TWI578399B - Method for producing nanowires - Google Patents

Description

Method of making nanowires

This invention relates to a method of making nanowires using nucleic acids as a transitional support structure. The method applies a metal-DNA complex film to a solid support. The micron to nanometer-scale metal wires are fabricated by controlling the capillary force of the coffee ring effect and scraping the nucleic acid metal nanoparticle film to accumulate the nanoparticles at the edge of the cut-out region. In other embodiments, the invention removes nucleic acids by enzymatic hydrolysis to obtain the final metal wire. The invention further provides a wafer comprising a circuit made by the method.

Deoxyribonucleic acid (DNA) template methods have been used to fabricate micron to nanoscale metal lines for the past several decades. Although this manufacturing method is very effective, the output per unit time and controllability are always low. The present invention provides a novel method for fabricating micron to nanoscale silver (Ag) lines on a germanium (Si) wafer using natural capillary forces in a scribing or "writing" manner. The drying effect of the coffee ring caused by the capillary force causes the DNA molecules with silver to diffuse toward the edge of the scribe region and deposit along the scribed pattern. The DNA transition support structure is then removed using an enzyme-assisted etching method to leave the silver lines on the wafer. This technology is expected to improve the current DNA-assisted metal nanopattern and nanostructure forming method, enabling it to be applied to nanoelectronics.

In recent years, DNA-assisted micron and nanostructure forming methods have been extensively studied and can be applied to various fields. This structure, including metal wires (such as silver wires), exhibits excellent spatial resolution and flexibility. Exploring the above characteristics: When I am a strand of DNA As a template for forming metal nanoparticles, the high specificity of stranded DNA allows metal nanoparticles to be formed along the backbone of DNA [4]. Thus, the DNA molecule allows the metal to selectively bind to it, thereby providing a flexible and nano-sized template forming effect. For wire processes where resolution is not possible with traditional microelectronics, DNA electronics can be self-compensating to provide the right tools. However, the DNA-assisted metal wire patterning method still cannot solve the problem of low output per unit time in the industrialization process. The point is that we must first deal with the ability and controllability of flexible "writing" and then talk about how to reduce the cost and complexity of related processes. Recently, a number of concise design structures have been proposed which overcome the above problems, emphasizing the alignment and reproducibility of the steerable patterns. However, these methods still lack the decisive steps required to achieve industrial-level controllability and precision, and thus do not have the commercial viability of actual production.

In view of the above, one of the objects of the present invention is to manufacture a metal nanowire based on a DNA transition support structure in a commercially viable manner, in particular to provide a nanowire in a controlled manner for solid support. The method of the surface allows us to design and fabricate circuits on solid supports to create tantalum wafers.

In order to solve the above problems, a first aspect of the present invention provides a method of fabricating a micron to nanowire on a support material, comprising the steps of: (a) providing a solid support material; (b) providing a nucleic acid comprising A liquid composition with metal nanoparticle is applied to the surface of the support material to obtain a solid support material having at least one region of the surface covered by the liquid composition and at least one region not covered by the liquid composition. Thereby producing at the edge between the area covered by the liquid composition and the area not covered by the liquid composition Micron to nanowire; and (c) the nucleic acid can be removed if desired.

Preferably, the metal is selected from the group consisting of platinum, iron, cobalt, nickel, gold, silver, copper, iron oxide, copper oxide, zinc oxide, and alloys thereof, and more preferably silver (Ag).

In a preferred embodiment, the nucleic acid is selected from the group consisting of single-stranded (ss) or double-stranded (ds) DNA, PNA or RNA, and more preferably double-stranded DNA.

In a preferred embodiment, step (c) must be performed. Preferably, the step (c) is carried out by enzyme etching, preferably using a nuclease, and particularly preferably using a ribozyme.

For the purposes of the present invention, one preferred embodiment of the solid support material is bismuth (Si), more preferably a wafer.

In another embodiment, a surface tension reducing agent, preferably a surfactant, is added to the liquid composition.

In the case of step (b), the step preferably comprises the step of applying the liquid composition to the solid support material and then removing portions of the liquid composition from the surface of the solid support material to achieve a solid support The material, at least one region of its surface is covered by the liquid composition, and at least one region is not covered by the liquid composition. The desired way of performing the removal is to scrape, cut or remove the liquid composition by scribing. In the present invention, scraping, cutting, or by scribing removal means removing the liquid composition to a depth that is as direct as the solid support material.

Thus, the method of the present invention provides a simple way to apply a predetermined pattern of metal nanowires to a solid support, such as a tantalum wafer, as will be further explained below. If a scraping method is used, one preferred embodiment of the predetermined pattern is a line such as a circuit.

In step (b) of an embodiment of the method, after applying the liquid composition to the surface of the solid support material, the liquid composition is still dried to obtain a surface on the solid support material and comprising A gel-like film of the metal nanoparticles and the nucleic acid. To facilitate the drying, a desiccant, such as a solvent, preferably ethanol, may be added. For example, the drying can be air drying, preferably air drying for at least 1, 2, 3, 4, 5, 6, 7 hours or longer. One alternative to the drying is to apply the liquid composition to the solid support material in the form of a gel or film. An advantage of using the gel-like or film-like composition of the nucleic acid/metal nanoparticle is that the film can be easily scraped off from the surface, thereby producing a controlled edge. The shape of this edge is the template for the subsequently prepared nanowire. Thus, the sharper the edge, the higher the nanowire density on the solid support material.

The principles of the invention are described in detail below. In summary, the micron to nanowire is fabricated in such a manner that the nucleic acid/metal nanoparticle diffuses to the edge. As the nucleic acid-metal material diffuses toward the edge, it accumulates at the edge and forms a strand structure. The principle that contributes to the diffusion is the so-called "coffee stain ring effect".

The problem to be solved by the present invention can be solved by a method for fabricating a germanium wafer having micron to nanowires, the method comprising the steps of: (a) providing a germanium wafer; and (b) providing a nucleic acid comprising a liquid composition with a metal nanoparticle composite; (c) applying the liquid composition to the surface of the tantalum wafer; (d) drying the tantalum wafer to obtain a nucleic acid/metal nanoparticle on a surface a wafer of particle film; (e) removing portions of the nucleic acid/metal nanoparticle film from the surface of the germanium wafer, thereby fabricating an edge for the film on the surface of the germanium wafer; and (f) removing the solvent if necessary The nucleic acid is preferably an enzyme hydrolysis method, and more preferably a deoxyribonuclease.

Preferably, step (e) comprises scraping off the surface of the germanium wafer or removing the film by scribing (as described above).

Also as described above, it is preferable to perform step (f).

Other aspects of the invention pertain to a solid support or tantalum wafer made by the methods described herein.

The present invention further provides a method of fabricating a circuit wafer comprising performing one of the foregoing methods.

Another aspect of the invention pertains to a computer comprising the solid support, tantalum wafer or wafer of the present invention.

Yet another aspect of the invention pertains to a micron to nanowire made by the method of the invention.

The content of the present invention has been explicitly described above in accordance with certain preferred embodiments. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention to the principles and scope of the invention.

Figure 1: Atomic Force Microscopy (AFM) imaging. Contact type AFM imaging shows: (a) optical image before enzyme etching, (b) optical image after enzyme etching, (c) height change, and (c) silver The three-dimensional structure of the line.

Figure 2: Elemental composition analysis. Images (a), (b), and (c) show the distribution of silver nanoparticles on the germanium wafer. The measurement position of the silver distribution in the figure is at the green point (representing the different points in the wafer substrate), the inside of the film, the line material and the cutting area.

In the present invention, the inventor overcomes the aforementioned problems with two innovative concepts, the concept of which is to induce DNA-silver molecules to flow toward a controlled scribe line by capillary force, and the concept second is to support the DNA transition on the 矽 wafer. The structure is subjected to enzyme etching. The technique proposed by the present invention utilizes the self-assembly property of DNA-silver nanoparticle (NP) film before scribing, and the capillary force generated by the "drying" effect after scribing induces the nanoparticle to move to the scribing. At the same time, a metal-DNA pattern is formed on the film.

The unwanted DNA material is then removed by enzyme etching to produce only silver lines on the wafer. The results of the atomic force microscopy (AFM) confirmed the above results and showed a granular strand structure. Scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) confirmed the deposition of significantly larger amounts of silver nanoparticles on the strands. The above observations confirm the metal area of the surface scan and show the submicron to nanometer scale of the silver assembly. Thus, potential applications of the method include micron to nanoscale resolution that can be used to fabricate patterned metal lines. The inventor believes that this application can completely reduce the component pitch and improve the wiring density in a controlled manner to meet the miniaturization of electronic devices.

Materials and Methods

Preparation of germanium wafer substrate

Wafers measuring 20 inches x 0.5 mm (single-sided polished, <100>, n-type, Undoped) was purchased from Sigma, UK and kept refrigerated (about 4 ° C) before use. The wafers used in this experiment were used only once and were obtained directly from the supplier, so no additional cleaning was required.

Cultivation of silver nanoparticles

The freeze-dried pBR322 DNA (MW 2.9 x 106 Da) from Escherichia coli RR1 (Sigma, UK) was placed in a vial and mixed with 0.5 ml of deionized water (18.2 MΩ.cm). 400 μL of this DNA solution and 400 μl of silver nanoparticle dispersion (particle size of 10 nm, concentration of 0.2 mg.mL ^-1 ) were mixed in an aqueous buffer (Sigma, UK) to form a mixture. This solution was cultured overnight to facilitate metal silver aggregates to bind to DNA molecules.

Manufacture of DNA-silver nanoparticle lines

50 microliters of the DNA-silver nanoparticle solution was dropped onto the tantalum wafer using a micropipette. After 15 minutes, a drop (10 μl) of ethanol was dropped on the above droplets, left overnight, and allowed to air dry. After scribing with a surgical knife, it was observed that a separation phenomenon was visually observed (i.e., a cut-out region was formed). The DNA transition support structure is then removed by enzyme hydrolysis. The wafer containing the DNA-silver nanoparticle film was immersed in 10 ml of a 1 mM potassium phosphate buffer solution (pH 7.4, which contained a deoxyribonuclease I (concentrated in 2 mg.mL ^-1 from bovine pancreas). The company and the concentration of 2mM magnesium chloride (Sigma, UK), wait for the enzyme to work.

AFM imaging

AFM surface and electrical imaging (Veeco Dimension 3100) was performed with an AFM probe having a contact tip (model SCM-PIC and containing germanium doped with antimony (n)).

SEM-EDX measurement

Elemental analysis was carried out by a SEM-EDX instrument (model Verios 460, manufactured by FEI, USA).

Example 1: Manufacturing of Silver Microwires

The process consists of three main stages: self-assembly of DNA-silver nanoparticle suspensions, formation of lines by scribing or writing, and removal of DNA by enzymatic hydrolysis [8]. In the first stage, a drop (50 microliters) of the above suspension was dropped onto a clean crucible wafer, and then about 10 microliters of ethanol was applied and allowed to air dry. The role of ethanol is to concentrate and dehydrate the DNA to exhibit mechanical stability on the wafer [9]. After the water molecules were dried overnight and evaporated, a gel-like film residue was observed. The cut-out area is then formed by scribing, and the depth of the cut is directly to the wafer, thereby effectively separating the edges of the cut-out area. The gel-like nature of this mixed film allows the DNA-silver nanoparticles to move flexibly toward the resection zone. This phenomenon is evidenced by the higher material density in Figure 1a, which is caused by capillary flow from the edge of the ablation zone. The DNA transition support structure is then subjected to enzymatic etching, and the enzyme used is DNase [8]. The optical image shows the difference between before and after etching: the substrate becomes cleaner after being treated with enzyme, as shown in Figure 1b.

Example 2: Surface morphology of silver wire

Figure 1 clearly shows the silver wire structure produced by the method of the present invention. The optical image shows a higher material density on both sides of the scribe line (Fig. 1a). This observation coincides with the "coffee ring" effect [10] produced by the capillary force when the solution droplets are dried, and finally forms a continuous granular strand structure (Figs. 1c and 1d). The measurement results show an average height of about 200 to 400 nm, with occasional protrusions up to 800 nm and width measurements less than 10 microns. The above values demonstrate that this experiment has successfully produced sub-micron to nanoscale scales.

Example 3: SEM-EDX Analysis

The inventors performed elemental composition analysis along different regions of the wafer substrate to prove that the silver wire was successfully fabricated in this experiment (Fig. 2). The results of the analysis show that the percentage of silver along the strand structure is significantly higher than the percentage of silver in other regions. Figure 2 particularly shows the distribution of silver on the wire (a), the distribution of silver in the film (b), and the distribution of silver in the ablation zone. As expected, under the action of capillary forces, the metal nanoparticles were deposited only along the strand structure, and almost no deposition was observed in the other two regions.

The technology described in this paper proposes two innovative approaches that will break through the major development bottlenecks of current DNA-assisted metal micron to nanowire processes. Compared with other methods, the main advantage of the method of the present invention is that the natural capillary force is used to drive the DNA-silver nanoparticles to diffuse toward the physically formed cleavage region or scribe region, and then DNA is carried out by DNase. Biochemical enzyme etching of the transition support structure produces a pure silver wire structure. The second step described above makes a significant contribution to how to make a clean, only wire material that can be integrated into the substrate of the nanoelectronics architecture. The first step described above improves the controllability and flexibility of the "writing" process of the metal wire by using capillary force, which is different from the case where any wire and pattern are produced in the literature [6, 7, 11-13].

The capillary force is generated when the water is evaporated from the edge, and the rate of water replenishment at the edge of the body varies with the position within the droplet. Based on this phenomenon, the DNA molecules "drag" the silver nanoparticles toward the edge, and the silver nanoparticles form a strand after deposition. The evaporation process may also induce Marangoni flow in the droplets, but this flow condition is not conducive to the deposition of DNA-silver nanoparticles along the edges [14]. The powerful Marangoni flow allows the particles to redistribute and return to the center. The addition of a surface tension reducing agent can disturb the Marangoni flow, which may thereby promote the deposition of DNA-silver nanoparticles along the strand region, thereby improving the structural and electrical properties of the silver wire.

The resolution of "writing" can also be greatly improved and easily manipulated through the use of lithography and other nanoscale technologies [15-16]. The pattern can be easily written in this way, and the nanometer resolution of the strands may even contribute to the study of single molecule electronics. In addition, the assembly and patterning procedure proposed by the present invention provides flexibility in terms of low cost and process complexity compared to the literature [1-3, 6, 7, 11-13]. Therefore, the inventors expect that the above-mentioned recent discovery and reduction in writing width can accelerate the development of general nano patterning and nanoelectronics.

references:

1. Fu, et al., Nanomaterials and nanoclusters based on DNA modulation. Curr. Opi. Biotech. 28, 33-38 (2014).

2. Peng, et al., Self-assembly of λ-DNA networks/Ag nanoparticles: Hybrid architecture and active-SERS substrate. J. Coll. & Interf. Sci. 317, 183-190 (2008).

3. Yun, J.M. et al., DNA Origami Nanopatterning on Chemically Modified Graphene. Angew. Chem. Int. Ed. 50, 1-5 (2011).

4. Braun, E. et al., DNA-templated assembly and electrode attachment of a conducting silver wire. Nat. Lett. 391, 775-778 (1998).

5. Sara, A. et al., Adsorption of DNA on colloidal Ag nanoparticles: Effects of nanoparticle surface charge, base content and length of DNA. Coll. Surf. B: Biointerf. 116, 439-445 (2014).

6. Gu, Q. et al., DNA nanowire fabrication. Nanotech. 17, R14-R25 (2006).

7. Hamedi, M. et al., Electronic polymers and DNA self-assembled in Nanowire transistors. small 3, 363-368 (2013).

8. Abdelhady, H.G., Direct real-time molecular scale visualization of the degradation of condensed DNA complexes exposed to DNase I. Nucleic Acids Res. 31(14), 4001-4005 (2003).

9. Peng, et al., Self-assembly of λ-DNA networks/Ag nanoparticles: Hybrid architecture and active-SERS substrate. J. Coll. & Interf. Sci. 317, 183-190 (2008).

10. Deegan, et al., Contact line deposits in an evaporating drop. Phy. Rev. E 68, 042601-1 (2003).

11. Russel, C., et al., Gold Nanowire Based Electrical DNA Detection Using Rolling Circle Amplification. ACS Nano 8(2), 1147-1153 (2014).

12. Dai, et al., Fabrication of nanopatterned DNA films by Langmuir-Blodgett technique. Mat. Lett. 4, 423-429 (2005)

13. Sun, L. et al., Fabrication of silver nanoparticles ring templated by plasmid DNA. Appl. Surf. Sci. 252, 4969-4974 (2006).

14. Hu, H. & Larson, R.G., Marangoni Effect Reverses Coffee-Ring Depositions. J. Phy. Chem. B 110 (14), 7090-7094 (2006).

15. Jin, Z. et al., Metallized DNA nanolithography for encoding and transferring spatial information for graphene patterning. Nat. Comm. 4:1663.

16. Pradhan, A.K., Self-Assembly of DNA Nanostructures on electron beam lithographically patterned templates for biomedical and nanoelectronic sensor applications. J. The Electrochem. Soc. 161(2), B3023-B3027 (2014).

Claims (9)

A method of fabricating a germanium wafer having micron to nanowires, comprising the steps of: (a) providing a germanium wafer; and (b) providing a liquid composition comprising a composite of nucleic acid and metal nanoparticle; c) applying the liquid composition to the surface of the tantalum wafer; (d) drying the tantalum wafer to obtain a tantalum wafer having a nucleic acid/metal nanoparticle film on the surface; (e) from the crucible Removing a portion of the nucleic acid/metal nanoparticle film from the surface of the wafer to create an edge for the film on the surface of the wafer; and (f) removing the nucleic acid by hydrolysis as needed, preferably using an enzyme Hydrolysis, especially in the case of deoxyribonuclease. The method of claim 1, wherein the step (e) comprises scraping off the surface of the germanium wafer or removing the film by scribing. The method of claim 1 or 2, wherein the metal is selected from the group consisting of platinum, iron, cobalt, nickel, gold, silver, copper, iron oxide, copper oxide, zinc oxide, and alloys thereof, preferably silver. (Ag). The method of any one of claims 1 to 3, wherein the nucleic acid is selected from the group consisting of single-stranded (ss) or double-stranded (ds) DNA, PNA or RNA, preferably double-stranded DNA. The method of any one of claims 1 to 4, wherein step (f) is mandatory. The method of any one of claims 1 to 5, wherein the micron to nanowire of the step (e) is produced in such a manner that the nucleic acid/metal nanoparticle composite is diffused to the film. edge. A solid support or twine produced by the method of any one of claims 1 to 6 circle. A method of manufacturing a circuit wafer, comprising the method of any one of claims 1 to 6. A computer comprising a solid support, a crucible wafer or a wafer of claim 7 or 8.