KR20090081532A - Fabrication method of nano-cyclindrical template and nanoparticle array - Google Patents

Abstract

A method for fabricating a nano-cylindrical template and a nanoparticle array is provided to uniformly form nano-patterns. A method for fabricating a nano-cylindrical template and a nanoparticle array comprises: a first step of spin coating styrene-methacryl acid methyl block copolymer and a PEO coated gold nanoparticle solution on a substrate; a second step of annealing the substrate in a solvent under predetermined humidity condition in order to vertically arrange nano-cylindrical PMMA domain on the substrate; and a third step of selectively removing the vertically arranged PMMA domain so as to form a nanoporous template.

Description

Fabrication method of nano-cyclindrical template and nanoparticle array}

 The present invention relates to a nano-cylindrical template and a method for producing a nano-dot array, and more particularly to producing a nano-cylindrical template or nano-dot array using PS-b-PMMA block copolymer and PEO coated gold nanoparticles. It is about a method.

The spatial arrangement of nanostructures such as inorganic nanoparticles of the host matrix or domains in the block copolymer thin film has a wide application range from block copolymer lithography to catalysts and solar cells. .

Here, it is important to control the orientation and position of the nanoparticles or polymer domains. Recently, research has been published that the position of nanoparticles can be easily controlled by the ratio of d / L (d: particle size, L: block copolymer domain size).

If d / L ≥ 0.3, the nanoparticles are located at the center of the domain due to chain stretching penalty, while if d / L is less than 0.3, they move out of the interface.

In block copolymers, conventional approaches to control the orientation of PS-b-PMMA (styrene-methyl methacrylate block copolymer) systems have been used in order to neutralize the interfacial energy between the substrate and the polymer copolymer. The coalescence is used to form a pattern through thermal annealing.

However, according to the prior art, when the molecular weight of the polymer copolymer exceeds 100 kg / mol has a disadvantage that the pattern is not formed well. (Ting Xu, Ho-Cheol Kim, Jason DeRouchey, Chevery Seney, Catherine Levesque, Paul Martin, CM Stafford, TP Russell, Polymer 42 , 9091, 2001)

In addition, since a 6 nm-thick random polymer copolymer is present between the substrate and the pattern, an element requiring direct contact with the substrate requires an etching process, thereby making the process complicated and difficult.

Furthermore, the pattern formation method according to the prior art was not suitable when a large area pattern was required because the domain of the pattern was 500 nm or less.

The patterning of poly (styrene-b-ethylene oxide) through solvent annealing has been announced (Seung Hyun Kim, Matthew J. Misner, Ting Xu, Masahiro Kimura, Thomas P. Russell, Adv. Mater. 16 , 226, 2004). There is a problem that the removal of the PEO domain is not easy. Another example of a polymer copolymer using solvent annealing is poly (styrene-b-methylmethacrylate-b-ethylene oxide) triblock copolymer, which has a domain size of several micrometers and has the advantage of easy removal of PMMA and PEO blocks. Somewhat difficult to do (Joona Bang, Seung Hyun Kim, Eric Drockenmuller, Matthew J. Misner, Thomas P. Russell, Craig J. Hawker, J. Am. Chem. Soc. 128 , 7622, 2006).

In the present invention, to solve the problems of the prior art as described above, to propose a method for producing a nano-cylindrical template and a nano dot array in a simple process using a large molecular weight polymer copolymer that is easy to purchase and synthesis.

Another object of the present invention is to provide a method of manufacturing nano-cylindrical templates and nano-dot arrays that are easy to remove domains after the formation of a pattern.

It is still another object of the present invention to provide a nano-cylindrical template and a nano dot array manufacturing method capable of producing a large area pattern.

According to a preferred embodiment of the present invention to achieve the above object,

a) spin coating a substrate with a styrene-methyl methacrylate (PS-b-PMMA) block copolymer and a PEO coated gold nanoparticle solution having a predetermined volume fraction for the block copolymer; (b) annealing the solvent under preset humidity conditions to vertically align the cylindrical PMMA domain on the substrate; And (c) selectively removing the vertically oriented PMMA domain to form a porous nano template.

According to another aspect of the invention, (a) a styrene-methyl methacrylate (PS-b-PMMA) block copolymer and a PEO coated gold nanoparticle solution having a predetermined volume fraction for the block copolymer to the substrate Spin coating; (b) annealing the solvent under preset humidity conditions to vertically align the cylindrical PMMA domain on the substrate; And (c) removing the polymer on the substrate by reactive ion etching the substrate in an oxygen plasma atmosphere.

According to another aspect of the invention, as a method of manufacturing a nano-pattern,

Vertically aligning the PMMA domain on the substrate using a styrene-methyl methacrylate (PS-b-PMMA) block copolymer and hydrophilic PEO coated gold nanoparticles, wherein the vertically oriented PMMA domain is a nanocylinder A nanopattern manufacturing method applied to at least one of a mold template and a nano dot array is provided.

According to the present invention, there is an advantage in that a nanopattern can be manufactured by a simple process.

In addition, according to the present invention there is an advantage that can form a nano-pattern uniformly over the entire area.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, the same reference numerals will be used for the same means regardless of the reference numerals in order to facilitate the overall understanding.

According to the present invention, styrene-methyl methacrylate (poly (styrene-b-methylmethacrylate), hereinafter referred to as 'PS-b-PMMA') block copolymer and PEO coated gold nanoparticles (hereinafter, 'Au-PEO' Is provided.

1 to 2 illustrate a thin film manufacturing process for manufacturing a nano-pattern such as a nano-cylindrical template and a nano dot array according to the present invention.

1 to 2, a solution including the PS-b-PMMA block copolymer 20 prepared as described above and Au-PEO nanoparticles 21 having a predetermined volume fraction compared to the block copolymer is provided. (Step 100).

The solvent in step 100 is benzene, preferably, the volume fraction of Au-PEO nanoparticles may be 1.9 vol% to 3.2 vol%.

The solution provided in step 100 is then spin coated onto the silicon substrate to a constant thickness (step 102).

Next, solvent annealing is performed under controlled humidity under saturated benzene vapor for the thin film formed on the substrate by spin coating (step 104).

In step 104, the preferred relative humidity is 70-90%, forming a saturated benzene vapor atmosphere to speed up the evaporation rate in solvent annealing.

In the present invention, the Au-PEO nanoparticles have hydrophilic properties, and water vapor condensed during solvent annealing interacts with the hydrophilic PEO coated gold nanoparticles 21 in the PMMA domain 24 to form the PMMA domain 22 on the substrate. ) Is oriented vertically in the form of a cylinder. Gold core 23 is disposed in PMMA domain 22.

In addition, in the above, the volume fraction of Au-PEO nanoparticles can be determined within a range that makes the pore size of the vertically oriented PMMA domain uniform.

If the PMMA domain is vertically oriented as such, UV irradiation and acetic acid / water treatment are performed (step 106).

In step 106, the vertically oriented PMMA domain is removed by UV irradiation, and Au-PEO nanoparticles with hydrophilic properties are easily dissolved and removed in water.

This completes a nano-cylindrical template with uniform cylinder shapes over the entire area and uniform pore sizes for each cylinder.

Meanwhile, after step 104, reactive ion etching may be performed on the thin film on the substrate under an oxygen (O ₂ ) plasma atmosphere (step 108).

Here, reactive ion etching is a process for removing all the polymer on the substrate. In the step 108 described above, reactive ion etching and vacuum annealing may be performed together, and the vacuum annealing may be performed by agglomerating Au-PEO nanoparticles remaining in the previous PMMA domain after etching to obtain a uniform nano dot as shown in FIG. 2. Allow arrays to be formed.

Hereinafter, the method of manufacturing a nano-cylindrical template and a nano dot array according to the present invention will be described in detail through the following experimental procedures and results.

PS -b- PMMA

PS-b-PMMA showed a cylindrical microstructure and was synthesized by living anionic polymerization. The total molecular weight was 140 kg / mol and polydispersity was determined to be 1.06.

Au - PEO  Nanoparticles

In the synthesis of Au-PEO, PEO (PEO-SH, Mn = 2 kg / mol) having a thiol end group and a gold precursor (HAuCl ₄ ) are first dissolved in dry THF (TETRAHYDROFURAN, hydroforming), and then nitrogen atmosphere. Synthesis under 15 minutes under.

Gold nanoparticles were synthesized by dropwise addition of superhydride (1.0 M Li (C2H5) 3BH in THR from Sigma-Aldrich), reducing agent under nitrogen, and no further gas The accumulation continued until it did not evaporate.

Polymer coated gold nanoparticles (Au-PEO) was separated from PEO-SH by membrane filtration (MWCO 30000 Da, Millipore, Inc.) using DMF (dimethylformamide, dimethylformamide).

Finally, PEO coated gold (Au-PEO) nanoparticles were redispersed in methanol and washed three times by membrane filtration.

Thin Film Preparation

The solution is prepared in a mixture of PS-b-PMMA block copolymer (1 wt%) and Au-PEO nanoparticles (0 to 10 wt% compared to the block copolymer) having various weight fractions for the above-described block copolymer in a benzene solvent. It became.

The solution was spin coated onto a silicon substrate and the thin film thickness was maintained at 40 nm for all samples.

These thin films were solvent annealed under controlled humidity conditions. The whole solvent annealing process was performed in a home-built glove box chamber at room temperature. The entire glove box was continuously supplied with humid air, which is produced by bubbles with warm water. The relative humidity in the chamber was controlled by mixing dry air or adjusting the water temperature.

Once the desired humidity is reached (90% in this experiment), a constant throughput of the entire process is maintained. Within the glove box chamber is a large number of sealed small chambers under saturated benzene vapor, a glass vessel inverted on a large glass Petri dish, and the relative humidity is like a large external chamber.

The membrane is annealed for at least 12 hours and the inverted glass container is simply removed from the petri dish in a large glove box, so that under given humidity conditions benzene in the expanded thin film can evaporate.

The same experiment was carried out for the comparative example of the present invention even under a slow evaporation rate condition of relative humidity of 50% or less.

analysis( Characterization )

After solvent annealing, the surface morphology of the thin film is depicted by scanning force microscopy (SFM) in non-contact mode. SFM used an n-type Si tip etched on cantilevers (ACTA, Applied NanoStructures) with a resonant frequency of 300 kHz and a modulus of elasticity ranging from 25 to 75 N / m. The back of the cantilever was coated with 30 nm thick Al.

SEM images of the thin films were obtained after UV irradiation followed by treatment with acetic acid and DI (deionized water).

The thin film is then platinum coated by ion sputtering and the SEM is operated at 15 keV (Hitachi S-4300).

For TEM measurements, thin films are separated from silicon oxide substrates using a 6: 1 buffer oxide etchant (J.T.Baker). The film floats on DI water and is transferred to carbon-coated copper mesh grids for TEM. Images were obtained using a 200keVFEI Tecnai G2 microscope operating without staining.

The weight fraction of the Au core and the PEO ligand are measured by thermal gravimetric analysis (TGA). Using the density of PEO (~ 1.2g / cm3) and the density of gold cores (~ 19.3g / cm3), the weight fraction of Au-PEO particles is converted into volume fraction.

The 1, 3, 5, 7, and 10 wt% Au-PEO nanoparticle weight fractions used in this experiment were equal to 0.6, 1.9, 3.2, 4.5 and 6.5 vol% volume fractions, respectively.

As described above, in this experiment, the volume fraction of Au-PEO nanoparticles relative to the PS-b-PMMA block copolymer was in the range of 0.6 to 6.5 vol%.

In addition, in order to exclude the influence of the PEO domain arrangement according to the thin film thickness in this experiment, the thickness in all samples was kept constant at 40nm.

The synthesized Au-PEO nanoparticles were mixed with a PS-b-PMMA double block copolymer having a gold core diameter of 4.0 ± 1.0 nm, a total diameter of 10.7 ± 2.5 nm, and a total molecular weight of 140 kg / mol. In early spin coating, it was found that most of the Au-PEO nanoparticles were selectively placed within the PMMA domain.

First experiment

SFM images were obtained at high evaporation rates and high relative humidity conditions (90%) with volume fractions of Au-PEO nanoparticles of 0 and 4.5 vol%, respectively.

FIG. 3 (a) shows a thin film when the volume fraction of Au-PEO nanoparticles is 0 and the volume fraction of Au-PEO nanoparticles is 4.5 vol% under fast evaporation rate and high relative humidity conditions. 3C is an enlarged view of FIG. 3B.

Comparing Figures 3a and 3b, it can be seen that the effect of the Au-PEO nanoparticles in the form of the PS-b-PMMA thin film is large.

That is, in the absence of Au-PEO nanoparticles, the cylindrical PMMA microdomains are aligned parallel to the substrate, as shown in FIG. 3A, whereas in the case of Au-PEO nanoparticles of 4.5 vol%, FIG. As shown, the vertical orientation of the microdomain is obtained.

In FIG. 3B, black dots were observed within the bright PMMA domain. In FIG. 3C, which is enlarged, the black point is more clearly confirmed. Here, the large points on the thin film surface are agglomerates of Au-PEO nanoparticles that can be easily removed by water washing.

In the above, the humidity condition is controlled to 90%, but the present invention is not limited thereto, and the same result may be obtained even under a humidity condition of 70% or more.

Second experiment ( Comparative example )

SEM images were obtained by varying the volume fraction of Au-PEO nanoparticles at high evaporation rates and low relative humidity (50%).

4 (a) to 4 (d) show SEM of PS-b-PMMA thin films when the volume fraction of Au-PEO nanoparticles is 0, 1.9, 3.2, and 4.5 vol%, respectively, under fast evaporation rate and low relative humidity conditions. Image.

As shown in Figs. 4A to 4D, the cylindrical microdomains are arranged very weakly by solvent annealing under low humidity conditions, and no black spots as shown in Fig. 3B were observed.

This suggests that the vertical orientation of the PMMA domain is induced by the interaction between water vapor and hydrophilic Au-PEO nanoparticles provided under high humidity conditions.

During the solvent annealing process, the thin film is initially expanded with benzene under saturated benzene atmosphere. Once the membrane is out of the inner chamber, the solvent (benzene) in the membrane will evaporate from the top surface. Thus the surface cools down and then reaches the dew point.

Under high humidity conditions in the glove box chamber, water vapor condenses on the cooled surface and interacts with the hydrophilic Au-PEO nanoparticles in the PMMA domain.

As a result, the interaction of water vapor with Au-PEO nanoparticles causes hexagonal dense arrays on the thin film surface. As the solvent evaporates further, the PMMA domains containing Au-PEO nanoparticles grow vertically, leading to the vertical orientation of the cylindrical microdomains.

However, under low humidity conditions the dew point decreases so that no water condenses and thus no vertical orientation is induced.

As a result, the parallel orientation of the cylindrical microdomains is observed under low humidity conditions as shown in FIGS. 4A-4D.

3rd experiment

For complete investigation of the structure and morphology of these nanocomposites, solvent annealing was performed on thin films with volume fractions of 0, 0.6, 1.9, 3.2, 4.5 and 6.5 vol% under high humidity conditions, and the PMMA domain. This was removed by UV irradiation, followed by washing with acetic acid and water.

5 (a) to (f) are SEM images of the PS-b-PMMA thin film when the volume fractions of Au-PEO nanoparticles are 0, 0.6, 1.9, 3.2, 4.5 and 6.5 vol%, respectively.

In the absence of Au-PEO nanoparticles, a cylindrical microdomain orientation parallel to the substrate is shown as in the SFM image of FIG. 3A (see FIG. 5A).

As shown in FIG. 5B, the parallel orientation described above continues until the Au-PEO nanoparticles have a volume fraction of 0,6 vol%, but as shown in FIG. 5B, the volume fraction of Au-PEO nanoparticles. At 1.9 vol%, the orientation changes dramatically.

As shown in FIGS. 5C and 5D, when the volume fraction of Au-PEO nanoparticles is 1.9 and 3.2 vol%, a cylindrical microdomain orientation perpendicular to the thin film appears, wherein the diameter of the microdomain pores is 24.2 ±. 2.5 nm, and has a periodicity of 67.2 ± 2.5 nm.

In addition, the horizontal arrangement area of the cylindrical microdomains is larger than 1 × 1 μm, which is a typical grain size for PS-b-PMMA block copolymers oriented by thermal annealing on a random copolymer brush. Significantly larger than 200-300nm.

This improved horizontal arrangement may be due to Au-PEO nanoparticles rather than PS-b-PMMA itself. That is, under controlled high humidity conditions, the hydrophilic Au-PEO nanoparticles in the PMMA domain induce vertical as well as horizontal orientation, which is similar to that observed in PEO containing (based) block copolymers.

When the volume fractions of the Au-PEO nanoparticles reach 4.5 and 6.5 vol%, a horizontal array of fragments is caused.

As shown in FIG. 5E, when the volume fraction of Au-PEO nanoparticles is 4.5 vol%, the pore size distribution becomes large from 22 to 45 nm, resulting in a twisting hexagonal structure of the cylinder. Cylindrical microdomains, on the other hand, still maintain vertical orientation.

On the other hand, as shown in FIG. 5F, when the volume fraction of Au-PEO nanoparticles is 6.5 vol%, the pore size distribution is further increased to 22 to 60 nm, and such irregular pore size is applied to the block copolymer without disturbing the shape. This is because of the inherent limitations of the amount of nanoparticles that can be mixed.

The third experiment confirmed that the volume fraction of Au-PEO nanoparticles is preferably kept within a predetermined range for the block copolymer.

4th experiment

To confirm that the cylindrical microdomains are maintained for the entire block copolymer film, the shape was examined at the substrate interface. The substrate was removed by treatment through the HF solution, and the free film suspended on the HF solution surface was transferred to another substrate.

6 (a) and 6 (b) are SEM images of the bottom of the thin film shown in FIGS. 5 (c) and 5 (f).

6A and 5C, the top and bottom structures of the thin film are essentially the same once the PMMA and Au-PEO particles are removed. This makes it clear that the vertical orientation of the cylindrical microdomains is maintained throughout the block copolymer membrane, so these membranes can function as templates for lithographic applications. This is the same even when comparing FIG. 6B and FIG. 5F.

5th experiment

The distribution of Au-PEO nanoparticles in the PS-b-PMMA membrane was examined by TEM. 7 is a TEM image of a film comprising 4.5 vol% Au-PEO nanoparticles.

The bright areas correspond to the PMMA domains, while the PS matrix appears with a dark background and Au-PEO nanoparticles can be identified as black dots. A high resolution image of the gold core was inserted. In Fig. 7 it can be clearly seen that most of the Au-PEO nanoparticles are present in the PMMA domain.

Experiment 6 Comparative example )

The arrangement of the thin film according to the invention can be obtained by rapid evaporation under high humidity conditions.

To emphasize the importance of the solvent evaporation rate in the solvent annealing process, the shape of the membrane was investigated after solvent annealing under slow evaporation rate conditions. To this end, benzene solvent can leak from the internal chamber for more than 24 hours while high humidity conditions are maintained, allowing it to evaporate very slowly.

8 (a) and (b) are SEM images of the PS-b-PMMA thin film when the volume fractions of Au-PEO nanoparticles are 1.9 and 3.2 vol%, respectively, under slow evaporation rate and high relative humidity conditions.

8A and 8B were compared with SEM images of thin films obtained by rapid evaporation under the same volume fraction and high relative humidity conditions, as in FIGS. 5C and 5D.

Slow evaporation of the solvent under high humidity conditions did not lead to vertical orientation of the cylindrical microdomains. Instead very weak alignments and mixed cylindrical domain orientations were obtained. This is because slow benzene evaporation results in negligible cooling of the membrane surface and prevents condensation of water vapor.

Mixing the hydrophilic Au-PEO nanoparticles into the PS-b-PMMA block copolymer through the above experiments and performing solvent annealing under high humidity conditions and fast solvent evaporation rate conditions induces cylindrical PMMA microdomain orientation. can confirm.

This clearly contrasts with the orientation observed under the absence of nanoparticles and under low humidity conditions and low evaporation rates.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

1 to 2 is a view showing a thin film manufacturing process for manufacturing nano-cylindrical template and nano dot array according to the present invention.

FIG. 3 (a) shows a thin film when the volume fraction of Au-PEO nanoparticles is 0 and the volume fraction of Au-PEO nanoparticles is 4.5 vol% under fast evaporation rate and high relative humidity conditions. 3c is an enlarged view of FIG. 3b.

4 (a) to 4 (d) show SEM of PS-b-PMMA thin films when the volume fraction of Au-PEO nanoparticles is 0, 1.9, 3.2, and 4.5 vol%, respectively, under fast evaporation rate and low relative humidity conditions. image.

Figure 5 (a) to (f) is a SEM image of the PS-b-PMMA thin film, respectively, when the volume fraction of Au-PEO nanoparticles are 0, 0.6, 1.9, 3.2, 4.5 and 6.5 vol%.

6 (a) and 6 (b) are SEM images of the bottom of the thin film shown in FIGS. 5 (c) and 5 (f).

FIG. 7 is a TEM image of a membrane comprising 4.5 vol% Au-PEO nanoparticles. FIG.

8 (a) and (b) are SEM images of PS-b-PMMA thin films when the volume fractions of Au-PEO nanoparticles were 1.9 and 3.2 vol%, respectively, under slow evaporation rates and high relative humidity conditions.

Claims (14)

(a) spin coating a substrate with a styrene-methyl methacrylate (PS-b-PMMA) block copolymer and a PEO coated gold nanoparticle solution having a predetermined volume fraction for the block copolymer; (b) annealing the solvent under preset humidity conditions to vertically align the cylindrical PMMA domain on the substrate; And (c) selectively removing the vertically oriented PMMA domain to form a porous nano template. The method of claim 1, The PEO coated gold nanoparticles have a 1.9 to 3.2 volume fraction as compared to the PS-b-PMMA block copolymer. The method of claim 1, The step (b) is a nano-cylindrical template manufacturing method comprising the step of evaporating the benzene solvent at a high evaporation rate under saturated benzene vapor. The method of claim 1, The humidity conditions are nano-cylindrical template manufacturing method in the relative humidity range of 70 to 90%. The method of claim 1, The PEO coated gold nanoparticles have a hydrophilic property nano-cylindrical template manufacturing method. The method of claim 5, Water vapor condensed during the solvent annealing interacts with hydrophilic PEO coated gold nanoparticles in the PMMA domain. The method of claim 1, In step (c), Irradiating UV to remove the PMMA domain; And Including washing the substrate with acetic acid and water, The PEO coated gold nanoparticles are easily mixed by the water nano-cylindrical template manufacturing method. The method of claim 1, Wherein said volume fraction is determined within a range that makes the pore size of said vertically oriented PMMA domain uniform. The method of claim 1, The template is a nano-cylindrical template manufacturing method having pores of hexagonal dense structure. (a) spin coating a substrate with a styrene-methyl methacrylate (PS-b-PMMA) block copolymer and a PEO coated gold nanoparticle solution having a predetermined volume fraction for the block copolymer; (b) annealing the solvent under preset humidity conditions to vertically align the cylindrical PMMA domain on the substrate; And (c) removing the polymer on the substrate by reactive ion etching the substrate in an oxygen plasma atmosphere. The method of claim 10, And vacuum annealing the substrate after step (c). As a method of manufacturing a nano pattern, Vertically aligning the PMMA domain on the substrate using a styrene-methyl methacrylate (PS-b-PMMA) block copolymer and hydrophilic PEO coated gold nanoparticles, Wherein said vertically oriented PMMA domain is applied to at least one of a nano-cylindrical template and a nano dot array. The method of claim 12, wherein the hydrophilic PEO coated gold nanoparticles have a volume fraction within a predetermined range for the block copolymer such that the pores of the PMMA domain are uniform. The method of claim 12, The vertical orientation of the PMMA domain is formed when the benzene solvent evaporates at a rapid evaporation rate under saturated benzene vapor under a predetermined humidity condition.

Images