JP2019218528A - Nitride nanoparticle and production method of the same - Google Patents

Abstract

To provide a production method for chemical synthesis of a nitride semiconductor crystal, by which an impurity level in the nitride semiconductor crystal can be reduced by using ammonia as a nitrogen source.SOLUTION: A nanoparticle having a group III element nitride region containing any of In, Ga and Al is provided, in which a content concentration of an alkali metal in the group III element nitride region is 1 at% or less. A production method of a nitride nanoparticle is provided, which comprises synthesizing a group III element nitride by mixing a source material containing a source of the group III element and a photocatalyst in a solvent to prepare a solution and bubbling the solution with ammonia gas while heating, stirring and irradiating the solution with light.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a nitride nanoparticle and a method for producing the same, and more particularly to a nitride nanoparticle having high luminous efficiency and a method for producing the same.

  For example, the surface area of a spherical particle is proportional to the square of the radius, and the volume of the spherical particle is proportional to the cube of the radius. Reducing the particle diameter by a factor of 10 reduces the surface area to 1/100 and the volume to 1/1000. It is expected that as the size of the particles is reduced, the specific gravity of the effect of the surface on the physical properties and the effect of the volume on the physical properties will change. It will be understood that particles whose typical dimensions such as the length of one side are on the order of nm may exhibit different physical properties from particles whose side length is, for example, μm or more.

  Particles having such dimensions on the order of nm are called nanoparticles. Core / shell type nanoparticles with a shell grown on the core have the potential for the shell to protect the core or to form a highly crystalline epitaxial shell on the crystalline core. Have. In recent years, research has been conducted to develop materials having new optical properties and the like by actively utilizing nanoparticles.

  It is conceivable to adopt a compound semiconductor having desired emission characteristics as the first shell, and to form a core with an appropriate compound semiconductor as an underlayer for crystal-growing the first shell. If an attempt is made to form a layered structure using only compound semiconductors, the lattice constants generally differ, making it difficult to achieve lattice matching. Lattice mismatch causes the crystal lattice to be distorted, which causes a reduction in luminous efficiency and reliability. Lattice matching can be realized by using a mixed crystal whose composition is selected so as to obtain a desired lattice constant.

  When the second shell is grown on the first shell formed on the core, the first shell has a configuration sandwiched between the core and the second shell. If the first shell is a light emitting layer, and the core and the second shell transmit light emitted from the first shell, light can be emitted in all directions.

  Attention has been focused on nitride semiconductors as III-V semiconductors. When crystallizing a nitride semiconductor by chemical synthesis, a nitrogen source containing an alkali metal has been used as a nitrogen source of the nitride semiconductor.

A core formed of a group II-VI mixed crystal semiconductor, a first shell formed of a group III-V mixed crystal semiconductor lattice-matched to the core, or further a second shell lattice-matched on the first shell; Are formed to form lattice-matched nanoparticles, and a core is etched to expose a specific plane orientation, and then a lattice-matched shell is grown (for example, Patent Documents 1 and 3).
Using a II-VI semiconductor and a III-V semiconductor, a plurality of lattice-matched stacks are formed on a core, and then a II-VI component is etched to form a III-V semiconductor only configuration. (For example, Patent Document 2).

  When a nitrogen source containing an alkali metal is used as the nitrogen source of the nitride semiconductor in the chemical synthesis, there is a concern that the alkali metal is taken into the semiconductor crystal and becomes an impurity, which has an undesirable effect.

  When growing a nitride semiconductor by a vapor growth method, ammonia is used as a nitrogen source. Ammonia decomposes to produce nitrogen and hydrogen, and hydrogen, an element other than nitrogen, can easily escape out of the crystal and is unlikely to have any adverse effects as impurities. However, the decomposition temperature of ammonia is, for example, 800 ° C. or higher, and decomposition is not promoted in a temperature range of chemical synthesis performed using a solvent, and the ammonia is not a good nitrogen source.

JP-A-2006-145972 JP-A-2006-148028 WO2016 / 125435

  A nitride semiconductor crystal having a low impurity concentration is required. In the chemical synthesis of a nitride semiconductor crystal, a manufacturing method capable of lowering the impurity level in the nitride semiconductor crystal is required. If ammonia could be used as the nitrogen source, the impurity concentration could be reduced.

  In chemical synthesis for growing nitride semiconductor crystals, a photocatalytic material is mixed into a solution, the solution is heated, and ultraviolet light is irradiated while introducing ammonia gas as a nitrogen source. A manufacturing method for forming nanoparticles is provided. By using ammonia as the nitrogen source, the concentration of the alkali metal contained as an impurity in the nitride semiconductor nanoparticles is reduced.

FIG. 1A is a side view schematically showing a configuration of a nitride semiconductor nanoparticle synthesis apparatus, and FIG. 1B is a schematic side view showing a step of forming a mixed solution by charging a raw material and a photocatalyst into a reaction vessel containing a solvent. is there. FIG. 2 is a schematic perspective view showing the formed nitride semiconductor nanoparticles. In Example 1, InN nanoparticles are used, and in Example 2, InGaN nanoparticles are used. FIG. 3 is a side view schematically showing a configuration of a manufacturing apparatus of the nanoseed base material. FIG. 4 is a schematic perspective view of the nanoseed base material 35 exposing a specific crystal plane by etching. FIG. 5 is a side view schematically showing the configuration of the optical etching apparatus.

Reference Signs List 10 synthesis device, 11 reaction vessel, 12 light irradiation device, 13 temperature sensor,
14 heater, 15 stirrer, 16 ammonia supply line,
17 inert gas supply line, 18 vacuum replacement line, 19 vacuum pump,
20 ammonia abatement equipment, 22 solution, 23a synthesis solvent,
23b indium iodide, 23c anatase type titanium dioxide,
23d gallium iodide, 25 nitride semiconductor nanoparticles,
30 nanoseed base material manufacturing device, 31 reaction vessel, 33 solution, 35 base material,
36, 37 ports, 38 temperature measuring section, 39 heater, 41 light source,
42 lenses, 43 monochromator, 44 optical fiber,
45 rod lens,

  Hereinafter, the manufacturing process of the nitride semiconductor nanoparticles will be described with reference to Examples. First, a manufacturing process of InN and InGaN will be described as an example of a nitride semiconductor.

Example 1: (Preparation of InN nanoparticles)
FIG. 1A shows a schematic configuration of the synthesis apparatus. The synthesis device 10 includes a reaction vessel 11, a light irradiation device 12, a temperature sensor 13, a heater 14, a stirrer 15, an ammonia supply line 16, an inert gas supply line 17, a vacuum replacement line 18, a vacuum pump 19, and an ammonia removal equipment 20. It is composed of The temperature sensor 13 can measure the temperature of the contents in the reaction container 11. The heater 14 can heat the container. The stirrer (rotary blade) 15 can stir the contents. An inner cylinder made of platinum, iridium, boron nitride, or the like may be used in the reaction vessel 11.

  The light irradiation device 12 includes a light source for inducing a photocatalytic effect of the photocatalyst agent in the reaction container 11. High-purity nitrogen, argon, or the like can be used as the inert gas. Further, the gas supply line can be replaced by a vacuum pump connected to the vacuum replacement line. The reaction vessel 11 is preferably made of glass, but may be made of stainless steel. However, in this case, it is necessary to provide a viewing window to enable light irradiation.

  Next, a synthesis method will be described. All operations for sample preparation are performed in glove boxes using vacuum dried (140 ° C.) instruments and equipment.

  Referring to FIG. Indium iodide (165 mg, 0.36 mmol) 23b as an indium source and anatase type titanium dioxide (50 mg) 23c as a photocatalytic material are charged into a reaction vessel 11 containing diphenyl ether (20 ml) as a synthesis solvent 23a.

  As shown in FIG. 1A, after setting the reaction vessel 11 in the synthesis apparatus 10, high-purity nitrogen is flowed through the inert gas supply line 17 while sufficiently stirring using the stirrer 15, thereby purging the inside of the reaction vessel. To form a solution 22. Thereafter, ammonia gas as a nitrogen source is introduced into the reaction vessel 11 at a rate of 100 ml / min through the ammonia supply line 16.

  The solvent used may be octyl ether, octylbenzene, octylamine, trioctylphosphine, triphenylphosphine, or the like, in addition to diphenyl ether. Aromatic solvents such as benzene, toluene and xylene can also be used. However, since the vapor pressure is high, it is necessary to use a container capable of sealing the solvent.

  The titanium dioxide is preferably fine particles. This is to reduce variations in the photocatalytic effect in the synthesis solution. The use of nanoparticle titanium dioxide enhances the photocatalytic effect and is more preferable.

  The solution is rapidly heated to 300 ° C. while irradiating the ultraviolet rays from the light irradiation device 12 and kept at 300 ° C. for 10 hours. Thereafter, the synthesis is terminated by cooling to room temperature. Ammonia gas is switched to argon on the way.

  To prevent coagulation of the nanoparticles, butanol is added to the reaction solution as an anticoagulant and stirred for 10 hours. Thereafter, purification is performed by repeating centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (diphenyl ether) is dissolved and toluene in which the nanoparticles are dispersed. Unnecessary raw materials and solvents are completely removed.

  The synthesis temperature is effective as long as the ammonia gas starts to decompose even a little. Chemical synthesis may be possible even at a temperature at which the solvent in the liquid phase becomes invisible. The temperature may be approximately 800 ° C. or less, preferably 200 to 500 ° C., and more preferably 250 to 450 ° C. in view of the reaction efficiency and the decomposition temperature of the solvent.

  FIG. 2 is a perspective view schematically showing nitride semiconductor nanoparticles 25 having an average particle size of about 4.5 nm formed of InN by the above-described process.

  Next, a manufacturing process of the mixed crystal InGaN nanoparticles will be described.

Example 2: (Preparation of InGaN nanoparticles)
1A is used. In a solution forming step similar to FIG. 1B, gallium iodide is added as a gallium raw material.

  As shown in FIG. 1B, in a reaction vessel 11 containing diphenyl ether (20 ml) as a synthesis solvent, gallium iodide (108 mg, 0.24 mmol) 23d and indium source indium iodide (165 mg, 0 .36 mmol) 23b and an anatase type titanium dioxide (50 mg) 23c as a photocatalyst material are charged.

  As shown in FIG. 1A, after setting the reaction vessel 11 in the synthesis apparatus 10, high-purity nitrogen as an inert gas is flowed through the inert gas supply line 17 while sufficiently stirring using the stirrer 15, and the reaction is performed. The purging of the container 11 is performed. Thereafter, ammonia gas is introduced into the reaction vessel 11 at a rate of 100 ml / min through the ammonia supply line 16.

  All operations for sample preparation are performed in glove boxes using vacuum dried (140 ° C.) instruments and equipment. The solvent used may be octyl ether, octylbenzene, octylamine, trioctylphosphine, triphenylphosphine, or the like, in addition to diphenyl ether. Aromatic solvents such as benzene, toluene and xylene can also be used. However, since the vapor pressure is high, it is necessary to use a container capable of sealing the solvent.

  The titanium dioxide is preferably fine particles. This is to reduce variations in the photocatalytic effect in the synthesis solution. The use of nanoparticle titanium dioxide is more preferable because the photocatalytic effect is enhanced.

  The mixture is rapidly heated to 350 ° C. while irradiating ultraviolet rays emitted from the light irradiating device 12 and kept at 350 ° C. for 10 hours. Thereafter, the synthesis is terminated by cooling to room temperature. Ammonia gas is switched to argon on the way.

  To prevent coagulation of the nanoparticles, butanol is added to the reaction solution as an anticoagulant and stirred for 10 hours. Thereafter, purification is performed by repeating centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (diphenyl ether) is dissolved and toluene in which the nanoparticles are dispersed. Unnecessary raw materials and solvents are completely removed.

  The synthesis temperature is effective as long as the ammonia gas starts to decompose even a little. The temperature may be approximately 800 ° C. or less, preferably 200 to 500 ° C., and more preferably 250 to 450 ° C. in view of the reaction efficiency and the decomposition temperature of the solvent.

Through the above steps, nitride semiconductor nanoparticles 25 formed of In _0.60 Ga _0.40 N and having an average particle size of about 5 nm as shown in FIG. 2 can be manufactured.

  Note that if Al is substituted for Ga and aluminum iodide is used as a raw material instead of gallium iodide, an InAlN mixed crystal can be produced. Next, an embodiment in which a II-VI group semiconductor (ZnOS) is grown as a seed and an InGaN shell lattice-matching is formed on the seed will be described.

Example 3: (Preparation of nanoparticles with InGaN shell on ZnOS seed)
Fabrication of high quality InGaN nanoparticles using ZnOS nanoseed that lattice matches with nitride nanoparticles. First, ZnOS nanoseed is prepared in advance by hot injection. As ZnOS nanoseed, ZnO _0.72 S _0.28 base material particles will be synthesized.

  FIG. 3 is a side view schematically showing an apparatus 30 for manufacturing a nanoseed base material. A 300 ml quartz flask is prepared as the reaction vessel 31. In addition to the outlet, the quartz flask 31 has a port 36 in which the inside of the flask can be replaced with an inert gas (Ar), a port 37 having a plurality of dedicated syringes into which a reaction precursor can be injected, and a temperature measuring unit to which a thermocouple is attached. 38. Argon (Ar) is used as the inert gas. The quartz flask 31 is set on a mantle heater 39.

As a reaction precursor, diethyl zinc (Zn (C ₂ H ₅ ) ₂ ) sealed with an inert gas, octylamine (C ₈ H ₁₇ NH ₂ ) bubbled with oxygen, bis (trimethylsilyl) sulfide (bis (trimethylsilyl) sulfide) ) Is prepared for each syringe. 4.0 mmol of diethyl zinc (Zn (C ₂ H ₅ ) ₂ ), 2.8 mmol of octylamine (C ₈ H ₁₇ NH ₂ ) bubbled with oxygen gas, and bis (trimethylsilyl) sulfide (bis (trimethylsilyl) sulfide) To prepare 1.2 mmol, 410 μl of diethyl zinc, 460 μl of octylamine, and 250 μl of bis (trimethylsilyl) sulfide are prepared.

Here, octylamine to which oxygen has been bubbled is prepared in advance by bubbling octylamine (C ₈ H ₁₇ NH ₂ ) with oxygen for 2 minutes. Note that by changing the ratio of the reaction precursor, the composition of the nanoparticles can be changed.

  As a reaction solvent, 8 g of tri-n-octylphosphine oxide (TOPO) and 4 g of hexadecylamine (HDA) are put into a reaction vessel. The mixture is heated to 300 ° C. using a mantle heater while stirring the liquid 32 with an inert gas (Ar) atmosphere using a stirrer to dissolve everything.

When the temperature of the reaction solvent reaches 300 ° C., the reaction precursor is quickly charged from each syringe. Crystal nuclei of ZnO _0.72 S _0.28 are generated by thermal decomposition of the reaction precursor. Immediately after the injection of the reaction precursor, the temperature is rapidly cooled to 200 ° C. If the temperature is kept at 300 ° C., much of the reaction precursor is used for nucleation, and nuclei of various sizes are generated with the passage of time. Rapid quenching can prevent new nucleation in the reaction solvent. Thereafter, the reaction solvent is reheated to 240 ° C., and the temperature is kept constant for 240 minutes to grow ZnO _0.72 S _0.28 . Thus, nano-sized base material particles 35 having a particle size distribution centered at 20 nm can be synthesized.

  Thereafter, the reaction vessel is naturally cooled to 100 ° C., and heat-treated at 100 ° C. for 1 hour. Thereby, the surface of the base material particles can be stabilized (surface stabilization treatment). Thereafter, the mixture is cooled to room temperature, butanol is added to the reaction solution as a coagulation inhibitor to prevent aggregation of the base material particles, and the mixture is stirred for 10 hours (anti-aggregation treatment). Purification is performed by repeating centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (TOPO) is dissolved and toluene in which the base material particles are dispersed. By repeating, unnecessary materials and solvents are completely removed (purification treatment).

As shown in FIG. 4, the ZnO _0.72 S _0.28 base material particles 35 thus obtained are etched to form nanoseed having a (0001) plane (C plane) as a specific plane. The synthesized ZnO _0.72 S _0.28 base material particles have been subjected to a surface treatment, an aggregation prevention treatment, and a purification treatment, and are in a state of being dispersed in methanol. The methanol is vaporized to concentrate the base material particles. However, if completely vaporized, the base material particles will aggregate. Therefore, a slight amount of methanol is left, and ultrapure water as a photoetching solution is added.

  Nitric acid (61% by volume) is added in order to selectively expose the (0001) plane having a specific plane orientation. The mixing ratio of the etchant is ultrapure water: nitric acid (61% by volume) = 600: 1. Oxygen is bubbled through the solution maintained at 25 ° C. for 5 minutes.

  FIG. 5 is a side view schematically showing the configuration of the optical etching apparatus. Light from a light source 41 such as a mercury lamp is supplied to a monochromator 43 via a lens 42, and the single-wavelength light is incident on the solution 33 in the flask 31 via an optical fiber 44 and a rod lens 45.

The mixed solution (etching solution) 33 after bubbling is contained in the flask 31. The etching liquid 33 is irradiated with light having an emission wavelength of 405 nm (3.06 eV) and a half width of 6 nm. This light has a wavelength sufficiently shorter than the absorption edge wavelength of the ZnO _0.72 S _0.28 base material particles. As a light source, light obtained by dispersing a mercury lamp with a monochromator is used. The ZnO _0.72 S _0.28 base material particles having different absorption edge wavelengths due to the difference in particle size absorb light and cause a photodissolution reaction, and the surface is dissolved in the photodissolution solution and the diameter gradually decreases. Go.

As the etching progresses, the absorption edge wavelength shifts to a shorter wavelength. In addition, nitric acid, which has a selective etching effect, assists the photo-etching so that a (0001) crystal plane appears. Light is irradiated until the absorption edge wavelength becomes shorter than the wavelength of irradiation light and the photolysis reaction stops. The irradiation time is 20 hours. After the etching is completed, sufficient washing with water is performed to completely replace the etching solution. In this manner, ZnO _0.72 S _0.28 nanoseed particles having a uniform size and a dominant (0001) plane (C plane) can be obtained.

Please refer to FIG. 6 ml of the prepared aqueous solution containing ZnO _0.72 S _0.28 nanoseed having dominant (0001) plane is extracted and freeze-dried. Gallium iodide (108 mg, 0.24 mmol) as a gallium source, indium iodide (165 mg, 0.36 mmol) as an indium source, and an anatase-type photocatalytic material were placed in a reaction vessel 11 containing a synthesis solvent diphenyl ether (20 ml). Titanium dioxide (50 mg) is charged. After the reaction vessel 11 is set in the synthesis apparatus 10, the residual gas is discarded using the vacuum replacement line 18 while sufficiently stirring using the stirrer 15, and high-purity nitrogen is flown using the inert gas supply line 17. Then, purging of the reaction vessel 11 is performed. Thereafter, ammonia gas is introduced into the reaction vessel 11 from the ammonia supply line 16 at a rate of 100 ml / min.

  Fine particles of titanium dioxide are preferred in order to reduce the variation in the photocatalytic effect in the synthesis solution. The use of nanoparticulate titanium dioxide is more preferable because the photocatalytic effect is enhanced. As the solvent, octyl ether, octylbenzene, octylamine, trioctylphosphine, triphenylphosphine, and the like can be used in addition to diphenyl ether. Aromatic solvents such as benzene, toluene and xylene can also be used. However, since the vapor pressure is high, it is necessary to use a container capable of sealing the solvent.

  The mixture is rapidly heated to 350 ° C. while irradiating the mixture 22 with ultraviolet light from the light irradiation device 12, and is kept at 350 ° C. for 10 hours. The synthesis takes place relatively slowly because the decomposition of ammonia takes some time. Thereafter, the synthesis is terminated by cooling to room temperature. On the way, the ammonia gas is switched to argon. To prevent coagulation of the nanoparticles, butanol is added to the reaction solution as an anticoagulant and stirred for 10 hours. Finally, purification is performed by repeating centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (diphenyl ether) is dissolved and toluene in which the nanoparticles are dispersed. Unnecessary raw materials and solvents are completely removed.

As a result, high-quality nanoparticles in which an In _0.60 Ga _0.40 N nitride semiconductor is epitaxially grown on ZnO _0.72 S _0.28 nanoseed having a (0001) plane (C plane) dominantly can be produced. In addition, it is also possible to add a capping agent at the time of synthesis. In that case, hexadecanethiol, zinc stearate, or the like may be used.

ZnO _0.72 S _0.28 nanoseed can also be selectively removed. This may be achieved by utilizing the difference in etching rate between the nitride semiconductor and the nitride semiconductor. For example, it is possible to remove ZnO _0.72 S _0.28 nanoseed using diluted hydrochloric acid or the like. Even when ZnO _0.72 S _0.28 nanoseed is stacked so as to be covered with the In _0.60 Ga _0.40 N nitride semiconductor, the crystallinity near the interface between adjacent crystal planes or near the interface is low, so that the etching solution Easily penetrates to the nanoseed surface and can be removed.

  The synthesis temperature may be a temperature at which decomposition of the ammonia gas starts even if a little. The temperature may be approximately 800 ° C. or less. Preferably it is 200-500 degreeC, More preferably, it is 250-450 degreeC from the relationship of reaction efficiency and the decomposition temperature of a solvent.

Thereby, an In _0.60 Ga _0.40 N nitride semiconductor having an average particle size of about 5 nm can be manufactured.

  In Examples 1 to 3, it was confirmed that the photocatalytic material did not adversely affect the synthesis of nitride nanoparticles. Even if the photocatalyst is contained in the final nanoparticles, there is no problem in its function.

  A comparative example using sodium amide as a nitrogen source was tested.

Comparative Example 1 (Example of producing InN using sodium amide)
All operations relating to sample preparation were performed in a glove box using vacuum-dried (140 ° C.) instruments and equipment.

  Indium iodide (165 mg, 0.36 mmol) as an indium source and sodium amide (500 mg, 12.8 mmol) as a nitrogen source were charged into a reaction vessel containing diphenyl ether (20 ml) as a synthesis solvent. After setting the reaction vessel in the synthesizer, high-purity nitrogen was passed as an inert gas while sufficiently stirring.

  The mixture was rapidly heated to 300 ° C. and kept at 300 ° C. for 1 hour. Thereafter, the mixture was cooled to room temperature to complete the synthesis. Butanol was added to the reaction solution as an anticoagulant to prevent aggregation of nanoparticles, and the mixture was stirred for 10 hours. Finally, purification was carried out by repeated centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (diphenyl ether) is dissolved and toluene in which the nanoparticles are dispersed. Unnecessary raw materials and solvents were completely removed. An InN nitride semiconductor having an average particle size of about 4.5 nm was produced.

Comparative Example 2 (Example of producing InGaN using sodium amide)
All operations relating to sample preparation were performed in a glove box using vacuum-dried (140 ° C.) instruments and equipment.

  Gallium iodide gallium iodide (108 mg, 0.24 mmol), indium source indium iodide (165 mg, 0.36 mmol), nitrogen source sodium amide were placed in a reaction vessel containing diphenyl ether (20 ml) as a synthesis solvent. (500 mg, 12.8 mmol), respectively. After setting the reaction vessel in the synthesizer, high-purity nitrogen was passed as an inert gas while sufficiently stirring.

The mixture was rapidly heated to 300 ° C. and kept at 300 ° C. for 1 hour. Thereafter, the mixture was cooled to room temperature to complete the synthesis. Butanol was added to the reaction solution as an anticoagulant to prevent aggregation of nanoparticles, and the mixture was stirred for 10 hours. Finally, purification was carried out by repeated centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (diphenyl ether) is dissolved and toluene in which the nanoparticles are dispersed. Unnecessary raw materials and solvents were completely removed. An In _0.60 Ga _0.40 N nitride semiconductor having an average particle size of about 5 nm was produced.

  When the fluorescent X-ray analysis and the high-frequency inductively coupled plasma (ICP) analysis of Comparative Examples 1 and 2 were performed, it was found that sodium was contained at about 10% with respect to the group III element (indium and gallium).

  In each of the comparative examples, when the group V material was changed to lithium amide, lithium nitride, or potassium amide, it was found that high-frequency inductively coupled plasma (ICP) analysis detected lithium or potassium at a similar level or higher.

  In Examples 1, 2, and 3, the alkali metal content was 1% or less in consideration of the measurement limit. This indicates that the incorporation of alkali metals such as sodium into nanoparticles is suppressed by using ammonia as the nitrogen source.

  The optical characteristics of the InN nitride nanoparticles of the samples prepared in Example 1 and Comparative Example 1 were compared. A dispersion in which the same amount of nanoparticles was dispersed was used for optical characteristics. For the measurement of the optical characteristics, QE-2100 (manufactured by Otsuka Electronics Co., Ltd.) was used.

  Both the sample of Example 1 and the sample of Comparative Example 1 were nanoparticles having an emission center at a wavelength of 800 nm. The luminous efficiency of the sample of Example 1 was about 1.5 times the luminous efficiency of the sample of Comparative Example 1.

  The samples prepared in Example 2, Example 3, and Comparative Example 2 were all nanoparticles having an emission center at a wavelength of 600 nm. Comparing the luminous efficiencies, the sample of Example 2 had a luminous efficiency about 1.5 times that of the sample of Comparative Example 2, and the sample of Example 3 had about twice the luminous efficiency of the sample of Comparative Example 2.

  It is considered that the reason that the luminous efficiency of the sample of Example 3 was higher than the luminous efficiency of the sample of Example 2 is that the crystallinity of the nitride nanoparticles was improved by using the nanoseed.

  If the composition ratio of In and Ga is changed, for example, the In / Ga ratio is reduced and the particle size is reduced, the emission wavelength changes to the higher energy side, and light emission up to ultraviolet light is possible. Conversely, if the In / Ga ratio is increased and the particle size is increased, the emission wavelength changes to a lower energy side, and infrared light emission is possible.

Further, although the example in which the periphery of the ZnOS core is covered with the InGaN shell is described, a ZnOS layer may be further laminated on the shell. It is also possible to stack an InAlN shell on the InGaN shell. The core may be an In _0.60 Ga _0.40 N nitride semiconductor and may be covered with an In _0.67 Al _0.33 N shell.

  The nanoparticles described above can be used as phosphors. For example, it can be used by enclosing it in an LED or a film for a backlight. There is also a possibility that the p-type layer, the light-emitting layer, and the n-type layer are stacked, and a p-side electrode and an n-side electrode are formed to have a light emitting function.

Claims (10)

  A nanoparticle having a group III element nitride region containing any of In, Ga, and Al, wherein the alkali metal content of the group III element nitride region is 1 at% or less.   The nanoparticles according to claim 1, wherein the group III element nitride region includes a photocatalytic material.   The nanoparticles according to claim 2, wherein the photocatalytic material is anatase-type titanium dioxide.   The nanoparticle according to any one of claims 1 to 3, further comprising a ZnOS nanoseed region, wherein the group III element nitride region has a shape covering the ZnOS nanoseed region.   A light source coating comprising the nanoparticles according to claim 1. In a solvent, a solution containing a raw material containing a group III element source and a photocatalyst is formed,
The solution is heated, stirred, and irradiated with light while bubbling ammonia gas in the solution to synthesize a group III element nitride.
A method for producing nitride nanoparticles.   The method for producing nitride nanoparticles according to claim 6, wherein the photocatalytic material includes at least one of anatase-type titanium oxide, brookite-type titanium oxide, zinc oxide, iron oxide, tungsten oxide, and strontium titanate.   The method for producing nitride nanoparticles according to claim 6, wherein the solvent includes at least one of diphenyl ether, octyl ether, octyl benzene, trioctyl phosphine, triphenyl phosphine, benzene, toluene, and xylene.   The method for producing nitride nanoparticles according to any one of claims 6 to 8, wherein the group III element source includes a group III element iodide, and there is no material other than the ammonia to be a nitrogen source.   The method for producing nitride nanoparticles according to claim 6, wherein a temperature at which the solution is heated is in a range of 200 ° C. to 500 ° C. 11.

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