JPS6242576A - Nonlinear resistance element and manufacture of same - Google Patents

Abstract

PURPOSE:To obtain a nonlinear resistance element which has a conductive switching function by attaching a lead electrode to a thin film of a mixture of manganese oxide and bismuth oxide. CONSTITUTION:2-Ethyl hexanates, which are easy to be formed into a film, are employed as compounds of Mn and Bi and these compounds are applied by spin-coating with methyl isobutyl keton as solvent to the surface of a glass substrate 1 on which an Au thin film electrode 4 is provided. The substrate is then baked in the atmosphere at 550 deg.C for 60min to form an activation layer 2 and an Au thin film electrode 3 is formed. With this constitution, a nonlinear resistance element, which has switching characteristics with a threshold voltage Vth, a threshold current Ith, a holding voltage Vh and a holding current Ih, can be obtained with high productivity and at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to nonlinear resistive elements with functions such as conductive switching.

BACKGROUND OF THE INVENTION A nonlinear resistance element that performs conductive switching is known as an OVONIC element, and uses an amorphous semiconductor mainly composed of chalcogen elements as its material. It is also known that similar electrical properties are found in transition metal oxides, such as hematite, magnetite, nickel ferrite, nickel zinc ferrite,
Nickel oxide etc. have been reported. These conventional nonlinear resistance elements use materials in the form of thin films or sintered bodies, but it is advantageous to construct them with thin films from the viewpoint of low threshold voltage, and they exhibit relatively stable characteristics. Most amorphous semiconductor devices are of the thin film type.

The basic structure of this is shown in FIGS. 2 and 3.

In the figure, 1 is the base, 2 is the active layer, and 3.4
is an electrode.

As described above, it can be divided into a sandwich type (FIG. 2) in which the formed film is used in the direction of its thickness, and a planar type (FIG. 3) in which the film is used in the direction of its surface. In either case, the active layer is usually formed by vacuum evaporation or sputtering.

Problems to be Solved by the Invention As mentioned above, in conventional nonlinear resistance elements exhibiting switching characteristics, the active layer cannot be formed using a vacuum method.
This is not only disadvantageous in terms of manufacturing yield and productivity, but also increases costs for applications that require devices to be constructed on very large substrates. I can't.

An object of the present invention is to provide a nonlinear resistance element having switching characteristics that solves these problems and a method for manufacturing the same, and to enable these elements to be manufactured with high productivity and at low cost.

Means for Solving the Problems In order to achieve the above object, the present invention adopts a method of applying a solution of a metal compound and thermal decomposition to form an active layer. As a metal compound, it dissolves in an appropriate solvent,
It only needs to form a film when the solution is applied and dries.
For example, inorganic acid salts such as nitrates, organic acid salts such as acetates,
Complexes and organic metals with an alkyl group attached to the metal can be used. There are many compounds that can be used to form thin films using this method, but the inventors found a mixture of manganese oxide and bismuth oxide as a compound that exhibits switching properties, and used this for the active layer.

A thin film of a mixture of functional manganese oxide and bismuth oxide can be easily obtained by dissolving a compound of manganese and bismuth in a solvent, coating the mixture on a substrate, and thermally decomposing the mixture. At this time, by considering the combination of the compound and the solvent, a very stable solution can be obtained and can be stored as an ink for a long period of time. By introducing such a formation method, dip,
Since construction methods such as spraying and printing can be used,
A uniform film over a large area can be produced with high productivity and at low cost. In addition, the thin film obtained by pyrolysis is
It exhibits switching characteristics in which the threshold voltage and sustaining current change depending on the film thickness, distance between electrodes, composition, etc., and the stability of these characteristics is very good.

Example The present invention will be explained below with reference to Examples.

(Example 1) In order to make the sandwich type element shown in FIG.
A coating solution for forming a thin film of a mixture of manganese oxide and bismuth oxide was prepared with the composition shown in the table.

As the compound of manganese and bismuth, 2-ethylhexanoate, which is very easy to form into a film, was used, and as the solvent, methyl isobutyl ketone was used. These coating solutions were spin-coded onto a glass substrate on which a thin gold film was formed as an electrode, dried at room temperature, and fired in the air at 560°C for 60 minutes to form an active layer. A thin film was formed. When the I-V characteristics of these elements when voltage is applied are measured with a curve tracer, an I-4 curve as shown in FIG. 1 is obtained. The measurement results are shown in Table 1. In this table, vth (threshold voltage) and "t" in FIG.
h (threshold current), vh (sustaining voltage), and h (maintaining current) are shown as numerical values. All these values are 50)4
This is the value when swept at the frequency of z. The thickness of the active layer was measured by etching a part of this thin film to form a step and using a contact type surface roughness meter.

Furthermore, we applied harmonics of ±1 sV at 5 Hz to these devices to examine the stability of their characteristics, and found that each device was operated continuously for 10 days (equivalent to over 4 million switching times). Even after the test, no fluctuation of more than ±6 inches was observed in the values shown in Table 1, and the stability of the properties was considered to be sufficient for practical use.

(Hereinafter referred to as "Kinshiro") (Example 2) Using a coating solution having the same composition as in Example 1, a sandwich-type element was constructed by replacing the electrode with an indium oxide thin film doped with tin. The manufacturing method except for the electrodes is exactly the same as in Example 1. When these IV characteristics were measured with a curve tracer, IV curves as shown in FIG. 1 were similarly obtained, and the results are shown in Table 2. The sample numbers in the table correspond to those in Table 1, and the same positives indicate that the active layer was formed using the same coating solution. Sweep frequency is 50
It is a hermitage. From this table, it can be seen that almost the same results as in Example 1 were obtained, although there were some variations.

Further, stability tests similar to those in Example 1 were conducted, and it was confirmed that the characteristics were stable even after switching approximately 4 million times or more.

(Example 3) A thin gold film was formed on a glass substrate, a part of this thin film was etched to create a gap of several tens of microns in width, the gold thin film separated by this was used as an electrode, and the example was applied on top of this. An active layer was formed using the same coating solution as in Example 1. The formation conditions are the same as in Example 1. In this way, the planar type element shown in FIG. 3 was produced. When a DC voltage is applied to these and the knee V characteristics are measured, the first
A knee 7 curve as shown in the figure was obtained. The results are shown in Table 3. Similarly, the sample size corresponds to that of Example 1. It can be seen that the threshold voltage increases in response to the larger inter-electrode spacing compared to the sandwich type element. It was confirmed that the stability of the properties in these cases was sufficient for practical use.

(Leaving space below) (Example 4) A stainless steel wire with a diameter of 1H was immersed in the coating solution in column 4 of Example 1, pulled up at a speed of about 5xz/sec, dried, and fired at SOO''C for 90 minutes. Then, a thin film of a mixture of manganese oxide and bismuth oxide was formed on the surface of the stainless steel wire, and a silver electrode was further formed on the surface of this film to construct the device. IIh voltage 1.4mm, Yh voltage 2.8V
, Ih was 2.3 mm, and switching characteristics similar to Examples 1 to 3 were observed.

In Examples 1 to 4, the firing temperature was 500 to 550'C in view of the heat resistance of the substrate and electrode materials used.
For example, when using a heat-resistant substrate such as alumina, this temperature can be raised to the heat-resistant temperature of the substrate. Regarding the compounds to be used, any inorganic acid salts such as nitrates and sulfates, organic acid salts such as acetates, complex salts, metal alkoxides, etc., which can be dissolved in an appropriate solvent, can be used without any problem. Further, as the electrode material, metals other than those used in this embodiment such as copper, aluminum, and zinc, conductive oxides such as cadmium stannate and antimony-doped tin oxide, or carbon can also be used.

Effects of the Invention As described above, the nonlinear resistance element of the present invention consists of a thin film of a mixture of manganese oxide and bismuth oxide and an electrode for taking electrical leads from the thin film of a mixture of manganese oxide and bismuth oxide. By applying a solution of a compound dissolved in a solvent onto a substrate, drying it, and then baking it in the atmosphere, it is possible to provide a nonlinear resistance element with switching characteristics at a high productivity and at a low cost. Its practical usefulness is great in that it can be easily manufactured even over a large area.

[Brief explanation of the drawing]

FIG. 1 is a current-voltage characteristic diagram of the nonlinear resistance element of the present invention,
FIG. 2 is a sectional view showing the structure of a Sandinch type non-linear resistance element, and FIG. 3 is a sectional view showing the structure of a Brehner type non-linear resistance element. 1st drawing style

Claims (2)

[Claims] (1) Consisting of a thin film of a mixture of manganese oxide and bismuth oxide, and an electrode for taking electrical leads from this thin film,
A nonlinear resistance element characterized by having conductive switching characteristics. (2) A nonlinear resistance element characterized by forming a thin film of a mixture of manganese oxide and bismuth oxide by applying a solution of a manganese compound and a bismuth compound dissolved in a solvent onto a substrate, drying it, heating it, and baking it. manufacturing method.