JPH04145664A - Driving method for organic electronic element - Google Patents

Abstract

PURPOSE:To continuously vary conductivity between electrodes, to preserve the state and to perform a multi-level recording by continuously varying a voltage value to be applied between electrodes of an organic electronic element for holding an organic thin film between a pair of electrodes. CONSTITUTION:After a base electrode 3 is formed on a substrate 1, a single molecule accumulated film layer (Langmuir-Blodgett LB method) 4. Then an upper electrode 2 is so formed as to perpendicularly cross the electrode 3, a voltage to be applied between the electrodes 2 and 3 is continuously varied to continuously vary conductivity between the electrodes, and the state is preserved. That is, the absolute value of the voltage value is varied in a range of 1 to 12V, the thickness of the layer 4 (organic thin film 4) is varied in a range of 4Angstrom to 1,000Angstrom , and formed of organic compound containing at least one type of pi electrons. Thus, many memory states can be realized in one cell to record in a high packing density, and hence a multi-level recording (analog recording) can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a driving method for causing an organic electronic device to exhibit multilevel (analog) recording performance.

[Prior Art] Conventionally, in order to increase the capacity of memory devices, in devices using inorganic materials such as St, it has been attempted to increase the density of memory cells by devising the memory cell structure and constituent circuits, reducing the number of constituent elements, etc. It is being considered to do so. Further, as another means for increasing the capacity, there is multi-value recording using a CCD digital memory or a memory using a photochemical hole burning effect.

[Problems to be solved by the invention] However, inorganic substances originally have
Since the process is complicated and includes a high temperature process, there is a problem in that the number of substrates on which devices can be formed is limited. In addition, since memory using the photochemical hole-burning effect requires extremely low temperatures,
There is a problem that imposes major restrictions on practical application.

The present invention was made in view of the above-mentioned problems, and it is an object of the present invention to enable a device to exhibit multi-level recording performance (analog recording performance) without requiring a complicated manufacturing process or being subject to major practical limitations. This is an issue that must be solved.

[Means and effects for solving the problem] The present inventors,
In order to solve the above problems, we focused on an element with a structure in which an organic thin film is sandwiched between a pair of electrodes, which can be manufactured by a simple process, and completed the present invention as a result of intensive research on the electrical characteristics of the element. be.

That is, in the present invention, by continuously changing the voltage value applied between the electrodes of an organic electronic device in which an organic thin film is sandwiched between a pair of electrodes, the conductivity between the electrodes is continuously changed, and The above problem has been solved by a method for driving an organic electronic device, which is characterized by preserving its state.

In other words, the method for driving an organic electronic device of the present invention enables multi-value recording (analog recording) to be realized in an organic electronic device in which an organic thin film is sandwiched between a pair of electrodes.

The present invention will be explained in detail below.

In general, most organic materials exhibit insulating or semi-insulating properties, and there is a wide variety of organic materials that can be used as organic thin films of organic electronic devices used in the present invention.

Examples of structures of dyes suitable as organic materials used in the present invention include phthalocyanine, dyes having a porphyrin skeleton such as tetraphenylporphyrin, azulene dyes having squarylium groups and croconic methine groups as bonding chains, quinoline, benzothiazole, Cyanine-based similar dyes, such as benzoxazole, in which two nitrogen-containing heterocycles are bonded by a squarylium group and a croconic methine group, or cyanine dyes, fused polycyclic aromatics such as anthracene and pyrene, and aromatic ring and heterocyclic compounds and polymers of diacetylene groups, derivatives of tetraquinodimethane or tetrathiafulvalene, analogs thereof, charge transfer complexes thereof, and metal complex compounds such as ferrocene and trisbipyridine ruthenium complexes, etc. can be mentioned.

Examples of polymeric materials suitable as organic materials used in the present invention include addition polymers such as polyacrylic acid derivatives, condensation polymers such as polyimide, ring-opening polymers such as nylon, and biopolymers such as bacteriorhodopsin. etc.

Regarding the formation of organic thin films, it is possible to specifically apply vapor deposition methods, cluster ion beam methods, etc., but the controllability and
Among the known conventional techniques, the Langmuir-Blodgett method (LB method) is extremely effective due to its ease and reproducibility.

According to this LB method, it is possible to easily form a monomolecular film of an organic compound having a hydrophobic site and a lignophilic site in one molecule or a cumulative film thereof on a substrate, and the thickness is on the order of a molecule. Moreover, it is possible to stably supply a uniform and homogeneous ultra-thin organic film over a large area.

The LB method is a molecule with a structure that has a hydrophilic site and a hydrophobic site, and when the balance between the two (amphiphilic balance) is maintained appropriately, the molecule has a hydrophilic group on the water surface. This is a method of creating a monomolecular film or a cumulative film thereof by utilizing the fact that the film becomes a monomolecular film downward.

It goes without saying that any organic material other than those mentioned above that is suitable for the LB method is also suitable for the element used in the present invention. For example, biomaterials (e.g. bacteriorhodopsin and cytochrome C) and synthetic polypeptides (PBLG), which have been actively researched in recent years, can also be applied, but organic materials with a relatively large π electron level are preferable. .

The monomolecular film can be transferred layer by layer onto the surface of arbitrary substrates having various materials and shapes, such as glass resin. Using this method, forming a monolayer or a cumulative film thereof,
This can be used as an organic thin film of an organic electronic device used in the present invention.

Furthermore, according to the LB film, the thickness of the organic thin film can be freely controlled on the molecular order, but in the present invention, the
The recording function, that is, the memory property is more likely to be expressed in the film thickness of human beings (preferably 10 to 10
It is preferable to have a film thickness in the range of 0.0000000000000000000000000000000000000000000000000000000000000000000. Further, when a cumulative film is formed by the LB method to form an organic thin film, the number of layers is preferably about 1 to 50. With the above-mentioned number of calendars and film thickness, the preferred resistance value in terms of memory characteristics is desirably several MΩ or more in a high resistance state.

On the other hand, the electrode material for sandwiching the LB film may be any material as long as it has high conductivity, such as Au.

Pt, Ag, Pd, A9. Metals such as In, Sn, and Pb and their alloys, as well as graphite and silicide,
Further, there are many other materials including conductive oxides such as ITO, and their application to the element of the present invention can be considered.

Conventionally known thin film techniques are sufficient for forming electrodes using such materials. Further, as for the electrode material directly formed on the substrate, it is preferable to use a conductive material such as a noble metal or an oxide conductor such as ITO that does not leave an insulating oxide film on the surface when forming the LB film.

In the present invention, by continuously changing the voltage value applied between the electrodes of the organic electronic device having the above structure, the electrical conductivity of the organic electronic device is continuously changed, and the state (
conductivity).

The applied voltage pattern is not particularly limited, and includes, for example, a rectangular wave, a triangular wave, a sawtooth wave, and the like. For example, when a rectangular wave is applied to an element according to the present invention, as the wave height (pulse height) of the rectangular wave increases, the resistance value of the element after the rectangular wave is applied can also be increased. Moreover, the element resistance is uniquely determined by the pulse height, and each resistance state is preserved even after the rectangular wave is applied.

The wave height (pulse height) of the applied voltage is also not particularly limited, but 2
In order to stably drive the element related to the present invention, it is preferable to change the voltage within the range of 2V to 12V.
It is more preferable to change it within the range of OV.

Moreover, the voltage sweep time (pulse width) is also not particularly limited.

Here, the organic electronic device according to the present invention is in a low resistance state (
103Ω order) to high resistance state (1o7Ω or more)
Therefore, when performing the method for driving an organic electronic device according to the present invention, it is desirable to set the initial state of the organic electronic device to a low resistance state or a high resistance state by applying a voltage. Due to the characteristics of the element, it is more preferable for the initial state to have a low resistance for analog recording. The applied voltage pattern, wave height, and voltage sweep time at this time are not particularly limited, but it is preferable to apply a triangular wave when creating a low resistance state, and a rectangular wave when creating a high resistance state.

[Example] Example 1 An organic electronic device as shown in FIG. 1 was produced as shown below. In FIG. 1, 1 is a substrate, 2 is an upper electrode, 3 is a lower (underlying) electrode, and 4 is a monomolecular cumulative film layer (LB film layer).

On a glass substrate 1 (#7059 manufactured by Corning) which had been hydrophobically treated by being left in saturated vapor of hexamethyldisilazane (HMDS) overnight, Cr was deposited as an undercoat layer to a thickness of 500 by vacuum evaporation, and then Au was deposited by the same method (to a film thickness of i ooo) to form a striped base electrode 3 with a width of 1 mm. Using such a substrate as a carrier, a polyimide monomolecular film 4 was formed as follows.

Polyamic acid (molecular weight approximately 200,000) at a concentration of 1 x 10-3
% (g/g) of dimethylacetamide solution,
It was spread on an aqueous phase of pure water at a water temperature of 20°C to form a monomolecular film on the water surface. The surface pressure of this monomolecular film was set to 25 mN/
m, and while keeping this constant, the substrate was moved across the water surface at a rate of 5 mm/min, immersed, and pulled up to accumulate a Y-type monomolecular film. By repeating this operation, a 12-layer cumulative film was formed.

Further, these films were heated at 300° C. for 10 minutes to form polyimide.

Next, a width of 1 mm is placed on the film surface perpendicular to the base electrode 3.
A strip-shaped AJ2 electrode (1,500 membranes) was deposited on the substrate to form the upper electrode 2 while keeping the substrate temperature below room temperature.

There was a second
Voltage sweep time Looms as shown in the figure, Note height -7V (A
A triangular wave of 0.3 °C was applied (using a green electrode) to bring the element into a low resistance state. After that, the pulse width is increased to 10 as shown in Figure 3.
A rectangular wave with a pulse height of 1 (V+ is negative) [V] was applied.

When we measured the element resistance R, [Ω] after applying a rectangular wave as shown in Fig. 3 with different pulse heights vI, we found that the pulse height vI
The relationship between the absolute value IV11 of IV11 and the element resistance R1 after application of the rectangular wave of pulse train 1 is as shown in FIG. That is, as the value 1 of the pulse height V was continuously changed, the element resistance R1 after application of the rectangular wave continuously increased. For example, as shown in Figure 3, when a rectangular wave with a pulse height of about 14 V is applied, the element resistance after applying the rectangular wave is I
The resistance was on the order of KΩ, and when the pulse height was set to about -5V, the element resistance became IOKΩ. Also, set the pulse height to -4~
-5■, the element resistance after applying a square wave is IK
It changed continuously from Ω to IOKΩ. Furthermore, by changing the pulse height in steps of -6V, -7V, etc., the element resistance increases by approximately one order of magnitude after applying the square wave.If the pulse height is set to about -10V, the element resistance increases to 100MΩ. When the pulse height was changed continuously from -10V to 100MΩ, the element resistance after applying the square wave changed continuously to 100MΩ.In this way, the pulse height was changed from -4 to -10V.
When varied between V, the element resistance varies from about IKΩ to 10
It is possible to continuously change the resistance between approximately 0 MΩ, and to have an element resistance that corresponds one-to-one to the pulse height. Moreover, the state (electrical conductivity) had memory properties.

By continuously changing the voltage value applied to the element as described above, it was possible to continuously change the resistance value of the element and maintain that state.

Example 2 In this example, an element produced in the same manner as in Example 1 was used. Between the upper and lower electrodes, a pulse width of 10tLs as shown in Fig. 5,
A rectangular wave with a pulse height of −7 V (with the Aj2 electrode on the + side) was applied to bring the element into a high resistance state. Thereafter, a rectangular wave as shown in FIG. 3 was applied.

When we measured the element resistance R2 after applying a rectangular wave as shown in Fig. 3, we found that the absolute value of the pulse height ■, V+ l [
V] and pulse height V, the element resistance Rg[
Ω], as shown in Figure 6. That is, as the absolute value of the pulse height vI is increased from 1 to 1, the element resistance R after applying the square wave decreases very rapidly at 3V, and becomes 3V.
When the resistance value R2 exceeded (2), the resistance value R2 increased continuously. For example, when a rectangular wave with a pulse height of 13 V is applied as shown in FIG. 3, the element resistance after application of the rectangular wave rapidly changes from about 1.0 MΩ to about IKΩ. When the pulse height is set to -4V, the element resistance further decreases to the minimum (approximately IKΩ). Furthermore, when the pulse height was varied between 12 V and 14 V, the element resistance after application of the rectangular wave continuously varied from IOKΩ to IKΩ. Furthermore, increase the pulse height from 14■ to 15V.
.

When changing IV increments to -6V, ..., the element resistance after applying the square wave becomes thicker by approximately one digit (
When the pulse height is set to about -7V, the element resistance becomes IMΩ.
When the pulse height was continuously changed to -7V, the element resistance after applying the square wave was continuously changed to IMΩ. When the pulse height is changed from 12V to 14cm in this way, the element resistance changes continuously and rapidly from about 10MΩ to about IKΩ, and when the pulse height is changed from 14V to 17cm. When the element resistance is changed between IKΩ
It is possible to continuously change the resistance between approximately 1.0 and IMΩ, and also to have an element resistance that corresponds one-to-one to the pulse height. Moreover, the state (electrical conductivity) had memory properties.

By continuously changing the voltage value applied to the element as described above, you can change the resistance value of the element very rapidly, or change the resistance value of the element continuously and preserve its state. I was able to do it.

Example 3 In this example, the same element as in Example 1 was used. In order to bring the element into a low resistance state, a voltage sweep time Looms and a wave height of 7V were applied between the upper and lower electrodes as shown in Figure 7 (the Aβ electrode was set to the + side).
A triangular wave was applied. Furthermore, the pulse width 1 as shown in Figure 8
A rectangular wave of 0 μs and a pulse height of 2 [V] (V: positive) was applied. After that, the element resistance R, [Ω] was measured. Element resistance R after applying a square wave of pulse height v2 and pulse height ■2
The relationship between 3 is as shown in Figure 9.

That is, as the pulse height 2 was increased, the element resistance R3 after application of the rectangular wave continuously increased. For example, as shown in Figure 8, when a rectangular wave with a pulse height of about +3V is applied, the element resistance after applying the rectangular wave is on the order of IOKΩ, and when the pulse height is changed in 1v increments of 4V, 5V, etc. As the pulse height increases, the element resistance becomes approximately 100Ω, and when the pulse height is set to approximately IOV, the element resistance becomes approximately IOMΩ. Further, when the pulse height was varied between 2V and IOV, the element resistance could be continuously varied from about IOKΩ to about IOMΩ. In this way, by changing the pulse height between 2V and IOV, the element resistance after applying the square wave can be continuously changed from about IOKΩ to about 10MΩ, and it corresponds one-to-one to the pulse height. It is possible to obtain a certain element resistance.

Moreover, the state (electrical conductivity) had memory properties.

By continuously changing the voltage value applied to the element as described above, it was possible to continuously change the resistance value of the element and maintain that state.

Example 4 In this example, the same element as in Example 1 was used. In order to bring the device into a high resistance state, a pulse width of 101.0 mm is applied between the upper and lower electrodes as shown in FIG. LS, a rectangular wave with a pulse height of 7 V (with the A9 electrode on the + side) was applied. Furthermore, a rectangular wave with a pulse width of 10 μs and a pulse height of 2 [V] as shown in FIG. 8 was applied.

Thereafter, the element resistance R4 [Ω] was measured. The relationship between the pulse height 2 and the element resistance R4 after the application of the rectangular wave of pulse height 2 was as shown in FIG.

In other words, as the pulse height 2 increases, the element resistance after applying the square wave once decreases very rapidly until the pulse height reaches 4V.
Above that, it increased continuously. As shown in Figure 10,
When a square wave with a pulse height of about 2V is applied, the element resistance after applying the square wave is on the order of 10MΩ, but when the pulse height is set to 3■, the element resistance decreases rapidly, and the pulse height is 4V.
When the pulse height reaches 4V, the element resistance becomes the minimum (on the order of 100KΩ), and when the pulse height is increased to 4V or more, the element resistance increases rapidly.When the pulse height becomes about 6V, the element resistance becomes IO again.
The resistance is on the order of MΩ, and when the pulse height becomes about 9V, the element resistance becomes on the order of 100MΩ. Also, when the pulse height is changed between 1v and 9v, the element resistance becomes 10'
It was possible to continuously change the resistance between the order of Ω and 10 7 Ω. In this way, when the pulse height is changed between 2V and 4V, the element resistance changes continuously and rapidly between about 10MΩ and 10OKΩ, and when the pulse height is changed between 4V and 9V, the element resistance changes continuously and rapidly between about 10MΩ and 10OKΩ. The element resistance can be changed continuously and rapidly from about 100KΩ to about 10MΩ, and the element resistance can be made to correspond one-to-one to the pulse height.

Moreover, the state (electrical conductivity) had memory properties.

By continuously changing the voltage value applied to the element as described above, it was possible to continuously change the resistance value of the element and preserve that state.

Example 5 A monomolecular film of squarylium bis-6-octyl azulene (SOAZ) was accumulated on a substrate on which the substrate 1 was treated and the base electrode 3 was formed in the same manner as in Example 1, using the following method. Ta. The accumulation method is described below.

5OAZ was dissolved at a concentration of 0.2 mg/mj2 or an oo form solution was prepared with K HCOs tep H6, 71i adjusted CdCJ2. Concentration 5X10-'mo℃/I2, water temperature 2
It was developed on an aqueous phase at 0°C to form a single molecule on the water surface.

After waiting for the evaporation of the solvent, the surface pressure of the membrane was reduced to 20
mN/m, and while keeping this constant, the substrate was gently immersed in a direction across the water surface at a speed of 10 mm/min, and then gently pulled up at a rate of 5 mm/min.
A two-layer Y-type single-layer 9 film accumulation was performed. By repeating this operation an appropriate number of times, a 12-layer cumulative film was formed on the substrate.

Next, an upper electrode 2 is placed on the organic thin film 4 as in Example 1.
Afi was deposited as a.

Example 1 Regarding the tangible electronic device created as described above
From , the absolute value of the voltage is calculated using the same method as in Example 4, and
When investigating the relationship between element resistance, similar results were obtained.

That is, as the absolute value of the voltage value increased, the element resistance increased continuously. Moreover, the state (electrical conductivity) had memory properties.

In the examples described above, the LB method was used to form the organic thin film, but as mentioned above, any film formation method that can create an extremely thin (uniform insulating) organic thin film can be used other than the LB method. Possible.Specifically, vacuum evaporation method, electrolytic polymerization method, C
The range of usable organic materials is expanded, including the VD method.

Regarding the formation of the electrode, as already mentioned, any film forming method that can form a uniform thin film on the organic thin film layer can be used, and is not limited to vacuum evaporation or sputtering.

Furthermore, the present invention does not limit the substrate material or its shape in any way.

Also, although we have described the applied voltage pattern as a rectangular wave,
A triangular wave, a sawtooth wave, etc. may be used, and the present invention is not limited to this in any way.

[Effects of the Invention (2) The method for driving an organic electronic device of the present invention makes it possible to continuously change the conductivity of the device and give the state memory properties. Therefore, a large number of memory states can be realized in one element, making high-density recording possible. As a result, multi-value recording (analog recording) became possible.

■ According to the present invention Film thickness can be controlled on the order of A8 molecules.

B. Not restricted by the material of the substrate.

There is a high degree of freedom in selecting the C9 element constituent materials.

D. Highly compatible with molecular electronics and bioelectronics in the future.

Multi-value recording (
It can now be used as an analog recording (analog recording) element.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing the structure of an organic electronic device used in the present invention. FIG. 2 is an applied voltage pattern used in Example 1, FIG. 3 is an applied voltage pattern used in Examples 1 and 2, and FIG. 4 is a graph showing the relationship between voltage value and element resistance in Example 1. Figure 5 shows the applied voltage pattern used in Example 2;
The figure is a graph showing the relationship between voltage value and element resistance in Example 2, Figure 7 is the applied voltage pattern used in Example 3, Figure 8 is the applied voltage pattern used in Examples 3 and 4, and Figure 9 is the applied voltage pattern used in Examples 3 and 4. The figure is a graph showing the relationship between voltage value and element resistance in Example 3,
Figure 10 shows the applied voltage pattern used in Example 4;
The figure is a graph showing the relationship between voltage value and element resistance in Example 4.

Claims (4)

[Claims] (1) By continuously changing the voltage value applied between the electrodes of an organic electronic device in which an organic thin film is sandwiched between a pair of electrodes, the conductivity between the electrodes can be continuously changed, and the state can be changed continuously. A method for driving an organic electronic device characterized by storage. (2) The method for driving an organic electronic device according to claim 1, characterized in that the absolute value of the voltage value is changed in the range of 2V to 12V. (3) The method for driving an organic electronic device according to claim 1, wherein the organic thin film has a thickness in the range of 4 Å to 1000 Å. (4) The method for driving an organic electronic device according to claim 1, wherein the organic thin film is composed of an organic compound having at least one type of π-electron system.