A review is given on radiation damage of insulating crystals arising from energy imparted to solids into electronic excitation. Emphasis is placed in describing the mechanism. The role of the exciton- phonon interaction in the production of radiation damage is described and the radiation damage processes in a few typical insulators such as alkali halides, alkali earth fluorides and silicon dioxide are described.
This article reviews mainly structural studies on solid halogens, analogous to solid hydrogen, which have been found to undergo successive phase transitions induced by pressure. An extensive x-ray diffraction measurement incorporated with a diamond-anvil cell has revealed both molecular dissociation taking place at 21 GPa and an fcc lattice realized above 55GPa in iodine. These phenomena have been predicted only theoretically in solid hydrogen for a long time. A brief review has also been made on theoretical study of the phase stability and metallic character.
Composite films of metal-crystallites embedded in 001 and 110 single crystalline MgO films are prepared by the simultaneous vacuum deposition technique. The single crystalline nature is useful for electron microscopy and measurement of the physical properties. The epitaxially grown metal-crystallites of a few nm in size are analyzed by high resolution electron microscopy and micro-diffraction. The heat treatment of the as-grown composite films brings about change of the crystal habit for gold in MgO, grain-growth and phase-transformation for iron and formation of spinel for titanium. The specific resistivity and magnetic property are measured for gold - MgO and iron-MgO composite films to understand the relation between the structures and properties.
Si (111) surface topography changed during Si molecular beam epitaxial growth were observed by reflection electron microscope images using microprobe reflection high-energy electron diffraction (RHEED) . When RHEED intensity oscillations were observed at low substrate tempe-rature (350°C), it was found that the shape of atomic steps on the substrate was preserved during the growth and the surface topographies changed repeatedly with the period of the oscillations. When almost no oscillations were observed at higher substrate temperature (500°C), the shape of the atomic steps changed during the growth. These observations provide direct evidence that RHEED intensity oscillations occur as the result of layer-by-layer two-dimensional nucleation growth.
Application of X-ray two-wavelength method to the study of the commensurate-incommensurate phase transition of Rb2 ZnCl4 is described. The temperature and electric field dependences of the incommensurate satellite reflection, its position and width, are studied in detail. The results are mainly discussed in connection with some dielectric properties in thf incommensurate phase.