JP5521197B2 - Method for forming wire-like projections on metal material surface, and metal material provided with the wire-like projections - Google Patents

Description

  The present invention relates to a method of forming a wire-like projection on the surface of a metal material by sputter etching, and a metal material including the wire-like projection.

  As a material used for an electrode such as an electric double layer capacitor, a hollow carbon nanotube is known. Carbon nanotubes are produced, for example, by evaporating carbon by arc discharge in an inert gas atmosphere and then aggregating them (Patent Document 1).

  When the electrode is made of a metal material, it is desirable that the surface area of the metal material be large in order to ensure a large electric capacity. In order to realize this, it is considered effective to form protrusions on the surface of the metal material by sputter etching or the like. The inventors of the present application have confirmed that conical protrusions are formed on the surface of a metal material by performing sputter etching using argon ions (Patent Document 2).

JP-A-6-280116 JP 2006-63390 A

  By the way, the conical protrusion disclosed in Patent Document 2 has a low height and therefore does not have a large aspect ratio. To increase the surface area of the metal material greatly, a protrusion having a larger aspect ratio is made of the metal material. It needs to be formed on the surface.

  In addition, the method disclosed in Patent Document 1 is to obtain carbon nanotubes as a simple substance, and is not a technique for increasing the surface area of the material.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for forming a wire-like protrusion on a metal material surface capable of greatly increasing the surface area of the metal material, and the wire-like protrusion. It is to provide a metal material comprising an object.

In order to achieve the above object, a method for forming a wire projection on a metal material surface according to the first aspect of the present invention includes:
A first sputtering step of generating a plasma in the chamber by introducing high-frequency power while introducing an inert gas into the chamber, and performing sputter etching on the surface of the metal material installed in the chamber;
After the first sputtering step, while introducing water or hydrogen into the chamber in addition to the inert gas, plasma is generated in the chamber by the output of the high frequency power, and the surface of the metal material is A second sputtering step for performing sputter etching;
It is characterized by having.

  Preferably, the metal material is an aging metal material.

Preferably, in the first and second sputtering steps, the high-frequency power is output with the same magnitude,
A value obtained by dividing the time for performing the sputter etching in the second sputtering step by the time for performing the sputter etching in the first sputtering step is 0.2 or more and 0.3 or less.

  The metal material according to the second aspect of the present invention includes a wire-like protrusion formed by the method according to the first aspect.

  According to the present invention, a conical protrusion is formed in the first sputtering process, and a wire-shaped protrusion is formed from the tip of the conical protrusion in the second sputtering process. Since the wire-shaped protrusion has an extremely large aspect ratio, the surface area of the metal material is greatly increased by forming the wire-shaped protrusion.

It is a flowchart which shows the process which forms a wire-shaped protrusion on the surface of a metal material in embodiment of this invention. It is the schematic which shows the high frequency magnetron sputtering device used by the process of FIG. It is the photograph which image | photographed the surface of the board | substrate with which the conical protrusion (1st protrusion) was formed with the scanning electron microscope. It is the photograph which image | photographed the surface of the board | substrate with which the wire-shaped protrusion (2nd protrusion) was formed with the scanning electron microscope. It is a graph which shows the relationship between the average diameter of the bottom face of a conical protrusion, and the average diameter of a wire-like protrusion. It is a graph which shows the result of X-ray analysis of a conical protrusion, a wire-like protrusion, etc. It is a figure for demonstrating the formation mechanism of the protrusion to a substrate surface. It is the figure and photograph which expand and show a conical protrusion and a wire-like protrusion.

  FIG. 1 is a flowchart showing a process of forming wire-like projections on the surface of a metal material in the embodiment of the present invention. FIG. 2 is a schematic view showing a high-frequency magnetron sputtering apparatus 1 used in the process of FIG. Hereinafter, with reference to FIG. 1, 2, the formation procedure of the wire-shaped protrusion in this Embodiment is demonstrated.

  First, the substrate K which is an aging metal material is subjected to solution heat treatment (step S1). An aging metal material is an alloy, and when heated to a high temperature, all the alloy elements are uniformly dispersed. Refers to a metal that gathers and forms another phase. The solution heat treatment, also called quenching, refers to an operation in which the alloy is once held at a high temperature and all alloy elements are uniformly distributed and then rapidly cooled.

  In step S1, for example, the substrate K is heated with a heating device and then cooled with water. The heating of the substrate K is performed in an argon atmosphere from the viewpoint of preventing the oxidation of the substrate K. In addition, when using the board | substrate K which performed the solution heat treatment previously, step S1 is abbreviate | omitted.

  After step S1, the substrate K is placed in the chamber 3 of the high frequency magnetron sputtering apparatus 1 (step S2). As shown in FIG. 2, the high-frequency magnetron sputtering apparatus 1 includes the above-described chamber 3, a supply pipe 4, a high-frequency power source 5, and an exhaust device 6. The high-frequency magnetron sputtering apparatus 1 can supply argon gas, which is an inert gas, or distilled water into the chamber 3 through the supply pipe 4, and the high-frequency power source 5 outputs high-frequency power, so that the inside of the chamber 3 Plasma is generated. The supply pipe 4 is provided with valves 14 and 15, and the supply amount of argon gas or distilled water can be adjusted by opening and closing the valves 14 and 15. The exhaust device 6 can discharge the gas in the chamber 3 through the exhaust pipe 9 by the operation of the diffusion pump 7 and the oil rotary vacuum pump 8, and can reduce the pressure in the chamber 3.

  A sample stage 10 is provided inside the chamber 3. A holder 11 having a high thermal conductivity is placed on the sample stage 10, and the substrate K is placed on the holder 11 so that a surface a to be sputter-etched (hereinafter referred to as a substrate surface a) faces upward. The sample stage 10 has a water cooling pipe 12 (inflow side) and a water cooling pipe 13 (outflow side). When cooling water flows through the water cooling pipes 12 and 13, the temperature of the holder 11 decreases, and the substrate The surface b opposite to the surface a (hereinafter referred to as the substrate bottom surface b) is cooled.

  After step S2, argon gas is introduced into the chamber 3 from the supply line 4 and high-frequency power is output to the high-frequency power source 5, thereby generating plasma in the chamber 3 and sputter etching of the substrate surface a. Is performed (step S3). The sputter etching in step S3 is performed for a time t1 until the first protrusion E is formed on the substrate surface a. In step S3, cooling water is supplied to the water cooling pipes 12 and 13 to cool the substrate bottom surface b, thereby generating a temperature gradient (gradient in which the temperature decreases from the substrate surface a toward the substrate bottom surface b) on the substrate K. In this state, sputter etching is performed. In step S <b> 3, distilled water is not introduced into the chamber 3 from the supply pipe 4.

  FIG. 3 is a photograph of the substrate surface a on which the first protrusion E is formed, taken with a scanning electron microscope. The first protrusion E has a conical shape that narrows toward the tip, and is formed on the entire substrate surface a. Hereinafter, the first protrusion E is referred to as a conical protrusion E.

  After step S3 (after the elapse of time t1), in addition to the argon gas, distilled water is also introduced into the chamber 3 from the supply line 4, and the high-frequency power is continuously output to the high-frequency power source 5 to thereby output the chamber. Plasma is generated in the substrate 3, and the substrate surface a is sputter-etched (step S4). In step S4, as in step S3, the cooling water is caused to flow through the water cooling pipes 12 and 13 in order to generate a temperature gradient in the substrate K. By this step S4, the second protrusion Y is formed on the substrate surface a. Thus, the process of FIG. 1 ends.

  In the process of FIG. 1, a step of polishing and degreasing and cleaning the substrate surface a may be added between step S1 and step S2. By doing so, oxides, rust, irregularities, and oils present on the substrate surface a are removed, so that the sputter etching amount on the substrate surface a can be made uniform. Moreover, it can prevent that the board | substrate K and the high frequency magnetron sputtering apparatus 1 are contaminated by scattering of oil etc.

  FIG. 4 is a photograph of the substrate surface a on which the second protrusion Y is formed, taken with a scanning electron microscope. FIG. 4A shows the substrate surface a at the same magnification as in FIG. FIG. 4B shows the substrate surface a at an enlargement factor of 1/2 of FIG.

  The second protrusion Y grows in a wire shape from the tip of the conical protrusion E within a partial range of the substrate surface a, has a large aspect ratio, and has conductivity. Hereinafter, the second protrusion Y is referred to as a wire-like protrusion Y.

  Next, the use of the metal material on which the wire projection Y is formed will be described.

  As described above, since the wire-shaped protrusion Y has a large aspect ratio, the surface area of the metal material is greatly increased by forming the wire-shaped protrusion Y on the metal material (substrate K). Therefore, the metal material on which the wire-shaped protrusion Y is formed can greatly increase the electric capacity by being used for an electrode, and can be used for an electric double layer capacitor of an electric vehicle.

  In addition, since the wire-shaped protrusion Y is formed on the metal material, the electron emission area of the metal material is increased. For this reason, the metal material in which the wire-shaped protrusion Y is formed can be used for an emitter or a catalyst.

  Further, the conical protrusion E has a sharp tip and is hard and excellent in wear resistance. For this reason, a metal material can be used as contact conveyance means, such as a grip roller, by providing the conical protrusion E.

  Next, a description will be given of a test performed to confirm a factor affecting the formation of the wire-shaped protrusion Y. In this test, a plurality of substrates K1 to K11 were prepared, and the process of FIG.

  The substrates K1 to K11 are formed by cutting SKH51 (JIS) steel, which is an aging metal material, with a fine cutter, and have a square shape with a thickness of 5 mm and a planar shape with a side length of 13.5 mm. Table 1 shows chemical components of SKH51 steel.

  In step S1, the substrates K1 to K11 are heated to 1323K using a high-frequency heating apparatus (manufactured by Sekisui Electronics Co., Ltd .: MU-1700), held at 3.6 ks, and then subjected to solution heat treatment by water cooling. It was. The temperature increase rate up to 1323 K is 500 K / min when the temperature of the substrates K1 to K11 is from room temperature to 973 K, is 300 K / min when the temperature is from 973 K to 1273 K, and the temperature is 1273 K. And 1323K to 100K / min.

In step S2, substrates K1 to K11 subjected to solution heat treatment were placed in chamber 3 of high frequency magnetron sputtering apparatus 1 (FIG. 2). The high-frequency magnetron sputtering apparatus 1 used in this test has a maximum output of a high-frequency power source 5 of 800 W, and the inside of the chamber 3 is operated at 4.3 × 10 ⁻⁴ Pascal (by operation of the diffusion pump 7 and the oil rotary vacuum pump 8). The pressure can be reduced to Pa).

In step S3, first, the pressure in the chamber 3 was reduced to about 4.3 to 7.5 × 10 ⁻⁴ Pa. Then, high-frequency power is supplied to the high-frequency power source 5 while introducing argon gas having a purity of 99.999% into the chamber 3 at a flow rate of about 5.7 sccm so that the pressure in the chamber 3 is maintained at 5.0 Pa. Was output to perform sputter etching of the substrates K1 to K11.

  In step S4, sputter etching of the substrates K1 to K11 was performed by outputting high-frequency power to the high-frequency power source 5 while introducing distilled water into the chamber 3 in addition to argon gas.

  Table 2 shows data on the conditions of steps S3 and S4 in this test, the shape of the conical protrusion E and the wire protrusion Y formed in steps S3 and 4, and the like.

  The output of the high-frequency power P in step S3 was set to 500 W for the substrates K1 to K9, and 300 W for the substrates K10 and K11.

  The sputter etching time t1 in step S3 is set in the range of 2.0 ks to 3.0 ks for the substrates K2 to K6 and K9 and K10, and is shorter than 2.0 ks for the substrate K1 (1. 8 ks), and the substrates K7, K8, and K11 were set to a time longer than 3.0 Ks (3.2 ks to 3.3 ks).

  The flow rate QH2O of distilled water in step S4 was set to 3.0 ml / min for the substrates K1 to K5 and K7 to K11, and 15.0 ml / min for the substrate K6.

  The output of the high-frequency power P in step S4 is set to the same value (500 W) as that in step S3 for the substrates K1 to K9, and is changed from the value in step S3 for the substrates K10 and K11 (300 W → 500 W). .

  The sputter etching time t2 in step S4 was set to 0.6 ks for the substrates K1 to K7 and K10 and K11, 0.34 ks for the substrate K8, and 0.3 ks for the substrate K9. .

  After performing sputter etching in steps S3 and S4, the surface a of the substrates K1 to K11 was observed with a photograph taken with a scanning electron microscope. As a result, conical protrusions E were formed on the substrates K1 to K9.

  The conical protrusion E had an average height hr of 0.27 μm or more and 1.15 μm or less, and an average diameter dr of the bottom surface of 0.23 μm or more and 1.02 μm or less.

  In addition to the conical protrusions E, wire-like protrusions Y were also formed on the substrates K2 to K6. Further, there was no substrate K in which the conical protrusion E was not formed and only the wire protrusion Y was formed. From this, when the conical protrusion E is formed, it is considered that the wire-shaped protrusion Y is formed.

  The wire-shaped protrusion Y grows from the tip of the conical protrusion E, has an average length lw of 1.16 μm to 5.79 μm, an average diameter dw of 0.21 μm to 1.44 μm, and an aspect ratio Was extremely large. All the wire-like protrusions Y formed on the substrates K2 and K4 to K6 had a diameter of a micrometer (μm). In the substrate K3, in addition to the wire-shaped protrusion Y having a diameter of micrometer (μm), a wire-shaped protrusion Y having a diameter of nanometer (nm) was also formed.

Figure 5 is a graph showing the mean diameter d _r of the bottom surface of the conical projections E, the relation between the average diameter d _w of the wire-like protrusion Y. Of the substrate K2~K6 both conical projections E and the wire-like protrusion Y is formed, the average diameter d _w of the wire-like protrusion Y is the average diameter d _r of the bottom surface of the conical projections E 0 There was no substrate K smaller than .75 times. From this, it is considered that the size of the conical protrusion E affects the thickness of the wire protrusion Y.

  In the substrates K7 to K9 on which only the conical protrusions E were formed without forming the wire-shaped protrusions Y, the increase rate ΔS of the surface area due to the formation of the protrusions was 23.52% at maximum (substrate K8 Data reference). On the other hand, in the substrates K2 to K6 on which the wire-shaped protrusions Y were also formed, the surface area increase rate ΔS due to the formation of the protrusions was a maximum of 39.93% (see data on the substrate K5). From this, when the wire-shaped protrusion Y was formed, it was confirmed that the surface area of the metal material (substrate K) increased compared to the case where only the conical protrusion E was formed.

  In order to confirm the components of the conical protrusion E and the wire protrusion Y, X-ray analysis and analysis by an electron probe microanalyzer (hereinafter referred to as EPMA analysis) were performed. FIG. 6 is a graph showing the results of X-ray analysis of the conical protrusion E, the wire protrusion Y, and the like.

  Peaks were confirmed at 2θ = 43 °, 63 °, 82 °, 97 °, and 117 ° for the wire-like protrusion Y, the conical protrusion E, and the substrate K. Moreover, in the wire-like protrusion Y and the conical protrusion E, a peak was confirmed even at 2θ = 114 °. This peak at 2θ = 114 ° corresponds to a peak due to CrC. In the EPMA analysis, Fe, Cr, Mo, and V components were detected from the wire-like protrusion Y and the conical protrusion E. From the above analysis results, it is considered that the wire-like protrusion Y and the conical protrusion E are made of CrC containing some Fe, Mo, and V.

  Based on the above test results, the formation mechanism of the wire-like protrusions Y and the conical protrusions E is considered as follows. FIG. 7 is a view for explaining the formation mechanism of protrusions on the substrate surface a. FIG. 8 is an enlarged view and a photograph of the conical protrusion E and the wire protrusion Y. FIG. 8A is an enlarged view of range A in FIG. 7C, and FIG. 8B is a photograph of the state shown in FIG. 8A.

In the process of performing sputter etching while introducing argon gas into the chamber 3 in step S3 of FIG. 1, the substrate surface a is sputter-etched by Ar ⁺ and the temperature gradient generated in the substrate K causes the inside of the substrate K Carbon dissolved in is supplied to the substrate surface a (FIG. 7A). Thereby, the carbide | carbonized_material precipitates on the substrate surface a and grows, and the conical protrusion E is formed (FIG.7 (b)).

In step S4 of FIG. 2, in the process of performing sputter etching while introducing distilled water into the chamber 3 in addition to argon gas, the substrate surface a is sputter-etched by Ar ⁺ and H ⁺ (FIG. 7 ( c)). Since H ⁺ has a smaller sputtering rate than Ar ⁺ , the amount of decrease in the thickness of the substrate K due to sputtering (sputtering amount) is suppressed to be smaller in step S4 than in step S3. Thereby, since the heat conduction distance d from the substrate bottom surface b to the substrate surface a is kept substantially constant, the temperature drop caused on the surface a by the cooling of the bottom surface b can be suppressed to a small value. In this situation, the tip of the conical protrusion E is selectively heated by the plasma concentration, so that carbide grows from the tip of the conical protrusion E and the wire-like protrusion Y is formed ( FIG. 8). As the sputter etching time t2 in step S4 becomes longer, the wire-like projection Y grows and the length lw and the diameter dw of the wire-like projection Y are estimated to increase (FIG. 7B). → FIG. 7 (c)).

  As shown in Table 2, the high frequency power P output in steps S3 and S4 is set to 500 W for the substrates K2 to K6 on which the wire-like protrusions Y are formed, and the sputter etching time t1 in step S3 is set. Is set to 2.0 to 3.0 ks, and the sputter etching time t2 in step S4 is set to 0.6 ks. Based on this, the value t2 / t1 obtained by dividing the sputter etching time t2 by the sputter etching time t1 with the same magnitude of the high frequency power P output in steps S3 and S4 is 0.2 or more and 0.3 or less. Thus, it is considered that the wire-like protrusions Y can be reliably formed by adjusting the sputter etching times t1 and t2.

Here, in the above-described embodiment, the case where argon gas is used as the inert gas supplied into the chamber 3 is shown. It may be supplied into the chamber 3. The ions of these inert gases also have a higher sputtering rate than H ⁺ as with Ar ^+, and even when the above inert gas is used, the wire projection Y Is formed.

Further, since it was considered that H ⁺ was generated in the chamber 3 even when hydrogen gas was introduced into the chamber 3, a test was conducted in which hydrogen gas was introduced into the chamber 3 instead of distilled water in step S 4. . Also in this test, the high-frequency magnetron sputtering apparatus 1 of FIG. 2 was used, and hydrogen gas was supplied into the chamber 3 through the supply pipe 4. In this test, the pressure in the chamber 3 is adjusted to 5.0 Pa by adjusting the flow rates of the argon gas and hydrogen gas introduced into the chamber 3 by opening and closing the valves 14 and 15. The partial pressure was controlled to 3.3 Pa, and the partial pressure of argon gas was controlled to 1.7 Pa.

  As a result of the test, the high-frequency power output in the conditions under which the wire-shaped protrusion Y is formed when distilled water is introduced, that is, in steps S3 and S4 is the same (for example, the high-frequency power in steps S3 and S4 500 W), a condition that a value t2 / t1 obtained by dividing the sputter etching time t2 of step S4 by the sputter etching time t1 of step S3 is 0.2 or more and 0.3 or less (for example, the time t1 is 2 ks to 3 ks, It was confirmed that the wire-like protrusion Y was formed at time t2 of 0.6 ks).

  The metal material with wire-like protrusions formed according to the present invention is applied to contact transporting means such as electric double layer capacitors for electric vehicles, storage battery electrodes, fluorescent lamps and plasma TV emitters, coating intermediate layers, and grip rollers. can do.

DESCRIPTION OF SYMBOLS 1 High frequency magnetron sputter apparatus 3 Chamber 4 Supply line 5 High frequency power supply 6 Exhaust apparatus 7 Diffusion pump 8 Oil rotary vacuum pump 9 Exhaust line 10 Sample stand 11 Holder 12, 13 Water-cooled pipes 14, 15 Valve E 1st protrusion (Conical protrusion)
Y Second protrusion (wire-like protrusion)
K, K1, K2, K3, K4, K5, K6, K7, K8, K9, K10, K11 Substrate t1 Sputter etching time in the first sputter process t2 Sputter etching time in the second sputter process

Claims (4)

A first sputtering step of generating a plasma in the chamber by introducing high-frequency power while introducing an inert gas into the chamber, and performing sputter etching on the surface of the metal material installed in the chamber;
After the first sputtering step, while introducing water or hydrogen into the chamber in addition to the inert gas, plasma is generated in the chamber by the output of the high frequency power, and the surface of the metal material is A second sputtering step for performing sputter etching;
A method of forming a wire-like protrusion on the surface of a metal material.   The method of forming a wire-like protrusion on the surface of the metal material according to claim 1, wherein the metal material is an aging metal material. In the first and second sputtering steps, the high-frequency power is output with the same magnitude,
The value obtained by dividing the time for performing the sputter etching in the second sputtering step by the time for performing the sputter etching in the first sputtering step is 0.2 or more and 0.3 or less. Or the formation method of the wire-shaped protrusion to the metal material surface of 2.   A metal material comprising a wire-like protrusion formed by the method according to claim 1.