CN113488433A - Funnel-shaped gallium nitride nanowire and preparation method thereof - Google Patents
Funnel-shaped gallium nitride nanowire and preparation method thereof Download PDFInfo
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- 239000002070 nanowire Substances 0.000 title claims abstract description 135
- 229910002601 GaN Inorganic materials 0.000 title claims abstract description 58
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 title claims abstract description 57
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 238000005229 chemical vapour deposition Methods 0.000 claims abstract description 51
- 239000003054 catalyst Substances 0.000 claims abstract description 49
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims abstract description 47
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 44
- 229910052733 gallium Inorganic materials 0.000 claims abstract description 41
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- 239000010409 thin film Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 15
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 14
- XCZXGTMEAKBVPV-UHFFFAOYSA-N trimethylgallium Chemical compound C[Ga](C)C XCZXGTMEAKBVPV-UHFFFAOYSA-N 0.000 claims description 13
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 7
- 229910052737 gold Inorganic materials 0.000 claims description 7
- 239000010931 gold Substances 0.000 claims description 7
- 229910052759 nickel Inorganic materials 0.000 claims description 7
- 229910052594 sapphire Inorganic materials 0.000 claims description 5
- 239000010980 sapphire Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 3
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- MSNOMDLPLDYDME-UHFFFAOYSA-N gold nickel Chemical compound [Ni].[Au] MSNOMDLPLDYDME-UHFFFAOYSA-N 0.000 description 2
- 125000004433 nitrogen atom Chemical group N* 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
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- AJNVQOSZGJRYEI-UHFFFAOYSA-N digallium;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Ga+3].[Ga+3] AJNVQOSZGJRYEI-UHFFFAOYSA-N 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/77—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate
- H01L21/78—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices
- H01L21/82—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
- H01L29/0657—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by the shape of the body
- H01L29/0665—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by the shape of the body the shape of the body defining a nanostructure
- H01L29/0669—Nanowires or nanotubes
Abstract
The invention provides a funnel-shaped gallium nitride nanowire and a preparation method thereof, and relates to the technical field of nano materials. The invention provides a preparation method of funnel-type gallium nitride nanowires, which comprises the steps of carrying out first chemical vapor deposition on a gallium source and ammonia gas on a substrate loaded with a catalyst with a specific thickness in a reactor, and growing the nanowires according to a VLS mode and a VS mixed mode under the condition of high gallium source/ammonia gas flow ratio to prepare pyramid-shaped nanowires with catalyst particles at the top ends; and then changing the chemical vapor deposition condition, realizing VLS growth by using a catalyst at the top end of the nanowire under the condition of low gallium source/ammonia gas flow ratio, and continuously growing a cylindrical nanowire at the top end of the pyramid-shaped nanowire to prepare the funnel-shaped gallium nitride nanowire. The preparation method is simple and rapid, and breaks through the single morphological structure of the gallium nitride nanowire.
Description
Technical Field
The invention relates to the technical field of nano materials, in particular to a funnel-shaped gallium nitride nanowire and a preparation method thereof.
Background
Gallium nitride nanowires belong to one-dimensional nanomaterials, and the geometrical shapes of the gallium nitride nanowires limit electrons, holes and photons in two dimensions, so that the nanowires have special properties which cannot be possessed by some bulk materials, and the gallium nitride nanowires become potential basic components for manufacturing nano electronic devices and photoelectric devices. Gallium nitride nanowires have not only excellent electron transport properties, but also significant surface conductivity not possessed by bulk materials.
At present, two types of nanowires can be generally obtained by using MOCVD (metal organic chemical vapor deposition) method to prepare gallium nitride nanowires, one is cylindrical nanowires grown according to VLS mode, as shown in fig. 1, and the other is tapered and prismatic nanowires grown according to VS mode, as shown in fig. 2 and 4.
The gallium nitride nanowire is prepared by adopting a Vapor-Liquid-Solid (VLS) growth mechanism, and the growth principle of the gallium nitride nanowire is shown in figure 3. In general, a metal having high solid solubility, such as nickel or gold, is used as a catalyst material and deposited on the surface of a substrate in advance to form a thin film. Under the action of high temperature in the growth process, the metal film can be melted into tiny metal droplets. At this time, a gaseous reaction source containing gallium and nitrogen is introduced, gallium atoms and nitrogen atoms decomposed at high temperature continuously enter the catalyst liquid drops, and solid gallium nitride crystals are precipitated in the metal liquid drops after supersaturation is achieved. A significant feature of the VLS mechanism is therefore that the metal droplet is always on top of the nanowire during the entire growth process.
Under the VLS growth mechanism, the diameter of the nanowire is determined by the radius of the metal liquid drop, so that the nanowire is in a slender cylindrical form, the nanowire does not grow radially, the diameter is uniform, and the conical nanowire with a sharp top end and a thick bottom cannot be grown.
Another mechanism for nanowire growth is gas-Solid (VS, Vapor-Solid). The VS mechanism is a catalyst-free growth technology compared with the VLS mechanism, and the liquid metal catalyst represented by L is absent. Theoretically, nanowires of any material can be prepared by using the VS mechanism as long as the reaction gas can reach a suitable supersaturation degree and provide nucleation sites. The VS growth mechanism is simpler than VLS, due to the lack of a catalyst, and thus there is no complex multi-substance interface, only the gaseous reactant and solid substrate interface, where the crystalline material will nucleate. Two interfaces are introduced after crystal nucleation: gaseous and crystalline interfaces, and crystalline and substrate interfaces. The gaseous and crystal interface determines whether the crystal can continue to grow to form a nanowire after nucleation, and the crystal and substrate interface determines the crystal quality of the nanowire.
Catalyst particles do not exist at the top end of the nanowire grown in the VS mode, and the nanowire grows in the radial direction and the axial direction simultaneously, so that the diameter of the nanowire is possibly uneven, and the surface appearance is poor in quality compared with a VLS mechanism. Control over the morphology of the nanowires is relatively difficult.
As shown in fig. 4, only elongated cylindrical nanowires (b in fig. 4) can be generally obtained using the VLS growth mode, and pyramidal and prismatic nanowires (a and c in fig. 4) can be obtained using the VS growth mode. However, due to the characteristics of the VS growth mode, it is impossible to continue to grow nanowires with a smaller diameter on the pyramid or prism-shaped nanowires by controlling the reaction parameters to form a "funnel" shape. At the same time, the top of the nanowire grown in VS mode has no catalyst particles. It is also impossible to continue growing cylindrical nanowires on top of nanowires using VLS mode. Therefore, no report related to the "funnel" type gallium nitride nanowire is seen at present.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The first purpose of the invention is to provide a preparation method of funnel-shaped gallium nitride nanowires, which is simple and rapid and can prepare gallium nitride nanowires in a funnel shape.
The second purpose of the invention is to provide a funnel-type gallium nitride nanowire.
In a first aspect, the invention provides a preparation method of a funnel-type gallium nitride nanowire, which comprises the following steps:
performing first chemical vapor deposition on a gallium source and ammonia gas on a substrate, and then performing second chemical vapor deposition by changing conditions to prepare a funnel-shaped gallium nitride nanowire;
the chemical vapor deposition is carried out in a reactor;
the operating conditions of the first chemical vapor deposition are as follows:
the temperature is 740-760 ℃; the air pressure is 250to 350 Torr; the flow rate of the gallium source is 3.2-4.8 sccm; the flow rate of the ammonia gas is 16-24 sccm;
the operating conditions of the second chemical vapor deposition are as follows:
the temperature is 830-880 ℃; the air pressure is 250to 350 Torr; the flow rate of the gallium source is 1.6-2.4 sccm; the flow rate of the ammonia gas is 32-48 sccm;
the gallium source comprises trimethyl gallium;
the substrate is loaded with a catalyst film, and the thickness of the catalyst film is 8-12 nm.
As a further technical scheme, the operating conditions of the first chemical vapor deposition are as follows:
the temperature is 745-755 ℃; the air pressure is 280-330 Torr; the flow rate of the gallium source is 3.6-4.4 sccm; the flow rate of the ammonia gas is 18-22 sccm;
preferably, the operating conditions of the first chemical vapor deposition are as follows:
the temperature is 750 ℃; the air pressure is 300 Torr; the gallium source flow rate is 4 sccm; the flow rate of ammonia gas was 20 sccm.
As a further technical scheme, the operating conditions of the second chemical vapor deposition are as follows:
the temperature is 840-860 ℃; the air pressure is 280-330 Torr; the flow rate of the gallium source is 1.8-2.2 sccm; the flow rate of the ammonia gas is 36-44 sccm;
preferably, the operating conditions of the second chemical vapor deposition are as follows:
the temperature is 850 ℃; the air pressure is 300 Torr; the gallium source flow rate is 2 sccm; the flow rate of ammonia gas was 40 sccm.
As a further technical solution, the substrate includes a sapphire substrate.
As a further technical scheme, a gallium nitride film is also arranged between the substrate and the catalyst film;
preferably, the thickness of the gallium nitride film is 2.4-3.6 μm, and preferably 3 μm.
As a further technical scheme, the catalyst thin film comprises a nickel thin film and a gold thin film.
According to a further technical scheme, the thicknesses of the nickel thin film and the gold thin film are respectively and independently 4-6 nm, and preferably 5 nm.
As a further technical scheme, the time of the first chemical vapor deposition is 700-900 s, preferably 800 s.
According to a further technical scheme, the time of the second chemical vapor deposition is 24-36 s, and preferably 30 s.
In a second aspect, the present invention provides a funnel-type gallium nitride nanowire.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a preparation method of funnel-type gallium nitride nanowires, which comprises the steps of carrying out first chemical vapor deposition on a gallium source and ammonia gas on a substrate loaded with a catalyst with a specific thickness in a reactor, and growing the nanowires according to a VLS mode and a VS mixed mode under the specific condition of high gallium source/ammonia gas flow ratio to prepare pyramid-shaped nanowires with catalyst particles at the top ends; and then changing the chemical vapor deposition condition, realizing VLS growth by using a catalyst at the top end of the nanowire under the specific condition of low gallium source/ammonia gas flow ratio, and continuously growing a cylindrical nanowire at the top end of the pyramid-shaped nanowire to prepare the funnel-shaped gallium nitride nanowire. The preparation method is simple and rapid, and breaks through the single morphological structure of the gallium nitride nanowire.
The funnel-shaped gallium nitride nanowire prepared by the preparation method has unique morphological characteristics, and the thick diameter of the bottom can form large-area contact with a substrate to form good electrical contact; the diameter of the top part is thin, so that the integral resistance value of the nanowire can be regulated, the diameter of the nanowire can be controlled through the thickness of the catalyst, and the nanowires with different resistance values can be obtained. These features offer new possibilities for their flexible application in nanowire devices. Meanwhile, the axial and radial heterojunction and the multi-quantum well structure are further manufactured on the basis of the funnel-shaped nanowire, so that the application field of the heterojunction and the multi-quantum well structure can be further widened.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a cylindrical nanowire grown in VLS mode;
FIG. 2 is a pyramid-shaped nanowire grown in the VS mode;
FIG. 3 shows the growth principle of preparing cylindrical nanowires by VLS mode growth;
FIG. 4 illustrates different types of nanowires grown in two modes;
FIG. 5 is a schematic view of a funnel-shaped GaN nanowire according to the present invention;
FIG. 6 is a diagram of an MOCVD apparatus;
FIG. 7 is a view of a substrate structure;
FIG. 8 is a view showing the structure of a reaction chamber;
FIG. 9 shows the pyramidal nanowires prepared by the first chemical vapor deposition process provided in example 1;
FIG. 10 shows a funnel-shaped nanowire prepared in example 1;
FIG. 11 shows a funnel-shaped nanowire prepared in example 2;
fig. 12 shows the funnel-type nanowires prepared in example 3.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to embodiments and examples, but those skilled in the art will understand that the following embodiments and examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. Those who do not specify the conditions are performed according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
In a first aspect, the invention provides a preparation method of a funnel-type gallium nitride nanowire, which comprises the following steps:
performing first chemical vapor deposition on a gallium source and ammonia gas on a substrate, and then performing second chemical vapor deposition by changing conditions to prepare a funnel-shaped gallium nitride nanowire;
the chemical vapor deposition is carried out in a reactor;
the operating conditions of the first chemical vapor deposition are as follows:
the temperature is 740 to 760 ℃, and for example, but not limited to 740 ℃, 744 ℃, 748 ℃, 752 ℃, 756 ℃ or 760 ℃;
the gas pressure is 250to 350Torr, and for example, but not limited to, 250Torr, 270Torr, 290Torr, 310Torr, 330Torr or 350 Torr;
the gallium source flow rate is 3.2-4.8 sccm, such as but not limited to 3.2sccm, 3.6sccm, 4sccm, 4.4sccm or 4.8 sccm;
the flow rate of the ammonia gas is 16-24 sccm, such as but not limited to 16sccm, 18sccm, 20sccm, 22sccm or 24 sccm;
the operating conditions of the second chemical vapor deposition are as follows:
the temperature is 830-880 ℃, for example, but not limited to 830 ℃, 840 ℃, 850 ℃, 860 ℃, 870 ℃ or 880 ℃;
the gas pressure is 250to 350Torr, and for example, but not limited to, 250Torr, 270Torr, 290Torr, 310Torr, 330Torr or 350 Torr;
the flow rate of the gallium source is 1.6-2.4 sccm, such as but not limited to 1.6sccm, 1.8sccm, 2sccm, 2.2sccm or 2.4 sccm;
the flow rate of the ammonia gas is 32-48 sccm, such as but not limited to 32sccm, 36sccm, 40sccm, 44sccm or 48 sccm;
the gallium source includes, but is not limited to, trimethyl gallium, which may also include, for example, metallic gallium or gallium oxide, or other gallium sources known to those skilled in the art;
the substrate is loaded with a catalyst film, and the thickness of the catalyst film is 8-12 nm, such as but not limited to 8nm, 9nm, 10nm, 11nm or 12 nm. The growth mode of the gallium nitride nanowire is influenced by the thickness of the catalyst, and the preparation of the funnel-shaped nanowire is realized by adopting a catalyst film with a specific thickness and regulating and controlling the airflow ratio of the gallium source/ammonia gas.
According to the preparation method of the funnel-type gallium nitride nanowire, a gallium source and ammonia gas are subjected to first chemical vapor deposition on a substrate loaded with a catalyst with a specific thickness in a reactor, the nanowire grows according to a VLS mode and a VS mixed mode under specific conditions, and as shown in c in fig. 4, the pyramid-shaped nanowire with catalyst particles at the top end is prepared; and then changing the chemical vapor deposition conditions, realizing VLS growth by using a catalyst at the top end of the nanowire, continuously growing a cylindrical nanowire at the top end of the pyramid-shaped nanowire, and preparing the funnel-shaped gallium nitride nanowire, wherein the schematic diagram of the funnel-shaped gallium nitride nanowire is shown in FIG. 5.
The principle of nanowire shape control in the invention is as follows:
the morphology of the gallium nitride nanowires can be controlled by controlling the thickness of the catalyst film and the flow ratio of TMGa/ammonia gas. The thickness of the catalyst thin film directly affects the diameter of the catalyst droplets formed at high temperature, and thus determines the surface energy size of the catalyst droplets. The flow ratio of TMGa and ammonia determines the chemical potential of the gaseous reactants. When a thick catalyst (10nm) is used, the surface energy of the droplets is higher due to the larger radius of the formed catalyst droplets, and at this time, if the TMGa/ammonia gas flow is lower, the surface energy of the catalyst will be greater than the chemical potential of the gaseous reactants, resulting in that the nanowires cannot grow according to the VLS mode, but grow according to the VS mode. In this mode, the TMGa/ammonia gas flow ratio changes the difference in chemical potential between the gaseous reactants and the substrate and the difference in chemical potential between the diffusing atoms and the substrate. When the TMGa/ammonia gas flow is relatively low, the nanowire growth rate decreases as the temperature remains constant. The decrease in growth rate indicates that not enough gallium atoms have diffused into the catalyst droplets at the top of the nanowires. However, considering that the total number of gallium atoms in the system is not reduced, the diffusion distance of the gallium atoms on the substrate surface and the side wall of the nanowire is reduced due to the reduction of the chemical potential, and the gallium atoms cannot diffuse and move from the substrate surface to the top end of the nanowire. Gallium atoms may diffuse to the nanowire sidewalls to form clusters that react with nitrogen atoms in the gas phase to form gallium nitride, resulting in radial growth of the nanowire. The cone-shaped nanowire with a thick bottom and a sharp top can be obtained, but catalyst particles cannot be reserved at the top of the nanowire. At the moment, the chemical potential of the gaseous reactants in the reaction chamber is increased by increasing the airflow ratio of TMGa/ammonia gas until the chemical potential is larger than the surface energy of the catalyst liquid drop, the nanowire grows according to the VLS and VS mixed mode simultaneously, the conical nanowire is obtained, and the catalyst particles are reserved at the top end of the nanowire. Therefore, by changing the reaction conditions and further carrying out VLS mode growth by using the catalyst particles, the funnel-type nanowire structure can be obtained.
In some preferred embodiments, the operating conditions of the first chemical vapor deposition are as follows:
the temperature is 745-755 ℃; the air pressure is 280-330 Torr; the flow rate of the gallium source is 3.6-4.4 sccm; the flow rate of the ammonia gas is 18-22 sccm;
preferably, the operating conditions of the first chemical vapor deposition are as follows:
the temperature is 750 ℃; the air pressure is 300 Torr; the gallium source flow rate is 4 sccm; the flow rate of ammonia gas was 20 sccm.
In the invention, gallium nitride nanowires are simultaneously grown according to a VLS mode and a VS mode by further optimizing and adjusting the first chemical vapor deposition conditions to obtain pyramid nanowires, and catalyst particles are kept at the top ends of the nanowires.
In some preferred embodiments, the operating conditions of the second chemical vapor deposition are as follows:
the temperature is 840-860 ℃; the air pressure is 280-330 Torr; the flow rate of the gallium source is 1.8-2.2 sccm; the flow rate of the ammonia gas is 36-44 sccm;
preferably, the operating conditions of the second chemical vapor deposition are as follows:
the temperature is 850 ℃; the air pressure is 300 Torr; the gallium source flow rate is 2 sccm; the flow rate of ammonia gas was 40 sccm.
In the invention, the catalyst particles realize further growth of the cylindrical nanowires according to a VLS mode by further optimizing and adjusting the conditions of the second chemical vapor deposition, and the nanowires with the appearance closer to the funnel shape are prepared.
In some preferred embodiments, the substrate includes, but is not limited to, a sapphire substrate, such as a silicon substrate, or other substrates known to those skilled in the art. The sapphire substrate has low cost, high stability, high mechanical strength and easy treatment and cleaning.
In some preferred embodiments, a gallium nitride film is further included between the substrate and the catalyst film. On one hand, the gallium nitride film is the same as the nanowire material, so that the nanowire with high crystal quality and good growth directionality can be obtained; on the other hand, the gallium nitride film is conductive, so that the gallium nitride film can be used as a bottom electrode of the nanowire, and the nanowire can be conveniently electrified when a device is manufactured by using the nanowire subsequently.
Preferably, the thickness of the gallium nitride thin film is 2.4 to 3.6 μm, and may be, but is not limited to, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, or 3.6 μm, preferably 3 μm.
In some preferred embodiments, the catalyst thin film includes a nickel thin film and a gold thin film.
In some preferred embodiments, the thickness of the nickel thin film and the gold thin film is 4 to 6nm, such as but not limited to 4nm, 5nm or 6nm, preferably 5 nm.
In some preferred embodiments, the time of the first chemical vapor deposition is 700-900 s, for example, but not limited to 700s, 740s, 780s, 820s, 860s or 900s, and preferably 800 s.
In the invention, the pyramid-shaped nanowire with proper size is prepared and obtained by further optimizing and adjusting the time of the first chemical vapor deposition.
In some preferred embodiments, the time of the second chemical vapor deposition is 24 to 36s, and for example, but not limited to, 24s, 26s, 28s, 30s, 32s, 34s or 36s, and preferably 30 s.
In the invention, the cylindrical nanowire with proper length is prepared by further optimizing and adjusting the time of the second chemical vapor deposition, and the cylindrical nanowire is combined with the pyramid-shaped nanowire to obtain the gallium nitride nanowire in a funnel shape.
In a second aspect, the present invention provides a funnel-type gallium nitride nanowire.
The funnel-shaped gallium nitride nanowire is prepared by the preparation method provided by the invention, the nanowire in the shape of a funnel has unique morphological characteristics, and the thick diameter of the bottom can form large-area contact with a substrate to form good electrical contact; the diameter of the top part is thin, so that the integral resistance value of the nanowire can be regulated, the diameter of the nanowire can be controlled through the thickness of the catalyst, and the nanowires with different resistance values can be obtained. These features offer new possibilities for their flexible application in nanowire devices.
The invention is further illustrated by the following specific examples and comparative examples, but it should be understood that these examples are for purposes of illustration only and are not to be construed as limiting the invention in any way.
Example 1
The funnel-type gallium nitride nanowires were prepared by the MOCVD method, and the MOCVD equipment diagram is shown in fig. 6.
Trimethyl gallium (TMGa) is selected as a gallium source. TMGa needs to be placed in a cryogenically sealed container. Nitrogen (mixed with 5% hydrogen to assist growth) is used as carrier gas to be introduced into the TMGa solution, and the gallium source is carried into the reaction chamber. Because ammonia gas has a low decomposition temperature (less than 650 ℃), ammonia gas is generally selected as a nitrogen source to react with a gallium source at a high temperature to prepare the gallium nitride nanowires. A gallium nitride film with the thickness of 3 microns is deposited on the surface of the sapphire substrate, a nickel-gold film catalyst (figure 7) is prepared by a magnetron sputtering method, and the nickel-gold film catalyst is placed on a graphite boat in a reaction chamber (figure 8).
Firstly, starting a mechanical pump to pump vacuum, and introducing nitrogen into the reaction chamber when the internal air pressure of the reaction chamber reaches about 50Torr to ensure that the air in the quartz tube is exhausted completely. Finally, the pressure in the reaction chamber is kept stable at 300Torr, a water cooling machine and a radio frequency heating device are operated to carry out first chemical vapor deposition, so that the nanowire grows simultaneously according to a VLS mode and a VS mode, and the pyramid-shaped nanowire (as shown in figure 9) is obtained, wherein the operation conditions are shown in the following table.
Because VLS and VS mixed mode growth is realized in the first step, and simultaneously the catalyst particles are reserved at the top ends of the nano pyramids, the reaction conditions can be further changed, the second chemical vapor deposition is carried out, the catalyst particles realize further growth of the cylindrical nanowires according to the VLS mode, and the operation conditions are shown in the following table, so that the funnel-shaped nanowires are obtained, and are shown in FIG. 10.
| Growth temperature | Air pressure | Flow of gallium source | Flow of ammonia | Growth time |
| 850℃ | 300Torr | 2sccm | 40sccm | 30s |
Example 2
A method for preparing funnel-type gallium nitride nanowires, which is different from the method of embodiment 1 in that:
the first chemical vapor deposition conditions were as follows:
the second chemical vapor deposition conditions were as follows:
| growth temperature | Air pressure | Flow of gallium source | Flow of ammonia | Growth time |
| 830℃ | 350Torr | 1.6sccm | 48sccm | 24s |
The prepared funnel-type gallium nitride nanowire is shown in fig. 11.
Example 3
A method for preparing funnel-type gallium nitride nanowires, which is different from the method of embodiment 1 in that:
the first chemical vapor deposition conditions were as follows:
the second chemical vapor deposition conditions were as follows:
| growth temperature | Air pressure | Flow of gallium source | Flow of ammonia | Growth time |
| 880℃ | 250Torr | 2.4sccm | 32sccm | 36s |
The prepared funnel-type gallium nitride nanowire is shown in fig. 12.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A preparation method of a funnel-type gallium nitride nanowire is characterized by comprising the following steps:
performing first chemical vapor deposition on a gallium source and ammonia gas on a substrate, and then performing second chemical vapor deposition by changing conditions to prepare a funnel-shaped gallium nitride nanowire;
the chemical vapor deposition is carried out in a reactor;
the operating conditions of the first chemical vapor deposition are as follows:
the temperature is 740-760 ℃; the air pressure is 250to 350 Torr; the flow rate of the gallium source is 3.2-4.8 sccm; the flow rate of the ammonia gas is 16-24 sccm;
the operating conditions of the second chemical vapor deposition are as follows:
the temperature is 830-880 ℃; the air pressure is 250to 350 Torr; the flow rate of the gallium source is 1.6-2.4 sccm; the flow rate of the ammonia gas is 32-48 sccm;
the gallium source comprises trimethyl gallium;
the substrate is loaded with a catalyst film, and the thickness of the catalyst film is 8-12 nm.
2. The method according to claim 1, wherein the operating conditions of the first chemical vapor deposition are as follows:
the temperature is 745-755 ℃; the air pressure is 280-330 Torr; the flow rate of the gallium source is 3.6-4.4 sccm; the flow rate of the ammonia gas is 18-22 sccm;
preferably, the operating conditions of the first chemical vapor deposition are as follows:
the temperature is 750 ℃; the air pressure is 300 Torr; the gallium source flow rate is 4 sccm; the flow rate of ammonia gas was 20 sccm.
3. The method according to claim 1, wherein the second chemical vapor deposition is performed under the following conditions:
the temperature is 840-860 ℃; the air pressure is 280-330 Torr; the flow rate of the gallium source is 1.8-2.2 sccm; the flow rate of the ammonia gas is 36-44 sccm;
preferably, the operating conditions of the second chemical vapor deposition are as follows:
the temperature is 850 ℃; the air pressure is 300 Torr; the gallium source flow rate is 2 sccm; the flow rate of ammonia gas was 40 sccm.
4. The method of manufacturing according to claim 1, wherein the substrate comprises a sapphire substrate.
5. The method according to claim 4, further comprising a gallium nitride film between the substrate and the catalyst film;
preferably, the thickness of the gallium nitride film is 2.4-3.6 μm, and preferably 3 μm.
6. The production method according to claim 1, wherein the catalyst thin film includes a nickel thin film and a gold thin film.
7. The method according to claim 6, wherein the thickness of the nickel thin film and the gold thin film is 4 to 6nm, preferably 5 nm.
8. The method according to claim 1, wherein the time for the first chemical vapor deposition is 700 to 900s, preferably 800 s.
9. The preparation method according to claim 1, wherein the time of the second chemical vapor deposition is 24-36 s, preferably 30 s.
10. The funnel-shaped gallium nitride nanowire prepared by the preparation method of any one of claims 1 to 9.
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