KR20170126926A - Monocrystalline diamond and how to grow it - Google Patents

Abstract

A single crystal diamond having a full width half maximum corrected after considering the Rayleigh width of a 514.5 nm laser, showing the presence or absence of negatively charged silicon vacancies according to diamond quality; A concentration level of neutral substituted nitrogen at an absorption coefficient of 270 nm; 10.6 μm wavelength FTIR transmittance value; Represents the concentration of positively charged substituted nitrogen when the peak height is 1332.5 cm < ^{-1 &} gt ;; When the wavelength is 3123 cm ^-1 , it indicates the absence of nitrogen-vacancy-hydrogen defect species; The normalization of the spectrum when the primary Raman peak is 552.37 nm using 514.5 nm laser excitation; A black sector or a white sector, and a retardation to a thickness of the diamond plate; Or when the diamond is placed under 355 nm laser irradiation at room temperature in the dark room.

Description

Monocrystalline diamond and how to grow it

The present invention relates to growing single crystal diamond. In particular, the invention relates to growing diamond by chemical vapor deposition (CVD) processes.

Monocrystalline diamond as well as polycrystalline diamond are grown using various CVD techniques. Polycrystalline diamond is not a potential material for new applications, although it has characteristics similar to monocrystalline diamond.

For example, the thermal conductivity of polycrystalline diamond does not exceed the thermal conductivity of natural diamond. Indeed, in polycrystalline diamond, grain boundaries act as scattering centers of phonons, deteriorating thermal properties and other properties, thereby hindering the excellence of diamond's excellent properties. The presence of incineration grain boundaries as well as diagonal grain boundaries is a major drawback in the use of polycrystalline diamond.

Although there is a clear preference for using single crystal diamonds in many applications, it is difficult to grow single crystal diamonds having the same texture, transparency, purity and finish as natural diamonds. Although monocrystalline diamond has superior properties compared to polycrystalline diamond, microscopic and macroscopic graphite and non-graphite inclusions, feather (long line defect) are very common in CVD growth type single crystal diamond. As a result, the possibility of using CVD growth type single crystal diamond as a gem-quality product is reduced.

Raman spectroscopy and X-ray diffraction (XRD) As a result of the detailed characterization of the defects in the grown diamond, it was found that the defects in the single crystal diamond included graphite regions having a size in the submicron to several microns range.

Another difficulty in growing monocrystalline CVD diamond is the growth rate. Adding nitrogen to the CVD gas allows a growth rate of 70-100 microns per hour, but defects are rampant, and defect density generally increases with growth rate.

For example, Derwent's summary of Japanese Publication No. JP 07277890 discloses a method for synthesizing diamond for use as a semiconductor, an electronic component or an optical component, or for use in a cutting tool. In particular, the process disclosed in JP 07277890 discloses a method of increasing the growth rate of a diamond containing nitrogen at a ratio of 3 to 1000 ppm of hydrogen in nitrogen or in the presence of a gas containing oxygen at a ratio of 3 to 100% .

(PNAS, 1 October 2002, Vol. 99, No. 20, 12523-12525) by Yan et al. Discloses a method for producing single crystals by microwave plasma chemical vapor deposition (MPCVD) at a growth rate in the range of 50 to 150 microns per hour A method of manufacturing a diamond is disclosed.

The method includes a CVD process carried out at 150 torr, and a step of adding nitrogen to the CVD gas to give a ratio of 1 to 5% of nitrogen versus methane _{(N 2 / CH 4.)} . Yann et al. Believe that nitrogen at the stated rate improves growth rate by producing more soluble growth sites. This is thought to be the result of the growth transition from the <111> crystal plane to the <100> crystal plane.

The importance of nitrogen content in CVD gases has been recognized in U.S. Patent 5,015,494 (Yamazaki) which teaches how to grow diamonds with customized properties for dedicated applications.

Yamazaki discloses a step of forming diamond by electron cyclotron resonance CVD and a step of adding nitrogen to prevent "growth of lattice defects by external stress or internal stress ". Nitrogen-compound gas to carbon-compound gas of 0.1 to 5% nitrogen. The resulting diamond has a nitrogen concentration of 0.01 to 1 wt%.

Additionally, Yamazaki discloses a requirement to add boron gas to the CVD gas to form the boron nitride deposited on the substrate to improve adhesion of the formed diamond to the substrate.

According to Yan et al. And Yamazaki, nitrogen is required for two purposes. In particular, nitrogen is used to improve the growth rate of the CVD growth type single crystal diamond and to prevent lattice defects in the electron cyclotron resonance CVD growth type single crystal diamond.

It is an object of the present invention to provide a CVD process for growing monocrystalline diamond with substantially no defects.

Applicants have conducted extensive experimental work on the role of nitrogen in conjunction with diborane in the CVD process to grow single crystal diamond. Experimental work has shown that the use of the amount of nitrogen proposed by Yan et al. And Yamazaki suggests that a diamond representing nitrogen-based defects such as microcracks, micro-inclusions and the like is grown. Experimental work has also shown that very small amounts of nitrogen gas, optionally in combination with diborane, oxygen, and helium in the CVD gas, produce very high quality, substantially defect free, single crystal diamond useful as gemstones, and nitrogen determined to be beneficial by the Applicant And diborane was found to be significantly lower than the ratio of nitrogen to carbon disclosed in Yamazaki.

In particular, Applicants have found that a CVD gas containing a relatively small amount of nitrogen in combination with diborane in a gas mixture forms a CN with an optical center associated with CN bonds and CBN bonds that causes deterioration of the color and purity of the single crystal diamond . A high nitrogen concentration in the gas mixture results in micro-inclusions and growth cracks in the crystal. Due to the difference in bond length between nitrogen-carbon, carbon-carbon, and boron-carbon, this defect serves as the center of phonon scattering, thereby reducing the electrical, optical and mechanical properties of the single crystal diamond formed.

It is believed that the shape of the inclusions depends on the nitrogen concentration in the CVD gas.

Additionally, Applicants have found that a relatively small amount of nitrogen is required, but in order to prevent growth of graphite inclusions in the diamond deposited by CVD process and to increase the growth rate, And at least some of the nitrogen must be present in the CVD gas.

The present invention provides a method of forming a single crystal diamond by chemical vapor deposition,

(a) providing at least one diamond seed;

(b) exposing the seed to conditions for growing diamond by chemical vapor deposition comprising the steps of: providing a reaction gas comprising a carbon-containing gas and a nitrogen-containing gas for growing diamond;

(c) controlling the amount of said nitrogen-containing gas relative to the other gases in said reactant gas so as to grow a diamond that does not contain defects and graphite inclusions by step-wise growth of said nitrogen-containing gas in said reactant gas The amount is in the range of 0.0001 to 0.02% by volume, and further contains diborane in the reaction gas; And

(d) controlling the diborane and the nitrogen-containing gas source in such a manner as to provide a concentration of atomic fraction of nitrogen of 0.3 or less to produce single crystal diamond suitable for use as gemstones and other suitable uses, And nitrogen are added to improve the optical absorption to improve the transparency and color of the single crystal diamond so that a smaller amount of impurities are contained in the single crystal diamond and at the same time is suitable for all appropriate applications.

The amount of the nitrogen-containing gas in the reaction gas may be in the range of 0.0001 to 0.02% by volume.

The reactive gas may further comprise diborane.

The diborane may be provided in the range of 0.00002 to 0.002% by volume.

Thus, when Applicants use a relatively small amount of nitrogen in combination with diborane gas selectively in the CVD gas, the growth mechanism of the diamond is such that the layer of diamond with the edge formed by the step grows front as an edge And it is found that it is a mechanism of expression growth. This growth mechanism differs from the layer growth mechanism, which is typical of CVD processes and can be performed using relatively large quantities of nitrogen in CVD gases.

The monocrystalline diamond grown by the stepwise growth mechanism by nitrogen and diborane, as described herein, lacks microscopic and macroscopic graphite inclusions and defects associated with growth of the diamond by layer growth, especially nitrogen-based inclusions. As a result, the diamond grown by the step-wise growth mechanism has improved optical, electrical and mechanical properties as compared to the diamond grown by layer growth in which a high concentration of nitrogen in the gas mixture is used.

At least some nitrogen must be contained in the CVD gas to prevent graphite inclusions from forming in the grown diamond.

Preferably, the amount of the gas containing nitrogen and diborane in the reaction gas is 0.00002 to 0.02% by volume.

Preferably, the nitrogen-containing gas is selected from one or more of any of the following groups: hydrogen in the N _2, oxygen in N _2, helium in N ₂ or N ₂ containing N ₂ and diborane in nitrous oxide.

Preferably, the chemical vapor deposition conditions comprise maintaining the seed at a temperature in the range of from 750 to 1200 &lt; 0 &gt; C.

Preferably, the chemical vapor deposition conditions comprise maintaining the seed at a pressure in the range of 120 to 160 mbar.

Preferably, the carbon-containing gas comprises methane.

Preferably, the reactive gas also comprises hydrogen.

Preferably, the chemical vapor deposition occurs in the presence of a microwave plasma and is generated by hydrogen in the reaction gas.

Preferably, the reactive gas has the following relative amounts: methane 20-80 sccm (standard cubic centimeter per minute), hydrogen 300-800 sccm, nitrogen 0.0005-0.2 sccm, diborane 0.0001-0.01 sccm, oxygen 1-10 sccm. The present invention also provides gem-quality single crystal diamond formed according to the method of the present invention.

Preferably, the method is characterized by producing a gem quality diamond.

Preferably the seed should be oriented in the (100) crystal orientation.

Diamonds grown to a thickness of 2 mm on the seed are not precisely oriented in the (100) crystal orientation, lose orientation, and other crystal orientations are also present.

We have found that the crystal orientation of the diamond grown to a thickness exceeding 2 mm is confirmed, and that other crystal orientations can also be present in small amounts. Figure 10 shows an orientation mapping image of (a) CVD and (b) commercial HPHT single crystal diamond and (c) color coordinates.

Figure 11 shows an EBSD (100) inverse pole figure of (a) CVD and (b) HPHT single crystal diamond. These figures also clearly show that there is also a small area containing other orientations.

However, the first layer of 0.5 mm is a (100) crystallographic orientation, and no other orientation is present. As the diamond crystal grows, a small orientation of crystal grains is also formed and this orientation is lost.

In another aspect, a single crystal diamond is provided. This single crystal diamond,

Lt; RTI ID = 0.0 &gt; (FWHM) &lt; / RTI &gt; after considering the Rayleigh width of the 514.5 nm laser,

b) the presence or absence of a negatively charged silicon void defect depending on the quality of the diamond,

c) represents the concentration level of a specific value of neutral substituted nitrogen [N _s ⁰ ] when the absorption coefficient is 270 nm,

d) a FTIR transmittance of a specific value when the wavelength is 10.6 μm,

Represents the concentration of a specific value of positively charged substituted nitrogen [N _s ⁺ ] when the peak height is 1332.5 cm ^-1 ,

f) the absence of a nitrogen-vacancy-hydrogen defect (NVH ⁰ ) species when the wavelength is 3123 cm ^-1 ,

g) normalization of the spectrum when the primary Raman peak is 552.37 nm using 514.5 nm laser excitation,

h) represents a black sector or white sector and has a refractive index n, where n = R / t, where R = retardation, t is the thickness of the diamond plate,

i) exhibit red and blue brilliance when the diamond is placed under 355 nm laser irradiation at room temperature in a dark environment.

In some embodiments: i) the single crystal diamond has a dimension of 3 X 3 X 2.16 mm ³ ; ii) Monocrystalline diamond represents a corrected FWHM (FWHM) of 1.11 cm ^-1 when the primary Raman mode of the diamond is concentrated at 1333.27 cm ^-1 ; iii) Monocrystalline diamond has a negatively charged It indicates the presence of a ^{silicon-public} defect (SiV); iv) Monocrystalline diamond indicates the concentration level of neutral substituted nitrogen [N _s ⁰ ] of 0.111 ppm (111 ppb) when the absorption coefficient is 270 nm; v) When the wavelength is 10.6 μm, the single crystal diamond is 70.84 % FTIR transmittance; vi) Monocrystalline diamond represents the concentration of substituted nitrogen [N _s ⁺ ] in an amount of 0.248 ppm (248 ppb) when the peak height is 1332.5 cm ^-1 μm after introduction of the linear baseline; vii) the single crystal diamond has a resistivity of 6.4 E + 4? m; Or viii) any combination of i) to vii).

In some embodiments: i) the single crystal diamond has dimensions of 3 X 3 X 0.64 mm ³ ; ii) the monocrystalline diamond represents a corrected FWHM of 1.13 cm ^-1 when the primary Raman mode of the diamond is concentrated at 1332.14 cm ^-1 ; and iii) the monocrystalline diamond is negatively charged at 738 nm It does not indicate the presence of ^{silicon-public} defect (SiV); iv) Monocrystalline diamond shows the concentration level of neutral substitutional nitrogen [N _s ⁰ ] of 0.0684 ppm (68.4 ppb) when the absorption coefficient is 270 nm, v) Monochromatic diamond is 71.4 % FTIR transmittance; vi) Monocrystalline diamond represents the concentration of substituted nitrogen [N _s ⁺ ] charged in an amount of 0.138 ppm (138 ppb) when the peak height is 1332.5 cm ^-1 after introduction of the linear baseline; vii) the single crystal diamond has a resistivity of 1.2 E + 15 Ωm; Or viii) any combination of i) to vii).

In some embodiments of the single-crystal diamond, SiV at 738 nm ^- phono zero line (zero line phono; ZPL) form the strongest feature (feature).

In some embodiments of the single-crystal diamond of zero it includes phono line (ZPL) form the strongest features, a neutral ^{nitrogen-concentrated} SiV a 738 nm nitrogen charged to the public defects and negative public defect (NV ^{0 / -} ) are shown at 575 nm and 638 nm, respectively, and a broad fluorescent background (FB) centered at about 700 nm is present due to the phonon side band of NV ⁰ and NV ^- .

In some embodiments of single crystal diamond, the single crystal diamond is a gem diamond because it has a weight of more than 0.01 carats.

This patent or patent application file contains one or more drawings made in color. A copy of this patent or patent application publication with color drawing (s) will be provided by the Patent Office upon application and payment of the required fee.

Hereinafter, embodiments of the present invention will be described by way of example only with reference to the accompanying drawings.

Figure 1 is a Fourier transform infrared (FTIR) spectrum of diamond deposited by a CVD process using nitrogen in CVD gases in the range of 0.0002 to 0.002%. The diborane flow rate in the mixture is maintained at 0.0001-0.0005%. It should be noted that there is no BN band and N-related peaks at 500 - 1500 cm¹.
2 is an FTIR spectrum of a diamond deposited by a CVD process using nitrogen in a CVD gas in the range of 0.005 to 0.02% in the state where diborane is 0.0008 to 0.001%.
3 is a photoluminescence spectrum of a diamond deposited by the CVD process according to the present invention using nitrogen in a CVD gas in the range of 0.0001 to 0.02% by volume; the diborane flow rate in the mixture is maintained at 0.00005 to 0.0005%. For a minimum flow rate of 0.007 sccm (0.0012% by volume), the peak at 575 nm corresponds to the nitrogen center. This shows that the sample prepared according to the present invention is nitrogen-free and has substantially fewer nitrogen center defects. The concentration of lightness increases as the nitrogen flow rate increases by volume%.
Figures 4 to 6 are optical microscope images at high magnification of diamonds grown by a CVD process comprising 0.02% nitrogen and 0.001% diborane in accordance with the present invention, showing the stepwise growth of diamond.
In Figure 4, an image of a sample of diamond was grown at a flow rate of 0.03% nitrogen in the flow rate of the CVD gas. The steps in the growing decision are clear. This step is a line in which diamond grows according to the present invention.
Figure 5 is an optical microscope image at high magnification of diamond grown by a CVD process comprising 0.02% nitrogen and 0.001% diborane in accordance with the present invention, showing the stepwise growth of diamond. Stepwise growth can be clearly seen. However, the step is not an obvious straight line, it is uneven and defective.
Figure 6 is an optical microscope image at high magnification of diamond grown by a CVD process comprising 0.02% nitrogen and 0.001% diborane in accordance with the present invention, showing the stepwise growth of diamond.
Figures 7 and 8 are optical micrographs of diamonds deposited by a CVD process using nitrogen in CVD gases in amounts of 0.0005% by volume and 0.0008% by volume, respectively, with 0.0001% and 0.0002% diborane. This optical micrograph also shows the stepwise growth mechanism of diamond growth. Nitrogen is used in an amount less than that specified by the present invention and generates graphite (black) inclusions in the sample.
9 is an optical micrograph of a diamond deposited by a CVD process using nitrogen in a CVD gas in an amount of 0.0012% by volume in accordance with the present invention. This shows a clean growth with black graphite inclusions and uniformly spaced steps.
Figure 10 shows (a) an orientation-mapping image of CVD and (b) commercial HPHT single crystal diamond and (c) color coordinates.
Figure 11 shows an EBSD (100) inverse pole figure of (a) CVD and (b) HPHT single crystal diamond.
Figure 12 shows a plot of the first Raman mode of diamond concentrated on 1332.27cm 1332.14cm ^-1 and ^-1 for each of S1 and S2 in accordance with two embodiments of the present invention.
Figure 13 shows a UV-Vis transmission spectrum that is uncorrected for scattering and return loss according to two embodiments of the present invention.
Figure 14 shows a plot of the absorption coefficient in the same spectral range as Figure 13 after adjusting the absorption coefficient from 800 nm to 0 according to two embodiments of the present invention.
15 shows the FTIR transmission at a resolution of 4 cm &lt; ^-1 &gt; that is not corrected for scatter and return losses according to two embodiments of the present invention.
Figure 16 shows absorption coefficients in the same spectral range as Figure 15 according to two embodiments of the present invention.
Figure 17 shows the absorption coefficient at 3500 to 2500 cm &lt;&quot; ¹ &gt; according to two embodiments of the present invention.
Figure 18 shows a room temperature Raman / photoluminescence spectrum using a 514.5 nm laser excitation according to two embodiments of the present invention.
Figure 19 shows a table listing the intensities of various fluorescent features.
Figure 20 shows a corresponding retardation map measured using our settings after cross-polarized transmission image (white light) and after operation of the Glazer.
21 is a table showing the maximum Δ derived for a black sector and a white sector using a maximum delay value from a color scale in accordance with two embodiments of the present invention.
Figure 22 shows a sample under 355 nm laser irradiation at room temperature in a dark room.
23 shows the resistivity of the single crystal diamond according to the first embodiment of the present invention.
Fig. 24 shows the resistivity of the single crystal diamond according to the second embodiment of the present invention.

The following are incorporated herein by reference: Singapore Patent Application No. 200804637-7 filed on June 18, 2008, PCT Patent Application No. PCT / SG2009 / 000218, filed June 18, 2009, September 2010 U. S. Patent Application Serial No. 12 / 933,059, filed on March 16, U.S. Serial No. 14 / 642,422, filed March 9, 2015;

A method for growing a single crystal diamond according to the present invention includes a CVD process using a microwave plasma.

The diamond is grown on a substrate comprising a diamond seed which may have a size of 3 x 3 mm to 5 x 5 mm. The method is performed in a microwave plasma chamber. Depending on the size of the chamber, a number of seeds may be used to grow the diamond during a single run of the present invention.

The crystallographic orientation of the seed is determined, and seeds having an orientation other than (100) are excluded. The seed having the orientation of the substrate 100 is polished with an optical finish having a roughness of the order of microns for the CVD process.

Once the seed is placed in the chamber, the temperature inside the chamber is raised from ambient to a temperature in the range of from 750 to 1200 ° C, and the pressure inside the chamber is reduced to a pressure in the range of 120 to 160 mbar.

The chamber is supplied with a gas for growth of diamond which contains methane (CH ₄ ), hydrogen (H ₂ ), nitrogen (N ₂ ), and helium (He) Through the chamber. However, nitrogen gas can be delivered to the chamber along with diborane, oxygen, hydrogen and helium.

Nitrogen and diborane gas are supplied in an amount that includes 0.0001 to 0.02% by volume of the gas for growing the diamond.

An electric field surrounding the seed is applied so that a plasma is generated from the gas in the chamber. This electric field is generated by a magnetron operating at 6000 watts and 2.45 Ghz. The generated electric field ionizes the hydrogen gas to form a plasma in the vicinity of the diamond seed. Under these process conditions, the diamond is grown on the diamond seed.

The growth pattern of the diamond is step-wise as shown in Figs. 3 to 5, so that diamond having substantially no defects and impurities can be grown.

For comparison, the same process conditions were used with the feed of nitrogen varied from 0.005 to 0.02% by volume of the feed gas, i. E. Nitrogen was changed to contain at least 10 times the amount of nitrogen supplied according to the invention.

FTIR analysis of the sample is used to determine the concentration and binding of nitrogen and boron in the sample. The FTIR spectra of the samples grown according to the present invention and the samples grown according to the modified boiling feed are shown in Figures 1 and 2, respectively.

The FTIR spectrum of the diamond grown according to the present invention (Fig. 1) shows the dominant CC mode at 1978 cm ^-1 , 2026 cm ^-1 and 2160 cm ^-1 in the two phonon regions. An interesting result, however, is that no nitrogen-related bands are observed in the FTIR spectra of these samples.

The FTIR spectrum (FIG. 2) of a sample grown with nitrogen ranging from 0.005 to 0.02% and 0.0008 to 0.001% diborane (FIG. 2) shows a clear and robust discrimination characteristic of the boron-nitrogen centers in the sample with some typical nitrogen centers. In particular, the significant band associated with the boron-nitrogen center is evident at 1370 cm ^-1 . The bands at 1210 and 1280 cm &lt;&quot; ¹ &gt; can belong to the nitrogen center with the CC bands at 1978 cm ^-1 , 2026 cm ^-1 and 2160 cm ^-1 . The nitrogen center in this diamond sample can exist in a number of configurations as described below.

- single atom substitution:

The characteristic peaks of the FTIR spectrum are at 1130 and 1350 cm ^-1 , and the EPR gives a "g" value of 2.0024 for this center. The center exhibits weak discrimination characteristics in samples of approximately 1100 cm &lt;&quot; 1 &gt; in samples grown with nitrogen ranging from 0.005 to 0.02%.

- "A" Aggregate:

480-490 cm ^-1 and 1282 cm ^-1 are characteristic peaks of the A-aggregate in FTIR. This peak is evident in FIG. 2 for samples made with a much higher concentration of nitrogen than the present invention. A agglomerates are also present in large concentrations in the natural diamond samples used as substrates in this example case.

- "B" aggregate:

The B-aggregates in the diamond are thought to consist of 4/8 nitrogen atoms paired with carbon atoms. These peaks are mostly evident in natural diamonds and may not be present in the samples of the present invention.

- N3 Center:

The N3 center is not activated in the FTIR and therefore is not shown in Figures 1 and 2. However, the N3 center exhibits a sharp band at 415 nm in photoluminescence (PL) and UV spectroscopy. The center consists of three nitrogen atoms surrounding the vacancy (V).

- Platelet:

The playtreat consists of one or two additional atomic layers inserted into the diamond grating. The detailed nature of the playtreat in the diamond lattice is still under analysis. However, the fact that a corresponding IR band is observed only in diamonds containing significant amounts of nitrogen suggests that the playtreat contains nitrogen, possibly consisting of some or all of the nitrogen. The position of the playtreat peak varies from 1354 to 1384 cm ^-1 per sample. This change in location is due to susceptibility to deformation in which the playtite is induced in the crystal by the A-aggregate and B-aggregate defects. The presence of playtreat absorption indicates that the A-aggregates begin to diffuse and form B-aggregates. The peak position of the playtreat is inversely related to the size of the playtreat.

From the outlined results, we can conclude that nitrogen is present in the form of a monosubstituted form and a low concentration of A-aggregates in the sample grown at a nitrogen flow rate ranging from 0.005 to 0.02%.

Photoluminescence spectroscopy was performed on samples prepared with a nitrogen gas flow rate of 0.0002 to 0.002% by volume and a diborane flow rate of 0.00002 to 0.0005%. The results of this spectroscopy are shown in FIG. 3 and show peaks at 639 nm (1.94 eV) and 575 nm (2.14 eV) corresponding to NV and (NV) ^- centers of nitrogen. Thus, the sample produced according to the present invention is nitrogen-free, but substantially less nitrogen sensor defects than results from using relatively high concentrations of nitrogen in CVD gases, according to Yamazaki. Boron can not be seen in the PL spectrum because it can compensate nitrogen and improve the optical transparency and purity of the diamond single crystal.

An optical microscope image of a sample grown at a nitrogen concentration in the range according to the present invention is shown in the images of FIGS. 4 and 5. This image is taken in the range of 500-5000 magnification, and the stepwise growth of the diamond is evident from the surface of the diamond shown in this image.

Figure 4 is an image of a sample of diamond grown at a nitrogen flow rate of 0.03% in the flow rate of CVD gas. The steps of the growing crystal are evident in Fig. This step is a line in which diamond grows according to the present invention. The surface morphology of the sample is evident in Figures 5 and 6, where high density growth steps are apparent.

The dense growth step on the surface of the sample grown at the nitrogen flow rate according to the invention is also evident in Fig. This growth step is due to the spiral potential observed in the crystal growth process of many materials and is a distinct identification characteristic that the diamond according to the system of the present invention grows with the help of dislocation and stepwise growth mechanism.

Choosing a relatively small amount of nitrogen in the CVD gas ensures the purity and quality of the diamond. The selection of a relatively small amount of nitrogen also leads to the growth of the diamond in a stepwise fashion with the edge of the diamond growing as a front formed by the step. The occurrence of stepwise growth is evident in Figs. 4-6.

In the situation where less than 0.001% by volume of nitrogen is present in the CVD gas, the diamond grows with graphite inclusions, which adversely affect the properties of the diamond.

For example, Figures 7 and 8 illustrate graphite (dark) inclusions in CVD grown diamond using 0.0005 to 0.0008% by volume nitrogen with no diborane. In each of Figures 7 and 8, the steps in the layer of diamond are irregular and have defects which are thought to be due to graphite inclusions.

In contrast, CVD diamond grown in a gas containing 0.0012% by volume of nitrogen and 0.0008% of diborane flow in accordance with the present invention comprises regular equidistant steps and is substantially free of graphite inclusions as shown in Figure 9 . It is believed that these diamonds are derived from a CVD process involving at least 0.001% by volume nitrogen with diborane in the CVD gas.

In particular, this critical volume of nitrogen is believed to be essential for planting diamonds containing impurities and defect free steps.

Concentrations of nitrogen above 0.0016% by volume on the gas result in microscopic and macroscopic graphite inclusions. These inclusions and defects adversely affect the properties of the diamond formed.

The stepwise growth mechanism in the nitrogen concentration region specified in the present invention is not easy to incorporate defects and inclusions in the formed diamond, and the resulting diamond appears to be advantageous because it contains substantially no defects and inclusions. These formed diamonds are gem quality and have properties that approach electrical, optical and mechanical properties and natural diamond properties superior to other diamond forms grown by CVD.

The gem-quality products produced by this method are also known as single crystal diamonds.

In one embodiment of the present invention, the single crystal diamond S1 has a dimension of 3 X 3 X 2.16 mm ³ . In the second embodiment of the present invention, the single crystal diamond S2 has a dimension of 3 X 3 X 0.64 mm ³ . In another embodiment, the single crystal diamond may have other suitable dimensions.

According to one aspect of the present invention, a single crystal diamond exhibits a corrected full width half maximum (FWHM) after considering the Rayleigh width of a 514.5 nm laser.

As shown in FIG. 12, the monocrystalline diamond shows a corrected FWHM (FWHM) of 1.11 cm ^-1 when the primary Raman mode of the diamond is concentrated at 1333.27 cm ^-1 , according to the first embodiment of the present invention.

According to another embodiment of the present invention, a single crystal diamond exhibits a corrected FWHM (FWHM) of 1.13 cm ^-1 when the primary Raman mode of the diamond is concentrated at 1332.14 cm ^-1 .

In accordance with one aspect of the present invention, single-crystal diamond is a silicon public defect (SiV ^-) negatively charged depending on the quality of the diamond to the presence or absence.

As shown in FIG. 13, a single crystal diamond represents the presence of a negatively charged silicon vacancy defect (SiV ^- ) at 738 nm in accordance with the first embodiment of the present invention.

According to another embodiment of the invention, the single crystal diamond is a silicon public defect (SiV ^-) charged negatively at 738 nm does not show the presence of.

According to one aspect of the present invention, a single crystal diamond exhibits a specific value of the concentration level of neutral substituted nitrogen [N _s ⁰ ] when the absorption coefficient is 270 nm.

As shown in Fig. 14, the monocrystalline diamond has a concentration level of neutral substituted nitrogen [N _s ⁰ ] of 0.111 ppm (111 ppb) when the absorption coefficient is 270 nm according to the first embodiment of the present invention .

According to another embodiment of the present invention, a single crystal diamond exhibits a concentration level of neutral substituted nitrogen [N _s ⁰ ] of 0.0684 ppm (68.4 ppb) when the absorption coefficient is 270 nm.

According to one aspect of the present invention, a single crystal diamond exhibits a specific value of FTIR transmittance when the wavelength is 10.6 mu m.

As shown in FIG. 15, the single crystal diamond exhibits an FTIR transmittance of 70.84% when the wavelength is 10.6 μm according to the first embodiment of the present invention.

According to another embodiment of the present invention, the single crystal diamond exhibits an FTIR transmittance of 71.4% when the wavelength is 10.6 mu m.

According to one aspect of the present invention, the single crystal diamond exhibits a specific value of the positively charged concentration of substituted nitrogen [N _s ⁺ ] when the peak height is 1332.5 cm ^-1 .

As shown in Fig. 16, the monocrystalline diamond, according to the first embodiment of the present invention, has a peak height of 1332.5 cm &lt;&quot; ^{1 &} And the concentration of the substituted nitrogen [N _s ⁺ ].

According to another embodiment of the present invention, the monocrystalline diamond has a substituted nitrogen (N _s ⁺ ) charged in an amount of 0.138 ppm (138 ppb) when the peak height is 1332.5 cm ^-1 after introduction of the linear baseline. .

As shown in Figure 17, a single crystal diamond, according to the present invention, when a wavelength of 3123 cm ^-1 day, a nitrogen-paper no hydrogen defects (NVH ⁰⁾ - public.

As shown in Fig. 18, according to one aspect of the present invention, a monocrystalline diamond shows the normalization of the spectrum when the primary Raman peak using 514.5 nm laser excitation is 552.37 nm. SiV which is concentrated in the 738 nm ^- phono zero line (ZPL) of a forms the strongest feature. ZPL of neutral and negatively charged nitrogen-vacancy defects (NV ^{0 / -} ) are shown at 575 nm and 638 nm, respectively. ⁰ NV and the Nv- ^- due to the phonon side band, a large fluorescence background (FB) concentrated to about 700 nm is present.

Figure 19 shows a table listing the intensities of various fluorescent features.

According to one aspect of the present invention, a single crystal diamond represents a black sector or white sector (see Fig. 20), having a refractive index n of n = R / t, where R = retardation, .

21 is a table showing the maximums derived for the black and white sectors using the maximum delay value from the color scale. In Fig. 20, [Delta] n for the color sector indicated by the red ellipse point is not calculated because our adapted procedure can not determine the order of the interference. However, based on the classic Michel Levy Birefringence color chart, it is reasonable to assume a size that is one step higher than the white sector.

As shown in Figure 22, according to one aspect of the present invention, a single crystal diamond exhibits red and blue luminosity when the diamond is placed under 355 nm laser irradiation at room temperature in a dark environment. The blue glow is derived from the glass sample holder.

23 shows the resistivity of the single crystal diamond according to the first embodiment of the present invention. As shown, the resistivity of the single crystal diamond is 1.0E + 14? M to 1E + 16? M.

24 shows the resistivity of single crystal diamond according to another embodiment of the present invention. As shown, the resistivity of the single crystal diamond is 1.0E + 14? M to 1E + 16? M.

Gem diamonds may be made of single crystal diamond as discussed in this section. Jewelry diamonds have a weight greater than 0.01 ct.

References herein to any prior art should not be considered to be construed as an admission or any form of indication that this prior art forms part of the common general knowledge in Australia or any other country.

Many modifications may be made to the preferred embodiments of the invention described above without departing from the spirit and scope of the invention.

It is to be understood that the term " comprises "and its grammatical variants as used herein are equivalent to the term " comprises ", and should not be considered to exclude the presence of other features or elements.

While the invention has been described in conjunction with the preferred embodiments, it should be understood that modifications and variations can be utilized without departing from the spirit and scope of the invention, as will be readily appreciated by those skilled in the art. Accordingly, such modifications may be made within the scope of the invention and within the scope of the following claims.

Claims (31)

As a single crystal diamond,
Lt; RTI ID = 0.0 &gt; (FWHM) &lt; / RTI &gt; after considering the Rayleigh width of the 514.5 nm laser,
Indicates the presence or absence of negatively charged silicon vacancies depending on the quality of the diamond,
Represents a specific value of the concentration level of the neutral substituted nitrogen [N _s ⁰ ] when the absorption coefficient is 270 nm,
When the wavelength is 10.6 [mu] m, it indicates the FTIR transmittance at a specific value,
Represents a specific value of the concentration of the positively charged substituted nitrogen [N _s ⁺ ] when the peak height is 1332.5 cm ^-1 ,
Shows the absence of a nitrogen-vacancy-hydrogen defect (NVH ⁰ ) species when the wavelength is 3123 cm ^-1 ,
Shows the normalization of the spectrum when the primary Raman peak using 514.5 nm laser excitation is 552.37 nm,
(N) where n = R / t, where R = retardation, t is the thickness of the diamond plate,
When the diamond is placed under 355 nm laser irradiation at room temperature in a dark environment,
Monocrystalline diamond. The method according to claim 1,
Wherein the single crystal diamond has a dimension of 3 X 3 X 2.16 mm ³ ,
Monocrystalline diamond. 3. The method of claim 2,
The single crystal diamond, showing a half value width (FWHM) of when the first Raman mode of the diamond is focused on 1333.27 cm ^-1, 1.11 cm ^{-1-corrected,}
Monocrystalline diamond. 3. The method of claim 2,
The single crystal diamond shows the presence of a negatively charged silicon vacancy defect (SiV &lt; ^{- &} gt;) at 738 nm,
Monocrystalline diamond. 3. The method of claim 2,
The monocrystalline diamond exhibits a concentration level of neutral substituted nitrogen [N _s ⁰ ] of 0.111 ppm (111 ppb) when the absorption coefficient is 270 nm.
Monocrystalline diamond. 3. The method of claim 2,
Wherein the single crystal diamond has an FTIR transmittance of 70.84% when the wavelength is 10.6 mu m,
Monocrystalline diamond. 3. The method of claim 2,
Wherein said single crystal diamond exhibits a concentration of substituted nitrogen (N _s ⁺ ) charged in an amount of 0.248 ppm (248 ppb) when said peak height is 1332.5 cm ^-1 μm after introduction of a linear baseline,
Monocrystalline diamond. 3. The method of claim 2,
Wherein the single crystal diamond has a resistivity of 1.0 E + 14? M to 1E + 16? M,
Monocrystalline diamond. The method according to claim 1,
Wherein the single crystal diamond has a dimension of 3 X 3 X 0.64 mm ³ ,
Monocrystalline diamond. 10. The method of claim 9,
The single crystal diamond, showing a half value width (FWHM) 1 Raman order mode of the diamond when it is concentrated in the 1332.14 cm ^-1, of 1.13 cm ^-1 correction,
Monocrystalline diamond. 10. The method of claim 9,
The single crystal diamond does not exhibit the presence of a negatively charged silicon vacancy defect (SiV &lt; ^{- &} gt;) at 738 nm,
Monocrystalline diamond. 10. The method of claim 9,
The monocrystalline diamond exhibits a concentration level of neutral substituted nitrogen [N _s ⁰ ] of 0.0684 ppm (68.4 ppb) when the absorption coefficient is 270 nm.
Monocrystalline diamond. 10. The method of claim 9,
Wherein the single crystal diamond has an FTIR transmittance of 71.4% when the wavelength is 10.6 m,
Monocrystalline diamond. 10. The method of claim 9,
Wherein said monocrystalline diamond exhibits a concentration of substituted nitrogen [N _s ⁺ ] charged in an amount of 0.138 ppm (138 ppb) when said peak height is 1332.5 cm ^-1 after introduction of a linear baseline,
Monocrystalline diamond. 10. The method of claim 9,
Wherein the single crystal diamond has a resistivity of 1.0 E + 14? M to 1E + 16? M,
Monocrystalline diamond. The method according to claim 1,
SiV in the 738 nm ^- phono zero line (zero line phono; ZPL) is to form the strongest feature (feature),
Monocrystalline diamond. 17. The method of claim 16,
Neutral nitrogen-charged public flaws and Well nitrogen-public flaws (NV ^{0 / -)} of the ZPL are respectively 575 nm and look at 638 nm, about 700 nm focused a large fluorescence background (FB) The NV ⁰ and NV on ^- Lt; RTI ID = 0.0 &gt; of the &lt; / RTI &gt;
Monocrystalline diamond. The method according to claim 1,
Wherein said single crystal diamond has a weight greater than 0.01 carat, and thus said single crystal diamond is a gem diamond,
Monocrystalline diamond. A method of forming a single crystal diamond by chemical vapor deposition,
(a) providing at least one diamond seed;
(b) exposing the seed to conditions for growing diamond by chemical vapor deposition comprising the steps of: providing a reaction gas comprising a carbon-containing gas and a nitrogen-containing gas for growing diamond;
(c) controlling the amount of said nitrogen-containing gas relative to the other gases in said reactant gas so as to grow defects and diamonds not containing graphite inclusions by step growth, wherein the nitrogen- Containing gas is in the range of 0.0001 to 0.02% by volume and further comprises diborane in the reaction gas; And
(d) controlling the diborane and the nitrogen-containing gas source in such a manner as to provide a concentration of atomic fraction of nitrogen of 0.3 or less to produce single crystal diamond suitable for use as gemstones and other suitable uses, And nitrogen are added to improve the optical absorption to improve the transparency and color of the single crystal diamond suitable for all suitable applications and to contain less amount of impurities in the single crystal diamond,
Method of forming single crystal diamond. 20. The method of claim 19,
Wherein the diborane is provided in a range of 0.0002 to 0.002% by volume,
Method of forming single crystal diamond. 20. The method of claim 19,
Wherein the nitrogen-containing gas is selected from any one or more of the group comprising nitrogen in hydrogen, nitrogen in oxygen, nitrogen in helium, nitrogen in nitrogen dioxide, or nitrogen in diborane.
Method of forming single crystal diamond. 20. The method of claim 19,
Wherein the chemical vapor deposition comprises maintaining the seed at a temperature in the range of &lt; RTI ID = 0.0 &gt; 750 &lt; / RTI &
Method of forming single crystal diamond. 20. The method of claim 19,
Wherein the chemical vapor deposition comprises maintaining the seed at a pressure ranging from 120 to 160 mbar.
Method of forming single crystal diamond. 20. The method of claim 19,
Wherein the carbon-containing gas comprises methane.
Method of forming single crystal diamond. 20. The method of claim 19,
Wherein the reactive gas further comprises hydrogen,
Method of forming single crystal diamond. 20. The method of claim 19,
Wherein the chemical vapor deposition is performed by hydrogen in the reaction gas in the presence of a microwave plasma,
Method of forming single crystal diamond. 27. The method of claim 26,
The microwave plasma is generated by a magnetron operating at 6000 watts and 2.45 GHz,
Method of forming single crystal diamond. 20. The method of claim 19,
The reaction gas is passed through the reaction chamber at a gas flow rate of about 30 l /
Method of forming single crystal diamond. 20. The method of claim 19,
The seed is oriented in a (100) crystal orientation,
Method of forming single crystal diamond. 20. The method of claim 19,
The relative amount of the reactive gas,
Methane 20-80 seem (standard cubic centimeter / min),
Hydrogen 300-800 sccm,
Nitrogen 0.0005-0.2 sccm,
0.0001 - 0.01 sccm diborane; And
Lt; RTI ID = 0.0 &gt;
Method of forming single crystal diamond. 20. The method of claim 19,
The diamond seed has a size of 3 x 3 mm x 0.5 mm,
Method of forming single crystal diamond.

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