Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2000-03-13
2001-12-25
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S692100, C428S690000, C428S900000, C204S192200, C204S192220, C204S192240, C204S192250
Reexamination Certificate
active
06333111
ABSTRACT:
DISCLOSURE OF THE INVENTION
This invention relates to a convenient and efficient method for producing spherical layered aluminum fine particles, the surface layer of which is covered with several nanometers of alumina, the interior of which is metallic aluminum fine crystals, and which are useful for an element of a quantum device that utilizes a single electron tunneling phenomenon. More particularly, the present invention relates to a method for producing layered aluminum fine particles using a fine particle generating device that features magnetron sputtering; layered aluminum fine particles obtained by this method; and the application of these layered aluminum fine particles to a single electron tunneling device element.
BACKGROUND OF THE INVENTION
The production of elements on the sub-micron order is considered the limit with today's semiconductor technology for increasing density and integration, and some technique completely different from conventional fine processing technology (such as lithography) is needed in order to create even finer elements. It is believed that if the elements of a device could be smaller than sub-micron, then it would be possible to fabricate a quantum device (single electron tunneling device) that would control individual electrons, rather than controlling the flow of groups of electrons as in semiconductors produced up to now, and this has become an area of fervent research of late (publication 1).
The layered aluminum fine particles obtained with the present invention are single crystals of metallic aluminum whose surface is covered with an oxide insulator (alumina), and when these are placed on a substrate, it should be possible to create an electronic device based on single electron tunneling, which utilizes the passage of electrons one by one through this insulation layer (publication 2: an example is given of single electron tunneling in metallic ultrafine particles placed on a substrate). Therefore, these layered aluminum fine particles are believed to contribute greatly to obtaining an ultrafine semiconductor intended for a single electron tunneling quantum device. Most conventional methods for manufacturing fine particles containing aluminum involved evaporation in a gas method (publication 3: the generation of ultrafine particles by evaporation in a dilute gas method is discussed), but the fine particles obtained with these methods were all fine particles of alumina, and there are no cases of the production of layered aluminium fine particles that can be used for elements in a quantum device that utilizes single electron tunneling, such as are obtained with the present invention.
In view of this, in an effort to solve the above problem, the inventors used a fine particle generating device featuring magnetron sputtering to generate layered aluminum fine particles, and analyzed the particles thus generated using a transmission electron microscope (TEM) and electron beam diffraction. They also examined the dependence of particle size on the shape of the fine particle generating source, the temperature, and so on.
As a result, it was learned that when the distance from the aluminum sputtering target to the aperture attached to the distal end of the generating source is set at about 100 mm, and the aperture vicinity is cooled with liquid nitrogen, layered aluminum fine particles with a diameter of about 5 to 500 nm are generated through the aperture.
Furthermore, the inventors arrived at the present invention upon discovering that when the vicinity of the outlet from the fine particle generating source is not cooled with liquid nitrogen, layered aluminum fine particles the same as those mentioned above can be generated by shortening the distance between the aluminum sputtering target and the aperture to about 30 to 50 mm.
SUMMARY OF THE INVENTION
The present invention provides a method for producing layered aluminum fine particles, and applications to single electron tunneling quantum devices. The present invention further relates to a method for producing spherical metallic aluminum fine particles (layered aluminum fine particles), characterized in that metallic aluminum is supplied into a mixed gas of helium and 1×10
−7
to 3×10
−7
torr water vapor by sputtering induced by argon gas discharge to generate aggregates, after which this product is released into a vacuum to generate single crystals in which the surface layer is covered with alumina; a method for producing layered aluminum fine particles with a particle diameter of 5 to 500 nm, characterized in that the above-mentioned layered aluminum fine particles are placed in a flow of helium gas, released into a vacuum via an aperture, and deposited directly onto a substrate; a method for producing the above-mentioned layered aluminum fine microparticles, wherein the vicinity of the outlet from the particle generating source is cooled with liquid nitrogen, or the distance between the aluminum target and the aperture is set at 30 to 50 mm; layered aluminum fine particles obtained by the above methods; and a single electron tunneling quantum device element that makes use of layered aluminum fine particles obtained by the above methods.
DETAILED DESCRIPTION OF THE INVENTION
An object of the present invention is to provide a convenient and efficient method for producing metallic aluminum fine particles, with which single electron tunneling control is possible, and whose surface layer is an extremely thin insulation layer.
In order to solve the above problem, the present invention is such that metallic aluminum is supplied into a mixed gas of helium and 1×10
−7
to 3×10
−7
torr water vapor by sputtering induced by argon gas discharge to generate aggregates by impact with the helium yielding aluminum fine particles (single crystals). The surface of the fine particles is oxidized into a surface layer of alumina through the action of the trace amount of water vapor contained in the helium gas here, and this is how layered aluminum fine particles are produced. Also, the present invention is a method for producing layered aluminum fine particles with a particle diameter of 5 to 500 nm, characterized in that the above-mentioned particles are placed in a flow of helium gas, released into a vacuum via an aperture, and deposited directly onto a substrate. A preferred embodiment of this is a method for producing layered aluminum fine particles in which the vicinity of the outlet from the particle generating source is cooled with liquid nitrogen, or the distance between the aluminum target and the aperture is set at 30 to 50 mm. Other embodiments of the present invention are the layered aluminum fine particles obtained by the above method, and the application thereof to a single electron tunneling quantum device element.
The present invention will now be described in further detail.
In the present invention, metallic aluminum is supplied into a mixed gas of helium and 1×10
−7
to 3×10
−7
torr water vapor by sputtering induced by argon gas discharge to generate aggregates by impact with the helium yielding aluminum fine particles. After this, the surface layer of the microparticles is converted into alumina through the action of the trace amount of water contained in the helium gas, as a result of which spherical fine particles are generated that are covered with several nanometers of alumina surface layer, and that have metallic aluminum single crystals in the interior. A method for producing fine particle that makes use of a sputter gun is an effective method for producing an actual thin film sample because it allows a large quantity of fine particles to be generated continuously (magnetron sputtering gas aggregation method). This has been proven in Germany by Helmut Haberland (H. Haberland, M. Moseler, Y. Qiang, O. Rattunde, Y. Thurner, and Th. Reiners: Proceedings of the Conference on Beam Proceedings of Advanced Materials, Cleveland, Ohio, USA, pp.
1
-
7
(1995)).
FIG. 1
is a concept diagram of the fine particle sour
Goto Masahiro
Igarashi Kazuo
Murakami Jun-ichi
Tai Yutaka
Tanemura Sakae
Agency of Industrial Science and Technology
Kiliman Leszek
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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