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The perfection of synthetic diamond and cubic boron nitride crystals
Journal of Crystal Growth 6 (1970) 199—202
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North-Holland Publishing Company, A msterdnnz
THE PERFECTION OF SYNTHETIC DIAMOND AND CUBIC BORON NITRIDE CRYSTALS°
J. MATECHA and J. KVAPIL Monokrystaly, Turnov, Czechoslovakia
Received 25 April 1969; revised manuscript received 10 July 1969
The perfection of synthetic diamond and cubic boron nitride crystals has been determined by the Laue back-reflection method, It has been established that transparent diamond crystals give mostly perfect Laue back-reflections. Only some crystals, which contain opaque planes of {l 10} orientation, give photographs
with elongated diffuse spots. Both types of Laue back reflections are given also by opaque diamonds. The cubic boron nitride crystals studied have always given perfect Laue back reflections.
1. Introduction Carbon and boron nitride have similarstructures.The usual hexagonal modifications of both these materials are stable tinder normal conditions. The cubic form of carbon’) and boron nitride2) are prepared according to thermodynamic conditions from their hexagonal modifications under high temperatures and pressures in the presence of catalysts. Examples of both materials are shown in figs. I a and lb. Considerable attention has been given to the morphology of both of these materials3), while only little is known about their perfection. Twinning and s1ip46) has been observed in synthetic diamonds, In this work we have determined the perfection of these crystals by the Laue back-reflection method and we have compared the results obtained with observations in transmitted light,
the ratio was 1:2. The composition of the reaction products showed that there was a longitudinal temperattire gradient in the cell (a) (graphite layers were distinguishable from diamond layers), while the temperature gradient in the cell (b) was lower. The catalysts used were nickel in the case of diamond and magnesium in the case of boron nitride. Indirect heating of the samples was used in both cases. Parts of the isolated reaction products were powdered and identified by the Debye—Scherrer method. Single crystals with dimensions of O.3—O.5 mm were visually selected and fixed on rods of borosilicate glass. These samples were investigated by the Laue backreflection method. The Laue transmission method always gave an intense continuous darkening of the film, so that it was not used. Optical investigations of the transparent crystals were made with a conventional microscope.
2. Experimental
3. Results
The transformations of the graphite and of the hexagonal boron nitride to the respective cubic modifications have been made in a modified “belt” system apparatus. The applied pressure was 60—75 kbar and the temperature 1500—1800 °C. Two different cylindrical reaction cells were used. In one, (a), the length to diameter ratio was 2:1; in the other, (b),
Diamond single crystals grown in the cell (b) (small temperature gradient) always gave perfect Laue (fig. 2a) reflections, as did most of the diamond crystals synthesized in the cell (a). The remaining transparent as well as the opaque single crystals from the latter cell gave Laue back-reflection with elongated diffuse spots (fig. 2b). Optical observation of the transparent crystals how
This paper was presented at the 7th Annual Meeting of the European High Pressure Research Group in Bonn, Germany, 9—11 April 1969. *
199
e (1) Single crystals which gave perfect Laue back-
5
200
j. MA1 ECHA ANt)
a
J. KVAPIL
-
Fig. I (a)
Fig. I (b) Fig. I.
Examples of thc sing)c crystals. (a) diamond; (hi cuba. boron nitride.
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THE PERFECTION OF SYNTHETIC DIAMOND AND CUBIC BORON NITRIDE CRYSTALS
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____
Fig. 2 (a)
Fig. 2.
201
Fig. 2 (b)
Fig. 2 (c) Laue back-reflection photographs of single crystals. (a) perfect diamond; (b) mosaic diamond; (c) cubic boron nitride. Conditions: ~0 mA, 40kv, exposure 35 mm, film ORWO RF 44.
reflections contained irregularly oriented inclusions at most. (2) Single crystals which gave diffuse Laue spots contained dark planes (lamellae) of ~1 l0} orientation (fig. 3). Similar lamellae with orientation ~ll0} or
Ill } have very occasionally been observed by Varma7) in natural diamonds. Besides a certain resemblance of the photomicrograph to those which have been described by Patel and Ramachandran6) in the investigation of slip, we are
202
J. MATECHA AND J. KVAPJL
dealing here not with a discontinuity of the surface level but with internal defects as the Iamellae do not change their ro~itionwhen the microscope is focussed
observed crystals gave perfect Laue back-reflections (fig. 2c). 4. Summary Single crystals of synthetic diamonds have mostly relatively perfect structures. Only a small proportion of the crystals gave Laue back-reflections with diffuse spots. In these crystals it was possible to observe lamellae of {l lO} orientation. With regard to the method of the preparation of defective crystals, it is possible to consider that their mosaic texture originates as a consequence of the growth in a temperature gradient. For cubic boron nitride single crystals it has not been possible to establish any mosaic misorientation. References
Fig. 3.
Diamond single crystal with inner Iamellae (Laue backreflection of this crystal is that in fig. I b) is observed in the [1001 direction, and is partially submerged in methylene iodide. Magnification: 300><.
to different depths in the crystal. The picture of the defects also does not change in polarized light. We have probably to deal with the segregation of impurities (catalyst) on {llO} planes of the growing fine mosaic crystal. The presence of Ni causes no anomalous X-ray reflections such as those described previously8). A closer study of the defects indicated (e.g. by X-ray topography) which has been made on natural diarnonds°) was not useful in this case as the crystals were too small. We have tip till now been unable to observe similar defects in cubic boron nitride single crystals and, contrary to previous observations’0), all of the
I) F. B. Bundy, H. T. Hall, H. M. Strong and R. H. Wentorf, Nature 176 (1955) 51. 2) R. H. Wentorf, Jr., J. Chem. Phys. 26 (1957) 956; 34 (1961) 809; 36(1962)1990. 3) N. E. Filonenko, V. I. lvanov and L. I. Feidgun, Doki. Akad. Nauk SSSR 164 (1965) 1286; Z. V. Bartoshinski, Ind. Diamond Res. 27(1967) 269; S. Fakasu, Seramikkusu 1(1966) 724; V. A. Nikitin, T. N. Bezrukov, VS. Varagin, V. P. Butuzov and G. V. Chatelishvili, Fiz. Tverd. Tcla 10 (1968) 263. 4) N. F. Filonenko, G. M. Zerctskaya, N. M. Kamentscva and L. I. Feldgun, DokI. Akad. NaLik SSSR 179 (1968) 81. 5) S. Tolansky, Nature 185 (1960) 203. 6) A. R. Patel and N. Ramachandran, J. Phys. Chern. Solids 28 (1967) 1849. 7) R. Varma, Phil. (1967) 611, 621, 657. 8) C. S. 1.K.Futergendler and Mug. G. V.16Chatelishvili, Kristallogratiya 13(1968)120. 9) T. Evans and R. K. Wild, Phil. Mug. 12 (1965) 479; R. K. Wild and T. Evans, Phil. Mag. 15 (1967) 267. 10) M. I. Sochor and S. I. Futergendler, DokI. Akad. Nauk SSSR 182 (1968) 1071.
~
North-Holland Publishing Company, A msterdnnz
THE PERFECTION OF SYNTHETIC DIAMOND AND CUBIC BORON NITRIDE CRYSTALS°
J. MATECHA and J. KVAPIL Monokrystaly, Turnov, Czechoslovakia
Received 25 April 1969; revised manuscript received 10 July 1969
The perfection of synthetic diamond and cubic boron nitride crystals has been determined by the Laue back-reflection method, It has been established that transparent diamond crystals give mostly perfect Laue back-reflections. Only some crystals, which contain opaque planes of {l 10} orientation, give photographs
with elongated diffuse spots. Both types of Laue back reflections are given also by opaque diamonds. The cubic boron nitride crystals studied have always given perfect Laue back reflections.
1. Introduction Carbon and boron nitride have similarstructures.The usual hexagonal modifications of both these materials are stable tinder normal conditions. The cubic form of carbon’) and boron nitride2) are prepared according to thermodynamic conditions from their hexagonal modifications under high temperatures and pressures in the presence of catalysts. Examples of both materials are shown in figs. I a and lb. Considerable attention has been given to the morphology of both of these materials3), while only little is known about their perfection. Twinning and s1ip46) has been observed in synthetic diamonds, In this work we have determined the perfection of these crystals by the Laue back-reflection method and we have compared the results obtained with observations in transmitted light,
the ratio was 1:2. The composition of the reaction products showed that there was a longitudinal temperattire gradient in the cell (a) (graphite layers were distinguishable from diamond layers), while the temperature gradient in the cell (b) was lower. The catalysts used were nickel in the case of diamond and magnesium in the case of boron nitride. Indirect heating of the samples was used in both cases. Parts of the isolated reaction products were powdered and identified by the Debye—Scherrer method. Single crystals with dimensions of O.3—O.5 mm were visually selected and fixed on rods of borosilicate glass. These samples were investigated by the Laue backreflection method. The Laue transmission method always gave an intense continuous darkening of the film, so that it was not used. Optical investigations of the transparent crystals were made with a conventional microscope.
2. Experimental
3. Results
The transformations of the graphite and of the hexagonal boron nitride to the respective cubic modifications have been made in a modified “belt” system apparatus. The applied pressure was 60—75 kbar and the temperature 1500—1800 °C. Two different cylindrical reaction cells were used. In one, (a), the length to diameter ratio was 2:1; in the other, (b),
Diamond single crystals grown in the cell (b) (small temperature gradient) always gave perfect Laue (fig. 2a) reflections, as did most of the diamond crystals synthesized in the cell (a). The remaining transparent as well as the opaque single crystals from the latter cell gave Laue back-reflection with elongated diffuse spots (fig. 2b). Optical observation of the transparent crystals how
This paper was presented at the 7th Annual Meeting of the European High Pressure Research Group in Bonn, Germany, 9—11 April 1969. *
199
e (1) Single crystals which gave perfect Laue back-
5
200
j. MA1 ECHA ANt)
a
J. KVAPIL
-
Fig. I (a)
Fig. I (b) Fig. I.
Examples of thc sing)c crystals. (a) diamond; (hi cuba. boron nitride.
—
THE PERFECTION OF SYNTHETIC DIAMOND AND CUBIC BORON NITRIDE CRYSTALS
-~
____
Fig. 2 (a)
Fig. 2.
201
Fig. 2 (b)
Fig. 2 (c) Laue back-reflection photographs of single crystals. (a) perfect diamond; (b) mosaic diamond; (c) cubic boron nitride. Conditions: ~0 mA, 40kv, exposure 35 mm, film ORWO RF 44.
reflections contained irregularly oriented inclusions at most. (2) Single crystals which gave diffuse Laue spots contained dark planes (lamellae) of ~1 l0} orientation (fig. 3). Similar lamellae with orientation ~ll0} or
Ill } have very occasionally been observed by Varma7) in natural diamonds. Besides a certain resemblance of the photomicrograph to those which have been described by Patel and Ramachandran6) in the investigation of slip, we are
202
J. MATECHA AND J. KVAPJL
dealing here not with a discontinuity of the surface level but with internal defects as the Iamellae do not change their ro~itionwhen the microscope is focussed
observed crystals gave perfect Laue back-reflections (fig. 2c). 4. Summary Single crystals of synthetic diamonds have mostly relatively perfect structures. Only a small proportion of the crystals gave Laue back-reflections with diffuse spots. In these crystals it was possible to observe lamellae of {l lO} orientation. With regard to the method of the preparation of defective crystals, it is possible to consider that their mosaic texture originates as a consequence of the growth in a temperature gradient. For cubic boron nitride single crystals it has not been possible to establish any mosaic misorientation. References
Fig. 3.
Diamond single crystal with inner Iamellae (Laue backreflection of this crystal is that in fig. I b) is observed in the [1001 direction, and is partially submerged in methylene iodide. Magnification: 300><.
to different depths in the crystal. The picture of the defects also does not change in polarized light. We have probably to deal with the segregation of impurities (catalyst) on {llO} planes of the growing fine mosaic crystal. The presence of Ni causes no anomalous X-ray reflections such as those described previously8). A closer study of the defects indicated (e.g. by X-ray topography) which has been made on natural diarnonds°) was not useful in this case as the crystals were too small. We have tip till now been unable to observe similar defects in cubic boron nitride single crystals and, contrary to previous observations’0), all of the
I) F. B. Bundy, H. T. Hall, H. M. Strong and R. H. Wentorf, Nature 176 (1955) 51. 2) R. H. Wentorf, Jr., J. Chem. Phys. 26 (1957) 956; 34 (1961) 809; 36(1962)1990. 3) N. E. Filonenko, V. I. lvanov and L. I. Feidgun, Doki. Akad. Nauk SSSR 164 (1965) 1286; Z. V. Bartoshinski, Ind. Diamond Res. 27(1967) 269; S. Fakasu, Seramikkusu 1(1966) 724; V. A. Nikitin, T. N. Bezrukov, VS. Varagin, V. P. Butuzov and G. V. Chatelishvili, Fiz. Tverd. Tcla 10 (1968) 263. 4) N. F. Filonenko, G. M. Zerctskaya, N. M. Kamentscva and L. I. Feldgun, DokI. Akad. NaLik SSSR 179 (1968) 81. 5) S. Tolansky, Nature 185 (1960) 203. 6) A. R. Patel and N. Ramachandran, J. Phys. Chern. Solids 28 (1967) 1849. 7) R. Varma, Phil. (1967) 611, 621, 657. 8) C. S. 1.K.Futergendler and Mug. G. V.16Chatelishvili, Kristallogratiya 13(1968)120. 9) T. Evans and R. K. Wild, Phil. Mug. 12 (1965) 479; R. K. Wild and T. Evans, Phil. Mag. 15 (1967) 267. 10) M. I. Sochor and S. I. Futergendler, DokI. Akad. Nauk SSSR 182 (1968) 1071.