A single-layer organic nanofilm and its preparation and characterization method

Abstract

The present invention discloses a single-layer organic nanofilm and a preparation and characterization method thereof. The single-layer organic nanofilm comprises a single-layer monomer molecule chemically bonded by S atoms and Au atoms and an Au (111) electrode; the monomer molecule has a structure as shown in the following formula (I): #imgabs0# In formula (I), R1 is ‑NO2 or ‑NH2, and R2 is ‑SCH3 or ‑SH. Preparation method: providing an atomically flat Au (111) surface; evacuating the preparation cavity to a vacuum degree of less than 1×10 ‑8 mbar, the evaporation source containing the monomer molecules is heated and degassed, and the vacuum degree in the preparation chamber no longer changes before proceeding to the next step; thermal evaporation deposition is performed, and the temperature is controlled to maintain the pressure in the preparation chamber at 1×10 ‑7 mbar, a single-layer organic nanofilm was obtained. Characterization method: The single-layer organic nanofilm was characterized using a scanning tunneling microscope. The scanning conditions were a bias voltage of ‑1 V and a tunneling current of I t It is 0.3nA.

Description

Technical Field

[0001] The invention relates to the field of new materials, and in particular to a single-layer organic nanofilm and a preparation and characterization method thereof. Background Art

[0002] Self-assembly is the autonomous organization of components into various patterns or structures without human intervention. The entire process is becoming increasingly well known in nature and technology. They involve many different types of interactions from the molecular to the planetary system scale. At the same time, self-assembly is also one of the few practical strategies for making nanostructures. Therefore, it will become an important part of nanotechnology.

[0003] There are two approaches to fabricating nanomaterials: bottom-up and top-down. Self-assembly strategies offer a way to assemble these components into larger, functionally integrated systems. Although self-assembly originated from the study of molecules, it is in principle a strategy applicable at all scales. Therefore, self-assembly offers a solution for preparing ordered structures from nanometers to micrometers, a size range that is important for the development of nanotechnology and, by extension, microelectronics.

[0004] The invention of the scanning tunneling microscope (STM) has opened a new door for people to understand the material world. It allows people to intuitively understand the microscopic world at the atomic scale. At the same time, STM can manipulate atoms, which makes it possible for people to use STM to construct new materials. Therefore, once STM came out, it played a huge role in physics, chemistry, materials, biology and other fields. As a tool, STM has also become a good choice for exploring molecular self-assembly structures. At the same time, the closed circuit formed by the STM tip-molecule-gold substrate also provides a platform for studying the conductance of single-molecule junctions or circuits composed of molecules, making STM have great application prospects in the field of molecular electronics research.

[0005] The patent specification with the publication number CN 115020625 A discloses an organic semiconductor molecular nano-layered structure and its preparation method, which is prepared at the solid-liquid interface by the molecular deposition self-assembly method and the molecular arrangement state is recorded by STM technology. Since the organic semiconductor molecules used have strong mutual forces, the organic semiconductor molecular nano-layered structure described in the patented technology will inevitably have a multi-layer structure, and it is difficult to ensure that there is only a single-layer structure.

[0006] The patent specification with the publication number CN 113136548 A discloses a method for preparing two-dimensional porous nanomaterials based on the self-assembly of diphenylacetylene molecules. Under ultra-high vacuum conditions, two-dimensional nanomaterials with uniform porous structures are prepared on the surface of a single crystal by self-assembly of diphenylacetylene molecules. The two-dimensional porous nanomaterial layer obtained by this patented technology is also a multi-layer structure, specifically a two-dimensional porous nanomaterial layer assembled by diphenylacetylene molecules on the surface of a single crystal through hydrogen bonding interactions; diphenylacetylene first forms a first layer of disordered monolayer on the surface of a metal single crystal, and then forms a two-dimensional porous nanomaterial area with annular protrusions on the surface of the first layer as the second layer, and the second layer is an annular area formed by self-assembly of diphenylacetylene molecules through hydrogen bonding interactions. Summary of the invention

[0007] The present invention provides a single-layer organic nanofilm, which adopts a thermal deposition method, uses S atoms in molecules to form stable chemical bonds with Au atoms on the surface of an atomically smooth Au (111) electrode, and uses the Au (111) electrode with a flat surface as a template to self-assemble into an ordered single-layer film, and uses a scanning tunneling microscope (STM) to characterize it at a molecular resolution scale. The preparation method of the above organic nanofilm is simple, and it has a single-layer ordered structure, the organic molecules are closely arranged, the structure is stable, and the film is completely destroyed and desorbed from the surface after being treated at 250°C or even 300°C. This highly ordered single-layer organic film shows great potential in the research and application of new materials, molecular electronics and other related fields.

[0008] The specific technical solutions are as follows:

[0009] A single-layer organic nanofilm comprises a single-layer monomer molecule chemically bonded by S atoms and Au atoms and an Au (111) electrode;

[0010] The monomer molecule has a structure as shown in the following formula (I):

[0011]

[0012] In formula (I), R 1 For-No 2 or -NH 2 , R 2 For-SCH 3 or -SH.

[0013] In the single-layer organic nanofilm of the present invention, it can be observed under a scanning tunneling microscope that the monomer molecules are closely arranged, the structure is regular and orderly, and a single-layer film is formed in the form of self-assembly and arranged on the surface of the Au (111) electrode.

[0014] The present invention utilizes R 2The S atoms in the substituents can form stable chemical bonds with the Au atoms, and self-assemble to form an ordered monolayer film using the atomically flat Au(111) surface as a template. The Au(111) surface structure is a hexagonal structure with a lattice constant of 0.28nm. As a template, it has a small lattice mismatch with the benzene ring in the monomer molecule and is easy to make into a flat film. The two-dimensional lattice structure of other crystal planes is either a tetragonal structure or a more complex structure with serious lattice mismatch, which is not conducive to the preparation of the film.

[0015] The inventors also found that R 1 The substituent is -NO 2 or -NH 2 It is more conducive to the formation of a single-layer organic nanofilm.

[0016] The present invention also provides a method for preparing the single-layer organic nanofilm, wherein the single-layer organic nanofilm is prepared by self-assembling the monomer molecules on the surface of the Au (111) electrode, and specifically comprises the steps of:

[0017] (1) Providing an atomically flat Au(111) surface;

[0018] (2) Evacuate the preparation chamber to a vacuum degree less than 1×10 -8 mbar, heating and degassing the evaporation source containing the monomer molecules, wherein the heating and degassing temperature does not exceed the melting point of the monomer molecules, and the vacuum degree in the preparation chamber does not change any more, and then proceeding to the next step;

[0019] (3) Raise the evaporation source temperature for thermal evaporation deposition, control the temperature, and maintain the gas pressure in the preparation chamber at 1×10 - 7 mbar, to obtain the single-layer organic nanofilm.

[0020] In a preferred embodiment, the method for preparing the single-layer organic nanofilm, in step (1), using Ar + The Au(111) electrode surface was ion sputtered at a sputtering energy of 2-3 KeV, and then annealed at 700°C. After multiple Ar + Sputtering-annealing cycles were used to obtain an atomically flat Au(111) surface.

[0021] Further preferably, in the method for preparing the single-layer organic nanofilm, in step (1), in an Ar + During the sputtering-annealing process, Ar + The ion sputtering time was 10 min and the annealing time was 10 min.

[0022] In a preferred embodiment, in the method for preparing the single-layer organic nanofilm, in step (2), the purity of the monomer molecules contained in the evaporation source is greater than 99.9%.

[0023] In a preferred embodiment, in the method for preparing the single-layer organic nanofilm, in step (2), the heating degassing temperature is 55°C.

[0024] In a preferred embodiment, in the method for preparing the single-layer organic nanofilm, in step (2), the heating and degassing time is 30 minutes.

[0025] In a preferred embodiment, in the method for preparing the single-layer organic nanofilm, in step (3), the thermal evaporation deposition time is 20 to 50 minutes.

[0026] A preferred method for preparing a single-layer organic nanofilm comprises the following steps:

[0027] (1) Providing atomically flat Au(111) surface: using Ar + The Au(111) electrode surface was ion sputtered at a sputtering energy of 2-3 KeV for 10 min, followed by annealing at 700 °C for 10 min. After more than ten Ar + Sputtering-annealing cycles to obtain an atomically flat Au(111) surface;

[0028] (2) Evacuate the preparation chamber to a vacuum degree less than 1×10 -8 mbar, heating and degassing the evaporation source containing monomer molecules with a purity greater than 99.9%, the heating and degassing temperature is 55°C, which does not exceed the melting point of the monomer molecules, and the heating and degassing time is 30min. When the vacuum degree in the preparation chamber no longer changes, proceed to the next step;

[0029] (3) Raise the temperature of the evaporation source for thermal evaporation deposition, control the temperature (about 100°C), and maintain the pressure in the preparation chamber at 1×10 -7 mbar, and thermal evaporation deposition for 20 to 50 min to obtain the single-layer organic nanofilm.

[0030] As a general inventive concept, the present invention also provides a method for characterizing the single-layer organic nanofilm, wherein the single-layer organic nanofilm is characterized by using a scanning tunneling microscope, and the scanning conditions are a bias voltage of -1V and a tunneling current I t It is 0.3nA.

[0031] The inventors have found through a large number of experimental studies that the best characterization of a single-layer organic nanofilm can be obtained under the above scanning conditions.

[0032] Compared with the prior art, the present invention has the following main advantages and features:

[0033] The present invention proposes a "bottom-up" method for preparing a single-layer organic nanofilm. On the surface of an Au (111) electrode, a self-assembly method is used to successfully prepare a single-layer organic nanofilm with a compact and regular structure, which shows great potential in related research and applications such as new materials and molecular electronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of the molecular structure of an organic monomer according to Example 1 of the present invention;

[0035] Figure 2 This is a photo of an atomically flat surface of Au(111) without adsorbed molecules under a scanning tunneling microscope. A large platform larger than 30nm can be observed, and atomic resolution can be obtained through fine scanning.

[0036] Figure 3 Schematic diagram of the device structure for preparing a single-layer organic nanofilm structure in Example 1 of the present invention, with reference to: 1. heating stage, 2. Au (111) electrode, 3. evaporation source, 4. Ar + Sputtering gun;

[0037] Figure 4 This is a scanning tunneling microscope photograph of a single-layer organic nanofilm structure prepared in Example 1 of the present invention;

[0038] Figure 5 This is an STM photo of the single-layer organic nanofilm prepared in Example 1 of the present invention after being heated at 150° C.;

[0039] Figure 6 This is an STM photo of the single-layer organic nanofilm prepared in Example 1 of the present invention after being heated at 200° C.;

[0040] Figure 7 This is a STM photo of the desorption of the single-layer organic nanofilm prepared in Example 1 of the present invention after heating at 250°C;

[0041] Figure 8 This is a schematic diagram of the molecular structure of an organic monomer according to Example 2 of the present invention;

[0042] Fig. 9 This is a scanning tunneling microscope photograph of a single-layer organic nanofilm structure prepared in Example 2 of the present invention;

[0043] Fig.10 This is an STM photo of a single-layer organic nanofilm prepared in Example 2 of the present invention after being heated at 150° C.;

[0044] Fig.11 This is an STM photo of a single-layer organic nanofilm prepared in Example 2 of the present invention after being heated at 200° C.;

[0045] Fig.12 This is a STM photo of the desorption of the single-layer organic nanofilm prepared in Example 2 of the present invention after heating at 250°C;

[0046] Fig.13 This is a STM photograph of the desorption of the single-layer organic nanofilm prepared in Example 2 of the present invention after being heated at 300°C. DETAILED DESCRIPTION

[0047] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0048] The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers.

[0049] Example 1

[0050] The structure of the device for preparing a single-layer organic nanofilm structure in this embodiment is as follows Figure 3 As shown, it includes a preparation cavity, and the preparation cavity is provided with:

[0051] A heating stage 1, which can be used to anneal the Au (111) electrode 2 and heat a single layer of organic nanofilm to investigate its thermal stability;

[0052] An Au (111) electrode 2 disposed on a heating platform 1;

[0053] Ar + The sputtering gun 4 can be used to perform Ar sputtering on the Au(111) electrode 2. + Ion sputtering;

[0054] The evaporation source 3 may be loaded with monomer molecules and equipped with a heating device.

[0055] The above-mentioned device structure is used to prepare a single-layer organic nanofilm, wherein the monomer molecular structure used is as follows Figure 1 As shown, specifically including:

[0056] Step 1: In the preparation of the cavity, first use Ar + The sputtering gun 4 performs Ar sputtering on the Au(111) electrode 2. + Ion sputtering, sputtering energy 2KeV, sputtering time ten minutes, and then annealing treatment using heating stage 1, annealing temperature 700℃, annealing time ten minutes. + After the sputtering-annealing cycle, the Figure 2 The atomically flat Au(111) surface shown;

[0057] Step 2: Prepare the chamber and evacuate it to a vacuum level lower than 1×10 -8 mbar, first degas the evaporation source 3 loaded with organic monomer molecules with a purity greater than 99.9%, and control the degassing temperature at about 55°C, taking care not to exceed the melting point of the molecules. Degassing takes about 30 minutes, and when the vacuum degree no longer changes, proceed to the next step;

[0058] Step 3: Perform thermal evaporation deposition, raise the temperature to about 100°C, monitor the pressure in the vacuum chamber, control the temperature, and maintain the vacuum degree at 1×10 -7 mbar, start to deposit molecules, the deposition time is 20 to 50 min, and a single-layer organic nanofilm can be obtained.

[0059] Characterization of single-layer organic nanofilm: The prepared single-layer organic nanofilm was characterized using a scanning tunneling microscope. The scanning conditions were a bias voltage of -1 V and a tunneling current of I t The structure of the monolayer organic nanofilm can be seen in the high-resolution STM image obtained, such as Figure 4 shown.

[0060] The film was transferred back to the heating stage 1 for annealing treatment. The annealing temperatures were 150°C, 200°C, and 250°C, respectively. The film was then characterized using a scanning tunneling microscope according to the above characterization method. The corresponding film photos were as follows: Figures 5 to 7 As shown, it can be seen that at 150°C and 200°C, the single-layer organic nanofilm can still maintain good stability, and the monomer molecules are still evenly distributed on the surface of the Au(111) electrode and firmly bonded. When heated to 250°C, some monomer molecules detach from the surface of the Au(111) electrode, and the Au(111) electrode is exposed.

[0061] Example 2

[0062] The structure of the device for preparing a single-layer organic nanofilm structure in this embodiment is as follows Figure 3 As shown, it includes a preparation cavity, and the preparation cavity is provided with:

[0063] A heating stage 1, which can be used to anneal the Au (111) electrode 2 and heat a single layer of organic nanofilm to investigate its thermal stability;

[0064] An Au (111) electrode 2 disposed on a heating platform 1;

[0065] Ar + The sputtering gun 4 can be used to perform Ar sputtering on the Au(111) electrode 2. + Ion sputtering;

[0066] The evaporation source 3 may be loaded with monomer molecules and equipped with a heating device.

[0067] The above-mentioned device structure is used to prepare a single-layer organic nanofilm, wherein the monomer molecular structure used is as follows Figure 8 As shown, specifically including:

[0068] Step 1: In the preparation of the cavity, first use Ar + The sputtering gun 4 performs Ar sputtering on the Au(111) electrode 2. + Ion sputtering, sputtering energy 2KeV, sputtering time ten minutes, and then annealing treatment using heating stage 1, annealing temperature 700℃, annealing time ten minutes. + After the sputtering-annealing cycle, the Figure 2 The atomically flat Au(111) surface shown;

[0069] Step 2: Prepare the chamber and evacuate it to a vacuum level lower than 1×10 -8 mbar, first degas the evaporation source 3 loaded with organic monomer molecules with a purity greater than 99.9%, and control the degassing temperature at about 55°C, taking care not to exceed the melting point of the molecules. Degassing takes about 30 minutes, and when the vacuum degree no longer changes, proceed to the next step;

[0070] Step 3: Perform thermal evaporation deposition, raise the temperature to about 100°C, monitor the pressure in the vacuum chamber, control the temperature, and maintain the vacuum degree at 1×10 -7 mbar, start to deposit molecules, the deposition time is 20 to 50 min, and a single-layer organic nanofilm can be obtained.

[0071] Characterization of single-layer organic nanofilm: The prepared single-layer organic nanofilm was characterized using a scanning tunneling microscope. The scanning conditions were a bias voltage of -1 V and a tunneling current of I t The structure of the monolayer organic nanofilm can be seen in the high-resolution STM image obtained, such as Fig. 9 shown.

[0072] The film was transferred back to the heating stage 1 for annealing treatment. The annealing temperatures were 150°C, 200°C, 250°C, and 300°C, respectively. The film was then characterized using a scanning tunneling microscope according to the above characterization method. The corresponding film photos were as follows: Figures 10 to 13 As shown in Figure 2, it can be seen that at 150℃, 200℃, and 250℃, the single-layer organic nanofilm can still maintain good stability, and the monomer molecules are still evenly distributed on the surface of the Au(111) electrode and firmly bonded. When heated to 300℃, Fig.13 As shown, the monomer molecules are separated from the surface of the Au(111) electrode, and the Au(111) electrode is exposed.

[0073] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A single-layer organic nanofilm, characterized in that: It includes a single-layer monomer molecule chemically bonded to Au atoms by S atoms and an Au (111) electrode with an atomically flat surface; The monomer molecule has a structure as shown in the following formula (I): In formula (I), R1 is -NH2, R2 is -SH; The single-layer organic nanofilm is prepared by self-assembly of the monomer molecules on the surface of the Au (111) electrode, specifically comprising the steps of: (1) Providing atomically flat Au(111) surface: using Ar + The Au(111) electrode surface was ion sputtered at a sputtering energy of 2-3 KeV, and then annealed at 700°C. After multiple Ar + Sputtering-annealing cycles to obtain an atomically flat Au(111) surface; (2) Evacuate the preparation chamber to a vacuum degree less than 1×10 -8 mbar, heating and degassing the evaporation source containing the monomer molecules, wherein the heating and degassing temperature does not exceed the melting point of the monomer molecules, and the vacuum degree in the preparation chamber does not change any more, and then proceeding to the next step; (3) Raise the temperature of the evaporation source for thermal evaporation deposition, control the temperature at 100°C, and maintain the pressure in the preparation chamber at 1×10 -7 mbar, to obtain the single-layer organic nanofilm; the thermal evaporation deposition time is 20 to 50 minutes.

2. The method for preparing a single-layer organic nanofilm according to claim 1, characterized in that: The single-layer organic nanofilm is prepared by self-assembling the monomer molecules on the surface of the Au (111) electrode, which specifically includes the steps of: (1) Providing atomically flat Au(111) surface: using Ar + The Au(111) electrode surface was ion sputtered at a sputtering energy of 2-3 KeV, and then annealed at 700°C. After multiple Ar + Sputtering-annealing cycles to obtain an atomically flat Au(111) surface; (2) Evacuate the preparation chamber to a vacuum degree less than 1×10 -8 mbar, heating and degassing the evaporation source containing the monomer molecules, wherein the heating and degassing temperature does not exceed the melting point of the monomer molecules, and the vacuum degree in the preparation chamber does not change any more, and then proceeding to the next step; (3) Raise the temperature of the evaporation source for thermal evaporation deposition, control the temperature at 100°C, and maintain the pressure in the preparation chamber at 1×10 -7 mbar, to obtain the single-layer organic nanofilm; the thermal evaporation deposition time is 20 to 50 minutes.

3. The preparation method according to claim 2, characterized in that: In step (1), in an Ar + During the sputtering-annealing process, Ar + The ion sputtering time was 10 min and the annealing time was 10 min.

4. The preparation method according to claim 2, characterized in that: In step (2), the purity of the monomer molecules contained in the evaporation source is greater than 99.9%.

5. The preparation method according to claim 2, characterized in that: In step (2), the heating degassing temperature is 55°C.

6. The preparation method according to claim 2, characterized in that: In step (2), the heating and degassing time is 30 minutes.

7. The method for characterizing a single-layer organic nanofilm according to claim 1, characterized in that: The single-layer organic nanofilm was characterized by a scanning tunneling microscope under the following scanning conditions: bias voltage -1 V, tunneling current I t It is 0.3nA.

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