USO0RE43 868E
(19) United States (12) Reissued Patent
(10) Patent Number: US RE43,868 E (45) Date of Reissued Patent: *Dec. 25, 2012
Chow et a]. (54)
NANOFIBER SURFACE BASED CAPACITORS
(75)
Inventors: Calvin Y. H. Chow, Portola Valley, CA (US); Robert DubroW, San Carlos, CA
(56)
References Cited U.S. PATENT DOCUMENTS 3,697,786 A 4,599,677 A
(Us)
4,959,745 A
(73) Assignee: Nanosys, Inc., Palo Alto, CA (US)
4,967,316 A
5,019,468 A
(*)
Notice:
5,027,253 5,121,288 5,172,304 5,187,640 5,196,396 5,252,835
This patent is subject to a terminal dis claimer.
(21) Appl.No.: 12/970,774 (22) Filed:
Dec. 16, 2010
5,332,910 A 5,384,685 A
Related US. Patent Documents
Issued:
Appl. No.: Filed: US. Applications: (63)
(52)
11/840,414 Aug. 17, 2007
DE
7/1994 Haraguchi et a1. 1/1995 Tong et a1.
10053276 Cl
l/2002
(Continued) OTHER PUBLICATIONS U.S. Appl. No. 07/958,506, ?led Oct. 7, 1992, Cromack et a1.
(Continued) Primary Examiner * Nguyen T Ha
(74) Attorney, Agent, or Firm * Andrew L. Filler
(57) ABSTRACT This invention provides navel capacitors comprising nano?
(2006.01)
US. Cl. ...... .. 361/303; 361/302; 361/311; 361/312;
361/313; 361/321.1 (58)
Lauffer et a1. Metroka et a1. OZaWa et a1. Metroka et a1. Lieber Lieber et a1.
FOREIGN PATENT DOCUMENTS
Dec. 16, 2008
Continuation of application No. 11/ 507,267, ?led on Aug. 21, 2006, noW Pat. No. 7,295,419, Which is a continuation of application No. 11/330,557, ?led on Jan. 12, 2006, noW Pat. No. 7,116,546, Which is a continuation of application No. 11/075,361, ?led on Mar. 8, 2005, noW Pat. No. 7,057,881.
Int. Cl. H01G 4/005
5/1991 Miyabayashi 6/1991 6/1992 12/1992 2/1993 3/1993 10/1993
7,466,533
(60) Provisional application No. 60/554,549, ?led on Mar. 18, 2004. (51)
9/1990 Suguro 10/1990 Goebel et a1.
(Continued)
Reissue of:
(64) Patent No.:
A A A A A A
10/1972 Smith 7/1986 Lawless et a1.
Field of Classi?cation Search ............. .. 361/301.2,
361/301.4, 321.1, 321.2, 306.1, 302*305, 361/311*313, 306.3, 301.5, 508509, 511512 See application ?le for complete search history.
ber enhanced surface area substrates and structures compris ing such capacitors, as Well as methods and uses for such
capacitors. 17 Claims, 3 Drawing Sheets
230
l/l
220
200
US RE43,868 E Page 2 US. PATENT DOCUMENTS
33581333: 2433; 18391189191 ’
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7,301,199 B2* 7,317,047 B2*
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Fig. 1
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Fig. 2
US RE43,868 E
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Sheet 2 of3
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Sheet 3 of3
US RE43,868 E
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US RE43,868 E 1
2
NANOFIBER SURFACE BASED CAPACITORS
of issues arise to limit the effectiveness of such measures. A
?nal, but not trivial, problem concerns cost. Larger devices/ surfaces/ structures that are needed, e.g., to allow the proper
Matter enclosed in heavy brackets [ ] appears in the original patent but forms no part of this reissue speci?ca
capacitance, can be quite expensive.
tion; matter printed in italics indicates the additions made by reissue.
(and devices, etc. comprising capacitors) which have enhanced surface areas which would have the bene?ts of, e. g.,
CROSS-REFERENCE TO RELATED APPLICATIONS
increased capacitance per unit area footprint. The current invention provides these and other bene?ts which will be apparent upon examination of the following.
Thus, a welcome addition to the art would be capacitors
SUMMARY OF THE INVENTION
This application is a continuation of US. patent applica tion Ser. No. 11/507,267, ?led Aug. 21, 2006 now US. Pat. No. 7,295, 419, which is a continuation of US. patent appli cation Ser. No. 11/330,557, ?led Jan. 12, 2006, now US. Pat. No. 7,116,546, which is a continuation of US. patent appli cation Ser. No. 11/075,361, ?led Mar. 8, 2005, now US. Pat.
No. 7,057,881, which claims bene?t of, and priority to, US. Provisional Application No. 60/554,549 ?led Mar. 18, 2004, each of which is hereby incorporated by reference in its
In some aspects the current invention comprises an electric capacitor which has at least one electrode surface that com
prises a plurality of nano?bers. In typical embodiments, the electrode surface is comprised of a conductive material (e. g., a metal, a semiconducting material, a polymer, a resin, etc.). In some, but not all, preferred embodiments, the electrode 20
entirety.
surface and/or the nano?bers of the electrode surface are comprised of silicon. While in some embodiments the elec trode surface and its nano?bers are of the same material (e. g.,
silicon, etc.), in other embodiments the surface and the
FIELD OF THE INVENTION
nano?bers are of different materials from one another. Addi
The invention relates primarily to the ?eld of nanotechnol
25
ogy. More speci?cally, the invention pertains to capacitors comprising nano?bers and nano?ber enhanced suf?ce areas,
the electrode surface.
as well as to the use of such capacitors in various applications and devices.
In other embodiments of the invention, the capacitor also 30
comprises a dielectric of a nonconductive material which
covers substantially all members of the plurality of nano?bers (and the electrode surface on which the nano?bers exist). The
BACKGROUND OF THE INVENTION
Various con?gurations of nanostructures (e.g., nano?bers,
dielectric, thus, exists between the electrode surfaces (or “electrode plates” or the like) of the capacitor. Such dielectric
nanowires, nanocrystals, etc.) have attracted widespread interest for their novel properties in electrical, chemical, opti
tionally, while the nano?bers are optionally grown in place upon the electrode surface, they are also optionally grown upon a different surface and subsequently placed/ attached to
35
can optionally be composed of one or more of a number of
cal and other similar applications. Nanostructures have a broad possibility of uses, such as semiconductors for nanos
materials, e.g., oxides, nitrides, various nonconductive poly mers, ceramics, resins, porcelains, mica containing materials,
cale electronics, optoelectronic applications (e.g., in lasers,
glass, vacuum, rare earth oxides, gas (e.g., air, inert gases, etc.), or other typical dielectrics used in electronic capacitors.
LEDs, etc.) photovoltaics, sensors, etc. Correspondingly, capacitors are pervasive electronic ele ments. Often, it is quite desirous to place capacitors of par ticular capacitance, durability, and/or construction within extremely small spaces. In almost all instances, however, the ef?ciency or use of such devices is limited, at least in part, by the area of the surface which is in contact with, or comprises, the electrode plates of the capacitor. This limitation is true in several
40
dielectric comprises a grown oxide layer and/or a naturally occurring oxide layer. The dielectric can comprise, e.g., a 45
In various embodiments, the dielectric, e.g., oxide layer, comprises a desired thickness (depending upon, e.g., the desired capacitance and other parameters such material con 50
certain footprint area). Thus, the capacitance is limited by,
struction, etc.). For example, the dielectric, e.g., oxide layer, can comprise a thickness from about 1 nm or less to about 1 um, from about 2 nm or less to about 750 nm, from about 5 nm or less to about 500 nm, from about 10 nm or less to about 250 nm, or from about 50 nm or less to about 100 um. The
inter alia, the footprint of the surfaces which comprise the capacitor. One answer to such problem is to increase the siZe
of the footprint involved. However, besides being inelegant., such response is often problematic due to cost restraints and
metal oxide such as aluminum oxide or tantalum oxide, etc.
The dielectric can also comprise silicon oxide.
aspects. First, space limitations (or “footprint” limitations) are of concern. For example, for de?ned materials, a certain capacitance can exist per unit area of a surface (i.e., within a
Those of skill in the art are quite familiar with a broad range of materials used as dielectrics and capable of use as dielec trics in the current invention. In some embodiments, the
siZe limitations imposed on the footprint itself (e.g., the
dielectric, e.g., oxide layer, can also comprise a thickness that is substantially equivalent to the thickness of the electrode
capacitor might need to be placed in a limited space in a
surface(s).
55
device, etc.)
In typical embodiments, the capacitors herein also com prise a second electrode surface. Such second surface can
In a number of conventional or current applications, the
surface area of a capacitor’s electrode sui?ce is increased by providing the material making up the surface with a number
60
of holes or pores (e.g., by etching a metal plate, etc.). By providing such matrix as a porous solid, rather than just a solid surface, one increases the amount of available surface area without increasing the amount of space that the material
comprise, e.g., a layer of material deposed upon the dielectric which covers the plurality of nano?bers and the ?rst electrode surface. In such embodiments, the second surface material can comprise a conductive material (e.g., similar to the optional composition of the ?rst electrode surface such as a
occupies (i.e., the footprint size). While such porous matrices
metal, a semiconducting material, a polymer, a resin, etc.). In various embodiments, the two electrode surfaces canbe of the
do increase the surface area of the electrode surface, a number
same composition, or can be of different composition. In
65
US RE43,868 E 3
4
some embodiments, the second surface comprises an evapo
These and other objects and features of the invention Will become more fully apparent When the folloWing detailed
rated or sputtered electrically conducting material. Such evaporated/ sputtered materials can include, e. g., aluminum,
description is read in conjunction With the accompanying
?gures.
tantalum, platinum, nickel, a semiconducting material, poly silicon, titanium, titanium oxide, an electrolyte, gold, etc.
BRIEF DESCRIPTION OF THE DRAWINGS
The various embodiments of capacitors herein can have a number of different densities of nano?bers per unit area out
FIG. 1, Displays a schematic diagram of a generalized
line (i.e., per footprint area). For example, the density of the
capacitor.
members of the plurality of nano?bers can range from about
FIG. 2, Displays a schematic diagram representing an
0.1 1 nano?ber per square micron or less to at least about 1000
enhanced surface area capacitor.
nano?bers per square micron, from about 1 nano?ber per
FIG. 3, Panels A and B, Display photomicrographs of
square micron or less to at least about 500 nano?bers per square micron, from about 10 nano?bers per square micron or less to at least about 250 nano?bers per square micron, or from about 50 nano?bers per square micron or less to at least
enhanced surface area substrates such as can form the basis
for enhanced surface area capacitors. FIG. 4, Displays a graph comparing the surface area of a nano?ber enhanced area against varying distances betWeen nano?bers.
about 100 nano?bers per square micron.
Also, in various embodiments (e.g., in those Wherein the nanostructures comprise nano?bers, nanoWires, or the like as opposed to nanocrystal or other similar nanostructures Whose
DETAILED DESCRIPTION
20
structural pro?le is not substantially cylindrical or tubular), the length of the members of the plurality of nano?bers can
The current invention comprises a number of different
optionally range from about 1 micron or less to at least about 500 microns, from about 5 micron or less to at least about 150 microns, from about 10 micron or less to at least about 125 microns, or from about 50 micron or less to at least about 100
embodiments focused on nano?ber enhanced area surface
substrates and uses thereof in capacitors. As Will be apparent 25
microns; and Wherein the diameter of the members of the plurality of nano?bers ranges from about 5 nm or less to at least about 1 micron, from about 10 nm or less to at least about 500 nm, from about 20 nm or less to at least about 250 nm, from about 20 nm or less to at least about 200 nm, from about 40 nm or less to at least about 200 nm, from about 50 nm or
ence to medical use and beyond. It Will be appreciated that 30 enhanced surface areas herein are sometimes labeled as
“nano?ber enhanced surface areas” or, alternatively depend ing upon context, as “nanoWire enhanced surface areas,” etc.
less to at least about 150 nm, or from about 75 nm or less to at least about 100 nm.
In yet other embodiments, the capacitors of the invention
A common factor in the embodiments is the special mor
phology of nano?ber surfaces (typically silicon oxide nanoW 35
can comprise an electrode surface that, because of the nano? bers present, is considerably greater in surface area than other
typical electrode surfaces of similar or substantially equal footprint. For example, the density of the members of the plurality of nano?bers can optionally increase the surface area of the electrode surface from at least 1.5 times to at least 100,00 times or more, at least 5 times to at least 75,000 times or more, at least 10 times to at least 50,000 times or more, at least 50 times to at least 25,000 times or more, at least 100 times to at least 10,000 times or more, or at least 500 times to at least 1,000 times or more, greater, in comparison to an area
40
ires herein, but also encompassing other compositions and forms). For example, the vastly increased surface area pre sented by such substrates is utiliZed in, e.g., creation of improved capacitors for a Wide variety of uses. In most aspects herein, it is thought that such bene?ts accrue from the
unique morphology of the nano?ber surfaces (especially form the vastly increased surface area), but the various
45
embodiments herein are not necessarily limited by such theory in their construction, use, or application. In some embodiments, the nano?bers are optionally functionaliZed With one or more entity.
Again, Without being bound to a particular theory or mechanism of operation, the concept of the majority of ben
of substantially equal footprint of an electrode surface With out nano?bers
Additionally, in other embodiments, the capacitors of the invention can comprise a farad capacity that, because of the nano?bers present, is considerably greater in amount than that of other typical electrode surfaces of similar or substan
upon examination of the present speci?cation, ?gures, and claims, substrates having such enhanced surface areas present improved and unique capacitance aspects that are bene?cial in a Wide variety of applications ranging from materials sci
50
e?ts of the invention is believed to operate, at least in part, on the principle that the nano?ber surfaces herein present a greatly enhanced surface area in relation to the same footprint area Without nano?bers.
Capacitors
tially equal footprint. For example, the farad capacity of the
Capacitors, in general and in speci?c applications, are
capacitors of the invention can comprise from about at least
quite Well knoWn in the art. Various types of capacitors, e.g.,
1.5 times to at least 100,00 times or more, at least 5 times to at least 75,000 times or more, at least 10 times to at least 50,000 times or more, at least 50 times to at least 25,000 times or more, at least 100 times to at least 10,000 times or more, or at least 500 times to at least 1,000 times or more greater
55
capacitance than a capacitor having an electrode surface of
60
An electrical charge proportional to the voltage can then be stored in the capacitor When a voltage is applied across the electrodes. Thus, in FIG. 1, electrodes 100 and 200 (alter nately termed “electrode plates,” “electrode surfaces,” or
65
The electrodes are typically electrically connected to other components via connections such as 400. The capacitance
electrolytic capacitors, are replete throughout the literature. FIG. 1 shoWs the basic components of a capacitor in a gen
eraliZed fashion. In typical capacitors, a dielectric material is
layered betWeen tWo conductive electrodes (typically metal).
substantially equal footprint but not comprising a plurality of nano?bers. In yet other aspects, the invention comprises a device
Which comprises any of the capacitors of the invention. For
example, timepieces, remote controls, medical devices, radios, computers, electronic equipment, etc. Which have a capacitor herein are also aspects of the invention.
“opposing plates” or the like) are separated by dielectric, 300.
“C” of a parallel-plate capacitor is given by Equation 1,
US RE43,868 E 6
5
surface. A dielectric (e.g., a metal oxide) is then typically E
A
C:%.
formed/placed over the increased surface area. Those of skill
Equation 1
in the art Will be knoWledgeable about such practices and their corresponding use in construction of capacitors. Once the surface area electrode has been covered With a
In Equation 1, “A” represents the area of the two plates in the
dielectric, the opposing electrode can touch, or effectively touch, the dielectric. For example, a Wet electrolytic solution can exist betWeen the dielectric (touching and ?lling the
capacitor, While “E0” represents the dielectric permittivity of vacuum or free space (8.85>
surface variations) and the opposing electrode. Dry electro lytic material can also ful?ll a similar role. In either case, the
capacitance depends upon the thickness of the dielectric (e.g.,
solutions betWeen the dielectric and the opposing electrode, in effect, become extensions/part of the opposing electrode. Nano?ber-enhanced Capacitors The capacitors of the present invention provide large capacitance values per footprint area of electrode plate, thus, alloWing construction of quite small and/or quite poWerful
the distance betWeen the electrodes), the dielectric constant of the dielectric, and the area (or effective area) of contact
betWeen the plates of the capacitor. Thus, greater capacitance can be achieved through, e.g., increasing the dielectric con
stant of the dielectric (e. g., by choosing a particular dielectric material), increasing the electrode surface areas (e. g., by
capacitors. The capacitors herein have one or more electrode
making the electrode plates larger, etc.), decreasing the dis
plate Which comprises nano?ber surfaces. As explained beloW, such nano?ber surfaces can optionally encompass
tance betWeen the electrodes, or combinations thereof. As
described beloW, a number of traditional capacitors (e.g.,
20
electrolytic capacitors) optimize capacitance by etching/
tals, etc.) Which vastly increase the surface area of the elec trode plates. As explained above, increasing the surface area of the electrodes in a capacitor increases its capacitance. FIG. 2 displays a schematic diagram illustrating one pos
roughening the surface of the electrode to increase the surface area “A.”
It Will be appreciated that choice of dielectric material is an
effective means of manipulating the qualities of capacitors.
25
sible embodiment of the current invention. As seen In FIG. 2,
30
an electrode plate, 200, comprises a number of nano?bers, 230, upon it. In preferred embodiments, such nano?bers and electrode plate are “coated” With a dielectric, 220, (e. g., typi cally an oxide layer), Which dielectric is then “coated” With another material to form the second, or opposing, electrode
For example, metal oxides can be used as material for dielec trics. In other Words, speci?c oxides are based upon the com
position of the electrode plates in the capacitor, e.g., alumi num oxides as dielectrics upon aluminum electrode plates,
etc. In many capacitors, aluminum oxide and tantalum oxide
myriad nanostructures (e.g., nanoWires, nanorods, nanocrys
plate, 210. In typical embodiments, the surface of the electrode plate
(typically tantalum pentoxide) are often chosen. Thus, in
many types of capacitors (typically electrolytic capacitors) different metals (e. g., tantalum, aluminum, Zinc, niobium and
(e.g., the area betWeen nano?ber attachments) is comprised of
Zirconium) are coated With an oxide through an electrochemi
a conductive material (e. g., typically a metal, a semiconduct
plate by placing the metal in the proper chemical solution and
ing material, an electrically conductive polymer or resin, etc.). Additionally, the nano?bers themselves are preferably comprised of electrically conductive material(s) such as, e. g.,
running an electric current through it. The thickness of such
metals, semiconducting materials, electrically conductive
cal process. For example, a thin layer or coating of A1203
35
(aluminum oxide) can be formed on an aluminum electrode
oxide layers (e.g., less than a micrometer, etc) can be manipu lated through changes in reaction conditions. The oxide layer
polymers, resins, etc. The electrode plate surface and/or the 40
thus formed, comprises the dielectric of the capacitor. Typical dielectrics made of metal oxides can be quite effective in
capacitors, and can Withstand extremely high ?elds Without breakdoWn. Various arrangements of such capacitors can be
rectifying (typical) or non-rectifying (often constructed With tWo opposing layers of oxidiZed material).
45
As an often related point, the thickness of the dielectric, Which also in?uences the capacitance, see Equation 1, can depend upon the choice of material for the dielectric. For
example, oxide layers (e.g., racial oxide layers as described above) are quite thin. Those of skill in the art Will be familiar With such thin oxide layers, eg from usage in electrolytic capacitors, etc. Such thinness also increases the capacitance in addition to the dielectric constant component/in?uence of the dielectric material itself because the thinness/thickness of the dielectric is often the distance, or is effectively the dis
50
55
coats or covers substantially all nano?bers and/or all areas of 60
plates through, e.g., constructing the electrode plates from activated carbon ?bers, etching or sintering of the surfaces of increased surface area 30-100 times greater than an unetched
face of the electrode plate. Thus, the dielectric closely con forms to the shape of the nano?bers and the electrode plate, in effect, forming a coating over them. The dielectric typically
the electrode plate Which comprises the nano?bers.
have increased the surface area of one or both of the electrode
the electrode plates (e.g., etching metal), etc. For example, etching (e.g., chemical etching With acids) can produce an
nano?bers and the rest of the body of the electrode plate, such features (i.e., the nano?bers and the plate surface) can option ally be comprised of the same material or can optionally be comprised of different materials. For example, the nano?bers can optionally comprise silicon/ silicon compounds While the electrode plate can optionally comprise an electrically con ductive metal. The possible difference in composition betWeen the nano?bers and the plate surface can arise, e.g., because the plurality of nano?bers can optionally be groWn upon a different surface, harvested, and then deposited/at tached to the electrode plate surface. Also, as can be seen in FIG. 2, capacitors of the invention comprise a dielectric that typically “coats” the nano?ber sur
tance, betWeen the electrode plates. Yet another method of modifying capacitance is through change of the effective areas of the electrode plates. Those of skill in the art Will be quite familiar With various means used to increase such effective areas. For example, some capacitors
nano?bers on the plate are optionally comprised of silicon or silicon compounds. No matter the exact composition of the
65
In many embodiments, the dielectric comprises an oxide layer, typically an oxide of the material(s) Which form the nano?bers/electrode plate. For example, in some embodi ments herein the dielectric comprises a silicon oxide layer coating the nano?bers/electrode plate. In yet other embodi ments, the dielectric is one or more of: an oxide, a nitride, a
polymer, a ceramic, a resin, a porcelain, a mica combining material, a glass, vacuum, a rare earth oxide, a gas, etc. Those
US RE43,868 E 7
8
of skill in the art Will be familiar With other typical dielectrics used in electronic capacitors and Which are capable of use in the present invention. In any case, as With typical capacitors,
comprise nano?bers that range in diameter from about 5 nm or less to at least about 1 micron, from about 10 nm or less to at least about 500 nm, from about 20 nm or less to at least about 250 nm, from about 20 nm or less to at least about 200 nm, from about 40 nm or less to at least about 200 nm, from about 50 nm or less to at least about 150 nm, or from about 75
the dielectric in the present invention consists of a noncon
ductive material. In embodiments Wherein the dielectric comprises an oxide layer, such layer can be, e.g., a grown oxide layer or a natu
nm or less to at least about 100 nm.
rally occurring oxide layer. Again, typical oxide layers herein
In the capacitors herein, the addition of the nano?bers to
comprise silicon oxides. Those of skill in the art Will also be aWare of methods of manipulating thickness and other
the electrode surface can increase the surface area of the
electrode surface (in comparison to an electrode surface Which does not have nano?bers) by at least 1.5 times to at least 100,00 times or more, by at least 5 times to at least 75,000 times or more, by at least 10 times to at least 50,000
growth/construction aspects of such oxide layers in order to achieve the desired dielectric parameters. For example, par ticular environmental conditions present during the groWth/ construction of oxide layers can in?uence the thickness of the
times or more, by at least 50 times to at least 25,000 times or more, by at least 100 times to at least 10,000 times or more, or by at least 500 times to at least 1,000 times or more. Such
oxide layer, etc. In various embodiments, the dielectric (e.g., the oxide layer) comprises a thickness of from about 1 nm or less to about 1 um, from about 2 nm or less to about 750 nm, from
comparisons are typically made by comparing similar “foot i.e., similar or substantially similar
prints” of electrode plates, about 5 nm or less to about 500 nm, from about 10 nm or less to about 250 nm, or from about 50 nm or less to about 100 um. 20 area outlines. In yet other embodiments, the thickness is substantially equivalent to the thickness of the electrode surface compris ing the nano?bers. In typical embodiments herein, the capacitor comprises a second electrode plate, i.e., an opposing electrode plate that is on the opposite side of the dielectric than the electrode plate
An example of the increase in effective area of an electrode plate of the invention can be seen in FIG. 4. The graph in FIG. 4 compares the surface area of a nano?ber enhanced area
against the distance betWeen the nano?bers on the area. Thus, 25
comprising the nano?ber surface. In preferred embodiments, this second electrode plate comprises a layer of material
deposed upon the dielectric (i.e., covering the plurality of nano?bers on the ?rst electrode plate). See, e.g., FIG. 2. As
30
With typical capacitors, the second electrode plate is also electrically conductive, e.g., is composed of electrically con ductive material(s) such as metals, semiconducting materials, conductive polymers, conductive resins, etc. In order to achieve the close mating betWeen the second electrode plate and the complex nano?ber surface (i.e., coated With the
10 nm nanoWires With a 2 nm aluminum/aluminum oxide
coating that are stacked 10 nm apart Would produce a surface area that Would be ten times greater than any surface reported in the literature.
Also, Within the capacitors herein, addition of nano?bers to the electrode surface/plate can increase the farad capacity of the capacitor by about at least 1.5 times to at least 100,00 times or more, by at least 5 times to at least 75,000 times or more, by at least 10 times to at least 50,000 times or more, by
dielectric), the second electrode plate is preferably evapo
at least 50 times to at least 25,000 times or more, by at least 100 times to at least 10,000 times or more, or by at least 500 times to at least 1,000 times or more in relation to a capacitor Which does not comprise a nano?ber enhanced surface.
rated or sputtered onto the dielectric. For example, an elec
Again, such comparisons are typically made against similar
trically conductive metal (e.g., aluminum, tantalum, plati num, titanium, nickel, gold, etc.), a semiconducting material,
35
or substantially similar footprint or outline areas. 40
The current invention also includes devices comprising
capacitors With nano?ber enhanced surfaces (i.e., typically nano?ber enhanced electrode plates). Myriad examples of
polysilicon, titanium oxide, or an electrolyte, etc. can be used as the material of the second electrode plate. In some embodi
ments, the second electrode plate can optionally comprise an
such devices can be contemplated. Those of skill in the art
electrolytic solution (either liquid or non-liquid) Which, in
Will appreciate the Wide range of devices capable of compris
effect, acts as the second electrode plate. Those of skill in the art Will be familiar With similar electrolytic set-ups from
45
traditional electrolytic capacitors, etc. In the various embodiments herein, the capacitors (i.e., the electrode plates comprising the nano?ber surfaces) can have various densities of nano?bers Within footprint areas. For example, some embodiments comprise nano?ber densities of
and small siZe) can comprise/utilize the current invention. Nonlimiting examples of such devices can include, e. g., time 50
about 1000 nano?bers per square micron, from about 1 nano?ber per square micron or less to at least about 500 55
square micron or less to at least about 250 nano?bers per square micron, or from about 50 nano?bers per square micron or less to at least about 100 nano?bers per square micron.
Also, in different embodiments herein, the length of the nano?bers Within the capacitors can be of different lengths. For example, the length of the nano?bers herein can range from about 1 micron or less to at least about 500 microns, from about 5 micron or less to at least about 150 microns, from about 10 micron or less to at least about 125 microns, or from about 50 micron or less to at least about 100 microns.
pieces, Watches, radios, remote controls, nanodevices, medi cal implant devices (e. g., pacemakers, prosthetic devices With electrical components, etc.), How through capacitors, e. g., for Water puri?cation or solute sorting/ separation.
from about 0.1 1 nano?ber per square micron or less to at least
nano?bers per square micron, from about 10 nano?bers per
ing/utilizing these capacitors. Basically, any device requiring a capacitor (especially a capacitor of large farad capability
60
Characteristics of Nano?ber Surface Substrates As noted previously, increased surface area is a property that is sought after in many ?elds (e. g., in substrates for assays or separation column matrices) as Well as the current capaci tors. For example, ?elds such as tribology and those involving separations and adsorbents are quite concerned With maxi miZing surface areas. Other inventions by the inventor and coWorkers have focused on such applications. See, e. g., NANOFIBER SURFACES FOR USE IN ENHANCED SURFACE AREA APPLICATIONS, U.S. Ser. No. 10/792, 402, ?led Mar. 2, 2004. The current invention offers capaci
tors, and applications of such, having surfaces that are 65
increased or enhanced With nano?bers (i.e., increased or
Also, such various embodiments can comprise nano?bers of
enhanced in area in relation to structures or surfaces Without
various diameters as Well. Thus, different embodiments can
nano?bers, such as “planar” surfaces).
US RE43,868 E 9
10 for example, the intended use of the enhanced area surfaces, e.g., the speci?c parameters such as amount of capacitance and/or capacitance per unit area needed, the conditions under
A “nano?ber enhanced surface area” or a capacitor or
capacitor electrode surface With an “enhanced surface area,” etc. herein corresponds to a capacitor or capacitor electrode
Which they Will be used (e.g., temperature, pH, presence of light (e.g., UV), atmosphere, etc.), the durability of the sur faces and the cost, etc. In typical and preferred embodiments
surface comprising a plurality of nano?bers (e.g., nanoWires, nanotubes, nanospheres, etc.) attached to a substrate so that the surface area Within a certain “footprint” of the substrate is
the nano?bers are electrically conductive. The ductility and breaking strength of nanoWires Will vary depending on, e. g., their composition. For example, ceramic ZnO Wires can be more brittle than silicon or glass nanoWires, While carbon nanotubes may have a higher tensile strength. As explained more fully beloW, some possible materials
increased relative to the surface area Within the same footprint
Without the nano?bers. Such footprint corresponds to outlin ing the parameters of the measurement area.
As explained in greater detail beloW, in typical embodi ments herein, the nano?bers (and often the electrode surface substrate) are composed of silicon and/or silicon oxides. It Will be noted that such compositions convey a number of
used to construct the nano?bers and nano?ber enhanced sur
bene?ts in certain embodiments herein. Also, in some embodiments herein, one or more of the plurality of nano? bers is functionaliZed With one or more moiety. See, beloW. HoWever, it should also be noted that the current invention is
faces herein, include, e.g., silicon, ZnO, TiO, carbon, and
not speci?cally limited by the composition of the nano?bers
or small molecules can optionally be used as coating materi als on the nano?bers, e.g., betWeen the nano?bers and the
carbon nanotubes. See beloW. The nano?bers of the invention are also optionally coated or functionaliZed, e.g., to enhance
or add speci?c properties. For example, polymers, ceramics
or of the substrate or of any functionaliZation, unless other
Wise noted. Thus, as an illustrative, but not limiting, example, FIGS. 2 and 3 present schematic and actual representations of nano? ber enhanced surface area substrates of the invention, such as Would be constructed Within capacitors herein. FIG. 2 shoWs a schematic of a nano?ber capacitor. FIG. 3 displays photo micrographs of an enhanced surface area nano?ber substrate such as Would form the basis for a nano?ber plate element. It Will be noted that the number and shape and distribution of the
20
dielectric, etc. The optional coatings can impart characteris tics such as Water resistance, improved electrical properties, etc. Additionally, speci?c moieties or functional groups can also be attached to or associated With the nano?bers herein.
25
Of course, it Will be appreciated that the current invention is not limited by recitation of particular nano?ber and/or substrate compositions, and that, unless otherWise stated, any
merely to illustrate the myriad possible embodiments of the
of a number of other materials are optionally used in different embodiments herein. Additionally, the materials used to com prise the nano?bers can optionally be the same as the material used to comprise the substrate surfaces or they can be differ ent from the materials used to construct the substrate surfaces.
current invention. The various embodiments of the current invention are
In yet other embodiments herein, the nano?bers involved can optionally comprise various physical conformations such
nano?bers alloWs ample opportunity for increased surface area, etc. Again, it is to be emphasized that such examples are
30
adaptable to, and useful for, a great number of different appli cations. For example, as explained in more detail beloW, various permutations of the invention can be used in, e. g., any number of devices requiring capacitors. Other uses and
as, e.g., nanotubules (e.g., holloW-cored structures), nano 35
nanostructures are all optionally used in increasing the sur face area of the electrode surfaces, etc. While typical embodi
embodiments are examined herein.
As Will be appreciated by those of skill in the art, in numer ous materials the surface properties can optionally provide a great deal of the functionality or use of the material. For example, in various embodiments, the adherence or coverage of the dielectric is provided by or aided by interaction of the nano?ber elements With appropriate functionaliZation moi eties. As also Will be appreciated by those of skill in the art, many aspects of the current invention are optionally variable (e.g.,
40
It is to be understood that this invention is not limited to
45
particular embodiments only, and is not intended to be nec 50
should therefore not be taken as necessarily limiting the cur
55
terms are understood to have the same meaning as commonly
used in the art to Which they pertain. For the purpose of the present invention, additional speci?c terms are de?ned
throughout. A) Nano?bers 60
The term “nano?ber” as used herein, refers to a nanostruc
ture typically characterized by at least one physical dimen sion less than about 1000 nm, less than about 500 nm, less than about 250 nm, less than about 150 nm, less than about
In typical embodiments herein the surfaces (i.e., the nano?ber enhanced area surfaces) and the nano?bers them selves can optionally comprise any number of materials. The actual composition of the surfaces and the nano?bers is based upon a number of possible factors. Such factors can include,
essarily limiting. As used in this speci?cation and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a nano?ber” optionally includes a plurality of such nano?bers, and the like. Unless de?ned otherwise, all scienti?c and technical
iZed in one or more Ways, e. g., through attachment of moieties
or functional groups to the nano?bers, other embodiments comprise nano?bers Which are not functionaliZed. Nano?bers and Nano?ber Construction
different combinations of nano?bers and substrates and optional moieties, etc. Which are optionally present in a range
of lengths, densities, etc.). It is also to be understood that the terminology used herein is for the purpose of describing
rent invention. Also, it Will be appreciated, and is explained in more detail beloW, that the length to thickness ratio of the nano?bers herein is optionally varied, as is, e.g., the compo sition of the nano?bers and the dielectric. Furthermore, a variety of methods can be employed to bring the ?bers in contact With surfaces. Additionally, While some embodiments herein comprise nano?bers that are speci?cally functional
ments herein recite “nano?ber,” such language should not be construed as necessarily limiting unless speci?ed to be so.
particular con?gurations, Which can, of course, vary (e.g.,
surface chemistries on the nano?bers, surface chemistries on any end of the nano?bers or on the substrate surface, etc.).
Speci?c illustration of various modi?cations, etc. herein,
rods, nanocrystals, nanoWhiskers etc. A variety of nano?ber types are optionally used in this invention including carbon nanotubes, metallic nanotubes, metals and ceramics. Such
65
100 nm, less than about 50 nm, less than about 25 nm or even less than about 10 nm or 5 nm. In many cases, the region or
characteristic dimension Will be along the smallest axis of the structure.
US RE43,868 E 11
12
Nano?bers of this invention typically have one principle axis that is longer than the other tWo principle axes and, thus,
can be groWn/constructed in, or upon, variously con?gured
have an aspect ratio greater than one, an aspect ratio of 2 or
ping cylinder, etc. See infra.
greater, an aspect ratio greater than about 10, an aspect ratio greater than about 20, or an aspect ratio greater than about 100, 200, or 500. In certain embodiments, nano?bers herein have a substantially uniform diameter. In some embodiments, the diameter shoWs a variance less than about 20%, less than about 10%, less than about 5%, or less than about 1% over the region of greatest variability and over a linear dimension of at
In various embodiments herein, the nano?bers involved are optionally groWn on a ?rst substrate and then subsequently
surfaces, e.g., on a ?at substrate that is rolled into an overlap
transferred to a second substrate Which is to have the enhanced surface area. Such embodiments are particularly
useful in situations Wherein the substrate desired needs to be ?exible or conforming to a particular three dimensional shape
that is not readily subjected to direct application or groWth of nano?bers thereon. For example, nano?bers can be groWn on such rigid surfaces as, e.g., silicon Wafers or other similar substrates. The nano?bers thus groWn can then optionally be
least 5 nm, at least 10 nm, at least 20 nm, or at least 50 nm. For
example, a Wide range of diameters could be desirable due to cost considerations and/or to create a more random surface.
transferred to a ?exible backing. Again, it Will be appreciated, hoWever, that the invention is not limited to particular nano? ber or substrate compositions. For example, nano?bers are optionally goWn on any of a variety of different surfaces,
Typically the diameter is evaluated aWay from the ends of the nano?ber (e.g. over the central 20%, 40%, 50%, or 80% of the
nano?ber). In yet other embodiments, the nano?bers herein have a non-uniform diameter (i.e., they vary in diameter along their length). Also in certain embodiments, the nano?bers of this invention are substantially crystalline and/ or substan
including, e.g., ?exible foils such as aluminum or the like.
Additionally, for high temperature groWth processes, any 20
tially monocrystalline.
metal, ceramic or other thermally stable material is optionally used as a substrate on Which to groW nano?bers of the inven
tion. Furthermore, loW temperature synthesis methods such
Once again, it Will be appreciated that the term nano?ber, can optionally include such structures as, e. g., nanoWires,
as solution phase methods can be utiliZed in conjunction With
nanoWhiskers, semi-conducting nano?bers, carbon nano
an even Wider variety of substrates on Which to groW nano?
tubes or nanotubules and the like.
25
growth/attachment. As one example, the groWth of nano?bers on a surface
they are heterogeneous (e. g. nano?ber heterostructures) and can be fabricated from essentially any convenient material or
materials. The nano?bers can comprise “pure” materials, substantially pure materials, doped materials and the like and can include, in various combinations, insulators, conductors,
30
35
of a number of different materials, unless otherWise stated. Composition of nano?bers can vary depending upon a
appreciated by such skilled persons, the nano?bers of the invention can, thus, be composed of any of a myriad of pos sible substances (or combinations thereof). Some embodi
due to the nano?bers). As Will be appreciated, speci?c embodiments and uses herein, unless stated otherWise, can 40
optionally comprise nano?bers groWn in the place of theiruse and/or through nano?bers groWn elseWhere, Which are har vested and transferred to the place of their use. For example, many embodiments herein relate to leaving the ?bers intact
on the groWth substrate and taking advantage of the unique 45
properties the ?bers impart on the substrate. Other embodi ments relate to groWth of ?bers on a ?rst substrate and transfer of the ?bers to a second substrate to take advantage of the
ments herein comprise nano?bers composed of one or more
organic or inorganic compound or material. Any recitation of speci?c nano?ber compositions herein should not be taken as
unique properties that the ?bers impart on the second sub
necessarily limiting. Additionally, the nano?bers of the invention are optionally constructed through any of a number of different methods, and examples listed herein should not be taken as necessarily limiting. Thus, nano?bers constructed through means not speci?cally described herein, but Which fall Within the param
place. Available methods, such as groWing nano?bers from gold colloids deposited on surfaces are, thus, optionally used herein. The end product Which results is the substrate upon Which the ?bers are groWn (i.e., With an enhanced surface area
number of factors, e.g., speci?c functionaliZation (if any) to be associated With or attached to the nano?bers, durability, cost, conditions of use, etc. The composition of nano?bers is quite Well knoWn to those of skill in the art. As Will be
using a gold catalyst has been demonstrated in the literature. Applications targeted for such ?bers are based on harvesting them from the substrate and then assembling them into devices. However, in many other embodiments herein, the nano?bers involved in enhanced surface areas are groWn in
and semiconductors. Additionally, While some illustrative
nano?bers herein are comprised of silicon (or silicon oxides), as explained above, they optionally can be comprised of any
bers. For example, ?exible polymer substrates and other simi lar substances are optionally used as substrates for nano?ber
The nano?bers of this invention can be substantially homo geneous in material properties, or in certain embodiments
strate. 50
For example, if nano?bers of the invention Were groWn on, e.g., a non-?exible substrate (e.g., such as some types of
silicon Wafers) they could be transferred from such non ?exible substrate to a ?exible substrate (e.g., such as a con
ductive ?exible metallic material). Again, as Will be apparent
eters as set forth herein are still nano?bers of the invention 55 to those of skill in the art, the nano?bers herein could option and/ or are used With the devices and methods of the invention. ally be groWn on a ?exible substrate to start With, but different
desired parameters may in?uence such decisions.
In a general sense, the nano?bers of the current invention
often (but not exclusively) comprise long thin protuberances
A variety of methods may be employed in transferring
(e. g., ?bers, nanoWires, nanotubules, etc.) groWn from a solid,
nano?bers from a surface upon Which they are fabricated to
optionally planar, substrate. Of course, in some embodiments herein, the ?bers are detached from the substrate on Which they are groWn and attached to a second substrate. The second
substrate need not be planar and, in fact, can comprise a myriad of three-dimensional conformations, as can the sub
60
another surface. For example, nano?bers may be harvested into a liquid suspension, e.g., ethanol, Which is then coated onto another surface. Additionally, nano?bers from a ?rst surface (e.g., ones groWn on the ?rst surface or Which have been transferred to the ?rst surface) can optionally be “har
strate on Which the nano?bers Were groWn originally. In some 65 vested” by applying a sticky coating or material to the nano?
embodiments herein, the substrates are ?exible. Also, as
explained in greater detail beloW, nano?bers of the invention
bers and then peeling such coating/material aWay from the ?rst surface. The sticky coating/material is then optionally
US RE43,868 E 13
14
placed against a second surface to deposit the nano?bers.
the substrates), and any optional functionaliZation of the
Examples of sticky coatings/materials Which are optionally
nano?bers and/or substrates, and the like can be varied. For
used for such transfer include, but are not limited to, e.g., tape
example, the length, diameter, conformation and density of
(e.g., 3M Scotch® tape), magnetic strips, curing adhesives
the ?bers can be varied, as can the composition of the ?bers
(e. g., epoxies, rubber cement, etc.), etc. The nano?bers could be removed from the growth substrate, mixed into a plastic,
and their surface chemistry. C) Density and Related Issues In terms of density, it Will be appreciated that by including
and then surface of such plastic could be ablated or etched aWay to expose the ?bers. The actual nano?ber constructions of the invention are
more nano?bers emanating from a surface, one automatically increases the amount of surface area that is extended from the
optionally complex. For example, FIG. 3 is a photomicro
basic underlying substrate. This, thus, increases the amount
graph of a typical nano?ber construction. As can be seen in
of intimate contact area betWeen the surface and the dielectric
FIG. 3, the nano?bers form a complex three-dimensional
and, indirectly, to the opposing electrode plate coming into
pattern. Possible interlacing and variable heights, curves,
contact With the nano?ber surfaces. As explained in more
detail beloW, the embodiments herein optionally comprise a
bends, etc. can form a surface Which greatly increases the surface area per unit substrate (e. g., as compared With a planar
surface Without nano?bers). Of course, in other embodiments herein, it should be apparent that the nano?bers need not be as complex as, e.g., those shoWn in FIG. 3. Thus, in many embodiments herein, the nano?bers are “straight” and do not tend to bend, curve, or curl. HoWever, such straight nano?bers are still encompassed Within the current invention.
density of nano?bers on a surface of from about 0.1 to about 1000 or more nano?bers per micrometer2 of the substrate
surface. Again, here too, it Will be appreciated that such density depends upon factors such as the diameter of the individual nano?bers, etc. See, beloW. The nano?ber density 20
B) FunctionaliZation
of the surface. Therefore, the density of the nano?bers herein typically has a bearing on the increased capacitance of the
Some embodiments of the invention comprise nano?ber and nano?ber enhanced area surfaces in Which the ?bers include one or more functional moiety (e.g., a chemically
reactive group) attached to them. FunctionaliZed nano?bers are optionally used in many different embodiments, e.g., to confer increased electrical conductance to the nano?bers, to help the dielectric adhere/bond to the nano?bers, etc. Bene? cially, typical embodiments of enhanced surface areas herein are comprised of silicon oxides, Which are conveniently modi?ed With a large variety of moieties. Of course, other
25
For example, a typical ?at planar substrate, e.g., a silicon
30
35
surface comprises about 1 square micron in surface area (i.e., the sides and tip of each nano?ber present that much surface area). If a comparable square micron of substrate comprised from 10 to about 100 nano?bers per square micron, the avail able surface area is thus 10 to 100 times greater than a plain ?at surface. Therefore, in the current illustration, an enhanced
Will be familiar With numerous functionaliZations and func
tionaliZation techniques Which are optionally used herein.
surface area Would have 10>< to 100>< more surface area per
square micron footprint. It Will be appreciated that the density
Further relevant information can be found in CRC Hand 40
of nano?bers on a substrate is in?uenced by, e. g., the diameter
of the nano?bers and any functionaliZation of such ?bers, etc. Different embodiments of the invention comprise a range of such different densities (i.e., number of nano?bers per unit
Press. Details on conductive and other coatings, Which can
also be incorporated onto nano?bers of the invention by plasma methods and the like can be found in H. S. NalWa
(ed.), Handbook of Organic Conductive Molecules and Poly mers, John Wiley & Sons 1997. See also, US. Pat. No. 6,949,
area per square micron (i.e., Within a square micron foot print). HoWever, if such a substrate surface Were coated With nano?bers, then the available surface area Would be much greater. In some embodiments herein each nano?ber on a
positions (e.g., polymers, ceramics, metals that are coated by
book of Chemistry and Physics (2003) 83rd edition by CRC
enhanced surface area materials because such density is a factor in the overall area of the surface.
oxide chip ora glass slide, Will typically comprise “x” surface
embodiments herein are comprised of other nano?ber com
CVD or sol-gel sputtering, etc.) Which are also optionally functionaliZed for speci?c purposes. Those of skill in the art
in?uences the enhanced surface area, since a greater number of nano?bers Will tend to increase the overall amount of area
45
206. Additionally, details regarding relevant moiety and other
area of a substrate to Which nano?bers are attached). The number of nano?bers per unit area can optionally range from about 1 nano?ber per 10 micron2 up to about 200 or more
chemistries, as Well as methods for construction/use of such,
nano?bers per micron2, from about 1 nano?ber per micron2
can be found, e.g., in Herrnanson Bioconjugate Techniques Academic Press (1996), Kirk-Othmer Concise Encyclopedia
up to about 150 or more nano?bers per micron2; from about 10 nano?bers per micron2 up to about 100 or more nano?bers per micron2; or from about 25 nano?bers per micron2 up to about 75 or more nano?bers per micron2. In yet other embodi
of Chemical Technology (1999) Fourth Edition by Grayson et al. (ed.) John Wiley & Sons, Inc., NeW York and in Kirk Othmer Encyclopedia of Chemical Technology Fourth Edi tion (1998 and 2000) by Grayson et al. (ed.) Wiley Inter science (print edition)/John Wiley & Sons, Inc. (e-format). Details regarding organic chemistry, relevant for, e.g., cou
50
ments, the density can optionally range from about 1 to 3 nanoWires per square micron to up to approximately 2,500 or more nanoWires per square micron. 55
In terms of individual ?ber dimensions, it Will be appreci ated that by increasing the thickness or diameter of each individual ?ber one Will, again, automatically increase the overall area of the ?ber and, thus, the overall area of the
60
nano?bers herein can be controlled through, e.g., choice of
pling of additional moieties to a functionaliZed surface of nano?bers can be found, e.g., in Greene (1981) Protective
Groups in Organic Synthesis, John Wiley and Sons, NeW
substrate and, hence, the electrode plate. The diameter of
York, as Well as in Schmidt (1996) Organic Chemistry
Mosby, St Louis, Mo., and March’s Advanced Organic Chemistry Reactions, Mechanisms and Structure, Fifth Edi tion (2000) Smith and March, Wiley Interscience NeW York
compositions and groWth conditions of the nano?bers, addi tion of moieties, coatings or the like, etc. Preferred ?ber
ISBN 0-471-58589-0. Those ofskill in the art Will be familiar
With many other related references and techniques amenable for functionaliZation of the nano?bers herein. Thus, again as Will be appreciated, the substrates involved, the nano?bers involved (e. g., attached to, or deposited upon,
65
thicknesses are optionally betWeen from about 5 nm up to about 1 micron or more (e.g., 5 microns); from about 10 nmto about 750 nanometers or more; from about 25 nm to about 500 nanometers or more; from about 50 nm to about 250 nanometers or more, or from about 75 nm to about 100
US RE43,868 E 15
16
nanometers or more. In some embodiments, the nano?bers
those skilled in the art, as Well as methods mentioned or
comprise a diameter of approximately 40 nm. In addition to diameter, surface area of nano?bers (and
described herein. In other Words, a variety of methods for making nano?bers and nano?ber containing structures have
therefore surface area of a substrate to Which the nano?bers
been described and can be adapted for use in various embodi ments of the invention. The nano?bers can be fabricated of essentially any conve
are attached and, thus, of the electrode plate) also is in?u enced by length of the nano?bers. Of course, it Will also be understood that for some ?ber materials, increasing length
nient electrically conductive material (e.g., a semiconducting material, a ferroelectric material, a metal, ceramic, polymers,
may yield increasing fragility. Accordingly, preferred ?ber lengths Will typically be betWeen about 2 microns (e.g., 0.5
etc.) and can comprise essentially a single material or can be heterostructures. For example, the nano?bers can comprise a
microns) up to about 1 mm or more; from about 10 microns to about 500 micrometers or more; from about 25 microns to about 250 microns or more; or from about 50 microns to about 100 microns or more. Some embodiments comprise nano?
semiconducting material, for example a material comprising a ?rst element selected from group 2 or from group 12 of the
periodic table and a second element selected from group 16
bers of approximately 50 microns in length. Some embodi ments herein comprise nano?bers of approximately 40 nm in diameter and approximately 50 microns in length.
(e.g., ZnS, ZnO, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe,
Nano?bers herein can present a variety of aspect ratios. Thus, nano?ber diameter can comprise, e.g., from about 5 nm up to about 1 micron or more (e.g., 5 microns); from about 10
a ?rst element selected from group 13 and a second element
BaS, BaSe, BaTe, and like materials); a material comprising
selected from group 15 (e.g., GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, and like materials); a material comprising a group 14 element (Ge, Si, and like materials); a material such
nm to about 750 nanometers or more; from about 25 nm to 20 about 500 nanometers or more; from about 50 nm to about as PbS, PbSe, PbTe, AlS, AIR and AlSb; or an alloy or a mixture thereof. 250 nanometers or more, or from about 75 nm to about 100
nanometers or more, While the lengths of such nano?bers can
comprise, e. g., from about 2 microns (e.g., 0.5 microns) up to about 1 mm or more; from about 10 microns to about 500 micrometers or more; from about 25 microns to about 250 microns or more; or from about 50 microns to about 100
25
microns or more
other embodiments, the nano?bers can comprise, e.g., sili
Fibers that are, at least in part, elevated above a surface are
particularly preferred, e.g., Where at least a portion of the
30
?bers in the ?ber surface are elevated at least 10 nm, or even
at least 100 nm above a surface, in order to provide enhanced surface area available for coating With a dielectric and the
opposing electrode plate. Again, as seen in FIG. 3, the nano?bers optionally form a
complex three-dimensional structure. The degree of such complexity depends in part upon, e.g., the length of the nano?bers, the diameter of the nano?bers, the lengthzdiam eter aspect ratio of the nano?bers, moieties (if any) attached to the nano?bers, and the groWth conditions of the nano?bers, etc. The bending, interlacing, etc. of nano?bers, Which help
35
electrically conductive. It Will be appreciated that in some embodiments, the nano?bers can comprise the same material as one or more 40
of nano?bers per unit area as Well as through the diameter of
comprise any one or more of the same materials or types of 45
As previously stated, some, but by no means all, embodi ments herein comprise silicon nano?bers. Common methods
through manipulation of these and other parameters.
for making silicon nano?bers include vapor liquid solid 50
groWth (VLS), laser ablation (laser catalytic groWth) and
55
thermal evaporation. See, for example, Morales et al. (1998) “A Laser Ablation Method for the Synthesis of Crystalline Semiconductor NanoWires” Science 279, 208-211 (1998). In one example approach a hybrid pulsed laser ablation/chemi cal vapor deposition (PLA-CVD) process for the synthesis of
bound to a ?rst surface), the ?ber can still provide an enhanced surface area due to its length, etc.
semiconductor nano?bers With longitudinally ordered het
As Will be appreciated, the current invention is not limited by the means of construction of the nano?bers herein. For example, While some of the nano?bers herein are composed
erostructures, and variations thereof can be used. See, Wu et
al. (2002) “Block-by-Block GroWth of Single-Crystalline
of silicon, the use of silicon should not be construed as nec
essarily limiting. For example, a number of other electrically
60
Si/SiGe Superlattice NanoWires,” Nano Letters Vol. 0, No. 0. In general, multiple methods of making nano?bers have been described and can be applied in the embodiments herein. In addition to Morales et al. and Wu et al. (above), see, for
conductive materials are optionally used. The formation of nano?bers is possible through a number of different approaches that are Well knoWn to those of skill in the art, all of Which are amenable to embodiments of the current inven
tion. Typical embodiments herein can be used With existing methods of nanostructure fabrication, as Will be knoWn by
materials as do the nano?bers (e.g., such as the materials
illustrated herein).
area of nano?ber substrates herein is optionally controlled
D) Nano?ber Construction
substrate surface (i.e., a surface to Which the nano?bers are
attached or associated), While in other embodiments, the nano?bers comprise a different material than the substrate surface. Additionally, the substrate surfaces can optionally
affect the degree of enhanced surface area available, are
Also, in some, but not all, embodiments herein, the nano? bers of the invention comprise bent, curved, or even curled forms. As can be appreciated, if a single nano?ber snakes or coils over a surface (but is still just a single ?ber per unit area
con, glass, quartz, plastic, metal, polymers, TiO, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, PbS, PbSe, PbTe, AlS, AlP, AlSb, SiOl, SiO2, silicon carbide, silicon nitride, polyacrylonitrile (PAN), polyetherketone, polyimide, aromatic polymers, or aliphatic polymers that are
optionally manipulated through, e.g., control of the number the nano?bers, the length and the composition of the nano? bers, etc. Thus, it Will be appreciated that enhanced surface
In some embodiments herein, the nano?bers are optionally comprised of silicon or a silicon oxide. It Will be understood by one of skill in the art that the term “silicon oxide” as used herein can be understood to refer to silicon at any level of oxidation. Thus, the term silicon oxide can refer to the chemi cal structure SiOx, Wherein x is betWeen 0 and 2 inclusive. In
65
example, Lieber et al. (2001) “Carbide Nanomaterials” US. Pat. No. 6,190,634 B 1; Lieber et al. (2000) “Nanometer Scale Microscopy Probes” US. Pat. No. 6,159,742; Lieber et al. (2000) “Method of Producing Metal Oxide Nanorods” US. Pat. No. 6,036,774; Lieber et al. (1999) “Metal Oxide Nano
US RE43,868 E 17
18
rods” US. Pat. No. 5,897,945; Lieber et al. (1999) “Prepara
Synthesis of nanostructures, e.g., nanocrystals, of various composition is described in, e.g., Peng et al. (2000) “Shape
tion of Carbide Nanorods” US. Pat. No. 5,997,832; Lieber et
al. (1998) “Covalent Carbon Nitride Material Comprising C2N and Formation Method” US. Pat. No. 5,840,435; Thess, et al. (1996) “Crystalline Ropes of Metallic Carbon Nano tubes” Science 273:483-486; Lieber et al. (1993) “Method of Making a Superconducting Fullerene Composition By React ing a Fullerene With an Alloy Containing Alkali Metal” US. Pat. No. 5,196,396; and Lieber et al. (1993) “Machining
control of CdSe nanocrystals” Nature 404: 59-61 ; Puntes et al.
(2001) “Colloidal nanocrystal shape and siZe control: The 5
736 to Alivisatos et al. (Oct. 23, 2001) entitled “Process for
forming shaped group III -V semiconductor nanocrystals, and product formed using process”; US. Pat. No. 6,225,198 to Alivisatos et al. (May 1, 2001) entitled “Process for forming shaped group II-VI semiconductor nanocrystals, and product formed using process”; US. Pat. No. 5,505,928 to Alivisatos et al. (Apr. 9, 1996) entitled “Preparation of III-V semicon
Oxide Thin Films With an Atomic Force Microscope: Pattern and Object Formation on the Nanometer Scale” US. Pat. No.
5,252,835. One dimensional semiconductor heterostructure nanocrystals, have been described. See, e.g., Bjork et al. (2002) “One-dimensional Steeplechase for Electrons Real
ductor nanocrystals”; US. Pat. No. 5,751,018 to Alivisatos et
al. (May 12, 1998) entitled “Semiconductor nanocrystals covalently bound to solid inorganic surfaces using self-as sembled monolayers”; US. Pat. No. 6,048,616 to Gallagher et al. (Apr. 11, 2000) entitled “Encapsulated quantum siZed doped semiconductor particles and method of manufacturing
iZed” Nano Letters Vol. 0, No. 0. It should be noted that some references herein, While not speci?c to nano?bers, are typically still applicable to the
invention. For example, background issues of construction conditions and the like are applicable betWeen nano?bers and
other nanostructures (e.g., nanocrystals, etc.). Also, While
case of cobalt” Science 291 :21 15-21 17; US. Pat. No. 6,306,
20
same”; and US. Pat. No. 5,990,479 to Weiss et al. (Nov. 23, 1999) entitled “Organo luminescent semiconductor nanoc
described generally in terms of nano?bers and the like, again, it Will be appreciated that nanospheres, nanocrystals, etc. are
rystal probes for biological applications and process for mak ing and using such probes.”
also optionally used to increase the surface area and capaci tance of the embodiments herein. See above.
nanoWires, having various aspect ratios, including nano?bers
In another approach Which is optionally used to construct nano?bers of the invention, synthetic procedures to prepare
Additional information on groWth of nano?bers, such as 25
With controlled diameters, is described in, e.g., Gudiksen et
al. (2000) “Diameter-selective synthesis of semiconductor nanoWires” J. Am. Chem. Soc. 122:8801-8802; Cui et al.
individual nano?bers on surfaces and in bulk are described,
for example, by Kong, et al. (1998) “Synthesis of Individual
(2001) “Diameter-controlled synthesis of single-crystal sili
Single-Walled Carbon Nanotubes on Patterned Silicon
con nanoWires”Appl. Phys. Lett. 78:2214-2216; Gudiksen et
Wafers,” Nature 395:878-881, and Kong, et al. (1998) “Chemical Vapor Deposition of Methane for Single-Walled Carbon Nanotubes,” Chem. Phys. Lett. 292:567-574. In yet another approach, substrates and self assembling monolayer (SAM) forming materials can be used, e.g., along With microcontact printing techniques to make nano?bers,
30
35
such as those described by Schon, Meng, and Bao, “Self
assembled monolayer organic ?eld-effect transistors,” Nature 413:713 (2001); Zhou et al. (1997) “Nanoscale Metal/Self
Assembled Monolayer/Metal Heterostructures,” Applied Physics Letters 71 :61 1; and WO 96/29629 (Whitesides, et al.,
40
published Jun. 26, 1996). In some embodiments herein, nano?bers can be synthe siZed using a metallic catalyst. A bene?t of such embodiments alloWs use of unique materials suitable for surface modi?ca tions to create enhanced properties.A unique property of such nano?bers is that they are capped at one end With a catalyst,
45
50
55
substrate surface is optionally chemically modi?ed (typi cally, but not necessarily, Without affecting the gold tip) in order to give a Wide range of properties useful in many appli cations. 60
area, the nano?bers are optionally laid “?at” (i.e., substan
tially parallel to the substrate surface) by chemical or elec trostatic interaction on surfaces, instead of end-linking the nano?bers to the substrate. In yet other embodiments herein,
techniques involve coating the base surface With functional groups Which repel the polarity on the nano?ber so that the ?bers do not lay on the surface but are end-linked.
al. (Apr. 27, 1999) entitled “Metal oxide nanorods”; US. Pat. No. 5,997,832 to Lieber et al. (Dec. 7, 1999) “Preparation of carbide nanorods”; Urbau et al. (2002) “Synthesis of single crystalline perovskite nanoWires composed of barium titanate
nos. WO 02/17362, and WO 02/080280.
GroWth of branched nano?bers (e.g., nanotetrapods, tri pods, bipods, and branched tetrapods) is described in, e.g.,
surface areas (i.e., in relation to the surfaces Without the
In other embodiments, to increase or enhance a surface
12:298-302; Cui et al. (2000) “Doping and electrical transport in silicon nanoWires” J. Phys. Chem. B 104: 52 1 3-521 6; Peng et al. (2000), supra; Puntes et al. (2001), supra; US. Pat. No. 6,225,198 to Alivisatos et al., supra; US. Pat. No. 6,036,774 to Lieber et al. (Mar. 14, 2000) entitled “Method of producing metal oxide nanorods”; US. Pat. No. 5,897,945 to Lieber et
al. (2002) “Ferroelectric Properties of Individual Barium Titanate NanoWires Investigated by Scanned Probe Micros copy” Nano Letters 2, 447; and published PCT application
These resulting “fuZZy” surfaces, therefore, have increased nano?bers) and other unique properties. In some such embodiments, the surface of the nano?ber and/or the target
method for the synthesis of crystalline semiconductor nanoW ires” Science 279:208-211; Duan et al. (2000) “General syn thesis of compound semiconductor nanoWires” Adv. Mater.
and strontium titanate” J. Am. Chem. Soc., 124: 1 186;Yun et
typically gold. This catalyst end can optionally be function aliZed using, e.g., thiol chemistry Without affecting the rest of the ?ber, thus, making it capable of bonding to an appropriate surface. In such embodiments, the result of such functional iZation, etc., is to make a surface With end-linked nano?bers.
al. (2001) “Synthetic control of the diameter and length of single crystal semiconductor nanoWires” J. Phys. Chem. B 105:4062-4064; Morales et al. (1998) “A laser ablation
65
June et al. (2001) “Controlled synthesis of multi-armed CdS nanorod architectures using monosurfactant system” J. Am. Chem. Soc. 123:5150-5151; and Manna et al. (2000) “Syn thesis of Soluble and Processable Rod-, ArroW-, Teardrop-, and Tetrapod-Shaped CdSe Nanocrystals” J. Am. Chem. Soc. 122:12700-12706. Synthesis of nanopar‘ticles is described in, e.g., US. Pat. No. 5,690,807 to Clark Jr. et al. (Nov. 25, 1997) entitled “Method for producing semiconductor particles”; US. Pat. No. 6,136,156 to El-Shall, et al. (Oct. 24, 2000) entitled “Nanopar‘ticles of silicon oxide alloys”; US. Pat. No. 6,413,489 to Ying et al. (Jul. 2, 2002) entitled “Synthesis of nanometer-sized particles by reverse micelle mediated tech niques”; and Liu et al. (2001) “Sol-Gel Synthesis of Free Standing Ferroelectric Lead Zirconate Titanate Nanopar ticles” J. Am. Chem. Soc. 123:4344. Synthesis of
US RE43,868 E 19
20
nanoparticles is also described in the above citations for growth of nanocrystals, and nano?bers such as nanoWires, branched nanoWires, etc. Synthesis of core-shell nano?bers, e.g., nanostructure het
4000 C. in the presence of a gold catalyst. HoWever, as pre viously stated, silicon nano?bers can be too brittle for some applications to form a durable nano?ber matrix (i.e., an enhanced surface area). Thus, formation and use of, e.g., SiN is optionally utiliZed in some embodiments herein. In those
erostructures, is described in, e.g., Peng et al. (1997) “Epi taxial growth of highly luminescent CdSe/CdS core/shell
embodiments, NH3, Which has decomposition at about 3000
nanocrystals With photostability and electronic accessibility”
C., is used to combine With silane to form SiN nano?bers
J. Am. Chem. Soc. 119:7019-7029; Dabbousi et al. (1997)
(also by using a gold catalyst). Other catalytic surfaces to
“(CdSe)ZnS core-shell quantum dots: Synthesis and charac
form such nano?bers can include, e.g., Ti, Fe, etc. Forming carbide and nitride nano?bers directly from a melt can sometimes be challenging since the temperature of
teriZation of a siZe series of highly luminescent nanocrystal lites” J. Phys. Chem. B 101:9463-9475; Manna et al. (2002)
“Epitaxial groWth and photochemical annealing of graded
the liquid phase is typically greater than 10000 C. HoWever, a nano?ber can be groWn by combining the metal component With the vapor phase. For example, GaN and SiC nano?bers
CdS/ZnS shells on colloidal CdSe nanorods” J. Am. Chem.
Soc. 124:7136-7145; and Cao et al. (2000) “GroWth and
properties of semiconductor core/ shell nanocrystals With
have been groWn (see, e.g., Peidong, Lieber, supra) by expos ing Ga melt to NH3 (for GaN) and graphite With silane (SiC).
lnAs cores” J. Am. Chem. Soc. 122:9692-9702. Similar approaches can be applied to groWth of other core-shell nano
Similar concepts are optionally used to form other types of
carbide and nitride nano?bers by combing metal-organic
structures. See, for example, US. Pat. No. 6,207,229 (Mar. 27, 2001) and US. Pat. No. 6,322,901 (Nov. 27, 2001) to BaWendi et al. entitled “Highly luminescent color-selective materials.”
20
dimethoxy dineodecanoate on a carbon surface to form TiC.
GroWth of homogeneous populations of nano?bers, including nano?ber hetero structures in Which different mate rials are distributed at different locations along the long axis
of the nano?bers is described in, e.g., published PCT appli cation numbers W0 02/ 17362, and WO 02/080280; Gudik
25
used to form the nano?bers, as Well as, the core materials for
the nano?bers (e. g., Si, ZnO, etc.) and the substrates contain
620; Bjork et al. (2002) “One-dimensional steeplechase for
ing the nano?bers, are all also variable from one embodiment 30
“Block-by-block groWth of single-crystalline Si/SiGe super
to another depending upon, e.g., the speci?c enhanced nano?ber surface area capacitor to be constructed. The present invention can be used With structures that may fall outside of the siZe range of typical nanostructures. For
lattice nanoWires” Nano Letters 2, 83-86; and US patent
application publication 2004/0026684. Similar approaches can be applied to groWth of other heterostructures and applied to the various devices, methods and systems herein.
It Will be appreciated that in such embodiments, the tempera ture, pressure, poWer of the sputtering and the CVD process are all optionally varied depending upon, e.g., the speci?c parameters desired in the end nano?bers. Additionally, sev
eral types of metal organic precursors and catalytic surfaces
sen et al. (2002) “GroWth of nanoWire superlattice structures for nanoscale photonics and electronics” Nature 4151617
electrons realized” Nano Letters 2:86-90; Wu et al. (2002)
vapor species, e.g., tungsten carbolic [W(CO)6] on a carbon surface to form tungsten carbide (WC), or titanium
example, Haraguchi et al. (US. Pat. No. 5,332,910) describes 35
In some embodiments the nano?bers used to create
nanoWhiskers Which are optionally used herein in design and construction of capacitors. Semi-conductor Whiskers are also
enhanced surface areas canbe comprised of nitride (e.g., AlN,
described by Haraguchi et al. (1994) “Polarization Depen
GaN, SiN, BN) or carbide (e.g., SiC, TiC, Tungsten carbide,
dence of Light Emitted from GaAs p-n junctions in quantum Wire crystals” J. Appl. Phys. 75(8):4220-4225; Hiruma et al. (1993) “GaAs Free Standing Quantum SiZed Wires,” J. Appl. Phys. 74(5):3162-3171; Haraguchi et al. (1996) “Self Orga
boron carbide) in order to create nano?bers With high strength and durability. Alternatively, such nitrides/carbides are used as hard coatings on loWer strength (e.g., silicon or ZnO)
40
nano?bers. While the dimensions of silicon nano?bers are
excellent for many applications requiring enhanced surface area (e.g., see, throughout and US patent application publi cation 20040206448.) other capacitor applications can
45
require nano?bers that are less brittle and Which break less
easily. Therefore, some embodiments herein take advantage of materials such as nitrides and carbides Which have higher
bond strengths than, e.g., Si, SiO2, or ZnO. The nitrides and carbides are optionally used as coatings to strengthen the
50
nano?ber construction/design, etc. Which can also be ame nable to the methods and devices herein.
Some embodiments herein comprise methods for improv ing the density and control of nanoWire groWth as is relates to generating a nanostructured surface coating of substrates.
Weaker nano?bers or even as nano?bers themselves.
Carbides and nitrides can be applied as coatings to loW
strength ?bers by deposition techniques such as sputtering and plasma processes. In some embodiments, to achieve high strength nanocoatings of carbide and nitride coatings, a ran dom grain orientation and/or amorphous phase is groWn to
niZed Fabrication of Planar GaAs NanoWhisker Arrays”; and YaZaWa (1993) “Semiconductor NanoWhiskers” Adv. Mater. 5(78):577-579. Such nanoWhiskers are optionally nano?bers of the invention. While the above references (and other ref erences herein) are optionally used for construction and deter mination of parameters of nano?bers of the invention, those of skill in the art Will be familiar With other methods of
Such methods include repetitive cycling of nano?ber synthe 55
sis and gold ?ll deposition to make “nano-trees” as Well as the co-evaporation of material that Will not form a silicon eutec
avoid crack propagation. Optimum conformal coating of the
tic, thus, disrupting nucleation and causing smaller Wire for
nano?bers can optionally be achieved if the ?bers are groWing perpendicular to a substrate surface. The hard coating for ?bers in such orientation also acts to enhance the adhesion of the ?bers to the substrate. For ?bers that are randomly ori
mation Such methods are utiliZed in the creation of ultra-high 60
ented, the coating is preferential to the upper layer of ?bers. Further information on coating nanostructure surfaces (e.g.,
surface roughness, etc., and, thus, the ability of control nucle
to deposit a dielectric layer or to construct a second electrode
plate) is presented herein. LoW temperature processes for creation of silicon nano? bers are achieved by the decomposition of silane at about
capacity surface based structures through nano?ber groWth technology for, e. g., nano?ber based capacitors. Use of single-step metal ?lm type process in creation of nano?bers limits the ability to control the starting metal ?lm thickness,
65
ation from the surface. In some embodiments of nano?ber enhanced surfaces it can be desirable to produce multibranched nano?bers. Such
US RE43,868 E 21
22
multibranched nano?bers could allow an even greater increase in surface area than Would occur With non-branched
placement on substrates so as to generate spatially de?ned
regions to Which to apply speci?c chemistry (e.g., dielectric
nano?ber surfaces. To produce multibranched nano?bers gold ?lm is optionally deposited onto a nano?ber surface (i.e., one that has already groWn nano?bers). When placed in a
deposition). In such approaches, the term “substrate” relates to the material upon Which the Wires are groWn (or, in some
embodiments, placed or deposited). In different situations, substrates are optionally comprised of, e.g., silicon Wafer,
furnace, ?bers perpendicular to the original groWth direction
glass, quartz, or any other material appropriate forVLS based nanoWire groWth or the like. HoWever, in typical embodi
can result, thus, generating branches on the original nano? bers. Colloidal metal particles can optionally be used instead of gold ?lm to give greater control of the nucleation and
ments Wherein the nano?bers are to be used in situ, the sub
branch formation. The cycle of branching optionally could be repeated multiple times to generate additional branches. Eventually, the branches betWeen adjacent nano?bers could
In some embodiments herein, micro-patterning of enhanced surface area substrates is optionally created by
optionally touch and generate an interconnected netWork.
lithographically applying planar regions of gold to a substrate
Sintering is optionally used to improve the binding of the ?ne In yet other capacitor embodiments, it is desirable to form ?ner nano?bers (e.g., nanoWires). To accomplish this, some
as the standard groWth initiator through use of conventional lithographic approaches Which are Well known to those of skill in the art. Nano?bers (e.g., VLS nanoWires) are then groWn, e. g., in the manner of Peidong Yang, Advanced Mate
embodiments herein optionally use a non-alloy forming
rials, Vol. 13, No. 2, January 2001.
strate is preferably electrically conductive.
branches.
material during gold or other alloy forming metal evapora tion. Such material, When introduced in a small percentage can optionally disrupt the metal ?lm to alloW it to form
20
smaller droplets during Wire groWth and, thus, correspond ingly ?ner ?bers. In yet other embodiments, post processing steps such as vapor deposition of materials can alloW for greater anchoring
25
In other embodiments, patterning can be created by chemi cally precoating a substrate through conventional litho graphic approaches so that deposition of gold colloids is controlled prior to groWth of nano?bers (e.g., by selective patterning of thiol groups on the substrate surface). In yet other embodiments, nano?bers are optionally pre-groWn in a conventional manner Well knoWn to those of skill in the art
(see, e.g., above) and then selectively attached to regions of the substrate Where the spatially de?ned pattern is required.
or mechanical adhesion and interconnection betWeen nano?
bers, thus, improving mechanical robustness in applications requiring additional strength as Well as increasing the overall
Of course, in yet other embodiments, “laWns” of nano?bers
surface to volume of the nano structure surface. Additionally,
forming an enhanced surface area substrate are selectively
typical embodiments herein have deposition of material(s) to
30
form the dielectric.
It should be appreciated that speci?c embodiments and illustrations herein of uses or devices, etc., Which comprise nano?ber enhanced surface area capacitors should not be construed as necessarily limiting. In other Words, the current
35
invention is illustrated by the descriptions herein, but is not constrained by individual speci?cs of the descriptions unless
40
necessarily limiting on other uses/applications Which com prise the enhanced surface area nano?ber structures of the current invention.
In some embodiments, the invention comprises methods to selectively modify or create enhanced surface area substrates as Well as such enhanced substrates themselves and capacitor devices comprising the same. As Will be appreciated, and as is described herein, such methods and devices are applicable to
or deposited in certain selected areas (or any combinations thereof). Those of skill in the art Will be aWare of numerous other patterns, etc. Which can optionally be Within embodi ments herein.
While, certain methods of patterning, sub strate/nano?ber/
speci?cally stated. The embodiments are illustrative of vari ous uses/ applications of the enhanced surface area nano?ber
surface capacitors and constructs thereof. Again, the enu meration of speci?c embodiments herein is not to be taken as
patterned through removal of nano?bers in preselected areas. Other embodiments can optionally comprise nano?ber laWns that have areas selectively cleared of nano?bers (thus, creat ing nano?ber islands, etc.) or can have nano?bers only groWn
45
dielectric/ etc. composition and the like are illustrated herein, it Will again be appreciated that such are illustrative of the range included in the invention. Thus, such parameters can be changed and still come Within the range of the invention. For example, as illustrated above, creation of enhanced surface areas is optionally accomplished in any of a number of Ways, all of Which are encompassed herein. For example, as
described in greater detail in co-pending and commonly assigned U.S. PatentApplication Ser. No. 60/61 1,1 16 entitled “Nanostructured Thin Films and Their Uses,” ?led Sep. 17, 2004, the entire contents of Which are incorporated by refer
a Wide range of uses and can be created in any of a number of 50 ence herein, nanostructured surfaces can be made from a
Ways (several of Which are illustrated herein). As Will be appreciated, the enhanced surface areas pro
variety of materials including insulating inorganic materials
vided by surfaces containing nano?bers can provide signi?
layer. The insulating inorganic material may also be formed form a deposited metal layer. For example, the insulating
cant advantages as an integral part of a capacitor. HoWever, in some embodiments, e.g., in manufacturing or as required by some devices, multiple capacitors or multiple nano?ber areas
such as a native oxide layer or a deposited oxide or nitride
55
inorganic material may be selected from the group of mate
rials including aluminum (Al), alumina (A1203), ZnO, SiO2,
to be incorporated into capacitors are created on the same
ZrO2, HfO2, a hydrous form of these oxides, a compound
substrate. Therefore, some embodiments herein comprise methods that can alloW spatially controlled chemistry to be
oxide such as SiTiO3, BaTiO3 PbZrO4 or a silicate. In one
applied to nano?ber-enhanced surfaces (e.g., application of dielectric material(s) and/or material(s) to comprise an opposing electrode plate, etc.), and/ or to spatially control the placement of the nano?bers themselves upon the substrate. Such control can facilitate the utility of enhanced nano?ber surfaces in real applications. Several approaches are included in the embodiments herein for selectively patterning areas of nano?ber groWth or
example, the ?lm layer is made from alumina or aluminum 60
Which can be deposited on the substrate (e.g., one or more
electrode plates) using a variety of Well-knoWn techniques such as thermal evaporation and sputtering including physical vapor deposition (PVD), sputter deposition, chemical vapor
deposition (CVD), metallorganic CVD, plasma-enhanced 65
CVD, laser ablation, or solution deposition methods such as
spray coating, dip coating, or spin coating etc. Ultra-thin metal ?lms (e. g., ?lms less than about 5 nm in thickness) may
US RE43,868 E 23
24
be deposited by atomic layer deposition (ALD) techniques. The thin ?lm preferably has a thickness less than about 1000 nm, for example, betWeen about 5 and 400 nm, for example, betWeen about 5 and 200 nm, for example, betWeen about 10
tion 2005/0181195. Those of skill in the art Will be familiar With many other related references and techniques amenable for functionaliZation of surfaces herein. While the foregoing invention has been described in some
and 100 nm. The ?lm layer may then be con?gured to have a
detail for purposes of clarity and understanding, it Will be
nano structured surface, for example, by boiling the ?lm layer,
clear to one skilled in the art from a reading of this disclosure that various changes in form and detail can be made Without departing from the true scope of the invention. For example, all the techniques and apparatus described above can be used
autoclaving it, etc. for a su?icient time (e.g., betWeen about 3 to 60 minutes, for example, betWeen about 5 to 30 minutes) to convert the ?lm into a highly ordered nano structured surface having pore siZes less than about 200 nm. The nanostructured ?lm layer can also be formed by other means such as the formation of porous alumina ?lms via the anodiZation of
in various combinations. All publications, patents, patent applications, or other documents cited in this application are
incorporated by reference in their entirety for all purposes to
aluminum metal in acidic solution (e.g., phosphoric, oxalic,
the same extent as if each individual publication, patent,
or sulfuric acid solutions). See, e.g., Evelina Palibroda, A.
patent application, or other document Were individually indi cated to be incorporated by reference for all purposes. What is claimed is: 1. A device comprising ?rst and second opposing elec trodes and a dielectric layer disposed betWeen the ?rst and
Lupsan, Stela Pruneanu, M. Savos, Thin Solid Films, 256, 101 (1995), the entire contents of Which are incorporated by reference herein. Other textured surfaces other than alumina or aluminum can also be used including, for example, Zinc oxide (ZnO) nanostructured surfaces and the other material
surfaces described above. LoW-temperature solution-based approaches to forming ZnO nanotextured surfaces are
20
Wherein the nano?bers comprise a core and one or more
described, for example, in “LoW Temperature Wafer-Scale Production of ZnO NanoWire Arrays,” Lori E. Greene et al., AngeW. Chem. Int. Ed. 2003, 42, 3031-3034, the entire con tents of Which are incorporated by reference herein. The nanostructured ?lm layer can also optionally be coated or functionaliZed, e.g., to enhance or add speci?c properties. For example, polymers, ceramics, or small molecules can
coatings disposed about the core. 2. The device of claim 1, Wherein the one or more coatings comprise a nitride or a carbide. 25
3. The device of claim 1, Wherein the core of the plurality of nano?bers comprises silicon or a silicon containing com
pound. 4. The device of claim 1, Wherein the core of the plurality
optionally be used as coating materials. The optional coatings can impart characteristics such as Water resistance, improved
second electrodes, Wherein the dielectric layer comprises a plurality of nano?bers disposed Within a dielectric material,
30
mechanical, optical (e.g., enhancement of light coupling) or electrical properties. The nanostructured ?lm layer may also
of nano?bers comprises ZnO, Si or SiO2. 5. The device of claim 1, Wherein the dielectric material comprises a nonconductive material.
6. The device of claim 1, Wherein the dielectric material
be derivatiZed With one or more functional moieties (e.g., a comprises an oxide, a nitride, a polymer, a ceramic, a resin, a chemically reactive group) such as one or more silane groups, porcelain, a mica containing material, a glass, a rare earth e.g., one or more per-?uorinated silane groups, or other coat 35 oxide, or a gas.
7. The device of claim 1, Wherein the dielectric material comprises an oxide layer. 8. The device of claim 1, Wherein the dielectric material
ings such as diamond coatings, a hydrocarbon molecule, a ?uorocarbon molecule, or a short chainpolymer of both types of molecules Which may be attached to the ?lm layer via silane chemistry. Those of skill in the art Will be familiar With numerous functionaliZations and functionaliZation tech
comprises a naturally occurring oxide layer. 40
9. The device of claim 1, Wherein the dielectric material
niques Which are optionally used herein (e.g., similar to those
comprises silicon oxide.
used in construction of separation columns, bio-assays, etc.). For example, details regarding relevant moiety and other
of nanoWires comprise a silicon or silicon containing com
10. The device of claim 9, Wherein the core of the plurality
pound.
chemistries, as Well as methods for construction/use of such,
can be found, e.g., in Hermanson Bioconjugate Techniques Academic Press (1996), Kirk-Othmer Concise Encyclopedia
of Chemical Technology (1999) Fourth Edition by Grayson et al. (ed.) John Wiley & Sons, Inc., NeW York and in Kirk Othmer Encyclopedia of Chemical Technology Fourth Edi tion (1998 and 2000) by Grayson et al. (ed.) Wiley lnter science (print edition)/John Wiley & Sons, Inc. (e-format).
45
SiN or BN. 12. The device of claim 2 or 10, Wherein the one or more
coatings includes a carbide material comprising SiC, TiC, 50
of Chemistry and Physics (2003) 83’d edition by CRC Press. Details on conductive and other coatings, Which can also be
bers are groWn on a surface of at least one of said ?rst and 55
No. 6,949,206. Details regarding organic chemistry, relevant for, e.g., coupling of additional moieties to a functionaliZed surface can be found, e.g., in Greene (1981) Protective
second electrodes.
17. A device comprising first and second opposing elec trodes and a dielectric layer disposed between the first and second electrodes, wherein the dielectric layer comprises a
York, as Well as in Schmidt (1996) Organic Chemistry
Mosby, St Louis, Mo., and March’s Advanced Organic
ISBN 0-471-58589-0, and US. patent application publica
second electrodes. 15. The device of claim 14, Wherein the plurality of nano? bers are groWn by a VLS groWth process. 16. The device of claim 1, Wherein the plurality of nano? bers are deposited on a surface of at least one of said ?rst and
60
Groups in Organic Synthesis, John Wiley and Sons, NeW Chemistry Reactions Mechanisms and Structure, Fifth Edi tion (2000) Smith and March, Wiley Interscience NeW York
Tungsten carbide or boron carbide.
13. The device of claim 1, Wherein the plurality of nano? bers comprise a plurality of nanoWires. 14. The device of claim 1, Wherein the plurality of nano?
Further relevant information can be found in CRC Handbook
incorporated onto the nanostructured ?lm layer of the inven tion by plasma methods and the like can be found in H. S. NalWa (ed.), Handbook of Organic Conductive Molecules and Polymers, John Wiley & Sons 1997. See also, US. Pat.
11. The device of claim 2 or 10, Wherein the one or more
coatings includes a nitride material comprising AlN, GaN,
plurality of nano?bers disposed within a dielectric material, 65
wherein the nano?bers comprise a core. *
*
*
*
*
