Patent Application
20110000703
The present invention concerns nanodevices using a carbon nanotube (subsequently described as “CNT”) as a material, CNT supporting bodies such as CNT holding bodies that are necessary for the production processes of said nanodevices, and their production methods.
Recently, carbon nanotube (CNT) has been attracting attention as a new material for causing a rapid progress in nanotechnology. As examples of nanodevices in which a CNT is used as a material, there are quantum effect transistors using a CNT as a circuit element, and CNT probes for atomic force microscopes, among others.
In the following, a CNT probe is explained as an example of CNT nanodevices. Scanning probe microscopes (SPM) that can detect physical property information of a specimen surface at atomic level, such as scanning tunneling microscopes (STM) and atomic force microscopes (AFM), are being developed. To obtain physical property information of a specimen surface by means of an SPM, a probe is necessary that detects the information by contacting the specimen surface directly. In addition, AFM, which is one type of SPM, can measure the surface unevenness of a DVD disk in high resolution by means of a CNT probe, and it is a measuring device that is indispensable for surface physical property measurement of DVD disks. Also, an SPM equipped with a CNT probe can be used for measurement of not only the surface configuration of a specimen, but also of the electric and magnetic physical properties among others. For example, a magnetic force microscope (MFM), which is one type of SPM, is used for measuring the magnetic domain structure of a specimen from the magnetic force between a ferromagnetism probe and the specimen.
Conventionally, a probe comprised a silicon cantilever in which a protruded portion is formed on a cantilever portion, and a sharpening processing was done on the tip end of this protruded portion. The sharp tip end of this protruded portion becomes the probe point, and physical/chemical interaction with the specimen surface is detected by contacting this tip end to the specimen surface. Information on the physical properties, such as atomic structure information, magnetic information, functional group information, and electronic information among others, is thus obtained.
It is only natural that the resolution of the physical property information becomes higher as the probe point becomes sharper. However, even if a sharpening processing is done on the tip end of a protruded portion by semiconductor technology, decreasing the diameter of a tip end to less than few tens of nm is difficult by the current engineering level. Under this background, carbon nanotube was discovered. H. Dai and others, in NATURE (Vol. 384, pp. 147-150 (14 Nov. 1996)) (Non-Patent Document 1), proposed a carbon nanotube probe in which a carbon nanotube is bonded to said protruded portion.
Diameter D of a carbon nanotube is about 1 to several tens of nm, and axis length L is several micrometers. Its aspect ratio (L/D) reaches from several hundreds to several thousands, and it has an optimum property as a probe for SPM. It has been put to practical use as a CNT probe in which a CNT is adhered to a protruded portion of the cantilever.
The present inventors already have invented and disclosed two methods for fastening a CNT more strongly to said protruded portion of a cantilever, an indispensable step for production of a CNT probe. The first is a method where a carbon nanotube is coated and fastened onto a protruded portion surface by a coating film, and it has been published as Japanese Patent Laid-Open Bulletin No. JP2000-227435 (Patent Document 1). The second is a method where the base end portion of a carbon nanotube is fused to a protruded portion surface by electron beam irradiation or electric current application, and it has been published as Japanese Patent Laid-Open Bulletin No. JP2000-249712 (Patent Document 2).
[Patent Document 1] Japanese Patent Laid-Open Bulletin No. JP2000-227435
[Patent Document 2] Japanese Patent Laid-Open Bulletin No. JP2000-249712
[Non-Patent Document 1] H. Dai et al., NATURE, Vol. 384, pp. 147-150 (14 Nov. 1996)
In manufacture of a nanodevice, when a function under dynamic load is assumed, as it is for a CNT probe, a highly accurate and strong member fastening technique to a selective nanosize spot area is indispensable. A property of the smallest possible tip end curvature and the least possible damage by abrasion is desired for a probe material for a scanning probe microscope. Because CNT has a diameter of nanometer size and a superior mechanical strength, it can give a much more superior capability than a conventional silicon cantilever.
Now, when a CNT is attached, it is necessary for it to be fastened firmly so that it does not detach from the probe during the probe use by a stress application at the time of scanning or exposure to the atmosphere. The fastening treatment of a CNT, as indicated in Patent Document 2 for example, is done inside a scanning electron microscope (SEM) by beam-irradiating an electron beam onto the fastening portion area were the CNT has been placed, decomposing the residual hydrocarbon in the environment, depositing amorphous carbon (a-C) in a vicinity of the CNT root, and thus fastening the CNT.
However, when amorphous carbon is used for fastening a CNT, the low electroconductivity of amorphous carbon becomes a serious flaw. Among nanodevices using a CNT, there are many that require a high electroconductivity. As for examples, there are a scanning tunneling microscope (STM), which is one type of said SPM, and an electronic circuit in which a CNT is used as a nanoelectronic part such as a nanotransistor. However, because amorphous carbon has no crystallinity, and moreover, because atoms whose electronic structure is sp3 are present in a large quantity among the carbon atoms forming the amorphous carbon, a large number of electrons are localized, and do not contribute to an electric current. Therefore, amorphous carbon has a low electroconductivity, and it is unsuitable for said uses that require a high electroconductivity. To increase the performance of said nanodevice, it is necessary to make the binding site with the CNT highly electroconductive.
Also, as for a CNT that is amenable to the fastening treatment by the above fastening method, a multilayered CNT with diameter of several nanometers is the limit because of the resolution of SEM. That is to say, using the above fastening method, a probe using a small-diameter CNT, such as one with a monolayer or two layers, cannot be produced. Also, a transmission electron microscope (TEM) is capable of a high resolution observation in comparison with a normal SEM, but because an observation is done under a high vacuum (approximately 10−5 Pa), amorphous carbon does not deposit in a vicinity of the CNT root even when an electron beam is irradiated, and a CNT cannot be fastened.
Therefore, the object of the present invention is to offer a CNT nanodevice that uses a small-diameter CNT such as one of monolayer or two layers, and a CNT supporting body such as a CNT holding body that is necessary for a production process of such device, together with their production method, by solving the above problems, and making a strong CNT fastening treatment possible under a high vacuum state with an extremely few residual hydrocarbon in the environment.
The first form of the present invention is, in a CNT supporting body in which a CNT is fastened to a supporting portion of said CNT supporting body, said CNT supporting body, characterized in that a bottom graphite layer is formed on a surface of said supporting portion, a fastening portion of said CNT is arranged to contact a surface of said bottom graphite layer, and furthermore, said CNT is fastened to said supporting portion by a top graphite layer coating said fastening portion.
The second form of the present invention is, in a CNT supporting body in which a CNT is fastened to a supporting portion of said CNT supporting body, said CNT supporting body, characterized in that a fastening portion of said CNT is arranged on a surface of said supporting portion, a top graphite layer is formed on said surface of said supporting portion of and near said fastening portion, and said CNT is fastened to said supporting portion by said top graphite layer coating said fastening portion.
The third form of the present invention is the CNT supporting body of the first or second form, wherein at least an amorphous carbon layer is formed at an outside surface of said top graphite layer.
The fourth form of the present invention is the CNT supporting body of any one of the first to third forms, wherein said supporting body is a cantilever, said supporting portion is a protruded portion formed to be protruded from said cantilever, said fastening portion is a base end portion of said CNT, and said CNT supporting body is a CNT probe in which said base end portion of said CNT is fastened to said protruded portion, and a tip end portion of said CNT is protruded from said protruded portion.
The fifth form of the present invention is the CNT supporting body of any one of the first to third forms, wherein said supporting body is a circuit board, said CNT is a circuit element, said supporting portion is a joining portion where said CNT is joined, said fastening portion is an end portion of said CNT, and said CNT supporting body is a CNT circuit board in which said end portion of said CNT is fastened to said joining portion.
The sixth form of the present invention is the CNT supporting body of any one of the first to third forms, wherein said supporting body is a knife edge, said supporting portion is an edge portion from which said CNT is protruded, said fastening portion is an end portion of said CNT, and said CNT supporting body is a CNT cartridge in which said end portion of said CNT is fastened to said edge portion.
The seventh form of the present invention is the CNT supporting body of any one of the first to sixth forms, wherein a site in which said CNT is fastened to said supporting portion by said top graphite layer and/or said bottom graphite layer is one place or more.
The eighth form of the present invention is, in a production method of a CNT supporting body in which a CNT is fastened to a supporting portion of said supporting body, said production method of a CNT supporting body, characterized in that a carbon material layer is formed on a surface of said supporting portion, a carbon material comprising a carbon molecule or an organic matter being deposited in said carbon material layer, a fastening portion of said CNT is brought into contact with a surface of said carbon material layer for positioning said fastening portion on said surface, an electron beam or an ion beam is irradiated on said fastening portion and/or a region subject to irradiation at a vicinity of said fastening portion to decompose said carbon material layer, and said fastening portion is coated by a carbon film formed by said decomposition so that said CNT is fastened to said supporting portion.
The ninth form of the present invention is, in a production method of a CNT supporting body in which a CNT is fastened to a supporting portion of said supporting body, said production method of a CNT supporting body, characterized in that a fastening portion of said CNT is positioned on a surface of said supporting portion, a carbon material layer is formed by depositing a carbon material comprising a carbon molecule or an organic matter on said surface of said supporting portion on or near said fastening portion, said carbon material layer is decomposed by irradiating an electron beam or an ion beam on said fastening portion and/or a region subject to irradiation at a vicinity of said fastening portion, and said CNT is fastened to said supporting portion by coating said fastening portion with a carbon film formed by said decomposition.
The tenth form of the present invention is the production method of a CNT supporting body of the eighth or ninth form, wherein said carbon material layer is formed by positioning said carbon material of a predetermined mass in a container, putting said supporting body in said container then sealing said container, vaporizing said carbon material by heating said container, and depositing said carbon material on a surface of said supporting body including said supporting portion.
The eleventh form of the present invention is the production method of a CNT supporting body of the tenth form, wherein a carbon material solution of a predetermined concentration is prepared in which said carbon material is mixed in a solvent, a predetermined volume of said carbon material solution is poured into said container, said solvent is removed from said container by an application of heat, and said carbon material of a predetermined mass is caused to remain and be arranged in said container.
The twelfth form of the present invention is the production method of a CNT supporting body of the tenth or eleventh form, wherein said carbon material adhered on said surface of said CNT supporting body is removed by washing said CNT supporting body with a washing solvent or heating said supporting body, after said fastening portion of said CNT has been fastened to said supporting portion by coating with said carbon film.
The thirteenth form of the present invention is the production method of a CNT supporting body in any one of the eighth to eleventh forms, wherein said carbon film is an amorphous carbon film or a graphite film.
The fourteenth form of the present invention is the production method of a CNT supporting body of any one of the eighth to thirteenth forms, wherein said carbon molecule is a fullerene or a metal-including fullerene.
The fifteenth form of the present invention is the production method of a CNT supporting body of any one of the eight to thirteenth forms, wherein said organic matter includes a component aside from carbon, and said carbon film is formed by said decomposition during which said component aside from carbon is vaporized and dispersed.
The sixteenth form of the present invention is the production method of a CNT supporting body of any one of the eighth to fifteenth forms, wherein said supporting body is cantilever, said supporting portion is a protruded portion formed to be protruded from said cantilever, said fastening portion is a base end portion of said CNT, and said CNT supporting body is a CNT probe in which said base end portion of said CNT is fastened to said protruded portion so that a tip end portion of said CNT projects from said protruded portion.
The seventeenth form of the present invention is the production method of a CNT supporting body of any one of the eighth to fifteenth forms, wherein said supporting body is a circuit board, said CNT is a circuit element, said supporting portion is a joining portion to which said CNT is joined, said fastening portion is an end portion of said CNT, and said CNT supporting body is a CNT circuit board in which said end portion of said CNT is fastened to said joining portion.
The eighteenth form of the present invention is the production method of a CNT supporting body of any one of the eighth to fifteenth forms, wherein said supporting body is a knife edge, said supporting portion is an edge portion from which said CNT protrudes, said fastening portion is an end portion of said CNT, and said CNT supporting body is a CNT cartridge in which said end portion of said CNT is fastened to said edge portion.
According to the first form of the present invention, a bottom graphite layer is formed on a surface of a supporting portion, and furthermore, a CNT is fastened by a top graphite layer that coats a fastening portion of said CNT. Therefore, said CNT and said supporting portion become electrically conductive through the graphite layers having a high electroconductivity. By this, parts that are high efficient can be provided for uses that require an electron conduction, and these parts can be used for producing highly sensitive and highly efficient electronic and electric apparatuses.
Because graphite is formed only from carbon atoms having the sp2 electronic structure, free electrons are present in high density. Also, its crystallinity is high in comparison with amorphous carbon, and therefore, the mobility of said free electrons is high. Furthermore, because the structure of graphite resembles that of CNT, when graphite bonds with a CNT, a strong contact may be attained through the affinity between the graphite and the CNT. Therefore, an obstruction of the electron movement at the interface of said bond can be lessened. For these reasons, the electroconductivity is high within a graphite layer and at the interface between a CNT and the graphite layer. When said CNT is used as a conduction material of electrons that comprise electricity, this high electroconductivity is useful in lowering the loss of said electricity upon guiding the conducted electrons that comprise said electricity to said supporting portion.
For example, when said CNT is used as a probe of a scanning tunneling microscope (STM), for a tunneling current that conducts through said probe to be detected, it is necessary that said tunnel current is guided to the supporting portion of said probe. If the electroconductivity at the joining portion between said probe and said supporting portion is low, the loss of said tunnel current becomes high, and therefore, the sensitivity of said STM decreases. By making said joining portion a graphite layer, the loss of said tunnel current can be lowered, and therefore, a highly sensitive STM can be provided.
Also, when a CNT is used as a circuit element in an electric circuit, for said electric circuit to be operational, it is necessary that the electric current conducting through said CNT be guided to the supporting portion supporting said CNT. When the electric resistance of the binding portion between said CNT and said supporting portion is high, the electric current guided to said supporting portion decreases, and therefore, the performance of said electric circuit decreases. By making said joining portion a graphite layer, a drop in the electric current at said joining portion can be prevented, and therefore, a highly efficient electric circuit can be provided.
According to the second form of the present invention, the top graphite layer is coated over the surface of a fastening portion of a CNT and the surface of a supporting portion at its vicinity, and said CNT is fastened to said supporting portion by said graphite layer. Because of this, by means of a simplified structure, one can obtain a CNT supporting body in which the electroconductivity of said CNT and the binding site of said support member is high.
In the first form, a bottom graphite layer and a top graphite layer are present, and the electrical conduction and the adhesion between said CNT and said supporting member depend upon both graphite layers. However, when the top graphite layer is in contact directly with the supporting portion and also with the CNT, said electrical conduction and said adhesion can be attained from only said top graphite layer, and therefore, a bottom graphite layer is not necessary. Therefore, in this form, said top graphite layer comes into contact directly with said CNT and said support member, and the structure of said CNT supporting body is simplified.
In this form, it is not necessary for said CNT and said supporting member to be in a direct contact. For example, amorphous carbon may exist between said CNT and said supporting portion. Under this condition, because said amorphous carbon has a low electroconductivity, the electrical conduction between said CNT and said supporting portion becomes dependent upon said top graphite layer. Therefore, high electroconductivity of said top graphite layer becomes even more important.
According to the third form of the present invention, because an amorphous carbon layer is formed at least on an outside surface of a top graphite layer, said graphite layer is reinforced by said amorphous carbon layer. Therefore, a joining portion between a CNT and a supporting portion that is mechanically strong and highly electroconductive can be obtained.
The amorphous carbon layer here is formed on the top graphite layer, at the surface at the opposite side (outside surface) of the surface that is in contact with the supporting portion (inside surface). However, said amorphous carbon layer may be formed continuously beyond the periphery of said graphite layer. Also, said amorphous carbon layer may come into a direct contact with said supporting portion and said fastening portion. In this case, said amorphous carbon layer provides reinforcement to the bond with said supporting portion and said fastening portion of said graphite layer.
According to the fourth form of the present invention, the supporting portion is a protruded portion formed to be protruded from the cantilever, the fastening portion is a base end portion of a CNT, and the tip end portion of said CNT is a CNT probe. Because of this, graphite that is a high electroconductivity material is present as a joining portion between said CNT and said supporting portion, and therefore, a scanning probe microscope (SPM) having a high sensitivity can be obtained.
Among said SPMs, as for those that examine physical properties from electrical characteristics, there exist a scanning tunneling microscope (STM), a Kelvin probe force microscope (KFM), and an electrostatic force microscope (EFM), among others.
Just as described in the explanation of the first form, to obtain a high sensitivity in these SPMs, it is necessary that the probe, the cantilever, and their joining portion are highly electroconductive. Therefore, the graphite layer in the present invention can be used to obtain high electroconductivity of said joining portion, and furthermore, to join strongly the CNT that is said probe and the supporting portion that is the protruded portion of the cantilever.
According to the fifth form of the present invention, because said supporting body is a circuit board, said CNT is a circuit element, and said supporting portion is a joining position where said CNT is joined, a high-performance electronic circuit can be obtained even if the utilized electric current is minute.
CNT can be used as electronic parts such as a transistor, a diode, a capacitor, and an inductor among others. Because these electronic parts are minute, it is anticipated that a high performance can be achieved by using a lower electric current than electronic parts in which a silicon p-n junction is used.
However, if an electric current loss occurs at the joining portion between these CNT circuit elements and the board, the high performance of these CNT circuit elements cannot be achieved. By using a graphite layer of the present invention as said joining portion, a highly efficient CNT circuit whose electric current consumption is minute can be obtained.
According to the sixth form of the present invention, because said supporting body is a knife edge, said supporting portion is an edge portion from which a CNT protrudes, and said CNT supporting body is a CNT cartridge, said CNT is fastened stably on said CNT cartridge, and therefore, a movement of said CNT to the protruded portion of cantilever is facilitated.
In a CNT cartridge, the CNT is usually set up in a non-adhered state on the edge portion. However, under this condition, a possibility exists where said CNT falls off during the knife edge movement. By fastening said CNT to said edge portion, the movement of said CNT to another supporting portion can be made easy and sure. After the movement, both supporting portions are separated by cutting said CNT with an electron or ion beam.
According to the seventh form of the present invention, because the site where the CNT is fastened to the supporting portion is one place or more, the flexibility in production can be improved.
To obtain a CNT supporting body on which a high electroconductivity is present between the CNT and the supporting portion, and the CNT is fastened strongly to the supporting portion, it is not necessary that the graphite layer is formed on the entire surface of said supporting portion, and also, it is not necessary for the graphite layer to be formed on the entire area where the CNT exists on the surface directly above said supporting portion. That is to say, to obtain a CNT supporting portion of the present invention, it may be formed only partially on said surface and said area.
Also, it is not necessary for said graphite layer to be formed continuously. Even if said graphite layer is formed in an island shape in said area, a strong joining portion with a high electroconductivity can be obtained. Such island-like graphite layer can be obtained in, for example, the eighth form, by irradiating an electron or ion beam at two sites or more.
The graphite layer in this form can be more easily produced than the graphite layer formed on the entirety of said surface or said area, and moreover, a strong fastening with a high electroconductivity can be obtained.
According to the eighth form of the present invention, a carbon material layer is formed on a surface of said supporting portion, a carbon material comprising a carbon molecule or an organic matter being deposited in said carbon material layer, a fastening portion of said CNT is brought into contact with a surface of said carbon material layer for positioning said fastening portion on said surface, an electron beam or an ion beam is irradiated on said fastening portion and/or a region subject to irradiation at a vicinity of said fastening portion to decompose said carbon material layer, and said fastening portion is coated by a carbon film formed by said decomposition so that said CNT is fastened to said supporting portion. Because of this, the carbon structure can be rebuilt, and said fastening portion can be coated by the decomposition of said carbon material layer comprising carbon, which also comprises said CNT, and said CNT can be fastened strongly to said supporting portion. Therefore, a strong CNT fastening treatment becomes possible by doing the decomposition of said carbon material layer under an extremely high vacuum with very little residual hydrocarbon in the environment, while doing a high resolution observation inside a transmission electron microscope (TEM) in which observation is done under high vacuum (to 10−5 Pa). Moreover, through the CNT fastening treatment under a high resolution observation, production of a CNT supporting body that could not be realized by a conventional fixed method, such as a CNT nanodevice using a small-diameter CNT such as a monolayer or two layers, becomes possible. By the way, as for an electron microscope for use in a fastening treatment, one that has a high-resolution performance just like said TEM is preferable. A high-resolution SEM, which can make an observation under high vacuum in a similar manner as a TEM, can also be used.
A CNT supporting body to which the present invention can be applied is a CNT measuring probe comprising a CNT probe in which the base end portion of the CNT is fastened to the protruded portion of the cantilever, and a CNT nanodevice such as a quantum effect transistor in which a CNT is fastened and mounted on a circuit board as a circuit element. Also, the present invention can be applied to a CNT holding body for supporting a single or multiple CNTs and transporting them at a given position during a device production process.
The present inventors, as a result of examining various kinds of carbon substance materials, obtained a knowledge that fullerene (Cn: n≧60) is favorable as said carbon molecule. For example, in the case of fullerene C60, an electron beam-induced reaction is caused by an irradiation of, for example, an electron beam, the spherical shell-like structure of the C60 molecules disintegrates and transforms into a layered amorphous structure, a carbon structure reconstruction is caused at the center of the electron beam irradiation area, the carbon atoms in the irradiation area bond covalently, and fastening of a CNT becomes possible. Furthermore, it became clear that a transformation into a graphite (black lead) structure occurs when an electron beam irradiation is done. From this knowledge, fullerene makes it possible to give an electrical conduction property to the deposited matter of said fastening portion, and it is suitable for a CNT supporting body. Also, the irradiation area can be formed selectively into an amorphous or a graphite structure by an adjustment of the electron beam irradiance. In particular, it can be transformed into an area to which an electrical contact is possible by the formation of the graphite layer. Therefore, a wide development in application becomes possible in nanodevices among others.
In said eighth form, the fastening portion of said CNT is positioned after forming said carbon material layer on the surface of said supporting portion, but the present invention also includes a form in which said carbon material layer is formed after placing said fastening portion. That is to say, according to the ninth form of the present invention, a fastening portion of said CNT is positioned on a surface of said supporting portion, a carbon material layer is formed by depositing a carbon material comprising a carbon molecule or an organic matter on a surface or surfaces of said fastening portion and/or of said supporting portion at a vicinity of said fastening portion, said carbon material layer is decomposed by irradiating an electron beam or an ion beam on said fastening portion and/or a region subject to irradiation at a vicinity of said fastening portion, and said CNT is fastened to said supporting portion by coating said fastening portion with a carbon film formed by the said decomposition. Because of this, just as in the eighth said form, said CNT can be fastened strongly to said supporting portion by rebuilding the carbon structure through the decomposition of said carbon material layer, and coating said fastening portion positioned beforehand on the surface of said supporting portion.
According to the tenth form of the present invention, said carbon material layer is formed by positioning said carbon material of a predetermined mass in a container, putting said supporting body in said container then sealing said container, vaporizing said carbon material by heating said container, and depositing said carbon material on a surface of said supporting body including said supporting portion. Because of this, for example, when fullerene C60 is used as said carbon material, during the sublimation of C60 by heating at 400° C., it becomes possible to control the thickness of the deposited C60 molecule film by varying the time (sublimation time) in which this heating temperature is maintained and the quantity of the sealed C60. Therefore, according to the present embodiment, said carbon material layer for fastening a CNT can be formed, compliant to various CNT nanodevices.
According to the eleventh form of the present invention, a carbon material solution of a predetermined concentration is prepared in which said carbon material is mixed in a solvent in said carbon material solution, a predetermined volume of said carbon material solution is poured into said container, said solvent is removed from said container by an application of heat, and said carbon material of a predetermined mass is caused to remain and be arranged in said container. Because of this, the concentration of said carbon material solution can be adjusted based on the solution method, the minimum quantity of said carbon material can be deposited on the surface of said supporting body, and a cost saving in the CNT fastening treatment can be sought. Especially, because fullerenes are relatively expensive carbon materials, reduction of materials cost can be realized by implementing the present embodiment.
According to the twelfth form of the present invention, said carbon material adhered on a surface of said CNT supporting body is removed by washing said CNT supporting body with a washing solvent or heating said supporting body, after said fastening portion of said CNT has been fastened to said supporting portion by coating with said carbon film. Because of this, the carbon material unnecessary for the fastening treatment can be collected and recycled by said washing or said removal, and a reduction in the production cost of a CNT supporting body can be achieved.
According to the thirteenth form of the present invention, by using as said carbon film an amorphous carbon film with a superior CNT fastening strength or a graphite film that has an electrical conductivity as well as a fastening strength, a CNT supporting body production method suitable for a CNT probe or a CNT nanodevice can be provided.
According to the fourteenth form of the present invention, a stronger CNT fastening can be realized by using said fullerene Cn as said carbon molecule. Also, by using a metal inclusion fullerene Cn-M (M: a metallic element), a CNT fastening and an endowment of electrical conduction property by the inclusion metallic element can be done.
According to the fifteenth form of the present invention, said organic matter includes a component aside from carbon, and said carbon film is formed by said decomposition during which said component aside from carbon is vaporized and dispersed. Because of this, just as with the carbon material layer from said carbon molecule, the said carbon film which is obtained from said organic matter can coat said fastening portion, and fasten said CNT strongly to said supporting portion, by rebuilding the carbon structure through the decomposition of said carbon material layer that, just like said CNT, comprises carbon. A carbon material solution of a predetermined concentration is prepared by mixing said organic matter into a solvent. When the solvent is removed by application of heat, there is a possibility that it evaporates excessively if the boiling point is low. Because of this, one with a high boiling point is preferable, and as the liquid, for example, benzene can be used. Also, for the organic substance, a substance that can form a nanosized film on said support surface is preferable. Other than an organic EL (electroluminescence) material such as diamine or anthracene, for example, an aromatic compound such as naphthalene, phenanthrecene, pyrene, and perylene among others, organic pigment molecules such as an organic molecule semiconductor, a cyanine dye, and beta-carotene among others, and an organic thin film materials such as porphyrin, sexiphenyl, sexithienyl, polytetrafluoroethylene, pentacene, paraffin, diacetylene, and phthalocyanine among others can be used. Formation of an organic substance into a thin film can be done by publicly known formation technique and vacuum deposition technique of oriented organic molecule films.
According to the sixteenth form of the present invention, in production of a CNT probe in which the base end portion of said CNT is fastened to said protruded portion formed to be protruded from said cantilever and the tip end portion of said CNT is protruded from said protruded portion, a small-diameter CNT can be fastened more strongly by forming said carbon material layer on said protruded portion. A more minute and highly precise CNT probe capable of a highly precise local measurement, which is a probe that is suitable for an SPM such as an MFM and an AFM, can be provided.
The present invention can also be applied to production of a nanodevice such as a quantum effect transistor. According to the seventeenth form of the present invention, a nanodevice comprising a CNT circuit board can be produced, in which said carbon material layer is formed at said joining position of said supporting portion, said CNT is a circuit element with a minute configuration, and the end portion of said CNT is fastened strongly to said joining portion of said circuit board.
The present invention can also be applied to a CNT holding body (knife edge) for CNT probe production shown in said Patent Document 1 or 2. That is to say, according to the eighteenth form of the present invention, for example, in a case where a CNT tip end portion is adhered to a knife edge, a CNT base end portion is extended from the knife point of said knife edge, and said CNT base end portion is fastened to the protruded portion of the cantilever, a CNT cartridge in which the end portion of said CNT is fastened more rigidly to said edge portion of said knife edge can be produced, by forming said carbon material layer on said fastening portion of said supporting portion.
In the following, the embodiments of the CNT supporting body concerning the present invention and its production method are explained in detail according to figures.
The present embodiment is a CNT probe in which the base end portion of a CNT is fastened to a protruded portion formed in a protruded manner on a cantilever, the tip end portion of said CNT projecting from said protruded portion, and an example of its manufacturing process.
Next, an enclosure treatment of silicon cantilever material 4 is done (see (6D) and (6E)). The aperture side of quartz tube 1 is connected to aspiration port 6, and a vacuum is pulled. Furthermore, a vacuum enclosure is done by heating and melting the vicinity of aspiration port 6 of quartz tube 1 with burner 7. Fullerene 3 is sublimated by heating at 400° C. quartz tube 1 whose aperture side has been vacuum-sealed (8). The sublimated fullerene 3 passes through glass wool materials 5, deposits on the surface of silicon cantilever material 4, and forms a carbon material layer. During this deposition process, impurities contained in fullerene 3 are removed through glass wool materials 5.
Through the above formation process, carbon material layer can be deposited and formed on the surface of silicon cantilever material 4. Below, verification experiments of the carbon material layer formation condition are explained. The verification experiments were done by changing the mixture concentration of fullerene C60 with respect to toluene, as well as the sublimation time (with heat application of 400° C.).
First, deposition of the fullerene molecular layer (carbon material layer) obtained by the above formation process was confirmed.
Furthermore, a verification of the carbon material layer formation condition was done on an object on which carbon material layer is formed, by forming a carbon material layer of the above fullerene on a knife edge for use in a CNT cartridge.
The formation process of a carbon material layer on knife edge 11 is explained. First, after a concentration adjustment of fullerene C60 is done, in the same manner as the steps in (6A) and (6B) of
The deposition state of the fullerene molecule layer (carbon material layer) obtained by the above formation process on the surface of knife edge 11 comprising a silicon piece was confirmed. In (10A) and (10B) of
Based on the above experimental results, production of fullerene molecule layers that were as thin as possible was attempted, varying the carbon material layer formation condition in various ways.
Next, a CNT fastening treatment using a carbon material layer concerning the present invention is explained. The fastening treatment is done by placing a CNT on the fullerene molecule layer shown in
To compare with the above experimental results, an irradiation experiment was done, using a fullerene molecule layer obtained by a different carbon material layer formation condition.
From the experiments in which the structural change process was observed with varying irradiation condition of the electron beam, a morphology transformation in three general stages (movement of fullerene molecules, structure destruction, structure reconstruction) was observed when electron beam irradiation was done on the fullerene molecule film. When an electron beam with a current density of 5×10−13 A/nm2 was irradiated in a region of a diameter of 15 nm on the fullerene molecule layer, an increase of film thickness was confirmed at the edge of the irradiation area after being irradiated for about 60 seconds (quantity of implantation (dose quantity): 2×108 electrons/nm2). In other words, it can be understood that the fullerene C60 molecules outside the radiation range had aggregated to the area where the energy was high. At that time, at the center portion of the irradiation area, the spherical shell-like structure of the C60 molecules began to break, and an amorphous condition was assumed. 120 seconds after the start, a carbon structure reconstruction occurred at the center of the irradiation area. At the part where amorphous carbon had deposited, a layer structure was observed. Although the crystallinity was imperfect, the correspondence to the graphite structure was confirmed from the spacing. From this result, it is thought that the deposited matter after irradiating an electron beam for 120 seconds (dose quantity: 4×108 electrons/nm2) is electrically conductive. In this state, it becomes possible for a CNT to be fastened.
(19B) and (19C) of
(19D), (19E), and (19F) of
As discussed above, upon using a molecule layer of fullerenes C60 in a carbon material layer, it undergoes an electron beam-induced reaction through irradiation of an electron beam, and the spherical shell-like structure of the Co molecules disintegrates and is transformed into a layered amorphous structure. It causes a reconstruction of the carbon structure at the center of the electron beam irradiation area, the carbon atoms in the irradiation area bond covalently, and thus a CNT fastening becomes possible. Furthermore, because the transformation into a graphite (black lead) structure upon an irradiation of an electron beam became clear, fullerene allows a deposited matter of said fastening portion to have an electrical conductivity, and therefore it is suitable for a CNT supporting body. Also, the irradiation area can be formed selectively into an amorphous or graphite structure by an adjustment of the electron beam irradiance. In particular, by the formation of a graphite layer, a modification can be made into an area where an electrical contact becomes possible, and a wide development in applications in nanodevices and such becomes possible.
In the following, steps for CNT fastening to a protruded portion of a cantilever using the CNT fastening method of the present embodiment is explained.
As shown in (16B) of
(20E) and (20F) of said figure are enlarged photographs, and they are, respectively, a TEM photograph of the vicinity of the irradiation area after the CNT placement and before the electron beam irradiation, and a TEM photograph of the vicinity of said area following the electron beam irradiation for 120 seconds. The fullerene before the irradiation was observed to have transformed into a material having a layer structure after the irradiation. The spacing in this layer structure coincides with the spacing in graphite. As thus described, a CNT can be fastened firmly without impairing electroconductivity, by depositing amorphous carbon on top of the graphite layer so as to cover the CNT root part.
The CNT supporting body production method concerning the present embodiment can be applied to production of not only CNT probes, but also nanodevices such as quantum effect transistors.
The present invention is not limited to the embodiments described above. Various modifications, design alterations, and others that do not involve a departure from the technical concept of the present invention are also included in the technical scope of the present invention.
According to the present invention, a highly precise CNT probe, a CNT nanodevice such as a quantum effect transistor, and a CNT holding body for use in device production can be provided, in which a minute CNT has been packaged and incorporated. Because of this, highly efficient electric and electronic devices utilizing the minuteness and high electroconductivity of CNTs can be provided. Therefore, a wide usage and high functionalization of these apparatuses can be expected.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-045920 | Feb 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/053496 | 2/26/2009 | WO | 00 | 8/26/2010 |
