ABSTRACT
The structural transition in electron-beam evaporated amorphous silicon (a-Si) thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with auto-correlation function (ACF) analysis. The density of Si nanocrystallites was found to decrease with the annealing temperature in samples annealed at 250–350°C. The results demonstrate the structure of homogeneous a-Si is more stable than that of nanocrystalline Si at 350°C or lower temperatures. As the annealing temperature was increased to 400°C, 5–15 nm polyciystalline Si crystallites were found to be distributed throughout the a-Si films. The density of embedded Si nanocrystallites in amorphous regions was found to increase in samples annealed at 400–450°C. The results are consistent with a thermodynamic model of homogeneous nucleation and growth of Si crystallites in a-Si.
