Bi(11\={1})薄膜結晶の融液成長の透過電顕その場観察

抄録

Dynamic behaviour of the solid-liquid interface and crystal defect during the melt growth of a Bi thin foil (99.9% in purity) has been observed using a transmission electron microscope and a TV imaging system. The (11\bar1) foil was melted and regrown with the same orientation as the original foil by cooling the melt at the rates from 8.3×10⁻³ to 2.7×10⁻¹ K/s. The growth interface was concave toward the melt when the cooling rate was low and it became nearly flat when the cooling rate was high. Moreover, three types of the interface motion were observed during crystal growth; (a) a vibrational motion of back-and-forth at the slow cooling rate, (b) a vibrational motion of advancement and stoppage at the intermediate cooling rate and (c) a steady advancement at the high cooling rate. The vibrational interface motion was found to be due to a small fluctuation of temperatures during crystal growth. However, no facet growth was seen at any cooling rate against expectation.
In the grown crystals various kinds of defects were observed: (1) short and long dislocations and dislocation loops, (2) lineage defects probably consisting of a dislocation array, (3) circular voids and (4) triangular defects not identified. The formation and behaviour of these defects during the melt growth and subsequent cooling processes were explained and their density and size were estimated. Among the defects generated in the crystals following three are most dominant; short dislocations of 0.1 μm in average length, dislocation loops of 0.05 μm in average diameter and circular voids of 0.03 μm in average diameter.