Abstract:
As the conventional nanowire technology has many restrictions, the present invention discloses a method for transferring a one-dimensional micro/nanostructure to diversify the fabrication and application of nanocomponents, wherein a micro/nanostructure having formed on one substrate can be arbitrarily transferred to another substrate, whereby a micro/nanostructure can be integrated with different substrates.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a one-dimensional micro/nanostructure, particularly to a method for transferring a one-dimensional micro/nanostructure. 
         [0003]    2. Description of the Related Art 
         [0004]    With the development of nanometric technology, many researches are dedicated to miniaturizing materials and components. The one-dimensional micro/nanostructures refer to linear/columnar micron/nanometric-scale materials, including nanowires. Nanowires are emerging materials in the fields of electronics and optoelectronics, such as integrated circuits, organic solar cells, field effect transistors, and gas detectors. A nanowire is characterized in its very great length-width ratio. Growing a nanowire means inhibiting the growth in two directions (such as x direction and y direction) and facilitating the growth in the third direct (z direction). Because of nanometric size, the quantum effect of nanowires brings about many amazing physical and chemical properties in comparison with bulk materials. 
         [0005]    No matter in a liquid, solid or gas phase, growing a nanowire includes two steps: nucleation and growth. When atoms or molecules are supersaturated in a solution, the atoms or molecules will cluster to nucleate. After nucleation, the atoms or molecules are apt to adhere to the nuclei. From the viewpoint of thermodynamics, a nanowire forms because stacking atoms or molecules in a specified direction has a greater energy drop. 
         [0006]    From the viewpoint of the reaction environment, methods for forming nanowires may be categorized into soft approaches and hard approaches. Hard approaches refer to the methods needing an unusual environment, such as high temperature, high vacuum or a hard template. The VLS (Vapor-Liquid-Solid) method proposed by Wager and Ellis in 1964 is a common method to grow III-V group or semiconductor nanowires. In the VSL method, a metallic catalyst is used as a medium to deliver vapor-phase atoms. The atoms diffuse through the liquid metal to the bottom substrate where the atoms stack to form nanowires. In the VLS method, a specified material has to be grown on a specified substrate (usually a substrate made of a similar material) lest crystalline mismatch occur. In 2007, Stelzner et al. grew silicon nanowires on a silicon substrate via different metals, such as gallium, indium, aluminum and gold. In 2005, Mohan et al. used an e-beam lithography technology to grow an indium-phosphide nanowire on an indium-phosphide substrate. Compared with the hard approaches, the soft approaches use a temperate environment of an ambient temperature, a normal pressure and a liquid solution. The hydrothermal method, SLS (Solution-Liquid-Solid) method, biochemical synthesis method, and surfactant method are the frequently used methods among the soft approaches at present. However, the nanowires fabricated with the latter three methods are randomly dispersed because the nucleation locations are arbitrary. The hydrothermal method is the popular method to fabricate ordered nanowires; especially, zinc oxide is the best example of epitaxy. The etching method for fabricating nanowires is a method that cannot be categorized into the abovementioned approaches. In the etching method, nanoparticles are used as the mask for etching a bulk material, and a RIE (Reactive Ion Etching) machine or an etching liquid is used to etch away the unmasked areas. Via controlling the etching time and etching gas (or liquid), the etching method can attain nanowires with different lengths and widths. The nanowires fabricated with the etching method, such as silicon nanowires, are neatly arranged and almost vertical to the substrate. However, the etching method has to carefully select the etching gas (or liquid) for different materials. In 2005, Chang et al. fabricated gallium-nitride nanowires via coating a nickel layer as the mask on a gallium-nitride bulk material and etching the gallium-nitride bulk material with a RIE machine using chlorine gas and argon gas. 
         [0007]    The VLS method and the hydrothermal method are the bottom-up methods and need a specific substrate or a specific seed layer. Strictly to say, the molding method does not grow nanowires but fills material into a mold to form nanowires; the mold is used as the substrate herein. The etching method etches the bulk material to form nanowires, and the bulk material is exactly the material of the nanowires. In the existing technologies, a specified nanowire needs a specified substrate. In other words, a nanowire cannot form on an arbitrary substrate. For example, a high-quality Ill-V group nanowire (such a GaAs, GaAlAs, InP, or InGaAsP nanowire) is hard to grow on a silicon substrate or a glass substrate. The abovementioned problem greatly restricts the application of nanowires. 
       SUMMARY OF THE INVENTION 
       [0008]    The primary objective of the present invention is to provide a method for transferring a one-dimensional micro/nanostructure, whereby a one-dimensional micro/nanostructure can be transferred from one substrate to another substrate, and whereby a one-dimensional micro/nanostructure can be integrated with different substrates, and whereby diverse nanowires can be developed and fabricated, and whereby the conventional problems are overcome. 
         [0009]    To achieve the abovementioned objective, the present invention proposes a method for transferring a one-dimensional micro/nanostructure, which comprises steps: providing a first substrate having a plurality of one-dimensional micro/nanostructures; providing a second substrate; coating a first curable adhesive on the second substrate; inserting the one-dimensional micro/nanostructures on the first substrate into the first curable adhesive on the second substrate; curing the first curable adhesive; separating the one-dimensional micro/nanostructures from the first substrate and transferring the one-dimensional micro/nanostructures to the second substrate. 
         [0010]    In the present invention, the one-dimensional micro/nanostructures can be further transferred to a third substrate in the same method. Similarly, the one-dimensional micro/nanostructures can also be transferred to a fourth substrate in the same method. 
         [0011]    Below, the embodiments are described in detail in cooperation with the drawings to make easily understood the objectives, characteristics and efficacies of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIGS. 1A-1I  are diagrams schematically showing a method for transferring a one-dimensional micro/nanostructure according to one embodiment of the present invention; 
           [0013]      FIGS. 2A-2G  are diagrams schematically showing that a first substrate has an additional selectively-etched layer according to another embodiment of the present invention; 
           [0014]      FIGS. 3A-3E  are diagrams schematically showing a method for transferring a one-dimensional micro/nanostructure according to yet another embodiment of the present invention; 
           [0015]      FIGS. 4A-4E  are diagrams schematically showing that one-dimensional micro/nanostructures are transferred from a second substrate to a third substrate according to still another embodiment of the present invention; 
           [0016]      FIGS. 5A-5D  are diagrams schematically showing that one-dimensional micro/nanostructures are transferred from a second substrate to a third substrate according to a further embodiment of the present invention; 
           [0017]      FIGS. 6A-6E  are diagrams schematically showing that one-dimensional micro/nanostructures are transferred to a fourth substrate according to a yet further embodiment of the present invention; 
           [0018]      FIGS. 7A-7D  are diagrams schematically showing that one-dimensional micro/nanostructures are transferred from a second substrate to a third substrate according to a still further embodiment of the present invention; and 
           [0019]      FIGS. 8A-8E  are diagrams schematically showing that one-dimensional micro/nanostructures are transferred from a second substrate to a fourth substrate according to a still yet further embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Refer to  FIGS. 1A-1I  for a method for transferring a one-dimensional micro/nanostructure according to one embodiment of the present invention. 
         [0021]    In this embodiment, a first substrate  10  is provided firstly, and then a plurality of one-dimensional micro/nanostructures  11  is formed on the first substrate  10 , as shown in  FIG. 1A . The one-dimensional micro/nanostructures  11  are micron/nanometric wire-like/column-like structures vertical to the substrate  10 , and the one-dimensional micro/nanostructure  11  has a sectional width of between 1 nm and 1000 μm, and a height of between 0.3 μm and 60 μm, as shown in  FIG. 1B . The nanowires or nanocolumns are made of a semiconductor material or another material, such as silicon, germanium, gallium arsenide, indium phosphide, germanium phosphide, antimony selenide, indium gallium nitride, a binary compound semiconductor, a ternary compound semiconductor, or a quaternary compound semiconductor. The one-dimensional micro/nanostructures  11  are formed on the first substrate  11  with a CVD (Chemical Vapor Deposition) method, an epitaxial method, a chemical etching method, a dry etching method, or another method. 
         [0022]    The material of the first substrate  10  is dependent on the material of the one-dimensional micro/nanostructures  11  and may be a semiconductor, a metal, or an insulating material. The material of a second substrate  20 , which is to be mentioned below, is dependent on the practical application and may be a plastic, a metal, a semiconductor, a ceramic, a transparent material, or a glass coated with a transparent conductive layer. 
         [0023]    Next, a second substrate  20  is provided, and a first curable adhesive  21  is applied onto the second substrate  20 , as shown in  FIG. 1C . The first curable adhesive  21  is a solidifiable liquid or gel, such as a sol, a gel, a polymeric material, a wax, SOG (Spin-On Glass), PMMA (polymethylmethacrylate), or, P3HT (poly(3-hexylthiophene)). If the second substrate  20  is made of a heat-resistant material, the first curable adhesive  21  may also adopt a molten metal. Next, the one-dimensional micro/nanostructures  11  of the first substrate  10  is inserted into the first curable adhesive  21  of the second substrate  20 , as shown in  FIG. 1D . The one-dimensional micro/nanostructures  11  may be completely submerged into the first curable adhesive  21 , as shown in  FIG. 1E . Alternatively, the one-dimensional micro/nanostructures  11  may be only partially submerged into the first curable adhesive  21 , as shown in  FIG. 1F . 
         [0024]    Considering the nanostructures are hard to be directly inserted into the first curable adhesive  21 , a second curable adhesive  12  is applied onto the one-dimensional micro/nanostructures  11  on the first substrate  10 , and then let the second curable adhesive  12  gradually permeate into the gaps of the one-dimensional micro/nanostructures  11 , as shown in  FIG. 1G . At the same time, the first curable adhesive  21  is also applied onto the second substrate  20 . Then, let the second curable adhesive  12  on the first substrate  10  insert into the first curable adhesive  21  on the second substrate  20 . In the present invention, the materials of the first curable adhesive  21  and the second curable adhesive  12  may be identical or different. 
         [0025]    Next, the first curable adhesive  21  is cured to bond the second substrate  20  to the first substrate  10 . At this time, the one-dimensional micro/nanostructures  11  are vertically stuck to the first substrate  10  and secured by the first curable adhesive  21 . Next, the one-dimensional micro/nanostructures  11  are separated from the first substrate  10  and transferred to the second substrate  20 , and the one-dimensional micro/nanostructures  11  are maintained about vertical to the second substrate  20 , as shown in  FIG. 1H  and  FIG. 1I . The one-dimensional micro/nanostructures  11  are separated from the first substrate  10  via various methods. For example, the one-dimensional micro/nanostructures  11  is separated from the first substrate  10  via ultrasonic vibration, knocking the lateral of the first substrate  10 , slightly knocking the surface, or pulling up the first substrate  10  with a pump. If the one-dimensional micro/nanostructures  11  are well stuck to the first curable adhesive  21 , the one-dimensional micro/nanostructures  11  can be detached from the first substrate  10  via directly lifting off the first substrate  10 . The first substrate  10  may also be removed with a chemical etching method. 
         [0026]    Refer to  FIGS. 2A-2G  for another embodiment of the present invention. If the one-dimensional micro/nanostructures  11  are too tough to be separated from the first substrate  10  with ultrasonic vibration or knocking, a selectively-etched layer  13  is formed in between the first substrate  10  and the one-dimensional micro/nanostructures  11 , as shown in  FIG. 2A . Refer to  FIGS. 2B-2G . In this embodiment, the one-dimensional micro/nanostructures  11  are transferred with the same steps described above. The first curable adhesive  21  is applied onto the second substrate  20 . Next, the one-dimensional micro/nanostructures  11  on the first substrate  10  are inserted into the first curable adhesive  21  on the second substrate  20 , as shown in  FIG. 2B . The one-dimensional micro/nanostructures  11  may be completely submerged into the first curable adhesive  21 , as shown in  FIG. 2C . Alternatively, the one-dimensional micro/nanostructures  11  may only be partially submerged into the first curable adhesive  21 , as shown in  FIG. 2D . Similarly, the second curable adhesive  12  is applied onto the one-dimensional micro/nanostructures  11  of the first substrate  10 , and let the second curable adhesive  12  gradually permeate into the gaps of the one-dimensional micro/nanostructures  11 , as shown in  FIG. 2E . Then, let first substrate  10  having the one-dimensional micro/nanostructures  11  contact the second substrate  20  coated with the first curable adhesive  21 . 
         [0027]    Next, the first curable adhesive  21  is cured to bond the second substrate  20  to the first substrate  10 , and the one-dimensional micro/nanostructures  11  are thus vertically stuck to the second substrate  20  by the first curable adhesive  21 . Next, the selectively-etched layer  13  is etched away with a chemical etching method or a dry etching method. Thus, the one-dimensional micro/nanostructures  11  are separated from the first substrate  10  without violently damaging the first substrate  10  and the one-dimensional micro/nanostructures  11 , as shown in  FIG. 2F  or  FIG. 2G . Naturally, the other methods mentioned above may also be used to separate the one-dimensional micro/nanostructures  11  from the first substrate  10 . 
         [0028]    The one-dimensional micro/nanostructures  11  transferred to the second substrate  20  are then used to fabricate the desired components. For example, the nanostructures are made of a III-V group light emitting material, and the second substrate is a Si substrate, and thus is realized the integration of optoelectronic components and silicon electronic components. 
         [0029]    Refer to  FIGS. 3A-3E  for yet another embodiment of the present invention. In this embodiment, the one-dimensional micro/nanostructures  11  on the second substrate  20  are further transferred to a third substrate  30 . 
         [0030]    Refer to  FIG. 3A . Firstly, a layer of welding material  31  is coated on a third substrate  30 . The welding material  31  can be fused together with the one-dimensional micro/nanostructures  11 . For example, if the one-dimensional micro/nanostructures  11  are made of a silicon material, silicon will be adopted as the welding material  31 . The material of the third substrate may be a plastic, a metal, a semiconductor, a ceramic, a transparent material, or a glass coated with a transparent conductive layer. 
         [0031]    Refer to  FIG. 3B . Next, let the welding material  31  on the third substrate  30  contact the one-dimensional micro/nanostructures  11  on the second substrate  20 . Refer to  FIG. 3C . Next, the welding material  31  and the third substrate  30  are heated to a temperature, at which the welding material  31  and the portion of the one-dimensional micro/nanostructures  11  contacting the welding material  31  are melted with the third substrate  30  maintaining at a solid state. Thus, the one-dimensional micro/nanostructures  11  and the welding material  31  are fused together, as shown in  FIG. 3D . Then, let the molten welding material  31  and the molten one-dimensional micro/nanostructures  11  cool down and solidify. Thus are joined together the one-dimensional micro/nanostructures  11  and the third substrate  30 . 
         [0032]    As shown in  FIG. 3C , an intense laser light  70  passes through the third substrate  30  and illuminates the welding material  31  and the one-dimensional micro/nanostructures  11  contacting the welding material  31 , wherein the laser light  70  is controlled to such an intensity that the welding material  31  and the portion of the one-dimensional micro/nanostructures  11  contacting the welding material  31  are melted with the third substrate  30  maintaining at a solid state. Refer to  FIG. 3E . Then, the first curable adhesive  21  of the second substrate  20  is removed with a solvent, and the one-dimensional micro/nanostructures  11  is separated from the second substrate  20  and transferred to the third substrate  30 . 
         [0033]    Refer to  FIGS. 7A-7D  for a still further embodiment of the present invention, wherein one-dimensional micro/nanostructures are transferred from a second substrate to a third substrate. In this embodiment, the transfer may also use the same method for the transfer from the first substrate to the second substrate. Firstly, a third curable adhesive  32  is applied onto a third substrate  30 , as shown in  FIG. 7A . Next, let the one-dimensional micro/nanostructures  11  on the second substrate  20  contact the third curable adhesive  32  on the third substrate  30 , as shown in  FIG. 7B . Next, the one-dimensional micro/nanostructures  11  are separated from the second substrate  20  via ultrasonic vibration, slight knockings, pump suction, chemical etching, or even directly lifting off the second substrate  20 , as shown in  FIG. 7C . Then, the first curable adhesive  21  is removed with a solvent; thus, the one-dimensional micro/nanostructures  11  are transferred to the third substrate  30 , as shown in  FIG. 7D . 
         [0034]    Refer to  FIGS. 4A-4E  for still another embodiment of the present invention, wherein the one-dimensional micro/nanostructures  11  are transferred from a second substrate  20  to a third substrate  30 . 
         [0035]    Firstly, a portion of the first curable adhesive  21  is removed with a chemical etching method or a dry etching method to partially reveal the one-dimensional micro/nanostructures  11 , as shown in  FIG. 4A . Alternatively, if the one-dimensional micro/nanostructures  11  on the second substrate  20  have been partially revealed, the second substrate  20  is directly adopted. Next, the revealed one-dimensional micro/nanostructures  11  are illuminated with an intense laser light  70  having such an intensity that the tops of the one-dimensional micro/nanostructures  11  are melted to form a film  22  covering the first curable adhesive  21 , as shown in  FIG. 4B  and  FIG. 4C . Then, let the film  22  cool down and solidify. As the film  22  and the one-dimensional micro/nanostructures  11  are of an identical material, they can be fused together easily. Next, as shown in  FIG. 4D , the film  22  is bonded to a third substrate  30  with a van der walls force technology, a silicon-glass anodic bonding technology, a liquid-solid alloying bonding technology, or a common LCD (Liquid Crystal Display) bonding technology, such as TAB (Tape Automated Bonding), ACF (Anisotropic Conductive Film), COG (Chip On Glass), COF (Chip On Film), etc. Then, the cured first curable adhesive  21  is removed with a solvent to separate the one-dimensional micro/nanostructures  11  from the second substrate  20 ; thus, the one-dimensional micro/nanostructures  11  is transferred to the third substrate  30 , as shown in  FIG. 4E . 
         [0036]    Refer to  FIGS. 5A-5D  for a further embodiment of the present invention, wherein one-dimensional micro/nanostructures are transferred from a second substrate to a third substrate. In this embodiment, the transfer may also use the same method for the transfer from the first substrate to the second substrate. Firstly, a third curable adhesive  32  is applied onto a third substrate  30 , as shown in  FIG. 5A . Next, the one-dimensional micro/nanostructures  11  on the second substrate  20  is inserted into the third curable adhesive  32  on the third substrate  30 , as shown in  FIG. 5B . Next, the third curable adhesive  32  is cured, and the one-dimensional micro/nanostructures  11  is separated from the second substrate  20  via ultrasonic vibration, slight knockings, pump suction, chemical etching, or even directly lifting off the second substrate  20 , as shown in  FIG. 5C . Then, the first curable adhesive  21  is removed with a solvent; thus, the one-dimensional micro/nanostructures  11  are transferred to the third substrate  30 , as shown in  FIG. 5D . 
         [0037]    Via the abovementioned methods, microstructures and submicrostructures can also be transferred from a first substrate to another substrate. The microstructure or submicrostructure is made of a semiconductor material or another material, such as silicon, germanium, gallium arsenide, indium phosphide, germanium phosphide, antimony selenide, indium gallium nitride, a binary compound semiconductor, a ternary compound semiconductor, or a quaternary compound semiconductor. The nanostructures (such as nanowires and nanocolumns), microstructures and submicrostructures are fabricated via etching a well crystallized chip or via a high-quality epitaxial process. Therefore, the nanostructures, microstructures and submicrostructures have the advantages of crystalline semiconductors. Further, after the nanostructures are separated from the substrate, the substrate can be used again. Therefore, the present invention will not consume too much semiconductor material. 
         [0038]    Refer to  FIGS. 6A-6E  for a yet further embodiment of the present invention, wherein one-dimensional micro/nanostructures are transferred to a fourth substrate. 
         [0039]    Firstly, a welding material film  33  is formed on a third substrate  30 , wherein the welding material film  33  and the one-dimensional micro/nanostructures  11  can be fused together. The welding material film  33  is melted by heating, and the one-dimensional micro/nanostructures  11  on the second substrate  20  are inserted into the molten welding material film  33  on the third substrate  30 , as shown in  FIG. 6A . After the welding material film  33  cools down and solidifies, the third substrate  30  is separated from the welding material film  33 , and the welding material film  33  is thus bonded to the one-dimensional micro/nanostructures  11 , as shown in  FIG. 6B . Next, a fourth substrate  40  is bonded to the welding material film  33 , as shown in  FIG. 6C . Next, the one-dimensional micro/nanostructures  11  are separated from the second substrate  20 , as shown in  FIG. 6D . Then, the first curable adhesive  21  is removed with a solvent, and the one-dimensional micro/nanostructures  11  are thus transferred to the fourth substrate  40 , as shown in  FIG. 6E . 
         [0040]    Refer to  FIGS. 8A-8E  for a still yet further embodiment of the present invention, wherein one-dimensional micro/nanostructures are transferred from a second substrate to a fourth substrate. The partially revealed one-dimensional micro/nanostructures  11  may also be transferred to a fourth substrate. Similarly to the abovementioned steps, a welding material film  33  is formed on a third substrate  30  and melted by heating, and the one-dimensional micro/nanostructures  11  on the second substrate  20  are inserted into the molten welding material film  33  on the third substrate  30 , as shown in  FIG. 8A . After the welding material film  33  cools down and solidifies, the third substrate  30  is separated from the welding material film  33 , and the welding material film  33  is thus bonded to the one-dimensional micro/nanostructures  11 , as shown in  FIG. 8B . Next, a fourth substrate  40  is bonded to the welding material film  33 , as shown in  FIG. 8C . Next, the second substrate  20  is separated from the one-dimensional micro/nanostructures  11 , as shown in  FIG. 8D . Then, the first curable adhesive  21  is removed with a solvent, and the one-dimensional micro/nanostructures  11  are thus transferred to the fourth substrate  40 , as shown in  FIG. 8E . 
         [0041]    The welding material film  33  can be bonded to the one-dimensional micro/nanostructures  11  with a laser light  70 . After the welding material film  33  is formed on the third substrate  30 , let the one-dimensional micro/nanostructures  11  contact the welding material film  33  on the third substrate  30 , the welding material film  33  and the tops of the one-dimensional micro/nanostructures  11  are melted by an intense laser light  70 . Thus is formed a film  33  covering the first curable adhesive  21 . After the film  22  cools down and solidifies, the film  33  and one-dimensional micro/nanostructures  11  are fused together. Then, the film  33  is separated from the third substrate  30  and only boned to the one-dimensional micro/nanostructures  11 . 
         [0042]    Via the abovementioned methods, the epitaxial semiconductor structures emitting an infrared ray having a wavelength of 1.3-1.6 μm can be placed on a silicon substrate. Thereby, an optical communication light source and IC can be integrated in an identical chip. Also, the epitaxial semiconductor structures for waveband detection can be placed on a silicon substrate. Thereby, an optical communication detector and IC can be integrated in an identical chip, which will greatly benefit future optical communication. Further, the epitaxial semiconductor structures emitting visible light can be placed on a transparent substrate or a plastic substrate. Thereby, the light emitted is easy to penetrate. Furthermore, after the nanostructures are separated from the semiconductor substrate, the semiconductor substrate can be reused, and the material cost is greatly reduced. Moreover, the semiconductor material can be placed on a non-conductive transparent substrate, a non-conductive plastic substrate, or another flexible substrate. Thereby are fabricated flex-electronics circuits and flex-optoelectronics components, displays and solar cells. 
         [0043]    The embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention. Therefore, any equivalent modification or variation according to the spirit of the present invention is to be also included within the scope of the present invention, which is based on the claims stated below.