KR102232199B1 - Method for preparation of ultrathin metal film using a template comprising monolayered graphene - Google Patents

Abstract

The present invention relates to a method of manufacturing an ultra-thin metal film using a template including a single-layer graphene formed on a solid substrate having a chemical functional group, and a use of the ultra-thin metal film thus produced.

Description

Method for preparation of ultrathin metal film using a template comprising monolayered graphene

The present invention relates to a method of manufacturing an ultra-thin metal film using a template including a single-layer graphene formed on a solid substrate having a chemical functional group, and a use of the ultra-thin metal film thus produced.

Controlling the nucleation and growth of metal clusters on solid substrates is a long-standing issue in a metal electrode deposition process for application to thin-film-based electronic devices. However, regardless of the type of material, all solid substrates inevitably have a large number of defect sites called kink atoms, step atoms, on the atomic scale, such as steps or terraces, with many forms of voids. Have. When metal atoms are deposited on the surface, the unintended defect sites may induce heterogeneous nucleation, resulting in non-uniform density due to irregular growth of individual initial nuclei. Non-uniform nucleation, which is not controlled at the initial stage, consequently leads to deterioration of the quality of thin metal films, including polycrystalline structures with grain-boundaries. In particular, in order to achieve ultra-thin metal electrodes required in advanced optoelectronics as well as next-generation electronic devices, homogeneous nucleation and growth of metal clusters precisely controlled at the atomic level are the minimum percolation threshold. It is essential to ensure high electrical conductivity while having a thickness).

Graphene, which has a large sheet form composed of _{hybridized SP 2} bonds of carbon atoms, is a perfectly flat and defect-free material. Therefore, since the discovery of graphene, it has attracted attention as the best template material for epitaxial growth of various two-dimensional materials. However, at the same time, since graphene is chemically inert, nucleation is difficult on pure graphene. Accordingly, there have been many attempts based on defect-engineering, chemical functionalization, and vapor deposition under intensive conditions, but all methods involved deformation or damage in the graphene's own lattice.

In addition, graphene has a unique property that exhibits transparency for most physicochemical measurements through a single atom thickness. In a previous study, the present inventors confirmed the transparency of graphene with respect to the atomic arrangement of the substrate surface using hydrothermally grown ZnO nanorods, and reduction of metal nanoparticles on the other surface of graphene from the supporting substrate at the bottom of the graphene The electron-transfer transparency of graphene was confirmed by observing the charge transfer to.

The present inventors, as a result of intensive research efforts to provide a conductive metal ultra-thin film having a thickness of 10 Å or less, when forming a single layer of graphene on a substrate having a functional functional group and using it as a template, due to the chemical transparency of graphene It was confirmed that it was possible to form a single metal nanocrystal uniformly grown on graphene, and accordingly, an ultra-thin metal electrode having a minimum electrical filtration critical thickness could be manufactured, and the present invention was completed.

In one aspect, the present invention provides a solid substrate having a chemical functional group on at least one side; And a first step of preparing a template including a single layer graphene formed on a surface containing a functional group of the solid substrate. And it provides a method of manufacturing an ultra-thin metal thin film having a thickness of 3 to 200Å, including a second step of forming a metal thin film on the single-layer graphene of the template.

As another aspect, the present invention provides a microneedle patch comprising a metal thin film manufactured by the above method and one or more microneedles attached to one surface thereof.

In another aspect, the present invention provides a skin cosmetic active device including a thin metal film manufactured by the above method and a light source providing visible light.

Hereinafter, the present invention will be described in detail.

In the present invention, when using a template to which a substrate having a functional group having a chemical function is attached and using the chemical transparency of graphene to form a metal thin film on the graphene of the template, the functional group having the chemical function and the metal atom Since the interaction of the metals is possible, uniform metal nucleation and crystal growth are possible, so even when manufactured in an ultra-thin shape of several Å, a continuous thin film can be formed without grain-boundaries, which could not be achieved with the prior art. It is based on the discovery that it can provide ultra-thin metallic films.

Specifically, the present invention is a solid substrate having a chemical functional group on at least one side; And a first step of preparing a template including a single layer graphene formed on a surface containing a functional group of the solid substrate. And it provides a method of manufacturing an ultra-thin metal thin film having a thickness of 3 to 200Å, including a second step of forming a metal thin film on the single-layer graphene of the template.

The chemical functional group includes, without limitation, a functional group capable of increasing the bonding force between the metal to be formed into a thin film and the template. For example, it may be a hydroxy group, a thiol group, or a perfluoroalkyl group, but is not limited thereto.

On the other hand, the metal that can be manufactured into an ultra-thin film by applying the manufacturing method according to the present invention is a metal having an initial island nucleation mode, and may be, for example, gold, silver, copper, aluminum, or platinum, but is not limited thereto. Does not. Furthermore, the manufacturing method of the present invention can be applied without limitation to the manufacture of an ultra-thin film of a material that can be thinned, such as a semiconductor, an organic semiconductor, or an oxide, as well as a metal.

The thin film formed by these metals can be manufactured from a few Å of ultra-thin to several hundred Å of thickness. For example, it may be manufactured in a thickness of 3 to 200 Å, 10 to 200 Å, 3 to 100 Å, or 10 to 100 Å.

The metal thin film thus produced is characterized by being continuously formed without grain-boundaries to exhibit conductivity. For example, a thin film formed with a thickness of less than 3 Å may be difficult to have conductivity due to discontinuity due to the presence of grain boundaries and/or low coverage.

For example, the solid substrate having a hydroxy group may be prepared by thermally oxidizing the silica substrate or treating it with oxygen plasma, but is not limited thereto.

Further, the solid substrate having a thiol group and a perfluoroalkyl group may be prepared by treating the solid substrate having a hydroxy group with mercaptoalkylalkoxysilane and perfluoroalkylalkoxysilane, respectively, but is not limited thereto. For example, the mercaptoalkylalkoxysilane is (3-mercaptopropyl)trimethoxysilane ((3-mercaptopropyl)trimethoxysilane; MPTMS), and the perfluoroalkylalkoxysilane is FAS-13 (1H, 1H, 2H). ,2H-perfluorooctyltriethoxysilane) may be used, but is not limited thereto.

In a specific embodiment of the present invention, a thermally oxidized silica substrate was treated with oxygen plasma to prepare a substrate having a hydroxyl group on the surface, which was treated with (3-mercaptopropyl)trimethoxysilane or FAS-13 solution, respectively. Thus, by forming a self-assembled monolayer, it was modified to have a thiol group or a perfluoroalkyl group. However, this is only an example and the scope of the present invention is not limited thereto.

The metal thin film formed in the second step can be separated from the template using an adhesive substrate. Because graphene has low adhesion to the metal thin film formed therein due to its low chemical reactivity, an adhesive substrate is attached to the other side of the metal thin film that is not in contact with graphene. Can be easily separated. At this time, in the case of using polydimethylsiloxane (PDMS), which is easily decomposed by stimulation such as heat, as the adhesive substrate, only the metal thin film can be recovered by heating and decomposing it.

Further, as described above, the substrate remaining after separating the metal thin film can be reused as a template in the first step.

Further, the present invention provides a microneedle patch including a metal thin film manufactured by the above-described method and one or more microneedles attached to one surface thereof.

As used herein, the term "microneedle" refers to a structure having a width, length, and height of several micrometers, and one end is acute and has a shape suitable for penetrating skin, etc., and the end is usually It may have a pointed or somewhat blunt conical or polygonal pyramid shape. However, as long as the above object can be efficiently achieved, its size or shape may be modified. Meanwhile, the microneedle may be a structure made of a biodegradable polymer, but is not limited thereto.

Since the microneedle patch of the present invention includes an ultra-thin metal film formed thinly at a degradable level, it can be attached to the skin directly or in a form including an additional adhesive substrate, or attached to the tissue by implantation in the body.

For example, the microneedles may carry drugs or cosmetics, and as the microneedles are decomposed, the drugs carried therein may be released and delivered intradermally.

As the drugs, hormones such as rosiglitazone (Rosi), CL316243, insulin, glucagon or PD-1 (Programmed cell death protein 1), EPO (erythropoietic), which are drugs for the treatment of obesity and/or diabetes, influenza Vaccines, arthritis treatments, and the like may be carried, but are not limited thereto.

Meanwhile, as a cosmetic, a serum, a basic nutritional agent, hyaluronic acid, botox, an acne treatment, an anti-wrinkle agent, a whitening agent or a hair loss treatment agent may be supported, but is not limited thereto.

Alternatively, for the purpose of promoting transdermal administration, after the drug or cosmetic is applied, a microneedle patch may be attached to the corresponding area.

In this case, the microneedle may be made of a material that is decomposed by heat above body temperature so that it can be decomposed when attached to the skin or implanted in the body.

The metal thin film according to the present invention generates heat when irradiated with visible light, thereby promoting decomposition of the microneedles.

On the other hand, the patch can be attached to the skin-adhesive substrate to facilitate attachment to the skin, and as described above, the metal thin film contained therein can promote the decomposition of the microneedle by generating heat by receiving visible light. , The substrate is preferably visible light transmittance, but is not limited thereto.

Furthermore, the present invention can provide a skin cosmetic active device including a metal thin film manufactured by the above method and a light source providing visible light.

For example, when the skin temperature is increased by massage or the like, it is known to promote blood circulation or metabolism, and to improve skin regeneration, elasticity and complexion. Accordingly, the metal thin film prepared by the method of the present invention exhibits an effect of generating heat when irradiated with visible light, and thus can be used in a device for skin cosmetic activation.

As the light source providing the visible light, not only a device designed to generate light of a specific wavelength or light of a specific wavelength range selected from a visible light region, that is, a wavelength range of 400 nm to 700 nm, but also a device such as sunlight Living light such as natural light or lighting that can be easily encountered in everyday life can be used without limitation.

Since the ultra-thin metal film prepared by the method of the present invention can exhibit electrical conductivity even when formed to a thickness of 10 Å or less, it can be used for an electrode for realizing an ultra-fine circuit, and can exhibit a heating effect by irradiation with visible light without power supply. In addition, since it is biodegradable when implemented as an ultra-thin type, it can be used in a skin beauty heating device.

1 is a diagram schematically showing a method of manufacturing a metal thin film and a mechanism of action thereof according to the present invention. (a) shows a process for forming a functional group layer treated with Si-OH on one surface of graphene. (b) shows the Raman spectrum before/after _{UV/O 3 treatment after applying PDMS.} (c) denotes the contact angle of the graphene thin film supported by the Si-OH functional group layer (bottom) before (top)/after (stop) and photooxidation (photooxidation) reactions, respectively, of the graphene thin film. (d) shows the process of transferring the graphene thin film supported by the Si-OH functional group layer to the TEM grid and depositing the metal. (e) shows a high-resolution transmission electron microscopy (HRTEM) image of gold deposited to a thickness of 3 Å on a pure graphene layer not supported by a Si-OH functional group. (f) is a diagram schematically showing the impossibility of depositing gold on pure graphene domains. (g) shows the HRTEM image of gold deposited to a thickness of 3 Å on the graphene layer supported by the Si-OH functional group layer. (h) schematically shows the gold nucleation process in the graphene domain supported by the Si-OH functional group layer.
2 is a diagram showing gold nucleation on pure graphene domains. (Top) and (Bottom) represent HRTEM images on the bilayer graphene and at the boundary between the single layer and the bilayer graphene, respectively. It can be seen that no nucleation occurs in both graphene domains regardless of the number of graphene layers.
3 is a diagram showing a mechanism for explaining the impossibility of nuclear growth of gold in the pure graphene domain. Specifically, on the graphene surface, the surface diffusion power of gold is very high, so that it moves to a relatively highly reactive contaminated portion, and thus, nuclear growth occurs only in that portion.
4 is an image of a phenomenon in which the gold particles move in real time due to the energy of TEM electron beam irradiation because the surface diffusion power of gold particles in the graphene domain is very high (time interval between images is 0.6 seconds).
FIG. 5 is a real-time photograph of an enlarged conversation between gold particles that have been moved for the same reason as in FIG. 4.
6 is a diagram showing the crystal form of gold particles grown on the graphene domain. Gold particles grown on graphene domains supported by a Si-OH functional group showed a single crystal shape, whereas gold particles grown in contaminated areas showed a polycrystalline shape even at a small size.
7 is a diagram showing an HRTEM image and an FFT pattern for a Si-OH functional layer and a graphene domain formed on the functional layer in the graphene domain supported by the Si-OH functional layer. (a) shows the difference in the HRTEM image according to the deposition pattern of the Si-OH functional group layer. (b) shows an HRTEM image in which graphene and a Si-OH functional group layer supporting the same were observed at the same time and an FFT pattern corresponding thereto. (c) is an EDS result showing an increase in the Si content according to the application of the Si-OH functional group layer.
8 is a diagram showing gold nuclei growth on a graphene template supported by a Si-OH functional layer. (a) shows a schematic diagram of a three-dimensional stacking of gold nanoparticles, a graphene layer, and a Si-OH support layer. All of (b) to (d) show HRTEM images representing epitaxial growth of gold nanoparticles and graphene layers and corresponding FFT pattern images. (e) shows the selective growth of gold nanoparticles in the center of the graphene domain supported by the Si-OH functional layer. (f) shows the process of uniform nuclear growth of gold atoms whose surface diffusivity is lowered due to the Si-OH support layer at a certain point, and when 7 arbitrary coordinates within the domain are set, the point where nuclear growth occurs is these points. This is the point where the sum of the distances from is the minimum value. (g) shows single crystal gold nanoparticles grown on graphene supported by the Si-OH functional group layer.
9 is a diagram showing the conductivity of a gold thin film grown on a graphene template supported by a chemical functional group according to the present invention. (a) shows the process of forming an ultra-thin metal electrode using a graphene template. (b) shows a digital image obtained after applying a 6 nm gold electrode on a graphene template (inside) and a sample in which the graphene template is absent (outside). (c) shows the UV-VIS spectrum in the region corresponding to each of (b). (d) shows the SEM image of the gold electrode at the boundary of the graphene template. (e) represents the electrical resistance measured in the region corresponding to (d) above. (f) shows the Raman spectrum of graphene measured before and after the gold electrode was deposited once on the graphene template and transferred. (g) is a digital image showing the process of forming and transferring electrodes on the graphene template. (h) is a chemical functional group supporting the graphene domain, a process of shortening the minimum electrical filtration critical thickness on the support layer containing perfluoroalkyl groups, thiol groups and hydroxy groups through different surface treatments, resistance according to the thickness of the thin film It is an AFM image showing the (inverse proportion to conductivity) and the morphology of the thin film formed at this time. (i) is a diagram schematically showing a voltage-driven heat generating device using an ultra-thin metal film. (j) shows the temperature change measured while increasing the voltage over time. The gold thin film according to the present invention exhibits a temperature of about 55° C. at 8.5 V. (k) A non-electrical drive type metal ultra-thin heat generating device using visible light and a schematic applied to accelerate the disassembly of the skin beauty patch. (l) is an image showing the temperature increase in the heat generating device provided with the thin film according to the present invention upon irradiation with visible light. (m) shows the acceleration of the microneedle decomposition rate for skin beauty by the ultra-thin metal heat generating device. (n) represents the biodegradation rate of the ultra-thin metal film over time.
10 is a diagram showing a difference in electrical resistance values of an ultra-thin metal film in a region with and without a graphene template.
11 is a diagram showing a change in the minimum electrical filtration critical thickness of a silver electrode formed on a graphene template supported or not supported by different chemical functional groups.
12 is a diagram showing an initial screen of a moving picture in which a temperature increase due to an ultra-thin metal film is observed in real time.

Hereinafter, the present invention will be described in more detail through examples. These examples are for explaining the present invention more specifically, and the scope of the present invention is not limited by these examples.

Experimental example 1: Characterization

Raman spectra were measured with a confocal Raman microscope (inViaTM, RENISHAW). To analyze the shape of the metal electrode, AFM (Digital instruments Nanoscope, Veeco ^® ) in tapping mode was used. The critical domain size for homogeneous nucleation was evaluated using image processing software (ImageJ, NIH). The transmittance of the metal electrode was measured with a UV-Vis spectrophotometer (LAMBDA 650). In order to observe the degradable property, field emission SEM (Hitachi S-4800) was used. The temperature measurement of the biomedical heater was performed using a thermal imaging IR thermometer (TG165 and T440, FLIR).

Example One: Graphene Synthesis of templates

Graphene was prepared on a 4.8 μm-thick copper thin film (Alfa Aesar) by low pressure chemical vapor deposition (CVD). Prior to the synthesis, the copper thin film was washed by immersing it in a nickel etchant (Transene, TFB). Specific growth conditions are as follows. First, a copper thin film was put in a reactor, and after reduced pressure, it was heated to 1000° C. and annealed for 20 minutes under _{100 sccm H 2 conditions.} In order to promote graphene growth, 30 sccm CH ₄ and 30 sccm H ₂ were introduced for 40 minutes. The furnace was cooled to room temperature.

Example 2: chemically supported ( Si -OH) Graphene

First, a polydimethylsiloxane (PDMS) base (SYLGARD ^® 184, Dow corning) was spin-coated at 500 rpm for 30 seconds on a silicon wafer. Graphene grown on a copper thin film was placed on a silicon wafer coated with PDMS, having two spacers (1.6 mm). For vaporization of the PDMS precursor, the sample was heated to 150° C. and maintained for 1 hour. After completing the PDMS coating, the sample _{was exposed to UV/O 3} for 5 minutes. UV/O ₃ Under irradiation, the PDMS layer was completely converted to _{a thin SiO x} layer with Si-OH at the end. To form metal nanocrystals, a SiO _x coated graphene/copper thin film was ^{transferred directly onto an Au QUANTIFOIL ®} TEM grid.

Using the photochemically oxidized siloxane layer, graphene supported by chemical (Si-OH) was prepared as follows (FIG. 1A). First, an ultra-thin polydimethylsiloxane (PDMS) layer having a thickness of several nm was deposited on graphene grown on a copper thin film through a vapor deposition method without the addition of a compound such as a solvent, an initiator or a linker. In _{order to convert to SiO x} , the PDMS-coated graphene sample was exposed to UV light for 5 minutes, and the organic PDMS was converted to _{inorganic SiO x through photochemical oxidation.} Photochemical conversion was confirmed step by step through Raman analysis (Fig. 1b) and contact angle measurement (Fig. 1c). At 497.5 and 647.6 cm ^-1 , the Si-CH ₃ symmetric peaks of PDMS were observed before oxidation, but _{completely disappeared in SiO x} photooxidized by substitution of Si-OH from Si- _{CH 3} after the reaction (Fig. 1b inset. ). PDMS-related peaks changed noticeably before and after photooxidation, while ^{the 2D and G peaks of graphene at 2665.1 and 1582.39 cm -1} were maintained during the process (Fig. 1B). Due to the hydrophobicity of CH ₃ in PDMS as well as _{the hydrophilicity of Si-OH in the SiO x} layer, the formation of Si-OH groups at the bottom of graphene was demonstrated by measuring the contact angle before and after the photooxidation reaction. Before PDMS coating, the untreated graphene exhibited a value of about 70°, but the contact angle after coating increased to about 90°. As the PDMS _{was converted to SiO x} , the contact angle was again lowered to 20° (Fig. 1c). This indicates that Si-OH groups were well formed on the entire surface of graphene from a macroscopic point of view.

Example 3: formation of metal crystals

Both supported and unsupported graphene on the TEM grid were simultaneously injected into a thermal evaporator chamber (Edwards vacuum). Initially, the chamber ^{was depressurized to 2.0×10 −6} mbar, and pure gold pellets (99.999%, iTASCO T) were placed in a molybdenum boat (iTASCO), and then evaporated with a current of 55 A. Deposition was performed at room temperature (300K) without heating or cooling. The thickness of the thin film was monitored with a quartz crystal microbalance (QCM).

Next, place both Si-OH supported graphene and un-supported graphene (e.g., pure graphene) on the Au QUANTIFOIL ^® TEM grid for metal deposition leading to TEM analysis. Suspended. In order to prevent contamination of the graphene surface during the transfer process, as shown in FIG. 1D, a direct (polymer-glass) transfer method was used.

1E shows a high-resolution TEM (HRTEM) image of an unsupported graphene domain after depositing gold to a thickness of 3Å by thermal evaporation. The diffraction pattern shown in the inset represents the defect-free [10-10] crystal plane of the single-layer graphene domain. Gold nanoparticles were grown along the edges contaminated with unwanted hydrocarbons, while few nanoparticles appeared on the defect-free graphene domains. In addition, there was no nucleation growth of gold nanoparticles even on the bilayer graphene domain (FIG. 2). According to classical nucleation theory, nucleation and growth are determined by two factors, thermodynamic and kinetic. Under thermodynamic equilibrium, nucleation is entirely determined by the surface energy. Since the surface energy of pure graphene without defects is lower than that for the gold surface, non-uniform nucleation in that region is not energetically favored. In addition, in the case of an actual thermal evaporation process, there is no thermodynamic equilibrium, and thus, vaporized gold atoms accessing the graphene domain can surface migrate across the inactive graphene domain to the edge region (FIGS. 1F and 3). . Dr. Anton's research has shown that metal atoms are highly mobile on the graphene surface (Anton, R.; Schneidereit, I., Phys. Rev. B, 1998, 58: 13874-13881), which is similar to that in the present invention. Coincided. However, in the present invention, also high surface diffusion was observed even in a larger metal cluster. 4 and 5 show in-situ fusion of two forms, that is, liquid-like and solid-like fusion, caused by surface diffusion of gold nanoclusters in the graphene domain. (coalescence) is shown. Liquid-like fusion based on mass-transfer was observed in clusters of small size, not only on the graphene surface but also on the general substrate. As the clusters grow larger, the solid-like fusion that occurs between gold nanoparticles of different crystal structures is not involved in mass transfer. There was only necking and broadening at the boundary. However, in the case of the graphene surface, the larger gold clusters moved along the graphene surface due to high surface diffusivity, and the size could be increased (FIG. 5).

1G shows a high-resolution TEM (HRTEM) image of gold nanoparticles grown on Si-OH supported graphene domains after depositing gold to a thickness of 3Å. Unlike the nanoparticles grown in the corners, all gold nanoparticles grown in the graphene domain showed a single crystal (FIG. 6). In general, nucleation occurs at more than one nucleation site, so uniform nucleation can lead to polycrystalline growth. Therefore, it was assumed that the single crystal growth on the supported graphene domain would result in uniform nucleation without uneven nucleation sites as in the case of uniform solution growth (Fig. 1h).

In order to explain the mechanism and detailed observation of the uniform nucleation on the supported graphene, the optimization conditions for the single layer coating of the _{SiO x layer having the Si-OH functional group at the terminal were confirmed using HRTEM images.} 7A shows HRTEM images of graphene domains including _{SiO x} layers of different thicknesses. For the Fast Fourier Transform (FFT) analysis, an appropriate region in which both the lattice domain of the single-layer graphene and the single-layer-like Si-OH layer supporting the rear surface can be observed at the same time was selected (Fig. 7A). Center image). 7B shows an HRTEM image (left) and a corresponding diffraction pattern (right, inset is a simulation image). The graphene pattern of [10-10] and _{the cyclic pattern of amorphous SiO x} appeared in synchrony, indicating that the graphene domain is well maintained under the support of _{amorphous SiO x from the bottom surface.} As such, this is also consistent with the above-described Raman analysis results (FIG. 1B). In addition, energy-dispersive X-ray spectroscopy (EDS) element mapping analysis (Fig. 7c) and atomic concentration profile on Si-OH supported graphene domains. (Fig. 7d) shows an increase in the Si component from about 0% to 0.14% compared to the non-supported graphene domain.

The back side supporting maintains the original lattice structure of graphene and enables the growth of the metal thin film along the lattice in the epitaxial plane. In particular, since conventional metals tend to grow in the form of three-dimensional isolated islands due to high cohesive energy, it has been difficult to form a continuous layer within a low deposition thickness. The deconvolutional image of HRTEM shown in FIG. 8A is a graphene template with three or four layers of single crystal gold nanocrystals, an un-deteriorate crystal graphene template, and a Si-OH terminal with a supported graphene template. The epitaxial in-plane growth results including the amorphous SiO _{x supporting layer were clearly shown.} More specifically, the epitaxial in-plane growth between the grown gold nanocrystals and graphene was decomposed by FFT analysis. 8B, 8C and 8D show HRTEM images and FFT patterns of triangular, polyhedral and rod gold nanocrystals. Regardless of the shape and size of the gold crystal, the gold (111) crystal plane was epitaxially aligned with the graphene (10-10) substrate through minimization of lattice mismatch. The mismatch angles measured between each gold crystal and graphene template were all less than 1° for triangular, polyhedral and rod-shaped gold nanocrystals.

On the other hand, the present inventors confirmed that the position of the gold crystal is always located in the center of the graphene domain (Fig. 8e). _{If the support of the SiO x} layer containing the Si-OH group at the lower end of the graphene domain allows the thermodynamic nucleation site to be transferred through the graphene monolayer through the mechanism of transparency, nucleation and growth are carried out in the entire area of the graphene surface. Can occur. Thus, this geometrically selective growth may also be evidence that chemical support induces kinetically controlled uniform nucleation rather than thermodynamic nucleation. The inventors hypothesized that if an atom reaching a distance from the edge portion is kineticly limited by the support, kinetic energy required for surface diffusion may be lost. If the above assumption is true, then these atoms may prefer to nucleate together with other atoms in the same situation through uniform nucleation. To confirm this assumption, arbitrary 1 to 7 positions in the graphene domain were selected for the image of FIG. 8F, and contour plots were drawn from these positions. As a result, as shown in FIG. 8F, the center position of the grown gold crystal was exactly the same as the darkest part of the contour line. This point indicates that the sum of distances from each selected position is the only point with the smallest value. The distance from each location is a ₁ , a ₂ ,... and a ₇ (FIG. 8F). Furthermore, whether or not uniform growth occurs is determined by the size of the clean graphene domain. FIG. 8G shows the critical size of the domain, and it was confirmed that ^{less than 1172 nm 2} did not induce uniform crystal growth due to the proximity of the location of the metal atom to the defect site. This indicates that if a perfectly pure graphene layer with no defect spots is implemented, crystal growth covering the entire graphene surface can be possible.

In the development of various advanced optoelectronics, ultra-thin metal electrodes with low filtration critical thickness have been required. Uniform nucleation and epitaxial in-plane growth on the graphene template enabled the manufacture of ultra-thin metal electrodes including chemically modified supporting substrates. As shown in FIG. 9A, first, a graphene template was prepared using a chemical vapor deposition (CVD) method, and then transferred onto a chemically modified supporting substrate by a conventional transfer method. An ultra-thin metal electrode was deposited within the percolation thickness on the supported graphene substrate by a thermal evaporation method. After the deposition was completed, the ultra-thin metal electrode was transferred to another desired substrate using a commercial adhesive medium. This indicates that the graphene template can be reused. 9B shows a digital image of a gold electrode deposited on a graphene template to a thickness of 6 nm. Although the graphene template itself had an absorption rate of 3.0%, the metal thin film area (inside the gray dashed line box) formed on the graphene template showed 5% higher visible light transparency than the growth portion without the template. In general, a gold thin film on a solid substrate exhibits a localized surface plasmon resonance due to its low transmittance in the visible region. The high transmittance of the metal thin film grown on the graphene template indicates that the graphene template induces the growth of a uniform continuous layer shape rather than the growth of a non-uniform isolated island shape, as shown in FIG. 9C. The SEM image clearly shows the different morphology at the grain boundary (Fig. 9d). The effect of the graphene template on the growth behavior can be attributed to the lowering of the filtration critical thickness due to the improvement of the electrical properties. The filtration critical thickness is an important parameter to implement a translucent metal electrode. As shown in FIGS. 9E and 10, the metal grown without graphene did not exhibit conductivity, whereas the metal thin film grown on graphene exhibited excellent conductivity even at the same thickness (6 nm). Even after completing the growth and transfer of the metal electrode, the Raman spectrum of the graphene template was similar to the strum recorded for the initial graphene template, which is graphene during the growth/transfer process, as shown in FIGS. 9F and 9G. This indicates that the quality of the template has not been degraded. From the above results, it was confirmed that graphene can be used as a hard and reusable template, which is a distinguishing advantage over other methods for providing a metal wetting inducer reported previously.

Example 4: Degradable Biomedical heater

The microneedle patch was obtained from Raphas ^®. Each patch before and after the penetration test was visually inspected under a microscope (LSM 5 EXCITER, ZWEISS). For photothermal heating, a microneedle patch supported by an ultra-thin metal heater was exposed to a halogen studio lamp (AlienBeesTM B1600, Paul C. Buff, INC). In the patch penetration test, lenofoam (a very pharmaceutical product) was introduced into the artificial skin. The ultra-thin metal electrode was immersed in an acidic solution (0.2 M FeCl ₃ ), and the change in shape with increasing immersion time was observed by SEM.

In order to confirm the possibility of utilizing the degradable ultra-thin metal electrode as a translucent biomedical heater, the temperature was measured while increasing the applied voltage. A schematic diagram of the measuring device is shown in Fig. 9i. 9J shows the temperature increase from 8.5V to 55°C, which is a sufficient value for application in heat-assisted skin care. On the other hand, the ultra-thin metal thin film exhibited thermal characteristics by local heating of LSPR in the visible light region. This property enables the metal thin film to produce useful thermal energy by visible light that exists in everyday life without supplying an external voltage. To confirm this, the light-heating effect on the degree of permeance of commercial microneedle cosmetics for skin care was confirmed. Figures 9i and 9k show schematic diagrams for this measurement. 9I and 12, the temperature of the microneedle patch to which the metal electrode is attached increased to 38.4°C as soon as it was exposed to the lamp. 9M shows the photothermal effect on microneedle dissolution after the patch is penetrated into artificial skin for 30 minutes. The length of the microneedles on the thermal heater is at least 210 μm, indicating that the ultra-thin metal heater improves penetration and dissolution of cosmetic needles in artificial skin. On the other hand, in the absence of the ultra-thin metal heater, the solubility increased by only 12% compared to the sample in which only the pure microneedle patch was present without the metal heater. Although the metal electrode is a useful material for a heater, it does not dissolve or decompose easily in a mild condition, causing a waste problem that is not always environmentally friendly when discarded after use. However, it was confirmed that the ultra-thin gold thin film according to the present invention was completely decomposed within 3 hours in a mild acidic solution, as shown in FIG. 9N. This is considered to be because the ultra-thin thickness allows most metal atoms to have high surface chemical reactivity. The degradable property may be one of the distinguishing advantages of the possibility of use as a tattoo or implantable electrode in the biomedical field.

Example 5: variously chemically Modified SiO ₂ materials

The thermally oxidized SiO ₂ /Si substrate _{was treated with O 2} plasma (Femto Science) at room temperature at 55W for 60 seconds. Thereafter, various chemical terminal functional groups on the substrate were immersed in 0.5 wt% aqueous solution of 1H,1H,2H,2H-perfluorodecyltriethoxysilane and (3-mercaptopropyl)trimethoxysilane for 30 minutes at room temperature. Was introduced. The remaining unreacted silane solution was washed 3 times with distilled water. In order to provide a sample having a Si-OH terminal functional group, the SiO ₂ /Si substrate was treated only with _{O 2} plasma without an additional chemical coating process. Self-were purchased from SigmaAldrich ^® used in the coating stage ilbunjacheung assembled.

9H shows the dependence of the filtration critical thickness on the chemical functionality of the lower substrate of the graphene template. The resistance of the sheet (solid black line) on the bare SiO _{2 substrate showed a filtration critical thickness of 8 nm.} However, on the graphene substrate supported by the substrate chemically modified by Si-OH (solid red line), MPTMS (solid blue line) and fluoroalkylsilane (FAS) (solid orange line), values of 6 nm, 5 nm and 5 nm were respectively Indicated. This indicates that the electronic perturbation of the graphene template is dependent on a specific chemical terminal functional group. In particular, since metal-thiol bonds are well known for specific interactions, the thinnest filtration critical thickness with the lowest sheet resistance was achieved at the 5 nm level on the substrate supported by MPTMS. The morphological AFM data in FIG. 9H showing an ultra-smooth surface of a gold thin film grown on MPTMS, but forming a non-percolated and isolated surface on an _{untreated SiO 2 substrate is also the result.} Supported. In addition, it was confirmed that the effect of the graphene substrate can be applied to other metals. 11 shows the filtration critical thickness of the silver thin film as a function of the deposition thickness.

Example 6: Transfer of ultra-thin metal electrodes

The deposition of the ultra-thin metal electrode on the graphene substrate was transferred by a contact printing method. The PDMS slab was brought into contact with the metal electrode. After completing conformal contact, the PDMS piece was removed from the substrate. The metal electrode was transferred to the surface of the PDMS piece due to the low adhesion between the metal electrode and the graphene template. A piece of PDMS supporting an ultra-thin metal electrode was brought into contact with another receiver substrate and heated to 60°C. After 5 minutes, the PDMS piece was retraced for transfer-printing.

<Conclusion>

The present inventors, by introducing homogeneous nucleation and epitaxial in-plane growth on chemically supported monomolecular layer graphene, a strong growth template for obtaining ultra-thin and smooth-surface metal electrodes Was excavated. Interestingly, the chemical supporting underneath the monolayer graphene can only contribute to the kinetic suppression of gold atoms, but the intrinsic graphene that can induce epitaxial in-plane growth through minimization of lattice mismatch. It is not possible to change the deformation or damage of the pin grid. Surface potential barrier calculations based on DFT (Discrete Fourier transform) can explain the inhibited surface diffusion of gold atoms by electrically disturbed graphene. In order to show the possibility of graphene as a versatile thin film growth template, it was developed as an ultra-thin translucent metal electrode. Such ultra-thin metal electrodes provide a new method of manufacturing degradable metal heaters to provide implantable and tattooable electrodes in various biomedical fields such as skin care, thermal therapy, and artificial e-organs. do.

Claims (12)

A solid substrate having a chemical functional group on at least one side; And a first step of preparing a template including a single layer graphene formed on a surface containing a functional group of the solid substrate. And
Including a second step of forming a metal thin film on the single-layer graphene of the template,
In the second step, kinetically controlled nucleation is induced by using the chemical transparency of the single-layer graphene to form the metal thin film,
The induction of kinetically controlled nucleation using the chemical transparency of the single-layer graphene performed in the second step is between the chemical functional groups of the solid substrate provided under the single-layer graphene and the metal atoms forming the metal thin film. A method of manufacturing an ultra-thin metal thin film having a thickness of 3 to 200 Å, wherein crystal growth is promoted in a nucleus that has already been formed rather than forming a new nucleus by the interaction.
The method of claim 1,
The method of manufacturing the metal thin film is continuously formed without grain-boundaries.
The method of claim 1,
The method of manufacturing the solid substrate by thermally oxidizing the silica substrate or treating with oxygen plasma to have a hydroxy group as a chemical functional group.
The method of claim 3,
The method of manufacturing the solid substrate having a hydroxy group is treated with a mercaptoalkylalkoxysilane or a perfluoroalkylalkoxysilane, respectively, to have a thiol group or a perfluoroalkyl group, respectively, as a chemical functional group.
The method of claim 1,
The manufacturing method further comprising a third step of separating the metal thin film formed in the second step using an adhesive substrate.
The method of claim 5,
After separating the metal thin film, the remaining substrate is reused as a template in the first step.
A microneedle patch comprising a metal thin film manufactured by the method of any one of claims 1 to 6 and one or more microneedles attached to one surface thereof.
The method of claim 7,
The microneedle is a patch that carries a drug or cosmetic.
The method of claim 7,
The patch that the microneedles are decomposed by heat above body temperature.
The method of claim 7,
The metal thin film is a patch to promote the decomposition of the microneedle by generating heat when irradiated with visible light.
The method of claim 7,
The patch is a patch that is attached to the visible light-transmitting skin-adhesive substrate.
A skin cosmetic active device comprising a metal thin film manufactured by the method of any one of claims 1 to 6 and a light source providing visible light.

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