A method for preparing beta-Ga2O3 nanostructures

Abstract

The application relates to a method for preparing a beta-Ga2O3 nanostructure, and relates to the field of semiconductor materials. The method uses Ga2O3 powder and graphite powder as raw materials, carries out ball milling and drying, grinds in a mortar, and then sieves through a 200-mesh screen; the materials are loaded into a long rubber balloon, compacted, sealed, vacuumized, and then subjected to isostatic pressing to prepare a cylindrical material rod with uniform thickness and density; pre-sintering is carried out in a tube furnace; the sintered cylindrical material rod is placed into an optical floating zone furnace, the output power of a halogen tungsten lamp of the floating zone furnace is adjusted, oxygen is introduced, and after light irradiation, a growth process of supersaturation precipitation through optical gasification is carried out to prepare the beta-Ga2O3 nanostructure. The nanostructure contains nanofilaments and nanobands, and the nanostructure has different sizes and various morphologies. The method accelerates the growth time of the gallium oxide nanostructure, improves the yield, and reduces the production cost. The prepared structure can be used as a surface enhanced Raman scattering (SERS) substrate, and the large specific surface area and rich adsorption sites enable strong SERS detection.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor materials and optical technology, in particular to a method for synthesizing and preparing a beta-Ga2O3 nanostructure. Background Art

[0002] Monoclinic β-Ga2O3 is a transparent, ultra-wide bandgap (~4.9 eV) oxide semiconductor material with high transmittance in the visible and near-ultraviolet regions, excellent thermochemical stability, and a high breakdown electric field strength. This semiconductor material also offers advantages such as low cost, high chemical stability, flexible surface modification, and good biocompatibility. The inherent optical and electronic properties of β-Ga2O3 make surface-enhanced Raman scattering (SERS) of β-Ga2O3 very attractive for applications such as reproducible SERS substrates and optoelectronic device characterization.

[0003] One-dimensional micro- and nanostructured β-Ga2O3 materials offer advantages such as large specific surface area and high surface state density. Researchers have reported various one-dimensional micro- and nanostructured β-Ga2O3 materials, including microwires, microrods, microribbons, nanowires, and nanoribbons. Device performance using these micro- and nanostructured β-Ga2O3 materials improves significantly with increasing surface-to-volume ratios. β-Ga2O3 nanostructures offer advantages such as larger specific surface area and higher surface state density.

[0004] In recent years, the main techniques for preparing β-Ga2O3 nanostructures include chemical vapor deposition, thermal evaporation, and physical vapor deposition. However, these methods also suffer from drawbacks such as cumbersome operation, long time consumption, low yield, high cost, small size, and single structure. For example, traditional chemical vapor deposition techniques for preparing β-Ga2O3 primarily utilize high-temperature tube furnaces, which require long heating times and a temperature gradient as the driving force for growth. As described in "A Method for Preparing Large-Sized Single-Crystal β-Gallium Oxide Nanoribbons," published in Chinese patent CN 109881246 B (authorization announcement date: September 22, 2020), catalytic particles are formed on the surface of a gallium nitride film through annealing. This process requires long heating times and multiple, rigorously controlled annealing temperatures to achieve gallium oxide growth. The gallium oxide raw material rods prepared in the present invention can serve as growth substrates, reducing secondary contamination from the substrate and catalyst, and the process is simple and rapid. Currently, most reported gallium oxide nanostructures are based on a single nanostructure and require long growth times, significantly increasing costs. Therefore, it is particularly important to find a preparation method that can effectively improve crystallization quality in a short period of time. The growth technology based on carbon thermal reduction reaction combined with optical vapor phase supersaturated precipitation method has the advantages of short growth cycle, high stability and high yield, and has become an effective way to achieve high crystal quality growth. Summary of the Invention

[0005] The purpose of the present invention is to propose a method for preparing β-Ga2O3 nanostructures in order to effectively improve the growth efficiency of nanostructures, while overcoming the problems of the existing preparation technology such as cumbersome, small size, and single size.

[0006] The technical principle of the carbothermal reduction reaction combined with optical vapor phase supersaturation precipitation proposed in this invention is as follows: First, graphite powder acts as a reducing agent to reduce Ga2O3 powder at temperatures above 1500°C, generating gaseous Ga2O or gallium vapor and oxygen vapor. Subsequently, in an oxygen-rich environment, the gaseous Ga2O reacts with oxygen molecules to form gallium oxide. Simultaneously, as the power increases and the gallium vapor rapidly increases, a large number of excess gallium atoms appear in the environment due to supersaturation of the solubility, reacting with oxygen molecules to form gallium oxide. Finally, the gallium oxide deposits in the nucleation zone and gradually grows upward to form nanostructures such as nanowires and nanoribbons. Using photons as energy carriers, the stable growth of gallium oxide nanostructures is achieved through vapor phase supersaturation precipitation in an oxygen-rich environment and a uniform temperature field.

[0007] The present invention is achieved through the following solutions

[0008] A method for preparing a β-Ga2O3 nanostructure, characterized by comprising the following steps:

[0009] Step 1: Mix Ga2O3 powder and graphite powder according to mass ratio.

[0010] Step 2: Pour the mixed powder of Ga2O3 powder and graphite powder into a nylon ball mill containing zirconium dioxide balls, then add ethanol to form a mixed solution, then seal the ball mill, screw it tightly, and place it on a roller ball mill for ball milling.

[0011] Step 3: Pour the mixed solution of Ga2O3 powder, graphite powder, and ethanol into a flat-bottomed glass disc, seal it with tin foil, and place it in a ventilated drying oven for drying to obtain a block mixture of Ga2O3 powder and graphite powder.

[0012] Step 4: Place the dried Ga2O3 powder and graphite powder block mixture into a mortar and grind with alcohol.

[0013] Step 5: The mixed powder of the ground Ga2O3 powder and graphite powder is sieved through a 200-mesh sieve to obtain a mixed fine powder.

[0014] Step 6: Place the mixed powder of Ga2O3 powder and graphite powder into a long rubber balloon, compact it, seal it, and evacuate it. Then, place the sealed balloon into the cylinder of an isostatic hydraulic press and press it to obtain a dense cylindrical powder rod.

[0015] Step 7: Place the cylindrical powder rod into an alumina ark and pre-fire it in a tube furnace to obtain a dense and uniform powder rod.

[0016] Step 8: Fix the cylindrical powder rod on the rotating bracket in the optical floating zone furnace, fine-tune the position of the rotating bracket to be in the light area of the halogen tungsten lamp, and seal the growth area by a quartz tube and lock the screw port up and down to ensure the airtightness of the growth chamber. Introduce O2 as the growth carrier gas into the growth chamber.

[0017] Step 9: Set the working parameters of the optical floating zone furnace on the control computer, and after the program is run, cool the grown nanostructure to room temperature.

[0018] In the above technical solution, in step 1, the purity of the Ga2O3 powder is 99.999%, and the mass ratio of the Ga2O3 powder and the graphite powder is 1:1.

[0019] In the above technical solution, in step 2, before the nylon ball mill jar is put into the roller-type ball mill, it is shaken up and down for 5 minutes to fully mix the Ga2O3 powder, the graphite powder, and the ethanol to obtain a uniform mixed solution, and the ball milling time is 24 hours.

[0020] In the above technical solution, in step 3, the drying time is 24 hours to evaporate all the ethanol to obtain a block-shaped mixture of dry-cracked Ga2O3 powder and graphite powder.

[0021] In the above technical solution, in step 4, the block-shaped mixture of Ga2O3 powder and graphite powder is ground with alcohol in a mortar for 2 hours.

[0022] In the above technical solution, in step 5, the ground mixture of Ga2O3 powder and graphite powder is sieved twice in a 200-mesh sieve to obtain a uniformly dispersed and uniformly sized fine powder mixture.

[0023] In the above technical solution, in step 6, the vacuumizing time is 30 minutes, and the pressing pressure is 68 MPa for 30 minutes to produce a cylindrical powder rod with uniform thickness and good density, and the diameter of the cylindrical powder rod is 6 mm and the length is 3 cm.

[0024] In the above technical solution, in step 7, the tube furnace pre-burning heating rate is 6℃ / min, and the temperature is raised to 500℃ and kept for 1h, and the atmosphere is air.

[0025] In the above technical solution, in step 8, the O2 rate is 100 mL / min; open the gas discharge valve to ensure that the carrier gas is introduced from the bottom of the growth chamber and discharged from the top.

[0026] In the above technical solution, in step 9, the operating parameters are: the heating power of the halogen tungsten lamp is 900 W / h, the time required to reach the heating power is 0.6 hours, and the heating power is maintained for 1.5 hours to complete the growth of the nanostructure. The rotation speed of the cylindrical powder rod is set to 100 rpm.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) A method for growing gallium oxide nanostructures is provided, which combines a carbon thermal reduction method and an optical vaporization supersaturated precipitation method. The preparation method is simple, not limited by substrate materials, has high stability, and is easy to reuse;

[0029] (2) Pre-firing in a tubular furnace makes the powder rods more dense and uniform, and improves their mechanical properties.

[0030] (2) Gallium oxide precursor rods are directly used as raw materials, without the need for substrates and catalysts, which is convenient and effective.

[0031] (3) The prepared gallium oxide nanostructures are different from the single-size structures previously produced. This method produces gallium oxide nanostructures with multiple sizes, including nanobelts, nanorods, nanowires, and nanowires. The nanobelts are relatively large, with a lateral dimension of up to 80 nm, and the nanowires have a diameter of approximately 20 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is an enlarged scanning electron microscope (SEM) image of the macroscopic image of the β-Ga2O3 nanostructured flocculent of the present invention.

[0033] Figure 2 This is an optical microscope image of the β-Ga2O3 nanostructured flocculent of the present invention.

[0034] Figure 3 This is a scanning electron microscope (SEM) image of the β-Ga2O3 nanostructure of the present invention.

[0035] Figure 4 This is a scanning electron microscope (SEM) image of the nanobelts in the β-Ga2O3 nanostructure of the present invention.

[0036] Figure 5 This is an enlarged scanning electron microscope (SEM) image of the nanobelts in the β-Ga2O3 nanostructure of the present invention.

[0037] Figure 6 This is a magnified scanning electron microscope (SEM) image of a single nanoribbon in the β-Ga2O3 nanostructure of the present invention.

[0038] Figure 7 This is a Raman spectrum diagram of the β-Ga2O3 nanostructure of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. The effects of the following embodiments are very similar and can be referred to in the accompanying drawings.

[0040] Implementation Case 1

[0041] A method for preparing a β-Ga2O3 nanostructure comprises the following steps:

[0042] Step 1: Mix Ga2O3 powder and graphite powder in a mass ratio of 1:1.

[0043] Step 2: Pour the mixed powder of Ga2O3 powder and graphite powder into a nylon ball mill filled with zirconium dioxide balls. Add ethanol to form a mixed solution. Seal the jar and tighten it. Shake the jar up and down for 5 minutes to thoroughly mix the Ga2O3 powder, graphite powder, and ethanol to form a uniform mixed solution. Then, mill the mixture on a roller ball mill for 24 hours.

[0044] Step 3: Pour the mixed solution of Ga2O3 powder, graphite powder, and ethanol into a flat-bottomed glass disc, seal it with tin foil, and place it in a ventilated drying oven for drying. The drying time is 24 hours to evaporate all the ethanol to obtain a blocky mixture of cracked Ga2O3 powder and graphite powder.

[0045] Step 4: Grind the bulk mixture of the dried Ga2O3 powder and graphite powder in a mortar with alcohol for 2 h.

[0046] Step 5: Sieve the mixture of ground Ga2O3 powder and graphite powder twice through a 200-mesh sieve to obtain a mixed fine powder with uniform dispersion and uniform particle size.

[0047] Step 6: Place the finely mixed Ga2O3 and graphite powders into a long rubber balloon, compact it, seal it, and evacuate it for 20 minutes. Then, press it at 68 MPa for 30 minutes. The sealed balloon is then placed in an isostatic press and pressed into a cylindrical rod with uniform thickness and good density, measuring 6 mm in diameter and 30 mm in length.

[0048] Step 7: Place the cylindrical powder rod in an alumina ark and pre-sinter in a tube furnace. Heat the rod to 500°C at a rate of 6°C / min and hold for 1 hour in an air atmosphere. After cooling, remove the rod from the tube furnace to obtain a dense and uniform powder rod.

[0049] Step 8: Fix the cylindrical powder rod on the rotating holder in the optical floating zone furnace, fine-tune the position of the rotating holder to be in the light area of the halogen tungsten lamp, seal the growth area by the quartz tube, and lock the screw port at the top and bottom to ensure the airtightness of the growth chamber. Open the gas discharge valve to ensure that the carrier gas is introduced from the bottom of the growth chamber and discharged from the top. Introduce O2 into the growth chamber at a rate of 100 mL / min.

[0050] Step 9: Set the working parameters of the optical floating zone furnace on the control computer, the heating power of the halogen tungsten lamp is 900 W / h, the time required to reach the heating power is 0.6 hours, the time to maintain the heating power is 1.5 hours, and the growth of the nanostructure is completed. Set the rotation rate of the cylindrical powder rod to 100 rpm. After the program is run, cool the grown nanostructure to room temperature.

[0051] Case 2

[0052] A method for preparing β-Ga2O3 nanostructures, comprising the following steps:

[0053] Step 1: Mix Ga2O3 powder and graphite powder in a mass ratio of 1:1.

[0054] Step 2: Pour the mixed powder of Ga2O3 powder and graphite powder into a nylon ball mill jar containing zirconia beads, then add ethanol to form a mixed solution, then seal the ball mill jar and tighten it. Shake the nylon ball mill jar up and down for 5 minutes to mix the Ga2O3 powder, graphite powder, and ethanol thoroughly to obtain a uniform mixed solution, then put it on a roller-type ball mill for ball milling for 24 hours.

[0055] Step 3: Pour the mixed solution of Ga2O3 powder, graphite powder, and ethanol into a flat glass disc, seal it with tin paper, and place it in a ventilated drying oven for drying. The drying time is 24 hours to evaporate all the ethanol, obtaining a block-shaped mixture of dry-cracked Ga2O3 powder and graphite powder.

[0056] Step 4: Grind the block-shaped mixture of dried Ga2O3 powder and graphite powder with a mortar and add alcohol, and the grinding time is 2 hours.

[0057] Step 5: Sieve the ground mixture of Ga2O3 powder and graphite powder twice through a 200-mesh sieve to obtain a uniformly dispersed and uniformly sized fine powder mixture.

[0058] Step 6: Pack the mixed fine powder of Ga2O3 powder and graphite powder into a long rubber balloon, seal it, vacuumize it for 20 minutes, and then press it at a pressure of 68 MPa for 30 minutes. Place the sealed balloon in the cylinder of an isostatic press for pressing, and make a cylindrical powder rod with uniform thickness and good density, with a diameter of 6 mm and a length of 30 mm.

[0059] Step 7: Place the cylindrical powder rod in an alumina ark and pre-sinter in a tube furnace. Heat the rod to 500°C at a rate of 6°C / min and hold for 1 hour in an air atmosphere. After cooling, remove the rod from the tube furnace to obtain a dense and uniform powder rod.

[0060] Step 8: Secure the cylindrical powder rod to the rotating bracket in the optical floating zone furnace. Finely adjust the bracket's position to ensure it is within the illumination area of ​​the halogen lamp. The growth area is sealed with a quartz tube. Tighten the upper and lower screws to ensure the growth chamber is airtight. Open the gas exhaust valve to ensure that the carrier gas enters the growth chamber from the bottom and exits from the top. Flow O2 into the growth chamber at a rate of 100 mL / min.

[0061] Step 9: Set the optical floating zone furnace operating parameters on the control computer: the halogen lamp heating power is 800 W / h, the time required to reach the heating power is 0.5 hours, and the heating power is maintained for 1.5 hours to complete the nanostructure growth. Set the cylindrical powder rod rotation speed to 100 rpm. After the program ends, cool the grown nanostructure to room temperature.

[0062] Implementation Case 3

[0063] A method for preparing a β-Ga2O3 nanostructure comprises the following steps:

[0064] Step 1: Mix Ga2O3 powder and graphite powder in a mass ratio of 1:1.

[0065] Step 2: Pour the mixed powder of Ga2O3 powder and graphite powder into a nylon ball mill filled with zirconium dioxide balls. Add ethanol to form a mixed solution. Seal the jar and tighten it. Shake the jar up and down for 5 minutes to thoroughly mix the Ga2O3 powder, graphite powder, and ethanol to form a uniform mixed solution. Then, mill the mixture on a roller ball mill for 24 hours.

[0066] Step 3: Pour the mixed solution of Ga2O3 powder, graphite powder, and ethanol into a flat-bottomed glass disc, seal it with tin foil, and place it in a ventilated drying oven for drying. The drying time is 24 hours to evaporate all the ethanol to obtain a blocky mixture of cracked Ga2O3 powder and graphite powder.

[0067] Step 4: Grind the bulk mixture of the dried Ga2O3 powder and graphite powder in a mortar with alcohol for 2 h.

[0068] Step 5: Sieve the mixture of ground Ga2O3 powder and graphite powder twice through a 200-mesh sieve to obtain a mixed fine powder with uniform dispersion and uniform particle size.

[0069] Step 6: Place the finely mixed Ga2O3 and graphite powders into a long rubber balloon, compact it, seal it, and evacuate it for 20 minutes. Then, press it at 68 MPa for 30 minutes. The sealed balloon is then placed in an isostatic press and pressed into a cylindrical rod with uniform thickness and good density, measuring 6 mm in diameter and 30 mm in length.

[0070] Step 7: Place the cylindrical powder rod in an alumina ark and pre-sinter in a tube furnace. Heat the rod to 500°C at a rate of 6°C / min and hold for 1 hour in an air atmosphere. After cooling, remove the rod from the tube furnace to obtain a dense and uniform powder rod.

[0071] Step 8: Secure the cylindrical powder rod to the rotating bracket in the optical floating zone furnace. Finely adjust the bracket's position to ensure it is within the illumination area of ​​the halogen lamp. The growth area is sealed with a quartz tube. Tighten the upper and lower screws to ensure the growth chamber is airtight. Open the gas exhaust valve to ensure that the carrier gas enters the growth chamber from the bottom and exits from the top. Flow O2 into the growth chamber at a rate of 100 mL / min.

[0072] Step 9: Set the optical floating zone furnace operating parameters on the control computer: the halogen lamp heating power is 700 W / h, the time required to reach the heating power is 0.3 hours, and the heating power is maintained for 1.5 hours to complete the nanostructure growth. Set the cylindrical powder rod rotation speed to 100 rpm. After the program ends, cool the grown nanostructure to room temperature.

[0073] Finally, the above embodiments of the present invention are merely examples to clearly illustrate the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not possible to enumerate all embodiments here. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for preparing β-Ga2O3 nanostructures, characterized in that: The following steps are involved: Step 1: Mix Ga2O3 powder and graphite powder in a mass ratio of 1:1; Step 2: Pour the mixed powder of Ga2O3 powder and graphite powder into a ball mill filled with zirconium dioxide balls, add ethanol to form a mixed solution, and then place it on a roller ball mill for ball milling for 24 hours; Step 3: Pour the mixed solution of the ball-milled Ga2O3 powder, graphite powder and ethanol into a flat-bottomed glass disc, seal it with tin foil and place it in a ventilated drying oven for drying for 24 hours to evaporate all the ethanol, thereby obtaining a blocky mixture of dried Ga2O3 powder and graphite powder; Step 4: Place the dried Ga2O3 powder and graphite powder in a mortar and grind with alcohol to obtain a mixed powder; Step 5: The mixed powder of the ground Ga2O3 powder and graphite powder is further placed on a 200-mesh sieve and passed through a 200-mesh sieve to obtain a mixed fine powder; Step 6: Place the mixed powder of Ga2O3 powder and graphite powder into a long rubber balloon, compact it, seal it, and evacuate it. Then, place the sealed balloon into the cylinder of an isostatic hydraulic press and press it to obtain a cylindrical powder rod. Step 7: Place the pressed cylindrical powder rod into an alumina ark and pre-fire it in a tube furnace. Set the temperature to 500°C and heat it in an air atmosphere for 1 hour. Step 8: Secure the cylindrical powder rod to the rotating bracket in the optical floating zone furnace. Adjust the rotating bracket's position so that it is within the illumination area of ​​the halogen lamp. The growth area is sealed with a quartz tube, and the upper and lower locking screws are tightened to ensure the growth chamber is airtight. O2 is introduced into the growth chamber as the growth carrier gas at a flow rate of 100 mL / min. The heating power of the halogen lamp is 900 W / h, and the heating time is 1.5 hours. Step 9: Cool the grown nanostructures to room temperature.

2. The method according to claim 1, wherein: In step 4, the bulk mixture of the dried Ga2O3 powder and graphite powder is placed in a mortar and ground with alcohol. After grinding for 2 hours, a mixed powder with uniform particle size is obtained.

3. The method according to claim 1, wherein: The heating rate of the pre-firing in step 7 is 6°C / min.

4. The method according to claim 1, wherein: In step 8, the time required for the halogen tungsten lamp to reach the heating power is 0.6 hours.

5. The method according to claim 1, wherein: In step 8, the rotation speed of the cylindrical powder rod is 100 rpm.

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