High-quality, wafer-level single-crystal multilayer boron nitride thin film, controllable preparation method and application thereof
By controlling the growth time and atmosphere conditions on a liquid copper substrate, high-quality, wafer-level single-crystal multilayer boron nitride thin films were prepared using Coulomb gravity-induced self-splicing technology. This solved the problem of inconsistent size and orientation in the prior art, and enabled the preparation of large-area, high-quality thin films for use in deep ultraviolet photodetectors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-21
- Publication Date
- 2026-03-17
AI Technical Summary
Existing methods can only produce boron nitride films with micron-level dimensions and inconsistent growth orientations, which limits their application in large-area, high-end devices.
Boron nitride thin films were grown on liquid copper substrates using CVD technology. By controlling the growth time and atmosphere conditions, high-quality, wafer-level single-crystal multilayer boron nitride thin films were prepared. Coulomb attraction was used to induce self-parallelism of crystal domains and seamless growth was achieved through a self-splicing process.
The fabrication of large-area, high-quality single-crystal multilayer boron nitride thin films has been achieved. The growth process is simple, safe, and low-cost, and the film has a uniform number of layers, making it suitable for the field of deep ultraviolet photodetectors.
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Figure CN116265625B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of two-dimensional thin film materials, specifically relating to a high-quality, wafer-level single-crystal multilayer boron nitride thin film, its controllable preparation method, and its applications. Background Technology
[0002] Two-dimensional materials, as important quantum materials, possess extremely small physical thicknesses, perfect interfaces, and excellent physical properties. Their rich system includes conductors (boron nitride), semiconductors (transition metal chalcogenides, black phosphorus, etc.), and insulators (boron nitride), making them core foundational materials for potentially transformative technological applications. Boron nitride, with its smooth, bond-free surface, is the best known two-dimensional insulator. Its high thermal stability (oxidation resistance up to 985℃, and heat resistance up to 2000℃ under inert gas protection) and stable mechanical properties have led to its widespread application in high-temperature mechanical equipment. Furthermore, boron nitride's non-toxicity, high chemical stability, high light transmittance, extreme hardness, and high Young's modulus provide a reliable foundation for its extensive applications, making it an indispensable member of future advanced devices. Currently, utilizing its insulating properties as a dielectric layer in field-effect transistors to improve their field-effect performance is the most common application. However, uncontrollable defects, disorder, and impurities during its fabrication limit its application.
[0003] Large-scale high-end device applications require large-area, high-quality single-crystal materials. Therefore, the research on the preparation of two-dimensional single-crystal materials has significant scientific and technological value. Current methods can only achieve single-crystal multilayer boron nitride sizes at the micrometer level, which is far from sufficient for device applications. Furthermore, inconsistent boron nitride growth orientation remains a problem. Therefore, how to prepare large-area, high-quality two-dimensional single-crystal multilayer materials has always been a hot research topic in nanotechnology, but its practical implementation faces enormous challenges. Summary of the Invention
[0004] The purpose of this invention is to solve the technical problems that the boron nitride thin films obtained by existing methods can only reach the micrometer level in size and have inconsistent growth orientation, and to provide a high-quality, wafer-level single-crystal multilayer boron nitride thin film, as well as its controllable preparation method and application.
[0005] One objective of this invention is to provide a controllable method for preparing high-quality, wafer-level single-crystal multilayer boron nitride thin films, the method comprising the following steps:
[0006] Using CVD technology, a liquid growth substrate is placed in the growth region, and a solid source is placed in the source region. Thin films are grown under a reducing atmosphere. By controlling the growth time, the number of layers in the single-crystal boron nitride film can be adjusted to obtain high-quality, wafer-level single-crystal multilayer boron nitride films.
[0007] Further specifying, the liquid growth substrate is liquid copper, liquid nickel, or a liquid copper-nickel alloy.
[0008] Further specifying, the solid source is a borane-ammonia complex, boric acid / ammonia, or urea / boric acid.
[0009] Further restrictions were imposed: the temperature in the growth zone was controlled at 1100-1200℃, the temperature in the source zone was controlled at 60-80℃, and the growth time was 6-25 minutes.
[0010] Further specified, the reducing atmosphere consists of hydrogen and argon in a volume ratio of 9:100.
[0011] Further specifying, the liquid growth substrate is obtained by cleaning, polishing and annealing liquefaction of metal foil.
[0012] Furthermore, the cleaning process is carried out sequentially using acetone, 5wt% dilute hydrochloric acid, and deionized water.
[0013] Furthermore, the polishing is described as electrochemical polishing of the metal foil in phosphoric acid / polyethylene glycol 400 (v / v = 3 / 1).
[0014] Furthermore, the annealing liquefaction temperature is 1090-1110℃, and the time is 20-40 min.
[0015] Furthermore, the annealing and liquefaction are carried out in the same reducing atmosphere as the growth process.
[0016] The second objective of this invention is to provide a high-quality, wafer-level single-crystal multilayer boron nitride thin film prepared by the above method, wherein the boron nitride thin film has up to five layers under a single crystal and a single crystal size of 6cm×7cm.
[0017] The third objective of this invention is to provide a high-quality, wafer-level single-crystal multilayer boron nitride thin film prepared by the above method as a large-size single-crystal two-dimensional material for use in the field of deep ultraviolet photodetectors.
[0018] The significant advantages of this invention compared to existing technologies are:
[0019] This invention provides a method for growing boron nitride thin films using liquid copper as a growth substrate. Leveraging the low spin barrier on the surface of liquid copper and its epitaxial effect, the self-parallelization of crystal domains is induced by Coulomb attraction within a closed CVD furnace. The self-rotation of the two grains causes the armchair-shaped ends of the BN and NB crystals to face each other, attracting surrounding free B and N atoms to form bonds, thereby achieving a seamless self-splicing process. This results in the self-parallel growth of single-crystal multilayer boron nitride thin films using liquid copper. Specific advantages are as follows:
[0020] 1) This invention obtains a smooth surface by cleaning and polishing the metal substrate in the early stage, realizing the transformation of self-parallel single crystal, and avoids the introduction of impurities by precisely controlling the reaction time of borane and ammonia, thus achieving the preparation of high-quality boron nitride thin films with the fewest particles.
[0021] 2) The method and equipment of the present invention are simple, convenient to operate, and easy to prepare large-area boron nitride thin films, which improves the safety and convenience of the preparation process; at the same time, it can significantly shorten the reaction time and reduce the production cost.
[0022] 3) The preparation method of the present invention can achieve control of the number of boron nitride thin films by simply changing the process parameters, and the number of wafer-level thin films grown is uniform, the number of layers in different regions is consistent, the roughness is low, and the controllability is good. The number of layers of single crystal boron nitride thin films can be controlled by precisely controlling the growth time. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the boron nitride thin film growth of the present invention;
[0024] Figure 2 This is a schematic diagram of the boron nitride thin film growth process of the present invention;
[0025] Figure 3 SEM images showing the evolution of boron nitride thin films over time; where I-6 min, II-9 min, III-12 min, IV-15 min, V-18 min, VI-25 min;
[0026] Figure 4 The diagram shows the distribution of electrostatic attraction between boron nitride domains calculated using density functional theory. The left side represents the domain rotation process under electrostatic attraction, and the right side represents the boron nitride self-parallel rotation process induced by electrostatic attraction.
[0027] Figure 5 Transmission electron microscopy images of boron nitride films with different numbers of layers in Examples 1-4 transferred onto a microgrid;
[0028] Figure 6 Transmission electron microscopy image of the number of boron nitride thin film layers transferred onto the microgrid in Example 5;
[0029] Figure 7 Transmission electron microscopy and diffraction pattern of a comparative boron nitride thin film transferred onto a microgrid;
[0030] Figure 8 These are spherical aberration transmission electron microscope (TEM) images of different regions of the boron nitride thin film from the self-parallel domains in Example 5.
[0031] Figure 9 This is a consistent selected area electron diffraction pattern of different regions on the boron nitride thin film of Example 5;
[0032] Figure 10 These are atomic force maps of different regions on the boron nitride thin film of Example 5;
[0033] Figure 11 The images show low-energy electron diffraction patterns in different regions of the boron nitride thin film in Example 5.
[0034] Figure 12 The diagram shows a deep ultraviolet photodetector based on the boron nitride thin film of Example 5 and its performance test results; a- schematic diagram of the ultraviolet detector, b- current-voltage curve, c- photoresponsivity and detectivity curves. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0036] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.
[0037] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.
[0038] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.
[0039] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.
[0040] Example 1: A controllable preparation method for a high-quality, wafer-level single-crystal multilayer boron nitride thin film according to this example is carried out according to the following steps:
[0041] S1: The copper foil was cleaned sequentially with acetone, 5wt% dilute hydrochloric acid and deionized water, each solution was used once, and each cleaning was ultrasonicated for 10 minutes;
[0042] S2: The cleaned copper foil was placed in a mixture of phosphoric acid / polyethylene glycol 400 (v / v: 3 / 1) and electrochemically polished under a voltage of 0.2V and a current of 0.01A.
[0043] S3: First, the polished copper foil is placed on a tungsten sheet and then placed in the growth region. It is annealed at 1100℃ for 30 minutes in a hydrogen / argon atmosphere (v / v = 9:100) to obtain a liquid copper growth substrate. Then, the borane-ammonia complex is placed as a solid source in the source region. A dual-temperature system is used to grow the thin film in a hydrogen / argon atmosphere (v / v = 9:100) using a CVD process. The temperature of the growth region is controlled at 1100℃, the temperature of the source region is controlled at 70℃, and the growth time is 6 minutes to obtain a high-quality, wafer-level single-crystal monolayer boron nitride thin film.
[0044] Example 2: A controllable preparation method for a high-quality, wafer-level single-crystal multilayer boron nitride thin film according to this example is carried out according to the following steps:
[0045] S1: The copper foil was cleaned sequentially with acetone, 5wt% dilute hydrochloric acid and deionized water, each solution was used once, and each cleaning was ultrasonicated for 10 minutes;
[0046] S2: The cleaned copper foil was placed in a mixture of phosphoric acid / polyethylene glycol 400 (v / v: 3 / 1) and electrochemically polished under a voltage of 0.2V and a current of 0.01A.
[0047] S3: First, the polished copper foil is placed on a tungsten sheet and then placed in the growth region. It is annealed at 1100℃ for 30 minutes in a hydrogen / argon atmosphere (v / v = 9:100) to obtain a liquid copper growth substrate. Then, the borane-ammonia complex is placed as a solid source in the source region. A dual-temperature system is used to grow the thin film in a hydrogen / argon atmosphere (v / v = 9:100) using a CVD process. The temperature of the growth region is controlled at 1100℃, the temperature of the source region is controlled at 70℃, and the growth time is 15 minutes to obtain a high-quality, wafer-level single-crystal double-layer boron nitride thin film with a single crystal size of 6cm × 7cm.
[0048] Example 3: A controllable preparation method for a high-quality, wafer-level single-crystal multilayer boron nitride thin film according to this example is carried out according to the following steps:
[0049] S1: The copper foil was cleaned sequentially with acetone, 5wt% dilute hydrochloric acid and deionized water, each solution was used once, and each cleaning was ultrasonicated for 10 minutes;
[0050] S2: The cleaned copper foil was placed in a mixture of phosphoric acid / polyethylene glycol 400 (v / v: 3 / 1) and electrochemically polished under a voltage of 0.2V and a current of 0.01A.
[0051] S3: First, the polished copper foil is placed on a tungsten sheet and then placed in the growth region. It is annealed at 1100℃ for 30 minutes in a hydrogen / argon atmosphere (v / v = 9:100) to obtain a liquid copper growth substrate. Then, the borane-ammonia complex is placed as a solid source in the source region. A dual-temperature system is used to grow the thin film in a hydrogen / argon atmosphere (v / v = 9:100) using a CVD process. The temperature of the growth region is controlled at 1100℃, the temperature of the source region is controlled at 70℃, and the growth time is 20 minutes. This yields a high-quality, wafer-level single-crystal three-layer boron nitride thin film with a single crystal size of 6cm × 7cm.
[0052] Example 4: A controllable preparation method for a high-quality, wafer-level single-crystal multilayer boron nitride thin film according to this example is carried out according to the following steps:
[0053] S1: The copper foil was cleaned sequentially with acetone, 5wt% dilute hydrochloric acid and deionized water, each solution was used once, and each cleaning was ultrasonicated for 10 minutes;
[0054] S2: The cleaned copper foil was placed in a mixture of phosphoric acid / polyethylene glycol 400 (v / v: 3 / 1) and electrochemically polished under a voltage of 0.2V and a current of 0.01A.
[0055] S3: First, the polished copper foil is placed on a tungsten sheet and then placed in the growth region. It is annealed at 1100℃ for 30 minutes in a hydrogen / argon atmosphere (v / v = 9:100) to obtain a liquid copper growth substrate. Then, the borane-ammonia complex is placed as a solid source in the source region. A dual-temperature system is used to grow the thin film in a hydrogen / argon atmosphere (v / v = 9:100) using a CVD process. The temperature of the growth region is controlled at 1100℃, the temperature of the source region is controlled at 70℃, and the growth time is 23 minutes. This yields a high-quality, wafer-level single-crystal four-layer boron nitride thin film with a single crystal size of 6cm × 7cm.
[0056] Example 5: A controllable preparation method for a high-quality, wafer-level single-crystal multilayer boron nitride thin film according to this example is carried out according to the following steps:
[0057] S1: The copper foil was cleaned sequentially with acetone, 5wt% dilute hydrochloric acid and deionized water, each solution was used once, and each cleaning was ultrasonicated for 10 minutes;
[0058] S2: The cleaned copper foil was placed in a mixture of phosphoric acid / polyethylene glycol 400 (v / v: 3 / 1) and electrochemically polished under a voltage of 0.2V and a current of 0.01A.
[0059] S3: First, the polished copper foil is placed on a tungsten sheet and then placed in the growth region. It is annealed at 1100℃ for 30 minutes in a hydrogen / argon atmosphere (v / v = 9:100) to obtain a liquid copper growth substrate. Then, the borane-ammonia complex is placed as a solid source in the source region. A dual-temperature system is used to grow the thin film in a hydrogen / argon atmosphere (v / v = 9:100) using a CVD process. The temperature of the growth region is controlled at 1100℃, the temperature of the source region is controlled at 70℃, and the growth time is 25 minutes. This yields a high-quality, wafer-level single-crystal five-layer boron nitride thin film with a single crystal size of 6cm × 7cm.
[0060] Comparative Example: The preparation method of a boron nitride thin film in this comparative example is carried out according to the following steps:
[0061] S1: The copper foil was cleaned sequentially with acetone, 5wt% dilute hydrochloric acid and deionized water, each solution was used once, and each cleaning was ultrasonicated for 10 minutes;
[0062] S2: The cleaned copper foil was placed in a mixture of phosphoric acid / polyethylene glycol 400 (v / v: 3 / 1) and electrochemically polished under a voltage of 0.2V and a current of 0.01A.
[0063] S3: First, the polished copper foil is placed on a tungsten sheet and then placed in the growth region. It is annealed at 1100℃ for 30 minutes in a hydrogen / argon atmosphere (v / v = 9:100) to obtain a liquid copper growth substrate. Then, the borane-ammonia complex is placed as a solid source in the source region. A dual-temperature system is used to grow the thin film in a hydrogen / argon atmosphere (v / v = 9:100) using a CVD process. The temperature of the growth region is controlled at 1100℃, the temperature of the source region is controlled at 70℃, and the growth time is 30 minutes to obtain a high-quality, wafer-level polycrystalline six-layer boron nitride thin film.
[0064] Testing and Experiment
[0065] (I) The growth and evolution process of boron nitride in Examples 1-5 was observed by scanning electron microscopy, and the results are as follows: Figure 3 As shown, from Figure 3 The evolution of the boron nitride thin film over time can be observed. Initially, boron nitride nucleates in relatively active areas on the liquid copper surface. As the raw material supply continues, the boron nitride nuclei gradually grow from a few micrometers to relatively uniform boron nitride domains. Subsequently, some areas fuse, and under the synergistic catalytic effect of copper vapor, a second layer of boron nitride also begins to nucleate and grow, with the grown domain size being approximately 10 micrometers. With the continued supply of raw materials, after approximately 15 minutes, the second layer of boron nitride is also epitaxially grown onto the first layer of single-crystal boron nitride to form a single-crystal thin film. After approximately 25 minutes, a five-layer single-crystal boron nitride thin film is finally epitaxially grown on the liquid copper substrate.
[0066] (II) The distribution of electrostatic attraction between boron nitride domains obtained in Example 5 was calculated using density functional theory, and the results are as follows: Figure 4 As shown, from Figure 4 As can be seen, two circular grains rotate on the liquid substrate under the influence of Coulomb forces, causing the N-ends and B-ends to face each other, completing the subsequent seamless splicing process. Due to the mutual attraction of Coulomb forces, this type of bonding is relatively stable. The latter two types of self-splicing are shown in the figure. The self-rotation of the two grains causes the armchair-shaped ends of BN and NB to face each other, attracting surrounding free B and N atoms to form bonds, also achieving a seamless self-splicing process. However, compared to the first splicing mode, this mode has relatively poor stability due to the repulsive effect of Coulomb forces. Considering the triple rotational symmetry of boron nitride grains, the maximum rotation angle for seamless splicing is 60°. Figure 4 The image on the right illustrates the electrostatic attraction-induced self-parallel rotation process of boron nitride. Two misaligned boron nitride domains rotate due to electrostatic attraction. Because of the triple rotational symmetry of boron nitride, the rotation angle is less than 60 degrees. The boron nitride thin film rotates under electrostatic attraction, ultimately achieving self-parallelism.
[0067] (III) Layer Representation:
[0068] The boron nitride thin films obtained in Examples 1-5 were transferred onto a microgrid using a hydrogen bubbling method. The number of boron nitride thin film layers was then observed using a transmission electron microscope. The results are as follows: Figure 5-6 As shown, from Figure 5 As can be seen, boron nitride film growth of 6 min yields a single layer, 15 min yields a double layer, 20 min yields a triple layer, and 23 min yields a quadruple layer. Figure 6 As can be seen, five layers were obtained after growing boron nitride film for 25 minutes.
[0069] Transmission electron microscopy and diffraction pattern of comparative boron nitride thin films, from Figure 7 It can be seen that when the boron nitride film obtained after 30 minutes of growth has six layers and a cross-sectional thickness of six layers, the diffraction spots of the boron nitride film in different regions show significant changes. This indicates that the catalytic effect of the grown six-layer boron nitride film is weakened due to the liquid copper, leading to the formation of a polycrystalline film.
[0070] (iv) Spherical aberration in different regions of boron nitride self-parallel domains obtained by transmission electron microscopy in Example 5, as shown in the following figures. Figure 8 As shown, where figures b, c, and d represent the spherical aberration at positions b, c, and d in figure a. Figure 8 As can be seen, the hBN sample exhibits a typical honeycomb structure with almost no surface defects, proving that the boron nitride thin film obtained in this invention has ultra-high crystal quality and lattice consistency.
[0071] (V) Characterization of Local Single Crystallization
[0072] The boron nitride thin film obtained in Example 5 was transferred onto a microgrid using a hydrogen bubbling method. Nine regions were then randomly selected for testing, resulting in consistent selected-area electron diffraction patterns for the nine regions, as shown below. Figure 9 As shown, from Figure 9 It can be seen that the boron nitride thin film obtained by this invention exhibits localized monocrystalline properties.
[0073] (vi) The boron nitride thin film obtained in Example 5 was transferred onto a silicon wafer using a hydrogen bubbling method. Then, five regions were randomly selected to obtain atomic force maps of the five regions as follows. Figure 10 As shown, from Figure 10 It can be seen that the boron nitride film obtained in Example 5 has five layers in different regions, which is consistent with the results obtained by transmission electron microscopy.
[0074] (vii) The single-crystal boron nitride film obtained in Example 5 was characterized at the centimeter level on the re-cured copper surface by low-energy electron diffraction. The results are as follows: Figure 11 As shown, from Figure 11As can be seen, the nine diffraction spots in different regions are completely identical, indicating that the boron nitride film is a centimeter-scale single-crystal film.
[0075] (viii) The performance of the deep ultraviolet photodetector was tested by transferring the single-crystal boron nitride thin film obtained in Example 5 onto a silicon wafer. The results are as follows: Figure 12 As shown, Figure 12 a is a schematic diagram of an ultraviolet detector constructed based on single-crystal hexagonal boron nitride. Figure 12 b shows the current-voltage curve of a hexagonal boron nitride single crystal. Under ultraviolet irradiation, the current of boron nitride increases significantly. When the voltage between the source and drain electrodes is 24V, the current can reach ~4×10⁻⁶. -13 A, Photoresponsivity and detectivity are two important indicators of photodetectors, from Figure 12 The optical responsivity and detectivity values obtained in c are 1.143 × 10⁻⁶. 2 mA / W, responsivity is 36 times that of polycrystalline boron nitride, and photodetector value is 6.2 × 10⁻⁶. 11 Jones.
[0076] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A controllable method for preparing high-quality, wafer-level, single-crystal boron nitride thin films, characterized in that, The method is performed according to the following steps: The liquid growth substrate is placed in the growth zone, and the solid source is placed in the source zone, thin film growth is performed under a reducing atmosphere, the number of layers of the single-crystal boron nitride film is regulated by controlling the growth time, and a high-quality, wafer-level single-crystal boron nitride film is obtained; The growth zone temperature is controlled at 1100 DEG C, the source zone temperature is controlled at 70-80 DEG C, and the growth time is 6-25 min; The liquid growth substrate is liquid copper; The solid source is borane ammonia complex; The reducing atmosphere is composed of hydrogen and argon in a volume ratio of 9:100; The liquid growth substrate is obtained by cleaning, polishing and annealing liquefaction of a metal foil; The annealing liquefaction temperature is 1100 DEG C, and the time is 30 min; The annealing liquefaction is performed under the same reducing atmosphere as the growth process.
2. The method of claim 1, wherein, The cleaning is performed in sequence with acetone, 5wt% dilute hydrochloric acid and deionized water, and the polishing is electrochemical polishing of the metal foil in phosphoric acid / polyethylene glycol 400, v / v=3 / 1.