JP3339137B2 - Synthetic diamond single crystal and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical component, a spectral crystal, a monochromator, a window material for a laser, a window material for radiation or radiation, an anvil, a semiconductor substrate, and a colorless transparent material having little distortion and the like. The present invention relates to a synthetic diamond having high purity and good crystallinity and a method for producing the same.

[0002]

2. Description of the Related Art Diamond has high hardness, high strength, excellent thermal conductivity and corrosion resistance, and good light transmission. From this, the diamond crystal can be used as a heat sink, wire drawing die,
It is applied to a wide range of applications, such as precision machining tools, optical components, laser windows, and anvils for generating ultra-high pressure. Most of naturally occurring diamonds are called type Ia and contain about 1000 ppm of nitrogen. Since nitrogen in the natural diamond is distributed in the crystal in an aggregated form, crystal defects and internal strain are large, and light is absorbed by the nitrogen in an infrared region. Also, there are large variations due to the rough.
Therefore, applicable applications are limited to heat sinks and tools. High-purity natural diamonds having a nitrogen impurity of several ppm or less are called type IIa, and such diamonds are rare, about 2% of the total amount of natural production. Natural type IIa diamond has few impurities,
Since it is colorless and transparent and has excellent light transmission characteristics, it is used for decorative applications, optical components, laser window materials, and the like. However, reflecting the complex growth process inside the earth, many defects and strains remain inside the crystal.
With respect to distortion, it is more than a synthetic diamond containing nitrogen. In addition, natural type IIa has a low yield, is extremely expensive, and has a considerable problem in obtaining it.

[0003] Ordinary diamond artificially synthesized under ultra-high pressure and high temperature is called type Ib and contains several hundred ppm of nitrogen. Since this nitrogen is contained in the diamond crystal as an isolated substitutional impurity, the crystal has a yellow color and is of low value for decoration. Further, nitrogen absorbs light in the infrared region and the ultraviolet region and cannot be used for optical components and window materials. The concentration of nitrogen is extremely different depending on the growth sector, and there is a large unevenness in the distribution of nitrogen inside the crystal. Therefore, there are many distortions in the crystal. On the other hand, it is known that by adding a nitrogen getter such as Al to a solvent metal during diamond synthesis, nitrogen in the synthesized diamond can be removed to about several ppm to obtain a synthetic IIa type diamond. However, when a nitrogen getter is added to the solvent metal, a large amount of inclusions are usually easily incorporated into the crystal, and the production yield of high-quality crystals is greatly reduced. For this reason, the production cost of the conventional synthetic type IIa diamond was higher than that of natural type IIa diamond. Also,
The removal of nitrogen from synthetic diamond was also limited to about 1 ppm, and the evaluation for decoration was about H to J on the GIA scale (JP-A-52-88289). Further, there was absorption by nitrogen in the ultraviolet region.

It is known that an element such as Ti or Zr is used as a nitrogen getter. If these are used as nitrogen getters, nitrogen can be removed efficiently, but Ti
A large amount of carbides such as C and ZrC were generated in the solvent, and these were incorporated into the diamond crystal, and almost no high-quality diamond was obtained. In contrast, the present inventors,
A substance that suppresses the formation of carbides of the IVa group element, so that at least one selected from the group IVa and Va group elements having high nitrogen removal efficiency is used as a nitrogen getter, and at the same time, inclusions are not taken into the crystal. By adding a substance that diffuses carbide or a substance that improves the activity of carbon in the solvent metal to the solvent metal, the nitrogen content is reduced to 0.1.
We succeeded in producing type IIa synthetic diamond without inclusions of less than ppm. However, the crystal still contained several ppm of boron, so that light was absorbed by boron in the infrared region, and there were some distortions and defects in the crystal.

[0005]

As described above, natural diamond has many defects and large distortion inside the crystal. Although natural IIa type diamond has few impurities,
Crystallinity such as defects and distortion is not good. For this reason, cracks are likely to occur during processing, and when used in fields that require the strength of diamond, such as an anvil for generating ultra-high pressure, a compression cell for FT-IR, and a window material for laser, it may be quickly broken in some cases. There was a problem that it would. Further, monochromators, semiconductor substrates, and the like require high crystallinity, and thus cannot be applied to this field. On the other hand, type IIa diamonds made by artificial synthesis are far superior to natural ones in terms of crystallinity, but they are not sufficient, have low processing yields, and have low mechanical strength compared to the original characteristics of diamonds. In addition, it cannot be applied to applications requiring crystallinity such as a monochromator and a semiconductor substrate.
In addition, conventional synthetic IIa type diamond crystals have several ppm
Therefore, there is a problem in the application as an optical component due to the absorption of light by the boron in the infrared region.
There were also some distortions and defects in the crystals. That is, in the synthesis of diamond by the temperature difference method, diamond powder is used as a carbon source, but commercially available synthetic diamond powder contains 10 to 1000 ppm of boron,
Natural diamond powder also contains tens to hundreds of ppm of boron and has large variations. When diamond is synthesized using such a carbon source, several ppm to more than ten p
It contains pm of boron and the crystals exhibit a blue color. For this reason, there is absorption by boron in the infrared region and the ultraviolet to visible region, which is not preferable as an optical component. Also, the concentration of boron is extremely different depending on the crystal growth sector.
There is a large unevenness in the distribution of boron inside the crystal. This is considered to be one of the reasons for poor crystallinity. By removing this boron almost completely, a crystal that is colorless and transparent and has few distortions and defects can be obtained. There was a problem. An object of the present invention is to provide a synthetic diamond single crystal that solves such a problem and a method for producing the same.

[0006]

The present invention for solving the above-mentioned problems is characterized in that (1) the crystal contains a nitrogen atom and a boron atom, and the number of the nitrogen atoms and the number of the boron atoms are substantially the same;
And the difference between the number of nitrogen atoms and the number of boron atoms is 1 × 1
0 ¹⁷ atoms / cm ³ to provide a synthetic diamond single crystal, characterized in that less, further the present invention contains a nitrogen atom and boron atom in (2) in the crystal, nitride number atom and the number of the boron atoms Are substantially the same, and the number of nitrogen atoms is
Provided is a synthetic diamond single crystal , wherein the difference from the number of boron atoms is 1 × 10 ¹⁶ atoms / cm ³ or less. The present invention also relates to a method for producing a synthetic diamond single crystal according to the above (1) or (2), wherein the present invention relates to a method for synthesizing a diamond single crystal by a temperature difference method under ultra-high pressure and high temperature. Adjust the amount of nitrogen getter added to the solvent metal , or add boron to the carbon source or the solvent metal so that the amount of nitrogen and the amount of boron to be taken in become approximately the same in terms of the number of atoms. It is intended to provide a production method characterized by adjusting the amount.

[0007]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that by leaving nitrogen to some extent in diamond, it is possible to compensate for bluening and crystallinity deterioration due to boron impurities derived from the raw material with nitrogen. Was found. As a result, a colorless and transparent diamond which contains boron and nitrogen by controlling the nitrogen removal amount but does not absorb boron or nitrogen optically, and a method of the present invention capable of producing the same has been achieved. Further, according to the present invention, it has been found that the strain in the crystal due to boron is alleviated and the crystallinity is also improved. Furthermore, when a nitrogen getter such as Al is used, it is difficult to remove nitrogen in diamond almost completely, but in this case, boron having the same amount as the amount of nitrogen remaining without being removed is crystallized. When added inside,
It was found that a colorless and transparent glass containing boron and nitrogen but having no optical absorption of boron or nitrogen was obtained. In addition, the inventors have found that the strain in the crystal due to nitrogen is alleviated and the crystallinity is also improved.

[0008] This point will be described in more detail. Fe-Al
When synthesized with a system solvent, the reaction of Al (Al + N = AlN) is weak, and the effect of removing nitrogen from the crystal is low. On the other hand, when Ti was added to the solvent, a high-quality high-purity diamond having a nitrogen content of 0.1 ppm or less and almost no inclusions could be synthesized. However, in the diamond synthesized with the Ti getter, the absorption of boron appeared in the infrared and near infrared which did not appear in the Al getter (content: about 0.2 ppm). From this, p
Boron acting as a type semiconductor (acceptor) and n
It was presumed that absorption due to nitrogen and boron would disappear because nitrogen acting as a type semiconductor (donor) forms an AD pair during crystal synthesis and is electrically neutralized. In other words, when synthesized with an Al getter, the effect of removing nitrogen is low, so that boron is sufficiently neutralized electrically with boron incorporated in the crystal and absorption is reduced. However, nitrogen is almost completely removed by using a nitrogen getter. It was thought that only absorption of the incorporated boron appeared. In order to confirm this effect, synthesis was attempted by actively adding boron under synthesis conditions in which a relatively large amount of nitrogen remained. As a result, the absorption of Ib-type nitrogen in the ultraviolet (at 4.6 eV) was significantly reduced in the (111) sector having a high boron content.

(Experiments and Results) Synthesis of Diamond by Addition of Boron 0.83 atomic% of Al was added to a Fe-based metal solvent, and boron was further added at 15, 30, and 50 ppm, respectively. A single crystal of diamond was synthesized by epitaxially growing a seed crystal by a temperature difference method. The synthesis conditions are 5.5
GPa was 1350 ° C. The raw materials used for the synthesis were selected to be high-purity containing no boron. Of these, the crystal synthesized by adding 30 ppm of boron became the most colorless and transparent, and was polished so that the (110) plane was the observation plane. Observation of crystal cross section FIG. 3 shows a schematic diagram of the crystal cross section. FIG. 4 shows the content of boron and the estimated content of nitrogen in each sector. The boron content was measured by preparing in advance standard data whose content was known by an ion implantation method and comparing the two by SIMS. The nitrogen content was estimated from the graph of FIG. 2 showing the relationship between the amount of Ti or Al getter added and the nitrogen content in the crystal. In FIG. 2, the horizontal axis represents the amount of the getter added (atomic%), and the vertical axis represents the nitrogen content in the crystal (pp
m), ○ indicates Ti, Δ indicates Al. Also, (11
1) UV-visible absorption spectra in the sector and the (100) sector were measured. FIG. 4 shows the results. In the (111) sector containing boron and nitrogen in almost equimolar amounts, the absorption of type Ib nitrogen (at 4.6 eV) is remarkably small, and the absorption spectrum is type IIa. In the (100) type sector, which contains little boron, absorption of type Ib nitrogen appears. In addition, both exhibited IIa type in the absorption in the infrared region. Consideration As described above, in the sector containing boron and nitrogen in substantially equivalent amounts, the absorption of the isolated and dispersed solid solution type Ib-type nitrogen decreases, so it is presumed that an AD pair is generated.

In the present invention, it is preferable that the numbers of atoms of nitrogen and boron contained in the diamond crystal are substantially the same. If the difference in the number of atoms between them is 10 ¹⁷ atoms / cm ³ or less, the diamond is much less strained than natural diamond or conventional synthetic Ib type diamond. That is, the first crystal is replaced with a synthetic diamond crystal (00
4) surface parallel arrangement to two half-width of X-ray diffraction rocking curve as measured with crystal method is 10 seconds or less, or half width of the peak of the Raman spectrum of 1332 cm ^-1 is either 2.3 cm ^-1 or more Unprecedented diamond with good crystallinity can be obtained. For example, natural IIa type diamond,
Seven to ten natural Ia-type diamonds and seven to ten Ib-type synthetic diamonds by a conventional method were prepared, and the rocking curve half-widths measured in the same manner as described above were 300 to 300, respectively.
3000 seconds, 200-600 seconds, 15-30 seconds,
The full width at half maximum of the Raman spectroscopy spectrum 1332 cm ^-1 peak is 2.15 to 3.5 cm ^-1 and 2.8 to 3.3 c, respectively.
m ⁻¹ , 2.4 to 2.6 cm ⁻¹ .

It is more preferable that the difference between the number of nitrogen atoms and the number of boron atoms contained in the diamond crystal is 10 ¹⁶ / cm ³ or less, and the crystallinity is further improved. in this case,
Synthetic diamond crystal (004) plane parallel to first crystal
The half-width of the X-ray rocking curve measured by the two-crystal method is 7 seconds or less, and the Raman spectrum 1332
The diamond has extremely high crystallinity with a half width at a peak of cm ^-1 of 2 cm ^-1 or less, and is sufficiently applicable to applications requiring high crystallinity such as a monochromator and a semiconductor substrate. Moreover, in this case, there is no absorption of light due to impurities such as nitrogen and boron other than the absorption of diamond itself from near-ultraviolet region to far-infrared region.
Since it is a colorless and highly transparent diamond crystal, it can also be used for decorative purposes. The color grade of the diamond crystal in this case is GIA scale, G color or higher, and is positioned at the highest grade as a diamond for decoration. Incidentally, the conventionally known synthetic IIa type diamond was of an intermediate level of about H to J in the same evaluation (Japanese Patent Application Laid-Open No. 52-88289). It will be clearly understood that

In order to synthesize diamond as described above, in a method of synthesizing a single crystal of diamond by a temperature difference method, the amount of nitrogen and the amount of boron incorporated into the crystal during the synthesis are almost the same in terms of the number of atoms. The amount of the nitrogen getter added to the solvent may be adjusted, or the amount of boron added to the carbon source or the solvent may be adjusted. Specifically, for example, it is as follows. (1) the amount of nitrogen getter added or reduced so that the same amount of nitrogen as the amount of boron contained as an impurity in the carbon source or the solvent raw material is taken into the diamond crystal remains in the crystal.
(2) Add a nitrogen getter to the extent that it does not hinder the crystal growth of diamond, and add boron or boron in a carbon source or solvent in advance so that the same amount of boron as nitrogen that could not be removed at this time is incorporated into diamond. The method includes adding a compound containing, for example, the type of the carbon source and the solvent to be used (boron content), the nitrogen removal efficiency of the nitrogen getter to be used, the degree of inhibiting crystal growth, and the like. What is necessary is just to select the method suitable for each case.

In the present invention, as the nitrogen getter to be added to the solvent, Al or Ti, Zr, Hf, V, N
Group IVa elements such as b and Ta, and Va group elements can be used. When a group IVa element or a group Va element is used as a nitrogen getter, it is preferable to add a substance that suppresses the formation of carbides of these elements. Such materials include, for example, Al, Ni, Cu, Zn, Ga, Ag, Cd, In, S
It is effective to add an element selected from n, Au, Tl and Pb to the solvent metal in an amount of 0.1 to 20% by weight. The experiment that led to such knowledge is as follows.

(A) Experiment Ti and Cu are added to a metal solvent, and pressure is determined by a temperature difference method.
The temperature was maintained at 5 GPa and a temperature of 1300 to 1400 ° C. for several tens of hours to grow diamond crystals of 1 to 2 carats. The entrapment of the solvent (metal inclusion) contained in the obtained crystals and the content of other inclusions were observed with a microscope.
Further, polishing was performed to a thickness of about 1 mm to measure an ultraviolet absorption spectrum, and the nitrogen amount was estimated based on an absorption of 4.6 eV. (b) Results and Discussion The addition of Ti to the metal solvent alone resulted in a large amount of inclusions, a large amount of impurities of more than 10 μm in addition to the involvement of the metal solvent, and almost no high-quality diamond crystals were obtained. Observing the cross section of the metal solvent after synthesis, several μm to several tens μm
Many foreign substances were observed, and as a result of analysis by EPMA, the foreign substances were found to be TiC. It is considered that the minute impurities in the diamond crystal were such that TiC was incorporated into the diamond crystal. Further, it is considered that the reason why the entrainment of the metal solvent is large is that the generation of a large amount of TiC in the metal solvent impeded the supply of carbon. When Ti is added and Cu is further added, the TiC observed in the solvent is reduced to 1 μm or less, and the amount is significantly reduced.
Inclusions in the resulting diamond crystals were also reduced. Cu
It seems that TiC was decomposed by the addition, or the production of TiC was suppressed. Table 1 shows the results of typical synthetic experiments. Nitrogen is almost completely removed when the amount of Ti added is 1.5% or more, and the situation does not change even when 1 to 3% of Cu is added. FIG. 5 shows an ultraviolet absorption spectrum of a diamond crystal synthesized by changing the addition amounts of Ti and Cu. When the Ti addition amount is 1.5%, absorption by nitrogen is hardly observed. Further, by adding Cu of the same level as that of Ti, the entrainment of the solvent (metal) and the amount of the minute impurities mixed are greatly reduced, and a high-quality diamond crystal can be stably obtained. FIG. 6 shows the criteria (++, +,-) for metal inclusion evaluation in Table 1.

[0015]

[Table 1]

In the production method of the present invention, examples of the solvent metal include metals such as Fe, Co, Ni, Mn, and Cr and alloys composed of these metals. Examples of the carbon source of the present invention include synthetic or natural diamond powder or graphite powder or a molded product. Seed crystals include small crystals of synthetic or natural diamond. In the present invention, at the time of diamond synthesis, Al, Ni, Cu, Zn, Ga, Ag, Cd, and the like are used to stabilize the initial crystal growth state between the seed surface and the solvent.
It is effective to arrange a buffer material made of an element selected from In, Sn, Au, Tl and Pb, for example, a buffer material such as an Al plate or a Cu plate. The thickness of the cushioning material is 0.0
It may be about 1 to 0.5 mm. As a result, crystal defects and distortion in the crystal due to unstable growth at the initial stage of crystal growth can be reduced. By adopting such means,
Distortion due to inclusion inclusions and crystal defects and distortion in the crystal due to unstable growth in the initial stage of crystal growth can be reduced.

Further, in the present invention, after the diamond is synthesized under ultra-high pressure and high temperature conditions generally used in the technical field of diamond synthesis by the temperature difference method, the temperature and pressure of the sample portion are reduced to normal temperature and normal pressure and depressurized. When the internal temperature is 30
0-1000 ° C., preferably 400-800 ° C.
It is more effective to release the pressure at a temperature of 500 ° C., more preferably 500 to 600 ° C., and it is possible to reduce the residual strain due to stress in the crystal.

[0018]

[Example 1]

FIG. 1 shows the configuration of a sample chamber used for diamond synthesis in the embodiment of the present invention. Here, a synthetic diamond powder having a B (boron) content of 11 ppm was used as the carbon source (1). As the solvent metal (2), Fe and Co having a B content of 2 ppm were used, and the solvent metal composition was Fe / Co = 60/40 (weight ratio).
To this solvent metal, 0.8% by weight of Ti was added as a nitrogen getter, and 1% by weight of Cu was simultaneously added. Seed crystal (3)
Used a diamond crystal having a size of 500 μm. Then, it was set in a heating graphite heater (5) so that a temperature difference of about 30 ° C. was obtained between the carbon source (1) and the seed crystal (3). Using an ultra-high pressure generator, the diamond is grown on the seed crystal while maintaining the pressure at 5.5 GPa and the temperature of 1300 ° C. for 70 hours, first lowering the temperature to room temperature, and then reducing the pressure to obtain a synthesized diamond. Was taken out. As a result, a 0.7-0.9 carat type IIa diamond crystal was obtained. As a result of quantitative analysis of nitrogen and boron in diamond by SIMS, 1.5 × 10 ¹⁷ atoms / c
m ³ and 1.2 × 10 ¹⁷ atoms / cm ³ . Observation of a polarized light transmission image of the obtained diamond with a polarization transmission microscope and evaluation of distortion revealed that distortion in the crystal was considerably small. When the half width of the rocking curve of the X-ray diffraction by the two crystal method in which the first crystal was arranged in parallel with the synthetic diamond crystal (004) plane was 7.0 seconds. Further, to measure the Raman spectrum in a double monochromator Raman spectroscopic device, was determined the half width of 1332 cm ^-1, it was 2.2 cm ^-1.

Example 2 Diamond was synthesized in the same manner as in Example 1 except that the amount of Ti was 1.5% by weight and the amount of Cu was 1.5% by weight. The resulting diamond is a slightly bluish crystal, SIMS
Analysis revealed that the nitrogen content was 1.0 × 10 ¹⁶ ppm atoms / c.
m ^-1 and boron were 1.2 × 10 ¹⁷ atoms / cm ^-1 .
When the infrared absorption spectrum was measured, absorption by boron was observed at around 2800 cm ^-1 . Observation of a polarized light transmission image of the obtained diamond with a polarizing microscope and evaluation of distortion revealed that distortion in the crystal was small. In addition, the first crystal is a synthetic diamond crystal (004) plane parallel.
It was 8.3 seconds when the half width of the rocking curve of the X-ray diffraction by the two-crystal method was measured. Also,
The Raman spectrum was measured with a double monochromator Raman spectroscopic device, was determined the half width of 1332 cm ^-1, it was 2.5 cm ^-1.

Example 3 0.00.4% by weight (based on carbon source) of boron was added to a carbon source, 1.5% by weight of Al was added as a nitrogen getter, and Cu was not added. Others were the same as in Example 1 to synthesize diamond. As a result, a 0.7-0.9 carat type IIa diamond crystal was obtained. SIMS
As a result of quantitative analysis of nitrogen and boron in diamond, 1.8 × 10 ¹⁷ atoms / cm ³ and 1.5 × 1
It was 0 ¹⁷ atoms / cm ³ . Observation of a polarized light transmission image of the obtained diamond with a polarized light transmission microscope and evaluation of distortion revealed that distortion in the crystal was considerably small. The first crystal is a synthetic diamond crystal (00
4) The half-width of the rocking curve of the X-ray diffraction by the two-crystal method with the plane parallel arrangement was measured and found to be 7.2 seconds. Further, to measure the Raman spectrum in a double monochromator Raman spectroscopic device, was determined the half width of 1332 cm ^-1, it was 2.2 cm ^-1.

Example 4 Diamond was synthesized in the same manner as in Example 3 except that the amount of Al added was 0.5% by weight. The obtained diamond was a slightly yellowish crystal. According to analysis by SIMS, the amount of nitrogen was 1.6 × 10 ¹⁶ ppm atom / cm ⁻¹ and the amount of boron was 1.5.
× 10 ¹⁷ atoms / cm ^-1 . When the infrared absorption spectrum and the ultraviolet-visible spectrum of the obtained diamond were measured, nitrogen absorption was recognized in each case. However, as a result of observing a polarized light transmission image with a polarizing microscope and evaluating distortion, it was found that distortion in the crystal was relatively small. Also,
Synthetic diamond crystal (004) plane parallel to first crystal
When the half width of the rocking curve of the X-ray diffraction by the two crystal method was measured, it was 8.5 seconds. Further, to measure the Raman spectrum in a double monochromator Raman spectroscopic device, was determined the half width of 1332 cm ^-1, it was 2.5 cm ^-1.

Example 5 A synthetic diamond powder having a B (boron) content of 7 ppm was used as the carbon source (1). Solvent metal (2) has a B content of 1p
pm Fe, Co, and the solvent metal composition was Fe / Co =
60/40 (weight ratio). To this solvent metal, 1.5% by weight of Ti was added as a nitrogen getter, and 1.5% by weight of Cu was simultaneously added. Others are the same as in Example 1.
IIa type diamond was synthesized. As a result, 0.7-
0.9 carats of colorless, transparent and good quality IIa diamond crystals were obtained. As a result of quantitative analysis of nitrogen and boron in diamond by SIMS, 1.1 × 10 ¹⁶
Atoms / cm ³ , 1.8 × 10 ¹⁶ atoms / cm ³ .
As a result of observing a polarized light transmission image of the obtained diamond with a polarization transmission microscope and evaluating the distortion, almost no distortion in the crystal was recognized. The half width of the rocking curve of the X-ray diffraction by the two-crystal method in which the first crystal was arranged in parallel with the synthetic diamond crystal (004) plane was 5.8 seconds. The Raman spectrum was measured with a double monochromator Raman spectrometer,
When the half width of 32 cm ^-1 was determined, it was 1.8 cm ^-1 . As described above, it was found that the diamond crystal was extremely excellent in crystallinity. In addition, as a result of measuring an ultraviolet-visible spectrum and an infrared spectrum, no light absorption by impurities such as nitrogen and boron was observed.
Experts evaluated the color grade as a gem diamond based on the GIA scale and found that it was F color, a grade corresponding to the highest grade natural high purity diamond.

[Embodiment 6] Between a solvent metal and a seed crystal, as a buffer material for stabilizing initial crystal growth, a thickness of 0.1 mm is used.
Except that an Al plate of 05 mm was arranged, the same as in Example 5
IIa type diamond was prepared. As a result, the half-width of the rocking curve was 5.7 seconds, and the half-width of the peak of the Raman spectrum was 1.6 cm ^-1 , which further improved the crystallinity.
Other characteristics were the same as in Example 5.

Example 7 After synthesizing diamond, the temperature was reduced and the pressure was reduced at the same time.
Except for completing the depressurization, the same as in Example 5
IIa type diamond was prepared. As a result, the FWHM of the rocking curve was 5.7 seconds, and the FWHM of the peak of the Raman spectrum was 1.6 cm ⁻¹ , and the crystallinity was improved. Other characteristics were the same as in Example 5.

[0025]

As is clear from the above description and the results of the examples, although the synthetic diamond single crystal according to the present invention contains nitrogen and boron as impurities, the contents of both are almost the same, and they are mutually compensated. Therefore, as in the case of high-purity type IIa diamond containing almost no impurities, there is no absorption of light by nitrogen or boron, and there is little distortion in the crystal. For this reason, defects such as cracks and cracks during processing are reduced, and a diamond anvil for generating ultra-high pressure,
When used as a diamond anvil for FT-IR,
Its life and stability are greatly improved. Furthermore, since it is possible to synthesize diamond having extremely high crystallinity and light transmission characteristics, it can be applied to monochromators, semiconductor substrates, and decorative applications. On the other hand, conventionally, it has been extremely difficult to completely remove nitrogen and boron. However, according to the production method of the present invention, even when nitrogen and boron remain to some extent in the diamond crystal, the amount of nitrogen getter added and The present invention is very industrially advantageous because a simple method of adjusting the amount of boron added can easily synthesize a diamond single crystal having the same light transmission characteristics and crystallinity as natural high-purity type IIa diamond. .

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of the configuration of a sample chamber in diamond synthesis according to the present invention.

FIG. 2 is a graph showing the relationship between the amount of Ti or Al getter added and the nitrogen content in the crystal.

FIG. 3 is a schematic explanatory view of a crystal cross section.

FIG. 4 is a diagram showing the boron content and the estimated nitrogen content in the (111) sector and the (100) sector, and the ultraviolet-visible absorption spectrum in each sector.

FIG. 5 is an ultraviolet absorption spectrum diagram of a diamond crystal synthesized by changing the addition amounts of Ti and Cu.

FIG. 6 shows the evaluation of metal inclusion in Table 1 (+
It is explanatory drawing which shows the reference | standard of +, +,-).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon source 2 Solvent metal 3 Seed crystal 4 Insulator 5 Graphite heater 6 Pressure medium

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-52-88289 (JP, A) JP-A-58-161995 (JP, A) JP-A-4-266020 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B01J 3/06 C01B 31/06 C30B 29/04

Claims (15)

(57) [Claims] 1. A crystal containing a nitrogen atom and a boron atom, wherein the number of the nitrogen atoms and the number of the boron atoms are substantially the same, and the difference between the number of the nitrogen atoms and the number of the boron atoms is 1
× 10 ¹⁷ atoms / cm ³ or less, a synthetic diamond single crystal characterized by the following: 2. The method according to claim 1, wherein the first crystal is a synthetic diamond crystal (00).
4) The synthetic diamond single crystal according to claim 1, wherein a half-width of an X-ray diffraction rocking curve measured by a two-crystal method with plane parallel arrangement is 10 seconds or less. 3. The Raman spectrum of 1332 cm ^-1
3. The synthetic diamond single crystal according to claim 1, wherein the half width of the peak of (b) is 2.3 cm ⁻¹ or less. 4. 4. The crystal contains a nitrogen atom and a boron atom, and the number of the nitrogen atoms and the number of the boron atoms are substantially the same.
And the difference between the number of nitrogen atoms and the number of boron atoms is 1
× 10 ¹⁶ atoms / cm ³ or less, a synthetic diamond single crystal characterized by the following: 5. The synthetic diamond single crystal according to claim 4, wherein no light is absorbed by nitrogen or boron from the near ultraviolet region to the far infrared region. 6. The synthetic diamond according to claim 4, which has a G color or higher on a GIA color scale.
Single crystal . 7. The first crystal is a synthetic diamond crystal (00
4) The synthetic diamond single according to any one of claims 4 to 6, wherein a half-width of an X-ray diffraction rocking curve measured by a two-crystal method in a plane-parallel arrangement is 7 seconds or less. Crystal . 8. Raman spectrum 1332 cm ^-1
The synthetic diamond single crystal according to any one of claims 4 to 7, wherein a half-value width of a peak of is 2 cm ^-1 or less. 9. A method of synthesizing diamond <br/> Mondo single crystals at very high pressure and temperature by the temperature gradient method, the nitrogen content and boron content to be incorporated into the crystal becomes the same extent the atomic during synthesis 9. The method according to claim 1, wherein the amount of nitrogen getter added to the solvent metal is adjusted, or the amount of boron added to the carbon source or the solvent metal is adjusted. A method for producing the synthetic diamond single crystal according to the above. 10. The synthetic diamond single bond according to claim 9, wherein Al is used as said nitrogen getter.
Method for manufacturing crystals . 11. The periodic table as the nitrogen getter
The method for producing a synthetic diamond single crystal according to claim 9 or 10, wherein at least one or more elements selected from group a and group Va elements are used. 12. The solvent metal according to claim 9, wherein a substance that suppresses the formation of carbides of elements of Group IVa and / or Va of the periodic table is added to the solvent metal.
The method for producing a synthetic diamond single crystal according to any one of the above. 13. The synthesis according to claim 9, wherein a buffer material for stabilizing the initial growth state of the crystal is disposed between the solvent metal and the seed surface. A method for producing a diamond single crystal . 14. The cushioning material is made of Al, Ni, Cu, Z
The method for producing a synthetic diamond single crystal according to claim 13, characterized in that it is at least one element selected from n, Ga, Ag, Cd, In, Sn, Au, Tl and Pb. 15. After synthesizing a diamond single crystal under ultra-high pressure and high temperature by a temperature difference method, when the temperature and pressure of the sample part are lowered to normal temperature and normal pressure and depressurized, the temperature of the sample part becomes 3%.
The method for producing a synthetic diamond single crystal according to any one of claims 9 to 14, wherein the pressure reduction is completed at a temperature of 00 to 1000 ° C.