JPH04310321A - Manufacture and surface treatment of metal probe - Google Patents

Abstract

PURPOSE:To enable a probe manufacture under a safe work environment and control and to reduce the burden of the equipment investment by using a sodium hydroxide water solution for an electrolyte with the specific density and specific voltage. CONSTITUTION:A probe having a sharp tip radius in 0.1mum-5mum can be formed with good redering in a short time of about several - twenty minutes, in the case of executing an electrolytic polishing until current is not flowed with the sodium hydroxide water solution of an electrolyte 3 being made in 2-4 normality and the electrolytic voltage fed to an AC power source 5 - being made in 30-40 volt AC voltage. AS well known, the sodium hydroxide water solution doesn't display toxicity like potassium cyanide and generates no noxious gas for corrosion as well, so it does no harm on a human body as well and its handling and management become extremely easy.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a scanning tunneling microscope (
The present invention relates to a method of manufacturing and a method of surface treatment of a metal probe having a sharp tip such as a probe in STM.

0002

2. Description of the Related Art Electrolytic polishing is widely known as a method for manufacturing metal probes used in STM. FIG. 3 is a configuration diagram of a general electrolytic polishing apparatus for realizing this electrolytic polishing method. In this figure, 1 is a metal material for forming the probe, such as a platinum wire, 2 is an electrode that is the opposite electrode of the platinum wire 1,
Reference numeral 3 indicates an electrolytic solution serving as a medium for electropolishing the platinum wire 1, 4 indicates an electrolytic bath containing the electrolytic solution, and 5 indicates an AC power supply for supplying electrolytic polishing energy. Conventionally, the electrolytic solution 3 has a concentration of 35 [
%] of hydrochloric acid and 2 [ml] of activator (New Edition Electrochemistry Handbook, edited by the Electrochemical Society, 1968)
February 25th, published by Maruzen), and a mixture of equal volumes of sodium cyanide at a concentration of 50% and 30% (Experimental Biology Course 5, Electrical Measurement Methods, edited by Hiramoto and Takenaka, published by Maruzen) is used.

With this configuration, the portion of the platinum wire 1 immersed in the electrolyte 3 is gradually eroded as the polishing time progresses, and the tip thereof is formed into a sharp point. In addition, platinum wire 1
Similar effects can be obtained by using an alloy wire containing platinum instead.

On the other hand, in order to improve the resolution of STM,
A surface treatment method is also known in which the tip surface of a metal probe is further sharpened. This includes a surface treatment method using platinum electrodeposition and a surface treatment method using a field ion microscope. The former method aims to improve the sharpness by forming fine irregularities on the tip of the metal probe using island-like precipitates generated in the initial stage of electric field deposition (see Japanese Patent Application Laid-Open No. 2-88904). ). The latter method uses field ion microscopy (FIM)
The aim is to obtain atomic resolution by observing and processing the atomic arrangement at the tip of a metal probe.

[0005]

[Problems to be Solved by the Invention] However, conventional metal probe manufacturing methods and surface treatment methods have the following problems to be solved.

That is, in the conventional method for manufacturing metal probes, hydrochloric acid is used as the electrolytic solution 3, so corrosive and harmful gases are generated from the electrolytic solution 3 and corrode metal products other than the platinum wire 1. , which also has a negative effect on the human body. In order to meet this requirement, the electropolishing apparatus shown in FIG. 3 must be constructed of corrosion-resistant material, and ventilation equipment is also required. Therefore, sufficient capital investment is forced.

Furthermore, since sodium cyanide is a highly toxic chemical, when it is used as the electrolytic solution 3, strict care and management are required, making it impossible to improve production efficiency.

Furthermore, when performing surface treatment on the probe, a method using platinum electrodeposition requires the preparation of a plating solution, a plating power source, etc. separately, and a method using FIM requires an expensive and large-scale vacuum system. do. All of these lead to an increase in the manufacturing cost of the metal probe.

The present invention was devised to solve the above-mentioned problems, and its purpose is to be able to manufacture metal probes in a safe working environment and under control, and to An object of the present invention is to provide a method for manufacturing a metal probe that can reduce the burden of equipment investment.

Another object of the present invention is to provide simple means,
Another object of the present invention is to provide a surface treatment method for a metal probe that can reduce processing costs.

[0011]

[Means for Solving the Problems and Effects] In order to achieve the above object, in the present invention, a part of platinum or a metal material containing platinum to be polished and an electrode opposite to the part to be polished are placed in an electrolytic solution. In a method for manufacturing a metal probe, the part of the metal material to be polished is formed into a sharp point by electrolytic polishing by applying a voltage of a predetermined value to the metal material and the electrode. It is characterized by being a sodium oxide aqueous solution.

[0012] Also, as a surface treatment method for a metal probe, a metal probe made of platinum or a metal material containing platinum and an electrode serving as a counter electrode of the metal probe are placed in a sodium hydroxide aqueous solution with a specified concentration of 1 to 6. The metal probe is immersed, and an alternating current voltage of 5 to 10 volts is applied to the metal probe and electrode to perform electrolytic polishing, thereby forming protrusions on the surface of the metal probe.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) A method for manufacturing a metal probe according to a first embodiment of the present invention is to use the metal probe manufacturing apparatus shown in FIG. Electrolytic polishing was attempted at 0.2 volts to 60 volts, using an aqueous sodium hydroxide solution as the electrolytic solution 3, and changing the specified concentration to various values.

As a result, when the concentration of the sodium hydroxide aqueous solution is within the range of 1N to 5N, it is possible to easily create a practical platinum probe or platinum alloy probe with a tip radius of 0.1 μm to several μm. , and it was found that it could be formed with good reproducibility.

A tip with a sharp tip can be formed even at a concentration outside the above range, but if the concentration is below 1N, the electrolytic reaction will be slow, resulting in poor work efficiency; if the concentration exceeds 5N,
Since sufficient convection of the electrolytic solution around the polished part does not take place, the polishing time needed to be adjusted to form a practical tip radius is extremely delicate, making it difficult to ensure reproducibility. . In addition, when the concentration was too high to the extent that the polishing time could not be adjusted, the tip of the probe became several tens of micrometers long, making it unusable as a probe for STM.

[0017] In the above manufacturing method, in particular, when the sodium hydroxide aqueous solution has a concentration of 2N to 4N, the electrolytic voltage is an AC voltage of 30 to 40V, and electrolytic polishing is performed until no current flows. It was confirmed that a probe having a sharp tip radius of 0.1 μm to 5 μm could be formed with good reproducibility in a short time of about several minutes to 20 minutes.

As described above, according to the method for manufacturing a metal probe according to this embodiment, a platinum wire or a platinum alloy wire is immersed in an aqueous sodium hydroxide solution, and a predetermined electrolytic voltage is applied to perform electrolytic polishing. It was found that the tips of platinum wires, etc. can be made sharp. In addition, in order to form a probe with a sharp tip radius in a short period of time with good reproducibility, the concentration of the sodium hydroxide aqueous solution should be adjusted to 2N to 4N, and the electrolytic voltage should be set to an AC voltage of 30 to 40V. It was confirmed that electrolytic polishing can be performed until no current flows.

As is well known, an aqueous sodium hydroxide solution is not toxic like potassium cyanide and does not emit corrosive harmful gases, so it does not have any adverse effects on the human body, and its handling and management are extremely easy. It becomes easier. Therefore, the manufacturing efficiency is significantly improved compared to the conventional manufacturing method in which a toxic solution is used as the electrolytic solution 3. In addition, there is no need to construct the electropolishing apparatus with corrosion-resistant materials and no ventilation equipment is required, so the burden of capital investment is significantly reduced.

[0020] In this embodiment, a case has been described in which electrolytic polishing is performed using the AC power source 5, but electrolytic polishing can also be performed using a sodium hydroxide aqueous solution under a DC voltage.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows a configuration diagram of an apparatus for realizing a method for surface treatment of a metal probe according to a second embodiment of the present invention. In the figure, 2 to 5 are the same parts as the metal probe manufacturing apparatus shown in FIG. 3, and 6 is a metal probe made of an alloy of platinum and iridium, the tip of which has been roughly processed in advance. . Further, as the electrolytic solution 3, a sodium hydroxide aqueous solution is used as in the first embodiment.

[0023] In this example, the apparatus having the above-mentioned configuration is used, and the metal probe 6 whose tip is shaped as shown in FIG. Electrolytic polishing was attempted by changing the concentration of the oxide and the electrolytic voltage supplied from the AC power source 5 to various values.

As a result, when the electrolytic voltage is an AC voltage of 5 volts to 10 volts and the concentration of the sodium hydroxide aqueous solution is in the range of 1 normal to 6 normal, the metal probe 6 as shown in FIG. It was confirmed that sharp protrusions were formed on the surface. This is because a so-called anisotropic polishing state occurs in which the polishing rate differs by more than one order of magnitude due to the action of the atomic plane, and the surface of the metal probe 6 is partially shaped into a triangular pyramid shape or a quadrangular pyramid shape.

The tip radius of these protrusions is more than an order of magnitude smaller than the tip radius of the metal probe 6 before treatment shown in FIG. 2(a), so it is as if the tip radius of the metal probe 6 itself is A similar effect can be obtained if the size is made smaller. therefore,
When this is used as an STM probe, its resolution is dramatically improved.

[0026] Note that when the concentration of the sodium hydroxide aqueous solution is 6
When the concentration exceeds the specified concentration and when the AC voltage exceeds 10 volts, electrolytic polishing is promoted and the surface of the metal probe 6 is smoothed, and when the concentration of the sodium hydroxide aqueous solution is less than 1 specified concentration, the electrolytic polishing takes time. It takes too much. Further, when the AC voltage is less than 5 volts, polishing is performed along the grain boundaries of the metal probe, so sharp protrusions are not necessarily formed on the surface.

As described above, in this embodiment, the surface of the metal probe 6 is immersed in a sodium hydroxide aqueous solution having a concentration of 1 to 6 normal, and an electrolytic voltage of 5 to 10 volts AC is supplied to the surface of the metal probe 6. Since sharp protrusions are formed on the surface, a simple surface treatment produces the same effect as if the tip of the metal probe itself were sharpened, making it suitable for STM, which requires high resolution. A metal probe can be obtained.

Further, the electrolytic solution 3 used in this example is a sodium hydroxide aqueous solution as in the first example, and the general equipment used for manufacturing (rough processing) metal probes can be used as is. This makes it possible to easily treat the surface of metal probes in a safe working environment.

[0029]

[Effects of the Invention] As explained above, in the method for manufacturing a metal probe according to the present invention, a sodium hydroxide aqueous solution is used as the electrolyte, so the probe can be manufactured in a safe working environment and under control. In addition, it is possible to achieve the excellent effect of significantly reducing the burden of equipment investment.

In particular, when the aqueous sodium hydroxide solution has a concentration of 2N to 4N and the electrolytic voltage is an AC voltage of 30 to 40V, and electrolytic polishing is performed until no current flows, the polishing time is about several minutes to 20 minutes. 0.1μm in a short time
Since a probe having a sharp tip radius of ~5 μm can be formed with good reproducibility, work efficiency is significantly improved.

[0031] Furthermore, in the method for surface treatment of a metal probe according to the present invention, the surface of the metal probe is immersed in an aqueous sodium hydroxide solution having a concentration of 1N to 6N, and an electrolytic voltage of 5 to 10 V AC is applied. By supplying the material and forming sharp protrusions on the surface, a simple surface treatment process can be performed.
This produces the same effect as if the tip of the metal probe itself were sharpened, and a metal probe suitable for STM, which requires high resolution, can be obtained.

Moreover, this method allows the same equipment used for rough processing of metal probes to be used as is, so it is not possible to use the conventional FIM method or electrolytic deposition method, which used expensive equipment such as FIM or plating equipment. It also has the practical effect of allowing the surface treatment of metal probes to be easily performed in a safe working environment.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an apparatus for realizing a method for surface treatment of a metal probe according to a second embodiment of the present invention.

FIG. 2 is a diagram showing changes in the tip shape of a metal probe according to a second embodiment of the present invention, in which (a) shows the tip shape before treatment, and (b) shows the tip shape after treatment.

FIG. 3 is a configuration diagram of a manufacturing apparatus for realizing a conventional metal probe manufacturing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Metal material for probe, 2... Electrode, 3... Electrolyte, 4... Electrolytic cell, 5... AC power supply, 6... Metal probe.

Claims (3)

[Claims] [Claim 1] A part to be polished of platinum or a metal material containing platinum and an electrode serving as a counter electrode to the part to be polished are immersed in an electrolytic solution, and a voltage of a predetermined value is applied to the metal material and the electrode. A method for manufacturing a metal probe in which a polished portion of a metal material is shaped into a sharp point by electrolytic polishing, characterized in that the electrolyte is an aqueous sodium hydroxide solution. . 2. The metal probe according to claim 1, wherein the electrolyte is an aqueous sodium hydroxide solution with a specified concentration of 2 to 4, and the voltage is an alternating current voltage of 30 to 40 volts. Production method. 3. A metal probe made of platinum or a metal material containing platinum and an electrode serving as a counter electrode of the metal probe are immersed in a sodium hydroxide aqueous solution with a specified concentration of 1 to 6, and the metal probe and electrode 1. A method for surface treatment of a metal probe, characterized in that a sharp protrusion is formed on the surface of the metal probe by applying an AC voltage of 5 to 10 volts to perform electrolytic polishing.