Method for growing nanowires

Abstract

The application provides a nanowire growth method, which comprises the following steps: forming a metal catalyst layer on a substrate surface, and vertically irradiating the substrate in a precursor solution by using a laser, so that the nanowire can be directly grown on the substrate, the growth speed of the nanowire is fast due to high laser energy, and the probability of bending of the nanowire in the growth process is reduced; in addition, the metal catalyst element and the doped atoms formed after reduction of the dopant are co-deposited and embedded in the nanowire lattice in the growth process of the nanowire, in-situ doping of the nanowire can be realized, the required doping concentration of the nanowire can be realized by adjusting the amount of the dopant containing the doping element, the doping concentration of the nanowire is not limited by the concentration of the metal catalyst element in the metal catalyst layer, and the requirement of different electrical properties of the nanowire is facilitated; finally, the nanowire growth method has the advantages of short reaction time, low cost and environmentally friendly raw materials.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor nanowire structure production technology, and in particular relates to a method for growing nanowires. Background Technology

[0002] An intrinsic semiconductor where the density of flowing holes exceeds the density of conducting electrons is called a P-type semiconductor; conversely, an intrinsic semiconductor where the density of conducting electrons exceeds the density of flowing holes is called an N-type semiconductor. On a semiconductor wafer (such as an ultrapure silicon wafer), injecting group III elements into the semiconductor as dopant—for example, boron—results in positively charged holes due to its trivalent nature, thus creating a P-type semiconductor. In a P-type semiconductor, holes are the majority carriers, and free electrons are the minority carriers; conductivity is primarily provided by holes, which are mainly supplied by impurity atoms. Similarly, doping a semiconductor wafer with group V elements (such as P and As) to replace silicon atoms in the crystal lattice creates negatively charged free electrons, forming an N-type semiconductor. In an N-type semiconductor, free electrons are the majority carriers, and holes are the minority carriers; conductivity is primarily provided by free electrons, which are mainly supplied by impurity atoms. The more impurities incorporated, the higher the electron concentration and the stronger the conductivity. The doping methods described above typically use a gas phase doping approach, in which high-purity gaseous dopant precursors (such as borane, phosphine, etc.) are implanted onto the surface of a semiconductor wafer. The concentration of impurity atoms on the semiconductor wafer surface increases with the diffusion time.

[0003] Similarly, when using PECVD (vapor phase) to grow one-dimensional nanomaterials, taking the growth of Si nanowires from SiH4 as an example, by changing the flow rate ratio of the reaction source gas and mixing B2H6 with SiH4 in a certain proportion, P-type Si nanowires can be obtained. This method can achieve doping of silicon nanowires while growing them. However, vapor phase doping is costly, high-purity gas sources are toxic, and the doping method is not environmentally friendly. In addition, due to the limitations of the process technology, although silicon-based semiconductor chips can achieve complex multilayer connections in 3D space, transistors can only be distributed on the surface of the bottom layer (achieving P and N doping through ion implantation of single-crystal Si) during the wafer fabrication process. This characteristic greatly limits the vertical stacking development of logic units in silicon-based chips, and the continuation of Moore's Law is limited to a two-dimensional plane.

[0004] Compared to the cost and toxicity of gas sources associated with gas-phase doping, a green, inexpensive, and rapid method is needed to obtain doped nanowire materials. Therefore, liquid-phase growth of doped nanowires has attracted widespread attention. Existing methods for liquid-phase growth of doped nanowires mainly include the following two:

[0005] The first method is microwave-assisted SLS growth (MW-SLS). 1-x Sn x Nanowires (Chem.Comm. 2015, 51, 12282) were obtained by bottom-up growth of Ge / Sn alloy nanowires using a microwave-assisted method. The average diameter of the nanowires was 190 nm ± 30 nm, and Sn was uniformly distributed within the Ge nanowires with an atomic percentage of 12.4 ± 0.7%. The growth temperature was approximately 230 °C. However, this method only yielded nanowire materials in solution.

[0006] The second method involves high-yield liquid-phase synthesis of germanium nanowires (J.AM.CHEM.SOC.2005,127,15718). This method uses Bi as a catalyst to grow germanium nanowires in the liquid phase. However, this method only synthesizes nanowires in the solution phase, and the resulting nanowires are aggregated into clusters resembling yarn balls. This is because the liquid-phase growth of nanowires requires high concentrations of precursors and catalysts, and the nanowires are prone to entanglement during growth, forming nanowire clusters. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for growing nanowires, which solves the problem that the existing liquid-phase synthesis method for doped nanowires only synthesizes dispersed nanowire materials or aggregated nanowire clusters in the liquid phase, and the doping concentration of the synthesized doped nanowires is limited by the concentration of the catalyst used, thus limiting the doping concentration of the doped nanowires.

[0008] To achieve the above and other related objectives, the present invention provides a method for growing nanowires, the method comprising the following steps:

[0009] S1. Provide a substrate and form a metal catalyst layer on the surface of the substrate;

[0010] S2. The substrate on which the metal catalyst layer is formed is placed in a precursor solution; wherein, the precursor solution includes a semiconductor element precursor for forming the desired nanowires and a dopant containing doped elements, and the metal catalyst element in the metal catalyst layer and the doped elements contained in the dopant are one or more of the main elements of Group III, IV and V.

[0011] S3, the substrate in the precursor solution is vertically irradiated with a laser. The thermal accumulation effect of laser heating causes the metal catalyst layer to liquefy into metal catalyst droplets. At the same time, the photothermal effect of the liquefied metal catalyst droplets under laser irradiation accelerates the redox reaction of the precursor in the precursor solution. The atoms generated by the catalytic redox dissolve into the metal catalyst droplets. When the atoms reach a saturation concentration in the catalyst droplets, they crystallize and grow epitaxially. In addition, the dopant elements in the dopant also undergo redox reactions simultaneously, forming corresponding dopant atoms, which dissolve in the metal catalyst droplets and co-deposit with the metal catalyst elements into the lattice of the nanowires, ultimately realizing the doped growth of the nanowires on the substrate.

[0012] Optionally, the method for forming the metal catalyst layer in step S1 includes: first forming a colloidal solution of metal nanoparticle catalyst using a solvothermal method, then drop-coating or spin-coating the colloidal solution of metal nanoparticle catalyst onto the surface of the substrate to form a colloidal liquid film of metal nanoparticle catalyst, and finally heating the substrate with the colloidal liquid film of metal nanoparticle catalyst to form the metal catalyst layer on the substrate.

[0013] Optionally, the method for forming the metal catalyst layer in step S1 includes: forming the metal catalyst layer directly on the substrate surface using a thin film deposition process.

[0014] Furthermore, the thin film deposition process is molecular beam epitaxy, electron beam deposition, sputtering, or vapor deposition.

[0015] Optionally, the metal catalyst element in the metal catalyst layer is one of indium, tin, and bismuth, or an alloy of two of indium, tin, and bismuth.

[0016] Further, the metal catalyst element of the metal catalyst layer is bismuth; the method for forming the metal catalyst layer in step S1 includes: S11, dissolving bismuth neodecanoate in 1-octadecene and heating it to above 100°C under an inert gas atmosphere to remove water and oxygen; S12, adding dodecanethiol to the solution obtained in step S11; S13, dissolving trioctylphosphine in the solution obtained in step S12 for reduction reaction to obtain a bismuth metal nanoparticle catalyst colloidal solution; S14, diluting the bismuth metal nanoparticle catalyst colloidal solution obtained in step S13 to the required concentration for later use; S15, taking a preset volume of the bismuth metal nanoparticle catalyst colloidal solution obtained in step S14 for fractionation and centrifugation to obtain a bismuth metal nanoparticle catalyst colloidal solution of the required size; S16, drop-coating or spin-coating the bismuth metal nanoparticle catalyst colloidal solution obtained in step S15 onto the surface of the substrate to form a bismuth metal nanoparticle catalyst colloidal liquid film, and heating the substrate with the bismuth metal nanoparticle catalyst colloidal liquid film to form a bismuth metal catalyst layer on the substrate.

[0017] Furthermore, the metal catalyst element of the metal catalyst layer is bismuth, and the method for forming the metal catalyst layer in step S1 includes: forming a bismuth metal catalyst layer with a thickness of 2 nm to 10 nm directly on the substrate surface using molecular beam epitaxy.

[0018] Optionally, the nanowires are germanium nanowires.

[0019] Furthermore, in step S2, the semiconductor element precursor for forming the desired nanowires is a solution of GeI2 inorganic salt dissolved in a degassed solution of trioctylphosphine and / or oleylamine.

[0020] Optionally, in step S3, a high-frequency, high-pulse-width pulsed laser is used to irradiate the substrate in the precursor solution.

[0021] Optionally, the substrate is a semiconductor substrate.

[0022] Furthermore, the surface material of the substrate is the same as the material of the desired nanowires.

[0023] Furthermore, in step S1, before forming the metal catalyst layer on the substrate surface, a surface treatment process is required on the substrate to remove impurities on the substrate and the intrinsic oxide layer on the substrate surface.

[0024] Furthermore, the process after step S1 and before step S2 includes: annealing the metal catalyst layer using a rapid annealing process to transform the metal catalyst layer into nanoparticles and alloy them with the substrate.

[0025] Furthermore, the rapid annealing process is either laser annealing or RTP annealing.

[0026] Furthermore, the rapid annealing process is a laser annealing process using a low-frequency, high-pulse-width pulsed laser.

[0027] As described above, the nanowire growth method of the present invention, by forming a metal catalyst layer on the substrate surface and vertically irradiating the substrate containing the metal catalyst layer in the precursor solution with a laser, enables the direct growth of the desired nanowires on the substrate. Due to the high laser energy, the growth rate of the desired nanowires is fast, reducing the probability of bending during growth and improving the uprightness and crystal quality of the nanowires. Furthermore, during nanowire growth, the metal catalyst element and the dopant atoms formed after reduction in the dopant co-deposit and embed into the nanowire lattice, enabling in-situ doping of the desired nanowires. The desired doping concentration can be achieved by adjusting the amount of dopant containing the dopant element, making the doping concentration of the desired nanowires not limited by the concentration of the metal catalyst element in the metal catalyst layer, thus facilitating the achievement of different electrical performance requirements for the desired nanowires. Finally, the nanowire growth method of the present invention has a short reaction time, low cost, and uses environmentally friendly raw materials. Attached Figure Description

[0028] Figure 1 The diagram shows a schematic of forming a metal catalyst layer on the substrate surface in the nanowire growth method of the present invention.

[0029] Figure 2 The diagram shows a schematic of the formation of an alloy catalyst particle layer using laser annealing in the nanowire growth method of the present invention.

[0030] Figure 3 The diagram shows an in-situ doped and upright nanowires formed by laser irradiation of a precursor solution in the nanowire growth method of the present invention.

[0031] Figures 4 to 7 The diagram shows a process for forming in-situ doped and upright nanowires in the nanowire growth method of the present invention.

[0032] Component designation explanation

[0033] 10 Substrates

[0034] 11 Metal catalyst layer

[0035] 12 Alloy catalyst particle layer

[0036] 13 Alloy catalyst droplets

[0037] 14 Required nanowires

[0038] 15-pulse laser

[0039] 16 Continuous Lasers

[0040] 17 Glove Box

[0041] 18 Catalyst droplets that have absorbed precursor atoms Detailed Implementation

[0042] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0043] Please see Figures 1 to 7 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0044] This invention provides a method for growing nanowires, the method comprising the following steps:

[0045] S1. Provide a substrate and form a metal catalyst layer on the surface of the substrate;

[0046] S2. The substrate on which the metal catalyst layer is formed is placed in a precursor solution; wherein the precursor solution includes a semiconductor element precursor for forming the desired nanowires and a dopant containing doped elements, and the metal catalyst element in the metal catalyst layer and the doped elements contained in the dopant are one or more of the third, fourth and fifth group elements.

[0047] S3, the substrate in the precursor solution is vertically irradiated with a laser. The thermal accumulation effect of laser heating causes the metal catalyst layer to liquefy into metal catalyst droplets. At the same time, the photothermal effect of the liquefied metal catalyst droplets under laser irradiation accelerates the redox reaction of the precursor in the precursor solution. The atoms generated by the catalytic redox dissolve into the metal catalyst droplets. When the atoms reach a saturation concentration in the catalyst droplets, they crystallize and grow epitaxially. In addition, the dopant elements in the dopant also undergo redox reactions simultaneously, forming corresponding dopant atoms, which dissolve in the metal catalyst droplets and co-deposit with the metal catalyst elements into the lattice of the nanowires, ultimately realizing the doped growth of the nanowires on the substrate.

[0048] The working principle of the nanowire growth method of the present invention is as follows: By forming a metal catalyst layer on the surface of a substrate, and vertically irradiating the substrate containing the metal catalyst layer in a precursor solution with a laser, the laser can precisely and uniformly distribute and focus energy on a limited area. Therefore, during the vertical irradiation of the substrate in the precursor solution, the laser irradiates the precursor solution, heating the substrate to a higher temperature. Through heat exchange, the precursor solution can be heated simultaneously. On the other hand, the laser irradiates the substrate in the precursor solution, melting the metal catalyst on the substrate into metal catalyst droplets. When the surface temperature of the metal catalyst droplets and the precursor solution rises to the temperature required for the redox reaction... At this time, the redox reaction of the precursor solution begins to proceed rapidly, continuously forming the required nanowire atoms. Under the catalysis of the metal catalyst droplet, the redox reaction on the surface of the metal catalyst droplet proceeds rapidly. The formed nanowire atoms are continuously absorbed by the metal catalyst droplet and reach saturation to precipitate, realizing the continuous epitaxial growth of the required nanowires. During the epitaxial growth process, the dopant elements in the dopant also undergo redox reactions simultaneously, forming corresponding dopant atoms, which dissolve in the metal catalyst droplet and co-deposit with the metal catalyst elements into the lattice of the nanowires until the concentration of nanowire atoms in the metal catalyst droplet becomes too low to precipitate, thus ending the growth and finally realizing the growth of nanowires.

[0049] The nanowire growth method of the present invention, by forming a metal catalyst layer on the substrate surface and vertically irradiating the substrate containing the metal catalyst layer in a precursor solution with a laser, enables the direct growth of the desired nanowires on the substrate. Due to the high laser energy, the growth rate of the desired nanowires is fast, reducing the probability of bending during growth and improving the uprightness and crystal quality of the nanowires. Furthermore, during nanowire growth, the metal catalyst element and the dopant atoms formed after reduction in the dopant co-deposit and embed into the nanowire lattice, enabling in-situ doping of the desired nanowires. The desired doping concentration can be achieved by adjusting the amount of dopant containing the dopant element, making the doping concentration of the desired nanowires not limited by the concentration of the metal catalyst element in the metal catalyst layer, thus facilitating the achievement of different electrical performance requirements for the desired nanowires. Finally, the nanowire growth method of the present invention has a short reaction time, low cost, and uses environmentally friendly raw materials.

[0050] The substrate material is not overly limited; for example, it can be a metal substrate, a semiconductor substrate, or an insulating substrate. Preferably, the substrate is a semiconductor substrate, such as at least one of the following materials: silicon, germanium, silicon germanium, silicon carbide, silicon germanium carbon, indium arsenide, gallium arsenide, indium phosphide, aluminum oxide, or other III / V compound semiconductors. It may also include multilayer structures formed from these semiconductors, or silicon-on-insulator, silicon-on-insulator stacked, silicon-on-insulator stacked, silicon-on-insulator, and germanium-on-insulator, or it may be a double-sided polished silicon wafer, etc. Most preferably, the surface material of the substrate is the same as the material of the desired nanowire, that is, the desired nanowire is homogeneously grown relative to the surface material of the substrate on which it is grown. For example, if the desired nanowire is a germanium nanowire, then the surface of the substrate is also a germanium material layer. Homogeneous growth results in low lattice mismatch and thermal mismatch between the desired nanowire and the substrate, making it easier to improve the growth quality of the desired nanowire.

[0051] As a preferred example, when the substrate is a semiconductor substrate, in step S1, before forming the metal catalyst layer on the substrate surface, a surface treatment process needs to be performed on the substrate to remove impurities and the intrinsic oxide layer on the substrate surface, so as to ensure the purity of the substrate surface and improve the formation quality of the metal catalyst layer on the substrate surface. For example, the substrate surface is cleaned with n-hexane, acetone and deionized water respectively for impurity cleaning, and the intrinsic oxide layer on the substrate surface is washed away with hydrofluoric acid or dilute hydrochloric acid.

[0052] As an example, there are two methods for forming the metal catalyst layer in step S1:

[0053] The first method includes: firstly, forming a colloidal solution of metal nanoparticle catalyst using a solvothermal method; then, drop-coating or spin-coating the colloidal solution of metal nanoparticle catalyst onto the surface of the substrate to form a colloidal liquid film of metal nanoparticle catalyst; and finally, heating the substrate with the colloidal liquid film of metal nanoparticle catalyst to form the metal catalyst layer on the substrate. In the metal catalyst layer prepared by this method, the metal catalyst exists in the form of nano-sized particles.

[0054] The second method involves forming the metal catalyst layer directly on the substrate surface using a thin-film deposition process. The thin-film deposition process can be, for example, molecular beam epitaxy, electron beam deposition, sputtering, or evaporation. The metal catalyst layer prepared using this method exists as nanoscale particles when the metal catalyst layer is thin, and as a film layer when the metal catalyst layer is thick.

[0055] In step S3, it is preferable to use a high-frequency, high-pulse-width pulsed laser to irradiate the substrate in the precursor solution to ensure that the laser energy increases the growth rate of the required nanowires.

[0056] As a preferred example, the required nanowires are germanium nanowires.

[0057] As a preferred example, the metal catalyst element in the metal catalyst layer is one of indium, tin, and bismuth, or an alloy of two of these elements, such as indium-tin alloy, indium-bismuth alloy, or tin-bismuth alloy. Different metal catalyst elements can cause the formed nanowires to have corresponding conductivity types. For example, indium and tin metal catalysts can form P-type conductive nanowires, and bismuth metal catalysts can form N-type conductive nanowires. The specific selection is based on actual needs. Since the concentration of the metal catalyst element in the metal catalyst layer is mainly determined by the required nanowire growth size, the size of the metal catalyst element in the metal catalyst layer limits the in-situ doping concentration of the formed nanowires. In this case, the dopant containing the dopant element added to the precursor solution can effectively supplement the in-situ doping concentration (or electrical performance) of the required nanowires, achieving in-situ doping with different electrical performance requirements. As a preferred example, when the metal catalyst element in the metal catalyst layer is selected as one of indium, tin, and bismuth, or an alloy of two of indium, tin, and bismuth, the dopant element contained in the dopant is also selected as one of indium, tin, and bismuth, or an alloy of two of indium, tin, and bismuth. The dopant can be an inorganic halide containing the above-mentioned dopant elements or a suitable organic compound containing the above-mentioned dopant elements, such as SnI2 dopant, SnI4 dopant, etc.

[0058] As a specific example, when the metal catalyst element in the metal catalyst layer is bismuth, there are two methods for forming the metal catalyst layer in step S1:

[0059] The first method includes: S11, dissolving bismuth neodecanoate in 1-octadecene and heating it to above 100°C under an inert gas atmosphere to remove water and oxygen, wherein the inert gas can be, for example, argon, nitrogen, or a mixture of argon and nitrogen; S12, adding dodecanethiol to the solution obtained in step S11; S13, dissolving trioctylphosphine in the solution obtained in step S12 to carry out a reduction reaction to obtain a bismuth metal nanoparticle catalyst colloidal solution; S14, diluting the bismuth metal nanoparticle catalyst colloidal solution obtained in step S13 to the required concentration for later use; S15, taking a predetermined volume of the bismuth metal nanoparticle catalyst colloidal solution obtained in step S14 and centrifuging it to obtain a bismuth metal nanoparticle catalyst colloidal solution of the required concentration; S16, drop-coating or spin-coating the bismuth metal nanoparticle catalyst colloidal solution obtained in step S15 onto the surface of the substrate to form a bismuth metal nanoparticle catalyst colloidal liquid film, and heating the substrate with the bismuth metal nanoparticle catalyst colloidal liquid film to form a bismuth metal catalyst layer on the substrate.

[0060] The second method includes: forming a bismuth metal catalyst layer with a thickness of 2 nm to 10 nm directly on the surface of the substrate using molecular beam epitaxy.

[0061] As a specific example, when the desired nanowire is a germanium nanowire, the semiconductor element precursor for forming the desired nanowire in step S2 is to dissolve GeI2 inorganic salt in a solution of degassed trioctylphosphine and / or oleylamine.

[0062] As a preferred example, the nanowire growth method of the present invention is most effective when carried out in an anhydrous, oxygen-free, and light-free environment. For example, it can be carried out in a glove box.

[0063] As a preferred example, the process after step S1 and before step S2 further includes: annealing the metal catalyst layer using a rapid annealing process to alloy the metal catalyst layer with the substrate. Specifically, the metal catalyst layer and the substrate form an alloy, which transforms into alloyed nanoparticles during annealing, forming an alloy catalyst particle layer. Because the alloy catalyst particle layer formed by the rapid annealing process has a specific contact angle with the substrate, during the growth of the desired nanowires, the alloy catalyst droplets obtained by laser irradiation of the alloy catalyst particle layer to melt it will not slide left and right or merge like non-alloy droplets, preventing droplet aggregation. This allows for the in-situ formation of alloy catalyst droplets, ensuring that the subsequently formed desired nanowires have a small diameter and high uniformity. Furthermore, because the alloy catalyst particle layer has a specific contact angle with the substrate, the formed alloy catalyst droplets themselves have a certain orientation, which is more conducive to the upright growth of the desired nanowires in their growth direction. Compared to the growth of pure liquid-phase nanowires without a substrate, which requires strict control of the ratio between the metal catalyst and the precursor to grow upright nanowires, this method makes it easier to grow upright nanowires.

[0064] Furthermore, the metal catalyst layer is annealed using a rapid annealing process to alloy the metal catalyst layer with the substrate. The rapid annealing process is preferably laser annealing or RTP annealing. Moreover, when selecting laser annealing, a low-frequency, high-pulse-width pulsed laser is suitable. This is to ensure the formation of a stable alloy catalyst particle layer while minimizing the risk of excessively high laser energy causing substrate temperature overheating and deformation, which could negatively impact the quality of the alloy catalyst particle layer.

[0065] To more clearly demonstrate the technical solution and effects provided by the present invention, the nanowire growth method of the present invention will be described in detail below with reference to a specific and preferred embodiment and accompanying drawings.

[0066] Example 1

[0067] This embodiment demonstrates the process of growing germanium nanowires on a germanium substrate using bismuth metal catalyst particles, specifically including the following steps:

[0068] Step A, as Figure 1 As shown, a germanium material substrate of appropriate size is taken, cleaned with acetone and water, and then the intrinsic oxide layer on the surface is removed with hydrofluoric acid or hydrochloric acid. Then, a metal catalyst layer 11 is formed on the surface of the substrate 10.

[0069] In this embodiment, two methods are used to achieve the process of forming a metal catalyst layer 11 on the surface of the substrate 10.

[0070] Method 1: In a reaction flask, using 0.4g–0.8g of bismuth neodecanoate as the raw material, add 4mL–4.3mL of 1-octadecene, and purge with argon or nitrogen inert gas at 115℃–130℃ to remove water and oxygen for 60min–120min. Then, transfer the reaction flask to glove box 17, add 0.1mL–0.3mL of dodecanethiol, and stir at 40℃–80℃ for 8min–12min, forming a yellow liquid in the reaction flask. Next, add 0.5mL–1.5mL of trioctylphosphine to the yellow liquid obtained in the reaction flask, and carry out a reduction reaction at 60℃–70℃ for 20min–40min. Then, let it stand for 1.5h–2.5h to obtain bismuth metal nanoparticles. The bismuth metal nanoparticle catalyst colloidal solution is then diluted to 1.5 to 2.5 times its original volume for later use. 0.8 mL to 1.2 mL of the diluted bismuth metal nanoparticle catalyst colloidal solution is taken and centrifuged to obtain catalyst particles of the desired size, resulting in a brownish-yellow supernatant. This supernatant is the bismuth metal nanoparticle catalyst colloidal solution of the desired concentration. Finally, the substrate 10 is physically fixed to the bottom of the reaction vessel in the glove box 17. The bismuth metal nanoparticle catalyst colloidal solution of the desired concentration is spin-coated or drop-coated onto the surface of the substrate 10 to form a bismuth metal nanoparticle catalyst colloidal liquid film. The substrate with the bismuth metal nanoparticle catalyst colloidal liquid film is then heated, thereby forming the metal catalyst layer 11 on the surface of the substrate 10.

[0071] The second method involves directly forming a 2nm to 10nm thick metal catalyst layer 11 of bismuth material on the surface of the substrate 10 using molecular beam epitaxy.

[0072] Step B, as follows Figure 2 As shown, the metal catalyst layer 11 is annealed using a pulsed laser annealing process or an RTP annealing process to form an alloy catalyst particle layer 12 between the metal catalyst layer 11 and the substrate 10, that is, to form an alloy catalyst particle layer 12 of germanium-bismuth material. Since there is no solvent during annealing, there is no solvent interference, and the alloy formation rate is very fast, which will not cause the fusion and slippage of low-melting-point catalysts on the substrate, and the alloy catalyst particle layer 12 can be formed in situ.

[0073] Step C: Laser path calibration for irradiating the precursor solution: Turn on the laser guide light, check the collimation of the optical path, and after confirming that there are no objects obstructing the optical path, move the stage to transmit the laser spot to the preset position, and then turn on the laser.

[0074] Step D, Preparation of the precursor solution: Weigh 0.1g–1.0g of GeI2 inorganic salt and 0.01g–1.0g of SnI4 inorganic salt in a glove box and place them in the transition chamber for later use (GeI2 should be stored in an inert gas environment, protected from light after opening); remove the reaction flask from the oven at 110℃–130℃ and quickly draw a certain volume, approximately 18mL–22mL, of a single-component solution of trioctylphosphine or oleylamine, or a mixed-component solution of trioctylphosphine and oleylamine, and place it in a container. In a reaction flask, argon gas is introduced at 110℃~130℃ for 1.2h~1.8h. After the solution cools to room temperature, the weighed GeI2 and SnI4 inorganic salts are transferred to a cooled single-component solution of trioctylphosphine or oleylamine, or a mixed-component solution of trioctylphosphine and oleylamine. The flask is sealed and sonicated in the dark for 15min~20min to completely dissolve the GeI2 and SnI4 inorganic salt powders, obtaining a clear, pale / orange-yellow precursor solution for later use. Generally, the precursor solution should be prepared fresh before use.

[0075] Step E, as Figure 3 As shown, laser-induced nanowire growth and in-situ doping are performed as follows: The substrate 10 containing the alloy catalyst particle layer 12 formed in step B is placed in a glove box 17, and the precursor solution obtained in step D is placed in the glove box 17. The precursor solution is irradiated with a continuous laser 16 with a wavelength of approximately 1064 nm, a power of approximately 25 W to 40 W, and a spot size of approximately 3 mm to 7 mm. Figure 4 As shown, with the irradiation of the continuous laser 16, the alloy catalyst particle layer 12 melts into alloy catalyst droplets 13, and the reduction reaction begins to accelerate, with the fastest reduction reaction rate near the surface of the substrate 10; as Figure 5 As shown, under the action of the bismuth catalyst, the reduction reaction on the alloy catalyst droplet 13 is the fastest. The germanium atoms formed enter the alloy catalyst droplet 13 and form catalyst droplets 18 that have absorbed precursor atoms. The germanium atoms are saturated and precipitated in the droplets to form... Figure 6 The desired germanium nanowires 14 are obtained; as the reduction reaction continues, the growth ends when the concentration of germanium atoms in the alloy catalyst droplets 13 becomes too low to precipitate, yielding nanowires 14. Figure 7The desired nanowire 14 is shown, and during the growth process, bismuth catalyst atoms and Sn dopant atoms from the dopant gradually embed into the lattice of the desired nanowire 14, achieving the desired in-situ doping effect. The final desired nanowire 14 has a diameter of approximately 20 nm to 500 nm and a length of 0.3 μm to 8 μm. Furthermore, since bismuth, the metal catalyst element used, is an N-type conductor (a metalloid conductor), its electrical stability is relatively poor in the semiconductor doping field. Tin, the dopant element used, is physically neutral, but in practice, due to surface defects, it exhibits P-type conductivity. Therefore, tin can effectively adjust the electrical stability of bismuth, thereby adjusting the electrical properties of the formed nanowire by changing the concentration of tin in the dopant, achieving the fabrication of nanowires with the desired electrical properties.

[0076] It should be noted that, depending on the actual needs of the reaction, there is no specific order of steps A to E above. According to the reaction logic, some steps need to be performed sequentially, while others can be performed separately. For example, steps A and B have a logical order, but there is no logical order between them and step C. Steps A, B, and C can be performed simultaneously or sequentially. Similarly, there is no logical order between steps A, B, and D. They can be performed simultaneously or sequentially.

[0077] In summary, this invention provides a method for growing nanowires. By forming a metal catalyst layer on the substrate surface and vertically irradiating the substrate containing the metal catalyst layer in a precursor solution with a laser, the desired nanowires can be grown directly on the substrate. Due to the high laser energy, the growth rate of the nanowires is fast, reducing the probability of bending during growth and improving the uprightness and crystal quality of the nanowires. Furthermore, during nanowire growth, the reduced dopant atoms from the metal catalyst and dopant are co-deposited and embedded in the nanowire lattice, enabling in-situ doping. The desired doping concentration can be achieved by adjusting the amount of dopant containing the dopant element, making the doping concentration not limited by the concentration of the metal catalyst element in the metal catalyst layer, thus facilitating the achievement of different electrical properties of the nanowires. Finally, the nanowire growth method of this invention has a short reaction time, low cost, and environmentally friendly raw materials. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0078] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for growing nanowires, characterized in that, The growth method includes the following steps: S1. Provide a substrate and form a metal catalyst layer on the surface of the substrate; S2. The substrate on which the metal catalyst layer is formed is placed in a precursor solution; wherein, the precursor solution includes a semiconductor element precursor for forming the desired nanowires and a dopant containing doped elements, and the metal catalyst element in the metal catalyst layer and the doped elements contained in the dopant are one or more of the main elements of Group III, IV and V. S3. The substrate in the precursor solution is vertically irradiated with a laser. The thermal accumulation effect of laser heating causes the metal catalyst layer to liquefy into metal catalyst droplets. At the same time, the photothermal effect of the liquefied metal catalyst droplets under laser irradiation accelerates the redox reaction of the precursor in the precursor solution. The atoms generated by the catalytic redox dissolve into the metal catalyst droplets. When the atoms reach a saturation concentration in the catalyst droplets, they crystallize and grow epitaxially. In addition, the dopant elements in the dopant also undergo redox reactions simultaneously, forming corresponding dopant atoms, which dissolve in the metal catalyst droplets and co-deposit with the metal catalyst elements into the lattice of the nanowires, ultimately realizing the doped growth of the nanowires on the substrate.

2. The method for growing nanowires according to claim 1, characterized in that, The method for forming the metal catalyst layer in step S1 includes: first, forming a colloidal solution of metal nanoparticle catalyst using a solvothermal method; then, drop-coating or spin-coating the colloidal solution of metal nanoparticle catalyst onto the surface of the substrate to form a colloidal liquid film of metal nanoparticle catalyst; and finally, heating the substrate with the colloidal liquid film of metal nanoparticle catalyst to form the metal catalyst layer on the substrate.

3. The method for growing nanowires according to claim 1, characterized in that, The method for forming the metal catalyst layer in step S1 includes: forming the metal catalyst layer directly on the substrate surface using a thin film deposition process.

4. The method for growing nanowires according to claim 3, characterized in that: The thin film deposition process is molecular beam epitaxy, electron beam deposition, sputtering, or vapor deposition.

5. The method for growing nanowires according to claim 1, characterized in that: The metal catalyst element in the metal catalyst layer is one of indium, tin, and bismuth, or an alloy of two of indium, tin, and bismuth.

6. The method for growing nanowires according to claim 5, characterized in that: The metal catalyst element of the metal catalyst layer is bismuth. The method for forming the metal catalyst layer in step S1 includes: S11, dissolving bismuth neodecanoate in 1-octadecene and heating it to above 100°C under an inert gas atmosphere to remove water and oxygen; S12, adding dodecanethiol to the solution obtained in step S11; S13, dissolving trioctylphosphine in the solution obtained in step S12 for reduction reaction to obtain a bismuth metal nanoparticle catalyst colloidal solution; S14, diluting the bismuth metal nanoparticle catalyst colloidal solution obtained in step S13 to the required concentration for later use; S15, taking a preset volume of the bismuth metal nanoparticle catalyst colloidal solution obtained in step S14 for fractional centrifugation to obtain a bismuth metal nanoparticle catalyst colloidal solution of the required size; S16, drop-coating or spin-coating the bismuth metal nanoparticle catalyst colloidal solution obtained in step S15 onto the surface of the substrate to form a bismuth metal nanoparticle catalyst colloidal liquid film, and heating the substrate with the bismuth metal nanoparticle catalyst colloidal liquid film to form a bismuth metal catalyst layer on the substrate.

7. The method for growing nanowires according to claim 5, characterized in that, The metal catalyst element of the metal catalyst layer is bismuth. The method for forming the metal catalyst layer in step S1 includes: forming a bismuth metal catalyst layer with a thickness of 2 nm to 10 nm directly on the substrate surface using molecular beam epitaxy.

8. The method for growing nanowires according to claim 1, characterized in that: The required nanowires are germanium nanowires.

9. The method for growing nanowires according to claim 8, characterized in that: In step S2, the semiconductor element precursor for forming the desired nanowires is a solution of GeI2 inorganic salt dissolved in a degassed solution of trioctylphosphine and / or oleylamine.

10. The method for growing nanowires according to claim 1, characterized in that: In step S3, the substrate in the precursor solution is irradiated with a high-frequency, high-pulse-width pulsed laser.

11. The method for growing nanowires according to claim 1, characterized in that: The substrate is a semiconductor substrate.

12. The method for growing nanowires according to claim 11, characterized in that: The surface material of the substrate is the same as the material of the desired nanowires.

13. The method for growing nanowires according to claim 11, characterized in that: In step S1, before forming the metal catalyst layer on the substrate surface, a surface treatment process is required on the substrate to remove impurities on the substrate and the intrinsic oxide layer on the substrate surface.

14. The method for growing nanowires according to any one of claims 1 to 13, characterized in that, The process includes, after step S1 and before step S2, annealing the metal catalyst layer using a rapid annealing process to transform the metal catalyst layer into nanoparticles and alloy them with the substrate.

15. The method for growing nanowires according to claim 14, characterized in that: The rapid annealing process is either laser annealing or RTP annealing.

16. The method for growing nanowires according to claim 15, characterized in that: The rapid annealing process is a laser annealing process using a low-frequency, high-pulse-width pulsed laser.

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