JP4930952B2 - Aluminum nitride nanoribbon - Google Patents

Description

The invention of this application relates to aluminum nitride nanoribbons.

Aluminum nitride is a III-V group compound having an optical band gap energy of about 6.2 eV, and is a compound having excellent heat resistance and chemical resistance. For this reason, application as an electronic substrate, packaging material, high temperature material, and structural material is expected. Aluminum nitride is also promising as a substrate for epitaxial growth of gallium nitride because it has a lattice constant close to that of gallium nitride.

With respect to such aluminum nitride, methods for producing an aluminum nitride thin film (for example, see Non-Patent Documents 1 and 2) and one-dimensional aluminum nitride nanowires (for example, Non-Patent Documents 3 and 4) have been proposed so far. It was known.

C.T.M.Ribeiro et al., Advanced Materials (Adv. Mater.), 2002, Vol. 14, p. 1154 E. Kuokstis et al., Applied Physics Letters, 2002, Vol. 81, p. 2755 Y. Zhang et al., Chemistry of Materials (Chem. Mater.), 2001, Vol. 13, p. 3899 C.Xu, Phys. Stat. Sol. A, 2003, Vol. 198, p. 329

However, since the conventional aluminum nitride nanowires and nanofibers are brittle and brittle, their performance has not been sufficiently exhibited in the stretched state or the bent state.

Accordingly, the invention of this application has an object to be solved to provide an aluminum nitride nanoribbon that is very flexible and has a very small thickness.

The invention of this application provides an aluminum nitride nanoribbon having a width of 800 to 900 nanometers and a thickness of 20 to 30 nanometers as a solution to the above problems.

According to the invention of this application, it is possible to provide a flexible aluminum nitride nanoribbon that is promising as a reinforcing material for ceramic composite materials, electronic substrates, packaging materials, high-temperature materials, structural materials, and the like. .

The aluminum nitride nanoribbon having a width of 800 to 900 nanometers and a thickness of 20 to 30 nanometers according to the invention of this application is obtained by heating a mixture of alumina powder and graphite powder while flowing an inert gas and then converting the inert gas to ammonia gas. It is obtained by switching and heating.

Specifically, a mixture of alumina powder and graphite powder is placed in a graphite crucible, and this crucible is placed in the center of a vertical high frequency induction heating furnace with a graphite induction heating cylindrical tube covered with carbon fiber as a heat insulating material. Deploy. After depressurizing the inside of the vertical high frequency induction heating furnace, heating is performed while flowing an inert gas, and then the inert gas is switched to ammonia gas and heating is continued. Then, a gray wool-like substance accumulates on the inner wall of the crucible. This gray deposit is an aggregate of aluminum nitride nanoribbons. Aluminum nitride nanoribbons are wide and very thin with a width of 800-900 nanometers and a thickness of 20-30 nanometers.

In this aluminum nitride nanoribbon, the production method is as described above. More specifically, the molar ratio of the alumina powder to the graphite powder is preferably in the range of 1: 1.5 to 1: 2. As for the number of moles of graphite powder, 2 moles per mole of alumina powder is sufficient. When the amount of the graphite powder is less than the above range, the alumina powder remains unreacted.

The flow rate of the inert gas is preferably in the range of 150 to 200 sccm. A sufficiently inert atmosphere can be maintained at a flow rate of 200 sccm. If the flow rate is less than 150 sccm, it is difficult to maintain a sufficiently inert atmosphere, and substances such as oxygen may be contained. The heating temperature in the inert atmosphere is preferably in the range of 1350 to 1600 ° C. Reactive gas production occurs sufficiently at 1600 ° C. If it is lower than 1350 ° C., the generation of reactive gas is not sufficient. The heating time in the inert gas atmosphere is preferably in the range of 0.4 to 0.5 hours. Reactive gas is sufficiently generated in 0.5 hours, and unreacted alumina powder remains in 0.4 hours or less. Preferable examples of the inert gas include argon or helium.

The flow rate of ammonia gas is preferably in the range of 200 to 250 sccm. If the flow rate is higher than 250 sccm, the crystal growth of aluminum nitride deviates from the equilibrium state. Cheap. A flow rate of less than 200 sccm is not sufficient to produce aluminum nitride nanoribbons. The heating temperature in the ammonia atmosphere is preferably in the range of 1400-1500 ° C. When the temperature exceeds 1500 ° C., the growth of the aluminum nitride crystal is in a non-equilibrium state, so that nanostructures of various forms such as a comb shape, a three-dimensional structure and a dendrite shape are formed, and a uniform nanoribbon structure is not formed. At a heating temperature of less than 1400 ° C., nanoribbons are not formed and nanowires are formed. The heating time in the ammonia atmosphere is preferably in the range of 2.5 to 3 hours. A sufficiently thin and wide aluminum nitride nanoribbon is obtained in 3 hours. A heating time of less than 2.5 hours is insufficient for the growth of wide aluminum nitride nanoribbons.

Next, an Example is shown and it demonstrates in more detail about the aluminum nitride nanoribbon of invention of this application.

A mixture of 2.5 g of alumina powder (purity 99.9%) manufactured by Wako Pure Chemical Industries, Ltd. and 0.5 g of graphite powder (purity 99.9%) manufactured by Wako Pure Chemical Industries, Ltd. is placed in a graphite crucible. The crucible was placed in the center of a vertical high-frequency induction heating furnace with a graphite induction heating cylindrical tube covered with carbon fiber as a heat insulating material. After reducing the pressure inside the vertical high frequency induction heating furnace to 1 to 2 Torr, the mixture in the crucible was heated at 1500 ° C. for 30 minutes while flowing argon gas at a flow rate of 200 sccm. Subsequently, the argon gas was switched to ammonia gas, the flow rate was 250 sccm, and heating was performed at 1500 ° C. for 3 hours. 0.7 g of gray wool-like material was deposited on the inner wall of the graphite crucible.

FIG. 1 is a photograph of a scanning electron microscope image of the obtained gray wool-like substance, and FIG. 2 is a photograph of a low-magnification transmission electron microscope image. From these photographs, it is confirmed that nanoribbons having a width of several tens of micrometers, a width of 800 to 900 nanometers, a width of 20 to 30 nanometers and a very thin thickness are formed.

FIG. 3 shows an X-ray diffraction pattern of the obtained gray deposit. It was found to be hexagonal aluminum nitride having a lattice constant of a = 3.114Å and c = 4.986Å.

FIG. 4 shows an X-ray energy dispersion spectrum of one nanoribbon. It was found to be aluminum nitride with a stoichiometric composition with an atomic ratio of aluminum to nitrogen of 1: 0.99. In addition, although the copper signal has appeared in FIG. 4, this copper signal originates in the copper grid used when observing a sample.

From the results of electron beam diffraction, it was confirmed that the obtained aluminum nitride nanoribbon was a single crystal and had no crystal defects or dislocations.

FIG. 5 shows a photoluminescence spectrum at room temperature measured using a 325 nm He—Cd laser as an excitation light source. The obtained aluminum nitride nanoribbon has a center of emission peak at 430 nm and exhibits blue emission of a broad emission band from 300 nm to 600 nm.

Of course, the invention of this application is not limited by the above embodiments.

As described in detail above, the invention of this application makes it possible to provide a flexible aluminum nitride nanoribbon having a wide width and a very small thickness. This aluminum nitride nanoribbon is expected to be used as a reinforcing material for ceramic composite materials, materials for electronic devices, optical devices, and the like.

It is a photograph of the scanning electron microscope image of the gray deposit obtained in the Example. It is a photograph of the low magnification transmission electron microscope image of the gray deposit obtained in the Example. It is a figure of the pattern of the X-ray diffraction of the gray deposit obtained in the Example. It is a figure of the X-ray energy dispersion spectrum of the aluminum nitride nanoribbon obtained in the Example. It is a figure of the photoluminescence spectrum of the single crystal aluminum nitride nanoribbon obtained in the Example.

Claims (2)

Aluminum nitride nanoribbons that are 800-900 nanometers wide and 20-30 nanometers thick. The aluminum nitride nanoribbon according to claim 1, comprising nitrogen and aluminum.