JP5795527B2 - Fabrication method of nanowire - Google Patents

Description

  The present invention relates to a nanowire forming method for forming a nanowire made of a group III-V compound on graphene.

Graphene is a sheet-like material with one to several atomic layers composed of carbon atoms two-dimensionally bonded to each other, and has carrier mobility exceeding 200,000 cm ² V ⁻¹ s ⁻¹ Has been reported and attracts attention as a material for high-speed devices (see Non-Patent Document 1). Recently, large-area single-layer or several-layer graphene sheets have been produced by roll-to-roll technology (see Non-Patent Document 2). This graphene sheet can be transferred to a plastic substrate that bends easily, and can be applied to transparent electronic and optical products that can be stretched and folded.

  If nanowires made of a III-V group compound having a diameter of nanometer scale can be grown on such graphene, for example, a highly efficient light-emitting / receiving element can be easily and inexpensively mounted on a flexible plastic substrate. It is expected to be applied to various technologies.

K.I.Bolotin et al., "Ultrahigh electron mobility in suspended graphene", Solid State Communications, vol.146, pp.351-355, 2008. S. Bae et al., "Roll-to-roll production of 30-inch graphene films for transparent electrodes", NATURE NANOTECHNOLOGY, vol.5, pp.574-578, 2010. Yong-Jin Kim et al., "Vertically aligned ZnO nanostructures grown on graphene layers", APPLIED PHYSICS LETTERS, vol.95, 213101, 2009. Y. J. Hong and T. Fukui, "Heteroepitaxy of Vertical InAs Nanowires on Thin Graphitic Films", Solid State Devices and Materials, KM-4-2, pp.1306-1307, 2001.

  However, at present, the formation of ZnO nanowires (see Non-Patent Document 3) and the formation of nanowires by selective growth (see Non-Patent Document 4) are only reported on graphene. Thus, at present, there is a problem that a technique for forming a nanowire of a III-V group compound on graphene has not been established.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to form a III-V group compound nanowire on graphene.

The method for producing a nanowire according to the present invention includes a metal fine particle forming step of forming metal fine particles composed of gold on graphene, and a metal-organic vapor phase epitaxy method using the metal fine particles as a catalyst. A nanowire forming step of forming the nanowire.

  In the nanowire manufacturing method, the nanowire may be grown in a direction along the plane of graphene. In addition, after the nanowire is formed, a III-V group compound constituting the nanowire is grown from the nanowire to form a thin film forming step of forming a thin film composed of the III-V group compound on the graphene. May be.

  In the nanowire manufacturing method, the nanowire may be grown in the normal direction of the graphene plane. For example, in the metal fine particle forming step, metal fine particles having a diameter of 10 nm or less are formed on graphene, and in the nanowire forming step, the metal fine particle is used as a catalyst by an organic metal vapor phase epitaxy method at 300 to 500 ° C. What is necessary is just to form the III-V compound nanowire with the growth temperature of the range.

  The nanowire manufacturing method includes a graphene forming step of forming graphene on a substrate made of SiC having a main surface of (0001) by pyrolysis, and in the metal fine particle forming step, gold is vacuum-deposited on the substrate. By doing so, metal fine particles may be formed on the graphene by forming gold fine particles along the steps of SiC and graphene.

  As described above, according to the present invention, it is possible to obtain an excellent effect that a nanowire of a III-V group compound can be formed on graphene.

FIG. 1 is an explanatory diagram for explaining a method of manufacturing a nanowire according to Embodiment 1 of the present invention. FIG. 2 is a photograph showing a result of observing a nanowire grown on a graphite substrate using gold fine particles having a diameter of 10 nm or less as a catalyst with a scanning electron microscope. FIG. 3 is a configuration diagram showing a state of the nanowires 304 grown on the graphene 101 on the substrate 103 in a direction parallel to the plane of the graphene 101. FIG. 4A is an explanatory diagram for describing a method of manufacturing a nanowire according to Embodiment 2 of the present invention. FIG. 4B is a photograph of an AFM image for illustrating a method of manufacturing a nanowire according to Embodiment 2 of the present invention. FIG. 4C is an explanatory diagram for describing a nanowire manufacturing method according to Embodiment 2 of the present invention. FIG. 4D is an explanatory diagram for explaining a nanowire manufacturing method according to Embodiment 2 of the present invention. FIG. 4E is an explanatory diagram for describing a method of manufacturing a nanowire according to Embodiment 2 of the present invention. FIG. 4F is an explanatory diagram for explaining a method of manufacturing a nanowire according to Embodiment 2 of the present invention. FIG. 5A is an explanatory diagram for describing a nanowire manufacturing method according to Embodiment 3 of the present invention. FIG. 5B is an explanatory diagram for explaining a method of manufacturing a nanowire according to Embodiment 3 of the present invention. FIG. 5C is an explanatory diagram for describing a nanowire manufacturing method according to Embodiment 3 of the present invention. FIG. 6 is a configuration diagram showing a configuration of an element manufactured using the nanowire manufacturing method according to Embodiment 4 of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, Embodiment 1 of the present invention will be described. FIG. 1 is an explanatory diagram for explaining a method of manufacturing a nanowire according to Embodiment 1 of the present invention. First, in step S101, as shown in FIG. 1A, metal fine particles 102 are formed on the graphene 101 (metal fine particle forming step). For example, the graphene 101 may be formed by pyrolysis on a substrate 103 made of SiC having a main surface of (0001).

Next, in step S102, as shown in FIG. 1B, a III-V group compound nanowire 104 is formed by metalorganic vapor phase epitaxy using the metal fine particles 102 as a catalyst (nanowire forming step). For example, the nanowire 104 made of GaP can be formed by metal organic vapor phase epitaxy that supplies Ga source gas and P source gas. For example, trimethylgallium (TMGa) may be used as the Ga source gas, and phosphine (PH ₃ ) may be used as the P source gas.

  In the above-described crystal growth of a group III-V compound semiconductor using the metal fine particles 102 as a catalyst, Ga and P generated by thermal decomposition of the source gas supplied in the gas phase are dissolved in the metal fine particles 102 and alloyed. When alloyed in this manner, the melting points of Ga and P are remarkably lowered, and for example, Ga and P become liquid at 480 ° C. In this state, when Ga and P are supersaturated in the metal fine particles 102, GaP nanowires 104 are formed as in liquid phase epitaxial growth. In the formation of such nanowires 104, since the raw material goes through the process of gas phase → liquid phase → solid phase, it is called a VLS (vapor phase—liquid phase—solid phase) method.

  Further, when the diameter (particle diameter) of the metal fine particles 102 is 10 nm or less and the growth temperature is in the range of 300 to 500 ° C., the nanowire 104 can be grown in the normal direction of the plane of the graphene 101.

  The nanowire 104 can also be grown in a direction along the plane of the graphene 101. If the nanowire 104 is formed in a direction along the plane, then the III-V group compound constituting the nanowire 104 is grown again from the nanowire 104, so that the III-V group compound is formed on the graphene 101. A thin film can also be formed. In this thin film formation, the growth temperature may be increased. By increasing the growth temperature, the crystal grows in the planar direction based on the nanowire 104. By doing so, a thin film of a group III-V compound with uniform crystallinity can be formed on graphene.

  Next, the background to the above-described present invention will be described. As a result of intensive studies by the inventors, it has been found that if gold fine particles having a diameter of about 10 nm are used as a catalyst, a nanowire of a III-V group compound can be formed on a graphite substrate. FIG. 2 is a photograph showing a result of observing a nanowire grown on a graphite substrate using gold fine particles having a diameter of 10 nm or less as a catalyst with a scanning electron microscope. 2A is a photograph of a nanowire made of GaP, FIG. 2B is a photograph of a nanowire made of InP, and FIG. 2C is a photograph of a nanowire made of GaAs.

  Gold is deposited on a graphite substrate made of Highly Oriented Pyrolytic Graphite (HOPG) to a thickness of about 1 to 5 nm, and then the graphite substrate is placed in a furnace of a metal organic chemical vapor deposition apparatus. The above-mentioned nanowire could be formed by supplying a predetermined source gas and heating it to a predetermined temperature. Gold fine particles are formed from a gold layer thinly deposited by heating.

In the case of GaP, TMGa is supplied as a source gas at a flow rate of 1 × 10 ⁻⁵ mol / min, phosphine is supplied at a flow rate of 5 × 10 ⁻⁴ mol / min, the substrate heating temperature is 480 ° C., and growth is performed. The time was 1 minute.

In the case of InP, TMIn is supplied as a source gas at a flow rate of 3 × 10 ⁻⁶ mol / min, phosphine is supplied at a flow rate of 2 × 10 ⁻³ mol / min, the substrate heating temperature is 410 ° C., and growth is performed. The time was 2 minutes.

In the case of GaAs, TMGa is supplied as a source gas at a flow rate of 7 × 10 ⁻⁶ mol / min, arsine (AsH ₃ ) is supplied at a flow rate of 2 × 10 ⁻⁴ mol / min, and the substrate heating temperature is 460. The growth time was 3 minutes.

  As shown in FIG. 2, nanowires grown in the normal direction of the substrate are observed. When metal fine particles having a large diameter are used, the difference between the size of the graphene (graphite) lattice and the growth nanowire lattice, particularly the influence of strain, is exerted, making it difficult to grow the nanowire perpendicular to the substrate. On the other hand, when the diameter is reduced to 10 nm or less, the influence of the strain described above is reduced, and it is interpreted that the vertical nanowire can be grown while maintaining the bonding by van der Faels force.

  Further, as shown in the schematic diagram of FIG. 3, nanowires 304 grown in a state along the plane of the graphene 101 can be formed on the graphene 101 on the substrate 103. As shown in FIGS. 2 (a) and 2 (c), GaP and GaAs nanowires have also been confirmed to grow laterally along the substrate.

  As described above, for the first time, it has been found that nanowires of III-V compounds can be formed by metalorganic vapor phase epitaxy using metal fine particles formed on a graphite substrate as a catalyst. The production method of nanowires in Form 1 was reached.

  Thus, according to Embodiment 1, it is possible to easily form a III-V compound nanowire on graphene. In addition, if nanowires are grown in the direction along the plane of graphene, a thin film in which the crystallinity of a group III-V compound is aligned can be grown on the graphene by growing crystals again from the grown nanowires. it can.

[Embodiment 2]
Next, Embodiment 2 of the present invention will be described with reference to FIGS. 4A to 4F. 4A to 4F are explanatory diagrams for explaining a method of manufacturing a nanowire according to Embodiment 2 of the present invention. 4A, 4C, 4D, 4E, and 4F are plan views showing states in the middle of fabrication. FIG. 4B is a photograph showing a result of observing a state during the production with an atomic force microscope (AFM).

  First, as shown in FIG. 4A, a substrate 403 made of insulating SiC having a main surface of (0001) is prepared, and the substrate 403 is heated to 1200 ° C., whereby two or three layers of graphene are formed on the surface of the substrate 403. 401 is formed. Subsequently, gold is vapor-deposited and heated to 500 ° C. to form metal fine particles 402 made of gold. Gold deposition may be performed while observing the surface of the substrate 403 (graphene 401) in a low-speed atomic microscope. By forming in this way, metal fine particles 402 having a particle diameter of 1 to 5 nm can be formed along the steps of the surface of the graphene 401 as shown in the AFM image of FIG. 4B.

Next, as shown in FIG. 4C, a nanowire 404 made of GaAs is grown in a direction along the plane of the graphene 401 by a metal organic vapor phase growth method using the metal fine particles 402 as a catalyst. For example, using a well-known metalorganic vapor phase epitaxy apparatus, the substrate heating temperature condition is 460 ° C., TMGa is supplied at 1 × 10 ⁻⁵ mol / min, and arsine is supplied at 5 × 10 ⁻⁴ mol / min. The growth time may be 10 minutes.

  Next, the graphene 401 is selectively removed by etching using the nanowire 404 as a mask, so that the graphene 401 is formed only between the nanowire 404 and the substrate 403 as shown in FIG. 4D. For example, the graphene 401 may be selectively etched by the well-known reactive ion etching using oxygen.

  Next, as illustrated in FIG. 4E, an insulating layer 405 made of silicon oxide is formed so that both ends of the nanowire 404 are exposed and the central portion of the nanowire 404 is covered. For example, the insulating layer 405 may be formed by forming a silicon oxide film by a well-known deposition method such as sputtering and patterning the formed silicon oxide film by a known lithography technique and etching technique.

  Thereafter, as shown in FIG. 4F, a gate electrode 406 is formed on the insulating layer 405. In addition, a source electrode 407 connected to the graphene 401 is formed at one end portion of the nanowire 404, and a drain electrode 408 connected to the graphene 401 is formed at the other end portion of the nanowire 404. For example, the gate electrode 406, the source electrode 407, and the drain electrode 408 may be formed simultaneously by a well-known lift-off method. Thus, a field effect transistor using the graphene 401 as a channel can be configured. As described above, the structure of this field effect transistor can be easily manufactured by an integrated circuit manufacturing technique that is generally used at present.

  According to the field effect transistor thus manufactured, the graphene serving as the channel is formed in the shape and dimensions of the nanowire. In addition, since the nanowires are in close contact with the graphene in a uniform state, the graphene is protected in the manufacturing process of the field effect transistor. For this reason, according to the above-described field effect transistor, transistor operation with relatively high mobility and excellent reproducibility can be expected.

[Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIGS. 5A to 5C. FIG. 5A to FIG. 5C are explanatory diagrams for explaining a method of manufacturing a nanowire according to Embodiment 3 of the present invention. 5A to 5C are cross-sectional views schematically showing a state in the middle of the production.

  First, a metal substrate made of nickel or copper is prepared, the metal substrate is heated (about 900 ° C.), and a hydrocarbon gas is supplied thereto to form graphene on the surface of the metal substrate. A substrate on which a metal film is formed may be used. Further, an alloy of nickel and copper may be used. Next, gold fine particles made of gold are formed on the formed graphene.

Next, nanowires made of AlGaAs are grown in a direction along the plane of graphene by metal organic vapor phase epitaxy using gold fine particles as a catalyst. For example, using a well-known metalorganic vapor phase epitaxy apparatus, the substrate heating temperature condition is 460 ° C., TMAl (trimethylaluminum) is 1 × 10 ⁻⁵ mol / min, TMGa is 5 × 10 ⁻⁷ mol / min. Min and arsine may be supplied at 2 × 10 ⁻⁴ mol / min and the growth time may be 3 minutes. By doing in this way, the nanowire which consists of AlGaAs whose Al composition is 95% or more is producible.

  Next, the graphene is selectively removed by etching using the nanowire as a mask so that the graphene is formed only between the nanowire and the metal substrate. For example, selective etching of graphene may be performed by the well-known reactive ion etching using oxygen.

  Next, the nanowire and graphene formed as described above are transferred to another substrate. As shown in FIG. 5A, nanowires 504 having graphene 501 formed thereon are transferred onto a substrate 505 made of silicon oxide. For example, after the graphene and nanowires manufactured on the metal substrate as described above are pressed against the substrate 505, the metal substrate may be dissolved using acid or the like.

  After transferring the nanowire 504 and the graphene 501 onto the substrate 505 as described above, AlGaAs (III-V group compound) constituting the nanowire 504 is grown from the nanowire 504, and as shown in FIG. The graphene 501 is covered with the nanowire 504. This is a state in which the graphene 501 is covered with AlGaAs and a thin film made of AlGaAs is formed on the graphene 501.

For example, using a metal organic vapor phase epitaxy apparatus, the substrate heating temperature condition is 550 ° C., TMAl is 1 × 10 ⁻⁵ mol / min, TMGa is 5 × 10 ⁻⁷ mol / min, and arsine is 2 × 10 ^{− It} may be supplied at ⁴ mol / min and the growth time may be 20 minutes. In this regrowth, unlike nanowire growth, the heating temperature is set to a higher temperature of 550 ° C. Thus, the core-shell structure which covered the circumference | surroundings of graphene with the III-V group compound can be formed by regrowth.

Next, the nanowire 504 formed to cover the graphene 501 is oxidized, so that the graphene 501 is covered with the oxide layer 506 as illustrated in FIG. 5C. For example, AlGaAs may be oxidized with water vapor. When water heated to 80 ° C. is bubbled with nitrogen to generate water vapor and the generated water vapor is supplied to the nanowire 504 heated to 440 ° C., AlGaAs is oxidized into oxidized AlGaO _x .

  Thus, after the graphene 501 is covered with the oxide layer 506, first, the oxide layer 506 at both ends of the graphene 501 is partially removed to expose both ends of the graphene 501. Next, a gate electrode is formed over the oxide layer 506 at the center of the remaining graphene 501, and a source electrode is formed at the end of one exposed graphene 501, and the end of the other exposed graphene 501 is formed. A drain electrode is formed on the part. Thus, a field effect transistor using the graphene 501 as a channel can be formed.

  According to the field effect transistor described above, the graphene serving as the channel is formed in the shape and dimensions of the nanowire. In addition, since the nanowires are in close contact with the graphene in a uniform state, the graphene is protected in the manufacturing process of the field effect transistor. For this reason, transistor operation with relatively high mobility and excellent reproducibility can be expected.

[Embodiment 4]
Next, Embodiment 4 of the present invention will be described with reference to FIG. FIG. 6 is a configuration diagram showing a configuration of an element manufactured using the nanowire manufacturing method according to Embodiment 4 of the present invention. In FIG. 6, the structure of the element is shown in a schematic cross-sectional view.

  First, a substrate made of SiC is prepared, and the substrate is heated to 1200 ° C. to form two or three layers of graphene on the surface of the substrate. Next, a gold colloid solution of gold fine particles having a particle size of 5 nm is dropped and spin coated to disperse the gold fine particles, thereby forming metal fine particles made of gold on the graphene.

  Next, by a metal organic chemical vapor deposition method using metal fine particles as a catalyst, first, a nanowire made of n-type InP is grown, followed by growing a nanowire made of non-doped InAsP, and subsequently made of p-type InP. Growing nanowires.

For example, using a metal organic vapor phase epitaxy apparatus, the growth temperature condition is 410 ° C., first, TMIn (trimethylindium) is 5 × 10 ⁻⁶ mol / min, and TBP (tertiary butylphosphine) is 5 × 10 ^−4. Mol / min, Si ₂ H ₆ (disilane) is introduced at 1 × 10 ⁻⁶ mol / min, and a nanowire made of n-type InP is grown for 5 minutes. Subsequently, TMIn was introduced at 5 × 10 ⁻⁶ mol / min, TBP at 5 × 10 ⁻⁴ mol / min, and TBAs (tertiarybutylarsine) at 5 × 10 ⁻⁵ mol / min, and from non-doped InAsP. The nanowire is grown for 10 seconds. Subsequently, TMIn 5 × 10 ⁻⁶ mol / min, TBP 5 × 10 ⁻⁴ mol / min, DEZn (diethyl zinc) 1 × 10 ⁻⁶ mol / min are introduced, and nanowires made of p-type InP are grown for 5 minutes. . By these things, the nanowire which consists of n-type InP, InAsP used as an active layer, and p-type InP can be grown on graphene.

  As described above, after the nanowire having the pin structure is grown, if an insulating layer is formed around the nanowire, the p-type InP is formed on the graphene 602 on the substrate 601 as shown in FIG. A nanowire 604 composed of a nanowire part 641, a nanowire part 642 serving as an active layer made of InAlP, and a nanowire part 643 made of n-type InP is formed, and an element in which the periphery of the nanowire 604 is covered with an insulating layer 605 can be formed. . On the nanowire portion 641, metal fine particles 603 made of gold are arranged.

  Here, the insulating layer 605 may be formed, for example, by depositing aluminum oxide by a well-known atomic layer growth method. The periphery of the insulating layer 605 may be filled with a permeable resin such as a resin such as benzocyclobutene or a polysiloxane silicone resin.

  In addition, after forming an aluminum oxide layer and embedding with a resin, the tip of the nanowire 604 (metal fine particles 603) is removed by, for example, removing a part of the resin and aluminum oxide by well-known reactive ion etching. Expose. Au / Zn / Ni is vapor-deposited on the tip of the nanowire 604 thus exposed to form a p-electrode, and Au / Ti is vapor-deposited on the exposed portion of the graphene 602 to form an n-electrode. For example, an optical device having a p-electrode and an n-electrode and having the nanowire portion 642 as an active layer is obtained. It can function as a light emitting element and a light receiving element depending on the polarity of the voltage applied to the n electrode and the p electrode. Note that SiC and graphene exhibit a transmittance of 90% or more with respect to 1.3 μm which is the emission wavelength.

  The above-described optical element can be used as a single photon light source used for quantum information communication. Further, since the above-described optical element can be formed with a very fine area with respect to the planar direction of the substrate, it becomes possible to integrate and form many optical elements in a predetermined area.

  As described above, according to the present invention, metal fine particles are formed on graphene, and the group III-V compound is crystal-grown by metal organic vapor phase epitaxy using the metal fine particles as a catalyst. Then, a nanowire of a III-V compound can be formed on the graphene. In addition, since the nanowire to be formed has a single crystal structure, if a group III-V compound is recrystallized and grown in the plane direction of the substrate based on the nanowire, the single crystal III- is formed on the graphite. A film of a V group compound can be formed.

  Conventionally, FETs using graphene have high mobility, and the channel portion is supported in a state of being separated from the others. For applications, materials for protecting the graphene surface have been sought. It was. On the other hand, as described above, according to the present invention, the graphene can be protected by the nanowire of the III-V group compound grown on the graphene.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, although the pin structure nanowire has been exemplified above, the present invention is not limited to this, and a quantum dot structure may be formed by manufacturing in the same manner. Also, the n-type and p-type formation positions may be exchanged.

  101 ... graphene, 102 ... metal fine particles, 103 ... substrate, 104 ... nanowire.

Claims (6)

A metal fine particle forming step of forming metal fine particles composed of gold on graphene;
And a nanowire forming step of forming a group III-V compound nanowire by metalorganic vapor phase epitaxy using the metal fine particles as a catalyst. In the manufacturing method of the nanowire of Claim 1,
A method for producing a nanowire, wherein the nanowire is grown in a direction along a plane of the graphene. The method for producing a nanowire according to claim 2,
After forming the nanowire, a thin film forming step of growing a group III-V compound constituting the nanowire from the nanowire to form a thin film composed of the group III-V compound on the graphene. A method for producing a nanowire, comprising: In the manufacturing method of the nanowire of Claim 1,
A method for producing a nanowire, wherein the nanowire is grown in a normal direction of a plane of the graphene. The method for producing a nanowire according to claim 4,
In the metal fine particle forming step, metal fine particles having a particle diameter of 10 nm or less are formed on the graphene,
In the said nanowire formation process, the nanowire of a III-V group compound is formed with the growth temperature of the range of 300-500 degreeC by the organometallic vapor phase growth method which used the said metal fine particle as a catalyst. The manufacturing method of the nanowire characterized by the above-mentioned. In the manufacturing method of the nanowire of any one of Claims 1-5,
A graphene forming step of forming the graphene on a substrate made of SiC having a main surface of (0001) by a thermal decomposition method;
In the metal fine particle forming step, the metal fine particles are formed on the graphene by forming gold fine particles along the steps of SiC and graphene by vacuum-depositing gold on the substrate. A method for producing a nanowire.