JP6606418B2 - Quantum dot assembly manufacturing method - Google Patents

Description

  The present invention relates to a quantum dot assembly and a method for manufacturing the same, and for example, relates to a quantum dot assembly having a uniform band gap and a method for manufacturing the same even if the variation in size and composition is large. A specific effect is exhibited in a quantum dot formed of a II-VI group ZnOS semiconductor material having a ternary system or higher composition.

  Quantum dots are formed using a semiconductor material, for example, particles having an average particle size of nanometer size. Here, the average particle size refers to the median diameter when the quantum dots are observed with a transmission electron microscope, the area equivalent circle diameter of each particle is calculated, and the equivalent diameter is distributed on a number basis. .

  With respect to quantum dots made of a binary crystal of II-VI group semiconductor material, for example, in liquid phase synthesis typified by a hot injection method, those having relatively uniform sizes and compositions can be obtained (see, for example, Non-Patent Document 1) ). However, in the case of a ternary mixed crystal, controllability of size and composition is not sufficient.

  In the quantum dot, the energy gap changes depending on the size and the composition of the crystal. The energy gap changes with the size because the quantum effect appears only when the size is nanometer.

  In particular, in a ternary mixed crystal, the emission spectrum broadens due to variations in size and composition, and it is difficult to manufacture quantum dots having a narrow-band emission spectrum. In addition, it is not practical to separate and sort quantum dots having variations in size and composition after manufacturing, which leads to a significant decrease in yield and a significant increase in cost.

For example, ZnO _x S _1-x quantum dots can be synthesized by a solution method such as a hot soap method or a solvothermal method using an autoclave, or a gas phase such as sputtering. However, it is difficult to control the size and composition of the quantum dots synthesized by these methods, and the synthesized quantum dot aggregates contain different sizes and compositions of quantum dots. For this reason, the half-value width of the emission spectrum of the quantum dot aggregate is broad as 50 nm to 200 nm, and it is difficult to realize a narrow emission spectrum.

FIG. 13 is a graph showing the relationship between the O composition x and size of ZnO _x S _1-x and the emission wavelength. ZnO _x S _1-x was synthesized with a design in which the O composition x was 0.6 and the size was 4.0 nm (emission wavelength 405 nm (3.06 eV)), and the O composition x of the synthesized ZnO _x S _1- x was changed to When variation occurs in the range of 0.4 to 0.8 and the size in the range of 3.0 nm to 6.0 nm, the emission wavelength extends in the range of 335 nm to 440 nm (3.70 eV to 2.84 eV). A broadening of the emission wavelength occurs, and it is very difficult to suppress the half-value width of the emission spectrum to less than 50 nm, for example.

  Even in the core / shell type quantum dots, for example, when the shell layer is composed of mixed crystal composed of three or more elements, it is difficult to control the mixed crystal ratio. In the assembly of quantum dots, when the composition ratio of the shell layer varies for each quantum dot, the band gap energy of the shell layer also varies for each quantum dot. Therefore, even if the band gap energy of the core layer (including the case of single composition, binary composition, mixed crystal composition of ternary or higher) is controlled to be constant, the confinement effect of the core layer is quantum. Changes for each dot. That is, the wavelength spectrum of the quantum dot aggregate is broadened and it is difficult to obtain a narrow emission spectrum.

Sigma-Aldrich website (http://www.sigmaaldrich.com/japan/materialscience/nano-materials/lumidots.html)

  An object of the present invention is to provide a quantum dot assembly having a small half-value width of an emission spectrum, for example, a half-value width of less than 50 nm, and a method for producing the same.

(A) A step of preparing a plurality of quantum dots composed of ZnO _x S _1-x and having a size exceeding 10 nm, wherein the target value of the composition ratio x is 0.6, and the variation range is 0. 4 to 0.8, a step of preparing a plurality of quantum dots, and (b) photoetching the plurality of quantum dots prepared in the step (a) to reduce the diameter of the plurality of quantum dots. Provides a method for producing an assembly of quantum dots having the step of uniformizing the band gap energy of the plurality of quantum dots.

  In the above-described photoetching, a plurality of quantum dots with varying band gaps due to variations in mixed crystal composition and / or size are introduced into an etchant and irradiated with light corresponding to the target band gap. The quantum dots having a narrower band gap than the irradiation light are dissolved by the excited carriers, and the band gap is widened. On the other hand, quantum dots having a wider band gap than the irradiation light do not absorb light and therefore do not dissolve. Thereby, the band gap of the aggregate | assembly of the quantum dot from which composition and size varied can be arrange | equalized uniformly, for example.

  FIG. 14 conceptually shows changes in quantum dots due to photoetching.

  Quantum dots having variations in composition and / or size are made uniform, for example, to a certain size by etching processing by light control. Etching proceeds only with quantum dots of a size that absorbs irradiated light. Further, the etching stops when the size of the quantum dot is reduced by the etching and the irradiation light is transmitted. In photoetching, quantum dots can be controlled to a desired constant size, for example, by selecting the wavelength of light.

  For example, when the composition of the ternary mixed crystal is single, the size and the energy gap are both constant. When the composition varies, the size varies, but the energy gap is constant.

  According to the present invention, it is possible to provide a quantum dot aggregate having a small half-value width of an emission spectrum, for example, a half-value width of less than 50 nm, and a method for producing the same.

FIG. 1A is a graph showing the relationship between the O composition x and the band gap energy in a mixed crystal of ZnO _x S _1-x , and FIG. 1B shows the relationship between the sizes of the ZnO and ZnS crystals and the emission wavelength (band gap energy). It is a graph to show. FIG. 2 is a schematic flowchart showing a method for manufacturing a quantum dot assembly according to the first embodiment. FIG. 3A is a schematic view of a production apparatus for producing quantum dots (base materials) using a hot injection method, and FIG. 3B is an assembly of quantum dot base materials (ZnO _x S _1-x nanoparticle aggregates). FIG. 4A is a schematic diagram of a photoetching apparatus, FIG. 4B is a schematic diagram of a quantum dot assembly (ZnO _x S _1-x nanoparticle aggregate) after light irradiation, and FIG. 4C is a diagram after light irradiation. 2 is a graph showing the relationship between the O composition x and size of the quantum dot assembly and the band gap energy (emission wavelength). FIG. 5 is a diagram for explaining band lineup of In _y Al _1-y N (0 <y <1) and ZnO _x S _1-x (0 <x <1). FIG. 6A is a schematic flowchart showing a method for manufacturing a quantum dot assembly according to the second embodiment, and FIG. 6B shows a quantum dot (core / shell structure) assembly manufactured by the manufacturing method according to the second embodiment. It is a schematic sectional drawing which shows. FIG. 7 is a schematic flowchart showing a method for manufacturing a quantum dot assembly according to the third embodiment. FIG. 8 is a cross-sectional view of a quantum dot manufactured by the manufacturing method according to the third embodiment and a diagram showing a target value of a band structure. FIG. 9 is a schematic flowchart showing a method for manufacturing a quantum dot assembly according to the fourth embodiment. FIG. 10 is a cross-sectional view of a quantum dot manufactured by the manufacturing method according to the fourth embodiment and a diagram showing a target value of a band structure. FIG. 11 is a schematic flowchart showing a method for manufacturing a quantum dot assembly according to the fifth embodiment. FIG. 12 is a cross-sectional view of a quantum dot manufactured by the manufacturing method according to the fifth embodiment and a diagram showing a target value of the band structure. FIG. 13 is a graph showing the relationship between the O composition x and size of ZnO _x S _1-x and the emission wavelength. FIG. 14 is a diagram conceptually showing changes in quantum dots due to photoetching.

A light-emitting nanoparticle (quantum dot) formed using a ternary ZnO _x S _1-x (0 <x <1) that is a II-VI group compound semiconductor will be described as an example.

First, the ZnO _x S _1-x mixed crystal will be briefly described.

FIG. 1A is a graph showing the relationship between O composition x and band gap energy in a mixed crystal of ZnO _x S _1-x . This figure shows the relationship between the particle sizes of 3 nm, 4 nm, 6 nm, and 20 nm. The curves are for 3 nm, 4 nm, 6 nm, and 20 nm in order from the top. A circle represents a position where x = 0.6 and a particle size of 4.0 nm. The range of the variation of the O composition x is 0.4 to 0.8, the range of the size variation is 3.0 nm to 6.0 nm, and the range is shown deeply. In the ZnO _x S _1-x mixed crystal, the composition variation is large.

For example, according to the prior art, when the O composition x = 0.6 in ZnO _x S _1-x and the target size is 4.0 nm, the O composition x in the range of 0.4 to 0.8, And the nanoparticle aggregate | assembly in which the particle | grains with the size of the range of 3.0 nm-6.0 nm are mixed is manufactured. (In the ZnO _x S _1-x mixed crystal, since the composition variation and the bowing effect are large, the synthesized nanoparticles are mainly composed of O composition x = 0.6 and size 4.0 nm. = 0.4, size 3.0 nm to O composition 0.8, size 6.0 nm nanoparticles)
When the variation of the O composition x is 0.4 to 0.8 and the size variation is 3.0 nm to 6.0 nm, the band gap energy is 2.84 eV to 3.65 eV (emission wavelength: 440 nm to 340 nm). Become.

The band gap energies of ZnO and ZnS are 3.2 eV and 3.8 eV, respectively, and the bowing parameter b is b = 3.0. A ZnO _x S _1-x (x = 0.6) mixed crystal having a particle size of 4.0 nm has a large bowing parameter, and therefore has a lower band gap energy than a binary crystal of ZnO and ZnS.

FIG. 1B is a graph showing the relationship between the size of ZnO and ZnS crystals and the emission wavelength (bandgap energy). The right curve represents the relationship between ZnO and the left curve represents ZnS. Since the ZnO _x S _1-x (0 <x <1) mixed crystal takes a value between the two curves shown in the figure, when the size is reduced to 20 nm or less, particularly 10 nm or less, the confinement of carriers due to the quantum effect causes The emission wavelength shifts to the shorter wavelength side (band gap energy is higher energy side).

  Note that the band gap energies of ZnO and ZnS (ZnO is 3.2 eV and ZnS is 3.8 eV) correspond to wavelengths of less than 390 nm and 330 nm, respectively.

From FIG. 1A and FIG. 1B, by controlling the mixed crystal composition and size of ZnO _x S _1-x (0 <x <1), low energy of about 2.7 eV that cannot be realized with a binary crystal of ZnO or ZnS ( 1A to high energy of about 6.0 eV (see FIG. 1B. In the case of ZnO _x S _1-x close to ZnS (x is close to 0) (0 <x <1), the quantum effect It can be said that the band gap can be changed up to 205 nm (the wavelength can be changed to less than 205 nm (energy conversion 6.0 eV)).

  FIG. 2 is a schematic flowchart showing a method for manufacturing a quantum dot assembly according to the first embodiment.

  In the first embodiment, first, a quantum dot base material is prepared and synthesized as an example (step S101). Next, processing for controlling the size of the quantum dot base material prepared (synthesized) in step S101 is performed. Specifically, the prepared quantum dot base material is etched by selective photoetching (step S102).

  In the particle processing in the selective photoetching step (step S102), for example, quantum dots (base material) are dispersed in a solution, and the dispersion is irradiated with narrowband light. As a result, only the large particles are etched by absorbing and activating light. Quantum dots of a size that absorbs light undergoes etching and becomes smaller in size. As the size decreases, the band gap increases due to the quantum effect. When the band gap is larger than the energy of the irradiation light, light is transmitted without being absorbed. Etching stops when light is transmitted. By the selective photoetching step (step S102), the band gap of each quantum dot is made uniform in the quantum dot assembly, and for example, only the quantum dots having the same band gap, that is, the same emission wavelength can be selectively synthesized. It becomes possible.

  In the first example, the target value of the O composition x of the finally produced quantum dots was 0.60, and the target value of the size was 4.0 nm.

  In the embodiment, a spherical quantum dot base material is formed. The quantum dots after selective photoetching are also spherical.

  FIG. 3A is a schematic diagram of a manufacturing apparatus that manufactures quantum dots (base material) using a hot injection method. The quantum dot base material synthesis step (step S101) will be described with reference to FIG.

  A quartz flask (300 cc) is prepared as a reaction vessel. In addition to the outlet, the flask is equipped with a port that can be replaced with an inert gas and a dedicated port that can inject the reaction precursor. TOPO (tri-n-octylphosphine oxide) and HDA (Hexadecylamine), which are reaction solvents, are placed in a flask and heated to 300 ° C. and dissolved in an inert gas atmosphere. For example, 8 g of TOPO, 4 g of HDA, and argon (Ar) as an inert gas are used. Stir with a stirrer to prevent uneven heating.

Next, as reaction precursors, diethylzinc (Zn (C ₂ H ₅ ) ₂ ) encapsulated with an inert gas (eg Ar), octylamine (C ₈ H ₁₇ NH ₂ ) bubbled with oxygen, and Bis (trimethylsilyl) ) Prepare each syringe filled with Sulfide (thiobis). By bubbling with oxygen, oxygen is taken into octylamine (C ₈ H ₁₇ NH ₂ ). For example, diethylzinc (Zn (C ₂ H ₅ ) ₂ ) is 4.0 mmol, oxygen-incorporated octylamine (C ₈ H ₁₇ NH ₂ ) is 2.4 mmol, and Bis (trimethylsilyl) Sulfide (thiobis) is 1.6 mmol. Adjust so that By this adjustment, ZnO _0.60 S _0.40 mixed crystal nanoparticles (O composition x = 0.60 is a target value) are synthesized in the first example. In order to synthesize ZnO _x S _1-x mixed crystal nanoparticles having a different O composition x, the above-described diethyl zinc (Zn (C ₂ H ₅ ) ₂ ), octylamine (C ₈ H ₁₇ NH ₂ ) and Bis (trimethylsilyl) Sulfide (thiobis) ratio may be changed.

When the reaction solvent reaches the reaction temperature, the reaction precursor is quickly put into the flask from each syringe. By the thermal decomposition of the reaction precursor, a core crystal of ZnO _x S _1-x is generated. If left as it is, most of the reaction precursor is consumed for nucleation, and nuclei of various sizes are generated with time. Therefore, immediately after the reaction precursor is injected, the temperature of the flask is rapidly cooled to 200 ° C. . Thereafter, the reaction solvent is reheated to 240 ° C., kept at a constant temperature for 40 minutes, and ZnO _x S _1-x is grown.

  The flask is naturally cooled to 100 ° C. and then held for 1 hour. As a result, the surface of the nanoparticles can be stabilized. This is called stabilization processing. Thereafter, butanol is added as a coagulation inhibitor to the reaction solution cooled to room temperature in order to prevent aggregation of the nanoparticles, and is maintained for 10 hours. This is called aggregation prevention processing. Finally, it is purified by repeating centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (TOPO) is dissolved and toluene in which nanoparticles are dispersed. Thereby, unnecessary raw materials and solvents are removed. This is called a purification process.

In this way, a large number of ZnO _0.60 S _0.40 nanoparticles (O composition x = 0.60 is the target value) are synthesized in the quantum dot base material synthesis step (step S101). FIG. 3B shows a schematic diagram of an aggregate of quantum dot base materials (ZnO _x S _1-x nanoparticle aggregate).

  In an embodiment, for example, all nanoparticles (matrix) are synthesized to a size larger than the size of the target particle. In the first example in which the target value of the O composition x of the finally produced quantum dot is 0.60 and the target value of size is 4.0 nm, the nanoparticles (base material) exceed 4.0 nm. Synthesized to a size, for example, a size exceeding 10 nm, or a size exceeding 20 nm.

  However, in the quantum dot base material (nanoparticle), there is a variation in the mixed crystal composition and the particle size (for example, there is a size variation in a range exceeding the target size. When nanoparticles exceeding 0.0 nm are synthesized, the size varies within a range exceeding 4.0 nm.) Therefore, the emission wavelength becomes wider (the half-value width of the emission spectrum is, for example, 50 nm or more).

  FIG. 4A is a schematic view of a photoetching apparatus. The selective photoetching process (step S102) will be described with reference to FIG.

The quantum dot base material (ZnO _0.60 S _0.40 nanoparticles) synthesized in step S101 has been subjected to surface stabilization treatment, aggregation prevention treatment, and purification treatment, and is in a state of being dispersed in methanol. Therefore, methanol is evaporated and the nanoparticles are concentrated. At this time, if the methanol is completely vaporized, the nanoparticles are aggregated. Therefore, it is preferable to leave the methanol slightly. Ultrapure water, which is a photo-etching solution, is added to the methanol / nanoparticle solution. Maintain at 25 ° C. and bubble with oxygen for 5 minutes.

After bubbling, it is transferred to a closed container (flask in FIG. 4A), and has an emission wavelength of 405 nm (3.06 eV) and a half-value width that is light having a wavelength sufficiently shorter than the absorption edge wavelength of ZnO _0.60 S _0.40 nanoparticles. The etching solution is irradiated with 6 nm light. A mercury lamp is used as the light source, and the light emitted from the mercury lamp is used after being separated by a monochromator.

In a ZnO _0.60 S _0.40 quantum dot assembly in which the absorption edge wavelength of the band gap varies due to variations in the mixed crystal composition and particle size, particles having a size that absorbs light absorb light. A photolysis reaction occurs, the surface dissolves in the photolysis solution, and the diameter gradually decreases. For this reason, as the etching proceeds, the absorption edge wavelength of each particle to be etched shifts to the short wavelength side. Light is irradiated until the absorption edge wavelength of the quantum dot aggregate becomes shorter than the wavelength of the irradiation light and the photodissolution reaction stops. Light irradiation is performed for 20 hours, for example.

FIG. 4B shows a schematic diagram of a quantum dot aggregate (ZnO _x S _1-x nanoparticle aggregate) after light irradiation. In the quantum dot aggregate after the light irradiation, quantum dots having different mixed crystal compositions are mixed. There is also a particle size distribution.

  FIG. 4C shows the relationship between the O composition x and size of the quantum dot aggregate after light irradiation and the band gap energy (emission wavelength). The four curves in this figure are the same as those in FIG. 1A. After the light irradiation, a quantum dot aggregate having an O composition x = 0.60 and a size of 4.0 nm, an O composition x = 0.80, a size 4.0 nm to an O composition 0.40, and a size 6.0 nm. It becomes.

  However, in the quantum dot aggregate after light irradiation, the emission wavelength of the quantum dots is made uniform. For example, an aggregate of nanoparticles having a band gap energy of 3.06 eV equal to the energy of the irradiation light is formed.

  As described above, only the nano-semiconductor particles having a constant emission wavelength are produced by the quantum effect by the selective photoetching in Step S102, for example, the O composition x varies in the range of 0.40 to 0.80. be able to. Even if the composition is different, the size is reduced by photoetching the nanoparticles (base material) having a size exceeding the target size, and a quantum dot aggregate having a target wavelength can be obtained.

By the selective photoetching step in step S102, for example, ZnO _0.60 S _0.40 mixed crystal nanoparticles (quantum dots) having the same band gap, that is, the same emission wavelength can be manufactured.

  In addition, the quantum dot aggregate after light irradiation (after selective photoetching) has a band gap larger than the band gap energy of the bulk mixed crystal due to the quantum effect. Have energy.

The emission spectrum of the aqueous solution in which the quantum dot aggregate (ZnO _0.60 S _0.40 nanoparticle aggregate) manufactured by the manufacturing method according to the first example was dispersed was evaluated using a spectrophotometer. An emission spectrum was observed using an excitation wavelength of 365 nm, and a half width of 45 nm of the emission spectrum was obtained.

In the first embodiment, the quantum dots are formed of a ternary semiconductor material having a band gap smaller than that of the binary system. In addition, quantum dots having different mixed crystal compositions are mixed in the quantum dot aggregate (ZnO _0.60 S _0.40 nanoparticle aggregate) manufactured by the manufacturing method according to the first embodiment. However, the band gap of each particle is made uniform, and the half-value width of the emission spectrum as the quantum dot aggregate is less than 50 nm (45 nm). Thus, in the aggregate | assembly of the quantum dot (nanoparticle fluorescent substance) manufactured with the manufacturing method of the quantum dot by 1st Example, the half value width of an emission spectrum is small (narrow spectrum narrowing of an emission wavelength is implement | achieved. ).

  The light applied to the quantum dots (base material) in the photoetching step (step S102) is, for example, light having a wavelength corresponding to the band gap (emission wavelength) to be finally obtained. In order to perform etching uniformly and in a short time, light having a narrow wavelength width and strong intensity is desirable. Specifically, monochromatic light obtained by passing light derived from a continuous light source such as a laser (continuous wave) or a mercury lamp through a monochromator or a filter can be suitably used. Light is guided to a container containing nanoparticles by an optical fiber, and irradiated to the quantum dots.

  In the embodiment, water (ultra-pure water) is used as the etching solution, but it is not particularly limited as long as the selection ratio of the etching rate between light irradiation and non-irradiation can be taken. In order to adjust the etching rate, the pH and the temperature of the etching solution may be adjusted.

  The quantum dot manufacturing method according to the embodiment uses the quantum effect that the band gap changes depending on the particle size. For this reason, it is desirable that the size of the quantum dot finally obtained through the selective photoetching process in step S102 be within a size region where the effect can be obtained sensitively. Referring to FIG. 1B, it can be seen that as the size decreases, the amount of change in the band gap (wavelength) increases, that is, the quantum effect is obtained with sensitivity. The size (average particle size) of the finally obtained quantum dots may be 20 nm or less, more preferably 10 nm or less.

In the step of synthesizing the quantum dot base material in step S101, the ZnO _x S _1-x particles that are the quantum dot base material are synthesized into a size larger than the finally required quantum dots. That is, for example, the size is synthesized to exceed 10 nm or 20 nm. There are variations in composition and size between quantum dots (base material particles). For example, the O composition x varies in the range of 0.40 to 0.80.

  In the first embodiment, the O composition is 0.60 and the S composition is 0.40. However, the present invention is not limited to this.

Then, the manufacturing method of the quantum dot aggregate | assembly by 2nd Example is demonstrated. The quantum dot assembly according to the second embodiment includes a core layer formed using a ternary In _y Al _1-y N (0 <y <1) crystal that is a III-V group compound semiconductor, and a II-VI group compound. It is a type II type light-emitting nanoparticle aggregate having a shell layer formed using a ternary ZnO _x S _1-x (0 <x <1) crystal that is a semiconductor. By forming the shell layer, for example, a highly reliable, chemically and thermally stable quantum dot can be obtained. Type II is a structure that utilizes interband transitions between adjacent materials and has different spatial positions where electrons and holes are confined.

First, with reference to FIG. 5, the band lineup of In _y Al _1-y N (0 <y <1) and ZnO _x S _1-x (0 <x <1) will be briefly described.

For example, it is ideal when the core layer is formed of In _y Al _1-y N (for example, y = 0.67) and the shell layer is formed of ZnO _x S _1-x (for example, x = 0.75). Type II junction with band lineup as shown in this figure. Unlike type I junctions, the luminescence transition occurs between the conduction band of ZnO _x S _{1-x and} the valence band of In _y Al _1-y N. Therefore, it is particularly suitable for light emission in a region having a small emission energy such as an infrared region.

However, ternary mixed crystal ZnO _x S _1-x (0 <x <1) is difficult to control the mixed crystal composition. For example, assuming that the target O composition is x = 0.75, assuming that a composition variation of about ± 30% occurs, a shell layer having an O composition range x of about 0.5 to 0.9 can be formed. As a result, the energy difference ΔEc in the valence band between the In _y Al _1-y N core layer and the ZnO _x S _1-x shell layer is 0 <ΔEc <0.49 eV. Further, the energy difference ΔEv between the conduction bands greatly changes as 0.95 eV <ΔEv <1.35 eV. In type II junctions, light emission occurs between the energy levels of the core and the shell. Therefore, a change in energy levels due to variations in composition ratio is a serious problem.

  FIG. 6A is a schematic flowchart showing a method for manufacturing a quantum dot assembly according to the second embodiment.

In the second embodiment, first, an In _y Al _1-y N core layer is formed (step S201a). Next, a ZnO _x S _1-x shell layer is formed so as to be stacked on the In _y Al _1-y N core layer formed in step S201a (step S201b). Then, the ZnO _x S _1-x shell layer is etched by selective photoetching (step S202).

  Step S201a and step S201b of the second embodiment are steps corresponding to step S101 of the first embodiment. Further, step S202 of the second embodiment is a step corresponding to step S102 of the first embodiment.

In step S201a, an In _y Al _1-y N core layer is synthesized using a liquid phase method such as a hot soap method. In step S201b, ZnO _x S _1-x wrapping the In _y Al _1-y N core layer is formed in a size larger than the final target size (thickness). For example, it is formed in a size (thickness) exceeding 10 nm or 20 nm. In ZnO _x S _1-x formed in step S201b, for example, composition variation exists in a range of approximately ± 30% with respect to the target composition.

In step S202, the etching solution including the core / shell structure formed in steps S201a and S201b, for example, water, is irradiated with light having an emission wavelength of 405 nm (3.06 eV) and a half-value width of 6 nm, as in the first embodiment. To do. In a ZnO _x S _1-x shell layer in which variation exists with a size (thickness) exceeding, for example, 10 nm by light irradiation, etching proceeds at a size that absorbs light, and the size becomes smaller (thinner). On the other hand, as the etching progresses and the size becomes smaller (thinner), the energy increases due to the quantum effect and light is transmitted. Etching stops when light is transmitted. By the selective photoetching step in step S202, a ZnO _x S _1-x shell layer made of, for example, ZnO _x S _1-x having the same band gap energy can be formed.

  FIG. 6B shows a schematic cross-sectional view of a quantum dot (core / shell structure) assembly manufactured by the manufacturing method according to the second embodiment. For example, quantum dots having different diameters and shell thicknesses are mixed in the quantum dot assembly manufactured by the manufacturing method according to the second embodiment. However, the band gap energy of the shell layer of each quantum dot is constant, for example.

In the assembly of the core / shell structure (ZnO _x S _1-x shell layer) manufactured by the manufacturing method according to the second embodiment, the same effects as the quantum dot assembly manufactured by the manufacturing method according to the first embodiment Is played. Furthermore, according to the manufacturing method according to the second embodiment, since the band gap energy of the shell layer can be made constant, type II type using a ZnO _x S _1-x shell layer in which various compositions are mixed. In the luminescent nanoparticle, a stable luminescence transition is possible.

FIG. 7 is a schematic flowchart showing a method for manufacturing a quantum dot assembly according to the third embodiment. The quantum dots manufactured in the third example are core-shell type quantum dots (light emission) having a structure in which a II-VI group semiconductor material ternary ZnO _x S _1-x (0 <x <1) core is covered with an AlN shell. Nanoparticles).

In the third embodiment, first, a quantum dot base material is formed, and the synthesized quantum dot base material is etched by selective optical etching to form a ZnO _x S _1-x core layer (step S301). Next, an AlN shell layer is formed on the ZnO _x S _1-x core layer formed in step S301 (step S302). Step S301 of the third embodiment is a step corresponding to steps S101 and S102 of the first embodiment.

FIG. 8 shows a cross-sectional view of a quantum dot manufactured by the manufacturing method according to the third embodiment and a target value of the band structure. In the third example, a structure in which a ZnO _0.60 S _0.40 core having a diameter of 2.0 nm was covered with an AlN shell having a thickness of 3.0 nm was targeted.

In the third embodiment, first, a ZnO _x S _1-x core layer is formed in the same procedure as in the first embodiment.

Next, an AlN shell layer is deposited on the ZnO _x S _1-x core layer. At this time, for example, a toluene solution in which ZnO _0.60 S _0.40 nanoparticles (core particles) prepared by the same procedure as in the first embodiment is dispersed is used. In addition, the following operation and synthesis | combination in 3rd Example are implemented in a glove box using the glass product and apparatus which were vacuum-dried (140 degreeC).

Together with 6 ml of a toluene solution in which ZnO _0.60 S _0.40 nanoparticles are dispersed, aluminum iodide (171 mg, 0.41 mmol) as a source of aluminum, sodium amide (500 mg, 12.8 mmol) as a source of nitrogen An aqueous solution (20 ml) containing hexadecanethiol (380 μl, 1.0 mmol) as a capping agent, zinc stearate (379 mg, 0.6 mol) and ZnO _0.60 S _0.40 nanoparticles was added to diphenyl ether (20 ml) as a solvent. ) Into the flask containing. Heat to 100 ° C. in an inert gas atmosphere and keep warm until there is no separate layer of water and other solvents. When the separated layer disappears, the reaction solution is heated to 225 ° C. and kept at 225 ° C. for 60 minutes. The reaction vessel is naturally cooled to 100 ° C., and then held for 1 hour. As a result, the surface of the nanoparticles can be stabilized. Thereafter, butanol is added as a coagulation inhibitor to the reaction solution cooled to room temperature in order to prevent aggregation of the nanoparticles, and stirred for 10 hours. Finally, it is purified by repeated centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (TOPO) is dissolved and toluene in which nanoparticles are dispersed. Thereby, unnecessary raw materials and solvents are removed.

Through such a procedure, nanoparticles in which a shell layer made of AlN is grown on a ZnO _0.60 S _0.40 core layer can be obtained.

The emission spectrum of the toluene solution in which ZnO _0.60 S _0.40 / AlN nanoparticles produced by the production method according to the third example was dispersed was evaluated using a spectrophotometer. An emission spectrum was observed using an excitation wavelength of 365 nm, and a half width of 45 nm of the emission spectrum was obtained.

Also in the quantum dot assembly (ZnO _0.60 S _0.40 / AlN nanoparticle assembly) manufactured by the manufacturing method according to the third embodiment, for example, the quantum dot _assembly manufactured by the manufacturing method according to the second embodiment The same effect is produced.

In the third embodiment, the shell layer is made of AlN, but is not limited to this. For example, an In _w Al _1-w N (0 <w <1) shell may be used. This will be described in the fifth embodiment.

FIG. 9 is a schematic flowchart showing a method for manufacturing a quantum dot assembly according to the fourth embodiment. The quantum dots manufactured in the fourth example are formed of a ternary ZnO _x S _1-x (0 <x <1) with a III-V group semiconductor material ternary In _z Ga _1-z N (0 <z <1) core. ) Type I core-shell quantum dots (light emitting nanoparticles) having a shell-coated structure. Type I is a structure in which a large band gap material is sandwiched between small band gap materials, and both electrons and holes are confined in a semiconductor material having a small band gap.

In the fourth example, first, an In _z Ga _1-z N nanoparticle base material is synthesized (step S401). Next, the In _z Ga _1-z N nanoparticle base material synthesized in step S401 is etched by selective photoetching (step S402) to form an In _z Ga _1-z N core layer. Further, a ZnO _x S _1-x layer is deposited on the In _z Ga _1-z N core layer formed in step S402 (step S403). Then, the ZnO _x S _1-x layer deposited in step S403 is etched by selective photoetching (step S404), and a ZnO _x S _1-x shell layer is formed on the In _z Ga _1-z N core layer. To do. Steps S401 and S403 of the fourth embodiment are steps corresponding to step S101 of the first embodiment, and steps S402 and S404 are steps corresponding to step S102 of the first embodiment.

FIG. 10 shows a cross-sectional view of a quantum dot manufactured by the manufacturing method according to the fourth embodiment and a target value of the band structure. In the fourth example, a structure in which an In _0.80 Ga _0.20 N core having a diameter of 1.5 nm was covered with a ZnO _0.05 S _0.95 shell having a thickness of 3.0 nm was targeted.

First, a manufacturing process (step S401) of the In _0.80 Ga _0.20 N nanoparticle base material will be described. In addition, the following operation and synthesis | combination in 4th Example are implemented in a glove box using the glass product and apparatus which were vacuum-dried (140 degreeC).

Gallium iodide (54 mg, 0.12 mmol) as a source of gallium, Indium iodide (220 mg, 0.48 mmol) as a source of indium, Sodium amide (500 mg, 12.8 mmol) as a source of nitrogen, Hexadecanethiol (380 μl, 1.0 mmol) as a capping agent and zinc stearate (379 mg, 0.6 mol) are charged into a flask containing diphenyl ether (20 ml) as a solvent. The mixture is rapidly heated to 225 ° C and held at 225 ° C for 60 minutes. Thereafter, the reaction vessel is naturally cooled to 100 ° C. and then held for 1 hour. As a result, the surface of the nanoparticles can be stabilized. Thereafter, butanol is added as an anticoagulant to the reaction liquid cooled to room temperature to prevent aggregation of the nanoparticles and stirred for 10 hours. Finally, it is purified by repeated centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (TOPO) is dissolved and toluene in which nanoparticles are dispersed. Thereby, unnecessary raw materials and solvents are removed. Through such a procedure, an In _0.80 Ga _0.20 N nanoparticle base material is obtained.

The In _0.80 Ga _0.20 N nanoparticle base material synthesized in step S401 is in a state of being dispersed in methanol. Therefore, methanol is evaporated and the nanoparticles are concentrated. At this time, if the methanol is completely vaporized, the nanoparticles are aggregated. Therefore, it is preferable to leave the methanol slightly. Ultrapure water, which is a photo-etching solution, is added to the methanol / nanoparticle solution. Maintain at 25 ° C. and bubble with oxygen for 5 minutes.

After bubbling, the light is transferred to a sealed container and irradiated with light having an emission wavelength of 405 nm (3.06 eV) and a half-value width of 6 nm, which is light sufficiently shorter than the absorption edge wavelength of the In _0.80 Ga _0.20 N nanoparticle matrix. (Step S402). A mercury lamp is used as the light source, and the light emitted from the mercury lamp is used after being separated by a monochromator. The In _0.80 Ga _0.20 N nanoparticle base material, which has variations in the absorption edge wavelength of the band gap due to the mixed crystal composition and size variation, absorbs light and causes a photodissolution reaction, and the surface is a photodissolved solution. Dissolves in the solution and gradually decreases in diameter. For this reason, as the etching proceeds, the absorption edge wavelength shifts to the short wavelength side. Light is irradiated until the absorption edge wavelength of the In _0.80 Ga _0.20 N nanoparticle matrix becomes shorter than the wavelength of the irradiation light and the photodissolution reaction stops. Light irradiation is performed for 20 hours, for example.

A number of In _z Ga _1-z N nanoparticles (core layer) formed in step S402 are nanoparticles (quantum dots) having an emission wavelength equal to each other, for example, although there are mixed crystal compositions and size distributions. is there.

  Thereafter, the aqueous solution in which the quantum dots are dispersed is freeze-dried to obtain a powder containing only the quantum dots, and is dispersed in octylamine using an ultrasonic disperser.

Subsequently, the step of depositing a ZnO _0.05 S _0.95 shell layer on the In _0.80 Ga _0.20 N core layer (step S403) will be described.

  A quartz flask (300 cc) is prepared as a reaction vessel. In addition to the outlet, the flask is equipped with a port that can be replaced with an inert gas and a dedicated port that can inject the reaction precursor. TOPO and HDA, which are reaction solvents, are placed in a flask and heated to 300 ° C. and dissolved in an inert gas atmosphere. For example, 8 g of TOPO, 4 g of HDA, and argon (Ar) as an inert gas are used. Stir with a stirrer to prevent uneven heating.

Next, as reaction precursors, diethylzinc (Zn (C ₂ H ₅ ) ₂ ) encapsulated with an inert gas (eg Ar), octylamine (C ₈ H ₁₇ NH ₂ ) incorporating oxygen, and Bis (trimethylsilyl ) Prepare syringes filled with a solution containing Sulfide (bis (trimethylsilyl) sulfide) and In _0.80 Ga _0.20 N nanoparticles. Incorporation of oxygen into octylamine (C ₈ H ₁₇ NH ₂ ) is performed by bubbling oxygen for 2 minutes. 4.0 mmol of diethyl zinc (Zn (C ₂ H ₅ ) ₂ ), 0.2 mmol of octylamine bubbling oxygen (C ₈ H ₁₇ NH ₂ ), 3 of Bis (trimethylsilyl) Sulfide (bis (trimethylsilyl) sulfide) Adjust to 8 mmol. Also, 2.0 ml of a solution containing In _0.80 Ga _0.20 N nanoparticles is prepared.

When the reaction solvent reaches the reaction temperature of 225 ° C., the reaction precursor is dropped from each syringe. The dropping speed is one drop every 30 seconds. After all of the reaction precursor has been added, the flask is cooled to 100 ° C. and incubated for 1 hour for annealing. As a result, the surface of the nanoparticles can be stabilized. Thereafter, the mixture is cooled to room temperature, butanol is added as an anticoagulation agent for preventing aggregation of nanoparticles, and the mixture is stirred for 10 hours. Finally, purification is repeated by repeated centrifugation (4000 rpm, 10 minutes) using dehydrated methanol in which the solvent (TOPO) is dissolved and toluene in which nanoparticles are dispersed. Thereby, unnecessary raw materials and solvents are removed. Thus, In _0.80 Ga _0.20 N / ZnO _0.05 S _0.95 nanoparticles are formed.

In _0.80 Ga _0.20 N / ZnO _0.05 S _0.95 nanoparticles are in a state of being dispersed in methanol. Therefore, methanol is evaporated and the nanoparticles are concentrated. At this time, if the methanol is completely vaporized, the nanoparticles are aggregated. Therefore, it is preferable to leave the methanol slightly. Ultrapure water, which is a photo-etching solution, is added to the methanol / nanoparticle solution. Maintain at 25 ° C. and bubble with oxygen for 5 minutes.

After bubbling, it is transferred to a sealed container and irradiated with light having an emission wavelength of 405 nm (3.06 eV) and a half-value width of 6 nm, which is light having a wavelength sufficiently shorter than the absorption edge wavelength of the ZnO _0.05 S _0.95 layer (step S404). ). A mercury lamp is used as the light source, and the light emitted from the mercury lamp is used after being separated by a monochromator. The ZnO _0.05 S _0.95 layer, which has variations in the absorption edge wavelength of the band gap due to the mixed crystal composition and size variation, absorbs light and causes a photodissolution reaction, and the surface gradually dissolves in the photodissolving solution. It becomes thinner. For this reason, as the etching proceeds, the absorption edge wavelength shifts to the short wavelength side. Light is irradiated until the absorption edge wavelength of the ZnO _0.05 S _0.95 layer becomes shorter than the wavelength of the irradiation light and the photodissolution reaction stops. Light irradiation is performed for 20 hours, for example.

In _0.80 Ga _0.20 N / ZnO _0.05 S _0.95 nanoparticles produced by the method according to the fourth embodiment have, for example, mixed crystal composition and size distribution, but have mutually equal emission wavelengths. Nanoparticles with

The emission spectrum of the toluene solution in which In _0.80 Ga _0.20 N / ZnO _0.05 S _0.95 nanoparticles produced by the production method according to the fourth example was dispersed was evaluated using a spectrophotometer. An emission spectrum was observed using an excitation wavelength of 365 nm, and a half width of 45 nm of the emission spectrum was obtained.

The quantum dot aggregate (In _0.80 Ga _0.20 N / ZnO _0.05 S _0.95 nanoparticle aggregate) manufactured by the manufacturing method according to the fourth embodiment is also manufactured by the manufacturing method according to the second embodiment. The same effect as that of the manufactured quantum dot aggregate is exhibited.

FIG. 11 is a schematic flowchart showing a method for manufacturing a quantum dot assembly according to the fifth embodiment. The quantum dots manufactured in the fifth example are II-VI group semiconductor material ternary ZnO _x S _1-x (0 <x <1) core with III-V group semiconductor material ternary In _w Al _1-w N. (0 <w <1) Type II type core-shell type quantum dots (light emitting nanoparticles) having a structure covered with a shell.

In the fifth example, first, a ZnO _x S _1-x nanoparticle base material is synthesized (step S501). Next, selective optical etching is performed on the ZnO _x S _1-x nanoparticle base material synthesized in step S501 (step S502) to form a ZnO _x S _1-x core layer. Further, an In _w Al _1-w N layer is deposited on the ZnO _x S _1-x core layer formed in step S502 (step S503). Then, selective photo-etching is performed on the In _w Al _1-w N layer deposited in step S503 (step S504), and the In _w Al _1-w N shell layer is formed on the ZnO _x S _1-x core layer. Form. Steps S501 and S503 of the fifth embodiment are steps corresponding to step S101 of the first embodiment, and steps S502 and S504 are steps corresponding to step S102 of the first embodiment.

FIG. 12 shows a cross-sectional view of a quantum dot manufactured by the manufacturing method according to the fifth embodiment and a target value of the band structure. In the fifth example, a structure in which a ZnO _0.75 S _0.25 core having a diameter of 1.0 nm was covered with an In _0.67 Al _0.33 N shell having a thickness of 3.0 nm was targeted.

First, a synthesis step (step S501) of the ZnO _0.75 S _0.25 nanoparticle base material will be described.

  A quartz flask (300 cc) is prepared as a reaction vessel. In addition to the outlet, the flask is equipped with a port that can be replaced with an inert gas and a dedicated port that can inject the reaction precursor. TOPO and HDA, which are reaction solvents, are placed in a flask and heated to 300 ° C. and dissolved in an inert gas atmosphere. For example, 8 g of TOPO, 4 g of HDA, and argon (Ar) as an inert gas are used. Stir with a stirrer to prevent uneven heating.

Next, as reaction precursors, diethylzinc (Zn (C ₂ H ₅ ) ₂ ) encapsulated with an inert gas (eg Ar), octylamine (C ₈ H ₁₇ NH ₂ ) bubbled with oxygen, and Bis (trimethylsilyl) ) Prepare each syringe filled with Sulfide (thiobis). Diethylzinc (Zn (C ₂ H ₅ ) ₂ ) is 4.0 mmol, oxygen-bonded octylamine (C ₈ H ₁₇ NH ₂ ) is 3.0 mmol, and Bis (trimethylsilyl) Sulfide (thiobis) is 1.0 mmol. Adjust to. By such adjustment, ZnO _0.75 S _0.25 mixed crystal nanoparticles are synthesized in the fifth example. In addition, in order to synthesize ZnO _x S _1-x mixed crystal nanoparticles having a different O composition x, the ratio of the materials constituting the reaction precursor may be appropriately changed.

When the reaction solvent reaches the reaction temperature, the reaction precursor is quickly put into the flask from each syringe. By the thermal decomposition of the reaction precursor, a core crystal of ZnO _x S _1-x is generated. If left as it is, most of the reaction precursor is consumed for nucleation, and nuclei of various sizes are generated with time. Therefore, immediately after the reaction precursor is injected, the temperature of the flask is rapidly cooled to 200 ° C. . Thereafter, the reaction solvent is reheated to 240 ° C., kept at a constant temperature for 20 minutes, and ZnO _x S _1-x is grown.

  The flask is naturally cooled to 100 ° C. and then held for 1 hour. As a result, the surface of the nanoparticles can be stabilized. Thereafter, butanol is added as a coagulation inhibitor to the reaction solution cooled to room temperature in order to prevent aggregation of the nanoparticles, and is maintained for 10 hours. Finally, it is purified by repeating centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (TOPO) is dissolved and toluene in which nanoparticles are dispersed. Thereby, unnecessary raw materials and solvents are removed.

In this way, a ZnO _0.75 S _0.25 nanoparticle matrix is synthesized. However, in the aggregate of nanoparticle base materials synthesized in step S501, the mixed crystal composition and particle size vary from particle to particle.

When the process proceeds to the In _w Al _1-w N shell layer formation step (step S503) with this variation present, the quantum effect changes for each ZnO _0.75 S _0.25 nanoparticle, resulting in variations in emission wavelength. Cause. Therefore, in step S502, selective photo-etching is performed in order to make the band gap of the entire ZnO _0.75 S _0.25 nanoparticles uniform.

The ZnO _0.75 S _0.25 nanoparticle base material synthesized in step S501 is in a state of being dispersed in methanol. Therefore, methanol is evaporated and the nanoparticles are concentrated. At this time, if the methanol is completely vaporized, the nanoparticles are aggregated. Therefore, it is preferable to leave the methanol slightly. Ultrapure water, which is a photo-etching solution, is added to the methanol / nanoparticle solution. Maintain at 25 ° C. and bubble with oxygen for 5 minutes.

After bubbling, it is transferred to a closed container and irradiated with light having a light emission wavelength of 405 nm (3.06 eV) and a half-value width of 6 nm, which is light having a wavelength sufficiently shorter than the absorption edge wavelength of ZnO _0.75 S _0.25 nanoparticles. A mercury lamp is used as the light source, and the light emitted from the mercury lamp is used after being separated by a monochromator.

ZnO _0.75 S _0.25 nanoparticles, which have variations in the absorption edge wavelength of the band gap due to variations in the mixed crystal composition and particle size, absorb light and cause a photodissolution reaction, and the surface dissolves in the photodissolution solution. The diameter gradually decreases. For this reason, as etching progresses, the absorption edge wavelength shifts to the short wavelength side. Light is irradiated until the absorption edge wavelength becomes shorter than the wavelength of irradiation light and the photodissolution reaction stops. Light irradiation is performed for 20 hours, for example.

By step S502, for example, a large number of ZnO _0.75 S _0.25 nanoparticles (ZnO _0.75 S _0.25 core layer) having the same emission wavelength are formed although there are mixed crystal composition and size distribution. The

Subsequently, the step of depositing an In _0.67 Al _0.33 N layer on the ZnO _0.75 S _0.25 core layer (step S503) will be described.

Aluminum iodide (80 mg, 0.20 mmol), which is a source of aluminum, together with an organic solvent in which ZnO _0.75 S _0.25 nanoparticles (51.7 mg, corresponding to 0.6 mmol) formed in step S502 are dispersed, Indium iodide (185 mg, 0.40 mmol) as a supply source of indium, hexadecanethiol (380 μl, 1.0 mmol) as a capping agent and zinc stearate (379 mg, 0.6 mol), diphenyl ether (20 ml) as a solvent Into a flask containing. The mixture is rapidly heated to 225 ° C and held at 225 ° C for 1 hour. Thereafter, the reaction vessel is naturally cooled to 100 ° C. and held for 1 hour. As a result, the surface of the nanoparticles can be stabilized. Thereafter, butanol is added as an anticoagulant to the reaction liquid cooled to room temperature to prevent aggregation of the nanoparticles and stirred for 10 hours. Finally, it is purified by repeated centrifugation (4000 rpm, 10 minutes) using alternately dehydrated methanol in which the solvent (TOPO) is dissolved and toluene in which nanoparticles are dispersed. Thereby, unnecessary raw materials and solvents are removed. Through such a procedure, nanoparticles in which a shell layer made of In _0.67 Al _0.33 N is grown on a ZnO _0.75 S _0.25 core layer are obtained.

Up to step S503, ZnO _0.75 S _0.25 / In _0.67 Al _0.33 N nanoparticles (base material) are synthesized, and the mixed crystal composition of the In _0.67 Al _0.33 N layer and The film thickness varies to some extent depending on the nanoparticles. If this variation exists, the band structure of the shell layer varies, which causes a problem that the emission wavelength from the nanoparticles becomes broad. Therefore, in step S504, the In _0.67 Al _0.33 N layer of ZnO _0.75 S _0.25 / In _0.67 Al _0.33 N nanoparticles is photoetched to _obtain In _0.67 Al _0.33. The quantum effect of the N layer is made uniform.

The ZnO _0.75 S _0.25 / In _0.67 Al _0.33 N nanoparticles (base material) formed in step S503 are in a state of being dispersed in methanol. Therefore, methanol is vaporized and the nanoparticles are concentrated. At this time, if the methanol is completely vaporized, the nanoparticles are aggregated. Therefore, a slight amount of methanol is left, and ultrapure water that is a photo-etching solution is added to the methanol and nanoparticle solution. Maintain at 25 ° C. and bubble with oxygen for 5 minutes.

After bubbling, it is transferred to a sealed container and irradiated with light having an emission wavelength of 405 nm (3.06 eV) and a half-value width of 6 nm, which is light having a wavelength sufficiently shorter than the absorption edge wavelength of the In _0.67 Al _0.33 N layer. A mercury lamp is used as the light source, and the light emitted from the mercury lamp is used after being separated by a monochromator.

In _0.67 Al _0.33 N layer, which has a variation in absorption edge wavelength of the band gap due to variations in mixed crystal composition and thickness, absorbs light and causes a photodissolution reaction, and the surface dissolves in the photodissolution solution. And gradually thin. For this reason, as etching progresses, the absorption edge wavelength shifts to the short wavelength side. Light is irradiated until the absorption edge wavelength becomes shorter than the wavelength of irradiation light and the photodissolution reaction stops. Light irradiation is performed for 20 hours, for example.

The ZnO _0.75 S _0.25 / In _0.67 Al _0.33 N nanoparticles produced by the method according to the fifth embodiment, for example, have a mixed crystal composition and a size distribution, but have the same emission wavelength. Nanoparticles with

The assembly of quantum dots (ZnO _0.75 S _0.25 / In _0.67 Al _0.33 N nanoparticles) manufactured by the manufacturing method according to the fifth embodiment is also manufactured by the manufacturing method according to the second embodiment. The same effect as that of the quantum dot assembly is produced.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not restrict | limited to these.

For example, in the examples, ternary ZnO _x S _1-x nanoparticles are given as an example using a II-VI group compound semiconductor, but the present invention is not limited thereto. For example, A _x B _1-x C _y D _1-y consisting of three or more elements (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, A and B are elements selected from the group consisting of Zn and Mg, C And D can be quantum dots formed using an element selected from the group consisting of O, S, Se, and Te.

In this quantum dot aggregate, quantum dots having different mixed crystal compositions are mixed. For example, quantum dots having different x by 0.05 or more, or quantum dots having y different by 0.05 or more are mixed. In the above A _x B _1-x C _y D _1-y quantum dot aggregate composed of three or more elements, the composition variation is large, and the variation of x and y is extremely less than 0.05. This is because it is difficult. (If the variation between x and y is less than 0.05, the half-value width of the emission spectrum of the quantum dot aggregate is, for example, less than 50 nm.)
However, the A _x B _1-x C _y D _1-y quantum dot assembly according to the present application does not have a wide emission spectrum due to the mixed crystal composition and size variation of the quantum dots. For example, the band gap is uniform, and the half width of the emission spectrum is narrowed to, for example, less than 50 nm. This is an effect of manufacturing a quantum dot assembly using, for example, selective photoetching.

The quantum dots may take a core / shell structure or may not take. For example, the core layer and the shell layer have a core / shell structure formed of a material (a material having a type II type quantum structure) that becomes a type II type junction using transition between adjacent interlayer bands, and the shell layer is the above A _{x B 1-x C y D} 1-y may be quantum dots are formed of. In the case of the core / shell structure, for example, quantum dot aggregates are mixed with quantum dots having different mixed crystal compositions of the shell layer (x different by 0.05 or more, or y different by 0.05 or more). However, the energy level of the shell layer does not vary due to variations in the mixed crystal composition and size. For example, as a result of manufacturing the shell layer by selective photoetching, the band of the shell layer of each quantum dot The gap energy (band gap energy of the shell layer confining the core layer) is made uniform regardless of the difference in the mixed crystal composition, for example, constant.

In the examples, ternary In _z Ga _1-z N nanoparticles and In _w Al _1-w N nanoparticles are given as examples using III-V group compound semiconductors, but are not limited thereto. For example, the quantum dots can be formed using Al _x Ga _y In _z N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1).

Also in this quantum dot aggregate, quantum dots having different mixed crystal compositions are mixed. For example, at least one of x, y, and z is mixed with quantum dots different by 0.05 or more. In the above Al _x Ga _y In _z N quantum dot assembly composed of three or more elements, the composition variation is large, and it is extremely difficult to make the x, y, and z variations less than 0.05. Because there is. (If the variation of x, y, z is less than 0.05, the half-value width of the emission spectrum of the quantum dot aggregate is, for example, less than 50 nm.)
However, the Al _x Ga _y In _z N quantum dot assembly according to the present application does not have a broad emission spectrum due to the mixed crystal composition and size variation of the quantum dots, and the band gap of each quantum dot is, for example, The half width of the emission spectrum is narrowed to less than 50 nm, for example. This is an effect of manufacturing a quantum dot assembly using, for example, selective photoetching.

The quantum dots may take a core / shell structure or may not take. For example, the core layer and the shell layer have a core / shell structure formed of a material (a material having a type II type quantum structure) that becomes a type II type junction utilizing transition between adjacent interlayer bands, and the shell layer is the Al layer. it may be _x Ga _y in _z quantum dots are formed of N. In the case of the core / shell structure, for example, quantum dot aggregates are mixed with quantum dots having different mixed crystal compositions of the shell layer (at least one of x, y, and z is different by 0.05 or more). However, the energy level of the shell layer does not vary due to variations in the mixed crystal composition and size. For example, as a result of manufacturing the shell layer by selective photoetching, the band of the shell layer of each quantum dot The gap energy (band gap energy of the shell layer confining the core layer) is made uniform regardless of the difference in the mixed crystal composition, for example, constant.

  In addition, in the Example, although the quantum dot of the core / shell structure etc. which covered the surface of the quantum dot with the II-VI group semiconductor material or the III-V group semiconductor material was demonstrated, in the quantum dot of a core / shell structure However, the core layer and the shell layer do not necessarily satisfy the lattice matching condition. However, in order to obtain quantum dots with good crystallinity, it is preferable that the lattice matching conditions are satisfied. The matching range has a difference in lattice constant within ± 1.0%. If it is within this range, there is almost no effect on the characteristics as a semiconductor in which the band gap is involved, but if it exceeds ± 1%, the characteristics are significantly deteriorated due to the decrease in crystallinity.

  Further, the core / shell structure (laminated structure) is not limited to two layers, and may be three or more layers.

  Further, the shape of the quantum dot is not particularly limited as long as the average particle size is, for example, 20 nm or less, and can take a spherical shape, a polyhedral shape, a flat plate shape, or the like.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.

  For example, it is possible to manufacture phosphors having a uniform emission wavelength in a narrow band, solar cells having uniform characteristics, and the like.

Steps S101 to S504

Claims (1)

(A) A step of preparing a plurality of quantum dots composed of ZnO _x S _1-x and having a size exceeding 10 nm, wherein the target value of the composition ratio x is 0.6, and the variation range is 0. 4 to 0.8, a step of preparing a plurality of quantum dots;
(B) photoetching the plurality of quantum dots prepared in the step (a) to reduce the diameter of the plurality of quantum dots, thereby uniformizing the band gap energy of the plurality of quantum dots; ,
The manufacturing method of the quantum dot aggregate | assembly which has.