Preparation method of two-dimensional layered phosphorus pentamer

Abstract

The invention discloses a preparation method of a two-dimensional layered phosphorus pentamer, which comprises the following steps: selecting indium phosphide as a precursor, and accurately preparing a single-layer phosphorene structure on an Ag (111) single-crystal substrate by virtue of a molecular beam epitaxy technology. The two-dimensional phosphorus pentamer prepared by the invention has high purity and shows typical semiconductor characteristics, so that the two-dimensional phosphorus pentamer shows huge potential application value in the fields of electronic devices, photoelectric devices and related emerging science and technology. The preparation process of the two-dimensional phosphorus pentamer provided by the invention has accurate and controllable process parameters, simplified operation flow and excellent repeatability, and experimental verification shows that each index of the two-dimensional phosphorus pentamer meets the strict requirements of industrial production, so that powerful technical support is expected to be provided for the development of related industries.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for preparing a two-dimensional layered phosphorus pentamer. Background Art

[0002] With the successful dissociation of graphene, two-dimensional materials have aroused great interest due to their series of novel physical and chemical properties and huge potential application prospects, especially atomically thick two-dimensional semiconductor materials, which have both efficient carrier mobility and a variety of excellent semiconductor properties, and are compatible with traditional complementary metal oxide semiconductor technology. They are considered to be potential materials for continuing Moore's Law and constructing new field-effect transistors and two-dimensional brain-like chips.

[0003] In 2014, two independent research works, one from Chen Xianhui's group at the University of Science and Technology of China, the other from Zhang Yuanbo's group at Fudan University, and the other from Ye D. Peide's group at Purdue University, successfully exfoliated phosphorene from bulk black phosphorus and prepared 2D phosphorene field-effect transistors, which showed good transistor performance at room temperature.

[0004] Phosphorene is defined as a single layer of black phosphorus with a unique honeycomb-like wrinkled structure, a band gap that can be adjusted with the number of layers (from 1.8 eV for a single layer to 0.59 eV for a five-layer), a high on-off ratio (105), a high carrier mobility (5000 cm2 V-1 s-1), a good current saturation effect and a quantum Hall effect, etc., making it one of the most anticipated two-dimensional semiconductor materials.

[0005] At present, common preparation methods for phosphorene include mechanical exfoliation, liquid phase exfoliation, pulsed laser deposition, molecular beam epitaxial growth, etc.

[0006] Due to the non-negligible overlap of electron density between phosphorus layers in black phosphorus, the top-down exfoliation method is difficult to exfoliate single-layer phosphorene crystals. Most of the exfoliated samples are few-layer phosphorene films. In addition, this method also has problems such as limited scale of exfoliated samples, irregular shape and oxidative degradation.

[0007] Pulsed laser deposition, a top-down method, uses pulsed lasers to bombard a target material. The high energy of the laser causes some of the target material to evaporate or even ionize, which then separates from the target and deposits on the substrate surface to form a thin film. However, this method cannot precisely control the thickness of the phosphorene film, making it difficult to produce a single layer of phosphorene. Achieving controlled growth of a single layer of phosphorene is essential for further research into its intrinsic physical properties and promoting its application. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a preparation method of a two-dimensional layered phosphorus pentamer in view of the defects involved in the background technology.

[0009] The present invention adopts the following technical solutions to solve the above technical problems: A method for preparing a two-dimensional layered phosphorus pentamer comprises the following steps: Step 1) Pre-treat the Ag(111) substrate: Step 1.1), place the Ag(111) substrate in an ultra-high vacuum MBE system; Step 1.2), the Ag(111) substrate was subjected to argon ion sputtering at room temperature to remove surface organic matter and trace impurities; Step 1.3), slowly heating the Ag(111) substrate to a preset first temperature threshold, maintaining the temperature for a preset first time threshold, eliminating surface point defects of the Ag(111) substrate and restoring lattice order; Step 1.4), repeat steps 1.2) to 1.3) until the surface of the Ag(111) substrate is smooth and free of obvious residual impurities; The surface of Ag(111) substrate can be monitored using scanning tunneling microscopy (STM), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED); Step 2), molecular beam epitaxy deposition; In step 2.1, high-purity indium phosphide powder is loaded onto an evaporation source equipped with a circulating water cooling system and heated to a preset second temperature threshold to obtain a stable phosphorus evaporation beam; Step 2.2), placing the Ag(111) substrate directly above the phosphorus source, and heating the Ag(111) substrate to a preset third temperature threshold; Step 2.3), turning on the phosphorus evaporation source in an ultra-high vacuum environment to deposit a phosphorus layer on the surface of the Ag(111) substrate; Low-energy electron diffraction can be used to monitor the changes in crystal diffraction spots in real time to determine the nucleation and growth of the phosphorus layer, and Auger electron spectroscopy can be used to infer the thickness of the deposited phosphorus layer. Step 3), annealing and crystallization; Step 3.1), heating the Ag(111) substrate with phosphorene deposited on the surface thereof, and maintaining its temperature at a preset third temperature threshold for a preset second time threshold; Step 3.2), cooled to room temperature and then taken out to obtain a two-dimensional layered phosphorus pentamer.

[0010] As a further optimization scheme for the preparation method of a two-dimensional layered phosphorus pentamer of the present invention, in step 1.2), argon ion sputtering is performed at an energy of 1.5 keV and 1×10-5 The Ag(111) substrate was sputtered at an argon pressure of 100 mbar for 30 min.

[0011] As a further optimization scheme of the preparation method of a two-dimensional layered phosphorus pentamer of the present invention, the preset first temperature threshold range is 700K-800K, and the preset first time threshold range is 5-10 minutes.

[0012] As a further optimization scheme of the preparation method of a two-dimensional layered phosphorus pentamer of the present invention, the preset second temperature threshold is 820K, and the preset third temperature threshold is 420K.

[0013] As a further optimization scheme for the preparation method of a two-dimensional layered phosphorus pentamer of the present invention, the voidage of the ultra-high vacuum environment in step 2.3) is less than 1×10⁻ 9 mbar.

[0014] As a further optimization scheme of the preparation method of a two-dimensional layered phosphorus pentamer of the present invention, the preset second time threshold range is 15-30 min.

[0015] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects: 1. This invention proposes for the first time a method for preparing high-quality, well-crystalline, and controllable-layer phosphorene, which overcomes the current difficulty in preparing single-layer phosphorene. 2. The present invention provides a novel method for preparing phosphorus pentamers, which has controllable process conditions, simple technology, good reproducibility, and is suitable for industrialization; 3. The grown phosphorene exhibits a well-defined crystal structure (lattice constant ≈0.42 nm), uniform large-area morphology, and a tunable band gap of approximately 2 eV, meeting the requirements of device integration. 4. The whole process does not require the use of toxic chemical reagents, the process is simple and green, and can achieve automated mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of high-resolution STM of the Ag(111) substrate surface in the present invention; Figure 2 is an STM schematic diagram of a two-dimensional phosphorus pentamer prepared in Example; Figure 3 is a schematic diagram of the Auger electron spectrum of the two-dimensional phosphorus pentamer prepared in Example; Figure 4 This is a schematic diagram of the scanning tunneling energy spectrum of a two-dimensional phosphorus pentamer. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings: The present invention can be implemented in many different forms and should not be considered to be limited to the embodiments described herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete and will fully convey the scope of the invention to those skilled in the art. In the accompanying drawings, components are enlarged for clarity.

[0018] The present invention discloses a method for preparing a two-dimensional layered phosphorus pentamer, comprising the following steps: Step 1) Pre-treat the Ag(111) substrate: Step 1.1), place the Ag(111) substrate in an ultra-high vacuum MBE system; Step 1.2), the Ag(111) substrate was subjected to argon ion sputtering at room temperature to remove surface organic matter and trace impurities; Step 1.3), slowly heating the Ag(111) substrate to a preset first temperature threshold, maintaining the temperature for a preset first time threshold, eliminating surface point defects of the Ag(111) substrate and restoring lattice order; Step 1.4), repeat steps 1.2) to 1.3) until the surface of the Ag(111) substrate is smooth and free of obvious residual impurities; The surface of Ag(111) substrate can be monitored using scanning tunneling microscopy (STM), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED); Step 2), molecular beam epitaxy deposition; In step 2.1, high-purity indium phosphide powder is loaded onto an evaporation source equipped with a circulating water cooling system and heated to a preset second temperature threshold to obtain a stable phosphorus evaporation beam; Step 2.2), placing the Ag(111) substrate directly above the phosphorus source, and heating the Ag(111) substrate to a preset third temperature threshold; Step 2.3), turning on the phosphorus evaporation source in an ultra-high vacuum environment to deposit a phosphorus layer on the surface of the Ag(111) substrate; Low-energy electron diffraction can be used to monitor the changes in crystal diffraction spots in real time to determine the nucleation and growth of the phosphorus layer, and Auger electron spectroscopy can be used to infer the thickness of the deposited phosphorus layer. Step 3), annealing and crystallization; Step 3.1), heating the Ag(111) substrate with phosphorene deposited on the surface thereof, and maintaining its temperature at a preset third temperature threshold for a preset second time threshold; Step 3.2), cooled to room temperature and then taken out to obtain a two-dimensional layered phosphorus pentamer.

[0019] The following is described with specific examples: Example

[0020] Using single crystal Ag(111) as substrate, phosphorus was grown by molecular beam epitaxy in an ultra-high vacuum system with a base pressure of less than 1 × 10 -10 mbar: Ag(111) substrate was sputtered by argon ions at room temperature for 30 min with the following parameters (1.5 keV, 1 × 10 -5 mbar); then, the Ag(111) substrate was heated to 800 K and annealed for 10 min; the argon ion sputtering and annealing cycles were repeated three times, and the surface was monitored by scanning tunneling microscopy (STM), Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED) until the surface was smooth and free of obvious residual impurities. Figure 1 As shown. Indium phosphide powder was loaded onto an evaporation source equipped with a circulating water cooling system and heated to 820 K to obtain a stable phosphorus evaporation beam. No signs of indium evaporation were detected at this temperature. An Ag(111) substrate was placed 15 cm above the phosphorus source. At the same time, the Ag(111) substrate was heated to 420 K. The deposition time was controlled between 1 and 10 minutes.

[0021] After the deposition is completed, the phosphorus evaporation source is turned off, and the Ag(111) substrate after phosphorus deposition is continued to be maintained at 420 K and annealed for 1-15 minutes to obtain phosphorene.

[0022] Figure 2 This is a scanning tunneling microscope (STM) image of the prepared two-dimensional phosphorene, from which it can be analyzed that the surface of the prepared phosphorene is relatively flat and has a periodic structure. Figure 3 This is the Auger electron spectrum of the two-dimensional phosphorus pentamer. It can be seen that there are only characteristic signal peaks of phosphorus element and Cu(111) substrate, indicating that the obtained sample has high purity. Figure 4 This is the scanning tunneling spectrum of the two-dimensional phosphorus pentamer, which shows that the prepared phosphorus pentamer has semiconductor properties. Example

[0023] Using single crystal Ag(111) as substrate, phosphorus was grown by molecular beam epitaxy in an ultra-high vacuum system with a base pressure of less than 1 × 10 -10 mbar: Ag(111) substrate was sputtered by argon ions at room temperature for 30 min with the following parameters (1.5 keV, 1 × 10 -5mbar); then, the Ag(111) substrate was heated to 800 K and annealed for 10 min; the argon ion sputtering and annealing cycles were repeated three times, and the surface was monitored by scanning tunneling microscopy (STM), Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED) until the surface was smooth and free of obvious residual impurities. Figure 1 As shown. Indium phosphide powder was loaded onto an evaporation source equipped with a circulating water cooling system and heated to 820 K to obtain a stable phosphorus evaporation beam. No signs of indium evaporation were detected at this temperature. An Ag(111) substrate was placed 15 cm above the phosphorus source, and the deposition time was controlled between 1 and 10 minutes. After deposition, the phosphorus evaporation source was turned off, and the Ag(111) substrate with phosphorus deposited was heated to 420 K and maintained for 15 to 30 minutes for annealing to achieve phosphorene crystallization.

[0024] The present invention adopts a molecular beam epitaxial growth method with a high vacuum environment, which has excellent controllability and can effectively circumvent the oxidation problem of phosphorene. The choice of phosphorus source directly affects the crystal structure of phosphorene, and thus affects the physical and chemical properties of phosphorene. Therefore, the selection of a suitable phosphorus source has a decisive influence on the structure, physical properties and performance of phosphorene. By regulating the growth process and balancing the phosphorus-phosphorus interaction and the interaction between phosphorus and the Ag(111) surface, a new two-dimensional phosphorus pentamer structure with semiconductor properties is constructed, and its semiconductor properties are revealed.

[0025] The present invention proposes a method for preparing high-quality, well-crystalline, and layer-controlled phosphorene, which solves the current problem of being unable to prepare single-layer phosphorene. The process conditions are controllable, the process is simple, and has good repeatability, making it suitable for industrialization. The grown phosphorene exhibits a good crystal structure (lattice constant ≈ 0.42 nm), uniform large-area morphology, and an adjustable band gap of approximately 2 eV, meeting the requirements of device integration. Moreover, the entire process does not require the use of toxic chemical reagents, the process is simple and green, and can achieve automated mass production.

[0026] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which this invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as such, will not be interpreted in an idealized or overly formal sense.

[0027] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a two-dimensional layered phosphorus pentamer, characterized in that: The following steps are involved: Step 1) Pre-treat the Ag(111) substrate: Step 1.1), place the Ag(111) substrate in an ultra-high vacuum MBE system; Step 1.2), the Ag(111) substrate was subjected to argon ion sputtering at room temperature to remove surface organic matter and trace impurities; Step 1.3), slowly heating the Ag(111) substrate to a preset first temperature threshold, maintaining the temperature for a preset first time threshold, eliminating surface point defects of the Ag(111) substrate and restoring lattice order; Step 1.4), repeat steps 1.2) to 1.3) until the surface of the Ag(111) substrate is smooth and free of obvious residual impurities; Step 2), molecular beam epitaxy deposition; In step 2.1, high-purity indium phosphide powder is loaded onto an evaporation source equipped with a circulating water cooling system and heated to a preset second temperature threshold to obtain a stable phosphorus evaporation beam; Step 2.2), placing the Ag(111) substrate directly above the phosphorus source, and heating the Ag(111) substrate to a preset third temperature threshold; Step 2.3), turning on the phosphorus evaporation source in an ultra-high vacuum environment to deposit a phosphorus layer on the surface of the Ag(111) substrate; Step 3), annealing and crystallization; Step 3.1), heating the Ag(111) substrate with phosphorene deposited on the surface thereof, and maintaining its temperature at a preset third temperature threshold for a preset second time threshold; Step 3.2), cooled to room temperature and then taken out to obtain a two-dimensional layered phosphorus pentamer.

2. The method for preparing a two-dimensional layered phosphorus pentamer according to claim 1, wherein: In step 1.2), argon ion sputtering was performed at an energy of 1.5 keV and a concentration of 1×10 -5 The Ag(111) substrate was sputtered at an argon pressure of 100 mbar for 30 min.

3. The method for preparing a two-dimensional layered phosphorus pentamer according to claim 1, wherein: The preset first temperature threshold ranges from 700K to 800K, and the preset first time threshold ranges from 5 to 10 minutes.

4. The method for preparing a two-dimensional layered phosphorus pentamer according to claim 1, wherein: The preset second temperature threshold is 820K, and the preset third temperature threshold is 420K.

5. The method for preparing the two-dimensional layered phosphorus pentamer according to claim 1, wherein: The vacuum of the ultra-high vacuum environment in step 2.3) is less than 1×10⁻ 9 mbar.

6. The method for preparing a two-dimensional layered phosphorus pentamer according to claim 1, wherein: The preset second time threshold ranges from 15 to 30 minutes.

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