KR101040323B1 - Nano structure, sensor comprising the same and method preparing thereof - Google Patents

Abstract

A substrate on which a plurality of electrodes are formed; And a nanostructure connecting the plurality of electrodes, wherein the nanostructure includes a plurality of indents.

Since the indentation of the nanostructure is smaller than the other portions, the current flowing through the nanostructure is substantially zero even when exposed to a small amount of gas analyte.

Nanostructure, sensor

Description

Nano structure, sensor comprising same, and method for manufacturing same {NANO STRUCTURE, SENSOR COMPRISING THE SAME AND METHOD PREPARING THEREOF}

Sensors that can detect gases, chemicals, biomolecules, etc. have been researched and developed for a long time. Sensors are used in a wide range of fields, including chemistry, pharmaceuticals, food, agriculture, environmental management, and medical, and require characteristics such as rapidity, selectivity, sensitivity, reproducibility, durability, low power consumption, and integration. In response to the demands of the sensor characteristics, researches on using nanostructures as sensing elements of sensors have been made. In particular, since the nanostructure has a large volume-to-surface area ratio, high sensitivity, and small constraints such as size, the nanostructure can satisfy a large portion of the characteristics required by the sensor.

Sensors using nanostructures detect gases through changes in their resistivity caused by chemical reactions between the gas to be detected and the nanostructures. That is, when a specific gas reacts with the nanostructure, the electrical resistivity changes accordingly, and thus the presence of the specific gas can be determined by monitoring the resistivity of the sensor. For example, zinc oxide (ZnO), tin oxide (SnO ₂ ), tungsten oxide (WO ₃ ), titanium oxide (TiO ₂ ), and the like, which are metal oxide semiconductors, may be external specific gas components such as H ₂ and CO. Contact with water, O ₂ , NO _x , CO ₂ , DMMP, CH ₄ , NH ₃ , alcohol, humidity, etc. changes the electrical resistivity due to gas adsorption and oxidation / reduction reactions occurring on the oxide surface. In particular, nanowires can exhibit high surface area ratio, high aspect ratio, and high sensitivity, low power, and high efficiency. In addition, silicon nanowires may be grown and used for the sensor. Sensors using silicon nanowires (SiNW) have very high detectability (untrasensitive) and are being studied in various fields such as biosensors and chemical sensors. Silicon nanowires have advantages such as high surface area to volume ratio, conductivity can be controlled by controlling doping of impurities, and applicable to biocompatibility. The mechanism when using these silicon nanowires as DNA sensors is to change the electric field on the surface of the silicon nanowires when they are combined with DNA, causing them to detect as sensors by causing changes in charge density.

With the development of sensors based on nanostructures, sensors with higher sensitivity are required.

In a first embodiment to be disclosed, a process of growing a plurality of nanorods on a substrate, separating the grown plurality of nanorods from the substrate and aligning them in the longitudinal direction of the nanorods, and the plurality of nanorods It is a method for producing a nanostructure comprising a step of bonding the rod in the longitudinal direction. At the junction of the nanorods, an indent having a smaller thickness than other portions is formed.

Moreover, 2nd Embodiment to disclose is a manufacturing method of the nanostructure containing the process of growing a silicon nanowire, and the process of forming a some indentation part in the said silicon nanowire.

In addition, a third embodiment to be disclosed includes a plurality of nanorods bonded in the longitudinal direction, wherein the bonded portion of the plurality of nanorods is a nanostructure forming an indentation portion.

Further, a fourth embodiment to be disclosed includes a substrate on which a plurality of electrodes are formed and a nanostructure connecting the plurality of electrodes, wherein the nanostructure is a sensor including a plurality of indentations.

In addition, a fifth embodiment to be disclosed includes a process of disposing a nanostructure on a substrate, and a process of forming a plurality of electrodes at both ends of the nanostructure, wherein the nanostructure includes a plurality of indentations , Manufacturing method of the sensor.

Sensor using nano structure

1A schematically illustrates a general form of a nanowire sensor. The nanowires 11 are formed of an n-type metal oxide and connect two electrodes 12. When power is applied to the two electrodes 12, the nanowires 11 serve as resistances, and the presence or absence of surrounding gas can be detected by changing the specific resistance of the nanowires 11 or the magnitude of the current. do. Specifically, referring to FIG. 1B, the surplus electrons in the nanowires 13 function as charge carriers. When the nanowires 13 are exposed to the oxidizing gas analyte, the surplus electrons are formed by the oxidizing gas. Will be trapped. By the oxidation reaction on the surface of the nanowire 13, the electron depletion region 14 is formed on the surface of the nanowire 13, thereby increasing the resistivity of the nanowire 13. FIG. 1B (15) shows a cross section of the nanowire, showing the electron depletion region 16 and the region 17 not. As such, the sensor using the nanowire may detect the presence of a desired analyte by measuring the specific resistance of the nanowire or the magnitude of the current through the nanowire.

On the other hand, since the specific resistance of the nanostructure is influenced by the shape design of the nanostructure, it can be seen that a more sensitive sensor can be manufactured by appropriately changing it.

2A and 2B schematically show a state change of a nanostructure having a plurality of indentations.

In one embodiment, the nanostructure (21 in FIG. 2A, 22 in FIG. 2B) includes a plurality of indentations (24 in FIG. 2A, 25 in FIG. 2B), wherein the indentation is thicker than other portions of the nanostructure. Means a small part. The thickness of the indentation part 24 (FIG. 2A, 25 in FIG. 2B) may be, for example, 3 nm or less. The nanostructures (21 of FIG. 2A and 22 of FIG. 2B) may perform a function of a sensor by connecting two electrodes as in the nanowire 11 of FIG. 1A.

FIG. 2A shows the nanostructure 21 in a state in which there is no gas analyte around it, that is, in a normal state. In this case, electrons can be transferred in the entire region of the nanostructure, so that a large current can flow. On the other hand, FIG. 2B shows the nanostructure 22 exposed to the surrounding gas. When the nanostructure 21 in the normal state is exposed to the surrounding gas analyte, an electron depletion region 26 is formed on the surface thereof so as to form the nanostructure 22 exposed to the gas. In the small indentation 25, the electrons of the entire indentation are trapped by the gas. Therefore, in the indentation portion 25 of the nanostructure 22 in the state exposed to the gas, all of the excess electrons are depleted, and substantially no current flows.

As such, when the nanostructure including the indentation part is used, the amount of change in the current sensed by the sensor may be abrupt even with a small amount of gas, thereby making it possible to manufacture a very sensitive sensor.

In addition, although one-dimensional nanowire is described as an example, the nanostructure including the indentation described above may be applied to a sensor using a two-dimensional network structure.

Indentation  Formation of Nanostructures Containing

Hereinafter, a method of forming a nanostructure including the above indentation is disclosed.

The formation of the nanostructure including the indentation includes a method of arranging a plurality of nanorods in a row and then bonding the nanorods to each other and applying anisotropic etching to the silicon nanowires. The term nanorod generally refers to a nanostructure having a shape similar to that of a nanowire, and refers to a nanostructure having an aspect ratio smaller than that of the nanowire.

Hereinafter, a method of forming an indentation portion by joining a plurality of grown nanorods in the longitudinal direction thereof is disclosed.

3A schematically illustrates the growth of the nanorods 31 on the substrate 32. Since the nanorods 31 grow in a direction perpendicular to the substrate 32 in a direction perpendicular to each other, the plurality of nanorods 31 may be aligned in the longitudinal direction thereof.

The nano rod may be an n-type metal oxide, and for example, SnO ₂ , ZnO, In ₂ O ₃ , WO _X , TiO _2, or the like may be used, but is not limited thereto.

The growth technique of the nanorods may be used, for example, a vapor-liquid-solid (VLS) mechanism. In the VLS mechanism, gaseous reactants saturate the catalyst in the liquid state on the substrate. Disruption of symmetry at the liquid-solid interface causes single crystal nanorod structures to agglomerate, and the nanorods grow epitaxially from the substrate. The growth of these nanorods continues until the dissolution rate by the catalyst of the material prevails at the solid material at the liquid / solid interface. As another example, a selective area epitaxy method may be used. In this method, the crystalline substrate is covered with a material that prevents epitaxy from occurring in certain regions, so that nanorods can be grown without a catalyst. In addition, those skilled in the art can readily appreciate that various methods such as molecular beam crystal growth system (MBE) can be used for the growth of nanorods.

The type of nanorods disclosed above and a method of growing the same are not limited thereto, and the nanorods and the method of growing the same are not particularly limited.

 FIG. 3B discloses a nanorod 33 separated from the substrate 32 and arranged in the longitudinal direction thereof. This is for the bonding of the nanorods to be described later, it should be arranged so that the plurality of nanorods are substantially aligned in the longitudinal direction. There may be a variety of ways to separate the nanorods from the substrate so that the nanorods maintain a constant orientation. For example, as shown in FIG. 3A, the nanorods may be arranged in the longitudinal direction by applying a constant pressure to the nanorods grown perpendicular to the substrate. For example, as shown in FIG. 4A, the nanorods may be arranged in the longitudinal direction by applying a constant pressure to the nanorods 41 grown vertically from the substrate 42. Specifically, the nanorods 41 grown vertically from the substrate 42 are attached to the substrate 42 with a constant orientation, and when a constant pressure is applied thereto, the nanorods are separated from the substrate while maintaining their alignment. May be In this case, the direction in which the pressure is applied may be mainly a direction perpendicular to the growth direction of the nanorods, and may be an oblique direction to the substrate surface as shown in FIG. 4a, without damaging the nanorods according to a specific embodiment. Its direction and size can be controlled to allow separation from the substrate. In addition, although pressure may be directly applied to the entire nanorods as shown in FIG. 4A, as shown in FIG. 4B, the nanorods are brought into contact with the flat plate 43 on the upper portion of the nanorods 41 by applying a constant pressure to the flat plate 43. The 41 can also be separated from the substrate 42.

In another example, an array of nanorods grown on a substrate 32 is deposited in a solution and then ultrasonically applied to separate the nanorods 31 from the substrate 32 and thereafter nanorods scattered within the solution. You can also arrange For example, after disposing a solution 48 in which the nanorods 46 are dispersed on the substrate 45 as shown in FIG. 4C, an appropriate pressure is applied to the plates 49 positioned at both ends of the substrate 45. In this case, the nanorods 46 dispersed in the solution are aligned in one direction. Thereafter, evaporation of the solution 48 leaves the nanorods on the substrate in an aligned state 47. In addition, the nanorods may be aligned and disposed so as to have a constant direction by applying an electric field at both ends of the nanorods. The method for arranging the nanorods disclosed above is illustrative and not limited thereto.

In this manner, the nanorods are bonded while the nanorods are aligned in the longitudinal direction. Bonding of the nanorods is bonded so as to extend in the longitudinal direction as shown in FIG. The nanorods are the fastest growing at their longitudinal ends, and generally the fastest growing portions are the most energetically unstable, so the longitudinal ends of the nanorods are joined to extend the nanorods into a one-dimensional structure. Can be used. That is, the plurality of nanorods are joined through opposite ends to form a nanostructure having a long aspect ratio.

As a specific example, a method of bonding nanorods will be described with reference to FIG. 5. First, as shown in FIG. 5A, a plurality of nanorods 51 are arranged in a line to supply solvent and simultaneously heat. In this case, water, an organic solvent, a surfactant, or the like may be used as the solvent. The heating temperature may range from room temperature to 200 ° C. In addition, the heating may be performed using a pressure tube. As such, when water and pressure are applied to the nanorods, both ends of the nanorods become unstable as shown in FIG. Then, when water is removed and heat is continuously applied, the ends of the unstable nanorods adjacent to each other are linked to each other as shown in FIG. 5 (c), and both ends of the nanorods grow in the longitudinal direction. At this time, when heating using a pressure tube, you may heat in the state which opened the pressure tube. If heat is continuously applied thereto, the growth portions of the ends of the nanorods are contacted as shown in FIG. 5 (d), and the contact portions are further grown to be bonded through the ends of the nanorods as shown in FIG. 5 (e). The junction between these nanorods forms an indentation.

Accordingly, the plurality of nanorods aligned in the longitudinal direction are joined to extend in the longitudinal direction to form one nanostructure, and the nanostructures thus formed become nanostructures having a plurality of indentations as shown in FIG. 2. . In addition, the size of the nanostructure may have a thickness of 3 nm or less at the indentation portion and a thickness of 10 nm or less at other portions.

Silicon nanoparticles as an example below Wire  using Indentation  A method of forming is disclosed.

6 schematically illustrates a method of growing silicon nanowires using Fe as a catalyst.

Laser ablation to the Fe—Si target (FIG. 6 (a)) creates a dense hot vapor phase, and the vapor phases of these Fe and Si species cool as they collide with the buffer gas. It condenses to -Si nano cluster 61 (FIG. 6 (b)). The temperature of the furnace can be adjusted to keep the Fe—Si nanoclusters 61 in the liquid state, and the nanowires grow as the liquid begins to supersaturate in silicon (FIG. 6C). In FIG. 6C, the nanowires grow in the direction of the arrow 62. The growth of the nanowires may continue to grow until the Fe—Si nanoclusters remain in the liquid state and the silicon reactant is available.

It will be appreciated that the growth of silicon nanowires can be used in various ways known in the art in addition to the disclosed methods.

7 discloses a nanostructure in which a plurality of indentations are formed in a silicon nanowire.

As a method of forming an indentation in the silicon nanowires, a method of selectively etching a region in which the indentation is to be formed through an anisotropic etching process may be used. Anisotropic etching means that a special surface in a certain direction in the crystal plane exhibits a very fast etching rate, so that the etching is directional, and the etching rate and the etching region through the anisotropic etching can be easily applied by those skilled in the art according to specific embodiments. have. As an example, when anisotropic etching is applied to the silicon nanowires 71 as shown in FIG. 7, the indentations 74 as in FIG. 7 are different as the etching rates of the (100) plane and the (111) plane differ. ) Can be formed. As an etchant used for anisotropic etching, for example, aqueous KOH solution, Ethylenediamine Pyrocatechol (EDP), 4-Tetramethylammonium hydroxide (TMAH), or the like may be used.

As described above, a nanostructure having a plurality of indentations may be formed through a method of bonding or anisotropic etching of the nanorods. Nanostructures having a plurality of indentations can be used in a sensor to produce a highly sensitive sensor.

Although the above description exemplarily illustrates a gas as a detection target of a sensor, a person skilled in the art may understand that the present invention is not limited thereto and may be applied to detection of various analytes such as biomolecules.

In addition, in addition to the various exemplary embodiments described above, those skilled in the art can readily recognize that modifications, substitutions, additions, and combinations of some of the configurations disclosed in the embodiments are possible. Therefore, it is interpreted that all such modifications, substitutions, additions, and combinations thereof are included within the scope of the technical idea disclosed by the present application.

1A schematically illustrates a general form of a nanowire sensor.

1B schematically illustrates the reaction of nanowires with analytes.

FIG. 2A schematically illustrates a normal state of a nanostructure including a plurality of indentations. FIG.

FIG. 2B schematically illustrates a state where a nanostructure including a plurality of indentations is exposed to an analyte. FIG.

3A shows nanorods grown on a substrate.

3B is a view showing the nanorods aligned in a constant direction.

4A-4C schematically illustrate a method of longitudinally arranging nanorods.

5 schematically shows a method of bonding nanorods.

6 schematically shows the growth of silicon nanowires.

7 schematically illustrates a method of forming a plurality of indentations in a nanostructure through anisotropic etching.

* Reference number *

11, 21, 71: nanostructure 12: electrode

13: n-type metal oxide nanorod 14, 16, 26: electron depletion region

24, 74: indentation 32, 42, 45: substrate 31, 41, 46, 51: nanorod

Claims (19)

Growing a plurality of nanorods on the substrate; Separating the grown plurality of nanorods from the substrate and aligning them in the longitudinal direction of the nanorods; And And bonding the plurality of aligned nanorods in a longitudinal direction. The method of claim 1, Bonding the plurality of nanorods in the longitudinal direction, Applying a solvent and heat to the plurality of nanorods; And And applying heat to the plurality of nanorods to bond the plurality of nanorods in a longitudinal direction. The method of claim 1, Wherein the plurality of nanorods forms an indent at the junction. The method of claim 1, The process of separating the plurality of nanorods from the substrate and aligned in the longitudinal direction of the nanorods, Disposing a plate on the plurality of nanorods so as to be parallel to the substrate; And Applying pressure to the plate to separate the plurality of nanorods from the substrate and align in the longitudinal direction. delete delete A plurality of nanorods bonded in the longitudinal direction, The junction portion of the plurality of nanorods forms an indent. delete delete The method of claim 7, wherein The nanostructure has a thickness of 3 nm or less. A substrate on which a plurality of electrodes are formed; And It comprises a nanostructure for connecting the plurality of electrodes, Wherein the nanostructure comprises a plurality of indents. delete The method of claim 11, The nanostructure includes a plurality of nanorods bonded in the longitudinal direction, wherein the indentation is formed in the junction portion of the plurality of nanorods. delete The method of claim 11, The thickness of the indentation is 3 nm or less. Disposing a nanostructure on the substrate; And Forming a plurality of electrodes at both ends of the nanostructure, The nanostructure comprises a plurality of indents. The method of claim 16, The nanostructure includes a plurality of nanorods bonded in the longitudinal direction, wherein the indentation is formed in the junction portion of the plurality of nanorods. delete The method of claim 16, The thickness of the said indentation part is 3 nm or less, The manufacturing method of the sensor.

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