Method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy and blue phosphorene

Abstract

The invention provides a method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy and blue phosphorene. The method comprises the following steps: S1, carrying out argon ion etching and high-temperature annealing treatment on a Cu (111) substrate; s2, in an ultrahigh vacuum environment, taking the black phosphorus block as a precursor, and depositing P atoms through a molecular beam epitaxy method to form blue phosphorene with a super-flat honeycomb lattice; the method has the advantages that the black phosphorus block is used as a precursor, P atoms are deposited on the surface of Cu (111) at a specific temperature by adopting a molecular beam epitaxy method, and large-area and high-quality blue phosphorene can be rapidly obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of the growth and preparation of two-dimensional materials, and more specifically, to a method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy and blue phosphorene. Background Art

[0002] In 2004, Andre Geim successfully obtained monolayer graphene material by repeatedly peeling highly oriented pyrolytic graphite with tape. This discovery demonstrated the stability of two-dimensional materials and revealed the excellent properties of graphene in mechanics, thermotics, optics, and electricity, thus initiating the research upsurge of two-dimensional materials. In 2014, the successful preparation of black phosphorene filled the gap between graphene and transition metal chalcogenides. Black phosphorene has intrinsic semiconductor properties, and its bandgap increases with the decrease of thickness. At the same time, it shows excellent carrier mobility, making it have application potential in electronic devices such as field effect transistors. In addition to black phosphorene, blue phosphorene (a theoretically proposed phosphorus allotrope) with the same wrinkled honeycomb lattice as stanene has also received increasing attention in recent years due to its relatively wide bandgap and excellent electrical properties. Density functional theory calculations show that under the action of tensile stress, buckled blue phosphorene can be transformed into a super-flat honeycomb lattice, showing a structure and properties similar to graphene.

[0003] Due to the lack of corresponding bulk materials, blue phosphorene can only be synthesized by a bottom-up method. The bottom-up methods mainly include: molecular beam epitaxy, chemical vapor deposition, atomic layer deposition, etc. Among them, the molecular beam epitaxy method has the following advantages compared with other methods: the growth occurs in an ultra-high vacuum environment, avoiding the participation of other impurities in the growth; the precursor is deposited on the substrate surface through an evaporation source, and precise control of the deposition flux can be achieved; epitaxial growth occurs on a specific substrate surface, and with the help of the interface effect, materials with specific structures can be grown. Therefore, currently, molecular beam epitaxy is one of the mainstream methods for preparing and directionally designing high-quality two-dimensional materials.

[0004] As the mainstream technology for two-dimensional material synthesis, molecular beam epitaxy has the following deficiencies in the preparation of blue phosphorene: ① Limited substrate selection: Traditional metal substrates (such as Au, Ag) have weak binding force with phosphorus atoms, resulting in low nucleation density and insufficient coverage; ② Narrow temperature window: Too high substrate temperature is prone to cause phosphorus atom agglomeration, and too low temperature cannot form a stable lattice; ③ Difficult chiral regulation: Existing processes are difficult to directionally induce the formation of chiral structures, resulting in random product structures. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy. Using bulk black phosphorus as a precursor and adopting the molecular beam epitaxy method to deposit P atoms on the Cu(111) surface at a specific temperature, large-area and high-quality blue phosphorene can be rapidly obtained. During the growth process, if the substrate is not clean enough, the substrate temperature is too high or too low, and the growth time is insufficient resulting in insufficient coverage, the best blue phosphorene cannot be obtained.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy, comprising the following steps:

[0008] Step S1, performing argon ion etching and high-temperature annealing treatment on the Cu(111) substrate;

[0009] Step S2, in an ultra-high vacuum environment, using bulk black phosphorus as a precursor and depositing P atoms by the molecular beam epitaxy method to form blue phosphorene with a super-flat honeycomb lattice.

[0010] Further, the argon ion etching parameters are: argon gas pressure of 1.5×10 -5 mbar, etching high voltage of 1 keV, single etching time of 15 min, and cycling 2 - 3 times.

[0011] Further, the temperature of the high-temperature annealing treatment is 800 °C and is maintained for 1 - 2 min.

[0012] Further, the pressure of the ultra-high vacuum environment is less than or equal to 2×10 -10 mbar.

[0013] Further, the evaporation temperature of the bulk black phosphorus is 240 - 260 °C.

[0014] Further, the substrate temperature is 480 - 520 °C.

[0015] Further, the deposition time of the P atoms is 8 - 12 min.

[0016] Further, the blue phosphorene has a chiral structure, its hexagonal superlattice period is 4.7 - 4.9 nm, and the unit cell lattice constant is

[0017] A kind of blue phosphorene, the blue phosphorene is a super-flat honeycomb lattice structure, has right-handed or left-handed chiral characteristics, and the coverage is greater than or equal to 95%.

[0018] Further, the surface of the blue phosphorene has no impurity pollution and is applicable to optoelectronic devices, spintronic devices or the catalytic field.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) The blue phosphorene prepared by the present invention has a super-flat honeycomb structure, is chiral, has a large area, and the size of the blue phosphorene is only limited by the area of the substrate;

[0021] (2) The surface of the blue phosphorene prepared by the present invention is free of impurity contamination and has potential application value in the fields of optoelectronics, spintronics, and catalysis;

[0022] (3) The preparation process of the present invention is simple, produces no harmful substances, is easy to prepare, has high production efficiency, and is suitable for large-scale preparation;

[0023] (4) The present invention selects blue phosphorene in group V elemental two-dimensional materials, uses black phosphorus bulk as a precursor, adopts molecular beam epitaxy, and realizes the rapid synthesis of blue phosphorene on the surface of a Cu(111) substrate by adjusting the substrate temperature and coverage during growth. The obtained blue phosphorene has the advantages of high quality, large area, and chiral structure. The introduction of chirality further enriches the physical and chemical properties of blue phosphorene, showing broad application prospects in the fields of optoelectronics, spintronics, valleytronics, and chiral catalysis. Brief Description of the Drawings

[0024] Figure 1 is a schematic diagram of the preparation process of the invention;

[0025] Figure 2 are STM images with different resolutions of the right-handed blue phosphorene obtained by depositing P atoms on the surface of Cu(111) at 500°C;

[0026] Figure 3 are STM images with different resolutions of the left-handed blue phosphorene obtained by depositing P atoms on the surface of Cu(111) at 500°C;

[0027] Figure 4 are STM images with different resolutions of the hexagonal blue phosphorene obtained by depositing P atoms on the surface of Cu(111) at 500°C.

[0028] Attached Reference Signs

[0029] 1. Argon ion etching gun; 2. Single crystal substrate; 3. Electron beam sample heating stage; 4. Black phosphorus bulk; 5. Evaporation source. Detailed Description of the Invention

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The same parts are represented by the same reference numerals. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the accompanying drawings, and the words "bottom surface" and "top surface", "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0031] Since molecular beam epitaxy is currently the mainstream technology for the synthesis of two-dimensional materials, it has the following shortcomings in the preparation of blue phosphorene: ①, limited substrate selection: traditional metal substrates (such as Au, Ag) have weak binding force with phosphorus atoms, resulting in low nucleation density and insufficient coverage; ②, narrow temperature window: too high substrate temperature can easily cause phosphorus atom agglomeration, while too low a substrate temperature cannot form a stable lattice; ③, difficulty in chirality regulation: the existing process is difficult to induce the formation of chiral structures in a directional manner, resulting in random product structures; therefore, the present invention designs a method for rapid synthesis of high-quality blue phosphorene based on molecular beam epitaxy, and the preparation diagram is as follows Figure 1 shown.

[0032] (1) Preparation: The metal substrate is a cap-shaped Cu (111) single crystal purchased from MaTeck, Germany, with a purity of 99.999%, an upper surface diameter of 8 mm, and a thickness of 3 mm. The precursor of P is a black phosphorus bulk sheet purchased from Nanjing Muke Optoelectronics Co., Ltd. with a purity of 99.999%.

[0033] (2) Characterization: The low-temperature scanning tunneling microscope (STM) model was BOSONLT-SPM. During the characterization process, the ultrahigh vacuum pressure was 2×10 -10 mbar, the scanning probe operating temperature is 77K, constant current mode is adopted, and the probe tip is an electrochemically corroded tungsten tip.

[0034] Example 1

[0035] Step S1, the Cu(111) substrate is subjected to argon ion etching and annealing treatment for 2-3 times to remove impurities on the Cu(111) surface, including water, adsorbed gas, organic matter, etc., to obtain a larger step for sample preparation and observation; Argon ion etching operation: the argon gas pressure is maintained at 1.5×10 -5 mbar, the added energy is 1 keV, maintained for 12-15 min; annealing operation: slowly heated to 800 ° C, at which time the sample turns red, and maintained for 1-2 min to obtain a wide platform and a clean surface Cu (111) substrate.

[0036] Step S2: The molecular beam epitaxy equipment is evacuated to a vacuum of 2×10 -10mbar, start the growth experiment. Use a quartz crucible to hold the bulk black phosphorus (first degas it to ensure no impurities enter during the formal experiment). Through the evaporation source, the evaporation temperature is 250 °C. During growth, the temperature of the Cu(111) substrate is maintained at 500 °C, the deposition time is 10 min, and then observe its morphology in a low-temperature STM.

[0037] As Figure 2 shown, Figure 2 a, b, and c in Figure 2 are STM images of blue phosphorene with different sizes grown on the Cu(111) surface. a in Figure 2 is a large-area STM image after P deposition, where the phosphorene sheets completely cover all the steps. It can be seen that the blue phosphorene prepared with the substrate maintained at 500 °C during P deposition has a large and continuous area, a flat surface. The corresponding magnified STM image is as shown in Figure 2 b in , showing a highly ordered hexagonal superlattice with a period of ~4.8 nm. The hexagonal supercell contains two helical triangles that rotate counterclockwise, presenting a right-handed chirality. At the center of the triangular shape, the honeycomb lattice is clearly visible.

[0038] Example 2

[0039] Step S1, perform 2 - 3 times of argon ion etching and annealing treatment on the Cu(111) substrate to remove impurities on the Cu(111) surface, including water, adsorbed gases, organic substances, etc., to obtain larger steps for sample preparation and observation. Argon ion etching operation: keep the argon gas pressure at 1.5×10 -5 mbar, the applied energy is 1 keV, and maintain for 12 - 15 min; annealing operation: slowly heat to 800 °C, at this time the sample turns red, and maintain for 1 - 2 min to obtain a Cu(111) substrate with a wide platform and a clean surface.

[0040] Step S2, evacuate the molecular beam epitaxy equipment to 2×10 -10 mbar, start the growth experiment. Use a quartz crucible to hold the bulk black phosphorus (first degas it to ensure no impurities enter during the formal experiment). Through the evaporation source, the evaporation temperature is 250 °C. During growth, the temperature of the Cu(111) substrate is maintained at 500 °C, the deposition time is 10 min, and then observe its morphology in a low-temperature STM.

[0041] As Figure 3 shown,Figure 3 Figures a, b, and c are STM images of left-handed blue phosphorene with different sizes grown on the Cu(111) surface, similar to Example 1. Figure 3 Figure a in [reference] is a large-area STM image after phosphorus deposition, and the corresponding magnified STM images are as shown in Figure 3 Figures b and c in [reference], showing a highly ordered hexagonal superlattice with a period of ~4.8 nm. The hexagonal supercell contains two helical triangles that rotate clockwise, presenting left-handed chirality. At the center of the triangular shape, the honeycomb lattice is clearly visible. Figure 3 Figure c in [reference] marks a unit cell, and the measured lattice constant

[0042] Example 3

[0043] Step S1: The Cu(111) substrate is subjected to 2 - 3 times of argon ion etching and annealing treatment to remove impurities on the Cu(111) surface, including water, adsorbed gases, organic substances, etc., to obtain larger steps for sample preparation and observation. Argon ion etching operation: The argon gas pressure is maintained at 1.5×10 -5 mbar, the applied energy is 1 keV, and it is maintained for 12 - 15 min; Annealing operation: Slowly heat to 800 °C, at this time the sample turns red, and it is maintained for 1 - 2 min to obtain a Cu(111) substrate with a wide platform and a clean surface.

[0044] Step S2: The molecular beam epitaxy equipment is evacuated to 2×10 -10 mbar, and the growth experiment is started. Use a quartz crucible to hold the black phosphorus bulk (first degas it to ensure no impurities enter during the formal experiment). Through the evaporation source, the evaporation temperature is 250 °C. During growth, the temperature of the Cu(111) substrate is maintained at 500 °C, the deposition time is 10 min, and then its morphology is observed in a low-temperature STM.

[0045] As shown in Figure 4 Figures a, b, and c are STM images of hexagonal blue phosphorene with different resolutions grown on the Cu(111) surface. Figure 4 Figure a in [reference] is a large-area STM image after P deposition. Different from the chiral structures shown in Example 1 and Example 2, the triangles in the hexagonal supercell here are not distorted. The corresponding magnified STM images are as shown in Figure 4 Figures b and c in [reference], Figure 4 Figure c in [reference] marks a unit cell, and the measured lattice constant Figure 4

[0046] ​The above are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy, characterized in that: Including the following steps: Step S1, performing argon ion etching and high-temperature annealing treatment on the Cu(111) substrate; Step S2, in an ultra-high vacuum environment, using bulk black phosphorus as a precursor, depositing P atoms by molecular beam epitaxy to form blue phosphorene with a super-flat honeycomb lattice.

2. The method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy according to claim 1, characterized in that: The argon ion etching parameters are as follows: argon gas pressure of 1.5×10 -5 mbar, etching high voltage of 1 keV, single etching time of 15 min, and 2 - 3 cycles.

3. The method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy according to claim 1, wherein: The temperature of the high-temperature annealing treatment is 800 °C and is maintained for 1 - 2 min.

4. The method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy according to claim 1, characterized in that: The air pressure in the ultra-high vacuum environment is less than or equal to 2×10 -10 mbar.

5. The method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy according to any one of claims 1, wherein: The evaporation temperature of the bulk black phosphorus is 240 - 260 °C.

6. The method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy according to any one of claims 1, characterized in that: The substrate temperature is 480 - 520 °C.

7. The method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy according to any one of claims 1, characterized in that: The deposition time of the P atoms is 8 - 12 min.

8. The method for rapidly synthesizing high-quality blue phosphorene based on molecular beam epitaxy according to claim 1, characterized in that: The blue phosphorene has a chiral structure, and its hexagonal superlattice period is 4.7-4.9 nm, and the unit cell lattice constant is 9. A blue phosphorene prepared by the method according to any one of claims 1-8, characterized in that: The blue phosphorene has a super-flat honeycomb lattice structure, has a right-handed or left-handed chiral feature, and the coverage is greater than or equal to 95%.

10. The blue phosphorene according to claim 9, characterized in that: The surface of the blue phosphorene has no impurity contamination and is applicable to optoelectronic devices, spintronic devices or the catalytic field.

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