JPH081968B2 - Ceramic superconducting device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ceramic superconducting device which constitutes a basic logic element of an electric circuit using a ceramic superconducting material.

<Prior Art> A Josephson element is known as a logic circuit element using a superconducting material, and 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 there.

<Problems to be solved by the invention> However, the insulating film of the above-mentioned Josephson device requires a thin film of about several tens of liters, but in order to manufacture this insulating film, advanced thin film manufacturing technology is required, It was difficult. Further, the Jyosefson element has a technical advantage that its operation speed is extremely high, but on the other hand, its output level does not change so much, and it has been difficult to use practically.

In view of the above points, the present applicant previously proposed a novel superconducting device that eliminates the problems of the logic circuit element composed of the Josephson element, that is, is easy to manufacture, and has excellent operating characteristics. Japanese patent application for a ceramic superconducting device capable of logical operation of, OR, XOR (exclusive OR)
Proposed as 63-29526.

The present invention aims at proposing a superconducting device capable of logical operation of NOT (inverter) in the same device, and by the logical operation of NOT and AND, OR, XOR proposed previously. All the basic elements of logical operations are available and all operations are possible.

<Means for Solving Problems> In order to achieve the above object, the ceramic superconducting device of the present invention is a ceramic superconductor having at least a pair of electrodes, and a current provided in the vicinity of the ceramic superconductor. A first and a second conductor for flowing a constant current, and a constant magnetic field generated by constantly flowing a constant current in the first conductor is always allowed to act on the ceramic superconductor. The magnetic field generated by the current flowing through the second conductor is made to act on the above ceramic superconductor.

That is, the present invention utilizes the weak coupling existing in the crystal grain boundaries of the ceramic-based superconducting material. Two conductors are arranged even if they are parallel to or intersecting with the superconductor, and they flow in these conductors. The magnetic field generated by the electric current is configured to affect the above superconductor.

The superconductor described above is Y ₁ Ba ₂ C in the preferred embodiment.
A ceramic superconducting film made of u ₃ O _7-X , which is formed long in one direction and is parallel to or intersects with this superconducting film.
Book current conductors are arranged.

Further, the above-mentioned ceramic superconductor and two conductors through which an electric current flows are provided on the same substrate, and the above ceramic superconductor and two conductors through which an electric current flows are laminated via an insulator. The ceramic superconductor and the two conductors for passing current may be arranged in close proximity to each other, or may be arranged so as to cross 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.

When using the ceramic superconducting device of the present invention, a constant magnetic field generated by constantly flowing a constant current through the first conductor of the two conductors provided near the ceramic superconductor is always applied to the ceramic superconductor. In this state, a current is caused to flow through the second conductor so that a magnetic field having a polarity opposite to that of the magnetic field generated by the first conductor acts on the ceramic superconductor, whereby a logical output is made from a pair of electrodes provided on the ceramic superconductor. To obtain the logic circuit element.

<Operation> The applicant found that the crystal grain boundary of the ceramic superconductor is 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 Magnetoresistance”. However, the present invention utilizes this phenomenon, in which a magnetic field generated by a current flowing through a conductor arranged in parallel with or intersecting with the superconductor is applied to the superconductor, and the superconductor is superconducted. The state and the state of changing to a normal resistor are detected.

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 applicant of the present invention also conducted various studies on the above-mentioned ceramic superconductor, and as a result, a certain kind of this superconducting material (having a weak bonding state between particles of the superconducting material) had 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. 7, the change characteristic of electric resistance with respect to application of a magnetic field is that a 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 system, is equivalent to an infinite number of Josephson bonds as shown in FIG.
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 due to the influence 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. Therefore, 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.

<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 consisting of a first and a fifth superconducting magnetic sensors 5 and 6 provided in parallel with each other in the vicinity of the superconducting magnetic sensor 1.
And the second conductor, the superconducting magnetic sensor 1 and the conductors 5 and 6 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 for a ceramic superconductor film used in this apparatus, in the film forming apparatus shown in FIG. 6, 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 manufacture the electrodes 21 and 22 and the conductors 5 and 6 for generating a magnetic field shown in FIG. 1, 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 present invention shown below 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. Similarly, a resistance suddenly appears in a certain magnetic field from the state of zero resistance, and the change of 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 distance between the centers of the conductor 6 and the conductor 5 and the superconducting magnetic sensor 1 is 50 μm, and the widths thereof are 30 μm, 30 μm and 50 μm.
m was patterned.

In the above configuration, when at least the superconducting magnetic sensor 1 is cooled to a temperature of 83 K or less, current is not passed through the conductors 5 and 6, and when no magnetic field is applied to the superconducting magnetic sensor 1, the terminals a and b are connected. Even if a current is passed through the sensor 1 through it, no output voltage appears between the terminals c and d due to the superconducting state, but a constant current I of 10 mA is applied to the conductor 5 through the terminals e and f.
By passing the current, the magnetic field created by the current breaks the superconducting state of the superconductor 3 and exhibits resistance, so that an output voltage of 20 μV is obtained between the terminals c and d corresponding to the current I. At this time, the constant current between the terminals a and b of the superconducting magnetic sensor 1 was 2 mA.

Current I ₁ that is always applied to conductor 5 and current I ₂ that is applied to conductor 6
Is the opposite direction, and the strength of the magnetic field acting on the superconductor 3 by the current I ₁ which is always flown in the conductor 5 is H ₁ , and the strength of the magnetic field acting on the superconductor 3 by the current I ₂ flowing in the conductor 6 is H ₂ , the strength of the critical magnetic field of the superconducting magnetic sensor 1 in the state where a predetermined constant current is flowing is H ₀ . At this time, the magnetic field of strength H ₁ due to the conductor 5 and the magnetic field of strength H ₂ due to the conductor 6 have opposite polarities.

Here, under the condition of H ₁ > H ₀ , | H ₁ −H ₂ | <H ₀ (1), the current is always passed through the conductor 5, and the current is not passed through the conductor 6. At that time, a voltage is generated between the terminals cd, and no voltage is generated only when a current is passed. That is, a logic output as shown in FIG. 3 is obtained, and becomes a NOT (inverter) logic output.

For example, when a current of ₁ mA of 10 mA was always applied and a current of I ₂ of 25 mA was applied to the conductor 6, an output voltage of 20 μV was obtained between the terminals cd only during the period when the current I ₂ was not flowing.

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 spacing between the superconductor 3 and the conductor 5 or the conductor 6 is appropriately selected, and the conductors 5 and 6 are provided at positions satisfying the above formula (1). Is also good.

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 simultaneously with the superconductor 3 of the superconducting magnetic sensor 1, which simplifies the manufacturing process of the device.

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 if it has a grain boundary, a high temperature superconductor of another component is used. Needless to say, similar results can be obtained.

The arrangement relationship between the superconductor 3 and the conductors 5 and 6 is not limited to the above 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. 5 (a) and 5 (b), the superconductor 3 and the conductors 5 and 6 may be crossed (for example, orthogonal) via a protective film 10 such as a polyimide film or SiO _2. It goes without saying that they may be stacked.

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

<Effects of the Invention> As described above, according to the present invention, superconducting magnetism utilizing weak coupling that naturally intervenes in a ceramic superconductor without using the Josephson junction for artificially producing an extremely thin insulating layer as in the conventional case. The present invention relates to logic circuit processing using a sensor, and the conductors are arranged in a plane as in the above-described embodiment, and the superconducting magnetic sensor used in the present invention is characteristically dependent on the magnetic field direction. Since it is possible to omit the step of forming the Josephson junction, it is possible to easily produce a large number of conductors while using a resin such as polyimide or SiO ₂ as a protective film.

The present invention enables logical operation of NOT (inverter), and by combining with AND, OR, XOR of the previously proposed invention of the ceramic superconducting device (Japanese Patent Application No. 63-29526), (AND-NOT) = NAND, (OR-NOT) = NOR, (XOR-NOT) = XNOR, and all logical operations are possible.

[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 configuration of still another embodiment of the ceramic superconducting device of the present invention,
FIGS. 5 (a) and 5 (b) are a plan view and a cross-sectional view, respectively, showing the structure of still another embodiment of the present invention, and FIG. 6 is a preparation of the ceramic superconducting film used in the preparation of the device of the embodiment of the present invention. FIG. 7 is a diagram showing a schematic configuration of the device, FIG. 7 is a diagram showing an example of characteristics of a superconducting magnetic sensor, and FIG. 8 is a diagram showing an equivalent circuit of the superconducting magnetic sensor. 1 ... Superconducting magnetic sensor, 21,21 ... Current electrode, 22,22 ...
... voltage electrodes, 3 ... superconductor, 5 ... first conductor, 6 ...
… Second conductor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Hashizume, 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (56) References JP 54-127645 (JP, A) Kazuo Fueki, Kitazawa Koichi ed. "Chemistry of oxide superconductors" (Shown 63-4-10) Kodansha pp.227-231

Claims (1)

[Claims] 1. A ceramic superconducting element having magnetoresistive characteristics that shows electric resistance when the superconducting state of weak coupling between superconducting fine particles is broken by an extremely weak magnetic field of strength H ₀ , and a constant current is always applied to generate. A first conductor that keeps a magnetic field of constant strength H ₁ constantly acting on the ceramic superconducting element; and a strength generated by the first conductor when an electric current is applied.
A second conductor for causing a magnetic field having a polarity opposite to that of H ₁ to be H ₂ to act on the ceramic superconductor, the magnetic field strength H ₀ , the magnetic field strength H ₁ , and the magnetic field strength. H ₂ satisfies the conditions H ₁ > H ₀ , | H ₁ −H ₂ | <H _0, and is a ceramic superconducting device that has the logical operation function of an inverter.