Solid phase crystallization of thin films of undoped amorphous Si prepared by plasma enhanced chemical vapor deposition has been studied by transmission electron microscopy (TEM). From the TEM images, the thermodynamic parameters for the amorphous and crystalline phases were extracted. These parameters were compared with those previously reported for evaporated, chemical vapor deposited, and self-implanted amorphous Si. We conclude that the thermodynamic parameters are very similar for different amorphous Si films, although the initial structure of the films is comparatively different from one to another. To explain this, the existence of an intermediate amorphous state is assumed and discussed.

No abstract

The effects of gold-particle incorporation on the structure of barium titanate (BaTiO 3 ) thin films was investigated. BaTiO 3 thin films (110 nm thick) with different gold concentrations were prepared via sol-gel processing and analyzed using X-ray diffractometry. The diffraction results showed that the crystal structure of the thin films changed from predominantly the cubic phase to the tetragonal phase, and the crystallite size increased as the gold concentration increased. Possible mechanisms for the goldenhanced crystallization have been discussed.

The kinetics of solid phase interaction between Al and a-Si:H have been investigated. The experiment led to the observation of low-temperature crystallization as has been reported. The crystallization temperature was found to be 300–350 °C from diffraction studies. From the x-ray photoelectron spectroscopy study, electron transfer from Al to Si was observed in the intermixing layer in samples annealed at RT and 200 °C whereas there is no evidence of the electron transfer for 300 and 350 °C annealed samples. To explain these results, a comparison is made with the interaction in the Cr/a-Si:H system previously reported and the interdiffusion model is proposed.

A model for the glass transition in a heating process has been proposed. In the model, noncrystalline solids are assumed to be assemblies of pseudomolecules or structural units. When the noncrystalline solid is heated, a bond breaking process becomes dominant compared with a rebinding process of broken bonds. At high temperature, successive bond breaking causes the fragmentation of the solid and the fragment size becomes smaller as the temperature further increases. Consequently, the solid begins to show some viscous behavior when the fragment size reaches a critical value. To construct mathematical expressions for the fragmentation model, we employed a simple rate equation for the bond breaking process first and then obtained the temperature dependence of dangling bond density in a noncrystalline solid. Second, the expressions for the fragment density and size as a function of temperature were obtained based on the following assumptions: ͑1͒ bond breaking takes place mainly at the boundaries between pseudomolecules, ͑2͒ once buds of microcracks are generated, successive bond breaking occurs mostly at the tip of the microcracks, and ͑3͒ the fragments are Voronoy polyhedra. Finally, the diffusion coefficient in the system was obtained by assuming the vacancy mechanism in solids and then the temperature dependence of viscosity was derived through Stokes-Einstein relation. To examine the present model, applications of the model to the phase changes of a-Si in heating processes are carried out and the results were discussed.