U.S. patent application number 09/939450 was filed with the patent office on 2002-08-29 for ring crystalline body and production method thereof.
Invention is credited to Okajima, Yoshitoshi, Sajiki, Kazuaki, Tanda, Satoshi, Tsuneta, Taku, Yamaya, Kazuhiko.
Application Number | 20020117467 09/939450 |
Document ID | / |
Family ID | 18911189 |
Filed Date | 2002-08-29 |
United States Patent
Application |
20020117467 |
Kind Code |
A1 |
Tanda, Satoshi ; et
al. |
August 29, 2002 |
Ring crystalline body and production method thereof
Abstract
To provide a ring crystalline body, which is a ring crystalline
body with a small diameter and formed with a thin line and capable
of providing electric conduction along the ring, and to provide a
production method of the ring crystalline body. A droplet is stuck
to a surface of a substrate and then the droplet is evaporated to a
discontinuous underlayer ring having an ultrafine three-dimensional
structure on the substrate surface. After that, when a transition
metal dichalcogenide, a transition metal trichalcogenide, or a
low-dimensional conductor as raw material gas is evaporated, a ring
crystalline body comprising the raw material is grown along the
underlayer ring.
Inventors: |
Tanda, Satoshi; (Hokkaidou,
JP) ; Sajiki, Kazuaki; (Kanagawa-ken, JP) ;
Tsuneta, Taku; (Hokkaidou, JP) ; Okajima,
Yoshitoshi; (Hokkaidou, JP) ; Yamaya, Kazuhiko;
(Hokkaidou, JP) |
Correspondence
Address: |
BELL, BOYD & LLOYD, LLC
PO BOX 1135
CHICAGO
IL
60690-1135
US
|
Family ID: |
18911189 |
Appl. No.: |
09/939450 |
Filed: |
August 24, 2001 |
Current U.S.
Class: |
216/2 |
Current CPC
Class: |
C30B 29/46 20130101;
H01L 39/24 20130101; C30B 9/00 20130101; C30B 23/00 20130101; H01L
39/2412 20130101; C30B 11/12 20130101; C30B 29/60 20130101 |
Class at
Publication: |
216/2 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 2001 |
JP |
2001-050188 |
Claims
What is claimed is:
1. A ring crystalline body comprising a circularly continuous
crystalline transition metal dichalcogenide or transition metal
trichalcogenide.
2. A ring crystalline body comprising a circularly continuous
crystalline low-dimensional conductor.
3. The ring crystalline body according to claim 1 or claim 2,
wherein the crystallinity is a single crystal.
4. A production method of a ring crystalline body comprising the
steps of: forming a continuous or discontinuous underlayer ring
having an ultrafine three-dimensional structure in the substrate
surface; and circularly growing a crystal along the underlayer
ring.
5. The production method according to claim 4, wherein the
underlayer ring is formed by sticking droplets of an underlayer
ring material to the substrate surface and evaporating the
droplets.
6. The production method according to claim 4, wherein the crystal
is grown by evaporation.
7. The production method according to claim 4, wherein the crystal
is grown by sputtering.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a ring crystalline body
comprising a circularly continuous crystalline material and a
production method thereof and particularly relates to a finely ring
crystalline body impossible to be produced by a conventional
etching method and a production method thereof.
[0003] 2. Description of the Related Art
[0004] A transition metal dichalcogenide (MX2) or a transition
metal trichalcogenide (MX.sub.3), which is a compound of a
transition metal (M) and a chalcogen (X=S, Se, Te), has drawn
attention since it has been confirmed that the substance has a
variety of electric and magnetic properties of from an insulator, a
semiconductor, a semimetal, to a metal and from ferromagnetic,
anti-ferromagnetic properties to Pauli paramagnetism.
[0005] Further, corresponding to the anisotropy of the crystal
structure and the electron structure of the substance, a
low-dimensional conductor which is a compound showing a high
electric conductivity in the one-dimensional or two-dimensional
direction, has the following characteristics: its property is
transformed (Peiers transition) from a metallic property to an
insulator at a low temperature; the maximum electric resistivity
appears at a low temperature and owing to it, super period lattice
strain (electric charge density wave) is caused: and Kohn anomaly,
that the modulus of elasticity is considerably lowered by lattice
vibration in specified cycles, takes place. A low-dimensional
conductor having these characteristic physical properties, which a
general three-dimensional conductor of such as a metal does not
have, has been expected to be applied for a variety of fields.
[0006] Further, the crystalline body comprising a continuously
circular crystalline ring is used as, for example, a
superconducting quantum interference device (SQUID). The SQUID is a
superconductor-based magnetic sensor with high sensitivity and is
capable of measuring extremely ultrafine magnetic flux density as
extremely low as 10.sup.-15 to 10.sup.-12 T by using Josephson
device in which a superconductor is weakly bonded and the SQUID is
used for measuring the magnetic field generated following the
activities of living bodies.
[0007] The ring crystalline body to be used for the SQUID has
conventionally been produced by forming a thin film comprising a
three-dimensional conductor with a prescribed size on the surface
of a substrate by a conventional thin film production method and
etching the thin film in ring-like shape.
[0008] In the production of SQUID, it is made possible to form a
fine ring with the diameter of about several .mu.m owing to the
progress of the etching technique. However, even although the
present etching technique makes it possible to narrow the diameter
of the ring, it can make the line width of the ring at thinnest
about 100 nm and further thinner width has therefore been expected.
Also, the method of etching the thin film has a problem that the
method is accompanied with much waste to make it difficult to
reduce the cost.
[0009] Further, it has been well known that a superconductive
material such as NbSe.sub.3 which is one of the above described
transition metal trichalcogenide and one-dimensional conductor,
NbSe.sub.2 which is one of the transition metal dichalcogenide and
two-dimensional conductor, and the like can be obtained in forms of
thin-film like or whisker-like crystals. In the case that a ring
crystalline body is produced by forming a thin film comprising
NbSe.sub.3 or NbSe.sub.2 and then etching the film, the obtained
body is a low-dimensional conductor, so that electric conductivity
along the ring cannot be obtained and it means that the obtained
ring crystalline body is impossible to be used for a SQUID, for
which electric conductivity along a ring is essential.
Consequently, a ring crystalline body comprising a
three-dimensional conductor has solely been used for a SQUID.
[0010] However, taking the capabilities as a superconductor into
consideration, a one-dimensional conductor as well as a
two-dimensional conductor is preferable as compared with a
three-dimensional conductor. If it is possible to obtain a ring
crystalline body of such a low-dimensional conductor having
electric conductivity along the ring, it is expected that the
capabilities of a SQUID are further improved. Moreover, a
one-dimensional conductor, a two-dimensional conductor, and a
three-dimensional conductor respectively have different manners to
have superconductivity and a ring crystalline body comprising a
low-dimensional conductor is therefore supposed to be useful for
purposes other than a SQUID.
SUMMARY OF THE INVENTION
[0011] Hence, an object of the present invention is to obtain a
ring crystalline body made of an ultra thin line with a fine
diameter, which a conventional etching technique could not provide,
and to obtain a novel production method thereof. Another object of
the invention is to provide a ring crystalline body capable of
reliably providing electric conductivity along the ring even if it
is a low-dimensional conductor and a production method thereof.
[0012] In order to achieve these objects, a first aspect of the
present invention provides a ring crystalline body comprising
circularly continuous crystalline transition metal dichalcogenide
or transition metal trichalcogenide.
[0013] Further, a second aspect of the present invention provides a
ring crystalline body comprising a circularly continuous
crystalline low-dimensional conductor.
[0014] The foregoing transition metal dichalcogenide or transition
metal trichalcogenide includes, for example, NbSe.sub.3,
NbSe.sub.2, TaSe.sub.3, TaSe.sub.2, TaS.sub.2, MoS.sub.2, and the
like. These NbSe.sub.3, NbSe.sub.2, TaSe.sub.3, TaSe.sub.2,
TaS.sub.2, MoS.sub.2, and the like are also low-dimensional
conductors.
[0015] The ring crystalline body comprising these materials has a
totally novel structure body. Such a transition metal
dichalcogenide, a transition metal trichalcogenide, or a
low-dimensional conductor includes a superconductive material. A
ring crystalline body comprising a superconductive material or the
like may be used, for example, as an element of a SQUID in an
optional shape. In the case of a circular shape, the ring
crystalline body makes it possible to precisely measure a scarce
signal emitted out a living thing and a living body and is thus
extremely useful.
[0016] Further, when a large number of the ring crystalline bodies
are partly cut and joined in a spring-like shape, a nano-spring can
be obtained and further, since the ring crystalline body made of
the above described materials can generate an intense magnetic
field in a narrow region, if a plurality of the ring crystalline
bodies are joined to be a coil-like shape, a nano-actuator can be
produced. Besides, a nano-ball bearing can be produced by disposing
the ring crystalline bodies double.
[0017] In addition to those, the ring crystalline body can be used
for a quantum computer, an ultrafine battery utilizing
inter-current function, a memory based on permanent current and the
like and applicable to a wide range of the application fields and
remarkably useful in the industrial sphere.
[0018] The shape of the ring crystalline body is approximately
circular or elliptical and the size is preferably approximately 0.1
to 10 .mu.m in the diameter in the case of the circular shape and
in the major axis in the case of the elliptical shape and several
to several tens nm in the line width.
[0019] Preferably, the crystallinity is a single crystal. Even in
the case the ring crystalline body is of a low-dimensional
conductor, if the crystallinity is a single crystal, electric
conductivity is obtained along the ring, so that the ring
crystalline body can be used as an element of a SQUID and its
application fields are widened.
[0020] In order to produce such an ultrafine ring crystalline body,
another aspect of the invention provides a novel production method
of the ring crystalline body comprising steps of forming a
continuous or discontinuous underlayer ring having an ultrafine
three-dimensional structure in the substrate surface and circularly
growing a crystal along the underlayer ring.
[0021] Usable for the material of the substrate is glass, quartz,
silicon, diamond, sapphire, and the like.
[0022] Further, the underlayer ring is to be a point of starting
the growth of the crystal and preferably a ring composed of solely
continuously circular particles of elements composing the crystal
to be grown thereafter or a ring composed of a large number of fine
particles comprising the elements arranged discontinuously and
circularly. Alternatively, the particles and ultrafine particles
may be of elements completely different from those composing the
crystal. Even in the case of ultrafine particles of elements
different from those of the crystal, these ultrafine particles are
not diffused in the crystal and do not become contaminant
substances in the crystal.
[0023] According to such a method, it is made possible to produce a
ring crystalline body with a size as extremely fine as 0.1 to 10
.mu.m diameter and 10 nm line width, which is impossible to be
produced by a conventional method. Further, the production speed is
high and mass production at a high efficiency on the bases of
industrial scale can be also possible. Moreover, since no costly
apparatus is required, an economical product can be provided.
[0024] Further, regarding the formed ring crystalline body, those
with any optional diameter size can be produced by changing the
size of the underlayer ring, and the line width and the thickness
of a ring crystalline body can optionally be adjusted by
controlling the growth of the crystal. Moreover, a ring crystalline
body can be formed into a tubular shape by increasing the thickness
of the ring crystalline body.
[0025] Further, since the ring crystalline body is made of a single
crystal, even if the crystal is, for example, a low-dimensional
conductor, electric current flows along the ring and therefore, the
ring crystalline body can be used as a material for a SQUID.
[0026] Incidentally, this method can make it possible to produce
not only a ring crystalline body comprising the transition metal
dichalcogenides, transition metal trichalcogenide, and
low-dimensional conductors, but also a ring crystalline body
comprising other metal materials and organic materials.
[0027] Preferably, the underlayer ring is formed by sticking
droplets of an underlayer ring material to the substrate surface
and evaporating the droplets.
[0028] The method for sticking droplets to the substrate surface
includes a method sticking droplets of an underlayer material by
evaporation and a method comprising the steps of putting an
ultrafine underlayer material on the substrate surface by atomic
tweezers, liquefying the underlayer material by heating the
substrate, and evaporating the liquefied droplets.
[0029] Such droplets become approximately perfectly circular in the
substrate surface and are evaporated by heating to leave ultrafine
particles in the circumferential parts of the approximately
perfectly circular shape. The materials of the droplets may
properly be selected taking their wettability to the substrate and
their surface tension into consideration.
[0030] The size of the underlayer ring is determined by the size of
the droplets and for example, in the case droplets of an underlayer
material are stuck to the substrate surface by evaporation, the
size of the droplets can be controlled by the supply amount of the
underlayer material to be evaporated and the temperature of the
substrate. The diameter of the droplets is preferably set to be
within a range from 0.1 to 10 .mu.m.
[0031] As the underlayer material, constituent elements of a
crystal to be grown can be used, however it is not limited to them.
For example, in the case of producing a ring crystalline body
comprising a transition metal dichalcogenide or a transition metal
trichalcogenide, chalcogen elements which are contained in the
crystalline body or chalcogen elements which are not contained in
the crystalline body may be used for the underlayer material.
Further other materials, for example, an inorganic material such as
Al.sub.2O.sub.3, MoS.sub.2 and the like, and an organic material
can be used for the underlayer material.
[0032] Incidentally, in the case the underlayer ring is required to
be approximately elliptical shape, for example, by using a Ni type
magnetic material as the underlayer material and applying an
electric field or a magnetic field to the droplets, the upper face
shapes of the droplets can be formed to be elliptical and by
evaporating the droplets in such a state, an approximately
elliptical underlayer ring can be produced.
[0033] Further, if a plurality of droplets are stuck to the
substrate surface while neighboring one another, underlayer rings
with a shape composed of a plurality of circles adjoined to one
another can be formed to make it possible to produce a plurality of
ring crystalline bodies adjoined to each other along the underlayer
rings.
[0034] Also preferably, the crystal is grown by evaporation or by
sputtering.
[0035] Means for, for example, thermal CVD and plasma CVD may be
employed for the evaporation and a technique conventionally
well-known as a film formation technique in the semiconductor
fabrication can be employed.
[0036] Various conditions at the time of crystal growth, the
temperature of the substrate, the flow rate of raw materials and
the like in the case of evaporation are controlled, so that the
line width and thickness of the ring crystalline bodies to be
obtained can freely be controlled and further the crystal structure
can also be freely controlled and ring crystalline bodies of a
single crystal can be formed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIGS. 1A and 1B schematically show a production method of an
underlayer ring in a production method of a ring crystalline body
according to the present invention.
[0038] FIGS. 2A and 2B schematically show a production method of an
underlayer ring in the production method of a ring crystalline body
according to the present invention.
[0039] FIG. 3 is an electron microscopic photograph of a ring
crystalline body of NbSe.sub.3, which is a preferable example of
the present invention.
[0040] FIG. 4 is an electron microscopic photograph of a ring
crystalline body in an 8-shape form, which is another preferable
example of the present invention.
[0041] FIG. 5 is an electron microscopic photograph of a ring
crystalline body in a tubular form, which is the other preferable
example of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] Hereinafter, a production method of a ring single crystal
body according to an embodiment of the present invention will be
specifically described with reference to the accompanying
drawings.
[0043] FIG. 1 and FIG. 2 are illustrations schematically showing a
production method of an underlayer ring.
[0044] At first, droplets 2 of the underlayer material is
evaporated on a surface 1a of a substrate 1 and stuck to it. The
side view of the droplet 2 at that time and a top plan view thereof
are respectively illustrated in FIG. 1A and in FIG. 1B. Since the
surface tension of the droplets 2 is changed according to the
temperature of the substrate 1, the diameter size of the droplets 2
can be controlled by the temperature of the substrate 1. The
pressure at that time is so controlled to be at the vacuum degree
at which the droplets and the equilibrium vapor pressure are
kept.
[0045] Further, the droplets 2 are heated by increasing the
temperature of the substrate 1 bearing the droplets 2 to evaporate
droplets 2. A side view of the substrate 1 after the evaporation is
illustrated in FIG. 2A and a top plan view thereof is illustrated
in FIG. 2B. When the droplets 2 of the underlayer material are
evaporated, the underlayer material becomes an inorganic polymer
during the melting and after melting and a large number of fine
particles 3a are discontinuously circularly arranged along the
circumferences of the droplets 2 to form an underlayer ring 3.
[0046] The substrate 1 having the underlayer ring 3 formed is then
subjected to a conventionally known treatment such as evaporation
or sputtering to produce a ring crystalline body with crystalline
properties along the underlayer ring 3. At that time, the
conditions of evaporation or sputtering are properly set, so that a
ring crystalline body of a single crystal or a polycrystal can be
obtained.
[0047] Hereinafter, the present invention will be described
according to specific examples given below.
EXAMPLE 1
[0048] A droplet of Se as an underlayer material was stuck to the
surface of a glass substrate by evaporation. The substrate
temperature was set to be about 300.degree. C. and the vacuum
degree was set to be about 133 to 1330 Pa at that time. When the
temperature of the substrate was heated up to 600.degree. C. to
evaporate the droplet, an approximately perfectly circular
underlayer ring with the diameter of 300 nm to 500 .mu.m was
formed.
[0049] When the substrate having the underlayer ring formed in such
a manner was heated in a tubular quartz furnace at 700 to
800.degree. C. while raw material gas (NbSe.sub.3) being passed
through the furnace to carry out evaporation, a crystal of
NbSe.sub.3 was grown circularly along the underlayer ring and a
ring crystalline body was produced. An electron microscope
photograph is shown in FIG. 3.
[0050] The ring crystalline body of NbSe.sub.3 was observed by
x-ray diffraction and electron beam diffraction to find it was a
single crystal. Further, an investigation carried out into the
electric conduction made it clear that electric conduction along
the ring was obtained. Further, in the case the ring crystalline
body of NbSe.sub.3 was further converted to be a superconductor and
used as a SQUID element, it was supposed to be possible to obtain a
highly capable SQUID.
[0051] Further, in the case of using S type TaS.sub.3 and NbS.sub.3
and Te type NbTe.sub.3, and TaTe.sub.3 in place of the Se for the
underlayer material to produce an underlayer ring in the same
manner as that in case of using Se and to carry out evaporation of
NbSe.sub.3 on the underlayer ring in the above described
conditions, a ring crystalline body of the same single crystal as
that of the case using Se was obtained.
EXAMPLE 2
[0052] In the same evaporation conditions as those of the example
1, droplets of Se and Ni were stuck to the substrate surface as
underlayer materials. After that, if the droplets were evaporated
in the same conditions as those of the example 1 while an electric
field or a magnetic field being applied to the droplets, an
underlayer ring with approximately elliptical shape was formed.
When NbSe.sub.3 was evaporated in the underlayer ring with the
elliptical shape, a ring crystalline body with an approximately
elliptical shape was obtained. The observation of the crystalline
body by an x-ray diffraction and an electron beam diffraction made
it clear that the obtained crystalline body was of a single
crystal. Further, the electric conduction along the elliptical
shape was obtained.
EXAMPLE 3
[0053] Two droplets of Se as a underlayer raw material were stuck
to the surface of a glass substrate while being adjoined to each
other in the same evaporation conditions as those of the example 1.
After that, an underlayer ring in an approximately 8-shape form in
which two circles are adjoined to each other was formed by carrying
out evaporation of droplets in the same conditions as those of the
example 1. While the underlayer ring being floated in vacuum in
form of a twisted approximately 8-shape, NbSe.sub.3 was evaporated
to obtain a continuous crystalline body composed of two circular
crystalline bodies adjoined to each other in form of a twisted
approximately 8-shape. An electron microscopic photograph of the
crystalline body is shown in FIG. 4. The observation of the
crystalline body by x-ray diffraction and electron beam diffraction
made it clear that the crystalline body with 8-shaped form was of a
solely single crystal. Further, the electric conduction continuous
along the 8-shaped form was obtained.
EXAMPLE 4
[0054] An underlayer ring of Se in an approximately perfect circle
shape of 300 nm to 500 .mu.m diameter was formed on a glass
substrate in the same conditions as those of the example 1. When
the substrate having the underlayer ring formed was heated in a
tubular quartz furnace at 700 to 800.degree. C. while NbSe.sub.2
being passed through the furnace to carry out evaporation, a
crystal of NbSe.sub.2 was grown circularly along the underlayer
ring and a ring crystalline body was produced.
[0055] The observation of the crystalline body of NbSe.sub.2 by
x-ray diffraction and electron beam diffraction made it clear that
the crystalline body was a single crystal. Further, the
investigation into the electric conduction made it clear that the
electric conduction along the circular shape was obtained. Further,
in the case the ring crystalline body of NbSe.sub.2 was further
converted to be a superconductor and used as a SQUID element, it
was supposed to be possible to obtain a highly capable SQUID.
EXAMPLE 5
[0056] An underlayer ring in an approximately perfect circle shape
was formed on a glass substrate in the same conditions as those of
the example 1 and when the substrate having the underlayer ring
formed was heated in a tubular quartz furnace at 700 to 800.degree.
C. while raw material gas (NbSe.sub.3) being passed through the
furnace to carry out evaporation, a crystal of NbSe.sub.3 was grown
circularly along the underlayer ring and a ring crystalline body
was produced. When the NbSe.sub.3 gas evaporation was continued, a
tubular ring crystalline body was obtained. An electron microscopic
photograph of the tubular ring crystalline body is shown in FIG.
5.
[0057] The observation of the tubular crystalline body of
NbSe.sub.3 by x-ray diffraction and electron beam diffraction made
it clear that the tubular crystalline body of NbSe.sub.3 was a
single crystal. Further, the investigation into the electric
conduction made it clear that the electric conduction along the
circular shape was obtained.
[0058] The present invention was not at all limited to the above
described examples and crystalline bodies in a twisted 8-shape form
just like so-called Mobius's strip and in a coil-like form can be
obtained by changing the various conditions at the time of the
underlayer ring formation and evaporation.
[0059] Further, besides the above described transition metal
dichalcogenide (MX.sub.2) or transition metal trichalcogenide
(MX.sub.3), a variety of combinations of M and X wherein M=Nb, Ta,
and Mo and X=S, Se, and Te are possible. Further, the ring
crystalline bodies comprising a variety of types of organic
materials can be produced.
* * * * *