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Growth hillocks on (100) faces of synthetic diamonds
TECHNICAL
190 REFERENCES
1. ASTM Special Technical PublicationNo. 265 (1959). 2. GRAHAM A. H.. LINDSAY R. W. and READ H. J., J. elecrrochem.Sot. 112.401(1965). 3. RANDIN J. P., MAIRE P. A., SAVRER E. and HINTERMANN H. E.. J. elecrrochem. Sot. 114. 442 (1967). 4. ALBERT P. A., KOVAC Z. LILIENTHAL H. R., McGUIRE T. R. and NAKAMURA Y., J. ODDS. .. Phys. 38,1258 (1967). 5. SENNE-IT R. S. and SCOTT G. D., J. opt. Sot. AM. 40,203 (1950). 6. BELSER R. B., J. uppi. Phys. 28,109 (1957). 7. GOLDSTEIN A. W., ROSTOKER W., SCHOSSBERGER ‘F. and GUTZEIT G., J. electrochem. sot. 104; 104 (1957).
-J. Phys. Chem. Solids Growth
hilkxks
Vol. 29,
pp. 190-192.
(NI (100) faces of synthetic d&UlODdS
(Received
10 July 1967)
STUDIES on the microstructures on the different faces of natural as well as synthetic diamonds have been made by number of investigators. Chief amongst them are HalTolansky and Sunagawa[21, perin]ll, Tolansky [3], Bovenkerk [4], Patel, Goswami and Ramanathan [ 51 and Seal [6]. The common features observed on (111) faces are the trigons and on (100) faces square shaped depressions. Williams[71 has reported growth hillocks on (111) faces of natural diamond and Pate1 and Ramanathan[8] have reported growth hillocks on the (111) faces of synthetic diamond. Growth hillocks on the (100) faces of synthetic diamond has been reported by Tolansky[9] but as they were not isolated and well defined no study has been made on them. Since Pate1 and Ramanathan (lot. cit.) reported growth hillocks on (111) faces of synthetic diamonds, we have been looking for similar features on its (100) faces. After examining some hundreds of these faces we succeeded in observing square shaped growth hillocks on (100) faces of a few crystals. This paper deals with the investigations made on them.
NOTES
Synthetic diamonds of cube-octahedral habit were obtained from G.E.C. (U.S.A.). They were all hardly some O-5 X 103 microns in size. The microstructures on different faces have been examined by multiple beam interferometry and phase contrast microscopy after depositing thin silver film on them. First (100) faces of those diamonds on the (111) faces of which the triangular growth hillocks were previously observed were searched but no growth hillocks were found on them and only dendrites shown in Fig. 1 (x450) were observed. We then examined (100) faces at random of some 100 crystals and ultimately found some square shaped hillocks on faces of a few crystals. Thus Fig. 2 (x450) represents the entire (100) face of the crystal on which the hillocks have been found. Figure 3 (x450) is the multiple beam interferogram taken on the face shown in Fig. 2 revealing the topography of the surface. Figure 4 (x1050) is a magnified picture of some region of Fig. 2 in which the shape and structure of the hillocks are clearly seen. The following points merit discussion. 1. The hillocks are square shaped and are oriented with their sides parallel to the cube edges. 2. They are all of the same shape but of different sizes and distributed all over the face. 3. All of them except few have flat tops. 4. Some hillocks on their tops have four sided features. 5. Sometimes faint growth steps on the side faces of square pyramids are observed. It was rather difficult to predict from the multiple beam interferogram whether the square shaped features were elevations or depressions. Fringes of equal chromatic order shown in Fig. 5 was therefore obtained on these features which clearly revealed that they were hillocks and the four sided features on their tops were depressions. The height of the hillocks measured varied between O-5 p to 0.8 p and the depths of the four sided depression on them varied from 0.2 p to
Fig. I. Dendrites
Fig. 3. lnterterogram
on (100) face ( x 330).
on the face shown (x 330).
in Fig. 2
Fig. 2. The entire face on which hillocks were observed ( x 330).
Fig. 4. A magnified portion of Fig. 2 ( x 770).
[Faring page 1901
Fig. 5. Fringes of equal chromatic.
Fig. 6. Light profile running over hillock (x770).
Fig, 7. The same region of Fig. 4 after etching in KNOs at 520°C for 4 hr ( x 770).
TECHNICAL 0.4 p.
This was also verified by a light profile method (Tolansky [ IO]). Thus Fig. 6 (X 1050) shows the multiple light profile running across the hillocks as well as the depressed features on its top. The light profile reveals that the square shaped feature is an elevation of O-8 p high and the four sided feature on its top is a depression of depth 0.3 /.L. Attention may be drawn to the following characteristics of the depressed features on the top of the hillocks. 1. They are all nearly of the same shape. 2. Their sizes are different. 3. Their orientations are also different. 4. All of them are located at the centre of the top of the hillocks. 5. The four sided features are all point bottomed. 6. The bottoms of the depressions are eccentric. In order to investigate the origin of the depressions on the top of the hillocks, the crystal surface shown in Fig. 2 was etched in KN03 at 520°C for 4 hr. Thus Fig. 7 (X1050) represents the etch pattern produced. It may be noted that 1. The square shape hillocks have been reduced in size. 2. The depressions on the top have enlarged. 3. New etch pits having shapes similar to the depressed feature on the top of the hillocks are formed. 4. The faint steps on the side faces of square shaped pyramids have receeded away from the hillocks. That the square shaped pyramids have the same orientation as that of the face on which they appear suggests that the pyramids might have been formed due to a process similar to one which produced the crystal face, i.e. due to growth. During the growth of the crystal there might have existed a few screw dislocations on the face at which growth might have taken place preferentially resulting into the square pyramids round them. Growth by screw mechanism leaves pointed tops
191
NOTES
instead of flat tops as observed. The flat tops can be explained by moving away of some of the screw dislocations before the growth ceased and thus produced the flat tops. This is also supported by the observation that pits are observed only on the top of some pyramids and not all. Those pyramids from where the dislocations have moved away, etching will not produce any pit on their tops while those in which the dislocations still exist they will be preferentially etched and thus produce the pits on their tops. The pits observed on the top of the pyramids indicate that after the growth ceased the crystal face might have been subjected to dissolution during which the sites of the dislocations are preferentially etched. That the pits on the top of the pyramids are oriented in a random fashion suggests that the tops of the pyramids may not be true (100) planes. That the bottom of the pits are not quite central suggest that the dislocations may be inclined to the surfaces. The absence of growth pyramids on (100) and (111) faces of the same crystal suggests that the conditions for such features to develop on them may be different. The notable absence of growth pyramids on the (100) faces of natural diamonds may be explained by assuming that even though such features may have been developed on them during growth, they might have been removed due to dissolution to which the natural crystals are usually subjected in, nature. The depressions formed due to etching are similar to those observed on the top of the hillocks suggest that their origin may be the etching process. authors are grateful to Dr. H. P. Bovenkerk of General Electric Company, U.S.A., for providing an adequate supply of synthetic-diamonds for carrying out the work.
Acknowledgements-The
Physics Sardar Vallabh Gujarat
Department, Pate1 University, Vidyanagar, State, India
A. R. PATEL N. RAMACHANDRAN
TECHNICAL
192 REFERENCES
1. HALPERIN A., Proc. phys. Sot. 67,538 (1954). 2. TOLANSKY S. and SUNAGAWA I., Nature, Land. 184,1526 (1959). 3. TOLANSKY S., Proc. R. Sot. A270,443 (1962). 4. BOVENKERKH. P.,Am. Miner. 46,952 (1961). 5. PATEL A. R., GOSWAMI K. N. and RAMANATHAN S., Proc. phys. Sot. 81,1053 (1963).
NOTES 6. SEAL M., Engelhard Industries Inc. Technical Bulletin Vol. II No. 2,58 (1961). 7. WILLIAMS A. F., Genesis ofthe Diamonds (1932). 8. PATEL A. R. and RAMANATHAN S., Physica 29, 889 (1963). 9. TOLANSKY S., First International Congress on Diamonds in Industry, Paris (1962). 10. TOLANSKY S., 2. Electrochem. 56,263 (1952).
190 REFERENCES
1. ASTM Special Technical PublicationNo. 265 (1959). 2. GRAHAM A. H.. LINDSAY R. W. and READ H. J., J. elecrrochem.Sot. 112.401(1965). 3. RANDIN J. P., MAIRE P. A., SAVRER E. and HINTERMANN H. E.. J. elecrrochem. Sot. 114. 442 (1967). 4. ALBERT P. A., KOVAC Z. LILIENTHAL H. R., McGUIRE T. R. and NAKAMURA Y., J. ODDS. .. Phys. 38,1258 (1967). 5. SENNE-IT R. S. and SCOTT G. D., J. opt. Sot. AM. 40,203 (1950). 6. BELSER R. B., J. uppi. Phys. 28,109 (1957). 7. GOLDSTEIN A. W., ROSTOKER W., SCHOSSBERGER ‘F. and GUTZEIT G., J. electrochem. sot. 104; 104 (1957).
-J. Phys. Chem. Solids Growth
hilkxks
Vol. 29,
pp. 190-192.
(NI (100) faces of synthetic d&UlODdS
(Received
10 July 1967)
STUDIES on the microstructures on the different faces of natural as well as synthetic diamonds have been made by number of investigators. Chief amongst them are HalTolansky and Sunagawa[21, perin]ll, Tolansky [3], Bovenkerk [4], Patel, Goswami and Ramanathan [ 51 and Seal [6]. The common features observed on (111) faces are the trigons and on (100) faces square shaped depressions. Williams[71 has reported growth hillocks on (111) faces of natural diamond and Pate1 and Ramanathan[8] have reported growth hillocks on the (111) faces of synthetic diamond. Growth hillocks on the (100) faces of synthetic diamond has been reported by Tolansky[9] but as they were not isolated and well defined no study has been made on them. Since Pate1 and Ramanathan (lot. cit.) reported growth hillocks on (111) faces of synthetic diamonds, we have been looking for similar features on its (100) faces. After examining some hundreds of these faces we succeeded in observing square shaped growth hillocks on (100) faces of a few crystals. This paper deals with the investigations made on them.
NOTES
Synthetic diamonds of cube-octahedral habit were obtained from G.E.C. (U.S.A.). They were all hardly some O-5 X 103 microns in size. The microstructures on different faces have been examined by multiple beam interferometry and phase contrast microscopy after depositing thin silver film on them. First (100) faces of those diamonds on the (111) faces of which the triangular growth hillocks were previously observed were searched but no growth hillocks were found on them and only dendrites shown in Fig. 1 (x450) were observed. We then examined (100) faces at random of some 100 crystals and ultimately found some square shaped hillocks on faces of a few crystals. Thus Fig. 2 (x450) represents the entire (100) face of the crystal on which the hillocks have been found. Figure 3 (x450) is the multiple beam interferogram taken on the face shown in Fig. 2 revealing the topography of the surface. Figure 4 (x1050) is a magnified picture of some region of Fig. 2 in which the shape and structure of the hillocks are clearly seen. The following points merit discussion. 1. The hillocks are square shaped and are oriented with their sides parallel to the cube edges. 2. They are all of the same shape but of different sizes and distributed all over the face. 3. All of them except few have flat tops. 4. Some hillocks on their tops have four sided features. 5. Sometimes faint growth steps on the side faces of square pyramids are observed. It was rather difficult to predict from the multiple beam interferogram whether the square shaped features were elevations or depressions. Fringes of equal chromatic order shown in Fig. 5 was therefore obtained on these features which clearly revealed that they were hillocks and the four sided features on their tops were depressions. The height of the hillocks measured varied between O-5 p to 0.8 p and the depths of the four sided depression on them varied from 0.2 p to
Fig. I. Dendrites
Fig. 3. lnterterogram
on (100) face ( x 330).
on the face shown (x 330).
in Fig. 2
Fig. 2. The entire face on which hillocks were observed ( x 330).
Fig. 4. A magnified portion of Fig. 2 ( x 770).
[Faring page 1901
Fig. 5. Fringes of equal chromatic.
Fig. 6. Light profile running over hillock (x770).
Fig, 7. The same region of Fig. 4 after etching in KNOs at 520°C for 4 hr ( x 770).
TECHNICAL 0.4 p.
This was also verified by a light profile method (Tolansky [ IO]). Thus Fig. 6 (X 1050) shows the multiple light profile running across the hillocks as well as the depressed features on its top. The light profile reveals that the square shaped feature is an elevation of O-8 p high and the four sided feature on its top is a depression of depth 0.3 /.L. Attention may be drawn to the following characteristics of the depressed features on the top of the hillocks. 1. They are all nearly of the same shape. 2. Their sizes are different. 3. Their orientations are also different. 4. All of them are located at the centre of the top of the hillocks. 5. The four sided features are all point bottomed. 6. The bottoms of the depressions are eccentric. In order to investigate the origin of the depressions on the top of the hillocks, the crystal surface shown in Fig. 2 was etched in KN03 at 520°C for 4 hr. Thus Fig. 7 (X1050) represents the etch pattern produced. It may be noted that 1. The square shape hillocks have been reduced in size. 2. The depressions on the top have enlarged. 3. New etch pits having shapes similar to the depressed feature on the top of the hillocks are formed. 4. The faint steps on the side faces of square shaped pyramids have receeded away from the hillocks. That the square shaped pyramids have the same orientation as that of the face on which they appear suggests that the pyramids might have been formed due to a process similar to one which produced the crystal face, i.e. due to growth. During the growth of the crystal there might have existed a few screw dislocations on the face at which growth might have taken place preferentially resulting into the square pyramids round them. Growth by screw mechanism leaves pointed tops
191
NOTES
instead of flat tops as observed. The flat tops can be explained by moving away of some of the screw dislocations before the growth ceased and thus produced the flat tops. This is also supported by the observation that pits are observed only on the top of some pyramids and not all. Those pyramids from where the dislocations have moved away, etching will not produce any pit on their tops while those in which the dislocations still exist they will be preferentially etched and thus produce the pits on their tops. The pits observed on the top of the pyramids indicate that after the growth ceased the crystal face might have been subjected to dissolution during which the sites of the dislocations are preferentially etched. That the pits on the top of the pyramids are oriented in a random fashion suggests that the tops of the pyramids may not be true (100) planes. That the bottom of the pits are not quite central suggest that the dislocations may be inclined to the surfaces. The absence of growth pyramids on (100) and (111) faces of the same crystal suggests that the conditions for such features to develop on them may be different. The notable absence of growth pyramids on the (100) faces of natural diamonds may be explained by assuming that even though such features may have been developed on them during growth, they might have been removed due to dissolution to which the natural crystals are usually subjected in, nature. The depressions formed due to etching are similar to those observed on the top of the hillocks suggest that their origin may be the etching process. authors are grateful to Dr. H. P. Bovenkerk of General Electric Company, U.S.A., for providing an adequate supply of synthetic-diamonds for carrying out the work.
Acknowledgements-The
Physics Sardar Vallabh Gujarat
Department, Pate1 University, Vidyanagar, State, India
A. R. PATEL N. RAMACHANDRAN
TECHNICAL
192 REFERENCES
1. HALPERIN A., Proc. phys. Sot. 67,538 (1954). 2. TOLANSKY S. and SUNAGAWA I., Nature, Land. 184,1526 (1959). 3. TOLANSKY S., Proc. R. Sot. A270,443 (1962). 4. BOVENKERKH. P.,Am. Miner. 46,952 (1961). 5. PATEL A. R., GOSWAMI K. N. and RAMANATHAN S., Proc. phys. Sot. 81,1053 (1963).
NOTES 6. SEAL M., Engelhard Industries Inc. Technical Bulletin Vol. II No. 2,58 (1961). 7. WILLIAMS A. F., Genesis ofthe Diamonds (1932). 8. PATEL A. R. and RAMANATHAN S., Physica 29, 889 (1963). 9. TOLANSKY S., First International Congress on Diamonds in Industry, Paris (1962). 10. TOLANSKY S., 2. Electrochem. 56,263 (1952).