Silicon ditelluride two-dimensional crystal material and preparation method thereof

Abstract

Provided are a two-dimensional crystal thin film material of silicon ditelluride and a preparation method thereof. According to an embodiment, the preparation method comprises the following steps: 1) performing rapid heating and rapid cooling treatment on a silicon single crystal under vacuum conditions, so as to obtain a reformed surface; and 2) depositing high-purity Te onto the surface of the substrate through an evaporation source. During the deposition process, the silicon single crystal substrate is kept at a set temperature, so that the Te and the silicon single crystal are fully reacted to form a two-dimensional crystal thin film SiTe2 with a periodic structure. The lattice arrangement period of the novel two-dimensional material can be determined through low-energy electron diffraction. The two-dimensional crystal thin film SiTe2 is directly grown by taking a silicon substrate as a reaction material, the research field of two-dimensional atomic crystal materials is expanded, and the two-dimensional crystal thin film SiTe2 has wide application potential in the field of future nanoelectronics.

Description

Technical Field

[0001] This application belongs to the field of nanomaterials technology, and more specifically, relates to a novel two-dimensional crystalline thin film material, silicon ditelluride (SiTe2), and a method for preparing the material. Background Technology

[0002] Since the discovery of graphene in 2004, the mysteries of two-dimensional materials have been unveiled. As a representative of two-dimensional materials, graphene exhibits excellent properties, such as high mechanical strength, with a thickness of 15,000 cm⁻¹ at room temperature. 2 Graphene's high carrier mobility (V·s) and excellent thermal conductivity have made it a popular material and a global research hotspot in recent years.

[0003] In semiconductor chip applications, the lack of a natural semiconductor band gap limits graphene's use in fields such as semiconductors. Researchers have therefore explored and studied other new two-dimensional materials. In recent years, experimental and theoretical studies have discovered other graphene-like two-dimensional atomic crystal materials, such as molybdenum disulfide, silicene, stanene, and boron nitride, continuously expanding the database of two-dimensional materials. These two-dimensional materials also exhibit a variety of novel electrical, thermal, and magnetic physical properties.

[0004] The Si-Te system is a novel two-dimensional material explored by researchers. The existence of SiTe2 has been theoretically predicted, and it is predicted to possess excellent properties, including extremely low lattice thermal conductivity and good electronic characteristics. This makes it a promising candidate for applications in thermoelectrics, flexible electrodes, and other fields. Currently, there are no experimental reports on the synthesis of two-dimensional SiTe2 materials. As a novel two-dimensional crystalline material, its successful preparation is a prerequisite for further research on its properties and application development. Therefore, finding a feasible method to prepare the two-dimensional crystalline material SiTe2 is extremely important. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide a method for preparing two-dimensional crystalline SiTe2 thin film materials. The method of the present invention can prepare a novel two-dimensional material exhibiting a two-dimensional periodic structure with a triangular lattice arrangement.

[0006] One aspect of the present invention provides a method for preparing SiTe2 thin film materials, characterized by comprising the following steps:

[0007] A reconstructed surface is obtained by processing a single-crystal substrate, wherein the single-crystal substrate is a silicon single crystal, under vacuum conditions; and

[0008] Tellurium atoms are evaporated and deposited onto the single-crystal substrate, and the single-crystal substrate is kept at a set temperature, so that tellurium and silicon react with each other to form a two-dimensional crystal material with a periodic structure.

[0009] In some examples, the processing of the single-crystal substrate includes:

[0010] The single-crystal substrate is heated in a vacuum at a rate greater than 400°C / s;

[0011] The predetermined holding time for the heated single-crystal substrate; and

[0012] The single-crystal substrate is cooled to obtain a reconstructed surface.

[0013] In some examples, the reconstructed silicon single crystal surface is a Si(111)7×7 structure.

[0014] In some examples, the set temperature is 350-400°C.

[0015] In some examples, the evaporation deposition is resistance heating evaporation deposition and / or electron beam evaporation deposition.

[0016] In some examples, the resistance heating evaporation deposition is performed as follows: the resistance wire is energized and heated to raise the temperature of the evaporation source to a predetermined temperature, causing the tellurium atoms to evaporate, and the evaporated tellurium atoms form a beam and are deposited on the substrate.

[0017] In some examples, the deposition time is 5-20 minutes.

[0018] In some examples, the preparation method also includes: slowly cooling the two-dimensional crystalline material obtained after deposition to room temperature.

[0019] Another aspect of the present invention provides a silicon ditelluride two-dimensional crystal material, characterized in that the crystal atoms are arranged in a triangular periodic pattern and expanded in an orderly manner in a two-dimensional plane to form a silicon ditelluride thin film material.

[0020] In some examples, the silicon distelluride thin film material has a lattice period of 0.44 nm, which is characterized by low-energy electron diffraction.

[0021] This invention prepares a two-dimensional atomic crystal thin film material, SiTe2, using molecular beam epitaxy. The grown film exhibits a triangular periodic arrangement across the entire surface of a silicon single crystal, as confirmed by low-energy electron diffraction patterns. The prepared SiTe2, as a novel two-dimensional material, expands the existing range of two-dimensional material compounds, laying the foundation for further research on its properties and application development. For example, it theoretically possesses extremely low lattice thermal conductivity and excellent electronic properties, thus showing potential applications in field-effect transistors and flexible optoelectronic devices. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used therein will be briefly described below.

[0023] Figure 1 A schematic diagram of the preparation process of a two-dimensional crystalline SiTe2 thin film material according to an exemplary embodiment of this application is shown.

[0024] Figure 2 A flowchart of a method for preparing a two-dimensional crystalline SiTe2 thin film material according to an exemplary embodiment of this application is shown.

[0025] Figure 3 shows the low-energy electron diffraction patterns of a high-quality single-crystal Si(111) surface and a two-dimensional SiTe2 thin film used in an exemplary embodiment of this application for preparing to grow a SiTe2 thin film.

[0026] Figure 4 shows a schematic diagram of low-energy electron diffraction of a simulated SiTe2 thin film in an exemplary embodiment of this application.

[0027] Figure 5 An atomic structure model of monolayer SiTe2 is shown. Detailed Implementation

[0028] Exemplary embodiments of this application will now be described in detail with reference to the accompanying drawings. It is obvious that the described embodiments are merely a part of the embodiments of this application, and not all of them, and it should be understood that this application is not limited to the exemplary embodiments described herein. Unless otherwise specified, the technical terms used herein have the meanings commonly understood by those skilled in the art.

[0029] As mentioned earlier, although two-dimensional SiTe2 materials can be predicted through calculations, existing technologies only produce bulk materials and have not disclosed a successful method for preparing two-dimensional materials. Therefore, this invention obtains two-dimensional SiTe2 thin film materials through molecular beam epitaxy. Figure 1 A schematic diagram illustrating the preparation process of an exemplary embodiment of this application is shown. Figure 1 As shown, by guiding Te atoms from the evaporation source to the surface of a silicon single crystal substrate and keeping the temperature of the substrate surface at a preset temperature, a two-dimensional SiTe2 crystal thin film material with an ordered structure can be formed on the surface of the silicon substrate.

[0030] Figure 2 A flowchart illustrating a method for preparing a two-dimensional crystalline SiTe2 thin film material according to an embodiment of this application is shown.

[0031] Reference Figure 2 Preparation method 10 may begin with step S12, whereby a silicon single crystal substrate is processed to obtain a reconstructed surface.

[0032] To avoid introducing impurities, each step of the preparation method of the present invention is preferably performed under vacuum conditions. For example, the silicon single crystal can be surface-treated in an ultra-high vacuum environment to obtain a clean and smooth surface. Specifically, the vacuum environment refers to a vacuum degree of 10... -10 -10 -7 mbar, for example, to achieve a vacuum level of 2-6 × 10 mbar in the deposition chamber via a molecular pump. -10 mbar vacuum environment can effectively remove gas molecules adsorbed in silicon substrate, thereby avoiding adverse effects of gas molecules on subsequent Te and Si reactions.

[0033] In this invention, single-crystal silicon serves as both a substrate and a reactant. Single-crystal silicon with a purity of 99.99% or higher can be selected as the substrate material. Without proper treatment, the surface of a single-crystal silicon crystal has a disordered structure, and no diffraction spots are visible in low-energy electron diffraction. To prepare a two-dimensional material, the surface of the single-crystal silicon needs to be treated to obtain an atomically flat surface.

[0034] In one embodiment, the silicon substrate can be processed using a rapid heating and then rapid cooling method. For example, the single-crystal silicon substrate can be heated in a vacuum deposition chamber at a heating rate greater than 400°C / s, preferably greater than 600°C / s. For instance, the silicon substrate can be heated to 1100-1300°C within 2 seconds by applying an electric current, and then the heated single-crystal substrate can be held at that temperature for a predetermined time, such as 5-10 seconds. After that, the single-crystal substrate can be cooled to obtain a reconstructed surface. For example, the current flowing through the silicon single crystal can be reduced and reduced to zero in a short time, followed by rapid cooling. Through this processing method, a reconstructed ordered surface structure can be obtained.

[0035] In one embodiment, a Si(111) single crystal is used as the substrate material. It is heated in a vacuum by an electric current, raising the substrate temperature to 1200°C within 2 seconds, maintaining this temperature for 6 seconds, and then reducing the current flowing through the Si single crystal to zero for 2 seconds, allowing it to cool naturally. Figure 3a As shown, by analyzing the low-energy electron diffraction pattern, it can be confirmed that the substrate surface obtained by this method has a 7×7 Si(111) crystal structure, which is beneficial for subsequent molecular beam epitaxy growth.

[0036] After processing the silicon substrate, step S14 can be continued to evaporate and deposit tellurium atoms onto the single crystal substrate, and the single crystal substrate is kept at a set temperature so that tellurium and silicon react with each other to form a two-dimensional crystal material with a periodic structure.

[0037] Experiments revealed that tellurium and silicon cannot react at any temperature to form SiTe2, or produce atomically thin crystalline films. Therefore, the reaction temperature needs to be controlled. The inventors found that only when the reaction temperature is controlled between 350-400℃ can the desired two-dimensional thin film material be prepared. If the temperature is below 350℃, tellurium may form a passivation layer on the surface, making it difficult for Te to fully react with the Si single crystal and distribute across the entire silicon single crystal substrate. If the temperature exceeds 400℃, it is difficult to obtain the desired two-dimensional crystal structure. Preferably, the reaction temperature is controlled between 360-375℃, which yields a two-dimensional material of relatively good quality.

[0038] To control the reaction temperature, the substrate surface can be heated by direct current and maintained at the aforementioned reaction temperature during the deposition process. This heating step can be performed before the heating and evaporation step of the tellurium source to prevent tellurium from depositing on the silicon substrate surface below the aforementioned reaction temperature. To avoid the influence of impurities, a tellurium source with high purity can be selected, for example, a tellurium source with a purity of 95% or higher.

[0039] In one embodiment, Te atoms can be deposited on the Si(111) surface using resistance heating evaporation deposition. For example, the evaporation source can be heated to a predetermined temperature by passing an electric current through a resistance wire to evaporate tellurium atoms. The evaporated tellurium atoms form a beam and are deposited on the substrate to form a two-dimensional SiTe2 crystal thin film with an ordered structure. The temperature of the evaporation source can be controlled to be lower than the heating temperature of the single-crystal silicon substrate to control the reaction process of Si and Te and obtain better SiTe2 crystallinity. Preferably, the resistance heating (K-cell) evaporation source can be heated to 220-250°C. When using an evaporation source with relatively low purity (e.g., the purity of the tellurium source is below 95%), it is especially important to control the temperature of the evaporation source to avoid evaporating impurities and affecting the quality of the two-dimensional thin film material. More preferably, the temperature is controlled to 230-235°C. The entire deposition process lasts for about 5-20 minutes, for example, 10 minutes.

[0040] In another embodiment, an electron beam evaporation source can be used as the Te source. For example, a high voltage can be applied to the emitted electrons generated by the energized wire to generate an electron beam that accelerates and bombards the tellurium source, causing it to sublimate. The tellurium atoms formed by the sublimation are then deposited on the silicon substrate under the constraint of the evaporation source port, which can also yield a two-dimensional SiTe2 crystalline thin film.

[0041] After the two-dimensional thin film material is obtained by depositing tellurium atoms, the preparation method can also proceed to step S16, which cools the two-dimensional crystal material on the substrate.

[0042] In one embodiment, the temperature of the silicon single-crystal substrate can be slowly reduced, for example, by natural cooling to room temperature, with the entire cooling process taking approximately 20 minutes. After cooling to room temperature, low-energy electron diffraction patterns reveal an ordered structure on a macroscopic scale, indicating that the prepared two-dimensional material is distributed throughout the entire silicon single-crystal substrate. Figure 3b As shown in the figure, the 7×7 structure of the Si(111) surface disappears, leaving only the 1×1 structure of the Si(111) surface, as shown in the circled part in the figure. The other diffraction points (2√3×2√3) are contributed by the two-dimensional material SiTe2 on the surface.

[0043] This exemplary embodiment obtains an atomic-level silicon ditelluride two-dimensional material thin film layer through the above preparation method, which solves the problem that only bulk materials can be obtained in the prior art, and provides a foundation for carrying out research on the physical properties of silicon ditelluride and the development of related device applications.

[0044] Another embodiment of the present invention provides a two-dimensional silicon distellide crystal material, which can be prepared, for example, by the method described above, such as... Figure 3b As shown, the SiTe2 crystal atoms are arranged in a triangular periodic pattern and expand in an orderly manner in a two-dimensional plane, which can form silicon ditelluride thin film materials.

[0045] To describe clearly Figure 3b Figure 4 shows a schematic diagram of the low-energy electron diffraction pattern of a simulated SiTe2 thin film. Figure 4a As shown, it depicts a schematic diagram of the diffraction points of a two-dimensional material prepared on a silicon single-crystal substrate. Si(111) diffraction points are represented by white dots, and new diffraction points are represented by gray dots. Based on the relationship of the reciprocal lattice vectors, the lattice arrangement in real space can be deduced, and the lattice period of the formed SiTe2 thin film can be determined in real space, such as... Figure 4b As shown. The gray arrows represent the lattice vectors of Si(111), and the black arrows represent the lattice vectors of the new structure. The lattice constant of the Si(111) single crystal is known, and its value is a. Si(111) Approximately 0.384 nm. Based on the real-space lattice arrangement, assume a SiTe2 Given the lattice constant of SiTe2, we can obtain the relationship: 3xa SiTe2 =2√3xa Si(111) The lattice constant α of SiTe2 can be calculated using this equation. SiTe2 The lattice period is approximately 0.44 nm, close to the lattice constant of bulk SiTe2 (0.428 nm). This lattice period of 0.44 nm corresponds to a trigonal periodic arrangement of silicon atoms on the substrate surface, such as... Figure 5The top view of the atomic structure model of monolayer SiTe2 is shown. At the same time, the side view shows that monolayer SiTe2 is a sandwich-like layered structure with tellurium-silicon-tellurium atoms stacked together. This also confirms that the present invention has successfully obtained a two-dimensional atomic-level crystalline thin film material.

[0046] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0047] In this text, words such as “including,” “contains,” and “has” are open-ended terms meaning “including but not limited to,” and are used interchangeably. The words “or” and “and” as used herein refer to the words “and / or” and are used interchangeably unless the context explicitly indicates otherwise. The word “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably.

[0048] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0049] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for preparing a two-dimensional silicon distelluride crystal material, characterized in that, Includes the following steps: In a vacuum environment, the single crystal substrate is processed by heating it to 1100-1300℃, then the heated single crystal substrate is kept at a certain temperature and then cooled to obtain a reconstructed surface. The reconstructed surface is a Si(111)7×7 structure and the single crystal substrate is a silicon single crystal. as well as Tellurium atoms are evaporated and deposited onto the single-crystal substrate, and the single-crystal substrate is kept at a set temperature, so that tellurium and silicon react with each other to form a two-dimensional crystal material with a periodic structure. The set temperature is 350-400℃.

2. The preparation method according to claim 1, wherein, The processing of single-crystal substrates includes: The single-crystal substrate is heated in a vacuum at a rate greater than 400°C / s; The predetermined holding time for the heated single-crystal substrate; and The single-crystal substrate is cooled to obtain a reconstructed surface.

3. The method of claim 1, wherein, The evaporation deposition is either resistance heating evaporation deposition or electron beam evaporation deposition.

4. The method of claim 3, wherein, The resistance heating evaporation deposition is performed as follows: the resistance wire is energized and heated to raise the temperature of the evaporation source to a predetermined temperature, causing the tellurium atoms to evaporate, and the evaporated tellurium atoms form a beam and are deposited on the substrate.

5. The method of claim 4, wherein, The deposition time is 5-20 minutes.

6. The method of claim 1 or 2, wherein, The method further includes: slowly cooling the two-dimensional crystal material obtained after deposition to room temperature.

7. A two-dimensional crystalline material of silicon ditelluride prepared according to the method of any one of claims 1-6. Crystal atoms are arranged in a triangular periodic pattern and expanded in an orderly manner in a two-dimensional plane to form a silicon ditelluride thin film material. The lattice period of silicon ditelluride is 0.44 nm, which is characterized by low-energy electron diffraction.

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