KR102452121B1 - n-type thermoelectric Metal Alloy Nanowire and the Fabrication Method Thereof - Google Patents

Abstract

The present invention relates to an alloy-based n-type thermoelectric nanowire. Specifically, the n-type thermoelectric nanowire according to the present invention is a bismuth-antimony binary alloy nanowire, and satisfies the following Equations 1 and 2.
(Equation 1)
1x10 ³ Sm ^-1 ≤ EC ≤ 1x10 ⁴ Sm ^-1
(In Equation 1, EC is the electrical conductivity of the binary alloy nanowire (electrical conductivity, Sm ^-1 ))
(Equation 2)
Z ≤ - 110 μVK ^-1
(In Equation 2, S is the Seebeck coefficient of the binary alloy nanowire (Seebeck Coefficient, μVK ^-1 ))

Description

Alloy-based n-type thermoelectric nanowire and its manufacturing method

The present invention relates to an alloy-based n-type thermoelectric nanowire and a method for manufacturing the same, and more particularly, an n-type having an excellent Seebeck coefficient while reducing thermal conductivity without significant loss of electrical conductivity due to a low-dimensional structural factor called nanowire. It relates to a thermoelectric nanowire and a method for manufacturing the same.

The thermoelectric effect is a phenomenon in which thermal energy and electrical energy are directly converted to each other, and applications are being sought in various fields such as local cooling of high direct circuits in industrial waste heat generators and semiconductors.

Thermoelectric figure of merit (ZT) is a function of Seebeck coefficient (S), thermal conductivity (κ), and electrical conductivity (σ), and each factor ( After the theoretical rationale for independently controlling S, σ, κ) was announced, a lot of attention has been paid to nano-thermoelectric materials.

Bi (bismuth), a semimetallic, has intermediate properties between metals and nonmetals, and is used as a thermoelectric material either alone or in an alloy form. In particular, since single crystal Bi nanowires have very small band overlap energy, the Seebeck coefficient (Seebeck coefficient) caused by the semimetal to semiconductor transition phenomenon through the quantum confinement effect according to the reduction in the diameter of the nanowire. coefficient) can be improved theoretically. In addition, in low-dimensional nanostructures such as nanowires, the mean free path of phonons is limited by low-dimensional structural factors, but the mean free path of electrons is not affected, so electrical conductivity ), by reducing the thermal conductivity due to phonon scattering, it is possible to overcome the limitations of bulk thermoelectric materials and increase the thermoelectric figure of merit (ZT).

However, research on low-dimensional nanostructures such as nanowires is concentrated on chalcogen systems such as Bi and Te, but Bi-chalcogen alloys are compositionally controlled by the volatility of low-dimensional structured chalcogens such as nanowires. It is difficult to manufacture nanowires of homogeneous quality, so there is a limit to commercialization.

Republic of Korea Patent Publication No. 10-2017-0026708

The present invention is to provide a non-chalcogen-based alloy nanowire having improved thermoelectric properties and a method for manufacturing the same.

The alloy-based n-type thermoelectric nanowire according to the present invention is a bismuth-antimony binary alloy nanowire, and satisfies Equations 1 and 2 below.

(Equation 1)

1x10 ³ Sm ^-1 ≤ EC ≤ 1x10 ⁴ Sm ^-1

In Equation 1, EC is the electrical conductivity (Sm ^-1 ) of the binary alloy nanowire.

(Equation 2)

Z ≤ - 110 μVK ^-1

In Equation 2, Z is the Seebeck coefficient of the binary alloy nanowire (Seebeck Coefficient, μVK ^-1 ).

In the alloy-based n-type thermoelectric nanowire according to an embodiment of the present invention, an elemental ratio of bismuth:antimony in the binary alloy may be 1:0.1 to 0.3.

In the alloy-based n-type thermoelectric nanowire according to an embodiment of the present invention, the binary alloy nanowire may have a superlattice structure.

In the alloy-based n-type thermoelectric nanowire according to an embodiment of the present invention, Z may be -110 μVK ^-1 or less.

In the alloy-based n-type thermoelectric nanowire according to an embodiment of the present invention, an element using energy dispersive X-ray spectroscopy according to a virtual analysis line crossing the nanowire perpendicular to the longitudinal direction of the binary alloy nanowire A line profile, which is a result of star strength analysis, may satisfy Equation 3 below.

(Equation 3)

0.9 ≤ I2/I1 ≤ 1

In Equation 3, I1 is an intensity ratio obtained by dividing the bismuth intensity in the region of 0.1D/2 from the center of the effective analysis line by the antimony intensity by using the analysis line located on the nanowire as the effective analysis line and the length of the effective analysis line as D. , and I2 is the intensity ratio obtained by dividing the center of the effective analysis line with the origin (0) and the bismuth intensity in the region of 0.5D/2 to D/2 divided by the antimony intensity.

In the alloy-based n-type thermoelectric nanowire according to an embodiment of the present invention, the minor axis diameter of the nanowire may be 50 to 500 nm.

The present invention includes a method for manufacturing the above-described n-type thermoelectric nanowire.

A method of manufacturing an n-type thermoelectric nanowire according to the present invention comprises the steps of: a) forming a bismuth thin film on a substrate having an oxide layer; b) growing bismuth nanowires by first heat-treating the substrate on which the bismuth thin film is formed; c) depositing antimony on the surface of the bismuth nanowire to prepare a bismuth-antimony core-sheath nanowire; and d) bismuth-antimony core-sheath nanowires are subjected to a second heat treatment to prepare bismuth-antimony binary alloy nanowires.

In the method of manufacturing an n-type thermoelectric nanowire according to an embodiment of the present invention, a ratio obtained by dividing the coefficient of thermal expansion of the substrate by the coefficient of thermal expansion of the oxide layer may be 3 or more.

In the method of manufacturing an n-type thermoelectric nanowire according to an embodiment of the present invention, the first heat treatment in step b) is 0.9 to 0.95 Tm(Bi) based on Tm(Bi), which is the melting point (°C) of bismuth. ) can be carried out.

In the method of manufacturing an n-type thermoelectric nanowire according to an embodiment of the present invention, the second heat treatment in step d) may be performed at a temperature satisfying Equation 4 below.

(Equation 4)

T _m (Bi) - 55℃ ≤ T ≤ T _m (Bi) + 40℃

In Equation 4, T is the second heat treatment temperature (°C), and T _m (Bi) is the melting point (°C) of bismuth.

In the method of manufacturing an n-type thermoelectric nanowire according to an embodiment of the present invention, the second heat treatment in step d) includes a low temperature heat treatment performed at a temperature lower than T _m (Bi) and a temperature higher than T _m (Bi). Including high-temperature heat treatment performed in, low-temperature heat treatment and high-temperature heat treatment may be alternately performed.

In the n-type thermoelectric nanowire according to the present invention, the quantum confinement effect according to band engineering and one-dimensional nanostructure (nanowire) generated when bismuth is alloyed with antimony, and the bismuth-antimony binary alloy nanowire It has a remarkably improved Seebeck coefficient by excellent compositional uniformity and excellent crystallinity, and an electrical conductivity almost similar to that of bulk bismuth-antimony alloy, and reduction and alloying of phonon mean free path due to low-dimensional structural factors such as nanowires. The thermal conductivity can be reduced by effective phonon scattering due to the large mass difference between antimony and bismuth by

1 is a view showing a transmission electron microscope (TEM) and a scanning transmission electron microscope (STEM) photograph and elemental analysis results of a core/sheath nanowire prepared for alloying in an embodiment of the present invention.
2 is a view showing a transmission electron microscope (TEM) and a scanning transmission electron microscope (STEM) photograph and elemental analysis results of the bismuth-antimony alloy nanowire prepared in an embodiment of the present invention.
3 is a scanning transmission electron microscope (STEM) photograph (FIG. 3(a)) of the bismuth-antimony alloy nanowire prepared in an embodiment of the present invention and bismuth and antimony analyzed along the yellow line in the STEM image. It is a diagram (3(b)) showing an Energy Dispersive X-ray Spectroscopy (EDS) line profile.
4 is a scanning electron micrograph showing a platform for measuring the electrical conductivity and Seebeck coefficient of the bismuth-antimony alloy nanowire prepared in an embodiment of the present invention, and the prepared bismuth-antimony alloy nanowire; It is a diagram showing the measurement of the Seebeck coefficient.

Hereinafter, the n-type thermoelectric nanowire of the present invention and a manufacturing method thereof will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, if there is no other definition in the technical terms and scientific terms used, it has the meaning commonly understood by those of ordinary skill in the art to which this invention belongs, and the gist of the present invention in the following description and accompanying drawings Descriptions of known functions and configurations that may be unnecessarily obscure will be omitted.

Also, the singular forms used in the specification and appended claims may also be intended to include the plural forms unless the context specifically dictates otherwise.

In this specification and the appended claims, the terms include or have means that a feature or element described in the specification is present, and unless specifically limited, one or more other features or elements are added. This does not preclude the possibility that it will be.

The alloy-based n-type thermoelectric nanowire according to the present invention is a bismuth-antimony binary alloy nanowire, and satisfies Equations 1 and 2 below.

(Equation 1)

1x10 ³ Sm ^-1 ≤ EC ≤ 1x10 ⁴ Sm ^-1

In Equation 1, EC is the electrical conductivity (Sm ^-1 ) of the binary alloy nanowire.

(Equation 2)

Z ≤ - 110 μVK ^-1

In Equation 2, Z is the Seebeck coefficient of the binary alloy nanowire (Seebeck Coefficient, μVK ^-1 ).

As described above, the thermoelectric nanowire according to the present invention is an n-type thermoelectric nanowire having a negative Seebeck coefficient, and is a bismuth-antimony binary alloy nanowire.

Antimony is a non-chalcogen element, and has low volatility compared to a chalcogen element, enabling the manufacture of nanowires of a homogeneous composition, and enables the manufacture of reproducible nanowires. In addition, the large mass between antimony and bismuth due to alloying with antimony, which is only 58% of the bismuth mass (molecular weight), along with the reduction of the phonon mean free path due to the low-dimensional structural factor of nanowires. The difference can effectively scatter phonons, effectively reducing the thermal conductivity. In addition, band engineering generated when bismuth is alloyed with antimony, quantum confinement effect according to one-dimensional nanostructure (nanowire), and excellent compositional uniformity and excellent crystallinity of bismuth-antimony binary alloy nanowire , - 110 μVK ^-1 or less, specifically - 115 μVK ^-1 or less, more specifically - 120 μVK ^-1 or less, and even more specifically - 125 μVK ^-1 or less, may have a Seebeck coefficient of bismuth nanowire or bulk It may have an electrical conductivity of 1x10 ³ Sm ^-1 to 1x10 ⁴ Sm ^-1 similar to the electrical conductivity of the bismuth-antimony alloy.

Specifically, the Seebeck coefficient of -110 μVK ^-1 or less is a Seebeck coefficient that is more than twice improved compared to the Seebeck coefficient of the bismuth nanowire having the same dimension (short axis diameter) as the thermoelectric nanowire according to the present invention, and the bismuth-anti- The Seebeck coefficient is more than 1.2 times improved compared to the Seebeck coefficient of Mony bulk. In this case, as both bismuth and bismuth-antimony alloys have n-type thermoelectric properties, they have a negative Seebeck coefficient as well.

In one embodiment, in the bismuth-antimony binary alloy nanowire, an elemental ratio of bismuth to antimony may be 1:0.1 to 0.3, specifically 1:0.10 to 0.25, and more specifically 1:0.15 to 0.25. Such a bismuth-antimony binary alloy composition is a composition in which a semimetal to semiconductor transition occurs by band engineering generated by alloying and the Seebeck coefficient can be further improved. Specifically, since the bismuth-antimony binary alloy nanowire satisfies the above-described composition, the Seebeck coefficient of - 120 μVK ^-1 or less, more specifically - 125 μVK ^-1 or less, and still more specifically - 130 μVK ^-1 or less can have

In one embodiment, the bismuth-antimony binary alloy nanowire may be a crystal of a binary alloy, specifically a polycrystalline to a single crystal, and more specifically a single crystal. For example, the bismuth-antimony binary alloy nanowire may be a single crystal, and may have a solid solution or a superlattice structure.

In one embodiment, the bismuth-antimony binary alloy nanowire may have an extremely uniform composition. Specifically, the bismuth-antimony binary alloy nanowire is a line profile that is the result of strength analysis for each element using energy dispersive X-ray spectroscopy along a virtual analysis line that crosses the nanowire perpendicular to the longitudinal direction of the nanowire. Equation 3 below may be satisfied.

(Equation 3)

0.9 ≤ I2/I1 ≤ 1

In Equation 3, I1 is an intensity ratio obtained by dividing the bismuth intensity in the region of 0.1D/2 from the center of the effective analysis line by the antimony intensity by using the analysis line located on the nanowire as the effective analysis line and the length of the effective analysis line as D. , and I2 is the intensity ratio obtained by dividing the center of the effective analysis line with the origin (0) and the bismuth intensity in the region of 0.5D/2 to D/2 divided by the antimony intensity. According to an imaginary line in which the analysis line crosses the nanowire perpendicular to the length direction of the nanowire, the length of the effective analysis line may correspond to the minor axis diameter of the nanowire. In this case, the line profile may be an intensity profile, but is not necessarily limited thereto, and a profile of the composition (atomic%) calculated using the detected intensity may be used. In this case, I1 and I2 are each region may correspond to the composition in Experimentally, the line profile was analyzed using a scanning electron microscope (SEM), a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM) to observe the as-fabricated as-fabricated nanowires for analysis. may be obtained by performing energy dispersive X-ray spectroscopy along an imaginary line perpendicular to the longitudinal direction.

Substantially, I2/I1 in Equation 3 may be 0.90 to 1.00, specifically 0.92 to 1.00, and more specifically 0.95 to 1.00. This value of I2/I1 means that the composition measured at the center of the nanowire and the composition measured at the edge of the nanowire are substantially the same. As described above, bismuth and antimony are alloyed and a semi-metal-semiconductor transition phenomenon may occur due to the accompanying band engineering. Accordingly, the uniform composition means that the semi-metal-semiconductor transition occurs throughout the nanowire, and phonon scattering due to the mass difference also occurs homogeneously.

In one embodiment, the minor axis diameter of the bismuth-antimony binary alloy nanowire may be 50 to 500 nm, specifically 50 to 300 nm, more specifically 50 to 150 nm. The minor axis diameter of such a binary alloy nanowire is a diameter that can effectively reduce the phonon mean free path due to low-dimensional structural factors and suppress deterioration of electrical conductivity. At this time, the long and short aspect ratio (aspect ratio) of the binary alloy nanowire may be 100 to 10000 level, but is not limited thereto.

In one embodiment, the bismuth-antimony binary alloy nanowire may have a uniform diameter. Specifically, when the maximum minor axis diameter is Dmax and the minimum minor axis diameter is Dmin in the size(s) of minor axis diameters randomly measured at 5 to 10 places in the longitudinal direction of the binary alloy nanowire, Dmax is within 1.1Dmin , specifically within 1.08 Dmin, more specifically within 1.05 Dmin.

The present invention includes a method for manufacturing the above-described n-type thermoelectric nanowire.

A method of manufacturing an n-type thermoelectric nanowire according to the present invention comprises: a) forming a bismuth thin film on a substrate having an oxide layer; b) growing bismuth nanowires by first heat-treating the substrate on which the bismuth thin film is formed; c) depositing antimony on the surface of the bismuth nanowire to prepare a bismuth-antimony core-sheath nanowire; and d) bismuth-antimony core-sheath nanowires are subjected to a second heat treatment to prepare bismuth-antimony binary alloy nanowires.

When the substrate having the oxide layer is subjected to the first heat treatment in step b), compressive stress is caused to the bismuth thin film formed in step a), thereby providing a driving force for generating bismuth nanowires from the bismuth thin film.

The thermal expansion coefficient of the oxide layer may be smaller than the thermal expansion coefficient of the substrate and the thermal expansion coefficient of bismuth so that compressive stress can be applied to the bismuth thin film during the heat treatment in step b), and bismuth nanowires are formed from the bismuth thin film during the heat treatment in step b). The ratio of the coefficient of thermal expansion of the substrate divided by the coefficient of thermal expansion of the oxide layer may be 3.0 or more, specifically 3.5 or more, more specifically 4.0 or more, even more specifically 4.5 or more, and may be substantially 10 or less so as to provide a driving force. . As a practical example, the thermal expansion coefficient of the substrate may be 2 to 5 x 10 ^-6 /°C, but is not necessarily limited thereto.

In terms of ensuring thermal stability during heat treatment and stably providing compressive stress to the bismuth thin film, the oxide layer may be an inorganic oxide layer, and the substrate may also be an inorganic substrate. In this case, the thickness of the oxide layer may be 300 to 500 nm, but is not necessarily limited thereto. In addition, the inorganic component of the inorganic oxide layer may be the same as the inorganic component of the inorganic substrate so that a strongly bound interface between the oxide layer and the substrate can be formed, and specifically, the inorganic oxide layer may be a surface oxide layer of the inorganic substrate. . For example, the inorganic substrate may be a silicon substrate, and the inorganic oxide layer may be a silicon surface oxide layer, but is not limited thereto.

In step a), the bismuth thin film may be formed using conventional physical vapor deposition including sputtering, and the thickness of the bismuth thin film may be at the level of 50 nm to 4 μm, so that the thin film can be uniformly and large compressive stress. The present invention is not limited thereto.

The heat treatment (first heat treatment) of step b) is a bismuth nanowire as a driving force of thermal stress (compressive stress) induced in the bismuth thin film by the substrate-oxide layer-bismuth thin film (bismuth thermal expansion coefficient = 13.4x10 ^-6 /°C) structure. The first heat treatment is based on T _m (Bi), the melting point of bismuth (°C, atmospheric pressure), to stably provide driving force for nanowire growth and to allow active material movement to occur. It may be performed at 0.90 T _m (Bi) to 0.95 T _m (Bi), and more specifically, it may be performed at 0.90 T _m (Bi) to 0.93 T _m (Bi). In this case, the first heat treatment may be performed in a vacuum or an inert atmosphere, and may be performed for 2 to 15 hours, but is not necessarily limited thereto.

After step b) is performed, step (c) of preparing a bismuth-antimony core-sheath nanowire by depositing antimony on the surface of the bismuth nanowire prepared in step b) may be performed. . Deposition of antimony may also be performed using physical vapor deposition including sputtering. At this time, in terms of preventing damage to the bismuth nanowire, which is a single crystal, during the deposition process, the rf power during sputtering (rf sputtering) may be 40W or less, specifically 30 to 35W level, but is not necessarily limited thereto. In the core-sheath structure nanowire, the thickness of the sheath, that is, the amount of antimony deposited, is sufficient as long as the amount (thickness) can satisfy the composition of the desired alloy, which can be easily controlled by the sputtering execution time.

After forming the core-sheath nanowire in step c), the bismuth-antimony binary alloy nanowire may be manufactured through the second heat treatment in step d). The second heat treatment may be a heat treatment for forming an alloy by diffusing the antimony of the sheath into the bismuth core. The second heat treatment may be performed at a temperature satisfying Equation 4 below.

(Equation 4)

T _m (Bi) - 55℃ ≤ T ≤ T _m (Bi) + 40℃

In Equation 4, T is the second heat treatment temperature (°C), and T _m (Bi) is the melting point (°C) of bismuth, and specifically, it may be the melting point under atmospheric pressure.

As described above, the composition of the n-type thermoelectric nanowire in the form of an alloy directly affects the semi-metal-semiconductor transition phenomenon. Accordingly, in order to manufacture an n-type thermoelectric nanowire having an excellent Seebeck coefficient, above all, it is preferable to form an alloy having a homogeneous composition in which a significant composition difference does not exist between the center and the edge of the nanowire. However, since the antimony present in the outer shell acts as a source of antimony and diffuses toward the inner bismuth, even when heat treatment is performed for a very long time, the nanowire with a higher antimony concentration than the center in the edge region of the nanowire There is a high risk of being manufactured.

To prevent such compositional non-uniformity, and substantially to form a bismuth-antimony alloy having a homogeneous composition between the nanowire central and edge regions, and to produce a single-crystal nanowire with improved crystallinity, the second step of step d) The second heat treatment may include a low temperature heat treatment performed at a temperature lower than T _m (Bi) and a high temperature heat treatment performed at a temperature higher than T _m (Bi). can Specifically, the heat treatment temperature (T(L), ℃) of the low-temperature heat treatment is T _m (Bi) - 55 ° C ≤ T (L) < T _m (Bi), more specifically, _m (Bi) - 40 ° C ≤ T (L) ≤ T _m (Bi) - may be 10 ℃, the heat treatment temperature of the high-temperature heat treatment (T (H), ℃) is T _m (Bi) ≤ T ≤ T _m (Bi) + 40 ℃, more specifically , T _m (Bi) + 5 °C ≤ T ≤ T _m (Bi) + 30 °C. When alternating between low-temperature heat treatment and high-temperature heat treatment, the daily high-temperature heat treatment time (t(H)) is 0.1 to 0.4 times (t(H)=0.1-0.4t(L)) of the daily low-temperature heat treatment time (t(L)) ), and the number of times of alternating low-temperature heat treatment per day and high-temperature heat treatment per day in the second heat treatment process may be 2 to 5 times. In this case, the second heat treatment time (total heat treatment time) may be 2 to 48 hours, but is not necessarily limited thereto.

The present invention includes an n-type thermoelectric nanowire manufactured by the above-described manufacturing method.

As described above, the present invention provides a thermoelectric nanowire having excellent n-type thermoelectric properties and a commercial and reproducible method for manufacturing a thermoelectric nanowire. In addition, since the thermoelectric element using the n-type thermoelectric nanowire provided in the present invention has an ultra-high-efficiency thermoelectric effect, it provides a basis for developing a new power generation system. In addition, by using the technology of the present invention, aerial weapon systems (fighters, helicopters, etc.), individual soldier weapon systems (walkie-talkie, radar, etc.), nuclear submarines, space generators, heat generators, aviation thermostats, military infrared detectors, missiles It can bring a higher level of development in various fields such as induction circuit coolers.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are only provided for easier understanding of the present invention, and the contents of the present invention are not limited by the following examples.

(Example)

After preparing a Si substrate on which a SiO ₂ surface oxide layer (400 nm thick) was formed, a Bi thin film was deposited on the oxide layer by rf sputtering. At this time, the sputtering conditions were 150W (rf), the Ar flow rate was 12 sccm, and the deposition time was 10 seconds in a vacuum of 1.0 ㅧ 10 ^-3 torr or less. Thereafter, Bi single crystal nanowires were grown by heat-treating the substrate on which the Bi thin film was formed at 250° C. for 5 hours in a high vacuum of 1.0 Ⅷ 10 ⁻⁵ torr or less.

Core-sheath nanowires were manufactured by depositing Sb, a thermoelectric material, on a substrate on which Bi single crystal nanowires were grown by rf sputtering. In order not to damage the crystallinity of the nanowires during Sb deposition, the lowest power of 30 W (rf) was used, the Ar flow was 12 sccm, and Sb deposition was performed for 10 seconds to satisfy the Bi _0.84 Sb _0.16 composition.

In order to produce alloy-type nanowires through interdiffusion of bismuth and intimony elements of core-sheath nanowires, low-temperature heat treatment at 265°C for 3 hours and high temperature at 290°C for 1 hour in a high vacuum of 1.0 x 10 ^-5 torr or less Using the heat treatment process as a unit process, the unit process was repeated 4 times to prepare an alloy nanowire.

1 is a view showing a transmission electron microscope (TEM) and a scanning transmission electron microscope (STEM) photograph and elemental analysis results of the prepared core / sheath nanowire, 1 (a) is a low magnification TEM photograph, Figure 1 (b) is A high-magnification STEM photograph, FIG. 1 ( c ) is a diagram illustrating Bi element mapping, and FIG. 1 ( d ) is a diagram illustrating Sb element mapping. As can be seen from Figure 1, it can be confirmed that the Sb shell is uniformly well formed on the Bi nanowire.

2 is a transmission electron microscope (TEM) and scanning transmission electron microscope (STEM) photograph and elemental analysis results of the prepared bismuth-antimony alloy nanowire, 2(a) is a low-magnification TEM photograph, FIG. 2(b) ) is a high-magnification STEM photograph, FIG. 2(c) is a Bi element mapping, and FIG. 2(d) is a diagram illustrating an Sb element mapping. It can be seen from FIG. 2 that a bismuth-antimony alloy nanowire having a uniform diameter and a smooth surface is manufactured, and it can be seen that the bismuth-antimony alloy nanowire is homogeneously alloyed by mutual diffusion of antimony and bismuth.

3 is a scanning transmission electron microscope (STEM) photograph of the prepared bismuth-antimony alloy nanowire (FIG. 3(a)) and an EDS line profile of bismuth and antimony analyzed along the yellow line in the STEM image. (3(b)). As can be seen from FIG. 3(b), the ratio of the strength of bismuth divided by the strength of antimony from the surface to the center over the entire area of the nanowire is substantially the same, so that Bi _{0 .} It can be seen that alloying was made with a homogeneous composition of _{84 Sb 0.16 .}

Figure 4 (a) is a scanning electron micrograph showing a platform for measuring the electrical conductivity and Seebeck coefficient of the prepared bismuth-antimony alloy nanowire (NW Bi _0.84 Sb _0.16 in the figure), Figure 4 (b) is the manufactured It is a view showing the electrical conductivity of the bismuth-antimony alloy nanowire, and FIG. 4 ( c ) is a view showing the measurement of the Seebeck coefficient of the prepared bismuth-antimony alloy nanowire. 4 (b) and 4 (c) in the Example, before antimony deposition, single crystal Bi nanowires (shown as NW Bi (ref) in the figure), have the same alloy composition as in the Example, but bulk BiSb alloy ( The electrical conductivity and Seebeck coefficient of bulk Bi _0.84 Sb _{0. 16} (Ref _{) in} the figure are shown together _. As can be seen from FIG. 4, the electrical conductivity of the prepared bismuth-antimony alloy nanowire is 3.29x10 ³ Sm ^-1 , which is similar to the electrical conductivity of the bulk phase of the same composition, so that deterioration of the electrical conductivity hardly occurs. It can be seen that the Seebeck coefficient -128 μVK ^-1 is significantly increased by alloying and nanowireization.

As described above, the present invention has been described with specific matters and limited examples and drawings, but these are only provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention is not limited to the above embodiments. Various modifications and variations are possible from these descriptions by those of ordinary skill in the art.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims described below, but also all those with equivalent or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

Claims (10)

It is a bismuth-antimony binary alloy nanowire, a single crystal of a solid solution or superlattice structure of bismuth and antimony, and an alloy-based n-type thermoelectric nano that satisfies Equations 1 and 2 below. wire.
(Equation 1)
1x10 ³ Sm ^-1 ≤ EC ≤ 1x10 ⁴ Sm ^-1
(In Equation 1, EC is the electrical conductivity of the binary alloy nanowire (electrical conductivity, Sm ^-1 ))
(Equation 2)
Z ≤ - 120 μVK ^-1
(In Equation 2, Z is the Seebeck coefficient of the binary alloy nanowire (Seebeck Coefficient, μVK ^-1 )) The method of claim 1,
In the binary alloy, the element ratio of bismuth: antimony is 1: 0.1 to 0.3 alloy-based n-type thermoelectric nanowire. delete The method of claim 1,
A line profile, which is a result of strength analysis for each element using energy dispersive X-ray spectroscopy, along a virtual analysis line crossing the nanowire perpendicular to the longitudinal direction of the binary alloy nanowire, satisfies the following Equation 3 Alloy-based n-type thermoelectric nanowires.
(Equation 3)
0.9 ≤ I2/I1 ≤ 1
(In Equation 3, I1 is the intensity obtained by dividing the bismuth intensity by the antimony intensity in the region from the center of the effective analysis line to 0.1D/2 by using the analysis line located on the nanowire as the effective analysis line and the length of the effective analysis line as D. ratio, where I2 is the intensity ratio obtained by dividing the center of the effective analysis line with the origin (0) and the bismuth intensity in the region of 0.5D/2 to D/2 divided by the antimony intensity) The method of claim 1,
An alloy-based n-type thermoelectric nanowire having a minor axis diameter of 50 to 500 nm of the nanowire. A method for manufacturing an n-type thermoelectric nanowire according to any one of claims 1 to 2 and 4 to 5,
a) forming a bismuth thin film on a substrate having an oxide layer;
b) growing a single crystal bismuth nanowire by first heat-treating the substrate on which the bismuth thin film is formed;
c) depositing antimony on the surface of the bismuth nanowire to prepare a bismuth-antimony core-sheath nanowire; and
d) A bismuth-antimony core-sheath nanowire is subjected to a second heat treatment to obtain a bismuth-antimony binary alloy nanowire, which is a solid solution of bismuth and antimony or a single crystal having a superlattice structure. manufacturing;
A method of manufacturing an alloy-based n-type thermoelectric nanowire comprising a. 7. The method of claim 6,
The ratio of the coefficient of thermal expansion of the substrate divided by the coefficient of thermal expansion of the oxide layer is 3 or more. 7. The method of claim 6,
The first heat treatment in step b) is performed at 0.9 to 0.95 T _m (Bi) based on T _m (Bi), which is the melting point (°C) of bismuth. 7. The method of claim 6,
The second heat treatment of step d) is a method of manufacturing an n-type thermoelectric nanowire is performed at a temperature that satisfies Equation 4 below.
(Equation 4)
T _m (Bi) - 55℃ ≤ T ≤ T _m (Bi) + 40℃
(In Equation 4, T is the second heat treatment temperature (℃), and T _m (Bi) is the melting point of bismuth (℃)) 10. The method of claim 9,
The second heat treatment in step d) includes a low temperature heat treatment performed at a temperature lower than T _m (Bi) and a high temperature heat treatment performed at a temperature higher than T _m (Bi), wherein the low temperature heat treatment and the high temperature heat treatment are alternately performed n -Manufacturing method of type thermoelectric nanowire.

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