TWI617691B - A production method for an integration sensor with Zinc oxide nano-sheets - Google Patents

Abstract

A method for manufacturing a nano-sheet zinc oxide structure-integrated sensor element is to form a seed layer of an aluminum film in a specific region of the sensor body, and immerse the sensor body in zinc nitrate, hexamethylenetetramine and In the aqueous solution of water, the volume concentration ratio of the aqueous solution of zinc nitrate and hexamethylenetetramine is 1 to 2, and the volume concentration of the zinc nitrate is at least 0.01 M or more, and the solution is placed in the oven by hydrothermal method to 90~ Baking at 100 ° C for at least 1 hour, the nano zinc oxide sheet structure is grown in a specific area of the sensor; by the above method, the nanometer can be grown in a specific area of the sensor in a simple and low cost manner. The sheet-like structure expands the area sensed by zinc oxide and enhances the sensitivity of the sensor produced for harmful gases and ultraviolet light sensing.

Description

Method for manufacturing nano flaky zinc oxide structure integrated sensor element

The invention relates to a method for manufacturing a sensor, in particular to a method for manufacturing a sensor element by using a nano-sheet zinc oxide structure, which can improve the sensitivity of the sensor element.

In recent years, due to the increasing environmental pollution and the need for safety concerns in the technology industry, the development and application of sensors have attracted much attention. With the help of sensors, it is possible to detect whether the concentration of harmful gases in the ambient air is maintained at a safe concentration. Within, it can ensure the safety of human beings in a harmless environment and ensure the safety of personal health and work environment.

The development of highly reliable and high performance gas sensors is receiving increasing attention. Gas sensors using metal oxide semiconductor (MOS) materials are widely used in monitoring systems in various environments, but general gas sensors only use a thin film to sense harmful gases, and the area of the film contact gas Fixing makes the sensitivity of the gas sensor limited. If it is necessary to detect flammable or toxic gases before the hazard occurs, it is necessary to strengthen the response of the sensor to harmful gases, so new materials are introduced to enhance the sense. The need for detector sensitivity.

The unique electrical properties of the emerging zinc oxide (ZnO) materials make them suitable for the fabrication of nano-optical components such as light-emitting diodes (LEDs), field emission devices, solar cells (Solar cells). ), field-effect transistor (FET) and other optoelectronics element. Zinc oxide (ZnO) adsorbs the material properties of gases and ultraviolet light, making it suitable for use in the production of photo detectors and gas sensors.

Since the material of zinc oxide (ZnO) can exhibit a nanostructure which is not identical according to the manufacturing method, if zinc oxide (ZnO) material can be properly controlled to form a nanostructure, zinc oxide (ZnO) material can be utilized. A sensor element having a large effective sensing area is fabricated to enhance the sensitivity of the sensor element to sense gas and ultraviolet light. Therefore, how to make a nano zinc oxide structure capable of absorbing more gas or ultraviolet rays under the same area by utilizing the characteristics of a zinc oxide (ZnO) material is an important subject for producing a high-sensitivity sensor element.

The sensitivity of existing thin film gas sensors is still insufficient to meet the needs of the technology industry and environmental testing. To this end, the present invention utilizes zinc oxide to be fabricated on the sensing film, and grows a sheet-like structure to enhance the area of the sensor for adsorbing gas and ultraviolet light, and utilizes this characteristic to improve the sensing efficiency for the element.

In order to achieve the above object, the present invention provides a method for manufacturing a nano-sheet zinc oxide structure-integrated sensor element, the method comprising the steps of: fabricating a sensor body: preparing a substrate, forming an electrode on a surface of the substrate Forming a conductive film on the electrode, forming a seed layer of an aluminum film on the surface of the conductive film to form a sensor body; and forming a nano zinc oxide sheet structure on the body of the sensor: zinc nitrate, The hexamethylenetetramine and water are poured into a container to form an aqueous solution, and the volume concentration ratio of zinc nitrate and hexamethylenetetramine in the aqueous solution is 1 to 2, and the volume concentration of the zinc nitrate is at least 0.01 M or more. The detector body is placed in the container and immersed in the aqueous solution, and then the container is placed in a baking box by hydrothermal method, and baked at a temperature of 90-100 ° C for at least 1 hour. The seed crystal is in the process. Layer of aluminum film as a catalytic layer involved in chemical reaction The nano zinc oxide sheet structure is grown on the seed layer of the sensor body to form a sensor, and the nano zinc oxide sheet structure is doped with aluminum.

Further, the electrode of the present invention refers to a fork electrode.

Further, the volume concentration of zinc nitrate in the aqueous solution of the present invention is 0.02 M; and the volume concentration of hexamethylenetetramine is 0.04 M.

Furthermore, the present invention performs the annealing step after the step of forming the nano zinc oxide sheet structure on the body of the sensor, and the nanometer of the sensor is performed at an annealing temperature of 350 ° C or higher. The zinc oxide sheet structure is annealed.

The invention can be formed into a nano zinc oxide sheet-like structure by hydrothermal method on the seed layer of the specific region of the sensor by the combination of the aqueous solution formulation, the volume concentration of the compound and the specific baking time. The structure in which the nano zinc oxide is three-dimensional and has a large contact air area expands the portion of the sensor that can be used for sensing, and enhances the amount of gas and ultraviolet light that the sensor adsorbs to enhance sensitivity.

Furthermore, since the hydrothermal method used in the present invention is a relatively inefficient method compared to the low pressure chemical vapor deposition method, the nano zinc oxide sheet structure is formed by the method, and the method is simple and low in cost. The utility model makes the sensitive sensor having the nano zinc oxide sheet structure easy to mass-produce and popularize.

10‧‧‧Substrate

11‧‧‧Electrode

12‧‧‧Electrical film

13‧‧‧ seed layer

14‧‧‧Nano Zinc Oxide Sheet Structure

A‧‧‧Specific area

B‧‧‧Sensor body

C‧‧‧Sensor

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block flow diagram of a method in accordance with a preferred embodiment of the present invention.

2 is a schematic diagram of a process for fabricating a sensor in accordance with a preferred embodiment of the present invention.

3 is an X-ray diffraction pattern of a zinc oxide sheet structure at different annealing temperatures in accordance with a preferred embodiment of the present invention.

Figure 4 is a graph showing the response of different gas measurements at 300 °C in accordance with a preferred embodiment of the present invention.

Figure 5 is a top plan view of an electron microscope at different concentrations for the same growth time in accordance with a preferred embodiment of the present invention.

Figure 6 is a cross-sectional view of an electron microscope at different concentrations for the same growth time in accordance with a preferred embodiment of the present invention.

Figure 7 is a top plan view of an electron microscope at different growth times of the same concentration in accordance with a preferred embodiment of the present invention.

Figure 8 is a cross-sectional view of an electron microscope at different growth times of the same concentration in accordance with a preferred embodiment of the present invention.

In order to understand the technical features and practical effects of the present invention in detail, it can be implemented in accordance with the contents of the specification, and further described in detail with reference to the preferred embodiments shown in the drawings.

Referring to the flowcharts shown in FIG. 1 and FIG. 2, the present invention provides a method for manufacturing a nano-chip zinc oxide structure integrated sensor component, the method comprising: preparing a substrate: the substrate 10 is a germanium substrate, first utilized The substrate 10 was separately shake-washed for 15 minutes in an ultrasonic wave washing machine with acetone, isopropyl alcohol, and deionized water, and the substrate 10 was blown dry using a nitrogen gun.

Forming an electrode on the surface of the substrate: defining a first pattern on the substrate 10 using a yellow lithography system, sequentially depositing titanium having a thickness of 30 nm and a thickness of 200 nm on the surface of the substrate 10 using an electron beam evaporation system (Electron Beam Evaporation) The gold is then lifted to define an electrode 11 which is a fork electrode and the area in which the substrate 10 is located in the middle of the electrode 11 is defined as a specific area A.

Forming a conductive film on the electrode: after defining a second pattern on the substrate 10 using a yellow lithography system, sputtering a tin dioxide (SnO ₂ ) on the surface of the substrate 10 using a radio frequency magnetron sputtering system, after lifting A conductive film 12 is formed on a specific region on the substrate, and the conductive film 12 is electrically connected to the electrode 11.

Forming a seed layer on the conductive film: defining a third pattern on the substrate 10 using a yellow lithography system, sputtering aluminum on the surface of the substrate 10 using a radio frequency magnetron sputtering system, and conducting electricity on the substrate 10 after lifting A seed layer 13 is formed on the surface of the film 12, and the seed layer 13 is an aluminum film and is located in the specific region A, thereby completing the fabrication of a sensor body B.

Forming a nano zinc oxide sheet structure on the body of the sensor: pouring zinc nitrate (Zn(NO ₃ ) ₂ ), hexamethylenetetramine (HMTA) and water into a container to form an aqueous solution, and making the nitric acid in the aqueous solution The volume concentration ratio of zinc (Zn(NO ₃ ) ₂ ) and hexamethylenetetramine (HMTA) is 1 to 2. As in the preferred embodiment, the volume concentration of zinc nitrate in the aqueous solution is 0.02 M, and hexamethylene The volume concentration of the amine was 0.04 M, and the sensor body B was placed in the container and immersed in an aqueous solution of zinc nitrate (Zn(NO ₃ ) ₂ ) and hexamethylenetetramine (HMTA), followed by water. The heating method puts the container and its contents into a baking box, and performs baking at a temperature of 90 to 100 ° C to grow the nano zinc oxide sheet structure, and the baking time is also the growth time as in the preferred embodiment. It is 1 hour, during which the aluminum thin film of the seed layer 13 participates as a catalytic layer in the chemical reaction, so that the nano zinc oxide sheet structure (ZnO Nanosheet) 14 grows in the seed layer 13 of the specific region A of the sensor body B. Above, and the nano zinc oxide sheet structure 14 is doped with aluminum, the reaction formula of the nano zinc oxide sheet structure growing is as follows: C6H12N4+6H2O → 6H CHO+4NH3 (1)

NH3+H2O → NH4++OH- (2)

Formula (1), hexamethylenetetramine (HMTA) is dissolved in water (H2O) to release ammonia molecules (NH3).

In the formula (2), the ammonium ion (NH4+) is a positive ion derived from the (NH3) ammonia molecule. The ammonium molecule (NH3) is combined with a hydrogen ion (H+) to form an ammonium ion (NH4+).

Formula (3), OH- combines with Al to form Zn-AlLDH-NO3, wherein the source of Al (aluminum) is the aluminum thin film of the seed layer 13.

Formula (4), Zn combines with OH- to form zinc oxide.

After one hour of baking, a nanometer zinc oxide sheet-like structure 14 is formed on the conductive film 12 of the sensor body B to form a sensor C. In the present invention, the sensor C is made of the nano zinc oxide sheet structure 14 , and the sheet structure of the nano zinc oxide sheet structure 14 can greatly increase the sensing area, so that the sensing is performed. The sensitivity of sensor C to detect harmful gases and ultraviolet light can be effectively improved. Furthermore, the nano zinc oxide sheet structure 14 of the present invention is doped with aluminum, and after doping a metal element such as aluminum, the carrier concentration and conductivity of the nano zinc oxide sheet structure 14 can be improved, and the carrier concentration is increased. The better the sensing effect of the high nano zinc oxide sheet structure 14 is.

Annealing treatment: Annealing the nano zinc oxide sheet structure 14 of the sensor C to improve the crystallization characteristics, as in the preferred embodiment, 0 ° C, 150 ° C, 250 ° C, 350 ° C, 450 ° C, 550 ° C Annealing temperature is annealed, as shown in Fig. 3, X-ray diffraction (X-ray diffraction) is used to analyze the X-ray diffraction pattern of the zinc oxide sheet structure at the annealing temperature, from the bottom The upper 0 ° C, 150 ° C, 250 ° C, 350 ° C, 450 ° C, 550 ° C lines can be found, the nano zinc oxide sheet structure 14 in the case of unannealed crystallinity is not quite good, the structure shown Like a polycrystalline structure, it shows a messy peak intensity; but after an annealing temperature of 350 ° C or higher, there is a significant peak of zinc oxide as shown in the figure (100), (002), (101), The crystallinity is stable, and the crystallinity of the nano zinc oxide sheet structure 14 is better, and the light absorption rate and the sensing effect are better.

As shown in FIG. 4, it is a nano zinc oxide sheet structure (0.02M ZnO nanosheet), a nano zinc oxide porous structure (0.005M ZnO nanosheet), and a nano zinc oxide columnar structure (ZnO). Nanorod) and pure sensing film (SnO ₂ ) in the operating environment of 300 ° C for alcohol (Ethonal), formaldehyde (HCHO), NO (nitrogen monoxide), CO (carbon monoxide) sensing results, of which NO and CO do not It has an influence due to an increase in the area of the surface structure, but for alcohol or formaldehyde, since the nano zinc oxide sheet structure 14 of the present invention has a large sensing area, it is compared with the nano zinc oxide porous spherical structure. Or the nano zinc oxide columnar structure, the degree of response of the sensing of the present invention is significantly higher, and the nano zinc oxide sheet structure 14 of the present invention is verified to have higher sensitivity for sensing harmful gases.

In the foregoing preferred embodiment, the volume concentration of zinc nitrate and hexamethylenetetramine in the aqueous solution for growing the nano zinc oxide sheet structure 14 (ratio 1:2), and the hydrothermal method are provided. The growth time of baking in the oven is two important parameters for the integrity of the nano zinc oxide sheet structure 14 .

In order to obtain the best choice of the above two parameters, the first experiment is to grow a nano-zinc oxide sheet structure at different concentrations, sputtering an aluminum film on the substrate, and then using five groups of the zinc nitrate by hydrothermal method. The volume concentration parameters of hexamethylenetetramine: 0.0025M and 0.005M in the first group, 0.005M and 0.01M in the second group, 0.01M and 0.02M in the third group, and 0.02M and 0.04M in the fourth group. The fifth group was 0.03M and 0.06M. After the growth of the nano zinc oxide sheet structure was completed on the aluminum film of the substrate for 1 hour, the surface structure was observed by field emission scanning electron microscopy (FE-SEM). Type.

As shown in FIG. 5, a growth time of 1 hour corresponds to a top view of a nano zinc oxide sheet structure at different concentrations, wherein (a), (b), (c), (d), (e) are respectively The concentration of zinc nitrate is 0.0025M, 0.005M, 0.01M, 0.02M, 0.03M (the concentration of zinc nitrate is 0.0025M is the abbreviation of the volume concentration parameter of zinc nitrate and hexamethylenetetramine is 0.0025M and 0.005M, and so on) The experimental results show that the concentration in Figure 5 is absolutely important for the formation of nano-sheet structure. If the concentration of zinc nitrate is less than 0.01M, the entire planar nano-sheet structure cannot be generated. When the zinc nitrate concentration is 0.01 M or more, the sheet structure having an average and a full surface growth is obtained, and the sheet-like structure having a higher zinc nitrate concentration has a dense density.

Further, as shown in Fig. 6, (a), (b), and (c) are cross-sectional views of a zinc oxide sheet structure having a zinc oxide concentration of 0.01 M, 0.02 M, and 0.03 M, which can be It is found that for a structure in which a sheet shape has been formed, when the zinc oxide concentration is 0.01 M or more, the growth height of the sheet structure having a higher concentration will be reduced, and the height of the sheet structure will be relatively higher when the concentration is lower. Increasingly, there is an inverse correspondence between the zinc oxide concentration and the height of the grown sheet structure.

The experiment is to grow a nano-zinc oxide sheet structure at different growth times. The aluminum film is sputtered on the substrate, and the volume concentration of the zinc nitrate is 0.01 M by hydrothermal method. The volume concentration of hexamethylenetetramine is The 0.02M aqueous solution is further composed of five long-term parameters: the first group is 0.5 hours, the second group is 1 hour, the third group is 2 hours, the fourth group is 3 hours, and the fifth group is 4 hours. Five groups of different time After the nano-zinc oxide sheet structure was grown on the aluminum film of the substrate, the surface structure pattern was observed by field emission scanning electron microscopy (FE-SEM).

As shown in Fig. 7, the top view corresponds to the top view of the nano zinc oxide sheet structure at different growth times, in which (a), (b), (c), (d), and (e) are respectively grown. The time is 0.5, 1, 2, 3, 4 hours. It can be seen that the growth time is 0.5 hours. Because the reaction time is too short, the sheet structure cannot be formed, but the growth time is not too high for the formation of the nano zinc oxide sheet structure. Great impact. As shown in Fig. 8, (a), (b), (c), and (d) are cross-sectional views of a nano zinc oxide sheet structure having a growth time of 1, 2, 3, and 4 hours. It can be found that the growth time has a proportional relationship with the height of the growing sheet structure.

Next is an experiment of growing a nano-zinc oxide sheet structure at different growth times, sputtering an aluminum film on the substrate, and then using five groups of the volume concentration parameters of the zinc nitrate and hexamethylenetetramine by hydrothermal method: first The parameters are 0.01M and 0.02M, the second group is 0.02M and 0.04M, the third group is 0.03M and 0.06M, and the four components are long-term parameters: the first group is 1 hour, the second group is 2 hours, The third group was 3 hours, and the fourth group was 4 hours. After the growth of the nano zinc oxide sheet structure on the aluminum film of the substrate for 1 hour, the field emission scanning electron microscope (FE-SEM) was used. Observe the structural form of the height of the section and make the height of the section observed above as the following table:

Based on the results of the above three experiments, it was found that the concentration at this time is proportional to the density of the nano zinc oxide sheet structure and inversely proportional to the height. At the same concentration, the growth time does not affect the formation of the nano zinc oxide sheet structure, but it has a proportional relationship with the growth height.

From the data of these experiments, the aqueous solution used in the present invention to form the nano zinc oxide sheet-like structure 14 on the seed layer 13 by hydrothermal method, in order to favorably grow the nano zinc oxide sheet on the seed layer 13, Structure 14, wherein the ratio of the volume concentration of zinc nitrate to hexamethylenetetramine is 1:2, and the volume concentration of zinc nitrate is above 0.01 M, and the growth time is at least 1 hour, when the sensor is used When the nano zinc oxide sheet structure 14 is annealed, the annealing temperature is 350 ° C or higher.

It can also be verified from the data of the foregoing experiments that the preferred embodiment of the present invention has selected an aqueous solution having a volume concentration of zinc nitrate of 0.02 M and a volume concentration of hexamethylenetetramine of 0.04 M because the volume concentration of zinc nitrate is at least 0.01M or more, but since the concentration is proportional to the density of the nano zinc oxide sheet structure, when the concentration is higher, the density of the nano zinc oxide sheet structure is larger, which may cause gas and illumination. The reaction area will be occupied by a structure with a higher density, and a high surface area response cannot be performed. Therefore, the volume concentration of zinc nitrate of a preferred aqueous solution should be 0.02 M, and the volume concentration of hexamethylenetetramine should be 0.04 M; Selecting for 1 hour for a long time is because the growth time is proportional to the height of the nano zinc oxide sheet structure 14, but the height is too high, and the sheet structure is transferred to the electrode and finally to the measuring instrument after the chemical reaction. The length may cause a burden on the transmission such as the loss of energy, etc., and the preferred height is about 2 μm, so that one hour is selected according to the combination of the concentration and the growth time.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of the claims of the present invention, and other equivalent changes or modifications which are not departing from the spirit of the present invention should be included in the present invention. Within the scope of the patent application.

Claims (4)

A method for manufacturing a nano-sheet zinc oxide structure-integrated sensor element, comprising the steps of: fabricating a sensor body: preparing a substrate, forming an electrode on a surface of the substrate, forming a conductive film on the electrode, Forming a seed layer of an aluminum film on the surface of the conductive film to form a sensor body; and forming a nano zinc oxide sheet structure on the body of the sensor: pouring zinc nitrate, hexamethylenetetramine and water into a container As an aqueous solution, the volume concentration ratio of zinc nitrate and hexamethylenetetramine in the aqueous solution is 1 to 2, and the volume concentration of the zinc nitrate is at least 0.01 M or more, and the sensor body is placed in the container and immersed in the aqueous solution. Then, the container is placed in a baking box by hydrothermal method, and baked at a temperature of 90-100 ° C for at least one hour. During the process, the aluminum film of the seed layer participates in the chemical reaction as a catalytic layer. The nano zinc oxide sheet structure is grown on the seed layer of the sensor body to form a sensor, and the nano zinc oxide sheet structure is doped with aluminum. A method of producing a nano-sheet zinc oxide structure-integrated sensor element according to claim 1, wherein the electrode is a fork electrode. The method for producing a nano-sheet zinc oxide structure-integrated sensor element according to claim 1, wherein the volume concentration of zinc nitrate in the aqueous solution is 0.02 M; and the volume concentration of hexamethylenetetramine is 0.04 M. The method for manufacturing a nano-sheet zinc oxide structure-integrated sensor element according to any one of claims 1 to 3, wherein the annealing is performed after the step of forming the nano zinc oxide sheet structure in the sensor body is completed In the step of treating, the nano zinc oxide sheet structure of the sensor is annealed at an annealing temperature of 350 ° C or higher.