Morphological transformation and kinetic analysis in the aluminum-mediated a-Si:H crystallization

We analyzed the amorphous–crystalline morphological transformation of a-Si:H films caused by applying an annealing treatment to the Al/a-Si:H system at low temperature (250 °C) during several hours. Optical micrographs show the growth of Si nuclei formed on the amorphous matrix and also a t2 dependence of the average area of these crystalline grains, which suggest a bidimensional growth. Also was investigated the growth kinetics in the μc-Si:H films considering the annealing time dependence of the crystalline fraction. The application of the Avrami equation showed a good description of the experimental results during this morphological and structural transformation. The low growth velocity measured Vg = 7.2 × 10−3 μm/min is a direct consequence of the low annealing temperature applied (250 °C), which reduces the silicon diffusion across the interface Al/a-Si:H. Infrared reflectance measurements show a relative diminishing of the intensity for Si–H wagging mode with annealing time, suggesting effusion of hydrogen to the surface of the μc-Si:H films.