A two-dimensional white phosphorus film, preparation method, application and device

Abstract

The present invention relates to a method for preparing a two-dimensional white phosphorus film, an application and a device. The method for preparing a two-dimensional white phosphorus film comprises the following steps: preparing a silicon substrate using a silicon wafer; degassing a cadmium source under vacuum conditions, and then heating to evaporate cadmium atoms to the surface of the silicon substrate, and epitaxially growing cadmium atoms to obtain a cadmium substrate; degassing black phosphorus under vacuum conditions, and then heating to a first temperature to obtain P 4 molecular beam, and then evaporate it to the surface of the cadmium substrate at the second temperature to obtain a P 4 A single-layer two-dimensional white phosphorus film composed of parallel arrangement of molecular dimers. The present invention also provides a single-layer two-dimensional white phosphorus film prepared by the preparation method. The present invention also provides an application of the single-layer two-dimensional white phosphorus film prepared by the preparation method, and the application of the two-dimensional white phosphorus film as nano ink. The present invention also provides a device for preparing the two-dimensional white phosphorus film as described in the present invention. The present invention prepares a two-dimensional white phosphorus film with specific structure and performance.

Description

Technical Field

[0001] The present invention relates to the technical field of thin film materials, and in particular to a two-dimensional white phosphorus film, a preparation method, an application and a device. Background Art

[0002] Two-dimensional thin film materials, due to their low dimensionality in a single direction and quantum confinement effects, exhibit excellent properties that are different from three-dimensional materials. On the one hand, two-dimensional thin film materials with atomic-level thickness not only show the enhancement of certain material properties, but may also show new areas that materials cannot cover. On the other hand, two-dimensional thin film materials can form macroscopic ultra-thin, transparent, and flexible electronic devices. Two-dimensional thin film materials have excellent electrical and thermal conductivity, ultra-high mechanical strength and good flexibility, as well as a large specific surface area and other characteristics, which have enabled two-dimensional thin film materials to be widely studied and applied in optoelectronic devices, energy conversion and storage, catalysis, sensing and other fields.

[0003] Phosphorene, a two-dimensional thin film material composed only of the element phosphorus (P), is a promising two-dimensional material that has attracted great interest from researchers in both basic research and potential applications. Phosphorus (P) is one of the most abundant elements in the earth's crust. It has unique properties in optoelectronic and electronic device applications, and scientists in the fields of physics, chemistry, and materials science are very interested in its related research. Elemental phosphorus has many allotropes, such as tetrahedral white phosphorus (P 4 ), black phosphorus, tubular red phosphorus and purple phosphorus. Among them, black phosphorene, as a P-type layered semiconductor material, is very similar to graphene in appearance, performance and structure, and the layers are stacked by van der Waals forces. In 2014, black phosphorene was successfully mechanically exfoliated from bulk black phosphorus. The successful application of black phosphorene in field-effect transistors and the novel optoelectronic properties of two-dimensional black phosphorus nanosheets have further stimulated people's interest in the research of two-dimensional phosphorus allotropes. With the successful preparation of black phosphorene, scientists have successfully prepared blue phosphorene on Au (111) and Cu (111) substrates using molecular beam epitaxial growth technology. In addition, purple phosphorene and ultra-thin red phosphorus nanosheets have also been successfully synthesized.

[0004] White phosphorus is the most common allotrope of phosphorus, consisting of P 4 Molecular composition. Compared with other allotropes, white phosphorus has higher activity and instability. So far, white phosphorus is still the only phosphorus allotrope that has not been synthesized by mechanical exfoliation and epitaxial growth. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a two-dimensional white phosphorus film, a preparation method, an application and a device to prepare a two-dimensional white phosphorus film with a specific structure and performance, thereby broadening the scope of use of white phosphorus and enhancing the application value of white phosphorus.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a two-dimensional white phosphorus film comprises the following steps:

[0008] S1. Preparation of silicon (111)-7×7 substrate: A silicon (111)-7×7 substrate is prepared by using a silicon wafer;

[0009] S2. Preparation of a cadmium (0001) substrate: degassing a cadmium source under vacuum conditions, and then heating the cadmium source to evaporate cadmium atoms onto the surface of a silicon (111)-7×7 substrate, where the cadmium atoms grow epitaxially to obtain a cadmium (0001) substrate;

[0010] S3. Preparation of two-dimensional white phosphorus film: Degas black phosphorus under vacuum conditions and then heat it to a first temperature to obtain P 4 molecular beam, and then evaporate it to the surface of the cadmium (0001) substrate at the second temperature to obtain a P 4 A single-layer two-dimensional white phosphorus film composed of molecular dimers arranged in parallel.

[0011] Among them, the purpose of degassing the cadmium source and black phosphorus is to obtain high-purity cadmium atoms and black phosphorus.

[0012] Experiments have proved that the prepared two-dimensional white phosphorus film has a flat two-dimensional structure at the atomic level. It not only has potential applications in optoelectronic devices and electronic devices, but also can realize the function of nano-ink, thereby using the white phosphorus film as nano-ink, effectively broadening the scope of use of white phosphorus and enhancing the application value of white phosphorus.

[0013] Preferably, in S3, the black phosphorus is degassed at a vacuum degree of 1.0×10 -10 mbar~1.2×10 -10 Degassing was carried out at a pressure of 100 mbar and a temperature of 200°C to 205°C for 1 h to 3 h.

[0014] Preferably, in S3, the first temperature is 175°C to 200°C.

[0015] Preferably, in S3, the second temperature is between -153°C and -183°C.

[0016] In the process of heating and in-situ deposition of black phosphorus onto the surface of the cadmium (0001) substrate, the temperature of the cadmium (0001) substrate is kept below zero in order to make P 4 The molecules are more easily adsorbed on the surface of the cadmium (0001) substrate.

[0017] Preferably, in S1, the preparation of the silicon (111)-7×7 substrate comprises: sequentially cleaning, degassing and annealing the silicon wafer to obtain the silicon (111)-7×7 substrate.

[0018] Preferably, the cleaning is ultrasonic cleaning using alcohol and acetone in sequence.

[0019] Preferably, the silicon wafer is degassed at a vacuum degree of 1.0×10 -10 mbar~1.2×10 -10 mbar and a temperature of 400°C to 600°C for 8h to 12h, and then cooled to room temperature.

[0020] More preferably, the degassing temperature of the silicon wafer is 500° C., and the insulation treatment time is 8 hours.

[0021] Preferably, the annealing adopts a cyclic annealing treatment, and the cyclic annealing treatment is to increase the temperature from room temperature to 1000 ~ 1300 ° C within 5 ~ 20 seconds, anneal for 13 ~ 18 seconds, cool down to 400 ° C, keep for 10 ~ 15 seconds, then increase the temperature from 400 ° C to 1000 ~ 1300 ° C within 5 ~ 20 seconds, anneal for 13 ~ 18 seconds, cool down to 400 ° C, keep for 10 ~ 15 seconds, and repeat this cycle for a total of 5 to 8 annealing times, commonly known as flash silicon.

[0022] Among them, the temperature is raised from room temperature to 1000 ~ 1300℃ within 5 ~ 20s, annealed for 13 ~ 18s, cooled to 400℃, and maintained for 10 ~ 15s as one annealing treatment.

[0023] Preferably, in S2, the cadmium source is degassed at a vacuum degree of 1.0×10 -10 mbar~1.2×10 -10 Degas for 1h~3h under the conditions of mbar and temperature of 60℃~80℃.

[0024] Preferably, in S2, the temperature of the heated cadmium source is 60°C to 80°C, the evaporation time of the cadmium atoms is 30min to 40min, and during the evaporation of the cadmium atoms onto the surface of the silicon (111)-7×7 substrate, the temperature of the silicon (111)-7×7 substrate is maintained at room temperature.

[0025] In the process of evaporating cadmium atoms onto the surface of the silicon (111)-7×7 substrate, the temperature of the silicon (111)-7×7 substrate is kept at room temperature in order to facilitate the diffusion of cadmium atoms and obtain a cadmium (0001) substrate surface.

[0026] Preferably, the cadmium source is metallic cadmium with a purity of 99.999%.

[0027] The present invention also provides a two-dimensional white phosphorus film prepared by the preparation method of the present invention.

[0028] The present invention also provides an application of the two-dimensional white phosphorus film prepared by the preparation method of the present invention, wherein the two-dimensional white phosphorus film is used as nano ink.

[0029] Preferably, the application method of the white phosphorus film is: transferring the two-dimensional white phosphorus film to a scanning tunneling microscope, placing the needle tip of the scanning tunneling microscope above the two-dimensional white phosphorus film under a vacuum environment and a third temperature condition, and moving the needle tip of the scanning tunneling microscope using writing strokes as a path to realize the writing function.

[0030] Preferably, the vacuum degree of the vacuum environment is 1.0×10 -10 mbar~1.2×10 -10 mbar.

[0031] Preferably, the third temperature is between -195°C and -200°C.

[0032] Preferably, the scanning voltage of the scanning tunneling microscope during the writing process is 1V~3V.

[0033] The present invention also provides a device for preparing the two-dimensional white phosphorus film as described in the present invention, comprising a vacuum preparation chamber, a sample holder, a sample transfer rod, a magnetic handle, a DC power supply, a cadmium source placement component, a first crucible, a second crucible, a water circulation cooling device and a heating furnace;

[0034] The sample holder is located inside the cavity of the vacuum preparation chamber;

[0035] One end of the sample transfer rod is connected to the sample rack, and the other end is connected to the magnetic handle;

[0036] The magnetic handle and the DC power supply are located outside the vacuum preparation chamber;

[0037] The cadmium source placement component is located at the bottom of the vacuum preparation chamber, with a portion located inside the cavity of the vacuum preparation chamber and another portion located outside the cavity of the vacuum preparation chamber;

[0038] The first crucible is arranged in the cadmium source placement component;

[0039] The heating furnace is located at the bottom of the vacuum preparation chamber, with a portion of the heating furnace located inside the cavity of the vacuum preparation chamber and another portion of the heating furnace located outside the cavity of the vacuum preparation chamber;

[0040] The second crucible is located in the heating furnace;

[0041] The heating furnace is built into the water circulation cooling device;

[0042] The sample rack, the cadmium source placement component and the water circulation cooling device are all connected to the DC power supply.

[0043] Beneficial effects of the present invention:

[0044] The method for preparing a two-dimensional white phosphorus film of the present invention comprises the following steps: firstly preparing a clean silicon (111)-7×7 substrate in an ultra-high vacuum environment by using molecular beam epitaxy technology; secondly preparing an atomically flat cadmium (0001) substrate; and thirdly depositing black phosphorus on the surface of the cadmium (0001) substrate to obtain a P 4 Two-dimensional white phosphorus film composed of parallel arrangement of molecular dimers.

[0045] The two-dimensional white phosphorus film prepared by the method of the present invention is known through experiments that the tip of the scanning tunneling microscope is moved on the surface of the two-dimensional white phosphorus film and the electric field of the tip is combined with the P 4 Molecular interactions cause the two-dimensional white phosphorus film structure to change from ordered to disordered, thereby enabling the writing of nano-ink, effectively broadening the scope of use of white phosphorus and enhancing its application value. It has promotion and application value in the field of thin film material technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a schematic structural diagram of a device for preparing a two-dimensional white phosphorus film according to the present invention;

[0047] Figure 2 This is an STM image of the two-dimensional white phosphorus film prepared in Example 2;

[0048] Figure 3 P 4 Schematic diagram of writing a molecular dimer (two-dimensional white phosphorus film) by applying a pulse voltage to the tip of a scanning tunneling microscope; a is the P before applying the pulse voltage 4 Molecular dimer morphology, b is P after applying pulse voltage 4 Molecular dimer morphology;

[0049] Figure 4 Schematic diagram of nano-ink after writing;

[0050] Figure 5 A schematic diagram showing the relationship between the voltage applied to the scanning probe and the depth of the writing stroke;

[0051] Among them, 1-vacuum preparation chamber, 2-sample rack, 3-sample transfer rod, 4-magnetic handle, 5-DC power supply, 6-cadmium source placement component, 7-first crucible, 8-second crucible, 9-water circulation cooling device, 10-heating furnace, 11-sample substrate. DETAILED DESCRIPTION

[0052] The following will describe the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, not for limiting the scope of protection of the present invention.

[0053] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0054] The present invention intends to disclose a two-dimensional white phosphorus film, a preparation method, an application and a device, so as to successfully prepare a two-dimensional white phosphorus film with a specific structure and performance, thereby broadening the scope of use of white phosphorus and enhancing the application value of white phosphorus.

[0055] The method for preparing the two-dimensional white phosphorus film comprises the following steps:

[0056] S1. Preparation of silicon (111)-7×7 substrate: A silicon (111)-7×7 substrate is prepared by using a silicon wafer;

[0057] S2. Preparation of a cadmium (0001) substrate: degassing a cadmium source under vacuum conditions, and then heating to evaporate cadmium atoms onto the surface of a silicon (111)-7×7 substrate, where the cadmium atoms grow epitaxially to form a cadmium (0001) substrate;

[0058] S3. Preparation of two-dimensional white phosphorus film: Degas black phosphorus under vacuum conditions and then heat it to a first temperature to obtain P 4 molecular beam, and then evaporate it to the surface of the cadmium (0001) substrate at the second temperature to obtain a P 4 A single-layer two-dimensional white phosphorus film composed of molecular dimers arranged in parallel.

[0059] Among them, the purpose of degassing the cadmium source and black phosphorus is to obtain high-purity cadmium atoms and black phosphorus.

[0060] Experiments have proved that the prepared two-dimensional white phosphorus film has a flat two-dimensional structure at the atomic level, which can realize the function of nano-ink, thereby using the two-dimensional white phosphorus film as nano-ink, effectively broadening the scope of use of white phosphorus and enhancing the application value of white phosphorus.

[0061] In some embodiments, in S3, the black phosphorus is degassed at a vacuum degree of 1.0×10-10 mbar~1.2×10 -10 Degassing was carried out at a pressure of 100 mbar and a temperature of 200°C to 205°C for 1 h to 3 h.

[0062] In some embodiments, in S3, the first temperature is 175°C to 200°C.

[0063] In some embodiments, in S3, the second temperature is between -153°C and -183°C.

[0064] In some embodiments, in S1, the preparation of the silicon (111)-7×7 substrate includes: sequentially cleaning, degassing and annealing the silicon wafer to obtain the silicon (111)-7×7 substrate.

[0065] In some embodiments, the cleaning is ultrasonic cleaning using alcohol and acetone in sequence.

[0066] In some embodiments, the silicon wafer is degassed at a vacuum of 1.0×10 -10 mbar~1.2×10 -10 mbar and a temperature of 400°C to 600°C for 8h to 12h, and then cooled to room temperature.

[0067] Exemplarily, the degassing temperature of the silicon wafer is 500° C., and the insulation treatment time is 8 hours.

[0068] In some embodiments, annealing adopts a cyclic annealing process, and the cyclic annealing process is to increase the temperature from room temperature to 1000 ~ 1300 ° C within 5 ~ 20 seconds, anneal for 13 ~ 18 seconds, cool down to 400 ° C, maintain for 10 ~ 15 seconds, then increase the temperature from 400 ° C to 1000 ~ 1300 ° C within 5 ~ 20 seconds, anneal for 13 ~ 18 seconds, cool down to 400 ° C, maintain for 10 ~ 15 seconds, and repeat this cycle for a total of 5 to 8 annealing times, commonly known as flash silicon.

[0069] In some embodiments, in S2, the cadmium source is degassed at a vacuum of 1.0×10 -10 mbar~1.2×10 -10 The cadmium source was degassed for 1 h ~ 3 h under the conditions of 100 mbar and a temperature of 60 ° C ~ 80 ° C.

[0070] In some embodiments, in S2, the heating temperature is 60°C to 80°C, and during the process of evaporating cadmium atoms onto the surface of the silicon (111)-7×7 substrate, the temperature of the silicon (111)-7×7 substrate is maintained at room temperature.

[0071] In some embodiments, the cadmium source is metallic cadmium having a purity of 99.999%.

[0072] In some embodiments, a two-dimensional white phosphorus film prepared by any of the above preparation methods is also provided.

[0073] In some embodiments, a two-dimensional white phosphorus film prepared by any of the above preparation methods is also provided for use as nano ink.

[0074] In some embodiments, the application method of the two-dimensional white phosphorus film is: the two-dimensional white phosphorus film is transferred to a scanning tunneling microscope, and the tip of the scanning tunneling microscope is placed above the two-dimensional white phosphorus film under a vacuum environment and a third temperature condition, and the tip of the scanning tunneling microscope is moved along a writing stroke as a path to realize the writing function.

[0075] In some embodiments, the vacuum degree of the vacuum environment is 1.0×10 -10 mbar~1.2×10 -10 mbar.

[0076] In some embodiments, the third temperature is between -195°C and -200°C.

[0077] In some embodiments, the scanning voltage of the scanning tunneling microscope during the writing process is 1V~3V.

[0078] In some embodiments, a device for preparing a two-dimensional white phosphorus film is also provided, comprising a vacuum preparation chamber 1, a sample holder 2, a sample transfer rod 3, a magnetic handle 4, a DC power supply 5, a cadmium source placement component 6, a first crucible 7, a second crucible 8, a water circulation cooling device 9 and a heating furnace 10;

[0079] The sample holder 2 is located inside the vacuum preparation chamber 1;

[0080] One end of the sample transfer rod 3 is connected to the sample rack 2, and the other end is connected to the magnetic handle 4;

[0081] The magnetic handle 4 and the DC power supply 5 are located outside the vacuum preparation chamber 1;

[0082] The cadmium source placement component 6 is located at the bottom of the vacuum preparation chamber 1, with a portion thereof located inside the cavity of the vacuum preparation chamber 1 and another portion thereof located outside the cavity of the vacuum preparation chamber 1;

[0083] The first crucible 7 is arranged in the cadmium source placement part 6;

[0084] The heating furnace 10 is located at the bottom of the vacuum preparation chamber 1, with a portion of the heating furnace 1 being located inside the cavity of the vacuum preparation chamber 1 and another portion of the heating furnace 1 being located outside the cavity of the vacuum preparation chamber 1;

[0085] The second crucible 8 is located in the heating furnace 10;

[0086] The heating furnace 10 is built into the water circulation cooling device 9;

[0087] The sample rack 2 , the cadmium source placement component 6 and the water circulation cooling device 9 are all connected to a DC power supply 5 .

[0088] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the device, two-dimensional white phosphorus film and application method of the present invention will be further described in detail in combination with specific embodiments and drawings. Obviously, the specific embodiments described are only part of the embodiments of the present application, not all of them. The following description of at least one exemplary embodiment is actually merely illustrative and is by no means a limitation on the present application and its application. Based on the specific embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of this application.

[0089] If no specific techniques or conditions are specified in the specific embodiments, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0090] Example 1

[0091] like Figure 1 As shown, a device for preparing a two-dimensional white phosphorus film includes a vacuum preparation chamber 1, a sample holder 2, a sample transfer rod 3, a magnetic handle 4, a DC power supply 5, a cadmium source placement component 6, a first crucible 7, a second crucible 8, a water circulation cooling device 9 and a heating furnace 10;

[0092] The sample rack 2 is located inside the vacuum preparation chamber 1, and is used to fix the sample;

[0093] One end of the sample transfer rod 3 is connected to the sample rack 2, and the other end is connected to the magnetic handle 4. The sample transfer rod 3 and the magnetic handle 4 are magnetically connected, so that the sample rack 2 is controlled to enter or exit the vacuum preparation chamber 1 through the sample transfer rod 3;

[0094] The magnetic handle 4 and the DC power supply 5 are located outside the vacuum preparation chamber 1;

[0095] The cadmium source placement component 6 is located at the bottom of the vacuum preparation chamber 1, with a portion thereof located inside the cavity of the vacuum preparation chamber 1 and another portion thereof located outside the cavity of the vacuum preparation chamber 1;

[0096] The first crucible 7 is arranged in the cadmium source placing part 6, and the first crucible 7 is used for placing the cadmium source;

[0097] The heating furnace 10 is located at the bottom of the vacuum preparation chamber 1, with a portion of the heating furnace 1 being located inside the cavity of the vacuum preparation chamber 1 and another portion of the heating furnace 1 being located outside the cavity of the vacuum preparation chamber 1;

[0098] The second crucible 8 is located in the heating furnace 10, and the second crucible 8 is used to place black phosphorus;

[0099] The heating furnace 10 is built into the water circulation cooling device 9, and the water circulation cooling device 9 is externally connected to a room temperature water source to stabilize the temperature of the heating furnace 10 during heating;

[0100] The sample rack 2, the cadmium source placement component 6 and the water circulation cooling device 9 are all connected to a DC power supply 5, and the sample, the cadmium source and the black phosphorus are heated by the DC power supply 5;

[0101] When preparing a two-dimensional white phosphorus film, a silicon wafer is placed at the position of a sample substrate 11 on a sample holder 2, a sample transfer rod 3 is magnetically attracted by a magnetic handle 4 and driven to move, the sample holder 2 with the silicon wafer is sent into a vacuum preparation chamber 1, a direct current power supply 5 is used to heat the silicon wafer, degassing, the direct current power supply 5 is turned off, the silicon wafer is naturally cooled to room temperature, and then annealing is performed to prepare a Si(111)-7×7 substrate; a cadmium source is placed in a first crucible 7 in a cadmium source placement component 6, a direct current power supply 5 is used to heat and degas the cadmium source, and then evaporated to the upper surface of the Si(111)-7×7 substrate, cadmium atoms are epitaxially grown, and a Cd(0001) substrate is formed; black phosphorus is placed in a second crucible 8, and then the second crucible 8 is placed in a heating furnace 10, the heating furnace 10 is controlled by the direct current power supply 5 to degas the black phosphorus, and then the sample transfer rod 3 is manipulated by the magnetic handle 4 to align the cadmium (0001) substrate with the second crucible 8, and the heating furnace 10 is controlled by the direct current power supply 5 to heat the black phosphorus, and P is obtained. 4 Molecular beam, evaporate it onto the surface of cadmium (0001) substrate, and obtain P 4 An atomically flat two-dimensional white phosphorus film composed of parallel arrangement of molecular dimers.

[0102] Example 2

[0103] A method for preparing a two-dimensional white phosphorus film using the device in Example 1 comprises the following steps:

[0104] S1. Preparation of silicon (111)-7×7 substrate: A Si (111)-7×7 substrate is prepared by using a silicon wafer, specifically comprising:

[0105] S11, selecting the (111) crystal plane of the Si substrate as the crystal orientation, cutting the silicon wafer into a size of 3 mm×15 mm, and successively placing it in alcohol and acetone for ultrasonic cleaning to obtain a silicon wafer substrate;

[0106] S12, put the cleaned silicon wafer substrate on the position of the upper sample substrate 11 of the sample rack 2, and use the magnetic handle 4 to drive the sample transfer rod 3 to move the sample rack 2 with the silicon wafer substrate into the vacuum preparation chamber 1, and control the vacuum degree in the vacuum preparation chamber 1 to 1.2×10 -10mbar ultra-vacuum environment, use DC power 5 to heat the silicon wafer substrate to 500°C, degas for 8 hours, then turn off the DC power 5 and let the silicon wafer substrate cool naturally to room temperature;

[0107] S14, using a DC power supply 5 to heat the degassed silicon wafer substrate from room temperature to 1200° C. within 15 seconds, annealing for 10 seconds, then rapidly reducing the current to zero, annealing for 10 seconds, and repeating this process for 7 times in total to obtain a clean Si(111)-7×7 substrate surface;

[0108] S2. Preparation of a cadmium (0001) substrate: degassing a cadmium source under vacuum conditions, and then heating to evaporate cadmium atoms onto the surface of a silicon (111)-7×7 substrate, and epitaxially growing the cadmium atoms to form a cadmium (0001) substrate, specifically comprising:

[0109] S21, at a vacuum degree of 1.2×10 -10 In an ultra-vacuum environment of mbar, a high-purity cadmium source is placed in a first crucible 7 in a cadmium source placement component 6, and a DC power supply 5 is used to heat the cadmium source to 70° C. for degassing for 2 hours, so that the cadmium source is fully degassed;

[0110] S22, operate the magnetic handle 4 so that the sample transfer rod 3 drives the sample holder 2 to move, ensure that the surface of the Si(111)-7×7 substrate on the sample holder 2 is aligned with the first crucible 7, heat the first crucible 7 to 65°C through the DC power supply 5, so that cadmium atoms evaporate and deposit on the clean surface of the Si(111)-7×7 substrate, and the deposition time is 35 minutes. During the deposition of cadmium atoms, the Si(111)-7×7 substrate is kept at room temperature, and the cadmium atoms grow epitaxially to form a cadmium (0001) surface, thereby obtaining a cadmium (0001) substrate. The obtained cadmium (0001) substrate is introduced into the scanning tunneling microscope cavity and cooled to minus 195°C for standby use;

[0111] S3. Preparation of two-dimensional white phosphorus film: Degas black phosphorus under vacuum conditions and then heat it to a first temperature to obtain P 4 molecular beam, and then evaporate it to the surface of the cadmium (0001) substrate at the second temperature to obtain a P 4 A single-layer two-dimensional white phosphorus film composed of parallel arrangement of molecular dimers, specifically comprising:

[0112] S31, at a vacuum degree of 1.2×10 -10 In an ultra-vacuum environment of mbar, high-purity black phosphorus is placed in a second crucible 8 in a heating furnace 10, and heated to 180° C. by a DC power supply 5 for degassing for 1.5 hours;

[0113] S32, manipulate the magnetic handle 4 so that the sample transfer rod 3 drives the sample holder 2 to move, ensure that the surface of the cadmium (0001) substrate on the sample holder 2 is aligned with the second crucible 8, and heat the second crucible 8 to 175° C. by the DC power supply 5 to obtain P 4 The molecular beam was used to evaporate the cadmium (0001) substrate surface at a temperature of -183°C. The deposition time was about 3 minutes, so that the P 4 An atomically flat two-dimensional white phosphorus film composed of parallel arrangement of molecular dimers.

[0114] The two-dimensional white phosphorus film prepared in Example 2 was analyzed by scanning tunneling microscopy. The results are as follows: Figure 2 shown.

[0115] in, Figure 2 a is a large-scale STM morphology image of a single-layer two-dimensional white phosphorus film grown on a cadmium (0001) substrate. Figure 2 b is a high-resolution STM morphology image of a single-layer two-dimensional white phosphorus film. Figure 2 a and Figure 2 From the analysis in b, we can see that the height of the prepared single-layer two-dimensional white phosphorus film is about 4.3 angstroms. 4 Molecular dimer composition.

[0116] Example 3

[0117] A method for preparing a white phosphorus film using the device in Example 1 comprises the following steps:

[0118] S1. Preparation of silicon (111)-7×7 substrate: A Si (111)-7×7 substrate is prepared by using a silicon wafer, specifically comprising:

[0119] S11, selecting the (111) crystal plane of the Si substrate as the crystal orientation, cutting the silicon wafer into a size of 3 mm×15 mm, and successively placing it in alcohol and acetone for ultrasonic cleaning to obtain a silicon wafer substrate;

[0120] S12, put the cleaned silicon wafer substrate on the position of the upper sample substrate 11 of the sample rack 2, and use the magnetic handle 4 to drive the sample transfer rod 3 to move the sample rack 2 with the silicon wafer substrate into the vacuum preparation chamber 1, and control the vacuum degree in the vacuum preparation chamber 1 to 1.2×10 -10 mbar ultra-vacuum environment, use DC power 5 to heat the silicon wafer substrate to 500°C, degas for 8 hours, then turn off the DC power 5 and let the silicon wafer substrate cool naturally to room temperature;

[0121] S14, using a DC power supply 5 to heat the degassed silicon wafer substrate from room temperature to 1200° C. within 15 seconds, annealing for 10 seconds, then rapidly reducing the current to zero, annealing for 10 seconds, and repeating this process for 7 times in total to obtain a clean Si(111)-7×7 substrate surface;

[0122] S2. Preparation of a cadmium (0001) substrate: degassing a cadmium source under vacuum conditions, and then heating to evaporate cadmium atoms onto the surface of a silicon (111)-7×7 substrate, and epitaxially growing the cadmium atoms to form a cadmium (0001) substrate, specifically comprising:

[0123] S21, at a vacuum degree of 1.0×10 -10 In an ultra-vacuum environment of mbar, a high-purity cadmium source is placed in a first crucible 7 in a cadmium source placement component 6, and a DC power supply 5 is used to heat the cadmium source to 80° C. for degassing for 1 hour, so that the cadmium source is fully degassed;

[0124] S22, operate the magnetic handle 4 so that the sample transfer rod 3 drives the sample holder 2 to move, ensure that the surface of the Si(111)-7×7 substrate on the sample holder 2 is aligned with the first crucible 7, heat the first crucible 7 to 75°C through the DC power supply 5, so that cadmium atoms evaporate and deposit on the clean surface of the Si(111)-7×7 substrate, and the deposition time is 30 minutes. During the deposition of cadmium atoms, the Si(111)-7×7 substrate is kept at room temperature, and the cadmium atoms grow epitaxially to form a cadmium (0001) surface, thereby obtaining a cadmium (0001) substrate. The obtained cadmium (0001) substrate is introduced into the scanning tunneling microscope cavity and cooled to minus 195°C for standby use;

[0125] S3. Preparation of two-dimensional white phosphorus film: degas black phosphorus under vacuum conditions, and then heat it to a first temperature to obtain P 4 molecular beam, and then evaporate it to the surface of the cadmium (0001) substrate at the second temperature to obtain a P 4 A single-layer two-dimensional white phosphorus film composed of parallel arrangement of molecular dimers, specifically comprising:

[0126] S31, at a vacuum degree of 1.0×10 -10 In an ultra-vacuum environment of mbar, high-purity black phosphorus is placed in a second crucible 8 in a heating furnace 10, and heated to 190° C. by a DC power supply 5 for degassing for 1 hour;

[0127] S32, manipulate the magnetic handle 4 so that the sample transfer rod 3 drives the sample holder 2 to move, ensure that the surface of the cadmium (0001) substrate on the sample holder 2 is aligned with the second crucible 8, and heat the second crucible 8 to 185° C. by the DC power supply 5 to obtain P 4 The molecular beam was used to evaporate the cadmium (0001) substrate surface at a temperature of -170°C. The deposition time was about 2 minutes, so that the obtained P4 An atomically flat two-dimensional white phosphorus film composed of parallel arrangement of molecular dimers.

[0128] Example 4

[0129] like Figure 3 As shown, a method for using the two-dimensional white phosphorus film prepared in Example 2 as nano ink comprises the following steps:

[0130] S1. The sample adsorbed with a single layer of two-dimensional white phosphorus film is transferred to a scanning tunneling microscope. The working environment is 1.0×10 -10 mbar ultra-high vacuum, temperature is minus 195°C;

[0131] S2. Place the tip of the scanning tunneling microscope above the single-layer two-dimensional white phosphorus film, set the scanning voltage to 3V, move the tip of the scanning tunneling microscope to the P near the tip. 4 The molecules will be affected by the electric field effect of the needle tip, adsorbed on the needle tip or deviate from their original position, leaving defects on the phosphor film; moving the scanning probe with voltage along the path of Chinese writing will leave continuous defects of a certain depth on the phosphor film, thus realizing the writing function, see Figure 4 .

[0132] from Figure 4 The traces of written Chinese characters can be clearly observed, which effectively proves that the two-dimensional white phosphorus film of the present invention can be used as nano-ink.

[0133] Among them, it was found through experiments that during the writing process, the voltage applied to the scanning tunneling microscope probe was proportional to the depth of the defect left on the white phosphorus film, see Figure 5 shown.

[0134] In summary, the method for preparing a white phosphorus film of the present invention uses molecular beam epitaxy technology in an ultra-high vacuum environment to first prepare a clean silicon (111)-7×7 substrate; secondly, prepare an atomically flat cadmium (0001) substrate; and thirdly, deposit black phosphorus on the surface of the cadmium (0001) substrate to obtain a parallel-arranged P 4 A single-layer two-dimensional white phosphorus film composed of molecular dimers.

[0135] The single-layer two-dimensional white phosphorus film prepared by the method of the present invention is known through experiments that the tip of the scanning tunneling microscope is moved on the surface of the two-dimensional white phosphorus film and the electric field of the tip is combined with the P 4 Molecular interactions cause the two-dimensional white phosphorus film structure to change from ordered to disordered, thereby enabling the writing of nano-ink, effectively broadening the scope of use of white phosphorus and enhancing its application value. It has promotion and application value in the field of thin film material technology.

[0136] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or change made by a person skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A method for preparing a two-dimensional white phosphorus film, characterized in that: The following steps are involved: S1. Preparation of silicon (111)-7×7 substrate: A silicon (111)-7×7 substrate is prepared by using a silicon wafer; S2. Preparation of a cadmium (0001) substrate: degassing a cadmium source under vacuum conditions, and then heating the cadmium source to evaporate cadmium atoms onto the surface of a silicon (111)-7×7 substrate, and epitaxially growing the cadmium atoms to obtain a cadmium (0001) substrate; S3. Preparation of two-dimensional white phosphorus film: Under vacuum conditions, black phosphorus is degassed and then heated to a first temperature to obtain a P4 molecular beam, which is then evaporated to a second temperature on a cadmium (0001) substrate surface to obtain a single-layer two-dimensional white phosphorus film composed of parallel arranged P4 molecular dimers.

2. The method for preparing a two-dimensional white phosphorus film according to claim 1, characterized in that: In S3, the black phosphorus is degassed at a vacuum degree of 1.0×10 -10 mbar~1.2×10 -10 Degassing for 1h~3h at 100mbar and 200℃~205℃; And / or, in S3, the first temperature is 175° C. to 200° C.; And / or, in S3, the second temperature is -153°C to -183°C.

3. The method for preparing a two-dimensional white phosphorus film according to claim 1, characterized in that: In S1, the preparation of the silicon (111)-7×7 substrate includes: sequentially cleaning, degassing and annealing the silicon wafer to obtain the silicon (111)-7×7 substrate.

4. The method for preparing a two-dimensional white phosphorus film according to claim 3, characterized in that: The cleaning is carried out by ultrasonic cleaning using alcohol and acetone in sequence; and / or, degas the silicon wafer to a vacuum of 1.0×10 -10 mbar~1.2×10 -10 mbar and 400℃~600℃ for 8h~12h, then cool to room temperature; And / or, the annealing adopts a cyclic annealing treatment, and the cyclic annealing treatment is to increase the temperature from room temperature to 1000-1300°C within 5-20s, anneal for 13-18s, cool down to 400°C, keep for 10-15s, then increase the temperature from 400°C to 1000-1300°C within 5-20s, anneal for 13-18s, cool down to 400°C, keep for 10-15s, and repeat this cycle for a total of 5-8 annealing times.

5. The method for preparing a two-dimensional white phosphorus film according to claim 1, characterized in that: In S2, the cadmium source is degassed at a vacuum degree of 1.0×10 -10 mbar~1.2×10 -10 Degassing for 1h~3h at mbar and 60℃~80℃; And / or, in S2, the temperature of the cadmium source is 60° C. to 80° C., the evaporation time of the cadmium atoms is 30 min to 40 min, and during the evaporation of the cadmium atoms, the temperature of the silicon (111)-7×7 substrate is maintained at room temperature; And / or, the cadmium source is metallic cadmium with a purity of 99.999%.

6. A two-dimensional white phosphorus film prepared by the preparation method according to any one of claims 1 to 5.

7. An application of a two-dimensional white phosphorus film prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The two-dimensional white phosphorus film is used as nano ink.

8. The use of the two-dimensional white phosphorus film according to claim 7, characterized in that: The application method is: transfer the two-dimensional white phosphorus film to a scanning tunneling microscope, place the needle tip of the scanning tunneling microscope above the two-dimensional white phosphorus film under a vacuum environment and a third temperature condition, move the needle tip of the scanning tunneling microscope along the writing strokes to realize the writing function.

9. The use of the white phosphorus film according to claim 8, characterized in that: The vacuum degree of the vacuum environment is 1.0×10 -10 mbar~1.2×10 -10 mbar; And / or, the third temperature is -195°C to -200°C; And / or, the scanning voltage of the scanning tunneling microscope during the writing process is 1V~3V.

10. An apparatus for preparing the white phosphorus film as claimed in claim 6, characterized in that: It comprises a vacuum preparation chamber (1), a sample rack (2), a sample transfer rod (3), a magnetic handle (4), a DC power supply (5), a cadmium source placement component (6), a first crucible (7), a second crucible (8), a water circulation cooling device (9) and a heating furnace (10); The sample holder (2) is located inside the vacuum preparation chamber (1); One end of the sample transfer rod (3) is connected to the sample rack (2), and the other end is connected to the magnetic handle (4); The magnetic handle (4) and the DC power supply (5) are located outside the vacuum preparation chamber (1); The cadmium source placement component (6) is located at the bottom of the vacuum preparation chamber (1), with a portion thereof being located inside the cavity of the vacuum preparation chamber (1) and another portion thereof being located outside the cavity of the vacuum preparation chamber (1); The first crucible (7) is arranged in the cadmium source placement component (6); The heating furnace (10) is located at the bottom of the vacuum preparation chamber (1), with a portion thereof being located inside the cavity of the vacuum preparation chamber (1) and another portion thereof being located outside the cavity of the vacuum preparation chamber (1); The second crucible (8) is located in the heating furnace (10); The heating furnace (10) is built into the water circulation cooling device (9); The sample rack (2), the cadmium source placement component (6) and the water circulation cooling device (9) are all connected to the DC power supply (5).

Images