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The morphology of fine metal crystallites
69
Journal of Crystal Growth 24/25 (1974) 69—75 © North-Holland Publishing Co.
THE MORPHOLOGY OF FINE METAL CRYSTALLITES RYOZI UYEDA Department of Applied Physics, Faculty of Engineering, Nagoya University, Nagoya, Japan Clear-cut habits were found for fine metal crystallites formed by evaporation of a metal in an atmosphere of inactive gases; helium, argon and xenon. A systematic investigation by electron microscopy on twenty-two kinds of metal for various formation conditions was carried out. Some of the distinct morphologies found so far are as follows: (1) Cubes for a-Cr, (2) octahedra for fcc metals, (3) rhombic dodecahedra for cs-Fe, 13-Mn and Be, (4) tristetrahedra for a-Mn, (5) icosatetrahedra for 6-Cr, (6) hexagonal plates and polyhedra for Be, Mg and Zn, (7) hexagonal rods with split ends for Te, (8) truncated triangular biprisms for fcc metals, (9) pentagonal decahedra and/or icosahedra for fcc metals and 7-Fe. Nos. 1 to 7 are single crystals, No. 8 are twinned and No. 9 are so-called multiply-twinned particles. Among the single crystals, the octahedra and rhombic dodecahedra, which are more or less truncated in many cases, are possibly Wulfi’ polyhedra for fcc and bcc crystals, respectively.
1. Introduction Fine metal crystallites of diameter less than 1 jim can be produced by a gas-evaporation method, i.e. the evaporation of a metal in an atmosphere of inactive gas. A study of these crystallites by electron microscopy was initiated in 1962 by the present author1) and then crystallographic and physical investigations were pursued in Japan. Particularly, the former were carried out at Nagoya University by Kimoto and Nishida2 8), Wada9”°)and Fukano1t), and by Yatsuya and other students in the author’s laboratory12~5).The results gave not only a beautiful collection of polyhedral crystals, but also insight into the fundamentals ofcrystal growth theory. This paper outlines the present state of the investigation. Some details of recent developments are given in two papers in this volume13’14). -
Fig. 1.
2. Experimental The evaporation is carried out in a work chamber such as that used for vacuum evaporation. Helium, argon or xenon gas is introduced into the chamber, after it has been highly evacuated. The metal vapour produced by heating is cooled and condensed in the gas atmosphere, resulting in a metal smoke. Fig. 1 shows a picture of magnesium smoke taken by Wada9) in an early experiment. Recent study has made it clear that the features ofsmoke vary with evaporation conditions. The main factors are the temperature and geometry of the evaporation source as well as the kind and pressure of the inert gas (fig. 1 of ref. 14). Typical smokes, which
Magnesium smoke in 6 Torr argon.
occur in the pressure range 5 to 30 Torr in the case of argon, look like the flame of a candle and consist of an inner, intermediate* and outer zone (see fig. I of ref. 13). Fig. 2 shows an electron micrograph of aluminium crystallites. In this figure, both large and small particles formed in different zones of the smoke are present. They can be obtained separately using a new technique, in which crystallites formed at each point in a smoke are collected. For many metals, crystallites with clearcut habit are formed, for example, in argon gas ofabout . . . The intermediate zone is also called the inner front because sometimes looks like a front in a smoke.
*
11—4
it
70
RYOZI UYEDA
case of chromium. Crystallites with clear-cut habits have a diameter of 100 A to I jim in most cases. The determination of three-dimensional shapes by the conventional electron microscopy requires a large amount of systematic work. Many micrographs and the corresponding diffraction patterns must be taken at several special orientations using a tilting stage. Techniques of shadow casting and cast-skin replication have also been adopted as auxiliary methods. The scanning electron microscope is most convenient for this purpose, but it is useful only for extraordinarily large crystallites (‘-..~ I jim) because ofits low resolving power. 3. Results Fig. 2.
Aluminium crystallites collected by the old technique.
20 Torr. The crystal size and habit vary according to the position of collection as well as the evaporation conditions. Clear-cut habits are formed only when the gas is free from impurities of active gases, except for the
The results of the investigation are summarized in table 1. Interesting examples will be briefly reviewed in this section. Beryllium. Rhombic dodecahedra (fig. 3) and thin hexagonal plates (fig. 4) were found. Strictly speaking,
TAaLE
1
Habits and structure of metal crystallites Metal Be Mg Al V Cr Mn
Co Ni Cu Ag Au Fe
Zn Ge Ga Se Cd In Sn Te Pb Bi
Habit
Structure
Rhombic dodecahedron Hexagonal plate (1st order) Various hexagonal polyhedra Hexagonal plate (1st order) Sphere (cuboctahedron) Complicated profiles Icosatetrahedron Cube and tetragonal prism Rhombic dodecahedron Tristetrahedron Rod Octahedron (truncated) Truncated triangular bipyramid Triangular plate (truncated) Pentagonal decahedron Icosahedron Rhombic dodecahedron (truncated) Triangular plate Pentagonal decahedron Hexagonal profile Triangular plate Complicated profiles Sphere Sphere Hexagonal profile Complicated profiles Cube and tetragonal prism Pear-shape Hexagonal rod Hexagonal profile Complicated profiles
11—4
hcp, bcc hcp hcp hcp fcc bcc A-15 bcc 13-Mn c~-Mn Unknown fcc fcc fcc fcc fcc bce bcc, fcc bcc, fcc hcp hcp Diamond Amorphous Amorphous hcp fcc Tetragonal Hexagonal Hexagonal fcc Rhombohedral
Reference 7,10,14 2,10 14 1,2,9 1,9,10,13 8 3,4 1,2 2,6 14 15 15 2,10,15 5,10,15 5,10,15 1,2,10,15 II 11 2,9,15 15 15 2 2 2,9,10 2 1,2 7,14 2,7 2 2
71
THE MORPHOLOGY OF FINE METAL CRYSTALLITES
Fig. 6. Fig. 3.
Icosatetrahedra of6-chromium.
Rhombic dodecahedron ofberyllium (cf. fig. 14).
the latter are truncated bipyramids. The latter are always hcp, while the former are sometimes bcc. It is reasonable to suppose that the former, which have
•
~ % ~1I ~ • J•
cubic symmetry, formed at a high temperature where the bcc phase is stable. When cooled to room temperature, the external shape is preserved, even though the
~•
internal structure undergoes the usual transformation to hcp. Magnesium. Hexagonal plates and polyhedra of various shapes were found. For details, see ref. 14. Aluminium. In the early experiments, the shape was
F
Fig. 4.
I
Hexagonal plate of beryllium.
•~~4~S ~
~~‘~r~:fu.
I
~
‘ ___
L
w~ Fig. 5.
~
•6
~1
~o
-
1
10
0.25 #~
6- Cr
Cubes and tetragonal prisms of a-chromium.
Fig. 7.
II —4
321
b.c.c. Cr Debye-rings of6- and a-chromium.
72
RYOZI UYEDA
4i~______
,~
4:- 4l~ •
•
-
•
I
•
• -
•
Lj:~ •
-
•
•
-
Fig. 8.
.
-
•
.
-
-
-‘
.
Tristetrahedron of cs-manganese (three projections).
usually spherical (fig. 2). A clear-cut habit, which is presumably cuboctahedron, was found recently (fig. 5 of ref. 13). It is inferred that the formation ofa clear-cut habit is disturbed by slight oxidation or surface adsorption which reduces the anisotropy of the surface energy. Chromium. Cubes and tetragonal prisms having the usual bcc structure (fig. 5) were found when the inactive
(a)
Fig. 10.
gas contained a trace of oxygen. This is the only example in which a clear-cut habit formed in an atmosphere with an oxygen impurity. In high purity gas, icosatetrahedra (fig. 6) of a new modification were found. This modification was named 6-chromium by Kimoto and Nishida3) and they determined its crystal structure to be A-15 (fig. 7). It is not yet clear whether this is a stable form of chromium at high temperatures. ~anganese. Rhombic dodecahedra of fl-form were found in the inner zone, tristetrahedra of tx-form in the intermediate zone, and rods of an unknown structure in the outer zone. The second of these is shown in fig. 8. This shows an example of how three-dimensional shapes can be determined by taking micrographs at several special orientations. Face centred metals. Four/types of habit were found: (1) octahedra (fig. 9) which are more or less truncated
(b)
Fig. 9.
~5
Pentagonal • decahedron of silver.
Octahedron of silver (two projections and cast-skin replica).
11—4
Ic)
73
THE MORPHOLOGY OF FINE METAL CRYSTALLITES
(a) Fig. 11.
(b)
Truncated triangular bipyramid of silver (two projections and cast-skin replica).
(2) truncated triangular bipyramids (fig. 11), (3) thin triangular plates (fig. 12) which are more or less truncated, and (4) pentagonal decahedra (fig. 10) and/or icosahedra. The latter habits are special to so-called multiply-twinned particles”’). Iron. A rhombic dodecahedron (fig. 13) was the typical habit. Three projections as illustrated in fig. 14 are seen in fig. 13. The shape was truncated in many cases and sometimes looked like a regular octagon. Recently, Fukano’ 1) prepared pentagonal decahedra (fig. 15) and triangular plates (fig. 16), both of which are characteristic of fcc metals. Some of the crystallites with these habits were of y-form (fcc), while others were of cL-form (bcc). These crystals formed between 910 and 1390 °C where the y-form is stable, and were quenched to room temperature. Crystallites having the fcc structure appear to be perfect, whereas those with the bcc structure are internally distorted (compare a and b of figs. 15 and 16). The distortion was evidently generated during the transformation from the y- to the cL-form. Tellurium. A pear-shape (fig. 17) was found in the inner zone and hexagonal rods in the outer zone. Both have the same hexagonal structure. Under certain conditions the ends of each rod were triply split (fig. 18).
4.
(c)
i
-
-
•
.
Fig. 12. w
•
-
o2
-
-
Triangular plate of silver. -
4
111)
S.
of the systematic study of crystal
size12”3), it is clear that crystals grow by the ordinary mechanism of vapour growth only during the initial stages of gas-evaporation. Further growth takes place by the coalescence of particles when they collide with each other in the upper part of a smoke where there is no vapour. Since the surface oxide hinders coalescence, irregular shapes as observed by Kimoto and Nishida2) may be formed in an impure atmosphere.
(100)
•
Fig. 13.
.
.
Rhombic dodecahedra of iron (cf. fig. 14).
The habits given in table 1 may be classified into three categories: single crystal, twinned and so-called multiply-twinned particles. The triangular bipyramid for fcc metals is twinned. The triangular plate for fcc
11—4
74
RYOZI UYEDA
ClIi)
Loin
(OIl]
(110]
-
(100]
-.
‘-.
~~ØT0II’
--
(Iii)
(01 I)
A
(001)
Fig. 15.
—
Fig. 17.
• • • . • Fig. 14. Illustrating three special projections of a rhombic dodecahedron. -• ~ :
Pear-shapes of tellurium.
~
.
-
Pentagonal decahedra of 7-iron (a) and cs-iron (b).
0.2 ?~ Fig. 18.
-
•-
•.
-
-
•
•
•
.
•
.
--
-
I. -
•
~•~•
-_______
(a) Fig. 16.
-
e
• - •- - - - L
-
-
-
-
I
500A
(I,) Triangular plates of 7-iron (a) and a-iron (b).
metals may also be twinned. It is presumably an extremely truncated form of bipyramid. Pentagonal decahedra and icosahedra are multiply-twinned partides1 6) There is a general trend that habits with a large surface area such as plates and rods are found in the outer zone, while those with a large volume such as
Rods of tellurium.
the rhombic dodecahedra and various hexagonal polyhedra are found in the inner zone. Multiply-twinned particles, which have a large area of twin boundary, are also found in the outer zone. It is worth noting that the octahedra and rhombic dodecahedra which are often more or less truncated are possibly Wulif polyhedra for fcc and bcc crystals, respectively, although this has not yet been exactly justified. It is of great interest to study crystallites having clear-cut habits formed in an extremely clean atmosphere. References
II —4
1) K. Kimoto, Y. Kamiya, M. Nonoyama and R. Uyeda, Japan. J. AppI. Phys. 2 (1963) 702. 2) K. Kimoto and I. Nishida, Japan. J. AppI. Phys. 6(1967)1047. 3) K. Kimoto and I. Nishida, J. Phys. Soc. Japan 22(1967) 744. 4) I. Nishida and K. Kimoto, submitted to Thin Solid Films. 5) K. Kimoto and I. Nishida, J. Phys. Soc. Japan 22 (1967) 940.
THE MORPHOLOGY
OF FINE METAL CRYSTALLITES
6)1. Nishida, J. Phys. Soc. Japan 26(1969)1225. 7)1. Nishida, unpublished. 8)1. Nishida and K. Kimoto, unpublished. 9) N. Wada, Japan. J. AppI. Phys. 6(1967) 553. 10) N. Wada, Japan. J. App!. Phys. 7 (1968) 1287. 11) Y. Fukano, unpublished, 12) 5. Yatsuya, S. Kasukabe and R. Uyeda, Japan. J. AppI. Phys. 12 (1973) 1675.
75
13) S. Yatsuya, S. Kasukabe and R. Uyeda, J. Crystal Growth 24/25 (1974) 319. 14) 5. Kasukabe, S. Yatsuya and R. Uyeda, J. Crystal Growth 24/25 (1974) 315. 15) 5. Yatsuya, K. Uyeda, S. Kasukabe, T. Ohno, T. Hayashi and R. Uyeda, unpublished. 16) Sh. Ogawa and Sh. Ino, Advances in Epitaxy and Endotaxy (VEB Deutscher Verlag, Leipzig, 197)) p. 183.
11—4
Journal of Crystal Growth 24/25 (1974) 69—75 © North-Holland Publishing Co.
THE MORPHOLOGY OF FINE METAL CRYSTALLITES RYOZI UYEDA Department of Applied Physics, Faculty of Engineering, Nagoya University, Nagoya, Japan Clear-cut habits were found for fine metal crystallites formed by evaporation of a metal in an atmosphere of inactive gases; helium, argon and xenon. A systematic investigation by electron microscopy on twenty-two kinds of metal for various formation conditions was carried out. Some of the distinct morphologies found so far are as follows: (1) Cubes for a-Cr, (2) octahedra for fcc metals, (3) rhombic dodecahedra for cs-Fe, 13-Mn and Be, (4) tristetrahedra for a-Mn, (5) icosatetrahedra for 6-Cr, (6) hexagonal plates and polyhedra for Be, Mg and Zn, (7) hexagonal rods with split ends for Te, (8) truncated triangular biprisms for fcc metals, (9) pentagonal decahedra and/or icosahedra for fcc metals and 7-Fe. Nos. 1 to 7 are single crystals, No. 8 are twinned and No. 9 are so-called multiply-twinned particles. Among the single crystals, the octahedra and rhombic dodecahedra, which are more or less truncated in many cases, are possibly Wulfi’ polyhedra for fcc and bcc crystals, respectively.
1. Introduction Fine metal crystallites of diameter less than 1 jim can be produced by a gas-evaporation method, i.e. the evaporation of a metal in an atmosphere of inactive gas. A study of these crystallites by electron microscopy was initiated in 1962 by the present author1) and then crystallographic and physical investigations were pursued in Japan. Particularly, the former were carried out at Nagoya University by Kimoto and Nishida2 8), Wada9”°)and Fukano1t), and by Yatsuya and other students in the author’s laboratory12~5).The results gave not only a beautiful collection of polyhedral crystals, but also insight into the fundamentals ofcrystal growth theory. This paper outlines the present state of the investigation. Some details of recent developments are given in two papers in this volume13’14). -
Fig. 1.
2. Experimental The evaporation is carried out in a work chamber such as that used for vacuum evaporation. Helium, argon or xenon gas is introduced into the chamber, after it has been highly evacuated. The metal vapour produced by heating is cooled and condensed in the gas atmosphere, resulting in a metal smoke. Fig. 1 shows a picture of magnesium smoke taken by Wada9) in an early experiment. Recent study has made it clear that the features ofsmoke vary with evaporation conditions. The main factors are the temperature and geometry of the evaporation source as well as the kind and pressure of the inert gas (fig. 1 of ref. 14). Typical smokes, which
Magnesium smoke in 6 Torr argon.
occur in the pressure range 5 to 30 Torr in the case of argon, look like the flame of a candle and consist of an inner, intermediate* and outer zone (see fig. I of ref. 13). Fig. 2 shows an electron micrograph of aluminium crystallites. In this figure, both large and small particles formed in different zones of the smoke are present. They can be obtained separately using a new technique, in which crystallites formed at each point in a smoke are collected. For many metals, crystallites with clearcut habit are formed, for example, in argon gas ofabout . . . The intermediate zone is also called the inner front because sometimes looks like a front in a smoke.
*
11—4
it
70
RYOZI UYEDA
case of chromium. Crystallites with clear-cut habits have a diameter of 100 A to I jim in most cases. The determination of three-dimensional shapes by the conventional electron microscopy requires a large amount of systematic work. Many micrographs and the corresponding diffraction patterns must be taken at several special orientations using a tilting stage. Techniques of shadow casting and cast-skin replication have also been adopted as auxiliary methods. The scanning electron microscope is most convenient for this purpose, but it is useful only for extraordinarily large crystallites (‘-..~ I jim) because ofits low resolving power. 3. Results Fig. 2.
Aluminium crystallites collected by the old technique.
20 Torr. The crystal size and habit vary according to the position of collection as well as the evaporation conditions. Clear-cut habits are formed only when the gas is free from impurities of active gases, except for the
The results of the investigation are summarized in table 1. Interesting examples will be briefly reviewed in this section. Beryllium. Rhombic dodecahedra (fig. 3) and thin hexagonal plates (fig. 4) were found. Strictly speaking,
TAaLE
1
Habits and structure of metal crystallites Metal Be Mg Al V Cr Mn
Co Ni Cu Ag Au Fe
Zn Ge Ga Se Cd In Sn Te Pb Bi
Habit
Structure
Rhombic dodecahedron Hexagonal plate (1st order) Various hexagonal polyhedra Hexagonal plate (1st order) Sphere (cuboctahedron) Complicated profiles Icosatetrahedron Cube and tetragonal prism Rhombic dodecahedron Tristetrahedron Rod Octahedron (truncated) Truncated triangular bipyramid Triangular plate (truncated) Pentagonal decahedron Icosahedron Rhombic dodecahedron (truncated) Triangular plate Pentagonal decahedron Hexagonal profile Triangular plate Complicated profiles Sphere Sphere Hexagonal profile Complicated profiles Cube and tetragonal prism Pear-shape Hexagonal rod Hexagonal profile Complicated profiles
11—4
hcp, bcc hcp hcp hcp fcc bcc A-15 bcc 13-Mn c~-Mn Unknown fcc fcc fcc fcc fcc bce bcc, fcc bcc, fcc hcp hcp Diamond Amorphous Amorphous hcp fcc Tetragonal Hexagonal Hexagonal fcc Rhombohedral
Reference 7,10,14 2,10 14 1,2,9 1,9,10,13 8 3,4 1,2 2,6 14 15 15 2,10,15 5,10,15 5,10,15 1,2,10,15 II 11 2,9,15 15 15 2 2 2,9,10 2 1,2 7,14 2,7 2 2
71
THE MORPHOLOGY OF FINE METAL CRYSTALLITES
Fig. 6. Fig. 3.
Icosatetrahedra of6-chromium.
Rhombic dodecahedron ofberyllium (cf. fig. 14).
the latter are truncated bipyramids. The latter are always hcp, while the former are sometimes bcc. It is reasonable to suppose that the former, which have
•
~ % ~1I ~ • J•
cubic symmetry, formed at a high temperature where the bcc phase is stable. When cooled to room temperature, the external shape is preserved, even though the
~•
internal structure undergoes the usual transformation to hcp. Magnesium. Hexagonal plates and polyhedra of various shapes were found. For details, see ref. 14. Aluminium. In the early experiments, the shape was
F
Fig. 4.
I
Hexagonal plate of beryllium.
•~~4~S ~
~~‘~r~:fu.
I
~
‘ ___
L
w~ Fig. 5.
~
•6
~1
~o
-
1
10
0.25 #~
6- Cr
Cubes and tetragonal prisms of a-chromium.
Fig. 7.
II —4
321
b.c.c. Cr Debye-rings of6- and a-chromium.
72
RYOZI UYEDA
4i~______
,~
4:- 4l~ •
•
-
•
I
•
• -
•
Lj:~ •
-
•
•
-
Fig. 8.
.
-
•
.
-
-
-‘
.
Tristetrahedron of cs-manganese (three projections).
usually spherical (fig. 2). A clear-cut habit, which is presumably cuboctahedron, was found recently (fig. 5 of ref. 13). It is inferred that the formation ofa clear-cut habit is disturbed by slight oxidation or surface adsorption which reduces the anisotropy of the surface energy. Chromium. Cubes and tetragonal prisms having the usual bcc structure (fig. 5) were found when the inactive
(a)
Fig. 10.
gas contained a trace of oxygen. This is the only example in which a clear-cut habit formed in an atmosphere with an oxygen impurity. In high purity gas, icosatetrahedra (fig. 6) of a new modification were found. This modification was named 6-chromium by Kimoto and Nishida3) and they determined its crystal structure to be A-15 (fig. 7). It is not yet clear whether this is a stable form of chromium at high temperatures. ~anganese. Rhombic dodecahedra of fl-form were found in the inner zone, tristetrahedra of tx-form in the intermediate zone, and rods of an unknown structure in the outer zone. The second of these is shown in fig. 8. This shows an example of how three-dimensional shapes can be determined by taking micrographs at several special orientations. Face centred metals. Four/types of habit were found: (1) octahedra (fig. 9) which are more or less truncated
(b)
Fig. 9.
~5
Pentagonal • decahedron of silver.
Octahedron of silver (two projections and cast-skin replica).
11—4
Ic)
73
THE MORPHOLOGY OF FINE METAL CRYSTALLITES
(a) Fig. 11.
(b)
Truncated triangular bipyramid of silver (two projections and cast-skin replica).
(2) truncated triangular bipyramids (fig. 11), (3) thin triangular plates (fig. 12) which are more or less truncated, and (4) pentagonal decahedra (fig. 10) and/or icosahedra. The latter habits are special to so-called multiply-twinned particles”’). Iron. A rhombic dodecahedron (fig. 13) was the typical habit. Three projections as illustrated in fig. 14 are seen in fig. 13. The shape was truncated in many cases and sometimes looked like a regular octagon. Recently, Fukano’ 1) prepared pentagonal decahedra (fig. 15) and triangular plates (fig. 16), both of which are characteristic of fcc metals. Some of the crystallites with these habits were of y-form (fcc), while others were of cL-form (bcc). These crystals formed between 910 and 1390 °C where the y-form is stable, and were quenched to room temperature. Crystallites having the fcc structure appear to be perfect, whereas those with the bcc structure are internally distorted (compare a and b of figs. 15 and 16). The distortion was evidently generated during the transformation from the y- to the cL-form. Tellurium. A pear-shape (fig. 17) was found in the inner zone and hexagonal rods in the outer zone. Both have the same hexagonal structure. Under certain conditions the ends of each rod were triply split (fig. 18).
4.
(c)
i
-
-
•
.
Fig. 12. w
•
-
o2
-
-
Triangular plate of silver. -
4
111)
S.
of the systematic study of crystal
size12”3), it is clear that crystals grow by the ordinary mechanism of vapour growth only during the initial stages of gas-evaporation. Further growth takes place by the coalescence of particles when they collide with each other in the upper part of a smoke where there is no vapour. Since the surface oxide hinders coalescence, irregular shapes as observed by Kimoto and Nishida2) may be formed in an impure atmosphere.
(100)
•
Fig. 13.
.
.
Rhombic dodecahedra of iron (cf. fig. 14).
The habits given in table 1 may be classified into three categories: single crystal, twinned and so-called multiply-twinned particles. The triangular bipyramid for fcc metals is twinned. The triangular plate for fcc
11—4
74
RYOZI UYEDA
ClIi)
Loin
(OIl]
(110]
-
(100]
-.
‘-.
~~ØT0II’
--
(Iii)
(01 I)
A
(001)
Fig. 15.
—
Fig. 17.
• • • . • Fig. 14. Illustrating three special projections of a rhombic dodecahedron. -• ~ :
Pear-shapes of tellurium.
~
.
-
Pentagonal decahedra of 7-iron (a) and cs-iron (b).
0.2 ?~ Fig. 18.
-
•-
•.
-
-
•
•
•
.
•
.
--
-
I. -
•
~•~•
-_______
(a) Fig. 16.
-
e
• - •- - - - L
-
-
-
-
I
500A
(I,) Triangular plates of 7-iron (a) and a-iron (b).
metals may also be twinned. It is presumably an extremely truncated form of bipyramid. Pentagonal decahedra and icosahedra are multiply-twinned partides1 6) There is a general trend that habits with a large surface area such as plates and rods are found in the outer zone, while those with a large volume such as
Rods of tellurium.
the rhombic dodecahedra and various hexagonal polyhedra are found in the inner zone. Multiply-twinned particles, which have a large area of twin boundary, are also found in the outer zone. It is worth noting that the octahedra and rhombic dodecahedra which are often more or less truncated are possibly Wulif polyhedra for fcc and bcc crystals, respectively, although this has not yet been exactly justified. It is of great interest to study crystallites having clear-cut habits formed in an extremely clean atmosphere. References
II —4
1) K. Kimoto, Y. Kamiya, M. Nonoyama and R. Uyeda, Japan. J. AppI. Phys. 2 (1963) 702. 2) K. Kimoto and I. Nishida, Japan. J. AppI. Phys. 6(1967)1047. 3) K. Kimoto and I. Nishida, J. Phys. Soc. Japan 22(1967) 744. 4) I. Nishida and K. Kimoto, submitted to Thin Solid Films. 5) K. Kimoto and I. Nishida, J. Phys. Soc. Japan 22 (1967) 940.
THE MORPHOLOGY
OF FINE METAL CRYSTALLITES
6)1. Nishida, J. Phys. Soc. Japan 26(1969)1225. 7)1. Nishida, unpublished. 8)1. Nishida and K. Kimoto, unpublished. 9) N. Wada, Japan. J. AppI. Phys. 6(1967) 553. 10) N. Wada, Japan. J. App!. Phys. 7 (1968) 1287. 11) Y. Fukano, unpublished, 12) 5. Yatsuya, S. Kasukabe and R. Uyeda, Japan. J. AppI. Phys. 12 (1973) 1675.
75
13) S. Yatsuya, S. Kasukabe and R. Uyeda, J. Crystal Growth 24/25 (1974) 319. 14) 5. Kasukabe, S. Yatsuya and R. Uyeda, J. Crystal Growth 24/25 (1974) 315. 15) 5. Yatsuya, K. Uyeda, S. Kasukabe, T. Ohno, T. Hayashi and R. Uyeda, unpublished. 16) Sh. Ogawa and Sh. Ino, Advances in Epitaxy and Endotaxy (VEB Deutscher Verlag, Leipzig, 197)) p. 183.
11—4