Numerous papers have been published about the microdefects in silicon crystals for these fifteen years. The important results among them are historically reviewed in this paper. First of all, the discovery and the various properties of the microdefects are introduced. Secondly, the transformation of the microdefects to the other types of the defects by heat treatment and the correlation of the microdefects with the other defects generated by device processes are explained. Thirdly, the nature and the origin of the microdefects are separately outlined of the two cases, namely FZ and CZ. In the first half of this section, the case of FZ is described, which contains the theory of the vacancy cluster, the observation of the microdefects by TEM, the interstitial silicon atoms and so on. In the last half of this section, the case of CZ is described, which contains the behaviour of oxygen atoms, the nucleation theory, the current topics and so on. Finally, the influence of the microdefects to device characteristics and the control methods of the microdefects, including both extrinsic gettering and intrinsic gettering, to improve device characteristics are generally reviewed.
In this paper, the studies on the growth forms and the growth mechanisms of ice single crystals grown from the vapor are described. A few problems on the temperature and supersaturation dependences on the growth forms of ice single crystals are presented. The growth forms of ice crystals below a few hundred micrometers in size remarkably vary with the water vapor diffusivity and those of ice crystals above several hundred micrometers in size slightly vary with the water vapor diffusivity. Moreover, the growth forms of ice crystals below a few hundred micrometers in size slightly vary with the thermal conductivity of the gas. Therefore, the growth forms of ice crystals depend not only on the temperature and the supersaturation, but also on the diffusion of water vapor and latent heat released by crystalization and the crystal size. In this paper, the roles of the diffusion of water vapor and latent heat on the growth forms of ice single crystals are described in detail. The outline of recent studies on the growth mechanism of ice single crystals grown from the vapor is described, too.
Supercooling phenomena of some hydrates such as Na_2S_2O_3・5H_2O is studied from the chemical potential difference of water molecules in molten and crystalline hydrate. These hydrates can be classified into two groups. One group has Δμ_<H_2O>>0 and nucleates with difficulty. The other group has Δμ_<H_2O>〜0 and nucleates very easily. Nucleating agents for these hydrates are discussed mainly on a point of view of the coordination structure of water molecules around Na ions in the crystalline hydrate. Interesting facts found for CaCl_2・ 6H_2O and the gas hydrate are given also. Essential requirements for the crystal structure of the nucleating agent are still open question.