Nanocrystalline floating gate memory based on silicon dioxide coated metal core-shell nanoparticle film and printing preparation method

Abstract

The invention belongs to the technical field of nano electronic devices and nano processing, and particularly relates to a nanocrystalline floating gate memory based on a silicon dioxide coated metal core-shell nanoparticle film and a printing preparation method. The preparation method comprises the following steps: firstly printing a core-shell nanoparticle film, performing chemical vapor deposition on a silane coupling agent modification layer on a single-layer film, and printing a polymer middle layer and an oriented active layer; the printing preparation technology has the advantages of being high in raw material utilization rate, good in controllability, high in repeatability and the like. The prepared core-shell nanoparticle film is low in roughness and high in particle number density, and can be used as a nanocrystalline floating gate / tunneling dielectric composite layer; the prepared organic semiconductor crystal has the advantages of high crystallinity, obvious orientation and low grain boundary density, and can be used as an active layer, and the nanocrystalline floating gate memory formed by the functional layers shows excellent electrical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanoelectronic devices and nanoprocessing, and specifically relates to a nanocrystalline floating gate memory based on a silicon dioxide-coated metal (such as Au@SiO2) core-shell nanoparticle film and a printing preparation method thereof. Background Art

[0002] Flash memory based on 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 has become very difficult to further reduce the device size of flash memory, resulting in difficulty in increasing its device density; and as the thickness of the tunneling dielectric layer continues to decrease, the storage stability of the device gradually decreases. Therefore, it is urgent to develop new memory devices with large capacity, low power consumption and high stability.

[0003] Nanocrystalline floating gate memory is one of the new types of memory that uses 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 nanocrystalline 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 upper active layer, which in turn affects the device's threshold voltage, mobility, switching ratio and other performance. AuNPs have become one of the most commonly used nanocrystalline floating gate materials due to their high work function and good chemical stability. The self-assembly of AuNPs with surface modified tunneling dielectric layers to form a monolayer film is an effective method for the integrated preparation of nanocrystalline floating gate / tunneling dielectric monolayers, especially polymer-grafted AuNPs monolayer films. However, polymer ligands are prone to aging and have poor thermal stability, which leads to a sharp decline in the performance of nanocrystalline floating gate memory during long-term use, or even failure. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a nanocrystalline floating gate memory and printing preparation technology based on a silicon dioxide-coated metal (such as Au@SiO2) core-shell nanoparticle film, and by optimizing the structure of the nanocrystalline floating gate / tunneling dielectric composite layer, the active layer and the interface between the two functional layers, a high-performance nanocrystalline floating gate memory is obtained. This solves the technical problem of high interface trap density between the nanocrystalline floating gate / tunneling dielectric single layer and the active layer and poor electrical performance of the nanocrystalline floating gate memory in the prior art.

[0005] According to a first aspect of the present invention, a printing method for preparing a nanocrystalline floating gate memory based on a metal core-shell nanoparticle film coated with silicon dioxide is provided, comprising the following steps:

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

[0007] (2) printing the nanoparticle ink obtained in step (1) on a substrate, and after the solvent dries, the metal core-shell nanoparticles coated with silicon dioxide form a thin film on the substrate, and the thin film serves as a nanocrystal floating gate and tunnel 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, wherein the polymer is 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 a film modified with a 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;

[0010] (5) Vapor-depositing source and drain electrodes on the organic semiconductor active layer to obtain a nanocrystalline floating gate memory based on a metal core-shell nanoparticle film coated with silicon dioxide.

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

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

[0013] Preferably, the core of the silica-coated metal core-shell nanoparticles is gold, platinum, silver or copper, and the shape of the core is one of sphere, rod, cube and polyhedron; the shell layer of the silica-coated metal core-shell nanoparticles is silica, and the shell layer thickness is 2 to 100 nm.

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

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

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

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

[0018] According to another aspect of the present invention, a nanocrystalline floating gate memory based on a metal core-shell nanoparticle film coated with silicon dioxide prepared by any one of the methods is provided.

[0019] Preferably, the thickness of the metal core-shell nanoparticles coated with silicon dioxide as the nanocrystalline floating gate and tunnel dielectric composite layer is 10-100 nm and the area is 0.01-10 cm 2 .

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

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

[0022] (2) The preparation method of the present invention first prints a metal core-shell nanoparticle film coated with silica, chemically vapor deposits a silane coupling agent modification layer on the monolayer film, prints a polymer intermediate layer and an oriented active layer. Compared with traditional spin coating, evaporation, electron beam deposition and other methods, the printing preparation technology used in the present invention has the advantages of high raw material utilization, good controllability and strong repeatability. The prepared silica-coated metal core-shell nanoparticle film has low roughness and high particle number density, and can be used as a nanocrystalline 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 nanocrystalline floating gate memory composed of the above functional layers exhibits excellent electrical properties.

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

[0024] (4) The present invention is based on the vertical phase separation behavior between polymer and organic semiconductor. The polymer intermediate layer and the organic semiconductor active layer can be prepared by one-step printing. Under the shearing action of the printing fluid, an active layer composed of oriented, large-sized crystals is obtained. The large-sized crystals 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 above-mentioned controllable functional layers, the prepared nanocrystal memory has a low threshold voltage (<1V), a large switching ratio (8.3×10 4 ) and a wide storage window (70V), and can be used for multi-level nanocrystal floating gate memory.

[0026] (6) The printing preparation technology used in the present invention has the advantages of high raw material utilization, strong controllability and good repeatability, and can be used in conjunction with a variety of solution processing methods to achieve full solution processing to prepare storage devices, sensor devices and optoelectronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart for the printing preparation of nanocrystal floating gate memory based on Au@SiO2 core-shell nanoparticle monolayer film.

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

[0029] Figure 3 (a) Transmission electron microscopy image and (b) gold core size statistics diagram of Au@SiO2 core-shell nanoparticles in a specific embodiment of the present invention.

[0030] Figure 4 (a) AFM image, (b) SEM image, (c) AFM image and corresponding (d) height map of Au@SiO2 core-shell nanoparticle monolayer film in a specific embodiment of the present invention.

[0031] Figure 5 This is a histogram of the surface energy of the Au@SiO2 core-shell nanoparticle monolayer before and after chemical vapor deposition of a silane coupling agent in a specific embodiment of the present invention.

[0032] Figure 6 (a) Optical microscope image, (b) atomic force microscope image, and (c) scanning electron microscope image of polymers and organic semiconductors printed on Au@SiO2 core-shell nanoparticle monolayer films in a specific embodiment of the present invention.

[0033] Figure 7 (a) device structure schematic diagram, (b) transfer, (c) output and (d) storage curves of a nanocrystal floating gate memory composed of a printed Au@SiO2 core-shell nanoparticle monolayer film, a polymer intermediate layer and an active layer in a specific embodiment of the present invention.

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

[0035] Fig. 9 The substrate temperature in Examples 1-3 is 35°C, and the printing speed is 1000 μm s -1 , 2000 μm s -1 , 4000 μm s -1 Corresponding liquid film length photos.

[0036] Fig.10 is a scanning electron microscope image of a monolayer of gold core-shell nanoparticles coated with silicon dioxide prepared at different substrate temperatures in Examples 4-6, with a printing speed of 2000 μm s -1The substrate temperatures are (a, b) 30°C, (c, d) 40°C, and (e, f) 45°C, respectively, where b, d, and f are high-resolution scanning electron microscopy images.

[0037] Fig.11 The printing speed described in Examples 4-6 is 2000 μm s -1 , photos of the liquid film length corresponding to substrate temperatures of 30℃, 40℃, and 45℃ respectively. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

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

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

[0041] S2. chemical vapor deposition of a silane coupling agent modified 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 modified layer;

[0043] S4. Evaporate source and drain electrodes (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, which is cleaned and used for printing Au@SiO2 core-shell nanoparticles.

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

[0046] Preferably, the core of the Au@SiO2 core-shell nanoparticle described in step S1 is gold, and the shape of the gold core is one of sphere, rod, cube and polyhedron; the shell layer of the Au@SiO2 core-shell nanoparticle is silicon dioxide, and the shell layer thickness is 2 to 100 nm.

[0047] Preferably, the silane coupling agent described 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 pentathiophene (PTA).

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

[0051] The printing preparation method of the Au@SiO2 core-shell nanoparticle film provided by the present invention comprises the following steps:

[0052] (1) Preparation of Au@SiO2 core-shell nanoparticle ink: The Au@SiO2 core-shell nanoparticle dispersion is concentrated by centrifugation and dispersed in an organic solvent to obtain Au@SiO2 nanoparticle ink;

[0053] (2) Printing of Au@SiO2 core-shell nanoparticle film: The Au@SiO2 core-shell nanoparticle ink obtained in step (1) is loaded into a printing device, and the nanoparticle ink is printed on a substrate according to a set "S"-shaped printing path and parameters. After the solvent dries, the Au@SiO2 core-shell nanoparticles form a thin 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 described in step (1) is 5 to 50 wt %.

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

[0057] The printing preparation method of the polymer intermediate layer and the organic semiconductor active layer provided by the present invention comprises the following steps:

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

[0059] (2) Printing of polymer and organic semiconductor mixed ink: The polymer and organic semiconductor mixed ink obtained in step (1) is loaded into a printing device, and the mixed ink is printed on the Au@SiO2 core-shell nanoparticle monolayer film treated with a silane coupling agent according to the set "S"-shaped printing path and parameters. 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 described in step (2) is at least one of an inkjet printer and an ink direct writing printing device.

[0062] The following are specific embodiments

[0063] Example 1

[0064] Figure 1 The process flow chart of printing preparation of nanocrystalline floating gate memory based on Au@SiO2 core-shell nanoparticle monolayer film includes the following steps:

[0065] S1. Printing Au@SiO2 core-shell nanoparticle film on substrate as nanocrystalline floating gate / tunneling dielectric composite layer.

[0066] Figure 2 Schematic diagram of the printing preparation of nanocrystal floating gate memory based on Au@SiO2 core-shell nanoparticle monolayer film.

[0067] Figure 3 (a) Transmission electron microscopy image of spherical Au@SiO2 core-shell nanoparticles and (b) gold core size statistics chart show that the Au@SiO2 core-shell nanoparticles are uniform in size and have good monodispersity, wherein the gold core size is 16.0±1.1nm and the shell thickness is 7.0nm.

[0068] Figure 4 The following are (a) atomic force microscopy images, (b) scanning electron microscopy images, (c) atomic force microscopy images, and (d) corresponding height images of the Au@SiO2 core-shell nanoparticle monolayer film prepared by printing in a specific embodiment of the present invention. Figure 4 The a in the figure shows the surface root mean square roughness (R q ) at 400 μm 2The range is only 0.8nm, which provides a very flat surface for subsequent printing of polymer intermediate layers and active layers. Figure 4 The number density of the Au@SiO2 core-shell nanoparticle film is as high as 2.3×10 10 cm 2 , which can provide abundant storage sites for large-capacity nanocrystal floating gate memory. Figure 4 Figures c and d show that the thickness of the Au@SiO2 core-shell nanoparticle film is 30.2±0.3nm, which is very close to the size of a single Au@SiO2 core-shell nanoparticle (30.0±1.1nm), indicating that the film is composed of a single layer of Au@SiO2 core-shell nanoparticles.

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

[0070] Figure 5 The surface energy bar graph of the Au@SiO2 core-shell nanoparticle monolayer before and after chemical vapor deposition of silane coupling agent in a specific embodiment of the present invention. The polar part of the film surface energy (σ p ) decreased by 45.5%, and the non-polar part of the surface energy (σ d ) increased by 21.0%, indicating that the hydroxyl groups on the film surface were replaced by silane coupling agent.

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

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

[0073] S4. Vapor-depositing Au source and drain electrodes on the active layer.

[0074] Figure 7Figure 1 shows the (a) device structure diagram, (b) transfer, (c) output and (d) storage curves of the nanocrystal floating gate memory prepared by printing in a specific embodiment of the present invention. Under the synergistic effect of the above-mentioned structure controllable functional layers, the prepared nanocrystal floating gate memory exhibits p-type field effect transmission characteristics, and has a low threshold voltage (<1V) and a high current switching ratio (8.3×10 4 ) and a large storage window (70V).

[0075] Example 2

[0076] Figure 8 The printing conditions of a and b are as follows: in the silica-coated metal core-shell nanoparticle ink, the mass fraction of the silica-coated metal core-shell nanoparticles is 17.6 wt %, the substrate temperature is 35 ° C, and the printing speed is 1000 μm s -1 Scanning electron microscopy images of the monolayer of gold core-shell nanoparticles coated with silica prepared under the same conditions show that when the printing speed is low, the solvent evaporates quickly, resulting in a shorter liquid film length ( Fig. 9 ), making it difficult for adjacent printed lines to merge into a liquid film, resulting in sub-monolayer and linear multi-layer nanoparticle films.

[0077] Example 3

[0078] The preparation method of the silicon dioxide-coated core-shell nanoparticle monolayer film in this embodiment is different from that in Example 2 only in that the printing speed is 2000 μm s -1 .

[0079] Figure 8 c, d in Example 3 are the substrate temperature of 35°C and the printing speed of 2000 μms -1 Scanning electron microscopy images of the monolayer of gold core-shell nanoparticles coated with silica prepared under the conditions of 1:1 and 1:2. It can be seen that when the printing speed is moderate, the liquid film length is moderate ( Fig. 9 ), adjacent printing lines can be fused into an ultra-thin liquid film, and the solvent evaporates to deposit the nanoparticles at the three-phase contact line. At the same time, the convection assembly drives the nanoparticles in the dispersion to move to the three-phase contact line to obtain a nanoparticle monolayer film.

[0080] Example 4

[0081] The preparation method of the silicon dioxide-coated core-shell nanoparticle monolayer film in this embodiment is different from that in Example 2 only in that the printing speed is 4000 μm s -1 .

[0082] Figure 8 e and f in Example 4 are the substrate temperature of 35°C and the printing speed of 4000 μms. -1Scanning electron microscopy images of the monolayer of gold core-shell nanoparticles coated with silica prepared under the same conditions show that when the printing speed is high, the liquid film length is longer, resulting in a weaker restriction effect of the liquid film ( Fig. 9 ), the proportion of multilayer films in the nanoparticle film increases.

[0083] Example 5

[0084] The preparation method of the silicon dioxide-coated core-shell nanoparticle monolayer film in this embodiment is different from that in Embodiment 3 only in that the substrate temperature is 30°C.

[0085] Fig.10 a and b in the example 5 are the printing speed of 2000 μm s -1 , Scanning electron microscopy image of a monolayer of gold core-shell nanoparticles coated with silica prepared at a substrate temperature of 30°C. It can be seen that when the substrate temperature is low, the low solvent evaporation rate leads to the suppression of convection, while the longer liquid film length weakens the confinement effect ( Fig.11 ), resulting in an inhomogeneous sub-monolayer film.

[0086] Example 6

[0087] The method for preparing the silicon dioxide-coated core-shell nanoparticle monolayer film in this embodiment is different from that in Embodiment 3 only in that the substrate temperature is 40°C.

[0088] Fig.10 c and d in Example 6 are the printing speeds of 2000 μm s -1 , the scanning electron microscope image of the silica-coated gold core-shell nanoparticle monolayer film prepared at a substrate temperature of 40°C, it can be seen that when the substrate temperature increases, the uniformity of the nanoparticle film is improved, and a nanoparticle monolayer film containing a small amount of multilayer structure is obtained.

[0089] Example 7

[0090] The method for preparing the silicon dioxide-coated core-shell nanoparticle monolayer film in this embodiment is different from that in Embodiment 3 only in that the substrate temperature is 45°C.

[0091] Fig.10 e and f in Example 7 are the printing speeds of 2000 μm s -1 , Scanning electron microscopy image of a monolayer of gold core-shell nanoparticles coated with silica prepared at a substrate temperature of 45°C. It can be seen that when the substrate temperature is high, the shorter liquid film length causes adjacent printed lines to be unable to merge ( Fig.11 ) to obtain single-layer and linear multilayer nanoparticle films.

[0092] Compared with the prior art, the printing preparation technology of the nanocrystalline floating gate memory based on the Au@SiO2 core-shell nanoparticle film described in the present invention has the advantages of simple operation, strong controllability, good repeatability, high raw material utilization rate, and easy large-scale production. The obtained Au@SiO2 film has low roughness and high nanoparticle number density. The prepared active layer crystals have large size and controllable orientation. The nanocrystalline floating gate memory thus constructed exhibits excellent electrical properties.

[0093] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A printing preparation method for nanocrystalline floating gate memory based on silicon dioxide-coated metal core-shell nanoparticle film, characterized in that: The following steps are involved: (1) dispersing silica-coated metal core-shell nanoparticles in an organic solvent to obtain silica-coated metal core-shell nanoparticle ink; (2) printing the nanoparticle ink obtained in step (1) on a substrate, and after the solvent dries, the metal core-shell nanoparticles coated with silicon dioxide form a thin film on the substrate, and the thin film serves as a nanocrystal floating gate and tunnel 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, wherein the polymer is 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 a film modified with a 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) Vapor-depositing source and drain electrodes on the organic semiconductor active layer to obtain a nanocrystalline floating gate memory based on a metal core-shell nanoparticle film coated with silicon dioxide.

2. The printing preparation method of nanocrystalline floating gate memory based on silicon dioxide-coated metal core-shell nanoparticle film according to claim 1, characterized in that: In the silica-coated metal core-shell nanoparticle ink, the mass fraction of the silica-coated metal core-shell nanoparticles is 5-50wt%; the printing speed in step (2) is 1000-4000μm / s; the temperature of the substrate in step (2) is 30-45°C.

3. The printing preparation method of nanocrystalline floating gate memory based on silicon dioxide-coated metal core-shell nanoparticle film according to claim 1, characterized in that: 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 film is a single-layer film in which the silica-coated metal core-shell nanoparticles are arranged in a single layer; the specific control parameters are as follows: the mass fraction of the silica-coated metal core-shell nanoparticles in the silica-coated metal core-shell nanoparticle ink is 10-20wt%; the printing speed in step (2) is 2000-2200μm / s; the temperature of the substrate in step (2) is 33-38°C.

4. The printing preparation method of nanocrystalline floating gate memory based on silicon dioxide-coated metal core-shell nanoparticle film according to claim 1, 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 sphere, rod, cube and polyhedron; the shell of the silica-coated metal core-shell nanoparticle is silica, and the shell thickness is 2 to 100 nm.

5. The printing preparation method of nanocrystalline floating gate memory based on silicon dioxide-coated metal core-shell nanoparticle film according to claim 1, characterized in that: The silane coupling agent is one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane and 3-aminopropylphenylsilane.

6. The printing preparation method of nanocrystalline floating gate memory based on silicon dioxide-coated metal core-shell nanoparticle film according to claim 1, characterized in that: The organic semiconductor is at least one of polythiophene, copper phthalocyanine, 6,13-bis(triisopropylsilylethynyl)pentacene and pentathiophene.

7. The printing preparation method of nanocrystalline floating gate memory based on silicon dioxide-coated metal core-shell nanoparticle film according to claim 1, characterized in that: The organic solvents in step (1) and step (4) are each independently selected from at least one of methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, formamide, acetamide, chloroform, toluene, o-xylene, mesitylene, chlorobenzene and o-dichlorobenzene.

8. The printing preparation method of nanocrystalline floating gate memory based on silicon dioxide-coated metal core-shell nanoparticle film according to claim 1, characterized in that: The printing in step (2) and step (4) is each independently selected from inkjet printing or ink direct writing printing.

9. A nanocrystalline floating gate memory based on a metal core-shell nanoparticle film coated with silicon dioxide prepared by the method of any one of claims 1 to 9.

10. The nanocrystalline floating gate memory based on a silicon dioxide-coated metal core-shell nanoparticle film according to claim 9, characterized in that: The thickness of the silicon dioxide-coated metal core-shell nanoparticles as the nanocrystalline floating gate and tunnel dielectric composite layer is 10-100nm and the area is 0.01-10cm 2 .

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