TWI431662B - Method of manufacturing nanowires and the field emission device using the same - Google Patents

Description

Manufacturing method of nanowire and field emission element produced using same

The present invention relates to a method of manufacturing a nanowire, and a field emission element manufactured using the method.

The field emission element has the advantages of small size, light weight, and can help release the electron beam and increase the amount of current emitted. Therefore, it can be widely used in the manufacture of high frequency high radiation amplifiers, low noise amplifiers, wireless RF oscillators, and illumination. Diodes, solar cells, field emission displays and various types of detectors.

Currently, in the field emission element, the field emission element can be divided into vertical and horizontal field emission elements according to the structure of the field emission source. Vertical field emission elements are typically fabricated as Field Emission Arrays (FEAs) with Spindt-type, with the anode and cathode separated by an insulating layer. Vertical field emission elements are typically spaced 60 to 200 μm apart, resulting in vertical field emission components that must operate in a vacuum environment and require a higher operating voltage (≧100 V). However, the horizontal field emission element can utilize solid-state semiconductor process technology to effectively control and shorten the distance between the anode and cathode and the field emission source, so that it can operate without high vacuum or high operating voltage. Therefore, field emission components can be applied to high-speed components, wireless RF oscillators and various types of detector applications to enhance the value of field emission components.

However, conventional nanowire manufacturing methods such as metal organic chemical vapor deposition (MOCVD), thermal evaporation, vapor solids (VLS) or electroplating (EPD) require expensive use. Catalysts participate in the reaction or process equipment, and the process steps are complicated, resulting in high cost of components, which does not meet economic effects. In addition, the general method for manufacturing a nanowire needs to be carried out under high temperature. When the nanowire is grown in such an environment, the characteristics of the element are disturbed, and the difficulty in manufacturing the element and the photoelectric characteristics are increased.

Therefore, there is an urgent need to develop a highly selective nanowire manufacturing method that has good field emission characteristics and stability, and reduces the manufacturing cost thereof to improve the application value of the field emission element.

The main object of the present invention is to provide a method for manufacturing a nanowire, which can integrate a hydrothermal method and a lateral growth technique, and appropriately grow the seed layer to control the growth direction of the nanowire to grow to a height. Selective nanowire.

Another object of the present invention is to provide a method of manufacturing a nanowire capable of controlling a tip-to-tip or a tip-to-plate gap to reduce an operating voltage and Improve the photoelectric characteristics and stability of the field emission components.

Still another object of the present invention is to provide a method for producing a nanowire which can reduce the process temperature required for making a nanowire and improve the photoelectric characteristics and stability of the field emission element.

A further object of the present invention is to provide a method for manufacturing a nanowire, which can produce a horizontal nanowire with high selectivity, and the two sides of the nanowire can be stacked and connected to each other for application. Various detectors can increase the sensitivity and operating speed of the detector.

In order to achieve the above object, the present invention provides a method for manufacturing a nanowire, comprising the steps of: (A) providing a substrate; (B) forming a first seed layer on the substrate, and the first seed layer Having a first sidewall; (C) forming a first electrode on the first seed layer, wherein the first electrode has a second sidewall and completely covering the first seed layer; (D) etching the first a seed layer such that a second sidewall of the first electrode protrudes from the first sidewall of the first seed layer; and (E) forms a plurality of first nanowires, and the first nanowires extend from the first The first side wall of the seed layer.

In addition, the present invention also provides a field emission device comprising: a substrate; and a cathode region disposed on the substrate, the cathode region comprising: a first seed layer disposed on the substrate and having a first a first electrode disposed on the first seed layer and completely covering the first seed layer, and the second sidewall of the first electrode protrudes from the first sidewall of the first seed layer And a plurality of first nanowires extending from the first sidewall of the first seed layer.

In the method of fabricating the nanowire of the present invention, a step (A') may be further included: forming an insulating layer on the substrate. Accordingly, the field emission device of the present invention may further include an insulating layer disposed on the substrate, and the insulating layer is located between the substrate and the cathode. Wherein, the present invention utilizes a yellow lithography technique to define a range of grown nanowires on an insulating layer or a glass substrate on a substrate, and sequentially deposits a seed layer and an electrode by an electron evaporation machine, and then etches the seed layer using an etching solution. The seed layer is suitably etched to provide a horizontal nanowire with high selectivity.

In the present invention, any material may be used as the substrate, and a tantalum substrate, a glass substrate, a quartz substrate, a semiconductor substrate, a metal substrate or a plastic substrate is preferably used as the substrate, and a tantalum substrate and a glass substrate are more preferably used. When the substrate used is a conductive substrate, it is preferred to first prepare an insulating layer of ceria or tantalum nitride having a thickness of about 300 to 500 nm by plasma enhanced chemical vapor deposition (PECVD); In the case of a substrate, a germanium dioxide insulating layer is preferably formed, and the thickness of the ceria insulating layer may be 300 to 600 nm, preferably 450 to 550 nm. When depositing the seed layer and the electrode, it can be deposited using any conventional deposition method, preferably using a DC/RF sputtering or evaporation method. The material for depositing the seed layer may be zinc aluminum oxide (AZO), indium zinc oxide (IZO), gallium zinc oxide (GZO), or zinc oxide (ZnO), preferably zinc aluminum oxide (AZO). Or zinc oxide (ZnO), more preferably zinc aluminum oxide (AZO). The material of the electrode may be platinum, tungsten, nickel, zinc, gold, tin, gallium or other metal which inhibits the growth of the nanowire, preferably platinum or tungsten, more preferably platinum. Wherein, the thickness of the seed layer is preferably from 90 to 500 nm, more preferably from 90 to 200 nm, most preferably from 90 to 120 nm; and the thickness of the electrode is preferably from 50 to 150 nm, more preferably from 50 to 100 nm. .

In the present invention, the seed layer is appropriately etched using an etching solution, and the etching solution may be phosphoric acid, hydrochloric acid or a mixed solution thereof, preferably a diluted phosphoric acid solution. The etching depth is 10 to 200 nm, preferably 10 to 100 nm. After proper etching of the seed layer, the electrode layer can be completely covered with the seed layer, and the sidewall of the electrode protrudes from the sidewall of the seed layer. The structure with the sidewall of the electrode protrudes to provide horizontal nanometer. The crystal nucleus of the line grows, and at the same time effectively inhibits the growth of the nanowire in the vertical direction. Therefore, a horizontal nanowire having a high selectivity can be formed by the structure in which the side wall of the electrode protrudes from the side wall of the seed layer. Therefore, the present invention can be easily processed, and a highly selective horizontal nanowire can be obtained without using expensive epitaxial or long crystal equipment and processes, thereby shortening the time required for the process and thereby saving costs. Improve the competitiveness of making nanowires.

The invention combines hydrothermal method and the side wall of the electrode to protrude from one side wall of the seed layer, so that the manufacture of the nanowire can be prepared in a lower temperature environment, using zinc nitrate (Zinc Nitrate) cyclohexamethylene. A mixed solution of tetraamine (HMT, hexamethylenetetramine), which grows a plurality of highly selective horizontal zinc oxide (ZnO) nanowires. The preparation method of the nanowire of the invention does not require an expensive catalyst to participate in the reaction, can save the cost in the process, and can be widely applied to fabricate a large-area photovoltaic element. The grown nanowire material may be ZnO, TiO ₂ , or SnO ₂ , preferably ZnO. The hydrothermal method may have a growth temperature of 60 to 90 ° C, preferably 75 to 90 ° C, more preferably 80 to 85 ° C. The growth time of the hydrothermal method may be from 30 to 400 min, preferably from 60 to 300 min, more preferably from 120 to 200 min, still more preferably from 150 to 180 min. Compared with the conventional process method, the manufacturing method of the nanowire in the invention can provide a relatively simple process step and can be prepared in a lower temperature (less than 90 ° C) environment to maintain the photoelectricity of the field emission element. Performance and current stability.

The present invention is applicable to the preparation of a tip-to-tip and tip-to-plate field emission element of a horizontal nanowire having high selectivity. The tip-to-tip field emission element of the horizontal nanowire includes a substrate and a cathode region, and further includes an anode region disposed on the substrate, the anode region comprising: a second seed layer, the system is disposed On the substrate, the second seed layer has a third sidewall, and the third sidewall corresponds to the first sidewall of the first seed layer; a second electrode is disposed on the second seed layer and completely Covering the second seed layer, the fourth sidewall of the second electrode protrudes from the third sidewall of the second seed layer, and the fourth sidewall of the second electrode corresponds to the sidewall of the second sidewall of the first electrode And a plurality of second nanowires extending from a third sidewall of the second seed layer, and a tip of the second nanowire corresponding to the first nanowire extending from the first sidewall of the first seed layer The tip. Here, the tip-to-tip distance (L _G ) can be controlled to be about 5 nm to 10 μm (preferably 5 nm to 5 μm), and the nanowire length is about 3 to 4 μm, and the linear density is about 3 to 5 μm ^-1 , preferably the average diameter and length of the nanowires are 100 nm and 3.5 μm. In addition, the growth condition of the hydrothermal method can be controlled to form a structure in which the tip of the first nanowire and the tip of the second nanowire are overlapped with each other, and the diameter and length are about 150 nm and 5 to 8 respectively. Mm of zinc oxide nanowire.

In addition, in the manufacture of the field-emitting element of the tip-to-plate of the horizontal nanowire, only a first seed layer is formed on the substrate or the insulating layer, and then the first electrode and the second electrode are formed, the first electrode system Formed on the first seed layer, and the second electrode is formed on the substrate or the insulating layer, and after proper etching, the nanowire is grown by using the structure to obtain a tip-to-plate with a highly selective horizontal nanowire. Field emission component. Accordingly, the field-emitting element of the tip-to-plate of the horizontal nanowire includes the same substrate and a cathode region, and further includes an anode region disposed on the substrate, and the anode region includes: The second electrode is disposed on the substrate, the second electrode has a fourth sidewall, and the fourth sidewall corresponds to the first sidewall of the first seed layer. Wherein, the method for manufacturing the nanowire of the present invention can control the distance between the nanowire and the sidewall of the electrode to be between 5 nm and 5 μm.

Since the thickness of the seed layer is proportional to the growing nanowire, the density of the grown nanowire increases with the thickness of the seed layer. Furthermore, the thickness of the electrode also affects the selectivity of the nanowire growth. Therefore, nanowires of different sizes, lengths, and densities can be prepared by controlling growth time, growth temperature, aqueous solution temperature, and other conditions of hydrothermal growth of nanowires. The growth rate of the hydrothermal growth zinc oxide nanowires in the horizontal and vertical directions is 1.1 to 1.3 μm/hr. By using the preparation method of the nanowire of the invention, when the time of growing the nanowire is elongated, the distance between the tip of the nanowire and the tip is affected, and the length of the nanowires on both sides can be increased by more than the distance between the two electrodes (L). _M ), that is, the two sides of the nanowires are connected to each other, thereby shortening the tip-to-tip distance (L _G ) of the nanowire. The structure in which the nanowires are overlapped with each other, and when the distance between the tip of the nanowire and the tip tends to be zero, the quantum effect of the one-dimensional nanowire can effectively improve the photoelectric performance of the component and apply it to the fabrication. Electronic components and detection components, such as photodetectors (ultraviolet light detectors), gas detectors, pressure detectors, light-emitting diodes and solar cells, can enhance the sensitivity and operating speed of the detector .

The invention provides a method for manufacturing a nanowire, which can be carried out at a lower process temperature and a low operating voltage, and at the same time, simplifies the process steps and reduces the cost, and forms a horizontal nanowire with high selectivity to cause field emission. The stability and reliability of the components are improved. In addition, the growth conditions of the horizontal nanowires can be controlled by hydrothermal method, such as growth time, growth temperature, aqueous solution temperature and other conditions of hydrothermal growth of the nanowire. The length of the horizontal nanowire and the tip-to-tip or tip-to-plate gap enable the horizontal nanowire prepared by the present invention to have a higher unit surface area ratio and a smaller cathode-anode spacing (less than 5 μm). With better field emission characteristics, effectively reducing the starting voltage to less than or equal to 10V, it can also ensure the photoelectric performance of the component, and it has good field emission current stability and enhances the field emission capability of the component. Therefore, the present invention can provide a method for manufacturing a preferred horizontal nanowire to enhance the competitiveness of the field emission device in the photovoltaic industry, the microelectronics industry, and the nanotechnology industry.

<First Embodiment>

1A to FIG. 1E are flowcharts showing a method for manufacturing a horizontal zinc oxide (ZnO) nanowire tip-to-tip structure field emission element according to a first embodiment of the present invention, and the manufacturing method thereof comprises the following steps: First, as shown in FIG. As shown in FIG. 1A, a substrate 11 was first washed with deionized water for 5 minutes, and then immersed in a mixed solution of sulfuric acid and hydrogen peroxide (H ₂ SO ₄ :H ₂ O ₂ =3:1) for 10 minutes, followed by Soaked in a hydrofluoric acid mixed solution (HF: H ₂ O = 1:100) for 20 seconds, and then mixed with ammonium hydroxide and hydrogen peroxide (NH ₄ OH: H ₂ O ₂ : H ₂ O = :1:5) Soak for 10 minutes, then soak for 10 minutes in a mixed solution of hydrochloric acid and hydrogen peroxide (HCl: H ₂ O ₂ : H ₂ O = 1:1:6), and finally in a hydrofluoric acid mixed solution (HF :H ₂ O=1:100) Soak for about 15-20 seconds. After soaking each of the above mixed solutions, the cells were washed with deionized water for 5 minutes, and then the substrate 11 was immersed in another mixed solution to complete the step of soaking and washing. Finally, it was blown dry with nitrogen to obtain a clean crucible substrate 11. Thereafter, an insulating layer 12 is further formed on the substrate 11. The clean crucible substrate 11 was placed in the center of a high-temperature furnace tube, and the cerium oxide insulating layer 12 was grown for 2 hours at a growth temperature of 900 ° C and a water vapor atmosphere. In the present embodiment, a ceria insulating layer 12 having a thickness of 500 nm is formed on the germanium substrate 11.

Next, a zinc aluminum oxide (AZO) seed layer is deposited on the insulating layer 12, and the position of the seed layer is defined by yellow lithography (as shown in FIG. 1B). In more detail, the DC/RF sputtering system or the evaporation system is used at a power of 90 W, a pressure of 7.6 x 10 ^-3 , an argon flow rate of 24 sccm, and a deposition rate of 0.4. Zinc aluminum oxide is deposited under the deposition conditions of /sec. Thereafter, the anode-to-cathode distance (L _M ) is defined by the yellow lithography technique to form a first seed layer 131 and a second seed layer 132 on the ruthenium substrate 11 (as shown in FIG. 1B ). Here, the distance between the anode and the cathode (L _M ) serves as a growth space for the subsequent nanowire. In this embodiment, the zinc aluminum oxide (AZO) seed layer is formed to have a thickness of 90 nm. The distance between the anode and the cathode (L _M ) can be controlled to be 3 μm or more. In the present embodiment, the distance between the anode and the cathode is controlled to be about 8 μm.

Thereafter, an electrode film is deposited on the above-mentioned zinc aluminum oxide (AZO) seed layer (as shown in FIG. 1C). Also use DC / RF sputtering system or evaporation system, power 90W, pressure 5x10 ^-3 , argon flow rate 30 sccm and deposition rate 0.4 Under the deposition condition of /sec, a film of the first electrode 141 and a film of the second electrode 142 are respectively formed, and the two electrode films are completely covered on the surfaces of the first seed layer 131 and the second seed layer 132. In this embodiment, the thickness of the electrode film is 100 nm.

Then, the first sidewall 1311 of the first seed layer 131 and the third sidewall 1411 of the second seed layer 132 are appropriately longitudinally etched using the diluted phosphoric acid solution. After soaking for 10 seconds with a phosphoric acid mixed solution (H ₃ PO ₄ :H ₂ O = 1:100), it was washed with deionized water for 5 seconds, followed by blowing with nitrogen. Here, both seed layers are subjected to appropriate longitudinal etching. In this embodiment, the depth of the longitudinal etching is 100 nm. The second sidewall 1321 and the fourth sidewall 1421 of the two electrode layers are respectively protruded from the first sidewall 1311 and the third sidewall 1411 of the two seed layers by using an etching step, as shown in FIG. 1D. With this structure, it is possible to provide a nanowire which grows in a very high horizontal direction while suppressing the growth of the nanowire in the vertical direction.

Finally, a zinc oxide (ZnO) nanowire 15 perpendicular to the sidewall of the seed layer is grown by hydro-thermal growth. 2 g of zinc nitrate (Zinc Nitrate) and 2 g of hexamethylenetetramine (HMT, hexamethylenetetramine) were dissolved in 800 ml of deionized water to prepare a mixed solution. Thereafter, in the present embodiment, the substrate 11 is placed in a closed container at a constant temperature of about 85 ° C, and allowed to stand for 180 minutes to obtain a zinc oxide nanowire having a diameter and a length of 40 to 100 nm and 1 to 4 μm, respectively. 15. Form a horizontal zinc oxide (ZnO) nanowire 15 tip-to-tip structure field emission element (as shown in Figure 1E).

The first embodiment of the present invention is constructed as a tip-to-tip field emission element structure of a nanowire 15 (as shown in FIG. 1E), and its structure includes a substrate 11, an insulating layer 12, a cathode region, and an anode region. The substrate is disposed at the bottom of the field emission device structure, and an insulating layer 12 is disposed on the substrate, and a cathode region and an anode region are further disposed on the insulating layer. The cathode region includes a first seed layer 131 disposed at a lowermost portion of the cathode region, and a first electrode 141 disposed above the first seed layer 131. The first electrode 141 has a third sidewall 1411; and the first electrode 141 is disposed on the first seed layer 131 and completely covers the first seed layer 131. In addition, the third sidewall 1411 of the first electrode 141 protrudes from the first sidewall 1311 of the first seed layer 131. The cathode region further includes a plurality of first nanowires 15 having a nanowire 15 extending from the first sidewall 1311 of the first seed layer 131. As in the structure of the cathode region, the anode region includes a second seed layer 132 disposed at the bottom of the anode region, and a second electrode 142 is disposed above the second seed layer 132, and the second electrode 142 is There is a fourth sidewall 1421, and the second electrode 142 is disposed on the second seed layer 132 and completely covers the second seed layer 132. In addition, the fourth sidewall 1421 of the second electrode 142 protrudes from the second sidewall 1321 of the second seed layer 132. The anode region further includes a plurality of second nanowires 15 having a nanowire 15 extending from the second sidewall 1321 of the second seed layer 132. Here, the tip end 151 of the second nanowire corresponds to the tip end 151 of the first nanowire extending from the first side wall 1311.

The horizontal zinc oxide (ZnO) nanowire prepared by the manufacturing method of the present invention is also identified by energy dispersive spectrum (EDS) and lattice diffraction. According to the energy scattering spectrum, the nanowire prepared by the invention is composed of zinc oxide; in addition, the results of lattice diffraction analysis show that the prepared horizontal zinc oxide (ZnO) nanowire has a main lattice orientation of ZnO. (0002) and ZnO (10) 3), showing that the horizontal zinc oxide (ZnO) nanowire prepared by the embodiment of the present invention has a good crystal structure, and the horizontal electron zinc oxide (ZnO) nanowire system is shown by a transmission electron microscope (TEM). Wurtzite crystal structure.

As shown in FIG. 1E, the tip-to-tip horizontal zinc oxide (ZnO) nanowire formed by the method of the first embodiment has a horizontal tip to the tip of the zinc oxide (ZnO) nanowire 15 It is about 100 nm. The tip of the zinc oxide (ZnO) nanowire 15 can be reduced to ≦5 μm from the tip, and the nanowire 15 has a higher surface-to-volume ratio. The structure of zinc oxide (ZnO) nanowires 15 grown by hydrothermal method and lateral growth technique can be easily controlled in terms of aspect ratio, selection, uniformity or density. In the present embodiment, when the distance between the two electrodes (L _M ) is 8 μm, the length of the horizontal zinc oxide (ZnO) nanowire 15 is 3.0 to 4.0 μm, and the linear density is about 3 to 5 μm ^-1 . The tip of the formed nanowire 15 has a tip-to-tip distance (L _G ) of 1.2 μm.

<Second embodiment>

2A to 2E are flow charts showing a method for manufacturing a horizontal zinc oxide (ZnO) nanowire tip-to-plate structure field emission device in a second embodiment of the present invention. The process conditions and methods of the second embodiment of the present invention are the same as the process conditions and methods described in the first embodiment, and the process steps are similar to those described in the first embodiment, except that after an insulating layer is formed, Only a first seed layer 131 is formed on the surface of the insulating layer 12 (as shown in FIG. 2B); therefore, a first electrode 141 is formed on the first seed layer 131, and a second electrode 142 is formed thereon. On the insulating layer 12 (as shown in Figure 2C). Thereafter, the first sidewall 1311 of the first seed layer 131 is separately etched (as shown in FIG. 2D). Here, the distance between the first seed layer 131 and the second electrode 142 can be controlled to be 5 nm to 5 μm, and the length of the horizontal tip-to-plate nanowire is about 3 to 4 μm, and the linear density is about 3. Up to 5 μm ^-1 ; the average diameter and length of the nanowires are 100 nm and 3.5 μm. Finally, as shown in Fig. 2E, the horizontal nanowire 15 is grown by hydrothermal method to prepare a horizontally-formed zinc oxide (ZnO) nanowire tip-to-plate structure field emission element.

Accordingly, the tip-to-plate field emission element structure of the second embodiment of the present invention has the structure of the substrate 11, the insulating layer 12 and a cathode region as in the first embodiment of the present invention. The difference is that the anode region on the insulating layer 12 includes only a second electrode 142, and the fourth sidewall 1421 of the second electrode 142 corresponds to the plurality of first nanowires 15, which are plural first. The nanowire 15 extends from the first sidewall 1311 of the first seed layer 131 (as shown in Figure 2E).

<Third embodiment>

As shown in Fig. 3, it is a structural diagram of a tip-to-tip zinc oxide (ZnO) nanowire according to a third embodiment of the present invention. The manufacturing method of this embodiment is similar to the first embodiment except that it has the following differences.

The substrate 11 is placed at a constant temperature of about 85 ° C and continuously allowed to stand for 300-360 minutes. By extending the growth time of the hydrothermal method, the length of the horizontal nanowires 15 on both sides can be made larger than the distance between the two electrodes (L). _M ), when the distance between the anode and the cathode is 8 to 10 μm, the length of the horizontal nanowire is 5 to 8 μm, that is, the two side nanowires 15 are overlapped with each other, thereby shortening the nanometer Line 15 tip to tip spacing (L _G ) to 1.2 μm. The manufacturing method of the nanowire of the present invention can be applied to the fabrication of the detecting component and improve the detecting capability of the component.

Referring to FIG. 4, there is shown a voltage-current graph of a tip-to-tip structure of a horizontal zinc oxide (ZnO) nanowire of the first embodiment of the present invention. In the sample, the tip-to-tip distance (L _G ) of the nanowire is 1.2 μm, the width of the electrode area is 500 μm, and the thickness of the AZO seed layer is 90 nm at three different environmental pressures (8.1×10 ^-7 , 5.3 Electrical measurement results of ×10 ^-4 and 7.6 × 10 ² torr). The experimental results show that the horizontal tip of the embodiment of the present invention has a nanowire in the range of 8.1×10 ^-7 to 7.6×10 ² torr in the ambient pressure. When the current reaches 10 A, the starting voltage is 2.15. 3.63 V; when the applied voltage is 9V, its emission current can be as high as 325~172 μA, its current density is equivalent to 722~382 A/cm ² , and the field emission enhancement factors (β) are calculated to be 5420, 5250, and 4835 respectively. Mm ^-1 , compared with the conventional nanowire field emission characteristics, the horizontal tip-to-tip structure zinc oxide (ZnO) nanowire prepared by the embodiment of the invention can improve the field emission capability and has a good field. Emission characteristics. In addition, the measured sample was observed by scanning electron microscopy (SEM), and it was found that the zinc oxide (ZnO) nanowire remained firmly attached to the side of the seed layer, that is, the horizontal tip of the present invention. The structure of zinc oxide (ZnO) nanowires has a relatively high mechanical stability.

Referring to FIG. 5, a pressure-current diagram of a tip-type structure of a horizontal zinc oxide (ZnO) nanowire tip according to a first embodiment of the present invention, wherein the tip-to-tip distance (L _G ) of the nanowire in the sample is 1.2 μm. The width (W) of the electrode area is 500 μm. The figure shows that when the applied voltage is 5V, 7V and 9V respectively and the pressure sensitivity of the field emission current increases by 10 times the ambient atmospheric pressure as the pressure rises, the field emission current is -22.9, -17.5 and -8.7μA. Variety. This result shows that the horizontal zinc oxide (ZnO) nanowire tip of the present invention has great potential for application to the detection of atmospheric pressure systems for the field-emitting element of the tip structure.

Please refer to FIG. 6, which is a current-time diagram of the tip-to-tip structure of the horizontal zinc oxide (ZnO) nanowire of the first embodiment of the present invention. The figure shows the results of the field emission current stability measurement of the sample for 2 hours when the applied voltage is 9V. The figure shows that when the pressure is 5.3×10 ^-4 -8.1×10 ^-7 and 7.6×10 ² torr, the field emission current varies by only about 3% (241 to 249 μA) and 7% (162 to 175 μA). In this embodiment, the stability of the field emission current is effectively improved by using a low operating voltage, high mechanical stability, and good thermal stability. Therefore, the horizontal zinc oxide (ZnO) nanowire tip prepared in this embodiment has excellent field emission current stability to the tip field emission element, and the tip structure is high in stability and is not easily damaged, for application to the field emission element. It provides good field emission reliability and stability.

<Comparative example>

Please refer to FIG. 7, which is a structural diagram of a tip-to-tip structure field emission element of a horizontal zinc oxide (ZnO) nanowire of a comparative example of the present invention. The preparation method of this comparative example was the same as that of the first embodiment except that this comparative example was not subjected to the step of appropriately longitudinally etching the diluted phosphoric acid in the first embodiment. Accordingly, the tip-to-tip field emission element structure of the comparative example (shown in FIG. 7) includes a substrate 71, an insulating layer 72, a cathode region, and an anode region. The substrate 71 is disposed at the bottom of the field emission device structure, and an insulating layer 72 is disposed on the substrate 71. The insulating layer 72 is further provided with a cathode region and an anode region. The cathode region includes a first seed layer 731 disposed under the cathode region, and a first electrode 741 disposed above the first seed layer 731. The first electrode 741 has a third sidewall 7411; and the first electrode 741 is disposed on the first seed layer 731 and completely covers the first seed layer 731, and the third sidewall 7411 forming the first electrode 741 is aligned. The structure of the first sidewall 7311 of the first seed layer 731 is here. The cathode region further includes a plurality of nanowires 75, the nanowires 75 extending from the first sidewall 7311 of the first seed layer 731. As with the structure of the cathode region, the anode region includes a second seed layer 732 disposed at a lowermost portion of the anode region, and a second electrode 742 disposed above the second seed layer 732. The second electrode 742 has a fourth sidewall 7421; and the second electrode 742 is disposed on the second seed layer 732 and completely covers the second seed layer 732, and the fourth sidewall 7421 of the second electrode 742 is aligned. The structure of the second sidewall 7321 of the second seed layer 732. The anode region also includes a plurality of nanowires 75, the nanowires 75 extending from the second sidewalls 7321 of the second seed layer 732.

Here, since the electrode protruding from the seed layer is absent, the growth of the nanowire 75 in the vertical direction cannot be effectively suppressed. Therefore, the nanowire 75 grows in a plurality of different directions to form a disordered nanowire 75 structure.

The above-mentioned embodiments are merely examples for convenience of description, and the scope of the claims is intended to be limited to the above embodiments.

11. . . Substrate

12. . . Insulation

131. . . First seed layer

1311. . . First side wall

132. . . Second seed layer

1321. . . Second side wall

141. . . First electrode

1411. . . Third side wall

142. . . Second electrode

1421. . . Fourth side wall

15. . . Nanowire

151. . . Tip of the nanowire

71. . . Substrate

72. . . Insulation

731. . . First seed layer

7311. . . First side wall

732. . . Second seed layer

7321. . . Second side wall

741. . . First electrode

7411. . . Third side wall

742. . . Second electrode

7421. . . Fourth side wall

75. . . Nanowire

L _M . . . Distance between two electrodes

L _G . . . Tip to tip distance

1A to 1E are flow charts showing a method of manufacturing a horizontal zinc oxide (ZnO) nanowire tip-to-tip structure field emission element according to a first embodiment of the present invention.

2A to 2E are flow charts showing a method of manufacturing a horizontal zinc oxide (ZnO) nanowire tip-to-plate structure field emission element according to a second embodiment of the present invention.

Figure 3 is a structural view of a tip-to-tip structure field emission element of a horizontal zinc oxide (ZnO) nanowire in a third embodiment of the present invention.

Fig. 4 is a graph showing the voltage-current curve of the tip-to-tip structure of the horizontal zinc oxide (ZnO) nanowire of the first embodiment of the present invention.

Fig. 5 is a pressure-current diagram of the tip of the horizontal zinc oxide (ZnO) nanowire according to the first embodiment of the present invention.

Figure 6 is a current-time diagram of the tip-to-tip structure of a horizontal zinc oxide (ZnO) nanowire of the first embodiment of the present invention.

Figure 7 is a structural view of a tip-to-tip structure field emission element of a horizontal zinc oxide (ZnO) nanowire in a comparative example of the present invention.

11. . . Substrate

12. . . Insulation

131. . . First seed layer

1311. . . First side wall

132. . . Second seed layer

1321. . . Second side wall

141. . . First electrode

1411. . . Third side wall

142. . . Second electrode

1421. . . Fourth side wall

15. . . Nanowire

151. . . Tip of the nanowire

L _M . . . Distance between two electrodes

L _G . . . Tip to tip distance

Claims (24)

A method of fabricating a field emission device includes the steps of: (A) providing a substrate; (B) forming a first seed layer on the substrate, and the first seed layer has a first sidewall; Forming a first electrode on the first seed layer and forming a second electrode on the substrate, wherein the first electrode has a second sidewall and completely covering the first seed layer, the second The electrode system has a fourth sidewall, and the fourth sidewall corresponds to the first sidewall of the first seed layer or the second sidewall of the first electrode; (D) etching the first seed layer to make the first a second sidewall of an electrode protruding from the first sidewall of the first seed layer; and (E) forming a plurality of first nanowires, and wherein the first nanowires extend from the first seed layer First side wall. The manufacturing method of claim 1, wherein in the step (B), a second seed layer is further formed on the substrate, the second seed layer has a third sidewall, and the third sidewall Corresponding to the first sidewall of the first seed layer; in the step (C), the second electrode is formed on the second seed layer, and the fourth sidewall of the second electrode corresponds to the a second sidewall of the first electrode; the second seed layer is further etched in the step (D) such that the fourth sidewall of the second electrode protrudes from the third sidewall of the second seed layer; Forming a plurality of second nanowires in the step (E), and the second nanowires extend from the third sidewall of the second seed layer, and the second nanowires The tip end corresponds to a tip end of the first nanowires extending from a first sidewall of the first seed layer. The manufacturing method according to claim 1, wherein in the step (E), the first nanowires are formed by a hydrothermal method. The manufacturing method according to claim 3, wherein the hydrothermal method has a growth temperature of 75 to 90 °C. The manufacturing method according to claim 3, wherein the hydrothermal method has a growth time of 60 to 300 min. The manufacturing method according to claim 1, wherein in the step (D), the etching liquid for etching the first seed layer is phosphoric acid, hydrochloric acid or a mixed solution thereof. The manufacturing method according to claim 1, wherein the material of the first seed layer is AZO, IZO, or GZO. The manufacturing method according to claim 1, wherein the first nanowires are metal oxide nanowires. The manufacturing method according to claim 8, wherein the materials of the first nanowires are ZnO, TiO ₂ or SnO ₂ . The manufacturing method of claim 1, wherein the substrate is a substrate, a glass substrate, a quartz substrate, a semiconductor substrate, a metal substrate, or a plastic substrate. The manufacturing method according to claim 1, wherein the material of the first electrode is platinum, tungsten, nickel, gold, tin or gallium. The manufacturing method of claim 1, wherein the step (A) further comprises a step (A') of forming an insulating layer on the substrate. A field emission device comprising: a substrate; a cathode region disposed on the substrate, the cathode region comprising: a first seed layer disposed on the substrate and having a first sidewall; An electrode is disposed on the first seed layer and completely covers the first seed layer, and a second sidewall of the first electrode protrudes from a first sidewall of the first seed layer; and a plurality of a nanowire extending from the first sidewall of the first seed layer; and an anode region disposed on the substrate, the anode region comprising: a second electrode disposed on the substrate, the anode layer The second electrode has a fourth sidewall, and the fourth sidewall corresponds to the first sidewall of the first seed layer or the second sidewall of the first electrode. The field emission device of claim 13 further comprising an insulating layer disposed on the substrate and located in the substrate and the cathode region. The field emission device of claim 13, wherein the anode region further comprises: a second seed layer disposed on the substrate, the second seed layer having a third sidewall, and the a third sidewall corresponding to the first sidewall of the first seed layer; a plurality of second nanowires extending from a third sidewall of the second seed layer, and wherein the tips of the second nanowires correspond to the first sidewalls extending from the first seed layer a tip of a nanowire; wherein the second electrode is disposed on the second seed layer and completely covers the second seed layer, and the fourth sidewall of the second electrode protrudes from the second crystal The third sidewall of the seed layer, and the fourth sidewall of the second electrode corresponds to the second sidewall sidewall of the first electrode. The field emission device of claim 15, wherein the tips of the first nanowires and the tips of the second nanowires are interdigitated. The field emission device of claim 15, wherein a distance between a tip of the first nanowire and a tip of the second nanowire is between 5 nm and 5 μm. The field emission device of claim 13, wherein the fourth sidewall of the second electrode corresponds to a first sidewall of the first seed layer. The field emission device of claim 18, wherein a distance between a tip end of the first nanowire and a fourth sidewall of the second electrode is between 5 nm and 5 μm. The field emission device of claim 13, wherein the materials of the first nanowires are ZnO, TiO ₂ , or SnO ₂ . The field emission device of claim 15, wherein the materials of the second nanowires are ZnO, TiO ₂ , or SnO ₂ . The field emission device of claim 13, wherein the substrate is a substrate, a glass substrate, a quartz substrate, a semiconductor substrate, a metal substrate, or a plastic substrate. The field emission device of claim 13, wherein the material of the first electrode is platinum, tungsten, nickel, gold, tin or gallium. The field emission device of claim 15, wherein the material of the second electrode is platinum, tungsten, nickel, gold, tin or gallium.