U.S. patent application number 10/117789 was filed with the patent office on 2003-10-30 for molecular electronic device using metal-metal bonded complexes.
This patent application is currently assigned to International Business Machines Corporation. Invention is credited to Kagan, Cherie R., Lin, Chun.
Application Number | 20030203168 10/117789 |
Document ID | / |
Family ID | 29248208 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030203168 |
Kind Code |
A1 |
Kagan, Cherie R. ; et
al. |
October 30, 2003 |
MOLECULAR ELECTRONIC DEVICE USING METAL-METAL BONDED COMPLEXES
Abstract
The present invention provides a molecular device including a
source region and a drain region, a molecular medium extending
there between, and an electrically insulating layer between the
source region, the drain region and the molecular medium. The
molecular medium in the molecular device of present invention is a
thin film having alternating monolayers of a metal-metal bonded
complex monolayer and an organic monolayer.
Inventors: |
Kagan, Cherie R.; (Ossining,
NY) ; Lin, Chun; (Croton-on-Hudson, NY) |
Correspondence
Address: |
Paul D. Greeley, Esq.
Ohlandt, Greeley, Ruggiero & Perle, L.L.P.
One Landmark Square, 10th Floor
Stamford
CT
06901-2682
US
|
Assignee: |
International Business Machines
Corporation
|
Family ID: |
29248208 |
Appl. No.: |
10/117789 |
Filed: |
April 5, 2002 |
Current U.S.
Class: |
428/200 |
Current CPC
Class: |
H01L 51/0579 20130101;
H01L 51/0078 20130101; H01L 51/0545 20130101; B82Y 10/00 20130101;
Y10T 428/24843 20150115; G11C 13/02 20130101; G11C 13/0014
20130101; G06N 99/007 20130101; H01L 51/057 20130101; H01L 51/0084
20130101; H01L 51/0595 20130101; H01L 51/009 20130101 |
Class at
Publication: |
428/200 |
International
Class: |
H01L 035/24 |
Claims
What is claimed is:
1. A molecular device comprising: a source region and a drain
region; a molecular medium extending between said source region and
said drain region; and an electrically insulating layer between
said source region, said drain region and said molecular
medium.
2. The molecular device of claim 1, wherein said source region and
said drain region are electrodes.
3. The molecular device of claim 1, wherein said electrodes and
said molecular medium are disposed on a substrate.
4. The molecular device of claim 1, further comprising a gate
region disposed in spaced adjacency to said molecular medium.
5. The molecular device of claim 4, wherein said gate region is
disposed on a substrate and below said insulating layer.
6. The molecular device of claim 1, wherein said source region,
said drain region and said molecular medium are disposed on said
insulating layer, and wherein said insulating layer is disposed on
said substrate.
7. The molecular device of claim 1, wherein said source region,
said drain region and said molecular medium disposed there between
are disposed in a vertical arrangement on an insulating material,
which is a substrate.
8. The molecular device of claim 7, further comprising a gate
region disposed between said substrate and said source region, said
drain region and said molecular medium.
9. The molecular device of claim 1, wherein said molecular medium
is a molecular switching medium.
10. The molecular device of claim 1, wherein said molecular medium
comprises a thin film having alternating monolayers of a
metal-metal bonded complex monolayer and an organic monolayer.
11. The molecular device of claim 10, wherein said thin film is
prepared by a process comprising the steps of: (1) applying onto a
surface of a substrate a first linker compound represented by the
formula:G1-Linker.sub.a-G2 to produce a primer layer of said first
linker compound on said substrate, wherein G1 is a functional group
capable of interacting with said surface of said substrate; G2 is a
functional group capable of interacting with a metal-metal bonded
complex; and Linker.sub.a is a difunctional organic group bonded to
G1 and G2; (2) applying onto said primer layer a layer of a
metal-metal bonded complex to produce a metal-metal bonded complex
monolayer on said primer layer; said metal-metal bonded complex
being selected from the group consisting of compounds represented
by the following formulas: 16and a combination thereof; wherein:
L.sub.ax is an axial ligand; L.sub.eq is an equatorial ligand;
wherein two equatorial ligands together form a bidentate ligand
Q--W; wherein each Q--W is independently selected from the group
consisting of: N--N, N--O, O--N, N--S, S--N, N--P, P--N, O--S,
S--O, O--O, P--P and S--S ligands; M is a transition metal; wherein
17 is a bridging group each selected independently from the group
consisting of: SO.sub.4.sup.2-, MoO.sub.4.sup.2-, WO.sub.4.sup.2-,
ZnCl.sub.4.sup.2- and a dicarboxylate; and wherein m is an integer
from 1 to 25, and n is 0 to 6; (3) applying onto said metal-metal
bonded complex monolayer a second linker compound represented by
the formula:G3-Linker.sub.b-G4 to produce on said metal-metal
bonded complex monolayer an organic monolayer; wherein G3 and G4
are the same or different functional groups capable of interacting
with a metal-metal bonded complex; and Linker.sub.b is a single
bond or a difunctional organic group bonded to G3 and G4; and
optionally (4) sequentially repeating steps (2) and (3) at least
once to produce said layer-by-layer grown thin film having
alternating monolayers of a metal-metal bonded complex monolayer
and an organic monolayer.
12. The molecular device of claim 11, wherein said transition metal
in said metal-metal bonded complex is selected from the group
consisting of: Cr.sub.2.sup.4+, Mo.sub.2.sup.4+, Re.sub.2.sup.6+,
Re.sub.2.sup.5+, Re.sub.2.sup.4+, Ru.sub.2.sup.5+, Ru.sub.2.sup.6+,
Rh.sub.2.sup.4+ and a combination thereof.
13. The molecular device of claim 11, wherein said substrate is
selected from the group consisting of: a metal, a metal oxide, a
semiconductor material, a metal alloy, a semiconductor alloy, a
polymer, an organic solid and a combination thereof.
14. The molecular device of claim 13, wherein said substrate is
selected from the group consisting of: Au, ITO, SiO.sub.2 and an
electrode.
15. The molecular device of claim 11, wherein said thin film has
from 1 to 100 alternating monolayers of a metal-metal bonded
complex monolayer and an organic monolayer.
16. The molecular device of claim 10, wherein said thin film is
prepared by a process comprising the steps of: (a) applying onto a
surface of a substrate a solution comprising: (i) a metal-metal
bonded complex selected from the group consisting of compounds
represented by the following formulas: 18and a combination thereof;
wherein: L.sub.ax is an axial ligand; L.sub.eq is an equatorial
ligand; wherein two equatorial ligands together form a bidentate
ligand Q--W; wherein each Q--W is independently selected from the
group consisting of: N--N, N--O, O--N, N--S, S--N, N--P, P--N,
O--S, S--O, O--O, P--P and S--S ligands; M is a transition metal;
wherein 19 is a bridging group each selected independently from the
group consisting of: SO.sub.4.sup.2-, MoO.sub.4.sup.2-,
WO.sub.4.sup.2-, ZnCl.sub.4.sup.2- and a dicarboxylate; and wherein
m is an integer from 1 to 25, and n is 0 to 6; (ii) a linker
compound represented by the formula:G3-Linker.sub.b-G4wherein G3
and G4 are the same or different functional groups capable of
interacting with a metal-metal bonded complex; and Linker.sub.b is
a single bond or a difunctional organic group bonded to G3 and G4;
and (iii) a solvent; and (b) evaporating said solvent to produce a
thin film of molecular medium on said substrate.
17. A molecular device comprising: a source region and a drain
region; a molecular medium extending between said source region and
said drain region, said molecular medium comprising a thin film
having alternating monolayers of a metal-metal bonded complex
monolayer and an organic monolayer prepared by layer-by-layer
growth; a gate region disposed in spaced adjacency to said
molecular medium, and an electrically insulating layer between said
gate region and said source region, said drain region and said
molecular medium.
18. The molecular device of claim 17, wherein said source region,
molecular medium and drain region are disposed upon a surface of a
substrate, said electrically insulating layer is disposed over said
molecular medium and extending from said source region to said
drain region, and said gate region is disposed over said
electrically insulating layer.
19. The molecular device of claim 17, wherein said gate region is
disposed as a gate layer upon a surface of a substrate, said
electrically insulating layer is disposed upon said gate layer, and
said source region, molecular medium, and drain region are disposed
upon said electrically insulating layer.
20. The molecular device of claim 18, wherein said substrate
comprises a flexible material.
21. The molecular device of claim 20, wherein said flexible
material comprises a plastic material.
22. The molecular device of claim 17, wherein said molecular medium
is a molecular switching medium.
23. The molecular device of claim 17, wherein said molecular medium
comprises a thin film having alternating monolayers of a
metal-metal bonded complex monolayer and an organic monolayer.
24. The molecular device of claim 23, wherein said thin film is
prepared by a process comprising the steps of: (1) applying onto a
surface of a substrate a first linker compound represented by the
formula:G1-Linker.sub.a-G2 to produce a primer layer of said first
linker compound; wherein G1 is selected from the group consisting
of: Cl.sub.3Si and SH; G2 is selected from the group consisting of:
4-pyridyl and 4-cyanophenyl; and Linker.sub.a is selected from the
group consisting of:C.sub.1-C.sub.8 alkylene, C.sub.1-C.sub.8
alkenediyl, C.sub.1-C.sub.8 alkynediyl and 1,4-arylene; (2)
applying onto said primer layer a metal-metal bonded complex to
produce on said primer layer a metal-metal bonded complex
monolayer; wherein said metal-metal bonded complex is selected from
the group consisting of compounds represented by the following
formulas: 20and a combination thereof; wherein: L.sub.ax is an
axial ligand; L.sub.eq is an equatorial ligand; wherein two
equatorial ligands together form a bidentate ligand Q--W; wherein
each Q--W is independently selected from the group consisting of:
N--N, N--O, O--N, N--S, S--N, N--P, P--N, O--S, S--O, O--O, P--P
and S--S ligands; M is a transition metal; wherein the group 21 is
a dicarboxylate bridging group selected from the group consisting
of compounds represented by the formulas: 22and mixtures thereof;
and wherein m is a n integer from 1 to 12 and n is 0 to 3; (3)
applying onto said metal-metal bonded complex monolayer a second
linker compound represented by the formula:G3-Linker.sub.b-G4 to
produce on said metal-metal bonded complex monolayer an organic
monolayer; wherein G3 and G4 are the same or different functional
groups capable of interacting with a metal-metal bonded complex;
and Linker.sub.b is a single bond or a difunctional organic group
bonded to G3 and G4; and optionally (4) sequentially repeating
steps (2) and (3) at least once to produce said layer-by-layer
grown thin film having alternating monolayers of a metal-metal
bonded complex monolayer and an organic monolayer.
25. The molecular device of claim 24, wherein said transition metal
in said metal-metal bonded complex is selected from the group
consisting of: Cr.sub.2.sup.4+, Mo.sub.2.sup.4+, Re.sub.2.sup.6+,
Re.sub.2.sup.5+, Re.sub.2.sup.4+, Ru.sub.2.sup.5+, Ru.sub.2.sup.6+,
Rh.sub.2.sup.4+ and a combination thereof.
26. A molecular device comprising: a source region and a drain
region; a molecular medium extending between said source region and
said drain region, said molecular medium comprising a thin film
having alternating monolayers of a metal-metal bonded complex
monolayer and an organic monolayer; and an electrically insulating
layer between said source region, said drain region and said
molecular medium.
27. The molecular device of claim 26, further comprising a gate
region disposed in spaced adjacency to said molecular medium.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a molecular device
including a source region and a drain region, a molecular medium
extending there between, and an electrically insulating layer
between the source region, the drain region and the molecular
medium. More particularly, the present invention relates to a
molecular device in which the molecular medium is a thin film
having alternating monolayers of a metal-metal bonded complex
monolayer and an organic monolayer.
[0003] 2. Description of the Prior Art
[0004] During the past three decades, considerable progress has
been made in the understanding of dinuclear compounds containing
multiple metal-metal bonds. Both the experimental and the
theoretical aspects of these compounds have been explored
extensively. These studies have provided a large body of
information particularly in the following areas: the reactivities
of the dinuclear cores, the strengths of metal-metal interactions,
the electronic transitions between metal-based orbitals and those
involving metal to ligand charge transfer, the redox activities of
the dinuclear core, and the correlation among these properties
(See, e.g., Cotton, Walton, Multiple Bonds Between Metal Atoms, 2nd
Ed., Oxford, 1993).
[0005] Efforts focusing on technologically important applications
of dinuclear compounds have led to many promising research areas,
such as inorganic liquid crystals (See, e.g., Chisholm, Acc. Chem.
Res., 2000, 33, 53), antitumor agents (See, e.g., Hall, et al, J.
Clin. Hematol. Oncol., 1980, 10, 25), and homogeneous and
photolytic catalysis (See, e.g., Doyle, Aldrichimica Acta, 1996,
29, 3; Nocera, Acc. Chem. Res., 1995, 28, 209).
[0006] Layer-by-layer assembly techniques to fabricate
multicomponent films has been explored in the literature. One of
the most developed systems grown layer-by-layer is the layered
metal phosphates and phosphonates. The films include multivalent
metal ions, e.g. Zr.sup.4+, and organic molecules terminated with
an acidic functionality, e.g. a phosphonic acid (See, e.g., Cao,
Hong, Mallouk, Acc. Chem. Res., 1992, 25, 420). Katz and co-workers
have used this method to align hyperpolarizable molecules into
polar multilayer films that show second-order nonlinear optical
effects (See, e.g., U.S. Pat. Nos. 5,217,792 and 5,326,626). A
similar approach has also been extended to other materials such as
polymers, natural proteins, colloids, and inorganic clusters (See,
e.g., Decher, Science, 1997, 277, 1232). This same technique has
also been applied to the production of other multilayers including
Co-diisocyanide, dithiols with Cu, and pyrazines with Ru (See,
e.g., Page, Langmuir, 2000, 16, 1172).
[0007] Among the existing examples, the driving force for the film
progression is mainly the electrostatical interaction between
polycations and polyanions; few examples involve other types of
interactions, such as hydrogen bond, covalent, or mixed
covalent-ionic. The present invention utilizes strong covalent
interactions, rather than ionic interactions, between the metals
and the ligands in a novel strategy to assemble nearly perfectly
packed mutilayers.
[0008] Despite the abundance of activity in these areas, these
efforts have been limited to the study and use of the metal-metal
bonded compounds in solution-based systems. To harness the
electronic, optical, and magnetic properties of metal-metal bonded
materials in solid-state applications and devices, development of
new methods for making thin films containing functional metal-metal
bonded complexes are needed.
[0009] Accordingly, the present invention provides a molecular
electronic device having a drain region, a molecular medium
extending there between, and an electrically insulating layer
between the source region, the drain region and the molecular
medium. The molecular medium in the molecular device according to
the present invention is a thin film having alternating monolayers
of a metal-metal bonded complex monolayer and an organic monolayer
prepared by layer-by-layer growth.
SUMMARY OF THE INVENTION
[0010] The present invention provides a molecular device
including:
[0011] a source region and a drain region;
[0012] a molecular medium extending between the source region and
the drain region; and
[0013] an electrically insulating layer between the source region,
the drain region and the molecular medium.
[0014] The present invention further provides a molecular device
including:
[0015] a source region and a drain region;
[0016] a molecular medium extending between the source region and
the drain region, the molecular medium including a thin film having
alternating monolayers of a metal-metal bonded complex monolayer
and an organic monolayer prepared by layer-by-layer growth;
[0017] a gate region disposed in spaced adjacency to the molecular
medium, and
[0018] an electrically insulating layer between the gate region and
the source region, the drain region and the molecular medium.
[0019] The present invention still further provides a molecular
device including:
[0020] a source region and a drain region;
[0021] a molecular medium extending between the source region and
the drain region, the molecular medium including a thin film having
alternating monolayers of a metal-metal bonded complex monolayer
and an organic monolayer prepared by layer-by-layer growth; and
[0022] an electrically insulating layer between the gate region and
the source region, the drain region and the molecular medium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 shows a 2-terminal lateral device structure
incorporating a metal-metal bonded layer as the active switching
medium between two electrodes.
[0024] FIG. 2 shows a 3-terminal lateral device structure
incorporating a metal-metal bonded layer as the active switching
medium between source and drain electrodes and separated from the
gate electrode by an insulator.
[0025] FIG. 3 shows a 2-terminal vertical device structure
incorporating a metal-metal bonded layer as the active switching
medium between two electrodes.
[0026] FIG. 4 shows a 3-terminal vertical device structure
incorporating a metal-metal bonded layer as the active switching
medium between source and drain electrodes and separated from the
gate electrode by an insulator.
[0027] FIG. 5 shows an atomic force microscope images showing the
layer-by-layer growth of the metal-metal bonded complex where
Rh--Rh is the metal-metal bond and 1,2-bis(4-pyridyl)ethylene is
the ligand.
[0028] FIG. 6 shows an atomic force microscope cross-sections
showing the layer-by-layer growth of the metal-metal bonded complex
where Rh--Rh is the metal-metal bond and 1,2-bis(4-pyridyl)ethylene
is the ligand. (corresponds to images in FIG. 1). The distance
between the metal electrodes is shown in (a) before layer-by-layer
growth of the metal-metal bonded complex. The metal-metal bonded
complex grows off the metal electrodes, narrowing the measured gap,
and spans the spacing between electrodes as the number of
metal-metal bonded and ligand layers are increased as shown for (b)
7 bilayers (where 1 bilayer is a metal-metal bonded layer and a
ligand layer), (c) 17 bilayers, and (d) 30 bilayers. Once the
spacing between the electrodes is spanned by the metal-metal bonded
complex, the I-V characteristics in FIG. 7 and FIG. 8 are attained
showing the electrical connection and negative differential
resistance.
[0029] FIG. 7 shows room temperature I-V characteristics of a
metal-metal bonded complex where Rh--Rh is the metal-metal bond and
zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine is the ligand.
The complex was grown layer-by-layer from Au electrodes using
mercaptan ethylpyridine as the linker. The device is fabricated in
the lateral geometry with an 80 nm spacing between metal
electrodes. The electrodes were deposited onto 40 nm thick
SiO.sub.2 on a degenerately doped silicon substrate.
[0030] FIG. 8 shows room temperature I-V characteristics of a
metal-metal bonded complex where Rh--Rh is the metal-metal bond and
1,2-bis(4-pyridyl)ethylene is the ligand. The film was grown
layer-by-layer from Au electrodes using mercaptan ethylpyridine as
the linker. The device is fabricated in the lateral geometry with
an 80 nm spacing between metal electrodes. The electrodes were
deposited onto 40 nm thick SiO.sub.2 on a degenerately doped
silicon substrate.
[0031] FIG. 9 shows an atomic force microscope images of a
spin-coated polycrystalline thin film of the metal-metal bonded
complex where Rh--Rh is the metal-metal bond and zinc
5,10,15,20-tetra(4-pyridyl)-21H,23H-porp- hine is the ligand. The
complex was deposited onto Au electrodes that were deposited on top
of an SiO.sub.2 on degenerately doped silicon substrate.
[0032] FIG. 10 shows room temperature I-V characteristics of a
metal-metal bonded complex where Rh--Rh is the metal-metal bond and
zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine is the ligand.
The complex was deposited on top of the device structures having Au
electrodes. The devices are fabricated in the lateral geometry with
(A) a 80 nm spacing and (B) a 295 nm spacing between metal
electrodes. The electrodes were deposited onto 40 nm thick
SiO.sub.2 on a degenerately doped silicon substrate.
[0033] FIG. 11 shows an atomic force microscope images of a
spin-coated polycrystalline thin film of the metal-metal bonded
complex where Rh--Rh is the metal-metal bond and
1,2-bis(4-pyridyl)ethylene is the ligand. The complex was deposited
onto Au electrodes that were deposited on top of an SiO.sub.2 on
degenerately doped silicon substrate.
[0034] FIG. 12 shows room temperature I-V characteristics of a
metal-metal bonded complex where Rh--Rh is the metal-metal bond and
1,2-bis(4-pyridyl)ethylene is the ligand. The complex was deposited
on top of the device structures having Au electrodes by
spin-coating. The devices are fabricated in the lateral geometry
with (A) an 80 nm spacing, (B) a 295 nm spacing, (C) a 385 nm
spacing between metal electrodes. The electrodes were deposited
onto 40 nm thick SiO.sub.2 on a degenerately doped silicon
substrate.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The present invention makes use of a molecular medium, which
includes alternating monolayers of a metal-metal bonded complex
monolayer and an organic monolayer prepared by layer-by-layer
growth as the active switching medium in two- and three-terminal
electronic devices. Such alternating monolayers of metal-metal
bonded complexes and organic compounds are molecular scale
composites of metal-metal bonded and organic layers. As a result,
these materials offer rich electrochemistry and electronic
properties for electronic device applications, while being simple
and easy to process at room temperature by methods, such as,
low-cost deposition from solution.
[0036] These complexs may be deposited from solution by techniques
such as spin-coating or by systematic layer-by-layer assembly. The
low-cost, solution based deposition is compatible with inexpensive,
large area electronic applications. In addition, the
low-temperature deposition conditions are compatible with a variety
of substrate materials, including plastics, for flexible electronic
applications.
[0037] The present invention provides a molecular electronic device
having a thin-film of alternating monolayers of a metal-metal
bonded complex monolayer and an organic monolayer prepared by
layer-by-layer growth of the thin-film.
[0038] The molecular device includes a source region and a drain
region; a molecular medium extending between the source region and
the drain region; and an electrically insulating layer between the
source region, the drain region and the molecular medium.
[0039] In one embodiment, the source region, the drain region and
the molecular medium disposed there between are disposed in a
vertical arrangement on an insulating material, which is a
substrate.
[0040] In another embodiment, the molecular device further includes
a gate region disposed between the substrate, the insulator, the
source region, the drain region and the molecular medium.
[0041] In still another embodiment, the molecular medium in the
molecular is a molecular switching medium.
[0042] In yet another embodiment, the thin film is prepared by a
process including the steps of:
[0043] (a) applying onto a surface of a substrate solution
including:
[0044] (i) a metal-metal bonded complex selected from the group
consisting of compounds represented by the following formulas:
1
[0045] and a combination thereof; wherein:
[0046] L.sub.ax is an axial ligand;
[0047] L.sub.eq is an equatorial ligand; wherein two equatorial
ligands together form a bidentate ligand Q--W; wherein each Q--W is
independently selected from the group consisting of: N--N, N--O,
O--N, N--S, S--N, N--P, P--N, O--S, S--O, O--O, P--P and S--S
ligands;
[0048] M is a transition metal;
[0049] wherein 2
[0050] is a bridging group each selected independently from the
group consisting of: SO.sub.4.sup.2-, MoO.sub.4.sup.2-,
WO.sub.4.sup.2-, ZnCl.sub.4.sup.2- and a dicarboxylate; and
[0051] wherein m is an integer from 1 to 25, and n is 0 to 6;
[0052] (ii) a linker compound represented by the formula:
G3-Linker.sub.b-G4
[0053] wherein G3 and G4 are the same or different functional
groups capable of interacting with a metal-metal bonded complex;
and Linker.sub.b is a single bond or a difunctional organic group
bonded to G3 and G4; and
[0054] (iii) a solvent; and
[0055] (b) evaporating the solvent to produce a thin film of
molecular medium on the substrate.
[0056] The processes described herein include layer-by-layer growth
of thin films having alternating monolayers of metal-metal bonded
complexes and organic molecules. Such films have utility in
solid-state applications.
[0057] The films are prepared by repeated sequential depositions of
metal-metal bonded units, e.g., dirhodium tetraformamidinate
complexes, on a prefunctionalized substrate, followed by a proper
organic linker, e.g., dipyridyl organic molecules, for the next
deposition sequence.
[0058] The deposition method is a self-assembling, tunable and
stepwise process. Upon application onto a substrate, the complexes
are adsorbed on the substrate. Thereafter, an organic monolayer is
applied. Thus, repeating the steps, a stepwise layer by layer
growth of the thin films can be achieved.
[0059] The multi-layered thin films can be grown layer-by-layer to
the desired thickness. The process includes the following
steps:
[0060] (1) applying onto a surface of a substrate a first linker
compound represented by the formula:
G1-Linker.sub.a-G2
[0061] to produce a primer layer of the first linker compound on
the substrate, wherein G1 is a functional group capable of
interacting with the surface of the substrate; G2 is a functional
group capable of interacting with a metal-metal bonded complex; and
Linker.sub.a is a difunctional organic group bonded to G1 and
G2;
[0062] (2) applying onto the primer layer a layer of a metal-metal
bonded complex to produce a metal-metal bonded complex monolayer on
the primer layer; the metal-metal bonded complex being selected
from the group consisting of compounds represented by the following
formulas: 3
[0063] and a combination thereof; wherein:
[0064] L.sub.ax is an axial ligand;
[0065] L.sub.eq is an equatorial ligand; wherein two equatorial
ligands together form a bidentate ligand Q--W; wherein each Q--W is
independently selected from the group consisting of: N--N, N--O,
O--N, N--S, S--N, N--P, P--N, O--S, S--O, O--O, P--P and S--S
ligands;
[0066] M is a transition metal;
[0067] wherein 4
[0068] is a bridging group each independently selected from the
group consisting of: S.sub.4.sup.2-, MoO.sub.4.sup.2-,
WO.sub.4.sup.2-, ZnCl.sub.4.sup.2- and a dicarboxylate; and
[0069] wherein m is an integer from 1 to 25, and n is 0 to 6;
[0070] (3) applying onto the metal-metal bonded complex monolayer a
second linker compound represented by the formula:
G3-Linker.sub.b-G4
[0071] to produce on the metal-metal bonded complex monolayer an
organic monolayer; wherein G3 and G4 are the same or different
functional groups capable of interacting with a metal-metal bonded
complex; and Linker.sub.b is a single bond or a difunctional
organic group bonded to G3 and G4; and optionally
[0072] (4) sequentially repeating steps (2) and (3) at least once
to produce the layer-by-layer grown thin film having alternating
monolayers of a metal-metal bonded complex monolayer and an organic
monolayer.
[0073] The length, functionality, direction of metal-metal vector,
and other physical and chemical properties of each layer can be
tuned by varying the metal-metal bonded units and the organic
linkers. Preferably, the thin film has from 1 to 100 alternating
monolayers of a metal-metal bonded complex monolayer and an organic
monolayer. More preferably, the thin film has from 30 to 40
alternating monolayers of a metal-metal bonded complex monolayer
and an organic monolayer.
[0074] The films are deposited from liquid solutions and therefore
they may be deposited on substrates having diverse topography and
configuration.
[0075] The following illustration describes the layer-by-layer
growth methods used according to the present invention to fabricate
metal-metal bonded compounds on a substrate. 5
[0076] As a substrate, any suitable material can be used. Suitable
substrates include, for example, a metal, a metal oxide, a
semiconductor, a metal alloy, a semiconductor alloy, a polymer, an
organic solid, and a combination thereof. The form of the
substrates can be a planar solid or a non-planar solid such as a
stepped or curved surface.
[0077] The following preferred substrates have been demonstrated:
Au, ITO and SiO.sub.2.
[0078] G1-Linker.sub.a-G2 groups are suitable molecular species
that can form a self-assembled monolayer include organic molecular
species having a functional group G1 capable of interaction with
the surface of the substrate forming a coated surface.
[0079] Examples of this group that can be designed into molecules
for interacting with or binding to a particular substate surface
with chemical specificity include one or more of the same or
different functional groups, such as phosphine oxide, phosphite,
phosphate, phosphazine, azide, hydrazine, sulfonic acid, sulfide,
disulfide, aldehyde, ketone, silane, germane, arsine, nitrile,
isocyanide, isocyanate, thiocyanate, isothiocyanate, amide,
alcohol, selenol, nitro, boronic acid, ether, thioether, carbamate,
thiocarbamate, dithiocarbamate, dithiocarboxylate, xanthate,
thioxanthate, alkylthiophosphate, dialkyldithiophosphate or a
combination thereof.
[0080] Functional group G2 on the tran direction of G1 is capable
of interaction with the next layer metal-metal boned molecules.
Examples of this group that can be designed into molecules for
interacting with or binding to a particular metal-metal bonded
molecule with chemical specificity include one or more of the same
or different functional groups. Thus, G2 in the first linker
compound can independently be: 4-pyridyl, 3-pyridyl, cyano,
4-cyanophenyl, 3-cyanophenyl, perfluoro-3-cyanophenyl and
perfluoro-4-cyanopheny.
[0081] There are two types of these molecules, G2a and G2b. G2a is
used for the axial direction linkage, such as nitrile, pyridyl,
trimethylsilane compounds; and the G2b is used for the equatorial
direction linkage, such as some bridging bidentate ligands with
(N,N), (N,O), (O,O), (O,S), (P,P), (N,S), and (S,S) donor sets.
Some typical examples of bidentate ligands are amidinates that are
a (N,N) donor set, acetamides that are a (N,O) set, carboxylates
that are a (O,O) set, thiocarboxylates that are a (O,S) set,
diphosphines that are a (P,P) set, mercaptopyrimidines that are a
(N,S) set, and dithiocarboxylates that are a (S,S) set.
[0082] The following molecules have been demonstrated: 6
[0083] on oxides surfaces, and 7
[0084] on Au surface.
[0085] III. 8
[0086] are suitable molecules containing at least one metal-metal
bonded unit.
[0087] 1. If the first monolayer ends with G2a group, examples of
these metal-metal bonded complexs can be containing one or more
than one metal-metal bonded units of which axial direction can
interact with or bind to G2a group, such as the molecules
containing one or more than one of the following metal-metal bonded
cores: Cr.sub.2.sup.4+, Re.sub.2.sup.6+, Re.sub.2.sup.5+,
Mo.sub.2.sup.4+, Re.sub.2.sup.4+, Ru.sub.2.sup.5+, Ru.sub.2.sup.6+,
Rh.sub.2.sup.4+. Preferred molecules suitable for use as the
molecular species that can interact with or bind to G2a group
include: tetrakis(carboxylato)dichromium,
tetrakis(carboxylato)dimolybdenum, tetrakis(amidinato)dichlorod
rhenium, tetrakis(amidinato)chlorodiruthenium,
tetrakis(carboxylato)dirhodium, tetrakis(amidinato)dirhodium,
bis(carboxylato)bis(amidinato)dirhodium, and complexes containing
more than one dimetal units.
[0088] If the first monolayer ends with G2b group, examples of
these metal-metal bonded complexes can be containing one or more
than one metal-metal bonded units of which equatorial direction can
interact with or bind to G2b group, such as the molecules
containing one of the following metal-metal bonded cores:
Cr.sub.2.sup.4+, Mo.sub.2.sup.4+, W.sub.2.sup.4+, Re.sub.2.sup.6+,
Re.sub.2.sup.5+, Re.sub.2.sup.4+, Ru.sub.2.sup.4+, Ru.sub.2.sup.5+,
Ru.sub.2.sup.6+, Os.sub.2.sup.6+, Rh.sub.2.sup.4+. Preferred
molecules suitable for use as the molecular species that can
interact with or bind to G2b group include:
tetrakis(carboxylato)dimetal (where the metal is the one of the
above), decakis(acetonitrile)dimetal (where the metal is Mo, Re,
and Rh).
[0089] The molecule that has been demonstrated is:
[Rh.sub.2(cis-N,N'-di-p-
-anisylformamidinate).sub.2].sub.2(O.sub.2CCH.sub.2CO.sub.2).sub.2.
9
[0090] are suitable molecules bearing two functional groups at both
ends. These functional groups will interact with or bind to the
previous metal-metal bonded unit terminated surface. Both G3 and G4
functional groups are every similar to G2.
[0091] Thus, G3 and G4 in the second linker compound can
independently be 4-pyridyl, 3-pyridyl, cyano, 4-cyanophenyl,
3-cyanophenyl, perfluoro-3-cyanophenyl and perfluoro-4-cyanopheny.
Linker.sub.b can be a single bond, an alkylene, an alkenediyl, an
alkynediyl, a 1,4-arylene, an arene-1,3,5-triyl, a
1,2,3-triazine-2,4,6-triyl, 4,4',4",4'"-(21H,23H-por-
phine-5,10,15,20-tetrayl) and zinc complex of
4,4',4",4'"-(21H,23H-porphin- e-5,10,15,20-tetrayl) and a
combination thereof. Further examples of G3-Linker.sub.b-G4 groups
include polynitriles, polypyridyls, ditrimethylsilanes, and organic
molecules containing at least two of any of the following donor
sets used as bridging bidentate ligands: (N,N), (N,O), (O,O),
(O,S), (P,P), (N,S), and (S,S), such as, N--N, N--O, O--N, N--S,
S--N, N--P, P--N, O--S, S--O, O--O, P--P and S--S ligands. Some
molecules with tetrahedral geometry may also be used as equatorial
linkers, such as SO.sub.4.sup.2-, MoO.sub.4.sup.2-,
WO.sub.4.sup.2-, ZnCl.sub.4.sup.2-.
[0092] Examples of the second linker compounds include compounds
represented by the following formulas: 10
[0093] and acetylene or diacetylene linkers represented by the
formulas:
--C.ident.C-- or --C.ident.C--C.ident.C--
[0094] which can be derived from derived from compounds represented
by the formula:
Me.sub.3Si--C.ident.C--Si--.ident.--.ident.--Me.sub.3
or
Me.sub.3Si--SiMe.sub.3
[0095] by desilylation of the trimethylsilyl group.
[0096] Preferred molecules carrying at least two required
functional groups include: 11
[0097] In a preferred embodiment, the process of the present
invention includes the steps of:
[0098] (1) applying onto a surface of a substrate a first linker
compound represented by the formula:
G1-Linker.sub.a-G2
[0099] to produce a primer layer of the first linker compound;
wherein G1 is selected from the group consisting of: Cl.sub.3Si and
SH; G2 is selected from the group consisting of: 4-pyridyl and
4-cyanophenyl; and Linker.sub.a is selected from the group
consisting of: C.sub.1-C.sub.8 alkylene, C.sub.1-C.sub.8
alkenediyl, C.sub.1-C.sub.8 alkynediyl and 1,4-arylene;
[0100] (2) applying onto the primer layer a metal-metal bonded
complex to produce on the primer layer a metal-metal bonded complex
monolayer; wherein the metal-metal bonded complex is selected from
the group consisting of compounds represented by the following
formulas: 12
[0101] and a combination thereof; wherein:
[0102] L.sub.ax is an axial ligand;
[0103] L.sub.eq is an equatorial ligand; wherein two equatorial
ligands together form a bidentate ligand Q--W; wherein each Q--W is
independently selected from the group consisting of: N--N, N--O,
O--N, N--S, S--N, N--P, P--N, O--S, S--O, O--O, P--P and S--S
ligands;
[0104] M is a transition metal;
[0105] wherein the group 13
[0106] is a dicarboxylate bridging group selected from the group
consisting of compounds represented by the formulas: 14
[0107] and mixtures thereof; and
[0108] wherein m is an integer from 1 to 12, and n is 0 to 3;
[0109] (3) applying onto the metal-metal bonded complex monolayer a
second linker compound represented by the formula:
G3-Linker.sub.b-G4
[0110] to produce on the metal-metal bonded complex monolayer an
organic monolayer; wherein G3 and G4 are the same or different
functional groups capable of interacting with a metal-metal bonded
complex; and Linker.sub.b is a single bond or a difunctional
organic group bonded to G3 and G4; and optionally
[0111] (4) sequentially repeating steps (2) and (3) at least once
to produce the layer-by-layer grown thin film having alternating
monolayers of a metal-metal bonded complex monolayer and an organic
monolayer.
[0112] In the first step, the substrates used for film growth can
be various kinds of metals, insulators, and semiconductors such as
glass, quartz, aluminum, gold, platinum, gold/palladium alloy,
silicon, thermally grown silicon dioxide on silicon, and
indium-tin-oxide coated glass. Since the films are deposited from
liquid solutions, they may be deposited on substrates having
diverse topography and configuration. The form of the substrates
can be a planar solid or a non-planar solid such as a stepped or
curved surface.
[0113] The second step of thin film deposition is to treat the
modified substrate with an appropriate compound containing at least
one metal-metal bonded unit from solution. Metal-metal bond units
will interact with N atoms through their axial directions or with
bidentate ligands through their equatorial directions. The opposite
direction that has not been used to interact with the molecular
template will be used as the site for the next step of the
layer-by-layer thin film growth. The metal atoms used in the
metal-metal bonded units may be any of the following: V, Nb, Cr,
Mo, W, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag.
[0114] In the third step, the metal-metal bond unit terminated
surface is treated with a solution containing molecules bearing at
least two functional groups. For axial linking these functional
groups may be any kind of nitrile or pyridyl containing N-donor
atoms. Thus, the organic molecules will be polypyridyls,
polynitriles, or will contain both pyridyl and nitrile
functionalities. For equatorial linkers, they can be organic
molecules containing at least two of any of the following donor
sets used as bridging bidentate ligands: (N,N), (N,O), (O,O),
(N,P), (P,P), (N,S), and (S,S). Some molecules with tetrahedral
geometry may also be used as equatorial linkers, such as
SO.sub.4.sup.2-, MoO.sub.4.sup.2-, WO.sub.4.sup.2-,
ZnCl.sub.4.sup.2-.
[0115] The next step is to repeat the above two steps to add
additional layers, but the metal-metal bonded units and organic
linkers are not required to be the same, as long as they have a
similar structural moiety. This provides a versatile means of
assembling multilayer heterostructures from various metal-metal
bonded building blocks, with essentially any desired sequence of
layers.
[0116] The scheme below illustrates an example of multilayer thin
film growth including of alternating layers of the redox active
metal-metal bonded supramolecules
[Rh.sub.2(DAniF).sub.2].sub.2(O.sub.2CCH.sub.2CO.su- b.2).sub.2
(DAniF=N,N'-di-p-anisylformamidinate), 1, and
trans-1,2-bis(4-pyridyl)ethylene, 2, on pyridyl functionalized
oxide substrates, such as quartz, indium-tin-oxide (ITO), and
silicon wafers that have a native or thermally grown silicon
dioxide surface.
[0117] The oxide substrates were cleaned as follows: each substrate
was first treated in UV/ozone for 30 min., then rinsed thoroughly
with acetone, dichloromethane, and water, and then dried in an oven
at 120.degree. C. for at least 2 h. The substrate was treated again
in UV/ozone for another 30 min. right before film deposition.
[0118] Substrates were first silated by immersion in a toluene
solution containing 1 mM 4-[2-(trichlorosilyl)]-ethylpyridine for
30 min. After rinsing with copious amounts of toluene and ethanol,
the substrates were vacuum-dried. Metal-metal bonded molecular
films were grown by first dipping the substrates into a 0.1 mM
toluene solution of molecule 1 for 2 h at -15.degree. C. and then
in a 0.1 mM ether solution of 2 for 30 min at room temperature,
with rinsing between steps.
[0119] After the first bilayer was deposited, the procedure was
repeated, but with the soaking time reduced to 1 min for each
solution, until the desired number of bilayers had been
obtained.
[0120] These steps can be schematically represented as follows:
15
[0121] FIG. 1 shows a cross-sectional view of a typical
two-terminal lateral electronic device 10. Device 10 includes a
metal-metal bonded complex material layer 12. Layer 12 is a
metal-metal bonded complex and serves as the active switching
medium between electrodes 14 and 16 fabricated on substrate 18.
[0122] FIG. 2 shows a cross-sectional view of a typical
three-terminal lateral electronic device 20 in the configuration of
a transistor. The transistor 20 includes a metal-metal bonded
material layer 22. Layer 22 is a metal-metal bonded complex and
serves as the channel between source and drain electrodes 24 and
26. The conductance of the metal-metal bonded complex is modulated
across an electrically insulating layer 28, such as a thin
SiO.sub.2 film, by a gate electrode 30, which may be a degenerately
doped silicon layer, all of which are fabricated on substrate
32.
[0123] FIG. 3 shows a cross-sectional view of a typical
two-terminal vertical electronic device 40. Device 40 includes a
metal-metal bonded complex material layer 42. Layer 42 is a
metal-metal bonded complex and serves as the active switching
medium between electrodes 44 and 46 fabricated on substrate 48. In
this case, electrode 44 is deposited on top of the metal-metal
bonded layer.
[0124] FIG. 4 shows a cross-sectional view of a typical
three-terminal veritcal electronic device 60 in the configuration
of a transistor. The transistor 60 includes a metal-metal bonded
material layer 62. Layer 62 is a metal-metal bonded complex and
serves as the channel between source and drain electrodes 64 and
66. The conductance of the metal-metal bonded complex is modulated
across an electrically insulating layer 68, such as a thin
SiO.sub.2 film, by a gate electrode 70, which may be a degenerately
doped silicon layer, all of which are fabricated on substrate 72.
In this case, electrode 64 is deposited on top of the metal-metal
bonded layer.
[0125] FIG. 5 shows AFM images of metal-metal bonded complex
assembled layer-by-layer from solution showing the complex spanning
the distance between Au electrodes as the number of bilayers is
increased from (a) 0 bilayers, (b) 7 bilayers, (c) 17 bilayers, and
(d) 30 bilayers. The Au electrodes were deposited onto 40 nm thick
SiO.sub.2 on a degenerately doped silicon substrate.
[0126] FIG. 6 shows line-cuts of the AFM images shown in FIG. 5.
The metal-metal bonded complex spans the distance between
electrodes, closing the separation between electrodes as the number
of bilayers is increased from (a) 0 bilayers, (b) 7 bilayers, (c)
17 bilayers, and (d) 30 bilayers.
[0127] Once the metal-metal bonded complex spans the distance
between electrodes, either by assembling the complex layer-by-layer
or by spin-coating a polycrystalline thin film in which the
metal-metal bonded units and the organic ligands self-assemble, the
electrodes are electrically connected.
[0128] Preliminary data demonstrating the desired negative
differential resistance in 2-terminal, lateral device structures is
shown for two metal-metal bonded complexes in FIGS. 7 and 8, where
the compound is assembled layer-by-layer, and in FIGS. 9 and 10,
where the compound is deposited by spin-coating from a solution in
chloroform (1.6 mg/mL) for 1 minute at spin speeds between
1500-2000 rpm.
[0129] FIG. 7 shows negative differential resistance in the I-V
characteristics for a metal-metal bonded complex in which Rh--Rh is
the metal-metal bonded unit and zinc
5,10,15,20-tetra(4-pyridyl)-21H,23H-porp- hine is the ligand. The
complex was grown layer-by-layer from Au electrodes using mercaptan
ethylpyridine as the linker. The device is fabricated in the
lateral geometry with an 80 nm spacing between metal
electrodes.
[0130] FIG. 8 shows negative differential resistance in the I-V
characteristics for a metal-metal bonded complex in which Rh--Rh is
the metal-metal bonded unit and 1,2-bis(4-pyridyl)ethylene is the
ligand. The compound was grown layer-by-layer from Au electrodes
using mercaptan ethylpyridine as the linker. The device is
fabricated in the lateral geometry with an 80 nm spacing between
metal electrodes.
[0131] FIG. 9 shows an AFM image of the metal-metal bonded complex
in which Rh--Rh is the metal-metal bonded unit and zinc
5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine is the ligand. The
complex was deposited by spin-coating from a solution in chloroform
to form a polycrystalline thin film with grain structure consistent
with the underlying structural motif of the metal-metal bonded
complex.
[0132] FIG. 10 shows negative differential resistance in the I-V
characteristics for a metal-metal bonded complex in which Rh--Rh is
the metal-metal bonded unit and zinc
5,10,15,20-tetra(4-pyridyl)-21H,23H-porp- hine is the ligand. The
complex was deposited by spin-coating from a solution in
chloroform.
[0133] FIG. 11 shows an AFM image of the metal-metal bonded complex
in which Rh--Rh is the metal-metal bonded unit and
1,2-bis(4-pyridyl)ethylen- e is the ligand. The complex was
deposited by spin-coating from a solution in chloroform to form a
polycrystalline thin film with grain structure consistent with the
underlying structural motif of the metal-metal bonded complex.
[0134] FIG. 12 shows negative differential resistance in the I-V
characteristics for a metal-metal bonded complex in which Rh--Rh is
the metal-metal bonded unit and 1,2-bis(4-pyridyl)ethylene is the
ligand. The complex was deposited by spin-coating from a solution
in chloroform.
[0135] The electronic properties of the metal-metal bonded
complexes may be tailored through chemistry. There is a wide-range
of metal-metal and organic ligands usable as the metal-metal bonded
complex. Metal-metal bonded complexes may be designed by choosing
the chemistry and structural motif of the complex. The flexibility
in the chemistry may be used to tailor the electronic properties of
the molecular devices.
[0136] The present invention has been described with particular
reference to the preferred embodiments. It should be understood
that variations and modifications thereof can be devised by those
skilled in the art without departing from the spirit and scope of
the present invention. Accordingly, the present invention embraces
all such alternatives, modifications and variations that fall
within the scope of the appended claims.
* * * * *