AFM and FTIR characterization of microcrystalline Si obtained from isothermal annealing of Al/a-Si:H

Abstract

Atomic force microscopy and Fourier transform infrared spectroscopy were used to investigate the morphology of the microcrystalline surface, and also the amorphous-crystalline structural transformation of a-Si :H films, isothermally annealed during several hours. Crystallization process was strongly influenced by the deposition of an Al layer on the surface of a-Si :H samples. Representative AFM images show the presence of grains, which increase in diameter with the annealing time. Relative crystallized fraction as a function of the annealing time can be described adequately by using the Avrami equation. The kinetic of this crystallization process suggest a two-dimensional growth of the Si nuclei. Fourier transform infrared measurements show the presence of an intense band near 512 cm–1 associated to Si–Si bonding. We observed the relative diminishing of the intensity of the Si–H wagging mode at 694 cm–1 with annealing time, suggesting effusion of hydrogen to the surface of microcrystalline films.