JP7030352B2 - Organic transistor and operation control device for organic transistor - Google Patents

Description

The present invention relates to an organic transistor and an operation control device for the organic transistor.

In recent years, the field of organic electronics has attracted attention, and an organic field effect transistor (OFFET) using an organic semiconductor film is known as one of the representative devices in this field. Since the organic semiconductor film can be formed at a low temperature, it can be formed on a plastic substrate having low heat resistance, and by using this technology, a lightweight and flexible organic field effect transistor can be obtained. Can be done. Further, since the organic semiconductor film can be formed by a coating method or a printing method, by using this, a field effect transistor can be obtained more easily and at a lower cost than when an inorganic semiconductor film is used. Can be done.

Non-Patent Document 1 discloses the operation of an organic transistor using a molecule (photoisomerization molecule) film exhibiting a photoisomerization reaction as an organic semiconductor film. The photoisomerized molecule becomes a ring-closed body when irradiated with ultraviolet light and exhibits conductivity peculiar to a semiconductor, and becomes a ring-opened body when irradiated with visible light and exhibits insulating properties. Therefore, when ultraviolet light and visible light are alternately irradiated, the photoisomerized molecule shows a reversible change in the structure of the open ring-closed ring, and the pi-conjugated system is significantly changed accordingly. , Insulator-semiconductor transition will occur. The organic transistor of Non-Patent Document 1 controls current by utilizing such properties of photoisomerized molecules.

However, the organic transistor of Non-Patent Document 1 causes an insulator-semiconductor transition in the organic semiconductor film by simultaneously irradiating the entire organic semiconductor film with ultraviolet light or visible light, and the entire organic semiconductor film is one. It is configured to form two channels. Therefore, when forming a logic circuit that realizes various operations as a device, it is necessary to use a plurality of organic transistors.

Optically and Electricly Driven Organic Thin Film Transistors with Diarylethene Photochromic Channel Layers ACS Appl. Mater. Interfaces, 5 (2013) 3625-3630

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organic transistor capable of realizing various operations by itself and an operation control device thereof.

The present invention provides the following means.
[1] A method for controlling the operation of an organic transistor provided with a photoisomerized molecular film having a ring-open structure as a semiconductor film for channel formation, in a state where a drain voltage and a gate voltage are applied to the organic transistor. Using a light source of irradiation light including visible light and ultraviolet light, and an optical system that guides visible light or ultraviolet light to a region of the irradiation light to be a channel of the photoisomerized molecular film and irradiates the channel. A method for controlling the operation of an organic transistor, which comprises a first step of irradiating a region to be exposed with ultraviolet light and a second step of irradiating at least a part of the region to be a channel with visible light.
[2] The operation control method for an organic transistor according to [1], wherein the irradiation intensity of ultraviolet light in the first step is 5 mW / cm ² or more and 100 mW / cm ² or less. [3] Described in any one of [1] or [2], wherein the photoisomerized molecule has diarylethene as a central skeleton and a pi-conjugated substituent attached to both ends thereof. Operation control method for organic transistors.
[4] An organic transistor comprising a photoisomerized molecular film as a semiconductor film for channel formation, comprising a plurality of electrodes formed on the photoisomerized molecular film separated from each other, and the photoisomerized molecule. However, among the photoisomerized molecular films, the channel region has a closed ring structure and the other regions have an open ring structure, and the channel region connects the electrodes. An organic transistor characterized by being present.
[5] The organic transistor according to [4], wherein the channel region connects the electrodes to form a logic circuit.
[6] The description according to any one of [4] or [5], wherein the photoisomerized molecule has diarylethene as a central skeleton and a substituent of a pi-conjugated system is attached to both ends thereof. Organic transistor.
[7] An operation control device for an organic transistor having the organic transistor according to any one of [4] to [6] and an irradiation means for visible light and ultraviolet light, wherein the irradiation means is visible light. The organic having a light source of irradiation light including ultraviolet light, and an optical system in which visible light or ultraviolet light of the irradiation light is guided to a region to be a channel of the photoisomerized molecular film and irradiated. Operation control device for transistors.

The organic transistor of the present invention includes a photoisomerized molecular film as a semiconductor film for channel formation. Photoisomerized molecules have the property of becoming a ring closure when irradiated with ultraviolet light and a ring opening when irradiated with visible light. The ring-closed body has the conductivity peculiar to the semiconductor, and the ring-opened body has the insulating property. Therefore, the photoisomerized molecular film can be made into a semiconductor by irradiation with ultraviolet rays, and can be made into an insulator by irradiation with visible light.

In the organic transistor of the present invention, by utilizing the properties of the photoisomerized molecule to irradiate only a specific region of the photoisomerized molecular film with ultraviolet light, only the irradiated portion is made into a semiconductor and locally. Channels can be formed. The shape of the channel can be arbitrarily designed and can be a shape constituting a desired logic circuit.

When the gate voltage and drain voltage are applied, the region irradiated with ultraviolet light (channel region) becomes conductive, but by irradiating at least a part of it with visible light, the irradiated region becomes an insulator. Therefore, this region is in a non-conducting state. By further irradiating the insulated region with ultraviolet light, this region is re-semiconductorized and becomes conductive. As described above, in the organic transistor of the present invention, since the conduction state of the channel region can be switched by using ultraviolet light and visible light, the current flowing through the logic circuit can be freely controlled, and by extension, it is a single unit. , Various operations can be realized as a transistor.

It is a perspective view which shows typically the structure of the operation control apparatus of the organic transistor which concerns on embodiment of this invention. (A)-(c) It is a figure which shows the example of the logic circuit which can be formed in the organic transistor which concerns on embodiment of this invention. (A)-(c) It is a figure which shows the example of the logic circuit which can be formed in the organic transistor which concerns on embodiment of this invention. (A)-(c) It is a graph which shows the electric property of the organic transistor which concerns on Example 1 of this invention. (A), (b) is a graph which shows the electric property of the organic transistor which concerns on Example 2 of this invention. It is a graph which shows the electric property of the organic transistor which concerns on Example 3 of this invention.

Hereinafter, the organic transistor according to the embodiment to which the present invention is applied and the operation control method thereof will be described in detail with reference to the drawings. In addition, in the drawings used in the following explanation, in order to make the features easy to understand, the featured parts may be enlarged for convenience, and the dimensional ratios of each component may not be the same as the actual ones. do not have. Further, the materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited thereto, and the present invention can be appropriately modified without changing the gist thereof.

<First Embodiment>
[Configuration of organic transistor operation control device]
FIG. 1 is a perspective view schematically showing a configuration of an organic transistor operation control device 100 according to the first embodiment of the present invention. The operation control device 100 includes an organic transistor 10 provided with a photoisomerized molecular film as a semiconductor film for channel formation, and visible light and ultraviolet light irradiation means (light irradiation system) 20 used for operating the organic transistor 10. is doing.

[Organic transistor configuration]
First, the configuration of the organic transistor 10 will be described. The organic transistor 10 includes an insulating film 12 formed on the substrate 11 and one main surface 11a of the substrate, a resin film 13 formed on the insulating film 12, and a photoisomerized molecule formed on the resin film 13. A film (semiconductor film) 14 and a first electrode 15 and a second electrode 16 formed so that at least one end thereof is in contact with the photoisomerized molecular film 14 are provided.

As the substrate 11, for example, a silicon substrate (highly doped Si substrate) having a resistivity of about 0.02 Ω · cm, which is doped with impurities such as phosphorus (P) at a high concentration (about 10 ¹⁸ cm ^-3 ), can be used. can. The substrate 11 functions as a gate electrode when the operation control device 100 for the organic transistor is operated.

As the insulating film 12, a SiO ₂ film formed by thermal oxidation or the like is used. The thickness of the insulating film 12 is preferably 100 nm or more and 400 nm or less. The insulating film 12 functions as a gate insulating film when the operation control device 100 for the organic transistor is operated.

The resin film 13 is made of an insulating polymer, and PMMA (acrylic resin) can be used as the material thereof. The resin film 13 is not an indispensable configuration, but by providing it, the influence of defects on the insulating film 12 is eliminated, and the n-type operation (electron current) of the operation control device 100 of the organic transistor is promoted. Will be done.

As the material of the first electrode 105 and the second electrode 106, for example, a metal such as Au, Pt, Pd or the like is used. When the operation control device 100 of the organic transistor is operated, one of the first electrode 105 and the second electrode 106 functions as a source electrode and the other functions as a drain electrode.

The photoisomerized molecule constituting the photoisomerized molecular film 14 has a central skeleton exhibiting a photoisomerization reaction, and has a structure in which substituents of a pi-conjugated system are appropriately attached to both ends thereof. When irradiated with ultraviolet light, the photoisomerized molecule becomes a closed ring body having conductivity peculiar to a semiconductor, and when irradiated with visible light, it becomes an open ring body having insulating property. That is, the photoisomerized molecule has a property that the molecular structure is reversibly changed between the case of irradiation with visible light and the case of irradiation with ultraviolet light.

Examples of the photoisomerized molecule include a diarylethene-based molecule showing a ring-opened-closed ring change, an azobenzene-based molecule showing a cis-trans change, and a spiropyran showing a polar-nonpolar change. Diarylethene, which undergoes a ring-open-closed change, has a significant change in the pi-conjugated system, resulting in a large change in electron level and electrical properties, and is more resistant to repeated photoisomerization reactions than others. Since it is extremely excellent, it is particularly preferable as the photoisomerized molecule of the present embodiment.

Examples of the substituent of the pi-conjugated system include a biphenyl group, a phenyl group, a thiophene ring and a fused ring thereof. Examples of molecular structures in which the photoisomerized molecule having a biphenyl group, a phenyl group, and a thiophene ring as substituents actually exhibited a semiconductor-insulator transition with the photoisomerization reaction are shown in the following chemical formulas (1) to (1) to (1) to (2). Shown in 3). In each chemical formula, the left side shows a ring-opening body (insulator), and the right side shows a ring-closing body (semiconductor).

Examples of other molecular structures that can be candidates for the photoisomerized molecule according to this embodiment are shown in the following chemical formulas (4) to (9).

Each of the molecular structures represented by the chemical formulas (1) to (9) has a structure in which pi-conjugated substituents are attached to both ends of the diarylethene central skeleton, or a structure in which they are linked.

The photoisomerized molecular film may be a film composed of only photoisomerized molecules, or various photoisomerized molecules may be formed on a polymer semiconductor film or a gate insulating film (mother) composed of other than photoisomerized molecules. It may be an added membrane. The photoisomerized molecule may be inserted at the interface between the conventionally used organic semiconductor film and the insulating film. It is known that the photoisomerized molecule captures or scatters the electric charge by the photoisomerization reaction to induce a reversible change in the amount of current regardless of the configuration. It is considered that it can be applied to the channel formation technology according to the above. Examples of the structure of the molecule constituting the polymer semiconductor film are shown in the following chemical formulas (10) and (11), and examples of the structure of the photoisomerized molecule added to the polymer semiconductor film are shown in the following chemical formulas (12) and (13). ).

The organic transistor 10 according to the present embodiment has a bottom gate / top contact type transistor structure in which a Si substrate is used as a gate electrode, but it may be a structure that can operate the transistor and irradiate light, for example, a top. It may have a gate / bottom contact type transistor structure or the like.

[Manufacturing method of organic transistor]
The organic transistor 10 according to the present embodiment can be manufactured mainly through the following steps 1 to 3.
[Step 1]
Thermal oxidation treatment is performed to form an insulating film (SiO ₂ film or the like) 12 on one main surface 11a of the substrate.
[Step 2]
By vacuum deposition, a photoisomerized molecular film 14 having an open ring (insulator) structure is formed only in a certain region on the insulating film 12 formed in step 1 through a shadow mask, either directly or via a resin film 13. do.
[Step 3]
A film formation process is performed by a vacuum vapor deposition method, a sputtering method, etc. through a shadow mask for the electrode, and a metal film for the electrode (first electrode 15, The second electrode 16) is formed.

The photoisomerized molecular film and the metal electrode can also be formed by a wet process such as a spin coating method, a spray method, or a microcontact printing method when the material has meltability. In this case, it can be formed by a low temperature process, and by using a plastic substrate such as polyacrylate, the technique according to the present embodiment can be developed as a technique in the field of flexible electronics.

[Structure of irradiation means]
Next, the configuration of the irradiation means 20 will be described. The irradiation means 20 includes a light source 21 for irradiation light including visible light and ultraviolet light, and an optical system 22 for guiding visible light or ultraviolet light to a region of the semiconductor film 16 as a channel and irradiating the irradiation light. ..

The light source 21 has an ultraviolet light source 21A that emits ultraviolet light and a visible light source 21B that emits visible light. The ultraviolet light source 21A and the visible light source 21B may be separate from each other or may be integrated with each other. FIG. 1 shows an example in which two light sources are separate from each other.

As the ultraviolet light source 21A, a light source that emits ultraviolet light having a wavelength of 200 to 350 nm that induces a photoisomerization reaction can be used, and an example thereof is a He-Cd laser light source that emits ultraviolet light having a wavelength of 325 nm. be able to. As the visible light source 21B, a light source that emits visible light having a wavelength of 500 to 650 nm that induces a photoisomerization reaction can be used, and an example thereof is a He-Ne laser light source that emits visible light having a wavelength of 633 nm. be able to.

Examples of the case where the two light sources are integrated include a case where the light source emits light in a wavelength range including 200 to 350 nm and 500 to 650 nm (for example, an Xe lamp). In this case, for example, by using a bandpass filter to block light outside the wavelength range of the ultraviolet light or visible light, irradiation equivalent to that when the light source is a separate body can be performed. However, in this case, it is difficult to minimize the irradiation spot diameter as in the case of using a laser light source, so that the resolution of optical processing performed by inducing a photoisomerization reaction is inferior.

The optical system 22 has a shutter, a mirror, and a shutter, a mirror, so that visible light or ultraviolet light among the light (irradiation light) emitted from the light source 21 can be guided to a region to be a channel of the photoisomerization molecular film and irradiated. Filters (beam splitters), lenses, etc. are arranged as appropriate.

FIG. 1 shows an example in which the optical system 22 is configured to guide the irradiation light by the following procedure. First, in the shutter 23, one of the lights emitted from the two light sources 21A and 21B is selected. Next, the selected light is reflected by the mirror 24 in the direction in which the organic transistor 10 is arranged. Next, unnecessary components of the reflected light are removed by the filter 25. Then, the light from which unnecessary components have been removed is converged by the lens (objective lens) 26 and irradiated to the photoisomerized molecular film 14 in the organic transistor 10.

The irradiation spot diameter can be controlled in the range of 2 to 100 μm by the magnification of the lens 26 and the core system of the optical fiber (not shown) into which the laser light is introduced, and here, it should be 1 μm or more and 10 μm or less. Is preferable.

The light irradiation position is controlled by relatively moving one or both of the optical system and the organic transistor. This movement can be performed using, for example, a movement stage using an actuator type movement mechanism, a piezo mechanism, or the like.

The actuator type moving mechanism is a drive device that induces mechanical movements such as rotational movements and translational movements by hydraulic pressure or voltage. For example, a hydraulic cylinder, an electric motor, and the like can be mentioned. The piezo mechanism is a phenomenon in which when a substance is deformed by applying pressure, the substance is polarized to generate a voltage (piezoelectric effect), and a phenomenon in which the substance is deformed (expanded or contracted) by applying a voltage (reverse voltage effect). ) Is used. In particular, an element capable of inducing slight expansion and contraction of a substance by applying a voltage by utilizing the reverse voltage effect and performing fine positioning is called a piezo element.

If it is a moving stage using a piezo mechanism, the position accuracy can be further improved. However, in this case, the movable distance is limited to about 100 μm. Therefore, by performing coarse movement with a mechanical movement mechanism such as a stepping motor, fine movement with a piezo mechanism, and precision movement with a combination of multiple movement mechanisms such as a piezo mechanism, a wide range of position control and high resolution can be achieved. Both processing can be achieved.

[Operation control method for organic transistors]
A method of controlling the operation of the organic transistor 10 by using the operation control device 100 of the organic transistor described above will be described.

First, a drain voltage and a gate voltage are applied to the organic transistor 10, and in this state, ultraviolet rays are applied to a region (channel region) of the photoisomerized molecular film 14 having an open ring (insulator) structure. Irradiate with light (first step). Irradiation of ultraviolet light is performed using the above-mentioned optical system 20. As a result, only the irradiated portion is transferred to the ring-closed body (semiconductor) structure, and the channel region is in a conductive state (on state). At this time, the channel region functions as a transistor channel capable of modulating the drain current with the gate voltage.

The irradiation intensity and irradiation time of the ultraviolet light in the first step are preferably 5 mW / cm ² or more and 50 mW / cm ² or less, 10 seconds or more and 200 seconds or less, respectively.

Next, visible light is applied to at least a part of the channel region having a ring-closed structure (second step). Irradiation of visible light is also performed using the above-mentioned optical system 20. As a result, only the irradiated portion is transferred to the ring-opening structure, and the channel region loses conductivity (off state). At this time, the drain current does not flow even when the gate voltage and the drain voltage are applied.

The irradiation intensity and irradiation time of visible light in the second step are preferably 100 mW / cm ² or more and 700 mW / cm ² or less, and 60 seconds or more and 600 seconds or less, respectively.

In the first step, the channel region irradiated with ultraviolet light connects the source electrode and the drain electrode, and the shape thereof can be freely designed according to the application. For example, it may have a linear shape of one or a plurality of lines, or it may have a branched shape in the middle. Further, the shape of the channel region may form a logic circuit as shown in FIGS. 2A to 2C.

FIG. 2A shows a circuit diagram (left side) and a truth table (right side) when the channel region constitutes an OR circuit. Here, two source electrodes S1 and S2 and one drain electrode D are connected by a transistor wire. The transistor wire extending from the drain electrode D is branched into two wires, and each of the two branched wires is marked with a circle. The position of this circle indicates the irradiation position of spot light (ultraviolet light, visible light). (The same applies to the following with respect to the ○ mark.)

The position marked with a circle is irradiated with visible light to become an insulator, and the current path is blocked. Therefore, the path including the circle is turned off. The OR circuit here is configured to irradiate the position marked with ultraviolet light with ultraviolet light in a path extending from at least one of the source electrodes S1 and S2, and to allow a drain current to flow when this path is turned on. ing.

FIG. 2B shows a circuit diagram (left side) and a truth table (right side) when the channel region constitutes an AND circuit. Here, too, the two source electrodes S1 and S2 and the one drain electrode D are connected by a transistor wire. The transistor wire extending from the drain electrode D is branched into two, and one branched before the branch point and one branched toward the source electrode S1 is marked with a circle.

The position marked with a circle is irradiated with visible light to become an insulator, and the current path is blocked. Therefore, the path including the circle is turned off. The AND circuit here irradiates the positions marked with ○ with ultraviolet light in both the path extending to the source electrode S1 and the path extending to the drain electrode with the branch point as a boundary, and these paths are turned on. It is configured so that the drain current flows only when becomes.

FIG. 2C shows a circuit diagram (left side) and a truth table (right side) when the channel region constitutes a NOT circuit. Here, one source electrode S and one drain electrode D are connected by a transistor wire. A circle is marked in one transistor wire connecting the source electrode S and the drain electrode D.

The position marked with a circle is turned into a semiconductor by being irradiated with ultraviolet light, and a current path is formed. Therefore, the path including the circle is turned on. Since the NOT circuit here is in the off state when the position marked with ○ is irradiated with visible light, the drain current does not flow, and when the visible light is not irradiated, the NOT circuit is in the on state. It is configured to allow drain current to flow.

Since the organic semiconductor itself does not have a carrier, the polarity of the transistor can be controlled by the work function of the material used for the source / drain electrode. For example, when an electrode such as gold having a work function close to the highest occupied orbital (HOMO) of the photoisomerized molecule is used as the source / drain electrode, it operates as a p-type transistor. Further, when an electrode such as magnesium or calcium having a work function close to the lowest empty orbital (LUMO) of the photoisomerized molecule is used as the source / drain electrode, it operates as an n-type transistor.

By applying the above-mentioned channel configuration to a transistor formed by appropriately selecting an electrode material so as to have a desired polarity, a CMOS logic circuit that can be reconstructed by light irradiation can be realized.

First, as shown in FIG. 3A, a plurality of p-type transistors T1 and n-type transistors T2 are installed. It is assumed that each transistor shares a substrate and a semiconductor film (photoisomerized molecular film), but is electrically separated.

Next, by performing local ultraviolet light irradiation as described above, the source / drain electrodes of each transistor can be changed to the source / drain electrodes of other transistors, the external power supply circuit Vdd, and the ground circuit by optical wiring. Connect to GND) etc. to build a logic circuit.

As an example, FIG. 3B shows a NAND circuit constructed by connecting by optical wiring (indicated by wavy lines). As shown in FIG. 3C, the NOR circuit can be constructed again by irradiating the NAND circuit with visible light to erase unnecessary optical wiring. By irradiating light without changing the electrode arrangement in this way, it is possible to realize a logic circuit that can be erased and rewritten.

As described above, the organic transistor 10 according to the present embodiment includes the photoisomerized molecular film 14 as a semiconductor film for forming a channel. Photoisomerized molecules have the property of becoming a ring closure when irradiated with ultraviolet light and a ring opening when irradiated with visible light. The ring-closed body has the conductivity peculiar to the semiconductor, and the ring-opened body has the insulating property. Therefore, the photoisomerized molecular film 14 can be made into a semiconductor by irradiation with ultraviolet rays, and can be made into an insulator by irradiation with visible light.

In the organic transistor according to the present embodiment, by utilizing the property of the photoisomerized molecule to irradiate only a specific region of the photoisomerized molecular film 14 with ultraviolet light, only the irradiated portion is made into a semiconductor. Channels can be formed locally. The shape of the channel can be arbitrarily designed and can be a shape constituting a desired logic circuit.

When the gate voltage and drain voltage are applied, the region irradiated with ultraviolet light (channel region) becomes conductive, but by irradiating at least a part of it with visible light, the irradiated region becomes an insulator. Therefore, this region is in a non-conducting state. By further irradiating the insulated region with ultraviolet light, this region is re-semiconductorized and becomes conductive. As described above, according to the organic transistor 10 according to the present embodiment, since the conduction state of the channel region can be switched by using ultraviolet light and visible light, the current flowing through the logic circuit can be freely controlled. As a result, it can realize various operations as a transistor by itself.

<Second embodiment>
The configuration of the operation control device for the organic transistor and the organic transistor having the irradiation means according to the second embodiment of the present invention will be described. The organic transistor according to the present embodiment is different from the organic transistor according to the first embodiment in that a logic circuit is formed in advance on the photoisomerized molecular film constituting the organic transistor. In other respects, it is the same as the organic transistor according to the first embodiment.

In this case as well, the channel region constituting the logic circuit can be brought into a state in which the conductivity is lost (off state) by irradiating at least a part thereof with visible light, and the channel region is irradiated with visible light. By irradiating the portion with ultraviolet light, it is possible to make the portion conductive (on state). That is, the organic transistor according to the present embodiment also repeats the step of irradiating ultraviolet light (first step) and the step of irradiating visible light (second step), similarly to the organic transistor according to the first embodiment. By doing so, the operation can be controlled.

Hereinafter, the effects of the present invention will be further clarified by examples. The present invention is not limited to the following examples, and can be appropriately modified and implemented without changing the gist thereof.

(Example 1)
The basic operation of the organic transistor of the present invention will be described with reference to FIGS. 4A to 4C. The following two steps were alternately repeated for the organic transistor 10 according to the first embodiment.
(1st step)
A drain voltage of -60 V (constant) and a gate voltage of 0 to 80 V are applied to the organic transistor, and in this state, for a certain region as a channel of a photoisomerized molecular film having an open ring (insulator) structure. , The lens is scanned and irradiated with ultraviolet light having a wavelength of 325 nm. Here, the irradiation intensity of ultraviolet light was set to 25 mW / cm ² , and the irradiation time was set to 180 seconds.
(Second step)
With the above voltage still applied, visible light having a wavelength of 633 nm is irradiated to at least a part of the channel region having a closed ring structure by irradiation with ultraviolet light. Here, the irradiation intensity of visible light was 700 mW / cm ² , and the irradiation time was 180 seconds.

As the substrate 11, a silicon substrate (highly doped Si substrate) having a resistivity of 0.02 Ω · cm, which was doped with impurities such as phosphorus (P) at a high concentration (about 10 ¹⁸ cm ^-3 ), was used. As the insulating film 12, a SiO ₂ film formed by thermal oxidation or the like was used. The thickness of the insulating film 12 was set to 300 nm.

As the material of the photoisomerized molecular film 14, a material having the molecular structure of the above chemical formula (1) was used. Gold was used as the material for both the first electrode 105 and the second electrode 106.

The electrical characteristics obtained by the organic transistor 10 of the first embodiment will be described with reference to FIGS. 4A to 4C. FIG. 4A is a graph showing the gate voltage dependence of the drain current flowing through the organic transistor 10. The horizontal axis of the graph shows the gate voltage [V], and the vertical axis shows the drain current [pA]. In this graph, the initial, first ultraviolet light irradiation, second ultraviolet light irradiation, third ultraviolet light irradiation, ... Are displayed as 0, 2, 4, 6, ..., respectively. The first visible light irradiation, the second visible light irradiation, the third visible light irradiation, ... Are displayed as 1, 3, and 5, respectively. The same applies to the graph of FIG. 4 (b) described later.

In the voltage range (-30V to -60V) used as a device, the drain current (2, 4, 6) when irradiated with visible light hardly flows regardless of the gate voltage, whereas ultraviolet light is emitted. The drain current in the case of irradiation (1, 3, 5) increases in proportion to the gate voltage.

From the above results, in the photoisomerized molecular film, only the portion irradiated with ultraviolet light is transferred to the closed ring body, and since the closed ring body functions as a semiconductor material, the portion irradiated with ultraviolet light has a drain current at the gate voltage. It can be seen that it functions as a transistor channel that can modulate. Further, from the above results, it can be seen that when visible light is scanned at the same position, the light is transferred to the ring-opening body, that is, the insulator, so that the drain current does not flow even if the gate voltage and the drain voltage are applied.

FIG. 4B is a graph showing how the drain current changes due to light irradiation in a state where a constant gate voltage and drain voltage are applied. The horizontal axis of the graph shows time [min], and the vertical axis shows drain current [pA]. From this graph, by alternately irradiating visible light and ultraviolet light, the insulator-semiconductor transition occurs repeatedly, and its switching operation can be confirmed.

FIG. 4C is a graph showing an optical switching operation in a state where a constant gate voltage and drain voltage are applied. The horizontal axis of the graph shows the number of cycles (Drawing Cycle), and the vertical axis shows the drain current [pA]. From this graph, it can be seen that the on state due to ultraviolet light irradiation and the off state due to visible light irradiation can be repeatedly and reversibly switched.

(Example 2)
Changes in the operation of the organic transistor due to an increase or decrease in the number of channels will be described with reference to FIGS. 5 (a) and 5 (b). As the sample of the organic transistor, the one having the same configuration as the organic transistor of Example 1 was used.

(Step A)
First, a drain voltage of -60 V (constant) and a gate voltage of 0 to 60 V are applied to the photoisomerized molecular film of the sample in a state where no channel is formed (written), and the current flowing at this time (drain current) is applied. ) Was measured.

(Steps B, C, D)
Next, the above voltage is applied to the photoisomerized molecular film of the same sample in a state where one channel is formed in the photoisomerized molecular film by irradiation with ultraviolet light having a wavelength of 325 nm, and the drain current flowing at this time is applied. It was measured. Similarly, the above voltage was applied in a state where two channels were formed in the photoisomerized molecular film and three channels were formed by ultraviolet light irradiation, and the drain current flowing at this time was measured respectively. .. Here, the irradiation intensity of ultraviolet light was set to 25 mW / cm ² , and the sweep speed was set to 0.2 μm / s.

(Step E)
Next, one of the three channels in the photoisomerized molecular film was erased by irradiating the photoisomerized molecular film of the same sample with visible light at a wavelength of 633 nm, and the above voltage was obtained with two channels remaining. Was applied, and the drain current flowing at this time was measured. Here, the irradiation intensity of visible light was 700 mW / cm ² , and the sweep speed was 0.2 μm / s.

(Steps F and G)
Similarly, by irradiating with visible light, the channels in the photoisomerized molecular film are erased one by one, and the above voltage is applied in a state where one channel remains and no channel remains. The drain currents that flowed when were measured respectively.

The measurement results of steps A to D and the measurement results of steps D to G are shown in the graphs of FIGS. 5A and 5B, respectively. The horizontal axis of the graph shows the gate voltage [V], and the vertical axis shows the drain current [pA]. It should be noted that steps A to G correspond to cases where the number of channels is 0, 1, 2, 3, 2, 1, 1, and 0, respectively.

From the graph of FIG. 5A, it can be seen that in the voltage range (-30V to -60V) used as the device, the total drain current increases as the number of channels increases. Further, from the graph of FIG. 5B, it can be seen that in the voltage range used as the device, the total drain current decreases as the number of channels decreases.

(Example 3)
The operation of the organic transistor having a branched structure in the channel will be described with reference to FIG. As the sample of the organic transistor, the one having the same configuration as the organic transistor of Example 1 was used.

FIG. 6 shows the correspondence between the nine types of states (a) to (i) of the channel region constituting the organic transistor and the drain current value obtained when the organic transistor is operated in each state. It is a figure. (A) to (i) will be described below.

(A) corresponds to the initial state consisting only of the ring-opening body (insulator), and no channel is formed.

(B) corresponds to a state in which one channel is written by ultraviolet light having a wavelength of 325 nm. The irradiation intensity of ultraviolet light was 5 mW / cm ² , and the sweep speed was 0.2 μm / s.

(C) corresponds to a state in which yet another channel is written by ultraviolet light having a wavelength of 325 nm with respect to (b). This formed a branched structure and increased the current path. The irradiation intensity of ultraviolet light was 10 mW / cm ² , and the sweep speed was 0.2 μm / s. Here, the photoisomerization rate of the added channel was increased by setting the irradiation intensity to about twice the irradiation intensity at the time of forming (b). The resulting drain current increased due to the increased photoisomerization rate of some of the channels and the increased current path.

(D) corresponds to a state in which visible light having a wavelength of 633 nm is irradiated to a point on the initially formed channel to locally insulate it. The drain current was reduced by the amount of insulation of the initially formed channel. The irradiation intensity of visible light was 700 mW / cm ² , and the sweep speed was 0.2 μm / s. The same applies to the irradiation of visible light in the following.

(E) corresponds to the state in which the portion irradiated with visible light in (d) is irradiated with ultraviolet light again. Irradiation with ultraviolet light restored the drain current that was reduced by irradiation with visible light. The irradiation intensity of ultraviolet light was 5 mW / cm ² , and the sweep speed was 0.2 μm / s.

(F) corresponds to the state in which the visible light is irradiated again to the portion irradiated with visible light in (d), and is in the same state as in (d). We were able to confirm the reproducibility of the effect of irradiation with visible light.

(G) corresponds to a state in which visible light having a wavelength of 633 nm is irradiated to a point on the channel formed in (c) with respect to (f) to locally insulate it. In this case, since there is no conducting current path, the configuration is the same as in the initial state (a).

(H) corresponds to a state in which the portion irradiated with visible light in (g) is made into a semiconductor by irradiation with ultraviolet light. This state is similar to (d) and (f), and the obtained drain current is recovered to the same extent as that obtained in (d) and (f).

(I) corresponds to a state in which the portion irradiated with visible light in (f) is made into a semiconductor by irradiation with ultraviolet light. This state is similar to (c) and (e), and the obtained drain current is recovered to the same extent as that obtained in (c) and (e).

These series of data demonstrate that the organic transistor of the present invention can operate as an "optical bulb" type transistor capable of turning the current value on and off with light.

The organic transistor of the present invention can be widely used in recent LSIs that are required to be miniaturized and have multiple functions.

100 Organic transistor operation control device 10 Organic transistor 11 Substrate 11a One main surface of the substrate 12 Insulation film 13 Resin film 14 Photoisomerized molecular film 15 First electrode 16 Second electrode 20 Irradiation means 21 Light source 21A Ultraviolet light source 21B Visible light source 22 Optical system 23 Shutter 24 Mirror 25 Filter 26 Lens

Claims (6)

It has an organic transistor and means for irradiating visible light and ultraviolet light.
The organic transistor is an organic transistor provided with a photoisomerized molecular film as a semiconductor film for channel formation.
A plurality of electrodes formed on the photoisomerized molecular film separated from each other are provided.
The photoisomerized molecule constituting the photoisomerized molecular membrane has a closed ring structure in the channel region and an open ring structure in the other regions of the photoisomerized molecular membrane. ,
The channel region connects the electrodes and
The insulating layer located on one side of the photoisomerized molecular film and
A resin layer located between the photoisomerized molecular film and the insulating layer is further provided.
The resin layer is in contact with the insulating layer at a portion overlapping the channel region between the electrodes in a plan view .
The irradiation means comprises a light source of irradiation light including visible light and ultraviolet light, and an optical system in which visible light or ultraviolet light of the irradiation light is guided to a region to be a channel of the photoisomerized molecular film and irradiated. Have and
The optical system is movable in the in-plane direction relative to the photoisomerized molecular film, and the irradiation region of the irradiation light by the optical system can be changed to a different position of the photoisomerized molecular film. Operation control device for organic transistors . The operation control device for an organic transistor according to claim 1, wherein the channel region connects the electrodes to form a logic circuit. The operation control of the organic transistor according to claim 1 or 2, wherein the photoisomerized molecule has diarylethene as a central skeleton and a substituent of a pi-conjugated system is attached to both ends thereof. Equipment . The operation control device for an organic transistor according to any one of claims 1 to 3, wherein the resin layer is made of PMMA. The operation control device for an organic transistor according to claim 2, wherein the logic circuit can be erased and rewritten by changing the irradiation region of the irradiation light by the optical system . The operation control device for an organic transistor according to any one of claims 1 to 5, wherein the optical system is a projection optical system that projects light from the light source onto the photoisomerized molecular film.

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