-shell nanoparticles in a specific embodiment of the present invention.

[0031] Figure 5 Surface energy bar graphs of a monolayer film of Au@Si02core-shell nanoparticles in a specific embodiment of the present invention before and after chemical vapor deposition of silane coupling agent.

[0032] Figure 6 (a) Optical micrograph, (b) Atomic force micrograph and (c) Scanning electron micrograph of a polymer and organic semiconductor printed on a monolayer film of Au@Si02core-shell nanoparticles in a specific embodiment of the present invention.

[0033] Figure 7 (a) Device structure schematic, (b) Transfer, (c) Output and (d) Storage curves of a nanocrystal floating gate memory consisting of a printed monolayer film of Au@Si02core-shell nanoparticles, a polymer interlayer and an active layer in a specific embodiment of the present invention.

[0034] Figure 8 Scanning electron micrographs of monolayer films of silica-coated gold core-shell nanoparticles prepared at different printing speeds as described in Examples 1-3, with a substrate temperature of 35°C and printing speeds of (a, b) 1000 μm s -1 , (c, d) 2000 μm s -1 , (e, f) 4000 μm s -1 , where b, d, f are high resolution scanning electron micrographs.

[0035] Figure 9 Corresponding liquid film length photographs for printing speeds of 1000 μm s -1 , 2000 μm s -1 , 4000 μm s -1 at a substrate temperature of 35°C as described in Examples 1-3.

[0036] Figure 10 Scanning electron micrographs of monolayer films of silica-coated gold core-shell nanoparticles prepared at different substrate temperatures as described in Examples 4-6, with a printing speed of 2000 μm s -1, the substrate temperature is (a, b) 30℃, (c, d) 40℃, (e, f) 45℃, wherein b, d, f are high-resolution scanning electron microscope images.

[0037] Figure 11 is the printing speed of 2000 μm s -1 , the substrate temperature is 30℃, 40℃, 45℃ corresponding to the liquid film length photo. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0039] The present application provides a printing preparation method of a nanocrystal floating gate memory based on a silica-coated metal (such as Au@SiO2) core-shell nanoparticle film, comprising the following steps:

[0040] S1. Printing an Au@SiO2 core-shell nanoparticle film on a substrate, used as a nanocrystal floating gate / tunneling dielectric composite layer;

[0041] S2. Chemical vapor deposition of a silane coupling agent modification layer on the Au@SiO2 core-shell nanoparticle monolayer film;

[0042] S3. Printing a polymer intermediate layer and an organic semiconductor active layer on the silane coupling agent modification layer;

[0043] S4. Evaporating a source-drain electrode (preferably Au) on the active layer.

[0044] Preferably, the substrate in step S1 is a Si substrate, on which a 300 nm thick SiO2 gate insulating layer is prepared by thermal growth, and after cleaning, it is used to print Au@SiO2 core-shell nanoparticles.

[0045] Preferably, the film area in step S1 is 0.01-10 cm 2 , and the thickness is 10-100 nm.

[0046] Preferably, the core of the Au@SiO2 core-shell nanoparticle in step S1 is gold, and the gold core shape is one of spherical, rod-shaped, cubic and polyhedral; the shell of the Au@SiO2 core-shell nanoparticle is silica, and the shell thickness is 2-100 nm.

[0047] Preferably, the silane coupling agent in step S2 is one of triaminopropyltrimethoxysilane, triaminopropyltriethoxysilane, and triaminopropylphenylsilane.

[0048] Preferably, the polymer material in step S3 is at least one of polyethylene, polystyrene, and polymethyl methacrylate.

[0049] Preferably, the organic semiconductor material in step S3 is at least one of polythiophene, copper phthalocyanine (CuPc), 6,13-bis(triisopropylsilylethynyl) pentacene (Tips-P5), and pentacene thiol (PTA).

[0050] Preferably, the Au source and drain electrode in step S4 is deposited on the active layer by a thermal evaporation method, and the vacuum degree of the evaporation cavity is less than 5*10 -4 Pa, and the evaporation rate is The thickness of the evaporated Au electrode is 40-60 nm, and the channel length and width of the metal mask used are 100 μm and 1500 μm, respectively.

[0051] The present application provides a printing preparation method of Au@SiO2 core-shell nanoparticle film, comprising the following steps:

[0052] (1) Preparation of Au@SiO2 core-shell nanoparticle ink: centrifugal concentration of Au@SiO2 core-shell nanoparticle dispersion liquid, and dispersion in an organic solvent to obtain Au@SiO2 nanoparticle ink;

[0053] (2) Printing of Au@SiO2 core-shell nanoparticle film: loading the Au@SiO2 core-shell nanoparticle ink obtained in step (1) into a printing device, and printing the nanoparticle ink on a substrate according to the set "S" shape printing path and parameters, and after the solvent is dried, the Au@SiO2 core-shell nanoparticles form a film on the substrate.

[0054] Preferably, the organic solvent in step (1) is at least one of methanol, ethanol, ethylene glycol, diethylene glycol, glycerol, formamide, and acetamide.

[0055] Preferably, the mass fraction of the nanoparticles in the Au@SiO2 core-shell nanoparticle ink in step (1) is 5-50 wt%.

[0056] Preferably, the printing device in step (2) is an inkjet printer or a direct ink writing printing device.

[0057] The present application provides a printing preparation method of a polymer intermediate layer and an organic semiconductor active layer, comprising the following steps:

[0058] (1) Preparation of polymer and organic semiconductor mixed ink: dissolving polymer and organic semiconductor in organic solvent according to a certain mass ratio to obtain polymer and organic semiconductor mixed ink;

[0059] (2) Printing of polymer and organic semiconductor mixed ink: loading the polymer and organic semiconductor mixed ink obtained in step (1) into a printing device, and printing the mixed ink on the Au@SiO2core-shell nanoparticle monolayer film treated with silane coupling agent according to the set "S" shape printing path and parameters, and after the solvent is dried, a polymer intermediate layer and an organic semiconductor active layer are prepared on the monolayer film.

[0060] Preferably, the organic solvent in step (1) is at least one of chloroform, toluene, o-xylene, mesitylene, chlorobenzene, and o-dichlorobenzene.

[0061] Preferably, the printing device in step (2) is at least one of an inkjet printer and an ink direct writing printing device.

[0062] The following is a specific embodiment

[0063] Example 1

[0064] Figure 1 A flow chart for printing preparation of nanocrystal floating gate memory based on Au@SiO2core-shell nanoparticle monolayer film, including the following steps:

[0065] S1. Printing Au@SiO2core-shell nanoparticle film on the substrate, used as nanocrystal floating gate / tunneling dielectric composite layer.

[0066] Figure 2 A schematic diagram for printing preparation of nanocrystal floating gate memory based on Au@SiO2core-shell nanoparticle monolayer film.

[0067] Figure 3 Transmission electron microscope image (a) and gold core size statistics (b) of spherical Au@SiO2core-shell nanoparticles, which can be seen that the Au@SiO2core-shell nanoparticles have uniform size and good monodispersity, wherein the gold core size is 16.0±1.1 nm and the shell thickness is 7.0 nm.

[0068] Figure 4 (a) Atomic force microscope image, (b) scanning electron microscope image, (c) atomic force microscope image, and (d) corresponding height map of the Au@SiO2core-shell nanoparticle monolayer film prepared by printing in the specific embodiment of the present application. From Figure 4 a in FIG. 4 can be seen that the root mean square roughness (R q ) of the surface of the film is 400 μm 2The thickness of the Au@SiO2 core-shell nanoparticle film is only 0.8 nm in the range, which provides a very smooth surface for the subsequent printing of the polymer interlayer and the active layer. Figure 4 b in FIG. 8 shows that the number density of the particles in the prepared Au@SiO2 core-shell nanoparticle film is as high as 2.3×10 10 cm 2 , which can provide abundant storage sites for high-capacity nanocrystal floating-gate memory. Figure 4 c and d in FIG. 8 show that the thickness of the Au@SiO2 core-shell nanoparticle film is 30.2±0.3 nm, which is very close to the size of a single Au@SiO2 core-shell nanoparticle (30.0±1.1 nm), indicating that the film is composed of a single layer of Au@SiO2 core-shell nanoparticles.

[0069] S2. Chemically vapor depositing a silane coupling agent modification layer on the Au@SiO2 core-shell nanoparticle monolayer film.

[0070] Figure 5 FIG. 9 is a surface energy column chart of the Au@SiO2 core-shell nanoparticle monolayer film before and after chemical vapor deposition of a silane coupling agent in the embodiment of the present application. After deposition of the silane coupling agent on the Au@SiO2 core-shell nanoparticle monolayer film, the polar part (σ p ) of the surface energy of the film is reduced by 45.5%, and the non-polar part (σ d ) of the surface energy is increased by 21.0%, indicating that the hydroxyl groups on the surface of the film are replaced by the silane coupling agent.

[0071] S3. Printing a polymer interlayer and an organic semiconductor active layer on the silane coupling agent modification layer.

[0072] Figure 6 FIG. 10 is (a) an optical microscope photo, (b) an atomic force microscope image, and (c) a scanning electron microscope image of the printed polymer and organic semiconductor on the Au@SiO2 core-shell nanoparticle monolayer film after silane coupling agent treatment in the embodiment of the present application. Figure 6 The results of a and b in FIG. 10 show that, under the shearing action of printing, oriented and large-size organic semiconductor crystals can be obtained and used as the active layer of nanocrystal floating-gate memory. Figure 6 The result of c in FIG. 10 shows that, after printing of the polymer and organic semiconductor, the structure of the monolayer film remains intact due to the excellent solvent erosion resistance of the SiO2 shell layer.

[0073] S4. Evaporating Au source and drain electrodes on the active layer.

[0074] Figure 7(a) Device structure schematic diagram, (b) Transfer, (c) Output and (d) Storage curve of the nanocrystal floating gate memory prepared by printing in the specific embodiment of the present application. Under the synergistic effect between the controllable functional layers mentioned above, the nanocrystal floating gate memory prepared exhibits p-type field effect transmission characteristics, and has low threshold voltage (<1V), high current on-off ratio (8.3×10 4 ) and large storage window (70V).

[0075] Example 2

[0076] Figure 8 The printing conditions of a, b in Table 1 are as follows: in the silica-coated metal core-shell nanoparticle ink, the mass fraction of the silica-coated metal core-shell nanoparticles is 17.6wt%, the substrate temperature is 35℃, and the printing speed is 1000μm s -1 The scanning electron microscope image of the silica-coated gold core-shell nanoparticle monolayer film prepared under the conditions of Table 1 can be seen that when the printing speed is low, the solvent volatilizes quickly, resulting in a short liquid film length Figure 9 ), which makes it difficult for adjacent printed lines to fuse into a liquid film, resulting in a nanoparticle film of sub-monolayer and line-shaped multilayer.

[0077] Example 3

[0078] The difference between the preparation method of the silica-coated core-shell nanoparticle monolayer film in this embodiment and that in Example 2 is only that the printing speed is 2000μm s -1 .

[0079] Figure 8 The conditions of c, d in Table 2 are that the substrate temperature is 35℃ and the printing speed is 2000μm s -1 The scanning electron microscope image of the silica-coated gold core-shell nanoparticle monolayer film prepared under the conditions of Table 2 can be seen that when the printing speed is moderate, the liquid film length is moderate Figure 9 ), adjacent printed lines can fuse into an ultrathin liquid film, and the solvent volatilization causes the nanoparticles to deposit at the three-phase contact line, while the convection assembly drives the nanoparticles in the dispersion liquid to move to the three-phase contact line, resulting in a nanoparticle monolayer film.

[0080] Example 4

[0081] The difference between the preparation method of the silica-coated core-shell nanoparticle monolayer film in this embodiment and that in Example 2 is only that the printing speed is 4000μm s -1 .

[0082] Figure 8 The conditions of e, f in Table 3 are that the substrate temperature is 35℃ and the printing speed is 4000μm s -1Scanning electron microscope images of the silica-coated gold core-shell nanoparticle monolayer film prepared below show that at higher printing speeds, the longer liquid film length leads to a weaker confinement effect of the liquid film. Figure 9 This results in an increased proportion of multilayer films in nanoparticle films.

[0083] Example 5

[0084] The method for preparing the silica-coated core-shell nanoparticle monolayer in this embodiment differs from that in Example 3 only in that the substrate temperature is 30°C.

[0085] Figure 10 In this context, 'a' and 'b' refer to the printing speed of 2000 μm / s described in Example 5. -1 Scanning electron microscope images of silica-coated gold core-shell nanoparticle monolayers prepared at a substrate temperature of 30℃ show that at lower substrate temperatures, the low solvent evaporation rate inhibits convection, while the longer liquid film length weakens the confinement effect. Figure 11 This process yields a non-uniform sub-monolayer film.

[0086] Example 6

[0087] The method for preparing the silica-coated core-shell nanoparticle monolayer in this embodiment differs from that in Example 3 only in that the substrate temperature is 40°C.

[0088] Figure 10 In this context, c and d refer to the printing speed of 2000 μm / s described in Example 6. -1 Scanning electron microscope image of a silica-coated gold core-shell nanoparticle monolayer film prepared at a substrate temperature of 40℃. It can be seen that the uniformity of the nanoparticle film is improved when the substrate temperature increases, resulting in a nanoparticle monolayer film with a small amount of multilayer structure.

[0089] Example 7

[0090] The method for preparing the silica-coated core-shell nanoparticle monolayer in this embodiment differs from that in Example 3 only in that the substrate temperature is 45°C.

[0091] Figure 10 In this context, 'e' and 'f' refer to the printing speed of 2000 μm / s described in Example 7. -1 Scanning electron microscope images of silica-coated gold core-shell nanoparticle monolayers prepared at a substrate temperature of 45℃ show that at higher substrate temperatures, the shorter liquid film length prevents adjacent printed lines from fusing. Figure 11 This yielded single-layer and linear multilayer nanoparticle films.

[0092] Compared with the prior art, the printing preparation technology of the nanocrystal floating gate memory based on the Au@SiO2 core-shell nanoparticle film has the advantages of simple operation, strong controllability, good repeatability, high raw material utilization, easy scale production, low roughness of the obtained Au@SiO2 film, high nanoparticle number density, large active layer crystal size, controllable orientation, and excellent electrical performance of the nanocrystal floating gate memory formed thereby.

[0093] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for printing preparation of nanocrystal floating gate memory based on thin film of silica-coated metal core-shell nanoparticles, characterized in that, The method comprises the following steps: (1) dispersing the silica-coated metal core-shell nanoparticles into an organic solvent to obtain a silica-coated metal core-shell nanoparticle ink; (2) printing the nanoparticle ink obtained in step (1) on a substrate, and after the solvent is dried, the silica-coated metal core-shell nanoparticles form a thin film on the substrate, which serves as a nanocrystal floating gate and a tunneling dielectric composite layer; (3) depositing a silane coupling agent modification layer on the thin film obtained in step (2); (4) dissolving a polymer and an organic semiconductor in an organic solvent, the polymer being at least one of polyethylene, polystyrene, and polymethyl methacrylate, to obtain a mixed ink of the polymer and the organic semiconductor; printing the mixed ink on the thin film modified by the silane coupling agent, and after the solvent is dried, a polymer intermediate layer and an organic semiconductor active layer are prepared from bottom to top due to the vertical phase separation behavior between the polymer and the organic semiconductor; (5) evaporating a source-drain electrode on the organic semiconductor active layer to obtain a nanocrystal floating gate memory based on a silica-coated metal core-shell nanoparticle thin film.

2. The method of claim 1, wherein the method is a printing method for preparing a nanocrystal floating gate memory based on a thin film of silica-coated metal core-shell nanoparticles, characterized in that, In the silica-coated metal core-shell nanoparticle ink, the mass fraction of the silica-coated metal core-shell nanoparticles is 5-50 wt%; in step (2), the printing speed is 1000-4000 μm / s; and in step (2), the temperature of the substrate is 30-45℃.

3. The method of claim 1, wherein the metal core-shell nanoparticle thin film is printed on a substrate. The concentration of the silica-coated metal core-shell nanoparticles in the silica-coated metal core-shell nanoparticle ink, the printing speed of the silica-coated metal core-shell nanoparticle ink, and the temperature of the printing substrate of the silica-coated metal core-shell nanoparticle ink are controlled so that the thin film is a monolayer film in which the silica-coated metal core-shell nanoparticles are arranged in a monolayer; the specific control parameters are as follows: in the silica-coated metal core-shell nanoparticle ink, the mass fraction of the silica-coated metal core-shell nanoparticles is 10-20 wt%; in step (2), the printing speed is 2000-2200 μm / s; and in step (2), the temperature of the substrate is 33-38℃.

4. The method of claim 1, wherein the method is a printing method for preparing a nanocrystal floating gate memory based on a thin film of silica-coated metal core-shell nanoparticles, characterized in that, The core of the silica-coated metal core-shell nanoparticle is gold, platinum, silver, or copper, and the shape of the core is one of a sphere, a rod, a cube, and a polyhedron; the shell layer of the silica-coated metal core-shell nanoparticle is silica, and the thickness of the shell layer is 2-100 nm.

5. The method of claim 1, wherein the metal core-shell nanoparticle thin film is printed on a substrate. The silane coupling agent is one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-aminopropylphenylsilane.

6. The method of claim 1, wherein the metal core-shell nanoparticle thin film is printed on a substrate. The organic semiconductor is at least one of polythiophene, copper phthalocyanine, 6,13-bis(triisopropylsilylethynyl) pentacene, and pentathiophene.

7. The method of claim 1, wherein the metal core-shell nanoparticle thin film is printed on a substrate. The organic solvent in step (1) and step (4) is independently selected from at least one of methanol, ethanol, ethylene glycol, diethylene glycol, glycerol, formamide, acetoamide, chloroform, toluene, o-xylene, mesitylene, chlorobenzene, and o-dichlorobenzene.

8. The method of claim 1, wherein the metal core-shell nanoparticle thin film is printed on a substrate. The printing in step (2) and step (4) is independently selected from inkjet printing or ink direct writing printing.

9. A nanocrystal floating gate memory based on a thin film of silica-coated metal core-shell nanoparticles prepared by the method of any one of claims 1-8.

10. The nanocrystal floating gate memory based on silica-coated metal core-shell nanoparticle thin films as claimed in claim 9 wherein, The thickness of the silicon dioxide coated metal core-shell nanoparticle as a nanocrystalline floating gate and tunneling dielectric composite layer is 10-100 nm, and the area is 0.01-10 cm 2 .

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