KR101446592B1 - Sensor having core-shell nano structure, and preparing method of the same - Google Patents

Abstract

materials; A sensing part including a core-shell nanostructure containing a core including a first metal oxide formed on the substrate, and a shell containing a second metal oxide formed on the core; And two electrode layers spaced apart from each other on the sensing part, wherein a thickness of the shell is equal to or less than a length of the divider, thereby forming a complete depletion layer in the entire shell. And a method of manufacturing a sensor including the core-shell nanostructure.

Description

TECHNICAL FIELD [0001] The present invention relates to a sensor including a core-shell nanostructure, and a method of manufacturing the sensor.

The present invention relates to a substrate; A sensing part including a core-shell nanostructure containing a core including a first metal oxide formed on the substrate, and a shell containing a second metal oxide formed on the core; And two electrode layers spaced apart from each other on the sensing part, wherein a thickness of the shell has a value equal to or less than a Debye length, thereby forming a complete depletion layer in the entire shell. And a sensor including the nanostructure.

A chemical sensor is a sensor that detects the change in the density of the conduction electrons on the surface of the semiconducting material caused by the chemical interaction of the chemical species as the substance to be sensed and the surface of the semiconducting material located in the sensing region, Which is a sensor that uses the electrical resistivity change as a sensing principle. For example, when the semiconducting material located at the sensing unit is a metal oxide, if a chemical species, which is a substance to be sensed, is adsorbed on the surface of the metal oxide, oxidation and reduction reactions occur on the surface of the metal oxide, The electrical resistivity is changed, whereby the chemical species can be detected.

In recent years, studies on a nano chemical sensor using a metal oxide in the form of a nanostructure such as a nanofiber, a nanorod, a nanotube, and a nanoribbon have been actively conducted as semiconducting materials included in the sensing part of the chemical sensor . This is because the surface area of the nanochemical sensor using the metal oxide in the form of the nanostructure is higher than that of the chemical sensor including the conventional bulk or thin film semiconductor material in the sensing portion, This is because we can expect. For example, research on nanochemical sensors including a nanostructure fabricated using a photolithography process in a sensing section has been reported. Also, for example, Korean Patent No. 1027074 entitled " Nanostructure Gas Sensor Having Metal Oxide Layer, Nanostructure Gas Sensor Array and Method for Producing the Same ", discloses a nanostructure gas sensor array having a high sensitivity nano- Discloses a chemical sensor.

When a highly sensitive nanochemical sensor capable of detecting a trace amount of gas can be developed by having superior sensitivity, it can be applied not only for defense and special purpose applications but also for making a safer society by being used in various business sites . Particularly, in the case of a reducing gas containing various volatile organic compounds (VOCs), it is highly harmful to the human body and the risk of explosion is high. Thus, by developing a highly sensitive nanochemical sensor, If detection is possible, its utility is expected to be very high. For example, in the case of CO, which is a kind of reducing gas, inhalation thereof may cause death by interfering with oxygen transport by forming carboxy-hemoglobin in the blood and reducing the gas exchange ability of red blood cells, A trace detection at a level of several hundred ppm is required. However, to date, there has been no research or report on highly sensitive nanochemical sensors having sufficiently high sensitivity to reducing gases.

Accordingly, the present inventors have developed a sensor including a core-shell structure in which a complete depletion layer is formed on the entire shell by controlling the thickness of the shell to be equal to or less than the Debye length, The present inventors have found that a trace amount of reducing gas can be detected with high sensitivity.

Accordingly, the present invention provides a substrate comprising: a substrate; A sensing part including a core-shell nanostructure containing a core including a first metal oxide formed on the substrate, and a shell containing a second metal oxide formed on the core; And two electrode layers spaced apart from each other on the sensing part, wherein a thickness of the shell has a value equal to or less than a Debye length, thereby forming a complete depletion layer in the entire shell. A sensor containing the structure, and a method of manufacturing a sensor containing the core-shell structure.

The present invention also relates to a substrate comprising: a substrate; Two electrode layers formed on the substrate so as to be spaced apart from each other; And a sensing portion including a core-shell nanostructure containing a core containing a first metal oxide formed on the electrode layer and a shell containing a second metal oxide formed on the core, wherein the thickness of the shell is Wherein a complete depletion layer is formed over the entire shell by having a value equal to or less than the length of the device, and a method of manufacturing a sensor containing the core-shell structure.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

According to a first aspect of the present invention, A sensing part including a core-shell nanostructure containing a core including a first metal oxide formed on the substrate, and a shell containing a second metal oxide formed on the core; And two electrode layers spaced apart from each other on the sensing part, wherein a thickness of the shell has a value equal to or less than a Debye length, thereby forming a complete depletion layer in the entire shell. A sensor comprising a nanostructure is provided.

A second aspect of the present application provides a substrate, comprising: a substrate; Two electrode layers formed on the substrate so as to be spaced apart from each other; And a sensing portion including a core-shell nanostructure containing a core containing a first metal oxide formed on the electrode layer and a shell containing a second metal oxide formed on the core, wherein the thickness of the shell is And a complete depletion layer is formed in the entire shell by having a value equal to or less than the length of the device.

A third aspect of the invention provides a method of forming a core comprising: forming a core comprising a first metal oxide on a substrate; Forming a sensing portion including the core-shell nanostructure by forming a shell containing a second metal oxide on the core; And forming two electrode layers spaced apart from each other on the sensing portion, wherein a thickness of the shell is less than or equal to a length of the device to form a complete depletion layer in the entire shell, A method of manufacturing a sensor including a structure is provided.

A fourth aspect of the present invention provides a method of manufacturing a semiconductor device, comprising: forming two electrode layers on a substrate, And forming a core including a first metal oxide on the core and forming a shell containing a second metal oxide on the core to form a core-shell nanostructure, and then sensing the core-shell nanostructure on the electrode layer, And forming a complete depletion layer in the entire shell by causing the thickness of the shell to be equal to or less than the length of the divider, thereby providing a method of manufacturing a sensor including the core-shell nanostructure .

The sensor including the core-shell nanostructure of the present invention is a sensor having particularly excellent sensitivity to the detection of a trace amount of reducing gas by forming the complete depletion layer by controlling the thickness of the shell layer to be equal to or less than the device length, . For example, in the case of CO, which is a reducing gas, when it is inhaled, it may cause death due to obstruction of oxygen transportation due to high adsorption force with hemoglobin. In this case, a sensor including the core- Such a risk can be prevented by detecting a very small amount of reducing gas using a high sensitivity.

Meanwhile, in the sensor including the core-shell nanostructure of the present invention, the core-shell nanostructure may be formed by forming a nanofiber network-shaped core using, for example, an electrospinning method, And the shell is formed on the core. Since the electrospinning method and the atomic layer deposition method correspond to a relatively simple method, the manufacturing cost and time can be saved.

In addition, when the shell portion is formed using the atomic layer deposition method, the number of atomic layer deposition processes and the shell thickness are linearly proportional to each other, The thickness of the desired shell can be formed by adjusting the thickness of the shell, so that the sensitivity of the sensor to the reducing gas can be improved by easily adjusting the thickness of the shell to be equal to or less than the device length.

Since the core-shell nanostructure included in the sensing part of the sensor of the present invention is a kind of nanostructure, it has a large volume and a large surface area. Therefore, it has an advantage that a larger area can be exposed to a gas to be detected. , There is an additional advantage that a large-area deposition can be performed at room temperature, and an advantage of being able to form an ultra-thin and light-weight material corresponding to the nanoscale.

In addition, the core-shell nanostructure included in the sensing portion of the sensor of the present invention has a compound that is different from that of the core and the shell to form a heterojunction at the interface between the core and the shell, There is an advantage in that it can be manufactured to have higher sensitivity than the structure or alloy nanostructure.

1 is a schematic diagram of a sensor including a core-shell nanostructure fabricated according to one embodiment of the present application.
FIG. 2 is a simplified diagram illustrating a process for fabricating a sensor including a core-shell nanostructure according to one embodiment of the present invention.
FIG. 3 is a schematic diagram illustrating a change in a depletion layer caused by the supply or removal of a reducing gas on the surface of a core-shell nanostructure according to an embodiment of the present invention. FIG.
FIG. 4 is a schematic diagram of a model of a depletion layer formed in a core-shell nanostructure fabricated according to an embodiment of the present invention, wherein E _C is a conduction band energy value, and E _F is a Fermi energy Fermi energy level.
5a is an FE-SEM image of CuO core nanofiber prepared according to one embodiment of the present invention, and Figs. 5b to 5f are FE-SEM images of CuO-ZnO core-shell nanofiber prepared according to one embodiment of the present invention, As an SEM image, the number of ALD cycles performed for ZnO shell formation in each of Figs. 5B to 5F is 40, 80, 200, 415, and 667 times.
6 is a graph showing that the thickness of the shell gradually increases linearly with the number of ALD cycles when fabricating the core-shell nanostructure according to one embodiment of the present application.
7A is a low-magnification TEM image of a core-shell nanofiber having a ZnO shell thickness of 50 nm prepared according to one embodiment of the present invention, and FIGS. 7B to 7D are graphs showing the O, Cu, Zn, and FIG. 7E is a graph of chemical composition analysis of the core-shell nanofibers analyzed using EDS.
FIG. 8 is an XRD pattern (x-ray theta-2 theta diffraction pattern) of CuO-ZnO core-shell nanofiber prepared to have various shell thicknesses according to one embodiment of the present invention and CuO nanofiber as a control group.
FIG. 9A shows the reaction curves of the CuO-ZnO core-shell nanofiber prepared to have various shell thicknesses according to an embodiment of the present invention and the CO gas of the CuO nanofiber as a control group, and FIG. 9a in a different manner.
10 is a schematic diagram of a nanostructure fabricated for use as a sensing portion of a sensor according to an embodiment of the present invention, a schematic diagram of electron transfer occurring in the nanostructure, a conductive band energy (EC), and a Fermi energy level (EF) FIG. 10A shows a case where the nanostructure is a CuO nanofiber as a control group, FIG. 10B shows a case where the nanostructure is a CuO-ZnO core-shell nanofiber with a complete depletion layer, FIG. And a CuO-ZnO core-shell nanofiber in which an incomplete depletion layer is formed.
FIG. 11A is an FE-SEM image of the SnO ₂ core nanofiber prepared according to an embodiment of the present invention, FIG. 11B is an enlarged view of FIG. 11A, FIGS. 11C and 11E are cross- SnO ₂ -ZnO core-shell, and FE-SEM image of a nano fiber, and Fig. 11d and 11f respectively is an enlarged view of Figure 11c and 11e.
12A is a low-magnification TEM image of a core-shell nanofiber having a ZnO shell thickness of 20 nm manufactured according to an embodiment of the present invention, and FIGS. 12B to 12D are graphs showing the O, Sn, Zn, and FIG. 12E is a graph of chemical composition analysis of the core-shell nanofibers analyzed using EDS.
13 is manufactured to have a wide range of shell thickness, in accordance with an embodiment of the present SnO ₂ -ZnO core-shell a nanofiber, and a control group of SnO ₂ nanofibers each XRD pattern (x-ray diffraction pattern of 2θ-θ) .
FIGS. 14A and 14B show reaction curves for CO gas of each of the SnO ₂ -ZnO core-shell nanofiber prepared to have various shell thicknesses according to an embodiment of the present invention and the SnO ₂ nanofiber as a control group, FIGS. 14C and 14D show reaction curves for NO ₂ gas of each of the SnO ₂ -ZnO core-shell nanofiber prepared to have various shell thicknesses according to one embodiment of the present invention and the control SnO ₂ nanofiber, respectively , And Figs. 14E and 14F show the results of Figs. 14A to 14D as a single graph.
15 is a schematic diagram of a nanostructure fabricated for use as a sensing portion of a sensor according to an embodiment of the present invention, a schematic diagram of electron transfer occurring in the nanostructure, a conductive band energy (EC), and a Fermi energy level (EF) 15A shows a case where the nanostructure is a SnO ₂ nanofiber as a control group, FIG. 15B shows a case where the nanostructure is a SnO ₂ -ZnO core-shell nanofiber with a complete depletion layer, FIG. And SnO ₂ -ZnO core-shell nanofiber in which the structure is an incomplete depletion layer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is "on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as "including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. The terms "about "," substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure. The word " step (or step) "or" step "used to the extent that it is used throughout the specification does not mean" step for.

Throughout this specification, the term "combination thereof" included in the expression of the machine form means one or more combinations or combinations selected from the group consisting of the constituents described in the expression of the machine form, And the like.

Throughout this specification, the term "Debye length" means that free electrons, which are negative particles given inside the plasma, are shielded by the surrounding positive particles and are able to move by their own kinetic energy It may be, but is not limited to, distance. Alternatively, the term "device length" refers to the distance over which a charge is removed. For example, when oxygen is adsorbed on the surface of an n-type shell, electrons, which are charge carriers of n- Type shell, a portion where electrons disappear is generated on the surface of the n-type shell. The term "device length" may be used to refer to the minimum distance at which electrons can move due to oxygen adsorption. But is not limited to. For example, the device length of an arbitrary shell material is determined by the inherent properties of the shell material, such as the dielectric constant, and the height of the potential barrier generated by the band bending phenomenon resulting from the heterojunction with the core material. But it is not limited thereto.

Throughout this specification, the term "depletion layer " refers to a space in which a charge carrier is deficient, for example, in the case of p-type semiconductors, In the case of an n-type semiconductor, it means a space in which electrons, which are charge carriers, are deficient, but the present invention is not limited thereto. Further, throughout the present specification, the term "complete depletion layer" may refer to a space in which the charge carrier is completely deficient, but is not limited thereto.

Throughout the present specification, the term "reducing gas" refers to a gas which promotes the reduction reaction of a substance reacting therewith and does not cause an oxidation reaction. The "reduction" in the reducing gas means a phenomenon of losing oxygen, But is not limited to, a phenomenon to be obtained, or a phenomenon to obtain an electron.

Throughout this specification, the term "core-shell nanostructure" is a generic term for a nanostructure having a core-shell structure, for example, a nanostructure as a core and a shell surrounded by an outer surface of the nanostructure But are not limited to, nanostructures.

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings.

According to a first aspect of the present invention, A sensing part including a core-shell nanostructure containing a core including a first metal oxide formed on the substrate, and a shell containing a second metal oxide formed on the core; And two electrode layers spaced apart from each other on the sensing part, wherein a thickness of the shell has a value equal to or less than a Debye length, thereby forming a complete depletion layer in the entire shell. A sensor comprising a nanostructure is provided.

For example, the core-shell nanostructure according to the first aspect of the present invention comprising a substrate, a sensing portion including the core-shell nanostructure formed on the substrate, and two electrode layers formed on the sensing portion, 1, but the present invention is not limited thereto.

A second aspect of the present application provides a substrate, comprising: a substrate; Two electrode layers formed on the substrate so as to be spaced apart from each other; And a sensing portion including a core-shell nanostructure containing a core containing a first metal oxide formed on the electrode layer and a shell containing a second metal oxide formed on the core, wherein the thickness of the shell is And a complete depletion layer is formed in the entire shell by having a value equal to or less than the length of the device.

For example, the core-shell nanostructure according to the second aspect of the present invention, including the substrate, the two electrode layers formed on the substrate, and the sensing portion including the core-shell nanostructure formed on the electrode layer, Shell nanostructure according to the present invention, the position of the electrode layer and the sensing portion are exchanged vertically, and the method of manufacturing the same is simplified as a schematic diagram of FIG. 2, but the present invention is not limited thereto.

According to an embodiment of the present invention, the sensor including the core-shell nanostructure may detect a reducing gas of about 100 ppm or less, but is not limited thereto. The sensor including the core-shell nanostructure according to the first or second aspect of the present invention has a complete depletion layer formed in the entire shell by controlling the thickness of the shell to be equal to or less than the length of the divider, Can be used particularly advantageously for detecting a trace amount of reducing gas, but is not limited thereto. For example, the sensor comprising the core-shell nanostructure may comprise less than about 100 ppm reducing gas, such as greater than about 0 ppm to less than about 10 ppm, greater than about 0 ppm to less than about 20 ppm, less than about 0 ppm From about 0 ppm to about 100 ppm, from about 10 ppm to about 20 ppm, from about 10 ppm to about 40 ppm, from about 10 ppm to about 10 ppm, About 10 ppm or more to about 100 ppm or less, about 20 ppm or more to about 40 ppm or less, about 20 ppm or more to about 70 ppm or less, about 20 ppm or more to about 100 ppm or less, or about 40 ppm or less But is not limited to, a small amount of a reducing gas of not less than about 70 ppm, not less than about 40 ppm and not more than about 100 ppm, or not less than about 70 ppm and not more than about 100 ppm. For example, a sensor comprising the core-shell nanostructure herein may be usefully used to detect trace amounts of reducing gas in the range of from about 0.1 ppm to about 10 ppm, but is not limited thereto.

In this regard, FIG. 3 is a cross-sectional view showing a case where a complete depletion layer is formed in the entire shell by controlling the thickness of the shell to have a value equal to or less than the length of the divider according to the first or second aspect of the present invention, FIG. 2 is a schematic view showing the advantage of sensing the gas, and that when the reducing gas is removed, the complete depletion layer of the shell is recovered by oxygen molecules in the atmosphere. In the case of the semiconductor gas sensor, the resistance change according to the thickness change of the depletion layer is used to detect the gas, and the sensing part of the semiconductor gas sensor has a state in which a certain depletion layer is formed Lt; / RTI > Specifically, when oxygen is adsorbed on the surface of the sensing portion of the sensor, electrons are drawn from the sensing portion surface of the sensor to become an oxygen negative ion, and thus, a depletion layer is formed on the surface of the sensing portion of the sensor due to electron deficiency. At this time, when a reducing gas is supplied to the sensor, the oxygen anion and the reducing gas react with each other, and some electrons return to the sensing portion of the sensor, so that the degree of electron deficiency of the depletion layer is weakened. Then, when the supply of the reducing gas is interrupted, oxygen adsorption in the atmosphere occurs again, and the degree of electron deficiency of the depletion layer is strengthened. Here, when the complete depletion layer is formed in the shell portion of the core-shell nano structure included in the sensing portion of the sensor according to the first or second aspect of the present invention, such a phenomenon is maximized, and a very small amount of the reducing gas But it is not limited thereto. In the case of the sensor including the core-shell nanostructure according to the first aspect or the second aspect of the present invention, when the amount of the reducing gas to be detected is excessively large, or when the oxidizing gas is applied as a sensing object, But the present invention is not limited thereto.

According to one embodiment of the invention, the core-sensor including a shell _{nanostructures, H 2, CO, CH 4} , NH 3, CH 3 OH, C 2 H 5 OH, C 3 H 8, H 2 S, It may be to detect a gas selected from the group consisting of dimethylamine, triethylamine, benzene, toluene, xylene, and combinations thereof, It is not. As described above, the sensor including the core-shell nanostructure of the present invention is optimized for sensing a very small amount of reducing gas, and accordingly, H ₂ , CO, CH ₄ , NH _{3 ,} CH ₃ OH, When a reducing gas such as C ₂ H ₅ OH, C ₃ H ₈ , H ₂ S, dimethylamine, triethylamine, benzene, toluene, or xylene is applied, high sensitivity can be expected but is not limited thereto. For example, a sensor comprising a core-shell nanostructure according to the first or second aspect of the present invention may be a sensing of a reducing gas comprising various volatile organic compounds (VOCs) It is not.

For example, the substrate may be a metal conductive substrate, or an insulating substrate, but is not limited thereto. For example, the substrate may be a silicon (Si) wafer, a metal conductive substrate such as an aluminum substrate, a quartz substrate, or an oxide substrate, but is not limited thereto. For example, the substrate may be an insulating substrate itself, or may have properties similar to those of an insulating substrate by including an insulating layer on the substrate, but the present invention is not limited thereto. For example, the insulating layer may include, but is not limited to, silicon oxide, silicon dioxide, silicon nitride, or various polymers.

According to an embodiment of the present invention, the first metal oxide and the second metal oxide may be oxides of different metals, but the present invention is not limited thereto. For example, by using an oxide of a metal different from each other as the first metal oxide included in the core and the second metal oxide included in the shell, it is possible to prevent the core and the shell of the core- Although heterojunctions can be formed, the present invention is not limited thereto. The heterojunction may contribute to the enhancement of the sensitivity of the sensor including the core-shell nanostructure of the present invention, but is not limited thereto. For example, the first metal oxide and the second metal oxide may have energy bamd structures that are different from each other, so that a complete depletion layer can be formed in the core-shell nanostructure of the present invention But is not limited thereto.

According to an embodiment of the present invention, the first metal oxide and the second metal oxide are each independently selected from the group consisting of Ti, Sn, Zn, Mn, Mg, Ni, W, Co, Fe, Ba, In, Zr, But are not limited to, oxides of metals selected from the group consisting of Bi, Pb, Ag, Cd, Y, Mo, Rh, Pd, Sb, Cs, La and combinations thereof. For example, the metal oxide semiconductor that can be used as the first metal oxide and the second metal oxide may be TiO ₂ , SnO ₂ , ZnO, MnO ₂ , MgO, NiO, WO _{3 ,} Co ₃ O ₄ , Fe ₂ O ₃ , BaTiO ₃ , In ₂ O ₃ , ZrO ₂ , CuAlO ₂ , Bi ₂ O ₃ , metal oxide composites (eg Ti doped SnO ₂ , Sn doped ZnO, Mg doped ZnO , Mn-doped ZnO, Ni of ZnO, Co-doped ZnO, Fe of ZnO, Mn doped with MgO, Ni the doped MgO, Co doped with MgO, Fe-doped MgO, Mg of MnO _2, Ni-doped doped doping Mn doped MnO ₂ , Co doped MnO ₂ , Fe doped MnO ₂ , Mg doped NiO, Mn doped NiO, Co doped NiO, Fe doped NiO, Mg doped Co ₃ O ₄ , Mn doped Co ₃ O ₄ , Ni doped Co ₃ O ₄ , Fe doped Co ₃ O ₄ , Mg doped Fe ₂ O ₃ , Mn doped Fe ₂ O ₃ , Ni doped Fe ₂ O ₃ , Co doped Fe ₂ O ₃ , Ag doped ZnO, etc.), PZT (hereinafter collectively referred to as solid solutions of PbZrO ₃ and PbTiO _3), Ag oxide, Cd oxide, Y oxide, Mo Be to include the storage, Rh oxide, selected from the Pd oxide, Sb oxide, Cs oxides, La oxides, and the group consisting of the combinations thereof, but is not limited to this.

According to one embodiment of the present invention, the shell may comprise, but is not limited to, nanoparticles of the second metal oxide. If the shell corresponding to the surface portion of the sensing portion includes a plurality of nano sized particles to have a rough surface, the surface area can be increased as compared with the case where the shell has a smoothing surface, The sensitivity of the sensor may be improved by expanding the adsorbable region, but the present invention is not limited thereto.

For example, the particle size of the first metal oxide included in the core may be larger than the particle size of the second metal oxide included in the shell, but the present invention is not limited thereto. For example, using the difference in particle size included in the core and the shell size, it can be seen that the core and the shell are composed of distinctly different materials, The presence of a heterojunction can be ascertained, but is not limited thereto. For example, the particle size of the second metal oxide contained in the shell is smaller than the particle size of the first metal oxide included in the core, so that a channel formed between the small particles constituting the shell It acts as an electron transfer path and contributes to the improvement of the sensitivity of the sensor, but the present invention is not limited thereto.

According to one embodiment of the disclosure, the core may comprise, but is not limited to, a nanofiber form having a diameter of from about 20 nm to about 200 nm. For example, the core can have a diameter of from about 20 nm to about 50 nm, from about 20 nm to about 80 nm, from about 20 nm to about 100 nm, from about 20 nm to about 130 nm, from about 20 nm to about 150 nm, from about 50 nm to about 150 nm, from about 50 nm to about 200 nm, from about 80 nm to about 80 nm, from about 50 nm to about 100 nm, from about 50 nm to about 130 nm, from about 50 nm to about 150 nm, From about 80 nm to about 150 nm, from about 80 nm to about 200 nm, from about 100 nm to about 130 nm, from about 100 nm to about 150 nm, from about 100 nm to about 200 nm , About 130 nm to about 150 nm, about 130 nm to about 200 nm, or about 150 nm to about 200 nm.

For example, the core may be in the form of a network of nanofibers, and electrospinning may be used to electrospray a solution comprising the precursor and polymer of the first metal oxide to form a core in the network form of the nanofibers But is not limited thereto. For example, the electrospinning method may include, but is not limited to, a method of electrospinning a solution containing a precursor of the first metal oxide and a polymer in an organic solvent. As the precursor of the first metal oxide, a precursor compound of a metal oxide generally used in the art can be used. As the polymer, a polymer generally used in the art in the case of the electrospinning can be used , But the present invention is not limited thereto.

For example, the thickness of the shell may be controlled to be equal to or less than the length of the divider to form a complete depletion layer throughout the shell, and the length of the divider may be a value determined according to the type of the compound constituting the shell. But is not limited to. Specifically, the length of the divider may be a value that is determined by an influence of a change in inherent property such as a dielectric constant depending on the kind of the compound constituting the shell, and a band derived from the heterojunction between the shell and the core But may be a value determined by the height of the potential barrier due to the bending phenomenon, but the present invention is not limited thereto. For example, when the material constituting the core is n-type SnO ₂ and the material constituting the shell is n-type ZnO, the device length formed on the surface of the shell may be about 69 nm, The length of the device formed in the heterojunction between the shell and the core may be about 53 nm, but is not limited thereto.

For example, the shell may include but is not limited to being formed using Atomic Layer Deposition (ALD). For example, the atomic layer deposition method may be performed a plurality of times, and the thickness of the shell may be adjusted to a value equal to or less than the device length by controlling the number of times of atomic layer deposition. However, the present invention is not limited thereto. For example, the shell may be formed on the outside of the core by using a chemical vapor deposition (CVD) method, a laser ablation method, or a template, no.

According to one embodiment of the present invention, the core-shell nanostructure may include, but is not limited to, a pn-type core-shell nanostructure or an nn-type core-shell nanostructure. For example, the pn type core-shell nanostructure may comprise a shell comprising a p-type metal oxide semiconductor and a shell comprising an n-type metal oxide semiconductor, such as CuO-ZnO, _{CuO-SnO 2, CuO-TiO} 2, NiO-ZnO, NiO-SnO 2, NiO-TiO 2. Co ₃ O ₄ -ZnO, Co ₃ O ₄ -SnO ₂ , or Co ₃ O ₄ -TiO ₂ core-shell nanostructures may be included in the pn-type core-shell nanostructure, but are not limited thereto. For example, the nn-type core-shell nanostructure may comprise a shell comprising an n-type metal oxide semiconductor and a shell comprising an n-type metal oxide semiconductor, wherein n -Type metal oxide semiconductor and the n-type metal oxide semiconductor included in the shell are different from each other, for example, Fe ₂ O ₃ -ZnO, In ₂ O ₃ -ZnO, SnO ₂ -ZnO, TiO ₂ - ZnO, ZnO-TiO ₂ , or TiO ₂ -SnO ₂ core-shell nanostructures may be included in the nn-type core-shell nanostructure, but are not limited thereto. When each of the pn type or nn type core-shell nanostructures is included in the sensing portion of the sensor, the sensitivity of the sensor to the reducing gas is higher than that in the case where the nanostructure composed of a single material is included in the sensing portion of the sensor However, the present invention is not limited thereto. In addition, the core-shell nanostructure of the present invention may be suitable for manufacturing a sensing portion of a sensor having high sensitivity, but is not limited thereto, as compared with an alloy heteronano structure produced by alloying two different materials.

In this regard, the depletion layer formed at the heterojunction portion of the interface between the shell layer and the two different materials in the core-shell heterononostructure of the present invention contributes to improvement of the sensitivity of the sensor. As described above, the sensing mechanism of the semiconductor gas sensor is related to the resistance change that occurs during the interaction between the gas molecules and the semiconductor material. When the sensor is exposed to the atmosphere, oxygen molecules are rapidly adsorbed on the surface to form anions, which lead to the formation of depletion layers on the surface because electrons are drawn from nearby surfaces. In the core-shell structure, a wide insulating layer is formed while the insulating surface layer is supported by the heterojunction formed at the interface between the shell and the core material. When exposed to a reducing gas such as CO, the anion is re-released during the reaction with CO gas molecules. In the core-shell structure, the depletion layer formed in the shell layer and the heterojunction portion causes a resistance change. The gas sensitivity of the core-shell structure can be greatly affected by the thickness of the shell. Specifically, when the shell layer is adjusted to a depletion layer size or less according to the present invention, the gas sensitivity can be greatly improved, but is not limited thereto.

For example, when a metal oxide semiconductor is an n-type semiconductor and is exposed to oxidative chemical species molecules such as O ₂ molecules and adsorbs an oxidizing species molecule on its surface, The electrons are lost to the species molecules to form a depletion on the surface, thereby increasing the electrical resistance. On the other hand, the metal-oxide semiconductor is an n- type semiconductor, H ₂ or by exposure to a reducing chemistry kinds of molecules, such as CO ₂ molecule when the reducing species molecules adsorbed on its surface, H ₂ or CO molecules are already metal oxide semiconductor combine with oxygen adsorbed on the surface to change to H ₂ O or CO ₂ being separated from the metal oxide semiconductor, the electron that was bound to the separated oxygen is excited is moved to the conduction band of the metal oxide semiconductor (conduction band) metal oxide The resistance of the semiconductor is reduced. The sensor including the core-shell nanostructure according to the first and second aspects of the present invention may detect a very small amount of the reducing gas with high sensitivity using the resistance change, but the present invention is not limited thereto.

According to one embodiment of the present invention, the electrode layer is formed of a single-layered electrode layer containing a metal selected from the group consisting of Au, Pt, Cu, and combinations thereof, or an electrode layer of Ti, Ni, Cr, But is not limited to, a multi-layered electrode layer that additionally contains a layer of a metal selected from the group consisting of combinations of the above. For example, among the metals included in the electrode layer, Au, Pt, or Cu may function substantially as an electrode, and Ti, Ni, or Cr among the metals included in the electrode layer may be in contact with other portions of the sensor layer But the present invention is not limited thereto. For example, as shown in the second schematic diagram of FIG. 2, the sensor of the present invention may include, but is not limited to, a multi-layered electrode layer including both an Au metal layer and a Ti metal layer. For example, the multi-layered electrode layer may include, but not limited to, an Ai metal layer serving as an electrode and a Ni metal layer for improving bonding properties at the same time. For example, in order to form the electrode layer, a sputtering method, an evaporation method, or the like can be used, but the present invention is not limited thereto.

A third aspect of the invention provides a method of forming a core comprising: forming a core comprising a first metal oxide on a substrate; Forming a sensing portion including the core-shell nanostructure by forming a shell containing a second metal oxide on the core; And forming two electrode layers spaced apart from each other on the sensing portion, wherein a thickness of the shell is less than or equal to a length of the device to form a complete depletion layer in the entire shell, A method of manufacturing a sensor including a structure is provided.

The third aspect of the present invention relates to a method of manufacturing a sensor including a core-shell nanostructure according to the first aspect of the present invention, and a detailed description of parts overlapping with the first aspect of the present invention is omitted, Although the description of the first aspect is omitted from the third aspect of the present application, the same can be applied.

A fourth aspect of the present invention provides a method of manufacturing a semiconductor device, comprising: forming two electrode layers on a substrate, And forming a core including a first metal oxide on the core and forming a shell containing a second metal oxide on the core to form a core-shell nanostructure, and then sensing the core-shell nanostructure on the electrode layer, And forming a complete depletion layer in the entire shell by causing the thickness of the shell to be equal to or less than the length of the divider, thereby providing a method of manufacturing a sensor including the core-shell nanostructure .

The fourth aspect of the present invention relates to a method of manufacturing a sensor including a core-shell nanostructure according to the second aspect of the present invention, and a detailed description thereof is omitted for the parts overlapping with the second aspect of the present invention. Although the description of the second aspect is omitted from the fourth aspect of the present application, the same can be applied.

For example, in the manufacturing method of the third or fourth aspect of the present invention, when forming the core-shell nanostructure, a firing step may be added after the step of forming the core, and the step of forming the shell The firing process may be added later, but is not limited thereto.

According to one embodiment of the invention, forming the core comprises forming the core into a nanofiber form by electrospinning a solution comprising a precursor of the first metal oxide and a polymer, i.e., using electrospinning , But is not limited thereto. For example, the electrospinning method may include, but is not limited to, a method of electrospinning a solution containing a precursor of the first metal oxide and a polymer in an organic solvent. As the precursor of the first metal oxide, a precursor compound of a metal oxide generally used in the art can be used. As the polymer, a polymer generally used in the art in the case of the electrospinning can be used , But the present invention is not limited thereto.

According to one embodiment of the disclosure, the shell may be formed using atomic layer deposition, but is not limited thereto. Alternatively, in addition to the atomic layer deposition method, for example, the shell may be formed on the outer side of the core by a method using a chemical vapor deposition (CVD) method, a laser ablation method, But is not limited thereto.

When forming the shell using the atomic layer deposition method, two important parameters are the temperature and the pressure inside the reactor. The temperature and the pressure inside the reactor depend on the vapor pressure of the material to which the atomic layer deposition is applied But the present invention is not limited thereto. For example, when diethylzinc [Zn (C ₂ H ₅ ) ₂ , DEZn] and H ₂ O are used as starting materials to form a ZnO shell layer, the temperature inside the reactor is set to about 150 ° C. The pressure in the reactor may be about 0.3 Torr to perform the atomic layer deposition, but the present invention is not limited thereto.

For example, the atomic layer deposition method for forming the shell may be repeated a plurality of times, but the present invention is not limited thereto. For example, when DEZn and H ₂ O are used as the starting materials for forming the ZnO shell layer, it is preferable to supply DEZn, ventilate using an inert gas such as nitrogen, and supply H ₂ O to the atom Layer deposition method. By repeating this process a plurality of times, it is possible to form a shell having an increased thickness linearly proportional to the number of times of execution, but the present invention is not limited thereto.

According to an embodiment of the present invention, the thickness of the shell may be adjusted to have a value equal to or less than the device length by controlling the number of times of atomic layer deposition. However, the present invention is not limited thereto. For example, the thickness of the shell may be controlled to be equal to or less than the length of the divider to form a complete depletion layer throughout the shell, and the length of the divider may be a value determined according to the type of the compound constituting the shell. But is not limited to.

According to an embodiment of the present invention, by forming a shell containing a second metal oxide different from the first metal oxide on the core, a heterojunction is formed at the interface between the core included in the core-shell nanostructure and the shell, , But is not limited thereto. The heterojunction may contribute to the enhancement of the sensitivity of the sensor including the core-shell nanostructure of the present invention, but is not limited thereto. For example, the first metal oxide and the second metal oxide may have energy bamd structures that are different from each other, so that a complete depletion layer can be formed in the core-shell nanostructure of the present invention But is not limited thereto.

According to one embodiment of the present invention, by forming the core using a p-type metal oxide and forming the shell using an n-type metal oxide on the core, the core-shell nanostructure of the pn type is manufactured , But is not limited thereto. For example, the core of the pn type-shell nanostructures, CuO-ZnO, CuO-SnO 2, CuO-TiO 2, NiO-ZnO, NiO-SnO 2, NiO-TiO 2. _{Co 3 O 4 -ZnO, Co 3} O 4 -SnO 2, or Co ₃ O ₄ -TiO ₂ core - but may be, including a shell nanostructures, without being limited thereto. When the pn type core-shell nanostructure is included in the sensing part of the sensor, it is possible to exhibit high sensitivity to the reducing gas in the sensor as compared with the case where the nanostructure composed of a single material is included in the sensing part of the sensor , But is not limited thereto. In addition, the core-shell nanostructure of the present invention may be suitable for manufacturing a sensing portion of a sensor having high sensitivity, but is not limited thereto, as compared with an alloy heteronano structure produced by alloying two different materials.

According to an embodiment of the present invention, there is provided a method of forming a core using n-type metal oxide and forming the shell on the core using n-type metal oxide different from n-type metal oxide included in the core , Thereby preparing the core-shell nanostructure of the nn type. However, the present invention is not limited thereto. For example, the nn type of core-shell nanostructure is _{Fe 2 O 3 -ZnO, In 2} O 3 -ZnO, SnO 2 -ZnO, TiO 2 -ZnO, ZnO-TiO 2, TiO ₂ -SnO ₂ or the core - shell nanostructures, but is not limited thereto. When the nn-type core-shell nanostructure is included in the sensing portion of the sensor, the sensor may exhibit high sensitivity to the reducing gas as compared with the case where the nanostructure composed of a single material is included in the sensing portion of the sensor , But is not limited thereto. In addition, the core-shell nanostructure of the present invention may be suitable for manufacturing a sensing portion of a sensor having high sensitivity, but is not limited thereto, as compared with an alloy heteronano structure produced by alloying two different materials.

According to an embodiment of the present invention, in the manufacturing method according to the fourth aspect of the present invention, the deposition of the core-shell nanostructure on the electrode layer as a sensing part may include that performed through a printing technique, It is not. For example, the core-shell nanostructure is mixed with a binder, and the core-shell nanostructure is printed on the electrode layer and then heat-treated to remove the binder. The core-shell nanostructure is deposited on the electrode layer as a sensing portion But is not limited thereto.

Hereinafter, one embodiment of the present invention will be described in more detail with reference to the schematic diagram of FIG.

1 is a schematic diagram of a sensor including a core-shell nanostructure fabricated according to one embodiment of the present application. 1, the sensor including the core-shell nanostructure includes a substrate 100, an insulating layer 110 formed on the substrate, a sensing portion 200 formed on the insulating layer, And the sensing unit may include a core 210 having a first metal oxide and having a nanofiber network shape and a second electrode layer 300 formed on the core 210, But is not limited to, a shell 220 including a metal oxide.

In the core-shell nanostructure located in the sensing portion 200 of the sensor of FIG. 1, the core 210 may be formed in a nanofiber network shape using electrospinning, and the shell 220 formed on the core But may be formed using atomic layer deposition, but the present invention is not limited thereto.

For example, the electrospinning method for forming the core 210 may be performed sequentially according to a process described below, but the present invention is not limited thereto.

First, a spinning solution for performing the electrospinning is prepared. The spinning solution may be prepared by mixing a first metal oxide precursor solution and a polymer solution for forming a core, and after mixing, the mixture may be stirred for a predetermined time to form a viscous solution. For example, the stirring may be performed at a temperature of about 40 째 C to about 80 째 C for about 3 hours to about 10 hours, but is not limited thereto.

Next, the spinning solution can be loaded into the syringe. For example, the viscous spinning solution may be injected into the syringe, and the syringe may be positioned at a certain height on the substrate 100 placed on a conductive material such as aluminum. At this time, the needle of the syringe and the base 100 may have a predetermined angle. For example, the syringe may be located at a height that is spaced from the substrate 100 by about 10 cm to about 50 cm, and the needle of the syringe and the substrate 100 may be at an angle of about 10 [deg.] To about 90 [ But is not limited thereto.

Next, the spinning solution may be spun onto the substrate 100. For example, by applying a predetermined positive voltage to the needle of the syringe and applying a predetermined negative voltage to the conductive material located under the substrate 100, the spinning solution is sprayed onto the substrate 100 by electrospinning To form a nanofiber network shaped core 210, but is not limited thereto. For example, the magnitudes of the positive voltage and the negative voltage may be about 5 kV to about 50 kV, respectively, but are not limited thereto. In addition, the feeding rate of the spinning solution to the base material 100 may be, for example, from 0.01 mL / h to 2 mL / h, but is not limited thereto.

Next, the core 210 may be calcined. The calcination may be performed to remove unwanted impurities from the nanofiber network shaped core 210 that may contain impurities immediately after electrospinning, for example, at a temperature of about 100 ° C to about 1000 ° C For about 3 hours to about 15 hours under a variety of atmospheres such as air, Ar, N ₂ , or O ₂ .

Meanwhile, after the core 210 is formed according to the electrospinning method described above, the shell 220 may be formed on the core 210 by, for example, atomic layer deposition. However, It is not. The shell 220 may be formed by a plurality of atomic layer deposition methods, and the shell 220 may be formed to have a desired thickness by controlling the number of times of atomic layer deposition. However, the present invention is not limited thereto. For example, the temperature inside the reactor in which the atomic layer deposition process is performed may be from about 100 ° C to about 300 ° C, and the pressure may be from about 0.1 Torr to about 0.6 Torr, but is not limited thereto. In addition, for example, the pulse length for each element in the atomic layer deposition method may be about 0.1 second to about 5 seconds, and the number of times of atomic layer deposition may be about one or more times, for example, about one time About 10 times, about 1 time to about 100 times, about 1 time to about 1000 times, about 1 time to about 10,000 times, but is not limited thereto.

1, the electrode layer 300 may be located on the sensing unit 200 including the core-shell nanostructure, and the first electrode layer 310 and the second electrode layer 320 may be spaced apart from each other But is not limited thereto. In addition, each of the first electrode layer 310 and the second electrode layer 320 may be connected to the core-shell nanostructure, but is not limited thereto. The electrode layer 300 may be formed by laminating one or more metal layers, and may be formed by a method commonly used in the art for forming electrodes such as a sputtering method or an evaporation method. However, the present invention is not limited thereto.

The sensor including the core-shell nanostructure formed according to the exemplary process as the sensing unit 200 may be applied to various fields as a sensor having excellent sensitivity to an extremely small amount of reducing gas, It is not.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

[ Example ]

One. CuO - ZnO  Preparation of core-shell nanofiber

CuO-ZnO core-shell nanofibers were prepared by a novel two-step process. First, CuO core nanofiber was synthesized by electrospinning, followed by deposition of a ZnO shell layer using ALD technology.

Polyvinyl alcohol (PVA) and copper acetate [(CH ₃ CO ₂ ) ₂ Cu] having a molecular weight of 80,000 were used as precursor compounds for the synthesis of CuO core nanofibers. For electrospinning, a 9 wt% liquid PVA solution was prepared by dissolving the PVA beads in distilled water. After stirring at 70 DEG C for 4 hours, the PVA solution was mixed with a 4.3 wt% copper acetate solution and further stirred at 70 DEG C for 6 hours. The viscous copper acetate / PVA solution was loaded into a glass syringe with a 21-gauge stainless steel needle. The nanofibers were uniformly electrospun on a SiO ₂ wafer located on a metal collector. The electrospun fibers were calcined at 600 < 0 > C under oxygen atmosphere for 48 hours, at which time a tube-type furnace was used. In order to minimize the loss of nanofibers in the atmosphere in the laboratory, the prepared samples were stored in a dust-collecting mask and vacuum conditions until measurement and characterization were performed.

In order to form a ZnO shell structure on the surface of the CuO nanofibers, a general ALD technique was used. In this embodiment, an ALD system having a horizontal wall reactor was used. Diethylzinc [Zn (C ₂ H ₅ ) ₂ , DEZn] and H ₂ O were used as precursors. In order to prevent a violent pre-reaction between the two precursors, DEZn and H ₂ O were separately introduced into the growth reactor, and the temperature and pressure conditions of the reactor were 150 ° C. and 0.3 Torr, respectively. DEZn was stored in a 0 ° C bubbler and H ₂ O was stored in a 10 ° C bubbler. The ALD pulse length was set to 0.12 seconds for DEZn dosing, 3 seconds for N ₂ purging, 0.15 seconds for H ₂ O addition, and 3 seconds for N ₂ purging. It corresponds to one cycle. The number of ALD cycles was regulated between 40 and 700 cycles. The average diameter of the CuO core nanofibers was about 130 nm, and the thickness of the ZnO shell layer was adjusted from 10 nm to 200 nm.

2. CuO - ZnO  Analysis method of core-shell nanofiber

The microstructure and phase of the core-shell nanofibers prepared according to the above process were measured using a field emission scanning electron microscope (FE-SEM), a transmission electron microscope (TEM), and an X-ray diffractometer Respectively. Elemental mapping was also performed in an energy dispersive spectroscopy (EDS) mode.

For the sensor sensitivity measurement, a sensor including the CuO-ZnO core-shell nanofiber was fabricated. To fabricate the dual-layer electrode of the sensor, about 50 nm of Ti and about 200 nm of Au were deposited on the substrate Sputtering method and interdigital electrode mask. The response of the sensor to CO, which is a reducing gas, was measured at 300 DEG C using a homemade gas dilution and sensing system. Sensitivity was (Sensitivity, S) is calculated according to the formula: in S = R _a / R _g or R _g / R _a (where, R _a corresponds to the first resistance and, R _g in the absence of feed gas Corresponding to the resistance when the measuring gas is present). The content of water vapor inside the CO container was kept below 3 ppm.

3. CuO - ZnO  Analysis results of core-shell nanofiber

The effect of ZnO shell layer thickness on the surface of CuO core nanofibers of the nanofibers was compared by performing microstructure, phase, and gas sensitivity analysis of the produced CuO-ZnO core-shell nanofibers, The effect of the heterojunction formed at the interface between the materials was also analyzed.

5A is an FE-SEM image of a CuO core nanofiber synthesized by an electrospinning method, which is irregularly dispersed on a SiO ₂ substrate. Referring to the illustration of FIG. 5A, it can be clearly seen that the CuO nanofiber includes nano-sized particles. A ZnO shell layer was deposited by the ALD method on the CuO core nanofibers. The FE-SEM images of the CuO-ZnO core-shell nanofibers prepared by varying the number of ALD cycles are shown in FIGS. 5B to 5F, and the number of ALD cycles performed for ZnO shell formation in each of FIGS. 5B to 5F is 40 Times, 80 times, 200 times, 415 times, and 667 times. Referring to the drawings, the large-sized particles constituting the CuO core nanofibers and the small-sized particles constituting the ZnO shell layer deposited on the CuO core nanofibers were clearly distinguished. It is presumed that the rough surface of the shell layer protrudes to provide an adsorption space for introduction of the measuring gas molecules and to improve the adsorption ability of the sensor. On the other hand, the heterojunction formed between the two different materials generates a potential barrier at their interface, forms a path through which electrons penetrate, and improves gas sensitivity.

Figure 6 relates to ZnO shell thickness in core-shell nanofiber. As the number of ALD cycles was increased, the ZnO shell thickness gradually increased. The increase in the ZnO shell thickness with increasing ALD cycles was almost linear. The rate of formation of the ZnO shell layer was calculated from the slope of the graph at about 0.305 nm / ALD cycle number, from which it was confirmed that the shell thickness can be adjusted to the nanometer level by controlling the number of ALD cycles.

The microstructure of the core-shell nanofibers was further analyzed using TEM. 7A is a low magnification TEM image of core-shell nanofibers having a ZnO shell thickness of 50 nm. 7B to 7D are graphs showing elemental mapping results of O, Cu, and Zn of CuO-ZnO core-shell nanofibers, and FIG. 7E is a graph showing the chemical composition analysis of CuO-ZnO core- to be. 7A to 7E, it was confirmed that Zn exists in the outer surface of the core-shell nanofiber, and Cu exists in the inner portion of the fiber, and the elements O, Cu, and Zn It is clear that the spatial division of From the result of the element mapping analysis, it was clearly confirmed that core-shell nanofiber having a shell thickness of 50 nm was formed. From the result of EDS analysis, ZnO was present on the surface portion of the core-shell nanofiber and CuO was present in the core portion I could confirm.

8 shows XRD patterns of CuO nanofiber and CuO-ZnO core-shell nanofiber. The XRD patterns of the CuO nanofibers were confirmed for comparison. CuO-ZnO core-shell nanofibers with shell thicknesses of 10 nm, 20 nm, 50 nm, 120 nm, and 200 nm, respectively, showed diffraction peaks proportional to the ZnO phase in addition to the peak due to the CuO phase, It was confirmed that the ZnO shell layer was formed on the core nanofiber. The increased intensity of the XRD peak was proportional to the increased thickness of the ZnO shell layer formed on the CuO nanofiber surface.

Experiments were conducted under a CO atmosphere of 1 ppm to 10 ppm to confirm the susceptibility of CuO nanofibers and CuO-ZnO core-shell nanofibers having various shell thicknesses to gases. All sensor responses were dependent on CO changes. Figure 9a shows the response curves of a sensor comprising CuO nanofibers and CuO-ZnO core-shell nanofibers, respectively, against CO gas at 300 ° C. Sensitivity different from the sensor comprising CuO nanofibers was observed in the sensor comprising the core-shell nanofibers. The p-type susceptibility of the CuO nanofiber was changed to n-type susceptibility as the ZnO shell thickness of the CuO-ZnO core-shell nanofiber was increased.

The response of sensors including CuO nanofibers increased when exposed to CO gas, but decreased when exposed to air, indicating typical p-type susceptibility. On the other hand, the reaction of the core-shell nanofiber with the ZnO shell thickness of 10 nm was further lowered, indicating the n-type susceptibility of the ZnO shell layer. Referring to FIG. 5B, in the case of core-shell nanofibers having a shell thickness of 10 nm, it is assumed that the surface of the CuO nanofiber is not uniformly coated by the ZnO shell layer. It is also assumed that when exposed to gas, gas molecules diffuse through channels formed between the ZnO particles present on the CuO nanofiber surface. Both the CuO core and the ZnO shell layer reacted with CO gas, and the n-type susceptibility of ZnO ultimately reduced the p-type susceptibility of CuO nanofibers. As the conductivity of the n-type material increases with exposure to CO gas, the reaction is expected to decrease. The gas susceptibility of the ZnO-CuO core-shell nanofibers under CO atmosphere was similar because the p-type CuO added to the n-type ZnO lowered the susceptibility, indicating that the reduced It was because of conductivity.

On the other hand, in the case of the core-shell nanofibers having a shell thickness of 10 nm or more, the core nanofibers were sufficiently coated with the particles of the ZnO shell layer. In CO atmosphere, the resistance of the sensor was decreased, while in the atmosphere, the resistance of the sensor was increased. When the core-shell nanofibers are exposed to CO gas, the CO gas molecules react with the chemically adsorbed oxygen on the ZnO surface as follows: [CO + O ₂ ^- → CO ₂ + 2e ^- ]. As a result, the free electrons reduce the resistance. On the other hand, when the supply of CO gas is interrupted, oxygen molecules in the air are rapidly adsorbed on the nanofiber surface, and the resistance is increased due to the electron adsorption on the nanofiber. Figure 9b relates to the relative reaction of core-shell nanofibers. The sensor including the core-shell nanofibers having a shell thickness of about 50 nm exhibited a reaction as high as about 4.2 as compared with other sensors. The sensor including the core-shell nanofiber having a shell thickness of 20 nm exhibited a relatively low response of about 1.9 as compared with the shell thickness of about 50 nm and exhibited n-type sensitivity, The possibility of diffusion of CO gas molecules through channels formed between ZnO particles located on the surface of CuO core nanofibers was reaffirmed. In core-shell nanofibers, when the shell thickness is less than or equal to the debye length, gas molecules can extract electrons from the core. The core-shell nanofibers exhibited p-type susceptibility when the shell thickness was 10 nm, while n-type susceptibility appeared when the shell thickness exceeded 10 nm. All of the above analyzes support that the ZnO shell thickness in the core-shell nanofiber acts as an important factor in the sensitivity of the sensor.

The response mechanism to the gas in the core-shell nanofiber is related to the depletion layer formed in the shell layer due to the adsorption of electrons by the chemically adsorbed gaseous species and the heterojunction formed between the shell layer and the core nanofiber . In this regard, FIG. 10 is a schematic diagram of a nanostructure fabricated for use as a sensing portion of a sensor according to an embodiment of the present invention, a schematic diagram of electron transfer occurring in the nanostructure, a conductive band energy (EC), and a Fermi energy level (EF) FIG. 10A shows a case where the nanostructure is a CuO nanofiber as a control group, FIG. 10B shows a case where the nanostructure is a CuO-ZnO core-shell nanofiber with a complete depletion layer, FIG. Is a CuO-ZnO core-shell nanofiber in which an incomplete depletion layer is formed. The adsorption of oxygen molecules on core - shell nanofibers with a shell thickness of 10 nm occurred on both the ZnO shell layer and the CuO surface and the oxygen molecules were assumed to diffuse along the channels formed between the small particles of the ZnO shell layer. Figure 10A shows relative band bending. On the other hand, the core-shell nanofiber having a shell thickness of 50 nm is a composite of band bending at the surface of the ZnO shell layer by adsorption of oxygen species and band bending at the heterojunction formed between the ZnO shell layer and the CuO core nanofiber A complete depletion layer was formed in the shell layer. Under the atmosphere, internal defects such as oxygen vacancies on the surface of the n-type ZnO shell layer are utilized as adsorption sites for oxygen molecules. Free electrons in the ZnO shell layer are removed by adsorbed oxygen molecules by the following reaction: [O ₂ (g) + e ^- → O ₂ ^- (adsorption)]. Reduction at the free charge density inside the ZnO shell depletes the surface charge state and generates a space charge region. As a result, band bending occurs at the surface of the ZnO shell layer. The thickness of the depletion layer by adsorption calculated by the following equation was about 69 nm:

<Equation>

;

;

In this equation,? _ZnO is the relative dielectric constant of ZnO of about 8.7,? ₀ is the permittivity of the vacuum, e is the electronic charge and N _D ⁺ (T) is the donor at room temperature The donor concentration is about 10 &lt; ¹⁷ &gt; cm &lt;&quot; ³ &gt;, and the potential barrier height is about 0.5 eV.

ZnO-CuO is a pn isotope heterostructure. Band bending in the ZnO-CuO heterostructure can be evaluated based on their energy band structure. And ZnO and the electron affinity (χ), the band gap (Eg), and the work function (W) that are required for the analysis of the energy band structure χ _ZnO and χ _CuO are respectively 4.29 eV and 4.07 eV of CuO, E _{g, ZnO} and E _{g and CuO} are 3.3 eV and 1.35 eV, respectively, and W _ZnO and W _CuO are 4.45 eV and 5.2 eV, respectively. Band bending occurs during the formation of a heterojunction between ZnO and CuO, which is schematically illustrated in the lower part of Figs. 10b and 10c. In this case, the difference between W _ZnO and W _CuO gave a build-in-potential at the interface between ZnO and CuO, which was equal to 0.75 eV. By substituting the built-in potential of 0.75 eV into? _S , the depletion layer width (W _d ) at the heterojunction can be calculated from the equation. The calculated W _d value was about 85 nm. As a result, as shown schematically in FIGS. 10B and 10C, the depletion layer width actually formed on the surface and the heterojunction was about 69 nm and about 85 nm, respectively, and a complete depletion layer was formed until the ZnO shell thickness was 50 nm And a partial depletion layer was formed when the ZnO shell thickness was 120 nm and 200 nm.

10A to 10C described above will be explained in different ways in order to facilitate understanding. 10A to 10C each show a band structure in which oxygen in the atmosphere is adsorbed before being exposed to a reducing gas. 10A is a CuO nanofiber as a control, FIG. 10B is a CuO-ZnO core-shell nanofiber in which a complete depletion layer is formed as a preferred embodiment, FIG. 10C is a CuO- -ZnO core-shell nanofiber. 10B in which the completeness of the depletion layer is different from that in FIG. 10C, the initial resistance shows a very large value in FIG. 10B, whereas the initial resistance in FIG. 10C is a relatively small value Of the respondents. Next, in the graphs shown in the middle portion and the bottom portion in each of FIGS. 10A to 10C, oxygen ions or molecules adsorbed on the shell surface by the sensor being exposed to the reducing gas are all desorbed through reaction with the reducing gas It is confirmed that the resistance change is induced by desorption of oxygen ions or molecules. By comparing the graphs, it can be seen that a sensor having a shell thickness less than a complete depletion layer exhibits a large resistance change when exposed to a small amount of reducing gas, and thus can be used as a highly sensitive sensor.

For example, when a CO gas is exposed to a core-shell nanofiber in which a complete depletion layer is formed in the shell, CO ₂ molecules are released by the interaction between the CO molecules and the oxygen species chemically adsorbed on the surface. The oxygen species are removed from the surface and re-emit electrons and restore the original band form. On the other hand, when the CO gas is exposed to the core-shell nanofibers formed with the partial depletion layer of the shell, the resistance change is reduced due to the presence of the conduction channel between the depletion layer of the shell and the heterojunction, . When the shell thicknesses are about 120 nm and 200 nm, the shell thickness for forming the complete depletion layer in the shell is exceeded, and the sensitivity to CO gas is lowered in this case.

4. SnO ₂ - ZnO  Preparation of core-shell nanofiber

The SnO ₂ -ZnO core-shell nanofiber was produced by a novel two-step process in the same manner as in Example 1. First, SnO ₂ core nanofiber was synthesized by electrospinning, followed by deposition of a ZnO shell layer using ALD technology.

Polyvinyl pyrrolidone (PVP) and tin chloride [SnO ₂ .2H ₂ O] having a molecular weight of 1,300,000 were used as precursor compounds for the synthesis of SnO ₂ core nanofibers. For electrospinning, 1.75 g of tin chloride was mixed with a 1: 1 by volume ratio of dimethylformamide (DMF) and ethanol solvent and stirred at 70 ° C for 30 minutes. A 8 wt% liquid solution was prepared by dissolving the PVP beads in the solution containing the precursor and further stirred for 8 hours. The viscous tin chloride / PVP solution was loaded into a glass syringe with a 21-gauge stainless steel needle. The nanofibers were uniformly electrospun on a SiO ₂ wafer located on a metal collector. The electrospun fibers were calcined at 600 &lt; 0 &gt; C under oxygen atmosphere for 4 hours, at which time a tube-type furnace was used. In order to minimize the loss of nanofibers in the atmosphere in the laboratory, the prepared samples were stored in a dust-collecting mask and vacuum conditions until measurement and characterization were performed.

In order to form a ZnO shell structure on the surface of the SnO ₂ nanofiber, a general ALD technique was used. In this embodiment, an ALD system having a horizontal wall reactor was used. Diethylzinc [Zn (C ₂ H ₅ ) ₂ , DEZn] and H ₂ O were used as precursors. In order to prevent a violent pre-reaction between the two precursors, DEZn and H ₂ O were separately introduced into the growth reactor, and the temperature and pressure conditions of the reactor were 150 ° C. and 0.3 Torr, respectively. DEZn was stored in a 0 ° C bubbler and H ₂ O was stored in a 10 ° C bubbler. The ALD pulse length was set to 0.12 seconds for DEZn dosing, 3 seconds for N ₂ purging, 0.15 seconds for H ₂ O addition, and 3 seconds for N ₂ purging. It corresponds to one cycle. The number of ALD cycles was regulated between 30, 80, 200, 350 and 650 cycles. The average diameter of the SnO ₂ core nanofiber was about 90 nm, and the thickness of the ZnO shell layer was adjusted to 20 nm to 90 nm.

5. SnO ₂ - ZnO  Analysis method of core-shell nanofiber

The microstructure and phase of the core-shell nanofibers prepared according to the above process were measured using a field emission scanning electron microscope (FE-SEM), a transmission electron microscope (TEM), and an X-ray diffractometer Respectively. Elemental mapping was also performed in an energy dispersive spectroscopy (EDS) mode.

For the sensor sensitivity measurement, a sensor including the SnO ₂ -ZnO core-shell nanofiber was fabricated. To fabricate the _dual- layer electrode of the sensor, about 50 nm thick Ti and about 200 nm thick Au Were sequentially deposited using a sputtering method and an interdigital electrode mask. The response of the sensor to CO, which is a reducing gas, was measured at 300 DEG C using a homemade gas dilution and sensing system. Sensitivity was (Sensitivity, S) is calculated according to the formula: in S = R _a / R _g or R _g / R _a (where, R _a corresponds to the first resistance and, R _g in the absence of feed gas Corresponding to the resistance when the measuring gas is present). The content of water vapor inside the CO container was kept below 3 ppm.

6. SnO ₂ - ZnO  Analysis method of core-shell nanofiber

The effect of the ZnO shell layer thickness on the surface of the SnO ₂ core nanofibers of the nanofibers was compared by performing the microstructure, phase, and gas sensitivity analyzes of the SnO ₂ -ZnO core-shell nanofibers produced, The effect of the heterojunction formed at the interface between the two types of materials was also analyzed.

11A is an FE-SEM image of an SnO ₂ core nanofiber synthesized by an electrospinning method, which is irregularly dispersed on a SiO ₂ substrate, and FIG. 11B is an enlarged view of FIG. 11A. 11C and 11E are FE-SEM images of SnO ₂ -ZnO core-shell nanofibers produced while increasing the number of ALD cycles. In FIG. 11C, the number of ALD cycles is 80 and in FIG. 11D, the number of ALD cycles is 350 And it was confirmed that the thickness of ZnO shell gradually increased as the number of ALD cycle was increased. FIG. 11D is an FE-SEM image showing an enlarged view of FIG. 11C, FIG. 11F is an FE-SEM image of FIG. 11E showing that the SnO ₂ -ZnO core-shell nanofiber includes nano-sized particles I could confirm it clearly. When reference to the drawings SnO ₂ cores of larger size constituting the nano-particles and fibers, the core of SnO ₂ small size particles constituting the shell ZnO layer deposited on the nanofiber have been clearly distinguished. It is presumed that the rough surface of the shell layer protrudes to provide an adsorption space for introduction of the measuring gas molecules and to improve the adsorption ability of the sensor. On the other hand, the heterojunction formed between the two different materials generates a potential barrier at their interface, forms a path through which electrons penetrate, and improves gas sensitivity.

The microstructure of the core-shell nanofibers was further analyzed using TEM. 12A is a low magnification TEM image of core-shell nanofibers having a ZnO shell thickness of 20 nm. 12b to 12d are element mapping results of O, Sn and Zn of SnO ₂ -ZnO core-shell nanofibers, respectively, and FIG. 12e shows the chemical composition of SnO ₂ -ZnO core-shell nanofibers analyzed using EDS Analysis graph. 12A to 12E, it was confirmed that Zn exists in the outer surface of the core-shell nanofiber, and Sn exists in the inner part of the fiber, and the elements O, Sn, and Zn It is clear that the spatial division of From the result of the element mapping analysis, it was clearly confirmed that core-shell nanofiber having a shell thickness of 20 nm was formed. From the result of EDS analysis, ZnO exists in the surface portion of the core-shell nanofiber and SnO ₂ exists in the core portion. .

13 shows XRD patterns of SnO ₂ nanofiber and SnO ₂ -ZnO core-shell nanofiber. The XRD pattern of the SnO ₂ nanofiber was confirmed for contrast. Shells each of SnO ₂ -ZnO 20 nm and 90 nm thickness of the core-shell nano-fibers ZnO SnO shell in the _second core nanofibers in addition to the peak due to the SnO ₂ exhibited a diffraction peak which is proportional to the ZnO, from which Layer can be confirmed. The increased intensity of the XRD peak was proportional to the increased thickness of the ZnO shell layer formed on the SnO ₂ nanofiber surface.

Experiments were conducted under a CO atmosphere of 1 ppm to 10 ppm to confirm the susceptibility of SnO ₂ nanofibers and SnO ₂ -ZnO core-shell nanofibers having various shell thicknesses to gases. All sensor responses were dependent on CO changes. 14A shows the response curves of a sensor comprising SnO ₂ nanofibers and SnO ₂ -ZnO core-shell nanofibers, respectively, against CO gas at 300 ° C.

When the core-shell nanofibers are exposed to CO gas, the CO gas molecules react with the chemically adsorbed oxygen on the ZnO surface as follows: [CO + O ₂ ^- → CO ₂ + 2e ^- ]. As a result, the free electrons reduce the resistance. On the other hand, when the supply of CO gas is interrupted, oxygen molecules in the air are rapidly adsorbed on the nanofiber surface, and the resistance is increased due to the electron adsorption on the nanofiber. 14B relates to the relative reaction of the core-shell nanofibers. The sensor including the core-shell nanofibers having a shell thickness of about 20 nm showed responses of 7.5, 7.6 and 8.5 for CO concentrations of 1, 5 and 10 ppm, and the core-shell Sensors containing nanofibers were reduced to 3.3, 4.4 and 7, respectively. Thin shell thickness over debye length results in reduced detection of the reducing gas, but exhibits improved response characteristics compared to sensors containing pure SnO ₂ and ZnO nanofibers. In a core-shell nanofiber, if the shell thickness is less than or equal to the divisor length, gas molecules can extract electrons from the core. The core-shell nanofibers exhibited p-type susceptibility when the shell thickness was 10 nm, while n-type susceptibility appeared when the shell thickness exceeded 10 nm. All of the above analyzes support that the ZnO shell thickness in the core-shell nanofiber acts as an important factor in the sensitivity of the sensor.

On the other hand, Fig. 14c and Fig. 14d was a measure of the response to NO ₂ gas instead of CO contrast to Figure 14a and Figure 14b. Further, Fig. 14e and 14f are on different substrate and showing the results of Fig. 14c and 14d is about response to the Figures 14a and 14b, NO ₂ gas is about the response to the CO gas as a single graph So that they can understand at a glance.

The response mechanism to the gas in the core-shell nanofiber is related to the depletion layer formed in the shell layer due to the adsorption of electrons by the chemically adsorbed gaseous species and the heterojunction formed between the shell layer and the core nanofiber . 15 is a schematic diagram of a nanostructure fabricated for use as a sensing portion of a sensor according to an embodiment of the present invention, a schematic diagram of electron transfer occurring in the nanostructure, a conductive band energy (EC), and a Fermi energy level (EF) FIG. 15A shows a case where the nanostructure is a SnO ₂ nanofiber as a control group, FIG. 15B shows a case where the nanostructure is a SnO ₂ -ZnO core-shell nanofiber with a complete depletion layer, FIG. And the nanostructure is a SnO ₂ -ZnO core-shell nanofiber in which an incomplete depletion layer is formed. The adsorption of oxygen molecules on core-shell nanofibers with a shell thickness of 10 nm occurred in both the ZnO shell layer and the SnO ₂ surface, and oxygen molecules were assumed to diffuse along the channels formed between the small particles of the ZnO shell layer . 15A shows relative band bending. On the other hand, the core-shell nanofibers having a shell thickness of 50 nm exhibit band bending at the surface of the ZnO shell layer due to adsorption of oxygen species and band bending at the heterojunction formed between the ZnO shell layer and the SnO ₂ core nanofiber A complex effect created a complete depletion layer in the shell layer. Under the atmosphere, internal defects such as oxygen vacancies on the surface of the n-type ZnO shell layer are utilized as adsorption sites for oxygen molecules. Free electrons in the ZnO shell layer are removed by adsorbed oxygen molecules by the following reaction: [O ₂ (g) + e ^- → O ₂ ^- (adsorption)]. Reduction at the free charge density inside the ZnO shell depletes the surface charge state and generates a space charge region. As a result, band bending occurs at the surface of the ZnO shell layer. The thickness of the depletion layer due to adsorption calculated by the above equation described in Example 3 was about 69 nm. For convenience of explanation, the equations are rewritten as follows:

<Equation>

;

;

In this equation,? _ZnO is the relative dielectric constant of ZnO of about 8.7,? ₀ is the permittivity of the vacuum, e is the electronic charge and N _D ⁺ (T) is the donor at room temperature The donor concentration is about 10 &lt; ¹⁷ &gt; cm &lt;&quot; ³ &gt;, and the potential barrier height is about 0.5 eV.

ZnO-SnO ₂ is a pn isotope heterostructure. Band bending in the ZnO-SnO ₂ heterostructure can be evaluated based on their energy band structure. The electron affinity of ZnO and SnO ₂ degrees and (χ), the band gap (Eg), and the work function (W) that is respectively are required for the analysis of the energy band structure χ _ZnO and χ _SnO2 4.29 eV and 4.07 eV, E _{g , ZnO} and E _{g, and SnO 2} are 3.3 eV and 1.35 eV, respectively, and W _ZnO and W _{SnO 2} are 4.45 eV and 5.2 eV, respectively. During the formation of the heterojunction between ZnO and SnO ₂ , band bending occurs, which is schematically shown in the lower part of FIGS. 15B and 15C. In this case, the difference between W and W _{SnO2 ZnO} built at the interface between ZnO and SnO ₂ - of - was given a potential (built-in-potential), the value was as 0.75 eV. By substituting the built-in potential of 0.75 eV into? _S , the depletion layer width (W _d ) at the heterojunction can be calculated from the equation. The calculated W _d value was about 85 nm. As a result, as shown schematically in FIGS. 15B and 15C, the depletion layer width actually formed on the surface and the heterojunction was about 69 nm and about 85 nm, respectively, and a complete depletion layer was formed until the ZnO shell thickness was 50 nm And a partial depletion layer was formed when the ZnO shell thickness was 120 nm and 200 nm.

When CO gas is exposed to core-shell nanofibers with a complete depletion layer in the shell, CO2 molecules are released by the interaction between the CO molecules and the chemically adsorbed oxygen species on the surface. The oxygen species are removed from the surface and re-emit electrons and restore the original band form. On the other hand, when the CO gas is exposed to the core-shell nanofibers formed with the partial depletion layer of the shell, the resistance change is reduced due to the presence of the conduction channel between the depletion layer of the shell and the heterojunction, . When the shell thicknesses are about 120 nm and 200 nm, the shell thickness for forming the complete depletion layer in the shell is exceeded, and the sensitivity to CO gas is lowered in this case.

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

100: substrate
110: insulating layer
200: sensing unit
210: core of core-shell nanostructure
220: shell of core-shell nanostructure
300: electrode layer
310: first electrode layer
320: Second electrode layer

Claims (19)

materials;
A sensing part including a core-shell nanostructure containing a core comprising a first metal oxide formed on the substrate, and a shell comprising second metal oxide nanoparticles formed on the core; And
And two electrode layers formed on the sensing portion and spaced apart from each other.
A sensor comprising a core-shell nanostructure,
Wherein the first metal oxide and the second metal oxide are each independently selected from the group consisting of Ti, Sn, Zn, Mn, Mg, Ni, W, Co, Fe, Ba, In, Zr, Cu, Al, Bi, Pb, , An oxide of a metal selected from the group consisting of Y, Mo, Rh, Pd, Sb, Cs, La, and combinations thereof,
A channel is formed between the second metal oxide nanoparticles, the channel serves as a movement path of electrons,
The core is in the form of a nanofiber having a diameter of 20 nm to 200 nm and a length of 2 탆 or more,
The core-shell nanostructure includes a core-shell nanostructure of a pn type or a core-shell nanostructure of an nn type,
The shell has a thickness equal to or less than the Debye length to form a complete depletion layer in the entire shell. The complete depletion layer is converted into an incomplete depletion layer by sensing the reducing gas, and when the reducing gas is removed The self-complete depletion layer is restored,
A sensor comprising a core-shell nanostructure.
materials;
Two electrode layers formed on the substrate so as to be spaced apart from each other; And
A core-shell nanostructure including a core including a first metal oxide formed on the electrode layer, and a shell including second metal oxide nanoparticles formed on the core,
A sensor comprising a core-shell nanostructure,
Wherein the first metal oxide and the second metal oxide are each independently selected from the group consisting of Ti, Sn, Zn, Mn, Mg, Ni, W, Co, Fe, Ba, In, Zr, Cu, Al, Bi, Pb, , An oxide of a metal selected from the group consisting of Y, Mo, Rh, Pd, Sb, Cs, La, and combinations thereof,
A channel is formed between the second metal oxide nanoparticles, the channel serves as a movement path of electrons,
The core is in the form of a nanofiber having a diameter of 20 nm to 200 nm and a length of 2 탆 or more,
The core-shell nanostructure includes a core-shell nanostructure of a pn type or a core-shell nanostructure of an nn type,
The shell has a thickness equal to or less than the Debye length to form a complete depletion layer in the entire shell. The complete depletion layer is converted into an incomplete depletion layer by sensing the reducing gas, and when the reducing gas is removed The self-complete depletion layer is restored,
A sensor comprising a core-shell nanostructure.
3. The method according to claim 1 or 2,
Wherein the sensor comprising the core-shell nanostructure senses a reducing gas of 100 ppm or less.
3. The method according to claim 1 or 2,
The sensor comprising the core-shell nanostructure may comprise at least one selected from the group consisting of H ₂ , CO, CH ₄ , NH _{3 ,} CH ₃ OH, C ₂ H ₅ OH, C ₃ H ₈ , H ₂ S, dimethylamine, Wherein the sensor detects a gas selected from the group consisting of triethylamine, benzene, toluene, xylene, and combinations thereof.
3. The method according to claim 1 or 2,
Wherein the first metal oxide and the second metal oxide are oxides of different metals.
delete delete delete delete 3. The method according to claim 1 or 2,
Wherein the electrode layer is a single layer electrode layer containing a metal selected from the group consisting of Au, Pt, Cu, and combinations thereof, or a single layer electrode layer selected from the group consisting of Ti, Ni, Cr, Wherein the electrode layer comprises a multi-layered electrode layer that additionally contains a layer of a metal that is not electrically conductive.
Forming a core comprising a first metal oxide on a substrate;
Forming a sensing portion including the core-shell nanostructure by forming a shell including the second metal oxide nanoparticles on the core; And
And forming two electrode layers spaced apart from each other on the sensing portion
Wherein the core-shell nanostructure comprises a core-shell nanostructure,
Wherein the first metal oxide and the second metal oxide are each independently selected from the group consisting of Ti, Sn, Zn, Mn, Mg, Ni, W, Co, Fe, Ba, In, Zr, Cu, Al, Bi, Pb, , An oxide of a metal selected from the group consisting of Y, Mo, Rh, Pd, Sb, Cs, La, and combinations thereof,
A channel is formed between the second metal oxide nanoparticles, the channel serves as a movement path of electrons,
The core is in the form of a nanofiber having a diameter of 20 nm to 200 nm and a length of 2 탆 or more,
The core-shell nanostructure includes a core-shell nanostructure of a pn type or a core-shell nanostructure of an nn type,
The shell has a thickness equal to or less than the Debye length to form a complete depletion layer in the entire shell. The complete depletion layer is converted into an incomplete depletion layer by sensing the reducing gas, and when the reducing gas is removed The self-complete depletion layer is restored,
A method of manufacturing a sensor comprising a core-shell nanostructure.
Forming two electrode layers spaced apart from each other on a substrate; And
Shell nanostructure is produced by forming a core containing a first metal oxide and forming a shell containing second metal oxide nanoparticles on the core, and then forming the core-shell nanostructure on the electrode layer, Deposition as a sensing part
Wherein the core-shell nanostructure comprises a core-shell nanostructure,
Wherein the first metal oxide and the second metal oxide are each independently selected from the group consisting of Ti, Sn, Zn, Mn, Mg, Ni, W, Co, Fe, Ba, In, Zr, Cu, Al, Bi, Pb, , An oxide of a metal selected from the group consisting of Y, Mo, Rh, Pd, Sb, Cs, La, and combinations thereof,
A channel is formed between the second metal oxide nanoparticles, the channel serves as a movement path of electrons,
The core is in the form of a nanofiber having a diameter of 20 nm to 200 nm and a length of 2 탆 or more,
The core-shell nanostructure includes a core-shell nanostructure of a pn type or a core-shell nanostructure of an nn type,
The shell has a thickness equal to or less than the Debye length to form a complete depletion layer in the entire shell. The complete depletion layer is converted into an incomplete depletion layer by sensing the reducing gas, and when the reducing gas is removed The self-complete depletion layer is restored,
A method of manufacturing a sensor comprising a core-shell nanostructure.
13. The method according to claim 11 or 12,
Wherein forming the core comprises forming the core in nanofiber form by electrospinning a solution comprising a precursor of the first metal oxide and a polymer, and forming a core-shell nanostructure Way.
13. The method according to claim 11 or 12,
Wherein the shell comprises a core-shell nanostructure formed by atomic layer deposition.
13. The method according to claim 11 or 12,
And adjusting the number of times of atomic layer deposition to adjust the shell thickness to be less than or equal to the device length.
13. The method according to claim 11 or 12,
Forming a shell containing a second metal oxide different from the first metal oxide on the core to form a heterojunction at an interface between the core included in the core-shell nanostructure and the shell Wherein the core-shell nanostructure comprises a core-shell nanostructure.
13. The method according to claim 11 or 12,
comprising forming the core using a p-type metal oxide and forming the shell using an n-type metal oxide on the core to produce the core-shell nanostructure of the pn type. A method for manufacturing a sensor comprising a shell nanostructure.
13. The method according to claim 11 or 12,
type metal oxide, and forming the shell on the core by using an n-type metal oxide different from the n-type metal oxide included in the core to form the core- Shell nanostructure, wherein the core-shell nanostructure comprises a core-shell nanostructure.
13. The method of claim 12,
Wherein the step of depositing the core-shell nanostructure on the electrode layer as a sensing part includes performing the step of depositing the core-shell nanostructure on the electrode layer by a printing technique.

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