KR101105824B1 - A method for manufacturing nanostructure, nanostructure manufactured by the same, apparatus for the same, and gas, UV sensor comprising the same - Google Patents

Abstract

Provided are a method for manufacturing a nanostructure, a nanostructure produced thereby, a manufacturing apparatus therefor, and a gas and UV sensor including the same.

Nanostructure manufacturing method according to the present invention comprises the steps of heating a liquid precursor of the material to be grown with a micro heater in contact with the precursor of the liquid phase; And

It characterized in that it comprises the step of growing a nanostructure of the material from the heated micro-heater, the nanostructure manufacturing method according to the present invention is performed at a relatively low temperature, it is excellent in economy and the like. In addition, unlike the VLS method which proceeds in the conventional gas phase, the present invention proceeds the nanostructure growth reaction in a liquid environment, and therefore is excellent in economics and safety, and more environmentally friendly. Furthermore, since the nanostructure is manufactured by heating the micro heater, various types of nanostructures can be manufactured according to the configuration thereof, and further, the nanostructure manufacturing pattern can be controlled according to conditions such as temperature. In addition, there is an advantage that can be integrated in the desired position on the device while synthesizing the nanostructure, through which the complexity that occurs in the integration and assembly process after the conventional nanostructure synthesis.

Description

A method for manufacturing nanostructure, nanostructure manufactured by the same, apparatus for the same, and gas, UV sensor comprising the same}

The present invention relates to a method for manufacturing a nanostructure, a nanostructure produced thereby, a manufacturing apparatus for the same, and a gas and a UV sensor comprising the same, more particularly, because it proceeds at a relatively low temperature, it is excellent in economy, etc., Unlike the VLS method performed in the conventional gas phase, the present invention proceeds with the nanostructure growth reaction in a liquid environment, thereby providing excellent safety and economical, more environmentally friendly nanostructure manufacturing method, and synthesis of functional nanostructures using a micro heater. And a method for integrating into a device, a nanostructure produced thereby, a manufacturing apparatus therefor, and a gas and UV sensor comprising the same.

NEMS is an abbreviation for Nanoelectromechanical systems. It is a field of micro-precision micromechanics in the nano-area, which is smaller than MEMS. One of the achievements of this NEMS is the fabrication of sensors and actuators based on nanowires.

One of the nanowire fabrication techniques widely used in NEMS of the prior art is the VLS (Vapor-Liquid-Solid) method, and the VLS (vapor-liquid-solid) method is a micrometer-sized single crystal growth by Wagner et al. In the 1960s. In recent years, many research groups have applied and tried to grow monocrystalline nanowire structures of inorganic compounds.

1 is a schematic diagram showing the VLS mechanism for nanowire growth.

Referring to FIG. 1, according to the solid / liquid phase equilibrium diagram of the mixture, when two metal materials are alloyed, they are melted at a lower temperature than the intrinsic melting point of the two materials. In the VLS method, nanoparticles of noble metals such as gold (Au) or silver (Ag), which are stable at high temperatures and have a relatively low melting point, are applied to a substrate, and a material or a precursor thereof to be grown at a high melting point is evaporated at a high temperature. . As the evaporated reaction gas dissolves in the liquid droplets of the precious metal, the supersaturated state is reached and the supersaturated reactant is eluted through the liquid state and eluted into the solid state to grow in one direction. Is grown. In general, in order to easily maintain the phase equilibrium, the growth material uses a metal, and for the metal compound structure such as a compound semiconductor, the atmosphere gas is controlled to control the form of the oxide or sulfide. First, gaseous reactant gas is dissolved in nano-sized droplets that act as catalysts, and as the concentration of the reactant gas increases, the phase equilibrium of the mixture creates a nucleation of the reactant and unites the core. Qualitative nanowires or nanorods are grown. Ideally, one-dimensional growth is maintained by the metal liquid nanodrops, and the width or thickness of the grown nanowires is determined by the size of the metal nanodrops.

However, the conventional VLS method has the following problems.

First, a high temperature is required to evaporate the material or precursor to be grown. In other words, since the precursor gas and the like must be dissolved in the liquid catalyst at a temperature above the eutectic melting point of the alloy, a considerably high temperature is required.

Secondly, not only a very high temperature, but also necessarily harmful or flammable gas must be used, there is a problem that the working environment is very harmful, dangerous.

For example, silicon nanowires (SiNW) are explosive, SiH4 is explosive, germanium nanowires (GeNW) are toxic and explosive, GeH4 is explosive, and carbon nanotubes are explosive. Methane should be used. In this case, it is very difficult to control and control the process environment, and in some cases, a worker is exposed to a dangerous environment.

Third, after synthesizing the nanostructures, it is necessary to accumulate and assemble the nanostructures, which leads to a problem that the overall process is complicated and economical is inferior.

Therefore, the present invention has been made to solve the above problems, the problem to be solved by the present invention is to provide a new bottom-up method of manufacturing nanostructures.

Another problem to be solved by the present invention is to provide a nanostructure manufactured by a new bottom-up method.

Another object of the present invention is to provide a manufacturing apparatus capable of manufacturing nanostructures in a new bottom-up method.

Another object of the present invention is to provide an application example of the prepared nanostructures.

In order to solve the above problems, the present invention comprises the steps of heating a liquid precursor of the material to be grown with a micro heater in contact with the precursor of the liquid phase; And growing a nanostructure of the material from the heated micro heater. The micro heater may be provided with seed particles for growing the nanostructure, and the manufacturing method may be performed in a container containing the liquid precursor. In one embodiment of the present invention, the container is a well structure made of a polymer material, and may be removed after the nanostructure is grown.

In an embodiment of the present invention, the micro heater is provided in the container, and the micro heaters are provided at electrodes spaced apart from each other, and the micro heaters may be heated by a voltage applied to the electrodes. In addition, as the nanostructures grow, the spaced electrodes may be connected by the nanostructures, and the nanostructures may grow in an anisotropic direction from the micro heater.

In another embodiment of the present invention, a non-polar chelate compound is added to the precursor, and the non-polar chelate compound binds to the side of the nanostructure and inhibits side growth of the nanostructure. In one embodiment of the invention the nanostructure is ZnO, wherein the nonpolar chelate compound is polyethyleneimide. In addition, the heating temperature of the micro heater is below the boiling point of the precursor solution, the nanostructure is made of MoO ₃ , Bi ₂ S ₃ , SnO ₂ , V ₂ O ₅ , MnO ₂ , PbS, CoFe ₂ O ₄ , WO ₃ It may include any one material selected from the group.

In order to solve the second problem, the present invention provides a nanostructure produced by the method.

In order to solve the above problems, the present invention is a container containing a liquid precursor of the nanostructure to be grown; It is provided in the container, provides a nanostructure manufacturing apparatus comprising a micro heater for locally heating the precursor of the liquid, the micro heater further comprises seed particles for reacting with the liquid precursor. Can be. In one embodiment of the present invention, the nanostructure is ZnO, wherein the precursor of the liquid phase includes Zn (NO ₃ ) ₂ 6H ₂ O. In one embodiment of the present invention, the micro heaters may be provided on electrodes spaced apart from each other.

The present invention provides a gas or UV sensor comprising the nanostructures, in order to solve the above problems.

Since the nanostructure manufacturing method according to the present invention proceeds at a relatively low temperature, it is excellent in economy and the like. In addition, unlike the VLS method which proceeds in the conventional gas phase, the present invention proceeds the nanostructure growth reaction in a liquid environment, and therefore is excellent in economics and safety, and more environmentally friendly. Furthermore, since the nanostructure is manufactured by heating the micro heater, it is possible to manufacture various types of nanostructures according to the configuration thereof, and to be integrated into a functional device at the same time as synthesis, and further, depending on the conditions such as temperature. The nanostructure fabrication pattern is controllable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

In addition, the nanostructures used in the present invention, including nanotubes, nanowires, nanocrystals, etc., means any structure having a nano unit size, the micro heater is applied to the thermal energy to grow the nanostructures in a liquid environment, It means any heater that can be manufactured, the dimensions or the form of which is freely selectable, which is also within the scope of the present invention.

Nano structure manufacturing method

Figure 2 is a schematic diagram for explaining a nanostructure manufacturing method according to the present invention.

Referring to FIG. 2, in the method of manufacturing a nanostructure according to the present invention, unlike a VLS proceeding in a vapor phase by evaporating a precursor, the nanostructure is directly grown in a precursor solution environment in a bottom-up manner. Therefore, the present invention focuses on the growth of the nanostructures in a controlled manner around the micro heaters when the nanostructures are grown by heating a precursor solution in a local and selective manner by a micro heater. will be. In this case, the initial generation, growth, integration, etc. of the nanostructures can be performed in one process step.

Figure 3 is a step of the nanostructure manufacturing method according to the invention.

Referring to FIG. 3, first, a liquid precursor of a material to be grown is heated by a micro heater in contact with the liquid precursor. Herein, the micro heater refers to a means capable of heating the liquid precursor to a fine scale to grow nanostructures such as nanocrystals from nanoparticles, and the size and shape thereof are limited by the embodiments described below. It doesn't work. Here, the selection of the precursor solution can be freely selected depending on the material to be grown into the nanostructure. For example, in the case of a ZnO nanowire _{Zn (NO 3) 2 · 6H} 2 O, SnO _2, if the nanowire case of _{SnCl 4 .5H 2 O, V 2} O 5 nanowires VOSO ₄ .xH ₂ O, MnO ₂ In the case of nanowires, KMnO ₄ / MnSO ₄ may be used as the precursor solution.

In one embodiment of the present invention, the micro heater is provided on two opposite electrodes, and the nanostructures grown in the micro heater are spaced apart from each other over time to physically connect the opposite electrodes, in which case between the two electrodes The nanostructures formed in the can be applied to various sensors.

In one embodiment of the present invention, the micro heater is provided with seed particles (Seed Particle) that can grow the initial nanostructures, the seed particles provide a growth position for the nanostructures to grow by the initial endothermic reaction. For example, in one embodiment of the present invention in which ZnO was grown, the seed particles were ZnO. In this way, nanoparticles of the same kind as the nanostructures to be grown can be used as seed particles, and the seed particle position and thermal energy applied to the seed particles promote nanostructure growth, in particular selective growth and integration. .

The precursor heated locally by the micro heater undergoes an endothermic reaction, and as a result of the reaction, the nanostructure grows only at the site heated by the micro heater. That is, the present invention provides a configuration in which a reaction in which a nanostructure is grown from the precursor is an endothermic reaction, and a point in which the precursor can be locally heated even in a liquid state, and the nanostructure obtained from the configuration is provided. The structure will be described in detail in the following experimental example.

Example  One

Target substance

In one embodiment of the invention the nanostructure was ZnO. However, the present invention is not limited thereto, and the present invention is applicable to any material for growing nanostructures by thermohydrochemical reaction, and the present invention is not limited in scope by the ZnO of the examples. For example, MoO ₃ used for displays, sensors, battery electrodes, catalysts, etc., Bi ₂ S ₃ used for photodiodes, photovoltaic devices, thermoelectric cooling devices, SnO ₂ used for gas sensors, photovoltaic devices, and photoelectric devices. , V ₂ O ₅ used in catalysts, electrochemical devices, MnO ₂ used as electrodes for electrochemical devices, ion sensors, IR detection sensors, PbS used as solar absorbers, transformer cores, antenna rods, magnetic memories, etc. The present invention can also be applied to CoFe ₂ O ₄ , a gas sensor, a catalyst, and WO ₃ used as an optical data reservoir. In addition, nanostructures can be grown by endothermic reaction, and any nanostructures in which the precursor can be liquid are within the scope of the present invention.

Manufacturing equipment

 Figure 4a is a schematic diagram of a nanostructure manufacturing apparatus according to an embodiment of the present invention, Figure 4b is a photograph of the actual nanostructure manufacturing apparatus.

Referring to FIG. 4A, a nanostructure manufacturing apparatus according to the present invention discloses a container 400 containing a precursor solution 410 of a nanostructure. In particular, unlike the gas chamber of the prior art in which gaseous gas is introduced into the interior, the present invention accommodates only liquid precursors and uses a relatively small container 400 compared to the gas chamber, and therefore, economical efficiency is significant even in a manufacturing apparatus. . In one embodiment of the present invention, the container 400 is a well structure formed in a polymer block such as PDMS, but the present invention is not limited thereto and may be any structure in which a liquid precursor solution may be volumetric.

A micro heater 420 is provided in the vessel 400, and the micro heater 420 is in contact with the precursor solution 410 in the vessel 400, thereby locally heating the precursor solution 410. , It will react. In an embodiment of the present invention using ZnO, the precursor solution 410 is Zn (NO ₃ ) _{2 ·} 6H ₂ O, and the growing nanostructure was ZnO nanowires. In this case, the micro heater 420 heated the precursor solution to a temperature of 100 ° C. or less, because when the aqueous solution-based precursor solution including water exceeds 100 ° C., the microbubble may boil and bubbles may occur. . However, the present invention is not limited thereto, and the heating temperature of the micro heater is freely selectable according to the properties of the selected solvent, and heating to below the boiling point of the selected solvent is possible. The reason for this is that when the solution itself is boiled as described above, selective nanostructure growth becomes difficult.

Example  2

Preparation of Nanostructures

First, a micro heater was fabricated through an exposure and etching process on a silicon-on-insulator (SOI) substrate, wherein the size of the micro heater was 3-4 microns in line width and 30-40 microns in length. However, the present invention is not limited to the dimensions of the micro heater according to the embodiment, and can be freely designed according to the nanostructure of the desired size, which is within the scope of the present invention. Afterwards, the Al microwire is connected to the silicon micro heater to enable electrical contact, and the ZnO nanoparticle solution dissolved in 30-50 nM concentration in ethanol has a diameter of 10 nm on the substrate on which the micro heater is manufactured. After drying, washing with ethanol solution was made to evenly spread the ZnO nanoparticle seeds.

After the particle is applied, the substrate is heated on a hot plate at a temperature of 180-250 ° C. so that the nanoparticles adhere well to the substrate. A polymer block is attached onto the substrate to make a well and to place the micro heater portion in the well. That is, in one embodiment of the present invention, the container in which the nanostructure is grown is a well structure made of a polymer material, and the container is removed after the nanostructure is manufactured.

Subsequently, a precursor solution, that is, a precursor solution containing Zn (NO ₃ ) _{2 ·} 6H ₂ O, HMTA, PEI, etc. in the case of ZnO nanowires, is dropped in a 1-2 drop polymer block well by using a syringe and the well is free. By covering with, it was possible to observe under a microscope and at the same time prevent the precursor solution from evaporating during nanostructure fabrication.

Subsequently, 2 to 3 V of electricity was applied to the electrodes at both ends of the heater, so that the micro heater was adjusted to a temperature of 90-95 ° C., that is, below the boiling point of the precursor solution, to slowly generate ZnO nanostructures. At this time, the length and density of the nanostructure is increased by continuously applying voltage while controlling the time until it grows to the length to be grown, which will be described in detail below. After fabricating the nanostructures, the polymer block, that is, the polymer well (container), was removed from the substrate, washed with a solvent such as ethanol, and dried with nitrogen gas.

Analysis of Nanostructures

5a to 5d are SEM images of nanowires grown in a liquid phase by local heating.

5A to 5D, it can be seen that a plurality of nanowires according to the present invention are grown in an anisotropic direction between the electrodes. In particular, the present invention used a non-polar chelate compound in order to induce growth of the nanostructures in the Z-axis, that is, the height direction, in one embodiment of the present invention was polyethylimide. The nonpolar chelate compound acts as a so-called inhibitor, acting on the side of the growing nanostructure to neutralize the polarity of the side, thereby lowering the side activity of the nanostructure.

FIG. 6 is a view for explaining growth in a height direction of a nanostructure by a nonpolar chelate compound such as polyethylimide.

Referring to FIG. 6, the nanostructures according to the present invention grow vertically, that is, in a height direction, because the cross section of the nanowires maintaining polarity acts as an adsorption region of Zn ions.

7A is a front view of a nanostructure according to an embodiment of the present invention, and FIG. 7B is an enlarged photograph of the nanostructure.

Referring to FIGS. 7A and 7B, nanostructures grown on different electrodes spaced from each other are met in the middle during growth, even if their starting points are spaced apart from each other, and the nanowires are physically bonded and connected at the intermediate points where they meet. Able to know. Through this junction, the physically and electrically separated electrodes can be interconnected and communicated. In particular, the configuration may provide a basic structure of various sensor elements for detecting a current change according to the resistance change of the nanostructures (such a resistance change may occur by gas adsorption, UV detection, etc.). In other words, the method for manufacturing nanostructures according to the present invention enables nanostructure production, growth and integration at the same time. This is one of the advantages of the present invention, which is distinguished from the prior art of manufacturing nanostructures in a separate step and then growing and integrating them again. Therefore, the nanostructure manufacturing method according to the present invention should be understood to include a method of integrating the nanostructures as well as the simple production, growth.

Nano structure pattern change

8A to 8D are SEM photographs showing various patterns of nanostructures, that is, nanowires, manufactured according to another embodiment of the present invention.

8A to 8D, the method of manufacturing a bare structure according to the present invention may produce various types of nanostructures according to types of heating temperature, time, seed material, and the like, and in any case, the nanostructure may be a micro heater. It can be seen that it is generated at the same position where the local heat is applied by.

In particular, referring to 8a to 8d, when ZnO nanowires are grown without laying ZnO nanoparticles as seed particles, the diameter of the grown nanostructure is increased (FIG. 8C), but on the contrary, high concentrations of ZnO nanoparticles (ie, seeds) are shown. When the seed particles are used as seed particles, the nanoparticles are densely deposited to obtain a nanostructure having a relatively small diameter (see FIG. 8A). On the other hand, when the concentration is low, the density of the nanoparticles is lowered, resulting in nanowires. It may not grow compactly, ie grow coarse. In addition, even when the growth time is very long, it can be seen that the diameter of the nanowire gradually increases, which will be described in more detail with reference to FIG. 9.

Growth of Nanostructures

9 is a SEM photograph showing the growth of nanostructures over time.

Referring to FIG. 9, it can be seen that over time, nanostructures grow continuously from spaced apart electrodes, and two nanowire structures are physically connected after 11 minutes. The physical connection of these nanostructures plays a very important role, in particular for the sensor devices described below. As described above, the method for manufacturing nanostructures according to the present invention has an advantage of enabling the integration of nanostructures over time. This is believed to be due to the features of the present invention that proceed in a liquid environment.

Experimental Example

UV  sensor

In this experimental example, the effect of UV sensing on the ZnO nanowires, the final nanostructures shown in FIG. In the present experimental example, a voltage was applied to one of the two electrodes, and then a current was measured at the other electrode. At this time, the current was measured when irradiated with UV light and when not irradiated. In other words, the present experimental example has electrical conductivity when the UV effect-UV light (365 nm) of the ZnO nanowires grown in one embodiment of the present invention is irradiated, but does not occur when the UV light is not irradiated. Using the effect-, it was tested whether the nanostructures made according to the invention could function as sensors.

10 is a graph showing the experimental results obtained in the present experimental example.

Referring to FIG. 10, it can be seen that a current flows when UV light is irradiated (UV on), but hardly flows when UV light is not irradiated (UV off).

The results suggest that the nanowires fabricated from the spaced electrodes perfectly function as sensors that electrically connect the two electrodes, and furthermore, the invention, which selectively grows nanostructures, is not only a UV sensor but also a gas sensor. It also shows a point that can be effectively used.

1 is a schematic diagram showing the VLS mechanism for nanowire growth.

Figure 2 is a schematic diagram for explaining a nanostructure manufacturing method according to the present invention.

Figure 3 is a step of the nanostructure manufacturing method according to the invention.

4A and 4B are schematic diagrams and photographs of a nanostructure manufacturing apparatus according to an embodiment of the present invention, respectively.

5a to 5d are SEM images of nanowires grown in a liquid phase by local heating.

FIG. 6 is a view for explaining growth in a height direction of a nanostructure by a nonpolar chelate compound such as polyethylimide.

7A is a front view of a nanostructure according to an embodiment of the present invention, and FIG. 7B is an enlarged photograph of the nanostructure.

8A to 8D are SEM photographs showing various patterns of nanostructures, that is, nanowires, manufactured according to another embodiment of the present invention.

9 is a SEM photograph showing the growth of nanostructures over time.

10 is a graph showing the experimental results obtained in the present experimental example.

Claims (19)

Contacting a micro heater including an electrode with a liquid precursor of a material to be grown, and then heating the micro heater by applying a voltage to the electrode; And Growing a nanostructure of the material from the heated micro heater, wherein the electrode of the micro heater is provided with seed particles for growing the nanostructure, and from the electrode by heating of the micro heater Nanostructures manufacturing method characterized in that the nanostructures are grown directly. delete The method of claim 1, The manufacturing method is a nanostructure manufacturing method characterized in that proceeds in a container containing the liquid precursor. The method of claim 3, The micro heater is a nanostructure manufacturing method characterized in that provided in the container. The method of claim 3, The container is a well structure made of a polymer material, characterized in that the nanostructures manufacturing method characterized in that removed after the growth of the nanostructures. The method of claim 1, The micro heater comprises electrodes spaced apart from each other, the nanostructures manufacturing method characterized in that the micro heater is heated by a voltage applied to the electrode. The method of claim 6, As the nanostructures grow, the spaced apart electrode is connected by the nanostructures method of manufacturing a nanostructures. The method of claim 1, The nanostructures are nanostructures manufacturing method characterized in that the growth in the anisotropic direction from the micro heater. The method of claim 1, The non-polar chelate compound is added to the precursor, the non-polar chelate compound is bonded to the side of the nanostructures, nanostructure manufacturing method characterized in that to inhibit the growth of the side of the nanostructures. The method of claim 9, The nanostructure is ZnO, wherein the non-polar chelate compound is a nanostructure manufacturing method, characterized in that the polyethyleneimide. The method of claim 1, Heating temperature of the micro heater is a nanostructure manufacturing method, characterized in that less than the boiling point of the precursor solution. The method of claim 1, The nanostructures are nanostructures comprising any one material selected from the group consisting of MoO ₃ , Bi ₂ S ₃ , SnO ₂ , V ₂ O ₅ , MnO ₂ , PbS, CoFe ₂ O ₄ , WO ₃ Manufacturing method. A nanostructure produced by the method according to any one of claims 1 and 3 to 12. delete delete delete delete 13. A gas sensor comprising a nanostructure produced by the method of any one of claims 1 and 3-12. 13. A UV sensor comprising a ZnO nanostructure made by the method of any one of claims 1, 3-12.

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