U.S. patent application number 10/889170 was filed with the patent office on 2006-07-06 for ultrahard diamonds and method of making thereof.
This patent application is currently assigned to Carnegie Institution of Washington. Invention is credited to Russell J. Hemley, Ho-Kwang Mao, Chih-shiue Yan.
Application Number | 20060144322 10/889170 |
Document ID | / |
Family ID | 34079231 |
Filed Date | 2006-07-06 |
United States Patent
Application |
20060144322 |
Kind Code |
A9 |
Hemley; Russell J. ; et
al. |
July 6, 2006 |
ULTRAHARD DIAMONDS AND METHOD OF MAKING THEREOF
Abstract
A single crystal diamond grown by microwave plasma chemical
vapor deposition annealed at pressures in excess of 4.0 GPa and
heated to temperature in excess of 1500 degrees C. that has a
hardness of greater than 120 GPa. A method for manufacture a hard
single crystal diamond includes growing a single crystal diamond
and annealing the single crystal diamond at pressures in excess of
4.0 GPa and a temperature in excess of 1500 degrees C. to have a
hardness in excess of 120 GPa.
Inventors: |
Hemley; Russell J.; (Chevy
Chase, MD) ; Mao; Ho-Kwang; (Washington, DC) ;
Yan; Chih-shiue; (Washington, DC) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Assignee: |
Carnegie Institution of
Washington
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20050034650 A1 |
February 17, 2005 |
|
|
Family ID: |
34079231 |
Appl. No.: |
10/889170 |
Filed: |
July 13, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60486435 |
Jul 14, 2003 |
|
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Current U.S.
Class: |
117/68 ;
386/E5.001; G9B/27.012; G9B/27.013; G9B/27.019; G9B/27.021;
G9B/27.051 |
Current CPC
Class: |
G11B 2220/20 20130101;
C30B 29/04 20130101; H04N 5/781 20130101; C30B 33/02 20130101; C01B
32/26 20170801; C30B 25/105 20130101; C23C 16/274 20130101; G11B
2220/65 20130101; H04N 9/8042 20130101; H04N 5/765 20130101; C23C
16/277 20130101; C23C 16/279 20130101; C01B 32/25 20170801; H04N
5/775 20130101; H04N 9/8205 20130101; H04N 5/76 20130101; C30B
33/00 20130101 |
Class at
Publication: |
117/068 |
International
Class: |
C30B 7/00 20060101
C30B007/00; C30B 21/02 20060101 C30B021/02; C30B 28/06 20060101
C30B028/06; C30B 23/00 20060101 C30B023/00; C30B 25/00 20060101
C30B025/00; C30B 28/12 20060101 C30B028/12; C30B 28/14 20060101
C30B028/14 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0002] This invention was made with U.S. government support under
grant number EAR-0135626 from the National Science Foundation. The
U.S. government has certain rights in the invention.
Claims
1. A single crystal diamond grown by microwave plasma chemical
vapor deposition annealed at pressures in excess of 4.0 GPa and
heated to temperature in excess of 1500 degrees C. that has a
hardness of greater than 120 GPa.
2. The single crystal diamond of claim 1, wherein the fracture
toughness is 6-10 MPa m.sup.1/2.
3. The single crystal diamond of claim 1, wherein the hardness is
160-180 GPa.
4. The single crystal diamond of claim 1, wherein hardness is
determined by the equation of H.sub.v=1.854.times.P/D.sup.2 in
which P is the maximum load used on the indenter to form an
indentation into the single crystal diamond and D is the length of
the longest crack formed by the indenter in the single crystal
diamond and h is the depth of the indentation into the single
crystal diamond.
5. The single crystal diamond of claim 3 having a fracture
toughness of 6-10 MPa m.sup.1/2.
6. A single crystal diamond having a hardness of 160-180 GPa.
7. The single crystal diamond of claim 6 having a fracture
toughness of 6-10 MPa m.sup.1/2.
8. The single crystal diamond of claim 6, wherein hardness is
determined by the equation of H.sub.v=1.854.times.P/D.sup.2 in
which P is the maximum load used on the indenter to form an
indentation into the single crystal diamond and D is the length of
the longest crack formed by the indenter in the single crystal
diamond and h is the depth of the indentation into the single
crystal diamond.
9. A method for manufacture a hard single crystal diamond
comprising: growing a single crystal diamond; and annealing the
single crystal diamond at pressures in excess of 4.0 GPa and a
temperature in excess of 1500 degrees C. to have a hardness in
excess of 120 GPa.
10. The method of claim 9, whereing growing single crystal diamond
includes microwave plasma chemical vapor deposition.
11. The method of claim 9, wherein growing single crystal diamond
occurs in an atmosphere of N.sub.2/CH.sub.4=0.2-5.0% and
CH.sub.4/H.sub.2=12-20% at a total pressure of 120-220 torr.
12. The method of claim 9, wherein annealing the single crystal
diamond results in a single crystal diamond having a hardness in
excess of 160-180 GPa.
13. The method of claim 9, wherein growing single crystal diamond
occurs in an atmosphere having a temperature of 900-1500 degrees
C.
14. The method of claim 9, wherein the annealing occurs for 1-60
minutes.
15. The method of claim 9, wherein annealing the single crystal
diamond results in a single crystal diamond having a hardness in
excess of 140-180 GPa.
Description
[0001] The present invention claims the benefit of Provisional
Application No. 60/486,435 filed on Jul. 14, 2003, which is hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to diamonds, and more
particularly, to an ultrahard diamond produced using a Microwave
Plasma Chemical Vapor Deposition (MPCVD) within a deposition
chamber.
[0005] 2. Description of Related Art
[0006] Large-scale production of synthetic diamond has long been an
objective of both research and industry. Diamond, in addition to
its gem properties, is the hardest known material, has the highest
known thermal conductivity, and is transparent to a wide variety of
electromagnetic radiation. Thus, diamond is valuable because of its
wide range of applications in a number of industries, in addition
to its value as a gemstone.
[0007] For at least the last twenty years, a process of producing
small quantities of diamond by chemical vapor deposition (CVD) has
been available. As reported by B. V. Spitsyn et al. in "Vapor
Growth of Diamond on Diamond and Other Surfaces," Journal of
Crystal Growth, vol. 52, pp. 219-226, the process involves CVD of
diamond on a substrate by using a combination of methane, or
another simple hydrocarbon gas, and hydrogen gas at reduced
pressures and temperatures of 800-1200.degree. C. The inclusion of
hydrogen gas prevents the formation of graphite as the diamond
nucleates and grows. Growth rates of up to 1 .mu.m/hour have been
reported with this technique.
[0008] Subsequent work, for example, that of Kamo et al. as
reported in "Diamond Synthesis from Gas Phase in Microwave Plasma,"
Journal of Crystal Growth, vol. 62, pp. 642-644, demonstrated the
use of Microwave Plasma Chemical Vapor Deposition (MPCVD) to
produce diamond at pressures of 1-8 Kpa in temperatures of
800-1000.degree. C. with microwave power of 300-700 W at a
frequency of 2.45 GHz. A concentration of 1-3% methane gas was used
in the process of Kamo et al. Maximum growth rates of 3 .mu.m/hour
have been reported using this MPCVD process.
[0009] Natural diamonds have a hardness between 80-120 GPa. Most
grown or manufactured diamonds, regardless of the process, have a
hardness of less than 110 GPa. Other than type IIa natural
diamonds, which have been annealed, diamonds have not been reported
to have a hardness of greater than 120 GPa.
SUMMARY OF THE INVENTION
[0010] Accordingly, the present invention is directed to a an
apparatus and a method for producing diamond that substantially
obviates one or more of the problems due to limitations and
disadvantages of the related art.
[0011] An object of the present invention relates to an apparatus
and method for producing diamond in a microwave plasma chemical
vapor deposition system having increased hardness.
[0012] Another object of the present invention is to enhance the
optical characteristics of a single crystal diamond.
[0013] Additional features and advantages of the invention will be
set forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
[0014] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described, a single crystal diamond grown by microwave plasma
chemical vapor deposition annealed at pressures in excess of 4.0
GPa and heated to temperature in excess of 1500 degrees C. that has
a hardness of greater than 120 GPa.
[0015] In another embodiment, A single crystal diamond having a
hardness of 160-180 GPa
[0016] In accordance with another embodiment of the present
invention, A method for manufacture a hard single crystal diamond
includes growing a single crystal diamond and annealing the single
crystal diamond at pressures in excess of 4.0 GPa and a temperature
in excess of 1500 degrees C. to have a hardness in excess of 120
GPa.
[0017] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention.
[0019] FIG. 1 is a diagram of an indenter for testing the hardness
of a diamond.
[0020] FIG. 2 is a picture of an indentation made on a diamond.
[0021] FIG. 3 is a graph showing the hardness and toughness of
annealed microwave plasma CVD-grown single-crystal diamonds in
comparison to type IIa natural diamonds annealed type IIa natural
diamonds, annealed type Ia natural diamonds and annealed type Ib
HPHT synthetic diamonds.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Reference will now be made in detail to the preferred
embodiments of the present invention, the results of which are
illustrated in the accompanying drawings.
[0023] The microwave plasma CVD-grown single-crystal diamond
referred to in this application were grown with the apparatus
described in U.S. patent application Ser. No. 10/288,499 filed on
Nov. 6, 2002 entitled "Apparatus and Method for Diamond
Production," which is hereby incorporated by reference. In general,
a seed diamond is placed in holder that moves the seed
diamond/grown diamond as the diamond is grown. The inventors of
this application are also inventors in U.S. patent application Ser.
No. 10/288,499.
[0024] A microwave plasma CVD-grown single-crystal diamond having a
thickness of greater than 1 millimeter was deposited on type Ib
{100} synthetic diamond. In order to enhance the growth rate
(50-150 .mu.m/h) and promote smooth {100} face growth,
single-crystal diamonds were grown in an atmosphere of
N.sub.2/CH.sub.4=0.2-5.0%, CH.sub.4/H.sub.2=12-20%, 120-220 torr
total pressure, and 900-1500.degree. C. from a microwave induced
plasma within a CVD chamber. Raman spectra show a small amount of
hydrogenated amorphous carbon (a-C:H).sup.4 and nitrogen-containing
a-C:H (N:a-C:H).sup.4 giving rise to brown diamond at
<950.degree. C. and >1400.degree. C. Photoluminescence (PL)
spectra indicate nitrogen-vacancy (N-V) impurities. Single crystal
diamonds up to 4.5 mm in thickness have been fabricated at growth
rates that are as much as two orders of magnitude higher than
conventional polycrystalline CVD growth methods.
[0025] The microwave plasma CVD-grown single-crystal diamonds were
annealed at pressures in excess of 4.0 GPa, such as 5-7 GPa, and
heated to temperature in excess of 1500 degrees C., such as
1800-2900 degrees C., for 1-60 min in a reaction vessel using a
belt-type or anvil-type apparatus. The reaction vessel can be a
cell, such as that described in U.S. Pat. Nos. 3,745,623 or
3,913,280, which are hereby incorporated by reference. Such an
annealing treatment, reduces or eliminates the color in the
microwave plasma CVD-grown single-crystal diamond crystals, and
lightening the tint of the type Ib HPHT synthetic seed crystals.
Further, the hardness of the annealed microwave plasma CVD-grown
single-crystal diamond annealed CVD diamond (at least .about.140
GPa) is beyond that of annealed or unannealed type Ib HPHT
synthetic diamond (.about.90 GPa), annealed type Ia natural diamond
(.about.100 GPa), type IIa natural diamond (.about.110 GPa), and
annealed type IIa natural diamond (.about.140 GPa) and sintered
polycrystalline diamond (120-140 GPa).
EXAMPLE #1
[0026] A single crystal CVD diamond was grown with a
N.sub.2/CH.sub.4 ratio of 5% at a temperature of approximately 1500
degrees C. on a yellow type Ib HPHT synthetic diamond in a
microwave CVD chamber. The dimension of the microwave plasma
CVD-grown single-crystal diamond was one centimeter square and a
little larger than one millimeter in thickness. The color of the
microwave plasma CVD-grown single-crystal diamond was brown. The
brown microwave plasma CVD-grown single-crystal diamond on the type
Ib HPHT synthetic seed diamond was then placed as a sample in the
reaction vessel.
[0027] The reaction vessel was placed in a conventional HPHT
apparatus. First, the pressure was increased to a pressure of 5.0
GPa, and then the temperature was brought up to 2200 degrees C. The
sample was maintained at these annealing conditions for five
minutes, and then the temperature was decreased over a period of
about one minute to room temperature before the pressure was
released.
[0028] The sample was removed from the reaction vessel and examined
under an optical microscope. The brown microwave plasma CVD-grown
single-crystal diamond had turned to a light green translucent
color and remained firmly bonded to the yellow type Ib HPHT
synthetic diamond. The yellow color of the type Ib HPHT synthetic
diamond became a lighter yellow or a more translucent yellow. The
hardness was about 160 GPa.
EXAMPLE #2
[0029] Same as example #1 above, except the annealing conditions
were maintained for 1 hour. The brown microwave plasma CVD-grown
single-crystal diamond turned to a light green color, which was
more translucent than the light green color resulting in example
#1, and remained firmly bonded to the type Ib HPHT synthetic
diamond. The yellow color of the type Ib HPHT synthetic diamond
became a lighter yellow or a more translucent yellow. The hardness
was about 180 GPa.
EXAMPLE #3
[0030] A single crystal CVD diamond was grown with a
N.sub.2/CH.sub.4 ratio of 5% at a temperature of approximately 1450
degrees C. on a yellow type Ib HPHT synthetic diamond in a
microwave CVD chamber. The dimension of the microwave plasma
CVD-grown single-crystal diamond was one centimeter square and a
little larger than one millimeter in thick. The color of the
microwave plasma CVD-grown single-crystal diamond was a light brown
or yellow. In other words, a yellow or light brown that was not as
dark as the brown of the microwave plasma CVD-grown single-crystal
diamond in example #1 above. The yellow or light brown microwave
plasma CVD-grown single-crystal diamond on the type Ib HPHT
synthetic diamond was then placed as a sample in a reaction vessel.
The hardness was greater than 160 GPa.
[0031] The reaction vessel was placed in a conventional HPHT
apparatus. The pressure was increased to about to a pressure of 5.0
GPa, and then the temperature was rapidly brought up to about 2000
degrees C. The sample was maintained at these annealing conditions
for five minutes, and then the temperature was decreased over a
period of about one minute to room temperature before the pressure
was released.
[0032] The sample was removed from the reaction vessel and examined
under an optical microscope. The light brown microwave plasma
CVD-grown single-crystal diamond had become colorless and remained
firmly bonded to the yellow type Ib HPHT synthetic diamond. The
yellow color of the type Ib HPHT synthetic diamond also became a
lighter yellow or a more translucent yellow.
EXAMPLE #4
[0033] Same as example #1 except a colorless microwave plasma
single-crystal CVD-grown diamond in an atmosphere of
N.sub.2/CH.sub.4=5% at a temperature of .about.1200 degree C. was
annealed. After annealing, the microwave plasma single-crystal
CVD-grown diamond was blue. This blue microwave plasma
single-crystal CVD-grown diamond had a very high toughness of
>20 MPa m.sup.1/2. The hardness was about .about.140 GPa.
EXAMPLE #5
[0034] Same as example #1 except a colorless microwave plasma
single-crystal CVD-grown diamond in an atmosphere of
N.sub.2/CH.sub.4=0.5% at a temperature of .about.1200 degree C. was
annealed. The microwave plasma single-crystal CVD-grown diamond was
still colorless. This colorless microwave plasma single-crystal
CVD-grown diamond had a hardness of .about.160 GPa and toughness of
.about.10 MPa m.sup.1/2.
[0035] FIG. 1 is a diagram of an indenter for testing the hardness
of a diamond. A Vickers hardness test were performed on the
annealed microwave plasma CVD-grown single-crystal diamonds with
the indenter 1 shown in FIG. 1. The indenter 1 in FIG. 1 has an
impinging material 2 positioned on a mount 3. The impinging
material 2 can be silicon carbide, diamond or some other hard
material. The impinging material has a face with a pyramidal
Vickers indenter shape in which the sides of the pyramidal Vickers
indenter shape have an angle of 136.degree..
[0036] The indenter applies a point load to the test diamond 2
until an indentation or crack is formed in the test diamond 2. To
prevent elastic deformation of the indenter, the loads were varied
from 1 to 3 kg on {100} faces in the <100> direction of the
test diamonds. Dimensions of the indentation and the cracks
associate with the indentation are measured via optical microscopy.
FIG. 2 is a picture of an indentation made on a microwave plasma
CVD-grown single-crystal diamond.
[0037] By measuring the length D and height h of the indentation,
the hardness H.sub.v, of the test diamond can be determined from
the following equation (1): H.sub.v=1.854.times.P/D.sup.2 (1) P is
the maximum load used on the indenter to form an indentation into
the test diamond. D is the length of the longest crack formed by
the indenter in the test diamond and h is the depth of the
indentation into the test diamond, as shown in FIG. 1.
[0038] The fracture toughness K.sub.c of the test diamond can be
determined by using the hardness H.sub.v, from equation (1) in the
following equation (2):
K.sub.c=(0.016.+-.0.004)(E/H.sub.v).sup.1/2(P/C.sup.3/2) (2) E is
the Young's modulus, which is assumed to be 1000 GPa. P is the
maximum load used on the indenter to form the indentation into the
test diamond. The term d is the average length of the indentation
cavity in the test diamond, as shown in FIG. 2 such that
d=(d.sub.1+d.sub.2)/2. The term c is the average length of the
radial cracks in the test diamond, as shown in FIG. 2 such the
c=(c.sub.1+c.sub.2)/2.
[0039] Because of the uncertainties in determining hardness,
identical measurements were also performed on other diamonds. The
measurements on other diamonds were found to be in agreement with
published data on the other diamonds. The Vickers hardness tests
were done on the (100) faces of the various types of diamonds in
the (100) direction.
[0040] The indented surfaces of the annealed microwave plasma
CVD-grown single-crystal diamonds as viewed by optical microscopy
clearly differ from those of other (softer) diamonds. The annealed
microwave plasma CVD-grown single-crystal diamond exhibits square
crack patterns along <110> or <111>, no cross-like
cracked lines along <100>, and a water-print-like deformation
mark was produced on the surface of the annealed microwave plasma
CVD-grown single-crystal diamond by the pyramidal Vickers indenter.
In contrast, an annealed type IIa natural diamond has less square
crack patterns along (110) and (111) but still exhibits the
cross-like (100) cracks of softer diamonds. Such results indicate
that annealed microwave plasma CVD-grown single-crystal diamond is
harder than the indenter, and the pressure due to plastic
deformation of the indenter causes slippage of the softer {111}
faces.
[0041] The Vickers indenters typically cracked after .about.15
measurements on unannealed microwave plasma CVD-grown
single-crystal diamonds and type Ib natural diamonds. Further, The
Vickers indenters typically cracked after .about.5 measurements on
annealed type IIa natural diamonds, annealed type Ia natural
diamonds and annealed type Ib HPHT synthetic diamonds. However, the
Vickers indenter cracked after only one or two measurements on the
annealed microwave plasma CVD-grown single-crystal diamonds. These
observations further indicate that the annealed microwave plasma
CVD-grown single-crystal diamonds are harder than the measured
values indicate. Indeed, many annealed microwave plasma CVD-grown
single-crystal diamonds simply damaged the softer indenter. In such
instances, the indenter left no imprint whatsoever in the surface
of the annealed microwave plasma CVD-grown single-crystal
diamonds.
[0042] FIG. 3 is a graph showing the hardness and toughness of
annealed microwave plasma CVD-grown single-crystal diamonds in
comparison to type IIa natural diamonds annealed type IIa natural
diamonds, annealed type Ia natural diamonds and annealed type Ib
HPHT synthetic diamonds. As shown in FIG. 3, the annealed microwave
plasma CVD-grown single-crystal diamonds have much higher hardness
than type IIa natural diamond, as shown by the dotted square 10 in
FIG. 3. All of the annealed microwave plasma CVD-grown
single-crystal diamonds also have a higher hardness than the
reported range the reported range of hardness for polycrystalline
CVD diamonds, shown by the dotted square 20 in FIG. 3. The
microwave plasma CVD-grown single-crystal diamonds represented in
FIG. 3 have a fracture toughness of 6-10 MPa m.sup.1/2 with a
hardness of 140-180 GPa with indications that they may be
harder.
[0043] As the present invention may be embodied in several forms
without departing from the spirit or essential characteristics
thereof, it should also be understood that the above-described
embodiments are not limited by any of the details of the foregoing
description, unless otherwise specified, but rather should be
construed broadly within its spirit and scope as defined in the
appended claims, and therefore all changes and modifications that
fall within the metes and bounds of the claims, or equivalence of
such metes and bounds are therefore intended to be embraced by the
appended claims.
* * * * *