JPH0810770B2 - Ceramic superconducting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ceramic superconducting device that constitutes a basic logic element of an electric circuit using a ceramic superconducting material, and a structure that can be easily formed.

<Prior Art> A Josephson element is known as a logic circuit element using a superconducting material. This Josephson element has a structure in which an extremely thin insulating film is sandwiched between superconducting materials made of an alloy of niobium or lead. Is.

<Problems to be solved by the invention> However, the insulating film of the Josephson device described above requires a thin film of about several tens of liters, and in order to manufacture this insulating film, advanced thin film manufacturing technology is required, Was difficult. Further, although the Josephson element has a technical advantage that its operation speed is extremely fast, on the other hand, its change in output level is not so large that it is a practically difficult element to use.

The present invention was created in view of the above points, and is a novel superconducting device that eliminates the problems of the logic circuit element composed of the Josephson element, that is, easy to manufacture, and excellent in operating characteristics. It is intended to provide a superconducting device.

<Means for Solving the Problems> In order to achieve the above object, a ceramic superconducting device of the present invention is provided with a ceramic superconductor having at least a pair of electrodes, and provided in the vicinity of the ceramic superconductor. At least one conductor for passing an electric current is provided, and the magnetic field generated by the electric current passed through the conductor is made to act on the ceramic superconductor.

That is, the present invention utilizes weak coupling existing in the crystal grain boundaries of a ceramic-based superconducting material, in which at least one conductor is arranged parallel to or intersecting with the superconductor, and a current flowing through this conductor is used. The magnetic field generated by the above influences the superconductor.

The superconductor described above is Y ₁ Ba ₂ C in the preferred embodiment.
A ceramic superconductor film made of u ₃ O _{7 -X} , which is formed to be long in one direction, and at least one current conductor is arranged in parallel or intersecting with this superconductor film.

Further, the above-mentioned ceramic superconducting conductor and the conductor through which the current flows are provided on the same substrate, and further the above-mentioned ceramic superconducting conductor and the conductor through which the current flows are provided in a laminated state via an insulator. Alternatively, the ceramic superconductor and the conductor through which the current flows may be disposed in close proximity to each other, or may be disposed so as to intersect with each other.

Further, in another preferred embodiment of the present invention, one ceramic superconductor is provided with a conductor for passing an independent current on each side.

Further, when using the ceramic superconducting device of the present invention, a logical output is made from a pair of electrodes provided on the ceramic superconductor by passing a current in at least two conductors provided in the vicinity of the ceramic superconductor in the same direction or opposite directions. To obtain the logic circuit element.

Further, the ceramic superconducting device of the present invention has a substrate and a ceramic superconducting film formed on the substrate. The ceramic superconducting film is electrically divided into a plurality of parts, and at least one of the divided parts is formed. A magnetic field generated by a current flowing through one ceramic superconducting film is made to act on the other divided ceramic superconducting films.

In this case, in the ceramic superconducting film divided into the plurality of parts, the superconducting film between the superconducting part functioning as an element and the superconducting part for controlling the element part is not removed. Alternatively, the superconductor portion functioning as an element and the superconductor portion for controlling this element may be made into an insulator.

That is, the present invention described above utilizes the weak bond existing in the crystal grain boundary of the ceramic superconducting material, and the superconductor film is processed so as to be electrically divided into at least two. The magnetic field generated by the current flowing through the superconductor affects the other superconductors.

The above superconductor film is Y ₁ Ba in the preferred embodiment.
It is a ceramic superconductor film made of ₂ Cu ₃ O _7-X , and after the film is formed, it is electrically divided so that a current conductor formed by at least one superconductor is formed in the superconductor film. Will be placed. Above, the current conductor is 2
The logic circuit elements are arranged by arranging more than one line and passing the current in the same direction or the opposite direction and obtaining the output from the superconductor.

<Operation> The applicant has found that the crystal grain boundaries of the ceramic superconductor are broken by a weak magnetic field, and the superconductor changes from a superconducting state to a resistor, and Japanese Patent Application No. 62-233369 “Superconducting Magnetoresistive System”. The present invention utilizes this phenomenon, in which a magnetic field generated by a current flowing through a conductor arranged parallel to or intersecting with the superconductor is applied to the superconductor, It is designed to detect a superconducting state and a state in which a normal resistor is changed.

In more detail, the element made of a superconductive material having a crystal grain boundary composed of particles of ceramic, when the magnetic field is not applied, as shown in FIG. 11, the electrical resistance R ₀ shown by the element completely Although showing a value of zero, when a certain critical magnetic field H _C is applied, the element suddenly exhibits electric resistance, and the applicant found a new phenomenon in which the electric resistance rapidly increases with an increase in the applied magnetic field. We have filed an application, but the ratio of the resistance change ΔR to the initial resistance R ₀ of this device is ΔR / R ₀
Is an infinite element, which is a high-performance element that is incomparable to conventional magnetoresistive elements.

In other words, the direction of research on ceramic superconductors, which is being promoted by many research institutions in recent years, is to improve the critical temperature (T _C ), critical magnetic field (H _C ), and critical current (I _C ). The present applicant has also conducted various studies on the above-mentioned ceramic superconductor. As a result, a certain kind of this superconducting material (having a weakly-bonded state between particles of the superconducting material) has an extremely weak magnetic field (number We found that the weakly coupled superconducting state was broken by Gauss) and showed an electrical resistance, which rapidly increased with the strength of the applied magnetic field, and by using this low critical magnetic field phenomenon, a ceramic superconducting device that operates as a new logic circuit element was developed. It was created.

As shown in FIG. 11 above, the change characteristic of electric resistance with respect to the application of a magnetic field is that the ceramic superconducting material is a crystal body composed of many superconducting fine particles, and an extremely thin insulator or resistor is present at the grain boundary. Exists, or
The point of contact between particles is in a point state, that is, the grain boundaries are in point-like contact, and so-called weak superconducting state of superconductivity.In the superconducting state, electrons are free due to tunnel effect, etc. Moved to and showed zero electrical resistance. In other words, a polycrystalline superconducting material in a weakly coupled state, such as a ceramic, is equivalent to an infinite number of Josephson couplings, as shown in Fig. 12.
It can be regarded as an aggregate of 121, 121, ....

When a magnetic field is applied to such a material, the superconductivity of the Josephson couplings 121, 121, ... Is broken by the effect of the magnetic field, that is, the weak coupling state of superconductivity is broken by the application of a weak magnetic field, and the element exhibits electrical resistance. And the electric resistance increases as the strength of the magnetic field increases.

As is clear from the above principle, this property is determined by the absolute value of the magnetic field strength without depending on the direction of the applied magnetic field because the crystal grain boundaries are randomly arranged.

Further, according to the present invention, a current conductor is arranged in the vicinity of a superconductor to form a logic circuit element. In this case, however, the superconducting film is processed so that it is electrically divided to obtain a superconductor. By constructing a current conductor (formed by a superconductor) with, the manufacturability will be further improved.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

 FIG. 1 is a plan view showing an embodiment of the present invention.

In FIG. 1, reference numeral 1 is a ceramic superconductor 3, a pair of current electrodes 21 and 21 provided near both ends of the superconductor 3, and voltage electrodes 22 and 22 provided at an intermediate position between the electrodes 21 and 21.
Is a superconducting magnetic sensor, and 5 is a conductor provided in the vicinity of the superconducting magnetic sensor 1 in a parallel state. The superconducting magnetic sensor 1 and the conductor 5 are formed on a common substrate 7.

Next, a method for manufacturing the device shown in FIG. 1 will be described in detail.

First, in order to manufacture a magnetic sensor of a ceramic superconductor film used in this apparatus, in the film forming apparatus shown in FIG. 10, while the substrate 7 was stabilized zirconia and the heater 9 kept the substrate temperature at 400 ° C. _{Y (NO 3) 3 · 6H} 2 O, Ba (N
_{O 3) 2, Cu (NO} 3) 2 · 3H 2 O to _{Y 1 Ba 2 Cu 3 O 7} -X to become as weighed in predetermined amounts, intermittently nitrate aqueous solution from the injection device 11, toward the substrate 7 The film was formed into a uniform film having a thickness of 5 μm, and then annealed in air at 950 ° C. for 60 minutes and at 500 ° C. for 10 hours. The critical temperature of the ceramic superconducting film prepared in this way is that the resistance starts to drop from 100K,
It shows zero resistance at K.

Next, this ceramic high temperature superconductor is 50μm wide and long
In order to form the superconductor 3 by processing it to 30 mm, a resist was applied and processed into a thin stripe shape by an ordinary photolithography process to produce a superconductor portion of the superconducting magnetic sensor 1. This ceramic high temperature superconductor could be easily processed with a phosphoric acid-based etching solution. Next, in order to fabricate the electrodes 21 and 22 shown in FIG. 1 and the conductor 5 for generating a magnetic field, a wiring pattern made of a Ti vapor deposition film is formed again by the photolithography process and the lift-off method. The ceramic superconducting device of the invention was produced.

The ceramic superconducting magnetic sensor 1 used in the present invention is considered to be an assembly of Josephson junctions because the insulating layer and the point contact interposed in the grain boundary are weakly coupled, and the relationship between the applied magnetic field and the electric resistance is shown in FIG. As shown, a resistance suddenly appears in a magnetic field from the state of zero resistance, and the change in the resistance is extremely large. The magnitude of the magnetic field (threshold value) at which resistance suddenly appears can be controlled by the magnitude of the constant current flowing through the ceramic superconducting magnetic sensor 1.

On the other hand, when a current of 10 mA is applied to the conductor 5 composed of the Ti film shown in FIG. 1 through the terminals e and f, a magnetic field of 0.4 Gauss can be obtained at a distance of 50 μm. Therefore, as can be seen from the characteristics of the superconducting magnetic sensor shown in FIG. 2, when a constant current of 2 mA is applied to the sensor 1 through terminals a and b and a magnetic field of 0.4 gauss is applied, an output of 20 μV is obtained. You can get it.

From the above experimental results, in the structure shown in FIG. 1, the pattern shape was such that the conductor 5 had a width of 30 μm, a thickness of 1 μm, and a center-to-center distance from the superconducting magnetic sensor 1 of 50 μm.

In the above configuration, when at least the superconducting magnetic sensor 1 is cooled to a temperature of 83 K or less, no current is passed through the conductor 5 and no magnetic field is applied to the superconducting magnetic sensor 1, the terminals a and b are used. The output voltage does not appear between the terminals c and d even if a current is passed through the sensor 1 because it is in a superconducting state, but by passing a constant current I of a conductor 12 mA through the terminals e and f, the magnetic field created by the current is Since the superconductor 3 breaks the superconducting state and exhibits resistance, as shown in FIG.
Corresponding to the above, an output voltage of 20 μV was obtained between terminals c and d at a speed of 0.5 picoseconds. At this time, the constant current between the terminals a and b of the superconducting magnetic sensor 1 was 2 mA.

Next, as shown in FIG. 4, a case will be described in which two conductors 5 and 6 are provided in parallel in the vicinity of the superconductor 3 to form a logic element.

FIG. 4 shows that the conductors 6 and 5 and the superconducting magnetic sensor 1 have a center-to-center distance of 50 μm and a width of 30 μm.
It shows a case where a pattern is formed to 30 μm and 50 μm, and in the configuration shown in FIG. 4, the superconducting magnetic sensor 1 in which a constant current of 2 mA is passed when the current passed through the conductor 6 is about 20 mA.
A value of 20 μV was obtained as the output of

The currents I ₁ and I ₂ flowing in the conductors 5 and 6 are in the same direction, and the magnetic field acting on the superconductor 3 by the current I ₁ flowing in the conductor 5 is H ₁ and the current I ₂ flowing in the conductor 6 is the superconductor. Let H _{2 be} the magnetic field acting on 3 and H _{0 be} the critical magnetic field of the superconducting magnetic sensor 1 in the state where a predetermined constant current is flowing. H ₁ <H ₀ , H ₂ <H ₀ , H ₁ + H ₂ > H ₀ Under the condition of (1), an output voltage is generated between the terminals c and d as shown in FIG. 5 only when currents simultaneously flow through the conductors 5 and 6, and an AND logic output is produced. For example, when currents of 8 mA for I _{1 and} 15 mA for I ₂ are applied to conductors 5 and 6, respectively, the current I ₁
An output voltage of 20 μV or more was obtained between the terminals c and d only during the period when I ₂ and I ₂ were flowing simultaneously.

_{Further, H 1> H 0, H} 2> H 0, | H 1 -H 2 | <H 0 ... under the condition of (2), the current I ₁ flowing through the conductor 5 and the conductor 6 as shown in Figure 6, When the direction of I ₂ is reversed, as shown in FIG. 7, the output voltage is obtained between the terminals c and d only during the period when only _one of the currents I ₁ and I ₂ is present between the terminals c and d, The logical output of exclusive or is obtained. Also under this current condition,
When the currents I ₁ and I ₂ flow in the same direction, an OR logic output is obtained.

Although the current values I ₁ and I ₂ are appropriately selected in the above embodiment, the present invention is not limited to this. value
I ₁ and I ₂ are set to be equal and constant values, the distance between the superconductor 3 and the conductor 5 or 6 is appropriately selected, and the conductors 5 and 6 are placed at positions satisfying the above formula (1) or (2). It may be provided.

The arrangement relationship between the superconductor 3 and the conductors 5 and 6 is not limited to the above-mentioned embodiment, and the conductors 5 and 6 may be arranged on both sides of the superconductor 3 as shown in FIG. Further, the same action and effect can be obtained by forming the conductors 5 and 6 on the protective film such as polyimide resin or SiO ₂ formed on the superconducting magnetic sensor. Further, in this case, as shown in FIGS. 9 (a) and 9 (b), the superconductor 3 and the conductors 5 and 6 are laminated so as to intersect (for example, orthogonally) through a protective film 10 such as a polyimide film or SiO. It goes without saying that they can be placed.

Further, when manufacturing the device of the present invention, the method is not limited to the above-mentioned method, and the conductors 5 and 6 or the superconducting magnetic sensor 1 may be formed of a superconducting thin film by sputtering, MOCVD, electron beam method or the like. It is possible to obtain the result and also to expect the miniaturization of the processed shape.
In particular, when the conductors 5 and 6 are formed of a superconducting thin film, they can be formed at the same time as the superconductor 3 of the superconducting magnetic sensor 1, and the manufacturing process of the device is simplified.

The embodiment will be described below with reference to FIGS. 13 (a) to 13 (c).

In order to produce the ceramic superconductor film used in this example, in the film forming apparatus shown in FIG. 10 as described above, the substrate 7 was stabilized zirconia, the substrate temperature was kept at 400 ° C. by the heater 9, _{Y (NO 3) 3 · 6H} 2 O, Ba (N
_{O 3) 2, Cu (NO} 3) 2 · 3H the _{2 O Y 1 Ba 2 Cu 3} O 7-X to become as weighed in predetermined amounts, towards the intermittently substrate 7 nitrate aqueous solution from the injection device 11 5 [mu] m The film is formed into a uniform film having a uniform thickness and then annealed in air at 950 ° C. for 60 minutes and 500 ° C. for 10 hours to remove the substrate 131 from the substrate 131 as shown in FIG. 13 (a). A superconducting film 132 was formed on the entire surface. The electric resistance of the ceramic superconducting film produced in this way began to drop from 100K and became completely 0 at 83K.

Next, this ceramic superconducting film 132 is formed in FIG. 13 (b).
And as shown in (c), etching was performed for electrical division. The etching is performed by applying a resist, using a normal photolithography process, and using a phosphoric acid-based etching solution to electrically separate the superconducting film.
132a and 132b were obtained.

The ceramic superconductor film in this example is considered to be an assembly of Josephson junctions because the insulating layer and the point contact interposed in the grain boundary are weakly coupled, and the relationship between the applied magnetic field and the electric resistance is shown in FIG. As shown, a resistance suddenly appears in a magnetic field from the state of resistance 0, and the change in the resistance is extremely large. Further, the magnitude of the magnetic field where the resistance suddenly appears can be controlled by the magnitude of the constant current flowing in the superconductor.

When a current of 10 mA is passed between the electrodes ef shown in FIG. 13 (b), a magnetic field of 0.4 gauss can be obtained at a distance of 50 μm. Therefore, as can be seen from the characteristics of the superconductor shown in FIG. 2, if a constant current of 2 mA is passed between the electrodes ad, an output of 20 μV can be obtained between the electrodes cd.

From the above experimental results, the shape of the pattern is shown in FIG. 13 (b).
The width of the superconducting film 132b that acts as a current conductor of about 30 μm,
The center-to-center distance between the superconductor 132b and the superconductor 132a was set to 50 μm.

As a result, when the element is cooled below 38K, e
Since no magnetic field is generated when no current is passed between f,
Even if a current was passed through the superconductor 132a through the space, the output voltage did not appear between cd because of the superconducting state. Then, by passing a current of 10 mA between ef, the magnetic field created by the current breaks the superconducting state of the superconductor 132a, and as shown in FIG. 3, an output of 20 μV is generated between cd at a speed of 0.5 picoseconds. I was able to get it. However, the constant current between ab at this time is 2 mA.

Next, a pattern shown in FIG. 13 (c) is created by a photolithography technique, and superconductors 132b and 132c functioning as current conductors and a superconductor 132a functioning as a magnetic sensor are formed.
Center distance of 50μm, width of 30μm, 30μm, 50μ respectively
m.

In this configuration, the value of the current flowing between ab is 2 mA, and ef
When a current of 10 mA was passed between them, an output of 20 μV was obtained between cd.

In FIG. 13 (c), the currents of the superconductors 132b and 132c acting as current conductors are set in opposite directions, the current value of the superconductor 132b is I ₁ , the current value of the I superconductor 132c is I ₂ , and the superconducting current is I ₂ . A threshold magnetic field (11th magnetic field) that causes an output voltage in the body 132a.
If the current value that gives Bth) in the figure is I ₀ , I ₁ <I ₀ , I ₂ <I ₀ , I ₁ + I ₂ > I ₀ ……… (3) An output voltage is generated across cd only when current flows simultaneously. Therefore AND
The logic of.

Further, if the current directions of the superconductors 132b and 132c are the same, under the condition of I ₁ > I ₀ , I ₂ > I ₀ , | I ₁ −I ₂ | <I ₀ (4), A voltage is generated between cd only when only _{one of} I ₁ and I ₂ is present. Therefore exclusive OR
Is obtained. Under this current condition, if the current is reversed, the OR logic is obtained.

In the above-mentioned embodiment, the superconductor which functions as a magnetic sensor and the superconductor which functions as a current conductor are removed by etching in order to electrically separate them.
Similar effects can be obtained by modifying the material of the portion between them to an insulator.

As an example of this insulating material, the superconducting film of FIG. 13 (a) is used.
As shown in FIGS. 13 (b) and 13 (b), 132 was exposed to As ions by using the patterned metal mask. As a result, only the irradiated portion became an insulator, and showed the same device characteristics as when removed by etching. The reason why the superconductor becomes an insulator by the ion irradiation is considered to be that the crystal structure is disordered and becomes amorphous due to the damage caused by the irradiation.

Although the above example is confirmation of the basic operation, many methods such as mechanical removal (sandblasting), photoetching, modification of film quality by diffusion of different elements, etc. are applied as a method of electrically dividing the ceramic superconducting film. It is possible. If the superconducting film is electrically divided by these methods,
It is clear that the same effect can be obtained.

Further, the ceramic high temperature superconductor film used in the examples of the present invention was Y ₁ Ba ₂ Cu ₃ O _7-X , but the present invention is not limited to this, as long as it has a grain boundary. Needless to say, similar results can be obtained by using high-temperature superconductors containing other components.

Needless to say, if the produced superconductor is a ceramic superconductor having a grain boundary, the same effect can be obtained regardless of the production method such as sputtering, electron beam evaporation, or CVD method.

Further, the arrangement relationship of the conductors is not limited to the above embodiments.

<Advantages of the Invention> As described above, according to the present invention, superconductivity utilizing weak coupling that naturally intervenes in a ceramic superconductor without using a Josephson junction for artificially producing an extremely thin insulating layer as in the conventional art. The present invention relates to logic circuit processing using a magnetic sensor, and has a feature that conductors can be arranged in a plane as in the above-described embodiment, and the superconducting magnetic sensor used in the present invention has characteristics in the magnetic field direction. Since there is no dependency and the Josephson junction forming step can be omitted, it is possible to easily produce many conductors on top of resin such as polyimide or SiO ₂ as a protective film. Further, when the current conductor and the magnetic sensor according to the present invention are configured by electrically dividing the ceramic superconductor film, the method of manufacturing the element is further simplified.

[Brief description of drawings]

FIG. 1 is a plan view showing the configuration of an embodiment of the ceramic superconducting device of the present invention, FIG. 2 is a diagram showing an example of the characteristics of the ceramic superconducting sensor, and FIG. 3 is the output response of the superconducting sensor due to the current flowing through the conductor. FIG. 4 is a plan view showing the structure of another embodiment of the ceramic superconducting device of the present invention in which a plurality of electric field generating conductors are provided and the current directions are the same, and FIG. FIG. 4 is a diagram showing the relationship between the output response and the current of the conductor when the current directions of the conductors are the same, and FIG. 6 shows two conductors that generate an electric field in another embodiment of the present invention. FIG. 7 is a diagram showing the configuration when the current directions are opposite to each other, FIG. 7 is a diagram showing the relationship between the output response of the device of the embodiment of the present invention having the configuration of FIG. 6 and the waveform of the current flowing through the conductor, and FIG. 8 is the diagram of the present invention. The structure of yet another embodiment of the ceramic superconducting device is shown. Plan views, FIGS. 9 (a) and 9 (b) are respectively a plan view and a cross-sectional view showing the structure of still another embodiment of the present invention, and FIG. 10 is a ceramic superconducting device used for manufacturing the device of the embodiment of the present invention. Diagram showing a schematic configuration of a film manufacturing apparatus,
FIG. 11 is a diagram showing an example of characteristics of the superconducting magnetic sensor, FIG. 12 is a diagram showing an equivalent circuit of the superconducting magnetic sensor, and FIG. 13 (a).
11A to 11C are perspective views of the apparatus configuration for explaining another embodiment of the present invention. 1 ... Superconducting magnetic sensor, 21,21 ... Current electrode, 22,22 ...
… Voltage electrode, 3 …… Superconductor, 5,6 …… Conductor, 131 …… Substrate, 132 …… Superconducting film, 132a …… Superconductor functioning as a magnetic sensor, 132b, 132c …… Superconducting functioning as current conductor Body, ah ... Electrode terminals.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Nojima Hideo Nojima 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (56) References JP-A-62-115881 (JP, A) JP-A-59 -17175 (JP, A)

Claims (4)

[Claims] 1. A ceramic superconductor having a weak bond existing in a crystal grain boundary of a superconducting material and provided with at least a pair of electrodes, and at least one conductor provided in the vicinity of the ceramic superconductor and flowing a current. A ceramic superconducting device, comprising: a magnetic field generated by an electric current flowing through the conductor; 2. The ceramic superconducting device according to claim 1, wherein the ceramic superconductor and the conductor are arranged so as to intersect with each other. 3. The ceramic superconducting device according to claim 1, wherein a plurality of conductors for independently passing an electric current are arranged in the vicinity of the ceramic superconductor. 4. A substrate and a ceramic superconducting film having a weak bond existing at a crystal grain boundary of the superconducting material on the substrate, the ceramic superconducting film being electrically divided into a plurality of portions, and the divided portions. A ceramic superconducting device, characterized in that a magnetic field generated by a current flowing through at least one ceramic superconducting film is made to act on the other divided ceramic superconducting films.