JP4925037B2 - Optical nanoswitch - Google Patents

Description

The present invention relates to a light-controlled nanoswitch using an electron / ion mixed conductor for one electrode.

In recent years, nanoswitches using mixed electron / ion conductors have been proposed (Non-Patent Document 1).
. The operating principle of this nanoswitch is that by controlling the oxidation / reduction reaction of metal atoms by tunnel current, by generating metal atom bridges between electrodes installed in a minute space or by eliminating metal bridges, This is due to a system that controls on / off between the electrodes.

In this proposed nanoswitch, an electrode made of a mixed electron / ion conductor and a counter electrode made of metal are installed with an ultrafine vacuum gap of about 1 nanometer sandwiched therebetween. By controlling the tunnel current flowing between the two electrodes, an oxidation / reduction reaction occurs on the surface of the mixed electron / ion conductor, which is one of the electrodes, and an oxidation or reduction reaction of the metal atom is induced. The generation and disappearance of metal atom bridges are controlled, and the on / off operation of the switch is realized. In other words, by using the tunnel current flowing in the minute region,
The switch can be locally scaled to control the oxidation / reduction reaction, realizing a nanoscale switch.

However, since the nanoswitch according to the above proposal is configured so that the switch is on / off controlled by the current flowing between the two electrodes, the signal current path and the control current path are the same. Met. For this reason, when switching on / off, a voltage higher than the critical voltage of the oxidation / reduction reaction is applied, and at the time of reading, a voltage lower than the critical voltage is used to prevent an on / off malfunction during reading. It was. However,
In this method, since the voltage for control and readout is limited, there is a case where the combination is not successful due to a difference from a critical voltage value with other elements such as a silicon transistor.
Nature, 433 (2005), pp. 47-50, "Quantized Conductive Atom Switch"

In view of the above situation, the present invention provides a nanoswitch that does not use a current control to switch the switch, specifically, a novel nanoswitch based on light induction.

As a result of diligent research, the present inventors have arranged an electrode made of a waveguide whose tip is covered with an electron / ion mixed conductor and an electrode made of a metal with a gap between them so that light can enter the waveguide. By introducing, near-field light is generated from the waveguide tip, and the generated near-field light is
By injecting into the mixed electron / ion conductor covering the tip of the waveguide, the near-field light induces a reduction reaction in which the metal ions in the mixed electron / ion conductor are converted to metal. It has been found that metal atom bridges are formed between the electrodes by the metal atoms deposited by the reaction, whereby a switch-on state can be realized.
This invention is made | formed based on this knowledge, The structure is as follows (1)-(8).
(1) By using near-field light to induce reduction or oxidation reaction of metal ions in an electron / ion mixed conductor, a bridge composed of metal atoms is formed between at least a pair of electrodes arranged at a minute interval. An optical nanoswitch characterized by being formed.
(2) One of the electrodes is an electrode made of a waveguide whose tip is covered with an electron / ion mixed conductor, and the other is a counter metal electrode arranged with a gap (1) ) Optical nanoswitch.
(3) One of the electrodes is an electrode made of a waveguide whose tip is covered with a metal, and the other is a counter electrode made of an electron / ion mixed conductor arranged at intervals. The optical nanoswitch described in (1).
(4) The thickness of the waveguide tip is smaller than a half wavelength of light to be injected.
The optical nanoswitch described in 2) or (3).
(5) The thickness of the waveguide tip is 100 nanometers or less, (2
The optical nanoswitch described in any one of (4) to (4).
(6) The optical nano described in any one of (1) to (3), wherein the electron / ion mixed conductor is any one of a silver compound, a copper compound, and a lithium compound. switch.
(7) The optical nanoswitch described in any one of (1) to (6), wherein a gap between the electrodes is filled with an insulator.
(8) The optical nanoswitch described in any one of (1) to (7), wherein the gap between the electrodes is an insulating space.

The operation principle and specific mode of the optical nanoswitch of the present invention are summarized as follows [1] to [4].
[1] An electrode made of a waveguide whose tip is covered with a mixed electron / ion conductor and an electrode made of metal are arranged with a gap. By introducing light into the waveguide, near-field light is generated from the waveguide tip, and the generated near-field light is injected into the electron / ion mixed conductor covering the waveguide tip. The near-field light induces a reduction reaction of metal ions in the electron / ion mixed conductor, and a metal atom bridge is formed between the electrodes by the metal atoms deposited by the reduction reaction, so that the switch-on state is Realized.
At that time, when the introduction of light into the waveguide is blocked by adjusting the amount of the electron / ion mixed conductor to be small, the metal atoms deposited by the reduction reaction change to the original ionic state,
Crosslinks by metal atoms disappear autonomously. That is, an ultra-fine switch that can be operated by introducing or blocking light is established.
[2] As another means, an electrode made of a waveguide whose tip is covered with a metal and an electrode made of an electron / ion mixed conductor are arranged with a gap. Then, by introducing light into the waveguide, near-field light generated from the tip of the waveguide is injected into the electron / ion mixed conductor as the counter electrode. The near-field light induces a reduction reaction of metal ions in the electron / ion mixed conductor, and metal atoms deposited by the reduction reaction form a bridge between the electrodes.
A switch-on state is realized.
Even in this case, by adjusting the amount of the electron / ion mixed conductor to be small and blocking the introduction of light into the waveguide, the reduction reaction is restored to the original state, and the crosslinking by the metal atoms is autonomous. Disappear. That is, an ultrafine switch that operates by light is established.

[3] In the optical nanoswitch according to [1] or [2], a gap between the electron / ion mixed conductor portion and the metal portion needs to be filled with an insulating material including a vacuum space. .
[4] In the optical nanoswitch according to [1] to [2], the electron / ion mixed conductor may be Ag ₂ S, Ag ₂ Se, Cu ₂ S, Cu ₂ Se,
Furthermore, LiI or even Li—TiS ₂ may be mentioned.

By using the present invention, a nanoswitch that can be controlled on and off by light can be configured. Thus, unlike conventional control using electrical signals, on / off can be controlled by a line different from the signal path, so that a nanoswitch with extremely high controllability can be provided. Moreover, it can utilize as a switching element in what is called a field programmable device programmed by light irradiation.

Hereinafter, the present invention will be specifically described based on the drawings and examples. However, these are disclosed only as an aid for easily understanding the present invention, and the present invention is not limited thereto.

In the present invention, a light-controlled nanoswitch is formed by controlling the local metal atom reduction reaction on the surface of the mixed electron / ion conductor using near-field light. The structure and operating principle will be described in detail with reference to FIG.
In FIG. 1, the tip of the waveguide 1 is covered with an electron / ion mixed conductor 2. The film thickness of the mixed electron / ion conductor covering the tip of the waveguide is designed to allow the near-field light to pass therethrough. Although the maximum film thickness depends on the transmission coefficient that varies depending on the material, it is generally desirable to set the film thickness to 100 nanometers or less.

On the other hand, the metal electrode 3 is arranged with a gap as the counter electrode. When light 4 is injected into the waveguide 1, the light 4 generates near-field light 5 at a fine opening at the tip of the waveguide 1. The near-field light 5 excites metal ions in the electron / ion mixed conductor electrode 2 to induce a reduction reaction, and reduced metal atoms 6 are deposited on the surface. The deposited metal atoms 6 form a bridge between the electron / ion mixed conductor electrode 2 and the metal electrode 3 and are switched on.

Thus, according to the present invention, the switching operation can be controlled by a signal (light) from a line different from the two electrodes to be bridged. That is, a three-terminal element using a solid electrochemical reaction can be formed.

Since the element according to the present invention can be controlled on / off using a line different from the path of the signal current, it is a very convenient nanoswitch. In FIG. 1, the gap between the electron / ion mixed conductor electrode and the metal electrode is a vacuum gap, but it may be formed of an insulating organic molecular film or the like. In short, being electrically insulated is a necessary requirement for carrying out the present invention.

Hereinafter, the present invention will be described more specifically based on examples.

Example 1;
The operation principle of the optical nanoswitch shown in FIG. 1 will be described in detail with reference to FIG. In FIG. 2, only the main part of the switch is shown for simplicity. The light 4 injected into the waveguide 1
The near-field light 5 is generated at the tip of (Fig. 2a). By making the opening at the tip of the waveguide 1 smaller than the half wavelength of the light 4, the near-field light 5 can be generated and only the near-field light 5 can be transmitted through the electron / ion mixed conductor electrode 2. it can. This near-field light 5 excites a metal ion in the electron / ion mixed conductor electrode 2 and induces its reduction reaction. The reduced metal atoms 6 are deposited on the surface of the mixed electron / ion conductor electrode 2 (FIG. 2b). If the light 4 is continuously injected, finally, the reduced metal atoms 6 form a bridge between the electron / ion mixed conductor electrode 2 and the metal electrode 3 (FIG. 2c). That is, the switch is turned on.

Example 2;
In this embodiment, since the volume of the electron / ion mixed conductor electrode 2 covering the tip of the waveguide 1 is sufficient, the decrease in the metal ion concentration in the electron / ion mixed conductor electrode 2 due to the deposition of the metal atoms 6 is not caused. Almost negligible. For this reason, the bridge | crosslinking by a metal atom exists stably. In this sense, the switch according to the present embodiment is essentially a nonreciprocal switch. However, as will be described later, a reversible switch can be obtained by reducing the set amount of the electron / ion mixed conductor.
With reference to FIG. 3, another embodiment of the optical nanoswitch will be described.
The tip of the waveguide 11 is covered with a metal 12. The film thickness of the metal covering the waveguide tip needs to be designed so that near-field light can be transmitted. The maximum film thickness depends on the transmission coefficient which varies depending on the material, but it is desirable to set it to about 100 nanometers or less.

On the other hand, the electron / ion mixed conductor electrode 13 is disposed with a gap as the counter electrode. When light 14 is injected into the waveguide 11, the light 14 generates near-field light 15 at a fine opening at the tip of the waveguide. The size of the minute opening is designed to be equal to or smaller than the half wavelength of the light 14.

The near-field light 15 reaches the electron / ion mixed conductor electrode 13 which is a counter electrode, and the electrode 1
3 is excited to induce a reduction reaction, and reduced metal atoms 16 are deposited on the surface. The deposited metal atoms 16 form a bridge between the metal electrode 12 and the electron / ion mixed conductor electrode 13 and are switched on. Thus, according to the present invention, the switching operation can be controlled by a signal (light) from a line different from the two electrodes to be bridged.

In this embodiment, since the size of the electron / ion mixed conductor electrode 13 is sufficiently large, the concentration of metal ions in the electron / ion mixed conductor electrode 13 hardly changes even if the metal atoms 16 are deposited. Even if the injection of the light 14 is stopped, the deposited metal atoms 16 exist stably. That is, the optical nanoswitch according to the present embodiment is essentially an irreversible switch by setting a large set amount of the electron / ion mixed conductor. However, it is possible to make a reversible switch by reducing the set amount of the electron / ion mixed conductor.

Example 3;
Here, an embodiment of a reversible optical nanoswitch will be described with reference to FIG.
In the reversible optical nanoswitch, the size of the electron / ion mixed conductor 32 covering the tip of the waveguide 31 is designed to be small. Other portions are covered with a metal 34. Incident light 35 generates near-field light 36 at the tip of waveguide 31 (FIG. 4a). The near-field light 36 excites metal ions in the electron / ion mixed conductor 32 to induce a reduction reaction, and metal atoms are deposited. The deposited metal atoms form a bridge between the electrodes, and the switch is turned on (FIG. 4b).

Subsequently, when the irradiation with the light 35 is stopped, the deposition of the metal atoms stops. Here, in the reversible optical nanoswitch based on the present embodiment, since the size of the electron / ion mixed conductor portion 32 is small, the energy due to the decrease in the metal ion concentration inside the electron / ion mixed conductor 32 due to the deposition of metal atoms. High instability. Therefore, at the same time as the irradiation of the light 35 is stopped, the deposited metal atoms begin to dissolve in the electron / ion mixed conductor in order to eliminate this instability (FIG. 4c).
) Eventually, all the metal atoms are dissolved (FIG. 4d). That is, the switch is turned off.

Thus, a reversible optical nanoswitch can be fabricated by controlling the size of the electron / ion mixed conductor electrode. In this example, the example in which the electron / ion mixed conductor electrode covers the waveguide tip is described. However, as described in Example 2, the counter electrode is composed of the electron / ion mixed conductor. Even a nanoswitch can realize a reversible optical nanoswitch operation. That is, the size of the electron / ion mixed conductor portion of the counter electrode portion may be reduced. The size of the electron / ion mixed conductor portion in realizing the reversible optical nanoswitch described above is a factor that determines energy instability. (1) Gap size between electrodes (forms a bridge) The number of metal atoms required for (2), and (2) metal atom ion concentration (composition ratio) constituting the electron / ion mixed conductor.

Example 5;
An embodiment for realizing miniaturization of an optical nanoswitch will be described with reference to FIG.
In FIG. 5, the tip of the waveguide 1 is covered with the electron / ion mixed conductor 2. The film thickness of the electron / ion mixed conductor covering the front end of the waveguide is designed so that the near-field light can be transmitted. Although the maximum film thickness depends on the transmission coefficient that varies depending on the material, it is generally desirable to set the film thickness to 100 nanometers or less.
On the other hand, the metal electrode 3 is arranged with a gap as the counter electrode. When light 4 is injected into the waveguide 1, the light 4 generates near-field light 5 at a fine opening at the tip of the waveguide 1. The near-field light 5 excites metal ions in the electron / ion mixed conductor electrode 2 to induce a reduction reaction, and reduced metal atoms 6 are deposited on the surface. The deposited metal atoms 6 form a bridge between the electron / ion mixed conductor electrode 2 and the metal electrode 3 and are switched on.

The feature of this embodiment is that the tip diameter of the waveguide 1 is made extremely small. That is, the light source of the near-field light 5 becomes close to a point light source, and the near-field light 5 can be irradiated only to a very small region of the electron / ion mixed conductor 2. As a result, the size (diameter) of the metal atom bridge formed can be reduced. The size (diameter) depends on the size of the gap between the electron / ion mixed conductor electrode 2 and the metal electrode 3, but can be ideally 10 nanometers or less.

In this embodiment, the optical nanoswitch in which the electron / ion mixed conductor covers the tip of the waveguide has been described. However, the optical nanoswitch having the configuration described in the second and third embodiments may be used. ,
A similar effect can be obtained by sharpening the tip of the waveguide.

Example 5;
Here, an embodiment of another type of optical nanoswitch using near-field light will be described with reference to FIG. An electron / ion mixed conductor thin film 42 is formed on the surface of the glass substrate 41.
In contrast, a metal electrode 43 having a sharp tip with a gap is provided. Light 4
4 is injected from the back surface of the glass substrate 41. Here, the incident angle θ of the light 44 is set so that the light 44 is totally reflected. Then, the near-field light 45 is generated immediately below the metal electrode 43 by a strong electric field. As a result, a precipitation reaction of metal atoms occurs, and a bridge 46 is formed.

In the switch shown in FIG. 6, since the electron / ion mixed conductor thin film is formed over the entire surface, this switch performs an irreversible operation. It goes without saying that a reversible switch can be formed by reducing the size of the electron / ion mixed conductor portion directly under the metal electrode.

Example 6;
Here, an embodiment in which optical nanoswitches are integrated will be described.
In FIG. 7, the electron / ion mixed conductor thin film 52 is formed on the surface of the glass substrate 51. On the other hand, metal electrodes 53-56 having a sharp tip with a gap are provided. The glass substrate 51 is at an angle at which the light 57 is totally reflected on the upper and lower surfaces of the glass substrate 51.
Inject from the end face. By arranging the metal electrodes 53-56 at a position where the light 57 is totally reflected,
According to the principle described in the fifth embodiment, a bridge is formed by the deposited metal atoms between each metal electrode and the electron / ion mixed conductor electrode. In FIG. 7, the metal electrodes are arranged at regular intervals, but a circuit having an arbitrary pattern can be formed by arbitrarily arranging the metal electrodes.

Example 7;
FIG. 8 is used to explain another embodiment in which optical nanoswitches are integrated according to the present invention. In this embodiment, by using liquid crystal molecules, an optical nanoswitch that performs a switching operation can be selected, so that it can be applied to a programmable device. Here, for simplicity, description will be made using two optical nanoswitches. For optical nanoswitches in which the waveguides 61 and 62 are coated with the electron / ion mixed conductors 71 and 72, optical shutters 63 and 64 using liquid crystal molecules are installed on the waveguides 61 and 62. Yes. These optical shutters 63 and 6
4 can control whether or not light is injected into the front end of the waveguide by controlling the voltages 65 and 66 to be applied.

In FIG. 8, the optical shutter 63 is in an open state, and the light 67 reaches the tip of the waveguide 61. As a result, near-field light 68 is generated at the front end of the waveguide 61, and a metal atom bridge 69 is formed between the metal electrode 70 and the switch is turned on according to the principle described in the above embodiment. ing. On the other hand, since the optical shutter 64 is in the closed state, no light is injected into the waveguide 62, and the switch remains off. If the integrated optical nanoswitch according to this embodiment is used, any optical nanoswitch can be turned on by controlling the optical shutter, so that it can be used as a switching element of a field programmable device.

In this embodiment, an optical shutter using liquid crystal molecules is used. However, the effects described in this embodiment can be realized as long as the element can control the entrance of light, such as a mechanical shutter using a piezoelectric element. Needless to say. In addition, the tip of the waveguide is covered with metal, and the counter electrode is
Needless to say, it may be an ionic mixed conductor.

In recent years, various technologies of nano-level order have been attracting much attention and demand. The switch targeted by the present invention is not an exception, and there is a demand for realizing an ultrafine switch. The present invention can meet such a demand, and is expected to be greatly utilized in various switch element designs and contribute greatly to industrial development.

The schematic diagram of an optical nanoswitch. The figure explaining the operation principle of an optical nanoswitch. The schematic diagram of another optical nanoswitch. The figure explaining the principle of operation of a reversible optical nanoswitch. Schematic diagram of ultrafine optical nanoswitch. The schematic diagram of another optical nanoswitch. Schematic diagram of integrated optical nanoswitch. Schematic diagram of another integrated optical nanoswitch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Waveguide, 2 ... Electron / ion mixed conductor, 3 ... Metal electrode, 4 ... Light, 5
... Near-field light, 6 ... Metal atoms, 11 ... Waveguides, 12 ... Metal electrodes, ...
Electron / ion mixed conductor electrode, 14 ... light, 15 ... near-field light, 16 ... metal atom, 31 ... waveguide, 32 ... electron / ion mixed conductor, 34. ..Metal, 35 ..
-Incident light, 36-near-field light, 41-glass substrate, 42-electron / ion mixed conductor, 43-metal electrode, 44-light, 45-near-field light 46... Crosslinking 51
... Glass substrate, 52 ... Electron / ion mixed conductor thin film, 53, 54, 55, 56
..Metal electrodes, 57 ... light, 61, 62 ... waveguide, 63, 64 ... optical shutter, 65, 66 ... voltage, 67 ... light, 68 ... near field light , 69... Metal atom bridge, 70... Metal electrode, 71 and 72.

Claims (8)

Forming a bridge composed of metal atoms between at least a pair of electrodes arranged at a minute interval by inducing reduction or oxidation reaction of metal ions in an electron-ion mixed conductor using near-field light An optical nanoswitch characterized by 2. The electrode according to claim 1, wherein one of the electrodes is an electrode composed of a waveguide whose tip is covered with an electron / ion mixed conductor, and the other is a counter metal electrode arranged at a distance. 3. Optical nanoswitch to be used. 2. One of the electrodes is an electrode made of a waveguide whose tip is covered with a metal, and the other is a counter electrode made of an electron / ion mixed conductor arranged at intervals. Optical nanoswitch described in 1. The thickness of the waveguide tip is smaller than a half wavelength of the light to be injected.
Or the optical nanoswitch as described in 3. 5. The optical nanoswitch according to claim 2, wherein a thickness of the waveguide tip is 100 nanometers or less. 4. The optical nanoswitch according to claim 1, wherein the electron / ion mixed conductor is any one of a silver compound, a copper compound, and a lithium compound. 5. The optical nanoswitch according to any one of claims 1 to 6, wherein a gap between the electrodes is filled with an insulator. The optical nanoswitch according to any one of claims 1 to 7, wherein the gap between the electrodes is an insulating space.

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