KR101030434B1 - Method for formation of nanoholes using carbothermal reduction - Google Patents

Abstract

Forming an insulating layer on the substrate; Depositing metal or transition metal particles on the insulating layer; And forming nano holes in the insulating layer by a carbon thermal reduction reaction of the insulating layer having the metal particles formed thereon.

Carbon Molten Reduction, Nanoholes, Iron Nanoparticles, Arrays, Block Copolymers

Description

Method for formation of nanoholes using carbothermal reduction

The present invention relates to a simple chemical method that can directly produce nanometer-sized holes in an insulating layer without the use of toxic chemicals required for etching, complex pretreatment and expensive mechanical equipment.

Over the past two decades, ongoing efforts to develop new chemical synthesis methods for the synthesis of quantum-sized functional nanomaterials have led to the manufacture of nanomaterials of various sizes and shapes. The performance of next-generation electronics, such as memory, nanosensors, optoelectronic devices, and energy conversion systems, has been significantly improved. Among representative examples for synthesizing nanomaterials, solution chemistry is generally used successfully for the synthesis of 0-dimensional nanocrystals of metals and semiconductors, while chemical vapor deposition (CVD), gas phase Vapor-liquid-solid (VLS) and vapor-solid (VS) methods are mainly used for synthesizing one-dimensional materials, nanotubes, wires, belts and ribbons. More recently, modified VS methods have been applied to organic precursor molecules, resulting in unprecedented spiral organic ribbons and C ₆₀ single crystalline nanodisks.

One of the processes that need to be carried out to utilize synthesized nanomaterials as industrially and industrially meaningful systems is to arrange them in a systematic pattern. Several physicochemical surface shielding techniques have been used to align nanomaterials, including Langmuir-Blodgett and surface-programmed assemblies. Of these structures, nanohole arrays have received particular attention because they serve as direct sources for implementing integrated quantum memory devices and surface plasmon resonance sensors. Nanoholes are also available as nano-hosts for single molecule spectroscopy, artificial channels for the movement of incoming and outgoing ions and single biomolecules, and as zeptoliter beakers, nanometer-sized reactors. . To date, the arrangement of nanoholes has led to colloidal lithographic etching, nanoimprint lithography, the use of anodized aluminum oxide templates, and optical lithographic patterning based on block copolymers. Block copolymer-based optical lithographic patterning processes have been reported. However, these methods require time-consuming and complicated processes, and a new method of "directly" forming nanohole arrays having a diameter of 20 nm or less is urgently needed.

Recently, the inventors have discovered a new surface reaction which takes place between single layer carbon nanotubes (SWNT) and SiO ₂ surface (called carbon melt reduction. Korean application: 2007-0001626). According to the present reaction, the SiO ₂ surface may be thermochemically reacted with SWNTs to form SiO ₂ nano trenches having a width of 10 nm or less etched along the trajectories of the SWNTs. The inventors intend to apply this method to directly form nanoholes by inspiration from melting of SiO ₂ . As a result of in-depth study of the mechanism of carbon melt reduction, the inventors found that iron-catalyzed nanoparticles (NP) not only play a critical role in the growth of SWNTs but also play an important role in initiating carbon melt reduction. This means that an amorphous carbon or graphite layer surrounding iron NP can thermally promote the reduction of the SiO ₂ substrate, resulting in the formation of SiO ₂ nanoholes (C (on iron NP, s) + SiO ₂ ). (s) ↔ SiO (g) + CO (g)). In the present specification, the present inventors report the formation of nano holes having a diameter of 10 nm or less by inducing carbon melt reduction of SiO ₂ via iron NP. In addition, we report the successful fabrication of nanohole arrays formed from iron NPs arranged using block copolymer patterns.

When the substrate of the insulating layer on which the metal catalyst particles are deposited is reacted with oxygen, hydrogen, and hydrocarbon gases using chemical vapor deposition at a high temperature (> 700 ° C.), not only carbon nanotubes are formed, but the formed nanotubes are substrates of the insulator surface. It has been reported by the present inventors to reduce and form nanotrenches. The shape, width and length of the resulting nano trenches were observed to be consistent with those of the previously formed nanotubes, which were found to be due to carbon thermal reduction.

The technical problem to be achieved by the present invention is to provide a method for directly forming a nano-sized nano-hole directly in the insulating layer through a simple chemical method without the use of toxic chemicals, complicated pretreatment and expensive mechanical equipment required for etching will be.

The present invention to achieve the above technical problem,

Forming an insulating layer on the substrate;

Depositing metal or transition metal particles on the insulating layer;

Forming a carbon layer in contact with the metal particles; And

Carbon nano reduction of the insulating layer to form nano holes;

It provides a method for forming nano holes in the insulating layer comprising a.

According to one embodiment of the invention, the metal or transition metal particles are polymers, block copolymers, surfactants, micelles, micelles, Languir-Blodgett technology, surface-programmed assembly, solution evaporation method or Alignment through the step edge of the substrate, the use of electromagnetic fields, and the like.

According to one embodiment of the present invention, the nano holes of the insulating layer may be formed with a pattern.

According to one embodiment of the invention, the substrate is preferably selected from the group consisting of silicon wafer, sapphire, glass, quartz, metal, alumina, and plastic.

According to one embodiment of the present invention, the insulating layer is preferably formed of a compound containing silicon.

According to one embodiment of the present invention, the insulating layer is preferably formed of at least one selected from the group consisting of silicon oxide, silicon dioxide, silicon nitrate, and silicon nitride.

According to one embodiment of the present invention, the metal or transition metal particles are nickel (Ni), iron (Fe), cobalt (Co), yttrium (Y), molybdenum (Mo), aluminum (Al), rhodium ( Rh), rubidium (Ru), palladium (Pd), gold (Au), silver (Ag), copper (Cu), magnesium (Mg), chromium (Cr), manganese (Mn), tin (Sn), platinum ( Pt) or an alloy thereof is preferable.

According to one embodiment of the invention, the metal or transition metal particles are preferably deposited using spin-coating, solution injection and evaporation, metal deposition, sputtering or lithography.

According to one embodiment of the present invention, the carbon layer forming step and the carbothermal reduction step in contact with the metal particles may occur simultaneously.

According to one embodiment of the present invention, the carbon layer forming step and the carbon melt reduction step contacting the metal particles are preferably performed while simultaneously injecting hydrogen, argon and alcohol.

According to one embodiment of the invention, the content of the alcohol is preferably 0.01 to 70% of the total gas volume.

According to one embodiment of the present invention, the carbon layer forming step and the carbon melt reduction step contacting the metal particles are preferably performed while injecting water or oxygen, hydrogen, argon and hydrocarbon simultaneously.

According to one embodiment of the invention, the content of water is 0.01 to 10% of the total gas volume, the content of oxygen is preferably 0.01 to 5% of the total gas volume.

According to one embodiment of the invention, the carbon layer is preferably formed on the metal particles through a chemical reaction on a carbon-containing gas injecting a carbon source gas at 400 to 1500 ℃ or from 0 to 300 ℃ .

According to one embodiment of the invention, the carbon layer on the metal particles is preferably injected at the same time the solution phase containing the carbonization source gas and carbon group.

According to one embodiment of the present invention, the carbon layer on the metal particles may be formed through a chemical reaction of a polymer, a block copolymer, a surfactant, or a micelle on a solution.

According to one embodiment of the present invention, the metal or transition metal particles have an average diameter of 0.5 to 1000 nm, the nano holes of the insulating layer preferably has an average width of 0.5 to 1500 nm.

According to one embodiment of the invention, the carbon melt reduction reaction is preferably made while injecting oxygen and inert gas.

According to one embodiment of the invention, the content of oxygen is preferably 0.0001 to 30% of the total gas volume.

According to one embodiment of the invention, the carbon melt reduction reaction is preferably made at a temperature of 700 to 1700 ℃.

Hereinafter, the present invention will be described in more detail.

As described above, the method for forming nano-holes in the insulating layer using the carbon melt reduction reaction of one aspect of the present invention,

Forming an insulating layer on the substrate;

Depositing metal or transition metal particles on the insulating layer;

Forming a carbon layer in contact with the metal particles; And

And carbon nano reduction of the insulating layer to form nano holes.

In the present invention, the nano-holes formed in the insulating layer is induced by the metal or transition metal particles deposited on the insulating layer, so whether the arrangement of the nano holes is random according to the random arrangement or regular arrangement of the metal particles Perception is determined. It is more preferable to arrange the nano holes to have a pattern because a regular arrangement is more useful than a random arrangement of nano holes.

Many methods of aligning nanoparticles are known. According to one embodiment of the invention, the metal or transition metal particles are polymers, block copolymers, surfactants, micelles (micelle), Languir-Blodgett technology, surface-programmed assembly, solution evaporation method, It can be aligned through the step edge of the substrate, the use of electromagnetic fields and the like. The alignment (or pattern) includes not only geometric shapes such as line, hexagon, rectangle, triangle, etc., but certain units are repeated.

According to the exemplary embodiment of the present invention, the nano holes of the insulating layer may have a pattern. As will be described later, since the nano holes are generated by the melt-melting reduction reaction between the insulating layer and the carbon layer in the place where the metal particles were located, it can be predicted that the nano holes generated when the metal particles are arranged to be aligned on the insulating layer also have a predetermined pattern. Can be.

Next, the step of forming the insulating layer on the substrate will be described in detail.

The substrate is not particularly limited, and specific examples thereof include silicon wafers, sapphire, glass, quartz, metals, alumina, plastics, and the like.

The insulating layer is not particularly limited as long as it is a compound containing silicon, but may be formed of at least one selected from the group consisting of silicon oxide, silicon dioxide, silicon nitride, and silicon nitride. In this case, when the insulating layer is made of silicon dioxide, it is more preferable because of the high efficiency of nano hole formation according to the carbon melt reduction reaction.

Thereafter, after forming the insulating layer on the substrate, the insulating layer is deposited on the metal or transition metal particles, the metal or transition metal particles are nickel (Ni), iron (Fe), cobalt (Co), yttrium (Y), molybdenum (Mo), aluminum (Al), rhodium (Rh), rubidium (Ru), palladium (Pd), gold (Au), silver (Ag), copper (Cu), magnesium (Mg) , Chromium (Cr), manganese (Mn), tin (Sn), platinum (Pt) or alloys thereof, spin-coating, solution injection or evaporation, metal deposition, sputtering Or a lithographic method or the like.

Now, the carbon melt reduction reaction for etching nano holes in the insulating layer will be described.

The nano hole of the insulating layer is formed by a carbon thermal reduction reaction between the carbon layer in contact with the metal particles and the insulating layer formed on the substrate, the reaction is chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), thermochemical vapor deposition, and vapor phase synthesis.

In one embodiment, the main driving force for forming nano holes in the SiO ₂ layer, which is an insulating layer, is a SiO ₂ carbon melting reduction reaction in which a carbon layer in contact with the metal particles on the insulating layer serves as a reducing agent. The carbon layer (C) serves as a reducing agent to reduce and etch the insulating layer. For example, amorphous bulk silica (SiO ₂ (s)) emits SiO (g) and CO (g) as shown in the following formula, thereby reducing by carbon (C (s)) at least 1000 ° C. and under atmospheric pressure. It is known to become.

SiO ₂ (s) + C (s) ↔ SiO (g) + CO (g)

In the above formula, carbon from the carbon source serves as C (s) to thermally reduce SiO ₂ .

Therefore, in the step of forming nano holes in the insulating layer by a carbon thermal reduction reaction of the insulating layer on which the metal particles are formed, a carbon layer contacting the metal particles is first formed. The carbon layer is produced, for example, as an amorphous carbon or graphite layer, preferably in contact with the periphery of the metal particles.

The step of forming a carbon layer in contact with the metal particles and a carbon thermal reduction reaction may occur simultaneously. Therefore, there is an advantage that it is possible to form nano holes of the insulating layer while reducing fuel loss in a short time. In this case, by injecting hydrogen, argon and alcohol at the same time, the carbon layer forming step and the carbon melt reduction step in contact with the metal particles can be induced to occur at the same time. According to one embodiment of the present invention, the alcohol is one or more selected from the group consisting of methanol, ethanol, propanol and butanol and the content of the alcohol may be 0.01 to 70% of the total gas volume, more preferably of alcohol The content is in the range of 0.03 to 30% of the total gas volume (although alcohol is also an oxygen source, alcohol may not be used). The carbon layer forming step and the carbon melt reduction step in contact with the metal particles in the above range proceeds smoothly at the same time.

Alternatively, water or oxygen, hydrogen, argon and hydrocarbons may be injected simultaneously to induce a carbon layer forming step in contact with the metal particles and the carbon melt reduction step to occur simultaneously. In other words, injecting water or oxygen, hydrogen, argon and a carbon source gas into a chemical vapor deposition system for forming nanoholes on a substrate, the carbon layer formed at the same time as the carbon layer is formed on the metal particles on the insulating layer of the substrate. By acting as this reducing agent, the carbon melt reduction reaction of the insulating layer occurs. According to one embodiment of the invention, when oxygen is used as the oxygen source, the content of oxygen is preferably 0.01 to 5% of the total gas volume, more preferably 0.03 to 0.5% of the total gas volume. When water is used instead of oxygen, the water content is in the range of 0.01 to 10% of the total gas volume, more preferably in the range of 0.03 to 1.0% of the total gas volume. The carbon layer forming step and the carbon melt reduction step in contact with the metal particles in the above range proceeds smoothly at the same time. When using hydrocarbon as the carbon source, the hydrocarbon is preferably at least one selected from the group consisting of methane, ethane, acetylene, ethylene, butane and propane.

According to one embodiment of the invention, when the carbon layer forming step and the carbon melt reduction step in contact with the metal particles occur separately or simultaneously, the carbon layer is injected with a carbon source gas at 400-1500 ° C. or 0 It may be formed on the metal particles through a chemical reaction in the solution phase containing a carbon group at 300 ℃. In each case in this temperature range, the carbon phase gas or the solution phase containing the carbon group forms a carbon layer well on the metal particles. The carbon source is not particularly limited and may be, for example, one or more selected from the group consisting of methane, ethane, acetylene, ethylene, butane and propane mentioned above. Alcohol and the like may be used as a non-limiting example of the solution phase containing the carbon group, and a polymer, a block copolymer, a surfactant, or a micelle may be used in the solution phase. When a polymer, a block copolymer, a surfactant, a micelle, or the like is used in the solution phase, the solvent used is not particularly limited, but is preferably an organic solvent in which these are dissolved. In addition, the solution phase containing the carbonization source gas and the carbon group may be injected at the same time.

On the other hand, in order to form the nano holes through the carbon melt reduction reaction between the insulating layer and the carbon layer, side reactions such as nanotubes are formed by metal particles or nano trenches instead of nano holes are suppressed, and nano holes are generated. Find the best conditions to promote.

As a result of many attempts, the inventors have found that when oxygen is supported in addition to the carbon source supplied in the carbon melting reduction reaction, and when the size of the metal particles is somewhat large, the growth of single layer carbon nanotubes (SWNTs) is suppressed. Since nano trenches are derived from nanotubes, inhibiting the growth of SWNTs naturally inhibits the formation of nano trenches.

As conditions for promoting the production of nano holes, the metal or transition metal particles preferably have an average diameter of 0.5 to 1000 nm, more preferably has an average diameter of 0.5 to 300 nm. In the above range, nano trench formation is almost suppressed.

On the other hand, the step of forming a carbon layer in contact with the metal particles and the carbothermal reduction reaction may occur separately. In this case, the carbon layer is preferably formed on the metal particles by injecting hydrogen and carbon source gas at high temperature or by chemical reaction on a solution containing carbon source at room temperature. The gas of the carbon source is preferably at least one selected from the group consisting of hydrocarbons methane, ethane, acetylene, ethylene, butane and propane, and at least one selected from the group consisting of alcohols methanol, ethanol, propanol and butanol. The carbon source in the solution is preferably a polymer containing a carbon group, a block copolymer, a surfactant, or a micelle.

According to one embodiment of the invention, the carbon melt reduction reaction may be achieved while injecting oxygen and inert gas, in which case the content of oxygen is preferably 0.0001 to 30% of the total gas volume. More preferably the content of oxygen is in the range of 0.0003 to 1.0% of the total gas volume. When the oxygen content is in the above range, growth of single layer carbon nanotubes (SWNT) is almost suppressed. As the inert gas containing oxygen, helium, neon, argon, krypton, xenon, radon may be used, and argon may be preferably used.

According to one embodiment of the invention, the temperature of the carbon melt reduction reaction is preferably 700 to 1700 ℃, more preferably 800 to 1200 ℃. Within this range, growth of single-walled carbon nanotubes (SWNTs) is almost suppressed, resulting in the suppression of nano-trench formation and maximum generation of nano-holes.

Hereinafter, as an embodiment of the present invention with reference to the drawings, looking at the nano-hole forming step of the insulating layer taking the case where the insulating layer is SiO ₂ as an example.

1A shows an AFM image of iron NP formed on a SiO ₂ / Si substrate by a hydroxylamine-mediated method. To demonstrate SiO ₂ nanohole formation through carbon melt reduction, hydroxylamine mediated iron NP was sintered in 800 ° C. air for 5 minutes to produce iron NP on SiO ₂ / Si substrate (FIG. 1A). The resulting iron NPs showed a very narrow diameter distribution with an average diameter of 1.5 nm.

Introduced into the _{O 2, H 2, CH 4} , C 2 H 4 gas is 1.5, 500, 1000, 20 sccm ( per standard cubic centimeters), respectively, the SiO ₂ / Si substrate for at 900 ℃ 10 minutes including the iron NP When the substrate was transferred to the CVD system in which the O ₂ was injected, nano holes were formed at very low population. This is shown in Figure 1b. In this case, mainly nano trenches were formed. The high density of the nano trenches is essentially due to the size of the iron NPs because the diameters of these iron NPs are very suitable for the growth of single layer carbon nanotubes (SWNTs), resulting in nano trenches.

To investigate the relationship between iron NP size and nanohole density, ferritin-induced iron NPs are used that provide a much wider size distribution (4-15 nm) with a larger average diameter size (7.9 nm). Carbon melt reduction was performed. First, the pre-deposited ferritin protein was sintered in air at 800 ° C. for 5 minutes to prepare ferritin-mediated iron NP on an SiO ₂ / Si substrate. FIG. 1C shows an AFM image of ferritin-induced iron NP on a SiO ₂ / Si substrate (insertion figure is high magnification image with scale bar 100 nm).

Next, ferritin-induced on SiO ₂ / Si substrates at 900 ° C. for 10 minutes under conventional gas conditions of O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 1.5 / 500/1000/20/100 sccm Iron NP was subjected to CVD treatment with O ₂ . The AFM image after the said process is shown to FIG. 1D. As shown in FIG. 1D, the density of the nanoholes increased substantially despite the discovery of nanotrench and unreacted SWNTs. These results clearly suggest that SWNT growth is effectively inhibited by the use of large sized iron NPs in the CVD environment in which O ₂ is injected, which leads to the creation of more efficient nano holes. To further increase the nanohole density, the content of carbon gas source (C ₂ H ₄ ) was reduced in anticipation of highly inhibiting SWNT growth. C ₂ H ₄ was chosen over CH ₄ because C ₂ H ₄ tends to be actively pyrolyzed, thus contributing more to the growth of SWNTs. Indeed, when carbon melt reduction was performed at 900 ° C. for 10 minutes without C ₂ H ₄ (O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 1.5 / 500/1000/0/100 sccm), nano Nanoholes were selectively formed without trenches or unreacted SWNTs. This is shown in Figure 1e. FIG. 1E is a diagram showing an AFM image after CVD treatment in which ferritin-induced iron NP is injected with O ₂ without ethylene gas on a SiO ₂ / Si substrate, and an inset is a high magnification image with a scale bar of 100 nm.

After determining the optimized reaction conditions in which the nanoholes are mainly formed, an attempt was made to produce SiO ₂ nanohole arrays from iron NPs with regular patterns using block copolymers. FIG. 2A is a schematic diagram of two steps for forming a nanohole array on a SiO ₂ / Si substrate. FIG. The steps include 1) forming an iron NP array using a polystyrene-block-poly (2-vinylpyridine) (PS- b- P2VP) block copolymer and treating with an O ₂ plasma and 2) injecting O ₂ Forming a nano-hole array through carbon melt reduction in a CVD system. The spontaneous formation of the PS- b -P2VP micelle array containing iron ions in the nucleus of step 1) is shown in more detail in Figure 2b.

Block copolymer micelles usually provide a hexagonal aligned structure with a controlled amount of iron ions. The iron ions of the polystyrene-block-poly (2-vinylpyridine) (PS- b- P2VP) block copolymers in toluene solvent settle in the P2VP nucleus while the PS corona shell extends outward toward the solvent. To form a patterned iron NP array, a PS- b- P2VP micelle solution containing iron ions prepared in two different compositions (Micelle I and II) was spin coated onto a SiO ₂ / Si substrate.

First, 0.5 wt% of PS- b- P2VP micelle solution (Micelle I) dissolved in a 0.3 molar ratio of FeCl ₂ relative to 2VP units was spin coated onto a SiO ₂ / Si substrate. Iron NPs obtained after O ₂ plasma treatment showed a hexagonal arrangement as confirmed by atomic force microscopy (AFM) as well as a Fourier conversion pattern (inset of FIGS. 3B and 3B). The mean values of diameter, distance between iron NPs, and number of iron NPs at 1 × 1 μm ² were 3.5 ± 0.6 nm, 45.6 ± 4.3 nm, and about 550, respectively (FIGS. 3A-3C).

Carbon melt reduction of the iron NP samples thus arranged under previously optimized reaction conditions (O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 1.5 / 500/1000/0/100 sccm for 15 minutes at 900 ° C) As a result, nanoholes were clearly obtained without any nano trenches being observed (FIGS. 3D to 3F). Nanoholes were also examined with cross-sectional images of high-resolution transmission electron microscopy (HRTEM), which measured about 22.4 nm of nanohole width and about 45 nm of upper width, and measured at full-width at half maximum (FWHM). It showed a depth of about 5.2 nm. In addition, the AFM profile showed a top width of 40-50 nm in the nanoholes (tip radius <10 nm). Although the nanoholes were successfully created, the required nanoholes were placed in random positions and the hole density decreased by 16.5% compared to the original iron NP density. Such irregular formation of nanoholes and even coalesced nanoholes (called nanotraces) indicate that iron NPs migrated on the surface during the reaction and some were removed. The movement of iron NP is mainly due to the levitation of iron NP caused by carbon melt reduction occurring between iron NP and the underlying SiO ₂ under continuous gas flow. In order to suppress the movement (or movement) of iron NP, attempts were made to change two reaction environments. First, when the gas content of H ₂ is small compared with the present experiment, it was observed that the iron NP and the degree of migration became active, H ₂ concentration was increased. However, when the content of H ₂ gas was doubled to 1000 sccm, the arrangement pattern was destroyed despite the increase of the density of the nanoholes to 38.8% to some extent (FIGS. 3G to 3I).

Next, if the density of iron NP is very sufficient to generate attraction between the NPs, a new iron NP array sample with farther interparticle distance was used because the unstable movement of the floating iron NP would be accelerated further. To this end, a 0.3 wt% solution of PS- b- P2VP micelle (Micelle II) containing 0.2 molar ratio of FeCl ₂ per 2VP units was spin coated onto the substrate, as shown in FIG. 4a and inset. The hexagonal arrangement is well formed. The mean values of diameter, distance between iron NPs, and number of iron NPs at 1 × 1 μm ² were 3.2 ± 0.6 nm, 59.0 ± 5.6 nm, and about 270, respectively. Compared to the case where micelle I was used, the interparticle distance increased by about 30% while the diameter remained unchanged. Assuming that two iron NPs have the same magnitude, Equation (1) can be used to predict the London-van der Waals forces between the two iron NPs.

                                                              (One)

Where A is the Hamaker constant, d is the diameter of the particle, and r is the distance from the center to the center between the particles. When the Hamaker constant for iron NP (Fe ₂ O ₃ ) in vacuum is 23.2 × 10 ^-20 J, micelle I (d = 3.5 nm, r = 45.6 nm) and micelle II (d = 3.2 nm, r = 59.0 nm The van der Waals forces applied to iron NP in) were 4.23 × 10 ^-24 J and 2.26 × 10 ^-24 J, respectively. Thus, in micelle II, about half of the interparticle attraction was expected to limit the mobility of iron NP during the carbon melt reduction reaction.

Indeed, it was found that carbon melt reduction in iron NP array samples made with micelles II under optimized conditions significantly inhibited the movement of iron NP (FIG. 4B). However, due to the low reactivity, no nanoholes were apparently produced. This is not surprising because the suppressed migration of iron NP in this particular situation indirectly indicates that the efficiency of carbon melt reduction is also very low. Now, in order to continue to effectively inhibit the mobility of iron NP and increase the reactivity, the optimum reaction conditions were tuned in small increments as follows: 1) the content of O ₂ gas was doubled, and 2) the reaction time was increased. 4C shows an AFM image taken after 15 minutes of reaction at 900 ° C. under O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 3/500/1000/0/100 sccm. Although a small number of nanoholes were produced, most of the iron NPs remained in place first. The inset of FIG. 4C shows two nanoholes (green circles) and five iron NPs (red circles) on hexagonal vertices. After an extended reaction for 60 minutes, a nearly perfect nanohole array was finally formed (with an average hole distance of 59.8 ± 9.5 nm) without noticeable position shift and the hole density was higher than 80% compared to the iron NP array (FIG. 4D). The AFM profile shows that the top of the nanoholes is about 16 nm (FIG. 4E), whereby the diameter of the nanoholes in the FWHM will be about 8 nm.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

Example

Formation of Iron Nanoparticles (NP)

1) hydroxylamine-mediated formation

An SiO ₂ / Si substrate (about 500 nm thick SiO ₂ thermally produced on B doped Si, Silicon Valley Microelectronics) was immersed in 10 mL of deionized water, containing 5 mM FeCl ₃ .6H ₂ O ( aq) 10 μL was added and after 30 seconds, 100 μL of 40 mM NH ₂ OH.HCl (aq) was subsequently added. The total immersion time was 3 minutes. The SiO ₂ / Si substrate was washed thoroughly with deionized water and dried over flowing N ₂ gas and then sintered at 800 ° C. for 5 minutes in air.

2) ferritin-mediated formation

SiO ₂ / Si substrates were immersed in 2 μg / mL ferritin aqueous solution (Type VII: Human Heart, Sigma) for 5 minutes and then dried. The sample was sintered at 800 ° C. for 5 minutes in air.

Iron NP array

Polystyrene-block-poly (2-vinylpyridine), PS- b -P2VP, (M _n ^PS = 56 kg / mol, M _n ^P2VP = 21 kg / mol, Mw / Mn = 1.06, Polymer Source, Inc.) 0.5 Wt% (micelle I) or 0.3 wt% (micel II) was dissolved in toluene at 70 ° C and stirred for 4-5 hours. In toluene, PS- b -P2VP spontaneously formed spherical micelles, where solvophobic P2VP became a nucleus while solvophilic PS formed corona (Figure 2b). After cooling to room temperature, 0.3 mole ratio of FeCl ₂ .4H ₂ O was dissolved in the micelle solution for ₂ VP units for micelle I (or 0.2 molar ratio for micelle II) and the Fe ²⁺ salt was inside the nuclear P2VP moiety. The mixture was stirred vigorously for at least 3 days to sufficiently infiltrate the furnace. To form a micellar monolayer film containing Fe ions on a SiO ₂ / Si substrate, the solution was spin coated at 4000 rpm for 50 seconds. Finally, the organic moiety was removed by treatment with O ₂ plasma (SPI plasma-prepTM II) at 50 mA and 100 mTorr for 5 minutes and the sample was sintered in 800 ° C. air for 5 minutes.

SiO ₂  Formation of Nanohole Arrays

Samples in which iron NPs were arrayed were transferred into an O ₂ injected CVD system. Ar (350 sccm) and O ₂ (3 sccm) gases were introduced as transport gases during heating and O ₂ , H ₂ , CH ₄ , and Ar gases were introduced during the planned reaction time at 900 ° C. After the carbon melt reduction reaction, all gases except Ar gas (350 sccm) were blocked and then cooled to room temperature.

On the other hand, in another embodiment not described herein, the reaction gas O ₂ could be replaced with H ₂ O or alcohol vapor (methane or ethanol) and the amount was not the same or greater than five times the amount of O ₂ . In addition, in the case of using alcohol vapor, there was no need for a separate hydrocarbon gas.

In another embodiment not described herein, the formation of nano holes in a SiO ₂ substrate could also be formed by inducing a carbon melt reduction reaction in an iron NP sample surrounded by an already formed carbon layer (amorphous carbon or graphite layer). The synthesis of the carbon layer was the same as the above experimental method except for the injection of oxygen gas. That is, H ₂ / CH ₄ = 500/1000 sccm by 15 minutes at 900 ℃ it was possible to form a carbon layer. It was also possible to form a core-shell structure of the iron NP-carbon layer through a chemical reaction in solution phase at room temperature. Iron NP samples coated with PS- b- P2VP were spin-coated and aligned on a SiO ₂ substrate, and then the O ₂ plasma treatment was omitted so that the original carbon layer could be used as it was for the carbon melt reduction reaction. Subsequently, the substrate on which the iron NP coated with the carbon layer was deposited was transferred into the quartz tube of the chemical vapor deposition machine, and then 1000 sccm Ar gas and 3 sccm oxygen gas or 1000 sccm Ar gas and 3 sccm water vapor (or alcohol It was observed that the SiO ₂ nanoholes were formed on the SiO ₂ / Si substrate by the carbon melting reduction reaction by increasing the temperature to 900 ° C. and reacting for 60 minutes or more after flowing the vapor).

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1A is a diagram showing an AFM image of iron NP formed on a SiO ₂ / Si substrate by a hydroxylamine-mediated method.

FIG. 1 b shows SiO 2 by hydroxylamine-mediated method at 900 ° C. for 10 minutes under conventional gas conditions of O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 1.5 / 500/1000/20/100 sccm / Si diagram for iron NP formed on a substrate showing an AFM image after O ₂ is injected into the CVD processing.

1C is a diagram showing an AFM image of ferritin-induced iron NP on a SiO ₂ / Si substrate. (Inset is high magnification image, scale bar is 100 nm)

1D shows ferritin-on a SiO ₂ / Si substrate for 10 minutes at 900 ° C. under conventional gas conditions of O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 1.5 / 500/1000/20/100 sccm. the derived iron NP O ₂ is injected into a view showing an AFM image after the CVD processing.

Figure 1e is on the SiO ₂ / Si substrate ferritin - a view showing an AFM image after the induction of the iron without NP ethylene gas O ₂ are injected into CVD process. (O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 1.5 / 500/1000/0/100 sccm for 10 min at 900 ° C, inset is high magnification image with scale bar 100 nm)

FIG. 2A is a schematic diagram of two steps for forming a nanohole array on a SiO ₂ / Si substrate. FIG.

FIG. 2B shows in detail the spontaneous formation of the PS- b- P2VP micelle array containing iron ions in the nucleus, the first of two steps for forming nanohole arrays on a SiO ₂ / Si substrate.

FIG. 3A shows the iron NP array (using micellar I) on SiO ₂ / Si substrates.

FIG. 3B is an enlarged view of FIG. 3A (insertion diagram shows Fourier transformed pattern).

3C is a diagram illustrating the high magnification 3-D AFM image of FIG. 3A.

FIG. 3d shows 16.5 compared to the initial NP density after carbon melt reduction under gas conditions of O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 1.5 / 500/1000/0/100 sccm for 15 minutes at 900 ° C. Figure showing nanohole density of%.

3E is an enlarged view of FIG. 3D.

FIG. 3F is a diagram illustrating the high magnification 3-D AFM image of FIG. 3D.

Figure 3g is 38.8 compared to the initial NP density after carbon melt reduction under gas conditions of O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 1.5 / 1000/1000/0/100 sccm for 15 minutes at 900 ℃ Figure showing nanohole density of%.

3E is an enlarged view of FIG. 3G.

FIG. 3F is a diagram illustrating the high magnification 3-D AFM image of FIG. 3G.

4A shows an AFM image of an iron NP array on a SiO ₂ / Si substrate (using micellar II) and an inset is a diagram showing a Fourier transformed pattern.

4B shows AFM after CVD treatment with O ₂ implanted under optimized conditions (O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 1.5 / 500/1000/0/100 sccm for 15 minutes at 900 ° C.). It is a figure which shows an image.

4C shows an AFM image of partially formed nanoholes after 15 min reaction at 900 ° C. under changed gas conditions of O ₂ / H ₂ / CH ₄ / C ₂ H ₄ / Ar = 3/500/1000/0/100 sccm Figure (Inset shows high magnification image, scale bar is 50 nm. Red circle shown shows remaining iron NP and green circle shows nanohole).

FIG. 4D shows an AFM image of a nearly perfect nanohole array obtained from a long-term reaction for 60 minutes (Inset figure shows high magnification image and scale bar is 50 nm. Green circle shown shows nano hole) .).

FIG. 4E is a 3-D image of a nearly perfect nanohole array obtained from a long-term reaction of 60 minutes and shows the AFM width profile of a single nanohole.

Claims (20)

Forming an insulating layer on the substrate; Depositing metal or transition metal particles on the insulating layer; Forming a carbon layer in contact with the metal particles; And Carbothermal reduction of the insulating layer to form nano holes; Including; Wherein the carbon layer is formed on the metal particles by injecting a carbon source gas at 400 to 1500 ° C. or through a chemical reaction on a solution containing carbon groups at 0 to 300 ° C. to form nano holes in the insulating layer. The method of claim 1, The metal or transition metal particles may be polymers, block copolymers, surfactants, micelles, Languir-Blodgett technology, surface-programmed assemblies, solution evaporation methods or step edges of substrates, Characterized in that it is aligned through the use of electromagnetic fields. The method of claim 1, And the nano holes of the insulating layer are formed in a pattern. The method of claim 1, And wherein said substrate is selected from the group consisting of silicon wafers, sapphire, glass, quartz, metals, alumina, and plastics. The method of claim 1, And wherein said insulating layer is formed of a compound comprising silicon. The method of claim 1, And the insulating layer is formed of at least one selected from the group consisting of silicon oxide, silicon dioxide, silicon nitrate, and silicon nitride. The method of claim 1, The metal or transition metal particle is nickel (Ni), iron (Fe), cobalt (Co), yttrium (Y), molybdenum (Mo), aluminum (Al), rhodium (Rh), rubidium (Ru), palladium (Pd), gold (Au), silver (Ag), copper (Cu), magnesium (Mg), chromium (Cr), manganese (Mn), tin (Sn), platinum (Pt) or alloys thereof How to feature. The method of claim 1, The metal or transition metal particles are deposited using spin-coating, injection and evaporation of a solution, metal deposition, sputtering or lithography. The method of claim 1, And forming a carbon layer in contact with the metal particles and a carbothermal reduction step. The method of claim 9, Forming a carbon layer in contact with the metal particles and the carbon melt reduction step occurs while simultaneously injecting hydrogen, argon and alcohol. 11. The method of claim 10, Wherein the content of alcohol is from 0.01 to 70% of the total gas volume. The method of claim 9, Forming a carbon layer in contact with the metal particles and the carbon melt reduction step occur while simultaneously injecting water or oxygen, hydrogen, argon and hydrocarbons. 13. The method of claim 12, The water content is 0.01 to 10% of the total gas volume and the oxygen content is 0.01 to 5% of the total gas volume. delete The method of claim 1, And the carbon layer on the metal particles is formed by simultaneously injecting a solution phase comprising a carbon source gas and a carbon group. The method of claim 1, And the carbon layer on the metal particles is formed on the solution through a chemical reaction of a polymer, a block copolymer, a surfactant, or a micelle. The method of claim 1, The metal or transition metal particles have an average diameter of 0.5 to 1000 nm, and the nano holes of the insulating layer have an average width of 0.5 to 1500 nm. The method of claim 1, And the carbon melt reduction reaction is performed while injecting oxygen and an inert gas. The method of claim 18, The oxygen content is 0.0001 to 30% of the total gas volume. The method of claim 1, The carbon melt reduction reaction is characterized in that at a temperature of 700 to 1700 ℃.

Images