KR101200864B1 - Fabrication Method of Metal Silicide Single Crystalline Nanowire and The Oriented Metal Silicide Single Crystalline Nanowire - Google Patents

Abstract

The present invention is a catalyst-free, template-free condition, in which the length of the minor axis diameter is tightly controlled and has a constant orientation with respect to the substrate, and free-standing iron silicide nanowires on the substrate. The present invention relates to a method for producing iron nanowires prepared using the same, and in detail, the method according to the present invention includes a first precursor containing iron halide located at a front end of a reactor, and a rear end of the reactor. The second precursor containing silicon (Si) and carbon (C) located in the substrate, the substrate located in the rear end of the reactor is heat-treated in an atmosphere of flowing inert gas to produce iron silicide nanowires on the substrate, The relative growth rate in the short axis direction and the long axis direction of the iron silicide nanowires formed on the substrate is controlled by the mass ratio of silicon: carbon of the second precursor.

Description

Fabrication Method of Metal Silicide Single Crystalline Nanowire and The Oriented Metal Silicide Single Crystalline Nanowire

The present invention relates to a method for preparing iron silicide single crystal nanowires in a catalyst-free, template-free manner, in detail, the shortening of iron silicate single crystal nanowires without change in composition and structure. The length of the diameter is controlled, and relates to a method for producing an iron silicide single crystal nanowire having a constant orientation with the substrate by epitaxial growth on the substrate.

Silicide transition metals have received a lot of attention for a long time because of their potential applications in nanoscale electronics, photovoltaic, thermoelectric and spintronics devices (JD). Kim, WA Anderson, Nano Lett, 6, 1356 (2006); Y. Maeda, K. Umezawa, Y. Hayashi, K. Miyake, K. Ohashi, Thin Solid Films, 381. 256 (2001); I. Aoyama, H. Kaibe, L. Rauscher, T. Kanda, M. Mukoujima, S. Sano, T. Tsuji, Jpn. J. Appl. Phys, 44. 4275 (2005); AL Schmitt, JM Higgins, S. Jin, Nano Lett, 8. 810 (2008)). Among them, iron silicide is a paramagnetic semiconductor material exhibiting unusual electrical, optical, and magnetic properties depending on temperature, and the only transition metal consulator (Kondo insulator) exhibiting Kondo properties at room temperature to date. (S. Paschen, E. Felder, MA Chernikov, L. Degiorgi, H. Schwer, HR Ott, Phys. Rev. B ,. 56. 12916 (1997); E. Aeppli, JF Ditusa, Mater. Sci. Eng. B, 63. 119 (1999)).

Self-assembly metal silicide nanowires, on the other hand, are expected to have advantages such as perfect monocrystalline, metal resistivity, and compatibility in silicon-based device fabrication, and thus are self-assembled epitaxial. Much research is underway to develop silicified transition metal nanowires and silicified rare earth metal nanowires (HC Hsu, WW Wu, HF Hsu, LJ Chen, Nano Lett, 7. 885 (2007); Y. Chen, DAA Ohlberg) RS Williams, J. Appl. Phys, 91. 3213 (2002)).

However, all of the epitaxially self-assembled metal silicide nanowires reported so far are horizontally grown on a substrate, and there are many difficulties in applying them to the fabrication of a multifunctional and highly integrated three-dimensional integrated platform. Therefore, it is expected to synthesize nanowires which are arranged in a specific direction on a substrate and positioned as independent structures for manufacturing a three-dimensional composite structure device.

Recently, the synthesis of semiconductor nanowires such as ZnO, Si, and InP nanowires grown epitaxially at a constant angle with respect to a substrate has been reported, but for the synthesis of these nanowires, metal catalysts or additional film formation, etc. Pretreatment (P. Yang, H. Yan, S. Mao, R. Russo, J. Johnson, R. Saykally, N. Morris, J. Pham, R. He, HJ Choi, Adv. Funct. Mater. 12, 323 (2002); Al. I. Hochbaum, R. Fan, R. He, P. Yang, Nano Lett. 5, 457 (2005); L. Gao, RL Woo, B. Liang, M. Pozuelo, S. Prikhodko, M, Jackson, N. Goel, MK Hudait, DL Huffaker, MS Goorsky, S. Kodambaka, RF Hicks, Nano Lett, 9. 2223 (2009)).

However, no studies have been reported on silicified transition metal nanowires grown directionally and freely without a catalyst.

The present invention is a catalyst-free, template-free condition without the use of catalysts and templates, it is possible to precisely control the length of the short axis in a catalyst-free, template-free condition, epitaxial growth on the substrate has a certain direction, independently A method of making free-standing iron silicide nanowires is provided.

By regulating the growth of epitaxially synthesized metal silicide nanowires from the substrate, it is easier to use ohmic contacts or interconnects in future complementary metal-oxide-semiconductors (CMOS). It is expected to be applicable to the development of three-dimensional photonic and spintronic devices, which are expected to be applicable and are expected to realize high integration and high performance.

The present invention provides a method for producing iron silicide nanowires having a constant orientation and having a fixed direction in a catalyst-free, template-free condition, and having a length of several micrometers or more and a strictly short diameter diameter. Is controlled and epitaxially grown on the substrate to provide free-standing iron silicide nanowires with constant orientation.

The method for producing iron silicide nanowires according to the present invention comprises a first precursor containing iron halides located at the front end of the reactor, and a silicon (Si) and carbon (C) located at the rear end of the reactor. The iron precursor nanowires are manufactured on the substrate by heat-treating a two precursor material and a substrate located at the rear end of the reactor in an inert gas flowing atmosphere, and the silicon precursor of the second precursor material on the substrate by the mass ratio of silicon: carbon. The relative growth rate in the short axis direction and the long axis direction of the iron silicide nanowires formed is controlled.

Specifically, the short axis diameter of the iron silicide nanowire is controlled by the silicon: carbon mass ratio of the second precursor, and the composition and crystal structure of the second precursor are maintained by the change of the mass ratio of silicon: carbon of the second precursor. Iron silicide nanowires with controlled short axis diameters are produced.

The production method according to the present invention is characterized by reducing the uniaxial diameter of the iron silicide nanowires by reducing the silicon content of the second precursor, in detail, the mass ratio of silicon: carbon of the second precursor is 1: By controlling to 8 to 20, the iron silicate nanowire having a short axis diameter of 50 to 350 nm is produced.

In order to control the uniaxial diameter of the iron silicide nanowires, although the silicon: carbon mass ratio of the second precursor is changed, the iron silicide nanowires have a constant composition, and the iron silicide nanowires are made of Fe ₁ Si _1. There is a characteristic that is.

In order to control the uniaxial diameter of the iron silicide nanowires, although the silicon: carbon mass ratio of the second precursor is changed, the iron silicide nanowires have a constant crystal structure, and the iron silicide nanowires have a cubic system. It is characterized by a B20 type structure (space group P2 ₁ 3).

Furthermore, the iron silicide nanowires produced by the above production method are characterized by being single crystal without defects including twins.

Preferably, the second precursor is located below the substrate, the iron silicide nanowires are manufactured on the substrate, in the manufacturing method according to the present invention, the front end of the reactor is maintained at 450 ℃ to 600 ℃, The rear end of the reactor is maintained at 900 ℃ to 1000 ℃, the inert gas flows from the front end of the reactor to the rear end of the reactor, the flow rate of the inert gas is characterized in that 100 to 300 sccm.

In particular, the iron silicide nanowires may be epitaxially grown on the substrate, and by epitaxial growth, the iron silicide nanowires may have a constant orientation with respect to the surface of the substrate. And free-standing on the substrate.

Iron silicide nanowires according to the present invention is a first precursor containing iron halides located at the front end of the reactor, a second precursor containing silicon (Si) and carbon (C) located at the rear end of the reactor And, the substrate located in the rear end of the reactor is manufactured by heat treatment in the atmosphere flowing inert gas, characterized in that the iron silica nanowires whose uniaxial diameter is controlled by the silicon to carbon mass ratio of the second precursor.

The iron silicate nanowires with controlled short axis diameters are characterized by Fe ₁ Si ₁ , have a cubic B20 type structure (space group P2 ₁ 3), and are characterized by being single crystal without defects including twins. .

The major axis direction of the iron silicide nanowire is [110], and the short axis diameter of the iron silicide nanowire controlled by the mass ratio of silicon: carbon of the second precursor is 50 to 350 nm.

More particularly, the iron silicide nanowires are epitaxially grown on the substrate, have a constant orientation with respect to the surface of the substrate, and are free-standing on the substrate.

Iron silicide nanowire manufacturing method according to the present invention has the advantage that can strictly control only the uniaxial diameter of the nanowire without a change in composition and crystal structure, it has a constant orientation to the substrate surface and independently standing iron silicide nanowire It has the advantage of manufacturing, high purity and the advantage of mass production of iron silicide nanowires in a short time, and furthermore, the single iron silicide nanowires are single crystals with no defects including twin. There is an advantage that can be made of high quality iron silicide nanowires made.

1 is a configuration diagram showing an apparatus in which the manufacturing method of the present invention is performed,
2 is a diagram showing the diameter of the nanowire short axis according to the mixing ratio of the silicon powder and the carbon powder of the iron silicide nanowires prepared according to the production method of the present invention,
Figure 3 is a (a) transmission electron micrograph of the silicon silica nanowires directionally grown when the silicon: carbon mass ratio of the second precursor according to the manufacturing method of the present invention (attached photo: restriction field electron diffraction pattern ) And (b) high-resolution transmission electron micrograph (attached photo: two-dimensional fast Fourier transform pattern),
Figure 4 is a (a) transmission electron micrograph of the iron silicide nanowires grown directionally when the silicon: carbon mass ratio of the second precursor is 1: 8 according to the production method of the present invention (attached photo: restriction field electron diffraction pattern ) And (b) high-resolution transmission electron micrograph (attached photo: two-dimensional fast Fourier transform pattern),
5 is an X-ray diffraction pattern of iron silicide nanowires prepared according to the method of the present invention.
6 is a result of component analysis through a transmission electron microscope-energy dispersion analyzer (TEM-EDS) of the iron silicide nanowires prepared according to the method of the present invention.
7 is a scanning electron micrograph of the iron silicide nanowires prepared according to the manufacturing method of the present invention, (a) a low magnification scanning electron micrograph and (b) a high magnification scanning electron microscope photograph of iron silicide nanowires grown directionally on a sapphire substrate (Attachment: Scanning Electron Micrograph of Seed Observed with Nanowires on the Substrate), the red and green arrows in (b) indicate the growth direction of the nanowires on the substrate,
8 is a scanning electron micrograph of the iron silicide nanowires prepared according to the manufacturing method of the present invention, (a) scanning electron micrographs of various types of iron silicide seeds synthesized on a sapphire substrate, (b) to (j An enlarged scanning electron micrograph of three types of seeds, nanowire tips and roots grown in specific directions, and seed nanocrystals.

Hereinafter, a manufacturing method of the present invention will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided by way of example so that the spirit of the invention to those skilled in the art can fully convey. Therefore, the present invention is not limited to the following drawings, but may be embodied in other forms, and the following drawings may be exaggerated in order to clarify the spirit of the present invention. Also, throughout the specification, like reference numerals designate like elements.

Hereinafter, the technical and scientific terms used herein will be understood by those skilled in the art without departing from the scope of the present invention. Descriptions of known functions and configurations that may be unnecessarily blurred are omitted.

In the method for producing iron silicide nanowires of the present invention, a first precursor placed at the front end of the reactor, a second precursor placed at the rear end of the reactor, and a substrate placed at the rear end of the reactor are inert gas. Heat treatment in an atmosphere of flowing iron sulfide nanowires are formed on the surface of the substrate, characterized in that the iron silicide nanowires are produced in the catalyst-free and template-free conditions, the first precursor contains iron halide The second precursor contains silicon (Si) and carbon (C), and by controlling the relative content of silicon and carbon of the second precursor, the growth rate in the short axis direction and the long axis direction of the iron silicide nanowires are controlled. There is a characteristic that controls the relative growth rate between growth rates.

In detail, by controlling the mass ratio of silicon to carbon of the second precursor, the growth rate of the uniaxial direction of the iron silicide nanowires is controlled to precisely control the short axis diameter of the manufactured iron silicide nanowires.

At this time, in order to control the uniaxial diameter of the iron silicide nanowires, even if the mass ratio of silicon to carbon of the second precursor is changed, iron silicide nanowires having the same composition and the same crystal structure are produced, and the long axis of the nanowires to be manufactured. The length of the direction is hardly changed, and only the minor axis diameter is precisely controlled.

Specifically, in the manufacturing method according to the present invention, the short axis diameter of the iron silicide nanowires is shortened by reducing the silicon content of the second precursor and reducing the growth rate in the short direction of the nanowires.

More specifically, the silicon: carbon mass ratio of the second precursor is characterized in that 1: 8 to 20, and as the mass of carbon to silicon increases, the uniaxial diameter of the manufactured iron silicide nanowires decreases. There is this. Specifically, the silicon silica nanowires having a short axis diameter of 350 nm to 50 nm are manufactured by controlling the mass ratio of silicon: carbon of the second precursor to 1: 8 to 20.

In this case, the iron silicide nanowire having a length of several tens to several tens of micrometers and having a short axis diameter of 50 to 350 nm is characterized in that the composition is maintained as Fe ₁ Si ₁ , and a cubic B20 type structure (space group P2 ₁ 3). ) Structure is maintained.

At this time, the single nanowires are made of a single single crystal without a surface defect including a twin, characterized in that the single crystal iron silicide nanowires are produced.

As described above, the first core idea of the manufacturing method according to the present invention is a control factor which has a slight influence on the growth rate in the long axis direction of the nanowire and affects the growth rate in the short axis direction, and the silicon of the second precursor material. : Use mass ratio of carbon. Thereby, iron silicide nanowires having a length in a similar long axis direction and controlled strictly in length of a short axis diameter using a silicon to carbon mass ratio of the second precursor are produced.

As described above, the second core idea of the manufacturing method according to the present invention is a control factor influencing the growth rate in the uniaxial direction, using a silicon to carbon mass ratio of the second precursor, and containing iron halide. By separating the first precursor and the second precursor containing silicon and carbon into the front end and the rear end of the reactor, the substrate is placed at the rear end of the same reactor as the second precursor, and heat-treated in an atmosphere where an inert gas flows. To prepare iron silicide nanowires in which the uniaxial diameter of the nanowires is controlled while maintaining the same composition and crystal structure.

As described above, the third core idea of the manufacturing method according to the present invention includes the precursor (heated or vaporized and decomposed precursors) by thermal vaporization and vapor phase carriers of the precursors under catalyst-free and template-free conditions. By using this method, the complete single-crystal iron silicide nanowires are free from defects on the substrate (including 2-dimensional defects and twin planes). Accordingly, it is possible to mass-produce monocrystalline iron silicide nanowires having high purity and excellent crystallinity easily and in a short time.

In the manufacturing method according to the present invention, the iron silicide nanowires whose uniaxial diameter is controlled are characterized by being epitaxially grown on the substrate.

During the nucleation and growth of the iron silicide nanowires, as the iron silicide nanowires and the substrate have an epitaxial relationship, the iron silicide nanowires prepared on a substrate may be formed by randomly generating a plurality of iron silicide nanowires on a substrate. non-random) and is arranged in a certain orientation with respect to the surface of the substrate.

In this case, the constant directionality is the vector of the major axis direction of the iron silicide nanowire is a reference vector component of the substrate surface direction; A reference vector component in the substrate vertical direction; Or a reference vector component in a substrate surface direction and a reference vector component in a substrate vertical direction.

In order to produce iron silicide nanowires having a constant orientation with respect to the substrate surface, the substrate is preferably a single crystal substrate, the surface of the single crystal substrate is nucleation of the iron silicide, in particular 2-dimensional nucleation ) Is a surface of an insulator or semiconductor single crystal that easily occurs, and should be appropriately selected so that elastic stress or elastic strain and dislocation induced by lattice mismatch do not easily occur.

As described above, the non-conductor or semiconductor single crystal substrate can be easily generated as a two-dimensional nucleation of iron silicide, and can be used as a semiconductor or non-conductor that is chemically / thermally stable under heat treatment conditions for manufacturing nanowires, but substantially silicon single crystal. Group 4 single crystal selected from germanium single crystal or silicon germanium single crystal; Group 3-5 single crystal selected from gallium arsenide single crystal, indium single crystal or gallium single crystal; Group 2-6 single crystals; Group 4-6 single crystals; Sapphire single crystal; Silicon oxide single crystals; Or a laminated substrate thereof. The single crystal substrate may include a group 4 single crystal substrate in consideration of the crystal structure and lattice constant of bulk iron silicide; Group 3-5 single crystal substrate; Group 2-6 single crystal substrate; Group 4-6 single crystal substrate; Sapphire single crystal substrate; Silicon oxide single crystal substrate; Or these laminated substrates can be used, and the single crystal substrate which has the low water surface ((100), (110), (111) surface etc.) of a thermodynamically stable single crystal substrate as a surface can be used. An example of a substrate that can be used in the production of iron silicide nanowires is a sapphire single crystal substrate (m-plane).

As described above, the fourth core image according to the present invention uses a substrate which easily generates two-dimensional nucleation of the iron silicide, and uses a heat treatment temperature for a thermodynamically stable surface phase of the iron silicide material. By controlling the flow rate of the inert gas and controlling the nucleation and growth driving force delivered to the substrate surface to produce iron silicide nanowires having the aligned orientation (orientation to the substrate surface).

According to the first to fourth core idea, the method for producing iron silicide nanowires according to the present invention controls the temperature of the front end of the reactor (first precursor), and the flow rate of the inert gas to control the substrate The amount of the first precursor to be supplied to the substrate, the temperature of the rear end of the reactor (substrate and the second precursor) and the amount of the second precursor to be supplied to the substrate and the nuclei of the iron silicide on the substrate. By controlling the rate of production and growth, and controlling the mass ratio of silicon to carbon of the second precursor, the composition and structure are maintained, and independent structured iron silicide nanowires having a controlled uniaxial diameter and having a constant orientation are produced. .

The first precursor comprises powdered iron halides, the iron halides being iron fluoride, iron chloride, iron bromide, iron iodide or mixtures thereof. At this time, the iron halide includes anhydrous iron halides.

The second precursor includes silicon and carbon, and preferably includes a mixed powder of silicon powder and carbon powder. In order to control the amount of silicon supplied to the substrate independently of the temperature of the rear end of the reactor, to maintain the composition and crystal structure and to control the short axis diameter of the iron silicide nanowires produced on the substrate, The mass ratio of silicon to carbon is controlled to be 1: 8-20. Preferably, the second precursor further contains carbon (C).

The substrate located at the rear end of the reactor together with the second precursor may be positioned such that an inert gas flows from the second precursor to the substrate, and may be positioned above the second precursor, but not a second precursor. In order to more tightly control the short axis diameter of the nanowire by the mass ratio of silicon: carbon, the substrate is preferably placed on top of the second precursor.

The temperature of each of the front end of the reactor (first precursor) and the rear end of the reactor (second precursor and the substrate) may be determined by physical properties such as melting point, vaporization point, vaporization energy, and flow conditions of an inert gas. It is to be controlled in consideration of the pressure conditions during the heat treatment, the temperature of the front end of the reactor (first precursor) is characterized in that 450 ℃ to 600 ℃, the rear end of the reactor (second precursor and substrate) The temperature is characterized in that 900 ℃ to 1000 ℃.

The inert gas is characterized by flowing from 100 to 300 sccm from the front end of the reactor (first precursor) toward the rear end of the reactor (second precursor and substrate).

The pressure during the heat treatment is preferably a pressure range (normal pressure ± 0.1 atm) similar to the normal pressure, more preferably normal pressure.

The reaction temperature of the reactor, the flow conditions of the inert gas, the mixing ratio of carbon, the degree of vaporization of each precursor, the amount of vaporized precursor delivered to the substrate per hour, the nucleation and growth rate of iron silicide material on the substrate, the same heat treatment The size of the uniaxial diameter of the nanowires over time, the surface energy of the iron silicide material (nanowire) produced on the substrate, the degree of aggregation of the iron silicide material (nanowire) produced on the substrate, the shape of the iron silicide material formed on the substrate affects morphology.

Therefore, the uniaxial diameter is controlled to the most desirable quality and shape by the vapor phase transfer method using the precursors of the present invention at the temperature, the flow of the inert gas and the pressure during the heat treatment, the iron silicide nanowire having a certain orientation to the substrate It can be prepared. When the condition is out of the above range, quality problems such as agglomeration of a manufactured nanowire, a change in shape, and defects may occur, and there is a problem of obtaining particles, rods, etc., which are not in the form of nanowires.

Since the heat treatment time affects the density of the nanowires, the length of the nanowires, etc., the heat treatment time should be appropriately controlled according to the use of the iron silicide nanowires, but is preferably heat treated for 2 minutes to 1 hour.

During the heat treatment time, the vaporized precursors move to the substrate to participate in nucleation and growth, but at the same time, mass transfer (atomic or cluster unit material) through the gas phase and the substrate surface between the iron silicide materials already formed on the substrate Move).

Therefore, after the heat treatment, the substrate on which the iron silicide nanowires are formed may be reheat-treated to a temperature range in which material movement is possible while removing all the precursors, thereby controlling the density, size, and the like of the iron silicide nanowires.

The iron silicide nanowires produced by the above-described manufacturing method have a long axis length of several to several tens of micrometers, and are characterized by being iron silicide nanowires whose axial diameter is strictly controlled.

In detail, the iron silicide nanowire according to the present invention has a long axis length of 10 μm or more and has a uniaxial diameter controlled from 50 to 350 nm, and is characterized by a single crystal having no surface defects, regardless of the uniaxial diameter of Fe. _It has a composition of ₁ Si ₁ , has a crystal structure of a cubic B20 type structure (space group P2 ₁ 3) irrespective of uniaxial diameter, and has an independent structure that stands on its own substrate with a certain directivity without being supported by a support. have.

The major axis direction of the iron silicide nanowire is [110], and the short axis diameter of the iron silicide nanowire controlled by the mass ratio of silicon: carbon of the second precursor is 50 to 350 nm.

More particularly, the iron silicide nanowires are epitaxially grown on the substrate, have a constant orientation with respect to the surface of the substrate, and are free-standing on the substrate.

(Example)

A device and configuration similar to that of FIG. 1 were used, and the furnace was divided into an upstream zone and a downstream stream, and was independently provided with a heating element and a temperature control device.

The reactor consists of a quartz tube with a diameter of 1 inch and a length of 60 cm through which the gas passes, and a boat-shaped vessel made of alumina (60 mm in length, 8 mm in width, for injecting the first precursor in the center of the front end of the reactor) A height of 7 mm) was located, and a boat-shaped container (70 mm long, 15 mm wide, 10 mm high) made of alumina was placed in the center of the rear end of the reactor to inject the second precursor.

Argon was used as the inert gas, and argon gas was introduced into the front end of the reactor and exhausted to the rear end of the reactor, and a vacuum pump (not shown) is provided at the rear end of the reactor.

Anhydrous iron chloride (II) was used as the first precursor, and silicon (Si) powder: carbon (C) powder was mixed in the range of 1: 2 to 1:30 as the second precursor. Mixed powders were used.

In detail, the mixed powder was placed in the boat-type vessel, and a sapphire substrate (5 mm × 5 mm, m-plane) was placed on the mixed powder in the boat-type vessel, and then placed in the middle of the rear end of the reactor.

In detail, 0.05 g of anhydrous iron dichloride was placed in the boat front end (60 mm long, 8 mm wide, 7 mm high) and placed in the middle of the front end of the reactor.

Then, after performing a vacuum test of the furnace (furnace) using a vacuum pump, and after confirming that there is no leakage (leakage) inside the reactor, the inside of the reactor is adjusted to atmospheric pressure by flowing argon gas, the reaction at atmospheric pressure Purging was performed by flowing argon gas into the furnace for 20 minutes to remove other impurities. Thereafter, 200 sccm of Ar is flowed into the reactor under atmospheric pressure to form an Ar flow from the front end to the rear end of the reactor. The temperature of the front end of the reactor is maintained at 530 ° C., and the temperature of the rear end of the reactor is 950 ° C. Heat treatment was performed for 10 minutes in the state maintained.

The shape and structure of the synthesized iron silicide nanowires were observed using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). X-ray Diffractometer (XRD), Energy Dispersive X-ray Spectroscopy (EDS), High Resolution TEM (HRTEM), In addition, a limited area electron diffraction (SAED) pattern was used.

According to the embodiment, when only the silicon: carbon mass ratio of the second precursor is changed under the same heat treatment conditions, it can be seen that the nanoparticles and the nanorods are mainly manufactured, not the nanowires, when the silicon: carbon mass ratio is 1: 2. It was found that iron silicide nanowires having an orientation with respect to the substrate were produced in a mass ratio of silicon: carbon of 1: 8 to 20. In addition, it was found that when the mass ratio of silicon: carbon exceeds 1:20, the orientation of the substrate is lost and randomly produced iron silicide nanowires.

FIG. 2 is a view showing the average uniaxial diameter of nanowires as the mass ratio of silicon: carbon of the second precursor changes from 1: 8 to 20, synthesized under conditions of silicon: carbon = 1: 8 (mass ratio). FIG. The iron silicide nanowires have an average diameter of 300 nm, and the iron silicide nanowires synthesized under the condition of silicon: carbon = 1: 20 (mass ratio) have an average diameter of 90 nm.

That is, when only silicon gas pressure was reduced while the other conditions were kept the same, the minor diameter of the nanowires, which were several hundred nm while having long axis lengths of 10 µm or more with the orientation of the silicon nanowires, was tens of nm. It can be seen that the decrease.

In order to check whether the decrease in diameter affects the composition and structure of the nanowire as the silicon: carbon mass ratio is changed from 1: 8 to 20, the silicon: carbon mixing ratio is 1:20 and the silicon: carbon mixing ratio TEM measurements were performed on each of the iron silicide nanowires synthesized under these 1: 8 conditions.

FIG. 3 shows the transmission electron microscope observation results of the iron silicide nanowires synthesized under a silicon-carbon ratio of 1:20. FIG. 3 (a) is measured with respect to the iron silicide nanowires having a diameter of about 50 nm. One transmission electron micrograph, and the attached photograph shows the Selected Area Electron Diffraction (SAED) pattern. Figure 3 (b) is a high resolution transmission electron micrograph of the iron silicide nanowires, the attached picture is a two-dimensional Fast Fourier Transform (FFT) pattern obtained through a high resolution transmission electron micrograph. As a result of the analysis, it was confirmed that the nanowires synthesized from the diffraction pattern were cubic iron silicides, and the regular dot pattern and the high resolution transmission electron micrograph of the limited field electron diffraction pattern showed that the synthesized nanowires were single crystals. In addition, the lattice plane has a spacing of 0.313 nm, which almost coincides with 0.317 nm of (110) plane spacing of cubic iron silicide, and it can be seen that the nanowires are grown in the [110] direction.

Figure 4 shows the transmission electron microscope observation results of the iron silicide nanowires synthesized in a silicon: carbon mixing ratio of 1: 8 conditions, Figure 4 (a) is a transmission electron micrograph of the iron silicide nanowires, attached The picture shows the Selected Area Electron Diffraction (SAED) pattern. As a result of analyzing the diffraction pattern of the nanowires, it is confirmed that the synthesized nanowires have single crystallinity as they perfectly match the iron silicides of the cubic B20 type structure and show regular dot patterns. Figure 4 (b) is a high resolution transmission electron micrograph of the iron silicide nanowires, the attached picture is a two-dimensional Fast Fourier Transform (FFT) pattern obtained through a high resolution transmission electron micrograph. High resolution transmission electron microscopy shows clear lattice of single crystal nanowires. In addition, the lattice plane has a spacing of 0.312 nm, which is almost identical to the (110) plane spacing of iron silicide having a cubic B20 type structure, and the nanowires are grown in the [110] direction.

In addition, X-ray diffraction analysis was performed on each of the iron silicide nanowires synthesized under the condition that the silicon: carbon mixing ratio was 1: 8 to 20. As a result, X- of all the iron silicide nanowires prepared as shown in FIG. It was confirmed that all peaks in the line diffraction spectrum correspond to Cubic B20 type FeSi (space group P2 ₁ 3, JCPDS card No. 38-1397) having a cubic B20 type structure.

Through analysis of the transmission electron microscope-energy dispersion analyzer (TEM-EDS) spectrum, the component analysis of the nanowires synthesized under the conditions of the silicon: carbon mixing ratio of 1: 8-20 was performed. As a result, it was confirmed that iron (Fe) and silicon (Si) were present in a ratio of 1: 1 similar to the results observed in FIG. 6. In this case, copper (Cu) of FIG. 6 is a component of the TEM grid, and a total of fifteen TEM-EDS measurements are performed at three points on five different nanowires manufactured at a constant silicon: carbon mass ratio. It was. It was confirmed that the ratio of iron and silicon was 1: 1 in all the measured nanowires, and the same TEM-EDS measurement result was obtained even when the silicon: carbon mixing ratio was changed from 1: 8 to 20.

As a result of observing the macroscopic shape and the orientation of the nanowires synthesized under the conditions of silicon: carbon mixing ratio of 1: 8-20 by scanning electron microscopy, the average major axis length under all conditions was similar to that of FIG. It can be seen that iron silicide nanowires having a thickness of 10 µm or more are synthesized, and iron silicide nanowires having a constant orientation with respect to the substrate are synthesized.

FIG. 7 illustrates a scanning electron micrograph of iron silicide nanowires formed on an m-plane sapphire substrate when the mass ratio of silicon to carbon is 1: 8. As shown in FIG. 7, the root portion of the nanowires is shown. Is bonded to the substrate, and as the nanowires grow in the longitudinal direction, it can be seen that they are independent from the substrate in eight directions as indicated by arrows in FIG. In addition, seed nanocrystals were observed together with the nanowires as shown in the attached photograph of FIG. 7 (b) on the substrate. When the ratio of silicon to carbon is 1: 8, the average diameter of the nanowires is about 300 nm and the length is several micrometers, similar to the TEM observation result.

Through the TEM analysis, SEM analysis, TEM-EDS analysis and X-ray diffraction analysis, the nanowires synthesized under silicon: carbon = 1: 8-20 (mass ratio) conditions are single crystal iron silicide nanowires, and silicon: According to the mass ratio of carbon, nanowires having a uniaxial diameter of 50 to 350 nm are strictly controlled, and nanowires with a controlled uniaxial diameter are manufactured with the same composition and the same crystal structure. It can be seen that the nanowires are produced in an independent structure.

As mentioned above, when examining the sapphire substrate synthesized with iron silicide nanowires, seed nanocrystals are observed along with the oriented nanowires. In addition, it was observed that the appearance and orientation of the iron silicide nanowires and the seed nanocrystals grown in the respective directions were very similar (Figs. 8 (b) to (j)).

In order to closely analyze the growth of nanowires having a direction toward the substrate, the nanowires and seeds grown in each direction were magnified and observed. FIG. 8A is a scanning electron micrograph of the iron silicide nanocrystals observed from the same substrate as the synthesized iron silicide nanowires. 8 (b) to (j) show the tip portions (Fig. 8 (b) to (d)), the root portions (Fig. 8 (e) to (g)) of the iron silicide nanowires grown in specific three directions, respectively. Magnified scanning electron micrographs of the nanocrystals (FIGS. 8 (h) to (j)), which are expected to be seeds of grown nanowires, are shown. 8 (b) and 8 (e) correspond to nanowires grown from the seeds of FIG. 8 (h) (type I) and FIGS. 8 (c) and 8 (f) grown from the seeds of FIG. 8 (i). Corresponds to nanowires (type II). 8 (g) and 8 (g) correspond to nanowires grown from the seeds of FIG. 8 (j) (type III). In the case of Type I and Type II seeds, in addition to the seeds shown in FIGS. 8 (h) and 8 (i), there are three kinds of seeds which rotate by 90 °. Type I and type II seeds have asymmetric tetrahedral morphology, and in the case of nanowires grown from these seeds, the nanowires grow in the direction toward the longest edge of each seed, thus growing in four different directions. The wire is synthesized (direction indicated by the red arrow in Fig. 7 (b)). In the case of the type III seed, as in the case of the type I and type II seeds, there are three types of seeds that are rotated by 90 ° in addition to the seeds shown in FIG. 8 (j). consist of. The type III seed is almost tetrahedral, and looking at the direction of the nanowires that can grow along the edges, it is possible to grow in eight different directions as indicated by the red and green arrows in FIG. I could confirm that. Interestingly, out of a total of 12 seeds of type I, II, and III, growth is possible from all 12 seeds in the direction of the red arrow in FIG. 7 (b), whereas the possibility of nanowires growing in the direction of the green arrow is type III. It can be observed that only four seeds corresponding to the seeds have. Through the seed analysis, it can be expected that the nanowires grown in the direction of the red arrow of FIG. 6 (b) will have three times more density than the nanowires grown in the direction of the green arrow. As a result of the SEM observation, the ratio of the synthesized nanowires was approximately 77%. The nanowires grown in the direction of the red arrow were approximately 77%, and the nanowires were grown in the direction of the green arrow, approximately 23%. Almost matched with. From this, it can be inferred that directionally grown iron silicide nanowires were grown from iron silicide seed nanocrystals, and the type of seed nanocrystals and positions of seed nanocrystals were used to form a three-dimensional structure of iron silicide nanowires. It can be seen that the design is possible.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will recognize that many modifications and variations are possible in light of the above teachings.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (22)

A first precursor containing iron halide located at the front end of the reactor, a second precursor containing silicon (Si) and carbon (C) located at the rear end of the reactor, and a rear end of the reactor The substrate is heat-treated in an inert gas atmosphere to produce iron silicide nanowires on the substrate, and the short axis direction and the long axis of the iron silicide nanowires formed on the substrate by the mass ratio of silicon: carbon of the second precursor. Method for producing iron silicide nanowires, characterized in that the relative growth rate of the direction is controlled. The method of claim 1,
The uniaxial diameter of the iron silicide nanowires is controlled by the mass ratio of silicon: carbon of the second precursor. The method of claim 2,
A method of manufacturing iron silicide nanowires, wherein the iron silicide nanowires having a constant composition and crystal structure are maintained by controlling the silicon: carbon mass ratio of the second precursor and the uniaxial diameter is controlled. The method of claim 1,
And reducing the silicon content of the second precursor to reduce the short axis diameter of the iron silicide nanowires. The method of claim 3, wherein
The iron silicide nanowire is a method for producing iron silicide nanowires, characterized in that Fe ₁ Si ₁ . The method of claim 3, wherein
The iron silicide nanowires have a cubic B20 type structure (space group P2 ₁ 3). The method of claim 3, wherein
The iron silicide nanowire is a method for producing iron silicide nanowires, characterized in that the single crystal without a defect including the twin. The method of claim 1,
Method for producing iron silicide nanowires, characterized in that the mass ratio of silicon: carbon of the second precursor is 1: 8-20. The method of claim 8,
The uniaxial diameter of the iron silicide nanowires is a method for producing iron silicide nanowires, characterized in that 50 to 350nm. The method of claim 1,
The second precursor material is located below the substrate, characterized in that the iron silicide nanowire manufacturing method. The method of claim 1,
The front end of the reactor is maintained at 450 ℃ to 600 ℃, the rear end of the reactor is a method of manufacturing iron silicide nanowires, characterized in that maintained at 900 ℃ to 1000 ℃. 12. The method of claim 11,
The inert gas flows from the front end of the reactor to the rear end of the reactor, the flow rate of the inert gas is 100 to 300 sccm manufacturing method of iron silicide nanowires. The method of claim 8,
The iron silicide nanowires are epitaxially grown on the substrate. The method of claim 13,
The iron silicide nanowires have a predetermined orientation with respect to the surface of the substrate. The method of claim 13,
The iron silicide nanowires are free-standing on the substrate. A first precursor containing iron halide located at the front end of the reactor, a second precursor containing silicon (Si) and carbon (C) located at the rear end of the reactor, and a rear end of the reactor It is manufactured by heat-treating the substrate in an inert gas flowing atmosphere, the iron silica nanowires whose uniaxial diameter is controlled by the mass ratio of silicon: carbon of the second precursor,
The iron silicide nanowires are epitaxially grown on the substrate, and the iron silicide nanowires have an epitaxial relationship.
The iron silicide nanowires are characterized in that the iron silicide nanowires having an orientation arranged in parallel to each other in two or more directions with respect to the surface of the substrate. 17. The method of claim 16,
The iron silicide nanowires are iron silicide nanowires, characterized in that Fe ₁ Si ₁ . 17. The method of claim 16,
The iron silicide nanowires have a cubic B20 type structure (space group P2 ₁ 3). 17. The method of claim 16,
The iron silicate nanowires are iron silicide nanowires, characterized in that the single crystal without a defect including the twin. 19. The method of claim 18,
The major axis direction of the iron silicide nanowires is [110], and the minor diameter is 50 nm to 350 nm iron silicide nanowires. delete 17. The method of claim 16,
The iron silicide nanowires are free-standing on the substrate.

Images