JP4230861B2 - Hall array manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing a hole array, and in particular, easily and inexpensively manufactures a hole array in which fine and uniformly sized pores are formed in a uniform cycle and over a large area without going through complicated steps. Relating to possible ways.

  Porous materials having fine pores of submicron or nanometer scale are expected to be applied as catalysts, sensors, electronic / optical devices and the like. The production of porous materials has been studied with various materials such as metals, metal oxides, and polymers, and the production methods are diverse such as CVD, sol-gel, and electrodeposition. However, in general, the pores of the obtained porous structure are not orthogonal to the membrane surface, and it is difficult to produce a hole array structure in which cylindrical pores of uniform size are regularly arranged. .

  As a method for solving this problem, an anodized porous alumina having a structure in which pores are orthogonal to the film surface is used as a starting structure, and a hole array structure having a structure similar to the regular structure of porous alumina by a two-step transfer process. A method for obtaining the information has been proposed (for example, Non-Patent Document 1). According to this method, it is possible to produce a hole array structure in which the structure of anodized porous alumina is faithfully transferred. Since it consists of a staged process, it had the problem of being complicated.

As a method for solving these problems, a porous alumina in which the cell boundary portion is easily dissolved is produced by anodizing a chromium-containing aluminum plate, and this is etched to form a substance in the gap between cells. There has been reported a method of obtaining a hole array structure by a one-step transfer process in which filling is performed (for example, Non-Patent Document 2). ). By this method, a hole array structure having a pore period of 500 nm is obtained. However, since it is difficult to uniformly dissolve chromium in the aluminum base material, a hole array cannot be obtained with a fine pore period of less than 500 nm with good reproducibility.
H. Masuda, and K. Fukuda, Science, 268, 1466 (1995) Abstracts of the 68th Annual Meeting of the Electrochemical Society of 2001 p. 121

  Accordingly, the present invention provides a means for easily obtaining a hole array from a material in which pores arranged in a self-organizing manner are arranged in order to solve the above-described problems in producing a hole array expected to be used in various applications. It was made as a result of earnest examination about. The object is to provide a method for producing a hole array that can easily and inexpensively produce a hole array in which fine pores of uniform size are orthogonal to the membrane surface even in a large area without going through complicated steps. There is.

  In order to achieve the above object, the present invention utilizes a specific dissolution characteristic at the cell boundary portion of anodized porous alumina obtained using a high concentration sulfuric acid electrolyte, and has excellent pore diameter uniformity. You will get an array. That is, in the method for producing a hole array according to the present invention, a substance formed in a void formed by dissolving a cell boundary portion of porous alumina obtained by anodizing aluminum in an electrolytic bath containing 7 M or more sulfuric acid. It consists of a method characterized in that a hole array is obtained by filling.

As described above, in the method according to the present invention, anodized porous alumina obtained by anodizing aluminum in an electrolytic bath containing 7 M or more sulfuric acid is used for producing the hole array. Anodized porous alumina prepared under normal conditions cannot selectively dissolve the cell boundary, but the cell boundary is preferentially dissolved by using an aqueous solution containing 7M or more sulfuric acid in the electrolytic bath. Porous alumina is produced. At this time, if the number of cells per square centimeter of the surface area of aluminum is 5.0 × 10 ^{8 to} 3.0 × 10 ¹¹ , specific dissolution characteristics at the cell boundary appear surely. Therefore, in the method according to the present invention, it is preferable to form 5.0 × 10 ^{8 to} 3.0 × 10 ¹¹ alumina cells per square centimeter of aluminum surface area by anodic oxidation.

  Further, if the period of the formed pores is 500 nm or less, specific dissolution characteristics at the cell boundary appear. Therefore, in the method according to the present invention, it is preferable to produce a hole array having a pore period of 500 nm or less.

  By selectively dissolving the cell boundary portion of the porous alumina, voids are formed between the alumina cells, and the voids can be filled with a substance. By the above method, a hole array having a uniform pore diameter can be easily produced without going through complicated steps, for example, two steps in the conventional method as described above.

  As described above, according to the method for manufacturing a hole array according to the present invention, a hole array in which fine and uniformly sized pores are formed with a uniform period can be easily and inexpensively manufactured without going through complicated steps. can do. Also, since the porous alumina used as a material only needs to be anodized in a specific electrolytic bath, it can be easily manufactured up to a large one, and even a large hole array can be easily manufactured. .

Hereinafter, the present invention will be described in detail together with preferred embodiments with reference to the drawings.
FIG. 1 shows a hole array manufacturing method according to an embodiment of the present invention in the order of steps. Aluminum 1 is anodized in an electrolyte containing 7 M or more sulfuric acid to produce porous alumina 2 (step A). After the porous alumina 2 is produced, a support layer that functions as an electrode or a reinforcing layer is formed on the surface. Prior to the formation of the support layer, it is also preferable to polish the outermost layer of porous alumina as in Step B in order to facilitate filling of the material between the cells by the electrodeposition method. As a method for polishing the surface layer, in addition to mechanical polishing, polishing in vacuum such as ion milling can be used. In the example shown in FIG. 1, the support layer 3 is formed on the polished surface layer (step C). Any material and forming method may be used for the support layer 3. For example, a metal (for example, gold) is vapor-deposited on the sample surface, and a support layer having excellent strength can be formed by plating using this as an electrode. After the support layer 3 is formed on the surface of the porous alumina 2, the aluminum ingot portion is selectively dissolved and removed (step D). When anodization is performed using film-like aluminum formed on the substrate surface, it is necessary to remove the substrate and aluminum. The porous alumina 2 whose bottom is exposed by removing aluminum forms a void between the cells by immersing it in a solution that dissolves the cell boundary (step E). The liquid for dissolving the alumina cell boundary is not particularly limited, and for example, a general acidic aqueous solution such as phosphoric acid can be used. After the cell boundary portion is melted, porous alumina 4 having voids between cells serving as a template for producing a hole array structure in one step is obtained. The space between the cells is filled with the substance 5 (Step F). Various methods such as an electrodeposition method, a sol-gel method, and a CVD method can be used for filling the substance 5. Various materials such as metals, metal oxides, and polymers can also be used for the material 5 to be filled. After filling the space between the cells with the substance 5, the target hole array 6 can be obtained by dissolving the matrix alumina (step G).

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by this Example.
Example 1 (Preparation of titanium oxide hole array)
An aluminum plate having a purity of 99.99% and a size of 1.5 cm × 5 cm × 0.5 mm was electropolished and then anodized using a 0.3 M sulfuric acid aqueous solution at 16 ° C. for 12 hours at a direct current of 25V. Thereafter, the formed anodized alumina was dissolved using an aqueous solution consisting of 1.8% by weight of chromium oxide and 6% by weight of phosphoric acid to obtain aluminum having a regular depression array on the surface. Next, anodic oxidation was performed for 6 minutes at 25 VDC using an 11 M sulfuric acid aqueous solution at 0 ° C. The obtained anodized porous alumina was removed to a depth of 100 nm by using an ion milling apparatus. Thereafter, 50 nm of Au was vapor-deposited on the alumina surface, and Au was electrolytically deposited at a current density of −1 to −50 mA cm ⁻² to a thickness of 50 μm using an Au electrodeposition bath. The aluminum ingot portion of the sample was removed by dipping in a methanol solution saturated with iodine. After removing the aluminum ingot, porous alumina was immersed in a 1% by weight phosphoric acid aqueous solution at 30 ° C. for 7 minutes to selectively dissolve the alumina cell boundary portion. The obtained sample was electrodeposited for 3 minutes in a 0.05 M titanium chloride aqueous solution adjusted to pH 2.7 by adding a saturated aqueous sodium hydrogen carbonate solution at a current density of +0.5 mA cm ⁻² . Thereafter, heat treatment was performed for 3 hours at 450 ° C. in order to crystallize the deposited titanium oxide. The matrix-type anodized porous alumina was dissolved and removed in an aqueous solution containing 1.8% by weight of chromium oxide and 6% by weight of phosphoric acid to obtain a titanium oxide hole array.

  The obtained titanium oxide hole array 7 was excellent in having a uniform pore diameter and a uniform pore cycle (pore cycle 60 nm, pore diameter 40 nm) as shown in FIG. .

  The method for manufacturing a hole array according to the present invention can be applied to the manufacture of all types of hole arrays in which fine and uniform-sized pores of submicron or nanometer scale are required to be formed with a uniform period. Since a hole array having a relatively large area can be easily and inexpensively manufactured, a hole array applicable to various catalysts, sensors, electronic / optical devices, and the like can be manufactured.

It is explanatory drawing which showed the manufacturing method of the hole array which concerns on one embodiment of this invention in process order. 2 is a partial plan view of a titanium oxide hole array produced in Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aluminum 2 Porous alumina 3 Support layer 4 Porous alumina with a space | gap between cells 5 Filled material 6 Hole array 7 Titanium oxide hole array produced in Example 1

Claims (3)

  It is characterized in that a hole array is obtained by filling a void formed by dissolving a cell boundary portion of porous alumina obtained by anodizing aluminum in an electrolytic bath containing 7 M or more sulfuric acid. A method for manufacturing a hall array. The manufacturing method of the hole array of Claim 1 which forms 5.0 * 10 < ⁸ > -3.0 * 10 < ¹¹ > alumina cells per square centimeter of aluminum surface area by anodization.   The method for producing a hole array according to claim 1 or 2, wherein a hole array having a pore period of 500 nm or less is produced.

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