Self-catalyzed axial heterogeneous molecular beam epitaxy preparation method of indium antimonide nanowires

Abstract

The application provides a self-catalytic axial heterogeneous molecular beam epitaxy preparation method of indium antimonide nanowires, which can be applied to the technical field of self-catalytic preparation of semiconductor nanowires by molecular beam epitaxy. The method comprises the following steps: forming a gallium catalyst droplet on a substrate surface; introducing an arsenic beam current, taking the gallium catalyst droplet as a self-catalytic droplet, and epitaxially growing a gallium arsenide nanowire; after the epitaxial growth of the gallium arsenide nanowire is completed, under the condition that the arsenic beam current is maintained to be introduced, the gallium catalyst droplet located at the top end of the gallium arsenide nanowire is partially consumed to regulate the residual size of the gallium catalyst droplet; introducing an indium beam current, utilizing the characteristic that indium atoms have a low incorporation coefficient on the surface of gallium arsenide, and making the indium atoms gather at the residual gallium catalyst droplet and convert the residual gallium catalyst droplet into an indium catalyst droplet in situ; and introducing an antimony beam current, taking the indium catalyst droplet as a self-catalytic droplet, and epitaxially growing an indium antimonide nanowire at the top end of the gallium arsenide nanowire through a gas-liquid-solid growth mechanism.

Description

Technical Field

[0001] This invention relates to the field of molecular beam epitaxy autocatalytic preparation technology of semiconductor nanowires, and more specifically to an autocatalytic axial heterogeneous molecular beam epitaxy preparation method for indium antimonide nanowires. Background Technology

[0002] Indium antimonide (InSb), as a III-V compound semiconductor material, possesses the narrowest band gap, the highest electron mobility, extremely strong spin-orbit coupling effect, and a large Landé g-factor, making it a promising candidate for applications in high-speed electronic devices, infrared optoelectronic devices, and topological quantum computing devices. Particularly in topological quantum computing, heterojunction systems based on InSb nanowires and superconductors are considered the core carrier for realizing Majorana zero-mode detection and braiding operations, placing extremely stringent requirements on the crystal quality and electrical properties of the nanowires.

[0003] Currently, indium antimonide (InSb) nanowires are mainly prepared using molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD) techniques, and the growth methods can be classified into the following three categories:

[0004] The first type involves direct epitaxial growth on a semiconductor substrate. Indium antimonide (InSb) is one of the materials with the highest lattice constant among group III-V semiconductors, exhibiting a lattice mismatch of over 10% with commonly used substrates such as silicon (Si) and gallium arsenide (GaAs). This significant lattice mismatch makes directly epitaxially grown InSb nanowires highly susceptible to structural defects such as bending, twisting, polycrystalline formation, or severe stacking faults, severely degrading the crystal quality and electrical properties of the nanowires.

[0005] The second method involves epitaxial growth of indium antimonide (InSb) on the tips of pre-grown nanowire stems using axial heteroepitaxial growth. This method effectively mitigates the impact of substrate mismatch on the crystal quality of the InSb segment by selecting stem materials with minimal lattice mismatch with InSb. Researchers have already made some progress in epitaxially growing InSb on InAs nanowire stems.

[0006] The third category, the two existing preparation methods mentioned above, both rely on heterogeneous metal catalyst nanoparticles such as gold (Au) or silver (Ag) to guide gas-liquid-solid (VLS) growth. Taking gold (Au) catalysts as an example, their introduction will form deep-level impurities in semiconductor materials, degrading carrier transport characteristics. Furthermore, gold (Au) is incompatible with complementary metal-oxide-semiconductor (CMOS) processes, severely limiting the application of indium antimonide (InSb) nanowires in the integrated circuit field. Although there are autocatalytic growth schemes that do not rely on heterogeneous metal catalysts, i.e., using indium (In) itself as a catalyst, existing autocatalytic schemes generally face the following technical bottlenecks:

[0007] Firstly, existing self-catalytic indium antimonide (InSb) nanowire growth schemes typically use indium arsenide (InAs) nanowires as stems, hoping to guide the epitaxial growth of indium antimonide (InSb) through droplets formed by indium (In) itself at the top of the indium arsenide (InAs). However, indium (In) and arsenic (As) have a very strong chemical affinity. In molecular beam epitaxy (MBE) equipment, even after the arsenic (As) source is turned off, there is still a certain arsenic (As) background pressure inside the equipment (especially when using an As4 source). The residual arsenic (As) background readily reacts with indium (In) to form indium arsenide (InAs), causing the indium (In) catalyst droplets to crystallize and become ineffective, thus failing to form stable liquid-phase indium (In) droplets that can guide the growth of indium antimonide (InSb).

[0008] Secondly, existing self-catalytic indium antimonide (InSb) nanowires either suffer from crystal defects or have extremely narrow growth windows, making it difficult to achieve controllable growth of high-quality indium antimonide (InSb) nanowires. The size and morphology of the catalyst droplets, as well as the structural parameters such as the diameter and length of the nanowires, are difficult to control independently, further limiting the application of indium antimonide (InSb) nanowires in quantum transport devices.

[0009] Thirdly, at the device application level, almost all indium antimonide (InSb) nanowires currently used in Majorana-related research are grown using metal-organic chemical vapor deposition (MOCVD). However, MOCVD equipment cannot achieve low-temperature in-situ epitaxy of superconductors. The unavoidable disorder at the semiconductor-superconductor interface leads to a soft superconducting bandgap and mediocre Andreev bound states, which has long plagued transport measurements in hybrid systems. While molecular beam epitaxy (MBE) can theoretically solve this problem—superconductors can be epitaxially deposited in situ at low temperatures—antimony (Sb) acts as a surfactant under ultra-high vacuum conditions, strongly inhibiting axial growth. Therefore, growing indium antimonide (InSb) nanowires using MBE faces significant process challenges.

[0010] In summary, existing methods for preparing indium antimonide (InSb) nanowires suffer from several drawbacks, including reliance on heterogeneous metal catalysts to introduce deep-level impurities, high defect density due to lattice mismatch, easy crystallization of indium (In) droplets by background arsenic (As) leading to failure in autocatalytic methods, narrow growth windows hindering controllable structural parameters, and the inability of metal-organic chemical vapor deposition (MOCVD) to integrate with superconductors in situ. Therefore, there is an urgent need to develop an autocatalytic preparation method for indium antimonide (InSb) nanowires that does not rely on external catalysts, can stably construct indium (In) catalyst droplets, has a wide growth window, and is compatible with in-situ integration of superconductors via molecular beam epitaxy (MBE). Summary of the Invention

[0011] (a) Technical problems to be solved

[0012] To address the problems in existing indium antimonide (InSb) nanowire fabrication methods, such as reliance on heterocatalysts like gold (Au), susceptibility of indium (In) droplets to crystallization failure by background arsenic (As), narrow growth windows, and inability to integrate with superconductors in situ, this invention provides a self-catalytic axial heterogeneous molecular beam epitaxy method for preparing indium antimonide nanowires. This method uses self-catalytically grown gallium arsenide (GaAs) nanowires as template stems. After partially consuming the top gallium (Ga) catalyst droplet under an arsenic (As) beam, the low incorporation coefficient of indium (In) atoms on the gallium arsenide (GaAs) surface is utilized. The residual gallium (Ga) droplets are converted in situ into indium (In) catalyst droplets, and then indium (In) nanowires are epitaxially grown using the indium (In) droplets as autocatalytic droplets via a gas-liquid-solid (VLS) mechanism. The entire preparation process is carried out continuously in situ in a molecular beam epitaxy (MBE) device under an ultra-high vacuum environment. No heterogeneous metal catalysts such as gold (Au) or silver (Ag) are introduced into the process. The growth parameters at each stage can be independently optimized to broaden the process window, and the diameter and length of the nanowires can be independently controlled by suppressing the non-catalytic deposition of the sidewalls under low beam current conditions.

[0013] (II) Technical Solution

[0014] To address the aforementioned technical problems, embodiments of the present invention propose a method for preparing indium antimonide nanowires via autocatalytic axial heterogeneous molecular beam epitaxy.

[0015] According to a first aspect of the present invention, a method for preparing indium antimonide nanowires via autocatalytic axial heterogeneous molecular beam epitaxy is provided, comprising: forming gallium catalyst droplets on a substrate surface; introducing an arsenic beam and using the gallium catalyst droplets as autocatalytic droplets to epitaxially grow gallium arsenide nanowires on the substrate through a gas-liquid-solid growth mechanism; after the epitaxial growth of the gallium arsenide nanowires is completed, partially consuming the gallium catalyst droplets at the top of the gallium arsenide nanowires while maintaining the arsenic beam flow, thereby controlling the residual size of the gallium catalyst droplets; introducing an indium beam and utilizing the low incorporation coefficient of indium atoms on the gallium arsenide surface to cause indium atoms to aggregate at the residual gallium catalyst droplets and convert the residual gallium catalyst droplets in situ into indium catalyst droplets, wherein the residual gallium catalyst droplets serve as liquid-phase templates for reducing the independent nucleation energy barrier of indium atoms; introducing an antimony beam and using the indium catalyst droplets as autocatalytic droplets to epitaxially grow indium antimonide nanowires at the top of the gallium arsenide nanowires through a gas-liquid-solid growth mechanism.

[0016] In some exemplary embodiments, the substrate includes a Si(111) substrate.

[0017] In some exemplary embodiments, the epitaxial growth temperature of gallium arsenide nanowires is 500°C to 600°C, and the beam equivalent pressure ratio of arsenic to gallium is 15 to 25; the epitaxial growth temperature of indium antimonide nanowires is 350°C to 450°C, and the beam equivalent pressure ratio of antimony to indium is 1.2 to 2.5.

[0018] In some exemplary embodiments, the epitaxial growth of gallium arsenide nanowires, the partial consumption of gallium catalyst droplets, the in-situ conversion of gallium catalyst droplets to indium catalyst droplets, and the epitaxial growth of indium antimonide nanowires are all carried out continuously in situ in an ultra-high vacuum environment in a molecular beam epitaxy device, and the substrate is not exposed to the atmospheric environment throughout the entire process.

[0019] In some exemplary embodiments, partial consumption of the gallium catalyst droplet is achieved by turning off the gallium source after the epitaxial growth of gallium arsenide nanowires, while maintaining a continuous arsenic beam, causing at least one of the following processes: evaporation and desorption of gallium atoms in the gallium catalyst droplet and reaction with arsenic to generate gallium arsenide.

[0020] In some exemplary embodiments, the degree of partial consumption of the gallium catalyst droplets is controlled by the continuous introduction time of the arsenic beam to adjust the size of the remaining gallium catalyst droplets, thereby controlling the size of the subsequently formed indium catalyst droplets and the diameter of the indium antimonide nanowires.

[0021] In some exemplary embodiments, the temperature at which residual gallium catalyst droplets are converted in situ into indium catalyst droplets is 350°C to 450°C.

[0022] In some exemplary embodiments, during the process of converting residual gallium catalyst droplets into indium catalyst droplets in situ, the size of the indium catalyst droplets is controlled by adjusting the beam intensity or introduction time of the indium beam, thereby achieving the regulation of the diameter of indium antimonide nanowires.

[0023] In some exemplary embodiments, under the condition of a fixed beam equivalent pressure ratio of antimony and indium, the epitaxial growth of indium antimonide nanowires is carried out by using low beam current conditions, which suppresses the non-catalytic vapor deposition of indium atoms on the sidewalls of gallium arsenide nanowires, so that the diameter of the indium antimonide nanowires remains constant or substantially constant, and the length of the indium antimonide nanowires increases linearly with the growth time.

[0024] In some exemplary embodiments, the preparation method does not introduce gold or silver as a heterometallic catalyst throughout the entire process. Both the gallium catalyst droplet and the indium catalyst droplet are self-catalytic droplets, and the indium antimonide nanowire does not contain deep-level impurity elements introduced by gold or silver.

[0025] (III) Beneficial Effects

[0026] As can be seen from the above technical solutions, the self-catalytic axial heterogeneous molecular beam epitaxy method for preparing indium antimonide nanowires provided in this invention has at least the following beneficial effects:

[0027] (1) Elimination of deep-level impurities introduced by heterogeneous metal catalysts. In this invention, no heterogeneous metal catalysts such as gold or silver are introduced throughout the process. Both gallium catalyst droplets and indium catalyst droplets are self-catalytic droplets. The resulting indium antimonide nanowires do not contain deep-level impurity elements introduced by gold or silver. The preparation process is compatible with complementary metal oxide semiconductor processes.

[0028] (2) Overcoming the technical bottleneck of indium droplet crystallization failure. This invention uses gallium arsenide nanowires as growth template stems. Taking advantage of the physicochemical properties of the low incorporation coefficient of indium atoms on the surface of gallium arsenide, stable construction of indium catalyst droplets on the top of gallium arsenide nanowires can still be achieved even under the condition of arsenic background pressure in molecular beam epitaxy equipment. This avoids the problem of indium droplets failing due to crystallization by background arsenic in existing indium arsenide stem schemes.

[0029] (3) Residual gallium droplets serve as liquid-phase templates to reduce the nucleation energy barrier. In this invention, after the gallium catalyst droplets are partially consumed by arsenic beam treatment, the residual gallium catalyst droplets serve as pre-stored liquid-phase templates to reduce the energy barrier for indium atoms to independently nucleate at the top of gallium arsenide nanowires, promote the aggregation of indium atoms, and ensure that the catalyst droplets maintain morphological stability and position selectivity during the conversion process.

[0030] (4) The process parameters of each stage can be optimized independently, thus broadening the growth window. The present invention divides the growth process into four stages: gallium arsenide nanowire template growth, partial consumption of gallium catalyst droplets, in-situ conversion of catalyst droplets, and axial heteroepitaxial growth of indium antimonide. The substrate temperature, beam current, V / III ratio, and growth time of each stage can be optimized independently, thus expanding the process window of autocatalytic epitaxial growth.

[0031] (5) Achieving independent linear control of nanowire diameter and length. Under the condition of fixed antimony and indium beam equivalent pressure ratio, the present invention adopts low beam current growth to suppress non-catalytic vapor deposition of indium atoms on the sidewall of gallium arsenide nanowire, so that the diameter of indium antimonide nanowire remains constant and the length increases linearly with growth time.

[0032] (6) The crystal structure is complete and the interface is steep at the atomic level. The indium antimonide nanowires prepared by this invention have a pure zincblende structure without twins or stacking fault defects; the gallium arsenide / indium antimonide heterostructure interface has no mismatch dislocations, stacking faults, or amorphous transition layers, and there is no significant interdiffusion of elements on both sides.

[0033] (7) Possesses coherent quantum transport properties. The indium antimonide nanowires prepared in this invention have an electron mobility of 19,000 cm⁻¹. 2 / Vs, ballistic transport characteristics (quantized conductance plateau) and Kondo effect can be observed in short-channel devices, with a Landé g-factor of 41.

[0034] (8) Compatible with in-situ integration of superconductors. The entire process of this invention is completed in-situ continuously in a high vacuum environment in a molecular beam epitaxy device. The substrate is not exposed to the atmospheric environment. Superconductors can be epitaxially grown in-situ at low temperature in the same device to construct indium antimonide-superconductor heterojunction devices, providing a material basis for topological quantum computing research. Attached Figure Description

[0035] The above-described features, other objects, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0036] Figure 1 A flowchart illustrating a method for preparing indium antimonide nanowires by autocatalytic axial heterogeneous molecular beam epitaxy according to an embodiment of the present invention is shown.

[0037] Figure 2 This schematic diagram illustrates the autocatalytic axial heterogeneous molecular beam epitaxial growth process of indium antimonide nanowires according to an embodiment of the present invention.

[0038] Figure 3 A comparative schematic diagram of nanowire morphology under different beam current conditions according to embodiments of the present invention is shown, wherein (a) high beam current growth for 25 minutes; (b) high beam current growth for 60 minutes; (c) low beam current growth for 25 minutes; and (d) low beam current growth for 60 minutes.

[0039] Figure 4 The schematic diagram illustrates the microstructure and elemental distribution characterization results of indium antimonide nanowires according to embodiments of the present invention, wherein: (a) low-magnification transmission electron microscope image; (b) high-resolution transmission electron microscope image of the indium antimonide segment; (c) high-resolution transmission electron microscope image of the heterojunction interface region; (d) high-resolution transmission electron microscope image of the gallium arsenide segment; (e) high-angle annular dark-field scanning transmission electron microscope image of the nanowire tip; (f) energy spectrum surface scan of the tip region; (g) energy spectrum line scan along the axial direction through the catalyst region; (h) high-angle annular dark-field scanning transmission electron microscope image of the interface region; (i) energy spectrum surface scan of the interface region; (j) energy spectrum line scan along the axial direction through the interface region;

[0040] Figure 5 The microstructure of the cross-section of indium antimonide nanowires according to embodiments of the present invention is schematically shown, wherein (a) is a low-magnification, high-angle annular dark-field scanning transmission electron microscope panoramic image; (b) to (i) are high-resolution atomic-level images of different regions;

[0041] Figure 6 Transmission electron microscopy (TEM) images of gallium droplets at the tips of gallium arsenide nanowires under different arsenic beam treatment times according to embodiments of the present invention are illustrated, wherein (a) is a TEM image of the tip region of the gallium arsenide nanowire without arsenic beam treatment; (b) is a TEM image of the tip region after 7 minutes of arsenic beam treatment; (c) is a TEM image of the tip region after 10 minutes of arsenic beam treatment; and (d) and (e) are respectively... Figure 6 In the middle, (b) shows the high-resolution transmission electron microscope images corresponding to region 1 and region 2;

[0042] Figure 7 This schematic diagram illustrates the energy dispersive spectroscopy (EDS) results of an indium droplet prepared on gallium arsenide according to an embodiment of the present invention.

[0043] Figure 8 The following schematically illustrates a transmission electron microscope image of a cross-section of an indium antimonide nanowire according to an embodiment of the present invention and the corresponding energy dispersive spectroscopy (EDS) elemental distribution map, wherein (a) is a high-angle annular dark-field scanning transmission electron microscope image; (b) to (d) are EDS elemental distribution maps.

[0044] Figure 9 The following schematically illustrates the electrical transport characterization results of indium antimonide nanowires according to embodiments of the present invention, wherein: (a) scanning electron microscope image of mobility device; (b) pinch-off curve and mobility fitting; (c) scanning transmission electron microscope image of device cross section; (d) oxygen element energy spectrum surface scan; (e) scanning electron microscope image of short-channel device; (f) variation of differential conductance with back gate voltage and magnetic field;

[0045] Figure 10 Supplementary data on mobility and ballistic transport, and the Kondo effect, are schematically illustrated according to embodiments of the present invention, wherein: (a) reverse scan pinch-off curve and mobility fitting; (b) conductance of short-channel device as a function of back gate voltage and bias voltage; (c) scanning electron microscope image of another mobility device; (d) corresponding pinch-off curve and mobility fitting; (e) scanning electron microscope image of another short-channel device; (f) conductance plot at B=0T; (g) conductance plot at B=0.1T; (h) conductance as a function of magnetic field and bias voltage.

[0046] Figure label:

[0047] 10-Substrate; 11-Gas beam; 12-Gas catalyst droplet; 13-Arsenic beam; 14-Gas arsenide nanowire; 15-Indium beam; 16-Indium catalyst droplet; 17-Antimony beam; 18-Indium antimonide nanowire. Detailed Implementation

[0048] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0049] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0050] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0051] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0052] Traditionally, the preparation of indium antimonide nanowires mainly relies on gas-liquid-solid growth modes guided by heterocatalysts such as gold, or direct epitaxial growth methods. These traditional methods suffer from prominent problems such as deep-level impurity contamination due to heterocatalyst dependence, incompatibility with complementary metal-oxide-semiconductor processes, crystal defects due to lattice mismatch, narrow autocatalytic growth windows, and poor crystal quality. To address these issues, this invention proposes an autocatalytic molecular beam epitaxy method that precisely controls the composition of group III catalyst droplets. Using autocatalytic gallium arsenide nanowires as growth templates and catalyst supports, gallium catalyst droplets are in-situ converted into indium catalyst droplets, thereby achieving high-quality autocatalytic axial heteroepitaxial growth of indium antimonide nanowires.

[0053] Figure 1 A flowchart illustrating a method for preparing indium antimonide nanowires by autocatalytic axial heterogeneous molecular beam epitaxy according to an embodiment of the present invention is shown. Figure 2 The diagram illustrates the autocatalytic axial heterogeneous molecular beam epitaxial growth process of indium antimonide nanowires according to an embodiment of the present invention.

[0054] like Figure 1 and Figure 2 As shown, the method for preparing indium antimonide nanowires by autocatalytic axial heterogeneous molecular beam epitaxy according to an embodiment of the present invention includes steps S1 to S5.

[0055] In step S1, gallium catalyst droplets are formed on the substrate surface.

[0056] Step S1 corresponds to Figure 2 (a) in the example. Specifically, the substrate is first pretreated (corresponding to...). Figure 2 (a)). A silicon (111) substrate 10 is used as the growth substrate for gallium arsenide nanowires because silicon substrates are the most widely used substrate materials in the semiconductor industry, are highly compatible with complementary metal-oxide-semiconductor processes, and the (111) crystal plane is conducive to the vertical epitaxial growth of nanowires.

[0057] Before placing the substrate 10 into the molecular beam epitaxy (MBE) apparatus, it needs to be pretreated. The pretreatment process is as follows: the silicon (111) substrate 10 is immersed in a hydrofluoric acid solution (concentration of 8%) for about 40 seconds to remove the native oxide layer on the substrate surface and to etch tiny pits on the silicon (111) substrate to facilitate the subsequent deposition of gallium droplets. Subsequently, the substrate 10 is immersed in a mixed solution of sulfuric acid (98%) and hydrogen peroxide (30%) with a volume ratio of 4:1 for about 15 seconds to form a thin oxide layer on the substrate surface. This thin oxide layer helps the uniform nucleation and distribution of gallium catalyst droplets on the substrate surface. The pretreated substrate 10 is then sent into the growth chamber of the MBE apparatus. All subsequent steps are performed continuously in the high vacuum environment of the same MBE apparatus without atmospheric exposure, avoiding impurity contamination and interface oxidation problems during catalyst conversion, and ensuring the atomic-level sharpness and purity of the heterostructure interface between the gallium arsenide nanowires and indium antimonide nanowires.

[0058] Subsequently, gallium catalyst droplets are formed on the substrate surface. The pretreated substrate 10 is heated to an appropriate temperature, such as approximately 550°C, in a molecular beam epitaxy apparatus to remove residual oxides on the substrate surface and reconstruct the substrate surface atoms into an initial state suitable for nanowire nucleation. This temperature is the subsequent growth temperature of gallium arsenide nanowires; if the temperature is too high, the nanowires are prone to decomposition, and if the temperature is too low, axial growth of the nanowires is difficult. After the temperature stabilizes, the shutter of the gallium source furnace is opened to provide a gallium beam 11, depositing gallium atoms on the surface of the substrate 10. Because the thin oxide layer on the surface of the substrate 10 inhibits the uniform wetting of gallium atoms on the substrate surface, gallium atoms tend to aggregate to form isolated nanoscale gallium metal droplets 12. In this step, the gallium beam ingress time is approximately 2 minutes to ensure the formation of initial gallium catalyst droplets 12 with uniform size and appropriate distribution density, providing catalyst sites for the subsequent autocatalytic growth of gallium arsenide nanowires.

[0059] In step S2, an arsenic beam is introduced, and gallium catalyst droplets are used as autocatalytic droplets to epitaxially grow gallium arsenide nanowires on the substrate through a gas-liquid-solid growth mechanism.

[0060] Step S2 corresponds to Figure 2 (b) After the gallium catalyst droplet 12 is formed, the shutter of the arsenic source furnace is opened, and an arsenic beam 13 is introduced. Using the gallium catalyst droplet 12 as an autocatalytic droplet, gallium arsenide nanowires 14 are epitaxially grown on the substrate 10 through a gas-liquid-solid growth mechanism. This gallium arsenide nanowire 14 will serve as the substrate for the subsequent autocatalytic growth of indium antimonide nanowires and as the platform for the construction of indium droplets.

[0061] The gallium arsenide nanowire 14 is grown at a temperature of 500°C to 600°C, preferably 550°C; the V / III ratio is 15 to 25, preferably 20; and the growth time is 25 minutes. Under these conditions, the gallium arsenide nanowire grows vertically along the

[111] direction, and the gallium catalyst droplet 12 is held at the top of the nanowire.

[0062] In step S3, after the epitaxial growth of gallium arsenide nanowires is completed, the gallium catalyst droplet located at the top of the gallium arsenide nanowires is partially consumed while maintaining the arsenic beam flow, so as to control the residual size of the gallium catalyst droplet.

[0063] Step S3 corresponds to Figure 2 (c) After the gallium arsenide nanowire 14 has grown, the gallium source shutter is closed to terminate the gallium beam supply, but the arsenic source shutter remains open, allowing the arsenic beam 13 to continue flowing into the growth chamber for a specific period. During this time, the substrate temperature is maintained at the gallium arsenide nanowire growth temperature (e.g., 550°C). At this higher temperature, gallium atoms in the gallium catalyst droplet 12 are consumed through two pathways: first, some gallium atoms evaporate and desorb from the droplet surface, entering the gas phase environment; second, gallium atoms react with the introduced arsenic atoms to form gallium arsenide. The combined effect of these two mechanisms leads to a gradual decrease in the size of the gallium catalyst droplet 12.

[0064] The degree of partial consumption of the gallium catalyst droplet 12 is precisely controlled by the continuous flow time of the arsenic beam 13. In this embodiment, the continuous flow time of the arsenic beam is 5 minutes. By controlling the arsenic treatment time, the residual size of the gallium catalyst droplet can be adjusted, thereby controlling the size of the subsequently formed indium catalyst droplet and the diameter of the indium antimonide nanowires.

[0065] This step is one of the key steps to ensure the successful implementation of the method of the present invention: if the gallium catalyst droplet is completely consumed, the subsequent indium atoms will lose the pre-stored liquid phase template, making it difficult to form a stable indium catalyst droplet at the top of the gallium arsenide nanowire, resulting in the failure of indium antimonide nanowire growth; if the gallium catalyst droplet is not consumed enough, there will be too much gallium residue in the catalyst droplet formed by subsequent conversion, which will affect the crystal quality of indium antimonide nanowire.

[0066] In step S4, an indium beam is introduced. Taking advantage of the low incorporation coefficient of indium atoms on the surface of gallium arsenide, indium atoms are aggregated at the residual gallium catalyst droplets, and the residual gallium catalyst droplets are converted into indium catalyst droplets in situ. The residual gallium catalyst droplets serve as liquid-phase templates to reduce the energy barrier for independent nucleation of indium atoms.

[0067] Step S4 corresponds to Figure 2In step (d), after the gallium catalyst droplet 12 has been partially consumed to the target size, the arsenic source shutter is turned off to terminate the arsenic beam supply. Subsequently, the temperature of the substrate 10 is adjusted to a temperature range suitable for the formation of the indium catalyst droplet, i.e., the growth temperature of the indium antimonide nanowires. The growth temperature of the indium antimonide nanowires is 350°C to 450°C, preferably 400°C. After the temperature stabilizes, the indium source shutter is opened to introduce the indium beam 15.

[0068] Under conditions where the arsenic beam is turned off, indium atoms, upon reaching the tip of the gallium arsenide nanowire 14, do not crystallize to form indium arsenide. Instead, they aggregate on the tip surface of the gallium arsenide nanowire 14, forming metallic indium droplets 16. The formation of these indium droplets is a necessary condition for the autocatalytic growth of indium antimonide nanowires.

[0069] The residual gallium catalyst droplets serve as a pre-stored liquid-phase template, promoting the aggregation of indium atoms and lowering the energy barrier for independent nucleation of indium atoms at the top of gallium arsenide nanowires. This ensures that the catalyst droplets maintain morphological stability and positional selectivity during the conversion process. Specifically, this invention utilizes the low reactivity between indium and gallium arsenide—that is, the low incorporation coefficient of indium atoms on the gallium arsenide surface—making it difficult for indium to incorporate into the gallium arsenide lattice even under arsenic background pressure in molecular beam epitaxy equipment. This achieves stable construction of indium catalyst droplets at the top of gallium arsenide nanowires, fundamentally avoiding the technical bottleneck of indium droplets easily crystallizing and failing due to background arsenic when using indium arsenide stems in existing technologies.

[0070] In this embodiment, the indium beam 15 is introduced for 1 minute. By adjusting the beam intensity or introduction time of the indium beam, the size of the indium catalyst droplets 16 can be precisely controlled, thereby achieving the control of the diameter of the indium antimonide nanowires. See [link to documentation]. Figure 2 (e) in the middle.

[0071] In step S5, an antimony beam is introduced, and indium catalyst droplets are used as autocatalytic droplets to epitaxially grow indium antimonide nanowires on the top of gallium arsenide nanowires through a gas-liquid-solid growth mechanism.

[0072] Step S5 corresponds to Figure 2 (f) After the indium catalyst droplet 16 is fully formed, the antimony source shutter is opened and the antimony beam 17 is introduced. Using the indium catalyst droplet 16 as an autocatalytic droplet, indium antimonide nanowires 18 are epitaxially grown on the top of gallium arsenide nanowires 14 through a gas-liquid-solid growth mechanism.

[0073] The growth temperature of indium antimonide nanowires 18 is 350°C to 450°C, preferably 400°C; the beam equivalent pressure ratio (V / III ratio) of antimony to indium is 1.2 to 2.5, preferably 1.58.

[0074] Under the condition of a fixed equivalent pressure ratio of antimony and indium beams, the morphology of indium antimonide nanowires is controlled by adjusting the beam magnitudes of the indium and antimony beams. Specifically, epitaxial growth of indium antimonide nanowires under low beam current conditions can suppress the non-catalytic vapor deposition of indium atoms on the sidewalls of gallium arsenide nanowires, keeping the diameter of the indium antimonide nanowires constant or essentially constant, while their length increases linearly with growth time, thus achieving independent control of the nanowire diameter and length.

[0075] In this embodiment, the equivalent pressure of the indium beam is 1.53 × 10⁻⁶. -7 mbar, the equivalent pressure of the antimony beam is 2.43 × 10 mbar. -7 The growth is performed using mbar, and the growth time can be adjusted according to the target length. Under this beam condition, the length of the indium antimonide nanowire 18 increases linearly with the growth time, while the diameter remains essentially constant (approximately 150 nm). In this example, an indium antimonide nanowire with a length of approximately 2.6 μm and a diameter of approximately 150 nm was obtained when the growth time was 60 minutes.

[0076] After growth, all source furnace shutters were closed, and the substrate temperature was lowered to room temperature. Throughout the growth process, the molecular beam epitaxy (MBE) chamber was maintained under a high vacuum (background pressure better than 1 × 10⁻⁶). -9 mbar), all steps (steps S1 to S5) are completed continuously in situ under ultra-high vacuum conditions.

[0077] In this embodiment of the invention, the length of the finally obtained indium antimonide nanowires ranges from nanometers to micrometers, depending on the growth time; the diameter is in the nanometer range, depending on the catalyst droplet size and growth conditions. The prepared nanowires also possess advantages such as perpendicular orientation, good size controllability, and high crystal quality, making them easy to process into devices and enabling mass production, significantly reducing material and device processing costs. In particular, because the method of this invention does not introduce heterogeneous metal catalysts such as gold or silver, both the gallium catalyst droplet and the indium catalyst droplet are self-catalytic droplets, completely avoiding deep-level impurity contamination and incompatibility issues with complementary metal-oxide-semiconductor processes. The prepared indium antimonide nanowires can be directly integrated with mainstream semiconductor processes, providing a high-quality material platform for the development of indium antimonide nanowire-based high-speed electronic devices and topological quantum devices.

[0078] In step S5, the inventors further investigated the effect of beam conditions on the morphology of indium antimonide nanowires. Figure 3 A comparison of nanowire morphologies under different beam conditions according to embodiments of the present invention is shown. Figure 3 In the diagram, (a) and (b) are under high beam current conditions (the equivalent pressure of the indium beam is 0.97 × 10⁻⁶). -6 mbar, the equivalent pressure of the antimony beam is 1.53 × 10 -6Scanning electron microscope (SEM) images of cross-sections of samples grown for 25 minutes and 60 minutes (mbar), respectively. At 25 minutes of growth ( Figure 3 In (a) of the nanowires, the length is approximately 0.8 μm and the diameter is approximately 250 nm; when the growth time is extended to 60 minutes ( Figure 3 In (b), the length increases significantly to about 2.4 μm, and the diameter also increases significantly to about 400 nm. Figure 3 In the diagram, (c) and (d) represent the same V / III ratio but under low beam current conditions (the equivalent pressure of the indium beam is 1.53 × 10⁻⁶). -7 mbar, the equivalent pressure of the antimony beam is 2.43 × 10 mbar. -7 Samples were grown for 25 minutes and 60 minutes using a low beam current (mbar). Under low beam current conditions, when the growth time was extended from 25 minutes to 60 minutes, the nanowire length increased from approximately 0.8 μm to approximately 2.6 μm, while the diameter remained almost unchanged at approximately 150 nm. These results indicate that in autocatalytic gas-liquid-solid growth, high beam current leads to supersaturation of sidewall adsorbed atoms, inducing non-catalytic gas phase deposition and resulting in radial coarsening; while under low beam current conditions, sidewall adsorbed atoms are scarce, preferentially migrating to the top droplet via long-range surface diffusion, thus effectively suppressing radial growth and achieving independent control of nanowire diameter and length.

[0079] Figure 4 The microstructure and elemental distribution characterization results of indium antimonide nanowires according to embodiments of the present invention are shown. Figure 4 Image (a) is a low-magnification transmission electron microscope image of a single representative gallium arsenide / indium antimonide nanowire, clearly showing two axial segments: a gallium arsenide nanowire segment at the bottom and an indium antimonide nanowire segment at the top. The two segments are clearly defined, with a straight overall morphology and uniform diameter, indicating that the epitaxial growth of the indium antimonide nanowire segment maintains good growth stability after catalyst replacement. Figure 4 Images (b) to (d) are high-resolution transmission electron microscopy (TEM) images of the indium antimonide segment, the indium antimonide / gallium arsenide heterointerface region, and the gallium arsenide segment, respectively. The indium antimonide segment ( Figure 4 (b) shows highly ordered lattice fringes, without stacking faults or twin defects, indicating a pure zincblende structure. Gallium arsenide segment ( Figure 4 (d) in the image also exhibits single-crystal characteristics, with continuous and complete lattice fringes. In the indium antimonide / gallium arsenide interface region ( Figure 4 In (c) of the two materials, the lattice fringes are directly connected, and no mismatch dislocations, stacking faults, twins or amorphous transition layers are observed at the interface. Figure 4The insets in (c) at the bottom left and top right are Fast Fourier Transform patterns taken from high-resolution transmission electron microscopy (HRTEM) images of indium antimonide and gallium arsenide, respectively. HRTEM characterization confirms that the axial heteroepitaxial growth from the gallium arsenide stalk to the top indium antimonide segment achieves a crystal quality transition with extremely low defect density.

[0080] Figure 4 Image (e) is a high-angle annular dark-field scanning transmission electron microscope image of the tip region of a single indium antimonide nanowire, where spherical catalyst particles at the tip of the nanowire can be clearly observed. Figure 4 (f) in the figure shows the energy spectrum surface scan results for the corresponding region, which shows that indium and antimony are uniformly distributed on the radial cross section of the nanowire. The elemental surface scan of the catalyst particles at the top shows that indium signals are dominant, corresponding to the indium-antimony alloy catalyst. Figure 4 (g) represents the energy spectrum intensity distribution along the nanowire axis through the catalyst region. The quantitative results further confirm that the catalyst particles are mainly composed of indium, proving that the indium antimonide nanowires are grown through a self-catalytic gas-liquid-solid process. Figure 4 Image (h) in the image is a high-angle annular dark-field scanning transmission electron microscope image of the indium antimonide / gallium arsenide interface region. Since the contrast of high-angle annular dark-field imaging is approximately proportional to the square of the atomic number, the indium antimonide region (high atomic number) shows brighter contrast, while the gallium arsenide region shows darker contrast, forming a sharp and clear contrast boundary at the interface. Figure 4 In (i), the energy spectrum elemental surface scan of the interface region shows that gallium and arsenic signals are concentrated on the gallium arsenide side of the interface, while indium and antimony signals are concentrated on the indium antimonide side. There is no obvious elemental mixing on both sides of the interface. Figure 4 In the diagram, (j) represents the energy spectrum line scan along the nanowire axis through the interface, which quantitatively shows the spatial evolution of element intensity: the gallium and arsenic signals drop sharply to near zero at the interface, while the indium and antimony signals rise sharply and quickly reach a stable value, indicating that there is no obvious element interdiffusion between the indium antimonide segment and the gallium arsenide segment.

[0081] Figure 5 The microstructure of a cross-section of an indium antimonide nanowire according to an embodiment of the present invention is shown. Figure 5 Image (a) is a low-magnification, high-angle annular dark-field scanning transmission electron microscope panoramic image of the cross-section of indium antimonide nanowires, showing a near-hexagonal geometry. The contrast is uniform and continuous throughout the cross-sectional area, and no resolvable defects were observed. Figure 5 Images (b) to (i) in the diagram are high-resolution, high-angle annular dark-field scanning transmission electron microscope (TEM) atomic-level images of different regions of the cross-section. At high magnification, each region displays a highly ordered atomic arrangement. Figure 5 In the atomic images (b) to (i), indium and antimony atoms exhibit consistent atomic order from the center to the edge, with no structural differences between the interior and near-surface regions, and no lattice distortion caused by local strain fields was found.

[0082] Figure 6 Transmission electron microscopy images of gallium droplets at the tips of gallium nanowires under different arsenic beam treatment times according to embodiments of the present invention are shown. Figure 6 (a) is a transmission electron microscope image of the tip region of the gallium arsenide nanowire without arsenic beam treatment, showing obvious gallium droplets at the tip. Figure 6 (b) is a transmission electron microscope image of the tip region after arsenic beam treatment for 7 minutes, showing a significant reduction in gallium droplet size. Figure 6 (c) is a transmission electron microscope image of the tip region after arsenic beam treatment for 10 minutes. The gallium droplet has completely disappeared and the tip has become a flat surface. Figure 6 (d) and (e) in the text are respectively Figure 6 The high-resolution transmission electron microscope images corresponding to regions 1 and 2 shown in (b) show that the fast Fourier transform pattern corresponding to the white-framed area indicates that the interface between the droplet and the gallium arsenide tip has crystallized into an ordered gallium arsenide lattice. These results demonstrate that the residual state of the gallium catalyst droplet can be precisely controlled by adjusting the arsenic treatment time, achieving a gradual morphological evolution from a distinct gallium droplet to partial consumption and then to complete elimination.

[0083] Figure 7 The energy dispersive spectroscopy (EDS) results of indium droplets prepared on gallium arsenide according to an embodiment of the present invention are shown. The results indicate that the process can prepare high-purity indium droplets, confirming that the main component at the tip of the nanowire has been successfully converted from gallium to indium. The formation of these indium droplets effectively overcomes the catalyst preparation barrier in the epitaxy of indium antimonide nanowires, laying a solid foundation for the subsequent growth of indium antimonide nanowires.

[0084] Figure 8 Transmission electron microscope images of the cross-section of indium antimonide nanowires according to embodiments of the present invention and corresponding energy dispersive spectroscopy (EDS) elemental distribution maps are shown. Figure 8 Image (a) is a high-angle annular dark-field scanning transmission electron microscope image. Figure 8 Images (b) to (d) show the corresponding elemental surface area distribution maps in the energy dispersive spectroscopy (EDS). The elemental surface area scans show that indium and antimony are uniformly and continuously distributed across the entire nanowire cross-section, indicating a homogeneous matrix composition. In contrast, the arsenic signal exhibits slight inhomogeneity, appearing as isolated clusters rather than a uniformly dispersed distribution within the nanowire. This anomalous aggregation is attributed to the incorporation of arsenic precursors remaining in the reaction chamber during the early stages of growth, an effect that gradually weakens as growth progresses. Notably, because this invention uses an As4 source, the arsenic background pressure cannot be rapidly eliminated after gallium arsenide nanowire growth, resulting in detectable arsenic in the subsequently grown indium antimonide nanowires. Point-resolved energy dispersive spectroscopy analysis shows that the arsenic content in the indium antimonide nanowires is extremely low (approximately 4%). In future work, this background problem can be addressed by using a pyrolysis source to provide As2 instead of As4.

[0085] Figure 9 The electrical transport characterization results of indium antimonide nanowires according to embodiments of the present invention are shown. Figure 9 (a) is a scanning electron microscope image of the mobility device, with a channel length of approximately 1 μm. Figure 9 (b) in the figure is the pinch-off curve of the device (conductance G as a function of back gate voltage V). BG The gate voltage scanning direction changes from negative to positive. The bias voltage V is fixed at 10mV, and the current I is measured. G=1 / (V / IR) filter ), where R filter The series resistance contributed to the refrigerator filter (approximately 3.5kΩ). This is calculated using the formula G=(R... s +L 2 / (μC(V BG -V th ))) -1 Fit the pinch-off curve, where L is the channel length and R is the input. s For contact resistance, V th Here, μ is the threshold voltage, μ is the mobility, and C is the capacitance between the channel and the back gate. To extract the mobility, the capacitance must first be estimated. Figure 9 Image (c) shows a cross-sectional scanning transmission electron microscope image of the device after measurement, clearly identifying the back gate (p-type doped silicon) and SiO2. Based on Figure 9 In (c), C = 2.44 × 10⁻ is estimated using the finite element method. 17 F. Mobility fitting yielded μ = 19,000 cm⁻¹ 2 / Vs. Figure 9 The energy dispersive spectroscopy (EDS) in (d) highlights the surface oxides of the nanowires, which can serve as the primary source of disorder. To improve mobility, growth conditions can be optimized to remove residual arsenic from the indium antimonide nanowires, or a protective layer can be coated onto the indium antimonide surface to prevent oxidation.

[0086] Figure 9 (e) in the image is a scanning electron microscope image of a short-channel device with a channel length of approximately 320 nm. Figure 9 In this context, (f) represents the differential conductance G = dI / dV as a function of the back-gate voltage V. BG The variation of the magnetic field B is observed. The magnetic field direction is in-plane and approximately perpendicular to the nanowire. A conductivity plateau is observed as the magnetic field increases, indicating entry into the ballistic transport region and suppression of backscattering. Figure 9 The color of (f) in the diagram is marked with e. 2 The / h platform is "0.5". Below is a wire cut at 4.15T, where the 0.5, 1.0, and 1.5 platforms can be observed (with 2e). 2 (in units of / h). Based on the width of this 0.5 platform and its variation with the magnetic field, the extracted Landé g-factor is approximately 25.

[0087] Figure 10 Supplementary data on mobility and ballistic transport, as well as the Kondo effect, are shown according to embodiments of the present invention. Figure 10 (a) shows the pinch-off curve and mobility fit obtained by scanning the back gate voltage from the positive to the negative direction. The fitted mobility is approximately 16,000 cm⁻¹. 2 / Vs. Figure 10 In (b), the conductance G of the short-channel device varies with the back gate voltage V. BG The change in bias voltage V (B=6T) corresponds to the 0.5 platform in the diamond shape, with the zero bias line cut below. Figure 10 (c) in the image is a scanning electron microscope image of another mobility device. Figure 10 In the figure, (d) represents the corresponding pinch-off curve and mobility fitting, with the extracted mobility ranging from 11,000 to 12,000 cm⁻¹. 2 Between / Vs. Figure 10 (e) in the image is a scanning electron microscope image of another short-channel device. Figure 10 In the diagram, (f) and (g) show the conductivity of the device at B=0T and B=0.1T, respectively, with the magnetic field direction out of plane. The zero-bias conductivity peak under zero magnetic field splits at 0.1T, indicating the presence of the Kondo effect. Figure 10 (h) in V BG The conductivity G at 2.533 V varies with the magnetic field B and bias voltage V, and the line cuts at 0 T and 0.1 T respectively show the splitting of the Kondo zero bias peak. The Landé g-factor extracted based on the slope is approximately 41.

[0088] In this embodiment of the invention, the length of the finally obtained indium antimonide nanowires ranges from nanometers to micrometers, depending on the growth time; the diameter is in the nanometer range, depending on the catalyst droplet size and growth conditions. The prepared nanowires also possess advantages such as perpendicular orientation, good size controllability, and high crystal quality, making them easy to process into devices and enabling mass production, significantly reducing material and device processing costs. In particular, because the method of this invention does not introduce heterogeneous metal catalysts such as gold or silver, both the gallium catalyst droplet and the indium catalyst droplet are self-catalytic droplets, completely avoiding deep-level impurity contamination and incompatibility issues with complementary metal-oxide-semiconductor processes. The prepared indium antimonide nanowires can be directly integrated with mainstream semiconductor processes, providing a high-quality material platform for the development of indium antimonide nanowire-based high-speed electronic devices and topological quantum devices.

[0089] It is understood that, depending on the substrate material 10 used in the preparation, the growth conditions of the gallium arsenide nanowires 14, the catalyst droplet conversion conditions, and the growth conditions of the indium antimonide nanowires 18, the process parameters set in the above steps, such as substrate temperature, beam current, V / III ratio, and growth time, should be adjusted accordingly. For example, when a germanium substrate or other III-V semiconductor substrate is used instead of a silicon substrate, the substrate pretreatment method and the initial gallium catalyst droplet formation conditions may need to be optimized accordingly; when the arsenic source furnace is equipped with a pyrolysis source (providing an As2 beam), the arsenic background pressure can be eliminated more quickly, and the residual arsenic content in the indium antimonide nanowires can be further reduced. All of the above adjustments are reasonable modifications that can be implemented by those skilled in the art without creative effort under the teachings of this invention, and all fall within the protection scope of this invention.

[0090] Those skilled in the art will understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention can be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

Claims

1. A method for preparing indium antimonide nanowires via autocatalytic axial heterogeneous molecular beam epitaxy, characterized in that, include: Gallium catalyst droplets are formed on the substrate surface; An arsenic beam is introduced, and gallium arsenide nanowires are epitaxially grown on the substrate using the gallium catalyst droplets as autocatalytic droplets through a gas-liquid-solid growth mechanism. After the epitaxial growth of the gallium arsenide nanowire is completed, the gallium catalyst droplet located at the top of the gallium arsenide nanowire is partially consumed while maintaining the arsenic beam flow, so as to control the residual size of the gallium catalyst droplet. An indium beam is introduced, and the low incorporation coefficient of indium atoms on the surface of gallium arsenide is utilized to cause indium atoms to gather at the residual gallium catalyst droplets and convert the residual gallium catalyst droplets in situ into indium catalyst droplets. The residual gallium catalyst droplets serve as liquid-phase templates to reduce the energy barrier for independent nucleation of indium atoms. An antimony beam is introduced, and indium catalyst droplets are used as autocatalytic droplets to epitaxially grow indium antimonide nanowires at the top of gallium arsenide nanowires via a gas-liquid-solid growth mechanism.

2. The preparation method according to claim 1, characterized in that, The substrate includes a Si(111) substrate.

3. The preparation method according to claim 1, characterized in that, The epitaxial growth temperature of the gallium arsenide nanowires is 500°C to 600°C, and the beam equivalent pressure ratio of arsenic to gallium is 15 to 25. The epitaxial growth temperature of the indium antimonide nanowires is 350°C to 450°C, and the beam equivalent pressure ratio of antimony to indium is 1.2 to 2.

5.

4. The preparation method according to claim 1, characterized in that, The epitaxial growth of the gallium arsenide nanowires, the partial consumption of the gallium catalyst droplets, the in-situ conversion of the gallium catalyst droplets to indium catalyst droplets, and the epitaxial growth of the indium antimonide nanowires are all carried out continuously in situ under ultra-high vacuum conditions in a molecular beam epitaxy device, and the substrate is not exposed to the atmospheric environment throughout the entire process.

5. The preparation method according to claim 1, characterized in that, Partial consumption of the gallium catalyst droplet is achieved by the following method: after the epitaxial growth of the gallium arsenide nanowire is completed, the gallium source is turned off, while the arsenic beam is continuously supplied, so that the gallium atoms in the gallium catalyst droplet undergo at least one of the processes of evaporation and desorption and reaction with arsenic to generate gallium arsenide.

6. The preparation method according to claim 5, characterized in that, The degree of partial consumption of the gallium catalyst droplets is controlled by the continuous introduction time of the arsenic beam, so as to adjust the size of the remaining gallium catalyst droplets, and thus control the size of the subsequently formed indium catalyst droplets and the diameter of the indium antimonide nanowires.

7. The preparation method according to claim 1, characterized in that, The temperature at which the residual gallium catalyst droplets are converted in situ into indium catalyst droplets is 350°C to 450°C.

8. The preparation method according to claim 1, characterized in that, In the process of converting the residual gallium catalyst droplets into indium catalyst droplets in situ, the size of the indium catalyst droplets is controlled by adjusting the beam intensity or introduction time of the indium beam, thereby achieving the regulation of the diameter of the indium antimonide nanowires.

9. The preparation method according to claim 1, characterized in that, Under the condition of a fixed beam equivalent pressure ratio of antimony and indium, the epitaxial growth of the indium antimonide nanowires is carried out by using low beam current conditions, which suppresses the non-catalytic vapor deposition of indium atoms on the sidewalls of the gallium arsenide nanowires, so that the diameter of the indium antimonide nanowires remains constant or substantially constant, and the length of the indium antimonide nanowires increases linearly with the growth time.

10. The preparation method according to claim 1, characterized in that, The preparation method does not introduce gold or silver as a heterometallic catalyst throughout the entire process. Both the gallium catalyst droplet and the indium catalyst droplet are autocatalytic droplets. The indium antimonide nanowire does not contain deep-level impurity elements introduced by gold or silver.

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