Abstract
Some observed results on the growth of germanium single crystals, twin crystals and dendrites grown from supercooled melts by Czochralski method are described.
As to the external shape of single crystals, it is regular hexagonal, square or hexagonal when grown in ‹111›, ‹100› or ‹110› direction respectively from highly supercooled melts. These results are obtained on silicon as well as on germanium. If slowly formed, the crystals will be polyhedral bounded by most highly atom-packed {111} faces belonging to various systems regardless of crystalographic orientation of the seed.
Crystals, grown slowly from a seed crystal with one twin plane parallel to {111} and external faces parallel to {111} and {110}, grow into triangular or diamond-shaped plates. Occasionally however, these crystal plates keep on growing in ‹211› preferred growth direction perpendicualr to the melt.
Crystals grown slowly from a seed crystal with two parallel twin planes grow into triangular plates joined with diamond-shaped plates. Such complex crystal plates with two parallel twin Planes usually keep on growing in ‹211› direction.
If the withdrawal from the melt is made very rapidly in ‹211› growth direction of crystals, the crystals will grow by dendritic growth into long and thin tapes or sheets bounded by well developed {111} flat faces. It appears that the dendritic growth takes place at accute corners formed by two adjacent {111} surfaces in twin crystals, because nucleation occurs readily at corners.
