U.S. patent application number 17/362916 was filed with the patent office on 2021-10-21 for method of making graphene and graphene devices.
This patent application is currently assigned to VAON, LLC. The applicant listed for this patent is VAON, LLC. Invention is credited to Jim Busch, Lindsey Lindamood.
Application Number | 20210327707 17/362916 |
Document ID | / |
Family ID | 1000005685202 |
Filed Date | 2021-10-21 |
United States Patent
Application |
20210327707 |
Kind Code |
A1 |
Busch; Jim ; et al. |
October 21, 2021 |
METHOD OF MAKING GRAPHENE AND GRAPHENE DEVICES
Abstract
The present invention generally relates to a method of making
graphene and graphene devices.
Inventors: |
Busch; Jim; (Columbus,
OH) ; Lindamood; Lindsey; (Columbus, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VAON, LLC |
Bowling Green |
KY |
US |
|
|
Assignee: |
VAON, LLC
Bowling Green
KY
|
Family ID: |
1000005685202 |
Appl. No.: |
17/362916 |
Filed: |
June 29, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16988475 |
Aug 7, 2020 |
11081336 |
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17362916 |
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15825209 |
Nov 29, 2017 |
10777406 |
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16988475 |
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62427252 |
Nov 29, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/02672 20130101;
H01L 21/02488 20130101; H01L 21/02491 20130101; H01L 21/02527
20130101; C01B 2204/22 20130101; C01B 32/186 20170801; H01L
21/28247 20130101; H01L 21/02513 20130101; G01J 3/44 20130101; H01L
21/02115 20130101; H01L 21/02502 20130101; H01L 29/1606 20130101;
C01B 32/184 20170801 |
International
Class: |
H01L 21/02 20060101
H01L021/02; C01B 32/186 20060101 C01B032/186; H01L 21/28 20060101
H01L021/28; C01B 32/184 20060101 C01B032/184 |
Claims
1. A graphene device, comprising: an insulator layer, wherein at
least a top portion of the insulator layer is an electrical
insulator; a metal layer in contact with and covering part of the
top of the insulator layer; a graphene layer in contact with the
metal layer and the top of the insulator layer; an optional
passivation layer located between the insulator layer and the
metal/carbon layers and in contact with and covering a substantial
portion of the top of the insulator layer; and, an optional metal
adhesive layer located between the metal layer and either the
insulator layer or passivation layer if present.
2. The graphene device of claim 1, wherein: the passivation layer
is present.
3. The graphene device of claim 1, wherein: the metal adhesive
layer is present.
4. The graphene device of claim 1, wherein: the passivation and
metal adhesive layers are present.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This Application is a Continuation of U.S. application Ser.
No. 16/988,475 filed Aug. 7, 2020, which is a Divisional of U.S.
application Ser. No. 15/825,209 filed Nov. 29, 2017, issued as U.S.
Pat. No. 10,777,406 on Sep. 15, 2020, and which claims priority to
U.S. Provisional Application No. 62/427,252 filed Nov. 29, 2016,
all of which are incorporated herein in their entirety by
reference.
FIELD OF THE INVENTION
[0002] The present invention generally relates to a method of
making graphene and graphene devices.
BACKGROUND OF THE INVENTION
[0003] Graphene is a substance composed of pure carbon, with atoms
arranged in a regular hexagonal pattern similar to graphite, but in
a one-atom thick sheet. It is very light, with a 1-square-meter
sheet weighing only 0.77 milligrams. The structure of graphene is a
single planar sheet of sp.sup.2-hybrid bonded carbon atoms that are
densely packed in a honeycomb crystal lattice. Graphene is most
easily visualized as an atomic-scale chicken wire made of carbon
atoms and their bonds. The graphene atoms are arranged into a
two-dimensional honeycomb structure with the crystalline or "flake"
form of graphite consisting of many graphene sheets stacked
together.
[0004] Graphene is about 100 times stronger than steel; conducts
electricity better than copper; and is more flexible than rubber.
It is touted as possible replacement for silicon in
electronics.
[0005] Only identified in 2004, graphene is a single layer of
tightly packed carbon atoms making it the thinnest material ever
created and offering huge promise for a host of applications from
information technology to energy to medicine. Graphene can be made
by several methods such as scotch-tape or chemical ex-foliation,
chemical vapor deposition (CVD) induced growth, graphite oxide
reduction. The two primary methods of production are chemical
exfoliation and graphite oxide reduction. These methods
unfortunately only produce small flakes of graphene (usually
dispersed in a liquid medium). They also require use of aggressive
solvents to break graphene oxide apart from the carbon source (such
as graphite) and remove oxygen from graphene oxide to form
graphene. Epitaxial Growth on a substrate produces larger graphene
sheets (currently able to make up to 40'' square; and works by
exposing CH.sub.4 and H.sub.2 to a substrate (such as copper foil)
inside a high temperature furnace. This method requires etching of
substrate to remove and transfer the graphene sheet. It is overall,
a very costly and time consuming method to produce a large sheet of
graphene.
[0006] In view of the above, it would be useful to be able to make
graphene in a simpler, less costly way. It would also be useful to
be able to make graphene directly on a device, thereby eliminating
the need for transferring the graphene.
SUMMARY OF THE INVENTION
[0007] In an aspect, the present invention provides a novel
graphene device precursor.
[0008] In another aspect, the present invention provides a novel
method of making graphene.
[0009] In another aspect, the present invention provides a novel
graphene device.
[0010] These and other aspects, which will become apparent during
the following detailed description, have been achieved by the
inventors' discovery of a new method of making graphene.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows the Raman spectra from a device that had been
heated to 800.degree. C. The spectra were taken at a point 3 .mu.m
from a Ni edge. These spectra (and the remainder described herein)
are of the material that is located on the insulator layer.
[0012] FIG. 2 shows the Raman spectra from a device that had been
heated to 800.degree. C. The spectra were taken 50 .mu.m from a Ni
edge.
[0013] FIG. 3 shows the Raman spectra from a device that had been
heated to 800.degree. C. The spectra were taken 100 .mu.m from a Ni
edge.
[0014] FIG. 4 shows the Raman spectra from a device that had been
heated to 600.degree. C. The spectra were taken 5 .mu.m from a Ni
edge.
[0015] FIG. 5 shows the Raman spectra from a device that had been
heated to 600.degree. C. The spectra were taken 10 .mu.m from a Ni
edge.
[0016] FIG. 6 shows the Raman spectra from a device that had been
heated to 700.degree. C. The spectra were taken at a Ni edge.
[0017] FIG. 7 shows the Raman spectra from a device that had been
heated to 700.degree. C. The spectra were taken 50 .mu.m from a Ni
edge.
[0018] FIG. 8 shows the Raman spectra from a device that had been
heated to 700.degree. C. The spectra were taken 100 .mu.m from a Ni
edge.
[0019] FIG. 9 shows the Raman spectra from a device that had been
heated to 700.degree. C. The spectra were taken 200 .mu.m from a Ni
edge.
DETAILED DESCRIPTION OF THE INVENTION
[0020] In an aspect, the present invention provides a novel
graphene device precursor, comprising: an insulator layer, wherein
at least the top portion of the insulator layer is an electrical
insulator;
[0021] a metal layer in contact with and covering part of the top
of the insulator layer;
[0022] a carbon layer in contact with the metal layer and the top
of the insulator layer;
[0023] an optional passivation layer located between the insulator
layer and the metal/carbon layers and in contact with and covering
a substantial portion of the top of the insulator layer; and,
[0024] an optional metal adhesive layer located between the metal
layer and either the insulator layer or passivation layer, if
present.
[0025] In another aspect, the insulator layer is a thermal oxide
(thermal silicon oxide) layer (e.g., SiO.sub.2/Si). For the thermal
oxide wafer, at least the top portion of the wafer is SiO.sub.2
(i.e., insulating). Typically, the top and bottom portions of
thermal oxide wafers are SiO.sub.2. Additional examples of
insulators include crystalline quartz, sapphire, HBN, PBN, MgO,
YSZ, and SiC. The thickness of the insulator layer (e.g., a 285 nm
SiO.sub.2/Si wafer) can vary depending upon the characteristics
desired for the graphene device.
[0026] The metal layer covers only a part of the top of the
insulator layer (and passivation layer, if present). In another
aspect, the metal facilitates growth of graphene on the insulator
layer (and passivation layer, if present). Examples of the types of
metals that are useful are those having high carbon solubility
(e.g., >1.5 atom % @ 1000.degree. C.) and/or those having a
crystal structure that acts as a graphene template. The metal layer
can be one continuous piece (e.g., 2, 3, 4, 5 or more fingers
connected by a perpendicular strip), multiple non-touching sections
(e.g., 2, 3, 4, 5 or more non-connected strips or a plurality of
dots or islands of metal), or even a combination (e.g., connected
fingers and small non-connected dots or islands of metal located
between the fingers). As an example, the metal can be present in a
pattern that is useful to make an electronic device (e.g., an
interdigital electrode (IDE) pattern). In another aspect, a
sufficient amount of metal layer is present such that the graphene
grown, in accordance with the method described herein, connects the
different portions of metal (e.g., fingers, strips, dots,
etc.).
[0027] In another aspect, the metal layer is Ni. Other examples of
metals include Co, Re, Pd, and Pt. The thickness of the metal layer
can vary depending upon the characteristics desired for the
graphene device. Examples include from about 10, 20, 30, 40, 50,
60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190,
to 200 nm.
[0028] It is not uncommon for metals such as Ni, Co, Re, Pd, and Pt
to weakly adhere to an insulator layer (e.g., thermal oxide). Thus,
in another aspect, a metal adhesion layer is present between the
metal layer and the insulator layer (or between the metal and
passivation layers, if the passivation layer is present). Examples
of metal adhesion layers include Ti and Cr. Examples of the
thickness of the optional adhesive layer include from about 1, 2,
3, 4, 5, 6, 7, 8, 9, to 10 nm. The metal adhesive layer is present
in the same pattern as the metal layer (e.g., an IDE pattern).
[0029] The carbon layer is in contact with the metal layer and the
top of the insulator layer (or passivation layer if present).
Examples of the thickness of the carbon layer include from about
0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
15, 20, 25, 30, 35, 40, 45, to 50 nm (or more if desired). In
another aspect, the carbon layer is amorphous.
[0030] In the method described herein, heat is used to form
graphene. However, some of the insulator layers described herein
(e.g., thermal oxide) are not very stable at the upper temperature
ranges used. One way to protect thermally unstable layers is to
coat them with a passivation layer. Thus, in another aspect, a
passivation layer is present. The passivation layer is located
between the insulator layer and the metal/carbon layers and is in
contact with and covering a substantial portion of the top of the
insulator layer. The passivation layer is designed to cover a
substantial portion of the insulator layer and thereby protect it.
Examples of the thickness of the passivation layer include from
about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, to 20 nm (or more if
desired). The passivation layer is typically an oxide, such as
Al.sub.2O.sub.3, HfO.sub.2, Ta.sub.2O.sub.5, ZnO, TiO.sub.2, and
SiO.sub.2.
[0031] Alternatively, the passivation layer is present, but only in
the same pattern as the metal layer (and optional metal adhesive
layer). In this aspect, the passivation layer is designed to
protect the insulator layer from the metal layer during heating of
the precursor.
[0032] In another aspect, the present invention provides a novel
method of growing graphene, comprising:
[0033] (a) heating a graphene device precursor to a temperature
sufficient to initiate graphene formation; and,
[0034] (b) cooling the graphene device precursor.
[0035] Graphene refers to a layer of material, primarily comprising
graphene (a crystalline allotrope of carbon typically of a single
atomic plane of graphite having a 2-dimensional hexagonal lattice
structure of carbon atoms). The layer formed by the present
invention is typically from 1, 2, 3, 4, 5, 6, 7, 8, 9, to 10 atomic
layers in thickness.
[0036] In another aspect, the heating is conducted in a closed
furnace. Other examples of heat sources include a substrate heater,
microwave heater, RF heater, and UV heater.
[0037] In another aspect, the heating is conducted in a
substantially oxygen-free atmosphere.
[0038] In another aspect, the heating is conducted in the presence
of a substantially oxygen-free gas. An example of a gas is a
hydrogen-containing gas (e.g., forming gas). Examples of gases
include 95% Ar/5% H.sub.2 and 95% N/5% H.sub.2.
[0039] In another aspect, the precursor is heated to a temperature
of about 400.degree. C. Other examples of the temperature include
from about 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950,
to 1000.degree. C.
[0040] In another aspect, the temperature is maintained for about 1
minute. Other examples of the time the temperature is maintained
include from about 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50,
to 55 minutes and from about 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, to 5
hours.
[0041] In another aspect, the heating is conducted in the present
of an O.sub.2 scavenger. Examples of O.sub.2 scavengers include Ti
chips and a hydrogen-containing gas.
[0042] In another aspect, the heating is conducted in a vacuum.
Examples of the pressure at which the heating is conducted include
from about 500, 450, 300, 250, 200, 150, 100, 50, 25, 20, 10, 5, to
1 mT (mTorr or millitorr).
[0043] In another aspect, the cooling is conducted naturally.
Natural cooling refers to turning off the power to the heat source
(or removing the heat source) and letting the heat dissipate
without further assistance.
[0044] In another aspect, the cooling is accelerated. As an
example, accelerated cooling can be achieved by exposing the device
to ambient atmosphere.
[0045] In another aspect, the present invention provides a novel
graphene device, comprising:
[0046] an insulator layer, wherein at least the top portion of the
insulator layer is an electrical insulator;
[0047] a metal layer in contact with and covering part of the top
of the insulator layer;
[0048] a graphene layer in contact with the metal layer and the top
of the insulator layer;
[0049] an optional passivation layer located between the insulator
layer and the metal/carbon layers and in contact with and covering
a substantial portion of the top of the insulator layer;
[0050] an optional metal adhesive layer located between the metal
layer and either the insulator layer or passivation layer, if
present.
EXAMPLES
[0051] The following examples are meant to illustrate, not limit,
the present invention.
Example 1
[0052] A small sample of a 285 nm SiO.sub.2/Si wafer is cleaved via
a diamond scroll to be used as the insulating layer.
[0053] The oxide surface (SiO.sub.2) is then cleaned with acetone
and methanol. The surface is further cleaned by reactive ion
etching the surface in O.sub.2 prior to metallization to remove any
remaining organic substances.
[0054] An electron beam evaporation system (E-Beam) is then used to
deposit a 200 nm thick Ni layer (the metal layer) onto the oxide
surface in an electrode pattern.
[0055] A 10 nm layer of amorphous carbon is then deposited on the
surface of the device (over the metal/oxide layers or
metal/passivation layers) via filament carbon coater to complete a
graphene device precursor (carbon/metal/insulator).
[0056] The graphene device precursor is loaded into a tube furnace
along with boats of Ti chips. The tube furnace is pumped down to
.about.3.5E-2 Torr and then backfilled with forming gas (95% Ar/5%
H.sub.2) to achieve .about.50 mT. The temperature of the tube
furnace is run up to 800.degree. C. for one hour and then allowed
to cool naturally.
Example 2
[0057] Raman spectra obtained from a graphene device made according
to Example 1 are shown in FIGS. 1 (taken 3 .mu.m from a Ni edge), 2
(taken 50 .mu.m from a Ni edge), and 3 (taken 100 .mu.m from a Ni
edge).
Example 3
[0058] Raman spectra obtained from a graphene device made according
to Example 1, except that it was heated to 600.degree. C. are shown
in FIGS. 4 (taken 5 .mu.m from a Ni edge) and 5 (taken 10 .mu.m
from a Ni edge).
Example 4
[0059] Raman spectra obtained from a graphene device made according
to Example 1, except that it was heated to 700.degree. C. are shown
in FIGS. 6 (taken at a Ni edge), 7 (taken 50 .mu.m from a Ni edge),
8 (taken 100 .mu.m from a Ni edge), and 9 (taken 200 .mu.m from a
Ni edge).
Example 5
[0060] A small sample of a 285 nm SiO.sub.2/Si wafer is cleaved via
a diamond scroll to be used as the insulating layer.
[0061] A 5 nm passivation layer of Al.sub.2O.sub.3 is deposited via
atomic layer deposition onto the SiO.sub.2 (the top of the
insulator layer).
[0062] The oxide surface (Al.sub.2O.sub.3) is then cleaned with
piranha (3:1 H.sub.2SO.sub.4/H.sub.2O.sub.2). The surface is
further cleaned by reactive ion etching the surface in O.sub.2
prior to metallization to remove any remaining organic
substances.
[0063] An E-Beam is used to deposit a 5 nm layer of Cr (the metal
adhesive layer) in an interdigital electrode pattern.
[0064] The E-Beam is then used to deposit a 200 nm thick Ni layer
(the metal layer) on the Cr interdigital electrode pattern.
[0065] A 10 nm layer of amorphous carbon is then deposited on the
surface of the device via a filament carbon coater. Alternatively,
the carbon may be sputtered onto the device.
[0066] The graphene device precursor (e.g.,
carbon/metal/adhesive/passivation/insulator) is loaded into a tube
furnace along with boats of Ti chips. The tube furnace is pumped
down to .about.3.5E-2 Torr and then backfilled with forming gas
(95% Ar/5% Hz) to achieve .about.50 mT. The temperature of the tube
furnace is run up to 800.degree. C. for one hour and then allowed
to cool naturally.
[0067] Numerous modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise that as
specifically described herein.
* * * * *