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MORPHOLOGY OF FINE CRYSTALLITES FORMED BY GAS-EVAPORATION TECHNIQUE. FACE CENTRED METALS (Al, Co, Ni, Cu, Pd, In, Ag, Au AND Pb), SILICON AND GERMANIUM T. Hayashi, Y. Saito, S. Yatsuya, K. Mihama, R. Uyeda

To cite this version: T. Hayashi, Y. Saito, S. Yatsuya, K. Mihama, R. Uyeda. MORPHOLOGY OF FINE CRYSTALLITES FORMED BY GAS-EVAPORATION TECHNIQUE. FACE CENTRED METALS (Al, Co, Ni, Cu, Pd, In, Ag, Au AND Pb), SILICON AND GERMANIUM. Journal de Physique Colloques, 1977, 38 (C2), pp.C2-191-C2-194. .

HAL Id: jpa-00217080 https://hal.archives-ouvertes.fr/jpa-00217080 Submitted on 1 Jan 1977

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JOURNAL DE PHYSIQUE

Colloque C2, supplkment au no 7, Tome 38, Juillet 1977, page C2-191

MORPHOLOGY OF FINE CRYSTALLITES FORMED BY GAS-EVAPORATION TECHNIQUE. FACE CENTRED METALS (Al, Co, Ni, Cu, Pd, In, Ag, Au AND Pb), SILICON AND GERMANIUM T. HAYASHI (*), Y. SAITO, S. YATSUYA, K. MIHAMA and R. UYEDA (**) Department of Applied Physics, Faculty of Engineering, Nagoya University, Nagoya, Japan RbumC. - Co, Ni, Cu, Pd, Ag et Au pr6sentent des facibs nettement d6finis. 1) Octakdres. 2) Formes dCriv6es de 1) avec un nombre pair ou impair de plans communs. 3) Bipyramides triangulaires. 4) Plaques triangulaires. 5 ) DBcakdres ou icosabdres. Al, In et Pb prksentent des facibs moins nets : 1) et 2) seulement.

Le facibs de Ge est icosit6traCdrique et celui de Si est un polytdre limit6 par vingt quatre plans 31 1. Abstract. - Co, Ni, Cu, Pd, Ag and Au showed clean-cut habits : 1) Octahedra. 2) Shapes derived from 1) with odd or even number of twin planes. 3) Triangular bipyramids. 4) Triangular plates.

5) Decahedra or icosahedra. While Al, In and Pb, less clean-cut habits ; only 1) and 2). The habit of Ge is icositetrahedra and that of Si, the polyhedra bounded by eight 111 and twenty four 311 planes.

1. Introduction. - A gashevaporation is an experimental technique similar to the vacuum evaporation. However, it is carried out in an atmosphere of rarefied inactive gas. The evaporated metal vapour is cooled in the gas and form a smoke as seen in figure 1. A typical smoke consists of three zones : 1) dark inner zones, 2) bright intermediate zone and 3) dark outer zone. We collect smoke particles in each zone and study them by electron microscopy. It has been made clear that they are metal crystallites and show clean-cut habits in many cases [I]. In the present experiment, nine face centered metaIs (I), silicon and germanium were investigated. This paper describes the outline of the results, leaving details of experimental techniques and discussion elsewhere. 2. Face centered metals. - All the habits observed for these metals are categorized as shown in table I. Six metals, Co, Ni, Cu, Pd, Ag and Au (the first group) showed clean-cut habits under cats. 16, while three metals, Al, In and Pb (the second (*) Present address : Musashino Electric Communication Laboratow, N.T.T., Midori-cho, Musashino-shi, Tokvo. (**) present address : ~epartmentof Physics, ~ e i j Univerd sitv. - . Temvaku, - . Naszova. -(I) F.c.c. except for indium, which is face centered tetragonal.

FIG. 1 .

-

Metal smoke formed in a work chamber.

group), less clean-cut habits under only cats. 1 and 2. Figure 2 reproduces a general view of smoke

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1977240

T. HAYASHI, Y. SAITO, S. YATSUYA, K. MIKAMA AND R. UYEDA

C2-192

Crystal habits of f.c.c. metals Category

Shape

Twins

-

-

-

1 2a 2b 3

4

5a 5b 6

Truncated octahedra none R=0-40 Truncated octahedra even number R=40 Polyhedra (Fig. 4) odd number R = 40 Truncated triangular bipyramids one R=0-100 Truncated triangular plates several 1 R =0--x100 3 Pentagonal decahedra twinned Icosahedra particles Complicated polyhedra several

Ref.

1, 4

none none

under this category are found in the inner zone as well as in the intermediate zone. However, those with R -- 40 %, the largest of truncation degree, are found only in the inner part of the intermediate zone. It should be added that only this category gives single crystals and all the others in table I, twinned ones. 2 . 2 CAT. 2 POLYHEDRA DERIVED BY ADDING TWIN PLANES TO TRUNCATED OCTAHEDRA. -

Figure 4 illustrates polyhedra under this category

1, 4 1, 2

1, 3

none

FIG. 4. - Polyhedra of cat. 2b. (a) R

FIG. 2. - General view of metal smoke particles. Inscribed figures indicate the category nembers in table I.

particles in which many of the categories can be recognized. Each of them is described more in detail in the following paragraphs. 2 . 1 CAT. 1 OCTAHEDRA TRUNCATED BY (100).

- Figure 3 reproduces electron micrographs showing various degrees

(2)

of truncation. Crystallites

=0%

and (b) R = 40 %.

with one twin plane. The number of twin planes is found to be one to several. Provided that they are close to each other, the external shape is approximately truncated octahedra for even numbers (Cat. 2a) and polyhedra as shown in figure 4 for odd numbers (Cat. 2b). Figure 5 reproduces electron micrographs of particles under cats. 2a and b as well as cat. 1. In figures 5b and c the even or odd number of twin planes is distinguished from the contrast of thickness fringes. These particles are almost always with R = 40 % and found in the inner part of the intermediate zone. Figure 6 reproduces an electron micrograph and diffraction pattern of an aluminium particle. This particle has one twin plane (Cat. lb) as is clear from the illustrating diagrams. 2 . 3 CAT. 3 TRUNCATED TRIANGULAR BIPYRA- Figure 7 shows a- s t a ~ d a r dshape under this category. Actually, various degrees of truncation are found as reproduced in figure 8. The degree for each of a pair of pyramids is almost independent to each other and its value varies from almost zero to 100 %. MIDS.

-

2 . 4 CAT.4 TRUNCATED TRIANGULAR PLATES. The degree of truncation R = 0 % corresponds to 1

(a)

(b)

(c)

FIG. 3. - Electron micrographs, [001] projection, of truncated octahedra (Cat. 1). (a) Pd, R = 15 % ; (b) Pd, R = 30 % and (c) CU, R = 40 %. (2) Degree of truncation is conventionally defined as follows : it is zero for non-truncated shape and R % when the truncating planes cross each edge at R % of its whole length.

regular triangle and that of R = - x 10096, to 3 regular hexagon. Figure 9 reproduces electron micrographs and diffraction patterns. The degrees around R = 25 % are most frequently observed. From the analysis of diffraction patterns, it is proved that a crystallite under this category has several twin planes parallel to the plate. 2 . 5 CAT. 5 PENTAGONAL DECAHEDRA AND ICO- These polyhedra are the so-called

SAHEDRA.

MORPHOLOGY OF FINE CRYSTALLITES FORMED BY GAS-EVAPORATION

C2-193

(a) (b) (c) FIG. 5. - Copper particles of cat. 1 (a) : cat. 2a (b) and cat. 2b (c).

Twin plans

(a) (b) (c) FIG. 9. - Electron micrographs of truncated triangular plates. I (a)Co,R = O ; ( b ) C o , R = 2 5 % a n d ( c ) P d , R =-X100%. 3

multiply twinned particles studied in detail by Ogawa and Ino [5]. F I ~ ,0. .

-

I'winned particle of aluminium (Cat. 2b).

2 . 6 CAT. 6 IRREGULAR POLYHEDRA WITH NONPARALLEL TWINS. - This category includes all the

irregular particles which cannot be exactly defined. A reason for the difference between the first group and the second group is found in the vapour pressure as seen in table 11, viz. the values for the

FIG. 7.

-

Standard shape of truncated triangular bipyramid (Cat. 3).

Melting point and vapour pressure at it Metal

(a) (b) (c) (d) FIG. 8. - Electron micrographs of truncated triangular bipyrarnids (Cat. 3). (a) Cu, R ,= R2 = 60 % ; (b) CU, R I = R2 = 0 ; (c) Ni, R I = 0, Rz = 50 % and (d) Cu, R , = 0, R2 = 100 %.

TM(K)

PM(torr)

T. HAYASHI, Y. SAITO, S. YATSUYA, K. MIHAMA AND R. W E D A

C2- 194

FIG. 10.

FIG. 11.

-

Electron micrographs and diffraction pat

- Electron micrographs and diffraction patterns of germanium particles with an illustration of external shape.

first group are larger than lopStorr while those for the second ones, less than torr. Since the evaporation is carried out at the vapour pressure of around 10-I torr, the temperature for the second group is much higher than the melting point. For this reason the condensation takes place at temperatures much higher than the melting point for the second group, while it can take place near the melting point for the first group. Even for the first group, we infer, for various reasons, that it takes place at high temperatures in the inner part of the intermediate zone. Particles under cat. 1 with R .= 40 % have grown at high temperatures under an approximately thermal equillibrium state. Therefore, they are possibly Wulff polyhedra. Those under cat. 2 have also grown under similar conditions. However, twin planes have been introduced at the time of coalescence after the particles were a little cooled. Particles under cats. 3-6 have grown at lower temperatures in kinetic ways through some

imperfections. For this reason, they have sharp corners. No such particles are produced for the second group metals, even when the atmosphere gas is extremely clean. 3. Silicon and Germanium. - Figure 10 reproduces electron micrographs of the typical silicon particles. They are bounded by eight ( 1 11 ) and twenty four (31 1 ) planes. On the other hand, the typical germanium particles are bounded only by twenty four (31 1 ) planes. Since both silicon and germanium belong to diamond structure, it is strange that the afferent crystal habits take place. It is also strange that (3 11) prevails over the others because it is not the index for the lowest surface energy. However, the macroscopic features of smokes of these elements are different to each other and the typical habits are not expected to be the equilibrium forms, particularly for germanium. More detailed studies are necessary to make clear these problems.

References [I] UYEDA,R., J . Cryst. Growth 24/25 (1974) 69. [2] KIMOTO,K. and NISHIDA, I., Japan J. Appl. Phys. 6 (1967) 1047. [3] KIMOTO,K. and NISHIDA, I., J. Phys. Soc. Japan 22 (1967) -940.

(in Japanese) 44 (1975) 611. [4] UEDA,K., OYOBUTSURI, [5] OGAWA,Sh. and INO, Sh., Advances in Epitaxy and Endotaxy (VEB Deutscher Verlag fiir Grundstoff industrie, Leipzig), 1971, p. 183.