結晶成長過程の分子オーダーでのその場観察

抄録

A new method of “in-situ” observation of crystal growth processes has been developed. By this method, it is possible to observe on a TV screen the movement of growth layers with mono-molecular step heights spreading on the surfaces . The method has been applied to in-situ observation of growth processes of CdI₂ and NaCI crystals in aqueous solution by means of two baths flow system, where temperature and flow speed can be varied from 30 to 40°C, and 0 to 30 cm/sec ., respectively. The images of moving growth layers on a crystal face are observed by transmission phase contrast microscopy and are converted to video signals by a TV camera. Depending on the type of purposes, the images can be either directly recorded on a video tape recorder or after digitalization on a floppy disk in a micro-computer. The latter technique is more advantageous for the measurements of step velocities or for improving images by means of image processings. The followings have been observed as a result of preliminary application of this new method to the growth process of CdI₂ crystals from the aqueous solution. 1) Two different saturation temperatures are obtained for the spirals growing on one face of a single crystal. These spirals differ each other in their symmetries or in their step heights and show different dependencies of the advancing rates upon supersaturation. 2) when two types of spirals grow on a crystal, the advancing rate of one type of steps are influenced not only by the supersaturation for these steps but also by the supersaturation for the other type of spiral steps. 3) The process of twin formation due to the introduction of a stacking fault is visualized for the first time. The twin is generated at spiral centre by an accidental mistake in stacking and transmitted through the advancement of spiral layers.