HK1120781A - Colorless single-crystal cvd diamond at rapid growth rate - Google Patents

Description

Colorless single crystal CVD diamond with fast growth rate

Statement of government interest

The invention was made with government support according to national science fund grant, EAR-0421020. The government has certain rights in this invention.

Reference to material submitted by optical discs

Not applicable.

Sequence listing

Not applicable.

Technical Field

The present invention relates to a method for producing diamond. More particularly, the invention relates to a method of producing colorless single crystal diamond at a fast growth rate using Microwave Plasma Chemical Vapor Deposition (MPCVD) within a deposition chamber.

Background

The large scale production of synthetic diamond has long been a goal of research and industry. In addition to the properties of gemstones, diamond is the hardest material known, has the highest known thermal conductivity, and is transparent to many electromagnetic radiations. Therefore, it is very valuable because it is widely used in many industries in addition to its value as a gemstone.

For at least 20 years, methods have been available for producing small quantities of diamond by Chemical Vapor Deposition (CVD). As reported by B.V. Spitsyn et al in Journal of Crystal Growth, volume 52, page 219-226, "Vapor Growth of Diamond on Diamond and OtherS surfaces" the method involves the chemical Vapor deposition of Diamond on a substrate using methane or another simple hydrocarbon gas in combination with hydrogen at reduced pressure and temperatures of 800 deg.C to 1200 deg.C. The presence of hydrogen prevents the formation of graphite during diamond nucleation and growth. Growth rates of up to 1 micron/hour have been reported using this technique.

Subsequent work, such as Kamo et al reported in Journal of Crystal Growth, vol.62, p.642 & 644, "Diamond Synthesis from Gas Phase in MicrowavePlasma", demonstrated that Diamond can be produced using Microwave Plasma Chemical Vapor Deposition (MPCVD) at a frequency of 2.45GHz and with a microwave power of 300-700W at a pressure of 1-8 kPa and a temperature of 800-1000 ℃. In Kamo et al, a methane gas is used at a concentration of 1% to 3%. The maximum growth rate using this MPCVD method has been reported to be 3 microns/hour. In the above method and many other reported methods, the growth rate is limited to only a few microns per hour.

Until recently, the known higher growth rate methods have produced only polycrystalline forms of diamond. However, new methods for modifying single crystal chemical vapour deposition (SC-CVD) diamond have recently been reported, which open new opportunities for diamond applications in gemstones, optics and electronics [1, 2 ]. Several other groups have started growing SC-CVD diamond [3, 4, 5 ]. However, SC-CVD diamond as currently reported is relatively small, discolored and/or flawed. Large (e.g., over 3 carats, such as commercially available High Pressure High Temperature (HPHT) synthetic Ib yellow diamond), colorless, flawless synthetic diamonds remain a challenge due to slow growth and other technical difficulties [7, 8, 9 ]. SC-CVD diamonds can be light brown to dark brown in color without HPHT annealing, which limits their applicability as gemstones in optics, scientific research and diamond-based electronics [6, 7, 8 ]. SC-CVD diamond is characterized as type IIa, i.e., having less than 10ppm nitrogen, and having coloration and other optical properties due to various defects and/or impurities.

The addition of nitrogen gas produced 4.5mm thick single crystal brown SC-CVD diamond at a high growth rate of about 100 microns/hour and was deposited on cut SC-CVD seeds rather than on natural or HPHT synthetic substrates [1, 2 ]. The 10 carat diamond crystals are approximately 5 times as large as the SC-CVD diamonds reported in the commercial HPHT diamond and references [7, 8, 9, 10 ]. Single crystal diamonds of greater mass (greater than 100 carats) are required as anvils for high voltage research, while applications such as laser windows and substrates for diamond-based electronics require crystals with large lateral dimensions (greater than 2.5 centimeters). All the above applications require high optical quality (UV-visible-IR transmission) and chemical purity. Large SC-CVD diamonds currently produced have problems with brown color.

Attempts have been made to add oxygen to the growth of polycrystalline CVD diamond. The effects include extending the region of diamond formation [12], reducing the level of silicon and hydrogen impurities [13], preferentially etching non-diamond carbon [11, 14], and attempting to prevent diamond cracking due to the presence of impurities [13 ]. These attempts were directed to etching and synthesizing polycrystalline diamond, but not to producing SC-CVD diamond.

U.S. patent 6,858,078 to Hemley et al relates to an apparatus and method for diamond production. Although it has developed a method for rapidly producing single crystal CVD diamond, the disclosed apparatus and method can result in diamond produced having a light brown color.

Therefore, there is still a need to produce large, high quality single crystal diamonds at fast growth rates, and the produced diamonds are colorless (i.e., highly transmissive to UV-visible-IR).

Disclosure of Invention

Accordingly, the present invention is directed to a method of producing diamond that substantially obviates one or more problems due to limitations and disadvantages of the related art.

The object of the present invention relates to a method for producing diamond at a fast growth rate in a microwave plasma chemical vapour deposition system.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and 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.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, embodiments of the present invention include: controlling the temperature of the diamond growth surface such that all temperature gradients across the diamond growth surface are less than about 20 ℃, and growing single crystal diamond on the diamond growth surface with microwave plasma chemical vapor deposition at a growth temperature in a deposition chamber having an atmosphere comprising about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄。

In another embodiment, the method of producing diamond comprises: controlling the temperature of the diamond growth surface, and microwave plasma chemical vapor deposition at the growth temperature on the diamond growth surface in a deposition chamber having an atmosphere with a pressure of about 100 to about 300 torrA single crystal diamond grown on, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄。

In another embodiment of the present invention, the method for producing diamond comprises: controlling the temperature of the diamond growth surface, and growing single crystal diamond on the diamond growth surface using microwave plasma chemical vapor deposition at a growth temperature of about 700 ℃ to about 1100 ℃ in a deposition chamber, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄。

In another embodiment of the present invention, the method for producing diamond comprises: controlling the temperature of the diamond growth surface, and growing single crystal diamond on the diamond growth surface using microwave plasma chemical vapor deposition at a growth temperature in a deposition chamber, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄Wherein the growth rate is greater than about 50 microns/hour.

In another embodiment of the present invention, the method for producing diamond comprises: controlling the temperature of the diamond growth surface, and growing single crystal diamond on the diamond growth surface using microwave plasma chemical vapor deposition at a growth temperature in a deposition chamber, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄Wherein the diamond growth is in excess of 10 carats.

In another embodiment of the present invention, the method for producing diamond comprises: controlling the temperature of the diamond growth surface, and growing single crystal diamond on the diamond growth surface using microwave plasma chemical vapor deposition at a growth temperature in a deposition chamber, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄Which isThe diamond produced in (a) is substantially colourless and has a UV-VIS absorption spectrum substantially similar to that of an artificial HPHT type IIa diamond.

In another embodiment of the present invention, the method for producing diamond includes a diamond production method comprising: controlling the temperature of the diamond growth surface such that the temperature of the grown diamond crystals is in the range of 900 ℃ to 1400 ℃ and placing the diamond in a heat sink holder made of a material having a high melting point and a high thermal conductivity to minimize the temperature gradient across the diamond growth surface; growing single crystal diamond on a diamond growth surface using microwave plasma chemical vapor deposition in a deposition chamber having an atmosphere, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄。

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.

Drawings

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.

Fig. 1 is a diagram of a diamond production apparatus according to an embodiment of the invention, depicting a cross-section of a deposition apparatus having a sample holder assembly for holding a diamond stationary during a diamond growth process.

Fig. 2a is a perspective view of the deposition apparatus shown in fig. 1.

Fig. 2b is a perspective view of the diamond and sleeve of fig. 1.

Fig. 3 is a diagram of a diamond production apparatus according to an embodiment of the invention, depicting a cross-section of a deposition apparatus having a sample holder assembly for moving diamond during a diamond growth process.

Fig. 4 a-4 c depict cross-sectional views of a holder or thermal block that may be used in accordance with the present invention.

Fig. 5 is a diagram of a diamond production apparatus according to another embodiment of the invention, depicting a cross-section of a deposition apparatus having a sample holder assembly for moving diamond during a diamond growth process.

Fig. 6 is a flow diagram illustrating a process 600 according to an embodiment of the invention that may use the sample holder assembly shown in fig. 1.

Fig. 7 is a flow chart illustrating a process 700 according to an embodiment of the invention that may be used with the sample holder assembly shown in fig. 3 or the sample holder assembly shown in fig. 5.

FIG. 8 is a HPHT IIa diamond, for example, with a diamond comprising about 5% to about 25% O, in accordance with a method of the present invention₂Per unit CH₄And the presence of N₂UV-VIS spectra of SC-CVD diamond produced with gases as a component of the deposition chamber atmosphere.

FIG. 9 is a schematic representation of a process according to the present invention, e.g., with a composition comprising about 5% to about 25% O₂Per unit CH₄And the presence of N₂Photographs of SC-CVD crystals grown with gas as a component of the deposition chamber atmosphere.

FIG. 10 is a block of SC-CVD diamond formed by deposition on 6 {100} planes of an HPHT Ib substrate.

FIG. 11 is a graph of a process according to the present invention, e.g., with a catalyst comprising about 5% to about 25% O₂Per unit CH₄And the presence of N₂IR absorption spectrum (2500 cm) of SC-CVD diamond produced with gas as a component of the deposition chamber atmosphere^-1～8000cm^-1)。

Detailed Description

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Fig. 1 is a diagram of a diamond production system 100 in which a deposition apparatus 102 is depicted in cross-section, according to an embodiment of the invention. The diamond production apparatus 100 includes a Microwave Plasma Chemical Vapor Deposition (MPCVD) system 104 containing a deposition apparatus 102 and reactant and plasma controls 106. For example, MPCVD system 104 can be Seki AX6550 manufactured by Seki technotron corp. The system is capable of producing a power output of 6KW at a frequency of 2.45 GHz. As another example, MPCVD system 104 can be Seki AX5250 manufactured by Seki technotron corp. The system is capable of producing a power output of 5KW at a frequency of 2.45 GHz. As another example, MPCVD system 104 can be WAVEMAT MPDR 330313 EHP manufactured by Wavemat, inc. The MPCVD system is capable of producing a 6KW power output at a frequency of 2.45GHz and has a chamber volume of about 5,000 cubic centimeters. However, MPCVD system specifications can vary in terms of the size of the deposition area and/or the deposition rate depending on the scale of the deposition process.

The MPCVD system 104 includes a chamber within the deposition apparatus 102 that is at least partially defined by a bell jar 108 that seals the chamber. Prior to MPCVD operation, the chamber is evacuated of air. For example, the chamber is pumped down using a first mechanical type vacuum pump, and then the chamber is further evacuated using a second high vacuum type vacuum pump such as a turbo pump or a cryopump. A plasma is generated within the chamber by a set of plasma electrodes spaced apart within the chamber. Neither the pump nor the plasma electrode is shown in fig. 1.

The deposition apparatus 102 also includes a sample holder assembly 120 mounted within the chamber of the MPCVD system 104. As shown in fig. 1, the sample holder assembly is generally centrally located on the deposition chamber floor 122 of the deposition apparatus 102. The sample holder assembly 120 shown in fig. 1 is shown in cross-section. The sample holder assembly 120 can include a step 124 mounted in the floor of the deposition device 102.

As shown in fig. 1, the step 120 may be attached to the deposition chamber floor 122 using bolts 126a and 126 c. The step 124 may be molybdenum or any other type of material having a high thermal conductivity. In addition, coolant passing through coolant tubes 128 within the step 124 may be used to cool the step 124 during the process of growing diamond. The coolant may be water, refrigerant, or other type of fluid having sufficient heat carrying capacity to cool the step. Although the coolant tubes are shown in fig. 1 as U-shaped channels through the step 124, the coolant tubes 128 may have spiral channels or other types of channels within the step 124 to more effectively cool the step 124.

As shown in FIG. 1, a retaining ring 130 having retaining screws, such as screws 131a and 131c, is positioned over the step 124 of the sample holder assembly 120 for tightening the collets 132a and 132b around a sleeve 134 supporting a diamond 136. The sleeve 134 is a holder that is in thermal contact with the side surface of the diamond 136 near the edge of the upper surface of the diamond 136. Because the collet 132a and 132b are tightened to the sleeve 134 with the screws 131, the sleeve 134 holds the diamond 136 in a fixed position and acts to dissipate heat to prevent twinning or polycrystalline diamond formation along the edges of the diamond 136 growth surface.

The diamond 136 may include a diamond seed portion 138 and a grown diamond portion 140. The diamond seed portion 138 may be manufactured diamond or natural diamond. In one embodiment, the seed is one of natural colorless Ia diamond, colorless IIa diamond, HPHT synthetic yellow Ib diamond, and SC-CVD diamond. In another embodiment, the seed is SC-CVD diamond. In another embodiment, the seed is SC-CVD diamond with {100} planes. In another embodiment, the seed is SC-CVD diamond with 6 {100} planes. In another embodiment, all 100 upper surfaces of the seed have about 1mm²To about 100mm²The area of (a).

As shown in fig. 1, the upper or growth surface of the diamond 136 is positioned within a region of the plasma 141 having resonant power at a height H above the deposition chamber floor 122. The resonant power may be the maximum resonant power within plasma 141 or some degree thereof. The upper or growth surface of the diamond 136 is initially the diamond seed portion 138, as the diamond grows, and then the grown diamond portion 140.

As shown in fig. 1, the upper edge of the sleeve 134 is just below the upper surface or edge of the diamond 136 by a distance D. The distance D should be sufficiently large enough to expose the edge of the growth surface of the diamond 136 to the plasma 141. However, the distance D cannot be so great as to impede the heat dissipation effect of the sleeve 134, which prevents twinning or polycrystalline diamond formation along the edges of the growth surface of the diamond 136. Therefore, D should be within a specified distance range, such as 0mm to 1.5 mm. As shown in fig. 1, the distance D and the height H are manually set using the screws 131 of the fixing ring 130 by positioning the diamond 136 in the sleeve, positioning the sleeve in the collets 132a and 132b, and then tightening the screws 131.

Fig. 2 is a perspective view of the deposition apparatus shown in fig. 1. At the center of the deposition chamber floor 122 of fig. 2 is a circular step 124 having a central recess 125. As shown in fig. 2, the step 124 is secured in place with bolts 126 a-126 d. The step 124 may be made of molybdenum or other material having a high thermal conductivity. A retaining ring 130 having four screws 131 a-131 b is positioned in the groove 125 of the step 124 along with collets 132 a-132 b. Alternatively, the retaining ring 130 may be bolted to the step 124 to increase thermal conduction between the step and the retaining ring.

As shown in fig. 2a, a rectangular sleeve 134, which may be a short length of rectangular tubing or a sheet folded into a rectangle, is positioned in the collets 132a and 132b with the diamonds 136 therein. The sleeve 124 may be molybdenum or any other type of material having a high thermal conductivity. Tightening the screws 131 a-131 d on the collets 132 a-132 b tightens the sleeve 134 to the diamond 136, such that the sleeve 134 acts as a heat sink on the four side surfaces of the diamond 136. As shown in FIG. 1, the sleeve 134 is also in thermal contact with the step 124. The collets 132 a-132 b thermally contact the step 124 and act as a thermal block that transfers heat from the sleeve 134 into the step 124. The fastening of the sleeve 134 to the diamond 136 increases the quality of the thermal contact between the diamond and the sleeve. As shown in fig. 1, the sleeve 134 may also thermally contact the step 124. Although both the sleeve and the diamond are shown as rectangular in fig. 2a, the sleeve and the diamond may have any geometric shape such as oval, circular or polygonal. The shape of the sleeve or holder should be substantially the same as the diamond.

In the exemplary embodiment of the invention shown in fig. 1 and 2a, the step 124 may have a diameter of about 10.1 centimeters and the sleeve 134 may be about 2.5 centimeters wide. Regardless of the selected dimensions of the step and sleeve 134, the thermal block of the step 122, the molybdenum sleeve 124, and the collet 132 may be adjusted to provide optimal heat dissipation to the diamond 136. In addition, the channels and dimensions of the coolant channels 128 may be adjusted for greater cooling effectiveness, particularly if particularly large diamonds are to be produced. Additionally, a refrigerant or other cryogenic fluid may be used as the coolant.

Molybdenum is only one potential material for the step 124, retaining ring 130, collet 132, sleeve 134, and other components. Molybdenum is suitable for these components because of its high melting point, i.e., 2617 c, and high thermal conductivity. In addition, large graphite accumulations are not easily formed on molybdenum. Other materials having a high melting point above the processing temperature and a thermal conductivity comparable to molybdenum, such as molybdenum tungsten alloys or engineered ceramics, may alternatively be used in place of molybdenum.

Returning to fig. 1, another component of the diamond production system 100 is a non-contact measurement device, such as an infrared pyrometer 142, used to detect the temperature of the diamond seed 138 and the later-grown diamond 140 during the growth process without contacting the diamond 136. The infrared pyrometer 142 may be, for example, a MMRONM77/78 two-color infrared pyrometer available from Mikron Instruments, Inc. of Oakland, N.J. An infrared pyrometer 142 was focused on the diamond seed 138 or the later grown diamond 140 and the target area was measured to be 2 mm. The temperature of the growth surface of the diamond 136 was measured to within 1c of error by using an infrared pyrometer 142.

The diamond production system 100 of fig. 1 also includes an MPCVD process controller 144. An MPCVD process controller 144 is typically provided as a component of the MPCVD system 104. As is well known in the art, the MPCVD process controller 144 performs feedback control of a number of MPCVD parameters, including but not limited to process temperature, gas mass flow, plasma parameters, and reactant flow rates, by utilizing the reactant and plasma controls 106. The MPCVD process controller 144 operates in conjunction with the main process controller 146. The main process controller 146 takes input from the MPCVD process controller 144, the infrared pyrometer 142, and other measurement devices of other components in the diamond production system 100 and performs a level of control over the process. For example, the main process controller 146 may utilize the coolant controller 148 to determine and control the coolant temperature and/or coolant flow rate in the steps.

The main process controller 146 may be a general purpose computer, a special purpose computing system such as an ASIC, or any other type of computing system known for controlling an MPCVD process. Depending on the type of the main process controller 146, the MPCVD process controller 144 may be integrated into the main process controller to combine the functions of these two components. For example, the main process controller 146 may be a general purpose computer equipped with the LabVIEW programming language and LabVIEW program available from National Instruments, Inc. of Austin, Tex, such that the general purpose computer is equipped to control, record and report all process parameters.

The main process controller 146 in fig. 1 controls the temperature of the growth surface such that all temperature gradients across the diamond growth surface are less than or equal to 20 ℃. The precise control of the growth surface temperature and growth surface temperature gradient prevents the formation of polycrystalline diamond or twin crystals, so that large single crystal diamond can be grown. The ability to control all temperature gradients across the diamond 136 growth surface is affected by several factors, including the heat dissipation capability of the step 124, the positioning of the diamond upper surface in the plasma 141, the uniformity of the plasma 141 to which the diamond growth surface is subjected, the quality of heat transfer from the diamond edge to the step 124 through the holder or sleeve 134, the controllability of microwave power, coolant flow rate, coolant temperature, gas flow rate, reactant flow rate, and the detection capability of the infrared pyrometer 142. Based on the temperature measurements of the pyrometer 142, the main process controller 146 controls the temperature of the growth surface by adjusting at least one of the microwave power, the coolant flow rate, the coolant temperature, the gas flow rate, and the reactant flow rate of the plasma 141 such that all temperature gradients across the growth surface are less than 20 ℃.

Fig. 2b is a perspective view of the diamond 136 shown in fig. 1 depicting exemplary points P1, P2, P3, and P4 along the growth surface 137 of the diamond 136. Fig. 2b also depicts the distance D between the growth surface 137 or upper edge 139 of the diamond 136 and the edge 135 of the sleeve 134. Typically, there is a large temperature variation between the edge and the middle of the growth surface of the diamond, measured as a temperature difference across the growth surface. For example, the temperature gradient occurring between points P1 and P2 is greater than between points P1 and P3. In another example, the temperature gradient occurring between points P4 and P2 is greater than between points P4 and P3. Thus, the temperature of the growth surface of the diamond is controlled so that all temperature gradients across the growth surface are less than 20 ℃, taking into account at least the temperature measurement between the middle of the growth surface 137 and the edge 139. For example, the main controller 146 may control the temperature of the growth surface such that the temperature gradient between points P1 and P2 is less than 20 ℃.

The spot size of the infrared pyrometer may affect the ability to monitor the temperature gradient across the upper surface of the diamond and thus affect the growth rate of the diamond. For example, if the size of the diamond is large compared to the spot size of the infrared pyrometer, the temperature of each edge of the diamond growth surface may be outside the field of view of the infrared pyrometer. Therefore, diamonds with large growth areas should use multiple infrared pyrometers. Each of the plurality of pyrometers should be focused on a different edge of the diamond surface, if angled, preferably near the angle. Thus, as shown in fig. 1, the main process controller 146 should be programmed to integrate the overlapping fields of view of multiple pyrometers to produce adjacent "maps" of temperature across the diamond surface, or to interpolate between non-overlapping fields of view to produce a complete "map" of temperature across the diamond surface. Alternatively, the temperature gradient between a single edge or corner relative to the middle of the growth surface may be monitored as an indication of the maximum temperature gradient that exists across the diamond growth surface.

In addition to the infrared pyrometer 142 for temperature control, other process control instruments may also be included in the diamond production system 100. Additional process control instrumentation may include equipment for determining the type and quality of the diamond 136 while the growth process is in progress. Examples of such devices include visible, infrared and raman spectrometers, which are optical in nature and can be focused on the same spot as the infrared pyrometer 142 to obtain data on diamond structure and quality as growth proceeds. If additional equipment is provided, it may be connected to the main process controller 146 so that the main process controller 146 controls the meter and provides the results of the analysis method along with other status information. Additional process control instrumentation may be particularly useful in experimental setup, scaling up the process to produce larger diamonds, and quality control efforts of existing diamond production systems 100 and corresponding processes.

As the diamond 136 grows, both the distance D and the height H increase. As the distance D increases, the heat dissipation capability of the sleeve 134 for the upper edge 139 of the growth surface of the diamond 136 decreases. In addition, as the growth surface of diamond 136 extends into plasma 141, the characteristics of the plasma, such as temperature and/or uniformity, change. Periodically, the growth process is halted in the diamond production system 100 so that the position of the diamond 136 may be adjusted downward relative to the sleeve 134 to reduce the distance D and the diamond 136 and sleeve 134 may be adjusted downward relative to the deposition chamber floor 122 to reduce the height H. This repositioning causes diamond growth on the growth surface of the diamond 136 to occur within the desired resonant power region within the plasma 141, with the infrared pyrometer 142 and any additional instrumentation still focused on the growth surface of the diamond 136, with the effect of maintaining efficient thermal contact for heat dissipation from the edges of the growth surface of the diamond 136. However, for large scale production, it may be inconvenient to repeatedly interrupt the growth process, increasing the chance of introducing contaminants into the process if not done carefully.

Fig. 3 is a diagram of a diamond growth apparatus 300 in accordance with an embodiment of the invention, depicting a cross-section of a deposition apparatus 304 having a sample holder assembly 320, the sample holder assembly 320 being used to move a diamond 136 during a diamond growth process. Some of the components of the diamond growth apparatus 300 are substantially the same as those in the diamond production system 100 described above, and therefore the discussion above with respect to fig. 1 is sufficient to describe those components of fig. 3 that are numbered the same. For example, the pyrometers 142, the deposition chamber floor 122, the coolant pipes 128, and the bell jar 108 of FIG. 3 are substantially the same as those described in FIG. 1.

As shown in FIG. 3, the diamond 136 is seated on a diamond driver 360 within the sleeve 134 of the sample holder assembly 320. The diamond 136 is slidably disposed within the sleeve 134 on a diamond actuator 360 that translates along an axis substantially perpendicular to the growth surface. The diamond drive 360 projects beyond the step 324 and is controlled from below the step 324 by a diamond control, which is shown in fig. 3 as part of the coolant and diamond/holder control 329. The diamond actuator 360 is used to fix the height H between the growth surface of the diamond 136 and the deposition chamber floor 122. Although diamond actuator 360 is shown in fig. 3 as a screw, the diamond actuator may have any geometry that is capable of positioning the diamond 136 at a height or position above the floor of the deposition chamber. Those skilled in the art will recognize that components placed within the bell housing, such as the diamond drive 360, should be compatible with the vacuum in order to maintain the desired atmosphere while avoiding problems.

The drive means (not shown) for the diamond drive element 360 is a motor (not shown). However, the actuator may be any of a number of known types of actuators depending on the size of the diamond to be grown, the growth rate and the level of movement accuracy required. For example, if the diamond 136 is small in size, a piezoelectric actuator may be used. If the diamond 136 is relatively large or can be grown relatively large, a motorized, computer-controlled actuator is preferred. Regardless of the particular actuator used, the main process controller 346 controls the movement of the diamond drive 360 so that the diamond 136 may be automatically moved downward as diamond growth progresses.

Additionally, the holder actuator 362 protrudes beyond the step 324 and is controlled from below the step 324 with a holder control, shown in FIG. 3 as part of the coolant and diamond/holder control 329. The holder actuator member 362 translates along an axis substantially perpendicular to the growth surface for maintaining the distance D between the edge of the growth surface of the diamond 136 and the upper edge of the holder or sleeve 134. The diamond production system may have a diamond drive, a holder drive, or a combination of both.

The holder actuator piece 362 in fig. 3 is threaded into the step 324 and the diamond actuator piece 360 is threaded into the holder actuator piece 362. With this arrangement, the diamond and holder controls of the coolant and diamond/holder controls 329 shown in fig. 3 can move the diamond 136, the sleeve 134, or both the sleeve 134 and the diamond 136. Although the retainer drive member 362 in fig. 3 is shown as a threaded cylinder with an inner thread for the diamond drive member 360 and an outer thread for threading into the step 324, the retainer drive member may have any geometry that maintains a specified range of distances between the edge of the growth surface of the diamond 136 and the upper edge of the retainer or sleeve 134. Those skilled in the art will recognize that components placed within the bell housing, such as the holder actuator member 362 or a combination of both the holder actuator member and the diamond actuator member, should be compatible with vacuum in order to maintain the desired atmosphere while avoiding problems.

As shown in fig. 3, thermal block 364 is positioned within the recess of step 324. Retainer or sleeve 134 is slidably positioned within thermal block 364 such that thermal energy is transferred from sleeve 134 to step 324. The upper surface of thermal mass 364 can be shaped so that heat can be transferred from sleeve 134 while minimizing the electrical effect of thermal mass 364 on plasma 341. The thermal blocks 466a, 466b and 466c of fig. 4 a-4 c, respectively, are examples of other shaped thermal blocks having different cross-sectional shapes, or may be used in place of the thermal block 364 shown in fig. 3. The thermal block may be made of molybdenum. Other materials having a high melting point above this processing temperature and a thermal conductivity comparable to molybdenum, such as molybdenum-tungsten alloy or engineered ceramics, may be used as the thermal block for transferring heat from the diamond side to the step.

By minimizing the electrical effect of thermal mass 364 on plasma 341, the area within plasma 341 where diamond is grown will be more uniform. In addition, higher pressures may be used in growing diamond, which will increase the growth rate of single crystal diamond. For example, the pressure may vary from about 100 torr to about 300 torr and the single crystal growth rate may be between 50 microns/hour and 150 microns/hour. Because the uniformity, shape, and/or location of plasma 341 is not readily affected by thermal mass 364, higher pressures, such as 400 torr or higher, may be used and thermal mass 364 may be shaped to remove heat from the edges of the diamond growth surface and minimize the electrical effects of thermal mass 364 on plasma 341. In addition, the microwave power required to sustain the plasma 341 is as small as 1 to 2 kW. Otherwise, a lower pressure and/or increased microwave power would have to be used to maintain the uniformity, shape, and/or position of the plasma 341.

As the diamond 136 grows, both the distance D and the height H increase. As the distance D increases, the heat dissipation capability of the sleeve 134 to the upper edge of the growth surface of the diamond 136 decreases. In addition, as the growth surface of the diamond 136 extends into the plasma 341, the characteristics of the plasma, such as temperature, change. In diamond production system 300, the growth process is halted when diamond 136 reaches a predetermined thickness, as holder actuator 362 and diamond actuator 360 may be used during diamond growth to control distance D and height H with main process controller 346 via coolant and diamond/holder control 329. This repositioning, either manually or automatically under the control of the controller 144, causes diamond growth on the growth surface of the diamond 136 to occur within the desired resonant power region within the plasma 341. In addition, repositioning allows the infrared pyrometer 142 and any additional instrumentation to remain focused on the growth surface of the diamond 136, maintaining efficient heat removal from the edges of the growth surface of the diamond 136.

Fig. 5 is a diagram of a diamond production apparatus 500 in accordance with an embodiment of the invention, depicting a cross-section of a deposition apparatus 504 having a sample holder assembly 520, the sample holder assembly 520 being used to move the diamond 136 during the diamond growth process. Some of the components of the diamond production apparatus 500 are substantially the same as those in the diamond production apparatuses 100 and 300, and therefore, the discussion above with respect to fig. 1 and 3 is sufficient to describe those components of fig. 5 that are numbered the same. For example, the pyrometers 142, the deposition chamber floor 122, the coolant pipes 128, and the bell jar 108 of FIG. 5 are substantially the same as those described in FIG. 1. In another embodiment, the coolant and diamond/holder controls 329 and diamond drive 360 are substantially the same as those in fig. 3.

As shown in FIG. 5, the diamond 136 is positioned on a diamond drive piece 360 and within a shaped thermal block 566 that acts as a holder. By placing the diamond 136 directly within the shaped thermal block 566, thermal efficiency for heat dissipation from the diamond 136 is increased. However, plasma 541 may be more easily affected since the entire shaped thermal block is moved by holder actuator 562 in step 524 with the diamond holder controls, which are shown in fig. 3 as part of coolant and diamond/holder controls 329. Accordingly, the main process controller 546 should take into account factors such as other parameters that suitably control the plasma and/or growth process. Alternatively, a convex thermal block 364 as shown in FIG. 3, an angled thermal block 466b in FIG. 4b, an angled/cylindrical top thermal block 466c in FIG. 4c, or other geometric configurations may be used in place of the concave thermal block 566 of FIG. 5.

Fig. 6 is a flow diagram illustrating a process 600 according to an embodiment of the invention that may use the sample holder assembly shown in fig. 1. The process 600 begins with step S670, where a suitable seed diamond or in-process diamond is positioned in a holder. In a sample holder assembly 120 such as that of FIG. 1, the diamond seed portion 138 is placed in the sleeve 134 and the operator tightens the screws 131 a-131 d. Other mechanical means may be used to maintain the sleeve and diamond in place, for example a spring loaded collet, hydraulic or other mechanical means may be used to apply force to the holder or sleeve.

The temperature of the diamond growth surface, which may be a diamond seed or a grown diamond, is determined as described with reference to step S672. For example, the pyrometer 142 in fig. 1 takes measurements of the growth surface, which is the upper surface of the growing diamond portion 140, and provides the measurements to the main process controller 146. The determination is made so that the thermal gradient across the diamond 136 growth surface can be determined by the main process controller or the temperature of the edge of the diamond growth surface can be input into the main process controller.

As with reference to S674 in fig. 6, a main process controller, such as the main process controller 146 of fig. 1, is used in controlling the temperature of the growth surface. The main process controller controls the temperature by maintaining a thermal gradient across the growth surface of less than 20 ℃. While controlling the growth surface temperature, it is determined whether the diamond should be repositioned in the holder, as shown in step S675 of fig. 6. If the main controller does not control the temperature of the diamond growth surface to be less than 20 ℃ across all temperature gradients across the growth surface by controlling the plasma, gas flow and coolant flow, then halting the growth process allows the diamond to be repositioned in the holder, as shown in step S678 of FIG. 6, to better dissipate heat from the diamond and/or to better position the diamond within the plasma. If the master controller is able to maintain all thermal gradients across the diamond growth surface less than 20 ℃, then diamond growth occurs on the growth surface as shown in step S676 of fig. 6.

As shown in fig. 6, the temperature of the diamond growth surface is measured, the temperature of the growth surface is controlled, and diamond is grown on the growth surface until it is determined that the diamond should be repositioned. Although the acts of measuring, controlling, growing, and determining are shown and described as steps, they are not necessarily sequential and may be performed concurrently with one another. For example, the step of growing diamond on the growth surface may be performed while measuring the temperature of the diamond growth surface and controlling the temperature of the growth surface.

Repositioning of the diamond may be accomplished manually or with robotic machinery, as described with reference to step S678. In addition, as shown in step S673 of fig. 6, it may be determined whether the diamond has reached a predetermined or required thickness. The determination may be based on actual measurements by mechanical or optical means. In another example, the determination may be based on the length of the processing time given that the growth rate of the process is known. If the diamond has reached the predetermined thickness, the growth process is complete as described with reference to step 680 of FIG. 6. If the diamond has not reached the predetermined thickness, the growth process is resumed, and the process continues with measuring the diamond growth surface temperature, controlling the growth surface temperature, and growing the diamond on the growth surface until it is determined that the diamond needs to be repositioned, as shown in figure 6.

Fig. 7 is a flow diagram illustrating a process 700 according to an embodiment of the invention that may use the sample holder assembly shown in fig. 3 and 5. The process 700 begins with step S770 in which a suitable seed diamond, which may be a grown diamond, a manufactured diamond, a natural diamond, or a combination thereof, is positioned in a holder. In the sample holder assembly 320 of fig. 3, such as that shown in fig. 3, the diamond seed portion 138 is placed in the sleeve 134 on the diamond drive piece 360. In another example of a sample holder assembly, as shown in FIG. 5, the diamond seed portion 138 is placed in a shaped thermal block 566 on the diamond actuator 360.

The temperature of the diamond growth surface, which is the diamond seed or the diamond portion newly grown on the diamond seed, is determined as with reference to step S772. For example, the pyrometer 142 of fig. 3 takes measurements of the growth surface, which is the upper surface of the growing diamond portion 140, and provides the measurements to the main process controller 346. In another example, the pyrometer 142 of fig. 5 takes measurements of the growth surface, which is the upper surface of the diamond seed portion 138, and provides the measurements to the main process controller 546. This determination is made so that the main process controller can determine the thermal gradient across the diamond growth surface or at least input the temperature at the edges and in the middle of the growth surface into the main process controller.

As with reference to S774 in fig. 7, a main process controller, such as main process controller 346 or 546, is used in controlling the temperature of the growth surface. The main process controller controls the temperature of the diamond growth surface such that all temperature gradients across the growth surface are less than 20 ℃ while controlling the growth surface temperature, determining whether the diamond needs to be repositioned in the holder, as shown in step S775 of fig. 7. If the main controller has not been able to maintain the temperature of the diamond growth surface such that all temperature gradients across the growth surface are less than 20 c by controlling the plasma, gas flow and coolant flow, then the diamond is repositioned while it is growing, as shown in fig. 7, using a "yes" approach from step S775 to steps S776 and S778. By repositioning the diamond in the holder, heat dissipation from the edges of the growth surface is improved. In addition, the growth surface can be positioned within the plasma optimum region, consistent with maintaining all thermal gradients across the diamond growth surface less than 20 ℃. If the master controller can maintain all thermal gradients across the diamond growth surface to be less than 20 deg.C, then growth of diamond on the growth surface proceeds without repositioning as indicated by the "NO" path from step S775 to step S776 of FIG. 7.

Measuring the temperature of the diamond growth surface, controlling the temperature of the growth surface, growing the diamond on the growth surface, and repositioning the diamond in the holder until it is determined that the diamond has reached a predetermined thickness. As with reference to step S773 of fig. 7, it is determined whether the diamond has reached a predetermined or desired thickness. The determination may be based on actual measurements by mechanical or optical means. For example, a tracking program records the depth or amount of distance the diamond must be repositioned during the growth process. In another example, given that the growth rate of the growth process is known, the determination may be based on the length of the processing time. If the diamond has reached the predetermined thickness, the growth process is complete as described with reference to step 780 of FIG. 7. If the diamond has not reached the predetermined thickness, the growth process continues with the determination of the temperature of the diamond growth surface, the control of the temperature of the growth surface, the growth of the diamond on the growth surface and the repositioning of the diamond in the holder until it is determined that the diamond needs to be repositioned, as shown by the "no" path from S773 in S774 of fig. 7.

When performing processes 600 and 700, diamond growth may generally continue as long as the "step growth" condition can be maintained. In general, a "step growth" condition refers to growth of the growing diamond on the growth surface of the diamond 136 such that the diamond 136 is smooth in nature with no isolated "outages" or twins. The "step growth" condition can be confirmed visually. Alternatively, a laser may be used to scan the growth surface of the diamond 136. A change in laser reflectivity indicates the formation of "outages" or twins. The laser reflectivity can be programmed into the main process controller as a condition to stop the growth process. For example, in addition to determining whether the diamond is at a predetermined thickness, it may also be determined whether laser reflectivity is being received.

In general, methods according to exemplary embodiments of the invention are used to produce large, colorless, high quality diamonds with increased {100} growth rates, where growth occurs along three dimensions. In one embodiment of the invention, the gas mixture is treated with about 1% to about 50% O₂Per unit CH₄Oxygen is used in the ratio of (1). In another embodiment of the invention, the gas mixture is treated with about 5% to about 25% O₂Per unit CH₄Oxygen is used in the ratio of (1). Without wishing to be bound by theory, it is believed that the presence of oxygen in the gas mixture in the deposition chamber helps to reduce the introduction of impurities into the diamond, thus rendering the diamond substantially colorless. During the growth process, the methane concentration is in the range of about 6% to 12%. Hydrocarbon concentrations greater than about 15% can cause excessive deposition of graphite within the MPCVD chamber.

The processing temperature may be selected from the range of about 700 c to 1500 c depending on the particular type of single crystal diamond desired or if oxygen is used. Polycrystalline diamond can be produced at higher temperatures and diamond-like carbon can be produced at lower temperatures. In one embodiment of the present invention, the processing temperature may be selected from the range of about 700 ℃ to 1100 ℃. In another embodiment of the present invention, the processing temperature may be selected from the range of about 900 ℃ to 1100 ℃. During the growth process, a pressure of about 100 torr to 400 torr is used. In one embodiment, a pressure of about 100 to 300 torr is used. In another embodiment, a pressure of about 160 to 220 torr is used.

In one embodiment of the invention, the growth rate of the single crystal diamond is greater than about 10 microns/hour. In another embodiment, the growth rate of the single crystal diamond is greater than about 50 microns/hour. In another embodiment, the growth rate of the single crystal diamond is greater than about 100 microns/hour.

In one embodiment of the invention, the single crystal diamond is grown to be more than 1.2 cm thick. In another embodiment of the invention, the single crystal diamond is grown to a weight of more than 5 grams. In another embodiment of the invention, the single crystal diamond is grown to more than 10 carats. In another embodiment of the invention, the single crystal diamond is grown to over 300 carats.

In one embodiment, diamond is grown on up to 6 {100} planes of an SC-CVD diamond seed. In another embodiment, the diamond grown on up to 6 {100} planes of the SC-CVD diamond seed is greater than about 300 carats. In another embodiment, the growth of diamond may be substantially two-dimensional to produce laterally large crystals (e.g., at least about 1 square inch plates) by polishing one of the longer surfaces and then growing diamond crystals in a second orthogonal direction on that surface. In another embodiment, the growth of diamond may be three-dimensional. In another embodiment, the growth of the diamond is substantially cubic. In another embodiment, the substantially cubic diamond grown in three dimensions is at least 1 inch in each dimension.

The gas mixture may also include N₂. When using N₂At about 0.2% to 3% N₂Per unit CH₄To the gas mixture. At this concentration, N is added₂Addition to the gas mixture results in better utilization of the growth sites, increases the growth rate and promotes {100} plane growth.

FIG. 8 is a HPHT IIa diamond, for example, with a diamond comprising about 5% to about 25% O, in accordance with a method of the present invention₂Per unit CH₄And the presence of N₂UV-VIS spectra of SC-CVD diamond produced with gases as a component of the deposition chamber atmosphere. With N₂The gas produced SC-CVD diamond was light brown in appearance, exhibiting a broad band of about 270 nm. This is related to the presence of non-diamond carbon, nitrogen and vacancies in diamond. With dark brown appearance₂Gas produced SC-CVD diamond showed an increase in absorption below 500nm and a broad feature centered at 520 nm. This spectrum is not seen in natural diamond or HPHT grown synthetic diamond. Treatment with HPHT, such as annealing, can remove brown and broadband features. With the process of the invention, for example, with a catalyst comprising about 5% to about 25% O₂Per unit CH₄The deposition chamber atmosphere of (a) produced diamond that showed no broad band at 270nm or at 520nm, comparable to synthetic HPHT type IIa diamonds. Without wishing to be bound by theory, applicants believe that the addition of oxygen reduces the hydrogen impurity levels and the amount of non-diamond carbon.

FIG. 9 shows on the left a process according to the invention, for example, a process comprising about 5% to about 25% O₂Per unit CH₄By the deposition chamber atmosphere of (a), and the right side shows the use of N in the deposition chamber₂Instead of O₂Brown SC-CVD diamond produced. Both single crystal diamonds were about 5 x 1mm in size.

FIG. 10 shows the SC-CVD diamond mass deposited on 6 {100} planes of an HPHT Ib substrate, such as a 4X 1.5mm crystal as shown below. This is an attempt to further increase the diamond crystal size, where diamond quality CVD diamond was grown on 6 {100} planes of the substrate in sequence according to the method of the present invention. In this way, three-dimensional growth of colorless single crystal diamond can produce about 300 gram weights and about 1 inch per dimension of diamond.

FIG. 11 is a graph of a process according to the present invention, e.g., with a catalyst comprising about 5% to about 25% O₂Per unit CH₄And colorless SC-CVD diamond produced by the atmosphere of the deposition chamber of₂IR absorption spectrum (2500 cm) of brown SC-CVD diamond produced with gas as a component of the deposition chamber atmosphere^-1～8000cm^-1). With N₂The spectra of gas-produced brown SC-CVD diamonds were 2931, 3124, 6427, 6857, 7234 and 7358cm^-1Has a peak at it. According to the process of the invention at O₂These peaks are absent in the spectrum of the colorless diamond produced in the presence of the gas. Thus, the data indicate that the process according to the invention is carried out at O₂Colorless diamonds produced in the presence of gas are free of near-IR or intermediate-IR impurities due to hydrogen. This further demonstrates that the method of the invention produces very pure large single crystal diamonds at high growth rates.

Other aspects of the present invention will be understood in more detail from the following examples.

Example 1

The diamond growth process was carried out in the above-described MPCVD chamber in fig. 1. First, a commercial 3.5X 1.6mm was used³High Pressure High Temperature (HPHT) synthesis type Ib diamond seeds were positioned in the deposition chamber. The diamond seed had a polished smooth surface ultrasonically cleaned with acetone. The deposition surface is within two degrees of the 100 surface of the diamond seed.

The deposition chamber was then evacuated to 10^-3Base pressure of torr. The infrared pyrometer 142 was focused through a quartz window at an angle of incidence of 65 degrees on the diamond growth surface with a minimum of 2mm²Diameter spot size. Use 15% O₂/CH₄And 12% CH₄/H₂The gas concentration of (A) is under 160 torr of pressure to carry out diamondAnd (5) growing. The processing temperature is 1020 ℃, and the gas flow rate is 500sccm H₂、60sccm CH₄And 1.8sccm O₂. The deposition was allowed to continue for 12 hours.

The resulting diamond was 4.2X 2.3mm³Not polished, meaning about 0.7mm grown on the seed, at a growth rate of 58 microns/hour. Morphological representation of growth<100>Lateral growth rate ratio<111>The angular growth rate is fast. The growth parameter alpha is estimated to be 2.5-3.0.

The deposited diamond was characterized using optical microscopy, X-ray diffraction (XRD), raman spectroscopy, and Photoluminescence (PL) spectroscopy. Optical microscopy and X-ray diffraction studies of the resulting diamond confirmed that it was a single crystal. The UV-visible/near-infrared transmission spectrum of MPCVD grown diamond isolated from a seed diamond is different from that at N₂MPCVD diamond grown in the presence of gas is comparable to pure (type IIa) diamond.

While varying the processing temperature, a number of MPCVD diamonds were produced according to the guidelines of example 1. These experiments show that the processing temperatures used to produce various types of diamond during growth according to embodiments of the present invention vary over a range.

The color of the diamond formed by the methods discussed above may be changed by annealing. For example, the yellow color of a brown diamond may be annealed to a green diamond. Additional information regarding the diamonds produced in the above examples is described in the Proceedings of the National Academy of the sciences, Oct.1, 2002, Vol 99, No.20, pages 12523-12525 of the inventor entitled "Very High Growth Rate Chemical Vapor Deposition of Single-Crystal Diamond", incorporated herein by reference in its entirety. The diamond produced by the above method and apparatus is sufficiently large, defect-free, translucent to be useful, for example, as a window in high power laser or synchrotron applications, as an anvil for high voltage equipment, as a cutting instrument, as a wire die, as a component of an electronic (heat sink, substrate for electronic devices), or as a gemstone.

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.

Reference documents:

[1] yan, h.k.mao, w.li, 1.Qian, y.zhao and r.j.hemley, ultra hard diamond single-crystals from chemical vapor deposition, Physica Status solid, (a) 201: R24-R27(2004).

[2] Yan, y, k, vohra, h, k, mao and r, j, hemley, Very highgrowth rate chemical vapor deposition of single-crystal diamond, Proceedings of the National Academy of Science, 99 (20): r25-27(2002).

[3] Isberg, j. Hammersberg, e.johansson, t.wikstrom, d.j.twitchen, a.j.whitehead, s.e.coe and g.a.scarsbrook, High carrier quality in single-crystal-plant-deposited diamond, Science, 297: 1670-1672(2002).

[4] Chayahara, Y.Mokuno, Y.Horino, Y.Takasu, H.Kato, H.Yoshikawa and N.Fujiori, The effect of nitrogen addition degradation high-rate horizontal microwave plasma CVD, Diamond & Related Materials, 13, 1954-1958(2004).

[5] Williams and R.B. Jackman, High growth rate MWPECVD of single crystal digital, Diamond & Related materials, 13, 557-560(2004).

[6] Charles, 1.e.butler, b.n.feygelson, m.f.newton, d.i.carroll, j.w.steeds, h.darwish, h.k.mao, c.s.yan and r.j.hemley, charaterization of nitrogen-gated chemical vapor disposed single-crystalline probe and after high pressure, high temperature connecting, physical Status identification (a): 1-13(2004).

[7] Martineau, s.c.lawson, a.j.taylor, s.j.quinn, d.j.f.evans and m.j.crowder, Identification of synthetic diamond growth using Chemical Vapor Deposition (CVD), Gems & Gemology, vol.60: 2-25(2004).

[8]W.Wan，I. Moses，R.C.Linares，J.E.Shigley，M.Hall，and J.E.Bulter Gem-quality synthetic diamonds grown by a chemical vapordeposition(CVD)method，Gems & Gemology，39：268-283(2003).

[9] Kitawaki, a.abduriyim and m.okano (2005) Identification of cvd synthetic Diamond, geographic Association of All Japan, Research Laboratory Report (March 15, 2005).

[10] S.wo ddring and b.deljanin, Guide to laboratory creativity Growth and identification of HPHT & cvd iamonds. EGL USA book (2004).

[11] S.J.Harris and A.M.Weiner, Effects of oxyden on diamond growth, appl.Phys.Lett.Vol.55 No.21, 2179-.

[12] Y.liou, a.instektor, r.weimer, d.knight and r.messier, j.mater.res.5, 2305-.

[13] Sakaguchi, M.Nishitani-Gamo, K.P.Loh, S.Hishita, H.Handda and T.Ando, supression of surface cracks on (111) homology injection by oxygen addition, applied.Phys.Lett., 73, 2675-one 2677(1998).

[14] Tallaire, J.Achard, F.Silva, R.S.Sussmann, A.Gicquel and E.Rzepka, Oxygen plasma pre-streams for high quality homoepitalCVD diamond deposition, Phys.Stat.Sol., (a)2001, No.11, 2419-.

Claims (34)

1. A method of producing diamond, the method comprising:

i) controlling the temperature of the diamond growth surface such that all temperature gradients across the diamond growth surface are less than about 20 ℃, and

ii) growing single crystal diamond on the diamond growth surface by microwave plasma chemical vapor deposition at a growth temperature in a deposition chamber having an atmosphere, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄。

2. The method of claim 1, wherein the atmosphere has a pressure of about 100 to 300 torr.

3. The method of claim 2, wherein the pressure is about 160 to about 220 torr.

4. The method of claim 1, wherein the growth temperature is from about 700 ℃ to about 1100 ℃.

5. The method of claim 1, wherein the diamond growth is more than 1.2 centimeters thick.

6. The method of claim 1, wherein the diamond growth is in excess of 5 carats.

7. The method of claim 1, wherein the diamond growth is in excess of 10 carats.

8. The method of claim 1, wherein the diamond growth rate is greater than about 10 microns/hour.

9. The method of claim 8, wherein the diamond growth rate is greater than about 50 microns/hour.

10. The method of claim 9, wherein the diamond growth rate is greater than about 100 microns/hour.

11. The method of claim 1, wherein the atmosphere further comprises about 0.2% to about 3% nitrogen per unit CH₄。

12. The method of claim 1, further comprising the step of positioning a diamond seed in the holder.

13. The method of claim 12, further comprising the step of repositioning the diamond in the holder after the step of growing the single crystal diamond.

14. The method of claim 12, further comprising the step of repositioning the diamond in the holder while growing the single crystal diamond.

15. The method of claim 12, wherein the diamond seed is one of: natural colorless Ia diamond, natural colorless IIa diamond, HPHT synthetic yellow Ib diamond, and SC-CVD diamond.

16. The method of claim 15, wherein the diamond seed is SC-CVD diamond.

17. The method of claim 16, wherein the SC-CVD diamond seed has a {100} plane.

18. The method of claim 1, wherein the diamond is grown in three dimensions.

19. The method of claim 17, wherein the diamond seed has 6 {100} planes.

20. The method of claim 19, wherein the diamond growth is in excess of 300 carats.

21. The method of claim 1, wherein the diamond growth is substantially cubic.

22. The method of claim 1, wherein each dimension of the substantially cubic diamond is at least 1 inch.

23. The method of claim 1, wherein the produced diamond is colorless.

24. The method of claim 1, wherein the produced diamond has a UV-VIS spectrum substantially similar to an artificial HPHT type IIa diamond.

25. A diamond produced by the method of claim 1.

26. A method of producing diamond, the method comprising:

i) controlling the temperature of the diamond growth surface, and

ii) growing single crystal diamond on the diamond growth surface using microwave plasma chemical vapor deposition in a deposition chamber having an atmosphere comprising about 8% to about 20% CH at a growth temperature of about 700 ℃ to about 1100 ℃₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄。

27. A method of producing diamond, the method comprising:

i) controlling the temperature of the diamond growth surface, and

ii) growing single crystal diamond on the diamond growth surface with microwave plasma chemical vapor deposition in a deposition chamber having an atmosphere with a pressure of about 100 to 300 torr, at a growth temperature, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄。

28. A method of producing diamond, the method comprising:

i) controlling the temperature of the diamond growth surface, and

ii) growing single crystal diamond on the diamond growth surface by microwave plasma chemical vapor deposition in a deposition chamber having an atmosphere at a growth temperature, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄Wherein the growth rate is greater than about 10 microns/hour.

29. A method of producing diamond, the method comprising:

i) controlling the temperature of the diamond growth surface, and

ii) growing single crystal diamond on the diamond growth surface by microwave plasma chemical vapor deposition in a deposition chamber having an atmosphere at a growth temperature, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄Wherein the diamond growth is in excess of 5 carats.

30. A method of producing diamond, the method comprising:

i) controlling the temperature of the diamond growth surface, and

ii) growing single crystal diamond on the diamond growth surface by microwave plasma chemical vapor deposition in a deposition chamber having an atmosphere at a growth temperature, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄Wherein the produced diamond is substantially colorless and has a UV-VIS spectrum substantially similar to that of an artificial HPHT type IIa diamond.

31. A method of producing diamond, the method comprising:

i) controlling the temperature of the diamond growth surface such that the temperature of the grown diamond crystals is in the range of 900 ℃ to 1400 ℃ and placing the diamond in a heat sink holder made of a material having a high melting point and a high thermal conductivity to minimize the temperature gradient across the diamond growth surface; and

ii) growing single crystal diamond on the diamond growth surface by microwave plasma chemical vapor deposition in a deposition chamber having an atmosphere, wherein the atmosphere comprises about 8% to about 20% CH₄Per unit H₂And about 5% to about 25% O₂Per unit CH₄。

32. The method of claim 31, wherein all temperature gradients across the diamond growth surface are less than about 20 ℃.

33. The method of claim 31, wherein the diamond growth is in excess of 5 carats.

34. The method of claim 31, wherein the diamond growth rate is greater than about 10 microns/hour.