A two-dimensional organic semiconductor single crystal thin film based on a metal substrate and its preparation method

Abstract

The present invention discloses a two-dimensional organic semiconductor single crystal thin film based on a metal substrate and a preparation method thereof. The thin film comprises a substrate, an insulating layer, a metal layer, and an organic semiconductor thin film. The metal layer is prepared on the surface of the insulating layer, and the prepared metal surface is smooth and wettable to the solution for growing the organic semiconductor thin film. The organic semiconductor thin film material is a conjugated organic small molecule with an alkyl side chain. The preparation method comprises the following steps: growing an insulating layer on a substrate; preparing a metal layer on the surface of the insulating layer; preparing a solution; and adjusting growth parameters to grow a two-dimensional organic semiconductor single crystal thin film. By selecting a suitable substrate and growth conditions, the present invention achieves high-quality, large-scale, and controllable growth of a two-dimensional organic semiconductor single crystal thin film directly on a metal substrate. The thin film single crystal area reaches the millimeter level, providing a possible approach to simplifying the device structure and preparation process.

Description

Technical Field

[0001] The present invention relates to a semiconductor thin film and a preparation method thereof, and in particular to a two-dimensional organic semiconductor single crystal thin film based on a metal substrate and a preparation method thereof. Background Art

[0002] Two-dimensional organic semiconductor single-crystal thin films have been widely used in semiconductor devices such as organic diodes and organic transistors. Compared to bulk thin films, ultrathin two-dimensional organic semiconductor single-crystal thin films exhibit highly ordered carrier dynamics that can be controlled with molecular-level precision, due to their extremely low defect concentration and negligible interlayer screening effects. These thin films hold great potential for exploring the microscopic physical mechanisms of these devices.

[0003] Many conjugated organic compounds have good solubility in a variety of organic solvents and good self-assembly behavior, making them suitable for the efficient preparation of high-performance two-dimensional organic semiconductor crystals through solution methods. The surface tension and roughness of the substrate are key parameters that affect the crystallization process and determine the quality of the film. Metal surfaces are generally more hydrophobic and rougher than oxide surfaces. Therefore, it is still difficult to grow organic semiconductor films directly on metal surfaces. A common strategy to solve this problem is to use self-assembled monolayers to change the roughness and wettability of the metal surface to affect the crystallization process and achieve the purpose of metal surface modification. This increases the complexity of the process to a certain extent, introduces more variables, and may affect the performance of the device.

[0004] Therefore, the one-step growth of two-dimensional organic semiconductor crystal films directly on metal surfaces is of great significance for simplifying the device process containing metal / organic semiconductor structures, such as vertical diodes or bottom-contact transistors. Summary of the Invention

[0005] Objective of the invention: The objective of the present invention is to provide a high-quality two-dimensional organic semiconductor single crystal thin film that can be grown directly on a metal substrate;

[0006] The second object of the present invention is to provide a method for preparing the two-dimensional organic semiconductor single crystal thin film based on a metal substrate.

[0007] Technical solution: The two-dimensional organic semiconductor single crystal film based on a metal substrate described in the present invention includes a substrate, an insulating layer, a metal layer and an organic semiconductor film; the metal layer is prepared on the surface of the insulating layer, and the prepared metal surface is smooth and has wettability to the solution for growing the organic semiconductor film; the organic semiconductor film material is a conjugated organic small molecule with an alkyl side chain.

[0008] Among them, the conjugated organic small molecule is 2,9-dihexylnaphtho[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene or 2,9-tetracosylnaphtho[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene. These small molecule organic semiconductors with side chains have good solubility in a variety of organic solvents and have electrical properties such as high carrier mobility and good stability.

[0009] Among them, the metal is one of titanium, platinum, gold, silver or copper, its work function is relatively matched with the energy level of organic semiconductor materials, and it is easy to prepare, which is conducive to large-scale preparation of semiconductor films on metal substrates and application in various circuit applications.

[0010] Wherein, the material of the insulating layer is one of hafnium oxide, aluminum oxide or zirconium oxide.

[0011] Any of the above-mentioned methods for preparing a two-dimensional organic semiconductor single crystal thin film based on a metal substrate comprises the following steps:

[0012] (1) growing an insulating layer on a substrate;

[0013] (2) preparing a metal layer on the surface of the insulating layer, so that the surface of the metal layer is smooth and has wettability to the solution for growing the organic semiconductor thin film;

[0014] (3) preparing a growth solution, wherein the solvent of the solution used makes the metal wettable to the growth solution;

[0015] (4) Adjusting the growth parameters to grow a two-dimensional organic semiconductor single crystal thin film on the surface of the metal layer.

[0016] Among them, in step (1), atomic layer deposition is used to grow oxide, and the thickness of the oxide is 20 to 30 nm. Oxides with a thickness of less than 20 nm have fewer nucleation points, which is not conducive to thin film growth. As the thickness increases, the roughness of the oxide becomes larger and larger, which will cause the surface roughness of the subsequently deposited metal layer to increase. In addition, the number of nucleation points on the surface of the oxide exceeding 30 nm increases, which is not conducive to the growth of large-area single crystal thin films.

[0017] Wherein, in step (2), the metal layer includes a metal pattern and a metal film, the metal pattern is prepared by electron beam lithography, and then the metal pattern and the metal film are obtained by electron beam evaporation.

[0018] Wherein, in step (3), the contact angle of the solvent of the solution on the metal layer is 0-10°, and the extremely small contact angle indicates that the metal layer has high surface energy, which is conducive to the crystallization of the solution to form a thin film; that is, the metal has good wettability to the growth solution, which is conducive to the growth of the thin film; the solvent is one of toluene, chlorobenzene, and 1,2,3,4-tetrahydronaphthalene, which can dissolve a variety of organic semiconductors, and have boiling points of approximately 110°C, 131°C, and 207°C, respectively. Therefore, these solvents will not evaporate too quickly during the thin film growth process, which is conducive to the preparation of ultra-thin two-dimensional organic semiconductor crystals; organic small molecule powder is added to the solvent at a certain concentration to prepare a growth solution, and the solution is continuously placed in a water bath at 80-85°C for heating. Below 80°C, the organic small molecules are not fully dissolved in the solvent, and above 85°C, the organic small molecules are accelerated. The solution is denatured, and the solution can maintain its effectiveness for about one week at 80-85°C; in the step (3), the concentration of the solution is 0.25-0.45 mg / mL, and the saturated concentrations of 2,9-dihexylnaphtho[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene and 2,9-tetracosylnaphtho[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene in the solvent are 0.25 mg / mL and 0.45 mg / mL, respectively. The saturated solution can make the organic small molecules precipitate faster during the growth process. A concentration lower than the saturated solution concentration will make it difficult to form a film on the metal layer, and a concentration higher than the saturated solution concentration will cause a thicker block film or point-like polycrystal to appear on the ultra-thin two-dimensional organic semiconductor film, which is not conducive to the formation of a large-area uniform film.

[0019] Wherein, in step (4), the growth parameters adjusted are: the distance between the metal layer and the upper plate is set to 80-100 μm, the inclination angle of the upper plate is 10-15°, the temperature of the upper plate and the lower plate is 62-68°C, and the scraping speed of the upper plate is set to 2-3 μm / s. The distance between the metal layer and the upper plate is used to inject the solution to form a meniscus. The larger the distance, the easier it is to form a thinner film, but too large a distance will cause the film to be discontinuous or unable to form a film; a smaller inclination angle of the upper plate is also conducive to the evaporation of the solvent at the meniscus to form a film; the temperature of the upper and lower plates and the scraping speed of the upper plate jointly control the thickness of the film. The higher the temperature, the faster the solvent evaporates and the thicker the film. A lower temperature will make film formation difficult, while a higher temperature will cause cracks to form during the film growth process, and the film thickness becomes thinner as the scraping speed increases.

[0020] Among them, in step (4), the two-dimensional organic semiconductor single crystal film is grown by using a half-moon solution shearing method, and the growth solution is injected into the gap between the metal substrate and the upper plate. At the corresponding temperature, the upper plate is controlled to move continuously in one direction at a certain speed to complete the growth of the organic semiconductor film.

[0021] Principle of the invention: The present invention uses a metal with low surface roughness as a substrate and a solvent with good wettability on the metal surface, such as 1,2,3,4-tetralin, which provides a good prerequisite for the preparation of high-quality thin films; combined with the good solubility and self-assembly behavior of the organic conjugated small molecules containing alkyl chains 2,9-dihexylnaphthalene [2,3-b] naphtho [2',3':4,5]thiophene [3,2-d]thiophene and 2,9-tetradecylnaphthalene [2,3-b] naphtho [2',3':4,5]thiophene [3,2-d]thiophene in the solvent, the highly ordered growth of two-dimensional organic semiconductor thin films on the metal substrate is achieved, and large-area single crystals at the millimeter level are obtained.

[0022] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects: (1) The method for preparing a two-dimensional organic semiconductor single crystal thin film based on a metal substrate can directly achieve high-quality, large-scale, and controllable growth of a two-dimensional organic semiconductor single crystal thin film on a metal substrate by selecting a metal substrate, solvent, and thin film growth conditions with suitable conditions, and the area of ​​the thin film single crystal reaches the millimeter level; (2) The preparation method first prepares the metal and then grows the organic semiconductor thin film, thereby avoiding the damage to the organic film that may be caused by electron beam exposure and developing solution during the photolithography process, and can be used to simplify the preparation process of the device and improve the performance of the electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the preparation process of the two-dimensional organic semiconductor single crystal thin film based on a metal substrate prepared in Example 1;

[0024] Figure 2 This is a polarized optical microscope image of the two-dimensional organic semiconductor film based on the titanium metal strip pattern prepared in Example 1;

[0025] Figure 3 This is an atomic force microscope image of the two-dimensional organic semiconductor film based on the titanium metal strip pattern prepared in Example 1;

[0026] Figure 4 This is a polarized optical microscope image of a two-dimensional organic semiconductor film based on a platinum metal strip pattern prepared in Example 2;

[0027] Figure 5 The contact angle test results of the hafnium oxide film, titanium film and gold film prepared in Example 3 to the solvent 1,2,3,4-tetralin;

[0028] Figure 6 Atomic force microscope images of the hafnium oxide film, titanium film, and gold film prepared in Example 3;

[0029] Figure 7This is a polarized optical microscope image of the two-dimensional organic semiconductor single crystal thin film based on a metal substrate prepared in Example 3;

[0030] Figure 8 This is an atomic force microscope image of the two-dimensional organic semiconductor single crystal thin film based on a metal substrate prepared in Example 3;

[0031] Figure 9 Optical microscope images of two-dimensional organic semiconductor single crystal thin films based on metal substrates prepared under different growth conditions in Example 3;

[0032] Figure 10 This is an optical microscope image of an organic semiconductor film based on a metal substrate at a non-saturated solution concentration prepared in Comparative Example 1;

[0033] Figure 11 Optical microscope pictures of the organic semiconductor thin film based on the metal substrate prepared in Comparative Example 2 under the condition of changing the distance between the metal substrate and the upper plate of the device;

[0034] Figure 12 An optical microscope image of an organic semiconductor film based on a metal substrate prepared in Comparative Example 3 under the condition of changing the temperature of the upper plate and the lower plate;

[0035] Figure 13 This is an optical microscope picture of an organic semiconductor film based on a metal substrate prepared in Comparative Example 4 under the condition of changing the scraping speed of the upper plate. DETAILED DESCRIPTION

[0036] The present invention is described in further detail below.

[0037] Example 1

[0038] This embodiment is a 2,9-dihexylnaphtho[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene molecular film based on a titanium metal strip pattern on hafnium oxide, wherein 2,9-dihexylnaphtho[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene is denoted as C6-DNTT. The preparation method of the film includes the following steps:

[0039] (1) After cleaning the silicon substrate, place it in an atomic layer deposition chamber, evacuate the chamber, set the temperature to 150°C, and after the temperature stabilizes for 1 hour, use tetrakis(dimethylamino)hafnium as the metal source and water as the oxidation source. The pulse time of the hafnium source and oxidation source is 300ms and 20ms respectively, and the cleaning time between two pulses is 30s. Set 180 cycles to grow a 25nm hafnium oxide film;

[0040] (2) Electron beam lithography was used to write metal strip patterns on the hafnium oxide film. The metal strips were 5 μm wide and 10, 20, 50, 100, and 150 μm long. 30 nm of titanium was then deposited onto the written patterns by electron beam evaporation. The evaporation rate was controlled at 100 μm. After stripping, a patterned metal substrate is obtained;

[0041] (3) Prepare the growth solution by dissolving C6-DNTT in 1,2,3,4-tetralin to a saturated concentration of 0.45 mg / mL. Place the prepared solution in water at 80°C and heat it continuously in a water bath.

[0042] (4) A single-layer organic semiconductor film was grown on a metal substrate using a solution shearing method: the growth solution was injected into the gap between the metal substrate and the upper plate. The distance between the metal substrate and the upper plate of the device was set to 100 μm, the tilt angle of the upper plate was fixed to 15°, the temperature of the upper and lower plates was set to 64°C, and the movement speed of the upper plate was set to 2.5 μm / s. The upper plate was controlled to move continuously in one direction by an electric translation stage to complete the growth of the organic film. The thickness of the obtained single-layer C6-DNTT molecular film was about 2.5 nm.

[0043] Figure 1 Schematic diagram of the preparation process of the two-dimensional organic semiconductor single crystal thin film based on a metal substrate prepared in Example 1.

[0044] Figure 2 This is a polarized optical microscope image of the two-dimensional organic semiconductor film based on the titanium metal strip pattern prepared in Example 1, indicating that the present invention obtains a high-quality two-dimensional organic semiconductor film on the titanium metal strip pattern, and the single crystal area of ​​the film is several hundred microns, reaching the sub-millimeter level.

[0045] Figure 3 This is an atomic force microscope image of the two-dimensional organic semiconductor film based on the titanium metal strip pattern prepared in Example 1, showing that the thickness of the single-layer C6-DNTT molecular film is about 2.5 nm.

[0046] Example 2

[0047] This embodiment is a 2,9-tetracosylnaphtho[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene molecular film based on a platinum metal strip pattern on hafnium oxide, wherein 2,9-tetracosylnaphtho[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene is denoted as C 14 -DNTT, the preparation method of the film comprises the following steps:

[0048] (1) After cleaning the silicon substrate, place it in an atomic layer deposition chamber, evacuate the chamber, set the temperature to 150°C, and after the temperature stabilizes for 1 hour, use tetrakis(dimethylamino)hafnium as the metal source and water as the oxidation source. The pulse time of the hafnium source and oxidation source is 300ms and 20ms respectively, and the cleaning time between two pulses is 30s. Set 180 cycles to grow a 25nm hafnium oxide film;

[0049] (2) Electron beam lithography was used to write metal strip patterns on the hafnium oxide film. The metal strips were 1 μm wide and 10, 25, 50, and 100 μm long. 10 nm of platinum was then deposited onto the written patterns using electron beam evaporation. The evaporation rate was controlled at 100 μm. After stripping, a patterned metal substrate is obtained;

[0050] (3) Prepare the solution for growth and use 1,2,3,4-tetrahydronaphthalene as solvent to dissolve C 14 -DNTT, prepared to a saturated concentration of 0.25 mg / mL, the prepared solution was placed in 85°C water and continuously heated in a water bath;

[0051] (4) Growing a single-layer organic semiconductor thin film on a metal substrate using a solution shearing method: The growth solution was injected into the gap between the metal substrate and the upper plate. The distance between the metal substrate and the upper plate of the device was set to 80 μm, the tilt angle of the upper plate was fixed to 10°, the temperature of the upper and lower plates was set to 68°C, and the moving speed of the upper plate was set to 2.5 μm / s. The upper plate was controlled to move continuously in one direction by an electric translation stage to complete the growth of the organic thin film. 14 The thickness of the -DNTT molecular film is about 5nm.

[0052] Figure 4 This is a polarized optical microscope image of the two-dimensional organic semiconductor film based on the platinum metal strip pattern prepared in Example 2, indicating that the present invention obtains a high-quality two-dimensional organic semiconductor film on the platinum metal strip pattern, and the single crystal area of ​​the film is several hundred microns.

[0053] Example 3

[0054] The two-dimensional organic semiconductor single crystal thin film based on a metal substrate of the present invention is a 2,9-dihexylnaphtho[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene molecular thin film based on a metal thin film on hafnium oxide, and its preparation method includes the following steps:

[0055] (1) After cleaning the silicon substrate, place it in an atomic layer deposition chamber, evacuate the chamber, set the temperature to 150°C, and after the temperature stabilizes for 1 hour, use tetrakis(dimethylamino)hafnium as the metal source and water as the oxidation source. The pulse time of the hafnium source and oxidation source is 300ms and 20ms respectively, and the cleaning time between two pulses is 30s. Set 180 cycles to grow a 25nm hafnium oxide film;

[0056] (2) Electron beam evaporation of 30 nm titanium, 10 nm platinum, and 30 nm gold was directly performed on the hafnium oxide film to obtain titanium, platinum, and gold metal films. The evaporation rate was controlled at ~

[0057] (3) Prepare the growth solution by dissolving C6-DNTT in 1,2,3,4-tetralin to a saturated concentration of 0.45 mg / mL. Place the prepared solution in water at 80°C and heat it continuously in a water bath.

[0058] (4) A single-layer organic semiconductor film was grown on a metal substrate using a solution shearing method: the growth solution was injected into the gap between the metal substrate and the upper plate. The distance between the metal substrate and the upper plate of the device was set to 100 μm, the tilt angle of the upper plate was fixed at 15°, the temperature of the upper and lower plates was set to 62-66°C, the scraping speed of the upper plate was set to 2-3 μm / s, and the upper plate was controlled to move continuously in one direction by an electric translation stage to complete the growth of the film. By adjusting the temperature of the upper and lower plates and the scraping speed of the upper plate, semiconductor films with controllable thicknesses from single to triple layers can be obtained. When the temperature of the upper and lower plates and the scraping speed are 62°C, 2μm / s, 64°C, 2.5μm / s and 66°C, 3μm / s, respectively, a larger-area single-layer C6-DNTT film with a thickness of approximately 2.5nm can be obtained. When the temperature of the upper and lower plates and the scraping speed are 66°C and 2.5μm / s, respectively, a double-layer C6-DNTT film can be obtained. When the temperature of the upper and lower plates and the scraping speed are 66°C and 2μm / s, respectively, a triple-layer C6-DNTT film can be obtained, and the thickness of the second and third layers of the C6-DNTT film is approximately 3nm.

[0059] Figure 5 The contact angle test results for the hafnium oxide, titanium, and gold films prepared in Example 3 with respect to the solvent 1,2,3,4-tetralin are shown. Graph (a) shows that the contact angle of the hafnium oxide film with respect to the solvent 1,2,3,4-tetralin is only ~1.9°, graph (b) shows that the contact angle of the titanium film with respect to the solvent 1,2,3,4-tetralin is ~3.5°, and graph (c) shows that the contact angle of the gold film with respect to the solvent 1,2,3,4-tetralin is ~2.4°. Contact angles of less than 5° indicate that the hafnium oxide and metal films prepared in this invention have good wettability with the growth solution, facilitating crystallization of the solution on the metal substrate, thereby enabling direct film growth on the metal substrate.

[0060] Figure 6 These are atomic force microscope images, i.e., AFM images, of the hafnium oxide film, titanium film, and gold film prepared in Example 3; wherein a is the AFM image of the hafnium oxide film, b is the AFM image of the titanium film, and c is the AFM image of the gold film; the average surface roughness of the hafnium oxide film, the titanium film, and the gold film are 415 pm, 680 pm, and 585 pm, respectively. The extremely low surface roughness indicates that the hafnium oxide prepared by atomic layer deposition and the metal surface deposited by low-speed electron beam evaporation in the present invention are very smooth, which is also a key factor conducive to film growth.

[0061] The schematic diagrams of the preparation process of the two-dimensional organic semiconductor single crystal thin film based on the metal substrate in Example 3 are basically the same as those in Example 1, except for the metal pattern and the metal film.

[0062] Figure 7 These are polarized optical microscope images of the two-dimensional organic semiconductor single crystal thin film based on a metal substrate prepared in Example 3, wherein a is a polarized optical microscope image of a two-dimensional organic semiconductor single crystal thin film based on metal titanium, b is a polarized optical microscope image of a two-dimensional organic semiconductor single crystal thin film based on metal platinum, and c is a polarized optical microscope image of a two-dimensional organic semiconductor single crystal thin film based on metal gold; this shows that the area of ​​the two-dimensional organic semiconductor single crystal thin film based on a metal substrate of the present invention reaches the millimeter level, providing a reliable idea for realizing the preparation of large-area two-dimensional thin films on metals.

[0063] Figure 8 These are atomic force microscope images of the two-dimensional organic semiconductor single crystal thin films based on a metal substrate prepared in Example 3, where a is the AFM image of a single-layer thin film on metallic titanium, b is the AFM image of the first and second thin films on metallic titanium, and c is the AFM image of the second and third thin films on metallic titanium; the thickness of the single-layer C6-DNTT thin film on metallic titanium is about 2.5 nm, the thickness of the second and third C6-DNTT thin films is about 3 nm, and the morphology of the two-dimensional organic thin film on the metal is uniform and clean, indicating that the present invention has prepared high-quality two-dimensional organic semiconductor single crystal thin films based on a metal substrate.

[0064] Figure 9Optical microscope images of two-dimensional organic semiconductor single crystal thin films on metal substrates prepared under different growth conditions in Example 3. By varying the upper and lower plate temperatures between 62 and 66°C and the upper plate scraping speed between 2 and 3 μm / s, semiconductor films with 1 to 3 layers can be obtained. When the upper and lower plate temperatures and scraping speeds were 62°C, 2 μm / s; 64°C, 2.5 μm / s; and 66°C, 3 μm / s, respectively, large-area, uniform single-layer C6-DNTT films were obtained. When the upper and lower plate temperatures and scraping speeds were 66°C, 2.5 μm / s, and 66°C, 3 μm / s, respectively, large-area double-layer C6-DNTT films were obtained. When the upper and lower plate temperatures and scraping speeds were 66°C, 2 μm / s, respectively, large-area triple-layer C6-DNTT films were obtained.

[0065] Comparative Example 1

[0066] The organic semiconductor film based on a metal substrate of the present invention is a 2,9-dihexylnaphthyl[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene molecular film based on a metal film on hafnium oxide at a non-saturated solution concentration.

[0067] On the basis of Example 3, the concentration of the configured growth solution was changed, and the concentration of the 0.45 mg / mL C6-DNTT solution in step (3) of Example 3 was changed to 0.35 mg / mL and 0.55 mg / mL, respectively. The temperatures of the upper and lower plates and the scraping speed of the upper plate were set to 64°C and 2.5 μm / s in step (4) of Example 3, respectively, and the other conditions remained unchanged.

[0068] Figure 10 These are optical microscope images of the organic semiconductor film based on a metal substrate at a non-saturated solution concentration prepared in Comparative Example 1, where a is a microscope image of the organic semiconductor film based on a metal substrate when the solution concentration is 0.35 mg / mL. The discontinuous single-layer C6-DNTT film indicates that a solution below the saturation concentration is not conducive to the formation of a large-area film. b is a microscope image of the organic semiconductor film based on a metal substrate when the solution concentration is 0.55 mg / mL, indicating that a solution exceeding the saturation concentration can easily form many discrete thick films on a large-area single-layer C6-DNTT film, which is not conducive to the preparation of a large-area uniform film.

[0069] Comparative Example 2

[0070] The organic semiconductor film based on a metal substrate of the present invention is a 2,9-dihexylnaphtho[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene molecular film based on a metal film on hafnium oxide under the condition of changing the distance between the metal substrate and the upper plate of the device.

[0071] On the basis of Example 3, the temperatures of the upper and lower plates and the scraping speed of the upper plate in step (4) of Example 3 are selected as 64°C and 2.5 μm / s, respectively. Only the distance between the metal substrate and the upper plate of the device in step (4) of Example 3 is changed to 150 μm, and the other conditions remain unchanged.

[0072] Figure 11 This is an optical microscope picture of the organic semiconductor film based on the metal substrate prepared in Comparative Example 2 under the conditions of changing the distance between the metal substrate and the upper plate of the device. When the distance between the metal substrate and the upper plate of the device is 150 μm, the temperature of the upper plate and the lower plate is 64°C, and the scraping speed of the upper plate is 2.5 μm / s, the single-layer C6-DNTT film based on the metal substrate is not very continuous, indicating that increasing the distance between the metal substrate and the upper plate of the device will result in thinner film formation.

[0073] Comparative Example 3

[0074] The organic semiconductor film based on a metal substrate of the present invention is a 2,9-dihexylnaphthyl[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene molecular film based on a metal film on hafnium oxide under the condition of changing the temperature of the upper plate and the lower plate.

[0075] On the basis of Example 3, the scraping speed of the upper plate in step (4) of Example 3 is selected as 2.5 μm / s, and only the temperature of the upper plate and the lower plate in step (4) of Example 3 is changed, and the temperature of the upper plate and the lower plate is changed to 60°C, and the other conditions remain unchanged.

[0076] Figure 12 This is an optical microscope image of the organic semiconductor film based on the metal substrate prepared in Comparative Example 3 under the conditions of changing the temperature of the upper plate and the lower plate. When the distance between the metal substrate and the upper plate of the device is set to 100 μm, the temperature of the upper and lower plates is 60°C, and the scraping speed of the upper plate is 2.5 μm / s, the single-layer C6-DNTT film based on the metal substrate is relatively discontinuous, indicating that lowering the temperature of the upper and lower plates will cause the solvent to evaporate more slowly, thereby resulting in a thinner film thickness.

[0077] Comparative Example 4

[0078] The organic semiconductor film based on a metal substrate of the present invention is a 2,9-dihexylnaphthyl[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene molecular film based on a metal film on hafnium oxide under the condition of changing the scraping speed of the upper plate.

[0079] On the basis of Example 3, the temperatures of the upper plate and the lower plate in step (4) of Example 3 are selected to be 64°C, and only the scraping speed of the upper plate in step (4) of Example 3 is changed to 3.5 μm / s, and the other conditions remain unchanged.

[0080] Figure 13 This is an optical microscope image of an organic semiconductor film based on a metal substrate prepared in Comparative Example 4 under the conditions of changing the scraping speed of the upper plate. When the distance between the metal substrate and the upper plate of the device is set to 100 μm, the temperature of the upper and lower plates is 64°C, and the scraping speed of the upper plate is 3.5 μm / s, the single-layer C6-DNTT film based on the metal substrate is very discontinuous, indicating that in the volatile zone of solution growth, increasing the scraping speed of the upper plate will cause the film thickness to become thinner, and the faster speed of 3.5 μm / s makes it difficult to form a large-area single-layer C6-DNTT film.

Claims

1. A two-dimensional organic semiconductor single crystal thin film based on a metal substrate, characterized in that: The invention comprises a substrate, an insulating layer, a metal layer and an organic semiconductor film; the metal layer is prepared on the surface of the insulating layer, and the prepared metal surface is smooth and has wettability to the solution for growing the organic semiconductor film; the material of the organic semiconductor film is a conjugated organic small molecule with an alkyl side chain; the conjugated organic small molecule is 2,9-dihexylnaphthalene[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene or 2,9-tetracosylnaphthalene[2,3-b]naphtho[2',3':4,5]thiophene[3,2-d]thiophene.

2. The two-dimensional organic semiconductor single crystal thin film based on a metal substrate according to claim 1, characterized in that: The metal is one of titanium, platinum, gold, silver or copper.

3. The two-dimensional organic semiconductor single crystal thin film based on a metal substrate according to claim 1, characterized in that The insulating layer is made of one of hafnium oxide, aluminum oxide and zirconium oxide.

4. A method for preparing a two-dimensional organic semiconductor single crystal thin film based on a metal substrate according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Growing an insulating layer on the substrate; (2) Preparing a metal layer on the surface of the insulating layer to make the surface of the metal layer smooth and wettable to the solution for growing the organic semiconductor film; (3) preparing a growth solution, wherein the solvent used in the solution makes the metal wettable to the growth solution; (4) Adjusting the growth parameters to grow a two-dimensional organic semiconductor single crystal thin film on the surface of the metal layer.

5. The method for preparing a two-dimensional organic semiconductor single crystal thin film based on a metal substrate according to claim 4, characterized in that: In the step (2), the metal layer includes a metal pattern and a metal film, and the metal pattern is prepared by electron beam lithography, and then the metal pattern and the metal film are obtained by electron beam evaporation.

6. The method for preparing a two-dimensional organic semiconductor single crystal thin film based on a metal substrate according to claim 4, characterized in that: In the step (3), the contact angle of the solvent of the solution on the metal layer is in the range of 0 to 10°.

7. The method for preparing a two-dimensional organic semiconductor single crystal thin film based on a metal substrate according to claim 4, characterized in that: In the step (3), the solvent is one of toluene, chlorobenzene, and 1,2,3,4-tetrahydronaphthalene.

8. The method for preparing a two-dimensional organic semiconductor single crystal thin film based on a metal substrate according to claim 4, characterized in that: In the step (3), the concentration of the solution is 0.25-0.45 mg / mL.

9. The method for preparing a two-dimensional organic semiconductor single crystal thin film based on a metal substrate according to claim 4, characterized in that: In step (4), the adjusted growth parameters are: the distance between the metal layer and the upper plate is set to 80~100 μm, the inclination angle of the upper plate is 10~15°, the temperature of the upper plate and the lower plate is 62~70°C, and the scraping speed of the upper plate is set to 2~3 μm / s.

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