JPS6242583A - 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 iron oxide. CONSTITUTION:2-Ethyl hexanates, which are easy to be formed into a film, are employed as compounds of Mn and Fe 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 active 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 otained with high productivity and at a low cost.

Description

[Detailed description of the invention] Industrial applications It is.

A conventional 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, and disokel oxide. 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 safe 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 a base, 2 is an active layer, and 3° and 4 are electrodes.

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 2 is usually formed by vacuum deposition or sputtering.

Problems to be Solved by the Invention As mentioned above, in conventional nonlinear resistance elements exhibiting switching characteristics, the active layer is formed by a vacuum method.
Not only is this disadvantageous in terms of manufacturing yield and productivity, but it is also difficult to accommodate this for other reasons, such as higher costs for applications that require devices to be constructed on very large substrates. Can not.

An object of the present invention is to provide a nonlinear resistance element with special switching characteristics that solves the above-mentioned problems, and a method for manufacturing the same, so that these elements can 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 thermally decomposing it to form an active layer. The metal compound may be one that dissolves in a suitable solvent and forms a film when the solution is applied and dried, such as inorganic acid salts such as nitrates, organic acid salts such as acetates, complexes, and metals with alkyl groups. It is possible to use organic metals with . 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 iron oxide as a compound that exhibits switching properties, and used this for the active layer.

Function A thin film of a mixture of manganese oxide and iron oxide can be easily obtained by dissolving a compound of manganese and iron 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, methods such as dipping, spraying, and printing can be used, so that a uniform film can be manufactured over a large area with high productivity and at low cost. In addition, the thin film obtained by pyrolysis 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 iron oxide was prepared with the composition shown in the table. 2-ethylhexanoate, which is very easy to form into a film, was used as the compound of manganese and iron, and methyl in butyl ketone was used as the solvent. 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 exposed to sso' in the air.
An active layer was formed by heating and baking with C for 60 minutes, and a gold thin film was further formed on this thin film. When the IV percentage characteristics of these elements upon voltage application are measured using a curve tracer, an IV curve as shown in FIG. 1 is obtained. The measurement results are shown in Table 1. In this table, vt
h (threshold voltage), th (threshold current), vh (sustaining voltage), and Ih (maintaining current) are shown as numerical values. These values are all values when swept at a frequency of 60 ratio. The thickness of the active layer is measured by etching a portion of this thin film to form a step and using a contact type surface roughness meter.

Furthermore, when harmonics of ±16V were applied to these devices at 6 voltages to examine the stability of their characteristics, they were operated continuously for 10 days (corresponding to more than 4Q0 million switching times). Even after
No fluctuation of more than 5 degrees was observed, and the stability of the properties was considered to be sufficient for practical use.

(Example 2) A sandwich-type element was constructed using a coating solution having the same composition as in Example 1, and 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 shapes in the table correspond to those in Table 1, and the same samples indicate that the active layer was formed using the same coating solution. Sweep frequency is 50
It is Hz. From this table, it can be seen that almost the same results as in Example 1 can be obtained, although there are some variations.
A stability test similar to that of
It was confirmed that the characteristics were stable even after switching over 00,000 times.

(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 I-■ characteristics are measured, the first
An IV curve as shown in the figure was obtained. The results are shown in Table 3. Similarly, the sample grave corresponds to the plate 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.

Table 2 Table 3 (Example 4) A stainless steel wire with a diameter of 1ffflfl+ was immersed in the &4 coating solution of Example 1, pulled up at a rate of about 5 rlIn/CB:, and dried at 60°C at 90°C. A thin film of a mixture of manganese oxide and iron oxide was formed on the surface of the stainless steel wire by heating and baking for a minute, and a silver electrode was further formed on the surface of this film to construct an element. In this one, the sweep frequency is 60Hz, the voltage is 1h, 3V, and the voltage is 0.5 mA, V.
Examples 1 to 3 where h is s, ev and Ih is 2.5 mA
Similar switching characteristics were observed.

In Examples 1 to 4, the firing temperature was 500 to 560°C in view of the heat resistance of the substrate and electrode materials used. However, when using a heat-resistant substrate such as alumina, this temperature may be changed. It can be raised up to the heat-resistant temperature of the substrate. Regarding the compounds used, inorganic acid salts such as nitrates and sulfates,
Any organic acid salt such as acetate, complex salt, metal alkoxide, etc. that 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 is formed by coating a thin film of a mixture of manganese oxide and iron oxide on a substrate with an electrical solution, drying it, and then baking it in the atmosphere. By manufacturing the nonlinear resistance element with switching characteristics, it is possible to provide a nonlinear resistance element having switching characteristics with good productivity at a low cost, and its practical usefulness is great in that it is easy to manufacture even if it has 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 nonlinear resistance element, and FIG. 3 is a sectional view showing the structure of a Brehner type nonlinear resistance element. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 1 Current Figure 2

Claims (2)

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