CN108611679B

CN108611679B - Method for preparing gallium nitride nanowires by green catalyst-free method

Info

Publication number: CN108611679B
Application number: CN201810319100.9A
Authority: CN
Inventors: 王如志; 冯晓宇; 姬宇航; 张铭; 王波; 严辉
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2018-04-11
Filing date: 2018-04-11
Publication date: 2020-06-16
Anticipated expiration: 2038-04-11
Also published as: CN108611679A

Abstract

A method for preparing gallium nitride nano-wires without a catalyst in a green environment, belonging to the field of non-catalystThe field of preparation and growth methods of organic compound semiconductor materials. The invention adopts a Plasma Enhanced Chemical Vapor Deposition (PECVD) system to produce green and pollution-free N without using any catalyst₂The one-dimensional linear GaN nanostructure with excellent performance is prepared by taking the one-dimensional linear GaN nanostructure as a nitrogen source. The invention has low cost and simple process, and takes polished graphite as a substrate and gallium metal and carbon powder as precursors. In a PECVD system, the reaction pressure is adjusted to be 30Pa-50 Pa; the reaction temperature is 825-875 ℃; n is a radical of₂Flow rate of 10-40cm³/min；H₂Flow rate of 5-10cm³Min; the power of the radio frequency power supply is 80W-120W, and the product is obtained after reaction for 1-3 h. The product is a one-dimensional GaN nanowire with a hexagonal wurtzite structure, and has typical violet light emitting characteristics and excellent field emission performance.

Description

Method for preparing gallium nitride nanowires by green catalyst-free method

Technical Field

The invention relates to a method for preparing gallium nitride nanowires without a catalyst, belonging to the field of preparation and growth methods of inorganic compound semiconductor materials.

Background

GaN, SiC, diamond and other wide band gap compound semiconductor materials are the third generation semiconductor materials following the first generation Ge, Si element semiconductors, the second generation GaAs, InP compound semiconductors. GaN is a third generation wide band gap semiconductor material, with a band gap of 3.39eV at room temperature, and has many characteristics such as high electron mobility, good electrical and thermal conductivity, high breakdown field strength, good radiation resistance, high temperature resistance, and chemical corrosion resistance, and has become a preferred material for electronic devices with high energy, high temperature, and high requirements for working environment. Due to the continuous adjustability of band gaps of the III group nitride multi-element alloy taking the GaN as the matrix, the GaN can be used in blue, green and ultraviolet light-emitting diodes; full-color display; applications in the fields of lasers and sensors are receiving increasing attention.

At present, metal is usually used as a catalyst for preparing the GaN nanowire, but the purity of the GaN nanowire can be reduced by the catalyst, so that the difficulty of characterization and test is increased, and the improvement of the performance of the GaN nanowire is seriously restricted; and the conventional preparation method has expensive raw materials and has certain pollution and corrosion to the environment and equipment. Finding a preparation method which does not use a catalyst and is environment-friendly becomes a key for solving the problem that the GaN nanowire is widely applied to the field of micro-nano electronic devices, and is also a target which is constantly pursued by scientific researchers in the field.

Disclosure of Invention

The invention aims to provide a method for preparing gallium nitride nanowires without a catalyst. In a plasma enhanced chemical vapor deposition system, metal gallium and carbon powder with the mass ratio of 2:1 are used as gallium sources, ionic nitrogen is used as a nitrogen source, pretreated flake graphite is used as a substrate, and a gallium nitride nanowire is generated in a quartz tube through direct reaction. Under the condition of no catalyst, NH polluting and corroding environment and equipment is abandoned₃The high-quality gallium nitride nanowire is prepared by adopting raw materials which are low in cost and easy to obtain, simple experimental equipment and a simple process.

The invention provides a method for preparing a gallium nitride nanowire without a catalyst, which is characterized by comprising the following steps of:

(1) preparation of the substrate: respectively grinding the graphite flakes for 5-10 minutes by using 1000-mesh, 2000-mesh and 5000-mesh sand paper in sequence, and then polishing for 5-10 minutes by using silk polishing cloth to ensure that the surface roughness Ra is less than or equal to 0.8; ultrasonically cleaning the polished graphite flakes for 10 minutes by sequentially using acetone, ethanol and deionized water; then drying the substrate in a forced air drying oven with the constant temperature of 60-100 ℃ for at least 30min to keep the surface dry and clean, and taking the substrate as a substrate of a preparation material;

(2) preparing a precursor: respectively weighing gallium metal and carbon powder in a mass ratio of 2:1 to obtain a precursor of the preparation material;

(3) respectively placing the precursors prepared in the step (2) into corundum crucibles, placing the graphite substrate prepared in the step (1) above the precursors, then placing the crucibles into a reaction chamber of a Plasma Enhanced Chemical Vapor Deposition (PECVD) system, and arranging the following componentsNumber: the reaction pressure is 30Pa-50 Pa; the reaction temperature is 825-875 ℃; n is a radical of₂Flow rate of 10-40cm³/min；H₂Flow rate of 5-10cm³Min; the power of the radio frequency power supply is 80W-120W. Reacting for 1-3h to obtain the gallium nitride nanowire.

The invention has the following advantages and benefits:

(1) the method has the advantages that the graphite flake with low cost is used as the substrate, the surface of the graphite flake after pretreatment has a large number of active sites, nucleation and growth of the gallium nitride nanowire are facilitated, the gallium nitride nanowire is prepared in a mode of not using a catalyst, the influence of the catalyst on the appearance and performance of the gallium nitride nanowire is effectively avoided, the purity of gallium nitride is improved, meanwhile, the preparation cost is greatly reduced, and the process flow is simplified.

(2) Non-toxic and pollution-free ionic N is a nitrogen source, and the monocrystal gallium nitride nanowire with the length of 5-10 mu m and the diameter of about 50nm is prepared under the condition of low vacuum degree.

(3) The prepared gallium nitride nanowires have typical nanowire Photoluminescence (PL) characteristics. At an excitation wavelength of 280nm, intrinsic excitation light is shown at 365nm, and the corresponding band gap is 3.39 eV.

(4) The gallium nitride nanowire has excellent field emission performance, and the defined opening electric field is 10 mu A/cm²The on electric field is 4.8V/mum.

Drawings

FIG. 1 is an SEM photograph of gallium nitride nanowires prepared in example 1

FIG. 2 is an SEM image of gallium nitride nanowires prepared in example 2

FIG. 3 is an SEM image of gallium nitride nanowires prepared in example 3

FIG. 4 is an XRD spectrum of gallium nitride nanowire prepared in example 2

FIG. 5 is a Raman spectrum of gallium nitride nanowires prepared in example 2

FIG. 6 is PL map of gallium nitride nanowires prepared in example 2

FIG. 7 is a field emission current density map of gallium nitride nanowires prepared in example 2 (inset corresponding to FN curve)

The specific implementation mode is as follows:

the essential features of the invention are further illustrated below by way of examples, but the invention is by no means limited to the following examples. The settings of the main parameters involved in the examples are shown in the following table:

in the experiment, graphite is used as a substrate, and a series of pretreatment works are carried out on the surface of the graphite to form a site which is favorable for GaN nucleation on the surface, so that the preparation of the GaN nanowire without a catalyst is further completed. Grinding and polishing the surface of the graphite sheet so as to reduce the surface roughness and obtain a surface with complete crystal lattices; and (4) ultrasonically cleaning to remove various impurities on the surface of the graphite. In the experimental temperature rise process, partial sites on the graphite surface are oxidized into graphite oxide, so that the graphite surface is provided with functional groups (such as hydroxyl and carboxyl), the activation energy of the positions of the functional groups is higher, and the nucleation of GaN is promoted.

In the experimental reaction process, N is under the radio frequency action of PECVD₂And H₂N and H converted into active ionic states. H atoms and C atoms combine with residual oxygen in the chamber to prevent Ga₂O₃And (3) combining the N atoms and the Ga atoms to generate GaN, thereby obtaining the GaN nanowire. The reaction process can be expressed as:

Ga+C+H⁺+N⁺→GaN+H₂O+CO_X

the scanning electron microscope image of the product adopts a Quanta-250 type scanning electron microscope; the X-ray diffraction (XRD) pattern was obtained using a Bruker D-8Advance diffractometer (Cu K)_αThe radiation is transmitted to the outside of the container,

) (ii) a The model of the Raman spectrometer is a Renishaw laser micro-confocal Raman spectrometer; testing Photoluminescence (PL) performance using an F-7000 fluorescence spectrometer; the field emission performance is tested using a field emission test system.

Example 1

(1) Respectively grinding the graphite flakes for 10 minutes by using 1000-mesh, 2000-mesh and 5000-mesh abrasive paper in sequence, and then polishing for 5 minutes by using silk polishing cloth to ensure that the surface roughness Ra is less than or equal to 0.8; ultrasonically cleaning the polished graphite flakes for 10 minutes by sequentially using acetone, ethanol and deionized water; then drying the substrate in a forced air drying oven with the constant temperature of 60-100 ℃ for 30min, and taking out the substrate as a substrate for preparing the material;

(2) weighing 0.1g of metal gallium and 0.05g of carbon powder to obtain a precursor for preparing the material;

(3) respectively placing the precursors prepared in the second step into corundum crucibles, placing the graphite substrate prepared in the first step above the precursors, then placing the crucibles into a reaction chamber of a Plasma Enhanced Chemical Vapor Deposition (PECVD), and setting the following parameters: the reaction pressure is 48 Pa; the reaction temperature is 825 ℃; n is a radical of₂Flow rate 20cm³/min；H₂Flow velocity of 10cm³Min; the radio frequency power supply has a power of 80W. And reacting for 3 hours to obtain the gallium nitride nanowire.

Example 2

(1) Respectively grinding the graphite flakes for 10 minutes by using 1000-mesh, 2000-mesh and 5000-mesh abrasive paper in sequence, and then polishing for 10 minutes by using silk polishing cloth to ensure that the surface roughness Ra is less than or equal to 0.8; ultrasonically cleaning the polished graphite flakes for 10 minutes by sequentially using acetone, ethanol and deionized water; then drying the substrate in a forced air drying oven with the constant temperature of 60-100 ℃ for 30min, and taking out the substrate as a substrate for preparing the material;

(3) respectively placing the precursors prepared in the second step into corundum crucibles, placing the graphite substrate prepared in the first step above the precursors, then placing the crucibles into a reaction chamber of a Plasma Enhanced Chemical Vapor Deposition (PECVD), and setting the following parameters: the reaction pressure is 48 Pa; the reaction temperature is 850 ℃; n is a radical of₂Flow rate 20cm³/min；H₂Flow velocity of 10cm³Min; the radio frequency power supply has a power of 80W. And reacting for 3 hours to obtain the gallium nitride nanowire.

Example 3

(1) Respectively grinding the graphite flakes for 8 minutes by using 1000-mesh, 2000-mesh and 5000-mesh abrasive paper in sequence, and then polishing for 8 minutes by using silk polishing cloth to ensure that the surface roughness Ra is less than or equal to 0.8; ultrasonically cleaning the polished graphite flakes for 10 minutes by sequentially using acetone, ethanol and deionized water; then drying the substrate in a forced air drying oven with the constant temperature of 60-100 ℃ for 30min, and taking out the substrate as a substrate for preparing the material;

(3) respectively placing the precursors prepared in the second step into corundum crucibles, placing the graphite substrate prepared in the first step above the precursors, then placing the crucibles into a reaction chamber of a Plasma Enhanced Chemical Vapor Deposition (PECVD), and setting the following parameters: the reaction pressure is 48 Pa; the reaction temperature is 875 ℃; n is a radical of₂Flow rate 20cm³/min；H₂Flow velocity of 10cm³Min; the radio frequency power supply has a power of 80W. And reacting for 3 hours to obtain the gallium nitride nanowire.

Claims

1. A method for preparing gallium nitride nanowires without catalysts is characterized by comprising the following process steps:

(1) preparation of the substrate: grinding and polishing the graphite sheet to ensure that the surface roughness Ra is less than or equal to 0.8; ultrasonically cleaning the polished graphite flakes by using acetone, ethanol and deionized water in sequence; then storing in a blast drying oven with constant temperature of 60-100 ℃ to keep the surface dry and clean as a substrate of a preparation material;

(3) respectively placing the precursors prepared in the step (2) into corundum crucibles, placing the graphite substrate prepared in the step (1) above the precursors, then placing the crucibles into a reaction chamber of a plasma enhanced chemical vapor system, and setting the following parameters: the reaction pressure is 30Pa-50 Pa; the reaction temperature is 825-875 ℃; n is a radical of₂Flow rate of 10-40cm³/min；H₂Flow rate of 5-10cm³Min; the power of the radio frequency power supply is 80W-120W; reacting for 1-3h to obtain the gallium nitride nanowire.

2. The method according to claim 1, wherein the grinding and polishing of the graphite sheet are specifically: respectively grinding with 1000-mesh, 2000-mesh and 5000-mesh sandpaper for 5-10 min, and polishing with silk polishing cloth for 5-10 min.