JPH0256883A - Electrode fitting method for oxide crystal - Google Patents

Abstract

PURPOSE:To obtain good electric connection without applying a physical external force to a crystal by arranging an Au film in the middle and connecting an electrode member and the oxide crystal. CONSTITUTION:An Au film is formed on the surface of an oxide crystal, then a metal or an alloy with the melting point of 450 deg.C or below is melted on the Au film, an electrode member is brought into contact with this melted metal material, then this metal material is coagulated, and the electrode member is fixed to the coagulated body. The electrode member is fixed to the oxide crystal via the Au film, and the electrode member is electrically connected to the oxide crystal. The electrode member is safely fitted to the crystal with high connecting strength without applying any external force to the crystal, and both of them can be electrically connected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of attaching an electrode member to an oxide crystal,
In particular, the present invention relates to a method for attaching an oxide crystal electrode, which enables stable electrical connection between the oxide crystal and the electrode member from room temperature to lower temperatures.

[Prior Art] Conventionally, as a method for attaching a linear or plate-shaped electrode member to an oxide and electrically connecting the two, Zn, Ti, Sb, Al1. There are methods of attaching the electrode wires by using solder such as ceramic solder or In solder to which a small amount of Si or Cu is added, or by bonding after forming a thin film of metal such as Au.

[Problems to be Solved by the Invention] However, although solder for ceramics and In solder have a strong bonding force to sintered bodies, they cannot bond to substances with smooth surfaces such as single crystals. It has the disadvantage of being weak. In particular, there is a problem in that the bond is likely to peel off at low temperatures, and soldered oxide crystals cannot be used at low temperatures. Another disadvantage is that the soldering method cannot be applied to crystals as small as several scales.

On the other hand, in the method of bonding electrode wires,
There is a problem in that defects such as cracks and distortions occur in the oxide single crystal due to stress during bonding.

Although the development of oxide superconductors has progressed in recent years and various useful materials have been proposed, as mentioned above, there is no way to stably and reliably attach electrodes to these oxide superconductors at low temperatures. Since it has not yet been established, this point is an obstacle to further progress in the development and research of oxide superconductors.

The present invention has been made in view of such problems, and includes:
To provide a method for attaching an electrode to an oxide crystal, in which an electrode can be attached reliably and stably to the oxide single crystal without causing cracks, distortions, etc., even in the temperature range from low temperature to room temperature. The purpose is to

[Means for Solving the Problems] A method for attaching an electrode to an oxide crystal according to the present invention, a step of forming an Au film on the surface of the oxide crystal, and a metal or alloy having a melting point of 450° C. or less on the Au film. The method is characterized by comprising a step of melting the molten metal or alloy, a step of bringing an electrode member into contact with the molten metal or alloy, and a step of solidifying the metal or alloy to fix the electrode member to the oxide crystal.

[Function] In the present invention, after forming an Au film on the surface of the oxide crystal, a metal or alloy (hereinafter referred to as metal material) having a melting point of 450°C or less is melted on the Au film, and the electrode member is attached to the surface of the oxide crystal. After contacting the molten metal material, the metal material is solidified and the electrode member is fixed to the solidified body. This results in
The electrode member is fixed to the oxide crystal via an Au film,
An electrode member is electrically connected to the oxide crystal.

In this way, since the electrode member and the oxide crystal are connected by disposing the Au film in the middle, a good electrical connection can be established without applying any physical external force to the crystal. Furthermore, the presence of the Au film improves stability at high temperatures when the crystal is heated.

Further, by melting a metal material having a melting point of 450° C. or less on the Au film and solidifying the metal material in a state where the molten metal material and the electrode member are in contact with each other, the electrode member is transferred to the Au film through the metal material. Since it is fixed to the film and oxide crystal, the electrode member can be attached without applying any physical external force to the crystal.

The reason why this metal material is limited to one having a melting point of 450° C. or lower is that at high temperatures exceeding 450° C., there is a risk of deterioration of the crystal. In addition, in metal materials with a melting point exceeding 450°C, the electrical conductivity and the underlying Au
There are very few materials that have excellent wettability with membranes.

In addition to linear electrode members, there are also plate-shaped electrode members. Further, in the step of melting the metal material on the Au film, it is preferable that the metal material is heated together with the oxide crystal. It is difficult to form a sufficient bond between the Au film and the molten metal by only heating the metal locally with a soldering iron, etc., so it is preferable to keep the entire crystal at a temperature higher than the melting point of the molten metal. It is from.

Note that the oxide crystal to which the electrode wire can be attached according to the present invention is not limited by its crystal composition or surface properties, and the present invention can be applied to various oxide crystals.

[Example] Examples of the present invention will be described below in comparison with comparative examples thereof.

and 1 Takumi L Bi, Sr, Ca, Cu and 0 in atomic ratio Bi:Sr:
Ca:Cu:O=1:0.8:0.5:0.9
:4-terminal electrode wires were attached to oxide crystals (size: 2 mm x 2 mm x 0.2 + u) having a composition of: Then, the inter-terminal resistance was measured and the temperature vs. resistance characteristic was measured using a DC four-terminal method.

The reason why we selected the oxide crystal with the above composition is that this crystal is a superconductor that undergoes a superconducting transition at about 80°C, and its resistance versus temperature characteristics are known. This is because it can be easily evaluated. Furthermore, the reason why crystals of the above-mentioned size and size were used was to evaluate the possibility of attaching electrodes to minute crystals. Electrode attachment was carried out in the following steps.

■ Depositing an Au film on the crystal surface.

■Place a small amount of Pb-3n solder on the Au film.

(2) Heat the entire crystal to melt the Pb-3n solder.

■Immerse the Cu lead wire in melted Pb-3n solder.

K11 In was used as the molten metal, and electrode wires were attached in the same manner as in Example 1, and the inter-terminal resistance and temperature versus resistance characteristics were similarly measured using the DC four-terminal method.

11L-1 Similar measurements were made using ceramic solder (Comparative Example 1) and In solder (Comparative Example 2) by attaching lead wires to the crystal surface by ultrasonic soldering.

Crystals larger than Examples 1 and 2 and Comparative Examples 1 and 2 (size: 5 dragons x 4 dragons x 1 dragon) were used as crystals, and Comparative Examples 1 and 9 Comparative Examples 2 were used. Using the same ceramic solder (Comparative Example 3) and In solder (Comparative Example 4), lead wires were attached by the ultrasonic soldering method, and the same measurements were performed.

Ratio ffi After Au was deposited on the crystal surface, an Au wire having a diameter of 0.25+am was ball-bonded with a bonding weight of 50 g, and a 4-terminal electrode was attached, followed by similar measurements. The crystal size is the same as in Examples 1 and 2.

The measurement results of each of the above Examples and Comparative Examples are shown in Table 1 below.

In Examples 1 and 2 of Table 1, normal superconducting properties were measured, and
It was possible to measure temperatures down to the extremely low temperature of IOK. On the other hand, in each comparative example, the resistance between the terminals is extremely high, resulting in a semiconductor-like junction at the electrode interface (Comparative Example 3.4),
Although normal characteristics could be measured, the electrode connection was only at a level of 80 to 90 (Comparative Example 3.4);
-Furthermore, if it was impossible to attach the electrode to a minute part, satisfactory results such as Comparative Example 1.2) could not be obtained. In addition,
The reason why Comparative Examples 3 and 4 each have two different results is because there were variations in the characteristics obtained even when the electrodes were attached using the same method.

[Effects of the Invention] As explained above, according to the present invention, the electrode member can be stably attached with high bonding strength and the two can be electrically connected without applying any external force to the crystal. . As a result, in addition to making it possible to attach electrodes to minute crystals,
This provides an excellent effect of ensuring stable connection even at extremely low temperatures.

Therefore, the present invention can provide extremely useful technology for the development and research of superconducting oxides, and will make a significant contribution to the progress of superconducting technology.

Claims (3)

[Claims] (1) A step of forming an Au film on the surface of an oxide crystal, a step of melting a metal or alloy with a melting point of 450°C or less on the Au film, and a step of bringing an electrode member into contact with the molten metal or alloy. A method for attaching an electrode to an oxide crystal, comprising the steps of: solidifying the metal or alloy to fix the electrode member to the oxide crystal. (2) The method for attaching an electrode to an oxide crystal according to claim 1, wherein in the step of melting the metal or alloy, the metal or alloy is heated together with the oxide crystal. (3) The method for attaching an electrode to an oxide crystal according to claim 1, wherein the electrode member is linear or plate-shaped.