Transparent oxide film electrode and preparing method of the same

Abstract

The present invention relates to a transparent oxide film electrode and a method for manufacturing the same. A transparent oxide film electrode according to one embodiment of the present invention comprises: a first metal oxide layer; a second metal oxide layer; and a liquid metal layer comprising a residual liquid metal interposed between the first metal oxide layer and the second metal oxide layer.

Description

Technology Field

[0001] The present invention relates to a transparent oxide film electrode and a method for manufacturing the same. Background Technology

[0003] Amorphous metal oxides (AMOs) possess various useful properties for optoelectronics, digital memory devices, and thin-film transistors due to their high carrier mobility and optical transparency. Amorphous metal oxides are generally deposited via chemical or physical vapor deposition. These conventional deposition methods typically require vacuum environments, the use of highly toxic precursor gases, and long process times.

[0004] Amorphous metal oxides can be easily fabricated on gallium-based liquid metal (LM) surfaces. Metals exist as liquids at or near room temperature and exist in their natural form due to rapid oxidation in air. Amorphous metal oxides on liquid metal surfaces are self-passivated and very thin (< 5 nm). However, unlike conventional organometallic precursors for amorphous metal oxide deposition, gallium-based liquid metals have very low toxicity and a vapor pressure of virtually zero. Therefore, efforts have been made to develop new and inexpensive methods to print amorphous metal oxides from liquid metals by leveraging these capabilities.

[0005] Oxide thin films produced by conventional manufacturing methods have inconsistent shapes and sizes, and the maximum achievable oxide film size remains at the level of a few millimeters. Furthermore, there is a problem in that a significant amount of liquid metal residue remains after printing, which can degrade the performance of the printed oxide.

[0006] The aforementioned background technology is one that the inventor possessed or acquired in the process of deriving the disclosure of the present invention, and it cannot be considered as prior art disclosed to the general public prior to the filing of this application. The problem to be solved

[0008] The present invention is intended to solve the aforementioned problems, and the objective of the present invention is to provide a transparent oxide electrode and a method for manufacturing the same, which can obtain a large-area metal oxide thin film of excellent quality by directly printing it onto a desired substrate in a simple manner.

[0009] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0011] A transparent oxide film electrode according to one embodiment of the present invention comprises: a first metal oxide layer; a second metal oxide layer; and a liquid metal layer comprising a residual liquid metal interposed between the first metal oxide layer and the second metal oxide layer.

[0012] In one embodiment, the first metal oxide layer and the second metal oxide layer are each an oxide of a liquid metal, and the liquid metal may comprise at least one selected from the group consisting of gallium (Ga), indium (In), tin (Sn), zinc (Zn), eutectic gallium-indium (EGaIn), gallium-aluminum (Ga-Al), gallium-tin (Ga-Sn), gallium-zinc (Ga-Zn), and gallium-aluminum (Ga-Al).

[0013] In one embodiment, the metal oxide may comprise at least one selected from the group consisting of GaOx, Ga2O3, InOx, AlOx, SnO2, and ZnO.

[0014] In one embodiment, the transparent oxide film electrode may be amorphous.

[0015] In one embodiment, the thickness of the first metal oxide layer may be 1 nm to 10 nm, the thickness of the liquid metal layer may be 0.1 nm to 8 nm, and the thickness of the second metal oxide layer may be 1 nm to 10 nm.

[0016] In one embodiment, the roughness (rms roughness) of the surface of the transparent oxide film electrode may be 0.5 nm to 2 nm.

[0017] In one embodiment, the sheet resistance of the transparent oxide electrode is 5 × 10 2 Ω / sq to 5 × 10 8 It could be Ω / sq.

[0018] In one embodiment, the light transmittance of the transparent oxide electrode may be 85% to 99%.

[0019] A method for manufacturing a transparent oxide film electrode according to another embodiment of the present invention comprises: a step of filling a printer head comprising two spaced-apart glass substrates with liquid metal; and a step of forming a transparent oxide film electrode by moving the printer head on the substrate along the longitudinal direction of the substrate.

[0020] In one embodiment, the substrate is silicon (Si), silicon oxide (SiO2), aluminum oxide (Al2O3), magnesium oxide (MgO), silicon carbide (SiC), silicon nitride (SiN), glass, quartz, sapphire, graphite, graphene, polyimide (PI), polyester (PE), polyethyleneterephthalate (PET), poly(2,6-ethylenenaphthalate) (PEN), polymethyl methacrylate (PMMA), polyurethane (PU), fluoropolymers (FEP), polyvinylidene fluoride (PVDF), It may comprise at least one selected from the group consisting of polydimethylsiloxane (PDMS) and 3-mercaptopropyltrimethoxysilane (MPTMS) treated Au films.

[0021] In one embodiment, the step of forming the transparent oxide film electrode may be such that a first metal oxide layer and a second metal oxide layer are formed, respectively, at the upper portion where the liquid metal filled between the two glass substrates of the printer head exits the printer head and comes into contact with air, and at the lower portion where it comes into contact with the substrate, and a liquid metal layer containing residual liquid metal is interposed between the first metal oxide layer and the second metal oxide layer.

[0022] In one embodiment, in the step of forming the transparent oxide film electrode, the speed at which the printer head is moved along the longitudinal direction of the substrate on the substrate may be 0.001 mm / s to 5 mm / s.

[0023] In one embodiment, after the step of forming the transparent oxide film electrode, the method may further include the step of annealing the transparent oxide film electrode at a temperature range of 50°C to 1,500°C.

[0024] An electronic device according to another embodiment of the present invention includes a transparent oxide film electrode manufactured by a transparent oxide film electrode according to one embodiment of the present invention or by a method for manufacturing a transparent oxide film electrode according to another embodiment.

[0025] In one embodiment, the electronic device may be a digital memory device, a thin-film transistor, a flat-panel display, a curved display, a touch screen panel, a solar cell, an organic light-emitting diode, a smartphone, a tablet PC, a wearable device, an e-paper, an e-window, an electrochromic mirror, a transparent heater, a heat mirror, a transparent heater, a transparent transistor, a transparent strain sensor, or a flexible display. Effects of the invention

[0027] A transparent oxide film electrode according to one embodiment of the present invention can be manufactured by directly printing various oxides and can provide a large-area, high-quality thin film oxide including a liquid metal layer.

[0028] According to the method for manufacturing a transparent oxide electrode according to one embodiment of the present invention, anyone can easily and quickly print a metal oxide thin film using liquid metal. In addition, the metal oxide can be transferred to various substrates including polymers, which can be advantageous for fabricating flexible devices that require low-temperature processes. A high-quality thin film obtained through a vapor phase process can be obtained through a printing process, which is a solution process.

[0029] Furthermore, based on an understanding of the wetting, non-wetting, and flow of liquid metals, significant contributions to related fields are expected. Unlike conventional metal oxides, it is possible to obtain unique oxides with high conductivity that possess a multilayer structure of oxide and metal. The transparent oxide electrodes produced by this manufacturing method have high versatility and can be utilized in various fields such as semiconductors, electrodes, dielectrics, and encapsulation films. Brief explanation of the drawing

[0031] FIG. 1 is a schematic cross-sectional view of a transparent oxide film electrode according to one embodiment of the present invention. FIG. 2 is a flowchart for explaining a method for manufacturing a transparent oxide film electrode according to one embodiment of the present invention. FIG. 3 is a schematic diagram showing a method for manufacturing a transparent oxide film electrode according to one embodiment of the present invention. FIG. 4a is a photograph of a printing device used in an embodiment of the present invention. FIG. 4b is an image of a gallium oxide thin film electrode printed on various substrates according to an embodiment of the present invention. FIG. 5a is an optical image of a metal oxide electrode manufactured according to an embodiment of the present invention. Figure 5b is the AFM measurement result of a metal oxide electrode manufactured according to an embodiment of the present invention. FIG. 5c is a transmission electron microscope (TEM) image showing the selected region diffraction (SAED) pattern of a metal oxide electrode prepared according to an embodiment of the present invention. FIG. 5d is an image of a metal oxide electrode manufactured according to an embodiment of the present invention after multiple printing and annealing. FIG. 6a is a schematic diagram showing the advancing region of the meniscus of a liquid metal according to an embodiment of the present invention. FIG. 6b is a schematic diagram showing the receding region of the meniscus of a liquid metal according to an embodiment of the present invention. FIG. 7a is a graph showing three different printing results according to the height and speed of the printer head according to an embodiment of the present invention. FIG. 7b is a camera image showing three different printing results depending on the height and speed of the printer head according to an embodiment of the present invention. FIGS. 8a to 8c are drawings for explaining various printed forms according to embodiments of the present invention using the flow of a liquid film. FIG. 9a is a diagram showing the results of a thickness direction ToF-SIMS analysis of a printed gallium oxide thin film over time according to an embodiment of the present invention. Figure 9b shows the electron density distribution in the thickness direction according to the number of printed layers of a gallium oxide thin film according to an embodiment of the present invention. Figure 9c is density data of a three-layer printed gallium oxide thin film according to an annealing condition according to an embodiment of the present invention. Figure 9d is the Ga 2p3 / 2 XPS result of a single-layer printed gallium oxide thin film according to an annealing condition according to an embodiment of the present invention. FIG. 9e is a schematic diagram of the state of a gallium oxide thin film according to an annealing condition according to an embodiment of the present invention. Specific details for implementing the invention

[0032] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, various modifications may be made to the embodiments, and thus the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, and substitutions to the embodiments are included within the scope of the rights.

[0033] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0034] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the embodiments pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0036] In addition, when describing with reference to the attached drawings, identical components are assigned the same reference numeral regardless of drawing symbols, and redundant descriptions thereof are omitted. In describing the embodiments, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the embodiments, such detailed description is omitted.

[0037] In addition, terms such as first, second, A, B, (a), (b), etc. may be used when describing the components of the embodiments. These terms are used merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by the terms.

[0038] Components included in any one embodiment and components having common functions shall be described using the same names in other embodiments. Unless otherwise stated, the description in any one embodiment may also apply to other embodiments, and specific descriptions shall be omitted to the extent of overlap.

[0040] Hereinafter, the transparent oxide film electrode and the method for manufacturing the same according to the present invention will be described in detail with reference to the examples and drawings. However, the present invention is not limited to these examples and drawings.

[0042] A transparent oxide film electrode according to one embodiment of the present invention comprises: a first metal oxide layer; a second metal oxide layer; and a liquid metal layer comprising a residual liquid metal interposed between the first metal oxide layer and the second metal oxide layer.

[0043] FIG. 1 is a schematic cross-sectional view of a transparent oxide film electrode according to one embodiment of the present invention.

[0044] Referring to FIG. 1, a transparent oxide film electrode (100) according to one embodiment of the present invention includes a first metal oxide layer (110), a liquid metal layer (120), and a second metal oxide layer (130).

[0045] In one embodiment, the first metal oxide layer (110) and the second metal oxide layer (130) may each be an oxide of a liquid metal.

[0046] The above liquid metal may comprise at least one selected from the group consisting of gallium (Ga), indium (In), tin (Sn), zinc (Zn), eutectic gallium-indium (EGaIn), gallium-tin (Ga-Sn), gallium-zinc (Ga-Zn), and gallium-aluminum (Ga-Al).

[0047] Preferably, the liquid metal may be gallium (Ga).

[0048] In one embodiment, the metal oxide may comprise at least one selected from the group consisting of GaOx, Ga2O3, InOx, AlOx, SnO2, and ZnO.

[0049] Preferably, the metal oxide may be GaOx.

[0050] In one embodiment, the transparent oxide film electrode may be amorphous.

[0051] The fact that the transparent oxide electrode of the present invention is amorphous can be confirmed by the absence of rings or dots indicating the long-range order of specific crystal planes seen in crystalline materials in transmission electron microscopy (TEM) with a Selected-Area Electron Diffraction (SAED) pattern.

[0052] In one embodiment, the thickness of the first metal oxide layer may be 1 nm to 10 nm. If the thickness of the first metal oxide layer is less than 1 nm, a problem may arise that it is lower than the thickness of a typical natural oxide film of the metal (1 to 2 nm), and if it is greater than 10 nm, a problem may arise that it exceeds the entire printed oxide layer.

[0053] The thickness of the liquid metal layer may be 0.1 nm to 8 nm. A case where the thickness of the liquid metal layer is less than 0.1 nm cannot exist, and a case where it is greater than 8 nm may result in a problem that is difficult to exist when considering the thickness of the entire printed oxide layer (10 nm) and the sum of the thickness layers of the minimum natural oxide film of the first and second metal oxide layers (2 nm).

[0054] The thickness of the second metal oxide layer may be 1 nm to 10 nm. If the thickness of the second metal oxide layer is less than 1 nm, a problem may arise that it is lower than the thickness of a typical natural oxide film of the metal (1 to 2 nm), and if it is greater than 10 nm, a problem may arise that it exceeds the entire printed oxide layer.

[0055] In one embodiment, the roughness (rms roughness) of the surface of the transparent oxide film electrode may be 0.5 nm to 2 nm; 0.5 nm to 1.5 nm; 0.5 nm to 1 nm; 1 nm to 2 nm; 1 nm to 1.5 nm; or 1.5 nm to 2 nm.

[0056] If the thickness of the above transparent oxide film electrode is less than 0.5 nm, a problem may arise in that it is evaluated to be lower than the surface roughness of a single crystal state, which generally has the lowest surface roughness, and if it is greater than 2 nm, a problem may arise in that it is a state in which various impurities exist rather than a pure oxide film.

[0057] In one embodiment, the sheet resistance of the transparent oxide electrode is 5 × 10 2 Ω / sq to 5 × 10 8 Ω / sq; 5 × 10 2 Ω / sq to 5 × 10 5 Ω / sq; 5 × 10 2 Ω / sq to 5 × 10 3 It could be Ω / sq.

[0058] The sheet resistance of the above transparent oxide film electrode is 5 × 10 2 If it is less than Ω / sq, a problem may occur where it is lower than the minimum value among the experimental measurements, and 5 × 10 8 If it exceeds Ω / sq, a problem may occur where it exceeds the measurement range of the sheet resistance measuring equipment.

[0059] In one embodiment, the light transmittance of the transparent oxide electrode may be 85% to 99%.

[0060] A transparent oxide film electrode according to one embodiment of the present invention can be manufactured by directly printing various oxides and can provide a large-area, high-quality thin film oxide including a liquid metal layer.

[0062] A method for manufacturing a transparent oxide film electrode according to another embodiment of the present invention comprises: a step of filling a printer head comprising two spaced-apart glass substrates with liquid metal; and a step of forming a transparent oxide film electrode by moving the printer head on the substrate along the longitudinal direction of the substrate.

[0063] Conventional transparent oxide electrodes are formed in a planar form where the entire interior is filled with a transparent oxide electrode material such as ITO. Consequently, multiple processes such as deposition, drying, exposure, development, and etching must be performed to separate the transparent electrodes. As a result, since equipment is required for each process, the production line becomes complex and production costs may increase. On the other hand, the transparent oxide electrode according to the present invention utilizes a simple printing process, and the equipment used in the process is also simple. Therefore, the production line can be simplified, production costs reduced, and process efficiency increased. In particular, these effects can be further enhanced when implemented over a large area.

[0064] FIG. 2 is a flowchart for explaining a method for manufacturing a transparent oxide film electrode according to one embodiment of the present invention, and FIG. 3 is a diagram schematically showing a method for manufacturing a transparent oxide film electrode according to one embodiment of the present invention.

[0065] Referring to FIG. 2, a method for manufacturing a transparent oxide film electrode according to one embodiment of the present invention includes the step (210) of filling a printer head with liquid metal and the step (220) of forming a transparent oxide film electrode.

[0066] The step (210) of filling the printer head with liquid metal may be to fill the liquid metal between two spaced organic substrates of the printer head, as shown in FIG. 3.

[0067] The above liquid metal may comprise at least one selected from the group consisting of gallium (Ga), indium (In), tin (Sn), zinc (Zn), eutectic gallium-indium (EGaIn), gallium-aluminum (Ga-Al), gallium-tin (Ga-Sn), and gallium-zinc (Ga-Zn).

[0068] Preferably, the liquid metal may be gallium (Ga) or gallium-aluminum (Ga-Al).

[0069] The step (220) of forming the transparent oxide film electrode may be formed by moving the printer head on the substrate along the longitudinal direction of the substrate (printing direction in FIG. 3).

[0070] In one embodiment, the substrate is silicon (Si), silicon oxide (SiO2), aluminum oxide (Al2O3), magnesium oxide (MgO), silicon carbide (SiC), silicon nitride (SiN), glass, quartz, sapphire, graphite, graphene, polyimide (PI), polyester (PE), polyethyleneterephthalate (PET), poly(2,6-ethylenenaphthalate) (PEN), polymethyl methacrylate (PMMA), polyurethane (PU), fluoropolymers (FEP), polyvinylidene fluoride (PVDF), It may comprise at least one selected from the group consisting of polydimethylsiloxane (PDMS) and 3-mercaptopropyltrimethoxysilane (MPTMS) treated Au films.

[0071] In one embodiment, the step of forming the transparent oxide film electrode may be such that a first metal oxide layer and a second metal oxide layer are formed, respectively, at the upper portion where the liquid metal filled between the two glass substrates of the printer head exits the printer head and comes into contact with air, and at the lower portion where it comes into contact with the substrate, and a liquid metal layer containing residual liquid metal is interposed between the first metal oxide layer and the second metal oxide layer.

[0072] In one embodiment, in the step of forming the transparent oxide film electrode, the speed at which the printer head is moved along the longitudinal direction of the substrate on the substrate may be 0.001 mm / s to 5 mm / s; 0.001 mm / s to 1 mm / s; 0.001 mm / s to 0.1 mm / s; 0.001 mm / s to 0.01 mm / s; 0.01 mm / s to 5 mm / s; 0.01 mm / s to 1 mm / s; 0.01 mm / s to 0.1 mm / s; 0.1 mm / s to 5 mm / s; 0.1 mm / s to 1 mm / s; or 1 mm / s to 5 mm / s.

[0073] If the above moving speed is less than 0.001 mm / s, a problem may occur where it is lower than the minimum speed of the printing equipment, and if it exceeds 5 mm / s, a problem may occur where it exceeds the theoretically printable critical speed.

[0074] In one embodiment, after the step of forming the transparent oxide film electrode, the transparent oxide film electrode is at 50 ℃ to 1,500 ℃; 50 ℃ to 1,000 ℃; 50 ℃ to 800 ℃; 50 ℃ to 500 ℃; 50 ℃ to 300 ℃; 50 ℃ to 100 ℃; 100 ℃ to 1,500 ℃; 100 ℃ to 1,000 ℃; 100 ℃ to 800 ℃; 100 ℃ to 500 ℃; 100 ℃ to 300 ℃; 300 ℃ to 1,500 ℃; 300 ℃ to 1,000 ℃; 300 ℃ to 800 ℃; 300 ℃ to 500 ℃; It may further include a step of annealing in a temperature range of 500 ℃ to 1,500 ℃; 500 ℃ to 1,000 ℃; 500 ℃ to 800 ℃; 800 ℃ to 1,500 ℃; 800 ℃ to 1,000 ℃; or 1,000 ℃ to 1,500 ℃.

[0075] If the above annealing temperature is less than 50°C, a problem may arise where the annealing is ineffective, and if it exceeds 1,500°C, a problem may arise where it exceeds the maximum temperature range of a furnace, which is a general annealing equipment.

[0076] The metal oxide layer can be converted to transparent by the above annealing step.

[0077] According to the method for manufacturing a transparent oxide electrode according to one embodiment of the present invention, anyone can easily and quickly print a metal oxide thin film using liquid metal. In addition, the metal oxide can be transferred to various substrates including polymers, which can be advantageous for fabricating flexible devices that require low-temperature processes. A high-quality thin film obtained through a vapor phase process can be obtained through a printing process, which is a solution process.

[0078] Furthermore, based on an understanding of the wetting, non-wetting, and flow of liquid metals, significant contributions to related fields are expected. Unlike conventional metal oxides, it is possible to obtain unique oxides with high conductivity that possess a multilayer structure of oxide and metal. The transparent oxide electrodes produced by this manufacturing method have high versatility and can be utilized in various fields such as semiconductors, electrodes, dielectrics, and encapsulation films.

[0080] An electronic device according to another embodiment of the present invention includes a transparent oxide film electrode manufactured by a transparent oxide film electrode according to one embodiment of the present invention or by a method for manufacturing a transparent oxide film electrode according to another embodiment.

[0081] In one embodiment, the electronic device may be a packaging device, a digital memory device, a thin-film transistor, a flat-panel display, a curved display, a touch screen panel, a solar cell, an organic light-emitting diode, a smartphone, a tablet PC, a wearable device, an e-paper, an e-window, an electrochromic mirror, a transparent heater, a heat mirror, a transparent heater, a transparent transistor, a transparent strain sensor, or a flexible display.

[0083] The present invention will be described in detail below with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited or restricted by such examples.

[0085] [Example]

[0086] The printer head was prepared by attaching two glass slides at a 1 mm interval. The metal source was prepared by melting pellets at a temperature above the melting point and injecting them into the printer head. The Ga-In eutectic alloy was prepared by adding 25 wt% of In pellets to the Ga melt. The Ga-Al eutectic alloy was prepared by adding 1 wt% of Al powder to the Ga melt. Before adding the Al powder, surface oxides were crushed using a mortar and pestle. Polymer substrates were prepared by spin-coating the solution directly onto the desired substrate. For the gold substrate, a 100 nm thick layer of Au was deposited on the glass slide and treated with MPTMS to avoid metal-to-metal contact. 200 μl of MPTMS was dropped onto a glass Petri dish, followed by deposition treatment in a vacuum chamber for 2 hours. The vapor-treated samples were washed with IPA and DI water to remove residual chemicals. The hydrolysis and condensation of MPTMS treated on gold were carried out by immersing in dilute hydrochloric acid (3 wt%) for 1 hour followed by rinsing with DI water. The MPTMS-treated substrates were finally annealed on a hot plate (100 °C) for an additional time. All substrates, including silicon wafers, c-plane sapphire, and quartz, were solvent-cleaned in the order of acetone, isopropyl alcohol (IPA), and DI water before use. The LM was introduced into the printer head between two glass slides using a syringe. The printer head containing the LM was brought close to the target substrate until the LM meniscus contacted the substrate. Once the printer head touched the substrate, it was raised to a desired height (h). Printing was performed by moving the printer head or moving the printout at a desired speed. Multilayer stacking was performed by repeating the same printing process at the same location.

[0088] Experimental Example 1

[0089] FIG. 4a is a photograph of a printing device used in an embodiment of the present invention.

[0090] Similar to slot die printing, gallium (Ga) was filled as a liquid metal between two glass plates acting as a printer head. The substrate and printer head were heated to the melting temperature of the metal source, and printing was performed by moving the printer head over the substrate to form a meniscus. On the back of the printer head, an oxide thin film is transferred to the substrate without a liquid metal layer. As shown in Fig. 4, a large area of ​​oxide thin film (> 5 cm x 15 cm) was printed in a single print using a 5 cm wide printer head. This is expected to evolve into roll-to-roll printing.

[0091] FIG. 4b is an image of a gallium oxide thin film electrode printed on various substrates according to an embodiment of the present invention.

[0092] As shown in Fig. 4b, it was confirmed that oxide thin films can be transferred regardless of polyvinylidene fluoride (PVDF), 3-mercaptopropyltrimethoxysilane (MPTMS) treated Au film, polydimethylsiloxane (PDMS), and sapphire substrate.

[0094] Experimental Example 2

[0095] FIG. 5a is an optical image of a metal oxide electrode manufactured according to an embodiment of the present invention.

[0096] Referring to Fig. 5, a liquid metal alloy containing one or more metals produces an oxide film having a composition defined by the element with higher oxidizing power, showing a uniform large-area printing of gallium oxide (GaOx), indium oxide (InOx), and aluminum oxide (AlOx).

[0097] Figure 5b is the AFM measurement result of a metal oxide electrode manufactured according to an embodiment of the present invention.

[0098] As shown in Fig. 5b, large-area thin films of GaOx and InOx formed on a silicon substrate can be easily obtained by melting a metal source. The thickness of the printed oxides, measured by Atomic Force Microscopy (AFM), was approximately 4.5 nm in both cases, and they were atomically smooth with a root mean square roughness of 0.7 nm. Additionally, since elements of metal alloys compete for oxide skin formation, AlOx thin films can be selectively produced by alloying with oxidizing elements (such as Al) that have a higher melting point but are more oxidizing than gallium. The thickness of the printed AlOx thin film is 7.6 nm, and the rms roughness is 1.2 nm.

[0099] FIG. 5c is a transmission electron microscope (TEM) image showing the selected region diffraction (SAED) pattern of a metal oxide electrode prepared according to an embodiment of the present invention.

[0100] As shown in Fig. 5c, it was confirmed that GaOx is amorphous through transmission electron microscopy (TEM) with selected area diffraction (SAED) patterns. All oxide skins were confirmed to be amorphous by TEM and SAED.

[0101] FIG. 5d is an image of a metal oxide electrode manufactured according to an embodiment of the present invention after multiple printing and annealing.

[0102] As shown in Fig. 5d, it was confirmed that the thickness of the GaOx oxide skin can be controlled by multi-printing. It can be converted into a transparent oxide by annealing at a mild temperature (80 °C) for 24 hours or by wiping with a cotton swab.

[0104] Experimental Example 3

[0105] To analyze the printing process, the meniscus of the liquid metal was divided into an advancing region and a receding region. To visualize the movement of oxides during printing, the oxides in both regions were stained with Rhodamine dye to visualize the movement of the oxide surface during printing.

[0106] FIG. 6a is a schematic diagram showing the advancing region of the meniscus of a liquid metal according to an embodiment of the present invention, and FIG. 6b is a schematic diagram showing the receding region of the meniscus of a liquid metal according to an embodiment of the present invention.

[0107] In the advancing region of Fig. 6a, the Rhodamine dye moved downward and was transferred to the substrate. At this time, the dye was transferred at irregular heights rather than in a straight line, which is due to friction with the substrate.

[0108] In the receding region of Fig. 6b, it was observed that the Rhodamine dye behind the printer head maintained a straight line as it descended, indicating that the oxide settled onto the substrate as if flowing over liquid metal without any stress. Since the oxide film in the advancing region was transferred downwards close to the substrate first, followed by the oxide film in the receding region being transferred on top of it, it was confirmed that the resulting printed oxide was a double layer of natural oxide film.

[0110] Experimental Example 4

[0111] FIG. 7a is a graph showing three different printing results according to the height and speed of a printer head according to an embodiment of the present invention, and FIG. 7b is a camera image showing three different printing results according to the height and speed of a printer head according to an embodiment of the present invention.

[0112] Referring to Figures 7a and 7b, there are three main printing results: 1) stable oxide film printing at low height and low speed, 2) unstable liquid metal printing with oxide film at low height and high speed (> 5 mm / s), and 3) a situation where liquid metal detaches from the printer head at high height.

[0114] Experimental Example 5

[0115] FIGS. 8a to 8c are drawings for explaining various printed forms according to embodiments of the present invention using the flow of a liquid film.

[0116] As shown in FIG. 8a, the critical printing speed (S) for forming an intermediate liquid metal layer without the oxide film being stably printed without liquid metal, is required. crit It was presumed that ) exists. S crit It can be calculated using the equation below.

[0117]

[0118] Here, eq rec is the equilibrium receding contact angle, and l max is the macroscopic length (l) which is the liquid metal capillary length. max =√γ eff / ρg)), l min is the microscopic length (l min =a / θ eq rec ), a is the atomic size of liquid metal (1.87 Å). θ eq rec was ~14° regardless of height, and S at this time crit It was calculated to be approximately 5 mm / s, which is consistent with experimental results.

[0119] As illustrated in Fig. 8b, liquid metal retraction can occur towards the center even within the printer head. This occurs in the same way inside the head while printing begins and a stable meniscus is formed in the advancing and retracting regions. As this inward retraction occurs, the width of the outer liquid metal meniscus decreases, and necking occurs. The degree of this varies depending on the amount of liquid metal exposed to the outside rather than the printer head, and this changes with the height of the printer head.

[0120] If the height of the printer head is excessively high, as shown in Fig. 8c, the pressure caused by the internal fluid flow overcomes the surface tension, and the liquid metal does not follow the printer head and falls off onto the substrate.

[0122] Experimental Example 6

[0123] FIG. 9a is a diagram showing the results of a thickness direction ToF-SIMS analysis of a printed gallium oxide thin film over time according to an embodiment of the present invention.

[0124] Referring to Fig. 9a, the thickness direction analysis is based on GaO2 measured while sputtering and gradually etching a single-layer gallium oxide thin film sample. - This represents the signal. The printed samples were exposed to air for 15, 30, and 60 minutes to determine the chemical composition over time. These results confirm that the printed thin film contains gallium (Ga)-rich layers between oxygen (O)-rich layers. Over time, the degree of this compositional change gradually decreases, suggesting gradual film oxidation.

[0125] Figure 9b shows the electron density distribution in the thickness direction according to the number of printed layers of a gallium oxide thin film according to an embodiment of the present invention.

[0126] Referring to Fig. 9b, fitting the XRR results yields the results of the electron density change in the thickness direction of the sample. As a result, periodic increases and decreases in electron density can be observed within each film. Considering the electron densities of gallium (1.515 re / Å3) and gallium oxide (1.329 re / Å3 for GaO and 1.247 re / Å3 for Ga2O), it can be confirmed that the printed film has a gallium-rich intermediate layer between the two gallium oxide layers.

[0127] Figure 9c is density data of a three-layer printed gallium oxide thin film according to an annealing condition according to an embodiment of the present invention.

[0128] Referring to Fig. 9c, the density of each layer is calculated from the XRR results. The thin film immediately after printing exhibits periodicity and is 4–6 g / cm³. 3 It has a density in the range of 4.63 g / cm³ 3 (4.9 g / cm³ for the gallium-rich layer) 3 , for the oxygen-rich layer, 4.4g / cm² 3 It has an average of ). This periodicity of electron density gradually disappears after annealing.

[0129] Figure 9d is the Ga 2p3 / 2 XPS result of a single-layer printed gallium oxide thin film according to an annealing condition according to an embodiment of the present invention.

[0130] Referring to Fig. 9d, the Ga 2p3 / 2 peak was fitted to gallium metal (Ga0) at 1116.2 eV and gallium metal oxide (the sum of Ga+, Ga2+, and Ga3+) at 1118.2 eV. The gallium metal content was 18 at% in the thin film immediately after printing, decreased to 6 at% after annealing at 80 °C in ambient air, and decreased to 0 at% after annealing at 800 °C.

[0131] FIG. 9e is a schematic diagram of the state of a gallium oxide thin film according to an annealing condition according to an embodiment of the present invention.

[0132] Referring to Fig. 9e, the thin film immediately after printing has a gallium-rich intermediate layer between two oxygen-rich layers. This thin film undergoes oxidation through annealing at a low temperature (80°C) and becomes a uniformly amorphous oxide. When this thin film is annealed at 800°C, it is converted into a crystalline gallium oxide thin film.

[0134] Although the embodiments have been described above with reference to the limited drawings, those skilled in the art can apply various technical modifications and variations based on the above. For example, suitable results may be achieved even if the described techniques are performed in a different order than described, and / or if the components of the described system, structure, device, circuit, etc. are combined or assembled in a form different from described, or replaced or substituted by other components or equivalents.

[0135] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims set forth below. Explanation of the symbols

[0137] 100: Transparent oxide film electrode 110: First metal oxide layer 120: Liquid metal layer 130: Second metal oxide layer

Claims

Claim 1 A transparent oxide electrode comprising: a first metal oxide layer formed on the upper portion in contact with air of a liquid metal filled between two spaced glass substrates; a second metal oxide layer formed on the lower portion in contact with the substrate of the liquid metal; and a liquid metal layer comprising a residual liquid metal interposed between the first metal oxide layer and the second metal oxide layer; wherein the thickness of the first metal oxide layer is 1 nm to 10 nm, the thickness of the liquid metal layer is 0.1 nm to 8 nm, and the thickness of the second metal oxide layer is 1 nm to 10 nm. Claim 2 A transparent oxide electrode according to claim 1, wherein the first metal oxide layer and the second metal oxide layer are each oxides of a liquid metal, and the liquid metal comprises at least one selected from the group consisting of gallium (Ga), indium (In), tin (Sn), zinc (Zn), eutectic gallium-indium (EGaIn), gallium-aluminum (Ga-Al), gallium-tin (Ga-Sn), gallium-zinc (Ga-Zn), and gallium-aluminum (Ga-Al). Claim 3 A transparent oxide electrode according to claim 1, wherein the metal oxide comprises at least one selected from the group consisting of GaOx, Ga2O3, InOx, AlOx, SnO2, and ZnO. Claim 4 A transparent oxide film electrode according to claim 1, wherein the transparent oxide film electrode is amorphous. Claim 5 delete Claim 6 A transparent oxide electrode according to claim 1, wherein the roughness (rms roughness) of the surface of the transparent oxide electrode is 0.5 nm to 2 nm. Claim 7 In claim 1, the sheet resistance of the transparent oxide film electrode is 5 × 10 2 Ω / sq to 5 × 10 8 A transparent oxide electrode having Ω / sq. Claim 8 A transparent oxide film electrode according to claim 1, wherein the light transmittance of the transparent oxide film electrode is 85% to 99%. Claim 9 A method for manufacturing a transparent oxide film electrode according to claim 1, comprising: a step of filling a printer head comprising two spaced-apart glass substrates with liquid metal; and a step of moving the printer head on the substrate along the longitudinal direction of the substrate to form a transparent oxide film electrode. Claim 10 In claim 9, the substrate is silicon (Si), silicon oxide (SiO2), aluminum oxide (Al2O3), magnesium oxide (MgO), silicon carbide (SiC), silicon nitride (SiN), glass, quartz, sapphire, graphite, graphene, polyimide (PI), polyester (PE), polyethyleneterephthalate (PET), poly(2,6-ethylenenaphthalate) (PEN), polymethyl methacrylate (PMMA), polyurethane (PU), fluoropolymers (FEP), polyvinylidene fluoride (PVDF), A method for manufacturing a transparent oxide electrode comprising at least one selected from the group consisting of an Au film treated with polydimethylsiloxane (PDMS) and 3-mercaptopropyltrimethoxysilane (MPTMS). Claim 11 A method for manufacturing a transparent oxide film electrode according to claim 9, wherein the step of forming the transparent oxide film electrode comprises forming a first metal oxide layer and a second metal oxide layer, respectively, at the upper portion where the liquid metal filled between the two glass substrates of the printer head exits the printer head and comes into contact with air, and at the lower portion where it comes into contact with the substrate, and interposing a liquid metal layer containing residual liquid metal between the first metal oxide layer and the second metal oxide layer. Claim 12 A method for manufacturing a transparent oxide film electrode according to claim 9, wherein, in the step of forming the transparent oxide film electrode, the speed at which the printer head is moved along the longitudinal direction of the substrate on the substrate is 0.001 mm / s to 5 mm / s. Claim 13 A method for manufacturing a transparent oxide film electrode according to claim 9, further comprising the step of annealing the transparent oxide film electrode at a temperature range of 50 ℃ to 1,500 ℃ after the step of forming the transparent oxide film electrode. Claim 14 An electronic device comprising a transparent oxide film electrode of claim 1 or a transparent oxide film electrode manufactured by the method of manufacturing a transparent oxide film electrode of claim 9. Claim 15 In claim 14, the electronic device is a digital memory device, a thin-film transistor, a flat-panel display, a curved display, a touch screen panel, a solar cell, an organic light-emitting diode, a smartphone, a tablet PC, a wearable device, an e-paper, an e-window, an electrochromic mirror, a transparent heater, a heat mirror, a transparent heater, a transparent transistor, a transparent strain sensor, or a flexible display.

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