Active solid-state devices (e.g. – transistors – solid-state diode – Organic semiconductor material
Reexamination Certificate
2002-02-26
2004-07-06
Jackson, Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Organic semiconductor material
C257S017000, C257S022000
Reexamination Certificate
active
06759676
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a multiply-complexed one-dimensional structure, multiply-twisted helix, multiply-looped ring structure and functional material, especially suitable for use as highly functional materials based on a novel principle.
BACKGROUND ART
For application of a solid material to electronic or optical devices, physical properties of the material may restrict its applications. For example, in case of using a semiconductor material in a light emitting device, it will be usable in a device of an emission wavelength corresponding to the band gap of the material, but some consideration will be necessary for changing the emission wavelength. Regarding physical properties related to semiconductor bands, controls by superlattices have been realized. More specifically, by changing the period of a superlattice, the bandwidth of its subband can be controlled to design an emission wavelength.
Targeting on controlling many-electron-state structures by material designs, the Inventor proposed many-body effect engineering by quantum dot-bonded structures and has continued theoretical analyses ((1) U.S. Pat. No. 5,430,309; (2) U.S. Pat. No. 5,663,571; (3) U.S. Pat. No. 5,719,407; (4) U.S. Pat. No. 5,828,090; (5) U.S. Pat. No. 5,831,294; (6) J. Appl. Phys. 76, 2833(1994); (7) Phys. Rev. B51, 10714(1995); (8) Phys. Rev. B51, 11136(1995); (9) J. Appl. Phys. 77, 5509(1995); (10) Phys. Rev. B53, 6963(1996); (11) Phys. Rev. B53, 10141(1996); (12) Appl. Phys. Lett. 68, 2657(1996); (13) J. Appl. Phys. 80, 3893(1996); (14) J. Phys. Soc. Jpn. 65, 3952(1996); (15) Jpn. J. Appl. Phys. 36, 638(1997); (16) J. Phys. Soc. Jpn. 66, 425(1997); (17) J. Appl. Phys. 81, 2693 (1997); (18) Physica (Amsterdam) 229B, 146(1997); (19) Physica (Amsterdam) 237A, 220(1997); (20) Surf. Sci. 375, 403(1997); (21) Physica (Amsterdam) 240B, 116(1997); (22) Physica (Amsterdam) 240B, 128(1997); (23) Physica (Amsterdam) IE, 226(1997); (24) Phys. Rev. Lett. 80, 572(1998); (25) Jpn. J. Appl. Phys. 37, 863(1998); (26) Physica (Amsterdam) 245B, 311(1998); (27) Physica (Amsterdam) 235B, 96(1998); (28) Phys. Rev. B59, 4952(1999); (29) Surf. Sci. 432, 1(1999); (30) International Journal of Modern Physics B. Vol. 13, No. 21, 22, pp.2689-2703, 1999). For example, realization of various correlated electronic systems is expected by adjusting a tunneling phenomenon between quantum dots and interaction between electrons in quantum dots. Let the tunneling transfer between adjacent quantum dots be written as t. Then, if quantum dots are aligned in form of a tetragonal lattice, the bandwidth of one electron state is T
eff
=4t. If quantum dots form a one-dimensional chain, the bandwidth of one electron state is T
eff
=2t. In case of a three-dimensional quantum dot array, T
eff
=6t. That is, if D is the dimension of a quantum dot array, the bandwidth of one electron state has been T
eff
=2Dt. Here is made a review about half-filled (one electron per each quantum dot) Mott transition (also called Mott-Hubbard transition or Mott metal-insulator transition). Let the effective interaction of electrons within a quantum dot be written as U
eff
, then the Hubbard gap on the part of the Mott insulator is substantially described as &Dgr;=U
eff
−T
eff
, and the Mott transition can be controlled by changing U
eff
or t. As already proposed, the Mott-Hubbard transition can be controlled by adjusting U
eff
or t, using a field effect, and it is applicable to field effect devices (Literatures (5), (6), (11) and (14) introduced above).
On the other hand, reviewing the equation of &Dgr;=U
eff
−T
eff
−2Dt, it will be possible to control Mott-Hubbard transition by controlling the dimensionality D of-the system. For this purpose, the Applicant already proposed a fractal-bonded structure that can continuously change the dimensionality, and have exhibited that Mott-Hubbard transition is controllable by changing the fractal dimensions.
To enable designing of wider materials, it is desired to modify and control the dimension of materials by methods different from the fractal theory. For example, for the purpose of changing the nature of phase transition, it is first conceivable to control the number of nearest-neighbor elements among elements ago forming a material.
On the other hand, here is changed the attention to ferromagnetic phase transition taking place in the fractal-bonded structure. Of course, ferromagnetic materials are one of the most important magnetic storage materials. When using z as the number of nearest-neighbor atoms, k
B
as the Boltzmann constant, T as temperature, it is known that spontaneous magnetization M in the averaging theory describing ferromagnetic phase transition satisfies
M
=Tanh(
zM/k
B
T
)
The highest among temperatures T leading to solutions of M≠0 of this equation is the critical temperature T
c
. As readily understood from the equation, T
c
is proportional to z. When assuming a tetragonal lattice, since z=2D, it is expected that the critical temperature of ferromagnetic phase transition depends on the dimensionality of a material. The Inventor executed more exact Monte Carlo simulation, and showed that the critical temperature of ferromagnetic transition occurring in a fractal-bonded structure could be controlled by the fractal dimensions.
It is therefore an object of the invention to provide a multiply-twisted helix complementary with a fractal-shaped material and representing a new physical property, and a functional material using the multiply-twisted helix.
A further object of the invention is to provide a multiply-looped ring structure complementary with a fractal-shaped material and representing a new physical property, and a functional material using the multiply-looped ring structure.
A still further object of the invention is to provide a multiply-complexed one-dimensional structure complementary with a fractal-shaped material and representing a new physical property, and a functional material using the multiply-complexed one-dimensional structure.
SUMMARY OF THE INVENTION
The Inventor proposes a multiply-twisted helix as one of spatial filler structures. This is made by winding a spiral on a spiral structure as a base like a chromatin structure that a gene represents, and by repeating it to progressively fill a three-dimensional space. By adjusting the spiral pitch, the spatial filling ratio can be selected, and dimensionality of a material, i.e. the number of nearest-neighbor elements in this structure can be modified.
In other words, here is proposed a multiply-twisted helix in which spirals are made up by using a spiral structure as the base and using the spiral structure as an element. In this structure including hierarchically formed multiple spirals, one-dimensional vacancies penetrate the structure to form a structure as a porous material. However, by adjusting the turn pitch of the spirals, the number of nearest-neighbor elements can be changed. According to researches by the Inventor, the value of critical inter-electron interaction of Mott-Hubbard metal-insulator transition in this kind of structure can be controlled by the spiral pitch.
The multiply-twisted helical structure may be formed regularly; however, in case a multiply-twisted helical structure is actually made, bonding positions appearing among spiral layers possibly distribute randomly. The degree of the randomness can be new freedom of material designs. Taking it into consideration, for the purpose of clarifying the effect of the random distribution, exact simulation was conducted. As a result, introduction of randomness has been proved to increase the width of the Mott-Hubbard gap and enhance the Mott insulation. Therefore, the value of critical inter-electron interaction of Mott-Hubbard metal-insulator transition can be controlled not only by controlling the degree of randomness of the spiral turn pitch but also by controlling the degree of randomness regarding inter-layer bonding positions.
Still in the multiply-twisted helix, the
Hirata Shintaro
Ugajin Ryuichi
Ukita Masakazu
Jackson Jerome
Sonnenschein Nath & Rosenthal LLP
Sony Corporation
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