WO2004013915A1

WO2004013915A1 - Optical sensor, method for manufacturing and driving optical sensor, and method for measuring light intensity

Info

Publication number: WO2004013915A1
Application number: PCT/JP2003/009577
Authority: WO
Inventors: Yukihiro Sugiyama
Original assignee: Sanyo Electric Co.,Ltd.
Priority date: 2002-08-01
Filing date: 2003-07-29
Publication date: 2004-02-12
Also published as: AU2003252283A1; JPWO2004013915A1; JP3933664B2

Abstract

An optical sensor using molecules polarized when receiving light, wherein a pair of source electrode (5a) and drain electrode (5b) on a substrate is electrically connected to each other by a carbon nanotube (7). When photosensitive molecules constituting a layer (13) polarizable by receiving light are polarized by receiving light, the conductance of the carbon nanotube (7) is changed. With the change of the conductance, the value of current flowing between the source electrode (5a) and the drain electrode (5b) is changed, thereby allowing the current change to be detected. By manufacturing an oriented film of the carbon nanotube (7), connection between the source electrode (5a) and the drain electrode (5b) is made easy and excellent. An optical sensor small and having high precision and sensitivity, methods for manufacturing and driving an optical sensor, and a method for measuring light intensity are realized.

Description

Description Optical sensor, method for manufacturing and driving optical sensor, and method for detecting light intensity

The present invention relates to an optical sensor, a method for manufacturing and driving the optical sensor, and a method for detecting light intensity. Background art

In recent years, demands for downsizing and high sensitivity of optical sensors have been increasing enormously, and there is a strong demand for a sensor that can efficiently convert optical signals into electrical signals and detect them.

In view of these requirements, the present inventor has proceeded with the development of a sensor that uses a molecule that is polarized by light irradiation (hereinafter appropriately referred to as a photosensitive molecule) as a photodetection substance. If such photosensitive molecules can be used as the light detection part of an optical sensor, it is expected that optical information can be detected with high sensitivity and high accuracy.

From such a viewpoint, the present inventors have already published an image recognition element using bacteriorhodopsin (see Patent Document 1). Bacteriorhodopsin, a protein that constitutes the purple membrane (Purpiemmembrane) of halophilic bacteria together with lipids, is a photoreceptor protein and shows a differential response to light irradiation (Fig. 1).

The image recognition device described in Patent Document 1 uses the response of bacteriococcal dopsin for an image sensor that extracts the contour of a moving object, etc. It detects the induced current induced in the electrode. According to this image recognition device, since the induced current is detected, the noise is smaller than that of the image recognition device that detects the induced voltage. Thus, a signal can be detected even when the electrode is miniaturized. In addition, by using an alignment film of bacteriorhodopsin, it is possible to make the photodetector ultra-thin. it can.

Patent Literature 1 Japanese Patent Application Laid-Open No. 2000-002 6 7 2 2 3

Non-Patent Document 1 M e t o o d s i n En z y m o 1 o g y, 31, A, p p. 6 6 7-6 7 8 (1 9 7 4)

Disclosure of the invention

However, the signal due to the electric polarization of photosensitive molecules such as bacteriophage dopsin is small, and even when detecting the induced current, a sufficient induced current value is not necessarily obtained. Therefore, when using this signal as an optical sensor, amplification to obtain a sufficient current value may be necessary. Conventionally, since this amplification system requires a large-scale device, it was necessary to incorporate an optical sensor into a large-scale device.

In view of the above circumstances, an object of the present invention is to provide a small and highly sensitive optical sensor, a method for manufacturing and driving the optical sensor, and a method for detecting light intensity. According to the present invention, a substrate; a source electrode and a drain electrode formed on the substrate; a carbon nanotube electrically connecting the source electrode and the drain electrode; and a carbon nanotube provided on the carbon nanotube. A layer in which polarization is generated by light reception. In the optical sensor of the present invention, when light is irradiated, polarization occurs in a layer in which polarization is generated by light reception, and an induced charge is generated. Here, the carbon nanotube has the property that the conductance changes depending on the strength of the electric field, and thus the induced charge triggers the change in the conductance of the carbon nanotube, and the current flowing between the source and drain electrodes. The value changes. By detecting the change in the current value, the intensity of the received light can be detected.

Even though the signal due to polarization in the layer where polarization occurs due to light reception is small, the change in the current value between the source and drain electrodes caused by this signal is a large value. Therefore, an electric signal large enough to detect the presence or absence of light reception can be obtained.

Further, in the optical sensor of the present invention, since the highly conductive carbon nanotube is used for the wiring member connecting the source electrode and the drain electrode, the electrode is minute. However, a sufficient current value can be obtained. As a result, the size of the optical sensor can be reduced. This makes it possible to increase the number of source and drain electrodes per unit area, that is, the number of pixels.

According to the present invention, a step of forming a source electrode and a drain electrode on a surface of a substrate, a step of connecting the source electrode and the drain electrode with a force-pont nanotube, Forming a layer in which polarization occurs, and a method for manufacturing an optical sensor.

According to the method for manufacturing an optical sensor of the present invention, the source electrode and the drain electrode are connected by the carbon nanotube, and a layer in which polarization occurs due to light reception is formed on the carbon nanotube. Therefore, it is possible to stably manufacture a high-precision, small-sized optical sensor having a large number of pixels.

According to the present invention, in the above-described method for driving an optical sensor, a predetermined current is caused to flow between the source electrode and the drain electrode, and a change in the current value is detected. A method is provided.

The method for driving an optical sensor according to the present invention is characterized in that a predetermined current is flowing between a source electrode and a drain electrode, and the conductance of a carbon nanotube is changed according to the degree of polarization generated by light reception. It detects the change in the current value accompanying the current. The intensity of the received light is detected based on the magnitude of the change in the current value. Since the change in the current value is larger than when the polarization of the photosensitive molecule is directly detected, measurement with high sensitivity and high accuracy is possible.

According to the present invention, there is provided a method for detecting light intensity using a layer including a layer polarized by light reception and a carbon nanotube provided in the vicinity of the layer, comprising applying a voltage to the carbon nanotube, A light intensity detection method is provided, wherein a change in a current value in the carbon nanotube caused by light reception of the layer is detected, and a light intensity is detected from the change in the current value.

In the photodetection method of the present invention, the layer that is polarized by light reception by light irradiation is separated. And induces induced charge. Triggered by this induced charge, the conductance of the carbon nanotube changes, and the current flowing through the carbon nanotube changes. The light intensity can be detected by detecting the change in the current value. According to the method of the present invention, a relatively large change in current value can be obtained from a relatively small polarization signal, and the light intensity can be measured with high accuracy and sensitivity.

In the photodetection method according to the present invention, the layer polarized by the light reception may be configured to include pateriorhodopsin. This makes it possible to stably and reliably generate polarization in the layer that is polarized by light reception. Therefore, a light detection method with high accuracy and sensitivity can be provided.

In the optical sensor of the present invention, an insulating layer may be provided on a surface of the carbon nanotube. By doing so, it is possible to reliably insulate between the carbon nanotube and the layer that is polarized by light reception. Therefore, the operation stability of the optical sensor can be improved.

In the optical sensor according to the aspect of the invention, the insulating layer may be a polymer layer. By doing so, the surface of the carbon nanotube is covered well, and the insulating property can be secured stably. The polymer layer can be, for example, an organic polymer layer.

In the optical sensor of the present invention, the insulating layer may be a layer in which a polymer is wound around a side surface of the carbon nanotube. By doing so, the surface of the carbon nanotube can be uniformly coated. Further, the coating layer can be a strong and stable layer. Therefore, the operation stability of the optical sensor can be improved, and the reliability can be improved. In addition, by forming a layer in which the polymer is wound, the thickness of the coating layer can be reduced. For this reason, the conductance of the carbon nanotube can be more reliably changed.

In the present invention, the “polymer” refers to a molecule having a skeleton chain length sufficient to be wound around a carbon nanotube. Also, the polymer is carbon "Wound" on the side surface of the nanotube means that the molecular chain of the polymer wraps around the side surface of the tube and wraps around the surface of the carbon nanotube.

In the method for manufacturing an optical sensor according to the present invention, the step of forming an alignment film of carbon nanotubes may include a step of forming an insulating layer containing the coating molecules on a surface of the carbon nanotubes. By doing so, it is possible to reliably insulate the carbon nanotube from the layer polarized by light reception. In the method for manufacturing an optical sensor according to the present invention, a polymer may be used as the coating molecule, and a polymer layer may be formed on the surface of the carbon nanotube. In this case, the coverage of the insulating layer can be improved. Therefore, the surface of the carbon nanotube can be more stably insulated.

In the method of manufacturing an optical sensor according to the present invention, the protein is modified by spreading the dispersion in which the protein is dispersed as the coating molecule on a liquid surface, and the modified protein is wound around a side surface of the carbon nanotube. May be.

According to the production method of the present invention, a polymer can be wound on the surface of a carbon nanotube by a simple method. Therefore, the surface of the carbon nanotube can be coated by a simple method. Therefore, the insulating property of the surface of the carbon nanotube can be further ensured. .

In the present invention, the polymer can be a polypeptide. By using the polypeptide, the skeleton chain can be stably coated on the carbon nanotube. In the present invention, the polypeptide may be a denatured protein.

In the method for producing an optical sensor according to the present invention, the protein is denatured by using a protein as the polymer, and the dispersion is spread on a liquid surface to denature the protein. The denatured protein is wound around a side surface of the carbon nanotube. Can be made.

Denatured proteins, unlike native proteins, generally have exposed hydrophobic Become For this reason, the winding on the side surface of the carbon nanotube is more easily and reliably performed. Further, by spreading the protein dispersion on the liquid surface, the protein can be efficiently denatured by the interfacial tension between the dispersion and the liquid, and the hydrophobic portion can be exposed. In the present invention, “denaturation” of a protein refers to a collapse of the three-dimensional structure and inactivation of the function of the protein molecule, or a conformational change other than the cleavage of the primary structure constituting the protein molecule, that is, the amino acid sequence. The degree of conformational change is not particularly limited. In the present invention, the polypeptide may be a membrane protein. Since the membrane protein often has a region with high hydrophobicity, by using this, the protein can be efficiently adsorbed on the side surface of the carbon nanotube and can be stably wound.

As described above, the optical sensor of the present invention comprises: a substrate; a source electrode and a drain electrode formed on the substrate; a carbon nanotube for electrically connecting the source electrode and the drain electrode; And a layer in which polarization is generated by light reception. For this reason, a small signal due to polarization in the layer where polarization occurs due to light reception is used as a trigger, and a large electrical signal, that is, a change in the current value between the source and drain electrodes is obtained, and this change in the current value is detected. As a result, an optical sensor capable of detecting light with high accuracy and sensitivity and a driving method thereof are realized.

Further, according to the present invention, there is provided a method for manufacturing an optical sensor capable of stably manufacturing an optical sensor having high accuracy, sensitivity, small size, and a large number of pixels.

Further, according to the present invention, a voltage is applied to the carbon nanotube, a change in a current value in the carbon nanotube caused by light reception of the layer where polarization occurs due to light reception is detected, and the light intensity is determined from the change in the current value. For detection, a relatively large change in the current value can be obtained from a relatively small polarization signal, and a light intensity detection method capable of measuring light intensity with high accuracy and sensitivity is realized. BRIEF DESCRIPTION OF THE FIGURES Fig. 1 is a diagram showing light irradiation to pateriorhodopsin and its electrical response.

FIG. 2 is a sectional view showing an example of the optical sensor according to the embodiment.

FIG. 3 is a schematic diagram showing an example of the optical sensor according to the embodiment.

FIG. 4 is a cross-sectional view schematically showing a manufacturing process of the optical sensor according to the embodiment.

FIG. 5 is a perspective view schematically showing a part of the structure of the optical sensor according to the embodiment.

FIG. 6 is a diagram showing a method for producing an alignment film of carbon nanotubes.

FIG. 7 is a top view schematically showing a method of connecting a source electrode and a drain electrode using a carbon nanotube.

FIG. 8 is a cross-sectional view schematically illustrating a method of connecting a source electrode and a drain electrode using carbon nanotubes.

FIG. 9 is a cross-sectional view showing a method for producing a protein monolayer and a method for laminating the same.

FIG. 10 is a cross-sectional view showing a method for producing a denatured protein monolayer and a method for laminating the same.

FIG. 11 is a sectional view showing an example of the image recognition element according to the embodiment. Fig. 12 is a diagram showing the electric polarization characteristics of bacteriorhodopsin by light irradiation.

FIG. 13 is a diagram schematically showing an output image of the image recognition element according to the embodiment.

Fig. 14 is a diagram showing a A-A plot of the LB film of the purple film.

FIG. 15 is a cross-sectional view schematically showing a connection method using a carbon nanotube for a source electrode and a drain electrode.

FIG. 16 is a diagram showing an example of the configuration of the electrode according to the embodiment.

Fig. 17 is a diagram showing an AFM image of an alignment film of carbon nanotubes using a purple film as a support. Fig. 18 is a diagram showing an AFM image of an alignment film of carbon nanotubes produced without using a support.

FIG. 19 is a view illustrating a method of manufacturing a carbon nanotube structure according to an example.

FIG. 20 is a diagram showing a TEM image of the carbon nanotube structure according to the example.

FIG. 21 is a sectional view showing an example of the optical sensor according to the embodiment.

FIG. 22 is a cross-sectional view schematically showing a manufacturing process of the optical sensor according to the embodiment.

FIG. 23 is a top view schematically showing a method of connecting a source electrode and a drain electrode using carbon nanotubes.

FIG. 24 is a cross-sectional view schematically illustrating a method of connecting a source electrode and a drain electrode using a force-feed nanotube.

FIG. 25 is a cross-sectional view schematically illustrating a method of connecting a source electrode and a drain electrode using a carbon nanotube.

FIG. 26 is a sectional view showing an example of the image recognition element according to the embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the optical sensor according to the present invention will be described. FIG. 2 is a diagram showing an example of the configuration of the optical sensor according to the present invention. In FIG. 2, a substrate 3, a source electrode 5 a and a drain electrode 5 b provided on the substrate 3, a carbon nanotube 7 connecting them, and an insulation formed on the carbon nanotube 7 It includes a layer 11 and a layer 13 which is formed on the insulating layer 11 and is polarized by light reception.

In the layer 13 in which polarization is generated by light reception, molecules that are polarized by light reception (hereinafter, appropriately referred to as photosensitive molecules) exist, and the photosensitive molecules are polarized by light reception to generate induced charges. The induced charge changes the conductance of the carbon nanotube 7, so that the current flowing between the source electrode 5a and the drain electrode 5b The value changes.

FIG. 3 is a diagram schematically showing how the conductance of the carbon nanotube 7 changes. In FIG. 3, it is presumed that the electric charge generated by the photoelectric polarization of the photosensitive molecule changes the 7T electron field of the carbon nanotube 7, so that the conductance of the force tube 11 changes. Due to the change in the conductance of the carbon nanotube, the value of the current flowing through the carbon nanotube 7 changes. In the optical sensor of FIG. 2, the carbon nanotubes 7 are used to connect the source electrode 5 a and the drain electrode 5 b, and the carbon nanotubes 7 have a layer 13 on the upper side of which the polarization is generated by receiving light. The value of the current flowing between the source electrode 5a and the drain electrode 5b via the gate electrode changes.

By detecting a change in current value, a small signal by the photoelectric polarization of photosensitive molecules, can be detected as a current value changes in the order of nano amperes (1 0 _ ⁹ A). Therefore, a high-sensitivity optical sensor that converts an optical signal into an electric signal can be provided.

In the optical sensor of the present invention, a configuration may be employed in which the source electrode and the drain electrode are two-dimensionally arranged on the surface of the substrate. For example, the source and drain electrodes can be arranged as shown in FIG.

FIG. 16 is a diagram showing another example of the arrangement of the source electrode and the drain electrode. The arrangement of FIG. 16 includes a first electrode 101 and a second electrode 102 provided to be spaced from the first electrode 101 and to surround the periphery of the first electrode 101. And. One of the first electrode 101 and the second electrode 102 is a source electrode, and the other is a drain electrode. With such an electrode arrangement, it is relatively easy to connect the source electrode and the drain electrode with carbon nanotubes, and the productivity is improved.

In the optical sensor of the present invention, as in the optical sensor of FIG. 2, an insulating layer may be provided between the carbon nanotube and a layer in which polarization is generated by light reception. By doing so, the polarization due to the carbon nanotube and the light reception It is possible to prevent a current from leaking to a layer where the current is generated.

For example, the insulating layer can mainly contain proteins. By doing so, the thickness of the insulating layer can be reduced, so that the polarization generated in the layer where polarization occurs due to light reception can effectively lead to a change in the conductance of the carbon nanotube.

Further, the insulating layer may mainly contain denatured proteins. For example, it is possible to adopt a configuration in which the isolated layer contains modified bacteriorhodopsin.

In the optical sensor of the present invention, a layer in which polarization is generated by light reception may be configured to mainly include molecules that are polarized by light reception. For example, in the optical sensor of the present invention, a layer in which polarization is generated by receiving light may include a molecular alignment film that is polarized by receiving light. By doing so, the optical signals can be efficiently collected, so that the accuracy and sensitivity of the optical sensor can be improved. Further, it becomes possible to detect an optical signal for each minute area, and the optical sensor can be downsized.

In the optical sensor of the present invention, the layer in which polarization is generated by light reception may be a layer containing oriented Bacterio-mouth dopsin. Bacterial oral dopsin is a photosensitive molecule, has high structural stability among proteins, and accurately polarizes optical signals. Therefore, the accuracy and sensitivity of the optical sensor can be further improved. Further, the durability of the optical sensor can be improved. As a specific example of the layer containing the oriented bacteriorhodopsin, an oriented purple membrane can be exemplified.

FIG. 3 is a schematic configuration diagram of an optical sensor using a purple film. The layer 13 in which polarization occurs upon light reception is made of a purple membrane, and is composed of a photosensitive molecule, bacteriorhodopsin 41, and a lipid bilayer. In this specification, the protein monomolecular film 51 and the layer 13 where polarization is generated by light reception are appropriately illustrated in FIG. 2 including the case where the photosensitive molecule and other components are contained as described above. It is to be expressed in a way.

Further, the layer in which the polarization is generated by the light reception is formed by the oriented pateriorhodopsi. 03009577

11 may be a layer in which a plurality of layers including a layer are stacked. By doing so, the sensitivity of the optical sensor can be improved.

As the photosensitive molecule, for example, a synthetic polymer having a photoelectric conversion function or a biological substance can be used. As the biological substance, for example, a molecule having a porphyrin ring such as chlorophyll a can be used.

In the optical sensor of the present invention, the carbon nanotube may be any of a single-walled carbon nanotube (SWCNT) and a multi-walled carbon nanotube (MWCNT). Among them, SWCNT having metallic properties has a property that conductance is easily changed by the surrounding electronic environment, and thus can be suitably used as a wiring member for electrically connecting a source electrode and a drain electrode.

Hereinafter, an optical sensor and a method of manufacturing the same according to the present invention will be described in detail with reference to embodiments.

(First Embodiment)

FIGS. 2 and 3 show the optical sensor according to the present embodiment. A source electrode 5a and a drain electrode 5b connected by a carbon nanotube 7 are provided on the substrate 3, and an insulating layer 11 is formed on the surface of the source electrode 5a and the drain electrode 5b connected by the carbon nanotube 7. Is formed. The carbon nanotube 7 is SWCNT. On the insulating layer 11, a protein monomolecular film 51 is provided as a layer 13 where polarization is generated by light reception. A protective layer 15 is provided on the upper part of the layer 13 where polarization is generated by light reception. The transparent conductive layer 17 and the transparent substrate 19 are provided on the protective layer 15. They are provided in order. Although the transparent conductive layer 17 is grounded in FIG. 2, an offset voltage may be applied to the transparent conductive layer 17. In this case, for example, the substrate 3 can be grounded.

The optical sensor according to the present embodiment operates as follows. That is,

(I) A current flows between the source electrode 5a and the drain electrode 5b.

(II) The photosensitive molecules contained in the layer 13 where polarization occurs due to light reception Polarized by

(I I I) The conductance of the carbon nanotube 7 connecting the source electrode 5a and the drain electrode 5b changes with the above polarization as a trigger signal. Due to this change in conductance, the value of the current flowing between the source electrode 5a and the drain electrode 5b changes.

(IV) The light intensity is detected by measuring the change in the value of the current flowing between the source electrode 5a and the drain electrode 5b.

Alternatively, as described later in the second embodiment, instead of the step (I), a current is not applied while a voltage is applied between the source electrode 5a and the drain electrode 5b. The trigger signal in step II) may be used as a switch so that a current flows between the source electrode 5a and the drain electrode 5b. That is, it is assumed that no current flows when light is not received, and the current is turned on when light is received. By measuring this current value, the light intensity is detected.

As described above, in the photosensor of the present embodiment, the photoinduced charge of the photosensitive molecule is not taken out as it is as a detection signal, but is used as a trigger signal for changing the source-drain current. That is, the photo-induced charge of the photosensitive molecule is used as a trigger signal for a change in the conductance of the carbon nanotube disposed between the source and the drain, and the source electrode 5a and the drain electrode 5b changed by the trigger signal. It is configured so that the current value between them is detected.

When the carbon nanotubes 7 used in the optical sensor of the present embodiment are single-walled carbon nanotubes (SWCNTs), the conductance significantly changes according to the surrounding electronic state. Accordingly, in the optical sensor of the present embodiment, more to connect the source electrode 5 a and the drain electrode 5 b by SWCNT, a signal by photoelectric polarization of photosensitive molecule, nanoampere (1 0- ⁹ A) current of about It can be detected as a change. As a result, the sensitivity of the optical sensor can be improved as compared with the case where the photoelectron polarization of the photosensitive molecule is directly detected. Monkey,

In the optical sensor of the present embodiment, it has been experimentally confirmed that the polarization speed (reciprocal of the delay time) of bacteriorhodopsin monotonically increases in accordance with the increase in the intensity of light applied to the optical sensor. . Also, as the intensity of the irradiated light increases, the drain current flowing through the carbon nanotube increases due to the polarization of bacteriorhodopsin.

In addition, multi-walled carbon nanotubes (MW CN T) can be used as the carbon nanotubes 7. For example, when a semiconductor MWCNT is used, it is estimated that the source electrode 5a and the drain electrode 5b conduct when the photosensitive molecule is polarized by light reception. Further, the substrate and the source electrode 5a and the drain electrode 5b can be composed of a semiconductor.

Next, a method for manufacturing the optical sensor illustrated in FIG. 2 will be described. The optical sensor according to the present embodiment is manufactured by the following steps.

(i) a step of forming a source electrode 5a and a drain electrode 5b on the substrate 3, (ii) a step of connecting the source electrode 5a and the drain electrode 5b with the carbon nanotubes 7,

(ii) forming an insulating layer 11 on the carbon nanotubes 7;

(iv) forming a layer 13 on the insulating layer 11 where polarization occurs due to light reception,

(V) A step of forming a laminate by bonding the substrate 3 and the transparent substrate 19.

Hereinafter, each of these steps will be described with reference to the cross-sectional view shown in FIG.

(i) Step of forming source electrode 5 a and drain electrode 5 b on substrate 3 As shown in FIG. 4 (a), an electrode pair serving as source electrode 5 a and drain electrode 5 b is formed on one surface of substrate 3. To form When the source electrode 5 a and the drain electrode 5 b are two-dimensionally arranged on the surface of the substrate 3, for example, the configuration shown in FIG. 5 can be used. As the substrate 3, for example, an insulating material such as silicon, SiC, MgO, or quartz or a semiconductor material can be used.

Photolithography and dry etching or ゥ A mask is formed by, for example, etching. The source electrode 5a and the drain electrode 5b are formed by a method of bonding a thin metal plate on the substrate 3 provided with the mask, a method of depositing a metal on the substrate 3, a sputtering method, or the like. Examples of the metal constituting the source electrode 5a and the drain electrode 5b include metals that can form carbides such as Ti and Cr, low-resistance metals such as Au, Pt, and Cu, and alloys thereof. For example, an Au—Cr alloy can be used. In particular, it is preferable to use a metal capable of forming a carbide since the contact resistance between the source electrode 5a and the drain electrode 5b and the carbon nanotube 7 can be reduced. Au is preferable because it is a noble metal and has a low specific electric resistance.

When a noble metal such as Au or Pt or a metal having a low affinity for carbon is used for the source electrode 5 a and the drain electrode 5 b, the source electrode 5 a Preferably, an adhesive layer containing a metal capable of forming a carbide such as Ti or Cr is provided on the surfaces of a and the drain electrode 5b. As such an electrode, for example, an electrode in which a Ti layer is formed on Au can be used. By doing so, it is possible to reduce the contact resistance between the carbon nanotubes 7 and the source electrode 5a and the drain electrode 5b. As a method of forming the adhesive layer, a method of depositing a metal capable of forming a carbide on the surfaces of the source electrode 5a and the drain electrode 5b can be cited.

The thickness of the source electrode 5a and the drain electrode 5b can be, for example, 0.5 nm or more and 100 nm or less. The distance between the source electrode and the drain electrode of the source electrode 5 a and the drain electrode 5 b is appropriately designed according to the length of the carbon nanotube 7. For example, it is 50 nm or more and 10 tm or less. The source electrode 5a and the drain electrode 5b provided on the surface of the substrate 3 are connected to the current detecting means via wiring from the back side of the substrate 3 as described later in the fifth embodiment. can do. By doing so, the current value flowing between each source electrode 5a and the drain electrode 5b can be detected. Can be

(ii) Step of connecting source electrode 5a and drain electrode 5b by carbon nanotube 7

In FIG. 4A, the source electrode 5a and the drain electrode 5b formed on the surface of the substrate are electrically connected by a carbon nanotube 7, as shown in FIG. 4B. You. As the carbon nanotubes 7, for example, those having a length of 50 nm or more and 10 nm or less can be used. Also, SWCNT or MWCNT can be used.

Examples of a method of connecting the source electrode 5a and the drain electrode 5b with the carbon nanotubes 7 include a method of attaching a carbon nanotube alignment film to the surface of the substrate 3 and a method of AFM (atomic force microscope). There is a method of moving the carbon nanotube 7 using a probe or the like, and a method of growing the carbon nanotube 7 horizontally on the substrate 3 from the side surfaces of the source electrode 5a and the drain electrode 5b. In the present embodiment and the second embodiment, a method for attaching an alignment film of carbon nanotubes to the surface of the substrate 3 will be described. Other methods will be described later in the third embodiment and the fourth embodiment.

The step of connecting the source electrode 5a and the drain electrode 5b with the carbon nanotubes 7 includes the step of forming an alignment film of the carbon nanotubes 7, and the step of connecting the alignment film of the carbon nanotubes 7 to the source electrodes 5a and 5b. Attaching to the surface of the substrate on which the drain electrode 5 is provided. After that, a step of selectively removing the carbon nanotubes 7 attached to regions other than the source electrode 5a, the drain electrode 5b, and the region between the source electrode 5a and the drain electrode 5b is performed.

The alignment film of the carbon nanotubes 7 can be manufactured as follows. First, carbon nanotubes 7 and proteins are dispersed in a dispersion medium. As the dispersion medium, an aqueous solution of an organic solvent or the like can be used. For example, a 33 v / VDMF (dimethylformamide) aqueous solution can be used. The protein is a support that keeps the carbon nanotubes 7 oriented. You. As such a support, for example, purple membrane or doptic bacterium contained in purple membrane is used. Purple membranes can be isolated from halophilic bacteria such as Halobacterium salinar urn. For the separation of the purple membrane, for example, the method described in Methodsin Enzymo 1 ogy, 31, A, pp. 667-678 (1974) can be used. An excessive amount of carbon nanotubes 7 is added to the dispersion of the support, and dispersed using an ultrasonic disperser or the like. Aggregates of carbon nanotubes 7 remaining in the dispersion are removed.

As shown in FIG. 6, the dispersion of the carbon nanotubes 7 and the support obtained above is gently spread using a syringe or the like on the liquid surface of the lower layer liquid stretched in the water tank. Thus, a monomolecular film of the carbon nanotube 7 is obtained. In this embodiment, Langmuir trough 61 is used as the water tank, and pure water adjusted to pH 3.5 with HC 1 is used as the lower layer liquid.

Next, the monomolecular film of the carbon nanotube 7 is allowed to stand, and the protein is interfacially denatured by the interfacial tension of the lower layer solution. For example, when a purple membrane is used as a support, it is preferable to allow the bacteriorhodopsin in the purple membrane to stand at room temperature for 5 hours or more until the interface is denatured. By doing so, the aggregate of the denatured protein becomes a support for the carbon nanotubes 7, and the carbon nanotubes 7 can be maintained in an oriented state. The monomolecular film in which the carbon nanotubes 7 are arranged substantially in parallel is obtained by compressing using a movable barrier 63 of Langmuir Trough as a partition plate. For example, when a purple membrane is used as the support, it is preferable to compress at a compression rate of 20 cm ² Zmin until the surface pressure becomes 15 mNZm. The orientation of the carbon nanotube 7 is confirmed using AFM or the like. FIG. 6 is an AFM photograph of the alignment film of carbon nanotubes 7, and each carbon nanotube 7 is shown in a white circle.

FIG. 17 is a diagram showing an AFM image of a carbon nanotube oriented film produced using a purple film as a support. On the other hand, FIG. 18 is a diagram showing an AFM image when an alignment film of carbon nanotubes was similarly prepared without using a support. Figure In FIG. 17 and FIG. 18, a biomolecule visualization / measurement apparatus B MVM-X1 (Nano Scope IIIa manufactured by Digital Instruments) was used for AFM observation. Silicon single crystal (NCH) was used as a probe, and the measurement mode was tapping AFM. The measurement range was 4 mX 4 m (Z 10 nm).

From FIGS. 17 and 18, it can be seen that when the purple membrane was used as the support, the support component was attached to the surface of the carbon nanotube. Then, as shown in FIG. 17, it was confirmed that the use of the support improved the orientation of the carbon nanotubes, and the carbon nanotubes were arranged substantially in parallel. As shown in FIG. 18, when only the carbon nanotubes were used, although the alignment was performed to some extent, the orientation was lowered during the film formation. On the other hand, in the case of FIG. 17, the orientation state of the carbon nanotubes was maintained by the support mainly containing denatured bacterial mouth dopsin, so that high orientation could be maintained after the film formation. In FIG. 6, FIG. 17, and FIG. 18, single-walled carbon nanotubes manufactured by CNI (Oppen en dtype, diameter of about 1 nm, purification purity of about 93%) were used as the carbon nanotubes.

The alignment film of the carbon nanotubes 7 thus obtained is attached to the electrode surface obtained in the step (i) by a horizontal attachment method. The horizontal deposition method is a method in which the substrate is brought into contact with the liquid surface so that the substrate surface is horizontal to the alignment film on the water surface, and the substrate is pulled up, so that the alignment film on the water surface is attached to the surface of the substrate. As described above, an alignment film of carbon nanotubes 7 is formed on the surface of the substrate 3 provided with the source electrode 5a and the drain electrode 5b.

The following steps will be described with reference to the top view of FIG. 7 and the cross-sectional view of FIG. The steps in FIGS. 7 (a) to 7 (f) correspond to the steps in FIGS. 8 (a) to 8 (f).

First, as shown in FIG. 7A and FIG. 8A, a source electrode 5a and a drain electrode 5b are formed on the surface of the substrate 3. Next, as shown in FIGS. 7 (b) and 8 (b), the carbon Adsorb the alignment film of Ube7. Next, as shown in FIGS. 7 (c) and 8 (c), an insulating film 21 is formed on the surface of the carbon nanotube alignment film by using a plasma CVD method or the like. As the insulating film 2 1, for example, it can be used as S I_〇 _2. The thickness of the insulating film 21 can be, for example, not less than l nm and not more than 1 m.

Next, only the carbon nanotubes 7 adsorbed on the source electrode 5a and the drain electrode 5b and between the electrodes are left, and the carbon nanotubes 7 adsorbed on unnecessary portions are removed. 8 (d), a resist film 25 is formed on the substrate. Next, as shown in FIGS. 7 (e) and 8 (e), the insulating film 21 and the carbon nanotubes 7 where the resist film 25 is not applied are removed by a method such as dry etching or wet etching. . Then, the resist film 25 is removed using a solution that dissolves the resist film 25 without dissolving the insulating film 21.

As described above, the carbon nanotube 7 is provided between the source electrode 5a and the drain electrode 5b as shown in FIGS. 7 (f) and 8 (f), and unnecessary portions of the carbon nanotube 7 are removed. The obtained substrate 3 is obtained.

In the present embodiment, as described above, since the insulating film 21 is provided on the carbon nanotubes 7, the process (iii) can be performed without removing the insulating film 21, and a mask other than the insulator is applied. The manufacturing method can be simplified as compared with the case in which it is performed.

When the surface of the source electrode 5a and the drain electrode 5b contains a metal capable of forming a carbide, annealing is performed as appropriate in the steps after FIG. 7 (b) and FIG. 8 (b). By performing the method of heating to 0 ° C. or more, carbide is formed at the interface between the carbon nanotubes 7 and the source electrode 5a and the drain electrode 5b, and electrical contact can be increased.

After removing the insulating film 21, a mask is formed on the surface of the substrate 3 so that only the upper part of the electrode is used as an opening, and a metal layer serving as an electrode is further formed on each of the source electrode 5a and the drain electrode 5b. You can also. The formation of the metal layer is gold The method can be performed in the same manner as (i), such as a metal deposition method or a sputtering method. By doing so, the carbon nanotubes 7 connecting the source electrode 5a and the drain electrode 5b are sandwiched between the upper and lower metal layers, so that better electrical contact can be obtained. it can.

As described above, in the present embodiment, the source electrode 5a and the drain electrode 5b can be easily and efficiently connected by using the oriented monomolecular film of the carbon nanotubes 7. Then, as shown in FIG. 5, a set of the source electrode 5 a and the drain electrode 5 b is used as a pixel 9 to detect a current flowing between the pixels 9. Therefore, the pixel 9 can be miniaturized. For example, 100 million pixels Z cm ² can be obtained.

(iii) Step of forming insulating layer 11 on carbon nanotubes 7 As shown in FIG. 4 (c), the carbon nanotubes formed on the source electrode 5a and the drain electrode 5b in the step (ii) An insulating layer 11 is formed on the surface of 7.

As a method for forming the insulating layer 11, for example, there is a method in which a polymer such as polyimide is spin-coated on the surface of the substrate 3 on which the carbon nanotubes 7 are provided.

Further, for example, there is a method in which a polymer such as polyimide is formed as a monolayer film.

Alternatively, a film made of denatured protein is formed, and the film is attached to the surface of the substrate 3 provided with the source electrode 5a, the drain electrode 5b, and the carbon nanotube 7 on the surface by a horizontal attachment method or the like, and is insulated. It can also be used as layer 11. An example of a membrane composed of denatured protein is a denatured membrane of bacteriorhodopsin. Also, a purple membrane containing bacteriorhodopsin can be used. The purple membrane can be isolated from a halophilic bacterium such as Halobacterium salinarum (Halobabacterium salinarum) as in the step (ii).

Hereinafter, an example using a purple film will be described with reference to FIG. Bacterio The purple membrane containing rhodopsin 341 is dispersed in a dispersion medium 342 to prepare a protein developing solution 350. In a water tank filled with lower layer liquid 360? On the surface, spread it gently using a syringe 362 or the like. In the present embodiment, a Langmuir trough 361 is used as the water tank. When pateriorhodopsin 341 is used as the protein, for example, a 33 v / v% aqueous solution of dimethylformamide (DMF) can be used as the dispersion medium 342. At this time, as the lower layer solution 360, for example, pure water adjusted to pH 3.5 with HC1 can be used.

By allowing the protein monolayer obtained above the lower layer solution 360 to stand for a predetermined time, the protein is interface-denatured by interfacial tension, and a denatured protein monolayer 352 is obtained. In the case of bacteriorhodopsin 341, it is better to leave it at room temperature for at least 5 hours.

Next, using the movable barrier 363 of the Langmuir Trough 361 as a partition plate, the monomolecular film formed on the liquid surface of the lower layer liquid 360 is compressed until a predetermined surface pressure is reached. In the case of bacteriorhodopsin 341 it is compressed, for example, to a surface pressure of 15 mNZm.

The surface pressure is a one-dimensional pressure and is expressed as the force per unit length. The monomolecular film is formed in a sheet shape on the liquid surface of the lower layer liquid, and when compressed from the side, a one-dimensional force acts from the side of the film. At this time, the value obtained by dividing the force by the one-dimensional length in the lateral direction of the monolayer to which the force is applied is the surface pressure.

After the compression, the modified protein monomolecular film 352 is attached to the surface of the substrate 3 obtained in the step (ii) by the horizontal attachment method. Further, by repeating the horizontal attachment method, the denatured protein monolayer 352 can be accumulated. By changing the number of accumulated layers, the thickness of the insulating layer 11 can be changed. For example, since the thickness of one layer of the denatured protein monolayer 352 is about 1.5 nm, the thickness of the insulating layer 11 can be set to a predetermined thickness in units of 1.5 nm.

(iv) Form a layer 13 on the insulating layer 11 where polarization occurs due to light reception. As shown in FIG. 4D, on the surface of the insulating layer 11 obtained in the step (iii), a layer 13 in which polarization is generated by receiving light is formed. The layer 13 in which polarization is generated by light reception can be a monomolecular film or a stacked film of molecules in which polarization is generated by light reception.

The layer 13 in which polarization is generated by light reception can be, for example, a bacteriorhodopsin orientation film. The bacteriorhodopsin alignment film is preferably used because it causes stable polarization upon receiving light. Above all, purple membrane contains bacteriorhodopsin, which has relatively excellent durability, and is preferably used. The purple membrane can be isolated from a halophilic bacterium such as Halobacterium salinarum (Ha1 ob ct ter i urn sa lin a urn) in the same manner as in the step (ii).

The step of forming the layer 13 in which polarization is generated by light reception includes the steps of: spreading a dispersion liquid containing molecules that are polarized by light reception on a liquid surface to form an alignment film of molecules that are polarized by light reception; and polarizing by light reception. A step of attaching a molecular alignment film and a carbon nanotube 7 directly or via an insulating layer 11; and a step of attaching an alignment film of a molecule which is polarized by receiving light to the surface of the transparent substrate 19; including. The step of attaching an alignment film of molecules that are polarized by light reception to the surface of the transparent substrate 19 will be described later in step (V).

Hereinafter, an example of forming a purple Langumumuir-Blodgett (LB) film and forming a layer 13 in which polarization is generated by light reception will be described with reference to a process cross-sectional view of FIG.

First, a purple membrane containing bacteriorhodopsin 41 as a protein component is dispersed in a dispersion medium 42 to prepare a protein developing solution 50. The obtained protein developing solution 50 is gently developed using a syringe 62 or the like on the liquid surface of a water tank filled with the lower layer solution 60. In this embodiment, a Langmuir trough 61 is used as a water tank. When bacteriorhodopsin 41 is used, for example, a 33 vZv% dimethylformamide (DMF) aqueous solution is used as the dispersion medium 42. Can be. At this time, as the lower layer solution 60, for example, an acidic solution such as an aqueous solution of hydrochloric acid having a pH of 3.5 can be used. By doing so, a protein monolayer 51 is obtained above the lower layer solution 60. At this time, the orientation of the molecules forming the protein monolayer 51 becomes almost the same due to the effect of the interfacial tension of the lower layer solution 60. Here, the dispersion medium 42 is quiescent to volatilize. If a protein is used as the photosensitive molecule, set the standing time so that interface denaturation does not occur. For example, when using bacteriorhodopsin 41, the standing time is about 10 minutes.

Next, using the movable barrier 63 of the Langmuir trough 61 as a partition plate, the protein monomolecular film 51 formed on the liquid surface of the lower layer solution 60 is compressed until it reaches a predetermined surface pressure. For bacteriorhodopsin 41, for example, compress at a compression rate of 20 cm ² / min until the surface pressure reaches 15 in NZm.

Thereafter, a monomolecular film is attached to the surface of the insulating layer 11 by a horizontal attachment method. For example, when bacteriorhodopsin is used, the thickness of one monolayer is about 5 nm.

Further, by repeating the horizontal attachment method, a monomolecular film can be laminated on the surface of the insulating layer 11. When laminating, each time one layer is laminated, rinse with pure water and dry under N ₂ gas atmosphere. When the number of layers is changed, the thickness of the layer 13 where polarization occurs due to light reception can be changed, so that the sensitivity of the optical sensor can be adjusted.

When a hydrochloric acid aqueous solution having a pH of 3.5 is used as the lower layer solution, a first A plot of the purple LB film is as shown in FIG. In FIG. 14, C i is an index relating to the initial concentration of bacteriophage dopsin in the protein monolayer 51,

C i = (number of bacteriorhodopsin molecules on the lower liquid) XII. S nm ² , area of gas-liquid interface before compression

It is shown by the following formula. In the above formula, 11.5 nm ² is the area per one molecule of bacteriophage dopsin obtained by X-ray diffraction.

(V) Step of forming a laminate by bonding substrate 3 and transparent substrate 19 As shown in FIG. 4 (g), the substrates 3 and the transparent substrate 19 obtained by the above-described process are fixed in a state where the substrates are brought into contact with the respective substrate surfaces facing outward, thereby joining the substrates. Then, the optical sensor of FIG. 2 is obtained.

As shown in FIGS. 4 (e) and 4 (f), a transparent conductive layer 17 and a protective layer 15 are provided in this order on one surface of the transparent substrate 19. As the transparent substrate 19, a transparent material such as resin or glass can be used. Further, as the transparent conductive layer 17, for example, a light-transmitting conductive layer such as indium tin oxide (ITO) can be used. As the protective layer 15, for example, a transparent insulating material such as glass, resin, or a denatured protein film same as the insulating layer 11 can be used.

In the optical sensor obtained as described above, the conductance of the carbon nanotube 7 changes due to the polarization due to the light reception of the protein molecule, and the current flowing between the source electrode 5a and the drain electrode 5b changes. . By detecting this change, the presence / absence and intensity of light reception can be detected. In the optical sensor of the present embodiment, the value of the current flowing between the source electrode 5a and the drain electrode 5b is larger than that of the signal due to the polarization due to the light reception of the protein molecule, which is necessary for the conventional optical sensor. It is not necessary to connect to the large-sized amplifying device. Further, in the optical sensor of the present embodiment, the layer 13 in which polarization is generated by receiving light is a thin film of a photosensitive molecule, and therefore, is thin and has high sensitivity. Since a pair of the source electrode 5a and the drain electrode 5b connected by the carbon nanotubes 7 are used as the pixels 9, the number of pixels per unit area is high (FIG. 5). Further, the optical sensor according to the present embodiment is an element that converts an optical signal into an electric signal, and can change a current value between the source electrode and the drain electrode by light irradiation.

In the optical sensor according to the present embodiment, the source electrode and the drain electrode are formed two-dimensionally on the substrate surface as shown in FIG. 5, but they may be formed so as to be arranged in a line. Such a one-dimensional optical sensor can be used, for example, for non-contact dimension measurement, position measurement, facsimile pattern reading, and the like. (Second embodiment)

In the first embodiment, (ii) the step of connecting the source electrode 5a and the drain electrode 5b with the carbon nanotubes 7 may be performed by the following method.

First, as shown in FIGS. 15 (a) and 15 (b), as in the first embodiment, a force is applied to the substrate 3 on which the source electrode 5a and the drain electrode 5b are provided. The alignment film of the carbon nanotube 7 is adsorbed.

Next, as shown in FIG. 15 (c), a resist film 25 having openings above the source electrode 5a and the drain electrode 5b is formed. The resist film 25 can be formed by, for example, a photoresist method.

Next, as shown in FIG. 15D, a metal layer 27 is formed on the entire substrate on which the resist film 25 is provided. The metal layer 27 is appropriately selected from metals or alloys used for the source electrode 5a and the drain electrode 5b. The metal layer 27, the source electrode 5a, and the drain electrode 5b may use the same metal or different metals. The formation of the metal layer can be performed in the same manner as (i) production of the source electrode 5a and the drain electrode 5b on the substrate 3, such as a metal vapor deposition method and a sputtering method.

Then, as shown in FIG. 15 (e), the resist film 25 is removed with a stripper. By doing so, the metal layer 27 provided on the surface of the resist film 25 other than the upper portions of the source electrode 5a and the drain electrode 5b is removed.

Through the above steps, the source electrode 5a or the drain electrode 5b and the metal layer 27 are provided on the upper and lower portions of the carbon nanotube 7, respectively. By doing so, the contact between the carbon nanotubes 7 and the metal constituting each electrode can be further improved. Therefore, the contact resistance between the carbon nanotube 7 and the source electrode 5a and the drain electrode 5b can be reduced, and the value of the current flowing between the source electrode 5a and the drain electrode 5b can be increased. (Third embodiment)

That is, as another method of connecting the source electrode and the drain electrode with the carbon nanotubes 7, a dispersion of the carbon nanotube 7 is applied to the substrate 3 provided with the source electrode 5a and the drain electrode 5b. A method in which the carbon nanotube 7 is moved to a predetermined position using an AFM probe or the like may be used.

By doing so, the carbon nanotube 7 can be more precisely arranged between the source electrode and the drain electrode.

(Fourth embodiment)

In the first embodiment, (ii) the step of connecting the source electrode 5a and the drain electrode 5b by the carbon nanotube 7 may be performed by the following method.

In other words, as another method of connecting the source electrode and the drain electrode with carbon nanotubes, a method of attaching carbon nanotubes to the side surfaces of the electrodes, growing the carbon nanotubes horizontally on the substrate with the catalyst metal as a growth starting point, and connecting the electrodes. There is.

The catalyst metal is not particularly limited as long as it serves as a catalyst for the growth of carbon nanotubes. For example, a metal containing at least one of Fe, Co, and Ni is preferably used. An alloy such as Fe—Ni alloy or Ni—Co alloy may be used. In order to selectively attach the catalyst metal to a part of the source electrode 5a and the drain electrode 5b, vapor deposition, lithography, sputtering, patterning using a solution of the catalyst metal, or the like can be performed. At this time, it is effective to appropriately adjust the deposition temperature, the substrate material, the method of depositing the catalyst metal, and the like. Further, the catalyst metal can be patterned by, for example, a lift-off method. As a method for growing carbon nanotubes in a horizontal direction on a substrate with a catalyst metal as a growth starting point, a film formed by a chemical vapor deposition method (CVD method) is preferably used. As the CVD method, a plasma CVD method, a thermal CVD method, or the like can be used. A plasma CVD method capable of growing carbon nanotubes at a relatively low temperature is preferably used.

Source gases used for growth by the CVD method include saturated hydrocarbons such as methane, ethane, propane, butane, pentane, hexane, and cyclohexane; and unreacted gases such as ethylene, acetylene, propylene, benzene, and toluene. Saturated hydrocarbons; raw materials containing oxygen such as acetone, methanol, ethanol, carbon monoxide, or carbon dioxide; raw materials containing nitrogen such as benzonitrile; these may be used alone or in combination of two or more. it can.

As the carrier gas flowing into the reactor together with the raw material gas, for example, hydrogen or helium can be used, but its use is not essential.

In order to stably obtain a structure in which the carbon nanotubes grow in the horizontal direction of the substrate, there is a method of appropriately controlling the supply direction of the source gas and the growth temperature, and the method of forming the carbon nanotubes while applying a magnetic field or an electric field. It is effective to appropriately adopt a growth method.

According to the above method, the source electrode and the drain electrode can be connected by the carbon nanotube. Thereafter, an electrode can be formed on the carbon nanotubes by appropriately bonding a metal plate to the electrode surface or vapor-depositing a metal. By doing so, the carbon nanotube and the source electrode and the drain electrode are more appropriately bonded, so that the contact resistance can be reduced.

(Fifth embodiment)

In the first or second embodiment, an alignment film of carbon nanotubes is formed, and the source electrode 5a and the drain electrode 5b are connected by a carbon nanotube. Here, as described in the first embodiment, FIG. From FIG. 18, it was found that when the purple membrane was used as the support, the support component was attached to the surface of the carbon nanotube. As a result of further study by the present inventor, as will be described in detail in the examples described later, in the process of forming the alignment film, the support component is wound around the surface of the carbon nanotube to have a uniform thickness. It was found that a coating was formed.

In the present embodiment, an example of an optical sensor configured using such a coated carbon nanotube will be described. FIG. 21 is a diagram showing a configuration of the optical sensor of the present embodiment. The basic configuration of the optical sensor of FIG. 21 is the same as that of the sensor of the first embodiment (FIG. 2). In the optical sensor of FIG. 21, the same components as those of the nanocarbon manufacturing apparatus 125 described in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate. The optical sensor of FIG. 21 has a carbon nanotube structure composed of a carbon nanotube 105 whose surface is coated with a modifying molecule 125 instead of the carbon nanotube 7 of the optical sensor described in the first embodiment. The optical sensor of FIG. 2 is different from the optical sensor of FIG. 2 in that it has a body 131, and does not have an insulating layer 11 between the force-feeding nanotube 7 and a layer 13 in which polarization is generated by light reception.

The optical sensor shown in FIG. 21 schematically shows a state in which the modifying molecule 1229 is wound around the surface of the carbon nanotube 105 to form an insulating layer. Covers the surface of the carbon nanotubes 105 uniformly. Further, the insulating layer only needs to uniformly cover the surface of the carbon nanotube 105, and is not limited to a mode wound around the carbon nanotube 105.

With the configuration in which the modifying molecule 129 is wound on the surface of the carbon nanotube 105, a uniform thin coating layer consisting of a wound layer can be formed on the surface of the carbon nanotube 105. it can. Since the coating layer having a uniform thickness is formed, the operation stability of the optical sensor can be improved. Therefore, the reliability of the optical sensor can be improved. In addition, since the thin coating layer is formed, the polarization of the layer 13 in which polarization occurs upon receiving light can be accurately converted into a change in conductance of the carbon nanotube. Next, a method for manufacturing the optical sensor of FIG. 21 will be described. FIG. 22 is a cross-sectional view showing a manufacturing process of the optical sensor of FIG.

As shown in FIG. 22, first, the source electrode 5a and the drain electrode 5b are formed on the substrate 3 (FIG. 22 (a)). Next, the source electrode 5a and the drain electrode 5b are connected by the carbon nanotube structure 13 1 (FIG. 22 (b)), and a layer 13 on which polarization occurs due to light reception is formed thereon (FIG. 22 (b)). Figure 22 (c)). Then, a laminate is formed by joining the substrate 3 and the transparent substrate 19 (FIG. 22 (e)). Here, on one surface of the transparent substrate 19, a transparent conductive layer 17 and a protective layer 15 are provided in this order (FIG. 22 (d)). Thus, the optical sensor shown in FIG. 21 is obtained.

In the above steps, the method described in the first embodiment can be used for forming the source electrode 5a and the drain electrode 5b on the substrate 3 (FIG. 22A).

In addition, the connection of the source electrode 5a and the drain electrode 5b by the carbon nanotube structure 13 1 (FIG. 22 (b)) was obtained by forming an alignment film of the carbon nanotube structure 13 1. After the alignment film is attached to the surface of the substrate 3 and unnecessary portions of the carbon nanotube structure 131 are removed, the modifying molecules 129 on the source electrode 5a and the drain electrode 5b are removed. This method will be described later.

In addition, the formation of a layer 13 where polarization occurs upon light reception on the carbon nanotube structure 13 1 (FIG. 22 (c)) and the formation of a laminate by bonding the substrate 3 and the transparent substrate 19 (FIG. 22) For (e)), the method described in the first embodiment can be used.

Hereinafter, the steps of connecting the source electrode 5a and the drain electrode 5b with the carbon nanotube structure 13 1 (FIG. 22 (b)) will be described in detail. First, the alignment film of the carbon nanotube structure 13 1 is manufactured by using the method described in the first embodiment (FIG. 6). In the carbon nanotube structure 131, the thickness of the insulating layer covering the carbon nanotube 105 is For example, it can be 0.1 nm or more and 100 nm or less, and preferably 10 nm or less. By doing so, the thickness of the insulating layer can be reduced. For this reason, the conductance change of the carbon nanotube 105 due to the induced charge generated by the polarization of the layer 13 where the polarization is generated by the light reception can be increased. Therefore, an optical sensor with higher sensitivity can be obtained.

The alignment film is attached to the surface of the substrate 3 by a method such as a horizontal attachment method.

The removal of unnecessary portions of the carbon nanotube structure 1311 is performed by the steps shown in FIGS. FIGS. 23 (a) to 23 (e) are top views of the respective steps, and the corresponding sectional views are FIGS. 24 (a) to 24 (e).

FIGS. 23 (b) and 24 (b) show the structure of the carbon nanotube structure 1 on the substrate 3 (FIGS. 23 (a) and 24 (a)) on which the source electrode 5a and the drain electrode 5b are formed. FIG. 3 is a diagram showing a state in which an alignment film of No. 31 is adsorbed.

Patterning was performed to remove only the carbon nanotube structure 131 adsorbed to unnecessary portions, leaving only the carbon nanotube structure 131 adsorbed above the source electrode 5a and the drain electrode 5b and between the electrodes. A resist film 25 is formed (FIGS. 23C and 24C).

Next, by a method such as dry etching or wet etching, the carbon nanotube structure 131 in a region not having the resist film 25 on the upper portion is removed (FIGS. 23D and 24D). Then, the resist film 25 is removed using a solution that dissolves the resist film 25 without dissolving the modifying molecules 129 and the carbon nanotubes 105 (FIGS. 23 (e) and 24 (e)).

Thus, unnecessary portions of the carbon nanotube structure 131 are removed. Next, the removal of the modifying molecules 129 on the source electrode 5a and the drain electrode 5b is performed as follows. FIG. 25 is a cross-sectional view showing a step of removing the modifying molecule 129 on the electrode. ,

The source electrode 5a and the drain electrode are formed on the entire surface of the substrate 3 (Fig. 25 (a)) from which the unnecessary carbon nanotube A resist film 31 having an opening at the top of the electrode 5b is formed (FIG. 25 (b)). As a result, both ends of the carbon nanotube structure 13 1 are exposed.

Then, at least a part of the modified molecule 12 9 on the exposed side surface of the carbon nanotube structure 13 1 is removed by a method such as assing (FIG. 25 (c)). As a result, the carbon nanotubes 105 have no coating only on the electrodes. Oxygen plasma can be used for atshing. Alternatively, a plasma of nitrogen or a nitrogen-containing gas can be used.

After that, the resist film 31 is removed using a solution that dissolves the resist film 31 without dissolving the carbon nanotubes 105 (FIG. 25 (d)).

Thus, the modifying molecule 129 on the electrode is removed. The electrical connection between the carbon nanotube 105 and the electrode can be improved by removing the modifying molecule 125 on the electrode.

When the surface of the source electrode 5a and the drain electrode 5b contains a metal capable of forming a carbide, annealing is performed as appropriate in the steps after FIG. 23 (b) and FIG. 24 (b), for example, under vacuum. By heating at a temperature of at least 100 °, a carbide is formed at the interface between the source electrode 5a and the drain electrode 5b and the carbon nanotube 105, thereby increasing electrical contact. Can be. Similarly to the first embodiment, a mask is formed on the surface of the substrate 3 so that only the upper part of the electrode is an opening, and a metal layer to be an electrode is further formed on each of the source electrode 5a and the drain electrode 5b. You can also. By doing so, a structure in which the source nanotube 105 connecting the source electrode 5a and the drain electrode 5b is sandwiched between the upper and lower metal layers is obtained. Therefore, the electrical contact can be further improved.

Furthermore, a thin insulating film may be formed on the source electrode 5a and the drain electrode 5b by applying a mask on the surface of the substrate 3 so that only the upper part of the electrode is an opening. This can prevent direct contact between the source electrode 5a, the drain electrode 5b, and the carbon nanotube 105 exposed on these electrodes and the layer 13 where polarization occurs due to light reception. Also, as mentioned above, Even if a metal layer serving as an electrode is further formed on each of the source electrode 5a and the drain electrode 5b, the metal layer and the layer 13 where polarization occurs due to light reception should not be in direct contact. it can. Therefore, the accuracy of the optical sensor can be further improved.

As described above, in the present embodiment, since the modifying molecule 129 is wound around the outer periphery of the side surface of the carbon nanotube 105, the modifying molecule 129 is evenly distributed on the surface of the carbon nanotube structure 131. Insulating film is formed. Therefore, without forming an insulating film on the carbon nanotube 105, it is possible to attach the layer 13 where polarization is generated by direct light reception on the carbon nanotube structure 131. . Therefore, it is possible to stably supply an optical sensor having a simpler configuration.

In addition, the insulating layer on the surface of the carbon nanotube 105, that is, the layer of the modifying molecule 125 is uniform on the surface of the carbon nanotube 105 as a thin film having a thickness of, for example, about 0.1 nm or more and 100 nm or less. Is formed. For this reason, the polarization in the layer 13 where the polarization occurs due to the light reception is ensured while the insulation between the layer 13 where the polarization occurs due to the light reception and the carbon nanotube 105 is ensured. It can be accurately converted to a change in conductance. In addition, since the periphery of the carbon nanotube 105 is covered with the modifier molecule 129 with a uniform thickness, the operation stability of the optical sensor is improved. In addition, such a coating of the modifying molecule 129 suppresses the influence of the surrounding water from affecting the conductivity of the carbon nanotube 105. Therefore, the accuracy and sensitivity of the optical sensor can be further improved.

(Sixth embodiment)

The optical sensor according to the present embodiment has a configuration in which a plurality of electrode pairs including a source electrode and a drain electrode are two-dimensionally arranged on a substrate surface. The structure of each sensor unit is the same as in the first embodiment. The optical sensor of the present embodiment can be suitably applied to an image recognition element, an image sensor of a television camera, and the like. Hereinafter, an example in which the optical sensor according to the present embodiment is used as an image recognition element will be described. I will tell.

FIG. 11 shows an image recognition element 100 according to the present embodiment. The image recognition device 100 shown in FIG. 11 is manufactured in the same manner as in the first embodiment. In FIG. 11, for example, single crystal silicon is used for the substrate 3. A purple film is used for the layer 13 where polarization is generated by light reception. By doing so, a protein monomolecular film 51 containing bacteriorhodopsin 41 and lipid is obtained, and this is laminated to form a layer 13 in which polarization is generated by light reception. Also, a purple film is used for the insulating layer 11. When bacteriorhodopsin 41 is irradiated with light, electric polarization occurs, and the electric polarization characteristics are as shown in FIG. That is, when light is irradiated at time ti, electric polarization occurs, and this polarization gradually decreases with time. When to stop irradiation of light at time 1 _2, it occurs electric component electrode during light irradiation and opposite polarity, polarization with time gradually attenuated.

In the image recognition element 100 of the present embodiment, the current value flowing through the source electrode 5a and the drain electrode 5b of each pixel 9 is detected by the current detecting means 23. Therefore, the resolution is high and the sensitivity is high.

Further, when detecting the contour of a moving object using the image recognition element 100 of the present embodiment, it is possible to recognize the contour more precisely than in a conventional image recognition element.

In the conventional extraction of the outline of a moving object in an image, a difference image obtained by calculating a temporary difference between consecutive frame images of an image acquired by an input device such as a CCD is used. This method is hereinafter referred to as the “de-one-time difference method”. The overnight difference method takes advantage of the fact that the difference between two consecutive frame images is generally due to the portion of the image that corresponds to the contour of the moving object.

Therefore, the contour data of the moving object extracted by the data difference method depends on the background image data of the moving object. In other words, even if the light intensity of the moving object is constant, if the light intensity of the background around the moving object changes, the contour data, which is the difference value, will not be constant. For this reason, it was difficult to detect the contour with high accuracy under the condition where the light intensity of the background image changes. On the other hand, the image recognition element 100 according to the present embodiment can extract the outline of the moving object without taking a data difference, as described below. FIG. 13 shows an output image obtained by the image recognition element when a moving image including a moving object is irradiated on the image recognition element 100 in FIG.

In FIG. 13 (a), 1 1 1 is the input image at time t, 1 1 2 is the output image for the input image at t = Ί \, and 1 13 is the straight line の of the output image for the input image at t. The output current value of each is shown. Note that the input image refers to optical information, and it is assumed that the light of the moving object is first irradiated on the image recognition element 100 in section = 1 \.

Further, in FIG. 1 3 (b), 12 1 is the input image at t = T _2, 12 ₂ is the output image for the input image in t = T _2, 123 is the output for the input image that put in t = T ₂ The output current values on the straight line A の in the image are shown.

1: = 1 \ moves to the pixel 9 corresponding to the light-irradiated part of the moving object due to the electric polarization characteristics of the layer 13 (Fig. 12) where polarization occurs due to the light received by the image recognition element 100 An induced current of a predetermined value (+8 in Fig. 13 (a)) corresponding to the light intensity of the object is generated.

Next, the t = T _2, the pixels 9 which light moving object corresponding to the newly irradiated portions (in FIG. 1 3 (b) + 8) predetermined value induced current is generated in. On the other hand, the induced current to the pixel 9 corresponding to the portion where the light of the moving object is continuously irradiated from the time t = 1 \ is the electric current of the layer 13 where polarization occurs due to the light received by the image recognition element 100. It decreases to a predetermined value depending on the polarization characteristics (+8 to +5 in Fig. 13 (b)). Then, t = 1 ^ but the light of the moving object has been irradiated, the induced current to the pixel 9 corresponding to the portion where the light is no longer illuminated for t = T ₂ the mobile object, polarization is generated by the light-receiving Due to the electric polarization characteristics of the layer 13, the polarity changes to a predetermined value (15 in FIG. 13 (b)) of the reverse polarity according to the light intensity of the animal.

Therefore, the part of the moving object that is newly irradiated with light, The induced current value corresponding to the contour on the front side in the moving direction is a predetermined constant value (+8 in Figs. 13 (a) and 13 (b)) corresponding to the light intensity of the moving object. Become. In addition, the induced current value corresponding to the portion of the moving object that is no longer irradiated with light, that is, the contour on the rear side in the moving direction of the moving object, is a predetermined constant value according to the light intensity of the moving object (see FIG. In 1 3 (b), it is 1 5). As described above, when a moving object is detected using the image recognition element 100, if the luminance of the background is constant, the induced current value of the contour is constant. Further, the induced current value corresponding to the portion of the moving object that has been continuously irradiated with light and the portion that has been no longer irradiated becomes zero with the passage of time.

As described above, the in-contour image of the moving object extracted by the image recognition element 100 of the present embodiment is a real image. For this reason, even if the background of the input moving image is a complicated image with a pattern or the like, only the outline of the moving object in the moving image can be extracted and does not depend on the background image. Further, by searching for the contour of the moving object, the moving direction of the object can be extracted.

Further, in the image recognition element 100 of the present embodiment, since the pixels 9 are minute, the number of pixels per unit area can be increased to about 100 million. Therefore, the contour of the moving object can be extracted more precisely.

Further, the pixel 9 constituting the image recognition element 100 of the present embodiment has a current value flowing between the source electrode 5a and the drain electrode 5b due to a change in the conductance of the carbon nanotube 7 due to the polarization of the bacterial rhodopsin 41. Therefore, the change in the current value is relatively large, and the contour of the moving object can be detected with high sensitivity.

(Seventh embodiment)

The present embodiment relates to an image recognition element using the optical sensor according to the fifth embodiment. FIG. 26 is a diagram showing the image recognition element 29. In the image recognition element 29, the same components as those of the image recognition element 100 described in the first embodiment are denoted by the same reference numerals, and the description will be appropriately omitted.

In the image recognition element 29, the source electrode 5a and the drain electrode 5b P2003 / 009577

35 are connected by a tube structure. In the carbon nanotube structure 13 1, the modification molecule 1 29 is coated around the carbon nanotube 105 in a similar manner. A thin insulating layer of a modified molecule 129 is formed around the carbon nanotube structure 13 1. Therefore, polarization can be generated accurately and stably in the protein monomolecular film 51 without providing the insulating layer 11 between the layer 13 where polarization is generated by light reception and the carbon nanotube 105. . For example, a purple film can be used for the layer 13 in which polarization is generated by light reception.

The method described in the fifth and sixth embodiments can be used for manufacturing the image recognition element 29.

The present invention has been described based on the embodiments. The embodiments are exemplifications, and it is understood by those skilled in the art that various modifications can be made to the combination of each component and each manufacturing process, and that such modifications are also within the scope of the present invention. is there.

(Example)

In this embodiment, an example is shown in which a carbon nanotube structure in which the surface of a carbon nanotube is covered with an insulating layer of denatured bacterioporous dopsin is formed. FIG. 19 is a diagram showing a method for manufacturing such a carbon nanotube structure 1 17.

First, a purple membrane containing pacteriorhodopsin 102 was dispersed in a dispersion medium (FIG. 19 (a)). As the bacteriococcal dopsin 102, for example, a purple membrane or a bacteriococcal dopsin 102 contained in the purple membrane can be used. Purple membranes can be isolated from halophilic bacteria, such as Halobacterium um salinar um. For separation of the purple membrane, the method described in Methodsin Enzymology, 31, A, p. 667-678 (1974) was used. As the dispersion medium 103, a 33 vZv% DMF (dimethylformamide) aqueous solution was used. As the dispersion medium 103, 33 vZv% DMF (dimethyl Formamide) Not only an aqueous solution but also an aqueous solution of an organic solvent can be used.

To the dispersion of pacteriorhodopsin 102 was added an excess amount of force-pon nanotube 105, and the dispersion was performed for at least 1 hour using an ultrasonic disperser (Fig. 19 (b)). After the dispersion, remaining aggregates of carbon nanotubes 105 were removed. As the carbon nanotube, a multi-layer carbon nanotube manufactured by MTR Ltd. (Closeddendtpepe, diameter: 10 to 200 nm, purification purity: about 95%) was used.

The thus obtained dispersion liquid 107 (FIG. 19 (c)) was gently spread on the liquid surface of the lower liquid liquid 111 set in the water tank using the syringe 109 (FIG. 19 (d)). As a result, a monomolecular film of carbon nanotube 105 was obtained. In this example, Langmuir Trough 113 was used as the water tank, and pure water adjusted to pH 3.5 with HC1 was used as the lower layer liquid 111.

Next, the monomolecular film of the carbon nanotube 105 was allowed to stand still, and the bacteriorhodopsin 102 was interfacially denatured by the interfacial tension of the lower solution 111. In the case of using purple membrane, it is preferable to leave the membrane at room temperature for 5 hours or more until bacteriorhodopsin in the purple membrane is interface-denatured. . In this way, the modified bacteriorhodopsin 115 is wound around the side surface of the force-feeding nanotube 105 (Fig. 19 (f)).

The carbon nanotube structure 11.7 formed on the water surface was transferred to a TEM observation grid together with the supporting monomolecular film, dried, and observed as it was by a TEM (transmission electron microscope). FIG. 20 is a view showing a TEM image of the carbon nanotube structure 1 17.

As shown in FIG. 20, a layer of denatured bacterial mouth dopsin 115 was uniformly formed on the surface of carbon nanotube 105. The layer thickness was about 3 nm.

Thus, in this example, bacteriorhodopsin 102 and carbon nanotubes 105 were dispersed and developed on a liquid surface by a simple method. A carbon nanotube structure 1 17 was successfully produced.

An optical sensor can be stably manufactured by attaching the obtained carbon nanotube structure 117 on a substrate.

Claims

The scope of the claims

1. The substrate and

A source electrode and a drain electrode formed on the substrate,

A carbon nanotube for electrically connecting the source electrode and the drain electrode,

A layer provided on top of the carbon nanotube, the polarization being generated by light reception;

An optical sensor comprising:

2. The optical sensor according to claim 1, wherein the layer in which polarization is generated by receiving light mainly includes molecules that are polarized by receiving light.

3. The optical sensor according to claim 1, wherein the layer in which polarization is generated by the light reception includes bacteriococcal dopsin.

4. The optical sensor according to claim 1, further comprising an insulating layer on a surface of the carbon nanotube.

5. The optical sensor according to claim 4, wherein the insulating layer is a polymer layer.

6. The optical sensor according to claim 4, wherein the insulating layer is a layer in which a polymer is wound around a side surface of the carbon nanotube.

7. forming a source electrode and a drain electrode on the surface of the substrate; connecting the source electrode and the drain electrode with carbon nanotubes;

Forming a layer on the carbon nanotube on which polarization is generated by light reception;

A method for manufacturing an optical sensor, comprising:

8. The method for manufacturing an optical sensor according to claim 7, wherein the step of connecting the source electrode and the drain electrode with carbon nanotubes comprises: Producing an alignment film of carbon nanotubes,

Attaching the alignment film of the carbon nanotubes to the surface of the source electrode and the drain electrode;

Selectively removing carbon nanotubes adhering to regions other than the source electrode, the drain electrode, and a region between the source electrode and the drain electrode.

9. The method for manufacturing an optical sensor according to claim 8, wherein the step of producing an alignment film of a carbon nanotube comprises:

A step of forming, on a liquid surface, a dispersion liquid in which the carbon nanotubes and the coating molecules are dispersed in a dispersion medium to form an insulating layer containing the coating molecules on the surface of the carbon nanotubes. Manufacturing method of the sensor.

10. The method for manufacturing an optical sensor according to claim 9, wherein a polymer is used as the coating molecule, and a polymer layer is formed on a surface of the carbon nanotube.

11. The method for manufacturing an optical sensor according to claim 9 or 10, wherein the protein is denatured by spreading the dispersion in which the protein is dispersed as the coating molecule on a liquid surface, and the denatured protein. Is wound around the side surface of the carbon nanotube.

12. The method for manufacturing an optical sensor according to claim 11, wherein the protein is a membrane protein.

13. The method for producing an optical sensor according to any one of claims 8 to 12, wherein the step of forming an alignment film of carbon nanotubes comprises: dispersing a dispersion liquid containing carbon nanotubes and bacteriorhodopsin on a liquid surface. A method for manufacturing an optical sensor, comprising the steps of:

14. The method for manufacturing an optical sensor according to any one of claims 7 to 13. The method of manufacturing an optical sensor, wherein the step of forming a layer in which polarization is generated by light reception includes a step of forming a monomolecular film or a stacked film of molecules in which polarization is generated by light reception.

15. In the method of manufacturing an optical sensor according to any one of claims 7 to 14, the step of forming a layer in which polarization occurs by light reception includes a step of forming an alignment film of bacteriorhodopsin. A method for manufacturing an optical sensor, comprising:

16. The method of manufacturing an optical sensor according to claim 14 or 15, wherein the step of forming a layer in which polarization is generated by light reception includes:

Developing a dispersion containing molecules that are polarized by light reception on the surface of the liquid, and forming an alignment film of molecules that are polarized by light reception;

Attaching the alignment film of molecules polarized by the light reception and the carbon nanotubes, directly or via an insulating layer;

A method for manufacturing an optical sensor, comprising:

17. A method for driving the optical sensor according to any one of claims 1 to 5, wherein a predetermined current is applied between the source electrode and the drain electrode to detect a change in a current value. A method for driving an optical sensor, comprising detecting the intensity of light received by the optical sensor.

18. A method for detecting light intensity using a sensor including a layer polarized by light reception and a carbon nanotube provided in close proximity to the layer, comprising applying a voltage to the force-bon nanotube, A light intensity detection method comprising: detecting a change in a current value in the carbon nanotube caused by light reception of a layer; and detecting a light intensity from the change in the current value.

1 9. In the light intensity detecting method according to claim 1 8 claims, the light intensity layers polarized by the light receiving is characterized in that it comprises a bacteriophage port Dopushin detection method _c