JPS62140340A - Field emission type ion source - Google Patents

Abstract

PURPOSE:To make it possible to emit a stable ion beam by joinning the storage part of material to be ionized and a needle-shaped electrode using a material of specific character. CONSTITUTION:A storage room 2 for storing a material to be ionized 1 is fixed with a needle-shaped electrode 3 at a joint part 6 and a base 5 of the electrode 3 is held between heating elements 7a and 7b through partition walls 9a and 9b. A terminal used for the joint part 6 is the material having poor wettability with a material 1. It is obtained, for example, by kneading an aqueous mixture of some amount of powder of inorganic compound with relative high melting point such as Mo, the metal powder with relative low melting point such as Ni, and a colloidal carbon and then sintering it. By this means, the storage part 2 and the electrode 3 are fixed with each other, besides a stable ion beam can be obtained as the material 1 is not spilled out and crawled to the heating elements 7a, 7b.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a field emission type ion source capable of generating an ion beam from a melted substance to be ionized.

[Prior art and its problems]

Various proposals have been made regarding the structure of field emission type ion sources. For example, a storage part for a substance to be ionized is held by a heat-generating support member (Japanese Patent Laid-Open No. 58-658
(Japanese Patent Application Laid-Open No. 1983-29), in which an electrode is passed through the center of a plate-shaped heat-generating member, and the substance is attached near the penetration part (Japanese Patent Laid-Open No. 59-
101750).

However, in these methods, even if the exothermic member is a substance that has poor wettability with the substance to be ionized, when electricity is applied to emit ions, the material will not be absorbed by the storage part of the substance or the needle electrode. The substance protrudes, the surface of the heat-generating member becomes wet with the substance, and the electrical resistance of the member decreases.
This has the disadvantage that heating is no longer possible, which adversely affects the radiation amount of the ion beam.

In addition, tungsten (W) is generally used as the material for the needle-shaped electrode, and other materials include ceramics, carbon (% Publication No. 59-16385), and materials listed in Periodic Table 4.
Carbides, borides, and nitrides of elements in group 5 and periods 4 to 6 (Japanese Unexamined Patent Publication No. 132632/1982) are known as materials suitable for highly reactive substances to be ionized.

However, these materials have high melting points and are brittle, making it difficult to join them to the storage section and a portion of the heater using conventionally known simple methods such as spot welding. It's a trench, as exemplified in Japanese Patent Application No. 132662/1983.
In a structure in which a needle electrode is fixed with a carbon heater, there is no substantial storage part, so there is a lot of evaporation loss of the substance to be ionized, so the life as an ion source is short.

An object of the present invention is to provide a field emission type ion source that stably produces an ion beam without such drawbacks.

[Failure to solve the problem]

In order to obtain a stable ion beam, the present inventors conducted various studies on the structure of a field emission type ion source. As a result, the inventors discovered that the storage part of the substance to be ionized and the needle-shaped electrode were made of a material with poor wettability with the substance. By connecting the base of the needle-like electrode to a conductive member through a heating element: I) By holding the base of the needle-shaped electrode with a conductive member, a stable and long-life ion beam without the above-mentioned drawbacks can be obtained. I found it.

That is, the present invention provides a field emission type ion source in which a substance to be ionized is heated and melted and guided to the tip of a needle-shaped electrode, and an ion beam of the substance is obtained through an electric field. The field emission type ion source is characterized in that the joint portion with the needle electrode is made of a material having poor playability with the material, and the base of the needle electrode is held by a conductive support member via a heating element.

Hereinafter, the present invention will be explained according to the drawings.

FIG. 1 is a cross-sectional view of the field emission type ion source of the present invention, and FIG.
The figure is a perspective view of the main parts of the field emission type ion source of the present invention.

The storage section 2 for the substance 1 to be ionized is a cylindrical or square container, the bottom of which is penetrated by a needle-shaped electrode. The storage section is made by bending a heat-resistant metal plate such as tantalum (Ta), or made of metal such as Matahachitan (T), zirconium (Zr), niobium (Nb), or tantalum (T).
Ta, ), chromium (Cr), tungsten (W),
A sintered body of a boride, carbide, nitride, etc. (for example, WO2TaC, CrB2, TiN, etc.) such as molybdenum (MO) is processed by ultrasonic machining, electrical discharge machining, or the like.

The joint 6 between the needle electrode and the storage section is used not only to fix the needle electrode and the storage section, which have poor weldability, but also to prevent the substance to be ionized from protruding from the gap between the storage section and the needle electrode. To prevent this, the material of the joint must have poor wettability with the substance to be ionized. As a result of studying these materials, we found that MO, Cr,
Zr, 'ri.

Powders of inorganic compounds with relatively high melting points such as borides, carbides, and nitrides such as Ta and W: A, and Ni and Fe.

Comparatively low melting point metal powder such as Co and Pd: B, and colloidal carbon: C (trade name "Hitasol" manufactured by Hitachi Powder Metallurgy Co., Ltd.) in a weight ratio of 50 to 96% A and 38 to 5% B.
, C at a ratio of 2 to 45%, and a small amount of water added and kneaded is applied to the joint, and about 150,000
Sinter by heating for several minutes.

In the above formulation, powder A has the effect of imparting heat resistance to the joint! >, 51]%, the joint portion will be softened and deformed when the field emission type ion source is heated and used.

If it exceeds 9 degrees, a strong bond cannot be formed unless the sintering temperature is increased. If powder B exceeds 68 mm, the joint portion will be softened and deformed when the field emission type ion source is heated, as described above, and if it is less than 5 mm, sintering will not occur. Colloidal carbon: C can be mixed with components A and B to form a paste with fluidity suitable for application to joints. Furthermore, by sintering a material containing this C, there is an effect of preventing the joint portion from getting wet with the substance to be ionized. That is, when the C content is 2% or more, preferably 10% or more, the fluidity of the paste can be improved and cracking can be prevented during drying. On the other hand, if it exceeds 45%, sintering will be very difficult, the strength of the joint will be weak, and peeling will easily occur during use.

The base 5 of the needle electrode is held by conductive support members 8a and 8b, respectively, via heating elements 7a and 7b. Between the base 5 of the needle electrode and the heating element, there are partition walls 9a, 9 made of a molten substance to be ionized and a substance that is difficult to wet (for example, glassy carbon, pyrolytic graphite, carbon sheet).
By providing b, it is possible to completely prevent the substance from protruding into the heating element.

A suitable heating element is a cube made of pyrolytic graphite. The conductive support member is made of metal such as tantalum.

〔Example〕

Next, an example of a field emission type ion source according to the present invention will be described.

Example 1 A square with a cross section of 0.75 x O-75mm and a length of 5-
A prismatic WC sintered body (relative density 99 cm) of Dim was mechanically polished into a needle shape with a radius of curvature of 3 μm at the tip and used as a needle electrode.

A Ta plate with a thickness of 0 to 1 mm was processed into a cubic cup shape with a side of 2 mrn, and a square hole with a side of 0.8 mm was bored in the bottom to serve as a storage section. Mix ``Hitadel'' (trade name, manufactured by Haritate Powder Metallurgy Co., Ltd.) in the storage area in a ratio of 60:30:10 by weight, add water if necessary, apply a paste-like binder, and heat at 16,000C for 2 minutes. It was heated and sintered. Ushi, one side of pyrolytic graphite is 0.75
It was processed into a cube of mm and used as a heating element. A pyrolytic graphite plate with a thickness of 0-1 mm was used as a partition wall. The conductive support member was made of Ta. An alloy of Ni40Pd40B20 (atomic ratio) was placed as the substance to be ionized in the reservoir, and the mixture was heated at 920° in a vacuum of 7 x 10-7 torr.
When the ion beam was extracted by heating it to C and applying a voltage of 8 to the extraction electrode 10, the ion beam 11 with a total current of 50 μA was generated.
It operated stably over time. The fluctuation rate of the total current amount is 0
．． It was 5%/hour or less. After use, the ion source was disassembled and observed, but no alloy was observed on the joints 6, partition walls 9a, 9b, and heating elements 7a, 7b.

Example 2 A single crystal was manufactured from a sintered body of CrB2 by the floating zone method, the single crystal was processed into a square prism, and the tip was sharpened to a radius of curvature of 1.0 μm by electropolishing to form a needle-shaped electrode. And so.

A sintered body of WC (relative density 99%) with a diameter of 5 mvt.

It was processed into a cylinder with a height of 2.5mm, a depression with a diameter of 2.0mm and a depth of 2.0mm was made in the cylinder using an ultrasonic processing machine, and a hole with a diameter of 0.7mm was passed through the center of the depression. The object was used as a storage unit.

Insert the needle-like electrode into the reservoir, and add W2B5 powder, C○ powder, and colloidal carbon (same as in Example 1) to the gap between the hole at the bottom of the reservoir and the needle-like electrode at a weight of 60:20=20@ Apply a paste-like bonding agent by mixing at a ratio of 15%.
It was heated at 50°C for 6 minutes to sinter. The same heating element as in Example 1 was used. 1. Insert Au 60S i 26Be 14 alloy (atomic ratio) as the substance to be ionized in the storage section. 60 in a vacuum of OX 10-7 torr
After heating to 0°C, the ion beam was extracted with an extraction voltage of 6 K and V. However, the ion beam was stably produced at a total current of 10 A.
Obtained over 00 hours.

After use, when the ion source was disassembled and observed, it was found that the alloy was attached to the outside of the reservoir, since the reservoir is made of a material that is easily wetted by the alloy. However, no leakage of the alloy into the heating element was observed.

〔Effect of the invention〕

The field emission type ion source of the present invention can provide a stable ion beam since the substance to be ionized does not leak into the heating element during use.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a field emission type ion source of the present invention, and FIG. 2 is a perspective view of the main parts of the field emission type ion source of the present invention. 1...Substance to be ionized 2...Storage part 3...Acicular electrode 4...Tip 5 of the needle electrode 5...Base of the needle electrode 6...Joint parts 7a, 7b...・Heating elements 8a, 8b... Conductive support members 9a, 9b... Partition wall 10... Extracting electrode 11... Ion beam patent applicant Denki Kagaku Kogyo Co., Ltd. Figure 1 3-m-Harikokugi chair

Claims (1)

[Claims] In a field emission type ion source that heats and melts a substance to be ionized and guides it to the tip of a needle-shaped electrode to obtain an ion beam of the substance through an electric field, the joint between the storage part of the substance and the needle-shaped electrode is 1. A field emission type ion source comprising a substance having poor wettability with the above substance, and characterized in that the base of the needle electrode is held by a conductive support member via a heating element.