JP4756239B2 - Hollow spherical particles made of gallium nitride and method for producing the same - Google Patents

Description

  The present invention relates to hollow spherical particles made of gallium nitride that are useful as light emitting materials in the blue to ultraviolet region and materials for electronic devices with high temperature and high power, and a method for producing the same.

Among semiconductors having hollow particles, zinc sulfide hollow particles are manufactured by using silica as a template (see, for example, Non-Patent Document 1). Moreover, the hollow particle | grains of cadmium sulfide are manufactured from cadmium acetate and thioacetamide (for example, refer nonpatent literature 2). Furthermore, hollow particles of cadmium selenide are produced from cadmium hydroxide and sodium selenosulfate (see, for example, Non-Patent Document 3).
On the other hand, one-dimensional nanostructures such as gallium nitride nanowires, nanobelts, and nanotubes are already well known (see, for example, Non-Patent Documents 4 to 9).

K.P.Velikov, et al., Langmuir, 17, 4779, 2001 Y.Ma, et al., Langmuir, 19, 9079, 2003 J.J.Zhu, et al., Adv.Mater.15, 156, 2003 W.Q.Han, et al., Appl.Phys.Lett. 80, 303, 2002 C.C.Tang, et al., Appl.Phys.Lett. 83, 3177, 2003 C.C.Chen, et al., Adv. Mater. 12, 738, 2000 C.C.Chen, et al., J.Am.Chem.Soc. 123, 2791, 2001 J. Goldberger, et al., Nature, 422, 599, 2003 L.W.Yin, et al., Appl.Phys.Lett. 84, 3912, 2004

  However, the hollow spherical particles of gallium nitride are not yet known.

  In view of the above problems, an object of the present invention is to provide a novel hollow spherical particle of gallium nitride and a method for producing the same.

In order to achieve the above object, the hollow spherical particles made of gallium nitride of the present invention have a diameter of 15 to 20 nm and a wall thickness of 3.5 to 4.5 nm.
According to the hollow spherical particles made of gallium nitride of the present invention, nanometer-sized hollow spherical particles made of gallium nitride can be obtained. This nanostructure can be used as a light emitting material in the blue to ultraviolet region and a material for electronic devices with high temperature and high power.

According to the method for producing hollow spherical particles of gallium nitride of the present invention, gallium chloride powder is heated at 1000 to 1200 ° C. for 1 to 1.5 hours in a mixed gas stream of ammonia gas and inert gas, and then nitrided. It is characterized by synthesizing hollow spherical particles made of gallium.
In the above configuration, the flow rate ratio of ammonia gas to inert gas is preferably in the range of 40:60 to 60:40.
The sum of the flow rates of ammonia gas and inert gas is preferably in the range of 400 to 500 sccm.
According to the above configuration, nanometer-sized hollow spherical particles made of gallium nitride having nanometer-size dimensions are manufactured by heating gallium chloride powder in a mixed gas stream of ammonia gas and inert gas. be able to.

  According to the present invention, hollow spherical particles made of gallium nitride having a diameter of 15 to 20 nm and a thickness of 3.5 to 4.5 nm are obtained, and the production thereof is possible.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic view showing an example of an apparatus for producing hollow spherical particles made of gallium nitride of the present invention. A manufacturing method will be described using this apparatus as an example.
In the figure, a vertical high frequency induction heating apparatus 1 has an induction heating coil 3 around a reaction tube 2. A crucible 5 containing gallium chloride powder 4 is disposed in the center of the reaction tube 2, and a substrate 6 is disposed above the crucible 5. An arrow 7 represents an inert gas such as argon or a mixed gas of argon and a reaction gas supplied to the reaction tube 2. Here, it is preferable to use a high-frequency induction heating furnace using a high-frequency induction heating method as the heating device, but in this case, not only a vertical type but also a horizontal type may be used. The heating device is not limited to high frequency induction heating, and may be a heating device using lamp heating or resistance heating.

A method for producing hollow spherical particles made of gallium nitride using the apparatus of FIG. 1 will be described. In the figure, gallium chloride powder 4 is put in a crucible 5 made of boron nitride, and this crucible 5 is placed in the center of a vertical high frequency induction heating furnace 1. Further, a substrate 6 such as silicon or sapphire is installed above the crucible 5.
After reducing the pressure in the reaction tube 2, the crucible 5 and the gallium chloride powder 4 are preheated while flowing an argon gas 7. At this time, the crucible 5 is heated in the range of 1000 to 1200 ° C. of the gallium chloride powder 4.

  Next, heating is performed at the above temperature while flowing a mixed gas of ammonia gas and argon gas as an inert gas. The heating temperature of the crucible 5 and the gallium chloride powder 4 is preferably in the range of 1000 to 1200 ° C. When the heating temperature is lower than 1000 ° C., the product is not deposited on the substrate 6, which is not preferable. On the other hand, when the heating temperature is higher than 1200 ° C., hollow gallium nitride spherical particles cannot be obtained, resulting in nanowires or nanocrystals.

  The heating time at this time is preferably in the range of 1 to 1.5 hours. Since the growth of spherical particles is completed in 1.5 hours, it is not necessary to spend more time. Conversely, a heating time of less than 1 hour is not preferable because the growth of spherical particles does not end.

  The flow ratio of ammonia gas to argon gas is preferably in the range of 40:60 to 60:40. If the flow rate of ammonia gas is higher than this range, the rate of crystal growth is too fast and the product contains crystal defects, which is not preferable. Conversely, if the flow rate of the ammonia gas is less than the above preferred range, the amount of ammonia that reacts with gallium is not sufficient, so the amount of gallium nitride produced decreases, which is not preferred.

The sum of the flow rates of the mixed gas of ammonia gas and argon gas is preferably in the range of 400 to 500 sccm. sccm (standard cubic cm per minute) is a unit representing a flow rate when converted to 1013 hPa at 0 ° C. in cm ³ / min. If the sum of the flow rates is more than 500 sccm, the product is dissipated from the reaction system, which is not preferable. On the contrary, if the sum of flow rates is less than 400 sccm, the yield of hollow spherical particles decreases, which is not preferable.

  By performing such an operation, yellow powder is deposited on the substrate 6. As will be described later, this deposit is a gallium nitride hollow spherical particle having a diameter of 15 to 20 nm and a wall thickness of 3.5 to 4.5 nm.

Next, the present invention will be described in more detail with reference to examples.
3.0 g of gallium chloride powder 4 (manufactured by Wako Pure Chemical Industries, Ltd., purity 99.9%) was put in a boron nitride crucible 5, and this crucible 5 was installed in the center of the vertical high frequency induction heating furnace 1. . Further, a silicon substrate 6 was disposed at a position 20 cm above the crucible 5. After reducing the pressure in the reaction tube 2 to 266 to 399 Pa (2 to 3 Torr), the reaction tube 2 was heated at 1100 ° C. for 30 minutes while flowing an argon gas 7 at a flow rate of 250 sccm.
Thereafter, the mixed gas 7 of 50% ammonia gas and 50% argon gas was continuously heated at 1100 ° C. for 1.5 hours while flowing at a flow rate of 450 sccm. After the heating, when the vertical high frequency induction heating apparatus 1 was cooled to room temperature, 0.6 g of yellow powder was deposited on the silicon substrate 6 which was kept at about 650 ° C. during the heating.

(Comparative example)
Next, a comparative example will be described.
A part of the yellow powder sample obtained in the examples was further heated to 1150 ° C. in a stream of ammonia and argon and subjected to heat treatment for 1 hour.

  FIG. 2 is a diagram showing an X-ray diffraction pattern of the yellow powder synthesized in the example. The vertical axis in the figure is the diffracted X-ray intensity (arbitrary scale), and the horizontal axis is the angle (°), that is, an angle corresponding to twice the incident angle θ of the X-rays on the atomic plane. From FIG. 2, it was found that the yellow powder was hexagonal gallium nitride having lattice constants a = 3.186１７ and c = 5.178.

  FIG. 3 is a view showing a low-magnification transmission electron microscope image of the yellow powder synthesized in the example. In this case, the yellow powder was subjected to ultrasonic treatment in ethanol to use the dispersion as a sample, and the dispersion was dropped onto a copper grid coated with an amorphous carbon film, and a transmission electron microscope image was observed. From FIG. 3, it was found that the yellow powder was a collection of hollow spherical particles.

  FIG. 4 is a diagram showing a high-magnification transmission electron microscope image of the yellow powder synthesized in the example. From FIG. 4, it was found that the diameter of one yellow powder synthesized in the example was 15 to 20 nm and the wall thickness was 3.5 to 4.5 nm.

FIG. 5 is a diagram showing a measurement result of energy-dispersive X-ray analysis (EDX) of the yellow powder synthesized in the example. The vertical axis in the figure represents the X-ray intensity (arbitrary scale), and the horizontal axis represents the X-ray energy.
From FIG. 5, it was found that the yellow powder is gallium nitride composed of gallium (Ga) and nitrogen (N), having an atomic ratio of 1: 0.99, and having a stoichiometric composition. In addition, although the signal of copper is observed, this originates in the copper grid used as a jig | tool which attaches a sample.

  FIG. 6 is a diagram showing a low-magnification transmission electron microscope image of a comparative sample obtained by heating the yellow powder sample obtained in the example in an air stream of ammonia and argon and further increasing the temperature to 1150 ° C. It is. From FIG. 6, it was found that in the comparative example, spherical particles were coalesced by heat treatment and changed from spherical particles to nanotubes. Moreover, it turned out that the outer diameter of this nanotube is 20 nm, and the wall thickness is 3.5-5.0 nm.

FIG. 7 is a diagram showing a photoluminescence spectrum of the yellow powder synthesized in the example. Photoluminescence was measured at room temperature using 325 nm He-Cd laser light as excitation light. In the figure, the solid line shows the photoluminescence spectrum of hollow spherical particles made of gallium nitride synthesized in the example, and the dotted line shows the photoluminescence spectrum of bulk gallium nitride.
As is clear from FIG. 7, the photoluminescence spectrum of the hollow spherical particles made of gallium nitride synthesized in the example is 0.12 eV (13 nm) shorter than the photoluminescence of the bulk gallium nitride crystal, That is, it turned out that it was blue-shifting. This is thought to be due to the fact that the quantum confinement effect was exhibited because the size of the spherical particles of the present invention, such as the diameter and wall thickness, became smaller.

  According to the present invention, nanometer-sized hollow spherical particles made of gallium nitride can be obtained. Therefore, application to light emitting materials from blue to ultraviolet and materials for high-temperature high-power electronic devices is expected.

It is a schematic diagram which shows an example of the apparatus which manufactures the hollow spherical particle which consists of gallium nitride of this invention. It is a figure which shows the X-ray-diffraction pattern of the yellow powder synthesize | combined in the Example. It is a figure which shows the low magnification transmission electron microscope image of the yellow powder synthesize | combined in the Example. It is a figure which shows the high magnification transmission electron microscope image of the yellow powder synthesize | combined in the Example. It is a figure which shows the measurement result by the energy dispersive X ray analysis (EDX: Energy-Dispersive X-ray Analysis) of the yellow powder synthesize | combined in the Example. It is a figure which shows the low magnification transmission electron microscope image of the comparative example sample which heat-processed the yellow powder sample obtained in the Example by raising temperature to 1150 degreeC in the airflow of ammonia and argon. It is a figure which shows the spectrum of the photoluminescence of the yellow powder synthesize | combined in the Example.

Explanation of symbols

1: Vertical high frequency induction heating device 2: Reaction tube 3: Induction heating coil 4: Gallium chloride powder 5: Crucible 6: Substrate 7: Inert gas or mixed gas

Claims (4)

  A hollow spherical particle made of gallium nitride, characterized by having a diameter of 15 to 20 nm and a thickness of 3.5 to 4.5 nm. In a mixed gas stream of ammonia gas and inert gas, the gallium chloride powder is heated at 1000 to 1200 ° C. for 1 to 1.5 hours, on the substrate placed in the mixed gas stream and downstream of the gallium chloride powder. A method for producing hollow spherical particles made of gallium nitride, characterized in that hollow spherical particles made of gallium nitride are grown during said heating time.   The method for producing hollow spherical particles made of gallium nitride according to claim 2, wherein a flow ratio of the ammonia gas to the inert gas is in a range of 40:60 to 60:40.   The method for producing hollow spherical particles made of gallium nitride according to claim 2, wherein the sum of the flow rates of the ammonia gas and the inert gas is in the range of 400 to 500 sccm.