Ultrafine particles of TiH2 are formed by the H2 gas evaporation, the typical habit of which shows a dodecahedron. On the analysis of the habit, the growth of the particles is quite likely to be resulting from the martensitic transformation from the bcc structure to CaF2 structure owing to the hydrogen absorption. The desorption of the H2 from the TiH2 particles by a heat treatment in a vacuum brings about the formation of hcp Ti particle, while the absorption of H2 gas of Ti particles, in a hydrogen atmosphere, the formation of TiH2 particles with CaF2 structure. The formation of twins in a particle is always necessary for the transformations between TiH2 and Ti.
A growth model for atomic layer epitaxy (ALE) of GaAs by pulsed laser metal organic vapor phase epitaxy is reported. The physical processes of the model are surface reactions: the adsorption, desorption and decomposition of trimethylgallium (TMG) or triethylgallium (TEG) . These surface processes are expressed in terms of time constants Different decomposition time constants are assumed for TMG/TEG adsorbed on Ga and As terminated surfaces. It is found that an enhancement of the decomposition rate of TMG/TEG adsorbed on As compared to that on Ga terminated surfaces caused by laser irradiation is the main origin for the suspension of Ga deposition at 100% coverage.
The compound is a new material which has an intergrowth structure of rutile and β-gallia. The structure contains one-dimensional large channels with 3.4 to 3.6Å free diameter. Potassium ions which are accommodated in the channels show one-dimensional ionic conduction. The ionic conductivity is dependent on frequency as well as temperature and, in microwave frequency range, reaches into about 5 S/cm even at ambient temperature. The value is much larger than the microwave ion conductivity of Naβ-Al2O3. In addition, this material seems to be superior in one-dimensional properties of ion transport to priderites with the hollandite-type structure.